The feasibility of treating low-strength wastewater with an up-flow anaerobic sludge blanket (UASB) reactor, using a poly(vinyl alcohol)-gel carrier, at various temperatures and hydraulic retention times (HRTs) was examined. The temperature was decreased from 35 degrees C to 25 degrees C and then to 15 degrees C. The HRT was reduced from 2.0 h to 0.22 h. The COD removal rate reached 28 kg-COD m(-3) d(-1) at 35 degrees C, 16 kg-COD m(-3) d(-1) at 25 degrees C, and 6 kg-COD m(-3) d(-1) at 15 degrees C. The COD removal rate was reduced by half for each temperature reduction of 10 degrees C. 2011 Elsevier Ltd. All rights reserved.