Membranes are an effectivie tool for the removal of particles, microorganisms and organic matter from drinking waters. Compared with conventional treatment methods, membrane processes i) can provide higher quality of water, ii) minimize disinfectant demand, iii) are more compact, iv) provide easier operational control and v) require less maintenance and chemical additions. While there has been an upsurge of interest in membrane filtration process, however, membrane performance can be impeded by membrane fouling caused by concentration polarization, colloidal deposition and scaling on the membrane surface or inside membrane pore matrix. Membrane fouling lowers the economic efficiency of memrbane filtration by reducing permeate flux, shortening membrane life, and increasing of frequency of membrane cleaning.
The term of "self-cleaning" membrane has been used to describe a membrane that can degrade foulant on the membrane surface or that can catalyze reactions that degrade the foulants. Ozone, strong oxidant, can be used for membrane cleaning because it is expected to play a role in oxidizing foulants at membrane surface. Our previous studies have shown that the addition of ozone increases the permeate flux and the increase in the flux was dependent upon ozone gas concentration. The ozone dosage required to maintain the memrbane flux was small compared to that required to completely oxidize the organic matter, thus decreasing the costs associated with ozone production. Moreover, the formation of ozonation by-products such as bromate, aldehydes and biodegradable organic matter which can result in bacterial regrowth in distribuiton system can be reduced at the lower ozone dosage.