Removal Of Typical Pollutants In Drinking Water By Nanofiltration

The accuracy of nanofiltration Membrane filtration is between reverse osmosis and ultrafiltration, its unique nano-scale aperture make the work pressure low, has ion selectivity characteristics and be widely used in the field of drinking water treatment.The study focuses on the performance of removal of conventional pollutants and typical pollutants in drinking water, as well as influencing factors, and operating parameters optimization. The changes of pH, turbidity, permanganate index, conductivity and UV2 54 were studied by the experiment of removal of conventional pollutants. The results show that the pH is near neutral after the raw water filtered through the nanofiltration membrane and the water which pH between 6.2-6.7 treated by nanofiltration water comply with standards. The removal of UV₂₅₄ and ions by nanofiltration maintain highly efficient and stable, the UV₂₅₄ is below 0.002, the rate of desalination is about 90% and turbidity is about 0.1NTU after treatment, and nanofiltration membrane can remove 40%-50% of the permanganate index.We chose the chloroform, bromate and nitrobenzene as typical pollutants to research the performance of nanofiltration membrane. The study found that although the molecular weight of three kinds of material are very close, the removal rate of nanofiltration membranes is of great difference, the removal rate of chloroform is only 50%, nitrobenzene is 70% and bromate is higher than 90%. And the nature of contaminants also affected the performance of nanofiltration membranes. Through the study of affecting factors, we found that the ions in raw water have negative effect on the performance of nanofiltration membranes and when the ion concentration is elevated, the removal rate of substances has declining trend. And the presence of natural organic matter in water will promote the separation of organic matter, so that the removal rate of chloroform and nitrobenzene increased. And temperature has an impact on the performance of separation, the rising of temperature leads to increased flux of salt, and the removal rate of pollutants is decline.The work stress and recovery rate of nanofiltration has a great impact on the cost of water but has little effect on the separation performance of nanofiltration membrane. Reduce the work pressure, the rate of removal of some organic matter decline, while the removal of inorganic ions was not affected. Recovery rate has a significant impact on the performance of nanofiltration membrane, when the recovery rate increased, the rate of removal of various pollutants decreased. Study suggests that working pressure 0.4 MPa, recovery rate 50% is practical.