Weak ultrasound enhances nitrogen removal by heterotrophic nitrifying-aerobic denitrifying bacteria under per- and
Jingshen Zhang1, Jiahao Zhang2, Mingyue Zhao3
1Huang Huai Laboratory, Henan Academy of Sciences, Zhengzhou 450046, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Chemistry, Zhengzhou University, Zhengzhou 450001, China.
Abstract:
Per- and polyfluoroalkyl substances (PFAS), particularly perfluorooctanoic acid (PFOA), are increasingly detected in nitrogen-containing wastewater. This study investigated the inhibitory effects of PFOA on biological nitrogen removal (BNR) by heterotrophic nitrifying-aerobic denitrifying bacteria and assessed whether weak ultrasound could mitigate these effects. At 1 mg/L, PFOA reduced nitrate and ammonia nitrogen removal rates by 27.3 % and 7.9 %, respectively. Transcriptomic analysis revealed downregulation of nitrogen removal genes under both 1 mg/L and 100 mg/L PFOA stress. 100 mg/L PFOA also induced oxidative stress and cell membrane damage, further impairing nitrogen metabolism and overall BNR performance. Under 1 mg/L PFOA stress, weak ultrasound increased adenosine triphosphatase activity by 107.1 % compared with the non-ultrasound condition. Ultrasound enhanced bacterial growth, metabolism, and EPS secretion, thereby alleviating PFOA toxicity and improving nitrogen removal efficiency. This study proposed a practical strategy for mitigating PFAS interference in conventional wastewater treatment systems.
