An 11-month study was conducted to compare the performances of three laboratory plastic medium upflow anaerobic filters operating at 12.5°C, 21°C, and 30°C, treating dairy wastewater. Two of the reactors were started at 21°C and the third at 30°C. Steady-state operation of the three reactors was carried out at different hydraulic retention times (HRTs) of 1 to 6 days. It was found that the start-up of anaerobic filters was possible at 21°C without any adverse effect on its future performance. Temperature effects on organic removal efficiency were not found to be pronounced at high HRTs. The anaerobic filter at 30°C consistently achieved higher levels of performance compared to the other reactors at 12.5°C and 21°C. The anaerobic filter operating at 12.5°C was the most affected by changes in HRT. At an HRT of 4 days, average COD removals in the three anaerobic filters were approximately 92%, 85%, and 78% at 30°C, 21°C, and 12.5°C respectively. The volume of methane generation (m3/kg COD removed) was lower at lower temperatures; the amount of methane in biogas was found to be higher at lower temperatures.

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