The effect of wastewater components on the fouling of ceramic membranes

In this work, the effect of wastewater feed composition on the membrane fouling rate of 5 and 20 kD ultrafiltration ceramic membranes was investigated using statistical analysis of the experimental results (two way factorial design), with particular regard to the protein (meat extract and peptone), sodium alginate and calcium chloride components. A mathematical model was used to determine the major membrane blocking mechanisms and the effect of different feed components concentration on the blocking mechanisms. Polysaccharides are the major fouling compounds in extracellular polymeric substance (EPS), while protein compounds are an important part of EPS membrane fouling, their effect increases in the presence of polysaccharides. Sodium alginate calcium solutions fouled the membrane more severely, causing twice the increase of resistance (on average) than did meat extract calcium solutions. This study showed that irreversible fouling was the major fouling type in alginate calcium filtration experiments, while less of the fouling in the meat extract calcium filtration experiments was irreversible. The effect of changing the artificial wastewater components concentration on the fitting accuracy of the blocking models for the 20 kD pore size membrane was almost the opposite of the 5 kD pore size membrane. Increasing the calcium concentration increased the predication accuracy of the intermediate and complete blocking models, while the increase in alginate concentration reduced the cake filtration model prediction accuracy. After each experiment, the membrane was cleaned using different cleaning chemical concentrations. The best cleaning was achieved with increasing sodium hydroxide concentration in the cleaning solution. In general higher cleaning temperature and increasing cleaning time improved the membrane recovery, nevertheless; the effect was not as noticeable as the effect of increasing sodium hydroxide concentration.