biogas from human waste handbook

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BIOGASFROM

HUMANWASTE

Workshop held in Delhi. August 22-23. 1986.

CONSORTIUM ON RURAL TECHNOLOGY

352.j_.49611•

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BIOGASFRÖM

HUMANWASTE

Workshop held In Delhi. August 22-23. 1986.

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CONSORTIUM ON RURAL TECHNOLOGY

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FirstPublishedm 1987

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CONTENTS

Introduction

Prologue

Keynote Address

Y.K. Sharma

ShailendraNath Ghosh

MaheshwarDayal

1

III

3

BACKGROUND PAPER

Blogasfrom human wa.ste ShantaSatyanarayan,S.N Kaul,S D. Badrinath,S K Gadkari

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SOCIAL ASPECT

Nlghtsoil basedbiogasplant: Lis role in socialequalityandcommunitybenefitsand the problem of itssocialacceptance Savitri Madan 23

Socialaspectsof nightsoil biogas IshwarbhaiPatel 26

‘3uh1iî~l~1 ~ÎEIT~t~ 29

Socialaspectsof thenightsoil blogasplantprogramme through casestudies KrishnaMahapatra 30

,

Blogasplantsbasedon nlghtsoil Amulya ChakraborLy 32

HEALTH ASPECT ‘ ‘

Nlghtsoil Blogasplants: Health aspects S.R Kshirsagar 37

Nlghtsofl biogasplants: Healthaspectsanddesign H.N. Chanakya 44

Biogasfrom Nightsoil: Thehealthaspectanddesign S.M Navrekar 52

Blogasfrom humanwaste:Public healthandsocialaspects

Designaspectsof biogasplantsfedbyhumanexcretawith or withoutsuppiementaryfeedstocks

Designofbiogasplant on nightsoil

Nlghtsoil-fedbiogasplants:Basisfor design

Nlghtsoil basedblogasplants:Timetesteddesign-floatingdomeon waterjacketeddigester

Designand Implementation ofa pilotdemonstration communitynlghtsoil blogasscheme

Soineaspectson thedesignof family-sizeflxed-dome nightsoil biogasplants

Improved ilnicagesof latrine complextocommunitybiogasdigester

Malaprabha latrine bloga.splant: A newinnovativedesignfor utilization of biogasfrom latrine

Nlghtsoil biogasplants:Healthaspectsanddesign

Blogasfrom nlghtsoil:Thehealthaspectsanddesign

Nightsoil basedbiogasplants:A usefuldevicefor

rural healthanddevelopment

Healthaspectsof anaerobicdigestion

HealthandHyglene Issues

S.V. Mapuskar 59

YashwantSingh 65

RajamalP. Devdas,Lakshmi 66SantaRajagopal,GhanambalJagadeesan

DR. Gupta 68

DESIGN AND R&D ASPECT

LK. Sinha

N.B. Mazumdar 73

RahulParikh 74

AnilDhussa 78

SV Mapuskar 81

Anil DhussaRaymondMyles 86

Anjan K Kalia 91

S.K.Vyas 98

S.V. Mapuskar 99

H.N Chanakaya**

S.M. Navrekar

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1**Thesepapersdealbot!,wit!, bealthanddesignaspectsThesehavebeenprintedunderbealthaspects.Pleasereferto

that sectionfor thesepapers.

TREATMENT OF SLURRY AND ITS USE

Manurefrom anaerobictreatment of humanwaste

Biogasplant effluent handllngandutlilsation

A.C. Gaur

KC. Khandelwal

Anil Dhussa

105

110

~T~ï

STRATEGYFOR PROMOTION ANDJNTEGRATIONWITH OTHER DEVELOPMENT PROGRAMMES

Nightsoil basedbi~asplant strategyforpromotion and Integration wlt.hdevelopmentprojects

Promotlonal strategyon biogasprogrammes

Strategyfor promotion of blogasplantsfrom humanwasteIn rural areas

H N. Todankar

N B. Mazumdar,YashwantSingh

RaymondMyles

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124

ILECOMMENDATIONS 127

EPILOGUE ShailendraNathGhosh 133

LIST OF PARTICIPANTS 149

116

INTRODUCTION

YK Sbarma~/Secretary

Consortiumon Rural Technology

INTRODUCTION

Biogas plants have been accepted by now in the country~as a device for improvingthe quality of the life of the people. They help in recycling of the cattie wastes and produceboth fuel and manure from the same quantity of dung. At present it is understood thatover 3 million families own biogas plants plants in the country.

The majority of these biogas plants use cattie dung as the feedstock. At the sametime there are efforts to also use alterna-tive feedstocks like human excreta, and alsoother agricultural wastes, water hyacinth etc.

The safe disposal of night—soil/human excreta is of major consideration for any sanitaryprogrammes and one of them can be through feeding It into the biogas digesters.

It is agreed that the use of the gas from the nightsoil will be considered taboo bythe majority of our people. But at the same time there are many who have acceptedit more at ~ndividuaI level than at the community level.

Some of the community biogas plants direcily fed on human excreta are at Masoodpurvillage near Delhi; Sewagram, Wardha; Midnapur (West Bengal) and Puri in Orissa.

The gas produced from the plants established in Orissa and Midnapur is utilised forcooking purposes by the scheduled caste of community. Its use also produced the worst kindof reaction from the beneficiaries because the worst kind of reaction from the beneficiariesbecause the ground-work that was needed to be done for educating the people does notseems to have been done bef ore installation of such plants. This means if awareness andeducation programme is carried out before supplying this gas for cooking, it may notonly be used by the scheduled caste but also by others increasingly. At the same timenight-soil can be a very good alternative feedstock especially where cattie dung is notavailable, as in our urban areas. Such areas can be where large number of people resideat one place like school/college hostels, hospitals, police lines, Army units, Jhuggi-Jhopricolonies etc. etc.

Some of~theproblems that come to mmd ar~

1. In night soil fed biogas plant, what would be suitable mix of feeds and in whatproport ion.

2. How much of water should be added to the different kinds of feeds (so far as dungis concerned it is at 1 : 1 ratio)

3. On what basis would the digester be planned-on the basis of summer or the wintertemperature “ 1f the summer temperature is taken as a basis for the design, willnot the gas production suffer in winter ? 1f it is based on winter temperature willnot the digester volume have to be very large - and hence dernanding a higher

BIOGAS FROMHUMAN WASTE

surface area and higher costs.

4. What are the practical measures to prevent heat loss from the digester during thenight in winter ‘~ 1

5. What models would be preferable, floating dome of the KVIC model or a fixed domeof the 3anta type ? 1

6. What kind of repairs, how often and involvingwhat kind of service will be required ‘~

Will the service be available locally ? 17. What should be the arrangement for the post-digestion of the slurry ? Should the

effluent slurry be dried on sand feds or stored in lagoon pits or aerobically composted 1with other organic materials ?

8. Since the biogas plant fed with human excreta is required to be near the latrmne 1and also near the kitchen and yet at least 50 feet away from the water sources,there was a problem of reconciling these requirements.

9. How far should the slurry be stored so that it does not have the other problems.

1Considering the various problems associated with biogas plants fed fully or partially

with human excreta. The Consortium in collaboration with Actmon for Food Production(AFPRO) invited a workshop on biogas from human waste. A small working group to decideon the various issues associated with the subject was constituted. The folowing f ive aspectsof the nightsoil biogas plant were identified and institutions and individuals working onthe were invited to the workshop. These aspects are:-

1. Social aspects 12. Health aspects3. Design and R&D aspects4. Treatment of Slurry and its use5. Strategy for Promotion and Integration with other Development Pro’~rarnmes

The workshop was held on August 22nd and 23rd, 1986. The keynote address was 1delivered by Prof. Maheshwar Dayal, Secretary, Department of Non-conventional EnergySources, Government of India and the background paper was presented by the scientistsfrom NEERI - National Environmental Engineering Research Institute, Nagpur. Such aworkshop was very much welcomed and it generated a lot of interest and interactionbetween scientists and the social action groups. It was participated by about 75 participants 1drawn from Government Departments, Research Institutions and Voluntary Organisations.Based on the presentations, the papers, discussions and the recommendations made onthe different issues referred above, 1

The proceeding and the papers of the workshop have been edited by Sri ShailendraNath Ghosh. We are also grateful to him for writing the prologuc and the epilogue. 1

We hope that the publication of proceedings of Conference would be found usefuland generate further interest in the subject. 1

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PRØLØGUEShailendraNathGhosh

In order that the benefits of the discussions do not remain confined to the enciavesof specialists, it is necessary to explain a few fundamentals of -the biogas-cum-manureplant operation.

Biogas is ob-tained from decomposition of biological source material or biomass(i.e. organic waste) in a biological process. Since we are interested in methane gaswhich can serve as cooking fuel, produce light, and drive stationary engines, the biolo-gical agents have to be the methane producing bacteria which function only in an atmos-phere fçom which oxygen has been excluded (anaerobk bacteria). In the presence ofoxygen, the decomposing organic matter produces oniy carbon dioxide. Airtightnessis crucial to biogas plant functioning. This makes exacting demands on masonry skill.

Vol-taile solids content of the input is important~~Tt ~ the portion of a samplewhich can be burnt off and which represents the amount of organic matter really avail-able to the bacteria for their own nourishment and conversion into gases and single-ceilprotein biomas. Although a small paz-t of the volatile solids (such as lignin, hair, feathers)is usually non-digestible or very slowly digestible, volatile solid is the digestible orvery slowly digestible, volatile solid is the basis for calculating the gas potential anddetermining the loading rate and retention time. The non-volatile part of the inputrepresen-ts that portion of a sample which is left as ash when burnt. It is also calledfixed solids.

For anaerobic biogasification, the necessary nutrients are carbon, nitrogen andphosphorous. Of these, the •ratio between carbon and nitrogen is important becauseIt is the carbonaceous matter which is converted to gas and humus-building materials,and any nitrogen other than what is required by the bacteria will end up as ammoniawhich, when excessive, will be toxic to the bacteria. Organic ma-terial with a C:Nratio higher than 30:1 v~i1l produce a raw gas with less methane*(1) and more carbon-dioxide, while a C:N ratio substantially lower than 30:1 will produce excessive ammoniaand supress methanogenic bacteria. In international literature, there seems to be adifference of opinion. Some western sources say that the C/N ratio of 30:1 is the bestfor methane production. The Chinese sources say that this should be between 20:1and 25:1. Indian scene has no opinion on this mat-ter.

Nightsoil being low in C/N ratio-between 5:1 and 7:1 needs to be suppiementedby other materials which are high in callulosic content and low in nitrogen, such asexcremen-t of herbivorous animals, fallen leaves, fresh grass, vegetable staiks, garbageetc. In rural areas, where such materials are abundant, it should not be difficult tobring -the mixed feed to the optimal C/N ratio. But this requires a fair knowledgeof the C/N ratio as different kinds of materials available in the locale. China’s scien-tific bodies have made available to Chinese farmers the carbon/nitrogen ratios of thecommon materials usable in biogas digesters. It should be the responsibility of ourscientific bodies and our Universities and colleges to contribute such knowledge regardingmaterials specific to each locale.

The process of producing methane-rich gas involves a series of reactions in whichthree types of bacteria take part. These three types are : (i) the hydrolysing bacteriawhich transform the compounds into solubles and the heavy particles into simpler one

,so that these can be attacked by others; (ii) the acidogenic bacteria which convert

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BIOGASFROM HUMAN WASTE

the broken-down organic matter into organic acids, principally acetic acid; anc~ (iii)the methaneogenic bacteria which take up the acetic and convert it into methane,carbon dioxide etc.

Since a balance has to be maintained between these three stages, the rate ofloading has to be duly observed. 1f the organic mat-ter is added too rapidly, the hardyand quickly multiplying acidogenic bacteria will grow even faster and produce a surfeitof volatile acids, lowering the p1-! of the slurry to the detriment of the methanogenicbacteria.

The pH level of the digester slurry is a crucial factor. It is a measure of theacidic or basic (i.e. alkaline) nature of the slurry. What is the optimum pH Ievd --

on this question, there seems to be some difference.

According to some researchers, “the methogenic bacteria generally funcion inin the pH range of 6.4 to 7.5. with 7.0 or neu-tral p1-! being the optimum point”. Accor-ding to a Chinese source, “the environment must be kept either at the neutral pH levelor at sligh-tly alkaline”. According to still another Chinese source, “ideally, the pHin a pit should be a little on the alkaline or neutral, with a pH of 7.0 to 8.5”. Possiblya pH of 8.5. is tolerable with cattiedung as mnpu-t, whose potential for ammonia produc-tion is low. With nightsoil as an input, this level is risky. We can exclude the extremes 1of pl-1 6.4 and pH 8.5 from our consideration and seem to maintain pH between 7 and8. Significant deviations from this will mean digester failure. Low pH will mean acidtoxicity and high pH will mean ammonia toxicity to methane producing bacterial.This is the reason why it is necessary to frequently check and adjust the pH of theliquid. 1

The question is : how can a lay person check and adjust the pH. “A ChineseBiogas Manual says: 1

“The method of checking is simple. (1) Dip a piece of litmus into some of thefermentation liquid, immediately observe the change in colour, and compare this witha chart of colour to teil the pH of the liquid. (2) The people of Sichuan have observedthat a red or yellow flame in the gas generally corresponds to slight overacidity inthe fermentation liquid”.* 1

When this is observed, “one should remove some of the old material and replaceit with a compensating amount of new material, or add some lime or ash, to adjust 1the acidity and restore normal gas production”.

Temparature is a key factor in biogas plant operation. It is universally accepted 1(i) that the level of temperature decides not only the killing rate of pathogens butalso which group of methaneogenic bacteria will function in the digester. Althoughit is true that thermophilic range of temparature (48-60°c) kills the pathogens quicker,improves gas yields and completely diges-ts the slurry in a shorter detention period,it loses its justification on the ground that produc-tion of this order of temperaturerequires input of external energy. Moreover, the thermophilic methanogenic bacteriaare more sensi-tive to variations in the environment. Mesophilic methanogenic groupof bacteria, which functions at 30-40°c range, is mor~.suitable for household or commu-nity biogas plants. A constant range of temparature is important. A sudden rise orfail by even 2-3°Caffects the methane forming bacteria.

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BIOGAS FROM HUMAN WASTE

Although generally the above two temparature ranges are mentioned in literatureon biogas, the Chinese sources say that in Sichuan Province, they depend for fermenta-tion on the ordinary temparature of 10-30°c. An IRDC publication, too, reportingon the experience from the same province, says: “After operating for more than ayear, it was found that normal production can be achieved by keeping the temperatureat 20°c~ During the summer and autumn the tank’s temperature averages about 23°cand plenty of biogas is produced; in winter when temperatures range from 0 to 7°c

,

the tank’s temperature stays at about 10°cand biogas is stil! produced.

This should raise the question: why, then, do we find it so difficult to run biogasplan-ts even at temperatures ranging be-tween 13°c and 23°c ? Does this necessitateany pre-treatment of the “feedstocks” in India’s northernmost regions, particularlyin winter - as is done in the temperate regions in China ? The discussions that followare intended to answer these questions plus those that have been raised in the Introduc-tion.

(l)* Biogas produced by anerobic, decomposition, generally, consists of 60-10% methane.The remaining 30-40% is combination of carbon dioxide, hydrogen sulf mde andother gases.

(2)* Human excreta is rich in nitrogen. Its nitrogen content is 5-7% as -~comparedwith 1.7% in cattie dung. Human urine contains about 18% nitrogen.

*Those who prefer testing by a Chemical may draw a small quantity of slurry andput 2-3 drops of phenol phthalene.

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KEYNOTE ADDRESS

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KEYNOTE ADDRESSMaheshwarDayal

Secretary/Dept.of Non-ConventionalEnergySources,Ministry of Energy,Govt of India

At the outset, 1 would like to congratu—late the Consortium on Rural Technology(CORT) for taking the initiative in organi-sing this workshop on Biogas from HumanWastes. Not only the prospects of biogasgeneration from human was-te will bediscussed but also the problem areas.This is all the more important at thisjuncture when Government of India isembarking in a major way on irnplementingan integrated action plan for rural sanita-tion and when a major thrust has beengiven for energy generation from renewablesources.

The severity of the problems relatingto inadequate sanitary facilitates in ruraland urban areas hardly needs any emphasis.The latest statistics available revealthat only 0.72% of the rural populationhave access to sanitary facilities. Thesituation in urban areas is not muchbetter as 33% or more of the urban popu-lation have no toilet facilities worththe name. The obvious result is thatpeople have perforce to use open fields,farm land, ponds, flowing streams, streets,railway tracks etc. Consequent to increasein population, industries, urban centres,and transport facilities the abovementionedtraditional options have more than reachedthe limits. Apart from the direct andobnoxious effects such as foul smeil,pollution and filth, the untreated humanwaste causes disease, mosquito infestation,high infant mortality rate etc. It is saidthat the pathogens emanating from humanwas-te are responsible for nearly 80%of diseases in India and the cost in termsof medical treatment and lost productionon this account is around Rs. 450 croresper annum.. For women, particularly inthe rural areas, the problem of sanitationfacilities is particularly severe, as privacy

is declining with declining forest coverand increase of population.

Realising these difficulties, Govern-ment has taken up an integrated programmeof settirig up rural latrines during the7th Plan. It is expected that 80% ofthe urban areas and 25% of the ruralareas would have sanitary facilities bythe year 1990. Effective managementand proper disposal of the human wastewill be required at all times.

As you are all aware, worldwideeffect is continuing for developmentand use of alternate and renewable energysources. The production of biogas, inthis context, is gaining greater attention.The success of generating biogas fromcowdung and other animal wastes hadled to exploration of alternate materialas sources of biogas production, includinghuman waste, sewage sludge, agriculturalwastes and industrial wastes which conta-inorganic matter etc. A number of agenciesinciuding non-governmental organisationshave taken up the establishment of biogasplants based on nightsoil either as asupplementary feed or exclusively asfeed material. Utilisation of nightsoilfor biogas generation is advantageousand some form of its treatment is obliga-tory from social and health points ofview. Biogas plant enables productionof energy as a useful and badly neededcommodity while performing this treatment.Further, anaerobic digestion of humanwaste also yields manure rich in nitrogenwhich is safer to handle and reducesharmful pathogens, thus diminishing thechances of faeces-borne and relatedcommunicable diseases.

The National Project on Biogas Deve-

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BACKGROUND PAPER


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cases, environmental pollution and spreadof diseases. Dry conservancy system,though not desirable considering theaesthetic aspects, is likely to continuein majority of villages and towns in Indiafor the coming two or three decades,as the water carriage system is veryexpensive. In this paper an attempt hasbeen made to provide information aboutnightsoil digestion in laboratory scaleunits along with the data obtained onpilot plants. Some information has alsobeen documented regarding removalof parasites during nightsoil digestion.

Treatment Melhods

i) The most common method in voguein India is burial in the ground eitherby itself or with town refuse. Itof-ten create fly and odour nuisancealong with contamination of groundwater by percolation and leachingand may cause enteric diseasessuch as cholera, typhoid, dysentry,infectious hepatitis, helminthicdiseases and ameobic dysentry.

ii) Chemical treatment requires treat-ment using lime and ferrous suiphatein a clarifloculator. The sludgeis thickened, vacuum filtered andsludge cake is burnt in a rotarykun. The separated liquid is neutrali-sed, diluted and treated in thicklingfilter or in an activated sludgeprocess. The final effluents in theplants existing in Japan are reportedto have neutral pH 60 mg/l BOD,150 mg/I suspended solids, coliformsless than 300 MPN (most probablenumber) and viable ascarisova lessthan 5 per 100 ml. This methodhas limited application under Indiancontext due to costs of collectionand chemical treatment.

iii) Extensive work has been done inthe anaerobic digestion of cowdungand other organic materials. Theanaerobic digestion of organic waste

materials, aich as farm manure,litter, garbage and nightsoil, accom-panied by the recovery of -methanefor fuel, has been an importantdevelopment in rural sanitation.Some of the more important aspectsof recent advances are controlof temperature and introductionof mi.xing of digester contents.Efficiency of some of the digestionunits decreased in the followingorder:

Thermophilic (seeded and agiated);Thermophilic (agitated only); Thermo-philic (seeded only); Thermophilic(withou t agitation/seeding) Me sophi-lic (seeded and agitated); Me-~philic(seeded only).

iv) Pillai and his associates at Bangalorehave indicated that good activatedsludge can be developed from nightsoil. Activated sludge treatmentsystem will be an expensive proposi-tion under Indian situation. Thismethod of treatment is extensivelybeing used in Japan.

Gas composition was essentiallythe same under thermophilic and mesophi-lic conditions. Heat required for thermo-philic is about 2.5 times that for mesophi-lic one. Moreover, the digestion timeand reactor size are about one half forthe mesophilic one. 1-lowever the costof construction of both types of reactorsfor a certain volume of nighsoil is nearlythe same because there is higher costof construction of digester in one typeand the higher cost of heating elementin the other. Thermophilic digestion isrecommended only when cheap surplussource of heet is available. Prolongeduse of thermophilic digestion proces~may result in lysis of the micro-organismsand also results in the destruction ofpathogenic bacteria as well as parasiticova fontained in the nightsoil. Ram MohanRao reported that thermophilic digestionof nightsoil alone and of nightsoil and

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cowdung mixture in the ratio of 2:1 resul-ted in a volatile solids reduction of 45%and above, provided loa3ding rates werekept under 2.4 kg VS/m per day in bothcases ~‘ith gas production of 0.45 and0.35 m /kg of VS respectively. The speci-fic resistances of dhe sludges wer~ fou2dto be 1.63 x 10 and 0.6 x 10 s gfor nightsoil alone and nightsoil w~thcowdung respectively. The specific resis-tance of sludge u~ingnightsoi! at a loadingrate 2.8 Kg VS/m per day nearly doubled.

CompQsting of nightsoi! along withtown refuse has been and is still beingpractised in many parts of the world.But in many parts of India this kind oftrealment is pursued in a very haphazardmanner. This resuits in fly breeding,odour nuisance and high incidence ofhelminthic infections. All the detailsregarding decomposition has been documen-ted in a 5ionograph by World HealthOrgani sation.

Characteristics of Night Soil

The quality and composition ofhuman faeces and urine are presentedin Table 1. Table 2 describes the compo-si-tion of the nightsoil which w~s usedin laboratory and pilot plant studiesat NÈERI, Nagpur.

Faeces is rich in organic materialscontaining appreciable quantity of nitrogenand phosphorus. Data reported in Table2 indicate that on an average, nightsoilcontained 13.3% total solids of which8% were volatile solids.

TABLE-!: Quality and Composition of

Human Faecesand Urine

Approximate Quantity Faeces Urine

Water content inthe nightsoil percapita

Dry wt, per capita 35-70gram

Moisture, %Solids

Composition of Solids

66-8020-34

88-97

93-964-7

65-85*Organic matter, %

*Nitrogen (N), % 5-7 15-19

*potassium (K),% 0.83-2.1 2.6-3.6

*Carbon, % 40-55 11-17

*Calcium (Ca), % 2.9-3.6 3.3-4.3

*C/N ratio 5-10 0.6-1.1

TABLE-2: Characteristics of Nightsoilused in Laboratory/Piot PlantStudies at NEERI, Nagpur.

Parameters (Dry basis) AverageValues

pHMoisture %Total Solids, %Volatile Solids, %* Total Nitrogen (N) %* Total Phosphorus (o), %* Potassium (K), %

5.2-5.686.713.311.64.0

1.531.08

BOD TESTED OVER 5 DAYS AT 20°C

- in gram per gram of totalsolids 0.4467

- in gram per gram of volatilesolids 0.5155

COD in g/g of total solidsin g/g of volatile solids

1.06981.2344

BOD/COD/ratioBOD:N:P

2.4100:9:3.4

About 44.7% of total solids of 51.6%volatile Solids in nightsoil are easily

Approximate Composition (Dry Basis)

135-270gram

1.0-1.3Ii tre

50-70gram

* BOD/coD ~tio gives theproportionof biodegradableorganicmatterto the total organlcs It enables-usto decideon whetherallthe wastesareartractivefor biogas generatlonThehighertheratio themoretheexpectedbiogasEd

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this loading, it is possible to decom-pose more than 50% of volatilematter wit~i gas production greaterthan 0.5 m per kg of vola~ilesolidsfed (i.e. 0.92 to 1.12 m per kgof volatile solid decomposed). Thisgas would have a methane contentof 60-65%.

During the studies, it was observedthat the slurry in the digester separa-ted out into two distinct Iayers- sludge at the bottom and super-natant at the top. Up to 6.22 percent solid concentration in thefeed, the digested sludge driedquickly on a sandbad. The dewatera-bility of the sludge deterioratedwith increasing solid concentrationin the feed. Dried cake was blackin colour and had no smell. Digestednightsoil slurry had an average2.8 to 4.8% of N, 2.2 to 4.0% ofPhosphorus (P 05) and 0.5-1.6%of Potash (K2O~on dry basis. Thusthe manurial value of night soilis retained in the digested slurry.

Shanta’’ carried out laboratorystudies at 37°C using various propositionsof nightsoil and cowdung and the resultsare presented in Table 4.

Addition of nightsoil to cowdungcan stimulate biogas production. Whencowdung and nightsoil were added inequal proportion in volume, the gas produc-tion was 0.35 m

3/kg of volatile solidadded. The correspontling gas productionper kg VS of nightsoil and per kg VSadded. The corresponding gas productionper kg VS of nightsoil and per kg VScowdung - ~ach digested ~ separately -

were 0.49 m and 0.13 m respectively.The authors also observed that cow dunghas a potential to suppress ammoniatoxicity since the quantity of ammonia-cal nitroger~ released into the slurrywas low in the feed mixtures as comparedto night soil alone.

Removal of Pathogens 1Shanta’2 carried out laboratory

studies to determine the extent of removalof helminth parasites removals duringnightsoil digestion. at 37°C and resultsare presented in Table 5.

Ascaris eggs survive for longer 1periods than hooI~worms.Itis also observedthat the sludge and supernatant fromdigester still contain viable eggs.

Table -4: Effect of Addition of Cow Dung in Night Soil

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1Nightsoil

%Cow Du~i&

%Gas Production

m3/Kg/VSVolatile mat-terDestroyed (VSr)

Volatile mat-terAdded (VSa)

0 100 0.158 0.74025 75 0.210 0.86050 50 0.350 0.92075 25 0.400 0.920100 0 0.500 1.090

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Table - 5: Percent Reduction of Helminth Ova in Laboratory Night Soil Digester

Load- Deten- PH Influenting tion No4J~’~Litre

EffluentNo.Ova/Litre ReductionAscaris Hookworm Ascaris Hookwormrate time Ascaris Hookworm

Kg./ dVS.d

2.21 20 7.50 4000 58200 2080 21360 48.0 63.2

1.78 25 7.60 114000 - 18200 38324 1639 66.5 90.6

1.45 30 7.65 94110 21820 28248 1528 70.0 93.0

NEER! also conducted extensive 18 m3 and 29 m3 capacity nightsoil diges-studies on pilot nightsoil digesters atCentral prison, Nagpur to demonstratethe techniques of total recycle of human

ters are reported in Table 6 and 7. Removalof helminthic parasites from 18 m3 pilotplant is presented in Table 8. Details

wastes. The digesters were similar to about the gas production, compositionKVIC gas plants in all respec-ts except of gas, calorific value, manurial valuefor the addition of a manually operated etc. obtained from the pilot plants arehomogeniser to bring nightsoil into a reported in Table 9.suspension before it is fed to the digester.Nightsoil was homogenised into a slurryof 6 to 8% total solids. Once or twice

The study was carried Out at an averagedigester temperature of 28°C while the

in a week, the digested sludge from the ambient temperature varied betweennightsoil digester was withdrawn into 13°Cand 33°C.a sludge drying bed. The resuits for a

Table -6: Experimental Re9ilts obtained on 18 m~Capacity Pilot Plant.

Parameters1

S E T SII III IV

Average loading Kgof volati.~e solidadded/m /day

pH

Alkalinity, mg/litre

Total solids, %

Total valitile Soil %

Volatile acids, mg/litre

2.02 1.55

7.2-7.8 7.1-7.5

10,294 9,000

6.50 6.10

5.31 4.92

125.1 175.7

15

1.73 3.08

7.4-7.9 7.0-7.6

12,000 10,000

6.10 6.45

4.86 5.89

130 4246

- -~ -~


1

Total ammonia-N, mg/litre

CST

2100

1155.3

1875.8 1912

646.3 493

13021

1302 1VS reduction, %

Gas production, m3/kgVSa (volatile solid added)

0.245

same with in~reased loading rates up-to3.56 kg/VS/m /day but the dewatera-bility of the slurry decreased appr~ciably.*This is an important point because thearea for sludge drying will increase withincreased loading rates.

Table - 7: Experimental Re~iltsobtained on 29 Capacity Pilot Plant.1

pH

Alkalinity, mg/litre

Total Solids, %

Total Volatile Solids, %

Volatile acids, mg/litre

Total ammonia as N, mg/litre

CST

Volatile solid reduction, %

Gas production, m3/Kg of VSa(Volatile solid added)

1SETS

II

1.16 17.2-7.8

11000

5.9 14.6 1743

2162 11268 154

0.655

52.7

0.367

48.8 50.5

0.437

57.4

0.430

It was observed that there wasno clearcut separation of sludge andsupernatant and only slurry could bedischarged.* About 0.076 kg cake/capita/day with 50% mixture was produced.It was also noticed that the performanceof digester remained by and large the

11111

Parameters

Average loading, Kg VS/m3/day 2.00

7.1-7.6

8500

4.5

3.5

184

1701

2761

52

0.289

* ThesecontradictedTrivedis observacionsgivenearlier Ed

16

11111


Table - 8: Removal of Helminthic Ova in 1* m~Capacity Digester

Parameters 3Loading Kg/m a

Per Cent RemovalHook Worm Ascaris

1.99 66.0 ± 23.10 37.0 ± 22.61

1.60 70.0 ± 12.11 52.1 ± 16.51

1.79 65.3 ± 23.64 35.3 ± 22.7

Table - 9: Other Re~~ItsConcerning Gas Production Manurial Value, etc.

Parameters Value

Gas production/capacity/day 30.025 m

Methane, % 60.65

Carbon-di-oxide, % 30-35

Hydrogen Suiphide, % 0.05-0.10

Fuel Value, K cal/m3 5600-6500

Quantity of sludge produced 0.71 Litres wet/capitawith 5% total solids.

per day

Manurial value of sludge

-. Nitrogen, % 3.25

- Phosphorous, % 1.00

- Potassium, % 0.83

Practical Application

Based on the laboratory and plantstudies, it is possible to design nightsoildigesters for different population groupsup to 2000 persons. For higher population,data can be adopted for designing butinstead of one digester for the entire

17

community, several small units will haveto be built at different locations, ifmechanical units have to be kept low.This may also facilitate easy handlingand transportation of nightsoil from respec-tive localities to the treatment site.Community nightsoil digesters have beendesigned and oplerated successtully by

- - ~


1

Sulabh International.13 Badrinath, etal’4 have given elsewhere the specificdesign details of nightsoils diesters, whichwould be very useful in this connection.

Nightsoil collection and disposlwill continue for several more decadesin our country and it is necessary toconsider total recycling of nightsoil.It consists of digestion of nightsoil andrecovery of the biogas generated. Thedigested slurry will be filtered on sludgedrying beds and the dried sludge canbe used as manure. The filtrate fromdrying beds will be treated in an oxidationpond followed by polishing pond* to reduceBOD and other pollutants and also forremoval of bacterial and helminthic patho-gens. It. is possible to harvest fish fromthese ponds provided the effluent isdiluted with fresh water.

CONCLUSIONS: work.

1. Various methods that are beingadopted for treatment and disposalof nightsoil have been listed.

2. Laboratory studies carried Out atNEER! on nightsoil digestion revealedthe following:

c) Digesters become non-opera-tive if the free ammonia concen—tration exceeds 275 mg/litre.

d) Ascaris and helminthic parasitesare removed to the extentof 67% and 91% respectively

2. Acharya, C.N. - Preparation ofFuel Gas and Manure by AnaerobicFermentation of ORGANIC NutrientsICAR Res. series No. 15, I~dianCouncil of Agril. Research, NEWDELHI, 1958.

3. Henze, M. et al (Editor)- FixedFilm Fixed Bed Reactor, SymposiumVolume, Denmark, 1983.

* “PolishingPond” is meantfor ‘polishing up” thefiltrate fromthesludge-dryingbeds,i e for tmprovingits quality further Ed

18

111

111111

at a detention period of 25days.

3. Nightsoil addition can enhance theproduction of biogas in cowdungdigestion.

4. Data c~pcerning tjle performanceof 18 m and 29 m nightsoil diges-ters have been reported includingthe manurial value of the digestedsludge.

5. Total recyclying scheme for nightsoilhas also been indicated for futureuse for large population areas.

ACKNOWLEDGEMENT

The authors are thankful to Director,NEER!, Nagpur for his permission toprepare and publish this piece of rearch

REFERENCE

1. Horassawa, 1, et al - BiologicalStudies of Nightsoil Treatment-Publication of the Kubota Instt.of Sanitary Engg., Isaka, 1962.

11111

a) per capital contribution oftotal solids and volatile solidsis 64.7 g and 56.3 g per day.

b) For design purposes, totalsolids concentration in thefeed, detention time and loadingrates and important.

1111111

4. Ram Mohan Rao, 1.- LaboratoryStudies on Thermo-Philic Digestionof Night Soil - M.Tech. Thesis sub-mitted to Univ. of Nagpur, 1970.

5. Gotaas, H.B. - Composition - Sanitary

BIOGAS FROM HUMAN W~SIE

Disposal and Reclamation of OrganicWastes, WHO Monograph No. 31,Geneva, 1956.

6. Mudri, S.S. - Some Observationson Anaerobic Digestion of NightSoil - 3. Envn. Health (India), 2~133, 1967.

7. NEER!, !nternal Report, 1976.

8. Despande, C.V., Shanta, S. -Effectof Low Solids Concentration onAnaerobic Digestion - Submittedto 3. Asian Environment, 1985.

9. NEER!, Internal Report, 1974.

10. Trivedi, R.C. - Studies ~,p the Ammo-nia Nitrogen Behaviour in AnaerobicSystem with reference to Digestion

19

on Night Soil and other OrganicWastes Ph.D. Thesis, Nagpur Univér-sity, 1973.

11. Shanta, S. and Mohan Rao, GJ-.- Effect of Mixing Cow Dung andNight Soil in Anaerobic Digestion- NEERI !nternal Report, 1970.

12. Shanta, C. - Survival of HelminthicOva during Anaerobic Digestionof Night Soil, NEER!, !nternal Report,1970.

13. Night Soil Digestion Plant for SulabhInternational NEER!, !nternal Report,1982.

14. Badrinath, S.D., Gadkari, S.K. -

Design of Community Biogas Plant- Salient Features - JIPHE, Vol.1, 1982.

1

SOCLAL ASPECTS

1 Abstract

NIGHTSOIL BASED BIOGAS PLANT

Its roll in socialequalityandcommunitybenefitsandtheproblemof its socialacceptance

Smt.SavigriMadan*

Thirty four years back, nightsoil based biogas plants were constructed essentiallyas a ~Bhangi Mukti” measure (upliftment of scavengers). But its impçrtance for publichealth, women’s welfare, achieving successin afforestation, improvementof soil fertility,

production of better quality of crops and an aestheticallysatisfying environmentis immense.The sources of inhibitions that impede the spread of biogas plants are discussed.

The primacy of political will and the importance of highly motivated voluntary agenciesare emphasised.

Iniroduc tion

In our country, Late Appasaheb

1 Patwardhan pioneered the

of nightsoil based biogas plants moreI than thirty years back (sirx~e1953), mainlyas a social benefit programme for emanci-pation and uplif t of ~avengers (Bhangi

I Mukti). Later, in his capacity as chairmanof ‘Bhangi Mukti Samiti’ (which wasconstituted in 1957) of Gandhi Smarak

I Nidhi, he advocated and arranged financialhelp (subsidy) from Nidhi’s funds forthe construction of biogas plants. Conse-

I quently, Maharashtra Gandhi SmarakNidhi continued the work of constructionof nightsoil based biogas plants as apart of its ‘Bhangi Mukti Yojana’.

Ideologyof ‘Bhaogi Mukti Yojana’

Late Appasaheb Patwardhan passion-

I ately feit (i) that to force some oneelse to do our own dirty work is a sincommitted towards humanity. The sca-

I venger who does this job is treated asundignified, lowly and untouchable insocial structure. This can be changed

U if each person does his own dirty workhimself; and (ii) that in order to reducerepulsive feeling in doing this dirty work,

the methods and implements for thedisposal of nightsoil have to be improved.

RoJe of nightsoil based biogas plantsin “Bhangi Mukti”

Appasaheb Pathwardhan had fullyrealized the significant role that nightsoilbased biogas plant can play as a sourceof fertilizer, better health and energy.However, his stress was on the socialbenefitts (Bhangi Mukti) likely to bederived from the plants. The biogas plantdesign developed by him was a waterjacketed floating dome type plant modifiedfrom ‘Gramlaxmi’ design developed bySri Ja~hai Patel. Further, he lnsistedthat it ~ould be onsite disposal plantto which latrines were directly connected,SO that not even mechanical carriageof nightsoil was not involved. This plantcould be very easily maintained by anyfamily without some one else’s help.The scavenger then thus treed from dirtywork, could be rehabilitated by learningother ~<ills. With stigma of dirt gone,he. could be rehabilitated socially aswell. In the night of this thinking, theview that nightsoil based biogas plants

t MaharashtraGandhiSmarakNldhi, Pune

23


1

should be based primarily in scavenger’scolonies, to be maintained and used bythem is a very distorted view of theis~ie. In fact it would be a new deviceto perpetuate the social injustice metedout to the scavenger community. In Maha-rashtra several such ‘onsite’ disposalnightsoil based biogas plants are functioningin individual households and institutions.They are maintained by the familiesor institutions ihemselves.

Thus, by adopting a suitable designand methodology fort implementation,the nightsoil based biogas plant can plana very significant rofe in ‘Antyodaya’and social equality programmes.

Wo men’s WeLfare

In rural setup women face a consi-derable problem as regards attendingto nature’s cail. Nightsoil based biogasplant placed in one’s own family or amongsta group of houses will ease this problem.It would be feasible even if the householddoes not possess any cattie. The latrinecould serve the purpose. 1-lowever, ifat a little extra cost nightsoil biogasplant could be constructed, it wouldaugment their fuel supply and wouldreduce their work of collecting firewoo4.Time saved from this work could beused for recreation, care of childrenor for earning some extra income forfamily by stitching etc. Further, it willpartially improve their lot in the kitchen.

Benefit to family

There would be multiple benefitsfor the family. The time, which the familymembers spend in going to far awayfields for defecation, will be saved.The home airroundings will be clean,pleasan t and ae sthetically satisfying.In addition, the generated biogas willreduçte the expenditure on fuel. Further,manure of a very good quality will beavailable, which the family can use either

in their own farm or seil it.

Benefits for the Community

Latrine-connected biogas plants 1will yield other benefits

i) Cutting the trees for firewood willbe reduced in proportion to theavailable biogas~

ii) !ncidence of communicable diseaseswill be reduced due to lesser pollu-tion of water sources and lesserfaecal contamination of food throughflies and insects.

iii) Ailments in the cattle populatiorwould be reduced.

iv) Crops would be healthier if opendefecation in the fields is reduced.

v) Availability of organic manure ofhigh quality would be beneficialfor the crops.

Problemsin Social Acceptance

It can be said without any hesita-tion triat the nightsoil based .biogas plantsoffer benefits in terms of social, econo-mic, jiealth and environmental improve-ments. Yet, the programme of constructingnightsoil biogas plants may not be veryeasy to implement. Suitable technologyis not much of a problem. Necessaryfinancial input will also not be very diff i-

cult. The major hurdie will be a socialacceptance of these plants. Inhibitionto. use biogas and slurry from nightsoilbased biogas plants is noticed on severalgrounds. Efforts to deal with this inhibi-tion effectively will have to be madevery vigorously. Some important factorsresponsible for this inhibition could• beidentified.

1. Ignorance about the nature of biogasleads to a misconceived feelingthat these end-products are dirty

1

111111111111111

24

111


and unhygienic.

2. A wrong notion prevails that thenightsoil based biogas plant willmake their surroundings uncleanand foul smèlling.

3. A feeling exists that the grainsand vegetables grown in the farmwhere slurry is used as a fertilizer,will not be clean and wholesome.

4. A doubt about religious sanctitycreeps in one’s mmd. One feelsthat it is not right to use gas andfood obtained from dirt, for religiouspurposes.

5. Possibility of ridicule from neighboursand relatives weighs heavily onthe mmd of the user.

6. A fear of possibie non-acceptanceof eatables from the user’s homeby the villagers become a formidablede terrent.

Many more reasons could be enumera-ted. To counter these deterrents, educa-tional efforts will be required for tacklingthese problems. -

Improving Social Acceptance

It is not proposed to deal with detai-led measures for promotion in this paper,It would be adequate to put forth a generalperspec tive.

i) Role of Voluntary Agencies

l-Iighly niotivated voluntary agenciespossessing missionary zeal will

25

be an asset in promoting this work.However, it will yield better resultsif the Government identifies suchinstitutions, encourages them andheips them financially for this task.It would be worth rememberingthat the initial construction andpromotion of nightsoil based biogasplant was a totally voluntary andmnspired effort of Late AppasahebPatwardhan. Later it was continuedby Maharashtra Gandhi SmarakNidhi, which unfortunâtely gotvery limited back-up from elsewhere.

ii) The Government already has aninfrastructure for rural development.This machinery could be motivatedfor promotion of nightsoil basedbiogas plant. Voluntary agenciescan act as resource agencies forthe orientation of these personnel.

iii) Political wilk This is probably themost important factor. The decisionfor promoting nightsoil based plantsthrough out the country will haveto be a decision of the represen-tatives of the people. With thissupport, it will be easy to promotenightsoil based biogas plant as oneof the tools for social uplif t.

Coriclusion

It is feit that the social uplif t. aspectof nightsoil based biogas plant are verysignificant. With the political will andefforts of voluntary agencies and govern-mental infrastructure, nightsoil gas plantwill positively enrich rural social andcultural fabric.

Iniroduc tion

There are 46087 biogas plants, ir~Gujarat; 6467 latrines are connectedto biogas plants.The first biogas plantin Gujarat with public latrines connectedto it was constructed at Safai Vidyalaya,Vyara, Gujarat in 1958 on private property.The biogas thus produced was used tocook food for 15 employees and alsofor illumination. The digested sludgewas carried away by the municipal authori-ties. This success Story was repeatedin the post-basic schools and hostelsin Surat District. Biogas Plant TechnicianTraining courses of 3 months’ durationwere conducted. Yet, our people areyet to accept the use of biogas plantswith laWines connected. As per Manu-smriti, it is stated that latrine shouldbe located 400 steps away as defecationis considered dirty. In the conventionalcommunities orthodox people visit latrinesby putting on separate clothing. TheMohenjodaro excavations have revealedthe provisions of bathroom and drainagebut not of iatrines, implying therebythe prevalence of open defecationwhich corroborates belief in Manusmrutistatements.

The rural as well as urban communi-

- Ed.ties’ connections of laWines to biogas~lants are rather recent. In village Khoraj,Gandhinagar District (Gujarat), so me10 latrines have been connected to thebiogas plants, but the use become effec-tive after 15-18 months of construction.This was made possible by mass educationby a lOday workshop which incorporatedreiigious, scientific and educatiönalbasis of biogas plants. At Nadiad, Gujarat,16 latrines ‘used by 400 girl studentshad been connected to biogas plants.They did not accept the tea and snackscooked with biogas this indicated thedeep-roo ted prejudice. So me progre ssivefarmers with scientific approach connec-ted latrines to their biogas plants in1958. But even today a stigma is attachedto it so that food cooked with biogascannot be an offering to God.

In Vahelal, Ahmedabad District,a farmer has constructed a flat-roofedbiogas plant in his floor area with thelatrine connected to it. The cattle dung,too, is fed to it. The digested slurryis collected by the women in the houseand dumped in the compost pit. Suchillustrations are useful in shaking socialinertia and countering prejudices. Ithas been observed that the Advisi agri-cultural daily wage earners do not handle

• Principal, Safai Vidyalaya, Harijan Ashram, Ahmedabad

26

111SOCIAL ASPECTS OF

NIGHTSOIL BIOGAS PLANTSIshwarbhaiPatel 1

Ah~tract

The paper gives inspiring instancesof nightsoil based biogas-cum-manureproductionin Gujarat that shine through the mist of ignorant preju.dice. These experiencesshouldhelp overcome the pessimism that it will be long before nightsoil based biogas-cum-fer-tiliser plant becomessocially acceptable. Defects in biogas construction and planning,which came to the author’s notice during a survey of 120 samples,are listed. Constructivesuggestionsfor improving the efficiency of bio-degradation, increasing the temperatureregimen of biogas plants and for amendmentof govemmentalproceduresare given.

111111111111111111


Ihe digested slurry; in them the feelingis well entrenched that only the scavangingcommunity can do such jobs. Such trendsare based on “religious beliefs”.

A progressive farmer of Ramp(Ahmedabad) constructed two latrinesin his premises, one for own familyand other for the public who may notbe having such facility. He invites peopleto use the public latrine. Some 40 usersavail themselves of it. The owner runshis family kitchen from the biogas producetherefrom. In the Chetanawadi areaof Mehsana (Gujarat), a biogas plant,fed from 6 latrines serving 12 tenantsis in operation. The tenants get cookinggas at Rs. 35/- per month. The outgoingslurry is used as organic manure togrow vegetables. It is an excellent exampleof low-cost sanitation wmth recyclingof wastes. Another biogas plant is inoperation at the Pathey Hotel at KrishnaNagar on the National Highway whichprov’des easing facilities for passengers,drivers and conductors. The b~ogas isutilised in the hotel. In a decent largehotel Ahmedabad in a rural environment,Jivestock wastes and garbage are fedto the digester and the biogas fromit is used in the kitchen. The digested,drained, dried and parcelled out slud&ecakes are packed in 2 kg polythenebags and sold at Rs. 5/- each for thecity’s mndividual kitchen gardens. Suchexperiences should help demolish thesocial stigma attached to connectionof nightsoil to biogas plants.

Financial Subsidy for Latrine connectedBiogas Plants

The Government of Gujarat paysa aibsidy of Rs. 300/- to any biogasplant which admit wastes from latrine.This scheme initiated by the Rural Deve-lopment Department had a positiveimpact and gathered momentum, thanksto the co-operation of educational andother institutions. lt saved rural womenfrom smoke nuisance which affected

2~

their eyes. It has proved to be a blessingto them as the womenfolk can now haveprivacy during the daytime withouthaving to cover long distances. It leadsto better health because poor sanitationand unprotected water are responsiblefor 80% of prevalent diseases whichcause a loss of 73 million mandays.It saves an equivalent of Rs.500/- interms of production of gas and fertilizers.

Sulabh International has startedcommunity biogas plants with latrinesconnected to these. It is necessary topropagate the concept that waste iswealth when it is recycled. The implemen-tatmon becomes successful when themaintenance and cleaning is done bythe owner. It is observed that generally,the prosperous farmers avail themselvesof this scheme. It has not yet percolatedto the strata of landless labourers.

Ideally, the theory and practicego hand in hand but in reality, thereis always a gap. It is necessary to bridgethis gap. The following observationsare based on a survey of some 120 samples.

1. The field results hardly approach.50% of the figures claimed byscientific bodies.

2. The organising agency does not,in general, posses adequate know-ledge about biogas plants. Theavailable information does notreach the users.

3. The proportion of excreta andwater is 1:2 litres per use. Thisslows down biochemical reactionsand reduces the liberation of bio-gas.

4. Normally one large sludge dryingbed is provided but it is necessaryto have 4-5 small ones.

5. Distances of biogas carrying pipeswere found to be very long. It


1

should not exceed 20 m.

6. Biogas plant should not be underany shade or shadow at any timein the day. Only 70% plants werefound to be free from the shadowwalls and only 10% plants werefound to be away from Wees.

7. The priority of users was foundto be in the following order: cooking,mechanical gadgets, and manure.About 98% of biogas plants wereseen to be used for cooking purposes

8. For maintenance of gas pressurefor flow, the slurry must be fedtwice a day. In 95% of the biogasplants, feeding of slurry was done

only once a day.

9. The proliferation of biogas plantsis of national importance. It hasbeen observed that proceduresfor obtaining Sanchai and Subsidyare arduous and timeconsumingas was feIt by 75% of people understudy.

10. The organisers were found to berunning after target of numbers,forgetting the users and the nece-ssary oprational guidance is diffmcultto get.

Suggestions and Recommendation~

Nightsoil has been looked uponwmth repugnance. Because of maladiesassociated with nightsoil, the operationaland maintenance personal have beenlooked upon wmth disdain. Nightsoil,if misused or mismanaged, is hazardous.1f managed scientifically and carefully,it yields several benefits. Some empericalsuggestions from scientifmc and socialstandpoints are made below.

1. The size of gas dome may be reducedto get more pressure and effectiveanerobic biogradation. 1

2. Non-corrosive HDPE (high densitypolyethylene) or fibre-reinforcedplastic containers are availableas gas holders. These may be paintedblack for absorption of solar rays.

3. Attempts are needed to use localand inexpensive materials for cons-truction of biogas plants.

4. Intensive and effective trainingprogramme coupled with simplifiedprocedures for quick processingof applications along with theirrelevant publicity would go a longway in mass propagation of plantsfor decentralised harnessing ofrenewable resources of great nationali mportance.

1

only.

1111

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28

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29

~* t I~Siqï m3fllJ ~ 31S~fi!3T~9W~ ~sûç~ii~-it~t ~f~9i~hi 4~t ~w~iq~~ ~t~mar~i~ftmwmqft~ig’ ~fl~S~*ft

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1tirn t ~t ~5R°T~fM~4 ~* ~jT~4 t ~TF~&i*~ mft t itz wt 4~ ~iiffit ~niî aft~~si

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q~TSi fl tm ~m,twi~uaft,~aumaiïft 4 ~i~nï~auta~ti~9t9~~

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4 U3TW ~~ÎI91

SOCIAL ASPECTSOF THENIGHTSOIL BIOGAS PLANT PROGRAMME

THROUGH CASE STUDIESKrishnaMahapatra

1111

This paper presents the fruitsof certain case studies where communitybiogas plants were constructed withoutthe community’s participation in theformulation of schemes.

The social aspects are the mostsignificant aspects of a technology-inten-sive programme and may decide thelatter’s fate in terms of aiccess andfailure.

In the nightsoil-based biogas progra-mme, these.aspects have been of greatersignificance due to the sensitivity ofthe issue in the Indian socio-culturalcontext.

Very broadly speaking, such techno-logy-intensive programmes seem to havethree main aspects:

1. The te-chnical-including the skillinvolved, the resources etc.

2. The social-inciuding the beneficiarygroup attitude, the use concept

3. The organisational aspects - includingthe maintenance, the running ofthe programme etc.

This paper through case studiesof nightsoil based community biogasplan-ts at Puri, Varanasi, Masudpur andMidnapur tries to illustrate the signifi-cant role of social aspects in the positiveimplementation and working of the pro-gramme and seeks to give some sugges-tions.

The Puri, Varanasi and Midnapurplants are entirely for Harijan communi-ties.The Masudpur plant is a part ofa demonstration project of Khadi Gramod-yog, and the beneficiary group whichhas to pay for the gas aipply for cookingpurposes, is a mixed group in the neigh-bouring village complex comprising ofdifferent caste and class and awarenessbackgrounds.

While the Midnapur plant wasclosed down alter a few months offunctioning and was thus a total failure,the other three plants are in varmousstages of functioning under a wde rangeof constraints which range from purelysocial to the technical.

The Puri and Midnapur plants werefed by nightsoil carried from dry latrinesto the plants through the municipalitycollection system.

The Beriban (Varanasi), Masudpur(Haryana) plants were attached to latrineswhich were specially constructed tobe used by men, women and childrenof the villages.

In all these cases the gas waschief ly for cooking purpose except atBeriban where the use was to be forlighting which was a greater need forthe people.

From the study of the 4 communitybiogas plants significant aspects whichcome to light are~

1. The Puri programme was started

• Social Scientist, AFPRO, New Delhi

30

111

11111111

e tc.

11111


without the people’ s participation,but still was a relative successas the economic benefits overruledthe constraints of ethos and valuesand the feeling of discrimmnationas lhey were Harijans.

2. The Beriban programme at Varanasiwas an impractical idea underthe given conditions and thereforenon-functional. The most importantconstraint was the shortage ofwater. Next was the ethos of womenwho must not be seen going fornatures’ cali, with cans in hand- as it was something to be shyof, in view of the man-womanrelationship.

3. Masudpur programme was differentas the villagers using the gas forcooking did not have the feelingof abhorrence seen in the other

-~ -; -- -

31

areas but the use of latrines wasnot a practice here. The poormamntenance of laWines due toshortage of water added to thepropensity to avoid of the laWines.With several construction worksgoing on for multi-storeyed buildingsaround the village the villagerswere gradually fmnding a shortageof open grounds, but the !ayingdown of sewage system in thevillage had given them hope ofhaving their own latrines in theirhomes and til! such time theypreferred to “somehow manage”rather than go to the “closed cooped-up filthy latrine.”

The study of the four cases quiteclearly establish the need to ensurepeople’s participation at all levels ofplanning, implementation and management.

11

BIOGAS PLA.NTS BASED ONNIGHTSOIL

Al~2ruct 1The thirty latrine-connectedAFPRO-design-basedfamily-size biogas plants construc-

ted in Contûi sub-division (Midnapore district, West Bengal) have been operating withoutmuchtrouble so far as gas generationis concerned.In rural areas,themovementfor low-costlatrine and smokelesschullah has caught on. Progress in the programme for nightsoil-plus-otheranimal-wastebased biogas plants dependson innovations in (0 low-cost design;(ii) the technologyof using water hyacinth and varieties of foliage as inputs along withnightsoit and cattiedung; and (iii) the finding of usesfor the siurry as fish meal and thelike. The paper posits a few other questionsrequiring research based scientific advice.

The disappearanceof bushesand jungles has greatly reduced the scope for open-airdefecation. The resulting threat to women’s privacy has created a strong impulse fordomestic latrines. The grave shortage of fuelwood and the need for keeping the pondsclean as a sourceof water for cookingpurposeshave created a new awarenessfor night-soil-basedbiogas plants. People have come to feel that the alternative is helplessdepen-dence on tubewells that often go Out of repuir and the pollution of tanks by nightsoilwashedover from the roadside by rainwater.

Iniroduc tion

The Lok Shiksha Parishad, Narendra-pik evolved a system of latrine basedon a pan attached with a U-pipe andwithout any septic tank. The nightsoilis discharged into the digester of thebiogas plant (1.3 or 5 cum as may bethe case) by a pipe, In every case thelatrine-connec ted fixed-dome plantis fitted with an inlet chamber for feedingcowdung and outlet chamber for dischargeof the slurry according to the AFPROdesign. In this way nearly 30 biogasplants of family size (2 or 3 cum), cons-tructed during 1985 in f ive villagesin Contai Sub-division are found to beoperating without much irouble so faras gas generation is concerned.

-Ed.scrapings of carcass of dead animalsas inputs for quick generation of energy.The plant owners are reluctant to usesuch material. We. too, have not foundany literature which aiggests that suchmaterial can be fed into biogas plants.

Progress/innovation is necessaryin the following respect~

i) Low-cost design for domestic latrine-connected biogas plant digester.

ii) The utility of fresh slurry as fishmeal. It has to be well established.

iii) The proportion of materials likewater hyacmnth and similar varietiesof foliage in relation to cow dungor nightsoil for ensuring gas andlight at the rated capacity.

Besides, scientific advice is needed

* RK MissionLok Shiksha Parishad, Narendrapur, 24 Parganas, West Bengal

32

111

Arnulya Chakraborty

1

1111111111

In some cases where mixed feedingsystem was introduced, the DIC staffof the district suggested the use of on:

11


i) the pros and cons of substitutionof the inlet chamber steps by apipe as in the KVIC model. (Thisis generally advocated by DIC).

ii) the advisability of otherwise ofputting animal carcass of deadanimal s.

Inlegration with Development Programme

It is observed that the move forintroducing smokeless chullah and low-cost latrine has made some headwayin the rural areas.The programme forlow-cost nightsoil biogas plants shouldnow be emphasised. In fact, the responseof the villagers wherever we went andpropagated the utility of the biogasplants has been beyond our expectation.

Here again, the problem is thata large number of enthuiasts for biogasplants in the villages are without anycattle or poultry or piggery. Now, domes-tic biogas plant (even 1 cum size) cannotgenerate gas only by nightsoil fromthe smail-size and single-family systems,because it appears that the regularuse of connected laWine by 35 to 40persons will produce gas from the plantconsidered ~jfficient for only 5 to 6rnembers. In aich cases our advice hasbeen to collect cowdung from outsideor set up poultry farms or have goatfarm or piggery so that the additionalfeeding material may come from theirown household. These are, however,good as advice but cannot be practisedby villagers in general. The matter,however, requires some analytical studyby the experts so that some concreteaiggestions might be offered to thevillagers who are willing to have biogasplant fitted to latrines but have nocattie of their own.

From the Viewpoint of Domestic andSociai Samtation

The ordinary famiies in the villagesin different districts of our State (West

Bengal) are now responding very enthusias-tically to ôur education-cu m-mo tivationcamps for propagating biogas plantswith a stress on nightsoil. We have triedto examine the factors behind suchenthusiasm. 1 may cite here a very impor-tant factor behind aich motivation.It is the crisis in the traditional open-airtoilet system. In one education campheld in a village in North 24-Parganasdistrict in 3uly 1986 the heads of theMuslim as well as scheduled caste familiesargued that low-cost latrmnes are nowe ssentially required for womenfolk.The gradual disappearance of the villageforestry, bushes and jungles makes itextremely difficult for the women inparticular to go out to the traditionalopen-air latrine. Increasing populationand extension of housing are also creatingproblems in this matter.

In a similar education camp conduc-ted by us in the South 24-Parganas(near the Sundarbans) very recentlypeople showed eagerness for protectingthe village tanks from roadside by heavyram water. These tanks are the mainsource of water lor cooking and washing.Tubewelis are too few in number andonce a tubewell goes out of order, repairbecomes a problem for the PanchayatSamity. Therefore, a latrine is now-a-days a common demand in these areas.Wnen they were told that a digestercan produce cooking fuel and sorne lightin the evening, they were all for it.A public sector Bank has assured thatproposals sponsored by our institutionwill be financed by them.

These instances show that nightsoilbased biogas plants have now caughtthe imagination of the people. Our conten-tion is that the experts in the AFPRO,CORT, CART and the Non-conventionalEnergy Departmènt of the Governmenthave now to find Out how gas generationfrom nightsoil based digesters can beaugmented in an easy process practicablefor the villagers. The programme for

33


1

energy and sanitation is intimately connec-ted with the movement for pollutmon-freeenvironmen t.

Let us also consider the issue ofcommunity gas plants. Proposals fromabout half-a-doze areas have been madeto us for nightsoml-based communityplants in village areas where a particularvocational group of families reside ina cluster.In one such area, there are30 potters families, their total popula-tion being about 220 (adults and minorstaken together). Even if all of them

use the community laWines, the optimum

aas generated from the plant can serveonly about 30 of them, that is one memberper family. So, we cannot proceed withany such project unless additional feedingis available. That can be arranged fromoutside but a cost will be mnvolved bothfor the material and management.Wepropose to utilise water hyacinth thatis abundant in the marshy land nearby. But It may not be a permanentsolution. What is needed is a break-throughbyR&D.

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34 11

HEALTH ASPECTS

~

Abstract

NIGHTSOIL BIOGAS PLANTS

HealthAspects

S.R Kshirsagar*

This peper gives the waming that nightsoil-based biogas plants which are beingpropagated as a health protection and energy conservcition measure many themselvesturn out to be the source of disseminationof diseasesunless utmost care is taken atall stages. 1f the nightsoil is to be manually collected from elsewherefor feeding intothe digester, the scavengerscome into direct contact with pathogens.It is possible forthe pathogensto survive in large nuinbers in the digester and pass over to the effluent.Anaerobic cligestion over merely 30-35 days’ detention time is unhelpful for pathogendestructmon. Even the drying of effluents removed after this insufficient detention timedoes not help in making the manure innocuous. There are great hazards if the cropsgrown with such manure are eaten raw. The use of sludge on croplands or in fish farmscontaminate food articles widely. In the same manner as labourers are sewage-fedfarmssuffer from higher incidence of infections of helminthic and intestinal pathogens, theworkers on sludge-fedfarms, too, are likely to be victims.

The conclu.sion that flow from the above observationsis that a longer retentiontime in the digester(HRT) is necessarysince the optimal conditions in terms of tempera-ture, pH and moisture content are unavailable in field conditions. Sundrying on opensandbedsfor 10-20 days has been recommended.Aerobic compostingof the ~slurry withagricultural wastes, which at its peak period raises the temperature to over 60°C,hasbeenrecommended.

INTRODUCTIONEd.

Biogas generation through anaerobicdecomposition of organic matter is ?rot-new to our country. It has however presen-tly assumed greater importance and signi-ficance in the context of energy crisisand the need for development of renewablesources of energy.

Healiti Aspects

Although a variety of organic mater-ials such as cattle dung, water hyacinth,agricultural wastes, can be used as afeedstock for production of biogas, theuse of human excreta is advantageousb~causeof (i) its availability at all humansettlements and at 10w/no cost and thedire need for its treatment. While advoca-ting and recommending large scale use

* Sdentlst, NEERI, Nebru Marg, Nagpur - 440020

of human excremental matter for biogasproduction, attention must be paid tothe health aspects involved in its procure-ment and use in biögas Ünits and alsoin the disposal/use of the effluent becauseof the possible presence of pathogenicorganisms. Table No.1 gives commontypes of pathogenic organisms presentin human excremental matter and urine.

Handling of raw human excreta,even as feedstock for production of biogas,obviously resuits in a great occupationalhazard. The system of collection andconveyance of human excreta by handin tins or baskets and then feeding intothe gas plants manually is thereforehmghly objec-tionable from the viewpomntof the health of scavengers involved

37


in the system. They come into directçontact with the pathogens potentiallypresent in the excreta to be fed to biogasunits. These ri~<s can be reduced butnot eliminated altogether by resortingto mechanization of the different opera-tions. This will, of course, add to thecost and intricacy; and villages and smallerLowns in developing countries like oursmay not be able to afford such facilities.It is for these reasons and also fromthe sociological pomnt of view that thelow—cost sanitation system of ‘on-sitetreatment and disposal’ of human excretausing covered leaching pits is being advo-cated by sanitary engineers and it isnow’ being widely adopted both in ruralareas and small towns where conventionalsewerage system is not feasible. In thismethod, although biogas is not availablel,hu-man health is protected.2

When nightsoil is collected andis to be fed to biogas units, it is firsthomogenized in a mixing tank fitted,with paddies and water added ‘if necessary’to make the moisture content in thefeedstock to about 90-95%. This helpsin feeding it into the biogas units easilyby gravity and mixing it well with thedecomposing mass already present inthe digester-reactor units.

The Process of Anaerobic Decomposition

In this process, 1 acultative aerobmcand anaerobic type of saprophytic micro-organisms first break the complex organicmaterial fed to the digesters into simplercompounds forming organic acids andcarbo n-dioxide. The digester containe sa variety of bacteria which act success-ively upon the feed material and in theend of the methanogenic group of bacteriastabilise and mineralise the matter produc-ing methane gas. In order to achievemore complete destruction - of organicmatter in the process and to obtain maxi-mum amount of gas containing higher

1) Manure, however ran be recovered from this method, Ed.

proportion of methane in the shortestpossible time, the conditions ~f decomposi-tion in the digesters must be maintainedat their optimum levels by controllingparameters such as temperature, pH,moisture contents, etc. at 35-37°C, 7-7.5,and 90-95% respectively. Under aichconditions, the organic matter (excreta)fed to the digesters can get practicallyfully stabilized within a period o~ 20-25days. The detention period, however,is increased from 20-25 days to 30-35days to compensate for field conditionswhich may not be ideal.

It will be, however, observed thatconditions in biogas units are much thesame as are prevalent in the biogas ofliving human beings. These conditionsare taken advantage of by the pathogenicorganisms discharged by sick personsor by the Vectors which are thus potentia-Ily present in the extreta fed to digesters.Obviously, these pathogens will survivein the digestion processes in large numbers.Some reduction would, of course, occurdue to the competition for food materialfrom other microbes and also di~e toattack from predators. Thus, the processof anaerobic decomposition, even if carriedout in a controlled manner is not helpfulin destroymng the pathogenic organismswithin the detention period of 30-35days normally deployed. 1-lence the effluentslurries coming out of nightsoil-fed bio-gas units will be equally hazardous tohandle, dispose of or utilise in the fieldsas manure.

Again, some of the pathogenicorganmsms (e.g. those of amoebic dysentery)which can form cysts or the eggs ofsome of the helminths (e.g. ascari~) willremain -totally unaffected while passingthrough the anaerobic decomposition,in the digesters and the effluent slurrieswould contain these. Some of these maysink into the portion of the digestedsludge in a dormant form and can become

1111111111111111111111

2) This method, however, is not entirely free from hazards Groundwater contaminacion kas been reported from manyareas Ed

38


activ~and’ infectious on entering humansystems.

I Disposal/Utilisation of Effluents & DigestedSludge:

I The digested sludge and the effluentsfrom nightsoil-fed biogas plants containgood amÔunt of fertilizing elements

I aich as nitrogen, phosphorus and potash(2-3, 1.2-2.6, and 1.5-1.8 percent respec-tively). Besides, the humus is a very

I good soil builder and fertilizer. Sinceboth of these contain large amount ofmomsturË these are first dried on open

1 sand beds overlymng open jointed pipedrains. The moisture gets reduced due

I to both percolation and evaporationto about 50-60% when the solid cakeproduced on the surf ace of beds can

I be removed and utilised as farm manure.This cake manure would, however, containmany of the pathogenic organisms stili

I surviving and hence the workers removingit from the drying beds, transportingit or using it on the farms should be

I given protecting garments (i.e. gumbootsand rubber hand gloves) and be a~<edto observe personal hygiene so as to1 reduce/eliminate the health hazardin these operations. The crops to be

lgrown over the farms fertilized withbiogas plant effluents dried or otherwiseshould also be such which are not to

I be eaten raw. This will prevent anydanger of contamination of the loodarticles and the spread of epidemics

I amongst the consumers of the farm pro-duce.Ri~ of Infection and Methods of Dis-infec tion of Elf luent Slurries/Sludges

Table No.2 indicates the likelihood

1 of infiltration of pathogens into

- through sludge disposal and associatedI pathways. From this table it will beobserved that the pathway of distribution/marketing which is commonly used for

l utilisation of sludges on land or 1 ishfarms is more dangerous due to thehandlers’ direct contact with these patho-

gens. These are also likely to contamihatethe food articles which are being produced.Sea disposal can also cause contaminationöf fish and other foods obtained fromit. Likely danger to human health dependsupon the number of organisms potentiallypresent in each of the pathway and theinfective dose. Table No.3 gives someindication on these aspects.

NEER! has observed in its studieson sewage farms that labourer.s workingon such farms are having higher incidenceof infections due to helminthic and intesti-nal pathogens. Although in our countryreports are not available about epidemicswhich can be attributed specificallyto the use of sewage or sludges for fertili-zing the farms, any lack of data in thisrespect cannot be constructed as a positiveindicator of safety of handling and usingthis material (i.e. sewage and nightsoilsludges) for fertilizing land and fishfarms.

Bhabha Atomic Research Centre,Bombay has, of course, carried out fieldexperiments to demonstrate sterilizationof sewage sludges using radioactive isoto-pos. But these techniques are costlyand require specialised knowledge andskills and additional safety precautionsin handling and administering the requireddoses of radioactive aibstances to sewagesludges for disinfection. These may nottherefore be technically and economicallyfeasible for application to common bio-digester sludges in our country.

The simple and economical methodwhich is practicable for use in our countrywould be sun drying on open beds of sandonly. Sufficient space shotdd be availablefor the purpose near biogas plant sitesbecause aich natural drying may takefrom -10-20 days depending upon theclimate in the geographical locationof the plant, and the season at the place.During rainy seasons, again, this opendrying method may not work at someplaces. Erection of simple roof sheds

39


1

over drying beds and prevention of entryot storm water run--off to the dryingbed sites would help in regions of highrainfall intensities. Of course, this wouldinvolve additional initial investmentsfor the construction of roof sheds overthe drying beds but there is no recurringexpenditure and the method is simpleto opera-te.

Mixing of compostable type ofrefu se/agr icul tural residue and compcstingof the digested nightsoil/effluent slurryaerobically can also help quicker drying.The compost 50 obtained will also bericher in quality because the other ingre-dients will imbibe nitrogen from nightsoil.This method will also have the advantageof simultaneous treatment and disposalof refuse and biogas plant effluent.The aerobic composting is expectedto build higher temperatures (over 60°C)in the decomposing biomass for over

Table - 1: Bacteria.

5-6 days so as to destroy the pathogenspotentially present in the effluent slurriesof biogas plants and the resulting compostis safer to handle and use on the farms.Sufficient space must, however, be availa-bIe at the biogas (nightsoil) plants sitesfor the purpose.

Conclu sion

In an attempt to tap all possiblesources of non-conventional energy systems,the use of human excreta as a feedstockof biogas plants is being advocated.1-lowever, this feedstock (i.e. nightsoil)may contain a variety of organisms patho-genic to human beings. The process ofanaerobic decomposition does not elimi-nate all pathogens. Hence proper careshould be taken in not only handlingand feeding the raw material to thebiogas plants and in handling the slurrybut also in its use as manure.

BACTE I~A Salmonella (1700 types) Typhoid, paratyphoid& salmonellosis

1Shigella (4 species)

Enteropathogen ic:

Escherichia coli

Yersinia enterocol iticaCompylobacter jejuni

Vibrro cholerae

Leptospira Spp.

Gast roenter i t is

-do--do-

Cholera

Weil’s disease

VI RJSES Enterov i ruses:

1

Poliovirus (3 types)

40

Paralysis, meningitis,1

1

1111111111

Viruses and Parasitesin Wastewater and S ludges

Group Pa-thogens Diseases(1) (2) (3) 1

Bacillary dysentry 1111

1

BIOGAS FROM HUMAN W~STE

(1) (2) (3)

feve r

Echovirus (32 types)

Coxsackie virus A(23 types)

Coxsakie virus B(6 types)

New Enteroviruses(5 types)acute haemorrhagic

Hepatitis Type A(Entrovirus 72)

Gastroenter i t is virus(Norwalk type agents)

Rotavirus (4 types)(Reoviridae family)

Reovirus (3 types)

Adenovirus (41 types)

Meningi t is, respi ratorydisease, rach, diarrhoea,lever

Horpasgina, respi ratorydisease, meningitis fever

Myof ard i t is, congen i talheart anomalies, rash,lever, meningitis, respira-tory disease, pleurodynia.

Meningitis, encephalitis,respiratory disease,acute haemorrhagicconjuuctivit ies, lever

Infect ious hepat it is

Epidemic vomitting anddiarrhoea, fever

Epidemic vomitting anddiarrhoea, chiefly ofchi Idren.

Not clearly established.

Associated with respira-tory disease in childrenbut aetiology not clearlyestabl ished

PROTOZOA Entamoeba his tolyti ca Anoebic dysentry, Ijverabscessl, colonicu 1 ce rat i on

Giardia lambiaBallantidium coli

Diarrhoea, malabsorpt ionMild diarrhoea, coloniculcerat ion.

HELMI NTHS

Ascar is 1 umbr i co i des

(Roundworm)

41

Ascar ias is

~---~ :-. -

Necator americanus Anaemia

(Hookworm)

Taenia saginate Taeniais

I~f: “Feasibility for performing a risk assessment on pathogens” by Larry Fradkin~Steven Lutkenholf, Jery Strate, elliot Lomnitz, Barney Cornaby, JournalWater Pollution Control Federation, December, 1985, page 1185.

TABLE - III~latedto Slud~eDisDosal and Associated Pathwavs (a)

Disposal Method P a t h w a y ,

Surf ace Ground Direct Food Aerosol/ SedimentsWater Water Contact particu-

lates

Landfill **b **** * *** NA C

Landspread ** *** ** ** *** NAC

Distributing/Marketing

** ** *** **** ** NA C

Ocean Disposal NAC ***

Estimates likelihood of exposure along pathways. 1Comparisons of sludge disposal options may notbe valid.

c A Not Applicable

1~f: “Feasibility for performing a risk assessi-nent onPathogens” by Larry Fradkin, et al. Journal of WaterPollution Control Federation, Dec. 1985, page 1186.

BIOGAS FROM HUMAN WASTE 1Ancyclos~tomaduodenale(Hoohwt,rm)

1

AnaemiaAnaemia 1

11

Likelihood of Exposure of Pathogens to Humans as

111111111

a

b ~ Most Likely 1*** Likely

** Possible 1* Unlikely 1

42

1111


TABLE - III Likelihood of Exposure fromP athogens toHumans as l~1atedto the Number of OrganismsPotentially Present in Each Pathway and theInfectious Dose a.b

Number oforganisms/infectiousdose

P A T 1-1 W A Y SSuFface Ground Direct Food Aerosol/ SedimentsWater Water Contact particulates

Bacteria *** *** *** *** *** *

Viruses **** **** **** **** ** ****

I-Ielminths -- -- **** ****c -- **

Protozoa * -- ** ** -- **

a Many organisms/low infectious dose

= Many organisms/high infectious dose

** Few organisms/low infectious dose

* Few organisms/high infectious dose

= -- Presence unlikely/high or low rnfectious dose

b = This table is a qualitative estimate of likelihood.A more quantitative version of this table would be producedfrom the output of a risk assessment. -These riskassessment results possible could make the tablehomogenous such that comparisons can be madealong rows and columns.

c The ~ score for land based disposal sites; for oceandisposal the score would be**.

1~f: “Feasibility for performing a risk assessment on pathogens”by Larry Fradkin, et. al., Journal of Water Pollution ControlFederation, Dec. 1985, page 1186.

43

Abstract

NIGHTSOIL BIOGAS PLA.NTSHealthaspectsanddesign

HK Cbanakaya*

The paper explainswhy the cattle-dung-basedbiogasplant’s designcannot straightawaybe adopted as suitable for nightsoil-fed plants, why in nightsoil based biogas plants itis so very difficult to maintain the optimum solid concentration,why the residence timein nightsoil digesterhas to be longer and post-digestionsecondarytreatmentis an indispen-sable requirement. It also explains the design objectivesof nightsoil-basedbiogas plantsand the advantageof multiple types of feedstocksas in China and pinpoints a few areasfor in-depth research.

In the author’s opinion, the Hydraulic retention time of 35-52 days is insufficierttfor a nightsoil digester. (In this it differs from the backgroundpaper presentedby NEERI).The author makes the point that since the occurrenceof ova is the least in the middieportion of the digester column, the outlet should begin from there. It is necessarytodesist from feeding nightsoil into the plant for two months preceding the periodicalcleansing of the sludge from the digester bottom, which means, alternative arrangementsfor toile try has to be provided for, from the very beginning.

The pa per suggests that there must be post-digestion terminal treatment by eitherbiological or chemical means or by storage of at least one year’s duration in a soukingpit. Although its emphasisis on biological means- compostingor algeal culture - it leavesopen the debateover chemicalmeans.

The utilisation of human excreta(nightsoil) for the production of biogashas been of ten mentioned but has rarelyreceived adequate attention or put topractice effectively. This is in spiteof the fact that the very first biogasplant in the country (1897 in Matunga)utilised human excreta as feed. Theréare both sociological and technologicalissues (especially health) which haveto be considered before widespread appli-cation is thought of. Nightsoil biogaswould provide: (t) a source of energy;(ii) a source of fertiliser; and (iii) a methodfor the improvement of rural health

and sanitation.

Simple calculations can be madeto show that when the human excretaof a small village (adult population about250) is put to biogas production, theresultant biogas can be used to produceapproximately 10 KWh of electricity.This can be used for street lighting/domes-tic lighting/lif ting drinking water/runninga light industry etc. This shows thata large potential exists for the use ofbiogas energy towards meeting a partof the rural energy needs with concommit-tant improvements in the village sanitatio?~

ASTRA, indian Institute of Science, Bangalore

44

111

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Introduction

1Ed. 1

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and health.

While cattle and other animal dungare relatively free of human pathogensand consequently safe, the human excretahave to be handled with considerable careto guard against the reinfection processof faeceslorne pathogens. In case thisaspect is neglected (in nightsoil biogasplants), the primary objective of improve-ment in village health and sanitationmay not be realised at all. Dung-basedbiogas production has some superioradvantages, which are absent in nightsoil-based biogas production. In the former,

1. the optima! solids concentrationis 9%.

2. the feed (dung) and water is mixedby hand to bring down the concentra-tion of dung to 9%.

3. the optimum residence time (HRT)is based on economic corisiderattonsof the rate of gas production.

4. The effluent slurry is left in theopen for drying and handled withoutfear of pathogen infection.

From the above considerations it

can be seen that the present designsof biogas plants (in India) cannot be straight-away extended for use of human excretaand need modification.

The optima! so!ids concentrationof 9% TS (total so!ids) cannot normallybe maintained in excreta dischargedfrom the conventional toi!ets (exceptin the case of dry toilets) owing to thefact that for every normal use, about30-80 of dry solids’ discharged along with3-10 of water used for flushingetc. (Table 1 gives the daily productionof nightsoil in some areas of India andfor developing countries). The solidsconcentration in the above mentionedcase is too low for economical runningof biogas plants. It is thus necessary

145

to change the toilet design in such away that a maximum of 1 litre of waterof discharged (along with solids) percall. The resultant solids concentrationthen would be around 3-5%.

Manual mixing of feed as followedfor cowdung based biogas plants cannotbe adopted for nightsoil p!ants (wherenightsoil is collected from dry toilets)for obvious reasons and hence the dischargefrom the toilets should preferably besent directly into biogas plants withsome degree of mechanical agitationto ensure rapid decomposition and facili-tate the settling of ova trapped withinthe solids. Contact with pathogenic mate-ria! (injection) can occur during severalof the folowing operations normally carriedout in connection with a biogas plant.

a. Collection, transportation and mixinginto slurry.

b. Formation of areosols during theabove operations and their inhalation.

c. hand!ing, transport and treatmentof eff!uent slurry.

d. contamination and infection throughtools and implements used, washingwater etc.

Hence it is necessary to avoid theseinfection routes as much as possible,with minimal cost and sophistication.

The optimum residence times of35-52 days used in the conventional dungbased biogas plants has been arrivedat by optimising cost versus gas yields.This however, will not hold good fordigesters designed to be run on nightsoilbecause during this retention period manypathogens present in nightsoil are stiliviable and it would be dangerous to dis-charge such effluents into the open,permitting human handling and exposureto vectors of disease transmission. Theviability of the normaUy occurring patho-

— -


1

genic specials in human excreta, theirnumbers, and responses to environmentalconditions is presented in Table 21,2. Itcanbe seen from the table that in mostparts of our country (w.r.t. temperatureinside the digester), a substantial badof pathogens is likely to be dischargedin the effluent. It is then necessary toso modify the design that the pathogensare retained (or inactivated) within thedigester while only the excess waterand spent solids are discharged for second-ary treatment.

The above concept has l~een testedand studied in detail in China . Researchfindings show that ova of the majorpathogenic species present in nightsoilplants have the following characteristics(Table 3). Under the existing conditionsof specific gravity (1.005-1.010) andviscosity of slurry within the digester,majority of the pathogenic ova settledown under their own weight. The bacterialand viral pathogens however, were foundto be distributed throughout the digesterliquid and their numbers decreased withincreased residence times. As a resultit was proposed that the outlet for theseplants should be from the middle portionof the digester (where the occurrenceof ova was the least). However, as thislayer stil! contains bacterial and viralpathogens, further treatment is recommen-ded.

It is a continuously run biogas plantwith out!et as recommended above, plentyof liquid effluents is released, whilemost of the solids and pathogenic ovaare retained within the digester. Overa period of time the solids will accumulateand Ii!! up the digester necessitatingthe manual removal of the sludge inside.There being many pathogenic speciesin it, it has been recommended thatthe plant be not fed for about two monthsprior to emptying (for manure removal).Concomitantly, the digester and theattached toilet will be out of use forthe above period and alternatives have

46

to be devised.

In order to overcome the abovetwo problems, i.e. handling of an effluentwith bacterial and viral pathogens andoccasional emptying of the digester ofsolids containing pathogens of helminthic,protozoal, bacterial and viral origin,some degree of treatment has to becarried out to render this effluent harmless.It should be noted here that the aboveconsiderations of discharging liquid effluent(and no solids) with bacterial and Viralpathogens (but no hookworms) will occuronly when the digester is operated inthe same way as in China i.e. all formsof wastes are charged into the biogassuch as straw, human excrefa, piggerywaste and lots of water. The digesterin effect operates well below the optimumconcentration and the residence timesthere are very large (about 6 monthsor so). Thus, some form of terminaltreatment namely, composting, use ofchemicals etc. will have to be employed.The above mode of operation createsthe need to find an alternative for theexcreta disposal during the two monthsof inoperation preceding the sludge removalfor manurial purposes.

Recommendations

From the above discussions it isobvious that the existing dung-basedbiogas plants need some modificationsbefore these are operated with nightsoilas feed. The design objectives for thissystem will be as follow~

1. Operation of the plant at optimalor near-optimal solids concentration;

2. Optimisation of the retention times(HRT/SRT) based on gas yield, healthand economic consideration~

3. elimination or near-elimination ofhuman handling of pathogenic material;

4. generation of a simple and low cost

111111111111111111111


pathogen elimination system and

its optimisation.

5. reductions in the risk of re-infection.

The above criteria provide choicebetween two modes of operation forthe biogas plant

1. Construction of biogas plants withtoilets attached and connected direc-tly to the biogas plants, with provisionfor (i) the accumulation of sludgeand pathogenic ova and (ii) releaseof only the liquid effluents whichmay be discharged into soak pits(with care taken to ensure preven-tion of ground and subsoil water)or for employing other chemicaland biological methods. (This optionnecessitates removal of solid sludgefrom the digester occasionally andoperation under dilute conditionswith an alternate arrangement fortwo months for stopping feed tothe digester.

2. Construction of biogas plants connec-ted directly to toilets of low waterdischarge without provision for anysettling of solid and pathogenic ova.The effluents bearing all types ofpathogenic material is led to bea terminal treatment system forrendering it free of pathogens. Twosimple options are available, Theyare:

(i) leading the effluent into soakpits which are used in sequenceso that when one is full theother is put into operationwith a minimum residencetime of 1 year in the pits

(ii) leading the effluent to a compostpit and raising the temperatureof the material by compostingother organic wastes and con-sequent killing of pathogens.

Both the above mentioned options

47

have some limitations. The use of soakpits cannot be recommended on soilsof high water table and in cases of proxi-mity to domestic wells. Composting requireadequate knowledge of the process withrespect to effluent storage, handlingand composting techniques. This lattertechnique is likely to be difficult in areasof high rainfall. When the above-mentionedterminal treatment procedures are unsuita-bie due to many locale-specific reasons,there are other options to choose from,such as algal ponds, lagoon irrigation,etc. which are less effective.

For biogas production from nightsoii,several aspects need in-depth research.Data in the following areas would goa long way towards making nightsoilbiogas plants more effective.

(i) Pattern of diffusion, disinteg-ration of solids, its physicalbehaviour during decompositione tc.

(ii) optimum residence times withrespect to gas yields, pathogenkilI or inactivation and costs.

(iii) methods for organic solids-liquid separation and concentra-tion of solids (exclusion ofexcess water from digesterfeed).

Another important issue to be consi-dered during the planning of such biogasplants is the method of use. It is obviousfrom table 1 that even under ideal condi-tions the highest per capita gas availa-bility is unlikely to exceed 40 litres/day(about 220 KCal (t)/day). Since the percapita gas requirement is higher, it,

then, becomes necessary to run, largersystems rather than operating family-scale nightsoil based plants. Of course,the shortfall can be met by supplementingthe feed by other organic inputs. 1-lowever,when rura! health and sanitation is alsocombined with the objective of energy,


1

the energy output as biogas can be utibisedto lift water for domes~tic use, providefor street lighting, or other facilitiesas incentive to used the system. Thisbiogas and sanitation providing systemhas to be structured and planned accordingto localespecific and sociological needs.

Acknowledg ments

The author is greatful to Prof. K.S.Jagadish and Shri P. Rajabapaiah, ASTRA,USc, Bangalore for providing many usefulsuggestions and criticisms.

References

1. Feachem, R.G. Bradley, DJ. Garlick,

-1. and Mara, D.D. (1980), Appr~priateTechnology for Water Supp!y andSanitation: Health aspects of Excretaand sludge management. A stateof Art Review IBRD/World Bank.

2. Sichuan Provincial 0ff ice of BiogasDevelopment (1979), Biogas Technologyand Utilisation, Chengdu Seminar(1979).

3. Zandstra, lIse (Ed) (1986), Reclamationof Nutrients, Water and Energy fromWaste: A Review of selected IDRC-Supported Research (IDRC-MR 124e).

Table - 1: Characteristics of Human Waste

Source Ref. 1.

48

11

111111

1111111

Aver-age

Range Aver-ageTS%

Urine TotalAverageBOD5(g)

AverageBOD5 of

Faecesd-’ (g)

Indian: ruralUrban

385170

255-520110-240

New Delhi 311 19-1505

Dev. Country(Aver age)

- Urban 250 - 20 1.2 30-55 21.7

- Rural 350 - 15 1.2 - 21.7

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Table -3: Characteristics of some Pathogens

Source Ref.2

50

111

1

1Sp.gr. Settling

rate50%(h)

(Im falI)95%

(h)

Digester contents 1.005to

1.01

- -

Hookworm ova 1.060 4.0 20.0

Ascaris ova 1.14 - 8.0

Schistosoma ova 1.200 - 2.0

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BIOGAS FROM NIGHTSOILThe healthaspectsanddesign

SMNavrekar 1Abstract

The paper gives the criteria for an appropriate excreta disposal system and showsthat none of the pre-existing systems of disposals - namely, single-pit/twin-pit latrines,aqua privies, septic tanks and sewage treatment - is appropriate. Recyclying apart, each[aus on the sanitation criteria. For a proper appraisal of the issuesinvolved in sanitation,the papergives the classificationsof viruses, bacteria, protozoa and helminths, the dtseasesthey cause and the distancesthey can travel. Thus, pit latrmes often contaminategroundwater. Where the actual retention time is not very long, the effluents from aqua priviesand septic tanks are nearly as hazardousas fresh nightsoil; and although the conventionalsewageplant is regardedas sophisticated,~heefftuents from it contain a high percentageof viable pathogenson account of its provision for a short retention time. Only the biogasplant has the potential of an ideal system.

Here, again, the systemthat requires carriage of night.soil from elsewhereis hazar-dous. Onsite floating dome gas plant without water jacket causesodour and fly and mos-quito nuisanceand spreaddiseasesthrough them. Only the fixeddomesystemwith a compos-ting complementis the ideat.

The Navrekar model has attempted to resolve the controversy over retention timeby providing for pre-treatmentof nrghtsoil before feeding it to the digester. A liquefyingtank below the w.c. basin induces physical disintegration of the nightsoil and separatesthe helminths from the rest. The nightsoil so prepared would not require more than 40days retention time in the digester.

The paper gives a chart of temperature time r6latlonshlp for the elimination ofpathogens,organism-typewise,to show how anaerobic “lestion, coupled with the anaerobicprocessof compostingcan remove all health hazardsand produt e the much neededmariureand energy. Ed. 1lntroduction

1f we peep into the history ofhuman civilisation, we find that in ancienttimes there existed no specialised systemof waste disposa!. Though the act ofexcretion is as old as Man himself, thesystems for disposing these wastes cameinto existence only a century or twoago. As the knowledge of various sciences-especially microbiology and health science s-developed, many problems in the traditiona!waste disposal systems were identifiedand to overcome these problems, thescientists and technocrafts the worldover devised several excreta disposalS Centrefor Biogas& SanitationStudies,Govardhan,PostGanganagar(B 0 ), Via Nasik, Maharashcra

111

11111

11

systems to suit ~‘arious conditions.

An Ideal Excreta Disposal System

It is very important to note thatno specific design of su’-h a systern canbe genera!ised for the whole world. How-ever, an excreta disposal system is saidto be appropriate when (1) it is technicallyfeasible; (ii) is affordable; (iii) can bemaintained by users and fulfils theirexpectations; (iv) does not require carriageof excreta or offsite deposition of thesame by scavengers; (v) provides for

11111111

52


recycling the excrements by way ofbeneficial products; (iv) creates no healthhazards. The prominent waste disposa!systems in practice today are, (1) pit!atrines (2) aqua privies and septic tanks(3) twin pit latrines (4) conventiona!sewage treatment etc.

1f we judge these systems in thelight of the abovementioned criteriawe find that each of these has somemerits and dernerits and none is ahieto fulfil all of the essential criteria.

The Heaith Aspect

Keeping aside other factors it

will be worthwhile to elaborate the healthaspect of these systems which is ofutmost importance.

Human excreta is a potent agentwhich carries and transmits various deadlydiseases. The main pathogenic organismfound in nightsoil are.

1. Viruse~ Many viruses which infectthe intestinal tract are found infaeces, the main groups beingPolioviru~ses, Echoviru se s, Rotaviru-ses, Hepatitis ‘A’ virus.

Echoviruses are responsible forsimple fevers, diarrhoea and respi-ratory illness.

Hepatitis ‘At Virus is the casualagent of infectious hepatitis. Itsometimes leads to jaundice butdoes not show external symptoms.This is common in children. Recentresearch has revealed that thisvirus is re!ated to infant diarrhoea.

2. Bacteria

Human faeces contain many otherbacteria which do not cause diseases.These bacteria are useful as faecal mdi-cator while studying pollution of a givenarea. Escherichia coil is the commonfaecal indicator.

3. Protozoa - Protozoa or amoebamainly infect large intestine and causedysentery, diarrhoea, ulcer etc.

4. l-Ielemjnths (worms) Helminthsare another group of organismswhich are transmitted throughfaeces. These are parasitic organisms.Helemiriths cannot multiply in

Bacteria Disease Whetherthrough

excretedurine too

1. Salmonella typhi Typhiod Yes

2. Salmonella Paratyphoid Yes3. Shigella spp Bacillary dysentery No4. Vibrio Cholerae Cholera No5. Pathogenic E coil Diarrhoea or Gastroenteritis No6. Campylobacter Diarrhoea - No

Poliviruses cause symptoms likemnfluenza or meningtis. In somecases paralytic symptoms are alsoobserved. Many people in developingcountries harbour these virusesbut very few of them (one in onethousand) get actual illness.

-~ -~ --- -- - - - -

53

human body as they require secondaryhost like pig, cattle or snail forcompleting their life cycle. Hencetheir population in human bodycan increase only by repeatedinfections. The helminths can bebroadly classified in two groups

BIOGAS FROM HUMAI’4 WASTE

1

viz. round worms and flat worms.The most dangerous kind of flat

Protozoa Diseases

1. Entamoebahystolytica

Ulcer of colon,dysentery, liver

amoebicabscess

2.~

Giardialamblia

Diarrhoea andsorption.

Mal-ab-

3. Balantidiumcoil

Mild dmarrhoea,ulcer

colonic

worm is the tapeworm which isalso difficult to eradicdte.

Helminths excreted through faecesand the diseases caused by them:

Pit latrines - In single-pit latrines andtwopit latrines, the main hazard is causedby groundwater contaminatmon.The conta-minated water from the pit seeps inthe surrounding soil and finally reachesthe water sources, if any nearby, through

which the pathogens can find their wayto human ingestion.

The movement of protozoan cystsand helminth ova can ~e expected tobe very limited because “of their size.

Studies show that bacteria cantravel a distance of up to 30 metresin sand and fine soils and upto severalhundred meters in gravel and fracturedrock. Viruses can normally travel upto60m, the maximum recorded distancebeing 1.6 km. In an area where thereare many pit latrines there will alwaysbe a ri~<of pathogenic viruses and bacteriareaching the groundwater.

During ramny season, these latrinesare often filled wmth water causing thespread of filth all over the ground. Astudy in Ethiopia shows that 800 outof 836 wells from an area were contami-

1111111

nated by pathogens from pit latrines.

Aqua privies and septic tanks - 1In aqua privies and septic tanks

the pathogen removal is only by settlmngof the sludge. Where the retention timesare very short, the effluent may be as

Diseases caused by Protozoa

1

111111

Cammon name Scmentific Name Disease

1. Round worm Ascaris 1 imbriccmdes Ascariasis

2. Pmn Enterobius ver micularis Enterobiasis

3. Gastordicoides hommnis Gastrodiscoidiasis

4. Hookworm Necator americanus Hookworm

5. Threadworm Strongylomde s stercoralis Strongyloidasis

6. Tapeworm Taenia saginate Teeniasis

7. Whipworm Trichuris trichiura Trichuriasis

Pathogen elimination in various systems

54

11


hazardous as the fresh riightsoil. It is very

common that septic tanks and aqua privies

are not desludged at regular intervals.This results in building up of a sludgelayer resulting in decreasing the retentiontime capacity.

Conventional Sewage Treatment -

A common sewage treatment processcombines pre-treatment, primary sedimen-tation, ac tivated sludge/trickling filter,

secondary sedimentation etc. Thoughthis is considered to be the most sophisti-cated and technically sound systems,

the effluent from this system containshigh percentage of viable pathogens.This also is mamnly because of the very

low retention times (5 to 12 hours).

From the above discussion it canbe conciuded that none of the existingwaste disposal systems is totally freefrom health hazards.

The Biog,as system

On this background it can be statedthat a biogas system, which exploitsthe principle of anaerobic digestion,is the only ideal~ option for disposingof (recycling) the human waste providedit (i) mnvolves onsite treatment in a fixed-dome digester and (ii) is coupled witha weli-managed composting unit.

Biogas digesters using nightsoil

Onsite Treatment

Many attempts have been madefor long to dispose of nightsoil in biogasdigesters especially in China and India.The various design needs for this canbe summarised in a flow chart as under.

It will be seen that all the typeslisted under onsite treatment can befound under offsite treatment.

Among the various designs onlythe onsite fixed dome with adjoining com-post unit is the ideal one as all otherscarry some health risk or cause somenuisance whmch are as fol1ow~

0ff site treatment - This mnvolvescollection of nightsoil and its carriageto the site of the plant. This causeshealth hazards to the workers and odournuisance at the time of feedmng. Similarlymosquito and fly nuisance cannot beavoided. At the same time this practicedegrades man.

Onsite floating dome. The domegets corroded very rapidly and requireshigh initial expenses. The one withoutwater jacket floats directly into nightsoilwhmch causes the spread of pathogensthrough files. Odour, fly and mosquitonuisance is a common feature. Introduc-tion of water jacket avoids these kmndsof nuisance althogh the cost remamrisnearly the same.

0ff site Treatment

Floating Dome Fixed dome Floating dome

55

Fixed dome

Witl’iWater jacket

Withoutwater jacket

With waterjacket

Withoutjacket

water

With adjoining Without compost With adjomning Without adjomningcompost unit unit compost unit compost unit

- - ,‘~- --~


1

Onsite fixed-dome without compos-ting: - - The effluent coijilng out of thistype may contain some viable pathogensand it may, therefore, be unfit for agri-cultural re-use.

Onsite fixed-dome with composting:This surprisingly eliminates all the harmfulpathogens from human nightsoil.

A modified efficient design

It is of ten recommended that theretention time of a biogas digester beincreased to vaoid viable helminth ovain the effluent. Increasing the retentiontime naturally increases the cost of theunit. Similarly, it is only the Ascarisova which survive longer. 1f there isproper separation of these ova prior tothe discharge of the effluent, there isnot much harm.

A nightsoil-based biogas digesterdeveloped by Late Shri M.V. Navrekarhas some special features which avoidthese hazards.

It is an onsite fixed-dome typedigester. The nightsoil is received bya liquefyling tank below the w.c. basins.The liquefication of nightsoil takes placein this tank. The liquefied nightsoil passesinto the inter mediate siphon tank whichaliows only the liquefied excreta to flowinto the inlet of the biogas plant. Theliquefying tank provides two benefits(i) Primary physical disintegration ofexcreta takes place in this tank whichseparates the helminth ova from therest of the effluent and retains thernthere. (ii) As the liquefaction phase iscompleted outside the digester, the reten-tion period of it can be shorter (40 daysin this case).

Organism In-unheated anaerobicdigestion

The effluent coming out is divertedto compost pit where the garbage iscollected. Composting has a special abilityto kilI pathogens which is described inthe succeedrng paragraphs.

A unit of this kind is working satis-factorily in a Municipal College Hospita!at Sangmaner (Maharashtra). The secondone is proposed at Chopada (Maharashtra).

Pathogens Elimination in a Biogas Digester

The Helminth~ The ova of helminthsare denser than the nightsoil slurry andduring the liquefaction phase, settledown at the bottom. Within 20 hrs, 95%ova get settled. The hookworm ova surviveonly for 9 days under anaerobic conditionsand those of schistosoms and ascariscan survive up to 10 days. In a biogasdigester the outlet pipe is generally locatedat some specific height from the bottomleaving a certain space for sedimentation.1f the ova get separated perfectly, theycan be retained in this space for morethan 100 days causing their inactivation.

2. The Bacteria: The common patho-genic bacteria which spread throu~hfaeces are: (i) Salmonella sp (typhoidfever); (ii) Shigella sp (dysentry); (iii)

Vibrio Cholerae (cholera); (iv) Mycobac-ET1 w494 295 m543 295 lSBTterium tuberculosis (T.B.). These bacteriacannot airvive when subjected to anaero-bic condition at 22°-37° for about 20days (range 6 to 20 days).

Composting

Biogas digester, coupled with compos- 1tmng unit, eliminates all the chancesof pathogen survival. The temperaturesin a properly managed compost can reach

In Composirg 11

1. Enteric

May survive for over Killed rapidly at 60°C.

three months

56

111

111

11111111111


-Organism In-unheated anaerobic In compostingdigestion

2. SalmoneFlae May survive for severalweeks

Killed in 20 hrs at 60°C -

3. Shigellae Unlikely to survivefor more than a fewdays

Killed in hr~at 55°c or in 10 daysat 40°C

4. E-Coil May survive for severalweeks

Rapidly killed above 60°C

5. Cholera May survive for oneor two weeks

Killed rapidly 55°C

6. Lepotospire Survive for not morethan two days

Killed in 10 mts. at 50°C

7. Entamoabacysts May survive for threeweeks

Killed in 5 mts at 50°C and 1 dayat 40°C.

8. Hookworm ova Ova will survive Killed in 5 mts at 50°C and in 1hour at 45°C.

9. Ascaris ova Ova will survive formany months

Killed in 2 hrs. at 55°C in 20 hrs.at 50°Cand 200 hrs 4,5°C

10.Schistosome Ova may survivefor many months

Killed in 1 hr 50°C

11. Taenia Ova Ova will survive fora few months.

Killed in 10 mts. at 58°C and inover 4 hrs at 45°C.

as high as 50° - 60°C. This kills the patho-genic flora within a short period. Thefollowing table shows the ability of anaero-bic digestion and composting to kill patho-gens.

Epilogue

From the above discussion it canbe conciuded that Biogas technique canvery well be adopted to treat nightsoil.It implies no health hazards to the public.The system is so efficient in convertingthe wastes into energy and manure thatevery effort should be made to secure

the benefits from this system everywherein the country.

References

1. Feachem et al (1980) ‘Health aspectsof excreta and sullage Management- A state of the art review’. WorldBank Washington, USA.

2. Gunnerson C.G. & Stuckey D.C.(1986) ‘Anerobic Digestion Principlesand Practices for biogas systems’.World Bank UNDP, Washington,USA.

57

-~ ~

3. IDRC (International DevelopmentResearch Centre) (1981) ‘Sanitationin Developing Countries’, Proceedingsof a Workshop on training heldin Labatso, Botswana, 14-20 August,1980 - Canada.

4. Navrekar, S.M. (1985): ‘Conversionof conservancy Iatrines into biogaslatrines at the municipal cottage

hospita! Sangmaner’ Notes on Sani-tation 1 (1) Oct. 1985, 14-15.

5. Ibid (1986): ‘Facts about Nightsoil’ 1Notes on Sanitatmon 1(2) May1986: 2-9,

6. Shuval et al. (1981): Nightsoilcompostin~: World Bank, Washington,USA


1

1

1111

~11111111111

58 1

Abstract

NIGHTSOIL BASED BIOGAS PLALNTSA usefuldevicefor rural healthanddevelopment

S V. Mapu~kar

Both open defecation and cartage/manualcarriage of nighsoil are health hazards.Only pit latrines for cornposting, aqua privy and nightsoil based biogas plants are safe.Bogas plants are costlier than aqua privies but the returne these plants pay in termsof public health, bio-energy and manure are incomparably higher. Anaerobic digestionwith an assuredretention period of 40-45 daysat 32°C-35°Celiminate the viral, bacterialand protozoal pathogen. The retention period will also see the worrisorne helminth ovasettie at the bottom of the digester and get enmeshedin the heavy sludge. However,if the retention period is sought to be reduced to 25-30 days, the effluent will need tobe retained in the adjacentpit for a few months to rid it of its pathogens.

Observance of the guidelines for running biogas plants will irnprove rural health.

Jntroduction

Ed.

Nightsoil based biogas plants havebeen functioning efficiently and satisfac-torily since Late Appasaheb Patwardhanpioneered these plants more than thirtyyears ago. However apprehensions aboutthese plants persist even now. A fearpersists that aich plants and the useof slurry from these plants are likelyto pose health hazards. Is this fear realor misconceived? A closer look is veryessential.

Common Pathogens in Faeces

the fear is not without reason.Human excreta is a principal vehiclefor the transmission and spread of anumber of communicable diseases. Thedisease-causing organism from humanwastes spread to a new host via a numberof routes. Therefore, proper treatmentof human waste is very important sothat these organisms do not get an accessto new host. We must se� whether aparticular system for the treatmentof human waste is able to intercept

the pathogen in such a way that thespread of these diseases is prevented.

The common disease producingorganisms are from four groups (i) Viruses(ii) bacteria; (iii) Protozoa; (iv) Parasites.These are enumerated in Table No.1.

The comparative study of the beha-viour of these organisms in various systemsof treatment of human waste will giveus definite indication about the suitabilityof the particular treatment system. Thetreatment of human waste in biogasplant will have to be viewed in the samelight. -

Options for Night~il Di~osa1

As a preliminary, it would be desirableto review the present day common optionsavailable for nightsoil disposal in ruralareas. Broadly, two modes need to be~~~onsidered:

a) ‘Dry System’ disposal by various

5c)

~!OGASFROM HUMAN WASTE

1

b) ‘Wet System’ disposal by varioustypes of latrines inciuding biogasplant s.

There is, of course, the open defeca-tion practice which precludes any disposal.In this country, this has become therule rather than the exception. 70% ofthe population (nearly 48 crore people)of this country resort to open defecationeveryday anywhere, any time withoutany hesitation. This ghastly situationwill have to be consistantly kept in viewwhile discussing near-ideal methodologies.Open defecation means ~n abundantdose of pathogens to the environmentand people.

1. ‘Dry System’ disposal comprisestwo important groups

i) 0ff site disposal. Manual carriageor cartage system which is prevalentin most of the small and moderatelybig townships. Nearly 10% populationis covered by this system. Thissystem is worse than open defecationbecause this system keeps on sprink-ET1 w63 325 m272 325 lSBTl~g pathogens in areas which aredensely populated.

ii) Pit latrines of various de~igns aregradually getting popular in ruraland urban fringe areas. Nearly 10%of the population is covered bythis system. In this system nightsoilis digested ‘on site’ in the coveredpits, so that pathogens do not getaccess very easily to the ~rroundings.ThFs appears to be one of the promi-sing systems for developing countries.

2. ‘Wet System’ disposal systemscomprise two important groups.

i) ‘Onsite’ systems where water andanaerobes are essential part ofthe process. These systems are,mainly, septic tanks, aqua privy

latrines and our present topic ofdiscussion, the bïogas plants. Theseare essentially anaerobic digestionsystems with varying retentionperiods. Nearly 10% of the populationis covered by this system. In thissystem, pathogens do not find accessto the airroundings without beingappreciably impacted. This systemis another promising system forthe developing countries.

ii) ‘0ff site’ disposal: water carriagesystem of sewage disposal is availablein bigger townships and cities. Thelucky 10% in the country are coveredby this luxury. This system is supposedto deal with pathogens adequatelyif the treatment plants functionproperly. Unfortunately, in manycases, due to improper managementor “paucity of funds”, raw sewageis let out in the rivers, thus causinghealth hazard for downstream settle-ment.

Suffice it to say that ‘dry onsite’and ‘wet onsite’ systems are going tobe of some significance to this countryin riear future. 1Faecal Pathogen Survivaf after Treatmentof Faeces on Different Systems 1

The possibility of spread of pathogensthrough the above mentioned modes oftreatment of human waste has to bereviewed and compared. Also, the survivalof pathogens in the end products in eachsystem have to be seen.

‘Open defecatiori’ has to be doneaway with. We are all aware that itis our biggest health hazard. The ‘drysystem’ of offsite disposal by manualcarriage or cartage, too, need not beconsidered because the spread of pathogensthrough that system is self-evident. Thus,Out of the dry systems, only ‘onsite’pit and composting latrines need to beconsidered. Under the ‘wét system’,

means1111111111

11111111

60


the option ‘offsite’ water carriage sewage

system is very capital-intensive, water

use-intensive and requmres elaborate mana-

gement. 1f not managed properly, - itcreate health hazard through water orsomt pollutmon. Thus, from this group,

only ‘on site wet’ system essentiallyco mpr i sing anaerobic digestion proce ssdeserves consideration.

Thus, our studies will have to remainrestricted to only two systems, namely:

1. ‘dry onsite’ system of pit and compostIatrmne; and

2. ‘Wet onsite’ system mncorporatinganaerobmc digestion.

The presence or absence of pathogens

in the end products in each system issafe from the health point of view. Itwill help in deciding the operatmonal

requirementsfor making it a safe system.

It has been observed that the survivaltime for the pathogens depends on twoimportant factors.

i) Temperature; and

ii) Retention time. The higher thetemperature, the lower the reten-tion time required.

I In the case of pit latrmnes, wherethe pits are usually opened after morethan three months, all or most of the

l viral, bacterial and protozonal infectionsare eliminated. E-telminth ova, however,persist for several months (See TableNo. 2).

As far as ‘wet on-site’ systems

I are concerned, Immited data about aquaprivy and biogas systems are available.However, we can reach some conclusions

I by putting together the available dataabout aqua privy and anaerobic digestion

Jin biogas plant simulating conditmonsin Jaboratory. Table No.2 shows theseresults. From this it will be dear that

- -:- ~

61

in anaerobic digestion at 32°C - 35°C,viral, bactermal and protozoal pathogensare eliminated withmn a period of 44days. Thus, if a retentmon period of 40to 45 days is allowed for digestion, thesepathogens will not be present in theeffluent slurry from the biogas plant.Further, in bmogas plant it has been notedthat the helmmnthic ova settle down atthe bottom of the plant and remain en-meshed in settled sludge. Hence, theef-fluent is nearly free from ova. Thus,the effluent is likely to be free frommost infections. 1f it is proposed to reducethe retention period to about 25 to 30days, the effluent can be made pathogenfree by allowing it to settle and remainexposed to sunlight, in the manure pitsadjacent to outlet from biogas plant,for a few months. Table No.2 showsthe approximate time required for elimi-nating pathogens from the sludge.

Place of Biogas Plant in Safe Treatmentof Human Waste

The review about the availableoptions for nightsoil and survival charac-teristics of pathogens indicate that on-sitedisposal of nightsoil in biogas plant issafest from health point of view. Safetyis ensured by the following factors

m) retention and the digestion of night-soil for a specif mc period in anaerobiccond i tion s

ii) retention of digested slurry (effluent)in manure pits

mii) digested slurry does not attractflies and other insects

iv) raw nightsoil is not allowed anyexposure to airround~ngs, for whichchoice of suitable design is essential;

v) manual handling of nightsoml isab se nt.

Costwise, construction of biogas

~ ~ ~


1

plant will be costimer than pit privmesand only margmnally co’stlmer than aquaprivy. However, unlike pit privy or aquaprivy, in biogas plant there is an advanta-geous re-use of nightsoil in the sensethat biogas plant gives returns in termsof biogas for energy and fertilizer foragricultural use. TF~us, although biogasplant is initially capmtal-mntensive, inthe long run, it gmves much more returnson the additional mnvestment, makingmt a benefmcial propositmon.

Conclu sion

It is therefore feit that nightsoilbased bmogas plants is yet to get theprmde of place it deserves. Some peopietend to deprecate it overzealously onthe grounds of possible danger of health.

The truth is just the opposite. It is thedirect application of nightsoml in theform and the open defecatmon and manualcollection and dumping of nmghtsoml incompost pmts that leads to dangerousdissemination of pathogens through varmousmodes of transfer. The mode of channe-Hing excreta in the ‘onsite’ disposalbiogas plants and from there on to thefield is a direct health gamn. Nmghtsoilbased bmogas plants will actually helpin improving rura! health. In addition,these plants will play an important roleas a source of bmo-energ~ and a safe,desmrable organmc manure of very highqualmty. Thesc direct economic benefmtsadded to the benefits to public healtbmay provide a stronger motivatmon forbetter sanmtation.

Organ ism

1 Enteroviruses

Table -1 : Important Pathogens Excreted in Faeces

Di sea se

111

Polio Viruses

Echoviruse s

Coxsackie viruses

Reov iru se s

Poliomyelmtis

1

Advenovmruse s

Hepatitis virus

Rotaviruses

II Bacteria

Salmonella typhim

Salomonella poaratyph~i

Shigella

Vmbrio cholerae

1Infective Hepatitis 1Gas trc en ter i ti s

1Typhoid fever

Paratyphomd fever -

Bacillary Dysentery

Cholera

Pathogenic E. Coli

Campylobac ter

62

Dmarrhoea

Diarrhoea

11

11111111

1


:1 -

III Pro tozoa

Entamoeba Histolytica

Giardia lamblia

Balantidium Coli

IV Helminths

Ascaris lumbricoides

Enterobius vermicularis

Ankylostoma duo-denale

Strongyloides stercoralis

Taenia saginata

Taenia solium

Trichuris trichiura

Bac Ier ja

Salmonella typhii

Salmonella paratyphii

Shigella

Vibrio Cholerae

Pathogenic E. Coli

Protozoa

Entamoeba histolytica

Giardi~lamblia

Balantidium coli

63

Amoebic Dysentery

Diarrhoea

Diarrhoea

A scariasia

Enterobiasis

Hookworm infestation

Threadworm

Tape worm

Tape wor m

Whipwor m

Organism Disease

Table - 2 :Survival Time of Pathogensin ~me Excreta Disposal Systems

Organism Pit & Compos-ting latrineswith 3 monthsretention

Anaerobicdigestionat 32°C-35°C

Survivaltime insludge

Enteroviruses Less than 28 days 3 months3 months -

-do-- 4-5 weeks 1 month

-do- 4-6 weeks 1 month

-do- 9-10 days 1 month

-do- 7-14 days 5 days

-do- 4-8 days 5 days

-do- 3 weeks 2 weeks

-do- -do- -do-

-do- -do- -do-

- -~-~ - ~ -~~--


1111

Organism Pit & Compos-ting latrineswith 3 monthsretention

Anaerobicdigestionat 32°C-35°C

Survivaltime insludge

Hel minifis

Ascaris Lumbricoides Ova survive Ova survive Ova survive

Enterobmousver micularis

-do- -do- -do-

Ankylostoma dudenale -do- -do- -do-

Strongyloidessterooralis

-do- -do- -do-

Taenia saginata -do- -do- -do-

Tadnia solium -do- -do- -do-

Trichurms trmchiura -do- -do- -do-

64

HEALTH ASPECTS OFANAEROBIC DIGESTION

Yashwant Singh

The human excreta contains disease-causing organisms of hepatitis (infectious),gast roenteritis, respiratory illness, poliomeylitis (viral diseases); typhoid fever, salmo-nelloses bacillary dysentery, cholera, tuberculosis (bacterial); amaebiasis (protozoans);and various helminthicdiseases. -

Anaerobic digestion of human excreta provides biogas and effluent slurry asfertiliser. The questionsraised very pertinentlyare: whether (i) the anaerobicdigestionsignificantly affects the pathogensand (ii) the effluent is within the mark of safe disposal.

The reported data on the survival of the pathogenic micro-organisms in the anae-robic digestion process have a wider range of values. Temperature plays a very importantrole in the minimisation of these rrlicro-orqanisms. P~liovirus at temperature 35°Cis reduced by 98.5% within two dclys. Within the temparature range of 22-37°C Salmo-nella typhosa is reduced by 99% in 6 days while Salmonella spp. (causing salmonellosis)by 82-86% in 6-20 day’s. Mycobacterium tuberculosis at temparature 30°C is kifled100% but the detention days was not reported. All encysted helminths are destroyedexcept ascaris cysts which are able to survive even after 14 days at temparature 35°C.Other studies revealed efficacy of thermophilic digestion (48-60°CJ which destroyedascaris cysts corn pletely. When mesophilic operation (below 40°C) is followed by storageof digested slurry and its drying- for about six months, even the ascaris are destroyed.

In one study - Entamoelx~ histolytica cysts were reported - not to survive anaerobicdi~estion. In other studies, species similar ro E.histolytica, but having different culturalrequirernents was found in sludge digestion and Imhoff tanks.

Pathogens get killed inside the digester because of the change in environmentalconditions and lack of nutrients, apart from temparature. This die-off continues whenthe digested slurry is stored and even when it has bee applied to the soil. During storage,the reamining undigested part of human excreta getsdecomposedand stabilised providingunfavourable conditions for growth of most of the micro -organisms. The survi vingpathogens, if any, would get killed when the dried sludge or composted material isapplied to the soil; the soil microbes and soil environmental conditions can take careof theseseverlyweakenedpathogens.

Even Uien, in the first seasonof application of this dried sludge, the cultivationof carrot, radish and like plants is not advisablebecausea few viable pathogens(cystsand eggs) may adhere to the surface of the edible part of the plant and infect theconsumers. The cultivation of cereals is suggestedin the first year. Afterwards anycrop maybe grown.

Use of chemical disinfectantsand moist heat treatment (i.e. stearn sterlization),Wo, can effectivelydestroy the pathogenson human excreta but their costs are prohi-bitive. Ivloreover, these are merely destructive of pathogeris without any potentialfor converting wastesinto assets.

65

- ~--~ ---~---~--~ ;~_-~ ~ ~— ~ ~


Anaerobic micro-organisms gasify 80-90 per cent of the carbon substrate andyield only 10-20% of microbial celi sludge. The solid matter to be disposed of is, there- 1fore, much reduced. There is not much risk of odour or insect breeding when the digestedsludge is spread in the open.

To sam up, anaerobic digestion of human excreta removes most pathogens andthis controls the pollution of soil, water and air. The effluent’s subsequent storageand use in soild system as manure, with certain precautions, will reduce health hazardsvery considerably. This is better than any other treatment.

Resource 1“met hane Generation from Human, Animal and Agricultural Wastes”. National

Academy of Sciences, USA, Washington D.C. 1977.

RajammalPDevdas* 1Laksbm:SantaRajagopal~-~- GhanambaiJagadeesan* * *

Abstract 1India’s basic problem of safe water supply and sanitary disposal of human excreta

are interrelated. Improper disposal of nightsoil brings soil pollution, water pollution,and diseasessuch as typhoid, para-typhoid, cholera, hookworm. About 45 million peoplein India are infested with hookworms. The incidence of other excreta-related diseasestoo, is very high. In obeisanceto nature’s principle of recyclying and for increasing thesocial acceptanceof nightsoil-basedbiogas, the women’s college at Coimbatore starteda biogas plant based on the waste products of 66 girls plus 10 kg of cowdung per day.The biogas proved better than LPG as a cookingfuel.

Cleanliness next to godlmnes is aprime requirement closely related togood health. On the solid foundatmonof heallh, man’s happmness rests. Healthdepends on sanitation which is a wayof life. It is the quality of livmng thatis expressed in the clean home, cleanfarm, the clean business, the clean neigh-bourhood and the clean community. Aclean home and community are possiblewhen pollutmcn is arrested effectivelyby treating, utilizing or disposing ofwaste in and around the house.

Healili and I~nvironment

The health status - whether of

an indmvmdual or of a community or anatmon - is determined by the mnterplayof two ecological universes m.e. the internalenvironment of man himself and theex ternal environmeni which surroundshim.

Today the environment is beingpolluted as never before by the accurnula-tion of solid wastes. Everywhere theamounts of solid waste generated byevery person each day are increasmngas a result of social, econommc and techno-logmcal changes. At the same time, thethe land avaiiabie for deposmting wasteis getting correspondmngly reduced due

1

HEALTH AND HYGIENE ISSUES 1

111111111

• Director,Shrl AvinashlingamHomeScienceCollegefor Women,Coimbatore* * PrincipaiShri AvinashiirigamHomeSciencecollege for Women,Coimbatore• • • Asstt Prof of HomeManagement,ShnAvinashlingamHomeSciencecollegefor Women,Coimbatore

66

111


to increasing urbanization, and consequentincrease in area occupied by buildingsand industries.

Public health largely depends onthe efficiency with which all refuse iscollected and removed in the contextof the shrinking space. A number ofdi sposal methods including co mposting,and conversion of waste into energyand manures become-s extremely importantas measures for recycling. India’s basicproblems of safe water supply and sanitarydisposal of human excreta are ‘nterrelated.

Public HeaIth Importance

Human excreta consist of the solidand semi-solid residue (faeces) from thelarge intestine and the liquid (urine)excreted by the kidneys. Human excretais a source of infection. The health hazardsof improper excreta disposal are (i) soilpollution; (ii) water pollution; (iii) contami-nation of food~ (iv) propagation of flies.

The resuiting diseases are typhoid

and para-typhoid lever, dysentery,

hoea, cholera, hookworm disease, ascaria-

sis, viral hepatitis and similar othermntestinai infections and parasitic infesta-tions. These diseases are not only a burden

on the community in terms of mortalityand a low expectation of life but a basicdeterrent to social and economic progress.

Statistics indicate that the intestinalgroup of diseases claim about 5 million

lives every year while another 50 millionpeople suffer from these infections.Surveys carried out in the community

development block areas sl~ows thatthe enteric group of fevers is vei~ycommon

in rural areas - the annual incidencev~rying from 102 to 2119 per 100000of population. Hookworm disease is also

known to be highly prevalent~ about45 million people are estimated to be

infested with hookworm. A number ofdiseases and epidemics like cholera,typhoid, dysentery and hookworm thatoccur in rural areas very frequently arecaused by the absence of sanitary methodof disposal of excreta. The disease agentsin the excreta spread through the channelswater, fingers, flies, soil and food.

Recycling of Night~il

Variou~ researches have led to thediscovery of biogas scheme based oncowdung, nightsoil and finely choppedlef t-over fodder and vegetables. Thegobar gas plant system has gained accep-tability among the public. The nightsoilgas plant has not yet gained momentumamong the home-makers and the population.

The College Biogas Plant

A 2 cu.m. nightsoil biogas plant(R s. 3000/-) was, therefore, construc tedat Sri Avinashlingam House Science Collegefor Women, Coimbatore. The nightsoilfor the plant was collected from sixlatrines used by 66 adolescent girls.For enh~ncing the fermentation of night-soil, 10 l<g of cowdung was added daily.The nitrogen content of the slurry wasestimated to be 1.7 per cent. Laboratoryexperiments proved that nightsoil gasis a substitute for petroleum gas. Itwas being used in lighting a gas lampalso.

Conciusion

Nightsoil may be effectively utilizedfor gas product~on. The clearance ofnightsoil in this manner may lead tothe health and happiness of the popula-tion ensuring the nation’s prosperity.There is a wide scope for transferringthe national waste to a national wealth.

67

Abstract


PublichealthandSocialAspectsDR Gupta

Countering the view expressedby some that the slurry from biogas plants mightlead to wider dissemination of pathogens,the paper claims that the die-off rate (in thedigester) of the disease-producingorganisms of public health significance ranges from83 to 100 per cent at 22-37°” if the digestion time is not significantly lower than 14days”. The die-off process continues during the storage and drying up of the slurry andafter application to the soil due to pathogens’nutrient starvation and hostile environment.

The paper further analysesthe psychologicalfactors that inhibit the spread of lat rinebased biogas plant. Breaking the barrier of age-old taboo, therefore, becamesmore impor-tant.

Introduction

- Ed.

Nightsoil is the accumulation ofhuman faeces and urine collection withoutdilution by large volumes of water. Night-soil is generaily carted or carried byscavengers on the ~ou1ders or the head.Some public health aspects of the produc-tion of biogas by anaerobic digestionof nightsoil with or without animal wasteare discussed first.

Public Heallh A~ects

Potential hazards inherent in thebiogas plants ‘using nightsoil partiallyor wholly, are the reailts of two practice~

a) The handling involved in the useof nightsoil as a part of the wastefed to the digesters

b) The use in crop production, of thedigested slurry produced in biogasplants (digester).

As regards handling,

i) Although the use of dung from disea-sed animals may entail some danger,it would be less than that involvedin the use of human faeces if itwas to be handled physically, and

ii) In India, most of the night-soilbased biogas plants are directlylinked with Latrines as such nophysical handling of nightsoil isinvolved in charging them.

Anaerobic Digestion 1The following table gives the die-off

rate of enteric micro-organisms of publichealth significance in terms of temperatureand residence time during anaerobicdigestion. The table dernonstrates theimportance of the anaerobic digestionprocess in the treatment of human wastes:wilh few exceptions, pathogenic entericmic-ro-organisms are effec tively killedoff if the digestion time is not significantlysliorter than 14 days at a temperature

Organisms Category Tempera- Residence Die-offture °C Time (Days) (%)

11

111

111111111

111

Poliovirus Viral 35.2 2 98.5

68 11


Salmonella ssp

Sal monellatyphosa

Bacterial

-do-

22-37

22-376

6.20

6

82.96

99

Mycobac teriu mtuberculosisAscaris

Parasite cysts

-do-

Helmin thic

-do-

.30

29 15

30 10

1

not significantly lower than 30°C.

In view of the above, anaerobicdigestion produces sufficiently high rateof die-off of pathogenic micro-organisms.Anaerobic digestion of organic materialfor biogas production, therefore, providesa public health benefit beyond that ofany other ireatment imkely to be usedin rural areas.

The risk of indiscriminate dissemina-non of eggs of parasitic organisms isalso minimized when nightsoil is processedin biogas plants. »

It appears that thei-e is no otherpractical methoci of te sting human excreta-whether for disposa! or for return ofnutrients to the land as fertilizer- thatwill reduce the burden of pathogenicorganisms as much as anaerobic digestion.

Use of Digested Slurry as Manure

i) The public health hazards associatedwith the use as manure of the planteffluebt slurry/sludge will depend upon:

a) The incidence of viable pathogenicorganisms found in the nightsoil;

The survival rate of these organismsin the digester’s effluent slurry.

c) Storage time of the sludge prior

to the application of the land.

Storage and drying after the digestion

period will further minimize and perhapseliminate the risk of parasite eggs spread-Ing in the rural environment.

Effective destruction of pathogenicenteric micro-organisms does not precludethe survival of at least some micro-orga-nisms of public health significance despitedestruction of as much as 90% of suchorganisms.

Once the digested slurry has beenremoved from the night soil based plant,.micro-organisms that have survived theprocess continue to die-off because ofthe Jack of nutrients and the hostileenvironment. This die-off process continuesboth during storage, drying of, and afterthe dried slurry has been applied to thesoil.

The possibility of contaminatingcrops with these surviving pathogenscould be eliminated hy pasteurizationwhich is the practice in some Europeancountries. This process is so costly, however,that its economic feasibility is marginalfor India. -

Inhabitants of most villages areprobably already exposed to the entericdiseases endemic to their area. The intro-duction of biogas Plants for night soilalone or with animal wastes, therefore,should not create any new or additionalhealth hazards. On tht~ contrary, it shouldreduce the present health hazards ofdisposing of night soil significantly.

69

Not reported 100

90

100

~»»»‘-»~- ~-»~~J ~»~» ~-~-


1

CONCLUSION

In the final analysis, it will be desirablethat the Government institute schemeswhich encourage installation of latrinelinked or nightsoil based biogas plants.This can also very well serve as a catalystto the construction of nightsoil plantsas the economic value of the biogasand manure obtained from it becomesdear. In this way, the public he~lthhazardof the common practice in rural areasof defecating in the fields would be mini-mized. Furthermore, connecting the latrinesdirectI~y to household or community biogasplaièts would eliminate any health hazardconnected with direct handling of humanwaste.

Social Afpects

Various points discussed under/Public/Heal th/A spec ts represent the positiveconsidera tions for popularisa tion of par tiallyor wholly nightsoil based biogas piants.

The barrier to the acceptance insuch plants comes from social aspects.Following observations are made basedupon our involvement in the biogas progra-mme, which inciudes latrine whereverwe instal biogas plants.

We have succeeded in providinglatrine connections to 20% of the plants(40 plants). About 10% plant users haveworking latrines but there may still be2 to 3% plants owners who may notbe using these latrines. This highlightsa social resistance to the use of biogasproduced from nightsoil linked biogasplants.

In Punjab, from a case study of3 community biogas plants, which havebeen provided with a set of latrinesfor male and female members separately,it is found that latrines are not beingused.

The following social barriers areidentifzed to the acceptance of nightsoil

based linked biogas plants

i) Users or agriculture labourers hesi-tate to lift the digested slurry foruse aS manure.

ii) Due to ageold custom, nightsoilis expected to be handled/liftedby scavengers only and no bodyelse will touch it.

iii) Isolated users feel sliy of usinggas coming out of the nightsoillinked plant due to social stigmaattached to it. Though they them-selves may be quite liberal andconvinced about its fertiliser valueand +rarmless effect as cookingfuel, they may simply not do sofor fear of what other people willsay~ In a fev~ cases of househoidsh av ing nigh tsoil-linked dige ster,it was discovered that the guestsvisiting the family have been foundobjecting to eating food cookedwith gas coming out of such digesters.

CONCLUSION

It is feit that anaerobic digestionprocess provide immense fuel and fertilizervalue and better sanitary alternativefor disposal of human waste. A strongawareness needs to be created aboutthe values of disposing of nightsoil throughbiogas plants with or without animalwaste. Desirable change in the attitudeof the potential biogas users or otherwisewill come only through mass awarenessand education of the immense valueof processing of human waste throughanaerobic digestion. Age-old taboo ofnot handling nightsoil will have to bebroken.

Source~

(i) Methane Generation from Human,Animal and Agriculture as Wastes-National Academy of Sciences,Washington, D.C. 1977.

(ii) Our own case studies.

111111111111111111111

70

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1

DESIGN AND R&D ASPECTS

- ~ »-t- - -~

DESIGN ASPECTS OF BIOGAS PLANTSFED BY HUMAN EXCRETA WITH OR WITHOUT

SUPPLEMENTARY FEEDSTOCKSL K Sinha~ Dr MB Mazumdar*I

A~TRACT

The biogas plant is essentially an anaerobLc fermentor in which organic wastesare subjected to microbial digestion in the absence of free oxygen. Theoretically,there could be ma»ny design possibiliites but, in practice there are limitations due tocost considerations,scale of operation and managementdifficulties.

Since the processof anaerobic digestion may serve the purpose of waste treatment(for sanitation) and fertilizer production in addition to energygeneration, careful co-isi-deration of the objectives is the most important step. The primary aim of municipalsewage-sludgedigestion, for exampie, has been to stabilize the sludge for sanitation.Production of energy is secondary in this case and the treatment process is optimisedevenat the expenseof energyinput (in the form of heat/mechanicalenergy).

Digester process may be classified according to the operating temperature andalso according to the feeding schedule. There temerature ranges have been observedfor bio-mentanation - psychrophilic, mesophilic and thermophilic (increasing order oftemperature»). The first one is yet to he applied in a biogas digester. The relativelyslow rnesop~iilic range of operation is tavoured when the objective is to get energywith lower inputs of capit»al and managementin small scales of operation. On theother hand, the energy-and-capital intensive thermophilic range is preferred whendestruc-tion/reduction of pathogens is important and handling of large a nounts of wastes isinvolved, e.g. mu.nicipal sewage treatment. Depending in the situation, the feedingcould be in batches, continuous, or semi-corttinuous. The batch systern is applied indigestion of municipal sewagesludge and in multi-tank batch plants for sea.~onalagricul/-tural wuste.

The desirability of stirring a biogas pia-it is stiJl a matter of controversy. Normally,high-rate sophisticated sewage digesters and the KVIC (Khadi and Village IndustriesCorn mission) cowdung plants (Gobar Gas) have stirring arrangements aithough the speedand extent of stirring is quite different. Another important consideration is the materialof construction which ranges from uiasonry and mild steel to plastics and fibre giass-reincorced plastics. Understaridably, in the digestion aid disposal of human excreta,the design should ensure destruction (or redu~tionto the minimum passible level) ofpathogens. In small scalesof operations involved in a biogas plant, thermophilic digastionmay not be feasible. Under such circumstances,the design sho:ild provide for adequateretention time and if need be, secondary treatrnent of the effluent depending uponthe body receiving the final effluent dischzrge.

In this country, not much evidence is available about the use of human excretaas the sold feedstockof the biogasplant. In most of the cases,toilets have beenconnec-ted to the floating-dome cow-dunq fed biogas plant (gobar-gas) in hoth family as well

* Sulabh Instt. of Technical Research& Dev., Patna »

** SulabhInstt. of Tech. Res.& Dev., Delhi

as large community/institutional biogas plants. The only examples of large biogasplants fed by human excreta can be cound at the Sulabh Public Toilets. These arefixed-domeundergrounddigestersof masonryconstructio!I.

So far, the tendency has been to use empirical considerations for designing abiogas plant. Engineeringaspectsof the plant have been the main design consideratiorisand the microbiologicalaspectshavegenerally beenignored.

Abstract

DESIGN OF BIOGAS PLANT ON NIGHTSOILRahulParikh*

Selectionof a design for a biogas plant from night soil is gove-rnedby criteria -

digesterefficiency, cost of construction and public health aspects. Communitylatrinesat public utility places, institutions or dormitories are ideal places for introducing thenight soil biogas plants. The degree of hazard would be significantly less than thatto which people are currently exposed in the traditional disposal or use of night soil.In addition to this energy and fertilizer can be generated. Design of a digester, inletmechanismand outlet mechanismof a night soil biogas plant are discussed.

This paper deals with design aspectsof a biogas plant using night soil froma community or from centralised latrinessuch as public utmlity places, institution~and dor in itor les. Anaerobic treatmentof sewage is beyond the scope of thispaper.

To justify the construction of agas plant two prerequisites must be met:(i) optmmum gas should be extracted fromthe avaiJable amount of nightsoil in thesmallest possible size of a gas plant;and (2) least possible Water should befed to the digester along with nightsoil.This leads to the question of design ofa latrine pan, flushing arrangement,slope of the pipes carrying nightsoilto the gas plant. To justify the publichealth aspect, maximum killing of the

1pathogens and parasitic eggs should beachieved through anaerobic digestmon 1and subsequent treatment to the ei 1 luents1ur ry.

Subs idm a ry COfl 51dera t ion S invol veonsite requirements such as: (i) adequatespace for Biogas plant must be availableclose to the latrines and the place wherethe gas will be used; (ii) space mustbe provided adjacent to the digesterfor storing or composting the digestedsludge from the gas plant; and (iii) thebio-gas plant must not be constructedwithin 15 meter (50 ft) of a drinkingwater well.

Digester Design

There can be a digester fed exclu-

• ResearchEngineer,AgricultureTools ResearchCentre,Surlichi Campus,Hardoli - 394601 (Guj~rat)

7411

11111111

General Design Criteria

111

11111

1

sively by nightsoil or a digester withmixed leed materials. In general, withnightsoil, daily 1 ed (semi-continuous)digester should be selected, mainly forthe public health aspect.

Connecting individual latrine tothe “gobar” (cattie dung) gas plant isan accepted mechanism at many placesin India. Hygienic disposal of the nightsoilrather than increase in gas production,is a major achievement of these plantsin the plants with nightsoil as a primary~eed material it is desirable to add othersuitable organic wastes to increase eff 1-ciency of the digester. Nightsoil is avery low C/N (between 6:1 and 10:1)matter. Therefore, mixing of higherC/N materials i.e. materials having morecellulose, will promote gas production.

Parameters to be considered fordesigning a who1ly~ night&oil-fed digesterare mainly (i) organic loading rate; (ii)retention period and (iii) dilution by water.

Optimum loading rates for nightsoildigesters in India are reported as 1.04to 2.23 kg of volatile soli~s on a dry

weight basis, per day per m of digestervolume*. As volatile solids are 80 to90 per cent of the total soIid~sin nightsoil,

the total solids fed per m of digestervolume would be 1.8-2 kg, dry weight.Assuming 90% moisture in fresh nightsoil,

it would mean that 18-20 kg of wetfli~htsoi1 can be loaded everyday perm of digester capacity. Further, if

we assume that per capita contributionof wet nightsoil is only 500 gms on an

av~rage, it would then mean that onem of digester capacity should be providedfor 36-40 persons.Variation in any of

the above figures, as occurs in differentsituations, will change this porportion.An average daily gas production of 23-34

litres per capita was recorded from theplants with the above loading rate.

According to the above calculationsabout 20 Kg wet nightsoil should be loadedper day per one m 3 digester volume.1f no further dilution by urine or wateris assumed, the digester will functionat a retention period of about 50 days.in practice dilution, moderately in excessto extreme, will unavoidably occur. Thiswill reduce the retention period. To main-tam the desired retention period in suchcircumstances, the loading rate of solidshas to be decreased from the optimumvalue. This leads to increase in costof construction.

Public health aspect is anothercriterion for selecting the retention period.There are varieties of enteric pathogens,viruses and parasitic eggs in the nightsoiland urine that can infect human beingsthrough various media such as water,food and direct contact. It has beenreported that Ascaris egg mortality shouldbe above 95% which is the epidemotologically safe level. They neither grow nordie at 27°C for 40 days. Parasitic eggscan survive for 15-40 days at 20°C to30°C temperature.

Looking from a different angle,any anaerobic -treatment to nigh-tsoilwill mean significantly Iess hazard thanthat to which the people are currentlyexposed by the traditional methods ofnightsoil disposal. Therefore, a compromisehas to be made between average gasproduction per day and survival of patho-gens in the effluent slurry lor decidingthe retention period in the digester.In general It can be said that the choiceof the digester design is guided by thecriteria - digestion efficiency from micro-biological point of view, cost of construc-tion and public health aspect.

Inlet Mechanism

For a smali-scale nightsoil plant

• For temperateciimates,a ioading rareof 1 6 kg of volaulesolidesperm~of digestervolume is recommendedEd

75


where côntrol on use of water is possible,filtration and separation of liquid canbe avoided. For a large-scale plantone has to compare the cost of filtrationprocess with the cost of increaseddigester volume, considering the exi-gencies of each situation.

A cement pipe of suitable sizcis good enough as inlet pipe to the diges»»-ter in a fluating gas holder plant ora fixed-dome plant. In ~i nightsoil digesterpathogens and parasitic eggs settie atbottom of the digester. Therefore to

avoid stirring of the bottom slurry theinlet pipe should not open at the bottoni.

An appropriate feeding mechanismfor family or community biogas planiscould be pipe (china day or cast iron)from the latrine pan leading to a smalltank open to atmosphere: and the inletpipe of the digester can start from thebottom of this tank. Bottom of this inlettank should be above the level of overfiowof the effluen»t slurry, so that it remainsempty and a vent pipe connected tothe tank carries away the foul smell.The tank remains closed by a lid. Thepipes between the latrine pans and theinlet tank remains clean of nightsoilwi-th very little amount of water if thepipes have a proper slope which is about1 in 6. In this case a pan without water-seaied U-tiap can converiientiy be used.

Outlet Mechanism

Effluent slurry of a nightsoil plantcan be fed to an existing sewage systernor can be used for composting organicwastes or can be stored in pits beforemaking any use, depending upon the criteriainstalling ~ nightsoil plant.

outlet pipe in a floating gas holder plant.In both the cases the outlet should be30 to 60 cms. above the bottom of thedigester for least disturbing the extremebottom slurry where there is a concen-tration of live parasitic eggs. Reportson Chinese experience suggest that thenightsoil digester should be desludge0~cea year to prevent too much sludgebuilding up. Some parasitic eggs do survivein the sludge removed from the digester.Therefore, during such annual cleaningoperation, chemical treatment is suggestedto disinfect the sludge before it is used.

Relative levels in the constructionplay very significant role in functioningof a plant; therefore, they have to bedecided car efully. Normally, overflowof effluent slurry is a reference level.Top of the inlet pipe to the digestershould be at 10-15 cm higher level thanthat of the overfiow. Level of the latrinepans would have to be higher than thetop of the inlet pipe. The exact heightwould depend on the distance betweenthe two.

References:

1. Methane Generation from Human,Animal and Agricultural Wastes.National Academy of Sciences,1977.

2. Compost, Fertilizer, and Biogasproduction from Human and Farm~Vastes in the People’s ReDublicof China, IRDC, 1978.

3. Gobar Gas Manure Plant. Agricul-tural Tools Research Centre, Bardoli,1982.

There will be a slurry displacementtank in a fixed-dome plant and a simple

76

NIGHTSOIL-FED BIOGAS PLANTSBASIS FOR DESIGN

Anil Dbussa

111111111

11111111111

Abstract

1f their elimination is not complete,the effluent may be given a secondarytreatment by way of applying chemi-cals, oxidation and also composting.With the experience of compostinghabits of people having cowdungbased biogas plants, asking forcontrolled treatment will be toobig a demand on plant owners.Therefore, the only alternativeis to ge-t rid of most of the micro-organisms before the material comesOut of the biogas plant.

2. The available data on the kil] rateor stabilizing of parasitic eggsand bacteria is not absolutely con-clusive and can at best be usedas suggestive data with extra bitof caution. The kili rate dependsheavily on temperature as a totalremoval is reported within a fewhours to 4-5 days at 55°C. Whereassome parasite eggs survive for morethan F00 days at tempera’turesbetween 9 and 18°C, schistosmeeggs are reportedly killed within14 days at 26°C. Notably, It takesonly 30 days to kill 90% but 70-100days to kilI 99% of these schistosomeeggs’ in winter (temperature rangingfrom 9 to 18°C).Thus the first stepfor designing a nightsoil fed biogasplant is to 1ix an appropriate hydrauhcretention time (1—IRT) at which It

is planned to be operated. As faras possible the HRT should be fixedfor worst operating conditions.

3. The above discussions were basedon the assumptions that the elfluentfrom biogas plants fed with nightsoilwill be dried and used as manureand not be led into a water streamor drainage. For the latter cause,the norm of reduction of chemicaloxygen demand (COD) to a permissi-bIe limit also becomes as importantas the reduction of becteria andparasite eggs.

79

KVIC Model (Floatirig Drum) Plants

Digesters of this type of plantshave a high depth-to-diameter ratio.The input material enters the digesterbottom through a pipe and travels upwardsto the outlet pipe 1 itted at the top orcomes clown over the partition wall in-tothe outlet pipe placed at the bottomon the other side of the partitlon wall.It was designed to work as a typically“plug-flow digester” where plugs wereexpected to move vertically upwardsand downwards. Cattie dung slurry whichis quite thick can be expected to t ollowthis flow pattern to sorne extent butthe~e is all the possibility of inter-mixingof various vertically travelling layersi.e. the digested and the less digestedmaterial, which ultimately gives riseto short-circuiting. Therefore, the elf ectiveHRT will be less than the designed HRT.The ex-tent of intermixing of layers willbe much greater when the nightsoil is1ed in these digesters because its particlesize is smaller than that of cattle dung.The slurry formed by nightsoil is muchthinner and also not as homogenous asthe cattle dung slurry. Therefore, theeffective retention time of this typeof digesters for nightsoil will be lessthan that for cattie dung and much lessthan the designed HRT.

The extent of export circuttingcan be determined by using tracer techni-que. But as long as it is not done. asafeguard against short-circuiting sho-uld be provided in some manner whiledesigning a plant of KVIC type for night-soil if a plant of this type has to beinstalled.

3anata Biogas Plant

This one has a much shallowerdigester and the net movement* is hori-zontally from the inlet towards the outletside. The possibility of 1ntermi~ingbetweenless digested and the more digested m.~i»~r-

ial is less because it occurs more t~

- »»»;» » ~ ~ ~

there is a forced vertical movementof mass. However, the diameters ofJanata biogas plants of higher capacitiesare very large: therefore, as the movementof material IS Oflly from inlet to outletthere is no force acting on it in thedirection perpendicular to the line joiningthe inlet and outlet tank guiding thedirection off low. This results in non-utilization of some parts of digestervolume and also in shortcircuiting ofinputs. Even otherwise, the effectiveretention time in this case also willbe less than the designed HRT.

Design of Nightsoil Biogas Plant.

Based on the above discussions,the following sequence of operationsis formulated for designing a foolproofnightsoil-fed biogas plant:1. Fixation for HRT for given tempera-

ture.

2. Design of digester with an effectiveHRT of the fixed duration

3. Planning of complete hioeas produc-tion and distribution systems.

Criterion for fixation of HRT fornightsoil-fed biogas plarits has been out-lined above in para 2 under “controllingparameters”. The selected HRT should

- match the operating temperature whichmay vary from region to regioti undernatural conditions » or can be controlledby artificial means. While almost allthe family size plants are operated atambient tcmperature, large-size plantscan be designed for operation at controil-ed higher temperature e.g. 35°C or 55°Ce-tc. Once the HRT has been fixed, adigester is designed with an effective1-IRT of a given order. Care should betaken to avoid all possible chances atleast to minimise chances of short-circuit-ing. A truly plugf10w digester would

be an ideal choice whereas a constantlystirred digester is the worst. The effectiveHRT vis-a-vis the d~si~nedHRT fora partially mixed-feed digester withminimal vertical movement and withr»iost of the movement in the directionof flow (this will bc the case with atubular digester) is the closest to theplugf low.

After finalising the digester, otherparts of the biogas system are designed.The main considerations for this exerciseare that the input material is not exposedto atmosphere and a system for treat-ment of elf luent from the nightsoil biogasplant is planned as an integral part ofthe biogas system.

A biogas system was designed byAFPRO on the basis of these guidelinesfor a pilot demonstration project onbiogas from nightsoil for a colony inPuri, Orissa.2 The digeste~ employedi~s not of the tubular design but it isof Janata type with some modificationsto make It appropriate for nigh-tsoil.This system is not claimed to be perfectand there is need for more efforts inthis direction in order to effec-tivelyapply the anaerobic digestion technologyfor treating nightsoil and producing biogas.

References

1. Compost, Fertilizer and BiogasProduction from Human and FarmWastes in the People’s Republicof China by Michael G. McGarryand 3. Stainforth, published by IDRC,Ottawa, Canada.

2. Design and Implementation of a-Pilot Demonstration CommunityNightsoil Biogas Scheme: by AnilK. Dhussa and Raymond Myles,published in Changing Village, Vol.7, No.5, September - October, 1985.

• The heavierparticlemaygo down,the lighier maygo up but theoverall flow is horizontai Ed

80

1

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Abstract

NIGHTSOIL BASED BIOGAS PLANTSTIME TESTED DESIGN

Floatingdomeon WaterJacketedDigester

SV. Mapuskar

In Maharashtra, floating-dome water-jacketed digesters have been functioning satis-factorily for more than thirty years. Hence the fear that nightsoil-based plant mightbe hazardous or unfeasible is totally baseless. Several principles should be followed incase of these digesters. There should be no manual contact with nightsoil. Undigestednightsoil shoulci not be visible or exposed to surroundings. Aaequate arrangements foraeration and drying of slurry before its use in farms is essential. Maintenanceshould beeasy.

The author claims that the water-jacketed floating»-drum design, which has beenadopted by the Maharashtra Unit of Gandhi Smarak Nidhi, meets all requirements. Thereis, however, scope for further research for improvementsin respectof dilution, C/N ratio,bacterial content etc.

- Ed.

Introduction

t seems that there is plenty ofapprehension even in the minds of someof the learned technologists and scientistsabout the feasibility and safety of biogasplant working solely on human wastes(nightsoil). Many tend to take for grantedthat nightsoil based biogas plant is notfeasible or that It is hazarous. Mapyof these apprehensions are based on hypo-thetical assumptions not backed by exper-iences in the field or by laboratory data,which are, unfortunately, scanty. Thefacts show that in Maharashtra, theseplants have been functioning very satis-factorily for the last more than thirtyyears. 1f the facts do not tally with thehypothesis, we must try to find out wherethe hypothesis has gone wrong and notvice versa.Field experiences in Maharash-tra show us that nightsoilfed biogas plantsopera-te very satisfactorily. Therefore,if in some instances, there are any failuresor mulfunctioning, the reasons are morelikely to be found in the selection oftechnology or in operational and mainte-

nance routines. Hence, it would be desirableto review the design and technologywhich has been in use successfuliy inMaharashtra for the last thirty years.It would also be necessary to decideon the basic parameters and optimizationcriteria. These will help in arriving atdecisions about the suitable technologyand design to be used for nightsoil basedbiogas plants.

Basic Parameters and Operational Criteria

In addition to the criteria for cattle-dung based biogas plant, the followingimportant requirements need to be consi-dered so far as nightsoil based biogasplant is concerned.

i) There should not be any directhandling of excreta. When it isindispensable, it should be by hygienicmethods.

ii) Undigested nightsoil should notget exposed to surroundings. Flies,other insects and animals must

• MaharashiraGandhiSmarak,Nidhi, Kothrud, Poona

81

» -» ~» » »~» _~»-;~__;~ »» » - - » - »

iii) Aesthetically, there should be freedomfrom odour and unsightly conditions(faeces should not be visible atany stage).

iv) Surface soil should not be contami-nated.

v) Arrangements need to be madefor aeration and drying or for compost-ing of slurry béfore its use in farmas a manure.

vi) There should be no contaminationof surface or subsoil water.

vii) Maintenance should be easy andshould not evoke any repulsive feel-

viii) Cleansing water per user may bearound two litres (there need notbe 1:1~dilution as in cattle dung).

ix) Use of disinfectants for cleaningthe latrines should not be permitted.

While deciding on a suitable designfor nightsoil based plant these requirementswill have to be necessarily considered.

Late Appasaheb Patwardhan’s PioneeringEfforts since 1953

Late Appasaheb Patwardhan, aGandhian worker and visionary firedwith an obsession for ‘Bhang~ Mukti’and ‘Gram Safai’ programme, workedfeverishly since 1928 on the problemof nightsoil disposal, devzsing in the processseveral innovative designs for latrineas well as biogas plants. In 1953, hepioneered nightsoil based biogas plantsin India by constructing the first nightsoilbased biogas plant at Kankavali in Ratna-giri district of Maharashtra. He construc—ted many more such plants subsequently,creating a cadre of trained social workersin the process. The design which he devised

had a floating-dome-type gasholder movingon partially water jacketed digester.He had given thought to every importantt low that was likely to creep in andprovided solutions for the same. As ~result, even after thirty years, out ;ofall the designs now available, the designdeveloped by him remains the best.

Review of Salient Features of the Design

The water jacket digester designis similar to ‘Gramlaxmi’ design developedby Sri Jasbhai. Patel (which was lateradopted for propagatlon by KVIC). However,it has some important additional features:

1. The major difference is in the cons-truction of digester. In water jacketdesign, the lower portion of digesterdesign is similar. 1-lowever, thedesign differs in the upper f ivefeet. In water jacket design, theledge is made wider, and abovethe ledge in upper three feet ofdigester, an inner circular wallof 4 inch width is constructed leavinga gap of about 6 inches betw eenthe outer and inner walis. Thisannular gap of 3 feet depth is keptconstantly filled with water. The gasholder floats in this water jacket.The digesting slurry is completelycovered since it remains insidethe inner circular wall and is separa-ted from water jacket by this innerwall. Thus the slurry in digesteris completely covered by gas holder,doesn’t come in contact with atmos-phere and is obviously not visible.What is exposed to environmentis only the water from water jacketin which the gas holder floats.

2. About 6” wide belt around the outerside of inner wall should be lef tunplastered SO that the soaked waterwill prevent the gas from leakingthrough the brickwork of innerwall.

not ge-t access to it.

ings.

1

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82

3. The inlet pipe from the floor ofthe dinn chamber of the outsidelatrine should open at a level higherthan the floor of the digester, 1fnightsoil is the only feed beingused. Since the nightsoil has a ten-dency to float, the inlet pipe islikely to get choked frequently1f the inlet pipe is too near thef loor.

4. The top of the latrine seat is keptat height of 2 f eet above the slurrylevel, i.e. outlet level. 1f’ this isnot done, the lower end of theof the pan gets chocked frequently.Also, the nightsoil may come outfrom the cleaning chamber occasiona-Ily.

5. The water seal trap which is usedfor the latrine pan » should havea waterseal of only 15 mm to 22mm*. This will help in minimizingthe quantity of water needed forflushing. The water sea! traps atpresent available in market havea water seal of 50 mm to 70 mm.These are unsuitable. Use of ‘Sopa’(simple) latrine pan developed byAppasaheb Patwardhan has beenfound to be very suitable.

6. Water tap should be provided outsidethe latrine enciosure. 1f tap is provi-ded inside, excessive water wouldbe used despite intentions for frugaluse.

7. Latrine seats should be placed veryclose to the plant so that latrineto plant drainline is as short aspossible. Further, with ‘onsite’latrine sears, the problem of carryingnightsoil to the plant will not anse.

Effluent slurry may be allowedto dry or may be composted inthe manure pits. Two pits are alter-nately used.

83

9. Although not strictly within thescope of this paper, it may be men-tioned that many tirries, the latrinesconnected to cattle dung plantsdo not have adequate plinth height.This results in a backflow to thewaterseal trap leading to choking.In order to avoid this, the latrineplinth height should be atleast 1 1/2f eet above the top of dung feedingchamber.

Design Suitability Test

A review of the design characteristicsand functioning of various designs (pre-dominantly KVIC, Jariata and water jacket)in relation to the nightsoil feed, is self-revealing.

In KVIC design the gas holder floatsin the digesting slurry. As a result undi-gested slurry is present between theouter surface of gas holder and the wallof the digester. In the case of nightsoilleed, undigested nightsoil 1 inds accessto this annular gap through which it

is exposed to the surroundings. This givesrise to offensive foul smell. The insectsand animals get direct access to nightsoiland spread disease. The nightsoil is visible.Many times nightsoil also sticks to theoutside of the gasholder which needscleaning. With exposed nightsoil, thechances of soil pollution are ever present.

In Janata plant, slurry is constantlymoving between the digester and theinlet-outlet chambers. During such move-ments undigested nightsoil will enterinlet and outlet chambers, from whereit will give out foul sméliL. Also the insectsfind access to inlet and outlet chambers.In case, inlet and outlet chambers arenot covered properly there is a totalexposure of nightsoil. »

In water jacket design, as has beenalready discussed, the gas holder floatsin water jacket. The slurry is completelycovered as it lies inside the inner wall

• The trapsmanufacturedby NEERIor MaharashcraGandhiSmarakNidhI etc. havea 15 to 20 mmwaterseal Ed.

»»»~»-»~-»~‘» -»» ~

of the jacket.Thus, slurry is not exposedto atmosphere. Hence there is no smell.Flies, insects and animals cannot reachslurry. There is no soil contaminationas only digested slurry comes out fromoutlet pipe.

Thus, it is evident that water jacketdesign meets all requirements of a suitabledesign for nightsoil based biogas plant.Small sized ‘onsite disposal’ construc-tion not involving carriage, manual orotherwise, of nightsoil will be most advi-sable.Experience with Some Examples in theField:

In Maharashtra, since 1953, allnightsoil based biogas plants constructedby the late Annasaheb Patwardhan andhis worker volunteers, have water jackettype design. These have been functioningsatisfactorily. His work was later continuedby Maharashtra Gandhi Smarak Nidhi,using the same design. These plants arealso functioning satisfactorily for manyyears. A brief review of some of theseplants may be worthwhile.

1. First nightsoil based biogas plantconstructed at Kankavali in Ratnagiridistrict of Maharashtra State wasconstructed in 1953. The designused was water jacket type digester.A twelve-seat community latrineblock was attached to 300 cu. ft.capacity plant. The unit was main-tained by Gopuri Ashram of AppasahebPatwardhan. The gas was used inGopuri Ashram farm.

2. The biogas plant at MaharashtraGandhi Smarak Nidhi staff quarterswas constructed in 1967. The planthas water-jacket-type digester.The capacity is 70 cu. ft. It hasone latrine attached. The latrineis used by four families: the numberof users is around twenty. Gashas been given to one family. Manureis used for plantation.

84

3. The biogas plant at Dr. Jogalakar’shospital at village Shirval in Distt.Satara, Maharashtra was construc-ted in 1967. The design has waterjacket type digester. The capacityis 150 cu. ft. The input is froma block of 10 latrine seats on site.The owner has allowed villagersto use the latrines. 100 to 150 usersuse the latrines daily. Gas is usedin the hospita! and the owner’sresidence. Manure is used in theowner’s farm. The doctor is reportedto be saving about 70 litres ofkerosene per month.

4. The biogas plant in Dehu villagein Pune Dist. owned by Sri MohansinghPardeshi was constructed in 1978.It is a 6 cu.m. capacity plant withwater jacketed digester.Two latrinesare attached to the plant. The ownerhas allowed about 10 neighbouringfamilies to use the latrines, whopay Rs. 5/- per month per familyas maintenance charges to the owner.About 100 persons use the latrinedaily.The gas is sufficient for house-hold cooking of the owner’s familyof about 15 members. Through thesale of manure, the owner recoversabout Rs. 600/- annually. Thusthe plant has been a profitablebusiness for the family. This isan example which can be a guidelineelsewhere.

5. At Relegan Shindi Village in Ahrned-nagar Dist. Maharashtra, a biogasplant for backward class hostelhas been constructed.About 10 latrinesare attached (on site) to the plant.Hostel students and other villagersuse the latrines. The gas is usedfor the mass cooking and lightingin a temple.

6. 1 had an occasion to visit one commu- 1nity gas plant in village KarudayyaKaundan Patti in Tamilnadu. Thisis a rehabilitated village. The plant

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111

has a capacity of 40 cu.m. Theplant has a water jacketed digester.It was constn~cted by GandhigramTrust. 54 familiés use the latrines.It is one of the cleanest and elf icient-ly maintained community biogasplants.

These are only a few representativeexamp!es.These examples show th’~tnight-soil based biogas plants function verysatisfactorily. The design used in allthese cases has been of water jacketeddigester with floating gas holder. This

seems to be the best design for nightsoilbased biogas plant. Biogas from hümanwaste is a very sound and workable propo-sitiori provided suitable design is used.Biogas from human wastes is being usedfor the last thirty years. Fear is, therefore,unfounded. Of course, there is scopefor research as regards dilution, C/Nratio, microbiology, design etc. Fromthe available data and field experience,it can be concluded that nightsoil basedbiogas plant will be a valuable assetfor rural health, bio-energy, agricultureand rural development.

FLOATING DONE BIOCAS PLANTWITH WATERJACKET DIGESTER

(Sultable for Human Waste Treatment)

INLET PIPE

DIC~�STINGSUJRR~

PARTIT~O~~WALL

OIGESTERBR~CK NORX

FCLjNDAT~Q~»j

WATER 3AC~ET ?4P4ER WALL

GU~DEFgAME

TO MANIJPEPITS

~JTLET PIPE

85

Abstract

11

DESIGN AND IMPLEMENTATION 1OF A PILOT DEMONSTRATION COMMUNITY

NIGHTSOIL BIOGAS SCHEME

In India about two-thirds of the urban population use dry (i.e. flushless) latrines. Night-soil from these latrines is dumpedat pre-assignedplaces outside the city/town or municipallimits. However this causes immensepollution du2 to direct exposure to the atmosphere;at the sarne time it leads to wastage of organic material which has great potential forthe proauction of biogas as well as excellentorganic manure. AFPRO’s notable achievernentwas to provide technical assistancefor design and implementationof a cluster of threebiogas plants each of 20 cu.m. capacity - a dernonstration community nightsoil Biogasscheme for Acharya Harihar Colony, Puri, Orissa, at the request of Public Health Deptt.(PHD), Government of Orissa, Bhubaneshwar.Constructedin 1984, the entire schemehasbeen working well. It has the following main cornponents- I3iogas production system;Biogasdistribution system;Nightsoil feeding system;Effluent treatment system. Their characteris-tics are presentedhere. The differences between the K.V.I.C. model and the Janata Modelare also discussed.

- Ed.

1

Introduction

The safe disposal of nightsoil isa major consideration for any sanitaryprogramme. There are three major methodsof disposal of nightsoil, being adoptedat present in a large-scale sanitary progra-mme in India.The first being the compli-cated sewage system which involveshuge capital investment and time dura~on-for execution of the projects. The main-tenance cost of such schemes is quitehigh and according to National SampleSurvey of 1973-74 only 20% of urbanhousehoids are covered by sewerage.The same survey reveals that only 14%of urban households use the latrinesconnected with septic tanks, which formthe second method of nightsoil disposal. 1 Thethird method is through dry latrineswhich have been in use in practicallyall the towns of India and about 2/3rdof urban population still uses them. Thenightsoil from these dry latrines is dumpedin pre-assigned places outside the city/townor municipal limits everyday by scavenger

community. This causes immense pollutiondue to direct exposure to the atmosphereand at the same time leads to wastageof organic material which has greatpotential for the production of biogasas well as excellent organ~c manure.

Though attempts are being madeto convert the dry latrines in-to morehygienic low-cost latrines, it will takeyears before all will be converted. Reali-sing this problem, AFPRO (Action forFood Production), a non-profit technicalservice organisation, had constructeda commünity nightsoil biogas plant inMidnapur,2 for Midnapur Municipal Commi-ttee (MMC), West Bengal. This pilotstudy plant was designed and built byAFPRO in the year 1981 for the treatmentof human waste and also to get the twinbenefits biogas and organic manure.This plant was operated on the nightsoilco!!ected from the~dry !atrines in theMMC area. Many useful lessons withrespect to operational and socio-economicaspects were learnt from this pilot studyproject.3

• Action for FoodProduction(AFPRO),New Delhi

1

AnilK Dhussat— RaymondMyle?

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86


Later, the Public l-lealth EngineeringDepartment (PHD), Government of Orissadecided to set up a pilot demonstrationproject for converung some of the nightsoilavailable from the city of Puri, in-tobiogas and manure and approached AFPROthrough “Gram Vikas” for its design andconstruction.The project was locatedat nightsoil dumping site and the generatedgas supplied to a nearby sweepers’ colony(Acharya Harijar Colony). The projectenvisaged the generation of biogas fromnightsoil for supplying it to 60 houses.The total installed capacity of the commu-nity nightsoil plants scheme was proposedto be 60 cu m.

Background of the Plant DesignBiogas Production System.

There are two basic types of biogasin India, namely - (i) floating-drum type(KVIC model) and (ii) fixed-dome type(Janata model). The KVIC model plantshave digesters connected with inlet andoutlet pipes near the bottom and areseparated by a partition wall. The inputmaterial (feedstock) in the first halfof the digester is expected to travelupwards and over the partition wall in-tothe second half and downwards to theoutlet pipe to be discharged after comple-tion of the entire cycle of its hydraulicretention time (HRT). The expected flowpattern can be termed as “quasi-plugflow”. However, the nightsoil mixed withwater does not form a very homogenousmixture as is the case with cattle dungsiurry: hence, it cannot be expectedto follow the same flow pattern. Thereis all the likelihood of some shortcircuitingof raw-materials.

It is reported that 99.6% of hookw-orms die under anaerobic conditionswithin 70 days,4 at a temperature of 16°C.Therefore, the nightsoil must remainin the plant for over 70 days to becornefree from pathogens and parasitic ovaand should not be left exposed to theatmosphere during the fermentation (diges-

- ~— _~-~»»~.1 -~- - -

tion) period. The KVIC design for nightsoilbased biogas pla~tscannot be said to befully safe because it does not shut outpossibilities of the slurry’s escape Intooutlet pipe even before spending therequisite residence time in the digester.

The other population design, namedJanata biogas (fixed-dome) plant, has

the advanLage of having a large diameterand !ess depth, thus reducing the verticalmovement of raw material (The verticalmovement causes mixing of the moreand the less digested material and thereforethe possibility of shortcircuiting, as inthe case of KVIC plant, gets reducedin the Janata model). The Janata plant

for also has the advantage of having itsdigester completely covered from thetop, thus preventing foul smeil and pollu-tion from the digester.

87

The -3anata plant, however, hasthe disadvantages of a very large inletand it necessitates the exposure of freshfeedstock to the atmosphere for 2-3days. This will not be tolerable for anightsoil biogas plant because of itsobnoxious smel!.

For large plants (say 15 cu.m capacityand above), large diameter of the digesteris also undesirable because the inputmaterial (feedstock) would tend to flowstraight towards the outlet tank sincethere is no distinct force acting on it

to 1 low sideways. and no arrangementshave been made for guiding the flow.This means significant reduction in theeffective digester volume for largersizeplants.

Design of Nightsoil Plant Scheme forAcharya 1-larihar Colony, Puri

The com»riunity nightsoil biogasplants system at Puri, Orissa was designedon the basis of AFPRO’s previous exper-ience of implementing and operationof 15 cu.m. Janata biogas plants fedwith nightsoil at Midnapur, West Bengal,

BIOGAS FROMHUMANWASTE

1

and keeping in view the constraints anilimitations mentioned in para 2.1 to2.5 above in the two most popular Indianplant designs.

The design of (i) biogas productionsystern; (ii) gas distribution system; (iii)feeding system and (iv) effluent treatmentsystern, for the community nightsoilbiogas plant scherne at Acharya NariharColony, Puri are presented below:

Biogas Production System

The entire gas production capacityof 60 cum. gas was proposed to be metby three fixed~iome plants of 20 cum capacity each.The basic design ofthe 20 cu.m. fixeddome plant has beenadopted from the Janata biogas plants’operational concept. In the modifiedfixeddome plant design the inlet tankhas been removed and the mixing tankis connected with the digester througha pipe of 150 mm diameter. Since theupper portion (above the initial slurrylevel) of inlet and outlet tanks determinethe gas storage capacity of the plant,the displacement chamber design onthe outlet tank has been made largerto account for the removal of displacementchamber from the inlet side.

A “baff le wall” has been providedin the middie of the digester to ensurethe sideways movernent of the slurrycloser to the digester wall (instead ofletting it follow the shortest path tothe outlet) thus ensuring the effectiveutilisation of most of the digester volume.In order that the turbulence be keptat the minimum, the “baffie wall” isSO designed that the 1 eedstock goes aroundthe wall and not over the wall, as isthe case in the KVIC plant.

The dimensional sketch of 20 cum. fixed-dorne nightsoil biugas plantdesigned for 75 days HRT is given indrawing-l.

Biogas Distribution System

In the community nightsoil biogasscheme the gas produced at one spotis required to be distributed to 60 housesfor cooking. A distribution systern forthis type of scheme should be availableat all the points of utilisation (all the60 houses) at equal pressure. This isof utmost importance because the gasin the plant is availabie at rather lowpressure (between 0 and 90 cm of watercolumn) and variation in pressure affectsthe tlow of gas.S

The gas distributiori system hasbeen design~d for a maximum variationof 0.5 cm of water column pressure bet-ween any two houses or storeys.The gal-vanised iron pipe is recommended foruse in order to ensure the durabilityof the system and to minimise the recurr-ing maintenance cost.The piping layoutis given in diagram -2.

Nightsoil Feeding System

Nightsoil has to be made in theform of slurry by mixing it with water.The feeding system consists of a mixingtank which is fitted with a churner opera-ted either on a dual-fuel engine of 3HP or manually. Normally in a cattie-dungoperated plant system of this capacitythe mixing is done manually but sincethe fresh nightsoil has bad odour whichcannot be tolerated for a long time,mechanical m~xer has been designedfor this project.

Daily input of 700 litres of freshslurry containing about 10% dry matterIs recommended for each of ~hese plants.

Effluent Treatment System

Since the hydraulic retention time(HRT) of each biogas plant is kept at75 days, it is expected that the slurrycoming out of the plants after undergoinganaerobic fermentation for 75 days will

111111111111111111111

88

BIOGAS FROM HUMANWASTE

be free from pathogens and parasiticova. Therefore, the effluent, which willcontain about 92-93% water in it, needsto be dried bef ore it can be used asmanure.

Drying is planned to be done inpits of 3 feet depth.Total retention timefor effluent in the drying pit is keptat 90 days, also allowing for additionof some other bio-wastes for composting.

Conciusion

This innovation in the existing fixed-dorne (Janata plant) design has beendone by AFPRO with a specific purposeof efficient treatment of nightsoil. How-ever, other raw-materials which canbe made into a homogenous slurry formcan also be treated efficiently, if thesedesign changes are incorporateci in allcapacitles ( 1 to 30 cu m.) of existingpopular t ixed-dome (Janata plant) design.

The successful opera tional demons-tration of this community nightsoil biogasscheme will open up possibilities foracceptance of such pro)ects for efficienttreatment of nightsoil from dry latrinesfor giving the dual benefits of biogasand organic manure, thus making thetreatment of nightsoil on economicallyviable propo»sition.

References

1. B. Pathik, Sulabh Shauchalaya:

A Study of Direct Change

2. Raymond Myles & Ishrat Hussain:Community Nightsoil Janata BiogasPlants System for Harijan Colonyin Midnapur, West Bengal. Paperpresented at Panel meeting on BiogasTechnology organised by AFPROat Bardol~, Gujarat, from Sth to6th November, 1981.

3. Raymond Myles: Pilot DemonstrationProject on Low-cost Night SoilBiogas Plants for Community &Family use. Paper presented atthe International Seminar on HumanWaste Management for Low IncomeSettiement held at Bangkok, Thailand,trom January 16-22, 1983.

4. Michael G. McGarry and J.K. Stam-forth: Compost. Fertilizer and Biogas

Production from Human and FarmWastes in the People’s Republicof China, International DevelopmentResearch Centre (IDRC), Ottawa,Canada.

5. Anil K. Dhussa: Designing the BiogasDistribution System, published inBio-Energy Re-News, Issue of Juneand August, 1983, No. 2/1 & 2.

89

1111111111111111111111

FIXED DOME NIGHTSOIL BIOGAS PLANT.CAPACITY — 20 Cum (700 cft)

LONGITUD~NAL SECTON.

DE1~~ItSOF CONSTRUCTION MATERIAL LABOUR E MftSONSp.9TlCUL~95

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Abstract

SOME ASPECTS ON THE DESIGN OFFAMILY-SIZE FIXED-DOME

NIGHTSOIL BIOGAS PLANTSAnjanK Kaha*

Past extension withottt proper feedback from thé users and requisite research isleading to disappointmentsin Himachal Pradesh and also pQsing problems of health hazardsfrom these very digesters. The problem is not merely people’s prejudice against nightsoil: - -

inadequacy of technology is a mojor cause. In fixed-dome plants, there is excess.odourfrom inlet and outlet pipes, the light but undecomposednightsoil tends to flow to theoutlet tank and does not flow back to the fermentation chamber. Not m~ichresearch hasbeen done to correlate the hydraulic retention time, the varying temperature levels parti-cularly in the 13°C-23°Crange and the percentageinactivation of pathogens.

Detailed design of a familysize 3 cu.m gas capacity biogas plant, wtth a novel typeof baffie wall, has beensuggestedfor trial.

Introduction

- Ed.

Fast extension of familysize biogasplants in different 2arts of the countryover the years’ has proved the utility ofbiogas plants not only in providing aclean fuel for cooking and light but alsoin reducing the environmental pollution.Since these plants involve the use ofcattie dung, it is essential to have aminimum number of cattle heads formeeting dung requirements. Anotherbulky organic material that can be madeavailable for biogas production is thehuman excrement. Not much effort hasbeen made on the use of human excrementalone or in combination with cattie dungalthough the former is a better materialfor biogas production.2 Som e e f t ortshave been made by agencies like KVICand PRAD to attach latrines to cattle-dung-fed biogas plants with attachedlatrines,3 but utility of biogas plants remain-ed limited not only because of people’sinhibition but also on account of a lackof proper toolproof appropriate technology

suitable for different agro-climatic andgeographical conditions of the country.The research work conducted on theuse of cattledung-fed biogas plants runon nightsoil has mostly remained restric-ted4 to the gas plants with floating gasholder which is a technology adoptedsince 1900~.AFPRO designed6,7 a numherof fixeddome Janta Biogas Plants fedon nightsoil. But~their work has remainedmore or less restricted to communitybiogas plants when fed exclusively bynightsoil. The main limitation in theadoption of biogas production purelyon nightsoil is that human excrementfrom a family of 5-6 members cannotproduce suf ficient biogas by itself. However,this source can contribute to the overallbiogas production from familysize biogasplants, apart from providing a sanitarydisposal of the waste with almost negligibleadditional cost compared to constructionof a separate septic tank required forthe latrine. But a dilemma remains as

• HP Kiishi VishvaVidyalaya,Palanipur- 176062

1. -~ - -~ ---

91


1

to whether the design of fixed-domefamily-size biogas plant is suitable andsafe for the use of human excreta fromfamily latrine as the floating drum gasplant is. It is also not dear if a simpleattachment of a latrine pipe to the formercan serve the purpose. A number ofbeneficiaries in Himachal Pradesh - who,spurred by extension agencies, instal1e~pipes connecting latrines with 2-4 mfixed-dome Janta biogas plants - hadto discontinue the use of these latrinesdue to various problems. This paper discu-sses some practical aspects experiencedin this regard.

1. Unsatisfactory Design of LatrineAttached to Biogas Plant

Dilution of human waste for properanaerobic fermentation is a commonproblem with all types of bio-gas digestersusing this waste. Though nearly 2-3 timesdilution of human excrement is the mostsuitable8 to reduce solid content to 5-6% formaximum biogas production, sometimesmore and at other times less water isused by the users depending upon theirhabits which affects the rate of decom-position of this waste in all types ofbiogas plants. In fixed-dome biogas plantswith attached latrines the additionaldifficulties are as follows:

i) There is excess odour from thesewage pipe connected to thesebiogas plants. As the biogas getscollected in fixed dome of thegas plant, pressure is created whichdisplaces digesting slurry from thedigester not only into the inletand outlet tanks of the gas butalso in the sewage pipe which contaiiisfresh human excreta, thus resultingin the pushing of obnoxious smellinto the latrine. Even the userswho have water seal in their fatrineseat face this problem of bubblingout of these dispaced gases fromthe pipe to the latrine.

ii) As no specific guidelines are providedfor construction of latrines abovethe gas plants, these are of tenso constructed that the height oflatrine seat is just equal to thatof the slurry discharge hole ofthe outlet tank of these biogasplants. The two heights being thesame, a problem crops up. As thebiogas accumulation reaches theJimit of gas holder’s capacity, apart of fresh human excreta alongwith dung slurry is pushed backto the latrine seat, thus makingthe latrine unusable. The problemis more at places where the biogasplants are constructed with theirdome at the ground level or aboveit and the rest of the house andthe latrine is at a lower height.

II. Insanitary Conditions of the Outlet 1Tank of the Biogas Plant

Human excreta does not form ahomogenous slurry in the gas plant asno mechanical stirring is provided. Furtherphysico-chemical parameters of humanexcreta vary with the type of food takenby the family. Where human excrementis lighter than the slurry in the tank,it floats to the top in the fermentingchamber. It happens mostly when theusers consume more fat in their diet.As the slurry from the fermenting chamberis disposed to outlet tank, a part ofthis light undecomposed nightsoil comesin the outlet tank and being lighter,does not go back to the gas plant withthe cattle dung slurry, thus forming atop surface in the outlet tank. This crea-tes insanitary condition in the oultettank of the gas plant by creating odour-nuisance and attracting flies etc.

III. Incidence of Diseases due to Patho-genic Organisms and Parasite in 1the Sludge.

The improperly digested human 1excrement is unsafe for utilization as

1111111

11111111

92


a manure for crop production as it can

I result in spread of diseases of viral,bacterial, protozoan and helminthic origin9~l0.In most of the existing biogas plants, the

I ppe from latrine is attached to the centreof the digester wall. As the hydraulic

I retention time (HRT) of feed in theseplants is 55 days,Il the fresh dung slurryadded in the inlet is theoretically expected

I to come to the outlet tank after thisperiod. But since the human excretaenters the gas plant nearly in the centre

I of digester, it is expected to come outof the gas plant in less than 28 days.Further, since the human excreta is

I lighter than cattie dung slurry, it comesout of the digester even earlier due to

I short-circuiting of its path in the digester.This excreta is not decomposed becauseof its short retention time for anaerobic

I decomposition. Low bacterial activityin the ~as plants when the digester tem-peraturel2 remains between 13°Cand 23°C

I during different months of a year alsocauses inadequate digestion.The ill-digestedslurry contains various types of pathogenic

I organisrns and parasites. As the slurryfrom the gas plant which contains thisundecomposed human excreta is used

1 as manure directly in the fields eitheralone or along with water or by transpor-

I ting mechanically, it can cause seriousproblems of spread of faeces borne diseaseslike g astyroenteritis, typhoid, cholera,

I tuberculosis, dysentery hookworms, roundworms, pipe worms, tape worms etc.Thepathogens responsible for these diseases

I can be carried by direct contact or bythe edible portion of the drop, or byplant root systems whose cell wall barriers‘ these pathogens panetrate.l3 Thus, the anae-robic fermentation, if not complete,while producing biogas and manure, canresult in a serious health hazard.

Pomts for Attention

1) There is an urgent need to bringabout technology improvementsin the family-size fixed dome biogasplant for attaching a householdlatrine. The latrine attached tothe family-size hiogas plant maybe so constructed that the waterseal of the latrine seat is 20-30cm above the slurry discharge holeof the outlet tank of the biogasplant and preferably, above thetop of dome as well.

2) The lower end of the sewage pipemay be close to the inlet tank andpreferably 2-5 cm below the upperend of the outlet opening of thegas plant. This portion will be themost suitable for entry Öf hdrnanexcreta to the digester under gravitywhen there is nearly zero gas pressurein the gas plant.

3) To avoid the problem of obnoxioussmell in a latrine it is essentialthat a vent pipe may be providedto a latrine seat. It wil! not onlyavoid the entry of foul smell fromthe sewage pipe under pressureof gas in the gas plant but mayalso help in the downflow of humanexcreta in a pipe which will notgo smoothly from the water sealtrap due to inbuilt pressure of gassesin the pipe.

4) As the amount of water recommendedfor use in latrine with human excre-ment is 2-3 times (approximately,one litre), it may be advisablelko havea latrine seat with 25 mm waterseal trap as compared to 50 mmin a conventional flush latrine.This aspect needs engineering inves-tigation.*

5) Not much data are available corre-lating the residence time and thepercentage inactivation of pathogens

The following design aspects needstandardisation before adoption by masses:

93

• Thiswatersealtrapsmanufacturedby NEERJ andbytheMaharashtraUnit of GandhiSmarakNidhi are 15cm- 20cm Ed


and parasites in human excretaunder anaerobic conditions at differenttemperature ranges in 13°C-23°C,which is the temperature prevailingin the digesters of this region.Only limited data are availableat 35°C or 16°C’6 and then there aregeneral recommendations for diges-tion period of nightsoil when usedwith other wastes for adequatedestruction of pathogens. The periodfor which human excreta shouldremain in active anaerobic conditionsof the digester to have effectivecontrol of pathogens needs to beinvestigated.

Suggested Design of Biogas Plant

Keeping all these points into consi-deration, the detail of 3 m3 fixed-domelatrine-connected biogas plant is shownin Figure 1. It has a nightsoil chambercreated by the construction of a wallin its digester. Assuming that this chamberwill never be uniformily filled with humanexcrernent, its volume is proposed to

be nearly 1.5 times the total volumeof 90 days’ accumulated excrement’7 from5-6 persons diluted to 3 times with water.The height of the chainber wall shouldbe such that its corner touches the domebut its central part is about 10 cm lowerthan the dome. This chamber will notallow the light nightsoii to enter themain digester but will allow gases togo to the dome for use. One semi-circu-lar hole of dia 30 cm in this wall isproposed so that the level of the slurryin this chamber remains in equilibriumwith that in the main digester by theslurry’s movement through it duringvariable conditions of gas pressure inthe gas plant. To minimize the t low ofheavy nightsoil from this chamber to

1 the main digester, this hole is placednearly diagonaily to the sewage pipehole and nearly 15 cm above the floorSO that the movement of the heavy night-soli which goes to the floor is slightlyrestricted. The detail front view of thechamber wall is shown in Fig 2a andthe layout of latrine seat vent pipe andsewage pipe in Fig. 2b.

Table 1: Item-wise Cost of Construction of Latrine-attachedFamily-size Cattie—dung-fed Biogas Plant

AC Loose

coller

1.8m AC pipe 10 cm

2

1

25 145 1

11111111111111

Chamber Construction Latrine FittingsApprox. Item No.Cost.-Rs.

Approx.Cost.-Rs.

Item No.

Bricks 150 100 IWC (Chips) 1 100

Cement

Sand

1 bag

0.2 m3

60

20

AC P Trap

AC doorjunction

1

1

15

20 1Labour 70 AC Reducer

(100/50)1 15

AC Cowl 10 cm 1 15

94

fl5 115—‘ ~—1Zi~ ‘~—

T—XI

FIG 1. HPKVV 3m3 FAMILY SIZE CATTLEDUNG FED BIOGAS -PLANT WITHATTACHED LATRINE’

- 95

L-S~.ç11oHAT XX1

-.•t,,.125

S ~ .-

UP TOFR0~1AND 10 CMS. LESSFROM TH~CENTRAL PART

111111111

REDUCE.R 111

AC B~wD

AC SEWAGE PIPETO GAS PLANT

loo ~

ti) b)

FIG 2. a FRONT VIEW OF THE CHAMBER WALL.

b. LATR1NE SEAT, VENT P~PEAND SEWAGEPIPE ARRANGEMENT.

96

AC VENT PIPE5ocP

1704

111111111


Chamber Construction Latrine FittingsItem

AC Vent5 cm

pipe

No.

2

Approx.Cost.-Rs.

65

item No. Approx.Cost.-Rs.

250 300

Grand Total: 250+ 300 = 550/-

Item-wise estimate of cost requiredfor construction of nightsoil chambersuitable for 3 m3 family-size fixed-domebiogas plant and latrine assembly (exclu-ding the construction cost of latrinestructure) is given in Table 1, whichsuggestes that small additional cost ofRs. 550/- only on this plant will notonly provide a satisfactory sanitary latrinebut also produce 90 litres more biogasper day, apart from adding to the manurialcontents to the slurry from this gasplant.

Acknowledgement

The author is grateful to Dr. G.Dev, Director of Research,, H.P. KrishiVishva Vidyalaya, Palampur for his constantencouragement for research in this t ieldand for his valuable suggestions in preparingthis manuscript. Financial support providedby the ICAR under its AICRP on RenewableEnbergy Sources is greatly acknowiedged.

References:

1. Dept. of Non-Conventional EnergySources, Ministry of Energy, Govern-ment of India, Annual I~eports 1983-84, 1984-85, 1985-86.

2. China : recycling of organic wastesin agriculture: FAO Soil Bulletin40, 1977 page 61.

3. Advances in biogas technology Pub-lications and Information Div.,

_4~-_~_~-~I.-i

97

ICAR, New Delhi 1986, page 80.

4. Technology for human welfare andcommunity Services. Technologyfor Rural Development VolumeCSIR New Delhi page 107-110.

5. Gotaas, 1-larold B: Composting:Sanitary Disposal and Reciamationof organic waste. WHO Geneva1956. Page 171-193.

6. Raymond Myles & Ishrat Hussain:Cornmunity Night Soil Janta Biogasplants system for Harijan colonyin Midnapur, West Bengal paprerpresented at Panel meeting on Bio-gas technology, organised by AFPROat Bardoii Gujarat Nov.5-6, 1981.

7. Raymond Myles & A.K. Dhussa:Design and Implementation of aPilot Demonstration CommunityNight Soil Biogas scheme. Paperpresented at XXI ISAE Conventionheld at IARI, New Delhi April 4-7,1984.

8. Chawla, O.P. Fuel and Fertilizerfrom Night 50fl Indian Fmg. 29(12), 3-8, 1980.

9. Noble E. and Noble G. 1971. Parasi-tology 3rd ed. Philadelphia, Leaand Febiger.

10. Craig, C.F. and Faust, E.C. 1970.Clin ical Parasitology Philadelphia,Lea and Febiger

- - - - -


1

11. Kalia, Anjan K. Comparative studyof drumless and conventional plantsfor production of Biogas WaterHyacinth as source. Indian ChemicalEngineering 25 (1), 22-27, 1983.

12. Kalia, Anjan K. Annual Reportof ICAR, AICRP on RenewabieEnergy Sources for April and Agro-based Industries for Palampur centrepresented at 3rd Annual Workshop,of project held at TNAU, Coimba-tore, Feb. 1-2, 1986.

13. Rudolfs, W. Falk L.L.: and Rototzkie,R.A. Bacterial and Viral diseases.Sewage and Industrial wastes 22(10)1261-1281, 1980.

14. Bohra, C.P.: Annual Report of ICAR,AICRP on Renewable Sources (Energy)for Agril. and Agro-based Industriesfor CIAE, Bhopal presented at 3rd

Annual Workshop of Projectat TNAU, Coimbatore Feb1986.

15. Bertucci, 3. Lue-Hing C. Zenz,D. & Sechta 5.3. Inactivation ofViruses during anaerobic sludgedigestion. Jr. of the water PoliutionControl Federation 49 (7): 1642-51,1977.

16. Michael, G. Mc-Gorry and J.K.Stainforth: Compost Fert. and Biogasproduction from human and farmwastes in Peoples Republic of ChinaIDRC, Ottawa, Canada Publication.

17. Patnaik, B.R. Rajagopal, G., Kulkarni,D.N. and Dave, 3.N. Anaerobicdigestion of Night Soil seasonalvariation in the volatile matterreduction and gas prod. Envir Hlth7, 202-7.

Abstract

IMPROVED LINKAGE OF LATRINE COMPLEXTO COMMUNITY BIOGAS DIGESTER

SK Vyas

Recently the Governmentof India is laying great emphasis on Cornmtlnity Biogasprogramme. Along with the sanctionof Co~nunityBiogas complex,funds are also providedfor constructionof public latrines complexto serve three purposes.

1. To provide facilities for the poor section of society to avail of such facilities.

2. To increasebiogasproduction.

3. To improve the hygenic conditionsin the rural India.

The present systern of linking latrine complex to the digesters needs a lot ofimprovement for effective mixing of effluent from latrine complex, to avoid chokingand for better fermentation.

PunjabAgricultural University,Ludhiana

98

1

1

11

held1-2,

1

11111111

111

111

MALAPRABHA LATRINE BIOGAS PLANTA new innovativedesignfor utlizationof biogas

from latrine

SVMapuskar* -

Introduction

he author has innovated a systerr~for recovering biogas from “latrine plants”at a cost which is slightly higher thanthe cqnventional aqua privy latrinesof the same capacity. It is claimed thatthe plants built on this model have beenfunctioning satisfactorily since 1981.The plant comprises of three rectangularcompart ments. The physical featuresof these chambers and their functionsare given in the paper.

In both the pit privy and aquaprivy types of latrines, the gases generatedin the process of digestion of nightsoilare considered a nuisance and arrangementsare made to remove these via a ventpipe placed as high as possible. In caseof pit privy the gases contain mainlycarbon dioxide which is not very useful.In case of aqua privy, this socalled “nui-sance gas” is nothing but biogas.

Can this gas be trapped and usedas a fuel by planning some innovativedesign for latrine? Can this gas supplementthe fuel requirements of the t amily?With a view to providing an an5wer,this author thought of developing anappropriate design which would act asa bio-gas plant. Design of such a biogasplant as would have all the necessaryfeatures of a latrine was found feasiblein 1981.

New design for recovering biogas fromlatrrne

A biogas plant working on nightsoil

feed could be constructed in a very conven-

* Jyo(shaArogyaParbodhan,Dehu,Dist Poona

uonal manner. The latrine biogas plantsconstructed on the basis of this author’sdesign are functioning very satisfactorilyin and around Dehu in Pune Districtof Maharashtra for the last five years.The plant has been aptly termed ‘MAIM-PRABHA’ latrine biogas plant.

The land requirement for ‘Malaprabha’latrine plant is the same as for aquaprivy latrine. The additional design featuresincorporated in the construction of ‘Maia-prabha’ plant involve a small additionalcost over and above the estimated costfor aqua privy latrine of the same capacity.The additional cost is easily offset bythe saving in the cost of conventionalfuel.

Salient Features of the Design

The plant comprises three rectangu-lar compartments. Latrine superstructureis superimposed on first compartment.

nents:It consists of the following compo-

(i) Latrine seat and superstructure;(ii) iniet drop pipe; (iii) digestion andgas storage chamber; (iv) biogas outletpipe; (v) displacement window; (vi) dis-placement chamber; (vi) outlet chamber;(viii) siurry outlet pipe.

Latrine seat and superstructureare superimposed on the first chamberwhich is a digestion-cum-gas storagechamber. From the latrine pan an inletdrop pipe starts. This pipe is of rigidPVC. Its one end is embedded in theR.C.C. slab of the roof of the digestion

99


1

chamber. Its other end projects for about600 mm in the chamber. A zigzag PVCpipe fitting is saddled on to the inletpipe which is projecting in the digestionchamber. This fitting acts as a scumbreak-ing device. The digestion chamber isthe bigger of the three chambers. Itsroof consists of R.C.C. slab on top ofwhich the latrine is placed. The plasterof the wails and roof of this chamberis made leakproof against gas and vapourby multiple layers of cement-lime-mortarplaster. The chamber walls and the roofare painted with bituminous emulsionpaint.

The wall which separates this chamberfrom the second and the third chamber,has approx. 2 t t. x 2 t t. opening nearthe floor. This is a displacement windowwhich connects the digestion chamberwith the second chamber termed displa-cement chamber. Displacement chamberis connected to the third chamber calledoutlet chamber via a chamber interconnec-ting pipe. Slurry outlet pipe is placedat the upper edge of the outiet chamber(Refer to drawings).

Working of the Plant

From the latrine pan, the nightsoilenters the digestion chamber from inletpipe. It starts fermenting in digestionchamber, where anaerobic conditionsare present. As the digestion proceeds,the biogas is produced and moves towardsthe roof. It cannot escape through theiniet because the inlet pipe dips in thedigestion chamber slurry to the extentof 600 mm. The biogas thus gets accumu-lated in the top portion of the digestionchamber. As the gas increases, it startspushing the slurry downwards. Due tothe pressure, the slurry moves to thedisplacement chamber through the displace-ment window. As this slurry moves tothe displacement chamber, the fluidfrom displacement chamber moves tothe outlet chamber via the chamberinterconnection. From the outlet chamber

the excess fluid moves out through theoutlet as an effluent. During this processthe gas in the gas store is under pressureproportionate to the difference betweenthe fluid level in the digestion chamberand that in the displacement and outletchambers. Outlet level is kept at 100mm. above the level of the roof of diges-tion chamber so that the pressure onthe gas can be maintained. The gas whichis stored in gas storage space is let outthrough the gas outlet pipe which isfixed in the roof of the digestion chamber.From the gas outlet, the pipe connectionis led to the burner where the gas isused as and when required. While thegas is being used up, the slurry levelin diges.tion chamber will start risingtill the slurry in all three tanks attainthe same level. As the propulsion pressurefor the gas is provided by the differencein slurry levels in the three charnbers,the sizes of chambcts and outlet levelare adjusted in such a way that the propul-sion pressure for the gas will vary withinthe range of 10 cm to 50 cm. Duringthe up and down movement of the slurryin the digestion chamber, the scumbreakerwill keep on cutting the scum automati-cally.

1f for some reason, the gas remainsunused, the slurry level in digestion cham-ber will be pushed down till it reachesthe opening of inlet pipe and the excessgas will pass through inlet pipe and escapethrough the vent pipe attached to theupper end of the inlet pipe. Gases whichwill be liberated in displacement andoutlet chambers will also escape througha separate vent pipe, thus avoiding theodour completely. As the latrine seatis provided with waterseal, the latrinesuperstructure will also be free fromodour.

In the whole process, once the night-soil gets inside the plant via waterseal,it is not at all exposed to the surroundings.Obviously, it will not be visible, norwill it give any faecal pollution or any

1111111111111111

111

100

“MALAPRABHA” LATRINE BIOGAS PLANTSchematic Arrangement of Latrine & Plant Chambers

Explalning the Mode of FunctioningDeveloped by Dr.S.V. Mapuskar

JYOTSNA AROGYA PRABODHAN, DEHU, DIST. PUNE.

~ ,—- ~

.- GAS MO’~~eN’ ~—4. FUJIO ~OV~P.~Sp~r

VENT PIPE

FIJJIP

101

v


smell. Only the fufly digested odourlessand harmless slurry will come Out fromthe outlet. It can then be led to manurepits and from there on to the farm.

Retention Period and Capacity of thePlant

While calculating the total volumeof the plant and the digester chamber,it is presumed that the amount of waterentering the plant will be about 2 litresper user. Further, it is planned that about25 user will use one latrine seat. Thevolume of the digester is planned in such away that faeces of 25 users per day willhave a retention period of 40 days inthe plant. From- 25 users roughly onecu m of biogas would be available. Thus,the standard, which emerges, is to haveone latrine seat per 25 users to get 1cu m biogas per day with plant retentionperiod of 40 days. The dimensions forthe chambers are decided on this basis.The dimensions and the volume also tallywith the requirements scheduled foraqua privy latrines for the same numberof users.

Suitability as regards basic requirementsfor nightsoil based biogas plants

As has been already discussed,(i) the maintenance of the plant canbe easily done by the owner; (ii) nightsoilcarriage is not involved; (iii) nightsoil

is not exposed to surroundings: therefore,insects and animals cannot have accessto faeces; (iv) aesthetically, it is cleanand odourless; (v) due to retention periodof 40 to 45 days, the effluent is virtuallypathogen free.

Additional capital cost and the benefits 1received

As can. be seen from the design,additional expenditure involved overand above the cost for aqua privy latrineis very marginal, Rs. 1,000/- or so, whichis necessary for providing inlet pipe,gas outlet, scum breaker and a gas proofplastering for the first chamber. Thismarginally additional cost is recoveredthrough augmentation in fuel supply forthe family.

Conclusion

‘Malaprabha’ latrine biogas plantis a new innovative design developedfor recovering biogas from anaerobicallydigested nightsoil. Latrine is integratedwith biogas plant. Nightsoil is fed directlytrom the latrine seat to the plant. itsdesign features and mode of functioningare very convenient. The plant has provedto be very hygienic, harmless and veryeasy to maintain. Such plants are func-tioning very satisfactorily for the lastf ive years. The design thus is very promi-sing. 1

1111111

1111

111111111

102

111111

TREATMENT OF SLURRY AND ITS USE

-:~~-~ -

Abstract

MANURE FROM ANAEROBIC TREATMENTOF HUMAN WASTE

AC. Gaur~— K C. Kbandelal

The slurry from anaerobic digestion is a valuable organic manure which improvessoil fertility and increases agricultural production. The chernical cornposition of faecesand urine is such as contains almost all nutrients including trace elementsneededby the

plants. Urine has evenhigher nitrogen and potassiurncontent than the faeces.

Biogas plant slurry is richer in ammoniacal form of nitrogen than the solid organicrnanure produced aerobically.Therefore,this slurry could be applied on land and ploughedin immediatelyor it could be cornposted with soiid crop residues,farm wastes,city organic

U wastes etc.Mixing of phosphatesduring cornposting reduces ammonia losses. About 50%of the phosphorous content in the slurry is in the forrn which plants can early take up.

Pathogenic enteric bacteria get killed if the actual retention time in the digesteris 14 days at 35°C.The die-off rate of even the enteric viruses is 22% at this level ofternperatureand retention time. There is no cost-effectivernethod which can matchanaero-

bic digestion in the destruction of disease-producingorganisrns. Cornposting can kili rnostof the remainingpathogens.

The paper gives sorne data from China and the Phillipines on crop responsesto organicrnanures because systematicstudies in India on crop responses to organic manure have

made. The paper points to certain fields where R&D efforts are of prime irnpor-not beentance.

Introduction - Ed.

Human waste has been used iradi-tionally as manure after compostingwith other organic materials, such astown refuse, cattle waste etc.Nightsoilcontains relatively higher amounts ofplant nutrients, particularly N, P andK than cattie dung. Chinese and Japanesefarmers had maintained the productivityof their soils, mainly by extensive useof human excreta as manure. It is~recog-nized that if it is properly collectedand processed, it can be hygenicallysafe for land application. Human wasteis of economic importance as sourceof plant nutrients.

is achieved cost-effectively by the processof anaerobic digestion. The waste matteris recycled as manure for agriculturalfields. The Government of India hastaken up recently a programme of linkingof biogas plants with sanitary latrines.In the State of Gujarat and Mahara~itra,many beneficiaries have already optedfor biogas plants based on human wâstealone or mixture of human and cattlewaste. The spent slurry after some moretreatment is recommended for use asmanure.

Biogas Slurry as Valuable Manure

The use of spent slurry as manuareheips in its sanitary disposal with simul-Sanitary disposal of human waste

. I1ead,Dlvislo~of Microblology, IARI, New Delhi • • Principal, ScientificOfficer, D.N ES,New Delhi

105


1

taneously achieving the recycling ofmaterials as ~own in Fig.1.

[CR0PJ(

FOOD

[Straw J - HUMAN Spent Slurry J

Excreta

> Biogas Digestor

Fig. 1: Cyclic usages of organic materialsbuilt around biogas system foragricultural production.

It increases the ~ipply of organicmanure for improving ~il-fertility andincreasing agricul tural produc tion.

Quantity:

Human waste contains almost allplant nutrients including trace elementsThe daily per capita excretion of faecalmaterials (faeces and urine) is dependentupon many factors4viz., age of the person,diet, state of heaith, cimate etc.

The average faecal weight variesfrom 100 to 500 gm per capita per day.The quantity of urine varies from 1.0to 1.3 kg per capita per day. These figuresdepending on the population can helpin selecting an adequate size of biogasplant. It is, however, advisable to studythe availability of human w~ste in a

1given community before planning a biogas 1system.

Chemical Composition 1Average chemical composition of

nightsoil and urine is given in Table 1.

Table 1: Chemical composition of faeces 1Item Faeces Urine

Moisture (%) 70-85 93-96

Organic matter

(% dry wt.) 88-87 65-85Nitrogen (%) 5-7

(%) 3-5.4

K20 (%) 1-2.5 3-4.5

CaO (%) 4.5

An estimation of manurial valueof faeces and urine of human beingsshowed that 2.10 grams N, 1.64 gramsof P~O5and 0.73 grams K20 per personper d’ây was excreted and the correspondingvalues for urine were 12.1, 1.8 and 2.2per person per day.

Biogas digestion system avoidsthe loss of ammonia and hence slurryis richer in nitrogen content than solidorganic manure s produced aerobically.However, ammoniacal nitrogen is lostif the spent-slurry is sundried. Therefore,either slurry could directly be used forland application without drying whichwould provide both plant nutrients andwater or it could be used for compostingwith either solid crop residues, farmand city organic wastes or already humi-fied compsot for maturity before iransferto fields. During composting, it could

and urine.

15-19

2.5-5

4.5-6

1111111111111111

106


The organic acid~ present in slurryhelp in greater availability of phosphateand potash, to crop plants. About 50per cent of the total phosphorus contentin slurry is in available form.

Uses

It can be used either after dilutionwith water for manuring of fodder andcereal crops or directly applied to landand mixed. It is also used for manuringof fish ponds.

Improvement in Method Needed

Although the commonly used methodof drying of spent-slurry on simple sandbeds helps in the elimination of pathogensto some extent, the process leads toloss of ammoniacal and nitrate nitrogenthrough volatilization, deni trif ica tionand leaching. There is a need to improvethe method of slurry treatmert and tofind out the best form for its applicationto avoid losses of nutrients and harness

the maximum benefit of the product.

The spent slurry can be used forhastening the composting of refuse andfarm wastes. Thus the composting periodand losses are reduced. As soon as theC/N ratio of compost-spent slurry isreached around 20:1, its application toland is recommended because minerali-zation of plant nutrient starts at thisrange and heterotrophic activity is~ippor ted by chemoauto-trophic activity.

Public I-Iealth Aspects

With regard to public health aspectsduring handling of spent slurry, divergentviews have been expressed. Plate countsfor micro-organisms of the manuresand human excreta samples showed thepresence ~ in highest number of bacteria(38 x 10 ) in nightsoil. Some were patho-genic while some were non-pathogenicand normal commensals of gastro-intes-.tinal tract (Table 3.Next page).

It has, however, been demonstratedthat pathogenic enteric bacteria areeffectively killed ii the digestion timeis at least 14 days at a temperatureof 35°C. It also results in the dieoffof enteric viruses upto 22%. NEER! hasreported 66 to 90% removal of ascarisand hookworm but spent slurry stillcontains viable helminth eggs. Neverthe-less, there is hardly any other betterand cost-effective method of treatinghuman excreta th-at can reduce the burden

(SeeTable 3 an next page.)

be mixed with phosphatic fertilizersto reduce ammoniacal lösses.*

The composition of spent slurryfrom nightsoil biogas plants is given in Table2. During the process of rapid compos-

ting (aerobic in nature), the temperatureTable 2: Composition of spent slurry in the compost pits ot heaps rises above

from nightsoil biogas plant. 60°C up to 65°C or more which causesdeath of almost all kinds of pathogens

Item Percent on dry in a short period of a few hours to days.weight basis This also helps in increasing the quantity

of manure and thus allowing recyclingNitron 3.0 - 5.0 of more quantity of organic materials

in soils.2.5 - 4.4

K20 0.7 - 1.9

• Evenif rockphosphateis added,theorganicacidsin theslurrywill solubiHseIt It mayalsohenotedin thisconnecnonthatphosphatesolubilisingculture is availablenotonly from theUSSRbut alsofrom theMicrobiology of IARI, now headby Dr Gaur,theauthorof this paper Ed

107

BIOGAS FROM HUMANWASTE

1

Table 3

5 t/ha manure

Organisms isolated from farm manures and pre-digested nightsoil

5 t/ha manure + 60N+80(P205)

+ 100 (K2O)

5 t/ha manure~- 30+40+50

10 t/ha manure

108

2.37

3.95

3.63

2.79

3.13 1.93

4.33 4.09

3.77 3.44

3.39 4.70

1111111111111111

1

11

SampleBacteria

GroupFungi Others

Nightsoil Escherichia coli Rhizopus AscarisProteus vulgaris Penicilliu m lubricoidesCitrobacter Aspergillus (eggs)Aerobacter aerogenesPseudomonas aeroginosaStaphylococcusaureusSalmonellaParatyphi

Farm manures Escherichia coli Rhizopus Actinomycetes(poultry and Citrobacter Penicilliumcattle dung) Aerobacter Aspergillus

aerogenes MucorPseudomonas PilobolusBacillus

of pathogen, than anaerobic digestion. Central Luzon State University, the Philli-However, there is further scope to reduce pines, the highest yield of string beansthe pathogens by composting the slurry was obtained when the crop was manuredwith solid compostable materials. with nightsoil and the yield was further

increased when the full dose of fertilizerRe~onseof Crops was added. 1-lowever the difference was

not much (Table 4).In an experiment conducted at

Table 4: Yield of string bean when treated with orgarnc manures and fertilizers

—Treatment Yield of string bean ~jSg.J~i3 x 5 m. area plotCompost Nightsoil Pigdung

1

1


Field Experiments conducted in Chinashowed that use of spent slurry fromanerobic digestion of human waste, pigwaste and rice straw, had increased theyield of maize by 28%, rice by 10%,cotton by 24.7% and winter wheat by12.4%.

Systematic experimentations onthis aspect are yet to be carried outin India.

R & D Programme

For efficient recyclying of humanwastes as manure, R &D efforts areneeded in the following areas

a) On survival of pathogens and remedialmeasures.

b) For linking slurry treatment withcomposting to obtaining organo-mineral-biofer tilizer for efficientrecycling of night soil.

c) Mechanical devices for collectionof human waste and disposal ofspent slurry.

d ) Field trials on the use of differentforms of spent slurry as manure.

e) Effect of spent slurry on physico-chemical and microbiological proper-ties of soils.

References

1. Gaur, A.C.Neelakantan, S and Dargan,K.S. (1984) Organic manures, I.C.A.R.,New Delhi.

2. Khandelwal, K.C. (1982). NightSoil biogas system. Proceeding ofthe Workshop on Rural Sanitation.Institute of Social Studies Trust,New Delhi.

3. Utilisation of organic manure, ProjectField Demonstration No.17, F.A.O./UNDP Regional Project RASI75/004.

4. Subramanian, P.V.R.(1977).Digestionon Night Soil and Aspects of PublicHeal-th. Workshop on Biogas System.Feb. 28 - March 4, 1977, MDI,New Delhi.

-~:~

109

—Treatment Yield of string bean In Kg in3 x 5 m. area plot

PigdungCompost Nightsoil

10 t/ha manure + 60+80+100 3.65 3.84 3.53

10 t/na manure + 30+40+50 2.77 3.86 3.46

Ali~tract

This paper presentsan overview of the methods presently in vogue for the handlingof slurry; its diverse uses as a supplement to and replacementfor farmyard manure andchemical fertilizer; as an additive to Livestock feed and the economic advantage tobe derived from suchusage.

Research and Development in thefield of biogas technology has been largelyconfined to the areas of biogas generationsystem. Little attention has been paidto optimising the use of effluent inspiteof the fact that a plant is economicallynon-viable unless the benefits to be derivedfrom effluent use have been computed.It is also recognised that the major partof nitrogen fed into the digester is conser-ved during the digestion process.

The composition of the slurry obtainedfrom biogas plants depends upon thecompa-sition of raw materials fed intothe digesters. Normally 30-50% of theorganic matter fed in is decomposedin the biogas plants. Therefore, the slurrycontains about 50-70% of the organicmatter fed to the digester. This organicmatter is not further putrefiable. Hencethis reduces the problems of smeil andinsect development.

The constituent that is most importantfrom the point of view of soil nutrientis also conserved by anaerobic fermen-tation. Practically all the nitrogen presentin the raw material in organic or ammoniacnitrogen forrns, is retained in the digestedslurry. Results of a typical experimenton bench scale biogas plants using cattie

110

dung as the raw material are given inTable 1, which show that nearly 99%of the total nitrogen content is retainedin the effluent slurry. These r~sults alsoshow that 17% of the total original nitro-gen is available in ammonia form afterdigestion as against only 5.5% in theinput material.2 This however, dependsupon the total nitrogen in the materiali.e. the more the nitrogen content, thehigher is the ammonia fraction afterdigestiGn. In case of anaerobic digestionof rice straw the ammonia concentrationin the effluent has been reported tobe only 8-10%.

Improper tr~tment of biogas planteffluent, however~, may result in 10-30%loss of the total nitrogen content. There-fore, for better nitrogen economy, Itimplies that the higher the nitrogen contentof feed materials the greater is the needof proper storage and ~1reatment of eff-luent.

Effluent Treatment

The Biogas Plant effluent is mostlyused as manure but it can also be usedas feed for cattle and fish etc. The effluenthowever, has to be treated one wayor the other bef ore putting it to any

11

BIOGAS PLANT EFFLUENT 1HANDLING AND UTILISATION

AnilDhussa 111

Iniroduc tion

-Ed. 111111111111111

BIOGASFROMHUMANWASTE

use. Following are a few ways of treatingthe effluent.

1. Sun drying

2. Compost making

3. Filtration

4. Solid separation by centrifuge.

Sun Drying

Sun drying is practised in a largenumber of cases despite the fact thatalmost all the nitrogen present in theammonia form gets volatilized II exposedto sun. Since the slurry coming out ofthe Biogas Plants has over 90% moisture,and application of liquid manure is notalways feasible, it may have to be driedin sun. 1-lowever, if the purpose of dryingis ;only storage of slurry which can rarelybe used continuously, then, in order tominimize the loss of ammonia nitrogen,it should be stored in deep lagoons ortanks that present a minimum of surfacearea for ammonia volatilization.

Compost Making

Compost making is the most widelypracticed and recommended way of slurrytreatment. It is covered with farm wastesand other household wastes. This protectsit from exposure to sun and the presenceof slurry aids in quicker composting ofother wastes. The net result is conserva-tion of nitrogen, faster drying of slurryand recycling of other organic wastesto land.

Filtration

Problem of storage of slurry is of tenencountered for large scale operations.As has been stated earlier the BiogasPlant effluents contain over 90% moisture.Nitrogen loss as a result of sun dryingcan be prevénted if the moisture, isreduced by filiration. Since the materials

to be handled by a filtering device wouldbe too large and the material usuallyis fibrous, the filtration surf ace arearequired would also be too large. Thisis one constraint and it makes the systemtoo expensive.

Filtration by employing sand, stonesand leaf has been tried at few placesbut it’s practicability is yet to be establis—hed.

Cenirifugation

1f the solid separation for high nitrogencontent materials is required to be done,the sun drying and also filtration- whichis a slow process-can not be employed,nitrogen rich biogas plant effluent canbe used for suppiementing cattie feed1f the moisture is removed without losingits nutritive value. Centrifuge can beemployed for solid separation in suchcases.

Utilization of Biogas Plant Effluent

The biogas plant effluent is commonlyidentified to be of use only’ as manurewhich undoubtedly is the major use butit can also be used as feed for livestockfairly effectively.3 While the mineralfertilizers are effective inputs for increa-sing immediate crop production, theorganic manure plays a very significantrole in improving the soil and also forreplacing a part of the highly energy-intensive chemical fer til izer.4 Followingare the outcomes of a few experimentsconducted on the application of biogasplant effluent for the production of variou-~crops and for rearing livestocks (pigse tc.).

Compari9n of effect of Biogas PlantEffluent and Farm Yard Manure

Fixed quantitles of effluent and FYMwere applied for cultivation of differentcrops for comparing the effect of thesemanures. The result are given in Table

111


1

11. Though the effluent application gavehigher output in case of all the cropsthe difference in case of wheat and cottonwas maximum.

U~of Biogas Plant Effluent for CucumberProduc tion.

Varying quantities of biogas planteffluent and the recommended quantitiesof NPK fertilizer were applied on a fixedarea for comparing their effect on theyield of cucumber. It is observed thatthe total yield per plot is more in caseof 15 ton/ha slurry application than forthe recommended quantity of fertilizers.(ref er Table III).

U~ of Biogas Effluent witti or wilhoutFer tibzer for Tomato Production

Varying quantities of effluent withand without fertilizer were applied fortomato cultivation to compare theireffect on yield vis-a-vis yield by applica-tion of only recommended quantity offertilizer Yield for all levels of slurryapplication were much less than thecontrol.

When applied with half the recommen-ded quantity of fertilizer gave betteryields but stili less than that obtainedfrom application of full dose of fertilizer.Yields are given in table IV.

Effection on Biogas Effluent Utilizationon the Yield of Mungbean

The table V gives yields of mungbeanobtained from application of variouslevels of effluent alone and with halfthe recommended quantity of NPK. Thecomparison of these yields with thatobtained from the application of fulldose of NPK shows that the effect oflow level of effluent application is insig-nificant 20 ton/ha slurry with or withoutNPK has given almost same yield inboth cases. It may be conciuded thatthe leguminous crops don’t respond well

to the application of manures.

Use of Biogas Effluent for SunfiowerCul tivation

In case of ainflower, the use of biogasslurry alone or with 60 kg/ha Nitrogengave yields lower than the control (120kg/ha applications). However, 5 ton/haslurry application gave 27% higher yieldsthan the unfertilized plot which indicatedthe potential of biogas plant effluentas organic manure.

Utilization of Biogas Plant Effluent asa Component for Livestock ration

Biogas Plant effluent is commonlyused as manure therefore its use as live-stock ration has not been studied in depth.Following are the results of a few experi-ments on the use of effluent to suppiementthe ration for pigs, goats and chickenwith a view to reduce the cost of livestockration.

For goats, even upto 30% replacementof standard ration gave slight increasein the average daily weight gain comparedto standard ration.

For pigs, the average daily weightgain was a little less than control butthe cost of weight gain was lower forupto 20% slurry use.

For broilers, upto 30% sludge usedid not affect significantly the weightgain and the feed effect. But for layerseven 0.5% replacement of the standardration by sludge was not tolerable: itresulted in poor growth.

References

1. (1977), Methane Generation fromHuman, Animal and AgriculturalWastes, National Academy of Science,p. 48.

2. Idnani, M.A. and Varadarajan, S.

111111111111111111111

112


(1974)”Fuel gas and Manure by Anaero-bic Fermentation of Organic materials”,Technical Bulletin 46, Rev. ed. NewDelhi; Indian Council of AgriculturalResearch.

3. E. Cruz, M. Sambrano, E. Tagarino andD. Villanueva, (1982) Utilization ofBiogas Ration”, Utilisation of OrganicManures, Project Field Document

No. 17 of FAO/UNDP Regional ProjectRAS/75/004.

4. (1982) Clarita P.Aganon, Marilyn Suvaand Romeo Lopez, “Biogas SlurryUtulisation for Crop Production” Utili-sation of Organic Manures, ProjectField Document No. 17 of FAO/UNDPRegional Project RAS/75/004.

Total KjeldahlNitrogen (TKN)

(GM)

In 1.5 kg fresh dung

Nitrogen recovered

In gasses evolved

In digested slurry

Percent of TKN

Nitrogen recovered

after drying

Percent in TKN

0.005 0.005

Source: As given in Reference 2 above)

Yields kg/ FYMplotDige stereffluent

Table - 1: Distribution of Nitrogen in Biogas Generation Process

Nitrogen Input

AmmoniaNitrogen

(GM)

OrganicNitrogen

(GM)

3.805 0.13 3.575

In 500 ml innoculum 0.798 0.126 3.672

4.603 0.256 4.347

4.536 0.797 3.739

Total recovered 4.541 0.802 3.739

(98.7) (17.4) (81.2)

3.731 0.028 3.783

(81.1) (0.006) (80.4)

Table - II: Comparison of effect of Effluent and F”9

Crops

Rice 636.4

Kg. 1 ncrea se%

597.5 38.0 6.5

113

~ ~

Source: As given in Reference 2 above.

Table - III: Comparative Yields of Cucumber for Varying 1Quantities of Effluent vis-a-vis Fertilizer

Treatment Average yield per plot(Kg)

Control A (No manure of fertilizer)

Control B (recommended quantity of NPK)

5 t/ha slurry

10 t/ha slurry

15 t/ha slurry

20 t/ha slurry 6.2

(Source: As given in Reference 4 above)

Table - IV : Effect of Slurry Application on Production

Treatment Yuelds t/ha % increasecontrol

26.12

61.02 133.61

5 t/ha slurry 34.34 31.47

10 t/ha slurry 37.69 44.29

15 t/ha slurry 40.53 55.17

20 t/ha slurry 42.74 63.63

5 t/ha slurry 45-60-30 NPK 47.33 81.20

10 t/ha slurry + 45-60-30 NPK 47.53 81.97

15 t/ha slurry + 45-60-30 NPK 49.12 88.06

20 t/ha slurry + 45-60-30 NPK 54.56 108.88

(Source :As given in Reference 4 above)

114


1

Maize 555.9 510.4 45.5 8.9

Wheat 450 390.5 59.5 15.2

Cotton 154.5 133.5 21.5 15.7 1

3.70

6.78

3.2

4.57

7.36

11111

Control

Fertilizer aa 90-120-60 kg NPK

1111

111


Table -V: Effect of Biogas Slurry with and withouton Mungbean production

Treatment

mineral fertilizer

Computed Yieldkg/ha

% increaseover control

Control

NPK at 30-60-05 t/ha slurry

10 t/ha slurry

15 t/ha slurry

20 t/ha slurry

5 t/ha slurry

10 t/ha slurry

15 t/ha slurry

20 t/ha slurry

NP 15-30

NP 15-30

NP 15-30

NP 15-30

Table -VI : Effect of Biogas Slurry with and without

mineral fertilizer.

Upon production of Sunflo~ier

921.50

756.7 5

780. 38

7 74.38

8 75.25

796.12

820. 50

82 1.25

869.25

22.25

0.25

3.38

2.60

15.95

5.46

8.70

8.80

15.14

Treatment

Control

120 kg/ha N

5 t/ha slurry

10 t/ha slurry

15 t/ha slurry

5 t/ha 60 N

10 t/ha 60 N

15 t/ha 60 N

Computed yield kg/ha

1773.3 3

3233.3 3

24 26.67

2206.67

257 3. 33

2706.67

2226.57

2646.67

(Source: Reference 4 above)

115

764. 77

(Source: Reference 4 above)

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117

STRATEGYFOR PROMOTION AND 1NTEGRATION WITHOTHERDEVELOPMENT PROGRAMMES

é~�~~•~_

to this work.

Introduction

Our experience for last ~vera1

years ~ows that very large capacitynightsoil-based community biogas plantsattached to a block of ~veral latrine

~ats are very difficult to manage. Thecapacity is under-utilized because only

the families in the vicinity. of aich plantuse latrines. Families residing at a distancefrom the plant of ten resort to open defeca-

tion. In comparison, small plants distribu-ted conveniently all over the villagework more efficiently. Maintenance of

family owned plants is decidedly betterthan community-latrine-based plants.It is advantageous to convince the owner

thathe stands to gain if he allows neigh-

bouring families to use the latrine byrealizing no minal maintenance costsfrom them.

Encouragemënt for joining latrmneto the cowdung based biogas plant isalso essential. It should form a partof generali campaign for Lmproving socialacceptance of biogas from nightsoil.

-Ed~

Strategy for Improving- Social Acceptarice

Social non-acceptance or reluctantacceptance of biogas from human wasteis a major stumbling block in the promotionof nightsoil based biogas plant. Plannedefforts for mass education will be necessaryto remove the inhibitions. In educationalprogramme, stress must be given onthe facts that (i) biogas from nightsoilis identical with biogas from cattledung;(ii) it is harmless and is not dirty andunhygienic; (iii) nightsoil treatment inbiogas plant will avoid pollution in thevillage and in drinking water, keep thevillage clean and will be conducive tohealth; (iv) it will produce very highquality manure; (v) dirty scavenging workwill be avoided. Various mass educationmedia and audio-visual aids should beused for the purpose.

Establishing demonstration nightsoilbased biogas plants in every village,either individually or institutionally owned,

* MaharashtraGandhiSmarakNidhi, Pune

121

NIGHTSOIL BASED BIOGAS PLANT - -

STRATEGY FOR PROMOTION AND INTEGRATIONWITH DFJVELOPMENT PROJECTS -

FIN Todankar -

Abstrzct -

Community biogas plants should be distributed all over the village, it should notbe only one plant for the entire village. Joining latrines to cattledung-basedbiogas plants

is essential. Mass education ort the multi-faceted benefits of biogas plants, e~tablishingdemonstrationplants in every village, proving the relatednessof biogas plant to every

kind of welfare and developmentalwork, coordination with the efforts of voluntary organi-sations etc. should be the constituentsof the promotional strategy. The idec~that biogasplants are suitable for only the owners of sufficient numberof cattleheadsshould be given

up. At present institutional biogqs plants below 40 cu.m. do not get grants or subsidy;this should be revised. Hostels, hosp~tals,hotels, shouldbe encouragedto run biogasplants.Primary health centres, municipal offices could have demortstrationplants attached. Masons

constructing dung-basedgas plants be given training for ntghtsoil plants. Voluntary agencies-need to be approached for orienting the village and block-level governmentemployees

~-~L~—~-~ ~-.~-~-‘---~--- ‘°-;-~~.- ~--

BIOGAS FROMHUMAN WASTE

will be very useful for convincing theviliagers that these plants are harmless,beneficial and convenient. These demonstra-tions will accelerate the process of accep-tance. It is feit that public latrines shouldnot be used for this purpose as theirmaintenance is likely to be poor andmight defeat the purpose.

Planning the Programme for Implementation

A planned coordination betweenthe ex isting development programmesand the efforts of voluntary agenciesactive in the field can lead to a significantthrust to the programme for biogas fromhuman wastes.

At present in National Biogas Deve-lopment Programme (NBDP) while judgingthe feasibility of biogas plant, cattieheadsare considered a must. This needs tobe revised. Plant should be consideredfeasible if adequate number of latrineusers are available. NABARD also maybe advised accordingly. This will alsosoive the problem about loans, subsidyand rate of interest for nightsoil-basedbiogas plant financing.

At present institutional biogas plantsbelow 40 Cu.m. capacity do not get grantsor aibsidy. In case of nightsoii basedbiogas piants, this condition of minimumcapacity should be waived and financialassistance may be given irrespectiveof capacity.

A programme for conversion ofdry latrmnes into sanitary latrines is inprogre ss. Wherever fea sibie nightsoilbased biogas plants could be incorporatedin this conversion programme. Hostels,hospitals, hotels etc. should be encouraged~ construct biogas plants. Primary healthcentres, municipalities etc. could ~rveas good sites for demonstration plants.Government could actively consider suchsites under its control for the construc-tion of such plants.

In municipal or corporation areas,

122

gas plant construction should be permittedand actively encouraged. Even wheresewerage system exists, if biogas plant~are interposed near the building, thebad on municipai sewerage will be reduced.

New township development authoritiesapprove only aqua privy or septic tanklatrines. They do not allow biogas plants.They may be advised to allow constructionof nightsoil based biogas plants.

The construction know-how is atpresent available with many voluntaryagencies. Their assistance in implementa-tttn activities will be a valuable asset.

Developing Manpower and OrganizationalJnfrasiruc ture

Govern mental infrastructure alreadyexists in the form of village-level andblock-level staff for community develop-ment. What will be required is an orienta-tion of this staff.Voluntary agenciesat present working in the field can beuseful for this prupose. Their cadre ofdevoted social workers can be utilizedfor imparting the required training.

The masons who are already trainedunder NBDP can be given short trainingparticularly in the designs suitable fornightsoil-based biogas plants. This jobcould be entrusted to the voluntary agen-cie s.

As already mentioned all the involvedmanpower must also be specifically orien-ted towards working for improving socialaccep tance.

Involvement of Zilla Parishads,municipali ties township developmentauthorities also have to be made consciousabout the role which they can play inthe propagation of nightsoil based gasplants.

11111111111111111111

PROMOTIONAL STRATEGY ONBIOGAS PROGRAMMES

NB. Mazumdart~Ya~hzvantSingb *

Abstrnct

The importance of biogas technologyfor the developingeconomiesis wides recog-nized. Due to the decentralised nature of this technology, the extension activitiesare essential. Without a wide coverage,substantialbenef~tscannotbe derived. Obviously,programme implementation should be aimed at removal of promotional constraints -

both technical as well as socio-economic. The following areas would need immediateas well as longterm attention

1. Problem-basedresearch and developmentactivities to solve technical problems,such as optimisation of gas production under different environmental conditions,developmentof cheap and efficient utility systems, innovation in constructionmaterials etc.

2. A detailed survery of the potentialities of using biogas technologyon micro andmacro levelsvis-a-vis the existin~energyusepattern.

3. Cost-benefit analysis of the system, covering the benefits such as sanitation and

fertilizer, in addition to biogas.

4. Education to generateawarenessamongthe masses.

5. Governmentsupport inthe form of subsidyand incentives,policy formulation regar-ding allocation of building materialssuchas cement,mild steel etc.

6. Training of constructionpersonnelfor developingskilled manpower.

7. Management skills, especially rural managementsystems which can take careof suchfacilities on longterm basis. Biogasplants maybe constructedwith subsidyor grants but they must be maintained properly on day-to-day basis for whicha senseof involvementon the part of the beneficiaries is essential.

8. Setting up centre at block/district levels to render technical/managerial helpas well as procurementof materialsof constructionand utility systems.

9. Integration with other developmentprojects for smoothadoptionof the technology.

10. International cooperationattemptsto identify commonalitiesof approach, exchangeof ideasand expertisedeelopedfor mutual benefit. -

11. Assessingthe feedbackand so on.

This is a challenged with promises of a prosperousfuture instead of the dooms-

day.

• Suiabh Instt ofTechnicalResearch& Des’ Patna •. Sulab insu of Tech Res & Dev,Delhi.

123

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STRATEGY FOR PROMOTION OFBIOGAS PLANTS

FROM HUMAN WASTE IN RURAL AREAS

The need to dispose of human wastesafely in rural areas has been accepted.It remains to identify feasible technolo-gies and strategies to carry out the task.Anaerobic digesters are one of severalmeans by which nightsoil can be treated.They offer a further advantage: in theprocess they provide fuel for cookingor lighting and a relativeby safe manure.

Various Options for Using Human Excretafor Biogas

There are various options availablefor processing human waste in biogasdigester s.

a) Family-size biogas pbants on centper cent human excreta

A one cu.m. plant attached to alatrine used by 25-30 persons ina joint family will be able to meetthe basic lighting needs of aichfamily.

b) Family-size animal-dung-fed plantattached to latrine

A small family with 1 or 2 heads

of cattie or a few small anirnalse.g. goats, pigs, etc., can attachtheir latrine to a biogas digester.This mixed feed based digestershould be able to provide fuel forcooking and Iighting for the entirefamily and also organic manure.

c) Agricultural waste and erop residuebiogas digesters connected to latri-nes.

These plants Will be of the semi-batchtype for composting under anaerobicconditions and are feasibie onlyin rural areas. The size of digesterwill depend upon the average seasonalbiornass available wi-th the farmers.

d) Community biogas plants fed entirely 1with human excret’~a

Such piants can be used for cooking,lighting, pumping of drinking water,or generating electricity etc. forthe community. They faIl into twogroups

i) those nightsoil digesters whichare connected to community

* Head,TechnologyPromotionDepartrnent,AFPRO,N Delhi1

Abstrnct RaymondMyles

Human excreta can be processedin (0 family-sizebiogas pkints either as the exclusivefeed or together with animal dung; (ii) in communitybiogas plants fed wholly by humanwastes. (iii) in famlly-size or community biogas plants together with agricultural wastes,crop wastesetc. The author discussesthe social and institutional constraintsin the promo-tion of nightsoil-based digester and suggests a number of measures to motivate the potentialbeneficiaries and training of construction and maintenancepersonnel. He also pinpointsthe need for guidelines from authoritative bodies in science and technology on certainu.nresolved controversies, particularly regarding (i) the hydraulic retention time (HRT)in the digesterand (ii) the treatmentof digestedslurry to make it safe for use as manure.

Iniroduc tion

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1

11

124

BLOGAS FROMHUMAN WASTE

ii) those digesters that are loadedwith material collected from

Night~il digesler connected with commu-nity lairines

Such plants should be possible inmost villages. The gas can be used forlighting. The village panchayat couldmanage the latrmnes and digester.

Nightsoil digester fed with materialfrom dry lairines

At present, human waste is collectedfrom dry latrines and dumped at a pre-assigned spot. It could instead be fedinto digesters.

AFPRO has designed and built allbut one type of plants. Agricultural wasteand crop residue fed biogas digestersconnected to latrines remain to be buil-t.

Promotion of Nightsoil Digesters andConstraints in their Widespread Usage

Based on the feedback from a fewpilot study-cum-de monstration plantsby AFPRO, some of the problems andConstraints in promotion and acceptanceof nightsoil biogas plants are given below:

i) People have reservations aboutusing gas produced for human waste.

ii) Where rural people do not sharethese inhibitions, the present limi-tation is imposed by the very smallnumber of people vlho actuallyuse enclosed latrines rather thanopen space s.

iii) Technical guidance is not availableat the grass-root level to enablelarge-scale implementation. Afterinstallation, service for the nightsoil-fed digester is also lacking.

iv) Because of certain habits coupledwith. back of proper use, educationand cleaning facilities, the communitylatrines tend to degenerate andbecome very dirty. This keeps peopleaway. This coupled with the factthat people are used to defecatingin open areas tend to reduce- thefeed material. /

v) Under field conditions the pourflush latrines as they exist require1-3 litres of water to flush awaythe material. The water can bemore or less controlled to the requiredquantity in family-size latrine attac-hed to biogas plant, if they areproperly designed and constructed.However, in community latrineattached biogas plant the quantityof water is very difficult to controlwhich results in loo much of dilution

vi) The shortage of water is anotherconstraint on the large-scale adoptionof community nightsoilfed biogas

Strategy for Promotion of Nightsoil Plantin Rural Areas.

Biogas plants linked with familybatrines are becoming increasingly popularin Gujarat and Maharashtra. However,they have yet to gain acceptance inother states of India. AFPRO have cons-tructed a few nightsoilfed biogas digestersand would like to share some thoughtsfor promotion of such plants in ruralareas.

a) There is a wide difference of opinionwith regard to HRT (HyrdaulicRetention Time) for nightsoil plants.R&D institutes must provide definiterecommendations to designers andtechnical service agencies aboutthe optimal size of plant for eff i-cient treatment of human waste.

_~/_ ~

latrine; and

latrines.

of slurry.

plants.

- -~ - - ‘- ~‘,- - - -,

125

‘--~~-~,-~ ~


1

b) Recommendations are also neededwith regard to handling of digestedslurry so that it is rendered safebefore being used as manure.

c) Publicity and education materialis required to promote any programmefor popularising nightsoil plants.

d) Appropriate teaching aids are neededfor all categories of persons whowill promote, manage and use theplants and their effluent.

e) Technical staff needs to be trained.Such staff will include masons,supervisors, construction engineersand extension managers.

f) Potential beneficiaries need tobe motivated. A start may be madeby urging them to use the gas forligh ting.

g) Gas from community biogas plantscould be used for street lightingand for dual-fuel engines for opera-

ting pumps for drinking water.

h) The management of the digesterto ensure its smooth working andthe maintenance of public latrineshas to be worked out thoroughly.These should be managed by commi-ttees rather than lef-t to the whimof an individual.

i) Demonstration plants and batrinesshould be buil-t in different areasand this pilot scheme carefullymonitored. Such a demonstrationproject may provide insights whichwill help in the for mulation ofa nationab policy.

Conclusion

There is immense scope for nightsoil-fed biogas plants in the rural areas ofthis country. One must have patienceto implement such schemes and studythe various socio-economic and cubturalaspects connected with ihem.

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126

111

RECOMMENDATIONS OF THE WORKSHOPSOCIAL ASPECTS

1. Major objective of tuis programme should be the preservation of human dignitand protection of health. Biogas plan-ts preserves human dignity by providingprivacy and ridding the scavenger carrying other people’s excreta.

2. All programmes involving nightsoil disposal through anaerobic digestion be orientedto meet the needs of the community and should form part of a larger nationalgoal.

3. Education, training and propaganda would have to be organised to generate aware-ness of these social and national needs. In all these measures, benefits includinghealth and lessening of women’s drudgery (by providing fuel and fertilizer) mustbe emphasised apart from their economie value. -

4. Identification of target groups which will act as acceptors, users and promotersis riecessary. Special emphasis should be placed on women who suffer the mostfor (i) lack of cooking fuel and (ii) increasing loss of privacy, and who are pri-marily responsible for rearing a new generation.

5. Inhibiting factors, too, need to be identified. Economie status, age, fear of“dirtiness” and caste barrier were identified by the workshop. (Caste barrieris an inhibition to community biogas plants). Women’s propensity to avoid beingseen while entering the toilet is also an inhibitor. In thi5 there is a paradox:those, who suffer the most from the disappearing bushes and jungles and needmore privacy of the latrine, also tend to shy away from the latrines.

6. Persons disbocatecj from traditional carriage and cartage of night\soil must beabsorbed elsewhere so that they do not impede the adoption of nightsoil-fedbiogas plants.

7. User participation in planning and -implementation of biogas plants is the criticalfactor. On this will depend the success or failure of the programme. Womenwho are the main beneficiaries of the system, should be involved in the formulationand implementation of the projects as well as in the dissemination of information.

8. Voluntary agencies must be involved and enabled to play an increasing role inmotivating the people to dispose of nightsoil hygienicaby’ as also aestheticallythrough biogas plants.

9. Children should be educated in the use of toilets. The benefits of toilet-linkedbiogas plants should be inculcated in them through literature suitable for them,with illustration which should be brought out in regional languages.

10. Women’s education programrr~and onsite training should be organised by voluntaryagen~iesto generate awareress and acceptability of those systems.

II. Grants by the Government of India for plants fed wholly or partially by nightsoilshould be on a higher scale than for plants fed by other feed-5tocks. This wouldbe justified becuase nightsoil plants serve health objective much more.

127

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1BIOGAS FROM HUMAN WASTE 1

12. - School textbooks should inciude a chapter on sanitary toilet-linked biogas systems.

HEALTH ASPECTS

1. On site disposal systems for human waste are best suited for this country. ‘Onsite’disposal through anaerobic digestion in a biogas plant is hygienically desirableand is also a very promising system.

2. While designing biogas plant for treatment of human waste, the specific parametersfrom health point of view have to be given primacy over all other considerationssuch as gas production.

3. Raw human waste should not be manually handled.

4. Undigested or se mi-digested nightsoil should not be exposed to surroundings. 1Care must be taken to see that insects or animals do not get access to it.

5. Construction of toilets and feeding mechanism should be so devised that they 1are safe from health point of view and are easy to maintain hygienically andeconomically. 1

6. Pathogen survival time in the effluent slurry should be the primary concern inthe design for the plant. Reports indicate that retention time in the whole systemmight vary from 30 days to 9CJ days depending on the environrnental conditionson the site. The consensus in the workshop is to accept only those designs whichfulfill health parameters i.e. maximum pathogen elimination. 1

7. Field studies are needed on pathogen survival in effluent from biogas plant5.

8. In cost-benefit, the benefits for health should be included as a very important

consideratLon apart from the economic value of biogas plants products. iREPORT OF TEHNICAL SESSION ON DESIGN, RESEARCH AND DEVELOPMENT

1The most important parameter affecting anaerobic treatment of human waste

are organic loading rate, solid concentration value and retention period in the digester.Secondary parameters are: use of water and rate of gas production, non-exposure ofnightsoil to environrnent. These studies form basis of designing a nightsoil-fed biogasplant. 1

Sebection of a design for a nightsoil biogas plant is governed by the criteria:digester efficiency for gas production, cost of construction, and public health aspectsi.e. killing of enteric pathogens, viruses and parasitic eggs. These criteria were discussedat length. There was a consensus among all the participants that public health aspectsshould be the first requirement to be met by anaerobic digestion of nightsoil in a gasplant and subsequent treatment of effluent slurry. While designing biogas plant systemthere should be no compromise on the question of pathogen killing. In this connectionthe hydraulic retention period of nightsoil inside the anaerobic digester came up fre-

quently for discussion. There was a difference of opinion on this aspect. The suggested

1128

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BLOGAS FROM HUMAN WASTE

in-digester retention period varied from 30 days to 70 days. It was feit that the reten-tion period should be fixed for the worst operating conditions. Retention period ofnightsoil in the en-t ire system inside the digester and in the subsequent treatmentsystem is more critical. Retention period inside the anaerobic digester, and the methodand period of subsequent treatment of effluent slurry should be fixed on the basisof site situations. The difference between the designed retention period and the effec-tive retention period is important. Due to phenomenon of short circuiting, the effectiveretention period is of-ten less than the designed retention time. The digester shoulc4be designed to minimise the short circuiting of fresh charge.

Solid concentration in the digester was another topic of discussion. On the basisof labora-tory and pilot plant studies the suggested solid concentration was 3 to 8%.The digester gets sick or tend to fail beyond 8% solid concentr~tion. The fiush volumeof water per capita per use is a critical parameter for deciding solid concentrationin the digester. About 2 litres of flush volume was suggested to ensure 3% solid concen-tration and maximum gas production. This figure led to a discussion on how for Itis possible in practice to control use of flush water to a minimum. General experienceis that due to the use of more than the suggested amount of flush water, the solidconcentration inside the digester is much less than 3%, even below 1%. The designof latrine plan, flushing arrangement and feeding mechanism influence the water use;hence these should be a part of the system design. In designing the feeding mechanism,nightsoil should not be exposed to the surrounding at any stage, nor should manualhandling be albowed. The ques-tion of filtration of fresh charge to increase solid concen-tration in the digestion came up during the discussions but the detailed data were notavailable.

To increase gas production efficiency of a nightsoil biogas plant, concept ofmix feeding was introduced and discussed. Cattie dung and other soft biomas suchas kitchen wastes green weeds, soft agricultural and crop wastes can be added toa nightsoil digester subject to the convenience of the site.

Different design concepts and details of some designs were presented. The designswere basically modifications of KVIC floating gasholder~~design and the Janta fixed-dome design to suit nightsoil as a feed materiai. One design which is a conversionof aqua-privy in-to a biogas plant was also presented and discussed.

RECOMMENDATIONS

1. Design of a nightsoil biogas system should include design of latrine pan, feedingmechanism, digester design inlet, outle-t mechanism as well as subsequent treatmentof effluent slurry.

2. While keeping public health aspec-ts as the first requirement of a nightsoil biogassystern, it is recommended that the benefit-cost ratio be increased by improvinggas production efficiency and optimising manurial value.

3. The existing biogas plants running on nightsoil should be evaluated by competentage ncies to provide feed-back to ongoing design efforts.

129

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1BIOGAS FROM HUMAN WASTE

SLURRY TREATMENT AND ITS USE 1AGRICULTURAL ASPECTS 1

Human waste is an important resource of plant nutrients, in quantity next tocattie waste, (3.2N 0.77 P2 05 0.7K20 4~72). It is estimated that recycling of human -

waste in agriculture can help in adding of about 4.72 million tonnes of NPK to soils.

As spent slurry is rich in nitrogen, its drying leads to losses of nitrogen. Thusthe ulitmate contribution of nitrogen is reduced. Drying is not a desirable method.The other aspect that needs to be examined relates to bad of pathogens and enrichmentof slurry with rock phosphate; super phosphate and preparation of organo-minerai-bioferti-zer was also emphasised. 1

The problems associated with transportation of slurry, its handling and utilisationwas discussed and methods suitable for different situations were suggested. One methodwhich received attention was the addition of 15% ammonia solution at the rate of10” by weight to kil! pathogens, in the spent slurry. The importance of spent slurryin terms of its residual effect on crops was also discussed. 1

The following recommertdations emerged :-

1. An all-India Coordinated Research Project should be launched which should includeall aspects of this system such as

a. the digestion process.

b. designing of the system. 1c. devices & methods for disposal and utilization of spent slurry. 1d. agricultural aspects.

e. health and pollution aspects.

f. social and economic aspects. 1g. removal of H2S from gas.

Studies on survival of pathogens in the digester as well as during applicationof spent slurry in agricultural fields and fish ponds are particularly important.

2. Development of suitable mechanical devices to handle the effluent and thusto avoid its manual handling, should be encouraged.

3. Development of organo-mineral biofertilizer be encouraged.

4. Field trials need to be conducted on the use of different forms of spent slurry 1for manuring agricultural fields and fish ponds.

- 1130

1


5. Effect of spent slurry on physico-micro-biological proper-ties of soils shouldbe studied in depth. (The project may include all other aspects like health andsanitation, socio-economic be nefits and cost).

6. Spent slurry can be used for manuring crops after adequates dilution to bringdown B.O.D. level to 500 mil. It can also be used for composting of other organicwastes.

7. The above rnentioned studies need to be carried outs through selecred— ongoinginstitutions in different agro-climatic areas. Some of the institutions whichshould be involved are NEERI, Safai Vidyalaya, AFPRO, H.P. Krish Viswa Vidya-laya, Palampur, Tamil Nadu Agricultural University Coimbatore, Punjab Agricul-tural University Ludhiana, Thapar Poly-technics, Patiala etc.

STRATEGIES FOR PROMOTION AND INTEGRATION WIT1-I OTHER

DEVELOPMENT PROGRAMMES

The folbowing conciusions and recomrnendation emerged :-

i. There was need for exercising quality design and technical excellence.

ii. Appropriate and technologically fool-proof package should be developed. Needbased package, taking care of various situations and factors (soczo-econom!c,geographical etc.) be developed.

iii. People’s participation and involvement needs to be encouraged at every step-right from planning and implementation to maintenance and evaluation. Emphasisis to be given on social aspects of the programme.

iv. There was a great need for standardization of procedures, and communicationto special official sectors.

v. There should be an open mmd for sharing experiences, learning and technicalcoopertions at various levels and even at appropriate international level.

vi. It is feit that adôption of multi-disciplinary approach in close association withallied departrnents, as health, sanitation, agriculture, forestry, fishing, has tobe evolved for successful implementation of the programrne. Such integrationswill facilitate a package approach.

vii. There is a great need for creating mass awareness on the various aspects ofthe programme through appropriate promotional strategies for publicity withthe use of print media.

The use of print and non-print material, audio visual aids and Öther promotipnalmaterials is necessary as the use of educational media can play a very importantrole.

131

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1BIOGAS FROM HUMAN WASTE

viii. It is necessary to strengthen training programme at various levels ranging fromthe beneficiaries, masons, technical personnel and managers. 1

ix. The need for integration of the programme into the existing IRDP & NREPprogramrnes and the national voluntary socio-economic schemes was emphasised. 1

x. Management skills need to be involved at various levels.

xi. Ratjonal subsidies to be introduced and centres be opened at local level, blocklevel and in district HQs. for training and dissemination of technology. 1

xii. Where gas for cooking was not in de mand it could be used for lighting and farmmachinery. 1Assessment of feed-back and f0110w-up is required. Demonstration through UrjaVillage and Exhibition would help in this dissemination. 1

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132

1

EPILOGUEShailendra Nath Ghosh

A high-ranking Wes-tern scientist - 1 forgot the name - once said: “Mankind maysurvive atom bombs but it will not survive flush toilets”. He was pointing to a fundamentalprocess of Nature - namely, the biogeochemical cycle. Man takes nutrients from the soilthrough the plants; man must return the nutrients to the soil in a manner which benefitsthe soil. 1f this cycle is broken, the very process that preserves natura! ba!ance and supportslife on earth gets disrupted, imperilling not only man’s own existence but all life on earth.

A well-known nuciear physicist of this country once said: “We in India would possiblyhave to go in for gobar gas plants because we do not have enough energy resources”. Hewas only displaying his ignorance of the role of bio-geochemical cycle. Even if we hadoil reserves one hundred times those of Kuwait, we would still need, in our longterm interestof existence, to return nightsoil, animal and plant wastes to the sources that gave us suste-nance. 1f in the process of returning it, we can derive some further benefits such as fuelgas, so much the better.

Wastes recycled in a useful manner are a source of wealth. It is not that we merelyforgo this wealth if we neglect to recycle any of the wastes - human, animal or plant.These untreated wastes do not remain idle: they flow to wrong places, raise garbage heaps,breed flies, choke drains, raise river beds, pollute water, breed mosquitoes, create healthproblems and raise mounting demands for hospital beds. Resources, actual or potential,in the wrong places, are disruptive of life-support systems. Shri Maheshwar Dayal in hisKeynote address to this seminar pointed out that the pathogens from human wastes areresponsible for 80 per cent of the diseases in India. Even if this single source was responsible~or only half of this percentage of diseases, that would have been grave enough. Daya!’sstatement is- corroboration of one form of disruption of the life process consequent onour failure to recycle the wastes sensibly. There are several other deleterious aspects,besides.

Coming back to the question of flush toiiets, Wallace W. Wells in a chaDter “Meaning,Ecology, Design, Ethics” in the book “Solar Architecture” bemoans: “Next to population,the world’s number one problem is water. Half of the water used by the average familygoes for flushing the John”. . About flush toilets, David Del Porto went further. “The flushtoilet causes problems in the following ways: it disrupts the natura! water cycle by consuminglarge quantities of water that are not returned to the areas they came from: it po!lute~the ‘water that is used as a vehicle to transport the excreta; it pollutes the land thatis needed to dispose of the sludge from septic tanks or treatment facilities; It createslarge direct and hidden costs to design, construct and maintain the elaborate system that-extends from pumping fresh water from the ground to monitoring the effluent from a sewageplant; It requires a large amount of energy for construction and operation. These arethe major areas of impact, although there are ripple-effects in-to many other areas, suchas the medical problems for those who drink contaminated water or the rapid depletionof a farmer’s topsoil”.

At the pole opposite the flush toilet-cum-sewerage system is the composting toilet,also known as “humus toilet”, subserving the principle ~,f recycling. Run properly, It minimisesthe spread of pathogens, prevent5 enormous waste of water and construction material,and yields a bonanza in the form of manure. As for cattle dung, its recycling as farroyard

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manure has been traditional practice on global scale. But in recent ~tim’es, in a situationof growing firewood shortage, the dung is being increasingly burnt as fuel. A solution hasbeen found in the processing of dung in an anaerobic digester, which yields rnethane asfuel and slurry as manure. 1

As a device for production of bio-energy and return of nutrients to the soil, thebiogas plant is unique. Biogas plant can take nightsoil feed as well. Yet, the use of biogas 1plants has remained limited to a tiny fraction of the population, and the nightsoil biogasplants are stil! fewer. The number of nightsoil-fed biogas plants, whether on householdlevel or community level, has remained small everywhere, with the sole exception of China. 1

Many par-ticipants in the workshop organised by C~RT feit that this slow progresswas due entirely to the social taboo against nightsoil. But if that had been the only problem,the environmental engineers would not have been divided on the issue of using nightsoilas a feedstock for biogas plants. 1

There is no question that deep seated social prejudices exist against the processingof nightsoil in any form. Smt. Savitri Madan and Dr. D.R. Gupta have, on the basis of theirrich experiences, illustrated the stubborn nature of the problem. But it is also true thatstrong countervailing factors are operating now, illustrations of which were given in Dr.Amulya Chakravorty’s paper. The present writer is deeply convinced that the problem ofprejudice can be very effectively attacked by a new approach. An interesting experienceof a consensus is worth recounting here.

A few years back, in an Inter-University seminar organised by the Departmentof Environmental Science of the University of Rewa (in Madhya Pradesh), it was foundthat the participants were in support of nightsoii fed biogas plants but there was a generalattitude of pessimism about its social acceptability in near future. This impelled the presentwriter to make the following comments: “1 1 md among the participants in this Seminara large number of persons bearing surnames such as Pande and Misra. Let this Department,with its considerable strength of Faculty members and students, start within its campusa can-teen fuelled by nightsoil-based biogas. When the chapatis and pakoras of this canteenare eaten by these topcaste people, news will spread to the villages like wildfire and theage old prejudices will crumbie. My recommendation to the University Grants Commissionwill be that no recognitlon be given to any Department of Ecology of any College or tiniver-sity unless it has constructed nightsoil biogas plants and canteens fed by this gas”.

The participants in the Rewa Seminar all agreed that this could be a potent wayof countering the prejudices. The University authorities, the .University Grants Commission,and the Governments of the States and of the Union would be advised to take this construc-tive approach instead of merely lamenting over people’s prejudices. 1

1CHOICE BETWEEN ALTERNATIVES 1

Point : Counter-Point 1The problem facing nightsoil biogas plants is not merely the social prejudice. There

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are some very genuine problems which are inherent in the very use of nightsoil in aerobic•digester. Technology has not yet produced operationa! guidelines for different climaticregions with -their varying temperature regimens. There have not even been !arge-scaletests of (i) sanitary effectiveness; (ii) agricultural effectiveness; -and (iii) economic effective-ness of human faeces-fed biogas piants and their products, conducted by scientific bodies,the authority of whose finding could be the basis of a consensus. As a result, differentschools take different positions according to their predilections. Those who are inclinedto nightsoil processing in biogas plants keep arguing that whatever the imperfections andthe resulting hazards, the situation will be better than open dëfection. A school at theother end keeps arguing that human faeces-based effluent slurries, not quite free o frompathogens, will, by virtue of fluidity, spread the contamination wider.

The- arguments of the lat-ter school run as follows. Nightsoil’s biogas potential,however great per unit of excreta, is negligible in the total because the per head outputof human faeces in only one-twentieth (or even less) of the cattle’s per head output ofdung. This poten-tial is insignificant in comparison with the total potential of biogas fromcattle and plant wasres. This littie arrtount of methane is -not worth the risks of the faecaleffluent slurry, which would pollute a greater mass than the solid excreta ever could.Sanitary disp-osal of excreta can be achieved by other means such as anaerobic compostingof four to six months’ duration or aerobic composting of four i~o1 ive weeks’ duration.“Composting is recycling enough, so far as nightsoil is concerned. Let us not aspire forgas from nightsoil because the faecal siurry produced in the process is far from safe”.

At the bottom of all these objections is the feeling that at household or villagecommunity level, it is not possible to keep control over the quality of slurry and its subse-quent products.

Let us now see how safe and sound are these alternatives-pit latrines in rural areasand sewerage system in popular cities - proposed by this school.

To take the lat-ter (sewerage system) first.

Dimensionsof the Costsof SewerageSystem: The

Problem of Urban Areas

This system is prohibitively costly. The idea of covering the whole of the urban

area with sewerage is, therefore, foredoomed to failure. Moreover, it hurts at the verybasic principle of recycling. I-ts wastefulness and its perils from the pc~întof view of exis-tence have been discussed earlier. Even in a country like the USA, mafly towns are seeking

to avoid the sewering system. According to a study mentioned in the Proceedings of theAspen Energy Forum (USA), 19 77 the proposed sewering of the town of Groveland (Massa-chusetts) would require a one-time charge of $ 3,E~OO (which would include the hook-up

and plumbing work) in addition to annual tax increases and use-charges totalling $ 285per year for one residence”. It further went on to say that the town of Pepperell (Massa-

- chusetts) which had been using individual septic tank systems, was pressurized 1 or construc-ting a sewer system in order to improve water quality in the area. But~astudy of interceptorsewers and lateral sewer lines divided by the number of houses would be unbearably high:

and when the costs of in-house fixtures and plumbing and the operation and maintenancecosts of the plant etc. are taken into account this would be higher still. Since that wasa tiny town, the estimated cost per home, over a 20-30 year period, came to $ 30,000

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i.e. more than Rs. 3.5 lakhs. In India’s populous towns and under India’s cheaper material-and-labour cost structure even if the per-family construction cost comes to only ten thousandrupees and the cumulative maintenance cost (over twenty years) comes to another tenthousand, these are bound to prove unsustainable. This is the reason why the sewer systemin most cities is breaking up: and the uncovered sewers as also the storm water drainagechannels are being used for open defecation. It is indeed an irony that sewerage systems,which pollute the sources of drinking water for downstream populat!ons, are espoused asa measure for “safe” drinking water in relatively upstream regions.

II, in spite of these high costs of sewering, it has stil! been in vogue in cities, itis because 80-90 per cent of these costs have been paid out, in almost all countries, outof the state and federal revenues. This means, the r~ral populations have been made tocontribute, by way of taxes, to the maintenance of city sewers.

These should give us the perspective that the waterborne excreta disposal systemwill have to 1 ade away even from the urban settings and that “aerobic composting toilets”will have increasingly to come into vogue if biogasa plants fail to make headway incrowded cities. A1r~âdy,aerobic composting systems have been developed for apartmentbuildings in which excreta are moved to large containers in the basement. Swedish andNorwegian authorities did extensive testing of these toilets and found these satisfactoryin terms of sanitation. A number of States in the USA, inciuding Washington, Maine,Massa-chusetts and New Hampshire, too approved of these aerobic composting toilets more thana decade back on the conditiop. that suitable methods of disposal of graywater is developed.Composting by definition, is decomposition without putrefaction. Putrefaction makesit difficult for the soil and the plant to absorb the nutrients contained in the decomposingmaterial. Putrefaction can be stopped by mingling animal (including .human) waste withvegetational waste in the proportions ordained by Nature. As Sir Albert Howard usedto say, “Animal and Vegetables must be mixed in correct proportions in their death, asin their life, processes”. It is, therefore, heartening that the concept of connecting achu-te to dispose of the kitchen waste into the basement composting toilet has meanwhilebeen developed. This will add to humus building material, prevent putrefaction and enrichthe quality of the compost. 1

For every-thing there have to be safeguards and precautionary measures. Aerobiccomposting toilets, too, must guard against three .inajor possibilities for contaminationqf the environment. To quote David Del Porto, again, (i) “the first composting chambershould be constructed with a concave, waterproof bottom so that liquids will not seepout before they have had a chance to evaporate”; (ii) “the toilet should be carefully builtand screened to keep out insects which can transfer pathogens”; (iii) “the piles will needturning every week or two through an access door to keep th~process from going anaerobicand to bring the cooler outsides of the pile into the middle, and the tool used for thisshould be kept in a way (perhaps inside each chamber) so as not to allow transf er of patho-gens”. Finally, the toilet must be made aesthetically satisfying. Flower vases around canpossibly do this job. 1Pit Latrines 1

Now to the pit latrine. James Cameron Scott’s book “Health and Agriculture inChina”, based on investigations in early forties, contained a chapter “How Faecal-borneDiseases are Spread”. In order to study the pathways of the eggs of the intestinal roundworm,

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I Ascaris lumbricoides which is an index of faecal pollutions and could also be used as anindex of public health problem, his team t~oksamples of soils from the pit latrines, court-yards, living room floors from farm houses. The analyses showed that 85% of the samples

I from pit latrines, 60% from courtyards and 34%- from living rooms were positive. The pitlatrines, just across the courtyard and not far from the kitchen, were often the sourceof infestations. Scott’s conclusion: “Apart from the insanitary nature of the ~it latrine,

I ts low efficiency for conserving nitrogen points to the need to replace it with somethingbetter”.

I It is true that subsequently water-seal pit-latrines came up to lessen the hazardsof pathogen spread, insect breeding and odour. These are therefore, to be welcorned. Butif a large number of families in the village take it up, it will be difficult to resist widespread

1 groundwater contamination with ammonia (and pathogens). This is possibly thé reason whypeople generally are unenthusiastic about the use of pit latrines.

Even the PRAI-type water-seal pit latrine - developed by the Planning Researchand Action Institute of Uttar Pradesh - which was once regarded as quite suitable for

I small village communities (with an absorption pit about 3m deep and with Im diameter)has failed to evoke much response even though Sri Ishwarbhai Patei had made a spectacuiarbeginning by installing 1,96,000 PRAI-type latrines in the State of Gujarat.

All these experiences have led many concerned social thinkers to believe that theanswer lies in “the adoption of multi-faceted waste re-use system with obvious benefits

I to the viilagers”. These benefits include: (i) cooking fuel; (ii) composted material for soilhumus; (iii) algal culture; (iv) enrichment of fish ponds by purified waste water after second-ary treatmenv of the elf luent slurry. Therefore, there is likely to be a greater incentive

for better upkeep of the biogas plants.

COMPLEXITIES OF NIGHTSOIL AS A BIOGAS

PLANT FEED

I It will, however be wrong to underestimate the complexities of operating biogasplants fed wholly or partly by nightsoil. Certain problems are intrinsic to the nightsoilleed. A few characteristic differences between cattle dung and human excreta have caused.

I wide differences in their operational parameters. References to some of these differencesare interspersed in the Workshop’s papers. These are as foliows: (1) The excreta productionof an adult person is about 500 grams (it varies from person to person depending on foodhabi-ts, health of the individual, age etc.) while a cow would yield dung about twentytimes as much (10 kilograms) per day. A buffalo would yield even more. (2) Since thecattle

I dung contains much more celiulosic material which even the acid forming bacteria in thebiogas digester finds it difficult to break down, the gas production from a kilogram ofcattledung is only half as much as that from an equivalent quantity of nightsoil. (3) The

I nightsoil is richer in nutrients (N.P.K.) too. (4) Its pathogenic bad is generally high. (5)Nightsoil, which contains carbohydrates, protein compounds and fats, is difficult to homoge-nise: the fats tend to float on the slurry top and tend to travel quicker to the outlet chamber

I without giving off enough gas or shedding their pathogens. (6) In a digester fed by bothcattie dung and nightsoi!, the nightsoil particles pose a special problem. These being smallerin size and lighter in weight - presumably this is the result of the human habit of eating

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eooked loods to cause their easy breakdown in the intestines - the siurry gets differentiated:separate layers are formed, the lightest layer tends to float on the surface, form a scumand remain outside the zone of the methanogenic bacteria’s attack. (7) Nightsoil, havinga very low C/N ratio, has a tendency to produce ammonia. Excess ammonia in the digesterbecomes toxic to methane producing bacteria, thus inhibiting the production of the verygas which is of interest to the user. (8) Nightsoil feed is in greater need of stirring forutmost possible homogenisation in a mixing tank bef ore its entry in-to the inlet tank. Yet,this is the material which poses the greatest difficulty to stirring, by giving out offensivesmeil so long as it is kept in the pre-inlet tank exposed to the environment.

These are the reasons why the technology which is sufficient for operating cattle dung- 1fed biogas plants is not adequate for running plants which take nightsoil ever as a partialfeed. Everything - the proportion of different feeds, the pre-inlet preparation, the calcula-tions of in digester residence time, the utility or otherwise of a partition wall within thefermentation chamber, the distance and positional relation between the inlet point andthe outlet point, the dynamic of the slurry in different stages of digestion and the possibili- 1ties of their mix-up, the remedies against excessive scum formation, the survival rateof the pathogens in the effluent slurry, the methods and duration of post-digestion treatmentand the space requirements therefor - becomes a subject for critical re-examination whennightsoil is used as a leed. The CORT workshop has revealëd sharp differences on almosteach of these questions.

In what follows an attempt will be made to focus on these controversies and onthe un-raised, yet unclear issues so that these can form the subjects for research and futurediscussions. An attempt will also be made to delineate the areas of consensus which emerged

in the workshop.

1CON1ROVERSIESOVER SCIENCE QUESTIONS(PATHOGEN

SURVIVAL, FEED MIXES, SLURRY UTILISATION) 1The agreement was in recognition of biogas plant as a social need. That’the biogas—

cum-fertiliser pIants have become a crying need for reasons of public health, for facingthe deepening fuelwood crisis, for use of the digested slurry as soil fertiliser-cum-conditioner,for better cooking and relieving the women’s drudgery, and for reasons of people’s - moreso the womenfolk’s - privacy in defecation in the context of disappearing bushes and jungleswas unanimously acknowledged. Biogas plant is an aid to afforestation. Un!ess biogas plantsand solar cookers become ubiquitous, no amount of effort at afforestation can ensurethe safety of the new plan-tings. Afforestation, has to “walk on all fours” - conservationof old 1orests; widespread new plantings; biogâs plants; and solar cookers (the last two areto prevent the growing pressures for ~leforestation). 1

Biogas plant is a measure for high agricultural productivity and also for renewableenergy. It is, above al!, a health measure. By killing pathogens and by contributing to tastier 1and more nourishing lood production through manuring, it promotes health. Warnings were,of course, sounded by several participants that unless proper in-digester residence timeof the faecal liquid was allowed and meticulous secondary treatment given, this very instru-

ment of health promotion could turn into a tool for disease spread. The Ministry of Health,

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the Ministry of Agriculture, the Ministry of Forest and Environment, the Ministry of SocialWelfare, apart from the Department of Renewable Sources of Energy should, therefore,be deeply interested in biogas programme.

However, despite the near-unanimity on~the desirability of biogas plants, ther~were sharp differences among the participants on practically every scientific and techno-logical question.

The foliowing statements on the pathogen behaviour in the digester and the desiredresidence time would exemplify the divergences.

Dr. Shanta Satyanarayan et. al. of N~ERI, in their background paper, mentionedthat “at an average digester temperature of 28 C, some 67% Ascaris and 90% of hookwormeggs were destroyed during a detention period of 25 days”. In contrast, Rahul Parikh ofAgricultugai Tools Research Centre, Bardoli said: “they (ascaris eggs) neithe~grow nordie at 27 C for 140 days. Parasite eggs can survive for 15-40 days at 20-30 C temp-era-ture”.

Gaur and Khandelwai stated that “patho~,enicenteric bacteria get killed if their actualresidence time in the digester is 14 days at 35 C. The die-of f rate of even the entericviruses is 22% at this level of temperature and retention time”.

H.N. Chanakya expressed that “the enteric virus can persist for 180 days at 20_300C”. Though these two statements are not exactly contradictory, these have th~potentialto set of f two contrary trends. A biogas plant planner ~xpecting an average of 30 C temp-erature may plan for 30 days (instead of 14 days at 3) C) while another person expectingthe same temperature can insist on a minimum of 90 days.

Chanakya of ASTRA (Bangalore) considers residence time of 35-52 days insufficientfor digesters fed by nightsoil, while D.R. Gupta of Thapar Polytechnic (Patiala) regardsa residence ti~ne“not shorter than 14 days as sufficient” at a temperature not significantlylower than 30 C. Shri.Gupta’s reason is that at this level of operation, pathogenic entericmicro-organisms, with a few exceptions, are effectively killed. His justification for thisshort residence time rests on two grounds. His first ground, if rephrased, would appearlike this - “even at a level of operation, where 99% of pathogens are killed, there yvouldstill survive some micro-organisms of public health significance. Since we cannot in anycase destroy pathogens 100 per cent, why should we not be content with an elf luent slurrywhich has been rid of most pathogens.” His second ground: the surviving micro-organismswill continue to die off because of back of nutrients and hostile environment.

At Shri Gupta’s opposite pole are AFPRO’s Raymond Myles and Anil Dhussa whoplead that “nightsoil must remain in the plant for at least 70 days to become free frompathogens and parasitic ova” Since public health is the overriding consideration and alsobecause it is difficult to exercise control over millions of individual households’ practicesof composting etc, it is better to exercise utmost control in the digester design itself,“by fixing its hydraulic retention time for the worst operating conditions”. In plain words,the residence time should be planned on the basis of the winter temperature, and therefore,the digester’s volumetric capacity should be correspondingly large.

Dr. Mapuskar of Jyotsna Arogya Prabodhan (Dehu) Pune, does not favo~irthis appro-ach, for such a large volumetric capacity will mean heavier costs and be a deterrent

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to biogas plant propagation.Since an assured retention period of 40-45 days at 32-35°C elimi-nates the viral, bacterial, and protozoal pathogens and since the worrisome helminthova settle at the bottom of the digester and get enmeshed in the heavy sludge, thereis no reason to extend the retention period beyond 40-45 days, he argues. His sympathieswould be even for its reduction to 25-30 days provided a consciousness is generated foran assured retention period of the effluent for 25-30 days in an adjacent pit for secondarytreatment. i

Thus, the participant’s personal predilections had the overriding role in their prescrip-tions. This could happen because there has been no systematic study of the behaviourof pathogens, type-wise, in different 1 ield conditions. Nobody has sought to reconcilethe available data. After a finding has been ob-tained, none has even tried to indicatethe range within which it is expected to remain valid or to work out the method of conver-ting the ‘reported - values to different levels of temperature. Data without their sourcehave also been creating confusion. Shri D.R. Gupta’s data show a 90% die-of f of helminthicascaris within 15 days at 30°C while, according to Dr. Mapusk~r’s data, the ascaris ovasurvive in the slurry after 30 days of anaerobic digestion at 32-35 C and even thereafter,in the sludge. Our health research institutes had possibly no time to look into these dataeven though the nigh-tsoil is credited to be the source of “80 per cent of disease” * andbiogas plant its potentia! preventive.

Even the research done in a premier institute like NEERI has been perfunctory. 1Dr. Shanta Satyanaran could Jeport the resuits of a series of experiments carried outby herself and by Trivedi at 37 C. This temperature was chosen possibly because It wasconvenient for laboratory experiments. Hardly anybody would argue that this was a represen-tative -temperature of biogas plan-ts in any significant areas. Since there are large variationsin the digester temperature in different areas and in the same area in different seasons,it would be more helpful if NEERI and other research institutes could conduct pilot plantstudies in different temperature ranges - and better still, in different areas.

On the question of the preparation of the slurry for the final use, too, there arewide differences. Dr. Gaur and Dr. Khandelwal would have no objection if the slurry couldbe directly apphed to the soil without drying, provided it is pboughed in immediately. 1“Biogas digestion system avoids the loss of ammonia and hence slurry is richer in nitrogencontent than solid organic manures produced aerobically. However, ammoniacal nitrogenis lost if the spent slurry is sundried. Therefore, either the sluriy should directly be usedon land without drying, whlch will will providebotd plant nutrier~ and water or it shouldbe mixed up with either solid crop residues, farm and city organic. ‘wastes or already hurni-fied compost for maturity before transfer to fields. During composting, it should be mixedwith phospatic fertilisers to reduce ammoniacal losses~’.(Italicsadded)

The controversy relates to the first alternative (direct use -from the digester tothe soil). In their clearance to such direct application, the authors evidently had the ideathat the soil microbes would kill the rernaining pathogens in the spent slurry. Shri Kshir-sagar of NEERI, however, would call this approach extremely lax. He argues that “if labour-ers working on sewage farms are having a high inci~ence of infections from helminthicand intestinal pathogens, the workers who would be working with effluent slurries, too,

would certainly be vulnerable. Lack of data in this respect cannot be construed as a positive

1* Reference: Shri Maheshwar Dayal’s KeynoteAddress 1

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indicator of safety in handling and using this material (i.e. sewage and nightsoil sludge)for fertilising land and fish farms”. He has thus made out a case for sun-drying or aerobiccompos-ting of the effluent slurry. His warning against the direct utilisation of sludge(which is likely to contain the long-surviving ascaris and other pathogens) on land or fishfarms seems justified. Enteroviruses surviving in the slurry which have shortcircuitedtheir path (i.e. come out prematurely) and have also remained uncomposted can causeepidemics. Although the power of soil microbes in destroying the weakened pathogen isnot in doubt, it canriot automatically be accepted that direct application of effluent ~lurryis harmless. There are 1 indings that pathogens from raw nightsoil can penetrate the cel!wall barriers of plant root systems and get into human food sources. II this is- possiblefrom raw nightsoil, why not from ill-digested effluent as well?

There are no convincing data to set-de these differences. Sinha and Mazumdarof Sulabh International were very correct in saying that microbiological aspects havegenerally been ignored even though engineering aspects received some attention. Perhapsit is not microbiology alone, questions of science in general have been sidestepped.

Earlier, we have seen that our people do not have any guideline for mixes of feedsfor ideai C/N ratio. There are suggestions that 10% human excreta be mixed with a 40%combination of cattie dung, foliage and other crop residues and the remaining 50% bewater. This would mean a total of 90-95 per cent moisture content in the digester. Perhapsthis is a workable proposition. But since different crop wastes have different C/N values,the formula for mixes of feeds should be placed on a firmer basis and, as far as possible,locale-specific. This kind of a cail for concrete study can .be a challenge to the localinstitutions of higher learning. Education can thus be lifted from lifeless cramming andimbibing of patented formulae to a creative endeavour. “Know thy own environment”is the first principle in learning as also in all other activities.

Expectedly, the proportion of ammoniacal nitrogen is more in the digested siurrythan in the raw dunglexcreta. (Ammoniacal nitrogen is more suitable for uptake by plantlife). Anil Dhussa defined the proportion: whi!e it was only 5.5 per cent of the total nitrogenin the original raw material, it (ammoniacal form—of nitrogen) was as high as 17 per centin the biogas slurry. The sludge value, too, is rich. It is composed of the dead bodiesof anaerobic bactèria, the undigested or partially digested organic feed-stock, and allof the original inert (non-volatile) content of the input. Many scientists have tended tocail this whole organic residue effluent a “single-ceil protein biomass” (SCP), containingalmost twice the concentrations - per pound-of nitrogen, phosphorous, potassium and traceelements, as compared to these constituents in the organic material fed into the digester.It is claimed that because most of the nitrogen has been converted to stable protein inthe bacterial cell walls,losses due to ammonia release are much bower than from the manurewhich has been composted without the transformation through the biogas plant. “Thisnitrogen is released gradually over a three or four year span, thus reducing annual fertili-sation requirement~and increasing the organic matter percentage of the soil”

Now, if both the claims are correct - that is, on the one hand, we have a higherpercentage of quick-reiease ammonia in the slurry; and that we have in the sludge a much -

slower-release nitrogen than even in the organic manure - this would seem to offer thebest in both the worlds. Questions, however, naturally occur: Has any study been madein held conditions on these claimed comparative merits? This would require studies of’the resuits of applica-tion of organic manure on the one hand and of the product of aprocess of fermentation and transformation by biobogical agents, on the other. None of

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the scientific bodies in India has done this study, so far as we know. 1Another issue which occasioned sharp differences was the extent of water use

per cail and its effect on the moisture/solids content of the feed. NEERI scientists’ finding 1was that a 5-6% solid concentration is the optimum and 8.5% is the upper limit, whichmeant (i) that the moisture content should, at the very least, be 9 1.5% of the weightof the total content of the digester and (ii) that the optimal moisture content is 9 4-95per cent. Moisture content below 91.5 per cent would cause ammonia build-up inhibitingmethane production. Above 95 per cent, it would mean a f all in the rate of gas productionper unit volume of the digester. 1

It has been found that in India the water use per cail is qulte high and it diluesthe feed material 50 much that the solid concentration often comes to less than 3 percent. The workshop, therefore, proposed that the water use per call be limited to 2 litres.This invited sharp reactions. Is such limiting of water use conducive to personal hygiene7Is it possible to keep the latrine pan clean with this little use of water? The problemseems manageable when it is considered (i) that nightsoil would have to be a minor portionof the total feed-stock in the interest of keeping down ammonia production; and (ii) thatthe other types of feedstock would not require equal amounts of water for dilution.

IV 1CONTROVERSIES OVER DESIGN

ASPECTS

On the ques-tion of design also, there were sharp differences, particularly on theissue of part-ition wall in the fermentation chamber, as in the KVIC model. AFPRO technolo-gists feel that this partition, standing perpendicular~ and covering the entire diameter,is positively harmful in a nightsoil-fed biogas plant. The nightsoil slurry, a portion ofwhich has an inherent tendency to form a separate layer and float even in a raw state,gets an added impetus to travel upwards. While it overtops the partition wall to enterthe second chamber, there is an easy intermixing of the digested and the ili-digestedmaterial due to the downward movement of a portion of the slurry and upward movement —

of another in the second chamber of the fermentation tank. This eneables the raw orill-digested nightsoil to escape easily to the outlet chamber therefrom. 1

AFPRO concedes that even in the Janta model which it has adopted, there is scopefor shortcircuiting: its ex-tent, however, is much less. The school which has adopted theKVIC model does not agree. They allege that in the Janta model, wherein the inlet openingand the outlet opening face each other, the nightsoil has greater scope to escape, in anili-digested state, to the outlet tank, despite the larger distance provided for by wayof larger diameter. AFPRO is trylng to meet this criticism by providing for a baffie-wal!half-way through the diameter to maximise the sideways movement instead of the vertical.

Controversies like these would be solved by application of tracer techniques (isotopes)or at least by de~ailedchemical analyses of effluents from the plants of respective models.But no such comparative study is being done by any independent research body in thecountry.

Dr. Anjan Kalia of Himachal Pradesh Agricultural University has given his conceptof a separate chamber for fresh nightsoil within the fermentation tank, by the creation

- 142 1

BI0GAS FROM HUMAN WASTE

of a “baff!e wall” in a fixed-dome gas plant.

His purpose in creating a separate chamber for fresh nightsoil is to ensure thathuman excreta remains long enough in anaerobic conditions 50 that its pathogens couldbe effectively destroyed. Dr. Kalia has suggested a trial of this concept and it needsto be tried.

Another “design innovation” which was reported in the workshop was the modeldeveloped by the late Sri. M.V. Navrekar The avowed purpose of this design is to separatethe ascaris ova (which alone have the largest survival time) in the beginning and thusavoid lengthening the slurry’s residence time ip the digester. A liquefying tank undera W.C. basin to receive the nightsoil and an intermedzate siphon tank to separate theheavier constituents of the excre-ta (thereby the helminth ova) was suggested as the mecha-nism prior to the inlet into the biogas plant.

This raised questions as to (i) whether there are any data to prove that ascariseggs got removed in the beginning by this system and if any samples wére taken; (ii)whether heavy particles including silt and mud particles carried to the toilet by the users’shoes, too, do not se-ttle at the bottom of the liquefying tank, occupying most of the volume,requiring frequent clearing; (iii) how the likely Input of excess water is so be eliminated;(iv) whether the final slurry was tested for ascaris eggs after the usual residence timeand compared with the findings from conventional plants of the same residence time.1-Iere, too, unfortunately, there have been no scientific studies to substantiate or disprovethe claim.

Dr. Mapu~kar claimed that with an additional tnvestment of about one thousandrupees, an aqua privy could be made to yield biogas and-that this innovative design called“Malaprabha model” has been working satisfactorily in and around Dehu in Pune districtof Maharashtra for the last five years. This information startled the workshop participantsand was gree-ted with a lot of skepticism. The following questions were raised duringand after the workshop discussions. (i) It is possible to install all these additional facilities- several vents, cleaning windows, rigid PVC pipe and construction of leak-proof RCCfor the small additional amount suggested? II it is likely to cost more, why not have aproper biogas plant? (ii) 1f the privy is used by only f ive persons of a family, it mightgive only 0.2 cm. gas, which is of little use. It is worth considering only when it is usedby at least 25-30 persons (to meet five persons’ gas needs). But, then, would not the privyhave to be constructed outside the family home for the use of neighbours and passers-by?(iii) Flat roof is never good as a storage structure. Will not, therefore, leakage be a hauntingproblem? (iv) How of ten the sludge disposal be needed? Despite all this skepticism, thefact remains that these Malaprabha latrines have been in existence and there have beenno report of their hazards or wastefulness. In this case, too, one feels the lack of anyindependent body to do research, evalua-tion and extension work.

V

IMOGAS DESERVESTREATMENT AS A

FRONTIER SCIENCE

In the context of this vacuum, a question becomes pertinent: if we could afford

143


to spend Rs. 200 crores as annual subsidy to biogas ~S1ant~,could we not spend evenRs.10 crores for a National Institute for Biogas Research with centres in all regions? It issad to rel lect that our science advisers do not have any idea of the finely balanced natureof operation that a truly hygienic biogas-cum-fertilizer production demands or the complica- 1ted questions of science and technology ii involves. For human survival, research in thisfield is far more important than in laser therapy or space exploration of nuclear energy.The more deeply one goes into its intricacies, the more one becomes convinced that itdeserves to be treated as a “frontier science”.

China’s efforts in this direction have been exemplary. The Biogas Research Centre 1in China encompasses bioscience, environmental engineering and rural sanitation, structuralengineering, agricultural engineering, training, extension work, instrumentation etc. Itsmission-oriented research has taken China ahead of others in the field. In the contextof India’s foliar and crop residue characteristics, construction material and skill availabili-ties, intense research in this country in field conditions and laboratories has become urgent. 1

VI

THE CONSTRAINTS AND REMEDIES

We must now turn the physical constraints on the spread of biogas plants. We haveearlier mentioned the difficulty of reconciling the demands of its proximity to latrineand the kitchen, distance from water source, the availability of space for post-digestioncomposting etc. In Chine,se culture, which regards the frequent drinking of warm wateras an antidote to intestinal intestation, the series of post-digestion composting pits nearthe household may not be a problem. But in the context of India’s household situationsand sensi-tiveness, the ques-tion of space would appear to be a formidable problem. Thesolution is, therefore, of ten sought in the establishment of community biogas plants. 1-10w-ever laudable as an objective, It cannot succeed until cooperation has become a way oflife. In a social climate where, in the name of modernisation, we are propagating andreinforcing commercial and self-centred values, community gas p!ants can only be a casu-alty. People will tend only to draw its gas and fertilizer without contributing their shareof the Inputs. Even in a country like China, where the state control on people’s livesis much greater, community biogas plants are unlikely to prove a success at the presentstage of people’s concern for the society. The Chinese Biogas Manual says : “faced withthe costs of digesters - a number of people concluded that work should concentrate oncommunity rather than individual plants. The designs and experiences recorded in this

handbook demands a reappraisal of that judgement”. (ItaUcs ours). 1Tackling Space Shortage Problem

But would biogas plant movement t all to progress in India on the ground of a feeling —

of shortage of space in or near the household? Underground fixed-dome structure doesnot require much additional space. It can be built in the basement/courtyard. In China,two biogas plants per family is not uncommon: It helps solve the family’s easing problemwhen one plant is under desludging and cleaning operation. The requirements for widerspace, which arise from Indian sensitiveness to excreta, can be got over by taking biogas

science and technology to a level where it ensures (i) total absence of

1144 1


smell and (ii) freedom from causes of fear from pathogens. Clearly, this is possible. Maxi-

mum digestion and freedom from putrefaction go together; and effective digestion always

kills pathogens. Even if a small percentage (2% or so) of pathogens remains in the effluent,these will surely get killed in the aerobic compost pile where temperature rises muchhigher and faster. Even the egg of the roundworm or ascarid which, with its thick protective

albuminous sheath, has a remarkable capacity to survive long periods under severly adverseconditions, will not be able to escape.

Perfect digestion, even in North India’s winter nights, can be achieved by betterinsights into the working of Nature. Judicious combination of aerobic and anaerobic treat-men-t and understanding of the natural principle that the same forces that produce pathogensalso produce their toxins can help in achieving perfect digestion.

Benefits of Prior Flydrolysis in Colder

» Regions

The Chinese p~actice of prior composting of the vegetable waste inputs in thecolder regions is instrUc-tive. These wastes have in any case to be added when nightsotlis an input, in the interest of optima! operation. This method is as follows.

“In order to~increase the rate of fermentation and raise the gas output, materials

should be piled and composted before feeding into the pit - fibrous materials, especiallystraw, grass, weeds and maize stalks - must be thus treated because some of them havea waxy layer on the surf ace. Otherwise, not only is it a hard and lengthy process for

them to rot, but once fed into the pit, they float up to the surface and tend to mix evenlywith the other material. To pile and compost, cut the material into short pieces and pileup in layers about 50 cm. thick. It is best to sprinkle on (it) some material with a 2-5%

limeor ash content, and then also to pour on some animal manure or waste water, then

cake over the surface with day. In summer, this piling and composting should last 7-10days and in winter one month. When the material has thus been handled, the waxy surfacelayer is broken down,which in turn has-tens the breakdown -of the fibrous materia!”.

Evidently, this is softening of the inputs before feeding into the digester - i.e.prior hydrolysis, which is quicker under aerobic conditions. It is interesting that the inputspre-composted under basically aerobic conditions also imbibe anaerobic methanogenicbacteria discharged from the rumen of cattie along with the dung his initial inoculumdnd the initial hydrolysis speed up the fermentation.process in the t. This off sets thedisadvantages of the colder regions. This system of prior hydrolysis, however, needs tobe avoided in warmer regions.

There is yet another benefit of this pre-composting when old and ripened vegetablematerial are part of the feed-stock. This reduces their carbon/nitrogen ratio to near-opti--mum. Normally,their C/N ratio is very high between 60:1 and 100:1 (nitrogen contentbeing very low)-. With “pile rotting, the carbon-nitro~enratio can be reduced to 16:1-21:1,which approaches the ideal environment for methane microbe. This does happen, possiblydue to the release of carbon dioxide from the carbonaceous content of the biodegradingvegetable wastes under aerobic conditions.

Another practice of the Chinese is worth emulation. Before winter, they clean thepit and f ii! it with plen-ty of new material in order to better nourish the methane-producing

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microbes and stimulate them to greater gas production. When removing the old material,they leave one-third of the sediment layer. Better resuits are obtained when the newvegetable was-te inputs have been pile-rotted in advance.

People in India have already been (i) covering the fermentation chamber and thein!et and outlet chambers with straw; and (ii) surrounding the perimeter of biogas pitswith pile-rotting material during winter, to good effect. There is yet another techniquewhich raises the digester -temperature. It is the use of the solar heating technique topour heated water in-to the digester during winter, subject to the permissible limit of -

dilution. (Its scope, however, is limited in the context of the Indian habit of liberallyusing water for post-defecation c!eansing). 1

Toxins to pathogens 1It is a law of nature that the wastes which have higher pathogen loads are also

more productive of their toxins in the ferrnenting slurry.A series of experiments (in China)showed that “the ammonia content of the fecal liquid was L~~%higher after fermentationthan in the untreated pig faeces and urine. This factor would accelerate the death ofboth the parasite eggs and pathogens”. (Italics ours)

It is also a peculiar law of nature that urine. has a toxic effect on amoebae. 3.M.Watson- in his study (1945) on the effect of urine on Entamoebahistolytica proved this.Some Scientists concluded therefrom that “the Chinese hightsoil method (the use of rawliquid nightsoil combining the faeces and the urine), although apparently more likely 1to spread infection, may actually help to control it”. Biogas Plant followed by composting -

is a far greater advance on the raw nightsoil method and can be free of obnoxious smelland pathogens. Therefore, there should not be overconcern to keep the biogas plant and 1the compost pit at a great distance from the living rooms provided meticulousness isobserved in attaining the design objectives and testing of the slurry is done periodicallyfor its pathogen content.

Genuine problem of space exists but oversensitiveness or undue fears need notaggravate the sense of shortage.

Problemof Servicing 1One great o~tac1e to biogas movement is the lack of repair/servicing faci~ty

in the locales. Investors willing to set up biogas plants of ten point to the dysfunctionalbiogas plants and feel deterred. In a pattern of development, where al! technical handsseek better material prospects in servicing consumer durables and tie-ups with large 1industries, servicing for biogas plants cannot retain their interest for long. Fortunate!y,a new movement for turning common men and women in-to masons with a biogas mission~s being spearheaded by AFPRO, Agricultural Tools Research Centre at Bardoli, Gandhi 1Smarak Nidhi, Thapar Po!ytechnic and a few other voluntary agencies. This may turnthe tide. 1

Need for Reordering National Priorities

Every family in the ru~al area including the poorest must be enabled to have

1146

1


a biogas plant of its own. The poorest will naturally deserve the most generous subsidy,verging on a free gift. The Iandless family, lacking its own cattie, will need to runthe biogas plant on its own riightsoil and its collection of vegetational wastes. Subsidyon this scale, will, no doub-t, be a huge burden on the public exchequer but that willbe a far greater contribution to a lasting solution of the nation’s energy problem thanthe petroleum refineries and nuclear plants together can ever be. Biogas plant deservesthe highest priority as a public health promotion measure. Resources will be föund forit, only when the priori-ty to urban-centred hospitals (for cure, after allowing the propaga-tion of diseases) and chemical fertilizer plan-ts be reversed. It has to be recognised thatbiofertiliser is our greatest resource for soil fertility.

India’s soils have become seriously eroded everywhere. These need fertilising corn-posts universally. 1f a poor landless family ha~no space to adjom the gas plant on itsnarrow strip of homestead, the village panchayat must buy from it the effluent slurryto do the composting on the community’s land (for sale tÖ land holders). There can beno soil improvement bypassing the biofertiliser-cum-soil conditioner.

Biogas plant is vitally linked with all aspects of the society’s weil-being health,forestry, agriculture, energy, non-conventional resources, science and technology. It isbasic to our survival. Hence it needs to be the concern of all and demands high r~nkinginnationa! priorities in terms of allocation. I~ut“the plant can be dangerous”*in lax/handling.That is why it deserves utmost concern, care and vigil.

ACKNOWLEDGEMENT

The author is gra-teful to Sri A. Raman of NEER1 (Delhi Uni-t), Dr. K.C. Khandelwalof the Department of Non-conventional Energy Sources, Sri Rahul Patrikh of AgriculturalTools research Centre (Bardoli, Gujarat), Sri Raymond Mytes, Sri. Anil Dhussa and SriYashwantSingh of AFPRO (Action for Food Production) who gave their time and energyfor answering the author “endless” querries and providing the clarifications over severalsessions. The opinion expressed in this paper are, however, the author’s own.

*Jnternatjonal Reference Centre “Practical solutions in Drinking Water Supply andWastesDisposal in Developing Countries (422.03)

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Workshopon “Biogas from HumanWaste”22nd-23rdAugust ‘86.

LIST OF PARTICIPANTS

1. Sh. Banwari La! ChaudhriGram Seva SamitiP.O. RaisalpurDist. -Hoshangabad

2. Mrs. B.L. ChoudhriGram Sewa SamitiP.O.RaisalpurDist. Hoshangabad

3. Sh. Ramchandra Pd. SinhaGobar gas & Khad UtpadanYojana, Naya TolaMuzaffarpur,Bihar.

4. Sh.O.RadhakrishnaNon Conventional EnergyDevelopment Corpn. ofAndhra PradeshHyderabad

5. Dr. S.K. VyasProf. of Civil Engg.P.A.U., Ludhiana

6. Sh.D.R. GuptaPrincipalThapar PolytechnicPat iala.

7. Sh. ParasbhaiExecutive SecretaryPRDATAG. UdayagiriPhulbani

8. Sh. Sayed MustafaOREDABhubane shwar

9. Sh. S.P.SinghVikas SamitiJamuiBihar

149

10. Sh. Amulya ChakrabartyRamakrishna MissionLokasiksha ParishadNare ndrapur West Bengal

11. Sh. J.SwarupCSI RNew Delhi

12. Sh. M.P. MishraK.G.N.M.T.K. GramIndore

13. Sh. M.D. NaikMaharashtra GandhiSmarak NidhiKothrud, Pune

14. Sh. H.N. TodankarMaharashtra GandhiSmarak NidhiKothrud, Pune

15. Smt. Savitri MadanMaharashtra GandhiSmarak NidhiKothrud, Pune

16. Dr. S.V. MapuskarJyotsna Arogya PrabodhanDehu,Dist. Pune

17. Sh. GVVSDS PrasadVASORD1 1-5-422/ARed Hilis Hyderabad 500 004

18. Dr.Anjan K. KaliaH.P. Krishi Vishva VidyalayaPalampur (H.P.)

19. Smt.Devaki JamInstitute of Social Study5,Deen Dayal Upadhyaya MarsNew Delhi

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20. 5h. Uday Narain ChoudharyPRAYASRural Dev. ProjectPhulwarishariff - 801 505Patna, Bihar

21. Dr.N.B. MazumdarSulabh Inst~ituteofTechnical Research &DevelopmentAdalatganjPatna 800 001

22. Sh.Rahul ParikhAgri. Tools Research CentreBardoli 394 601Gujarat

23. Dr. Krishna MahapatraAFPRO25/lA Institutional AreaPankha RoadD-BlockJanakpuri.

24. Dr. (Mrs.) S.VermaKasturbagram NationalMemorial Trust, KasturbagramIndore (M.P.)

25. Dr. Mrs.S. SatyanaranaNEER!Nagpur - 20

26. Sh. J.B. SinghAFPRONew Delhi

27. Sh. K. C. KhandelwalDN ESNew Delhi

28. Sh. Y.P. AnandN. Rly.

30. Ms. Manju Mishralnstt. of SocialStudies5, Institutional AreaDeen Dayal Upadhyaya MargNew Delhi-2

31. Sh.Sharat ShashankVoice of America -

11 - Barakhamba Road’New Delhi - 2

32. Lt. Col. V. Kishore (Rtd)Dev. Alterna-tive22, Palam MargNew Delhi

33. Ms. Lalita BalakrishnanAIWC6, Bhagwan Dass RoadNew Delhi 110 002

34. Sri. Anil DhussaAFPRO25, A Institutional AreaD-Block, Pankha Road1 anakpur iNew Delhi 110 058

35. Ms.Shashi RajagopalInstitute of Social Studie5.Tharangh, RMV Extn.Bangalore - 80

36. Sri. Raymond MylesAFPRO, JanakpuriNew Delhi

37. Dr. Yashwant Singh 1Sulabh InternationalNew Delhi

38. Smt.R. BhatiaAFPRO, New Delhi

1

29. Sh. K.P. SukumaranDeptt. of Non-conventionalEnergy SourcesNew Delhi

150

39. Sri. Rajneesh AroraVikas BharatiVishnupur, Bihar

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40. Sri. P.P.S. GusainDevelopment Alternatives22, Palam MargVasant ViharNew Delhi 110 057

41. Sri. K.R. SwaminathariDept. of Bio-Energy -

Tamil Nadu Agri. UniversityCoimbatore 641 003

42. Dr. T.P. OjhaCIAE, Bhopal 462 001

43. Sri Sailen Ghosh42/22, East Patel NagarNew Delhi 110 008

44. Sri. P. ChaturvediGeneral SecretaryIAAS, New Delhi

45. Dr. SantoshCentre for Rural Developmentand Appropriate Techn.Indian Institue ofTechnologyHauz KhasNew Delhi 110 016

46. Dr. Maheshwar DayalSecret aryDept. of Non-conventionalEnergy SourcesCGO Complex, B-BlockLodi Road, New Delhi

47. Dr. M.L.DewanN-44, Panchshilla ParkNew Delhi 110 017

48. Sri. Bindeshwar PathakSulabh InternationalGandhi MaidanPatna

49. Sri .GroverJoint SecretaryDNES, New Delhi

151

50. Sri. S.K. JoshiDelhi Energy Dev.AgencyDelhi.

51. Sri. K.K.SinghDept. of Non ConventionalEnergy SourcesNew Delhi

52. Sri. T. babjeeNarasannapetaSrikakulam Dt. A.P.

53. Sri. 3.C. BhatiaHead of Dept.Chem. Engg.Arya Bhat PolytechnicDelhi Administration

54. Sri.G.L. Chaturvedi184, Mandakini EnclaveKalkajiNew Delhi - 19

55. Sh. R.I.ShahVikas, Dala! [-(ouseAhmedabacl - 9

56. 5h. S.P. MohanAFFORD5, DDU MargNew Delhi

57. 5h. J.S. D’SouzaAFPRO, 25/lA, Institu-tional AreaD-Block, JanakpuriNew Delhi - 50

58. 5h. Omkar NathConsultant30A/LI, KalkajiNew Delhi - 110 019

59. Sh. Yogesh BhaiH-72 South ExtensionPart-I, New Delhi

-~ ~ --‘ -- —‘---~-- - ----‘~~-- ~--- -- _~ --,


60. Sh. Venkata RamanaCentre for Science &E nv Iron me nt801, 95, Nehru PlaceNew Delhi

61. Sh.S.S. SekhonManager (Renewable Energy)Pb. Agro Industries Corpn.Ltd., SCO 311-312Sector 35-BChandig arh

62. Smt. Bulu‘SANK ALP’A-N-5OShalimarbaghNew Delhi 110 052

63. Sri. H.N. ChanakyaASTRA, liScBangalore 560 012

64. Shri Y.K. SharmaSecretaryConsortium on RuralD-320, Laxmi NagarDelhi - 110092

65. Mrs. Gnambal JagdeesanSri AvinashilingamHome Science ColegeCo imbat ore

66. Miss VennilaSri AvinashilingamHome Science CollegeCoi rnbat ore

67. Sr. K. Janardanan PillaiChairman, Kerala GandhiSmarak NidhiTrivandrum 695 014

68. Prof. William BoxtanDept. of SociologyUni. of New BurnsWick, FrederictownN. Brunswick

69. Sri. N. NigamShivalik, IITDelhi 110 016

70. Prof. K.R.SwaminathanAgrI. University1-lead, Divn. of MicrobiologyCoimbatore

71. Dr. A.C. GaurIARI, New Delhi

72. Sri. Bharat GuptaA/29A, MIG, Ashok Vihar-lIlDelhi 110 052

73. Mrs. Vrinda Gupta 1A/29A, MIG, Ashok Vihar-lilDelhi 110 052

74. Sri. Chandu Lal ChadrakarM P (Lok Sabha)

75. Sri.K. S. RadhakrishnaChairman, CORT

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Technology

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biogas from human waste handbook

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