i

. . . . . . . . . .

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The Leather Sector

Environmental ReportDDRRAAFFTT

ii

TTaabbllee ooff CCoonntteennttssPreface i

Executive Summary 1

1. The Environmental Technology Programme for Industry 2

1.1 Demonstration Project 2

2. The Leather Industry 3

2.1 A Profile 32.2 Raw Materials and Chemicals 3

2.2.1 Raw Materials 32.2.2 Processing Chemicals 32.2.3 Water 3

2.3 Process and Operation 32.4 In-House Environmental Conditions 4

3. Waste Generation 5

3.1 Wastewater 53.1.1 Source 53.1.2 Quantity 53.1.3 Characteristics 5

3.2 Solid Waste 63.2.1 Types of Solid Waste 83.2.2 Characteristics of Solid Waste 83.2.3 Disposal of Solid Waste 8

3.3 Air Emission 93.3.1Emissions from Generators and Boilers 93.3.2 Emissions from Process Activities 9

4. Environmental Impacts of Tannery Wastes 9

4.1 Pollutants of Tanneries and their Impacts 94.1.1 pH 94.1.2 Biochemical Oxygen Demand 94.1.3 Chemical Oxygen Demand 94.1.4 Sulphide 104.1.5 Chromium 104.1.6 Suspended Solids 104.1.7 Salts 104.1.8 Solvent Vapours 10

5. Remedial Measures 10

5.1 General Measures 105.2 Environmentally Clean Technologies 11

5.2.1 Review of Cleaner Technologies 115.2.2 Reuse of Chrome 12

5.3 Wastewater Treatment Technologies 135.3.1 Primary Treatment 135.3.2 Secondary Treatment 135.3.3 Feasible Technology 14

6. Wastewater Treatment System: PreliminaryDesigning and Cost Estimation 14

6.1 Wastewater Treatment for Wet FinishingProcesses 14

6.1.1 Design Data 156.1.2 Assumptions 156.1.3 Components of the Plant 156.1.4 Land Requirements 156.1.5 Final Effluent Quality 156.1.6 Estimation of Capital and

O&M Costs 176.2 Wastewater Treatment for Processing

Raw Hides to Finished Leather 176.2.1 Design Data 176.2.2 Assumptions 186.2.3 Land Requirements 186.2.4 Components of the Treatment

Plant 196.2.5 Final Effluent Quality 196.2.6 Estimation of Capital and

O&M Costs 19

List of Tables

Table 2.1: Number of Tanneries in Different Citiesof Pakistan

Table 3.1: Process-wise Water Consumption andWastewater Generation of a Tannery

Table 3.2: Quantity of Wastewater Discharge fromTanneries

Table 3.3: Characteristics of Sludge Wastewater(Process-Wise)

Table 3.4a: Characteristics of Composite Wastewaterof a Tannery

Table 3.4b: Characteristics of Composite Wastewaterof a Tannery

Table 3.5: Characteristics of Sludge in CompositeWastewater of Tannery-A

Table 3.6: Estimated Quantities of Solid Waste andDisposal Practices

Table 3.7: Characteristics of Solid WasteTable 5.1: A Brief Review of Cleaner TechnologiesTable 5.2: Summary of Cost-Benefit Analysis for

CRRPTable 6.1: Estimated Daily Pollution Loads of

Tannery A and BTable 6.2: Load of Aeration TankTable 6.3: Land Requirement (m2)Table 6.4: Final Effluent QualityTable 6.5: Estimated Investment Cost of a Treatment

Plant for (Wet) Finishing Tannery ProcessTable 6.6 Daily Pollution LoadTable 6.7: Load of Aeration TankTable 6.8: Land Requirement (m2)Table 6.9: Effluent Quality of Treatment PlantTable 6.10: Estimated Capital Cost of a Treatment

Plant with the Present Hydraulic Load ofa Tannery

List of Figures

Figure 2.1: General Processes Flow DiagramFigure 3.1: Drying Characteristics of SludgeFigure 4.1: Environmental Input of a Tanner

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List of Figures

Figure 5.1: Chrome Recovery and Reuse PlantFigure 6.1: Preliminary Layout of the Treatment Plant for

a Medium Size Segmented Tannery with aMechanical Dewatering System

Figure 6.2: Preliminary Layout of the Treatment Plant with Mechanical Dewatering System

Figure 6.3: Preliminary Layout of the Treatment Plantwithout Mechanical Dewatering System

Annexures

Annexure 1: List of Chemical Used in the TanningProcess

Annexure 2: National Environmental QualityStandards (NEQS)

Annexure 3A: Preliminary Design of a Treatment PlantAnnexure 3B: Preliminary Design of a Treatment Plant

iv

PPrreeffaacceeThis report has been prepared as part of the ETPIdemonstration project component - collaborative effortsbetween the industry and FPCCI - and aims to address theenvironmental pollution problems in the leathermanufacturing sector. This report has been prepared onthe basis of the findings of environmental audits of fourtanneries conducted by ETPI. The purpose of theenvironmental audits was to assess the nature and extentof the environmental problems and to develop solutionfor the tanning industry.

Audits have established the basis of the demonstrationproject. Findings and recommendation of audits are beingimplemented in the selected unit and disseminated to thesector as a whole. Industrial unit level informationremains confidential with ETPI. However, this program,at each stage shares the progress of the work with all itsstakeholder. This report gives an overview about theenvironmental aspects of tanneries along with thepossible investment required to abate these problems tomeet the present and future environmental legislation. Itis hoped that this effort will help to enable the localtanneries to initiate the efforts to combat the present andfuture environmental problems and to produce an

environmentally clean product. Further, this study maycontribute to the efforts which are being made by localresearch, education, policy making and monitoringinstitutions.

The environmental audits of four tanneries wereconducted jointly by two consulting firms of ETPIconsortium, hired by Federation of Pakistan Chamber ofPakistan (FPCCI) to execute the program. These firms areNational Environmental Consulting (NEC) PrivateLimited and HASKONING of the Netherlands. Thegeneral report has been prepared by the core team ofETPI.

This report was first prepared in April 1997 on the basisof three audits and now it is being revised by adding moreinformation obtained from the fourth audit conducted inthis sector. Further, more details have been given onenvironmental technologies.

We acknowledge the co-operation of Pakistan TannersAssociation (PTA) and Tanneries who participated in theprogram and extended their co-operation in all the aspectsof study.

Consulting Team:

Mr. Mohammad Iqbal Co-ordinator Technology; ETPIMr. Izhar-ul-Haque National Environmental Consulting (Pvt.) Ltd. (NEC), PakistanMr. J. A. S. Berns HASKONING, The Netherlands

April 1998

1

EExxeeccuuttiivvee SSuummmmaarryy

The Federation of Pakistan Chambers of Commerce &Industry (FPPCI) being the apex body representing all thebusiness, trade and industrial organisations of the country,has launched a comprehensive five year program, called“Environmental Technology Program for Industry(ETPI)”, with technical assistance from the NetherlandsGovernment. The major objective of ETPI is to initiatemeasures to combat the existing and the expectedindustrial pollution problems which will also enable theindustry to comply with the National EnvironmentalQuality Standards (NEQS) and the forthcoming ISO14000. The program is under implementation with theinvolvement of progressive industrial units. These unitshave willingly participated in the program for theimplementation of the demonstration project.

Pakistan’s leather and leather products industry is one ofthe major foreign exchange earners amongst themanufacturing goods sector. At present, about 90 % ofthe leather is exported in the finished form. There arepresently over 595 tanneries in the formal sector and anequally large number of tanneries exist in the informalsector. The major cluster of tanneries are located inKarachi, Kasur, Lahore, Sheikhupura, Gujranwala,Multan, Sialkot and Jahangria. For leather production,locally available raw material ( hides and skins) andpredominantly imported chemicals are used.

In the leather sector a variety of finished leather isprepared which includes upper, lining, and garment etc.,from salted raw skins/hides. The chrome tanning methodis widely applied for preparation of finished leather.However, vegetable tanning method and a combinationof chrome and vegetable tanning method is also used.Most of the chemicals are used to prepare the skins orhides for the tanning purpose. After performing theirfunctions these chemicals find their way into theenvironment.

The tanneries generate all the three categories of waste,i.e., liquid, air and solid wastes. The sources of airpollution in tannery are of two types; one is from thestack of generators and boiler and the other from theprocess. The emission here is below the NEQS standard.Hydrogen Sulphide and Ammonia generated fromdifferent sources such as washing of drums withammonia, effluent of de-liming processes and mixing oftanning and de-liming effluent. Although, the emissionsare intermittent they are nevertheless hazardous for thehealth of the workers.

The major solid wastes generated are dusted curing salt,wet trimmings, dry trimmings, wet shavings, buffings,raw material packing, etc. Except dust salt other solidwaste has a great attraction in local market. Poultry feedmanufacturers due to the protein content of fleshing, raw

trimmings, chrome shavings, dry trimmings, buffing dust,etc. collect this material from the tannery. The mainproblem associated with some of these wastes is theirchrome content. End use of chrome containing solidwaste varies in different parts of the country. In Punjab itis used for making leather board whereas in Karachi it isused for making poultry feed. During the process trivalentchromium (contained in the solid waste) is changed intohexavalent chromium (carcinogenic).

Wet processes of the tannery are the main source forgenerating the wastewater. Water consumption per kg ofraw hides varies from tannery to tannery. Consumption ofwater should not go beyond the normal requirement i.e.,50 litre/kg. However, it was found that tanneries aregenerally consuming more water as compared to thenormal required quantity. During the peak season, theproduction and wastewater generation doubles. Despitethe seasonal fluctuation, daily fluctuation in wastewatergeneration also exists due to variation in the quantity ofraw material processed daily. The characteristics ofwastewater shows that it is highly polluted with Bio-chemical Oxygen Demand (BOD5), Chemical OxygenDemand (COD), suspended solids, settleable solids, totalKjedhal Nitrogen, Sulphate and Chromium, Chloride, etc.A considerable quantity of Sludge is also present in thewastewater. Values of these parameters vary from tanneryto tannery due to different processes and raw materialutilisation.

Due to the high pollution level in wastewater, very severeenvironmental impacts are associated with its dischargeinto the environment without applying any measures.

Recommended remedial measures for the variousenvironmental problems are training of the workers,provision of safety items, improvement in the drainagesystem to avoid formation of hydrogen sulphide gas,installation of boards and notices about safety and healthregulations at working places of the tannery and a properarrangement to stop the use of tanned solid waste for thepreparation of poultry feed.

Implementation of cleaner technologies such as waterconservation, use of environment friendly chemicals,green fleshing of hides, application of hair savingmethods , recycling of sulphide liquor, Lime splitting andtrimming and chrome recovery and reuse can provideeconomical benefits and will help the local tannery tocombat the environmental problems.

Approximately 30% discharge of the unused chromecompound is a financial loss for a tannery. This can easilybe recovered from the spent tanning effluent and this canthen be reused without compromising the quality ofleather. Cost benefit analysis for chrome recovery andreuse plant has also been carried out which gives a pay-back period of 6-7 months.

A wastewater treatment system is inevitable and different

technologies are available in this regard. Two stage of

treatment are suggested i.e., primary (physio-chemicals)

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and secondary (biological). The characteristics of

wastewater permit low loaded activated sludge system for

biological treatment to bring down the level of BOD5,

COD, suspended solids, chrome, sulphide and pH. For the

removal of salt, in-house improvement is suggested. An

estimated investment cost for such a treatment system for

a tannery processing about 12000 kg of hides per day is

approximately 44 million with a cost of about 7-9 million

rupees for operation and maintenance.

The wastewater generated from tanneries involved insegmented production i.e., producing finished leather byusing wet blue also contains significant pollution levelwhich also needs to be treated before discharge into thelocal environment. The cost of a treatment system(primary and secondary) was estimated for two tanneries,the tannery processing 8000- 10,000 kg of wet blue perday would cost about Rs.10 million and for a tanneryprocessing 600 - 1500 kg of wet blue per day, the costwould approximately be Rs.3 million.

11.. TThhee EEnnvviirroonnmmeennttaall TTeecchhnnoollooggyy PPrrooggrraamm ffoorr IInndduussttrryyThe Environmental Technology Program for Industry(ETPI) is a joint project of the Federation of PakistanChambers of Commerce and Industry (FPCCI) and theGovernment of The Netherlands. The primary objectiveof ETPI is to promote the use of environmentally safetechnologies for the production of environmentally safeproducts by Pakistan's manufacturing/ industrial sector.

The FPPCI, with the assistance of the Dutch government,has hired a consortium of local and foreign consultingfirms to provide the required technical expertise andsupport. The members of the consortium are:

• National Environmental Consulting (NEC) (Pvt.).Ltd., Karachi-Pakistan; the lead consultant;

• HASKONING Royal Dutch Consulting Engineeringand Architects, The Netherlands;

• KRACHWERKTUIGEN (KWT), The Netherlands;

• Management for Development Foundation (MDF),The Netherlands; and

• Hagler Baily, Pakistan.

This five-year project began in 1996 and works withPakistani industries and their associations in identifyingthe most economical pollution prevention and abatementtechnologies and in implementing these solutions. Thefive components of the program include the developmentof a user-friendly database of relevant information,institutional networking within and between keyindustrial institutions of the country, dissemination andcommunication to promote cleaner industrial production,institutional support and training to create in-houseenvironmental capacity within Chambers and IndustrialAssociations, and Demonstration Projects in 20 selectedindustrial sub sectors to demonstrate the economicfeasibility and environmental efficacy of environmentaltechnologies.

Three representative industrial units were selected in eachsub-sector for preliminary environmental audits to assessthe extent and nature of the environmental problems.Based on the results of these audits, a general sub sectorreport is prepared in consultation with industry experts.The sub sector report highlights the key environmentalissues in that industrial sector, lists possible solutions formajor environmental problems in that sub sector, andrecommends the technologies that are most economically

feasible and environmentally appropriate to Pakistan'sindustrial conditions.

1.1 Demonstration Project

Each component of ETPI has been given a specificdefinition and carries its own objective, scope of the workand methodology. The present study is dealing with thedemonstration project component. Hence, in this report,this component will be discussed in detail.

Physical interventions in the form of demonstrationprojects are an integral part of the ETPI. A demonstrationproject is defined as a “project under which thoseenvironmental technologies will be implemented whichqualify both the technology and financial feasibilitycriteria and at the same time are relevant to the localindustrialists. Improvement in processing practices willalso be an essential part of the demonstration projects.”

Objectives of the demonstration project include:

• To establish live examples in the major industrialsectors of Pakistan for the direct dissemination ofenvironmental technologies in the country.

• To prepare a representative database in the shape ofindustry specific Environmental Audit forestablishing the environmental policy implication,financial and institutional support requirements.

• To create more awareness and committedconstituencies amongst industrialists for makingenvironmental investment.

• To identify industry sector specific research anddevelopment areas in the discipline of environmentand industry for local and international researchinstitutions.

For the implementation of the demonstration project, acomprehensive procedure for the selection of industries ineach sub sector has been developed. According to thisprocedure, three industries will be selected for anEnvironmental Audit from each sub sector. Subsequentlyone of these three will be selected for the demonstrationproject.

In the sub sector of leather manufacturing, instead ofthree Environmental audits, 4 have been carried out. Thefindings of these audits have been compiled in the presentreport. During the environmental audit work, it wasmentioned that the environmental audit report of theindividual tannery will be a confidential document andthat document must not be made accessible to every body.

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It was therefore decided to prepare a general report bytaking the inferences from these audits. However, it isdifficult to generalize the information obtained fromenvironmental audits for the whole sector. To overcome

this short coming help has been taken from secondaryinformation. This report has been prepared with an aimthat it will provide a general scenario about theenvironmental problems of local tanneries.

22.. TThhee LLeeaatthheerr IInndduussttrryy

2.1 A Profile

Pakistan’s leather and leather products industry is one ofthe major foreign exchange earners amongst themanufactured goods sector. At present about 90 % of theleather is exported in finished form. During the year1994-95 export earnings from leather and leather goodsamounted to US $ 648 million. About 40 million skinsand hides were processed during this year.

There are presently over 596 tanneries in the formalsector and equally large number tanneries exist in theinformal sector. Major clusters of tanneries are located inKarachi, Kasur, Lahore, Sheikhupura, Gujranwala,Multan, Sialkot, and Jahangria. For leather productionlocally available raw material (hides and skins) andimported process chemicals are used predominantly.

Table 2.1: Number of Tanneries in DifferentCities of Pakistan

Cities No. of Tanneries PercentageKarachi 170 28.5Multan 59 10.0Kasur 180 30.2Sheikhupira 24 4.0Sialkot 135 22.6Gujranwala 28 4.7Total 596 100

Source: NEC Survey.

2.2 Raw Material and Chemicals

2.2.1 Raw MaterialsIn the leather sector, sheep/goat skins and cow buffalohides (salted) are used as raw material for the productionof leather. Most of the raw material is obtained from thePunjab and Sindh provinces. However, imported rawmaterial is also used.

During the peak season, which starts every year after Eid-ul-Azha and extends up to two on three months, theprocessing in leather sector reaches to a level of aboutdouble the normal production. Normal production alsovaries from day to day depending on many conditionsincluding the availability of the raw skins and hides.Fluctuation in the use of raw material directly effectswaste generation.

2.2.2 Processing ChemicalsA variety of chemicals, from common salt (sodiumchloride) to the very fine finishing chemicals, are used inLeather sector. About 130 different type of chemicals areapplied in leather manufacturing, depending on the typeof raw material and the end product of the industry. Thesechemicals are divided into four major classes, described

below, as per their use. The list of chemical is given inannexure 1.

Pre-tanning Chemicals: These chemicals are used toclean and to prepare the skins for the tanning processes.These chemicals do not react with the skins’ fibre,therefore are not retained by the skins. These chemicalsafter performing their respective functions are dischargedwith the wastewater.

Tanning Chemicals: These tanning chemicals react withthe collagen fibres of the skin and convert them intoleather. As these chemicals react with the fibre, therefore,a considerable quantity is retained by the fibre.Nevertheless, a significant amount remains unused and isdischarged with the wastewater. Basic chrome sulphate isthe tanning chemical, which most widely used in localtanneries. This is an expensive chemical and also poses aserious environmental threat. Besides environmentalproblems, its discharge into wastewater is also a financialloss. Vegetable tanning materials are also used in localtanneries but their use is not common as compared tochromium.

(Wet) Finishing Chemicals: These chemicals are used toimpart certain properties, e.g. appearance, softness,flexibility, colour, strength, etc. as per the requirement ofthe finished product. These chemicals also react with thecollagen fibres of the tanned leather and again amaximum quantity of the applied chemicals is retained bythe skins. Whereas un-reacted or residual chemical isdischarged with the wastewater of the process.

Finishing Chemicals: Finishing chemicals are applied assurface coating material to impart the desired surfacefinish to the leather. Most of the applied quantity isretained by the surface of the leather. However, due tolimitations of the application procedure some quantitydoes go into the waste.

2.2.3 WaterAn extensive quantity of water is used in the leathersector. The data shows that 50 -150 litre of water is usedfor the conversion of one kg of raw skin into leather.Tannery wet processes are the major consumers of water.The water in the wet processes and operations is used as acarrier to facilitate all chemical reactions involved inleather processing. After completion of the process andoperation, the water leaves the system as wastewater inthe same quantity as added to the system. Groundwater isused as a major source of the processing water in Leathersector.

2.3 Process and Operation

In the leather sector a variety of finished leather isprepared including upper, lining, and garments fromsalted raw skins/hides. The Chrome tanning method is

4

widely used for the preparation of finished leather.However, vegetable tanning method and a combination ofchrome and vegetable tanning method is also beingapplied. The three tanneries selected for the audit underthe Environmental Technology Program for Industry

(ETPI) apply chrome tanning process for the productionof finished leather. A series of processes and operations areinvolved for the production of leather. These are describedas follows. The flow diagram of processes and operations isgiven in figure 2.1.

Figure 2.1: General Processes Flow Diagram

↓RAW MATERIAL (RAW SKINS/HIDES) WASHING

↓ ↓PRE – SOAK FAT LIQUORING & DYEING

↓ ↓SOAKING WASHING

↓ ↓SOAK WASH SAMMYING/SETTING

↓ ↓UNHAIRING & LIMING VACUUM DRYING

↓ ↓FLESHING AIR DRYING/STEAM DRYING

↓ ↓DELIMING STACKING HORIZONTAL

↓ ↓WASHINGS TOGGLING

↓ ↓BATING DRY SHAVING

↓ ↓DEGREASING TRIMMING

↓ ↓PICKLING BUFFING

↓ ↓CHROME TANNING SPRAYING/COATING/DRYING

↓ ↓WET BLUE STORAGE GLAZING/POLISHING

↓ ↓*SPLITTING OF WET BLUE IRONING

↓ ↓SORTING OF WET BLUE MEASURING

↓ ↓SHAVING OF WET BLUE SELECTION

↓ ↓WET BACK + PACKING

NEUTRALIZATION +RETANNING

Hide processing

2.4 In-House EnvironmentalConditions

In-house environmental condition and practices varyfrom tannery to tannery. However, the findings of theaudited tanneries reflect the following facts.

• Ventilation system is poor to fair.• Practices are conventional.• All processing chemicals are handled carelessly.• Use of gloves, aprons, goggles, and masks during

chemical handling is not common. Even if these

items are provided by the tannery, workers do notpay much attention. The un-usage of theseaccessories during work may be due to the andignorance and un-awareness of the workers.

• Information boards about safety and healthregulations are not installed in the tanneries.

• Loading and unloading of the skins/hides duringprocessing is normally carried out manuallywithout using gloves and proper clothes forprotection. Consequently the cloths of the workersbecome completely wet with the float of thedifferent tanning processes.

Wet Processes

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Table 3.1: Process-wise Water Consumption and Wastewater Generation of a Tannery

Processes Percentage of Water Used forProcess

Average Wastewater Generation(m3 / day) (12,000 kg/day)

(A) Processes = Raw - Wet Blue:Pre-soak washSoakingSoak wash

500500500

606060

Liming & Un-hairing 500 60De-limingWashing-1Washing-2

200200200

242424

Bating 200 24DegreasingWashing -1Washing -2Washing -3Washing -4

200200200200200

2424242424

Pickling/Tannin 80 9.6Water Consumption from raw to wet blue stage 465.6(B) Processes = Wet Back - Finished Leather:Same weight ( 10,000 kg) of the wet blue skins is processed daily throughout the year for onward wet finishing processesWet back 300 36Neutralisation Re-tanningWashing 200 24Fat liquoring / dying 200 24Washing 200 24Water Consumption in wet finishing 108Total Water Consumption (A+B)= Total Wastewater Generation

574

Source: ETPI Survey - calculated on the basis of water recipe provided by the tannery

33.. WWaassttee GGeenneerraattiioonnAll the three categories of waste, i.e. liquid, air and solid,are generated by the tanneries. Following sectiondescribes the source, disposal, characterisation andquantification of these wastes.

3.1 Wastewater

3.1.1 SourceWet processes of the tannery are the main source of thewastewater generation. Some mechanical operations alsocontribute small quantities of wastewater. Canteen,toilets, prayer hall or mosque also contribute a minorquantity of wastewater. Wet processes are highlightedin the flow diagram (Fig. 2.1). In the tannery processes,water is used as a chemical carrier to render the cleaningof raw hides and skins as well as to penetrate thechemicals facilitating reaction of chemical with collagenfibre of the skins. The process water, after completion ofthe process, is drained out as wastewater in the samequantity as it is added in the processes.

The wastewater is disposed off without any treatmentinto the local environment.

3.1.2 QuantityWater consumption per kilogram of raw hides variesfrom tannery to tannery. Generally water consumptionshould not go beyond the normal requirement i.e., 50

litre /Kg. However, it was found that the tanneries aregenerally consuming more water as compared to thenormal required quantity. In some cases waterconsumption reaches to a level which is three time higherto the normal, i.e., 150 litre /kg of raw hides. Waterconsumption at each processing stage, for a tanneryprocessing sheep and goat skins, has been summarised inTable 3.1.

During peak season the processing of raw skins/hidesdoubles, which directly effects the quantity ofwastewater generation. Despite the seasonal fluctuation,daily fluctuation in wastewater generation also exists dueto the variation in quantity of raw skins/hides processeddaily. The wastewater discharge is also intermittent andneeds to be equalised before treatment. The quantity ofwastewater discharged from different tanneries is givenin Table 3.2.

3.1.3 CharacteristicsTannery wastewater is highly polluted in terms ofbiochemical oxygen demand (BOD), chemical oxygendemand (COD), suspended solids, settleable solids, totalkjeldhal nitrogen, conductivity, sulphate, sulphide andchromium. The values of these parameters are very highas compared to the values mentioned in the NationalEnvironmental Quality Standards (NEQS) set by theGovernment of Pakistan (see annexure 2). Pollutantvalues of different tanneries are given in Table 3.3 and3.4.

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Wastewater from each tannery process contains differenttypes of pollutants. pH varies considerably from 3.3 to12.6. Similarly, a large variation exists in parameters likeBOD, COD, Chloride, Sulphate, TDS, TSS, settleablematter, etc. In addition to these parameters, resultsclearly show that the wastewater carries considerablequantities of chromium. The discharge of thesechemicals into wastewater is not only hazardous butalso a financial loss.

A considerable quantity of sludge was also present incomposite wastewater. The settleable matter isresponsible for the sludge generation. This sludgecontent is presented in Table 3.5 and represented infigure 3.1

Table 3.2: Quantity of WastewaterDischarge From Tanneries

S. No. Parameters Values1. Solid content 3.5-6.5%2. Volatile matter 20-483. Inorganic matter 51-74%4. Chromium (Cr) 0.37-0.75

Figure 3.1: Drying Characteristics ofSludge

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18Drying Time (1x15Minute)

Mo

istu

re R

emo

ved

(w

t %

)

Series1 Series2

Table 3.5: Characteristics of Sludge inComposite Wastewater ofTannery-A

Tanneries Wastewater Quantity/Kg of Hides or Skins

Tannery-A (Sheep & Goat Skins)• Raw to finished

upper and liningleather (12000kg/day)

48 litre/kg skins

Wet blue to finished upperand lining leather (10000kg/day)

11 litre /kg wet blue

Tannery -B (Sheep and goat skins)Wet Blue to finishedLeather (700-1740 kg/day)

*11 litre/kg wet blue**21 litre/kg wet blue

Tannery -C (Calf Hides)

(Raw calf hides to finishedleather) (12000 kg/day)

*32.5 litre/kg raw hides**150 litre kg/raw hides day

* As per recipe** Measured at drain

3.2 Solid Waste

The major solid wastes generated by the tanneries aredusted curing salt, wet trimmings, dry trimmings, wetshavings, dry shavings, buffing, raw material packing,etc.. Most of the solid wastes generated are separated atthe source.

In order to quantify the solid waste being generated fromindividual process/operation, some data was availablewith the management of tanneries. However, in case ofnon-availability of the data, known number ofskins/hides were weighed before and after theprocess/operation and the net difference was taken as theamount of solid waste. In this way, total amount of solidwaste was estimated for peak and average seasons. Table3.6 lists the details of solid waste quantity and theirdisposal methods. Following is the brief discussion onsolid wastes, their types and their generation.

Table 3.3: Characteristics Of Wastewater (Process-wise)

Parameter * Pre-Tanning Process Tanning and Wet Finishing Process

Soaking Liming De-liming Tanning Neutralization Re-tanning FatLiquoring

Top Dyeing

Ph 6.9 12.6 8.6 3.34 4.5 2.95 3.45 2.98

T. Solid 52,255 52,966 19,926 91,878 11,181 22,305 22,397 10,645

Total DissolveSolids

51,251 40,943 19,780 91,710 10,579 20,677 21,578 9,560

SuspendedSolid

980 12,000 161 146 594 1,561 758 585

SettleableMatter

3 240 2 5 4 38 280 110

Sulfates 1,100 2,300 12,600 32,000 2,332 4,660 7,050 1500

Sulfides 120 1,680 840 240 60 120 60 34

Total KjeldhalNitrogen

112 3,080 2,520 118 476 944 328 1,216

Phosphate 0.2 43 3 2 0.8 40 2 0.5

Chlorides 34,490 11,497 1,500 28,991 5,998 4,998 2,499 2,499

BOD (F) 5,800 6,600 1,620 480 1,770 2,640 2,400 3,375

COD (F) 30,000 37,600 5,200 2,080 5,000 8,400 6,000 5,800

Chromium - - - 6132 - - - -

• All values are in m/l. except pH.

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Table 3.4a: Characteristics Of Composite Wastewater Of A Tannery

Processing Raw Skins (Sheep & Goat) to Finished LeatherQuantity = 12000 Kg/day; Volume of wastewater = 574 m3/dayParameters

Values in Rangemg/l

Pollution Loadkg/day

Pollutionkg/kg raw material

pH 9.33 - 9.88 - -

BOD5 (Unfiltered) at 0 time settling 17840 - 22800 12040 - 13087 0.9 - 1.1

BOD5 (Unfiltered) at 30 minutes settling 12632 - 18620 7246 - 10688 0.6 - 0.9

BOD5 (Unfiltered) at 60 minutes settling 11050 - 14827 6343 - 8510 0.5 - 0.7

COD ( Unfiltered) at 0 time settling 57000 - 58000 32718 - 33292 2.7 - 2.8

COD (Unfiltered) at 30 minutes settling 48000 - 54000 27552 - 30996 2.3 - 2.6

COD (Unfiltered) at 60 minutes settling 41300 - 43000 23706 - 24682 2.0 - 2.1

Suspended Solid at 0 time settling 4270 - 4650 2451 - 2669 0.2 - 0.2

Suspended Solids after 30 minutessettling

532 - 1610 305 - 924 0.03 - 0.08

Suspended Solids after 60 minutessettling

505 - 890 290 - 511 0.02 - 0.04

Settleable matter after 30 min. settling 11 - 14 6 - 8 (m3/day ) 0.0005 - 0.0007 (m3/kg)

Settleable matter after 60 min. settling 10 - 10 - 574 (m 3/day) 0.0005 - 0.0005 (m3 /kg)

T. Phosphate at 0 time settling 18 - 19 10 - 11 0.0009 - 0.0009

Total Kjeldhal Nitrogen at 0 time settling 236 - 358 135 - 205 0.0113 - 0.0171

Conductivity �s/cm @ 0 time 18000 - 25500 - -

Sulphate as SO4 at 0 time settling 1814 - 3146 1041 - 1806 0.09 - 0.2

Sulphide as (S) at 0 time settling 288 - 292 165 - 168 0.01 - 0.01

Chromium (Cr) at 0 time settling * 64 - 133 37 - 76 0.0031 - .0064

* Estimated on the basis of chrome content in chrome tanning effluent (6132 mg/l.)

Table 3.4b: Characteristics Of Composite Wastewater Of A Tannery

Processing Raw Hides (Calf) to Finished LeatherQuantity = 5419 kg/day; Volume of wastewater = 814m3/dayParameters

Values in Rangemg/l

Pollution Loadkg/day

Pollutionkg/kg raw material

pH 7.35 - 7.67 - -

BOD5 (Unfiltered) at 0 time settling 1020 - 2640 830 - 2149 0.2 - 0.5

BOD5 (Unfiltered) at 30 minutes settling 840 - 2460 684 - 2002 0.2-0.5

BOD5 (Unfiltered) at 60 minutes settling 840 - 1740 684 - 1416 0.2-0.3

COD ( Unfiltered) at 0 time settling 1600 - 4080 1302 - 3321 0.3-0.8

COD (Unfiltered) at 30 minutes settling 1320 - 3800 1074 - 3093 0.2-0.7

COD (Unfiltered) at 60 minutes settling 1000 - 2680 814 - 1677 0.2-0.5

Suspended Solid at 0 time settling 820 - 1920 667 - 1563 0.2-0.4

Suspended Solids after 30 minutessettling

220 - 440 179 - 358 .04-0.08

Suspended Solids after 60 minutessettling

40 - 140 33 - 114 0.007-0.03

Settleable matter after 30 min. settling 20 - 40 16 - 33 0.004 - 0.007

Settleable matter after 60 min. settling 20 - 35 16 - 29 0.004-0.007

T. Phosphate at 0 time settling 5 - 6 4 - 5 0.001- 0.001

Total Kjeldhal Nitrogen at 0 time settling 20.16 - 30.24 16 - 24 0.0037-0.0056

Conductivity �s/cm @ 0 time 12760 - 25440 - -

Sulphate as SO4 at 0 time settling 800-860 651 - 700 0.15 - 0.16

Sulphide as (S) at 0 time settling 1.2- 2.6 1 - 2 < 1gm

Chromium (Cr) at 0 time settling * 41 33 0.0076 - 0.0076

• Estimated on the basis of chrome content in chrome tanning effluent (6132 mg/l.)

8

Table 3.6: Estimated Quantities of Solid Waste and Disposal Practice

Solid Waste Type WasteGeneration Rate

AverageQuantity (Kg/day)

Disposal

Dusted salt 0.1 kg/skin 1000 ThrownFleshing 0.25 kg/skin 2500 Sold to soap and poultry feed

makersRaw trimming 0.024 kg/skin 240 Sold to poultry feed makersWet shaving 0.116 kg/skin 1160 Collected from the tannery by

secondary usersDry trimming 0.024 kg/skin 240Dry shaving 0.034 kg/skin 340Buffing dust 0.002 kg/skin 20

Total 5500Cartons, bags, drums,Miscellaneous refuse

No consistent quantity Sold

Source: Data supplied by Tannery.Note: These quantities are based on the average figures (10,000 kgs./day)

3.2.1 Types of Solid WasteCuring Salt: During the handling of raw skins, adhereddusted salt, which is contaminated with blood, hair, dirtand certain type of bacteria is removed from the skinsand obtained as solid waste. This salt is partly reused inthe curing process and the remaining is indiscriminatelydumped in the undeveloped land near the tannery.

Raw Trimmings: Raw trimmings are cuttings from theedges of raw skins. The skins are trimmed specially atthe legs, belly, neck, and tail parts in order to give asmooth shape to the skins.

Fleshing: This is the flesh removed from the limedskins and is generated during the fleshing operationwhich is carried out after liming and un-hairingprocesses.

Splitting of Wet Blue: This operation is carried out inhides tanneries processing hides. After chrome tanning,the hide’s thickness ranges from 6-8 mm. Therefore, toget proper thickness the wet blue of the hide is sliced intotwo layers. Upper layer, which is having grain, is usedfor preparation of finished leather. Whereas, the lowerlayer is treated as a by-product. However, it is furtherprocessed and is used for manufacturing low grade shoeupper leather and as such is not considered as solidwaste.

Chrome Wet Shaving: After chrome tanning, skins orsplit hides are shaved to proper thickness by the shavingmachine. This operation produces chrome containingsolid waste usually called shaving.

Buffing Dust, Trimming and Dry Shaving:Buffing, adjustment of the thickness of leather andtrimming operations are responsible for the generation ofbuffing dust, cuttings (trimmings) and shavings,respectively. Tanneries mostly have a good buffing dustcollection system that does not allow the dust to spreadout around the working area. The dust is collected via thesuction machine in cloth bags.

3.2.2 Characteristics of Solid WasteBesides quantification of solid waste, characterisation ofsolid waste was also carried out. Four samples, each ofone kilogram, were taken from major types of solidwastes being generated, i.e. salt dusting, fleshing, wet

shaving and trimming, dry shaving, trimming andbuffing. This exercise was conducted to determine themajor constituents such as moisture, salt, lime,chromium, total and volatile solids, sulphide fats andproteins. Table 3.7 lists the characterisation of solidwastes of tannery processes.

Table 3.7: Characteristics of Solid Wastes

Type of Solid Waste

Constituents

DustedSalts

Fleshing WetTrimming& Shaving

DryTrimming,Shaving &Buffing

Mositure 118 - - -Proteins - 236 241 312Fats - 190.4 29.78 132Cr2O3 - - 14.2 26.84VolatileMatter

118 - - -

Salt 464 - - -Lime - 2.7 - -Sulphide - 1.96 - -

Source: Laboratory Analysis.Note: All values are in gm /Kg. unless otherwisespecified.

3.2.3 Disposal of Solid WasteWith the exception of dusted salt, all other solid waste isconsumed within the local market. Empty drums,cartons, chemical bags etc. have demand in the retailmarket. Contractors purchase these materials in bulkfrom the tannery and sell these in the retail market at aprofit. Therefore, it has become a source of income forthese people.

Poultry feed manufacturers, due to the protein content ofsome of the solid waste like. fleshing, raw trimming,chrome shaving, dry trimming, buffing dust, etc., collectthese materials from the tannery. The main problemassociated with some of these wastes is their chromecontent. The chrome content in these wastes ranges from14 -26 gm/kg. The chrome-tanned waste containschromium in trivalent form, which is less toxic ascompared to the hexavalent form of chromium, which iscarcinogenic. End use of chrome containing solid wastevaries in different parts of the country. In Punjab thissolid waste is used for making leather board whereas inKarachi this is used for making poultry feed.

9

Recently, a study of solid waste management was carriedout in Sector 7-A of Korangi Industrial Area under thePTA (Pakistan Tanners Association) EnvironmentalManagement Program. According to the study, poultryfeed mixed tannery solid waste was collected andanalysed. The results showed that the poultry feed,besides trivalent chromium, also contained hexavalentchromium. It seems that during the poultry feedpreparation, trivalent chromium is being changed into itshexavalent form. The mixing of heavy metal in poultryfeed in such a high quantity could produce severe healthproblems for human beings.

3.3 Air Emission

Sources of air pollution in tanneries are of two types.One is from stack of generators and boiler and the otherfrom the processes.

3.3.1 Emissions from Generators andBoilers

The generators, in the tanneries that were audited, areused only during power failures, which is mostly less

then two hours a day, on an average. Generators areusually diesel based.

The boiler is kept operational for approximately 12 hours/day. Samples of emission from the boiler stack werecollected and analysed.

3.3.2 Emission from Process ActivitiesHydrogen sulphide and ammonia are the major gasesemitted during the washing of the drum with ammonia,effluent of de-liming processes where ammoniumsulphate is used as a de-liming agent, and mixing oftanning and de-liming effluent. For these reasons,samples of air were collected from the liming section andtanyard/ dyeing section.

Laboratory results show very low values as compared tothe NEQS permissible limits. Therefore, apparently noenvironmental impacts are associated with the airemissions of the generator and boiler. In the dyeing andtanyard section of a tannery, ammonia emission weretraced in a quantity of 4.1 mg / Nm3, which is a healthhazard to the workers.

44.. EEnnvviirroonnmmeennttaall IImmppaaccttss ooff TTaannnneerryy WWaasstteessAs discussed in the previous Chapter, three types ofwastes are generated during the leather manufacturingprocesses. These are liquid, solid and gaseous emissions.It was observed that air emission values are very low ascompared to the limits laid down in the NEQS. Solidwaste is being collected by contractors for preparation ofpoultry feed. As far as liquid waste is concerned,tanneries are disposing off their un-treated wastewaterinto storm-water drains which finally find their way intonatural water bodies such as rivers and sea. Therefore,major environmental problems are generally associatedwith the wastewater of the tanneries. In this chapter, thegeneral environmental impacts are discussed. Further, thepollutants of tannery wastewater have been comparedwith the pollutants of sewage ( source: KWSB).

4.1 Pollutants of Tannery andtheir Impacts

4.1.1 pHThe pH of directly discharged tannery effluent variesfrom 3.5 to 13.5. Water with a low pH is corrosive towater-carrying systems and in unfavourablecircumstances, can lead to the dissolution of heavymetals in the wastewater. The high pH in tannerywastewater is produced by lime because it is used inexcess quantities and this causes scaling in sewers.Whereas, low pH of wastewater is caused by use of acidsin different tannery processes. A large fluctuation in pHexerts stress on aquatic environment which may killsome sensitive species of plants and animals living there.The NEQS recommends a value of pH in the range of 6 -10.

4.1.2 Biochemical Oxygen Demand (BOD5 )Large quantities of proteins and their degraded productsform the largest single constituent group in the effluent.They effect the environment which can be expressed bytwo composite parameters; Biochemical OxygenDemand (BOD5) and suspended solids.

BOD is a measure of the oxygen consuming capacity ofwater containing organic matter. Organic matter by itselfdoes not cause direct harm to aquatic environment, but itexerts an indirect effect there by depressing the dissolvedoxygen content of the water. The oxygen content is anessential water quality parameter and its reduction causesstress on the ecosystem. As an extreme example, a totallack of dissolved oxygen as a result of high BOD can killall natural life in an effected area.

Tanneries discharge wastewater containing BOD value inthe range of 1740 - 11050 mg/l. Whereas the NEQSrecommends a BOD value of 80 mg/l. Therefore, tannerywastewater is carrying about 20 - 140 times higher valueof BOD as compared to the NEQS limit. Further, theBOD value of tannery wastewater is 4 -20 times higheras compared to the BOD value (375 - 525 mg/l) ofsewage.

4.1.3 Chemical Oxygen Demand (COD)The Chemical Oxygen Demand (COD) is a measure ofoxygen equivalent to that portion of the organic matterin a sample which is susceptible to oxidation by a strongchemical oxidant. It is an important, rapidly measuredparameter for stream and industrial waste studies and forcontrol of waste treatment plants.

Along with the organic compounds immediatelyavailable to the stream organism, it also determinesbiological compounds that are not a part of immediatebiochemical load on the oxygen assets of the receivingwater.

With certain wastes containing toxic substances, this testor total organic carbon determination may be the onlymethod for determining the organic load. Where wastescontain only readily available organic bacterial food andno toxic matter, the results can be used to approximatethe ultimate carbonaceous BOD values. Compositewastewater of tanneries carries a COD value in a range

10

of 3800 - 41300 mg/l. Whereas according to the NEQS, avalue of 150 mg/l has been recommended for COD.Hence, tannery wastewater is carrying about 25 - 275times more pollution load in terms of COD. Sewagewater usually contains 1000 mg/l COD.

4.1.4 SulphideDue to sulphide discharged from the unhairing process,hydrogen sulphide is released at a pH value lower than8.5. This gas has an unpleasant smell even in tracequantities and is highly toxic to many forms of life. Inhigher concentrations, fish mortality may occur at asulphide concentration of 10 mg/l. Sulphide in publicsewer can pose structural problems due to corrosion bysulphuric acid produced as a result of microbial action.Sewage contains sulphide in the range of 15-20 mg/l andcomposite tannery wastewater contains 290 mg/l,whereas, the NEQS recommends a value of 1.0 mg/l.

4.1.5 ChromiumTrivalent chromium is released from the chrome tanningprocess. This is much less toxic than hexavalentchromium. For plant and animal life, the toxicity ofchromium salts is variable. The toxicity is a function ofthe species itself. Algae have been shown to beparticularly sensitive. Estuarine molluscs, althoughapparently unaffected in their own metabolism,accumulate trivalent chromium.

At present, tanneries are discharging chromium (133mg/l) in composite wastewater and in sludge (3 - 17.5gm/kg). It can be seen that wastewater of chrome tanningprocess, which is about 2 % of the total wastewater of thetannery, contains 6000 - 7000 mg/l of chromium (Cr).

The sewage of Karachi contains 0.1 to 0.5 mg/l of

chromium, whereas the NEQS recommends a value of1.0 mg/l.

4.1.6 Suspended SolidsSuspended solids, apart from being societal nuisance ,have their main effect when they settle. The layer soformed on the bottom of the watercourse, covers thenatural fauna on which aquatic life depends. This canlead to a localised depletion of oxygen supplies in thebottom waters. A further secondary effect is the reducedlight penetration and consequent reduction inphotosynthesis due to the increased turbidity of water.

Tanneries discharge wastewater containing 440 - 890mg/l of suspended solids. The Karachi sewage contains500-900 mg/l suspended solids, whereas the NEQSrecommends a value of 150 mg/l.

4.1.7 SaltsThe sodium chloride used in the tannery produces noeffect when discharged into estuaries or the sea, buteffects fresh water life when its concentration in astream or lake becomes too high. There is noeconomically viable way of removing salt from theeffluent. A similar problem also exists for sulphate usedas the chrome tanning salt. Sulphate in addition causescorrosion to concrete structures. The Chloride content oftanneries’ composite wastewater ranges from 5820 to14160 and the sulphate content varies from 860 to 1814mg/l.

4.1.8 Solvent VapoursFinishing chemicals like acetic acid, formaldehyde,ethylene glycol, etc. are used in the tannery processes.The vapours of these chemicals are very dangerous andcan affect the health of workers severely.

Figure 4.1: Environmental Input of a Tannery ( Raw Skins to Finished Leather)

55.. RReemmeeddiiaall MMeeaassuurreess

5.1 General Measures

• As tanneries do not have an environmentalmanagement system, therefore, this system must bedeveloped in tanneries, specially in the large and

medium sized ones. Environmental managementshould be a responsibility of the personnel inaddition to their routine duties.

• Short-term training on occupational health andsafety aspects , modern practices for the handling ofhazardous chemicals, etc. is required for the staff.

RAW SKINS 12000 KG

LEATHER 1400 Kg

BOD5 = 13680 COD = 34200 Suspended Solids = 2790 Chromium = 80 Sulphide = 173 Sludge = 3280

All values in Kg/day

WASTEWATER (600 M3/day)

UNTANNED Dusted Salt = 1000 Raw trimming = 240 Fleshing= 2500 TANNED Shaving = 1500 Trimming = 240 Buffing = 20Total = 5500 All values are in Kg./day

SOLID WASTE AND BY- PRODUCTS

11

• Installation of information boards on safety andhealth regulations at the work places of the tanneryare needed.

• Provision of safety gears like face protective shieldfor acid work specially in the pickling process, acidresistant gloves and aprons etc. Face masks to avoidinhalation of fumes of finishing chemicals, toxicgases, etc.

• The use of the safety gear should be implementedstrictly.

• Proper arrangements to stop the use of tanned solidwaste for the preparation of poultry feed. Simpledisposal to the landfill site may not be a propersolution to stop this practice, as the poultry feedmakers can get this material from these sites.Tanned solid waste materials can be used in leatherboard manufacturing, but in Karachi, a leather boardfactory does not exist. In the absence of a permanentsolution to this problem at present, it is suggestedthat this material can be disposed off after mixingwith other wastes, like circulation water of sprayplant that caries unused finishing material. Otherwaste that can be mixed with tanned solid waste is

curing salt. After mixing with this waste, tannedsolid waste will become contaminated and will notbe useful for poultry feed makers.

• Improvement in drainage system in order to avoidformation of hydrogen sulphide gas inside thetannery.

5.2 Environmentally CleanTechnologies

A number of cleaner technologies can be applied for themanufacturing of finished leather. The implementation ofcleaner production processes and pollution preventionmeasures can provide both economic and environmentalbenefits. However, the applicability of these technologiesvary from tannery to tannery due to the varying nature ofraw material, processing conditions and the type offinished leather.

5.2.1 Review of Cleaner TechnologiesSome of the cleaner technologies have been described inTable 5.1

Table 5.1: A Brief Review on Cleaner Technologies

Cleaner Technologies BenefitsWater Conservation The use of pit or paddle for soaking operations results in a higher consumption of water,

mainly for washing phase which are much less efficient than when using drums. Even fordrums it is recommended to operate the sequential washing instead of continuous washingwhich leads to the savings of enormous amount of water at each stage. Low floattechnologies would also reduce the water quantity. Although such conservation do notreduce the pollution load, however, they can lead to the reduction in the size of theeffluent treatment plant.

Use of Environment FriendlyChemicals

Enzymatic product are considered to be less toxic and can be a good replacement ofsulphide. Surfactants, if used, should be selected with respect to their biodegradability.Use of Penta Chloro Phenol (PCP) must be avoided. Replacement of ammonium sulphatewith weak acids (organic). Degreasing with surfactants instead of organic solvent. Use oftrivalent chromium for tanning purpose instead of hexavalent chromium (carcinogenic).Metal complex dyes, which contain restricted heavy metals and benzidine based dyesmust be replaced. The chlorinated fatliquoring agents and retanning products should bereplaced with the easily biodegradable products.

Green Fleshing of Hides Green fleshing just after deep soaking is a suitable procedure to obtain by-product at pHclose to neutral, which can then easily be processed to recover fats and proteins with goodmarketing possibilities and to save liming and unhairing chemicals. Further green fleshingalso improves the penetration of the chemicals and hence improves the quality of finishedleather.

Hair savings Methods Hair saving system use smaller quantities of sulphide as compared to hair destructionsystem, and allows easy separation of the protein constituted by the undissolved hair andhence imply less pollution than the hair dissolving process. The procedure results in asignificant reduction of COD, BOD5 , nitrogen, sulphide, total and suspended solids in thewastewater, besides a decrease of sulphide consumption. The hair saving would decreasethe organic load for treatment plant.

Recycling Liming Liquor Some of the liming unhairing techniques permit a direct reuse of the spent liquors afterdecantation and/or filtration. The procedure permits savings of water, sulphide, and lime.

Recycling of Un-hairing Liquors By reuse of un-hairing liquors after separation of insoluble substances by sedimentationimportant savings are claimed including 50 % sulphide, 40% lime and 60% of processwater.

Lime Splitting and Trimming Splitting and trimming is usually carried out after tanning which results in a by-product oflow quality containing chromium in it. If these operations are carried out with the pelt, theproduced by-product can be sold easily in the market than those resulting from splittingand trimming of wet blue (tanned hides/skins). The un-tanned solid waste will be a goodraw material for manufacturing of gelatin or animal feed. This will also results in areduction in the quantities of chemicals used for deliming, pickling, tanning andconsequently the load of the pollutants in wastewater will be considerably reduced.

Application of Weak Acids in De-liming Process

Application of weak acids (organic) can eliminate the discharge of ammonium salt fromdeliming process.

Chrome Reuse in the TanningProcess

See Section 5.2.1.

Source: “Introduction of Cleaner Technologies in Tannery Cluster of Punjab”

12

5.2.2 Reuse of ChromeQuite a few options are available for the reuse of thechrome discharged in the tanning effluent. Thesetechnologies do not completely eliminate the chromiumbeing discharged through the effluent or sludge.However, it can be seen as apart of a generalenvironmental plan of the tannery, since it reduces thenecessary amount of chromium being discharged into theenvironment, thus facilitating the treatment and disposalof a small amounts of chromium containing sludge.Chrome reuse option also provides financial benefits.

Direct Recycling of Chrome Tanning Float: Thisis the easiest method of chrome reuse. In this methodafter collection and sufficiently fine screening, the floatis controlled and the chromium amounts used in theprevious cycle are replaced by fresh chromium salts.Depending on the tanning technology in use, the degreeof exhaustion reached for each cycle may vary. Therecycling method may be repeated several times on thesame float. However, it is limited by the occurrence ofquality problems with delicate hides and by the need tocontrol residual float. This technology is suitable forsmall tanneries.

Recycling Of Chrome After Precipitation: Thisallows collection of the tanning float with the rinses, thatsometimes occur at the end of the tanning and theeffluent from various post-tanning stages (washing,dripping, sammying, etc). After collection, screening andstorage, the floats are precipitated with different types ofalkalies and bases including sodium hydroxide, sodiumcarbonate, magnesium oxide and even with lime. Thereuse of sludge after simple settling and acidification hasbeen experimented and practised. Schematic diagram ofa typical chrome recovery and reuse plant is shown infigure 5.1. Large plants have operated under this schemefor many years in Germany, Itally, South America andFrance. In Pakistan four chrome recovery plants havebeen installed under the same process.

Figure 5.1: Chrome Recovery & Reuse Plant

Cost-Benefit Analysis of a Chrome Recovery andReuse Plant (CRRP): For the estimation of a totalquantity of basic chromium sulphate (BCS) in thetanning effluent the maximum quantity of tanningeffluent and minimum value of chrome quantity has beenconsidered. Cost benefit analysis is given in thefollowing table. These cost are approximate costs andgiven only for a general idea about the investment andpay back period of the chrome recovery project.

Tanning Products that Improve the ExhaustionRate: For the past few years, tanning and basificationproducts have been available in the market which enablea tanning cycle to produce only small quantities ofchromium waste. These products are developed with theaim of bringing about the complete fixation of thechrome onto the protein fibres so that the exhaustedchrome tanning float contains little or no chrome.Chrome take up of over 90 % with exhaust of less that 1gm per litre is possible. This reduces the initial chromeoxide offer to about 1.8 % on the fleshed weight and stillobtains the same quantity of chrome fixed on the fibres.

Table 5.2: Summary of Cost Benefits Analysis for CRRP

1. Basic Data

- Raw goat Skins 3000 kg/day- Quantity of tanning float 80-100 % of “a”- Total volume of float (a*b/100) 2400 - 3000 litre- Basic Chromium Sulphate (BCS) applied in tanning process 7-8 % of “a”- Total BCS applied per day ( d*a/100) 210 - 240 kg/day- Chromium (Cr) in Tanning Effluent 7000 - 7500 mg/l- Total BCS in Tanning Effluent (c*f/170000) 123.5 kilo/day- pH 3.46 - 3.66

Description Amount Unit2. Capital Cost 683,000 Rs.

3. Operation and Maintenance Cost: A: Annual Operating Cost

- Manpower - Electricity - Chemicals - Maintenance ( @ 5% of Capital Cost ) - Miscellaneous( @ 5% of Capital Cost)

B: Depreciation Cost (@ 5% of Capital Cost)

60,0009,600

160,00017,00034,00034,000

Rs./yearRs./ yearRs./ yearRs./ yearRs./ yearRs. Year

TOTAL O & M Cost 314,600 Rs./ year

4. Benefits:- Total Recovered Chromium/day*- Total Recovered Chromium/annum (300 days)- Value of Recovered Chromium @ Rs. 36/kg

12437200

1,339,200

kg/day.Kg/year.Rs/year.

Net Profit = 3-2 1,024,600 Rs/year

5. Pay Back Period 7-8 months*: Calculated on the basis of 95% recovery.

13

5.3 Wastewater TreatmentTechnologies

Two levels of treatment are normally required fortreatment of the effluent from the tanneries. These areprimary and secondary treatment.

5.3.1 Primary TreatmentPrimary treatment system comprises of mechanicalscreening, pH equalisation (collection of effluent ofdifferent processes in a common tank), coagulation andflocculation and sedimentation.

Mechanical Screening: Removal of coarse,particulate flesh and hair is achieved by means ofperforated screens. The contribution of screening inreducing the BOD load is high, but the primary purposeis to prevent the blockage of pumps and sewers requiredfor further treatment of the effluent.

pH Equalization: The wide fluctuation in the effluent‘spH value as a result of different requirements of thetannery processes can be reduced by means of anequalization tank. This procedure can reduce theamplitude of pH fluctuation from 3.5 - 13 down toapproximately 8.5-10, as observed during the samplingprogramme.

Due to the equalization tank, the flow and composition ofthe effluent is also maintained more constantly forfurther treatment.

Physio-Chemical Processes: Coagulation andflocculation are applied to the tannery wastewater inorder to remove the suspended solid of the wastewater.This is carried out by the addition of coagulating andflocculating to the wastewater.

5.3.2 Secondary TreatmentIn secondary treatment, biological processes are used toremove most of the organic matter from the wastewater.This is achieved by using micro-organisms to convert theorganic matter into different gases and into cell tissues.Cell tissues have a specific gravity slightly greater thanthat of the water, the resulting tissue is removed from thetreated liquid by gravity settling.

For secondary or biological treatment of tannery effluent,the most widely used processes are aerobic. However,anaerobic process is also used for this purpose. On thebasis of these two processes, following major treatmenttechnologies are available:

• Activated Sludge• Aerated Lagoon• Facultative Ponds• Anaerobic Lagoon• Trickling Filter• UASB (Upflow Anaerobic Sludge Blanket)

The selection of the technology depends on many factorslike capital cost, availability of land, operation andmaintenance cost, efficiency of the process etc. In thefollowing sections, technical viability as per the availabletannery data, along with a brief process description ofthese technologies has been discussed.

Activated Sludge: During a biological treatment byactivated sludge, the wastewater to be treated is

introduced into a tank aerated by mechanical stirring orby compressed air. Here it mixes with the mass ofbacterial floc maintained constantly in suspension. Aftersufficient contact time, the mixture is clarified in asettling pond and sludge is recycled in the aeration tank.The excess sludge from the system is treated withprimary sludge. This is a proven technology for thetreatment of tannery wastewater and widely used all overthe world. Modified forms of this technology areavailable.

Aerated Lagoons: An aerated lagoon is an earthenbasin in which the oxygen required by the process issupplied by surface aerators. In an aerobic lagoon, all thesolids are maintained as suspension. To meet thesecondary treatment standards, this technology can safelybe used for the treatment of tannery effluent. However, itrequires a large area of land as compared to othertechnologies. For the present study, this technology is notbeing considered due to insufficient area of landavailable.

Facultative Ponds: Ponds in which the stabilization ofwaste is brought about by a combination of aerobic,anaerobic and facultative bacteria, are known asFacultative (anaerobic-aerobic) Stabilization Ponds.Three zones exist in a Facultative Pond:• a surface zone where aerobic bacteria and algae

exist in a symbiotic relationship;• an anaerobic bottom zone in which accumulated

solids are decomposed by anaerobic bacteria; and• an intermediate zone that is partly anaerobic, in

which the decomposition of organic waste is carriedout by facultative bacteria.

Conventional facultative ponds are earthen basins filledwith wastewater. In this pond, large solids settle out toform an anaerobic sludge layer. Soluble and colloidalorganic materials are oxidized by aerobic and facultativebacteria, using bacteria produced by algae growing nearthe surface. Carbon dioxide produced in organicoxidation serves as carbon source for the algae.Anaerobic breakdown of the solids in the sludge layerresults in the production of dissolved organic compoundsand gases such as carbon dioxide, hydrogen sulphide andmethane, which are either oxidized by the aerobicbacteria or vented to the atmosphere. In practice, oxygenis maintained in the upper layer of the facultative lagoonby the presence of algae and by surface aeration. In somecases, surface aerators have also been used. If a surfaceaerator is used, algae is not required.

Like an aerobic lagoon, this type of lagoon also requiresa large area of land. In addition, odour is also a problem.Therefore, this technology also does not look feasible forthe treatment of wastewater for the tanneries understudy.

Anaerobic Lagoon: Typically, an anaerobic lagoon isa deep earthen pond with appropriate inlet and outletpiping to conserve heat energy and to maintain ananaerobic condition. Anaerobic lagoons are constructedwith depths of up to 30 ft. The waste that is added in thelagoon settles down at the bottom. The partially clarifiedeffluent is usually discharged to another process forfurther treatment.

Usually, these ponds are anaerobic throughout the depth,except for an extremely shallow surface zone.Stabilization is brought about by the combination of

14

precipitation and the anaerobic conversion of organicwaste into carbon dioxide, methane, other gaseous endproducts, organic acids and cell tissues. Conversionefficiencies of BOD up to 70% can be achieved.

High sulphate concentration in the tanneries would causethe production of hydrogen sulphide gas and which canadversely effect the surrounding areas. This technologyalso requires a large land area, therefore, it is also notfeasible for treatment of wastewater of the tanneriesunder study.

Trickling Filter: The working principle of the tricklingfilter is by percolating the water to be treated through amass of porous or cavernous material, which serves assupport for micro-organisms. The necessary oxygenrequired for maintaining an aerobic state for fixing thebiomass to the support is generally supplied by naturalventilation. Due to natural ventilation, aeration cost isnot required. This technology is being used in Pakistanfor the treatment of domestic wastewater. This has notbeen tested for treatment of tannery wastewater on alarge-scale. Due to a heavy load of pollution in tannerywastewater, it’s performance is doubtful. Tanneries aredischarging wastewater containing 40 times more BODvalue as compared to domestic wastewater. Nitrificationis possible in this type of technology whereasdenitrification of wastewater is not possible. Therefore, itis not possible to apply this technology for the treatmentof wastewater of tanneries. However, it is a very simpletechnology and operation and maintenance cost is alsovery low as compared to the activated sludge technology.A small land area is required for this technology.

Upflow Anaerobic Sludge Blanket (UASB)Technology: As it is evident from its name, this is ananaerobic process based technology. This treatmentsystem is based on the upward flow of wastewaterthrough a sludge layer of active anaerobic micro-organisms. The wastewater is evenly distributed at thebottom of the reactor, and after a suitable hydraulicretention time in the reactor it leaves from the systemfrom top of the reactor. The contact between the micro-organisms of the wastewater is enhanced by theproduction of biogas, due to the rising bubbles whichprovide gentle mixing. There is no need for mechanicalmixing. This simplifies the design of the reactor. After

passing through the sludge bed, a mixture of biogas,sludge and water enters a three phase separator. Thebiogas is separated in a gas collector, whilst the sludge-water mixture enters a settling compartment, thusproviding effective sludge retention in the reactor. Theeffluent is discharged from the top of the reactor via anoverflow weir. The excess sludge is discharged from thebottom of the reactor at the regular intervals onto adrying bed.

This technology has been successfully applied for thetreatment of tannery wastewater diluted with domesticwastewater in India. On the basis of the same principle, aUASB treatment plant is also being installed in Karachi,for the treatment of tannery wastewater for a cluster ofmore than 160 tanneries, situated in sector 7 - A ofKorangi Industrial Area.

Besides other toxic waste present in the tannerywastewater for anaerobic process, sulphate concentrationis one of the more important factors. In the presence ofsulphate, an anaerobic process starts the generation ofhydrogen sulphide gas and at the same time theproduction of Methane gas is badly effected. Wastewaterof tanneries under study contains sulphate (SO4) in therange of 860 - 3,146 mg/l.

To overcome the problems of this technology, thetannery wastewater is treated after dilution with domesticwastewater in a ratio of 1:3. Due to this large quantitiesof domestic wastewater would be required. The tanneriesunder study cannot arrange this large quantity ofdomestic wastewater, therefore, this technology cannotbe considered for the treatment of wastewater forindividual tanneries

5.3.3 Feasible TechnologyOn the basis of the above discussions and the organic andhydraulic load of the tanneries, it is concluded that theActivated Sludge System can be selected for thetreatment of the wastewater of individual tanneries Inorder to take advantage of the local climatic conditions, itwould be better to consider the low loaded system of theactivated sludge process. Under this system, given localclimatic conditions, it would be possible to treatsecondary sludge in the same biological reactor.

66.. WWaasstteewwaatteerr TTrreeaattmmeenntt SSyysstteemm:: PPrreelliimmiinnaarryy DDeessiiggnniinngg aanndd CCoosstt EEssttiimmaattiioonnTwo types of tanneries participated in the ETPI program.One type of tannery was invloved in segmented productionby using wet blue as raw material to prepare finishedleather. The processes they conduct are usually referred toas “Wet Finishing Processes”. The other type of tannerywas a complete tannery, processing raw hides to preparefinshed leather. The wastewater treatment system for boththe type of tanneries has been described in the followingsections.

6.1 Wastewater Treatment for WetFinishing Processes

Tanneries under study manufacture finished leather bytaking “wet blue” as raw material. Wet blue is either

prepared in a separate unit of the same tannery or it ispurchased from another tannery. The processes employedto prepare finished leather from wet blue are called wetfinishing processes.

This designing is carried out to assess the total investmentcost alongwith the operation and maintenance cost of thewastewater treatment plant the for two tanneries A and Bemploying (wet) finishing process. The production of thesetanneries is as follows.

Tannery “A” processing 8000 kg to 10000 of kg skins(wet blue) per day.Tannery “B” processing 600 kg to 1500 kg of skins (wetblue) per day.

15

The suggested treatment plant comprises of a primary andsecondary level treatment system.

6.1.1 Design DataWater Quantities (Volumes): The daily liquid volumesof wastewater fluctuates between the values given belowdepending on the quantity of raw material processed daily:

Tannery “A” 80 -120 m3/dayTannery “B” 30 - 40 m3/day

Daily Pollution Loads: The maximum values of waterquantities 120 and 40 m3 /day of tanneries A and B,respectively, have been taken to cover the maximumfluctuation of the wastewater. Daily pollution loads aresummarized in Table 6.1 below:

Table 6.1: Estimated Daily Pollution Loads ofTannery A and B

Tannery A120 m3 /day

Tannery B40 m3 /day

Description Ave.Conc.(mg/l)

Load(kg/d)

Ave.Conc.(mg/l)

LoadKg/day

PH 3.5 3.5 4.00 4.00

BOD5 (20 C)total

1985 238 1468 58.72

BOD5 (20 C)settleable solid

955 115 261 1047

COD (total) 5755 691 6380 255.33

COD settleablesolid

3000 360 1648 66

Tot. suspendedsolids

5295 515 1042 42

Tot. KjNitrogen

483 58 264 10.56

Sulphate 5980 717 1009 400.36

Sulphide Nil Nil 0.4 0.0158

Phosphate 25.5 3 3.5 0.14Note: BOD suspended solids are based on the differenceof BOD at 0 time and BOD after 60 minutes settling.Source: Laboratory Analysis. 6.1.2 AssumptionsThe following assumptions have been made for thepreliminary design:• Wastewater quantity of the peak season has been taken

into consideration, maximum flow which means ahigher capacity, especially in aeration tanks andhydraulic capacity;

• The liquid effluent will be lifted (pumped) only oncefor the required water level in the plant;

• The removal efficiencies of the primary sedimentationtank are summarized in Table 6.2;

• The design of the aeration tank is based on a lowloaded activated sludge system (including sludgestabilization); and

• Mechanical dewatering is taken into consideration asrelatively high amounts of sludge are generated daily.

Table 6.2: Load of Aeration Tank

Tannery -ADescription Input to

PrimaryTreatmentkg/d

Efficiencyof PrimaryTreatment(%)

Output ofPrimaryTreatment*(kg/d)

Sludge(kg/d)

BOD5

Susp.solidsKj-NSulphide

23551558Nil

50 60 10 0

15320652Nil

309

Tannery - BDescription Input to

PrimaryTreatment(Kg/d)

EfficiencyofPrimaryTreatment(%)

Output ofPrimaryTreatment*(kg/d)

Sludge(kg/d)

BOD5

Susp.SolidsKj-N

58.7242

10560.016

4060100

351710

0.016

25

* Considered loads to the aeration tank for design of volumeand capacity.

6.1.3 Components of the PlantThe treatment plant will consist of the following:Water Handling• Collecting pit, including a pumping station;• Equalization tank (with mixers for stirring to prevent

settling). Addition of chemicals like lime andpolyelectrolyte will also be carried out at this stage;

• Primary sedimentation tank;• Aeration tank (aeration by surface aerators); and• Final sedimentation tank (including return sludge facilities).Sludge Handling• Primary sludge pumps (for pumping of primary sludge

from the sedimentation tank to the sludge thickener);• Excess sludge pumps (for pumping of excess sludge

from the return sludge pit to the sludge thickener);• Sludge thickener (to increase dry sludge concentration

i.e reduction of the sludge volume);and• Drying beds and belt filter press.

6.1.4 Land RequirementPreliminary layout of the treatment plant is presented inFigure. 6.1. Land requirement with and without a mechanicaldewatering system is shown in Table 6.3 below:

6.1.5 Final Effluent QualityDesigning has been carried out to produce effleunt to meetthe NEQS level. Table 6.4 shows the final effluent qualityafter treatment:

Table 6.3: Land Requirement ( m2 )

Tannery A Tannery BWith

MechanicalDewatering

WithoutMechanicalDewatering

WithMechanicalDewatering

WithoutMechanicalDewatering

1753 2777 160 212

16

Figure 6.1: Preliminary Layout of the Treatment Plant for a medium size segmented tannery with a Mechanical DeWatering System

Table 6.4: Final Efffluent Quality

Description InfluentConcentration ofTreatment Plant

(mg/l)

EffluentConcentration of TreatmentPlant (mg/l)

TanneryA

TanneyB

PHBOD5 (20 C) totalCOD (total)Tot. suspended solidsTot. Kj NitrogenSulphate

3.5198557555295583Nil

4.001468638010422640.4

7.5 - 860

15015025

Nil

6.1.6 Estimation of Capital and O&M CostsEstimated capital and operation and maintenance cost aresummarised in Tables 6.5. The process design is given inannexure 3 and 4

Table 6.5: Estimated Investment Cost ofTreatment Plant for (Wet) FinishingTannery Process

Description Tannery -A Tannery B

A: Civil Works

Grit chamberEqualization tankPrimary sedimentation tank.Aeration tankFinal settling tankComplete sludge thicknerSludge drying bedControl/Service room

4200049000070000

2275000105000392000228200100000

4000210000210005600003500039200015800050000

Sub Total 3702200 1430000

B: Mechanical Equipments

MixerPumpsScraper, skimmer, bridge etcSurface aeratorBelt filter press

10000070000050000

1500002500000

50000350000---------200000----------

Sub Total 3500000 600000

Total A + B 7202200 2030000

1. Electrical/ mechanicalwork ( 20 % total A+B)

1440440 406000

2. Contingencies (20% oftotal A+B)

1440440 406000

Total Cost of TreatmentPlant (million Rs)

10.1 2.85

Estimated Annual Operationand Maintenance Cost 15-20% of the total (million Rs)

1.5-2 0.4-0.6

Land Area Requirement (m2) 1753 -2777 160 -212

17

6.2 Wastewater Treatment forProcessing Raw Hides toFinished Leather

Tannery processing calf hides to produce finished shoeupper leather are considered here. On an average 1,000hides (approximately 12000 kg/day) are processed daily in anormal production period. The quantity of raw hides reachesupto 2000 hides /day in the peak season.

6.2.1 Design DataWater Quantities (Volumes): The daily liquid volume ofwastewater fluctuates in between the values given below,depending on the quantity of raw material, processed daily:• 1836 m3/day on an average (whole year);• 3672 m3/day in peak season (about 2 months).

Daily Pollution Loads: Daily pollution load has beencalculated on the basis of average and peak flows. Dailypollution loads are summarized in Table 6.6. Whereas,average values of each parameter is taken for designingpurpose.

Table 6.6: Daily Pollution Loads

Description Conc.(mg/l)

AverageLoad

1836 m3/d(kg/d)

Peak Load3672 m3/d

(kg/d)

BOD5 (20 C) totalBOD5 (20 C)settleable solidTot. suspended solidsTot. Kj NitrogenSulphate

174056013272526

3195102824364593.711

62390205648729187.422

Note: BOD5 suspended solids are based on the difference ofBOD5 at O time and BOD5 after 60 minutes settling.

6.2.2 AssumptionsThe following assumptions have been applied for thepreliminary design:

• As peak season is only two months per year, the design

capacity will be based on the average flow, a design for

a maximum flow means a high capacity, especially

aeration tanks and hydraulic capacity;

• The liquids effluent will be lifted (pumped) only once

for the required water level in the plant;

• The removal efficiencies of the primary sedimentation

tank are summarized in Table 6.7;

• The design of the aeration tank is based on a low

loaded activated sludge system (including sludge

stabilization); and

• Due to the availability of the land, drying bed has been

suggested.

Table 6.7: Load of Aeration Tank

Description Input toPrimary

Treatment(Kg/d)

Efficiencyof PrimaryTreatment

(%)

Output ofPrimary

Treatment(kg/d) *

Sludge (kg/d)

BOD5

Susp. SolidsKj-NSulphidePhosphate

319524364593.711

307010011

121839822.53.7

1705

• Considered loads to the aeration tank for design ofvolume and capacity.

6.2.3 Land RequirementsPreliminary layout of the treatment plant is presentedin Figure 6.2 & 6.3. Land requirement with andwithout a mechanical dewatering system is shown inTable 6.8 below:

Table 6.8: Land Requirement (m2)

With MechanicalDewatering

Without MechanicalDewatering

7838 13834

18

Figure 6.3: Preliminary Layout of the Treatment Plant without Mechanical Dewatering System

Figure 6.2: Preliminary Layout of the Treatment Plant with Mechanical Dewatering System

19

6.2.4 Components of the Treatment PlantThe treatment plant will consist of the following parts:

Water Handling• Collecting pit, including a pumping station;• Equalization tank (with mixers for stirring to prevent

settling);• Primary sedimentation tank;• Aeration tank (aeration by surface aerators); and• Final sedimentation tank (including return sludge

facilities).

Sludge Handling• Primary sludge pumps (for the pumping of primary

sludge from the sedimentation tank to the sludgethickener);

• Excess sludge pumps (for the pumping of excesssludge from the return sludge pit to the sludgethickener);

• Sluldge thickener (to increase the dry sludgeconcentration and reduction of the sludge volume);and

• Sludge drying beds and a mechanical de-wateringoption for sludge drying.

6.2.5 Final Efffluent QualityDesigning has been carried out to produce effluent to meetthe NEQS level Table 6.9 to show the final effluent qualityafter treatment.

Table 6.9: Effluent Quantity of TreatmentPlant

Parameters InfluentConcentrationof treatmentplant (mg/l)

EffluentConcentrationof TreatmentPlant (mg/l)

PHBOD5

CODSuspended SoildT.Kjeldhal NitrogenSulphideChromium*

7.661740267013232523

7.5-8801501501.25Nil< 0 .25

6.2.6 Estimation of Captial and O&M CostsThe estimated total cost of a treatment plant is given in table6.10. Process design in detail is given in annexure 5.

Table 6.10: Estimated Capital Cost of Treatment Plant with the Present Hydraulic load ofTannery

Description Estimated Cost (Rs.)A: CIVIL WORKS

1. Grit chamber2. Equalization tank3. Primary sedimentation tank.4. Aeration tank5. Final settling tank6. Complete sludge thickner7. Sludge drying bed8. Control/Service room

157,5003,500,000535,500

17,787,000766,500

1,218,000868,000100,000

Sub Total 24.9 millionB: MECHANICAL EQUIPMENT’S

1. Mixer2. Pumps3. Scraper, skimmer, bridge etc.4. Surface aerator5. Belt filter press

1,200,000400,000200,000

2,000,00030,000,000

Sub Total 6.8 millionTotal A + B 31.7 million

1. Electrical/ mechanical work ( 20 % total A+B) 6.34 million2. Contingencies (20% of total A+B) 6.34 million

Total Cost of Treatment Plant 44.38 millionAnnual Operation and Maintenance Cost per year(15-20% of total cost)

7 - 9 million

Land Area Requirement ( m2) 11,351- 13,834Note: Land cost is not inculded.

20

AAnnnneexxuurree 11::LLiisstt ooff CChheemmiiccaallss UUsseeddiinn tthhee TTaannnniinngg PPrroocceessss

S. No. NAME S. No. NAME S. No. NAMEI. PRE-TANNING CHEMICALS 25 BASANTAN J-Z/J-Z 25 GULF OIL 44

1 LIME POWDER 26 IRGAPADOL PN-NEW 26 MESLINIOUS

2 CHINA CLAY 27 IRGAPADOL FF4 27 GULF PUK 993 AMONIUM SULPHATE 28 BELLASOL -NG LIQ 28 GULF TUCH 45

4 SODIUM META BI SULPHATE 29 BOREX 29 NEOSON DOUBLE WHITE

5 KEROSENE OIL 30 DERMAGEN DM 30 NEOSON BLACK/D

6 SEA SALT 31 TANIGAN QF 31 NEOSON BEIGE7 SULPHURIC ACID 32 HESLINIOUS 32 NEOSON BROWN

8 SODIUM BI CARBONATE IV DYES 33 NEOSON YELLOW

9 CAUSTIC SODA 1 DERMA CARBON GS 34 NEOSON ORANGE

10 OROPON 2 DERMA BROWN 1288/1289 35 NEOSON VIOLET11 SODIUM FORMATE 3 DERMA BROWN 2G 36 NEOSON BLUE T

12 SODIUM SULPHIDE 4 DERMA BROWN 2RM 37 BAYFEROX - 915

13 BUSAN 30 5 DERMA BROWN 2490 38 EUKANOL RED-D

14 FORMIC ACID 6 DERMA RED 2201 39 EUK. BLUE/NEO.BLUE -M

15 MAGNISIUM OXIDE 7 DERMA RED BA 40 EUKANOL RUBIN N16 CHRMEND BASE FN/MD 8 DERMA GREY 2411 41 EUKANOL BRILLIANT BLACK

17 MERLO 89 9 DERMA DEIGE 2401 42 IRIODIN 100 (SILVER POWDER)

18 ARACITAK 10 DERMA BLUE 2222 43 IRIODIN 300 (GOLD POWDER)

19 SELLANTAN CF/LIG. 11 DERMA OLIVE 2402 44 LEVADERM LEMON LIQ.NII. TANNING MATERIAL 12 DERMA BORDEX 2430 45 LEVADERM YELLOW LIQ.N

1 PAK CHROME 13 DERMA BEIGE Z 46 LEVADERM ORANGE LIQ.N

2 CHROMOSOL BF 14 DERMA BROWN HGP 47 LEVADERM RED LIQ.NIII (WET) FINISHING CHEMICALS V FINISHING CHEMICALS 48 LEVADERM BORDEX LIQ.N1 BASINTAN DLN/LE/LV 1 MICRO BINDER AM 49 LEVADERM BLUE LIQ.N

2 TANIGAN AN 2 BINDER IF 50 LEVADERM NAVY BLUE LIQ.N

3 RETIGAN R7 3 BINDER ON 51 LEVADERM OLIVE GREEN LIQ

4 TANIGAN BN 4 E.M. FINISH G/PANAMOL 52 IRGADERM ORANGE M

5 TANIGAN PAK-N 5 WAX EG 53 IRGADERM BLACK N6 MAGNOPAL STD 6 LURAN LUSTER E 54 EULASOLAR RED GL LIQ

7 4 FBW 7 BINDER LUSTER E 55 LEVADERM ORANGE LIQ.N

8 CUTISAN SL 8 BINDER U KONZ/PO 56 LEVADERM RED LIQ.N

9 SUTISAN IK 9 EUKESOL OIL P 57 LEVADERM BORDEX LIQ.N10 TETRAPOL SAF 10 BAYSIN LUSTER K 58 LEVADERM BLUE LIQ.N

11 CHROPIPOL 11 PU BI 59 LEVADERM NAVY BLUE LIQ.N

12 L.LSAF(B.A.S.F). 12 GULF BINDER 001 60 LEVADERM OLIVE GREEN LIQ

13 OMBRELLON WR 13 GULF WAX 50 61 IRGADERM ORANGE M14 TENSECO/SELLASOL HH 14 GULF GROUND 72 62 IRGADERM BLACK N

15 TINO FIX 15 BAYDERM FINISH 80 UD 63 EULASOLAR RED GL LIQ

16 CARTON O POWDER 16 EUE DESPERSION 92 A 64 EUK. BLUE/NEO.BLUE -M

17 MIMOSA POWDER 17 AQUALAN AKU 65 EUKANOL RUBIN N

18 LIQUOR AMMONIA 18 K.S.3121 66 EUKANOL BRILLIANT BLACK19 OXALIC ACID 19 FROMAL-DE-HYDE 67 IRIODIN 100 (SILVER POWDER)

20 RELUGAN BTW 20 ETHYLENEGLYCOL 68 IRIODIN 300 (GOLD POWDER)

21 BASINTAN FC 21 ACITIC ACID 69 LEVADERM LEMON LIQ.N

22 BABRACHO 22 UNI WAX ST 70 LEVADERM YELLOW LIQ.N23 ALUMINUM SULPHATE 23 DP 5151 71 LEVADERM ORANGE LIQ.N

24 BASYNTAN WL 24 GULF WAX BR 72 LEVADERM RED LIQ.N

21

AAnnnneexxuurree 22::NNaattiioonnaall EEnnvviirroonnmmeennttaall QQuuaalliittyy

SSttaannddaarrddss ((NNEEQQSS))

Air Emissions(mg/Nm3 unless otherwise specified)

Parameter Standards1. Smoke 40% or 2 (Ringlemann Scale)2. Particulate matter

Boilers & furnaces:• Using oil• Using coal• Cement kilns• Grinding, crushing clinker coders, & related processes, metallurgical processes,

convertors, blast furnaces and cupolas

300500200500

3. Hydrogen chloride 4004. Chlorine 1505. Hydrogen fluoride 1506. Hydrogen sulphide 107. Sulphur oxides 4008. Carbon monoxide 8009. Lead 5010. Mercury 1011. Cadmium 2012. Arsenic 2013. Copper 5014. Antimony 2015. Zinc 20016. Oxides of nitrogen (NOX) 400

Noise Pollution

Nos Parameter Standard1. Noise level 80 db

Liquid Effluents(mg/litres unless otherwise defined)

Nos Parameter Standard1. Temperature 40oC2. pH Value (acidity/basicity) 6-10 pH3. 5-day biochemical oxygen at 20oC 804. Chemical Oxygen demand (COD) 1505. Total suspended solids 1506. Total dissolved solids 35007. Grease and oil 108. Phenolic compounds (as phenol) 0.19. Chloride (as Cl) 100010. Fluoride (as F) 2011. Cyanide (as Cn) 212. Anionic detergents (as MBAS) 2013. Sulphate (SO4) 60014. Sulphide (S) 1.015. Ammonia (NH3) 4016. Pesticides, herbicides fungicides and insecticides 0.1517. Cadminum 0.118. Chromium 1.019. Copper 1.020. Lead 0.521. Mercury 0.0122. Selenium 0.523. Nickel 1.024. Silver 1.025. Total toxic metals 2.026. Zinc 5.027. Arsenic 1.028. Barium 1.529. Iron 2.030. Manganese 1.531. Boron 6.032. Chlorine 1.0

22

Annexure 3:Preliminary Process Design of a Treatment Plant for

Segmented Tanneries {8000-10000 Skins (Wet Blue) / Day}Average Flow M3/d 120Characteristics (Average Value Load/per DayBOD (TOTAL) Mg/l 1984 Kg/d 238.08

S.S Mg/l 4295 Kg/d 515.4

Kj-N Mg/l 483 Kg/d 58

SULFIDE Mg/l 0 Kg/d 0

FLOW PER DAY M3/d 1200

TIME OF FLOW (12 – 7 PM) Hrs 7

GRIT CHAMBER

HYDRAULIC LOAD M3/hr 17

HYDRAULIC SURFACE LOAD M/hr 7

SURFACE AREA M2 2.4

EQUALIZATION TANK M3 70

RENTENTION TIME Hr 14.0

FLOW DISCHARGE Hr/d 24

FLOW M3/h 5.0

PRIMARY SEDIMENATION TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/HR 5.0

HYDR. SURFACE LOAD M/H 1

SURFACE M2 5.0

DIA METER M 2.5

DEPTH M 2

VOLUME OF EACH TANK M3 10

TOTAL VOLUME OF TANKS M3 10

RETENTION TIME Hr 2

EFFICIENCY OF PST

LOAD TO AERATION TANKBOD5 Kg/d 40% 1190.4 142.848 Kg/day

SS Kg/d 50% 1718 206.16 Kg/day

Kj-N Kg/d 10% 434/7 52.164 Kg/day

SULFIDE Kg/d 0% 0 0 Kg/day

SLUDGE REMOVED FROM PST

PRIMARY SLUDGE PRODUCTION Kg/d 373

SLUDGE CONC. % 3 Note: Lab result

SLUDGE VOLUME M3 12

PUMPING TIME Hrs 8

REQUIRED CAPACITY M3/hr 1.6

AERATION TANK

SLUDGE CONCENTRATION Kg/M3 4

ORG SLUDGE LOAD Kg BOD/D 0.11

VOLUME M3 325

NET DEPTH M 4

SURFACE AREA M2 81.2

RETENTION TIME OF WATER days 2.71

BOD REMOVAL % 95

OXYGEN REQ. BOD REMOVAL Kg/Kg 0.5

OXYGEN REQD. Kg/d 68

Endog.resp KgO/Kg ds.day 0.11

ODYGEN REQ. RES Kg/d 142.848

NITRIFICATION % 95

OXYG.REQD. Kg/d 226.5

23

DENITRIFICATION % 60 Note: Max denitrification = 62%

OXY.PRODUCTION Kg/d 136

SULFIDE OXIDATION % 100

OXY.REQD. Kg/d 0

TOTAL OXYGEN REQUIRED Kg/d 301

TOTAL OXYGEN REQUIRED Kg/hr 13

AERATION PEAK FACTOR 1.2

OXYGEN DEFICIT 1.24

ALPHA FACTOR 0.9

OXYGEN INPUT Kg/hr 21

OXYGEN INPUT Kg O/Kw 1.2

POWER REQD. Kw 17.3 x 24 x 365 = 151548 Kw/year

EXCESS SLUDGE (RATE) Kg d.s./Kg 0.6

BOD REMOVAL % 95

EXCESS SLUDGE PRODUCED Kg d.s./d 81

EXCESS SLUDGE CONC Kg/d/s/M3 10

EXCESS SLLUDGE PRODUCED M3/D 8

DISCHARGE HR (Pumping Time) hrs 8

REQUIRED CAPACITY M3/hr 1.0

RETURN SLUDGE CAPACITY M3/hr 5

FINAL SETTLING TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/hr 5.0

HYDRAULIC SURFACE LOAD M/hr 0.7

SURFACE AREA OF EACH TA M2 7

DIAMETER OF EACH TANK M 3.0

AVERAGE DEPTH M 2

VOLUME OF EACH TANK M3 14

TOTAL VOLUME OF TANKS M3 14

RETENTION TIME Hr 3

TOTAL SLUDGE PRODUCTION

PRIMARY SLUDGE (PST) Kg/d 372.552

EXTRA SLUDGE (FST) Kg/d 81.4

TOTAL SLUDGE Kg/d 454

PRIMARY SLUDGE M3/d 12

EXTRA SLUDGE M3/d 8

TOTAL SLUDGE M3/d 21

SLUDGE THICKNER

SLUDGE LOAD Kg d.s./da 30

SURFACE AREA M2 15

DIAMETER M 4.4

AVE.DEPTH M 3.5

VOLUME M3 53

SLUDGE CONCENTRATION % 3

SLUDGE VOLUME M3/d 15

MECHANICALDEWATERING

Note: Mechanical Dewatering will not be used in this case

DEWATERING TIME Hr/d 16

CAPACITY OF DEWATERING M3/hr 1

DRY SOLID CONCENTRATION % 20

SLUDGE VOLUME M3/d 2

SLUDGE DRYING BEDS

SLUDGE LOAD Kg/M2.d 1.2

SURFACE AREA M2 378

DRY SLUDGE CONC % 20

TOTAL VOLUME OF SLUDGE M3/d 2

24

Annexure 4:Preliminary Process Design of Treatment Plant for

Segmented Tanneries {600-1500 Kg Skins (Wet Blue) / DayAverage Flow M3/d 40CHARACTERISTICS (Average Value) Load/per DayBOD (TOTAL) mg/l 1468 Kg/d 58.72

S.S mg/l 1042 Kg/d 41.68

Kj-N mg/l 459 Kg/d 18

SULFIDE mg/l 0.6 Kg/d 0.02

FLOW PER DAY M3/d 40

TIME OF FLOW (6 AM – 7 PM) Hrs 12

GRIT CHAMBER

HYDRAULIC LOAD M3/hr 3

HYDRAULIC SURFACE LOAD M/hr 7

SURFACE AREA M2 0.5

EQUALIZATION TANK M3 30

RENTENTION TIME Hr 18.0

FLOW DISCHARGE hr/d 24

FLOW M3/h 1.7

PRIMARY SEDIMENATION TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/hr 1.7

HYDR. SURFACE LOAD M/h 1

SURFACE M2 1.7

DIA METER M 1.5

DEPTH M 2

VOLUME OF EACH TANK M3 3

TOTAL VOLUME OF TANKS M3 3

RETENTION TIME hr 2

EFFICIENCY OF PST

LOAD TO AERATION TANKBOD5 Kg/d 40% 880.8 35.232 Kg/day

SS Kg/d 60% 416.8 16.672 Kg/day

Kj-N Kg/d 10% 413.1 16.524 Kg/day

SULFIDE Kg/d 0% 0.6 0.024 Kg/day

SLUDGE REMOVED FROM PSTPRIMARY SLUDGE PRODUCT Kg/d 25

SLUDGE CONC. % 3 Note: Lab result

SLUDGE VOLUME M3 0.8

PUMPING TIME hrs 0.5

REQUIRED CAPACITY m3/hr 1.7

AERATION TANK

SLUDGE CONCENTRATION Kg/M3 4

ORG SLUDGE LOAD Kg BOD/D 0.11

VOLUME M3 80

NET DEPTH M 4

SURFACE AREA M2 20.0

RETENTION TIME OF WATER days 2.00

BOD REMOVAL % 95

OXYGEN REQ. BOD REMOVAL Kg/Kg 0.5

OXYGEN REQD. Kg/d 17

Endog.resp KgO/Kg ds.day 0.11

OXYGEN REQ. RES Kg/d 35.232

NITRIFICATION % 95

OXYG.REQD. Kg/d 71.7

DENITRIFICATION % 60 Note: Max denirification =62%

OXY.PRODUCTION Kg/d 43

25

SULFIDE OXIDATION % 100

OXY.REQD. Kg/d 0.05

TOTAL OXYGEN REQUIRED Kg/d 81

TOTAL OXYGEN REQUIRED Kg/hr 3

AERATION PEAK FACTOR 1.2

OXYGEN DEFICIT 1.24

ALPHA FACTOR 0.9

OXYGEN INPUT Kg/hr 6

OXYGEN INPUT Kg O/Kw 1.2

POWER REQD. Kw 4.6 40589 Kw/Year

EXCESS SLUDGE (RATE) Kg d.s./Kg 0.6

BOD REMOVAL % 95

EXCESS SLUDGE PRODUCED Kg d.s./d 20

EXCESS SLUDGE CONC. Kg/d/s/M3 10

EXCESS SLLUDGE PRODUCED M3/D 2

DISCHARGE HR (Pumping Time) Hrs 8

REQUIRED CAPACITY M3/hr 0.3

RETURN SLUDGE CAPACITY M3/hr 2

FINAL SETTLING TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/hr 1.7

HYDRAULIC SURFACE LOAD M/hr 0.7

SURFACE AREA OF EACH TANK M2 2

DIAMETER OF EACH TANK M 1.7

AVERAGE DEPTH M 2

VOLUME OF EACH TANK M3 5

TOTAL VOLUME OF TANKS M3 5

RETENTION TIME hr 3

TOTAL SLUDGE PRODUCTION

PRIMARY SLUDGE (PST) Kg/d 25.008

EXTRA SLUDGE (FST) Kg/d 20.1

TOTAL SLUDGE Kg/d 45

PRIMARY SLUDGE M3/d 1

EXTRA SLUDGE M3/d 2

TOTAL SLUDGE M3/d 3

SLUDGE THICKNER

SLUDGE LOAD Kg d.s./da 30

SURFACE AREA M2 2

DIAMETER M 1.4

AVE.DEPTH M 3.5

VOLUME M3 5

SLUDGE CONCENTRATION % 3

SLUDGE VOLUME M3/d 2

MECHANICALDEWATERING

Note: mechanical dewatering will notbe used in this case

DEWATERING TIME hr/d 16

CAPACITY OF DEWATERING M3/hr 0

DRY SOLID CONCENTRATION % 20

SLUDGE VOLUME M3/d 0

SLUDGE DRYING BEDS

SLUDGE LOAD Kg/M2.d 1.2

SURFACE AREA M2 38

DRY SLUDGE CONC % 20

TOTAL VOLUME OF SLUDGE M3/d 0

26

Annexure 5:Preliminary Process Design of a Treatment Plant for Tanneries

Processing Hides to Finished Leather (Appox. 2000 Kg/Day)

Average Flow M3/d 1836CHARACTERISTICS Load/per DayBOD (TOTAL) mg/l 1740 kg/d 238.08

S.S mg/l 1327 kg/d 515.4

Kj-N mg/l 25 kg/d 58

SULFIDE mg/l 2 kg/d 0

FLOW PER DAY mg/l 1836

TIME OF FLOW (6 AM – 7 PM) Hrs 13

GRIT CHAMBER

HYDRAULIC LOAD m3/hr 141

HYDRAULIC SURFACE LOAD m/hr 30

SURFACE AREA m2 4.7

EQUALIZAION TANK M3 1000

RENTENTION TIME hr 13.1

FLOW DISCHARGE hr/d 24

FLOW M3/h 76.5

PRIMARY SEDIMENATION TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/hr 76.5

HYDR. SURFACE LOAD M/h 1

SURFACE M2 76.5

DIA METER M 9.9

DEPTH M 2

VOLUME OF EACH TANK M3 153

TOTAL VOLUME OF TANKS M3 153

RETENTION TIME hr 2

EFFICIENCY OF PST

LOAD TO AERATION TANKBOD5 Kg/d 30% 1218 2236 Kg/day

SS Kg/d 70% 398.1 731 Kg/day

Kj-N Kg/d 10% 22.5 41 Kg/day

SULFIDE Kg/d 0% 0 4 Kg/day

SLUDGE REMOVED FROM PSTPRIMARY SLUDGE PRODUCT Kg/d 1705

SLUDGE CONC. % 5 Note: Lab results

SLUDGE VOLUME M3 ss12

PUMPING TIME hrs 8

REQUIRED CAPACITY m3/hr 1.6

Note: Excluding Spare Pumps

AERATION TANK

SLUDGE CONCENTRATION Kg/M3 4

ORG SLUDGE LOAD Kg BOD/D 0.11

VOLUME M3 5082

NET DEPTH M 4

SURFACE AREA M2 1270.6

RETENTION TIME OF WATER days 2.77

BOD REMOVAL % 95

OXYGEN REQ. BOD REMOVAL Kg/Kg 0.5

OXYGEN REQD. Kg/d 1062

Endog.resp KgO/Kg ds.day 0.11

OXYGEN REQ. RES Kg/d 2236.248

NITRIFICATION % 95

OXYG.REQD. Kg/d 179.3

DENITRIFICATION % 60

27

OXY.PRODUCTION Kg/d 108

SULFIDE OXIDATION % 100

OXY.REQD. Kg/d 7

TOTAL OXYGEN REQUIRED Kg/d 3378

TOTAL OXYGEN REQUIRED Kg/hr 141

AERATION PEAK FACTOR 1.2

OXYGEN DEFICIT 1.24

ALPHA FACTOR 0.9

OXYGEN INPUT Kg/hr 233

OXYGEN INPUT Kg O/Kw 1.2

POWER REQD. Kw 193.9

EXCESS SLUDGE (RATE) Kg d.s./Kg 0.6

BOD REMOVAL % 95

EXCESS SLUDGE PRODUCED Kg d.s./d 1275

EXCESS SLUDGE CONC. Kg/d/s/M3 10

EXCESS SLLUDGE PRODUCED M3/D 127

DISCHARGE HR (Pumping Time) Hrs 8

REQUIRED CAPACITY M3/hr 1.0

Note: Excluding Spare Pumps

RETURN SLUDGE CAPACITY M3/hr 77

FINAL SETTLING TANK

NUMBER OF TANKS 1

FLOW TO EACH TANK M3/hr 76.5

HYDRAULIC SURFACE LOAD M/hr 0.7

SURFACE AREA OF EACH TANK M2 109

DIAMETER OF EACH TANK M 11.8

AVERAGE DEPTH M 2

VOLUME OF EACH TANK M3 219

TOTAL VOLUME OF TANKS M3 219

RETENTION TIME hr 3

TOTAL SLUDGE PRODUCTION

PRIMARY SLUDGE (PST) Kg/d 1705.46

EXTRA SLUDGE (FST) Kg/d 1274.7

TOTAL SLUDGE Kg/d 2980

PRIMARY SLUDGE M3/d 34

EXTRA SLUDGE M3/d 127

TOTAL SLUDGE M3/d 162

SLUDGE THICKNER

SLUDGE LOAD Kg d.s./da 30

SURFACE AREA M2 99

DIAMETER M 11.2

AVE.DEPTH M 3.5

VOLUME M3 348

SLUDGE CONCENTRATION % 3

SLUDGE VOLUME M3/d 99

MECHANICALDEWATERING

DEWATERING TIME hr/d 16

CAPACITY OF DEWATERING M3/hr 6

DRY SOLID CONCENTRATION % 20

SLUDGE VOLUME M3/d 15

SLUDGE DRYING BEDS

SLUDGE LOAD Kg/M2.d 1.2

SURFACE AREA M2 2483

DRY SLUDGE CONC % 20

TOTAL VOLUME OF SLUDGE M3/d 15