| Humic acid, widely existing in water bodies has become one dominant factor for the continual water quality deterioration. Since 1980s, the technologies used for humic acid removal has been developed from conventional water treatment process to the present combination of TiO2 photocatalytic oxidation and membrane separation process. In this study, the removal of humic acid, and the fouling control by the combined TiO2 photocatalytic oxidation and microfiltration (PCO-MF) was stressed with the hope of providing some meaningful advices for the real engineering applications.It demonstrated that humic acid with a concentration of 50mg/L can not be removed completely by 0.2μm MF membrane, and severe fouling formed in the cross flow MF process. On the contrary, humic acid was adsorbed by TiO2 and degraded into smaller molecular weight organic acid under the irradiation of UV light. However, it was very difficult to remove all the degraded organic matter. Meanwhile, another issue of the recycle of TiO2 catalyst was brought up.In this study, it witnessed that the PCO-MF was able to remove color436, UV254 completely and the removal efficiency of TOC could be achieved over 85%. The removal efficiency of humic acid increased with the shortening of the wavelength of UV light and the extension of UV irradiation time. Humic acid was degraded until the complete mineralization into CO2 and H2O. TiO2 can adsorb humic acid and its degraded products to form into aggregated particles, size of which is larger than membrane pores. These aggregated particles were recycled into the feedtank. This study proved that the membrane fouling resulted from humic acid was attributed to the fraction with large molecular weight, which would be degraded gradually with the function of TiO2 photocatalytic oxidation; the fouling was controlled through the transition from irreversible fouling dominant to the reversible fouling dominant, as a result, the permeate flux was improved.
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