Citation:

Dugan, N., S. Smith, A. Boegehold, AND J. Lu. The Impact of Algicide Exposure on Cyanobacterial Responses to Oxidation. 17th Annual EPA Drinking Water Workshop, Cincinnati, Ohio, August 31 - September 02, 2020.

Impact/Purpose:

Drinking water treatment personnel, practicing engineers, state primacy agency personnel, and EPA regional office personnel are the target audience for this presentation. Information in this presentation will inform day-to-day treatment decisions, process design/selection decisions, and the review of regulatory compliance documents.

Description:

A series of bench-scale trials evaluated the impacts of CuSO4 and KMnO4 exposure on suspensions of toxin-producing Microcystis aeruginosa at CuSO4 doses of 0, 0.1, 0.5, and 1.0 mg Cu/L; and pH levels of 6, 7, and 8. Cell suspensions were exposed to CuSO4 for 24 hours, followed by 1.5 hours of KMnO4 exposure. Algicide exposure during the first 24 hours was associated with decreases in combined (intra+extracellular) microcystins and increases in extracellular microcystins. The magnitudes of observed changes in microcystin concentrations tended to increase with increasing pH and CuSO4 concentrations. During the final 1.5 hours, suspensions exposed only to CuSO4 exhibited stable to decreasing extracellular microcystins and stable to increasing combined microcystins. The magnitudes of declines in the extracellular/combined MC ratio tended to increase with increasing pH and algicide doses. By contrast, suspensions that had been exposed to both CuSO4 and KMnO4 tended either to larger increases or smaller decreases in extracellular MCs. Cell suspensions exposed to both KMnO4 and CuSO4 also exhibited outright decreases in combined MCs. Strong and statistically significant correlations were observed between microcystin concentrations and extractive chlorophyll-a, in vivo chlorophyll-a, and in vivo phycocyanin.

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