Comparing the effects of chlorination on membrane integrity and toxin fate of high- and low-viability cyanobacteria

• Published in: Water research (Oxford) 2020-06, Vol.177, p.115769-115769, Article 115769
• Main Authors: Li, Xi, Chen, Sheng, Zeng, Jie, Song, Weijun, Yu, Xin
• Format: Article
• Language: English
• Subjects: Cell viability; Chlorine; Cyanobacteria; Halogenation; Membrane integrity; Microcystis; Toxin fate; Water Purification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.115769

Occurrence of toxic cyanobacterial blooms in natural freshwaters could impair drinking water quality. Chlorine was often employed as an oxidant to treat algal-laden source waters in drinking water treatment plants. However, previous studies only focused on high-viability cyanobacteria at exponential phase. Whether the change of cell-viability of cyanobacteria could affect chlorination was unknown. Here, high- and low-viability Microcystis were collected from a whole life cycle of cyanobacteria in lab-scale, and effects of chlorination on membrane integrity and toxin fate of high- and low-viability Microcystis were subsequently investigated. Results showed chlorine exposure was lower for low-viability cells than high-viability cells with the same initial chlorine dosage, but low-viability cells were less resistant to chlorination, leading to higher rate of membrane damage (kloss) and intracellular toxin release (ki). For high-viability cells, there was no increase of extracellular toxin with sufficient chlorine exposure whereas it showed a continuous increase for low-viability cells mainly due to its lower rate of extracellular toxin degradation (ke, 26 ± 8 M−1 s−1) than intracellular toxin release (ki, 110 ± 16 M−1 s−1) (ke 30 mg min L−1) whereas chlorination could not work well for low-viability cells even with chlorine exposure of as high as 36 mg min L−1. These findings indicated chlorination may not be a feasible option to treat low-viability cyanobacteria during decline stage of cyanobacterial blooms. [Display omitted] •Chlorine decay was faster for low-viability Microcystis mainly due to increasing DOC.•Low-viability Microcystis was less resistant to chlorination than high-viability cells.•Rate constants of toxin release and degradation for high-and low-viability cells were compared.•Toxin risk would occur after chlorination for low-viability Microcystis.