Hydrothermal liquefaction of sewage sludge into biocrude: Effect of aqueous phase recycling on energy recovery and pollution mitigation

•The aqueous phase recycling improved the biocrude yield and energy recovery.•The recycling decreased the aqueous phase COD and yield.•Light organic matters were transferred to biocrude in the aqueous phase recycling.•The acids in aqueous phase promoted the dehydration and decomposition of SS.•The heavy metals in biocrude and aqueous phase were enriched to residues.