India seeks zero liquid discharge6 August 2007
This year's LERIG meeting, which took place just before the IILF in Chennai, took Benign Environmental and Sustainable Technologies as its theme. The meeting is organised annually by the Central Leather Research Institute with a full programme of presentations. This included two from invited overseas guests Dr Catherine Money, who is no stranger to the TDS/salt issue in India, and Dr Tilman Taeger of BASF Germany, who gave the B M Das Memorial Lecture and gave his Considerations on Sustainable Leather Manufacturing. We will be tackling both these presentations separately but Taeger's question: Sustainable leather production - still a dream? certainly gave the audience something to think about. He pointed out that common salt, sodium sulfide, lime, basic chrome sulfate, to name a few chemicals of high ecological concern, are still used daily. Numerous papers have been published, yet none of these substances have yet been replaced. He said that sodium sulfide could be replaced but the cost implications meant that this would probably never happen. Over the years a great deal of work on effluent treatment has been carried out under the auspices of Unido under a programme established in 1998. This is now nearing its conclusion and is due to end in July 2007. However, while there are a number of noteworthy common effluent treatment plants now operating in the country, there remains much still to be done and the handling of the used salt is one of the most pressing. We are publishing the latest conclusions on the work by Money and Chandra Babu on salinity in the next pages but their conclusion is inescapable: 'Recently the main focus for TN tanneries has been zero dicharge, not salt use reduction measures. Both approaches will be necessary to achieve satisfactory environmental outcomes: low TDS in effluent and less waste salt.' The company T Abdul Wahid have three tanneries which have achieved zero liquid discharge but admit that they have not conclusively found a way to deal with sludge. There are huge piles of used salt remaining to be dealt with at tanneries around the country and the government will have to address this problem at some stage. This will involve either trucking the salt to the sea or providing a pipeline. According to Dr S Rajamani, there are nearly 3,000 tanneries in India but only around 2,000 are in regular operation. They process 700,000 tons of hides and skins/year. The average wastewater discharge from these tanneries is about 100 million litres/day. There are more that 200 individual effluent treatment plants (ETPs) and 18 Common Effluent Treatment Plants (CETPs) and disposal of effluent with high Total Dissolved Solids (TDS) in land locked tannery clusters such as in Tamil Nadu, is one of the serious unresolved problems. There is also a pressing need for water recovery as water is becoming a scarce commodity. Dr R G Bhirhnd, Tata, spoke about the work his organisation is doing on finding byproduct uses for tannery waste. He said they were faced with a lack of technologies available for recycling hazardous waste from shaving and buffing dust, drum sludge and trimmings and the only way they are currently being handled is by taking them to landfill along with end of life products. Tata have been working hard to find solutions to the problem and they are offering to share their technology with others. The concept was to treat the solid wastes to separate the chrome from the organics. The organics then go for biomethanation and the chrome to be recycled. Tata commissioned their high rate biomethanation plant in September 2002. This is based on their own in-house R&D patented technology with support from UNDP/TIL/MNES and monitored by CLRI. The benefits of the biomethanation plant: * Environmentally friendly disposal of hazardous waste * Recovery of chrome as basic chromium sulfate * Converting hazardous, non-degradable waste to non-hazardous recyclable waste * Energy recovery from renewable non-conventional sources * Solving hazardous waste disposal problem saves soil/ground pollution * Sustainable clean technology while solving solid waste disposal problem Energy conservation is another added value with increased production of bio-gas (biomethanation plant). They have also conducted successful trials for hot water generation and have completed a pilot plant study on the bio-purification of biogas. And there is increased chromium recycling.