Hydrothermal pretreatment of sewage sludge for enhanced anaerobic digestion: Resource transformation and energy balance

The objective of this study was to evaluate the effect hydrothermal pretreatment (HTP) at 90, 125 and 155 °C on extent anaerobic digestion (AD) sewage sludge, energy balance, distribution availability N P. AD evaluated with four bench-scale mesophilic, semi-continuous digesters 20-d (Phase 1) 10-d 2) solids retention time (SRT), fed raw sludge (R1), 90 (R2), (R3) (R4) HTP sludge. two mixtures used in had high ultimate biodegradability (58.3 for Phase 1 56.9% 2). With exception 2 R4, increased organic matter destruction methane production. mixture resulted formation propionate levels, which led a lower significantly changed digesters’ bacterial communities, but minor archaeal communities. Abundance well-known degraders all very low; however, Proteiniphilum, is involved degradation intermediates pathway, found relatively abundance R4. highest net gain (?E) obtained control (i.e., without HTP) both phases. heat recovery greater than 85% required attain same as or higher. followed by reduction, overall crude protein removal release ammonium N. HTP-AD decreased P availability. Thus, recommended before after HTP-AD, respectively.