Engineering the anammox pathway in a full-scale AOA process for industrial wastewater treatment

The anammox process holds significant potential for municipal wastewater treatment, yet its full-scale application in industrial wastewater treatment plants (IWTP), particularly within endogenous denitrification-based processes, remains challenging. This study demonstrates the successful establishment of the anammox pathway in a full-scale (16,000 m³/d) anaerobic-aerobic-anoxic (AOA) process IWTP by implementing a synergistic control strategy that integrates low dissolved oxygen (DO: 0.5 - 1.4 mg/L) with residual ammonia (1.6 - 2.9 mg/L) at the aerobic outlet. During 450 days of operation, the system achieved stable and advanced nitrogen removal, with effluent NH₄⁺-N and total nitrogen (TN) averaging only 0.2 mg/L and 5.7 mg/L, respectively. Metagenomic and isotope tracing analyses identified that the anoxic zone biofilm as a functional hotspot for anammox, where the relative abundance of anammox bacteria (AnAOB), predominantly Candidatus Brocadia, was significantly enriched to 0.074%. This community contributed to 36.7% of the TN removal via dual pathways coupling anammox with endogenous and exogenous partial denitrification. Economically, the incorporation of anammox reduced aerobic zone aeration energy consumption by 18.2% and decreased external carbon dosage by 44.4%. This work provides a pioneering demonstration of anammox under complex water quality conditions and offers a viable technological route toward low-carbon wastewater treatment.