Performance of a pilot-scale sewage treatment: An up-flow anaerobic sludge blanket (UASB) and a down-flow hanging sponge (DHS) reactors combined system by sulfur-redox reaction process under low-temperature conditions

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 CODCr (465 ± 147 mg L−1; total BOD 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 DHS 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 °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.