Research
| Title： | Direct ammonia oxidation colony-driven DAAO process: construction strategy and optimization of denitrification efficacy |
|---|---|
| First author： | Mi, Yuwei; Wei, Dingqiu; Liu, Shuangjiang; Li, Defeng; Chen, Han; Zheng, Yijie; Chen, Mingming; Qiu, Dongru; Bao, Renbing; Xu, Jian; Hu, Zhiquan |
| Journal： | CHEMICAL ENGINEERING JOURNAL |
| Years： | 2025 |
| DOI： | 10.1016/j.cej.2025.166019 |
| Abstract： | Direct ammonia oxidation (Dirammox), a novel nitrogen metabolism pathway, has emerged as a promising strategy for wastewater treatment due to its simple metabolic process and high nitrogen removal efficiency. In this study, the Dirammox-Anaerobic-Anoxic-Oxic (DAAO) process was developed and operated continuously for 120 days to evaluate its efficacy in optimizing nitrogen removal from biological effluents. The results indicated a significant improvement in the removal efficiency of total nitrogen (TN) in the DAAO system, which increased by 15.21 %, reaching 93.71 %. Additionally, the effluent NOx-N concentration was reduced by a factor of 5, decreasing to 1.34 mg/L. Halving the reflux ratio significantly reduces wastewater treatment costs, with the high DAAO removal rate primarily attributed to the direct, one-step nitrogen removal facilitated by the enrichment of Dirammox bacteria. Furthermore, the efficient enrichment of Dirammox bacteria was demonstrated by semi-quantitative fluorescence in situ hybridization analysis and absolute quantification of dnfABC functional genes. The DAAO system decreased the abundance of genes related to the complete nitrification process, while enhancing Dirammox, dissimilatory nitrate reduction, and denitrification processes, leading to more efficient and comprehensive nitrogen removal. This study offers crucial theoretical support for the practical application of Dirammox in municipal wastewater treatment. |
