Effect Of Activated Sludge Form On Membrane Fouling In MBR System

Membrane bioreactor (MBR) is a newly developed process widely used in thefield of water treatment, which is combined membrane separation technology withconventional activated sludge. However, membrane fouling is a perdurableimpediment so far during the application of MBR. Aerobic granular sludge isinoculated into MBR system to develop membrane-granular sludge bioreactor(MGSBR) with the purpose of controlling membrane fouling in this study. TheMGSBR feasibility to treat synthetic wastewater, characteristics of aerobic granularsludge and the impact of different sludge structure on membrane fouling are deeplyinvestigated. Based on these investigations, the results are shown as follows.1. MGSBR system with aerobic granular sludge domesticated from anaerobicgranule had good removal performance of COD from synthetic wastewater withoutsludge discharge. COD removal efficiency amounted to about 95%. However, itsnitrification and denitrification ability should be improved by optimizing operatingconditions.2. The color of aerobic granular sludge changed from gold-yellow or yellow togrey-white and dark-yellow during the period examined. The mean diameter ofaerobic granular sludge decreased and its settling ability deteriorated with time inMGSBR. Its microorganism members changed after added to MGSBR system.3. For aerobic granular sludge in MGSBR system, the concentration of activeorganic matters and OUR declined. Compared with floc sludge MBR system, VSS/SSof aerobic granular sludge was higher than that of floc sludge, but lower in OUR.4. The mass of SS as well as colloids and dissolved matters on/in membranesurface increased with time in MGSBR system. SS absorbed on the membrane surfacemainly derived from floc sludge produced in MGSBR.5. SS and colloids in mixed liquid were the main foulants in MGSBR. The orderof relative contribution rate to membrane fouling was SS, colloids and dissolvedmatters within the first 10 min. Then it changed after 480 min, to the order of colloids,SS and dissolved matters at the end of period examined. The relative contribution rateof dissolved matters was less than SS and colloids.6. Membrane flux could be recovered to nearly 100% with acidic cleaningfollowed by NaClO cleaning. Chemical cleaning was necessary for the removal ofsoluble organic matters and colloids from membrane surface.7. The main foulant in MGSBR system was different from floc sludge MBR. InMGSBR system, SS was the main foulant within 10 min filtration, but colloids at theend of period examined. SS was the eternal matter during the period examined for thefloc sludge MBR.