Microbial synergy mechanism of hydrogen flux influence on hydrogen-based partial denitrification coupled with anammox in a membrane biofilm reactor.

The hydrogen-based partial denitrification coupled with anammox (H-PDA) biofilm system effectively achieves low-carbon and high-efficiency biological nitrogen removal. However, the effects and biological interaction mechanism of H flux with the H-PDA system have not yet been understood. This study assessed the effects of H flux on interactions among anammox bacteria (AnAOB), denitrifying bacteria (DB), and sulfate-reducing bacteria (SRB) coexisting in a H-PDA system. Results showed the simultaneous removal of 40 mg/L ammonium nitrogen (NH-N) and 50 mg/L nitrate nitrogen (NO-N) in the H-PDA system at a flux of 0.13-0.14 e eq/(m·d) without additional organic carbon. Candidatus_Brocadia was involved in H oxidation and was negatively associated with the heterotrophic Thauera genus (DB). The expression of nirS and dsrA was increased to 5.6 × 10 copies/gSS and 2.1 × 10 copies/gSS, respectively, with excessive H flux (0.17 e eq/(m·d). This study provides technical guidance for understanding and applying the H-PDA technology for low-carbon wastewater treatment.