High frequency ultrasonication enhances iron-catalyzed sulphate inactivation of Escherichia coli and Staphylococcus aureus

The ability of high frequency ultrasonication to improve sulphate radical-based water disinfection was investigated in the laboratory. Low doses of potassium persulfate and zero-valent iron inactivated Escherichia coli (5.74 log) and Staphylococcus aureus (4.82 log) within 40 min when supported by 600 kHz ultrasound applied at 3.09 W/mL. That was far better than the removal with potassium persulfate and iron alone, since neither PS nor Fe0 showed any killing effect on bacterial cells. Ultrasound at 3.09 W/mL was twice as effective as ultrasound at 6.81 W/mL with both bacteria. Nonlinear double Weibull and modified Hom models fitted the data well, showing an initial lag in the rate. SO4•ˉ made a greater contribution to the inactivation than •OH, but both induced cell lesioning, leakage and intracellular oxidation. The delivery effect mediated by 600 kHz ultrasound may promote the intracellular oxidation toward bacteria inactivation. Avoiding consumption by other competing impurities in water, further development should focus on the improvement of the utilization of SO4•ˉ generated for more efficient delivery for intracellular oxidation in water disinfection applications