Production of Reactive Oxygen Species during Redox Manipulation and Its Potential Impacts on Activated Sludge Wastewater Treatment Processes

Xiantang Liu; Danyu Huang; Changyin Zhu; Fengxiao Zhu; Xiangdong Zhu; Dongmei Zhou

doi:10.1021/acs.est.4c11301

Production of Reactive Oxygen Species during Redox Manipulation and Its Potential Impacts on Activated Sludge Wastewater Treatment Processes

Environ Sci Technol. 2024 Dec 17. doi: 10.1021/acs.est.4c11301. Online ahead of print.

Authors

Xiantang Liu¹, Danyu Huang¹, Changyin Zhu^{1

2}, Fengxiao Zhu³, Xiangdong Zhu⁴, Dongmei Zhou¹

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P. R. China.
² Co-Innovation Center for the Sustainable Forestry in Southern China, College of Ecology and Environment, Nanjing Forestry University, Nanjing 210037, P. R. China.
³ School of Environment, Nanjing Normal University, Nanjing 210023, P. R. China.
⁴ State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, P. R. China.

PMID: 39689161
DOI: 10.1021/acs.est.4c11301

Abstract

Reactive oxygen species (ROS) are ubiquitous in redox-fluctuating environments, exerting profound impacts on biogeochemical cycles. However, whether ROS can be generated during redox manipulation in activated sludge wastewater treatment processes (AS-WTPs) and the underlying impacts remain largely unknown. This study demonstrates that ROS production is ubiquitous in AS-WTPs due to redox manipulation and that the frequency and capacity of ROS production depend on the operating modes. The anaerobic/oxic continuous-flow reactor showed persistent ROS generation (0.8-2.1 μM of instantaneous H₂O₂), whereas the oxic/anoxic sequencing batch reactor (0.21-0.28 mM of H₂O₂ per cycle) and the anaerobic/anoxic digestion reactor (0.27-0.29 mM of H₂O₂ per cycle) exhibited periodic ROS production. Our results illustrated that ROS generated during redox manipulation can contribute to the removal of organic micropollutants. Due to their high activity, ROS can directly accelerate the abiotic oxidation of organic phenolics and Fe(II) minerals in sludges. ROS could also affect biotic nitrification by changing the microbial community composition and regulating the relative expression of functional genes, such as amoA, nrxA, and nrxB. This research demonstrates the ubiquitous production of ROS during redox manipulation in AS-WTPs, which provides new insights into pollutant removal and the abiotic and biotic elemental transformation in AS-WTPs.

Keywords: activated sludge wastewater treatment processes; elemental transformation; organic micropollutants; reactive oxygen species; redox manipulation.