Using sodium percarbonate to suppress vertically distributed filamentous cyanobacteria while maintaining the stability of microeukaryotic communities in drinking water reservoirs. (1st June 2021)

• Record Type: Journal Article
• Authors: Xu, Hangzhou; Pang, Yiming; Li, Yizhen; Zhang, Shasha; Pei, Haiyan
• Is Part Of: Water research. Volume 197(2021)
• Publication Date: 2021-06-01
• Subjects: Filamentous cyanobacteria -- Sodium percarbonate -- Microeukaryotic communities -- Co-occurrence network -- Drinking water source; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117111
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: SPC can suppress filamentous cyanobacteria in different water layers at full-scale. Sensitivity of filamentous cyanobacteria to SPC differed between species. 3.0 mg/L SPC has no major impacts on microeukaryotic communities. Protozoa and cryptophyta more sensitive to SPC than ochrophyta and chloroplastida. Stability of microeukaryote in treated surface water lower than treated bottom water. Abstract: The increasing frequency and intensity of blooms of toxin- and taste & odour-producing filamentous cyanobacteria in water sources is a growing global issue. Compared to the common spherical Microcystis genus, the removal of filamentous cyanobacteria is more difficult in drinking water treatment plants; hence, abatement and control of the occurrence and proliferation of harmful filamentous cyanobacteria within drinking water sources is important for water supply. In this study, the solid sodium percarbonate (SPC), Na2 CO3 ·1.5H2 O2, was used as an algaecide to eliminate the cyanobacteria distributed throughout the water column in the surface and bottom layer of a reservoir serving as a drinking water source. Results showed that although the oxidation capacity of SPC was higher in the surface water due to the higher light intensity than in the bottom water, 3.0 mg/L SPC can still suppress the harmful cyanobacteria in the bottom water after 36 h because the carbonate ion generated by SPC decomposition can act as an activator of H2 O2 to generate many reactive oxygen species — including superoxide radicals, carbonate radical anions, and hydroxyl radicals — even in the light-limited environment. The obtained inactivation rates for the main cyanobacteria in this reservoir followed the order: Pseudanabaena limnetica > Raphidiopsis curvata > Cylindrospermopsis raciborskii . 3.0 mg/L SPC has a slight impact on microeukaryotic communities according to the 18S rRNA gene sequencing, while 6.0 mg/L SPC changed the composition of eukaryotic phytoplankton and zooplankton clearly. Eukaryotic co-occurrence networks showed that although the network of eukaryotic plankton in treated surface water was more compact and clustered, stability of microeukaryotes in the treated surface water was lower than for the treated bottom water, owing to the higher oxidation capacity of SPC in the surface water. The results above not only have important implications for full-scale control of harmful cyanobacteria in drinking water sources, especially filamentous cyanobacteria with vertical distributions, but also help to ensure the health and stability of the whole aquatic ecosystem. Graphical abstract: Image, graphical abstract