Improving the treatment of waste activated sludge using calcium peroxide

•Underlying mechanisms of CaO2 disintegrating EPS and cell membrane are reviewed.•Sludge dewatering and minimization can be achieved effectively by CaO2.•Methane production from sludge anaerobic digestion can be enhanced significantly by CaO2-based treatment.•SCFA and hydrogen yield in sludge anaerobic fermentation can be improved prominently with CaO2 addition.•CaO2 can promote the removal of emerging contaminants via the generated free radicals oxidation and alkali. The treatment and disposal of waste activated sludge (WAS) has become one of the major challenges for the wastewater treatment plants (WWTPs) due to large output, high treatment costs and enriched substantial emerging contaminants (ECs). Therefore, reducing sludge volume, recovering energy and resource from WAS, and removing ECs and decreasing environmental risk have gained increasing attentions. Calcium peroxide (CaO2), a versatile and safe peroxide, has been widely applied in terms of WAS treatment including sludge dewatering, anaerobic sludge digestion and anaerobic sludge fermentation due to its specific properties such as generating free radicals and alkali, etc., providing supports for sludge reduction, recycling, and risk mitigation. This review outlines comprehensively the recent progresses and breakthroughs of CaO2 in the fields of sludge treatment. In particular, the relevant mechanisms of CaO2 enhancing WAS dewaterability, methane production from anaerobic digestion, short-chain fatty acids (SCFA) and hydrogen production from anaerobic fermentation, and the removal of ECs in WAS and role of experiment parameters are systematically elucidated and discussed, respectively. Finally, the knowledge gaps and opportunities in CaO2-based sludge treatment technologies that need to be focused in the future are prospected. The review presented can supply a theoretical basis and technical reference for the application of CaO2 for improving the treatment of WAS. [Display omitted]