Removal efficiency of phosphorus, cyanobacteria and cyanotoxins by the flock & sink mitigation technique in semi-arid eutrophic waters

WATER RESEARCH

卷:159

Article

de Lucena-Silva, Daniely^1,2  Molozzi, Joseline^1,2  Severiano, Juliana dos Santos^1,2  Becker, Vanessa³  de Lucena Barbosa, Jose Etham^1,2 

[1] Univ Estadual Paraiba, Dept Biol, Ctr Ciencias Biol, Lab Ecol Aquat, Campina Grande, Brazil

[2] Univ Estadual Paraiba, Dept Biol, Ctr Ciencias Biol, Lab Ecol Bentos, Campina Grande, Brazil

[3] Univ Fed Rio Grande do Norte, Ctr Tecnol, Dept Engn Civil, Lab Recursos Hidr & Saneamento Ambiental, Natal, RN, Brazil

关键词: Bentonite;    Lanthanum-modified bentonite;    Flocculation;    Microcystin;    Polyaluminium chloride;    Chitosan;    Aluminium sulphate;   

DOI  :  10.1016/j.watres.2019.04.057

来源: Elsevier

【 摘 要 】

Geoengineering techniques have been used to control phosphorus and cyanobacteria in lakes promising greater and quicker chemical and ecological recovery. Techniques that use coagulants and clays to remove particulates and dissolved phosphorus from the water column have received great. In this study, bench-scale flock & sink assays were carried out to evaluate the efficiency of the coagulants aluminium sulphate (SUL), polyaluminium chloride (PAC) and chitosan (CHI), alone and combined with natural bentonite clays (BEN) and lanthanum-modified bentonite (LMB), to remove of phosphorus from a eutrophic reservoir in a semi-arid region of Brazil. In addition, the study seeks to assess the effects on the cyanobacteria density and the intra- and extracellular concentrations of cyanotoxins after the application of these geoengineering materials. The SUL and PAC coagulants effectively reduced the total phosphorus (TP), reactive soluble phosphorus (SRP), turbidity, chlorophyll-a, cyanobacteria density and intracellular microcystin, whereas CHI showed a low removal efficiency. lanthanum-modified bentonite proved to be more effective than BEN; however, the application of the coagulants only was sufficient to successfully remove phosphorus and cyanobacteria from the water column. In addition, the efficiency of the flock & sink technique in cell removal varied among the cyanobacteria species. Small colonial species such as Aphanocapsa delicatissima, Merismopedia glauca and Merismopedia tenuissima were removed regardless of the treatment used, including those with CHI and BEN. As for the filamentous cyanobacteria, Cylin-drospermopsis raciborskii, Geitlerinema amphibium, Planktothrbc agardhii and Pseudanabaena catenata, removal was achieved only using PAC, SUL and LMB alone or when combined. The intracellular concentrations of saxitoxin and cylindrospermopsin and the extracellular fraction of these cyanotoxins and of microcystin were not influenced by the application of coagulants and clays. This indicates that cell lysis did not occur with the addition of the geoengineering materials. These results demonstrate that the flock & sink technique could be used for restoration of eutrophic waters. (C) 2019 Elsevier Ltd. All rights reserved.

【 授权许可】

Free