In this paper, startup performance of Upflow Anaerobic Hybrid Reactor and Upflow Anaerobic
Sludge Blanket reactors in anaerobic treatment of distillery spentwash has been studied under identical conditions of operation. Various effluent characteristics like pH, Electrical Conductivity, Chemical Oxygen Demand, Biochemical Oxygen Demand and Total Solids and other process parameters like biogas production and methane per cent in biogas were studied until the attainment of steady state. The startup of the reactors has been completed and steady state condition attained on 25th day of reactor operation in UAHR and 34th day in UASB reactor. The treated effluent characteristics of both reactors were fairly steady after attaining the steady
state condition. The pH of treated effluent during steady state condition was almost neutral for both reactors even though the influent had an acidic pH. The maximum COD, BOD and TS removal efficiencies were as high as 79.60%, 87.39% and 69.96% in UAHR as compared with UASB of 72.98%, 81.34% and 66.23%, respectively during the steady state period. The maximum volumetric gas production of 149 L m-3 produced more in UAHR than in UASB reactor during steady state condition. The population of total anaerobic bacteria and methanogenic bacteria also more as that of the other parameters in UAHR than in UASB reactor and it were 55.2 x 103 ml-1 and 40.0 x 102 ml-1 respectively in UAHR. It is found that from an overall assessment the
UAHR has proved superior in its performance compared to the UASB reactor during the startup process.