As of estimates made in 2002, India had more than 3000 tanneries with a total capacity of 700000 tonnes of hides and skins per year. The annual income from leather trade in India was about Rs 20000 crores. More than 90% of the tanneries were small or medium with a processing capacity of less then 2 to 3 tonnes of hides/skins per day. Most of the tanneries are located near river banks. The highest concentration of tanneries in India is on the banks of Ganga river (Kanpur, Unnao) in North India and the Palar river system in Tamilnadu.

Leather Production Technology and Pollution:

An animal skin consists of about 61% water, 34% fibrous proteins, 1% globular proteins, 2% lipids, 1% natural salts and some other ingredients including pigments. Out of three layers, the epidermis, dermis and the hypodermis it is the dermis which is later transformed into leather. The epidermis primarily composed of keratin has hair which is removed and the hypodermis has flesh and blood vessels which is also removed. In leather processing, the basic operations revolve round cleaning the skin of unwanted inter fibrillary material through a set of pre-tanning operations in the Beam House, processing the leather permanently by means of tanning and adding aesthetic value during the post tanning process. The starting material in most cases is raw hide or skin which has been preserved temporarily by the addition of common salt.

1. The Beam House process involves the removal of salt, dirt and hair  in the following processes:

(a)   Desalting and Soaking the hides to remove salt and other foreign material such as dirt and also to remove the moisture content.  This process uses a large amount of water about 20 m³ per ton of hide and generates conspicuous pollution. Soaking generates about 6-9 m³ per ton of effluents with a BOD from 1100 to 2500 mg/l, a COD of 3000-6000 mg/L, very high total solids and suspended solids, 15000 to 30000 mg/l of chlorides and 800-1500 mg/l of sulphates.

(b)   Unhairing and Liming – The process yields one of the most polluting effluent streams from tanneries. Liming opens up the collagen structure by removing interstitial material, fleshing removes excess tissue from the interior of the hide.  Unhairing is done by treating soaked hides in a bath containing sodium sulphide / Hydrogen sulphide and lime. About 3 to 5 m³ of effluent per tonne of hide/skin is expected to be discharged with a high pH of 10.0 to 12.8, a BOD of 5000 to 10000 mg/l and COD of 10000 – 25000 mg/l. The concentration of sulphides ranges from 200 to 500 mg/l, the total solids (24000 to 48000 mg/l) and sulphates (600-1200 mg/L) are also high.

(c)    Deliming and bating: A bath of ammonium salts and proteolytic enzymes is used to process the pelt. About 1.5 m³ of effluents are generated in the process at a pH of 7 to 9. The pollutants from the process include Calcium salts, Sulphide residues (30 to 60 mg/l), degraded proteins, residual proteolytic enzymatic agents, Chloride (1000 to 2000 mg/l), Sulphates (2000 to 4000 mg/l), BOD (1000 – 3000 mg/l) and COD (2500 to 7000 mg/l). Nitrogen based deliming agents are considered a long term environmental threat because of their impact on soil NOx values.

Sulphates are an important content of pretanning waste waters. They readily get reduced to sulphide under anaerobic conditions in waste water treatment plants like anaerobic lagoons, contact filters or up flow anaerobic sludge blanket reactors. A build up of sulphides makes the biomethanation of organic materials less effective apart from adding to the COD load. Ammonia is also given off as an air pollutant in the process.

Effluent

TANNERY EFFLUENT STANDARD (AFTER PRIMARY TREATMENT) : DISPOSAL CHANNEL/CONDUIT CARRYING WASTEWATER TO SECONDARY TREATMENT PLANT

*Note: The above standards will apply to those tannery units which have made full contribution to a Common Effluent Treatment (CETP) comprising secondary treatment. Those who have not contributed will be governed by earlier Notification No. S.O. 64 (E) dated January 18, 1988.

Source: EPA Notification

[G.S.R 742(E) dt. 30th Aug; 1990]

Tanneries : Effluent Standards

* For effluent discharged into inland surface waters BOD limit shall be made stricter to 30 mg/l by the concerned State Pollution Control Board.

Source: EPA Notification

[G.S.R. 415(E), 5th May 1992]

ACTION POINTS UNDER CREP FOR TANNERY SECTOR

Chrome Recovery

• All the chrome-tanning units in the country will have the Chrome Recovery Plant either on individual basis or on collective basis in the form of Common Chrome Recovery Plant and use the recovered chrome in the tanning process.
• Common Chrome Recovery Plant is to be installed and commissioned at Kanpur, for which the Feasibility Report has already been prepared.
• Recovered Chromium is to be utilized in tanning process

Waste Minimization Measures

• Waste minimization circles will be formed in all the clusters of tanneries in the country to implement waste minimization measures and for adoption of clean technologies.
• Efforts should be taken to implement the waste minimization measures in all the tanneries in the country and gradually made obligatory with time to the tannery units.

Reduction of Water Consumption in Tannery Units

• All the tanneries should install water meters and flow meters to measure actual consumption and waste water discharge.
• Water consumption rates will be brought down to 28 m 3 /tonne of hides by taking waste minimization measures.

Compliance of standards

All CETPs and ETPs should take the following measures:

• Employ qualified and well trained staff for O & M of the ETPs/CETPs.
• Installation of automatic monitoring instruments.
• Interlocking of manufacturing processes with ETP operation
• Separate Energy meters for ETPs/CETPs by December 2003.
• Open anaerobic lagoons should be converted into closed systems with gas recovery
• For health & safety of worker in the industry & ETP/ CETP the guidelines developed by CPCB should be implemented.
• All major tannery units should take-up environmental auditing on annual basis.
• Major tannery units & CETPs should attempt to obtain ISO-14000 certification
• Tannery units &CETP management should take-up modification/up-gradation of the CETPs/ETPs wherever necessary

Management of Total Dissolved Solids (TDS)

All tannery units to adopt the following

• Manual/mechanical desalting.
• Use of cleaner technology for less use of salt.
• Refrigerated transportation of hides
• High Rate Transpiration system for effluent treatment
• Treated wastewater will be mixed with the sewage & the treated effluent be used on land for irrigation.

Solid Waste Management

All the tannery units to adopt the following:

• Utilization of Process sludge for by-product recovery.
• Resource Recovery from process sludge and ETP sludge in the form of Biogas.
• Chromium recovery from tanned leather shavings.
• Safe disposal of hazardous sludge and non-hazardous solid wastes.

Salts from Solar Evaporation

All the tannery units to adopt the following:

• Reuse of recovered salt.
• Quality improvement of recovered salts for reuse
• Safe land disposal
• Sea disposal

Use of Boron bearing compounds will be dispensed with. By: December 2003

Ground water quality monitoring to be strengthened.

Sulphur recovery from sulphide bearing effluents to be explored.

The implementation of recommendations of the Task Force on leather tannery units constituted by the Ministry of Environment & Forests, Govt. of India in a phased manner.

It is being increasingly recognized that end of pipe solutions are not the ultimate strategy for waste management. Economic instruments have a major role to play. These also include cost cuttings through  recovery, reuse and recycle of waste materials as also a more prudent use of resources and a reduction in the quantity of effluents discharged. The ideal being achieving zero or near zero discharge. The use of clean process technologies to achieve these ends is of great advantage to tanners. It has been demonstrated that a Tannery with a production capacity of 2000 kg. of hides /skin per day might potentially save Rs. 1.4 million per month by adopting clean process technologies. A number of clean technology options for tanners have emerged.

Reduction in raw material consumption:
Salt consumption could be reduced by lowering the time between slaughtering and further treatment and by cooling the hides preferably below 4 degrees Celsius for good preservation up to 3 weeks. Fleshing and trimming could be practiced in the slaughter house. Dry salting can also minimize the use of salt for preservation of hides. Low environmental impact antiseptics have also been tried as a substitute for salt as a preservative. Preservatives like TCMTB, Isothiazolone products, potassium dimethyl dithiocarbamate, Sodium Chlorite, benzalkonium chloride, sodium fluoride and boric acid have also been used. Some of these have also been found to be useful for soaking, pickling and wet blue preservation.

In the beam house, a significant reduction in water consumption can be achieved by the use of new drums and processors to facilitate efficient draining and washing and the recycle of low floats.
As a part of clean process initiatives in the soaking process, the use of low polluting antiseptics has been tried. Fleshing of green hides after soaking is a cleaner alternative over fleshing after liming.
Upto 40% of sodium sulphide and 50% of lime can be saved by the direct recycling of the liming float. In order to maintain the quality of leather, unhairing and opening up processes should be done in separate stages. When tanning and pickling floats are separated they result in a saving of about 80% of salt and 20-25% of either formic or sulphuric acid. Salt concentrations in pickling floats can also be reduced by using non swelling agents.
Splitting on the lime is a cleaner technology than chromium tanned splitting as it reduces the amount of chromium used and gives off waste that can be easily used for the production of Gelatine.

Reduction of Pollutants at source:
Mechanical desalting by hand shaking, mechanical brushes or a drum type shaker can remove up to 10 % of salt added to the hides for processing. This can be reused for pickling after dissolution and removal of solids. Desalting of raw hides has resulted in a reduction of up to 15% salt loads at the salt pans in some tanneries at Tamil Nadu. A reduction of up to 15% of T.D.S. has also been observed due to use of enzyme based unhairing processes and better quality lime in tanneries. Segregating and reusing pickle and chrome tanning liquors also has the capacity to reduce the T.D.S by 10% in composite tannery waste waters. Clean processes have resulted in reduction of emission loads in composite waste waters from about 600 to 400 Kg. /ton of raw material.
Solvent recovery, extraction of brines and commercial reuse of recovered grease has been advocated as a clean process technology for degreasing.

Reduction of B.O.D. and C.O.D at source:
Mechanical desalting, use of enzyme assisted sulfide-reduced dehairing and cleaner chrome tanning have resulted in at least 30-40% reduction in the B.O.D. and C.O.D. loads per tonne of leather produced. Recovery of hair either when it is separated during the liming or at the end of the hair saving process and reutilization as a nitrogen source may in itself  bring down the C.O.D. loads by about 15-20% in the mixed effluents and a reduction of 25-30% in total nitrogen.

Reduction of Sulphide Loads:
A 50-60% reduction in the Sodium Sulphide loads required for dehairing has been observed by using enzyme based technologies. This has also demonstrated a net gain of 2% increase in the area of leather and could compensate for the increased cost of using enzymes. The reduction in sulphides has also demonstrated a potential ability to save atleast 8-10% of the cost of end of pipe treatment.

Reduction of Nitrogen Salts:
The use of ammonium salts in deliming is responsible for the generation of about 40% ammoniacal nitrogen.Various Nitrogen free deliming technologies are now available. The use of Carbon Dioxide is one such. The insertion of Hydrogen Peroxide before Carbon Dioxide reduces the creation of Hydrogen Sulphide.

The U.P. Pollution Control Board has identified 469 tannery industries in the state out of which 404 tanneries are treated in Kanpur.

1. Details of effluent treatment system in 404 tanneries installed at Kanpur is as follows:
2. Based on vegetable tanning system                                                          -           198
   1. I.            Primary effluent treatment system installed           -           102
   2. II.            Based on drying system                                                  -            24
   3. III.            Closed due to their own reasons                                -           48
   4. IV.            Closed by the orders of the Honorable Courts/Board            -           24
   5. Based on Chrome Tanning System                                               -           206
      1. I.            Having Chrome Recovery Unit/Member of Common     -           166

Chrome Recovery Unit/Primary

Effluent System installed.

1. II.            Closed due to their own reasons                                                   -           13
2. III.            Closed by the orders of the Honorable Courts/Board       -           27

A Common Chrome recovery unit has been established at Jajmau, Kanpur for small tannery industries by the Municipal Corporation financed by The Ministry of Environment & Forests, Government of India. Total 76 tanning industries are members of Common Chrome Recovery Plant and 90 chrome tanning units have installed their own chrome recovery units within their premises. Currently the total capacity of the common plant is not being utilized because of lack of drum dryer. As per the information form the Municipal Commissioner, finance is being sought from the Government of India for installing the Drum Dryer.

9 MLD industrial wastes is being generated from the tannery industries at Jajmau, which is put into the common conveyance system after primary treatment (installed in the premises of the individual industries) this combines with 27 MLD municipal waste water and is treated in a Combined Effluent Treatment Plant. The treated effluents have generally been observed to be beyond the prescribed norms. This is mainly because of week operation and maintenance management and the need for upgradation.

1. In addition to Kanpur, a total of 65 Tanneries are located in other districts as follows:

a.   Kanpur Dehat                                  -                       02

b.   Meerut                                               -                       04

c.   Muzaffer Nagar                               -                       01

d.   Mathura                                            -                       02

e.   Agra                                                    -                       03

f.    Gautambudh Nagar                      -                      04

g.   Ghaziabad                                        -                       03

h.   Barabanki                                         -                       05

i.    Unnao                                                -                       41

Out of these 26 industries are closed. The balance 39 tanneries have their own Pollution Control Systems or are joined to the 02 combined plants at Banthar Unnao and Unnao UPSIDC Site II.

Common Waste Management Industries

The Banthar Industrial Pollution Control Company

This Leather Technology Park set up on 286.16 acres at Banthar, Unnao, U.P. India on NH 25, 20 km from Kanpur and 9 kms from Unnao is an initiative of the government of U.P. to provide an integrated leather processing complex which includes a common effluent treatment plant and a common hazardous waste disposal facility. Based on an earlier model also working at Unnao, the constituent units of the region have come together and formed a separate company, registered under the companies act and with an objective to set up and operate the CETP and waste disposal facility. The Banthar Industrial Pollution Control Company looks after the installation, operation and maintenance of the 4.5 mld capacity CETP set up in an area of 12 acres and the common hazardous waste management facility set up in an area of 18 acres within the complex. Each constituent unit is expected to install an individual Chrome Recovery Unit and primary effluent treatment plant to ensure that primary standards prescribed by the Ministry of Environment and Forests, Government of India are complied with. The CETP was commissioned in October 2004 with a project cost of Rs. 6.00 with a promoters contribution of Rs 2.99 crores and a matching grant of Rs. 2.99 crores from CIB/ASIDE. The treated effluents from the CETP are discharged (through the UPSIDC drainage) finally into the City Jail drain which ultimately meets the river Ganga after a distance of 30 kms. The CETP is based on the Activated sludge process with a two stage aeration system and a polishing tertiary system.

Forty two tanning and allied industries constitute the member units. Presently (2008) 12 units were operating with a discharge of 1886 KLD effluent to the CETP

The unit operations consist of a Barscreen, grit chamber, equalization tank, flash mixer (lime alum), clarifloccnlator, 1^st stage Aeration tank, with a low speed 25 HP fixed surface aerators, 2^nd stage aeration tank with 10 low speed 15 HP fixed surface aerators, 1^st stage peripherally driven biological clarifier with central shell, 2^nd stage peripherally driven biological clarifier with central shell and a tertiary clarifier with dosing arrangements along with sludge drying beds. The treated effluents from the CETP have been able to achieve a pH of 7.5 (5.5 -9.0), suspended solids 98 mg/l (100 mg/l), BOD of 22.00 mg/l (30 mg/l), COD of 88 mg/l (250.00 mg/l) and a total chromium of 1.8 (2.0 mg/l). (The prescribed standards are mentioned in parenthesis.) Consents under section 25/26 of the Water (Prevention and Control of Pollution) Act 1974 have been granted to the CETP from 2005 through 2008. The cost of treatment works out to be Rs. 9.25/KL based on water consumed by the constituent tannery.

Joint effort have also been made for safe disposal of hazardous sludge generated not only from tanneries situated at Banthar but also from other industrial areas in Unnao. The secured landfill site has also been developed at Banthar, properly lined and with leachate collection and disposal facility. This is expected to cater to 3 to 5 years of sludge generation from all leather and allied industries at Unnao site I, II and III and Banthar. Industries have now formed a separate registered company by the name of “Industrial Infrastructure services (India) Ltd “. The project proposals submitted by this company for the development of a TSDF on 33 acres of land at CETP Banthar at a cost of Rs. 17 crores and cleared by the government of India shall benefit about 130 industries at Unnao. The TSDF has been commissioned w.e.f. October 2008.

The Unnao Tanneries Pollution Control Company:

Commissioned in 1995, this combined effluent treatment plant managed by the Unnao Tanneries Pollution Control Company treats 2.15 MLD effluents from 21 member industries (Tanning and Allied). The company was constituted as a sequel to the World Bank assisted ‘Industrial Pollution Control Project’ which envisaged the setting up of CETPs with 20% promoter’s contribution,25% subsidy from state government (Through the Department of Environment Budget), 25% Subsidy from Central Government and 30% soft loan from World Bank through I.D.B.I.. The CETP works are situated at A-7, Site-2, UPSIDC Industrial Area, Unnai, U.P., India and for the last about 14 years have served as a model for successful cooperative management of waste.

The effluent generated by member units is first subject to primary treatment in the generating industry. This necessarily consists of a Bar Green, Equalization Tank, Chemical dosing tank, settling tank, and sludge drying beds, The primary effluents are then transferred through underground conveyance system to the CETP for treatment. The Chrome tanning units separately treat and recover the basic chrome sulphate from spent chrome Liquor. This is reused in the tanning process.

At the CETP the primary treated effluents are treated by a two stage aerobic activated sludge process and treated effluent with a pH of 7.3 to 7.5, Suspended Solids of 60 to 90 mg/l , BOD of 20 to 29 mg/l, COD of 200 to 240 mg/l and very low quantities of chromium III (0.32 to BDC) discharged into the Loni drain which generally dries out on land but which meet the river Ganga at a distance of about 146 kms during the rainy season. The CETP consist of a Bar Screen Chamber, 2 Nos equalization/Holding Tanks with 12 hours detention, 1 No. clarifloccnlation tank, a primary aeration tank with a hydrometric retention  time of 24 hours, 4 aerators of 24 HP capacity each and an operating cycle of 4 days. This is followed by the 1^st stage secondary clarifier with a detention time of 3 hours. The second stage aeration tank also has 4 aerators of 20 HP, a detention time of 24 hours and operating cycle of 17 to 20 days and is followed by a 2.5 hours detention time 2^nd stage secondary clarifiers. The ETP sludges are dried in 28 sludge drying beds.