Effects of natural organic matters molecular weight distribution on the immersed ultrafiltration membrane fouling of different materials

Effects of natural organic matter molecular weight (MW) distribution in source water on the reversible and irreversible fouling of immersed ultrafiltration membranes of three different materials were systematically investigated using representative sources of natural waters. It was found from the bench-scale tests that the organic matters of the MW lower than 1 K and higher than 30 KDa were the main substances that induced reversible fouling regardless of the materials, and that of MW between 1 K and 5 KDa could cause reversible fouling for polyvinylidene fluoride (PVDF) and polysulfone (PS) membrane. As for the irreversible fouling, small organic molecules of the MW lower than 1 KDa were the main part due to the hydrogen bonds. In addition, the organic matters of MW between 1 K and 3 KDa can induce irreversible fouling for polyvinyl chloride and PVDF membrane. Results of long-term filtration tests showed that PVDF membrane was more vulnerable to small organic molecules due to its high electronegativity substances, and PS membrane had better resistance to organic fouling.