Hybrid water treatment process of carbon fiber microfiltration and photocatalyst-coated polypropylene beads: roles of humic acid, photo-oxidation, and adsorption

The effect of organic matters on membrane fouling was observed in a hybrid process of tubular carbon fiber microfiltration (MF) and polypropylene (PP) beads coated with TiO2 photocatalyst with periodic water back-flushing for advanced water treatment. Also, the treatment portions of membrane filtration, photocatalyst adsorption, and photo-oxidation were investigated by comparing the treatment efficiencies of (MF), (MF+TiO2), and (MF+TiO2+UV) processes. The periodic water back-flushing was performed during 10 s per 10 min filtration to reduce membrane fouling. As results, the organic matter, such as humic acid (HA), could be one of the main factors affecting membrane fouling, because the resistance of membrane fouling (R-f) increased significantly as increasing HA concentration. The treatment efficiencies of turbidity increased a little; however, those of dissolved organic matters (DOM) increased dramatically as increasing HA. As a result of investigating the roles of membrane filtration, adsorption, and photo-oxidation, the membrane fouling resistance was the minimum, and the final permeate flux was the maximum at (MF+TiO2+UV) process. It means that the photo-oxidation and adsorption could control the membrane fouling in this hybrid water treatment process. In DOM treatment efficiency, the proportion of MF was still very high as 70.5%; however, those of adsorption and photo-oxidation were 4.8 and 2.3%, respectively. It means that the role of adsorption was dominant than that of photo-oxidation to remove DOM in this hybrid water treatment process.