Cite this paper:
Kaixuan LIU, Lei JIANG, Jinsheng YANG, Shuzhan MA, Kaining CHEN, Yufeng ZHANG, Xiaoli SHI. Comparison of three flocculants for heavy cyanobacterial bloom mitigation and subsequent environmental impact[J]. Journal of Oceanology and Limnology, 2022, 40(5): 1764-1773

Comparison of three flocculants for heavy cyanobacterial bloom mitigation and subsequent environmental impact

Kaixuan LIU1,2, Lei JIANG2,3, Jinsheng YANG2,3, Shuzhan MA2,3, Kaining CHEN2, Yufeng ZHANG1, Xiaoli SHI2,4
1 Department of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, China;
2 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China;
3 University of Chinese Academy of Sciences, Beijing 100049, China;
4 Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaiyin 223001, China
Cyanobacteria can accumulate as a heavy biomass on the leeward side of large eutrophic lakes, posing a potential threat to public health. The mitigating capacity of three flocculants and their potential impacts on the major environmental features of water and sediments was evaluated. Results indicate that polyaluminum chloride (PAC) and ferric chloride (FeCl3) are efficient flocculants that can rapidly mitigate cyanobacterial blooms with chlorophyll-a concentrations higher than 1 500 μg/L within 15 min. In comparison, cationic starch with chitosan could only treat cyanobacterial blooms in chlorophyll-a concentrations of less than 200 μg/L. The addition of FeCl3 caused a decline in the pH value, while dissolved oxygen in the water column dropped to 2 mg/L during cationic starch with chitosan treatment for a high cyanobacterial biomass group. Thus, a combination of flocculants and oxygenators should be considered when treating high-concentration cyanobacterial blooms for emergency purposes. Additionally, the cell lysis of cyanobacteria caused by cationic starch with chitosan can result in an increase in total dissolved phosphorus and total dissolved nitrogen. Furthermore, the high accumulation of nutrients in sediments after the settling of cyanobacteria can cause high internal phosphorus pollution. The increase in the total organic carbon of the sediments can threaten lake restoration achieved by planting submerged macrophytes.
Key words:    cyanobacterial bloom    emergency control    flocculants    lake restoration   
Received: 2021-10-25   Revised: 2022-01-28
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