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Performance of upflow anaerobic sludge blanket and upflow anaerobic hybrid reactor in treatment of distillery spentwash was investigated under similar operating conditions. The reactors were initially fed with distillery spentwash having an average COD concentration of 1,22,000 mg L -1 with a HRT of 10 days and their performance was evaluated by operating at various HRTs viz., 10, 8, 7, 6, 5 and 4 days. Among the various HRTs, six days HRT was found to be ideal for the maximum reductions of COD, BOD and TS by 63.26, 70.80 and 57.20% respectively at OLR of 19.75 kg COD m -3 day -1 with UASB and 70.60, 78.50 and 62.45% at OLR of 19.25 kg COD m -3 day -1 with UAHR. The biogas yield of 0.30 and 0.31 m 3 kg -1 COD removed was recorded in UASB and UAHR. Population of total anaerobic bacteria and methanogenic bacteria are also high in UAHR than in UASB. The study concludes that upflow anaerobic hybrid reactor is superior in reducing the pollution load of distillery spentwash as compared to UASB.Keywords: upflow anaerobic sludge blanket; UASB; upflow anaerobic hybrid reactor; UAHR; hydraulic retention time; biogas production; treatment of distillery spentwash.Reference to this paper should be made as follows: Selvamurugan, M., Doraisamy, P. and Maheswari, M. (2014) 'High-rate anaerobic treatment of distillery spentwash using UASB and UAHR', Int.

Performance of full-scale upflow anaerobic sludge blanket (UASB) reactors treating distillery spentwash was evaluated. The plant was designed to handle 650 m 3 day -1 of distillery spentwash having an average chemical oxygen demand (COD) concentration of 112,400 mg l -1 with a HRT of 6 days. In the plant, the pH level of the influent varied from 3.50 to 4.40 but the pH of the treated effluent stabilized to a range of 7.36 to 7.68 during the study period. The operation of the reactors during study period revealed the stable conditions of the reactors, which is evident from the low COD, biochemical oxygen demand (BOD) and total solids (TS) contents in treated effluent. In the plant, the COD, BOD 5 and TS removal efficiencies were stabilized to the range of 62. 19-66.59, 72.42-77.11, and 58.47-60.46%, respectively at an organic loading rate of 2.15-4.60 kg COD m -3 day -1 . The biogas production was stabilized to the range of 48,290-135,115 m 3 week -1 with 60% methane content. The total quantity of biogas produced ranged from 0.40 to 0.57, 1.04 to 1.71 and 0.40 to 0.56 m 3 kg -1 removals of COD, BOD and TS, respectively. This study concluded that the treatment of distillery spentwash using UASB reactors contributed significantly for pollution load reduction besides generating renewable in-house bio-energy.