J Environ Sci (China). 2026 Apr;162:83-90. doi: 10.1016/j.jes.2025.04.071. Epub 2025 May 4.
ABSTRACT
Nitrogen oxides (NO), consisting of nitric oxide (NO) and nitrogen dioxide (NO), pose significant risks to human health and the environment, potentially causing respiratory and cardiovascular diseases. In contrast to extensive research on industrial NO emissions, there has been a paucity of attention on the dynamics of NO in wastewater treatment plants (WWTPs). This study investigated NO emission patterns in a pilot-scale WWTP, revealing that NO dominated NO emissions (0.013 % of the nitrogen load), peaking nocturnally (4 a.m.- 6 a.m.) and primarily originating from the oxic zone due to ammonia-oxidizing bacteria activity and aeration stripping synergistically increasing NO emission. NO emissions were minimal (0.003 % of the nitrogen load), with limited conversion from NO. Pearson correlation analysis identified ammonium removal efficiency and nitrate accumulation efficiency as key drivers of NO production. The microbial community composition was closely linked to NO emissions, with nitrifying bacteria such as Nitrosomonas contributing to NO generation in the oxic zone, while denitrifying bacteria like Methylotenera contributed to NO emissions under oxygen-limited conditions in the anoxic zone. This study enhanced the comprehension of the intricate processes of the nitrogen cycle during wastewater treatment and provided theoretical guidance for further optimization of WWTPs.
PMID:41765583 | DOI:10.1016/j.jes.2025.04.071