Physico‐chemical treatment of indigo dye wastewater

In the present study, colour removal and chemical oxygen demand removal from indigo dye wastewater have been evaluated using various coagulants/flocculants. Laboratory‐scale experiments were conducted using chemical coagulants–flocculants on synthetic as well as actual indigo dye wastewater and under ambient liquid temperature. Up to 99% colour removal was observed during treatment of synthetic indigo dye effluent with FeSO4, alum, polyelectrolyte and lime. Colour removal efficiencies of up to 97%, 97% and 95% were observed when denim plant wastewater (equalisation tank) was treated with alum, lime and FeSO4 at dosages of 2, 2.5 and 2.5 g/l, respectively. Up to 95%, 94% and 87% colour removal efficiencies were observed when denim plant (dyebath) wastewater was treated with alum, lime and FeSO4 at dosages of 225, 1000 and 225 mg/l, respectively.