Recouping the wastewater: a way forward for cleaner leather processing

Journal of Cleaner Production 11 (2003) 591–599www.cleanerproduction.net

Recouping the wastewater: a way forward for cleaner leatherprocessing

J. Raghava Rao, N.K. Chandrababu, C. Muralidharan, Balachandran Unni Nair∗,P.G. Rao, T. Ramasami

Chemical Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India

Received 24 August 2001; accepted 19 July 2002

Abstract

Leather processing employs copious amounts of water. This leads to the generation of enormous amounts of liquid effluent. Thehigh effluent volume requires huge investments for effluent treatment plants in order to meet the required specification for thedischarge of liquid effluents to various water bodies. Increasingly therefore, water use minimization in leather processing assumesgreater significance due to increased treatment costs. End-of-pipe treatment methods alone do not meet the requirements and hence,in-plant control measures are gaining importance. The new era of cleaner technology has begun in leather processing. Pre-tanningand tanning operations contribute about 57% of the water consumption in leather processing and the washings about 35%. Theproper adoption of integrated cleaner technologies provides a viable solution to the conservation of water in leather processing.This paper presents an integrated approach for water use minimization through recycling and optimization in leather processing.The integrated approach provides considerable reduction in the use of process water. 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Cleaner technologies in leather making; Greener technologies; Green chemistry; Water use reduction in leather making; Water and chemicalrecycling; Improved water management; Cleaner technologies; Process integration; In-plant pollution prevention measures in leather making

1. Introduction

Environmental concerns have been growing for thepast two decades. High industrial density, human popu-lation density and the use of old and polluting techno-logies all cause increasing levels of pollutant emissions[1]. This situation has highlighted the need for greenertechnologies. The protection of the environment hasbecome a global issue throughout the world.

Leather processing is an important activity in manydeveloping countries, which are dependant on the agroeconomy. It has been estimated that about 18 billion ft2

of leather are made annually around the world [2] witha trade value estimated to be approximately US$ 70billion. The processes employed in the manufacture ofleathers in several developing countries remains the tra-

∗ Corresponding author. Tel.:+91-44-491-1386; fax:+ 91-44-491-1589.

E-mail address: [email protected] (B.U. Nair).

0959-6526/03/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved.doi:10.1016/S0959-6526(02)00095-1

ditional process; it is often not optimized for chemicals,energy and water usage. The industry has gained a nega-tive image in society with respect to the environmentalunfriendliness of its processing methods [2]. The eco-logical degradation arising from commonly practicedleather processing techniques has been well-docu-mented. Although, several after-treatment methods fortannery wastewater have been explored and some havebeen adopted commercially, the need to prevent pol-lution through in-plant measures is gaining importance[3–5].

The theme of ‘cleaner technology’ signaled the startof a new era in leather manufacture about 20 years ago[6]. Ecological factors became the focus of much greaterattention. The principles of cleaner technology can besummarized as: (a) Prevention is better than reuse (b)Reuse is better than recycling and (c) Recycling is betterthan disposal. However, prevention is not simply achi-eved by omission but rather by replacement, reductionand improvement.

In-plant control measures for mitigating tannery pol-

592 J. Raghava Rao et al. / Journal of Cleaner Production 11 (2003) 591–599

lution generally aim at the reduction or elimination oftoxic wastes through process adjustments. It is now gen-erally believed that lasting solutions to the problem oftannery pollution rests in cleaner processing. In thiswork, an attempt has been made to highlight some of theemerging cleaner technological options based on processadjustments and recycling the wastewaters.

2. Wastewater in the leather industry: a point toponder

Leather making involves the stabilization of aputrescible collagenous matrix, animal skins, to protectthem from degradation by microorganisms and thermomechanical stress. Traditionally the leather processinginvolves pre-tanning (beam house operations), tanning,post-tanning and finishing processes [7]. Pre-tanningsteps are designed to clean the skin collagen fromunwanted materials and prepare them for tanning; tan-ning stabilizes the protein against putrefaction andfinally incorporation of an aesthetic appeal is the objec-tive of post-tanning and finishing.

The various chemical inputs into leather processingare demonstrated in Fig. 1. Water is the main mediumof transport for the chemicals. Many of the leather pro-cessing steps depend on the large use of water. Thisexplains, in part, the development of the industry alongthe river basins. The leather industry employs about 30–40 l of water per kg of hide processed [8]. With the

Fig. 1. Inflow–outflow diagram for leather processing.

present annual processing capacity of 0.9 billion kg ofhides and skins in India [9], it is estimated that nearly30–40 billion l of liquid effluent are generated annually.Globally, the liquid effluent from leather processingaccounts to 300–500 billion l. This gives rise to twomajor problems for the leather industry, viz., the avail-ability of good quality water and the need for treatmentof such large quantities of effluents, which requiresmajor investments in effluent treatment plants.

The pre-tanning operations consume nearly 15–22 lof water per kg of hide processed, while the tanningoperation consumes 1–2 l of water and post-tanning 2–4 l per kg of hide processed. Washings contribute 11.5–13 l of the water used for processing. The details ofwater consumption for each step are presented in Table1 [5,10]. Each of these operations gives rise to character-istic pollutant loads. The various pollutant loads from

Table 1Quantity of wastewater discharged for processing 1 t of skin/hide

Operation Quantity (m3)

Soaking 9.0–12.0Liming 4.0–6.0Deliming 1.5–2.0Pickling 1.0–1.5Chrome tanning 1.0–2.0Neutralisation 1.0–1.5Wet finishing 1.0–2.0Washings 11.5–13.0

593J. Raghava Rao et al. / Journal of Cleaner Production 11 (2003) 591–599

each operation are presented in Table 2. Treatment ofthe large volumes of effluents and their subsequent dis-charge into sewers, rivers etc. are only a short-term sol-ution, which adds to compounded problems of invest-ment and recurring expenditure. Other technologicaloptions to reduce the usage of water and to increase itsreuse are to be considered for evolving long-term sol-utions for the leather industry.

With mounting pressures from the environmentalagencies, the need to contain the discharge of toxic sub-stances as well as to dramatically reduce the biochemicaloxygen demand (BOD), chemical oxygen demand(COD) and total dissolved solids (TDS), is being felt inrecent years [11,12]. The Indian specifications for thedischarge of industrial effluents on various water bodiesare given in Table 3 [13]. To maintain the quality ofground water, cleaner technological options to containthe pollutants in the tannery wastewaters as well as tominimize the usage of water in processing are becomingincreasingly essential. Thus, in-plant pollution abatementmeasures are required. The strategy for in-process con-trol measures for pollution reduction should attempt tointegrate cleaner process options with the water manage-ment practices as the volume and load of the effluenthas a direct influence on the cost of the treatment plant.

3. Cleaner leather processing: emergingtechnological options

Prevention or reduction of pollution at source throughin-process control measures has gained importance inleather industry in recent times [3–5]. There is now anincreasing recognition that end-of-pipe treatment, in iso-lation, is not an adequate strategy to meet the require-ments of wastewater norms and standards [14]. Stra-tegies for pollution prevention and control need tointegrate cleaner process options with the better water

Table 2Characteristics of tannery waste watersa

Parameter Soaking Liming Deliming Pickling Chrome Dyeing and Composite (incl.tanning fatliquoring washing)

pH 7.5–8.0 10.0–12.8 7.0–9.0 2.0–3.0 2.5–3.0 3.5–4.5 7.0–9.0BOD 1100–2500 5000–10,000 1000–3000 400–700 350–800 1000–2000 1000–3000COD 3000–6000 10,000– 2500–7000 1000–3000 1000–2500 2500–7000 2500–8000

25,000Total solids 25,000–40,000 25,000– 3000–8000 30,000–70,000 25,000–60,000 3000–8000 15,000–25,000

35,000Dissolved solids 22,000–33,000 20,000– 1500–4000 29,000–67,000 24,000–57,500 2400–7000 13,000–21,000

25,000Suspended solids 3000–7000 5000–10,000 1500–4000 1000–3000 1000–2500 600–1000 2000–4000Chlorides as Cl� 15,000–30,000 4000–8000 1000–2000 20,000–30,000 15,000–25,000 500–1000 6000–9500Total chromium as Cr — — — - 2000–5000 40–100 100–250

a All values except pH are in mg/l.

Table 3Specifications for discharge of tannery effluentsa

Important Tolerance limits for industrial effluentscharacteristics discharged

Into inland Into public On land forsurface sewers irrigationwaters

Colour and odour Absent — AbsentpH 6.0–9.0 6.0–9.0 6.0–9.0Suspended solids 100 600 200BOD 30 350 100COD 250 — —TDS 2100 2100 2100Chlorides as Cl� 1000 1000 600Total chromium as Cr 2 2 2Hexavalent Cr 0.1 0.l 0.1Sulphide as S 2 2 2Sodium (%) — 60 60Boron as B 2 2 2Oil and grease 10 20 10

a All values except pH and sodium are in mg/l.

management practices [15]. The volume of effluent hasa direct bearing on the cost of end-of-pipe treatment. Thereuse of spent solutions (after removal of the unwantedmaterials) forms an integral part of in-process controlstrategy. The ideal approach is to target the zero or near-zero discharge of waste liquors. The progressive adop-tion of cleaner technologies by the tanners depends onthe following factors: (a) proven reduction of emissionloads in terms of quantity and quality; (b) quantifiableeconomic benefits to tanners through quality improve-ment, cost reduction and material saving; (c) ease ofapplication with minimum additional investments onhardware; and (d) trade advantages on account ofimproved environmental positioning in the global mar-


ket. A variety of technology options for cleaner leatherprocessing are given in Table 4.

4. Approaches to better water management

The water consumption of the pre-tanning and tanningoperations contribute to nearly 50% of the total waterused for leather processing. About 20 billion l of wateris being used annually in India and 200 billion, globallyfor these operations. Hence, the main unit operations,which require immediate attention to evolve in-plantcontrol measures, are

� Soaking� Liming� Deliming and bating� Pickling� Tanning

In order to overcome the treatment cost and avail-ability problem and also to ensure saving of chemicals,water and reduction of pollution load the approaches,which are of need, are: (a) recycling and reuse of spentliquors; and (b) optimization/rationalization of waterrequired for each operation. By adopting these tech-niques considerable amounts of water can be conservedin each of the pre-tanning and tanning operations.

5. Soaking

Soaking of salted skins/hides requires 25% of the totalwater consumption in conventional leather processingcompared to soaking of green skins/hides. Hence, recyc-ling of soak liquor becomes necessary for salted

Table 4Technologies options for cleaner leather processing

Process Improvements implemented

Pre-soaking Mechanical desaltingImprovised manual desalting

Soaking Counter current soakingUse of enzymes in soaking

Liming Enzyme assisted unhairingRecycling of lime liquorsHair saving technique

Deliming Organic acid based delimingCarbon dioxide based deliimingRecycling of deliming liquor

Pickling Recycling of pickle liquorSalt free organic acid pickling system

Chrome tanning High exhaust chrome tanningChrome recovery and reuse, chromerecyclingClosed pickle-tan loop

skins/hides, as there is a need to reduce the total con-sumption of water in leather processing. The primarysoak liquor contains large amounts of dirt and foreignmatter. Recycling of this stream is a challenge and callsfor removal of dirt and foreign matter and the use ofdisinfection methods prior to reuse. On the other hand,soaks II and III can be readily recycled for use in suc-cessive batches. The counter-current soaking method canbe advantageously employed as shown in Fig. 2. Thistechnique can provide a net saving of about 67% of thewater generally used for soaking operation. In thismethod hides/skins move in one direction while waterflows in the counter direction. With 12 l/kg ofhides/skins processed employing counter-current soak-ing technique, a saving of 8 l/kg of hides/skins processedis achieved. The physical properties of leathers obtainedby this counter current soaking method are comparableto that of the normally processed leathers.

6. Liming

The liming operation utilizes large quantities of water(4–6 l per kg processed). In this operation, recycling ofonce used lime liquor for the next lot provides reductionin the usage of water. Money and Adminis [16] havereported the recycling of lime–sulphide unhairing liquorsfor more than 20 cycles showing an overall 20-foldreduction in water consumption. However, the recyclingmethodology requires removal of suspended matter, tem-perature adjustments and replenishment with lime, sul-phide and water. A counter-current method similar tothat employed for soaking, can be used. This ensuresreduction of water use by 50% for this unit operation.The properties of the leathers obtained are comparableto those of the control leathers. Enzymatic unhairing isgaining importance in leather processing as a cleanbeamhouse process [17,18]. Enzyme-assisted unhairingfollowed by reliming with once used relimed liquorensures complete reduction of water. In addition, thismethodology leads to leathers with decreased growthmarks, increased area by 2% and smoother grain [18].

7. Deliming and bating

Use of ammonium salts adversely affects the effluentcharacteristics and creates unpleasant working con-ditions. Conventional deliming contributes to nearly 75–80% of the ammonia in the effluent [11]. Generally 1–2 l of water are used per kg of hides/skins processed atthis stage. It has been established that deliming and bat-ing can be effectively carried out as a floatless operationor with a minimum float of 20% without impairing anyphysical/chemical or grain characteristics of final leather[15]. This reduces the amount of water used in this unit


Fig. 2. Schematic representation of counter current soaking.

operation by 85%. Recycling of delimed liquor cannotbe carried out as the delimed liquor contains salts ofcalcium along with ammonium salts.

8. Pickling and tanning

The conventional pickling process employs 80–100%of water and 8–10% salt. The pH during this process isadjusted to 2.5–3.0 using sulphuric acid. Chrome tanningis commenced at this pH. Since the spent pickle liquorcontains high concentrations of neutral salts, the dis-charge of this liquor may cause adverse effects on thewater streams. Further, high sulphate concentrations inwaste streams can adversely affect the performance ofbiological treatment systems [19]. Conventional pro-cessing of leathers makes use of 50% of pickle float astanning float. A closed loop involving pickling and tan-ning would essentially help in use of pickle float as atanning float.

9. Pickle-tan closed loop system

More than 90% of the leather processing activity inIndia involves chrome tanning [20]. At the present rateof 0.9 billion kg of hides and skins processed in thecountry annually, the waste tanning streams account toa volume of nearly 1.8 billion l containing 2000–3000mg/l of chrome as Cr(III) [21]. The specifications for thepermissible levels of chromium in the industrial waste-waters stipulate the range of 0.3–2.0 mg/l [22].

Chrome recovery/reuse, adopted as an in-plant pol-lution control measure ensures nearly 99% of chromiumrecovery and is easy to adopt [23]. However, the super-

natant discharged from the recovery plant contains con-siderable amounts of neutral salts as well as magnesiumsulphate, which could render the ground water hard [24].This waste stream from the recovery plant containingless than 2 mg/l of chromium as Cr can be advan-tageously used for soaking and pickling operations [25].

A scientific solution to overcome the problem ofchrome pollution has been to increase the absorption ofchromium in tanning to minimize the wastage of chro-mium, if possible to near zero values [26,27]. One novelmethod developed and proven successful in commercialtanneries is the minimum waste high exhaust pickle-tanchrome tanning [27]. This cleaner technological optionforms the central approach to meet the socio-economicproblems in order to maintain the quality of theground water.

The novel system employs normal pickling followedby chrome tanning with a combination of alutan [28,29](an aluminium syntan with about 12% Al2O3) and basicchromium sulphate (BCS). The pickling is done withanhydrous sodium sulphate (5%) or sodium chloride(8%) and sulphuric acid to maintain the pH at 3.0–3.2as compared with the normal practice of using 8–10%sodium chloride at a pH of 2.5–3.0. Alutan is employedin the tanning bath along with 5% BCS instead of 8%BCS generally used in normal chrome tanning. Thechrome absorption levels achieved are above 90% duringtanning and the spent solution can be reused in pickling.In other words, the recycling method leads to thereduction in BOD, COD and TDS load in the effluent.

The closed-loop system involves the recycling of thespent tanning solution in the pickling operation. Thisensures no discharge of chemicals and also saving ofwater and chemicals to a large extent. Although thedirect recycling of the spent chrome solution from con-


Fig. 3. Pickle-tan closed loop system.

ventional chrome tanning has been reported [30], thehigher concentration of chromium in the waste solutionresults in grain coarseness in the processed leathers with-out pre-treatment [31]. The lower concentration of chro-mium in high exhaust chrome tanning system facilitatesthe direct recycling without affecting the quality of lea-thers. The flow diagram is given in Fig. 3. The recyclingcould be continued for at least 10 cycles and it is welldocumented in commercial tanneries involving the nor-mal production line that by employing closed loop sys-tem the quality of the leather is comparable to that ofconventional tanned leather.

The BOD, COD and TDS loads on the effluent treat-ment plants (ETP) generated from conventional chrometanning practice as well as by the alutan–BCS closedloop system with 10 recycles are shown in Table 5. Itis seen from the table that the usage of closed loop sys-tem results in the reduction of the effluent load on ETP’sby 90%. This contributes to maintaining the quality andminimizing the usage of water. The quantity of waterused for processing 1000 kg of hides/skins employingconventional process in comparison with minimum

Table 5Reduction in the pollution loads on ETP’s from the identified streamsof conventional and alutan–BCS closed loop leather-making systems

Process Load on ETP’s (mg/kg of hide processed)

BOD COD TDS

Conventional chrome 1270 6200 97,500tanning includingpicklingAlutan–BCS system 141 582 7000% Reduction 89 91 93

waste chrome tanning for 10 cycles is presented inTable 6.

It is observed from the above data that by using thenew high exhaust minimum waste closed loop system,a saving in water 15,800 l for a batch of 1 t pelt pro-cessed can be achieved, which results in approximatelyan 88% saving in the volume of water needed for theseoperations. The actual volume of wastewater to betreated is reduced to 12% of the total volume, whichmeans tremendous saving in the quantity of water andprocessing energy.

The use of the alutan–BCS system for tanning alsoprovides a reduction in the usage of post-tanning chemi-cals normally employed viz. retanning agents, 30–40%;fatliquors, 5–7% and dyes, 10–20% due to high uptakeof chromium and the presence of aluminium. Thisreduced use of chemicals leads to better utilization ofchemicals and reduction in pollution load on the onehand and savings in the overall manufacturing costs ofabout US$ 20–40 per t of hides/skins processed, on theother hand. Further, the alutan–BCS closed loop systemminimizes the leaching of chromium in post-tanningoperations as compared to conventional chrome tanning.

10. Washings

Water usage for washings in leather processing con-tributes to nearly 33–38% of the total water used. Thisincludes material (pelts/leather) washing, floor washingsetc. Proper addition of water to wash the materials andcontrolled usage for floor washings can reduce the quan-tity of water used for washings by 40–50%. The waterconsumption in leather processing can increase up to 50–80 l/kg of skin/hide processed due to inefficient usageof water [32]. The system of continuous water wash,whereby goods are run in a drum with a lattice dooropened and the water valve, fully open, is one of themajor operations that results in extensive wastage ofwater. The continuous washing in leather processingshould be controlled and batch type washings should beutilized. Over 50% of the water used can be saved by

Table 6Water usage for pickling and tanning operations employing conven-tional and advanced method (for 1 t of material processed)

Operation Quantity of water used (l)

Conventional process Alutan–BCS process

For 1 batch For 10 For 1 batch For 10batches batches

Pickling 1200 12,000 1300 2200Tanning 600 6000Total 1800 18,000 1300 2200


instituting batch washes. This alone can reduce waterusage for washing, tremendously.

11. Discussion

Leather processing employs large amounts of water,thereby, generating enormous volumes of liquid effluent,as well. The amounts of water consumption in pre-tanning/tanning and wet finishing operations are 55–59and 7–9%, respectively. The average consumption forwashings in leather processing is about 35%. This callsfor technological intervention in pre-tanning and tanningoperations. The water management technologies adoptedat various stages of operations lead to the reductions inthe amount of water consumed. Use of counter currentsoaking, counter current liming, reduced float for delim-ing and pickle-tan loop for pickling and chrome tanningprovides a reduction in the quantity of water used byabout 67, 50, 85 and 88%, respectively. This results inthe reduction of the percentage contribution of waterfrom pre-tanning and tanning operations from an averageof 57 to 19%. It is evident that there is an overall savingof 67% in the total quantity of water used for pre-tanningand tanning operations in leather processing. As theseare the most polluting streams in leather processing, thereduction in the quantity of water used for these oper-ations coupled with the recycling methodology reducethe pollution load on the effluent treatment plant. Withpresent annual processing capacity of 0.9 billion kg inIndia, the amount of water used for these operations,employing normal procedure is 21.2 billion l. This couldbe reduced to 6.9 billion l by the application of betterwater management technologies. The usage of the pic-kle-tan closed loop reduces the water usage by 88% fromthe identified streams. About 50% reduction in water

Fig. 4. Comparison of emission loads for conventional and advanced leather processing.

usage for washings can be achieved by employing con-trolled batch type washing of the material as well as floorand good house keeping. Employing water conservationmethodologies coupled with cleaner technologies, thequantity of water used for leather processing can bereduced from 40 l to less than 15 l for processing 1 t ofthe material. Thus, the better water management techno-logies bring about tremendous reduction in the quantityof water used in leather processing, thereby, reducingthe hydraulic load on the effluent treatment plants andreducing the costs of treatment.

12. Cleaner processing options in tanning sector: areal life study

India is a major source of leather in the global trade.About 10% of the World’s supply of leather is manufac-tured in India and of this, 60% of the production is fromthe state of Tamil Nadu. In the wake of the order of theSupreme Court of India, nearly 400 tanneries in TamilNadu faced closure. The Central Leather Research Insti-tute (CLRI) and The National Environmental Engineer-ing Research Institute (NEERI) have been able to workwith the entire tanning industry in Tamil Nadu and toenable the sector to gain environmental security throughapplication of cleaner technologies [33]. Althoughfurther improvements are required, there has been a sig-nificant impact due to adoption of cleaner technologiesin the leather sector in Tamil Nadu.

A vast number of critical technologies and optionshave now emerged to render leather processing cleaner.They include mechanical desalting, counter current soak-ing, enzyme-assisted unhairing, counter current liming,low float deliming, pickle-tan closed loop minimumwaste chrome tanning, and chrome recovery with con-


Table 7Water consumption for conventional and advanced leatherprocessing(For 1 t raw hides/skins processed to tanned leather)

Process Conventional (kl) Advanceda (kl) % Reduction

Soaking 12.0 4.7 61Liming/ 6.0 3.6 40reliming 0.84b 86b

Deliming 1.5 0.2 87Pickling & 1.8 0.21 88chrometanningWashings 7.5 3.5 53TotalWithout 21.3 8.71 (5.95)b 59 (72)b

washingsWith 28.8 12.21 (9.45)b 58 (67)b

washings

a Average water consumption per cycle, assuming 10 recycles.b Enzyme assisted dehairing followed by reliming with old

relimed liquor.

trolled washings. This basket of technologies has beenimplemented in various tanneries. A set of data collectedon the minimization of BOD, COD, TDS, chloride, sul-phide and chromium loads through the implementationof cleaner production methods in a group of 258 tan-neries are presented in Fig. 4. It has been demonstratedthat BOD and COD loads could be brought down by30–40%, whereas TDS reduction by 35–40%, sulphideby 50–80%, chlorides by 40–60% and chromium by 98–99% are feasible [33]. The amounts of water consump-tion for processing 1 t of raw hides to tanned leatherthrough conventional and advanced (cleaner) leatherprocessing are presented in Table 7. It is seen that the

Table 8Chemical consumption and costing for conventional and advanced leather processing (for 1 t raw hides/skins processed to tanned leather)a

Chemicals Conventional Advanced

Quantity (kg) Cost (US$) Quantity (kg) Cost (US$)

Alkali bate 5.0 6.00 5.0 6.00Alutan — — 10.0 14.00Ammonium chloride 17.5 2.98 17.5 2.98Basic chromium sulphate 80.0 48.00 50.0 30.00Formic acid 7.5 5.55 2.5 1.85Lime 200.0 24.00 130.0 15.60Preservative 2.5 4.00 3.5 5.60Salt (sodium chloride) 100.0 4.00 20.0 0.80Sodium bicarbonate 12.0 3.36 12.0 3.36Sodium formate 10.0 4.00 10.0 4.00Sodium sulphide 40.0 20.80 20.0 10.40Sulfuric acid 15.0 1.80 13.0 1.60Unhairing enzyme — — 10.0 24.00Water (kl) 28.2 5.08 11.3 2.03Total 489.5 129.57 293.5(303.5) 98.22 (122.22)

a The value in the parenthesis includes the use of enzyme-assisted dehairing.

reduction in the amount of water used for leather pro-cessing using advanced technologies is 58%, whereas theuse of enzyme-assisted unhairing results in 67%reduction. The chemical consumption and costing datafor both conventional and advanced leather processingare given in Table 8. It is seen that the quantity of chemi-cals can be reduced by 40% through the application ofadvanced technologies. This results in cost saving ofUS$ 31 for processing 1 t of raw hides. The implemen-tation of pickle-tan closed loop high exhaust tanningleads to an additional saving of about US$ 30, due tosavings in post-tanning chemicals. Although, the costreduction is low in enzyme-assisted unhairing, the over-all savings is US$ 77, which is higher than the chemicalbased advanced technologies. This is due to the netincrease in the area of crust leather by 2%. Theimplementation of such cleaner production systems hasled to saving of vital economic activity in the state ofTamil Nadu. The implementation of cleaner technologieshas also been demonstrated in Sri Lanka, Bangladeshand Nepal with comparable economic and environmen-tal benefits.

The cleaner technologies have multiple benefits in-terms of environmental clean up, improved labour pro-ductivity, material quality consistency and better inter-national image. Benefits will also accrue for the peopleliving in the vicinity of the beneficiary tannery units andthe working personnel. In addition, reduction in land andwater pollution, better work environment and improvedoccupational safety are the major benefits to accrue.


13. Conclusions

Industrial processes generate wastes, but if they canbe prevented, recycled and then treated, the productioncan be more secure and sustainable. Water use minimiz-ation in the leather processing assumes greater signifi-cance due to increased treatment costs. The leather pro-cessing with the recycle/optimization approach providesa saving in the amount of water used for pre-tanning andtanning operations by 67%. The savings in the usage ofwater with the present annual production capacity inIndia is 14.3 billion l. The reduction in the amount ofwater used for washings due to controlled washings is6.5 billion l. The overall reduction in the usage of waterin leather processing is 55–58%. Thus, the better watermanagement approach in industrial application plays avital role in the conservation of water. The proper choiceof operating conditions and in-house audit of processparameters can help leather makers make their processesmuch cleaner and more economical.

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[28] A product developed by CLRI and commercialized by M/sBalmer & Lawrie Co., India as Balsyn AL

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Documents

Recouping the wastewater: a way forward for cleaner leather processing