2. A SURVEY OF EFFLUENT TREATMENT PLANTS IN TANNING INDUSTRIES AROUND TIRUCHIRAPPALLI

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1 2. A SURVEY OF EFFLUENT TREATMENT PLANTS IN TANNING INDUSTRIES AROUND TIRUCHIRAPPALLI 2.1. INTRODUCTION Currently, the overall share of India in the global leather trade is around 3% (ITC, 1999). There are about 2100 tanneries located in India, with a processing tonnes of rawhides and skins (Velappan and Muralidharan, 2001). Major tannery clusters in India are located in the states of Tamil Nadu, West Bengal, Uttar Pradesh, and Punjab and they mostly come under small and medium scale industrial sector. The bulk of industrial pollution in India is caused by the small and medium scale industrial (SMIs) sector. A small scale unit is defined as any industry whose plant and machinery are valued at less that 1 crore. Though the quantity of industrial waste generated by individual SMIs may not be large, it aggregates to be a large percentage of the total, since almost 3 million SMIs are widely scattered throughout the country. SMIs account for over 40 percent of the total industrial output in the country and generate over 44 percent of hazardous wastes alone as compared to 13 percent generated by the large scale industry (Prasad, 1997). Government policies have been biased toward small industries as employment generators, even though small industries are highly polluting. The SSI policy has no thought on the environmental planning. Promotion of small enterprise is widely seen as a desirable way to achieve sustainable development; for that result, however, their pollution problems, among others, must be 25

2 overcome. To deal with the effluent in these SSIs, the concept of Common Effluent Treatment Plan (CETP) was introduced with a hope that not only it would help the industries in pollution abatement but also as a step towards the clean environment. The tanneries in India numbering about 3,000 are grouped into four major categories for effluent treatment management. Large, medium and a few small scale isolated tanneries numbering about 200 with sufficient land area and financial capabilities have set up independent effluent treatment plants. Tanneries located in clusters and not having enough land and financial capacity to put up individual effluent treatment units have to set up a CETP, if sufficient land is available nearby the cluster. The tanneries which are not able to put up individual or common effluent treatment plants near their existing locations have to be resettled in a new leather complex with CET Plant or closed down. It has been organized to set up 40 CET plants in India covering 2000 tanneries, with a financial outlay of more than 100 million US Dollars. Out of the 40 CET plants planned, 16 units are under operation and others are under various stages of implementation. The treatment capacity of the CET Plants ranges from 200 m 3 to 36,000 m 3 per day. Implementation and management of a common industrial effluent treatment plant is a difficult task. Main constraints are unpredictable seasonal and daily variations in the quality and volume of tannery effluent discharge, availability of appropriate technology, proper design engineering and finance for large capital investment, contribution for operational and maintenance cost by the seasonal units, frequent power failures and breakdowns, inadequate trained 26

3 manpower for operation and maintenance, sludge disposal problems and absence of an acceptable formulae in sharing the operation and maintenance costs of CET plants. Ministry of Environment and Forests have instructed various State Pollution Control Boards to examine the possibilities of establishing ETPs in various industrial estates in the respective states. Even central assistance upto 25 percent of the total cost of the ETP is being provided as a grant to the common effluent treatment plant on condition that the State Governments would give a matching contribution. The remaining cost has to be met by equity contribution by the industries and loans from financial institutions. Tamilnadu is a major contributor to leather industry and 60% of the tanneries are in this state, which are concentrated as large clusters in North Arcot District, Pallavaram, Erode, Tiruchirapalli and Dindigul. These tanneries let out their wastewater to surrounding land without treatment. There are nearly 1000 tanneries; most of them are of small scale producing less than 2 tonnes of hides and skins per day. For every ton of hides and skins processed, about cubic meters waste water is produced (Van Groenestijn et al., 1995). Increasing environmental pressure led Vellore Citizen Welfare Forum (Tamilnadu) to file a Public Interest Litigation (W.P.Civil No. 914 of in the Supreme Court of India. The Supreme Court by its order dated and had issued direction for the closure of tanneries which had not installed ETP individually or collectively. Thereafter all the tanners established their own ETP or CETP for the tannery waste water treatment. 27

4 Owing to the inherent nature of tanning processes in which, various chemicals were used, the effluent has high polluting potential. The Tamilnadu Pollution Control Board has stipulated stringent standards for the tannery effluent discharged outside. The efficiency of the installed ETP in the tanning industry has to be closely monitored. Hence the present survey has been undertaken to survey the ETP of various designs in the tanneries of Tiruchirappalli and to study their relative efficiency. 2.2 SURVEY OF EFFLUENT TREATMENT PLANTS Tiruchirappalli also called Rockfort city (10 o - 11 o 30 N; 77 : 45' - 78 o 50' E), is the fourth largest city and one of the active centres for tanning industries in Tamilnadu. For convenience the name of the city has been shortened as Trichy by the people of Tamilnadu. CETP in Trichy has finally been set up recently and the effluent discharges from the tanneries in Tiruchirappalli district are being treated, providing the much-needed relief to the people in the surrounding areas. There are eight major tanneries in the region, which soak over 18 tonnes of skins and hides per day. The plant has come up at a cost of Rs 2.8 crore. Of this Rs 1.78 crore had been contributed by the tannery owners, Rs 27 lakh by way of investment subsidy granted by the Central government and Rs 75 lakh has been provided by the Tamilnadu government. The project was earlier taken up in the early 90, s but ran into trouble owing to various reasons including stringent pollution rules laid by the high court, free import policy and excessive export duty imposed on leather products. 28

5 Meanwhile, the number of tanneries dwindled to thirteen from the existing 24 units in the area. The tanneries at Tiruchirappalli may not be as hazardous as those elsewhere since the units here use vegetable extracts (East India leather technology) for processing skins. The Trichy Tanners Association has also sought assistance from the Central government for the establishment of a secondary treatment plant which would adopt a reverse osmosis process. The project requires an investment of Rs 6.6 crore. Out of the 13 tanneries in the district, ten tanneries have established their own individual effluent treatment plant and remaining three tanneries are connected to a CETP. The ETP found in Trichy tanneries are of different designs and varied efficiency. A comparative study on design and functioning of their ETP would throw light on the up keeping of the ETPs and the relative merits of each system OBSERVATIONS A survey of ETP functioning in 13 tanning industries in Trichy was carried out in the month of January 2008 (Table 2.1). The designs of various sub units of the ETP ( Table 2.2) such as Pretreatment chamber, Equalisation Tank, Flash Mixture, Clariflocculator, Krofta, Aeration tank I, Aeration II, Pressure sand filter and Activated Carbon Filter and their functioning were surveyed. It was observed that the ETP in the tanneries of Trichy fall under any one of the following categories. 1. system with Tertiary Treatment (TSASTT) 2. Two Stage Aerobic System with Krofta (TSASK) 3. Two Stage Aerobic Settling tank (TSASCST) 29

6 system with Tertiary Treatment (TSASTT) The system of ETP has about 11 subunits namely pretreatment chamber. equalisation tank, flash mixture, clariflocculator, aeration tank I, clarifier 1, aeration tank II, clarifier II, sludge thickener, pressure sand filter and activated carbon filter (Fig. 1). The design involves a combination of physical, chemical, biological and tertiary treatment processes. The raw waste water flows by gravity from the manhole to the inlet of the screening chamber by which solid materials of larger size can be settled. The screened effluent flows into equalization tank for achieving uniform water characteristics. The constant flow of the equalized effluent is transferred to the flash mixture tank where alum solution is added to coagulate the suspended particles. The raw effluent after flash mixture flows to the clariflocculator, where poly electrolyte is added to flocculate the suspended particles. The clear effluent flows to the biological system. A two stage biological process is employed in the aeration tank for the degradation of organic pollutant load based on the activated sludge process. The activated sludge generally consists of bacteria, microorganisms like protozoa, rotifers etc. The process involves stabilization of organic matter by the action of various microorganisms in the presence of dissolved oxygen. The desired mixed liquor suspended solids (MLSS) levels are maintained by the recirculation of the sludge settled in the clarifier 1. The sludge that settles in the clarifier 1 can be continuously pumped back to the aeration tank 1 and the excess sludge to the sludge thickener. The effluent from the clarifier 1 flows by gravity to aeration tank II for the degradation of the 30

7 remaining pollutant load. The desired MLSS levels are maintained by the recirculation of the sludge settled in the clarifier II. The water from clarifier II is subjected to tertiary treatment by passing it through pressure sand filter followed by activated carbon filter to remove turbidity, colour and odour Two Stage Aerobic System with Krofta (TSASK) The system of ETP has about 6 units namely pretreatment chamber. collection tank, primary krofta, aeration tank I, aeration tank II, and secondary krofta (Fig. 2). combinations of physical, chemical and biological processes are involved in this system also. All the sub units in this system have functions as described above for TSASTT except krofta. The krofta system is a special mechanical device introduced to make the suspended solids to float by bubbling air through water and to remove it by moving scooper. This system draws air from the atmosphere through suction pump and it is pumped through effluent to enable the suspended matter float on the water. Moving scooper removes the floated suspended matter Two Stage Aerobic systems with Common (TSASCST) This treatment plant has 7 subunits namely pretreatment chamber. Equalization Tank, alum dosing tank, settling tank, aeration tank I, aeration tank II, and common settling tank (Fig. 3). This system involves a combination of physical, chemical and biological processes to remove suspended solids, oxygen demanding waste with high Chemical oxygen Demand (COD) and Biochemical Oxygen Demand (BOD). It is very similar to first system (TSASTT) with a difference that there is no tertiary treatment unit like pressure sand filter and activated carbon filter. 31

8 2.4. CONCLUSION After surveying all the treatment technology it was concluded that the system having TSASTT is more mechanized and efficient compared to the other two systems. It was also evident that the TSASK brings out the same efficiency without the installation of tertiary treatment unit like pressure sand filter and activated carbon filter. The third system namely TSASCST proved to be cost effective and less power consuming. It is also suggested that TSASCST would be more suitable to small tanning industries, processing less than 5 tonnes of skins and hides per day. The ETP system namely TSASTT and TSASK are more suitable to treat waste water from tanning industries processing above 5 tonnes of skins and hides per day. 32

9 Table 2.1. Survey of Effluent Treatment Plants in Tiruchirappalli District S.No Name of the Unit Production Capacity in tonnes/day ETP capacity in M 3 /day System of ETP A) Individual ETP M/s. N. Mohamed Mian Rowther Company Pvt. Ltd Selathar Tanning Induatry Pvt. Ltd Rasheeda Prime Tanners < K.M.S Tannery < V.M. Tanners < Bestan Leathers Company Trichy Prime Tannery Select Leather Company Sri Meenakshi Leathers Vignesh Leather Company B) CETP M/s.M.K.M Tanners <5 250 <5 250 <5 250 <5 <5 <5 2. M/s.Sabari Tannery <5 3. M/s.Fine Leather < system with Tertiary Treatment system with Tertiary Treatment system with Krofta

10 Table 2.2. Subunit composition of Three Types of Effluent Treatment System S. No. Two Stage Aerobic System with Tertiary Treatment (TSASTT) Two Stage Aerobic System with Krofta (TSASK) Two Stage Aerobic (TSASCST) 1. Pretreatment Chamber Pretreatment Chamber Pretreatment Chamber 2. Equalisation Tank Collection Tank Equalisation Tank 3. Flash Mixture Primary Krofta Alum Dosing Tank 4. Clariflocculator Aeration Tank I 5. Aeration Tank I Aeration Tank II Aeration Tank I 6. Clarifier I Secondary Krofta Aeration Tank II 7. Aeration Tank II Common 8. Clarifier II 9. Sludge Thickener 10. Pressure Sand Filter 11. Activated Carbon Filter

11 Fig system with common settling tank

12 Fig Two Stage Aerobic System with Krofta (TSASK)

13 Fig Two Stage Aerobic System with Tertiary Treatment (TSASTT)

Rawal Lake Water Treatment Plant Rawalpindi, Pakistan

Rawal Lake Water Treatment Plant Rawalpindi, Pakistan 1. Background Information Rawal Lake Water Treatment Plant is managed by the Water & Sanitation Agency (WASA) under the Rawalpindi Development Authority