Green initiative: use of cow dung slurry for treatment of industrial effluent.

This research dives into highlighting potential usage of cow dung as a co-substrate to reduce the organic carbon load of toxic industrial effluents through batch and semi continuous anaerobic process. One such effluent stream is released during caprolactam manufacturing having pH of about 2, 0.4% ammonical nitrogen, and COD up to 55,000 mg/L which varies often. In this study, a series of laboratory-scale experiments followed by pilot level experiments were laid to treat highly toxic industrial effluent in different ratios using cow dung as co-substrate in an anaerobic setup. The basic parameters to analyze the performance of system were chemical oxygen demand (COD) removal efficiency, reduction in ammonium sulfate concentration, biogas production and methane constitution within it, and effluent quality. Reduction in COD and ammonium sulfate concentration was observed to be 42.9% and 23.2% respectively at lab level, while methane concentration in biogas was improved from 39.5 to 69.5% after day 7 of the reaction. Furthermore, pilot scale trials were laid to verify the results of similar treatments on large scale, and they confirmed the lab scale results positively by observing a reduction of COD up to 43.8%, ammonical nitrogen by 18.7%, and methane production improvised from 36.7 to 76.32% after day 7 of the reaction. Semi- continuous reactor trial that was carried out for 22 days showed reduction in COD and ammonical nitrogen by 38.5% and 37.5% respectively which stayed consistent up to the 22nd day. This study contributes to the evolving body of knowledge on anaerobic digestion, particularly for the treatment of highly toxic caprolactam plant effluents, and highlights the value of cow dung slurry as an effective and sustainable co-substrate.