Evaluation of sequential dosing of potassium permanganate for microcystin‐LR removal

Abstract

Permanganate can be scavenged by dissolved organic matter (DOM), which decreases microcystin (MC) removal efficiency, and permanganate attack on cyanobacterial cells can damage cells, resulting in the release of additional MCs. Here, the impact of sequential permanganate doses on MC‐LR removal in the presence of two DOM isolates (terrestrial‐ and algal‐derived) was examined. Although sequential permanganate dosing reduced the competition for permanganate from each DOM isolate, the overall MC removal efficiency was not as high when multiple smaller doses of permanganate were applied compared to one single dose. Potassium permanganate was not observed to lyse Microcystis cells up to 10 mg L−1. Sequential permanganate dosing did not alter the extent of lysis observed for a model bacterium. Mathematical simulations of permanganate oxidation in the presence of DOM suggested that sequential dosing would be most beneficial for enhancing MC‐LR removal when a small portion of highly reactive DOM exists.

Introduction to the topical collection on harmful algal blooms

“…Potassium permanganate has been identified as an oxidant of interest, but dissolved organic matter can affect its ability to oxidize microcystins. Hurd et al (2023) presented an evaluation of a sequential permanganate dosing strategy to potentially decrease the competition of dissolved organic matter for permanganate oxidant, minimize cell lysis to avoid release of additional microcystins, and oxidize microcystins. Findings of this study concluded that sequential dosing was less effective at oxidizing microcystins compared with a single higher dose, but that this strategy may be effective in source waters with low concentrations of highly competitive organics.…”