Re-evaluation of the environmental hazards of nZnO to denitrification: Performance and mechanism

Xiao-Lin Ma; En-Jing He; Feng-Ting Cao; Yang-Yang Fan; Xiang-Tong Zhou; Xiang Xiao

doi:10.1016/j.chemosphere.2021.132824

Re-evaluation of the environmental hazards of nZnO to denitrification: Performance and mechanism

Chemosphere. 2022 Mar;291(Pt 2):132824. doi: 10.1016/j.chemosphere.2021.132824. Epub 2021 Nov 6.

Authors

Xiao-Lin Ma¹, En-Jing He², Feng-Ting Cao², Yang-Yang Fan³, Xiang-Tong Zhou⁴, Xiang Xiao⁵

Affiliations

¹ Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China; School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China.
² Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China.
³ Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China. Electronic address: fyy@ahu.edu.cn.
⁴ School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China.
⁵ Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China; School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China. Electronic address: xiaox@ustc.edu.cn.

PMID: 34752835
DOI: 10.1016/j.chemosphere.2021.132824

Abstract

Numerous studies have shown that zinc oxide nanoparticles (nZnO) have an inhibitory effect on wastewater biotreatment, where doses exceeding ambient concentrations are used. However, the effect of ambient concentrations of ZnO (<1 mg/L) on anaerobic digestion processes is not clear. Herein, this study comprehensively explored the impact of nZnO on the denitrification performance and core microbial community of activated sludge under ambient concentrations. Results showed that only 0.075 mg/L nZnO had shown a beneficial effect on nitrogen removal by activated sludge. When nZnO concentration reached 0.75 mg/L, significant enhancement of nitrate reduction and mitigation of nitrite accumulation were observed, indicating a remarkable stimulatory effect on nitrogen removal. Simultaneously, nZnO could weaken the sludge surface charge and improve the secretion of extracellular polymeric substances, thus enhancing sludge flocculation for denitrification. Microbial community analysis revealed that nZnO exposure increased the relative abundance of denitrifying bacteria, which could contribute to the reinforcement of traditional denitrification. Furthermore, exogenous addition of NH₄⁺ significantly inhibited the accumulation of nitrite, implying that nZnO had a potential to improve the denitrification process via a partial denitrification-anammox pathway. Considering current ambient concentration, the stimulatory effect shown in our work may better represent the actual behavior of ZnO in wastewater biotreatment.

Keywords: Anammox; Denitrifying bacteria; Nitrogen removal; Sludge; Zinc oxide nanoparticle.

MeSH terms

Anaerobic Ammonia Oxidation
Bioreactors
Denitrification*
Nanoparticles*
Nitrogen
Oxidation-Reduction
Sewage
Wastewater

Substances

Sewage
Waste Water
Nitrogen