[Membrane fouling control in a free-end comb-like hollow fiber membrane bioreactor]

A free-end comb-like hollow fiber membrane bioreactor was applied to treat wastewater. The results clearly showed that membrane fouling, defined as permeate flux decline, was greatly influenced by membrane module configuration. The permeate flux decline was much less for module b, demonstrating the superiority of module b over module a. Its permeate flux could be maintained in the range of 4.0 to 8.0 L x (m2 x h)(-1) under the operating conditions that temperature was 22-26 degrees C, the mixed liquor suspended solids (MLSS) concentration was 7500-10500 mg/L, aeration intensity was 200 L/h, suction time/ suspended time ratio was 9 min/1 min and suction pressure was 0.02 MPa. As this novel kind of membrane module resulted in high air scouring efficiency, relatively low aeration intensity was needed for the MBR maintenance. In addition, the permeate flux varied a little when suction time/ suspended time ratio changed from 12 min/1 min to 6 min/1 min. The performances of several different cleaning methods were tested and the results indicated that water cleaning + chemical cleaning + ethanol soaking had the best cleaning efficiency. SEM images clearly showed that the membrane surface became cleaner and the membrane holes became more visible after water cleaning + chemical cleaning, compared with water cleaning solely.