Application Of High Performance Ultrafiltration Membrane In Drinking Water Purification

In recent years, global water faced with crisis of pollution and shortage for human activities becoming more frequently. Water problem is much serious in our country, and the safety of drinking water has been a serious threat. At present, water treatment technology applied in most waterworks is the first generation technology (coagulation sedimentation-sand filter filtration-chlorine disinfection) and the second generation technology (the first generation technology+ozone-granular activated carbon) which can not conquar the chanllages we now have suffered. Ultra filtration technology, which has many excellent merits such as small area covered, high degree of automation and good water quality, is now gaining more and more attention.Ultrafiltration process includes submerged membrane filtration (SMF) and continuous membrane filtration (CMF) which has been widely used in area of purification drinking water. However, the problems such as high running cost and short circle of membrane and so on which lead membrane fouling have hindered application and development of membrane. So the membrane fouling and cleaning have been becoming an important research topic in the field of membrane application.The hollow fiber ultrafiltration membrane made from polyvinylidene fluoride that prepared by complex Thermally Induced Phase Separation was applied in this experiment. CMF and SMF processes were used to purify drinking water. The permeate flux, the influence of cleaning process on CMF membrane fouling, the influence of concentration ratio on SMF membrane fouling, the chemical cleaning process and the analysis of economic value was evaluated in this experiment.The optimal parameters of CMF were found to be 4.3～4.8m3/h backwashing velocity,0.027m3 total backwashing water,15～18m3/h aeration velocity, and 0.2-0.25 m3 total aeration volume. The SMF experiment showed that the longer the permeate time (i.e. concentration tatio) is, the faster the pollution rate is, and while concentration ratio increased, pollution rate increased quickly first and then slowly. It is found that the best running flux of CMF and SMF are 80 and 30-40L/m2h through membrane flux testing. While the permeate of CMF and SMF is about 180m3/m2, the membrane performance would be stable. The CMF process energy consumption is 0.063 kwh/t and water recovery rate is more than 98%. The SMF process energy consumption is 0.05 kwh/t.The chemical cleaning experiment shows that sodium hypochlorite can satisfy the requirements of daily cleaning, and sodium hypochlorite and citric acid can thoroughly clean membrance if the two was used timely. When sodium hypochlorite was used as cleaning agent,40 mins of CMF membrane component cleaning can satisfy the requirements. The SMF module could be cleaned by back washing and then dipped in water 30mins.The permeate qualified high quality which is better than national drinking water health standards, and was not affected by turbidity of upstream water and stabilized under 0.1 NTU.