Abstract:A new miniature system for cleaning RO (reverse osmosis) membranes by using alkaline solution and ultrasonic was set up and used for researching cleaning effect of inorganic and organic pollutants on the RO membrane by continuous monitoring cleaning solution’s conductivity and absorbance. Firstly, we screened the ultrasonic frequency and sound intensity, the result showed that the optimum frequency and sound intensity was 50 KHz and 0.636W cm-2 separately; Secondly, we screened the soaking time and ultrasonic time of the RO membrane, and the soaking time was not less than 60 min and the ultrasonic time was not more than 60 min. Then, under the screened conditions above, we investigated the effects of NaOH solution’s concentrations for cleaning the inorganic and organic pollutants on the RO membrane with this system. The results showed that the procedure of alkaline solution circular cleaning and ultrasound-assisted cleaning had very good efficiency for the inorganic pollutants on the RO membrane; the procedure of alkaline solution circular cleaning had only a little efficiency for the organic pollutants on the RO membrane, but the procedure of ultrasound-assisted cleaning had very good efficiency; the NaOH solution with concentration of 6 mmol L-1 had the best cleaning efficiency for the pollutants on the RO membrane and the elution rate of the dirt was 33%.