Dissolved Organic Matter Removal And Membrane Pollution Control Of Combined Ultrafiltration Process

Soluble organic matter and membrane fouling control were the key influencing factors for the wide application of ultrafiltration technology in drinking water treatment process. Appropriate pretreatment process can significantly improve the removal rate of the organic matter and effectively control membrane fouling. Static test, dynamic test and combination of production and application were used in the study of the impact on the removal of dissolving organic matter and membrane fouling control using coagulation, sedimentation, filtration as pretreatment unit. The operation parameters of the process unit are optimized. Compared two kinds of raw water, the study explored the effect of the combined ultrafiltration process on two different kinds of water, and then investigate the characteristic of different kinds of pollutant.The coagulation-ultrafiltration process reached the optimal operation while the coagulant dosing amount to 20 mg/L. Dynamic experiments showed the growth rate of the transmembrane pressure up to its minimum when coagulant dosage was 4 mg/L. The optimization of reaction time could improve the floc structure and increase the floc size, thereby improving the removal of organic matter. Study showed that the best flocculation time was 10 min.The particulate and organic matter removal was best at the coagulant dosage of 7 mg/L using coagulation-sedimentation-ultrafiltration process, the deteriorate of membrane flux is more slightly when coagulant dosage was 20mg/L. The research of flocculation time showd that the turbidity and the removal rate of organic matter was best when the flocculation time is 15 min. Shorten the reaction time in a certain extent can reduce contamination of ultrafiltration membrane. Prolonging the settling time can enhance the removal rate of the turbidity and the organic matter and the best settling time was 60 min. Membrane fouling degree of 60 min precipitation time in is the lightest.Research on the Size of 100000 tons/day of coagulation-sedimentation-filter-ultrafiltration combined process(first phase process) and coagulation–short range precipitation-ultrafiltration combined process(second phase process), results show that ultrafiltration driectly after coagulation can effectively reduce membrane pollution. A higher removal rate of organic matter bycoagulation-sedimentation process than phase ii, and the filter for the removal of organic matter had the effect of multiple safeguards.The ultrafiltration unit can significantly improve the removal of organic matter in phase ii. The water after sedimentation process caused serious membrane pollution, and the trans-membrane pressure rosed up to 47 kPa after running 24 h. After filtration that was 34 kPa. It showed that filtering technology can significantly reduce membrane pollution. After running 24 h, the transmembrane pressure rosed up to 17 kPa and 16 kPa respectively after coagulation- part precipitation-ultrafiltration process and coagulation-ultrafiltration process. The difference of membrane fouling is negligible.The experiment compared two kinds of water quality in dongying phase I and phase ii. Test results show that the two kinds of raw water were differences of DOC distribution. The organic matter ratio of first phase water less than 3kPa microns is higher than the second phase of raw water by 31.68%. The organic matter ratio of second phase water in 30 kPa~0.45 microns is higher than the first phase of raw water by 30.85%. The organic matter content and protein substances proportion of the first phase raw water was much more higher than the second phase raw water. The content of the protein-like substance and the humic-like substance of phase second was relatively low. And the proporation of humic-like substance is much more larger than the protein-like substance of the water of the second phase. Study on the particle size and charactrisstic of the two kinds of raw water shows that the protein class material which particle size between 100 kPa~0.45 microns of macromolecular is the main cause of the membrane fouling.