4w K&&YX{"K&SKm Y&$e& KW&

his chapter deals with health-based targets and related recommendations forhealth protection. The potential to relate protective mea$res that respond tohealth risks to guideline values or good practice is determined by the

compliance level that can be expected realistically. It is less practical to applyguideline values in small-scale settings, where procedural and best practice guidancemay offer abetter approach.

An attempt has been made to harmonize dre health-based targets presented in thisvolume with those in Volume 2 of the Guidelines (Safe use of wastewater inagriculture). Furthermore, issues specific to the safe use of excret4 urine andgreywater in agriculture are pointed out. Obviously, the risk of transmission ofpathogens through environmental pathways when unsanitized excreta are used inagriculture may lead to increased disease prevalence. Treatment of human excreta andother barriers against human exposure are considered tle most important precautionsagainst such transmission (see chapter 5).

Health-based targets need to be an integral part of the overall health policy,accounting for the trends in and relative importance of different transmissionpathways, on both individual and household levels as well as in tle overallmanagemsnt of public health. To ensure effective heal& protectior; the target needsto be realistic, relevant to local conditions and commensurate with resources availablefor required protection methods. Health-based targets aim to improve public healthoutcomes and should support the rational selection of health safeguards, interventionsand control measlaes, mainly in rclation to excreta and greywater treatment, exposr:reconfrol and safe handling.

The concqt of health-based targets applies uaiversally, irrespective of the level ofdevelopment. Although the targets tend to be set at the national level, they are appliedat the local level. Risks are subject to variability in perfonnance of technicalinstallalions and the frequency of exposure. lt is, therefore, necessary thatrecommendations be practical and take into account variability fuctors. Ad hoc wentsas well as behaviour may affect the health outcomes; thus, a 'lnultiple-barrier

approach" is needed.The targets axe part of an overall managemena and evaluation strategy in relation

to bealth protection goals and implementation of the scheme to use excreta andgroywater. In such contexts, any long-term effects also need to be considered. Wherepossible, the health-based targets should relate to quantitative risk assessment, takinginto accormt local conditions and hazards. Spidemiological inforrnation on localhandling and use ofexcreta and greywater in agriculture is scarce and scattered. Theavailable epidemiological iaformation on wastewater and sludge use can be partlyapplied in this sontext

With increasing frequency, regulations and guideliaes are based on the riskconcept. By applying QMRAs, based partly on predictions and assumptions,sanilation systems can be evaluated and compared with established limits foraccqtable risks. Treatrnent can also be adapted to reach a set of acceptable limits.Risk assessments can tlus be made quite site specific, depending on informaiionregarding, for example, the local health status of the population and behaviouralpattems. An approach of setting acceptable local risk limits, applicable for sanitationsysaems where the use of the excreia products is practised, will relate to a subsequentchange in the prevalence of infections. In developing countries with low sanitarystandards, the goal will be to reduce the number of infections by implementingsanitation per se, including introducing new, more efficient treatment or exposurereduction alternatives, combined with other interventions related to safe trealnent and

,arl,x

Guidelines for the safe use of wastanateti excreta and greywater

storage, hygiene/health edusation as well as provision of access to safe &inking-warer.

This volume of the Guidelines focuses on heatrnent, but also addresses othertechnical, practical and behavioural aspects in{ended to minimize the risk for diseasetransmission. Rules of thumb considered to obtain acceptable low risks are presentedwithout a bias towards numeric limits in small-scale systems.

4.1 Type of targets appliedHealth-based targets may be based on epidemiological evidence, risk assessmentpredictions, guideline values or performance. All have certain strengths andlimitations. Health outcome taryets based on epidemiological evidence are resourcedependent and need a developed institutional verification system. Risk assessmenttargets are based on validated predictions but may overestimate the actual risks, due tovariability in behaviour and exposure. Guideline values oten have limitations inexpressing the risks for a broad range of organisms. In many instances, perfomancetargets based solely on indicator organisms have limitations in expressing the risks.They should preferably be based on a rarrge of pathogens, considering theirpersistence under adverse treatment or environmental conditions. Performance targetsshould ensure that the performance assessment also reflects other, more vulnerablemicrobial groups and different conditions. All targets relate to variability and shorterperiods of decreased efficiency in a number of processes. The targets should alsoreflect background rates of disease. Performance assessment does not normally needto be based on experimental evaluations carrjed out on site, but can be approximatedusing international evaluations that take the prevailing local conditions into account. Itis, however, of value to put treatment performance evaluations in the hands ofcompetent national or regional authorities or insiifutions. Different types of targets aresummarized in Table 4. I in relation to excreta and greywater use in agriculture.

In cormection with the use of treated excreta and greywater, the health-basedtargets are related to exposure barriers and treatment performance in the overall riskassessment and risk management. Monitoring guideline values are mainly applicablein larger systems. The treatment altematives give different levels of safety as barriersagainst pathogen transmission. Performance targets are further specified below, whilethe technical options and management aspects are dealt with in chapter 5. Numericalguideline values can be used mainly for validation, but should be applied with cautionand always within a context of risk management sbategies.

4.2 Tolerable burdea of disease and health-based targetsThe commonly accepted metric for expressing and comparing the burden of disease isthe DALY (Murray & Acharya, 1997) (see also chapter 2). In the third edition of theGuidelines for drinking-water qualrty (WHO, 2A04a), a tolerable burden ofwaterborne disease fiom &inking-water consumption of S10-u DALY per psrson peryear was adopted. This level can be compared with a microbial self-limiting diarrhoeaand the corresponding case fatality rate ofapproximately I x l0-5 at an annual diseaserisk of I in 1000 (10-3), which is also about 1 x 10-6 DALY (l pDALy) per personper year (V/HO, 2004a). Since food crops fertilized with treated excreta or irrigatedwith treated gfeywater, especially those eaten uncooked, are also expected to be assafe as drinking-watero the same high health protection level of <10{ DALY perperson per year is applicable in tlis context as well.

For operational purposes, treatment and other management options to reduce thelevel ofpathogens and subsequant$ the degree ofexposure should aim at this target.

60

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Yolume 4: Excreta and greywater use in agriculture

Table 4.1 Natura *oolication and assessmeat of health-based tarcets

Typeoftrrgets Natureoftargets Application Aassssmcnt

Health outcome:epidemiology based

Reduction in delecteddisease inciderc€ orprevalence

Microbial with highmeasurable disexe burden

Through direct impactmeasu?menl, such x food-associated disease

Microbial hazards insitralions where diseaseburden cannot be dilectlymeasured

Public heallhsurveillance;analyticalepidemiology

Often difficult toasses actual impact

Multiple factors

QMRAPredictive tool

Needs to be related tolocal exposure

Risk-basdassessment

Quality tagets

Performanc€ atgets

Specifiedtechnology

Tolerable level ofriskdue to direct orindirect exposure

Relationship to otheralternative use,exposure or sanitationfacilities in localconaextGuideline valuc

Generic performancetargets for removal ofgroups oforganisms

Cxtomized targets

Guideline values lessapplicable

Authorities speci$specific processes orsystem approaches toaddress constituenthandling practices orbehaviours in relatiorto health effecls

Measuremenls of pathogensor indicator organisms, lessapplicable in:- smalf scale application- for urine due to rapid die-

offof indicators- for greywater due to grow&resulting in overestimationofrisk

Microbial contam inants

Healti effects in small-scalesettiags

Measurements mainlyvalid in assessment oftechnical performa*ceoftreatment offaeces

Shouldmainly beapplied within asimilar framework asfor the assessment ofwasterAratet use

Ensure validity ofmeasurementparameters (systemvalidarion)

Limitations inreflecting generalpaihogen risks

Compliance throughsystem assessment

Review by publichealrh authorities

Checklists

Recommended forsmall-scaleapplications.

Limiations based onlocal conditions

Compliance:!ssessment

Operation aadhandling

6 l

Guidelines for the safe use of wastewateti excreta and greywater

Camprylobacter, Cryptosporidium and rotaviruses were chosen as index organisms(Havelaar & Melse, 2003; WHO, 2$4a). An example of a calculation of the valuesfor tolerable infection risk is given in volume 2 of these Guidelines and is alsoapplicable in the context of this volume. The cited values accounting for the infectionratios are:

Rotavirus (industrialized countries)Rotavirus (developing countries)CampylobacterCrVptospoidium

1.4 x 10-37.7 x l}".a3.1 x l0-42.2 x l{3

Thus, the tolerable disease risks for tlese organisms are in the range l0-3-10i perperson per year. This is a conservative value, given that the currelt global incidenceof diarrhoeal disease in the age group 5*80* is in the range 0. 1 *l per person per year(see Volume 2 of these Guidelines).

Reliable epiderniological data relating to the safe use of excreta and greywater inagriculture are scarce. As an altemative, the range of tolerable disease risk can bededuced based on the QMRA, for which the risks resulting from exposure to faeces,urine and greywater were presented in chapter 3, for both its final use and handling. Inthis context, the current Guidelines are harmonized with the health aspects of the useof treated wastewater in agriculture, where the epidemiological appropriate level oflolerable risk for both crop consumers (unresticted inigation) and feldworkers(restricted irrigation) has been identifred (see Volume 2 of these Guidelines).

ln chapter 5, the combination of different primary and secondary treatmentbarriers is described that can achieve a risk reduction 1o t}re health-based target level.Knowledge (or estimation) of the volume of feated excreta or greywater to which ap€rson is exposed in the handling chain or that remains on the crop (ml or mg per 100g crop) following fertilizatiorl the withholding time and the die-off in the fietd willdetermine the degree of pathogen reduction required to achieve the tolerableadditional disease burden of <10- DALY per person per year. This step requires thenumbers of pathogens present in the untreated excreta or gre)'water to be known orestimated. In this context, the use of E. coli concentrations for vsrjfication monitoringis appropriate for treated excreta, but it is not for collected urine, due to a rapid die-offof dre bacteria in this medium. In greywater, a regrowth of E. coli sometimes occurs,which may lead to an overestimation of the risks if verification monitoring is based onthis parameter. It is suggested that E. coli guideline values, which are applicable forwastewater use, be applied cautiously for greywater. If applied they will give a levelof additional safety in this application, since the faecal load is usually 10&-1000 timesless than in wastewater. For helminth infectionsn the treatment verification monitoringlevel in terms of number of helminth eggs is presented in Table 4.2.The health-basedprotection to achieve the required pathogen reduction may consist of treatmenl aloneor may be a combination of several measures. A guideline value of <103 E. coli per100-ml is suggested for unrestricted irrigation with greywater. The target value of<10' E. coli per gram of Seated faecal material applied as fertilizers would thenen$tre a comparative level of safety against bacterial pathogens and probably againstviral pathogens as well. A clear value for parasitic protozoa does not exist.

The pathogen reduction that is needed in the on-site and off-site treatment ofexcreta is expressed as performance targets. This target for keated excrefa is based ona storage time in the on-site teatrnent for 12-t8 months of treatmen! (if only storageapplies) and is combined with a stated withholding period that will firther minimize

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Volume 4: Excreta and greywater use in agriculture

Table 4.2 Guideline values for verilicatioa monitoring in large-scale treatment systems ofgreywater. excreta and faecal sludge for ue in agriculture

Ilelminth eggs (number per .8. ca# (number per 100 ml)gram total solid3 or per litre)

TreaGd faeces and faecal sludse

Greywater for use in:. Restricted irrigation

<l/g total solids

<lllire

<1000/9 total solids

<105u

Relaxed io <106 whenexposure is limited or

regrowth is likely<l0r

Relaxed to <104 for high-growing leaf crops or drip

irrigation

. UnresficGd irrigation of cropseSten taw

<1/litre

u These values are acceptable due to the high :egrow*r potential of E. coli arrd o&er fecal coliforms ingreywaier.

risks to the consumers. This period applies as the treated excreta are applied as afertilizer and soil conditioner, which differs from the wastewater values, where thewater is mainly used for irrigation purposes. The verification in relation to targetvalues for t coli and helminths is, however, applicable for faeces afterst0rage/treaknent.

Strauss & Blumer:thal (1990) suggested &at one year of storage was su{ficientrmder tropical conditions (2&-30 oC), whereas at lower ayerage temperatures (17*20'C) 18 montls would be needed. Storage is especially beneficial in dry and hotclimates where rapid desiccation of the material takes place and low moisiure cootentsaid pathogen inactivation. Esrey et al. (1998) stated that there is rapid pathogendestruction at moisfure levels below 25% and that this level should be aimed for indry urine diversion toilets that are bassd on dehydration (i.e. storage). Low moisturecontent is also beneficial in order to reduce odour and fly breeding. Regrowth ofbacterial indicators and some pathogens (EHEC and Salmanella) may, however, occutafter application of moisture (water) or if the material is mixed with a moist soil, asindicated by results reported by Austin {2001).

The reduction of viruses in excreta is related to storage period and storageconditions. Figure 4.1 exemplifies this wi:h a risk calculation for rotavirus in relationto storage.

Protozoan cysts are sensitive to desiccation, and this also affects their survival onplant surfaces (Snowdon, Cliver & Converse, 1989; Yates & Gerba, 1998). Normalmoisture levels do not inactivate Ascaris eggs. Moisture levels below 5o/o ak needed(Feachem et al., 1983), but information on the corresponding inactivation time iscurrently lacking.

To treat excreta, thermophilic digestion (50 oC for 14 days) and composting inaerated piles for one month at 55-60 oC (plus 2*4 months of fuither maturalion) arerecommended and generally accepted procedures that will satisfy the reduction ofpathogens to achieve the health-based target values. Recommendations for treafiientof, for example, faecal sludge and orgaaic household waste (food waste) also rely onsuch temperatures (EC, 2000). Under controlled conditions, composting at 55*60 "Cfor l*2 days is sufficient to kill essentially all pathogens (Haug, 1993). The longerperiods stated give a handling margin. It is common thal cold zones form wi&in thedigested or compost material, resulting in local areas with less inactivation.

Guidelines for the safe use oJ'wastewater, excreta and grqwater

2 months,20 "C3 months, 20'C4 months,20'C5 months,20 "C6 months,20'C1-6 months,4 'C

log.,o P,"

E{Gct of storage rime on rotaviru, .tlltfi;liurlund, Ashbott & Strenstrdm, 2002)

* 4.3 Microbial reduction targetsThe approach adopted in lhese Guidelines focuses on risks from the chain ofexcretaand greywater use from collection to the consumption of food crops eaten. Data onhealth effects were used to assess the infectious disease risk and harmonize with theapproach takea in Volume 2 of the Guidelines. The analyses took account ofconsamption of crops eaten raw and of risks *om direct conlact with treated excreta(involving involuntary soil ingestion). Direct correlations between the relative risks ofwastewater and treated excreta applications have not been establi*red. However, theguideline values presented for both are in the same nrnge as exemplified for lscaris inBox 4.1.

Based on the exposure scenario for wastewater irrigation, it was shown that, inorder to achieve <10-6 DALY per person per year for rotavirus, total pathoganreductions of 6 log units for the consumption of leaf crops (letnrce) and 7 log rmits forthe consumption ofroot crops (onions) are required. Applying these values to excreta,this implies about an 8-9 log reduction for faeces (assuming a 100-fold dilution). Therisk from sourca-soparated urine and greywater relates to the faecal cross-coniamination that occurs. Based on measurements, this cross-contamination isusually less than 10-a of excreta, thus similar to a 100-fold dilution of wastewater witha need for a pathogen reduction of <4*5 log units as the performance target forunrestricted irrigation to achieve the tolerable additional disease burden of <10-oDALY per person per year.

As an example, in source-separated urine, the faecal cross-contamination wasestimated to be within a range of 1 .6-1 8.5 mg of faeces per litre of urine, with a meanof 9.1 * 5.6 mg/I, thus resulting in about a 5 log lower concentration of potentialpalhogens than in faeces. The faecal contamination of greywater was at a similarlevel, estimated to correspond to a faecal load of0.04 g/person per day. Because therisks associated with exposure to rotavirus are estimated to be the highest, this level of

64

0.4=o

F o'z

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Volume 4: Excreta and grelnvater use in agriculture

Box 4.1 Comparative performarce targeft for viable helminth eggs in *tsterf,rter,faecal matler and faecal sludge

. Wasa€water perfurmance target lor unrestricted irrigation: Sl egg/line

. Rw raae (wat€r requirements expressed in m/year), cornpared with an egg applicationrate on tfie soil, Re, of: Re < I 0' Rw (eggs/ha'year)

The use oftreated excreta or faecat sludge should ro1 enrich the soil wi* a higha eggconcentration thaa the quantity permitted by the application of irrigation water. Thesludge application nte depends on lhe egg concentralion in the torat solids Eg(expressed as eggs/g total solids). The sludge quattity apptied to the soil Rs thusamounts to: Rs < Re/Eg = l0'RwlEg (g total solidsiha'year).zYearly helminth load*om irrigation {rsing an average of, e.g., 500 mm/year): 5500 helminth eggs/m''yearpermissible. Application of treated faecal matter (same quantities as in goodagriculturalpracticeofnanure):10tmanurelha'yeuatzsYototalsolids(l kglm''yeat):250 g total solidVm2'year.

[he]niaths eggsltolerable 55001250:2 helmiath eggslg total solids{with 1000 mm/year:4 helminth eggslg toial solids)

Guideline value set to I helmirth egg/gtatal solids (to accor:nt for variability).

pathogen reduction will provide sufficient protsction against bacterial and protoz,oalinfections.

These log unit pathogen reduction levels may be achieved by the application ofappropriat€ health protection measures, each of which has its owr! nssociated log unitr€duction or range of reductions (Table 4.3). A combination of lhese measures is usedsuch that, for all combinatioDs, the sum of the individual log unit reductions for eachhealth protection measure adopted is equal to the required overall reduction. Severalof the steps are similar to what has been presented in Volume 2 of the Cuidelines,while the pathogen reduction due to treatment will differ. Trea:ed excreta afe alwaysapplied as a fertilizer in combination with planting or during the initial growttt period.Thus, a withholding period of normally more than one month applies, except forapplication of greywater, which is normally done for irrigation purposes.

In Volume 2 of these Guidelines, it was stated that in order to achieve the health-based target of <10-6 DALY per person per year for rotavirus, wastervater treatment isrequired to reduce the E. coli comt by 4log units or a similar patlogen reduction. Thecorresponding reduction of raw faecal material will thus be 6 log units, whilenormally a2logunit reduction will suffice for urine and greywater.

Microbial reduction targets for protection against helminth infections are based onthe results of microbiological studies. Although investigations related to risk shouldbe based on the number of viable eggs, in the microbiological investigations, thereduction refers to the percentage of viable eggs out of the total egg population andnot the actual numbers.

An effective health protection measure for removing helminth eggs from thesrrface of crops eaten uncooked (e.9. lettuce leaves) is washing the crop in a weakdetergent solution (washrng-up liquid is suitable) and rinsing thoroughly wirh safedrinking-water. Helminih eggs are very "sticky," so they easily adhere to cropsurfaces; the detergent solution releases them into the aqueous phase. This controlmeasure redr.rc€s the number of eggs on the crop surface by l*2log rmi* (8. Jirnenez-Cisneros, personal communication, 2005).

Guidelines for the safe use of wastewateti excreta and greywater

Table 43 Pathogen reductions achievable by verious health protection meNsures

Control measure' Pathogen Notesreduction0og unitg)

Excreta storage without *eshadditions

Greywater treatment

Localized (drip) inigation withurine (high-growmg crops)

Materials directly worked intothe soil

Pathogen die-off (wi&holdingtime one month)

Produce washing withwater

Produce disinfection

Producs peeling

Produce cooking

The required pathogen reduction to be achieved byexcreta treatmeit refers to the staied storage aimesand conditions il Tables 4.4-4.6 {below) withoutaddition offresl unlfeated excreta (faeces and|rine) as based on measulemenls and dskcalculations. Pathogen reductions for differenttreatment options are presented in chapter 5, andexamples ofrisk calculations h chapter 3.

Values relate to &e treatment options described inchapter 5. Generally, the highest exposurereduction is related to subsurface irrigation.

Crops, where the harvested parn arc not in contactwith the soil.

Should be done at the time when faeces or urine isapplied as a fertilizer.

A die-offof 0.5*2 log units per day is ciied forwastewater irrigation. The reduciion values citedhere are more conservative to account for a slowerdie-offof a fraction of the remaining organisms.The log unit reduction achieved depends onclimale {temperatlre, sanlight intensity, humidity),time, crop typ€ and other facts:s.

Washing salad crops, vegelables and *uit withclean water.

Washing salad crops, vegetables and fruit with aweak disinfectant solution ald rinsing with clernwafer.

Fruits, root crops.

Immersion in boiling or close-to-boiling waterutil the food is cooked ensures pathogendestruction.

l*>4

24

I

4-N

z

6-7

Sources: Beuchat (1998); Petterson & Ashbolt (2003); NRMMC & EPHCA (2005).

Treatment processes to achieve, or partially achieve, the pathogen reductionsexist. Different investigations show that in collected and stored dry faecal material, atime period of between 6 and 12 motths may suffice with the application of anelevated pH and high ambient temperature (Table 4.4 and Table 4.5). If the number ofhelminth eggs is <l per g total solids, then no additional health protection measuresare required in relation to this group of organisms, as the talget value is automaticallyachieved (this is the typical situation in most industrialized countries).

W 4.4 Verilication monitoringTo ensure that health-based targets are being met, it is important to developp€rformance targets that can be monitored. There are three types of monitoring:

. Validation js the initial testing to prove that a system as a whol€ and itsindividual components arc capable of meeting the performance targets an4thus, t}le health-based targets.

66

Volume 4: Excreta and greywater use in agriculture

. Operational monitoring is the routine monito*ng of parameters that can bemeasned raprdly (i.e. throlgh tests that can be performed quickly, parametersmeasured online, or thrcugh visual inspection) to inform managementdecisions to preyent hazardous conditions from arising.

. Verification monitoring is done periodically to show that the system isworking as intended. This type of monitoring usually requires morecomplicated or time-consuming tests that look at parameters such as bacterialindisators (8. coli) or helminth eggs.

Monitoring is further discussed in chapter 6. Verihcation monitoring requirementsfor treated fuecal sludge, urine and greywater are discussed below.

4.4.1 Treatment at excreta and grqwaterPathogen mrmbers in raw or trealed faecal sludge, exsreta or greywarer are notmeasured routinely (if at all). The performance of the on-site featrnent used topartially or wholly ensure <10- DALY per person per year cannot, therefore, bedetermined on the basis of pathogan verifieation monitoring, but instead is based onvalidation of the general treatment efficiency. Verification monitoring is applicablemainly in larger collection systems or when a secondary off-site Seatrnent aftercollection from a number of individual units is made. The microbiologicalperformance of the larger system or the off-site tr€tment is evaluated by determiningthe content of a pathogen indicator bacterium, such as E. coli, in the treated material.The same applies for larger greywater collection and lreatment systems, where theeffluent may be monitored for verifcation purposes. For large-scale sysiems or whensecondary off-site treatment is necessary, the values in Table 4.2 above apply.

When other exposure barriers are appropriate and can be anforced" the aboveguideline values can be relaxed based on national or local decisions - for example,when a public body has the legal authority to require that crop restrictions be followedregularly or when a strong project management exists. For fruits and vegetables,special restrictions may apply. For subsurface adsorption systems for greywatern noguideline values apply. However, the siting of such systems should not interfere withgroundwater quality. For pond systems for greywater treaknen! the risk of promotingmosquito breeding should be evaluated, and pond systems should not be opted forunder circumstances where vector breeding may have a substantial impact on healthwithout incorporating mosquito contol me:xures into their design and operation.

4.4.2 Other heabh protection mcssuresopmational heakh protection measures include the agricultural use practices and thepreceding treatrnent and kansport. Even if a treatrnent is validated and verificationmonitoring has been done, process steps or handling practices may periodicallymalfunction, resulting in a fertilizer product that is not completely safe. Therefore,additional measures should be taken in order to further minimize the risk for diseasetransmission. These measures are applicable independent of tle scale of the systern(special considerations for small syslems are provided in section 4.4.3). Thus:

. Excreta and faecal sludge should be treated before they are used as fertilizer,and the treatment methods should be validated.

. Fquipment used for, for example, tansportation of unsanitized faeces shouldnot be used for the keated (sanitized) product.

Guidelines for the safe use of wastewate\ excreta and greywater

' Precautions related to the handling of potentially infectious material should betaken wheir applyiag faeces to soil. These precautions include personalprotection and hygiene, including hand washing.

' Treated excreta and faecal sludge should be worked into the soil as soon aspossible and should not be left on the soil surface.

. Improperly sanitized excreta or faecal sludge should not be used forvegetables, fiuits or root crops that will be consumsd raw, excluding fruittregs.

' A withholding period applies for treated excreta aad faecal sludge. This periodshould be at least one month.

' The treatments given in Table 4.4 can be used as off-site secondary treatment(marerial removed *om toilet and primary *eatment at the household level).

Table 4l Additional treatments for excrete and faecal gludge off-site, at collection and trertmentstations fiom large-scrle wstems (municioal level)'

Treatment Criteril Comment

Alkaline pH >9 during >6 monthstrealrnent

Composting Temperature >50 oC for >lweek

Incineration Fully incinerated (<107ocarbol in ash)

Run in balch mode without addition of new material.

Composting is recommended mainly as aa off-site secondary treatment at a largescale, since the process may be diffrcult to run. Temperatures above 50 oC should beobtained in all material for at least one week. Times may need to be modified basedon local conditions. Large systems need a higher level of protection than what isrequired at the household level, and additional storage adds to safety. Storage atambient conditions is less safe, but acceptable, if the conditions above apply. Shorterstorage times can be applied for all systems in very dry climates where a moisturelevel below 2QYo is achieved. Sun drying or exposure to temperatures above 45 "Cwill substantially reduce the time required. Rewetting may result in growth ofSalmonella and E. coli.

4.4.3 Excras in small systemsFor smaller systems, validation together with operatiorcl monitoring apply. In small-scale systems in developing countries, it is impractical or even impossible to relateperformance to actual guideline values. Validation of dry collection of excreta fromlatrines in Viet Nam showed that it is possible to achieve a total die-off of Ascaris ovaand indicator viruses (>7 log reduction) within a six-month period (mean temperatre3l-37 oC, pH 8.5*10.3 in the faecal material and moisture content 2q-55%\(Carlander & Westrell, 1999; Chien et al., 2001). At lower temperafures(approximately 20 "C), longa storage times apply for a total destruction of Ascaris(Phi et a1.,20A4), although similar high reductions were found under cold conditionsin China (Wang, 1999;Lan et al., 2001). Addition of a pH-elevating chemical (e.g.lime or ash) has been shown to enhance the inactivation of pathogens in smallsystems. Other methods ao rcduce the pathogen content rely on elevation internperature, desiccation or prolonged storage at ambient conditions.

68

Temperature >35 oC and/or moisture <25Yo. LowerpH and/or wetter material will prolong the eliminationtime.

Minimum requirement. Longer time needed iftemperature requirement cannot be erxured.

Storage; 1.5-2 yearsambient:emperalure2-20"C

Storage; >l Yearambientaemperature>20-35'C

Volume 4: Excreta and greryoter use in agriculture

The practical options depend on the scale of the system (i.e. at household ormunicipal level). More technical options are available at tlle municipal scale.Implementation of treatment on an individual level has added difficulties, involvingpeople's (often well established) habits and practices. The scale also influences thecombinations of suitable primary and secondary treatments and barriers. Handlingsystems need to be adapted 1o the different treatments. Within operational monitoring,the on-site storage conditions givan in Table 4.5 apply.

Table 4.5 Recommendations for storrge tre8tment ofdra excretr rnd frecal sludge before use atthe household and municipal levels'

Treatm.nt Criteria Comment

Will eliminaie bacterial palhogens; regrowth of-5. coli andSalmonella may be considered if rewetted; will reduce viruses andparasitic protozoa below risk levels. Some soil-bome ova maypersist in low numbers.

Substantial io total iractivation of viruses, bacteria and protoma;inactivation of schistosome eggs (<l month); hactivation ofnernamde (roundworm) eggs, e.g. hookwor:n(AnqilostomalNecartor) and whipworn {Trichuris); survival of acertain percentage (1G-307o) ofz{scaris eggs (>4 montls), while amore or less co:nplete inactivation oflscanr eggs will occurwithin I year {Strauss, 1 985).

Iftemperature >35 "C and moisture <25%" lower pH and/or wettermaterial will prolong the time for absolute elimina,ion.

No addition of new material.

For operational verification, the following points should fixther be considered foron-site storage and collection:

. Primary treatment (in the toilet) includes storage and alkaline treahent byaddition of ash or lirne.

. pH elevation to above 9 is preferred which can be obtained by the addition ofalkaline material (e.g. lime or ash; 200*500 ml; enough to cover the freshfaeces) after each defecation. (Total elimination may not occur, but asubstantial reduction will be achieved.)

. Secondary off-site treaknents as for larger systems (municipal level),including alkaline treatrnents, composting or incineratioa (Table 4.5), can beapplied off-site and result in a further reduction when municipal collection isorganized.

. In small-scale sys&ms (household level), the faeces can be used after primaryon-site treatment if the criteria in Table 4.3 are fulfilled.

As for larger collection and application systems, the following points needconsideration:

Personal protection eqaipment should be used whur handling and applyingfaeces.Faeces should additionally be mixed into the soil in such a way that they arewell covered.A withholding period of one month should be applied, i.e. one monlh shouldpass betwean fertilization and harvest.

Alkalinerea8nent

pH >9 during>6 months

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Guidelines for the safe use af wastewatey, excreta and grqwater

4.4.4 Operational monitoringfor urine in large- and small-scale slsremsThe major risks in relation to collected urine relate to faecal cross-contaminatioa inthe source-separating toilets. Specific recommendations for large-scale systems mayneed to be adapted based on local conditions, accounting for behavioural factors andthe technical systems selected. If a system is clearly mismanaged (i.e. faeces can beseen in the urine bowl or other routes of cross-contamination are observed), prolongedstorage should be applied. The recommended storage times related to pathogenreduction at different temperatures are based on validation monitoring and riskassessment calculations (H0glund Ashbolt & Stenstrdm, 2AA2\. The operationalverification is divided between largc systems with a central collection and family-based systems (Table 4.6). These values are applicable for all systans where thecollected urine is mixed between several individual units and subsequently used as afertilizer for crops.

For an individual one-family system and when the urine is used solely forfertilization on individual plots, no storage is needed.

Table 4.6 Recommended guideline storage times for urine mirture' based on estimrted prthogencontent" and recommended croD for larger svstems"Storige Storagetemperature timefc)

Possible pathogens in the Recommcnded cropsurine mixture after storage

4 >l month Viruses, protozoa

4 >6 months Viruses

2A >l month Viruses

2B >6 months Probably none

Food and fodder crops that ar€ !o beprocessed

Food crops that are !o be processed,fodder cropso

Food crops that are to be procsssed,fodder crops"

All crops"

' Urine or urine and water. When diluted, it is assumed that ihe urine mixture has at least pH 8.8 and a. nitrogen conc€ntration ofat least I g/1.o Gnm-positive bacteria and spore-forming bac&ria are not included in the underlying risk

assessmerts, but are not normally recognized as causing any ofthe infections ofcotcsrn." A larger system in this case is a system where the urine mixfi:re is used to fertilize crops that will be

consumed by individuals other than members of the household from which the urine was collected.o Not grasslalds for production of fodder." For food crops tiat are conssmed raw, it is recommended that the urine be applied at least one monlh

before harvestiag and that it be incorporated into the ground if the edible parts grow above the soilsurface.

Sources: Adapted from Jdnssol et al. (2000); Hoglund (2001).

During storage, the urine should be contained in a sealed tank or container. Thisprevents humans and animals from coming in contact with the urine and hindersevaporation ofamrnonia, decreasing the risk ofodour and loss ofnitrogen. The urineshould preferably not be diluted. Concentrated urine provides a harsher environmentfor microorganisms, increases the die-offrate ofpathogens and prevents breeding ofmosquitoes; tlus, the less water that dilutes the urine, the better.

Specific recommendations include :he following:

. For vegetables, fruits and root crops consumed raw, a one-month withholdingperiod should always be applied.

. In areas where Schistosoma haeruqtobium is endemic. urine should not be usednear freshwater bodies.

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Volume 4: Excreta and greywater use in agriculture

. Urine should be applied close to the ground and preferably mixed with orwatered into the soil.

General recommendations for the use of urine are as follows:

. Direct use after collection or a short storage time is acceptable at the singlehousehold level.

. For larger sysftms, urine should be stored for iimes and under conditionsgiven in Table 4.6.

. An interval of at least one monlh should be observed between fertilization andharvesl.

. Additional stricter recommendations may apply on a local level, in the case of*equent faecal cross-contamination. The recommendations for storage timesare directly linked to agricultural use and choice ofcrop (Table 4.6).

Additional practices to minimize the risks include the following:

. When applyng the urine, precautions related to ihe handling of potentiallyinfectious material should be taken. These precautions could, inter alia,include wearing gloves and &orough hand washing.

. The urine should be applied using close-fo-the-grorurd fertilizing techniques,avoiding aerosol fonnation.

. The urine shauld be incorporated into the soil. This is best done mechanicallyor by subsequent application ofirrigation water.