The Destruction of Cyanobacterial Peptide Toxins by Oxidants Used in Water Treatment
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No WSAA 110
Initial studies carried out by the Australian Water Quality Centre into the effect of water treatment on the removal of cyanobacterial peptide toxins showed that some oxidants were effective in destroying peptide toxins. It was demonstrated that chlorine, permanganate and ozone rapidly oxidised the toxins under controlled conditions whereas mono chloramine, hydrogen peroxide and peroxide/UV had very little, if any effect in reducing toxin concentrations. It was also found that the reactions of chlorine with the peptide toxins was pH dependant.
This project extended upon the work already covered to give a more detailed and complete study of oxidants which included chlorine, monochloramine, permanganate, ozone, peroxone, and hydrogen peroxide. Their effects on live material in particular were investigated along with the effect of pH on the reaction of the oxidants with the peptide toxins. For completeness, methods and results from the previous study are included in this report.
As with the reaction of chlorine it was found that pH also had an effect on the reaction of ozone with the peptide toxins. In contrast pH had little effect on reactivity involving potassium permanganate and hydrogen peroxide. Live cultures of toxic Microcystis required increased doses of chlorine and ozone to oxidise toxins due to the oxidant demand of the sample. Potassium permanganate was not effective in destroying toxins in samples containing live cyanobacteria as it could not readily access intracellular toxin, presumably because cell lysis by the action of permanganate was relatively slow.
A relative rate study of the oxidants under investigation resulted in the following order of oxidising ability: peroxone, permanganate, chlorine, hydrogen, peroxide or mono-chloramine.