Impacts of ultrasound and ozone disinfection of WWTPs secondary effluent

Disinfection is the essential and final process of municipal wastewater treatment plant. The aim of this study was to investigate the impact of ultrasound on ozone disinfection effect. The results showed that combination of ozone and ultrasound can enhance the disinfection efficiency. After ultrasound combined with ozone treatment (US/O-3) for 5min, a 2.51 log reduction of fecal coliform and a 2.24 log reduction of total bacteria were achieved. As the ultrasound power density increased from 0 to 55 W/L, a 2.59 log reduction of fecal coliform and a 2.36 log reduction of total bacteria were achieved. However, as the power density increased to 99 W/L, the increase in the overall efficiency of disinfection was not obvious. Moreover, with frequency at 20 kHz, 28 kHz and 40 kHz, 2.49, 2.58, 2.62 log reductions of fecal coliform and 2.14, 2.46, 2.51 log reductions of total bacteria were achieved, respectively.