By-Products Formed in the Destruction of Algal Toxins by Oxidants such as Chlorine
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No URAA 129
Previous studies carried out at the Australian Water Quality Centre showed that chlorination was effective in oxidising and thus removing acute toxicity of cyanobacterial peptide hepatotoxins as determined by HPLC and mouse bioassay. Although acute toxicity was removed, it was not known whether the by-products from chlorination of the hepatotoxins were capable of producing subacute toxic effects. The aim of this project therefore was to determine the by-products produced from the chlorination of microcystins and to assess their potential toxicity.
A range of toxin producing and non-toxin producing cultures of Microcystis aeruginosa were chlorinated to determine the effect on measures of toxicity. The more common disinfection by-products as well as total halogenated organic components were also measured. Toxicity of the cultures was monitored via specific and non-specific toxicity assays such as the mouse bioassay, HPLC analysis, protein phosphatase inhibition assay and Ames mutagenicity assay in order to determine any trend between acute or subacute toxicity and chlorination of the toxin producing Microcystis cultures.
Protein phosphatase inhibition decreased after chlorination in strains of Microcystis which produced toxin. This was consistent with the elimination of acute toxicity in mice and HPLC analysis results. No correlation could be made between the results of Ames mutagenicity testing and the presence of microcystins. There was also no recognisable trend between any of the toxicity assay results and the presence of chlorinated disinfection by-products. It was found that chlorination of the various Microcystis cultures yielded similar chlorinated by-products. However different ratios of these compounds were found which implies the presence of different organo-halogen precursors in some strains.