Unveiling the microbial and metabolic mechanisms of a novel anaerobic/micro-aerobic/anoxic (AMA) strategy for nutrient removal and carbon utilization from low C/N high-strength ammonium wastewater.

Abstract

Achieving cost-effective advanced nitrogen removal with minimal external carbon input remains a key challenge in wastewater treatment plants processing high-strength ammonium wastewater with a low carbon-to-nitrogen (C/N) ratio. In this study, an anaerobic/micro-aerobic/anoxic (AMA) system was established to treat such wastewater at a C/N ratio of 2.5 by integrating simultaneous nitrification, anaerobic ammonium oxidation (anammox), and endogenous denitrification, collectively referred to as SNAED. The system achieved average removal efficiencies of 92.5% for NH4+-N, 89.9% for total nitrogen (TN), and 94.8% for COD, treating influent wastewater containing 200.0 mg/L of NH4+-N and 200.0 mg/L of TN. The relative abundance of Candidatus Brocadia reached 0.5%, indicating effective in situ enrichment of anammox bacteria (AnAOB). Metagenomic analysis revealed that the elevated abundances of narGHI, norBC, nosZ, and hdh were crucial for enhancing TN removal. Concurrently, the increased number of metagenomic reads (117,130 reads) affiliated with Candidatus Competibacter, a representative denitrifying glycogen-accumulating organism, and annotated to metabolic pathway categories indicates an enhanced functional potential for endogenous denitrification. A stable and functionally diverse microbial community, consisting of ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, AnAOB, denitrifying polyphosphate-accumulating organisms, and denitrifying glycogen-accumulating organism, was established and played a pivotal role in sustaining the SNAED process. These findings demonstrate that AMA system offers a sustainable and efficient strategy for low-energy nitrogen removal.