Harvesting of dissolved methane from anaerobic effluents for enhanced nitrogen removal in mainstream wastewater

The presence of dissolved methane in anaerobic effluents from wastewater treatment plants (WWTPs) significantly contributes to methane emissions. To mitigate this issue, this study introduced the Self-breathing Biofilm Reactor (SbBfR), which achieved a 94 % retention rate of dissolved methane during the aeration stage. Counter-diffusion and co-diffusion systems were established to enhance microbial interactions for both dissolved methane oxidation and nitrogen removal. These systems varied based on alignment or opposition of substrates with externally supplied oxygen. Specifically, the counter-diffusion system isolated oxygen and methane, favoring denitrifying anaerobic methane oxidizing microorganisms, achieving nitrogen removal rate of 175 mg N/L/d with an efficiency of up to 88 %. The spatial distribution patterns of aerobic and anaerobic microbes within the biofilms were characterized using 16S rRNA gene amplicon sequencing combined with cryosection and qPCR analysis. This approach provides a promising solution for reducing dissolved methane emissions from WWTPs while simultaneously achieving efficient nitrogen removal, offering valuable insights for practical wastewater treatment applications.