Performance of a wastewater treatment system utilizing a sulfur-redox reaction of microbes was investigated using a pilot-scale reactor that was fed with actual sewage. The system consisted of an up-flow anaerobic sludge blanket (UASB) reactor and a down-flow hanging sponge (DHS) reactor with a recirculation line. Consequently, the total COD(Cr) (465 +/- 147 mg L(-1): total BOO of 207 +/- 68 mg L(-1)) at the influent was reduced (70 +/- 14 mg L(-1); total BOD of 9 +/- 2 mg L(-1)) at the OHS effluent under the conditions of an overall hydraulic retention time of 12 h, a recirculation ratio of 2, and a low-sewage temperature of 7.0 +/- 2.8 degrees C. A microbial analysis revealed that sulfate-reducing bacteria contributed to the degradation of organic matter in the UASB reactor even in low temperatures. The utilized sulfur-redox reaction is applicable for low-strength wastewater treatment under low-temperature conditions. (C) 2010 Elsevier Ltd. All rights reserved.