Effect And Mechanism Of Micro Polluted Raw Water Treatment By Ultrafiltration

With the development of society and living standard improved, people are strict with drinking water quality. However, the microbial security caused by the bio-breeding and leaking in southern part of China, because of its climate character, is threatening people's health. The ultrafiltration is gained more attention for its better permeate water quality. The study includes the following contents: Firstly, the treatment effects and running conditions of ultrafiltration as the last drinking water treatment process. Secondly, specific performance facing to changes of water quality in the south of China. Thirdly, some mechanistic studies of membrane surface under different conditions.Results of long time running of pilot-scale study showed that after pretreatment of the sand filter carbon, the load of ultrafiltration had been largely reduced, such as organics and turbidity. After ultrafitration, the turbidity stabilized at 0.07-0.08NTU, particles over 2μm was less than 10/mL, zooplankton cannot be detected, algal cells is less than 50 000/L, which greatly ensure the biological safety of drinking water. It solved biological explosion in summer in the south of China. After a year of operation, the transmembrane pressure of the membrane had a 6kpa increase, and the specific membrane flux declined 1 L/(m~2·h·kPa).In the pilot-scale study, we found some effection of membrane. In a 90min filter cycle, the removal of water quality changes little, while the membrane flux decreased more than 0.2L/(m~2·h·kPa). Increasing filtration flux, larger particles is easier to be removed and the removal of organics increased slightly. Specific membrane flux decreased more than 0.4 L/(m~2·h·kPa), when the flux increased 40 L/(m~2·h). In low pH condition membrane removed more turbidity and organic matter, while it has a 0.3-0.4 L/(m2·h·kPa) specific flux raise under neutral pH conditions. Water quality was worse without carbon sand filter pretreatment, and the specific flux declined about 0.1 L/(m~2·h·kpa).There are changes on contact angle and roughness of membrane surface under different conditions. We found out that the process of pollutants adsorption on membrane surface is devided into two processes; first, the internal pore pollution, which causes the membrane contact angle increased, hydrophilicity decreased, roughness increased, and more pollutants would be prone to adsorption on it. Then the cake layer would formed. This cake layer becomed thick with filtration. Contact angle decreased on the contrary because of the hydrophilic pollutants in water. And the increasing of membrane roughness was slow down.