Study on pretreatment process of scale inhibition to reverse osmosis membrane

Reverse osmosis (RO) process is the most widely used method in the treatment of high mineralized mine water, but membrane fouling has been restricting the further development of RO process. During the RO treatment of high mineralized mine water, the scale pollution is easy to occur on membrane surface, which leads to the decrease of water production efficiency and service life of RO membrane. In this work, the control effects and operating cost of scale inhibitor pretreatment and electronic scale inhibitor apparatus pretreatment on RO membrane scaling were investigated respectively by simulating the component of high mineralized mine water and using the full cycle experiment method. And the SEM of RO membrane cross section under different pretreatment conditions was analyzed. The results showed that when the RO process was used to treat the simulated high mineralized mine water solution under the condition of no pretreatment, the RO membrane could be seriously polluted by scaling, and the membrane cross section thickness could reach 133 μm that was significantly higher than clean membrane cross section thickness (115 μm) after 17 hours. Using scale inhibitor and electronic scale inhibitor apparatus for pretreatment, the scale pollution of RO membrane could be well controlled, and the desalination rate was all above 90%. Compared with the electronic scale inhibitor apparatus pretreatment, the scale pollution degree of RO membrane was the lightest under the condition of scale inhibitor pretreatment. After 17 hours, the membrane flux was only decreased by 18.74%, and the membrane cross section thickness (118 μm) was closer to that clean membrane cross section thickness (115 μm). However, when the scale inhibitor was used for pretreatment, if the RO membrane was not cleaned after the RO equipment shut down, the scale inhibitor could remain on the membrane surface and affect the membrane separation performance. When electronic scale inhibitor apparatus was used for pretreatment, the separation performance of RO membrane was hardly affected by equipment shut down, and the operating cost per ton of water was significantly lower than that of scale inhibitor pretreatment.