Mitigating Cyanotoxins in Drinking Water Treatment

The frequency and magnitude of blue-green algae blooms have been increasing internationally and throughout the US.  This has resulted in a greater concern regarding the environmental, public health, and water quality impacts due to the growth of harmful algal blooms (HABs).  In order to protect human health, the WHO has issued drinking water guidelines for microcystin of 1.0 ppb and the US EPA has included microcystin in the contaminant candidate list 4 (CCL4).  Additionally, several state EPA agencies have implement their own finished drinking water guidelines, with some as low as 0.3 ppb.  This has challenged drinking water treatment plants (DWTP’s) with optimizing their treatment process to comply with current and future regulatory limits, while also ensuring a safe and quality product for their customers.

This presentation discusses the efficacy of permanganate preoxidation in mitigating the impact of microcystin toxins during drinking water treatment. As a first barrier during drinking water treatment, permanganate preoxidation can 1) remove extracellular microcystin toxins and 2) improve the performance of subsequent treatment processes. Permanganate has been shown it to be very effective for the destruction of extracellular cyanotoxins, and kinetic degradation rates are well understood. In addition, at the permanganate doses used for drinking water treatment (e.g 0.1-3.0 mg/L), research has that cell lysis does not occur. Finally, permanganate preoxidation has been observed to enhance the coagulation and removal of intact cells, which improves drinking water treatment performance and reduces risk of cell breakthrough. Both an overview of academic literature and results from jar tests using samples of active blue-green algae blooms will be presented. The application of permanganate will be presented in the context of multiple barriers designed to minimize the risk of microcystin breakthrough during drinking water treatment.