Enhancement of KMnO4 treatment on cyanobacteria laden-water via 1000 kHz ultrasound at a moderate intensity

1000 kHz high-frequency ultrasound at 0.12 and 0.39 W/mL intensity was used to enhance the inactivation of suspensions of Microcystis aeruginosa cells using KMnO4. With 10 mg/L of KMnO4, ultrasound at 0.12 W/mL intensity was found to be effective in inactivating the cyanobacteria within 10 min. A Weibull model was found to describes the inactivation well. Its concave shape shows that some cells have a certain resistance to this treatment. Cytometry and microscopic analysis confirm that the treatment damages cell integrity. Despite that the extracellular organic matter in the water was not significantly increased. The concentration of extracellular cyanobacterial toxins even decreased. The filtered suspension of inactivated cyanobacteria was used to cultivate mung beans, and the suspension did not hinder their germination. This provides a new idea for using cyanobacteria-laden wastewater. These findings suggest a technique for speeding up the oxidation of Microcystis cells using KMnO4 with ultrasound at moderate intensity, which provide new insights into the biological effects of ultrasound.

Automated summary

1000 kHz high-frequency ultrasound at 0.12 and 0.39 W/mL intensity was used to enhance the inactivation of Microcystis aeruginosa cells using KMnO4. Ultrasound at 0.12 W/mL intensity was effective in inactivating the cyanobacteria within 10 min with 10 mg/L of KMnO4. The Weibull model provided a good description of the inactivation, showing that some cells have resistance to the treatment. Cytometry and microscopic analysis confirmed cell damage, while the extracellular organic matter and cyanobacterial toxins were not significantly increased and even decreased. The inactivated cyanobacteria suspension did not hinder the germination of mung beans, suggesting a new idea for using cyanobacteria-laden wastewater. These findings provide new insights into the biological effects of ultrasound.