Anaerobic Biological Treatment of Distillery Wastewater – Study on Continuous Stirred Tank Reactor

Abstract

Various studies have verified that anaerobic treatment with the recovery of biogas appears to be the most promising technology for the treatment of distillery wastewater. The technologies currently used by distilleries for treatment of wastewater are bio-methanation followed by two-stage biological treatment and disposal in watercourses or for utilization on land for irrigation and composting with or without bio-methanation. These technologies treat the wastewater up to a certain extent. However, there are limitations posed by these technologies for full compliance with prescribed pollution control standards. For the better understand the performance of continuous stirred tank reactor (CSTR), anaerobic treatment of distillery effluent having very high chemical oxygen demand (COD) (110000–140000 mg/L) and biochemical oxygen demand (BOD) (55000–65000mg/L) was studied on CSTR. Under various organic loading rates (OLR), optimum conditions for maximum COD removal and biogas generation was found and are observed to be 0.09 kg COD/d to 0.12 kg COD/d OLR hydraulic retention time (HRT) of 14d and volatile fatty acids (VFA) to alkalinity ratio of around 0.2. Maximum COD removal efficiency was found to be around 72%. These performance figures are significant when operating the anaerobic bio digesters for the treatment of distillery effluent. Anaerobic CSTR can effectively be employed for the treatment of distillery effluent, but post-bio-methanation effluent still contains high organic concentration and needs to be treated further to meet the safe and acceptable pollution control limits for disposal into surface water or on land.