Effect of ozone and permanganate on algae coagulation removal--pilot and bench scale tests

Both pilot and laboratory scale experiments are conducted to compare the effect of ozone and permanganate preoxidation on algae removal by alum coagulation. Both appropriately dosed preoxidants are shown to be beneficial to algae coagulation removal. This may be attributed to a decrease in cell stability; however, overdosing may cause cell lysis and the release of organics, which could interfere with algae cell coagulation. The presence of calcium further enhances the beneficial effect of preoxidation on algae coagulation; however, this phenomenon is more significant for using permanganate than ozone. It is speculated that this is due to the fact that the positively charged calcium ions can serve as bridges to hold the negatively charged MnO(2) and algal cells together. Further, this behavior also explains the superior performance of permanganate preoxidation compared to that obtained using ozone for algae coagulation removal in pilot testing, as the source water contains high calcium content.