Environmental Tech.

7/27/2019 Environmental Tech.

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The Leather Sector

Environmental ReportDD R R AA FF TT


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TTaa bb llee oo f f CC oo nn ttee nn ttssPreface i

Executive Summary 1

1. The Environmental TechnologyProgramme 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 125.3 Wastewater Treatment Technologies 13

5.3.1 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 Wastewater of a Tannery

Table 3.4b: Characteristics of Composite Wastewater of 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 Tank Table 6.3: Land Requirement (m 2)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 Tank Table 6.8: Land Requirement (m 2)Table 6.9: Effluent Quality of Treatment PlantTable 6.10: Estimated Capital Cost of a Treatment

Plant with the Present Hydraulic Load of a 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 Plantwith 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


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PP r r ee f f aa cc eeThis report has been prepared as part of the ETPIdemonstration project component - collaborative efforts

between the industry and FPCCI - and aims to address theenvironmental pollution problems in the leather manufacturing sector. This report has been prepared onthe basis of the findings of environmental audits of four tanneries 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 demonstration project. 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 the

possible investment required to abate these problems tomeet the present and future environmental legislation. It

is 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 of Pakistan (FPCCI) to execute the program. These firms are

National Environmental Consulting (NEC) PrivateLimited and HASKONING of the Netherlands. Thegeneral report has been prepared by the core team of ETPI.

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 Tanners

Association (PTA) and Tanneries who participated in the program 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


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The Federation of Pakistan Chambers of Commerce &Industry (FPPCI) being the apex body representing all the

business, 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.

Pakistans leather and leather products industry is one of

the major foreign exchange earners amongst themanufacturing goods sector. At present, about 90 % of the leather is exported in the finished form. There are

presently 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) and

predominantly imported chemicals are used.

In the leather sector a variety of finished leather is prepared 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 or hides for the tanning purpose. After performing their functions 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 air

pollution in tannery are of two types; one is from thestack of generators and boiler and the other from the

process. 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 of tanning 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 main

problem associated with some of these wastes is their chrome 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 for generating the wastewater. Water consumption per kg of raw hides varies from tannery to tannery. Consumption of water 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, the

production and wastewater generation doubles. Despitethe seasonal fluctuation, daily fluctuation in wastewater generation also exists due to variation in the quantity of

raw material processed daily. The characteristics of wastewater shows that it is highly polluted with Bio-chemical Oxygen Demand (BOD 5), 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 various

environmental 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 proper arrangement to stop the use of tanned solid waste for the

preparation of poultry feed.

Implementation of cleaner technologies such as water conservation, 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 easily

be recovered from the spent tanning effluent and this canthen be reused without compromising the quality of leather. 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 differenttechnologies 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 BOD 5,COD, suspended solids, chrome, sulphide and pH. For theremoval of salt, in-house improvement is suggested. Anestimated investment cost for such a treatment system for a tannery processing about 12000 kg of hides per day isapproximately 44 million with a cost of about 7-9 millionrupees 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 per day would cost about Rs.10 million and for a tannery

processing 600 - 1500 kg of wet blue per day, the costwould approximately be Rs.3 million.

11 .. TThh ee EE nn vv iir r oo nn mm ee nn tt aa ll TTee cc hh nn oo lloo gg yy PP r r oo gg r r aa mm f f oo r r IInn dd uu ss tt r r yyThe 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 safe

products 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 sector report is prepared in consultation with industry experts.The sub sector report highlights the key environmentalissues in that industrial sector, lists possible solutions for major 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 work and methodology. The present study is dealing with the

demonstration project component. Hence, in this report,this component will be discussed in detail.

Physical interventions in the form of demonstration projects are an integral part of the ETPI. A demonstration project 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 local industrialists. Improvement in processing practices will also 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 of environmental technologies in the country.

To prepare a representative database in the shape of industry specific Environmental Audit for establishing 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 this

procedure, three industries will be selected for anEnvironmental Audit from each sub sector. Subsequentlyone of these three will be selected for the demonstration

project.

In the sub sector of leather manufacturing, instead of three 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 .. TThh ee LLee aa tt hh ee r r IInn dd uu ss tt r r yy

2.1 A ProfilePakistans leather and leather products industry is one of the major foreign exchange earners amongst themanufactured goods sector. At present about 90 % of theleather is exported in finished form. During the year 1994-95 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, the

processing 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 environmental

problems, 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 of the 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 is

discharged 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 Water An extensive quantity of water is used in the leather sector. 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 Leather sector.

2.3 Process and Operation

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


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widely used for the preparation of finished leather.However, vegetable tanning method and a combination of chrome and vegetable tanning method is also beingapplied. The three tanneries selected for the audit under the 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 Environmental

ConditionsIn-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 not pay much attention. The un-usage of these

accessories during work may be due to the andignorance and un-awareness of the workers. Information boards about safety and health

regulations are not installed in the tanneries. Loading and unloading of the skins/hides during

processing is normally carried out manuallywithout using gloves and proper clothes for

protection. Consequently the cloths of the workers become 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(m 3 / 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 36

Neutralisation 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 .. WW aa ss tt ee GG ee nn ee r r aa tt iioo nnAll 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 minor quantity 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 of the 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 water consumption reaches to a level which is three time higher to the normal, i.e., 150 litre /kg of raw hides. Water consumption at each processing stage, for a tannery

processing sheep and goat skins, has been summarised inTable 3.1.

During peak season the processing of raw skins/hidesdoubles, which directly effects the quantity of wastewater 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 of wastewater discharged from different tanneries is givenin Table 3.2.

3.1.3 CharacteristicsTannery wastewater is highly polluted in terms of

biochemical 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 Wastewater Discharge 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 of Sludge

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 18

Drying Time (1x15Minute)

M o

i s t u r e

R e m o v e d

( w t % )

Series1 Series2

Table 3.5: Characteristics of Sludge inComposite Wastewater of Tannery-A

Tanneries Wastewater Quantity/Kg of Hides or Skins

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

upper and liningleather (12000

kg/day)

48 litre/kg skins

Wet blue to finished upper and 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 of non-availability of the data, known number of skins/hides were weighed before and after the

process/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 their disposal 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

Suspended

Solid

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 Kjeldhal Nitrogen

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 3.6: 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 20Total 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 skins

and 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-hairing

processes.

Splitting of Wet Blue: This operation is carried out inhides tanneries processing hides. After chrome tanning,the hides 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 lower layer is treated as a by-product. However, it is further

processed and is used for manufacturing low grade shoeupper leather and as such is not considered as solidwaste.

Chrome Wet Shaving: After chrome tanning, skins or split 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 of buffing 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 of solid waste was also carried out. Four samples, each of one kilogram, were taken from major types of solidwastes being generated, i.e. salt dusting, fleshing, wet

shaving and trimming, dry shaving, trimming and buffing. This exercise was conducted to determine themajor constituents such as moisture, salt, lime,chromium, total and volatile solids, sulphide fats and

proteins. 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 132Cr 2O3 - - 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 bulk from the tannery and sell these in the retail market at a

profit. Therefore, it has become a source of income for these people.

Poultry feed manufacturers, due to the protein content of

some 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.


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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 feed

preparation, trivalent chromium is being changed into itshexavalent form. The mixing of heavy metal in poultryfeed in such a high quantity could produce severe health

problems 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 other from 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 of tanning 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 air emissions of the generator and boiler. In the dyeing andtanyard section of a tannery, ammonia emission weretraced in a quantity of 4.1 mg / Nm 3, which is a healthhazard to the workers.

44 .. EE nn vv iir r oo nn mm ee nn tt aa ll IImm pp aa cc tt ss oo f f TTaa nn nn ee r r yy WW aa ss tt ee ssAs discussed in the previous Chapter, three types of wastes are generated during the leather manufacturing

processes. 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 of

poultry feed. As far as liquid waste is concerned,tanneries are disposing off their un-treated wastewater into 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, the

pollutants 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 acids

in 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 (BOD 5 )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 (BOD 5) and suspended solids.

BOD is a measure of the oxygen consuming capacity of water containing organic matter. Organic matter by itself does 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 higher as compared to the BOD value (375 - 525 mg/l) of sewage.

4.1.3 Chemical Oxygen Demand (COD)The Chemical Oxygen Demand (COD) is a measure of oxygen equivalent to that portion of the organic matter in a sample which is susceptible to oxidation by a strongchemical oxidant. It is an important, rapidly measured

parameter for stream and industrial waste studies and for control of waste treatment plants.

Along with the organic compounds immediatelyavailable to the stream organism, it also determines

biological compounds that are not a part of immediate biochemical 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


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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 tanning

process. This is much less toxic than hexavalentchromium. For plant and animal life, the toxicity of chromium salts is variable. The toxicity is a function of the species itself. Algae have been shown to be

particularly 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 tanning

process, 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 of 1.0 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 the

bottom waters. A further secondary effect is the reducedlight penetration and consequent reduction in

photosynthesis 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 of tanneries 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 .. RR ee mm ee dd iiaa ll MMee aa ss uu r r ee ss

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 of hazardous chemicals, etc. is required for the staff.

RAW SKINS 12000 KG

LEATHER 1400 K

BOD 5 = 13680COD = 34200SuspendedSolids = 2790Chromium = 80Sulphide = 173Sludge = 3280

All values in K /da

WASTEWATER (600 M 3/day)

UNTANNEDDusted Salt = 1000Raw trimming = 240Fleshing= 2500

TANNEDShaving = 1500Trimming = 240Buffing = 20

Total = 5500All values are in K ./da

SOLID WASTE AND BY- PRODUCTS


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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 proper solution to stop this practice, as the poultry feedmakers can get this material from these sites.Tanned solid waste materials can be used in leather

board 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 spray

plant that caries unused finishing material. Other waste that can be mixed with tanned solid waste is

curing salt. After mixing with this waste, tannedsolid waste will become contaminated and will not

be useful for poultry feed makers. Improvement in drainage system in order to avoid

formation 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 of cleaner production processes and pollution preventionmeasures can provide both economic and environmental

benefits. However, the applicability of these technologiesvary from tannery to tannery due to the varying nature of raw material, processing conditions and the type of finished 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 for drums 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 of sulphide. 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 of trivalent 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, BOD 5 , 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 after decantation 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 process

water.Lime Splitting and Trimming Splitting and trimming is usually carried out after tanning which results in a by-product of

low quality containing chromium in it. If these operations are carried out with the pelt, the produced 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


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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 chromium

being 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 the

previous 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 of quality problems with delicate hides and by the need tocontrol residual float. This technology is suitable for small 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 of alkalies and bases including sodium hydroxide, sodiumcarbonate, magnesium oxide and even with lime. Thereuse of sludge after simple settling and acidification has

been experimented and practised. Schematic diagram of a 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 have

been 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 and

pay back period of the chrome recovery project.

Tanning Products that Improve the ExhaustionRate: For the past few years, tanning and basification

products have been available in the market which enablea tanning cycle to produce only small quantities of chromium 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 CRRP1. 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./year Rs./ year Rs./ year Rs./ year Rs./ year Rs. 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.


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5.3 Wastewater TreatmentTechnologies

Two levels of treatment are normally required for treatment of the effluent from the tanneries. These are

primary and secondary treatment.

5.3.1 Primary TreatmentPrimary treatment system comprises of mechanicalscreening, pH equalisation (collection of effluent of

different processes in a common tank), coagulation andflocculation and sedimentation.

Mechanical Screening: Removal of coarse, particulate flesh and hair is achieved by means of perforated 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 effluents pH 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 sampling

programme.

Due to the equalization tank, the flow and composition of the effluent is also maintained more constantly for further 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 the

basis 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 of these 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 or by compressed air. Here it mixes with the mass of bacterial floc maintained constantly in suspension. After sufficient 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 with

primary sludge. This is a proven technology for thetreatment of tannery wastewater and widely used all over the world. Modified forms of this technology areavailable.

Aerated Lagoons: An aerated lagoon is an earthen basin 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 safely

be used for the treatment of tannery effluent. However, itrequires a large area of land as compared to other technologies. For the present study, this technology is not

being considered due to insufficient area of landavailable.

Facultative Ponds: Ponds in which the stabilization of waste 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 facultative

bacteria, using bacteria produced by algae growing near the surface. Carbon dioxide produced in organicoxidation serves as carbon source for the algae.Anaerobic breakdown of the solids in the sludge layer results in the production of dissolved organic compoundsand gases such as carbon dioxide, hydrogen sulphide andmethane, which are either oxidized by the aerobic

bacteria or vented to the atmosphere. In practice, oxygenis maintained in the upper layer of the facultative lagoon

by 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 for the treatment of wastewater for the tanneries under study.

Anaerobic Lagoon: Typically, an anaerobic lagoon isa deep earthen pond with appropriate inlet and outlet

piping 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 for further treatment.

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


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precipitation and the anaerobic conversion of organicwaste into carbon dioxide, methane, other gaseous end

products, 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 the

biomass 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 not

been tested for treatment of tannery wastewater on alarge-scale. Due to a heavy load of pollution in tannerywastewater, its performance is doubtful. Tanneries aredischarging wastewater containing 40 times more BODvalue as compared to domestic wastewater. Nitrification

is 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 wastewater through a sludge layer of active anaerobic micro-organisms. The wastewater is evenly distributed at the

bottom 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 the

production of biogas, due to the rising bubbles which provide 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. The

biogas is separated in a gas collector, whilst the sludge-water mixture enters a settling compartment, thus

providing effective sludge retention in the reactor. Theeffluent is discharged from the top of the reactor via anoverflow weir. The excess sludge is discharged from the

bottom 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 of more than 160 tanneries, situated in sector 7 - A of Korangi Industrial Area.

Besides other toxic waste present in the tannerywastewater for anaerobic process, sulphate concentrationis one of the more important factors. In the presence of sulphate, an anaerobic process starts the generation of hydrogen sulphide gas and at the same time the

production of Methane gas is badly effected. Wastewater of tanneries under study contains sulphate (SO 4) 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 of domestic wastewater, therefore, this technology cannot

be considered for the treatment of wastewater for individual 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 .. WWaa ss ttee ww aa ttee r r TTr r ee aa ttmm ee nn tt SS yyss tt ee mm ::PP r r ee lliimm iinn aa r r yy DDee ss iigg nn iinn gg aa nn dd CC oo ss tt EE ss tt iimm aa tt iioo nn

Two types of tanneries participated in the ETPI program.One type of tannery was invloved in segmented production

by 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 is purchased 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.


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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 m 3/dayTannery B 30 - 40 m 3/day

Daily Pollution Loads: The maximum values of water quantities 120 and 40 m 3 /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 of Tannery A and B

Tannery A120 m 3 /day

Tannery B40 m 3 /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 255.33COD settleablesolid

3000 360 1648 66

Tot. suspendedsolids

5295 515 1042 42

Tot. Kj Nitrogen

483 58 264 10.56

Sulphate 5980 717 1009 400.36Sulphide Nil Nil 0.4 0.0158Phosphate 25.5 3 3.5 0.14

Note: 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 the

preliminary 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 low

loaded activated sludge system (including sludgestabilization); and Mechanical dewatering is taken into consideration as

relatively high amounts of sludge are generated daily.

Table 6.2: Load of Aeration Tank

Tannery -ADescription Input to

PrimaryTreatmentkg/d

Efficiencyof PrimaryTreatment(%)

Output of PrimaryTreatment*(kg/d)

Sludge(kg/d)

BOD5Susp.solidsKj-NSulphide

23551558

Nil

5060100

15320652

Nil309

Tannery - BDescription Input to

PrimaryTreatment(Kg/d)

Efficiencyof PrimaryTreatment(%)

Output of PrimaryTreatment*(kg/d)

Sludge(kg/d)

BOD 5Susp.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 and polyelectrolyte 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 ( m 2 )

Tannery A Tannery B

WithMechanicalDewatering

WithoutMechanicalDewatering

WithMechanicalDewatering

WithoutMechanicalDewatering

1753 2777 160 212


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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 of Treatment Plant

(mg/l)

EffluentConcentrationof TreatmentPlant (mg/l)

TanneryA

TanneyB

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

3.5198557555295583

Nil

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 of Treatment Plant for (Wet) FinishingTannery Process

Description Tannery -A Tannery B

A: Civil WorksGrit chamber

Equalization tank Primary sedimentation tank.Aeration tank Final settling tank Complete sludge thickner Sludge drying bedControl/Service room

42000

49000070000

2275000105000392000228200100000

4000

21000021000

56000035000

39200015800050000

Sub Total 3702200 1430000B: Mechanical EquipmentsMixer PumpsScraper, skimmer, bridge etcSurface aerator Belt filter press

10000070000050000

1500002500000

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

Sub Total 3500000 600000

Total A + B 7202200 20300001. Electrical/ mechanicalwork ( 20 % total A+B)

1440440 406000

2. Contingencies (20% of total 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 (m 2) 1753 -2777 160 -212


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6.2 Wastewater Treatment for Processing 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 of wastewater fluctuates in between the values given below,depending on the quantity of raw material, processed daily: 1836 m 3/day on an average (whole year); 3672 m 3/day in peak season (about 2 months).

Daily Pollution Loads : Daily pollution load has beencalculated on the basis of average and peak flows. Daily

pollution loads are summarized in Table 6.6. Whereas,average values of each parameter is taken for designing

purpose.

Table 6.6: Daily Pollution LoadsDescription Conc.

(mg/l)Average

Load1836 m 3/d

(kg/d)

Peak Load3672 m 3/d

(kg/d)

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

1740560

13272526

3195102824364593.711

62390205648729187.422

Note: BOD 5 suspended solids are based on the difference of BOD5 at O time and BOD 5 after 60 minutes settling.

6.2.2 AssumptionsThe following assumptions have been applied for the

preliminary 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 of Primary

Treatment(kg/d) *

Sludge(kg/d)

BOD5Susp. Solids

Kj-NSulphidePhosphate

31952436

4593.711

3070

10011

1218398

22.53.7 1705

Considered loads to the aeration tank for design of volume 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 (m 2)

With Mechanical

Dewatering

Without Mechanical

Dewatering7838 13834


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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


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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)

PHBOD 5CODSuspended SoildT.Kjeldhal NitrogenSulphideChromium*

7.661740267013232523

7.5-8801501501.25

Nil< 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 of Tannery

Description Estimated Cost (Rs.)A: CIVIL WORKS

1. Grit chamber 2. Equalization tank 3. Primary sedimentation tank.4. Aeration tank 5. Final settling tank 6. Complete sludge thickner 7. 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 EQUIPMENTS

1. Mixer 2. Pumps3. Scraper, skimmer, bridge etc.4. Surface aerator 5. 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 millionTotal 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- 13,834

Note: Land cost is not inculded.


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AAnn nn ee xx uu r r ee 11 ::LLiiss tt oo f f CC hh ee mm iicc aa llss UUss ee ddiinn tthh ee TTaa nn nn iinn gg PP r r oo cc ee ss ss

S. No. NAME S. No. NAME S. No. NAMEI. PRE-TANNING CHEMICALS 25 BASANTAN J-Z/J-Z 25 GULF OIL 441 LIME POWDER 26 IRGAPADOL PN-NEW 26 MESLINIOUS2 CHINA CLAY 27 IRGAPADOL FF4 27 GULF PUK 993 AMONIUM SULPHATE 28 BELLASOL -NG LIQ 28 GULF TUCH 454 SODIUM META BI SULPHATE 29 BOREX 29 NEOSON DOUBLE WHITE5 KEROSENE OIL 30 DERMAGEN DM 30 NEOSON BLACK/D6 SEA SALT 31 TANIGAN QF 31 NEOSON BEIGE7 SULPHURIC ACID 32 HESLINIOUS 32 NEOSON BROWN8 SODIUM BI CARBONATE IV DYES 33 NEOSON YELLOW9 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 T12 SODIUM SULPHIDE 4 DERMA BROWN 2RM 37 BAYFEROX - 91513 BUSAN 30 5 DERMA BROWN 2490 38 EUKANOL RED-D14 FORMIC ACID 6 DERMA RED 2201 39 EUK. BLUE/NEO.BLUE -M15 MAGNISIUM OXIDE 7 DERMA RED BA 40 EUKANOL RUBIN N

16 CHRMEND BASE FN/MD 8 DERMA GREY 2411 41 EUKANOL BRILLIANT BLACK17 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.N1 PAK CHROME 13 DERMA BEIGE Z 46 LEVADERM ORANGE LIQ.N2 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.N2 TANIGAN AN 2 BINDER IF 50 LEVADERM NAVY BLUE LIQ.N3 RETIGAN R7 3 BINDER ON 51 LEVADERM OLIVE GREEN LIQ4 TANIGAN BN 4 E.M. FINISH G/PANAMOL 52 IRGADERM ORANGE M5 TANIGAN PAK-N 5 WAX EG 53 IRGADERM BLACK N6 MAGNOPAL STD 6 LURAN LUSTER E 54 EULASOLAR RED GL LIQ7 4 FBW 7 BINDER LUSTER E 55 LEVADERM ORANGE LIQ.N8 CUTISAN SL 8 BINDER U KONZ/PO 56 LEVADERM RED LIQ.N9 SUTISAN IK 9 EUKESOL OIL P 57 LEVADERM BORDEX LIQ.N

10 TETRAPOL SAF 10 BAYSIN LUSTER K 58 LEVADERM BLUE LIQ.N11 CHROPIPOL 11 PU BI 59 LEVADERM NAVY BLUE LIQ.N12 L.LSAF(B.A.S.F). 12 GULF BINDER 001 60 LEVADERM OLIVE GREEN LIQ13 OMBRELLON WR 13 GULF WAX 50 61 IRGADERM ORANGE M14 TENSECO/SELLASOL HH 14 GULF GROUND 72 62 IRGADERM BLACK N15 TINO FIX 15 BAYDERM FINISH 80 UD 63 EULASOLAR RED GL LIQ16 CARTON O POWDER 16 EUE DESPERSION 92 A 64 EUK. BLUE/NEO.BLUE -M17 MIMOSA POWDER 17 AQUALAN AKU 65 EUKANOL RUBIN N18 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.N22 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


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AAnn nn ee xx uu r r ee 22 ::NNaa tt iioo nn aa ll EE nn vv iir r oo nn mm ee nn tt aa ll QQ uu aa lliitt yy

SS tt aa nn dd aa r r dd ss ((NNEE QQ SS ))

Air Emissions(mg/Nm 3 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 20

12. Arsenic 2013. Copper 5014. Antimony 2015. Zinc 20016. Oxides of nitrogen (NO X) 400

Noise Pollution

Nos Parameter Standard1. Noise level 80 db

Liquid Effluents(mg/litres unless otherwise defined)

Nos Parameter Standard1. Temperature 40 oC2. pH Value (acidity/basicity) 6-10 pH

3. 5-day biochemical oxygen at 20o

C 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 (SO 4) 60014. Sulphide (S) 1.015. Ammonia (NH 3) 4016. Pesticides, herbicides fungicides and insecticides 0.1517. Cadminum 0.118. Chromium 1.019. Copper 1.020. Lead 0.521. Mercury 0.01

22. 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


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Annexure 3:Preliminary Process Design of a Treatment Plant for

Segmented Tanneries {8000-10000 Skins (Wet Blue) / Day}Average Flow M3/d 120

Characteristics (Average Value Load/per DayBOD (TOTAL) Mg/l 1984 Kg/d 238.08S.S Mg/l 4295 Kg/d 515.4Kj-N Mg/l 483 Kg/d 58SULFIDE Mg/l 0 Kg/d 0FLOW PER DAY M3/d 1200TIME OF FLOW (12 7 PM) Hrs 7

GRIT CHAMBER HYDRAULIC LOAD M3/hr 17HYDRAULIC SURFACE LOAD M/hr 7SURFACE AREA M2 2.4

EQUALIZATION TANK M3 70RENTENTION TIME Hr 14.0FLOW DISCHARGE Hr/d 24

FLOW M3/h 5.0

PRIMARY SEDIMENATION TANK NUMBER OF TANKS 1FLOW TO EACH TANK M3/HR 5.0HYDR. SURFACE LOAD M/H 1SURFACE M2 5.0DIA METER M 2.5DEPTH M 2VOLUME OF EACH TANK M3 10TOTAL VOLUME OF TANKS M3 10RETENTION TIME Hr 2

EFFICIENCY OF PSTLOAD TO AERATION TANK

BOD5 Kg/d 40% 1190.4 142.848 Kg/daySS Kg/d 50% 1718 206.16 Kg/dayKj-N Kg/d 10% 434/7 52.164 Kg/daySULFIDE Kg/d 0% 0 0 Kg/day

SLUDGE REMOVED FROM PSTPRIMARY SLUDGE PRODUCTION Kg/d 373SLUDGE CONC. % 3 Note: Lab resultSLUDGE VOLUME M3 12PUMPING TIME Hrs 8REQUIRED CAPACITY M3/hr 1.6

AERATION TANK SLUDGE CONCENTRATION Kg/M3 4ORG SLUDGE LOAD Kg BOD/D 0.11VOLUME M3 325

NET DEPTH M 4SURFACE AREA M2 81.2RETENTION TIME OF WATER days 2.71BOD REMOVAL % 95OXYGEN REQ. BOD REMOVAL Kg/Kg 0.5OXYGEN REQD. Kg/d 68

Endog.resp KgO/Kg ds.day 0.11ODYGEN REQ. RES Kg/d 142.848

NITRIFICATION % 95OXYG.REQD. Kg/d 226.5


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DENITRIFICATION % 60 Note: Max denitrification = 62%OXY.PRODUCTION Kg/d 136

SULFIDE OXIDATION % 100OXY.REQD. Kg/d 0

TOTAL OXYGEN REQUIRED Kg/d 301TOTAL OXYGEN REQUIRED Kg/hr 13

AERATION PEAK FACTOR 1.2OXYGEN DEFICIT 1.24ALPHA FACTOR 0.9OXYGEN INPUT Kg/hr 21

OXYGEN INPUT Kg O/Kw 1.2POWER REQD. Kw 17.3 x 24 x 365 = 151548 Kw/year

EXCESS SLUDGE (RATE) Kg d.s./Kg 0.6BOD REMOVAL % 95EXCESS SLUDGE PRODUCED Kg d.s./d 81EXCESS SLUDGE CONC Kg/d/s/M3 10EXCESS SLLUDGE PRODUCED M3/D 8DISCHARGE HR (Pumping Time) hrs 8

REQUIRED CAPACITY M3/hr 1.0

RETURN SLUDGE CAPACITY M3/hr 5

FINAL SETTLING TANK NUMBER OF TANKS 1FLOW TO EACH TANK M3/hr 5.0HYDRAULIC SURFACE LOAD M/hr 0.7SURFACE AREA OF EACH TA M2 7DIAMETER OF EACH TANK M 3.0AVERAGE DEPTH M 2VOLUME OF EACH TANK M3 14TOTAL VOLUME OF TANKS M3 14RETENTION T

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