Investigation of cellular structure and metabolic activity of Microcystis cells treated by chlorination


 Frequent outbreaks of cyanobacterial blooms in lakes and reservoirs can result in the deterioration of drinking water quality. Chlorine has been used as an oxidant or algicide, to treat cyanobacteria-laden source waters, but influences of chlorination on the cellular structure and metabolic activity of cyanobacterial cells were not well understood. In this study, after chlorination with various initial dosages (0.5–8.0 mg L−1), the cellular size, cellular surface, and cellular structure of Microcystis cells were investigated, and both photosynthetic and respiratory activity of Microcystis cells were also analyzed. Results showed that chlorination of 1–8 mg L−1 could effectively decrease the metabolic activity of Microcystis cells and their cellular structures were severely destroyed (e.g., cell wall, cell membrane, and photosynthetic lamellar). Meanwhile, Microcystis aggregates induced an increase of their particle size distribution of 10–100 μm (1.2–1.9%) in these treatments. In contrast, low-level chlorination of 0.5 mg L−1 did not change the particle size distribution of 2–10 μm along with a slight destruction of cellular structures. Interestingly, this treatment could induce an increase of photosynthetic activity of Microcystis cells (19.0%), implying that insufficient chlorination might not be a proper algicide to control cyanobacterial blooms in lakes or reservoirs.