Anaerobic digestion of thickened waste activated sludge under calcium hypochlorite stress: Performance stability and microbial communities

Hypochlorite pretreatment has been proven effective in enhancing waste activated sludge (WAS) anaerobic digestion performances recently. In this study, two semi-continuous anaerobic sequencing batch reactors (ASBRs), one fed with Ca(ClO)(2) pretreated thickened WAS (TWAS) and one with raw TWAS, were operated at mesophilic conditions (35 degrees C) for 145 days. Three loading shocks were introduced to each reactor to compare the performance stability and resilience between the digestion of Ca(ClO)(2) pretreated TWAS and untreated TWAS. Microbial community shifts were quantified to reveal the microbiome responses to disturbances. The results suggested that 1% Ca(ClO)(2) enhanced the digestion of TWAS by inactivating and transforming the biomass to more easily digested substrates. Co-occurrence network analysis revealed that the strongest interactions in the microbial community occurred in the steady state of TWAS anaerobic digestion.

Automated summary

Hypochlorite pretreatment has been proven effective in enhancing waste activated sludge anaerobic digestion performances. This study compared the performance stability and resilience of digested sludge pretreated with 1% hypochlorite and untreated sludge. The results showed that hypochlorite pretreatment improved the digestion of sludge and increased the interactions within the microbial community.