Treatment of rice grain based biodigester distillery effluent (BDE) using inorganic coagulants

Abstract

The removal of COD and colour from biodigester effluent (BDE) of rice grain based alcohol distillery plant has been studied using inorganic coagulant such as CaCO₃, CuNO₃ and Na₂SiO₃. CuNO₃ is found to be more effective, among all coagulant. COD reduction of 78, 83 and 51% and colour reduction of 75, 78 and 41% is obtained using 60 mM CaCO₃, 40 mM CuNO₃ and 40 mM Na₂SiO₃ respectively, at their optimum initial pH_i. The pH of effluent-coagulant mixture play a major role in removal of pollutant from the BDE. CuNO₃ gives 83% COD reduction and 78% colour reduction along with good settling property. 82% settling occurred with alum in 25 min. The properties of filtrate and residues have also been analyzed.