Comparative study about ozonation to treat Microcystis-laden source water at the development and maintenance stage

Xi Li; XuanXuan Xian; Sheng Chen; Weijun Song; Xin Yu; Chang-Ping Yu

doi:10.1016/j.chemosphere.2023.140045

Comparative study about ozonation to treat Microcystis-laden source water at the development and maintenance stage

Chemosphere. 2023 Nov:341:140045. doi: 10.1016/j.chemosphere.2023.140045. Epub 2023 Sep 6.

Authors

Xi Li¹, XuanXuan Xian², Sheng Chen³, Weijun Song⁴, Xin Yu⁵, Chang-Ping Yu⁶

Affiliations

¹ CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China. Electronic address: xli@iue.ac.cn.
² College of The Environment & Ecology, Xiamen University, Xiamen, 361102, China. Electronic address: xxxian@stu.xmu.edu.cn.
³ College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China. Electronic address: chensheng@tongji.edu.cn.
⁴ College of Ecology and Resources Engineering, Wuyi University, Wuyishan, 354300, China. Electronic address: songweijun@wuyiu.edu.cn.
⁵ College of The Environment & Ecology, Xiamen University, Xiamen, 361102, China. Electronic address: xyu@xmu.edu.cn.
⁶ CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, 106, Taiwan. Electronic address: cpyu@iue.ac.cn.

PMID: 37683947
DOI: 10.1016/j.chemosphere.2023.140045

Abstract

The outbreak of toxic cyanobacteria blooms is hazardous to water safety. Ozonation has been used to treat cyanobacteria-laden source water. Generally, cyanobacterial blooms enter into a long-term maintenance stage from the bloom development, but how the changed bloom stage affects ozonation is still unknow. Herein, influences of ozonation on cell inactivation and microcystin removal of Microcystis at the development and maintenance stage, were investigated. Then, ozonation-assisted coagulation for Microcystis removal at the two stages was compared. Results showed no significant difference in the photosynthetic inactivation of Microcystis at both stages. Microcystis at the maintenance stage exhibited a lower loss of membrane integrity (268-480 M^-1 s^-1) than that at the development stage (413-596 M^-1 s^-1). However, the extracellular microcystin increased by 30-410% at the maintenance stage at a lower ratio of [O₃: DOC] (0.10-0.80) compared to the development stage (0.21-1.68), mainly ascribed to a decrease in the ozonation efficiency for microcystin removal. This finding might result from the elevated biomass and N-containing organics as competitors to reduce microcystin ozonation. Meanwhile, it was possible to generate fewer hydroxyl radicals to oxidize microcystin at the maintenance stage than that at the development stage. Besides, the removal ratio of Microcystis after ozonation-assisted coagulation, was reduced by 46-230% at the maintenance stage, due to the insufficient modification of cellular surface or elevated organics of 3-30 kDa. This work indicated that ozonation is effective to treat Microcystis at the development stage of a bloom whist pre-ozonation might be an inappropriate choice at the long-term maintenance stage.

Keywords: Bloom stage; Coagulation; Microcystin; Microcystis blooms; Ozonation; Photosynthetic inactivation.

MeSH terms

Cyanobacteria* / metabolism
Microcystins / metabolism
Microcystis* / metabolism
Ozone*
Water / metabolism

Substances

Microcystins
Water
Ozone