TheDestruction of Cyanobacterial Peptide Toxins by Oxidants Used in WaterTreatment

ReportNo WSAA 110

May 1996




Initialstudies carried out by the Australian Water Quality Centre into the effect ofwater treatment on the removal of cyanobacterial peptide toxins showed thatsome oxidants were effective in destroying peptide toxins. It was demonstratedthat chlorine, permanganate and ozone rapidly oxidised the toxins undercontrolled conditions whereas monochloramine, hydrogen peroxide and peroxide/UVhad very little, if any effect in reducing toxin concentrations. It was alsofound that the reactions of chlorine with the peptide toxins was pH dependant.


Thisproject extended upon the work already covered to give a more detailed andcomplete study of oxidants which included chlorine, monochloramine,permanganate, ozone, peroxone, and hydrogen peroxide. Their effects on livematerial in particular were investigated along with the effect of pH on thereaction of the oxidants with the peptide toxins. For completeness, methods andresults from the previous study are included in this report.


Aswith the reaction of chlorine it was found that pH also had an effect on thereaction of ozone with the peptide toxins. In contrast pH had little effect onreactivity involving potassium permanganate and hydrogen peroxide. Livecultures of toxic Microcystisrequired increased doses of chlorine and ozone to oxidise toxins due to theoxidant demand of the sample. Potassium permanganate was not effective indestroying toxins in samples containing live cyanobacteria as it could notreadily access intracellular toxin, presumably because cell lysis by the actionof permanganate was relatively slow.


Arelative rate study of the oxidants under investigation resulted in thefollowing order of oxidising ability: peroxone >ozone>>permanganate>chlorine>>hydrogen peroxide ormonochloramine.


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