Enhanced biogas production and hydrogen sulfide suppression in anaerobic digestion via ROS generated by in situ H2O2 dosing.

Anaerobic digestion (AD) of sewage sludge is often limited by slow hydrolysis and low methane production efficiency due to the high fraction of particulate organic matter. In this study, the effects of controlled in situ H2O2 dosing on AD of sewage sludge were investigated and the underlying mechanisms for enhanced methane production were explored. It was found that hydrolysis rates increased progressively with increasing H2O2 dosage, reaching 43.8 ± 8.8 % at 80 mg L-1 H2O2. This has resulted in a significant increase in methane production, with CH4 and CO2 production increased by 23.9 % and 34.2 %, respectively. Adding 20 mg L-1 H2O2 could suppress the H2S production from 788 ± 170 to 55 ± 98  ppm and higher H2O2 dose of 40 or 80 mg L-1 further decreased H2S below 5  ppm. H2O2 treatment was associated with altered substrate solubilization, and with shifts toward higher relative abundances of putative syntrophic and fermentative taxa and lower relative abundances of putative sulfate-reducing taxa, suggesting potential changes in carbon and sulfur metabolism. Microbial communities shifted toward energy conservation and oxidative stress mitigation strategies, adopting protective mechanisms (e.g., reactive oxygen species detoxification, sporulation and exopolysaccharides production), thereby sustaining fermentation performance.