Evaluation of pre-oxidation drinking water treatments for the removal of cyanotoxins produced by Microcystis aeruginosa
Start Date
23-5-2022 5:45 PM
End Date
23-5-2022 7:00 PM
Abstract
Occurrence of cyanobacterial blooms in freshwaters is increasing worldwide, affecting their water quality and ecosystems. Since these blooming events may be associated with the presence of cyanotoxins, their occurrence in freshwater reservoirs intended for drinking purpose may pose a serious threat for human health. In Italy, pre-oxidation of raw water with oxidants containing chlorine is a common practice within drinking plants to inactivate harmful organisms as Cyanobacteria, nevertheless their efficiency towards cyanotoxins is still debated. Here, two chlorine-based oxidants commonly used in Italian drinking water plants were tested on cultured Microcystis aeruginosa, and their effectiveness in removing cells and cyanotoxins was evaluated at increasing concentrations and exposure time. Both treatments were found to efficiently remove intracellular toxins from cyanobacterial biomass, especially at higher doses, whereas no major differences were observed when increasing exposure time. Nonetheless, a simultaneous increase of cyanotoxins in the extracellular fraction was observed, suggesting their possible release from cells to water. According to the treatment applied, different fate for toxins and unknown secondary metabolites was observed. Considerations for improvements of drinking water treatment to ensure safety and high quality standards of the final product are suggested, and innovative oxidant treatments to degrade cyanotoxins are discussed.
Evaluation of pre-oxidation drinking water treatments for the removal of cyanotoxins produced by Microcystis aeruginosa
Occurrence of cyanobacterial blooms in freshwaters is increasing worldwide, affecting their water quality and ecosystems. Since these blooming events may be associated with the presence of cyanotoxins, their occurrence in freshwater reservoirs intended for drinking purpose may pose a serious threat for human health. In Italy, pre-oxidation of raw water with oxidants containing chlorine is a common practice within drinking plants to inactivate harmful organisms as Cyanobacteria, nevertheless their efficiency towards cyanotoxins is still debated. Here, two chlorine-based oxidants commonly used in Italian drinking water plants were tested on cultured Microcystis aeruginosa, and their effectiveness in removing cells and cyanotoxins was evaluated at increasing concentrations and exposure time. Both treatments were found to efficiently remove intracellular toxins from cyanobacterial biomass, especially at higher doses, whereas no major differences were observed when increasing exposure time. Nonetheless, a simultaneous increase of cyanotoxins in the extracellular fraction was observed, suggesting their possible release from cells to water. According to the treatment applied, different fate for toxins and unknown secondary metabolites was observed. Considerations for improvements of drinking water treatment to ensure safety and high quality standards of the final product are suggested, and innovative oxidant treatments to degrade cyanotoxins are discussed.