Investigation of One-Step Shear Stress and Moderate Electric Field Combination for Controlling Microcystis Aeruginosa, a Bloom-Forming Cyanobacterium

Harmful algal blooms (HABs) pose significant threats to the contamination of drinking water and the quality of food production. In this study, the effectiveness of the simultaneous treatment of shear stress and moderate electric field (SS+MEF) for controlling the growth of cyanobacterium Microcystis aeruginosa was assessed. SS+MEF (rotational shear at 4000 and 9500 rpm, and MEF of 135 V/cm with 60 Hz) achieved inactivation and growth suppression of the cells after 40 min of treatment over a wide range of temperatures (10–40 °C). Following 72 h of incubation, the SS+MEF treatments reduced M. aeruginosa cell density by 222% relative to the temperature-only control. The impact of SS+MEF on the growth potential of M. aeruginosa was evaluated using the changes in the cyanobacterial pigments, chlorophyll-a (Chl-a) and phycocyanin (PC) after 72 h incubation, which indicated that M. aeruginosa growth was suppressed. Higher SS+MEF treatment temperatures (up to 40 °C) yielded greater inactivation efficiency after 72 h, reflected by a marked decline in pigments and mcyE gene abundance. The results show that M. aeruginosa was successfully inactivated by the electrophysical treatment, demonstrating the potential of such an alternative non-chemical process for water safety control.