Performance of down-flow hanging sponge (DHS) reactor coupled with up-flow anaerobic sludge blanket (UASB) reactor for treatment of onion dehydration wastewater

► We evaluated UASB - DHS system for onion dehydration wastewater treatment. ► The combined system was operated at two different overall HRT i.e., 11 h and 9.4 h. ► TCOD, TBOD, TSS and ammonia removal efficiencies at optimum condition were found to be 92%, 95%, 95% and 99%, respectively. ► The proposed system could be more viable option for treatment of wastewater generated from onion dehydration industry.