Degradation of Microcystins by UV in the Presence of Low Frequency and Power Ultrasonic Irradiation

Microcystins (MCs), produced by cyanobacteria(blue-green algae), are one of the most hazardous hepatotoxic toxins found in natural environment. Under the background of algae removal and growth inhibition by ultrasonic irradiation and microcystins degradation by Ultraviolet(UV) radiation, experiments were conducted to investigate the degradation of microcystins in order to evaluate the efficiency and feasibility of the combined ultrasound-UV catalytic system for purification of microcystins polluted water. The results showed that compared with the treatment using UV radiation and ultrasonic individually, the combined ultrasound-UV system could significantly enhance the degradation effect. In the combined process, the removal efficiency of Mc-LR and Mc-RR reached 20% and 18% respectively in the first 20 min and approximately 100% in 120 min of irradiation. When the water surface was covered with blue-green algae, the algae would removal after ultrasonic irradiation at 20 kHz and 2W. Furthermore, the concentration of Mc-LR and Mc-RR were 2% and 3% up but would decrease to nearly 0mg/L with subsequently UV irradiation. The results demonstrate that the combined ultrasound-UV provides an effective technology for the removal of microcystins from drinking water supplies.