Effects of membrane material and pretreatment coagulation on membrane fouling: fouling mechanism and NOM removal

The static adsorption test showed that hydrophobic organics adsorbed much more quickly than hydrophilic organics. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption ratio [C(t)/C(e)] was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions. The rate of flux decline for the hydrophobic membrane was significantly greater than for the hydrophilic membrane, regardless of pretreatment conditions. The pretreatment of raw water significantly reduced the fouling of the membrane. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. After this flux decline, the permeate flux decreased in the pore volume. This implies that all four mechanisms are valid when applying these filtration models. When the pretreatment coagulation applied, the kinetic constants, K-s, K-i, and K-c, showed lower values than UF alone process. Therefore, applying coagulation process before membrane filtration was found to be very effective in fouling reduction as well as critical flux increase due to the increase in particle size. For UF process alone, K-s was lower for the hydrophobic membrane, while K-i and K-c were higher for the hydrophilic membrane. That is, the result showed that decrease in the pore volume, which was caused by the particle deposition into the internal pore, was greater with the hydrophobic membrane than with the hydrophilic membrane.