Achieving advanced nitrogen removal with anammox and endogenous partial denitrification driven by efficient hydrolytic fermentation of slowly-biodegradable organic matter.

Anammox-based processes are pivotal for elevating nitrogen removal efficiency in municipal wastewater treatment. This study established a novel HF-EPDA system combined in-situ hydrolytic fermentation (HF) with endogenous partial denitrification (EPD) and anammox. Slowly-biodegradable organic matter (SBOM) was degraded and transformed into endogenous polymers for driving production of sufficient nitrite by EPD, further promoted the nitrogen removal via anammox process. Processes above formed positive feedback, guaranteeing the robustness and recoverability of system. After a 92-day suspension during operation, advanced nitrogen removal was still achieved with excellent nitrogen removal efficiency of 95.84 ± 1.73 %, treating with actual domestic wastewater and synthetic nitrate wastewater. Candidatus Brocadia and Candidatus Competibacter were dominant bacteria on biofilms responsible for the anammox and EPD process respectively, while the main hydrolytic fermentation organisms norank_o SBR1031 was enriched in floc sludge. This study highlights the reliable potential for expanding anammox application with simultaneous improvement of SBOM utilization.