Micro fine particles deposition on gravity-driven ultrafiltration membrane to modify the surface properties and biofilm compositions: Water quality improvement and biofouling mitigation

Micro fine particles (micro fine powdered activated carbon (MFPAC) or micro fine powdered zeolite (MFPZ)) were deposited on hydrophobic polyvinylidene fluoride (PVDF) membrane to enhance gravity-driven ultrafiltration performances. A distinct flux attenuation and permeate quality difference were observed between pristine and deposited membrne systems. The results indicated that both MFPAC-PVDF and MFPZ-PVDF membranes exhibited a high pure fluxes, a gentle flux downward trend and a high stable permeate flux compared to the pristine PVDF membrane. Additional, compared to the pristine membrane, the deposited membrane systems exhibited a significantly enhanced removal of TOC, NH4+-N, and TN (increased by 48%, 93% and 22% for the MFPAC-PVDF membrane, by 18%, 89%, and 20% for MFPZ-PVDF membrane). The improved performance of deposited membranes were attributed to both the changed initial surface properties and the subsequent biofilm characteristics. Owing to the presence of MFPAC and MFPZ filtration layer, the enhanced hydrophilicity due to the introduction of surface -C-O and -OH groups, as well as the decreased free energy of adhesion between membrane surfaces and foulants, impart deposited memrbanes promising potential of permeability improvement and fouling mitigation. Furthermore, the biofilm amounts and compositions of deposited membranes were also significantly influenced, presenting a reduction of accumulated organic compounds by 40 and 50%, repectively, compared to the pristine membrane, contributing to alleviated membrane fouling. The MFPAC could function as a live bacteria incubator, resulting in a higher bacteria bioactivity and enhanced degradation in the biofilm layer. While The MFPZ was in favour of hydrophilic protein cover to form a hydration shell on biofilm surface, helping to prevent the approach of hydrophobic foulants.