The mitigation efficacy and mechanism for H2S and CH4 emission from wastewater by adding bacterium-fungus mixture

Anaerobic conditions in wastewater systems produce H₂S and CH₄, leading to pipeline corrosion and environmental risks. While various chemical solutions have been proposed, they often suffer from secondary pollution. This study developed and optimized a microbial strategy to reduce H₂S and CH₄ emissions by simultaneously adding yeast and bacterial strain. Optimal results were obtained with a 1:2 ratio of Bacillus subtilis to Saccharomyces cerevisiae at 10⁷ CFU/mL, achieving reductions of 65.8 % for H₂S and 62.4 % for CH₄. The addition of bacterium-fungus mixture altered carbon and sulfur metabolic pathways, community structure, and functional gene abundance, which ultimately reduced H₂S and CH₄ emissions. Specifically, the increase in redox potential leads to the accumulation of other sulfur compounds such as S₂O₃²⁻. Additionally, elevated concentrations of long-chain fatty acids and decreased acetate concentrations limited the substrates required for CH₄ production. Community structure and metagenomic analyses confirmed these changes, showing reduced relative abundances of sulfate-reducing bacteria, methanogens, and associated functional genes, as well as increased genes abundance associated with organic sulfur synthesis and propionate/butyrate production. These findings demonstrate that addition of bacterium-fungus mixture can effectively modulate microbial community structure and metabolic pathways, offering a viable strategy for reducing H₂S and CH₄ emissions in wastewater.