Effect of calcium peroxide pretreatment on anaerobic digestion of primary and secondary sludge of A2/O process

In order to evaluate comprehensively the impact of calcium peroxide (CP) on anaerobic digestion (AD) of primary sludge (P-sludge) and secondary sludge (S-sludge) of anaerobic/anoxic/aerobic process, a series of batch experiments were conducted in the lab scale. Results showed that CP pretreatment could kill Fecal Coliform completely in 72.0 h and promote the solubilization of S-sludge more significantly than P-sludge. Compared with the control, the maximum CH4 production potential and the maximum specific CH4 production rate of P-sludge AD only increased by 11.2 % and 6.10 %, respectively, but those of S-sludge AD increased by 40.7 % and 58.4 % after the same pretreatment, indicating that CP pretreatment was more conducive to methane production of S-sludge. Moreover, the increase of alkalinity and initial acetate concentration of S-sludge was greater than that of P-sludge after pretreatment according to the process analysis of hydrolysis. Notably, CP pretreatment reduced the PO43−-P concentration and chromaticity in the AD supernatant of both sludges, which was beneficial to the subsequent treatment of biogas slurry. In addition, CP pretreatment increased the content of total nutrient and decreased the content of harmful heavy metals in both biogas residues. Conclusively, compared with P-sludge, CP pretreatment is more suitable for S-sludge AD. This work firstly provides a comprehensive evaluation of CP pretreatment to waste sludge produced in anaerobic/anoxic/aerobic process of wastewater treatment plant (WWTP), which is of great significance in enriching the pretreatment technology of waste sludge and promoting the application of CP pretreatment in WWTP. [Display omitted] •Effects of CP pretreatment are compared between P-sludge and S- sludge.•CP pretreatment increased P0 and Rmax of S-sludge greatly compared with P-sludge.•CP pretreatment could completely kill Fecal Coliform of both sludges in 72 h.•CP pretreatment lifted the content of total nutrients and Ca in both residues.•CP pretreatment reduced the chromaticity and P concentration in both supernatants.