terragreen may 2011 98

Green technology for tannery industry

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The leather processing sector is one of the oldest in India and ranks among the five most export-oriented

industries of the country. India’s large tannery industry plays an important role, both as a source of revenue generation through foreign exchange, as well as of employment opportunities. The production and export of leather and leather products from India have grown significantly over the last one-and-a-half decade. In the last three decades, the tannery industry has evolved to become a provider of knowledge on high-quality leather footwear, apparel, other products, as well as finished leather to the world market. India is the second largest footwear producer and third largest leather garment exporter in the world. According to the Andhra Pradesh Pollution Control Board, there are over 3000 tanneries spread all over India. About 80% of these tanneries are in the cottage and small-scale sector and about 20% are in the medium/large sector.

Unfortunately, these small-scale industries are playing havoc with the environment. For instance, since ages, they have been discharging untreated tannery effluent and sludge into the adjoining land areas and water bodies, causing immense pollution.

The tannery industry, which commonly uses basic chromium sulphate in the tanning process, is a major cause for the high

influx of chromium (Cr) to the biosphere, accounting for 40% of the total industrial use. The effluent coming out of the tanneries is treated by using conventional chemical methods that remove Cr and other contaminants (such as alkalinity, turbidity, dissolved and suspended solids, and so on) before being discharged into the water bodies. These chemical methods are only partially effective, expensive, and are not environmentally benign. Hence, there is an urgent need for using biological systems for the removal and recovery of Cr.

In India, about 0.9 billion kg of hides and skins are processed every year, releasing 30–40 billion litres of liquid effluent annually, which usually contains 2–8 gram/litre of Cr, which is a known carcinogen and toxic metal. Even in low concentrations, Cr is reported to adversely affect human and aquatic lives. The large number of tannery units in North India has converted the holy Ganges River into a dumping ground. Several analyses have revealed high concentrations of Cr even in the effluents supposedly “treated” by common effluent treatment plants (CETPs). The residues can be traced even in the crops cultivated with the water taken from the river. According to the Bureau of Indian Standard (BIS), the industrial effluent permissible discharge level of total Cr into inland water is below 2 milligram/litre. Recently, the Department of Environment,

Government of India, has identified the tannery industry as the biggest polluter in the country.

Since 1990, there has been growing awareness about the environmental damages resulting from the discharge of untreated effluents by tanneries into streams and rivers. Public interest litigation cases against tanneries culminated in court orders, directing the relocation or closure of the tanneries, which have neither erected effluent treatment plant (ETPs) nor connected to CETPs. Experts believe that untreated tannery wastes discharged in such a manner cause a wide range of health hazards. They have identified about 14 severe diseases, including skin diseases, gastric ulcers, asthma, kidney infections, and cancers, directly deriving from the wastes. The main centres of tanning industry in India are located in the states of Tamil Nadu, Andhra Pradesh, Uttar Pradesh, Bihar, Gujarat, Maharashtra, Karnataka, Punjab, Rajasthan, and West Bengal. The untreated tannery wastes discharged into the adjoining land areas create large wastelands, choked with heavy doses of different toxic elements, especially Cr.

In addition, experts fear that tanneries also cause the pollution of underground water. Soil sickness has become a cause of worry for farmers and plant growers across the world. Heavy wasteland generation and the pollution of adjoining land and water bodies have

now become major problems, necessitating the intervention of scientific tools for finding a sustainable solution. In India, the Central Pollution Control Board (CPCB) has identified tanneries as major polluters, and since 2003, it has focussed on chrome recovery and reusability, along with waste management as some of the major challenges. With growing awareness among the environmentalists, government authorities, as well as the industry representatives themselves, the need for a sustainable technology is now being felt to stop the tanneries from playing havoc on our health and environment.

TERI’s effort to develop a sustainable green technologyConsidering the above-mentioned problems and the existing demand, The Energy and Resources Institute (TERI) has initiated work in this area since 2003. The aim is to develop a sustainable green technology based on biological systems to remove Cr from tannery industry effluent. After seven years of research and study, TERI has now identified and developed a fungi-based treatment method for the removal of Cr from the absolute tannery industry effluent.

Although various potential microorganisms have been reported for the removal of Cr, all relevant studies have either been conducted in simulated effluent or in diluted industrial effluent, with modified physicochemical conditions. The feasibility of using these microorganisms in absolute industrial effluent conditions was not successful in the past, until the breakthrough achieved by Seema Sharma, Senior Research Fellow, and Dr Alok Adholeya, Director, Biotechnology and Management of Bioresources Division, TERI (2011).

The fungi-based treatment method developed by TERI is based on the ability of fungi to grow in absolute tannery industry effluent and accumulate Cr in the biomass, in presence of a selected carbon source. In laboratory conditions, within 25–35 days of incubation, the fungi make the effluent free from all contaminants, including Cr. The Cr-removal ability of fungi has been tested on various physicochemically different tannery industry effluents and found to be effective in the removal of Cr and other contaminants up to the desired level.

The fungi-based treatment method developed by TERI is able to overcome limitations, such as cell death by high concentrations of Cr, as well as the challenge of surviving and removing Cr from real industrial effluent, which could not be withstood by most of the studied microorganisms in the past. Repeated experimental studies with various physicochemically different tannery industry effluents have demonstrated that the treatment method developed by TERI has a strong potential for the removal of Cr from tannery industry effluent, within the industrial process, and that it could be ideal for developing a sustainable green technology. The developed technology can be adopted by small-scale and unorganized sector industries, which are a major source of Cr contamination in the environment, as well as by the big industries to remove Cr before discharging the effluent in the natural environment. The recovery of Cr from fungal biomass as a high purity salt is also possible through another green technology, currently being tested at a pilot scale. n

For more information, please contact Dr Alok Adholeya at aloka@teri.res.in.

Prepared bySeema Sharma, Senior Research Fellow, Biotechnology and Management of Bioresources Division, and Dr Alok Adholeya, Director, Biotechnology and Management of Bioresources Division, TERI. This study was supported by the Department of Biotechnology, Government of India.

terragreen may 2011

Chromium removal from tannery industry effluent, using novel fungal isolate

Uninoculated control

Growth after 35 days

Filtration

b) Filtered effluent

Growth after 10 days

a) Chromium-absorbed fungal biomass

a

b

Initial pH: 3.5

Biomass