Salinity reduction in tannery effluents in India and Australia

• Central Leather Research Institute, India
• Kreglinger Australia, Australia
• Black Diamond Industries, Australia

The leather industry is India's fourth largest export industry, employing 2.5 million people and having a target value of about A$10 billion in 2002. The preparation of leather requires the use of large amounts of salt. Tannery discharges are causing loss of agricultural production due to the salinisation of rivers and groundwater. It is also adding to the salinity of drinking water. In the past few years, Indian authorities have set stringent regulations for tannery discharges. Regulations for biochemical oxygen demand, chemical oxygen demand and chromium levels are now being met, though at considerable cost. However, levels of total dissolved solids (TDS) remain too high. If the tanning industry does not deal with this problem, it will face legal action and closures, leading to social and economic hardship. The leather industry is also important in Australia, where it accounts for A$1 billion in exports each year. As in India, salinity is a major problem, and new licensing charges for effluent disposal are a major threat to some Australian tanners.

Salt cannot be eliminated from tannery processes, but previous studies have suggested that total dissolved solid levels can be reduced by using chemicals or chilling rather than salt for short-term preservation, by processing 'green' rather than salted hides, by using improved 'pickle' recycle techniques and by using better chrome liquor recycling methods.

The project is working to develop, evaluate and widely apply practical, viable systems to eliminate or reduce salt use in hide and skin preservation and processing, in order to significantly reduce the salinity of tannery effluent in India and elsewhere.

For each project objective, the project team may research scientific and technical issues, fit methods to small and larger operating units in Indian conditions, demonstrate the methods in particular regions, establish the economic and other benefits of TDS reduction, ensure that hides and skins can be processed into suitable quality leathers and establish an educational and technology transfer program.

Scientists will use laboratory and industry-scale trials to determine how best to air-dry skins in Indian conditions. They will focus on drying rates; quality control; the need for preservatives, insecticides and additives in different conditions; and the best design for drying sheds. After evaluating the costs and benefits of the new technologies, economists will identify a range of options to encourage Indian skin merchants and tanners to adopt them.

In Australia, scientists will determine the minimum level of salt required, the need for chemical additives and handling requirements between salting and drying. Indian researchers and tanners will evaluate these methods and compare them with air drying.

Australian researchers will determine the best chilling techniques and chemical treatments for short-term preservation and transfer the results to the Indian situation through appropriate extension programs. They will also adapt chrome liquor and pickle recycling methods for Indian conditions.