Indian facility claims complete solution for water, effluent and salinity
04/02/2013
Ranitec, the Ranipet Tannery Effluent Treatment Company, in Tamil Nadu in southern India is receiving effluent from 90 tanneries. Following conventional effluent treatment, advanced processing is being applied that avoids any discharge of effluent from the site, with return of 95% of the effluent received back to the 90 tanneries for reuse in manufacture.
This avoids the problems of water provision or abstraction for a very significant concentration of tanneries, inland effluent discharges, and issues concerning increasing salinity in ground water.
This advanced processing is in two stages. The first involves a combination of ultra filtration and reverse osmosis that provides 75% water recovery, the remaining 25%, known as concentrate, being high in dissolved solids. The second stage employs thermal evaporation of the concentrate followed by condensation and recovery. It is calculated that 95% of the tannery effluent received is recovered, the balance being losses as normal evaporation as expected from effluent treatment and the dry salt recovered.
At present the recovered water – at a total dissolved solids level of 200 mg/l, a higher standard than required of drinking water – is returned to the tanners by tanker. Within one month a 25-kilometre pipeline will be brought into use for direct supply to these tanneries.
The recovered solids are mainly sodium chloride and sodium sulphate with other residual materials. These lightly coloured dry solids are being packaged in polypropylene bags and securely stored on site until a responsible use of this solid has been developed.
A full report will be published by World Leather in a special environmental issue later this year. The report will claim this is a world first: a combination of clean technology on behalf of the tanners, and considerable investment by Ranitec has created a massive water-tanning-effluent closed loop and set a global benchmark.
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