Reduced sulfide and methane in rising main sewer via calcium peroxide dosing: Insights from microbial physiological characteristics, metabolisms and community traits

Although the biocidal effect of calcium peroxide (CaO2) has attracted increasing attention in wastewater and sludge management, its potential in the reduction of sulfide and methane from sewer is not tapped. This study aims to fill this gap through the long-term operated sewer reactors. Results showed one-time dose of 0.2% (w/v) CaO2 with 12-h exposure decreased the average sulfide and methane production by 80% during one week. The electron paramagnetic resonance and free radical quenching tests indicated free radicals from CaO2 decomposing posed a major contribution on sewer biofilms (center dot OH>center dot O-2(-)>alkali). Mechanistic analysis revealed extracellular polymeric matrix breakdown (e.g., protein secondary structure) and cell membrane damage were caused by the increased lipid peroxidation of cells and exacerbated intracellular reactive oxygen species under CaO2 stress. Moreover, the intracellular metabolic pathways, such as electrons provision and transfer, as well as pivotal enzymatic activities (e.g., APS reductase, sulfite reductase and coenzymes F-420) were significantly impaired. RT-qPCR analysis unveiled the absolute abundances of dsrA and mcrA were decreased by 7.53-40.37% and 67.00-74.85%, respectively. Although this study broadens the application scope of CaO2 and provides in-depth understanding of advanced oxidation-based technology in sewer management, the pipe scale risk due to the release of calcium ions warrants further investigation.

Automated summary

This study fills the research gap regarding the potential of calcium peroxide (CaO2) in reducing sulfide and methane emissions from sewers. The results showed that a one-time dose of 0.2% (w/v) CaO2 with 12-hour exposure could decrease the average sulfide and methane production by 80% over one week. Mechanistic analysis revealed that CaO2 caused breakdown of the extracellular polymeric matrix, damage to cell membranes, and an increase in intracellular reactive oxygen species, leading to impaired metabolic pathways and enzymatic activities. Although this study expands the application of CaO2 and provides insights into advanced oxidation-based technology in sewer management, further investigation is needed to assess the pipe scale risk associated with the release of calcium ions.