Effects of calcium peroxide pretreatment on the substrate, microenvironment, and microbial community in an anaerobic digestion system of waste sludge

Abstract

In this study, the waste activated sludge (WAS) of wastewater treatment plants was pretreated with calcium peroxide (CP) for 48 h and then digested anaerobically at 35 ±1 ◦C. The effects of CP pretreatment on the substrate, microenvironment, and microbial community in the anaerobic digestion (AD) system of WAS were investigated. Results showed that the total volatile fatty acids in the pretreated sludge increased by 8.95 times compared with that in the control. Evidently, pH and oxidation reduction potential (ORP) increased when the CP-pretreated sludge was further subjected to AD, where NO3 N and H2O2 reached 29.65 mg/L and 11.8 mg/L, respectively, but the catalase (CAT) activity was inhibited. Additionally, CP-pretreatment activated the nitrifying bacterial phylum, inhibited the denitrifying genera, and selected the specific methanogens. However, CH4 production was still enhanced by 19.10 % unexpectedly although higher ORP was maintained in the AD system for a long time, which challenged the classical theory of AD. The acceptable feedback of the sludge AD system on CP pretreatment may be related to the change in H2O2 and CAT activities.

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ORCID for Yong-Qiang Liu: orcid.org/0000-0001-9688-1786

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