Studies on cleaning the polyvinylchloride ultrafiltration membrane fouled by sodium alginate

Hydrophilic natural organic matter, which is primarily composed of polysaccharide-like substances, has been found by some researchers to be the main foulant in ultrafiltration surface water. Sodium alginate, one kind of polysaccharide, was selected as model hydrophilic natural organic matter to investigate the fouling characteristics of a (polyvinylchloride) ultrafiltration membrane and the efficiency of cleaning the membrane fouled with sodium alginate. The permeate flux profile and the slight decrease in sodium alginate rejection resulted from the concentration polarization. Hydraulic flushing and chemical cleaning methods, under different cleaning conditions, were used separately to clean the fouled membrane. The results showed that most of the sodium alginate on the polyvinylchloride membrane can be removed by physical cleaning, which indicated that the fouling was highly reversible. Three chemical cleaning operating parameters, i.e. NaOH concentration, temperature and cleaning time, had significant influences on cleaning efficiency. During chemical cleaning, the flux recovery rates were over 100%, which were assumed to be the results of membrane surface modification caused by NaOH cleaning.