Influence of the Oxic-Settling-Anaerobic (OSA) Process on Methane Production by Anaerobic Digestion of Sewage Sludge

The present study evaluated different sludge-reduction mechanisms in the oxic-settling-anaerobic (OSA) process terms of their effects on methane productivity by anaerobic digestion sewage sludge. Two layouts were investigated for sludge return from an side-stream reactor (ASSR) to anoxic (scheme A) or aerobic B) a pre-denitrification plant. Biochemical methane-potential (BMP) assays performed excess revealed that scheme A promoted overall increase production OSA (20 mLCH4 gVSS−1d−1, +19%), although compared with control CAS plant significant decrease (31%) was obtained. Operating conditions caused occurrence cell lysis and EPS hydrolysis, thereby increasing biodegradability In contrast, B favoured uncoupling maintenance metabolism did not involve hydrolysis. Consequently, despite higher reduction (82%), (4 −41%) observed. Based results, implementing may allow high levels be maintained if specific are triggered waterline, also raising possibility co-digestion other feedstocks.