Anaerobic digestion of municipal sewage under psychrophilic conditions

The anaerobic digestion of municipal sewage was studied at psychrophilic temperatures (19 degrees C and 17 degrees C) in three up-flow anaerobic sludge bed reactors (UASB). A pulsed feeding system was operated for 430 d, during which different hydraulic retention time (HRT) (6, 8, 10, 12, 14, 18, 24 and 36 h) were tested. Granulation of the sludge was observed under the pulsed feeding strategy and a 6 h HRT. Low hydrolysis rates were obtained at HRTs lower than 10 h, as a result of an increased solids accumulation inside the reactor. An HRT of 14 h was identified as the most suitable HRT under the studied temperatures (19 degrees C and 17 degrees C), with methane yields of 136 and 117 mL CH4/g of removed chemical oxygen demand (CODremoved), respectively. (C) 2018 Elsevier Ltd. All rights reserved.