Treatment of High Concentration Dye Effluent at Small Scale Silk Dyeing Units in and around Bangalore, India

Karnataka State is known for silk sarees worn by millions across the Indian subcontinent.  A significant portion of the silk dyeing industry occurs within the informal economy, which produces silk yarn that is then woven into locally sold sarees. The invisible economy is currently dumping their dye wastewater with no treatment resulting in contaminated soils and groundwater. The silk industry in India employs over a million peasant families who do not have other opportunities or choices in their business-including lacking the means to treat their wastewater.

The dye effluent from a current dumping site near Bangalore was collected and treated with a specially designed low-cost  high surface area nanoclay particulate material. The dye which was deep reddish blue in colour was found to get adsorbed completely on to the nanoclay adsorbent  within 10 minutes of stirring at room temperature. There was a reduction in COD and BOD by 65 per cent resulting in an effluent which could be discharged into sewers as per the norms of State Regulatory Authority.

The adsorbed dye could be totally oxidized by treatment with hydrogen peroxide/ozone at about 40 ⁰C. It is observed that the adsorbent after treatment with hydrogen peroxide/ozone can be reused multiple times thus making this novel process economically available for the informal silk textile dyeing units.