Impacts of Potassium Permanganate and Powdered Activated Carbon on Cyanotoxin Release

Bench‐scale trials were performed to (1) expose Microcystis aeruginosa cells to potassium permanganate (KMnO 4 ) doses of 1, 3, and 5 mg/L at contact times (CTs) of 15, 30, and 90 min, pH levels of 7 and 9, and turbidities of 0.1, 5, and 20 ntu, respectively; (2) compare the impacts of oxidation alone and oxidation plus powdered activated carbon (PAC) for the final 60 min of CT; and (3) evaluate the impact of these treatment conditions on extracellular microcystins (MCs), extra‐plus intracellular (combined) MCs, cell membrane integrity, and chlorophyll a concentrations. Toxin releases from the cells were observed at both pH levels. The greatest toxin releases were observed at the lowest KMnO 4 doses. The toxin releases were accompanied by relatively stable total cell counts, increases in membrane‐compromised cells, and decreases in chlorophyll a. The application of 10 mg/L PAC resulted in extracellular toxin concentrations that were markedly lower than those observed in oxidant‐only situations.