Enhancing temperature-phased biological hydrolysis for methane generation by the optimization of biological hydrolysis time, inoculum, and sludge bypass

This work investigated the effect of biological hydrolysis (BH) time, biological hydrolysis inoculum (BHI), and sludge bypass (SBP) on the performance of temperature-phased biological hydrolysis (TPBH) in the treatment of waste activated sludge (WAS). Results showed that BH times and BHI significantly affected the hydrolysis and methane production of WAS. The TPBH treated WAS without BHI had achieved 66.62% sludge biodegradability compared to 57.33% with the untreated WAS. The sludge biodegradability of the TPBH treated WAS with BHI and the SBP were 73.13% and 69.68%, respectively. TPBH treatment with the BHI influenced the methane kinetic positively and as such, a higher methane enhancement of 22% achieved at 20% BHI ratio. This study showed that the methane yield of wastewater sludge can be enhanced with the addition of BHI and SBP and thus is of significance for the optimization of the TPBH-AD process design for anaerobic digestion (AD) performance enhancement. •Biological hydrolysis was studied for anaerobic digestion performance enhancement.•2–3 days of biological hydrolysis time was identified to be optimal.•Biological hydrolysis increased sludge biodegradability from 57.5% to 66.6%.•Biological hydrolysis inoculum enhanced the hydrolysis performance and CH4 production.