Calcium peroxide significantly enhances volatile solids destruction in aerobic sludge digestion through improving sludge biodegradability.

This work put up a novel strategy of applying calcium peroxide (CaO) in aerobic sludge digestion and provided insights into such system. The degradation percentage of sludge and total inorganic nitrogen production in the digesters with CaO at 0.02 g/g-VS-WAS increased by 25.8% and 18.8% of control. CaO addition allowed various key microbes related to organics degradation to accumulate in the system. Moreover, the modelling and chemical (i.e., excitation emission matrix (EEM) fluorescence and fourier transformation spectroscopy (FTIR)) analyses revealed that CaO addition enhanced sludge biodegradability with more release of biodegradable organics and increased degradation of recalcitrant organics, which can be transformed into biodegradable organics with the action of CaO. Subsequent transformation test indicated that CaO enabled to promote hydrolysis and catabolism of biodegradable substrates in sludge. Further investigations on function mechanism suggested that CaO carried on positive action for sludge aerobic digestion mainly through the enhancement by ·OH.