Research Of Aerobic Granular Sludge Membrane Bioreactor

Membrane Bio-Reactor(MBR) is a high-efficiency and tight wastewater treatmentprocess that has been rapidly developed and widely used. However, the MBR has two mainproblems during practical application: high cost and membrane fouling. DynamicMembrane Bio-Reactor (DMBR) has also drawn great intention in recent years. Instead ofusing micro filtration membrane, relatively large aperture membrane is used for thesolid-liquid separation, and the sludge cake composed of sludge and EPS plays animportant role in this process. Due to its low cost, the DMBR has high value for researchand application. However, during the membrane filtration process, the filtration substancesare retained or absorbed on the surface of membrane, which would cause membranefouling-the most serious problem greatly impairing the performance of DMBR systems.Aerobic granular sludge was cultivated in sequencing batch reactor(SBR)by reducingsludge settling time, enhancing the setting velocity and increasing COD loading rate,which using floccular activated sludge as seeding sludge．The granules cultivated in theexperiment were nearly spherical or elliptical in morphology. The diameter of granularsludge was in the range of0.5-2.0mm, and SVI and MLSS were41.3,7g/l respectively.Sludge granulation process is composed of the following steps：floecular activated sludgeâ†'activated sludge zoogloeaâ†'initial granulesâ†'mature of granules. Based on the studies ofphysicochemical and biological characteristics of the granules, it could be concluded thatthe formation mechanism of granular sludge was that combined the zoogloea of theactivated sludge with inorganic metal ions format nuclei at the beginning; and thenirreversible adsorption bonding were completed between extracellular polymericsubstances and microorganisms, nuclei gradually grow into the granular sludge inhydrodynamic shear force. The selection pressure due to shorten the setting time acceleratethe process.The treatment performances of an aerobic granular sludge membrane bioreactor,which combined aerobic granular sludge process with submerged nylon-mesh dynamicmembrane bioreactor (DMBR), were investigated, and the influences of operating factorssuch as filtrate flow rate and aeration rate on membrane fouling were studied. In addition,an analysis of the extracellular polymeric substances of sludge in the AGDMBR and theactivated sludge control reactor was performed to investigate into the fouling mechanismin different systems. The results showed that higher removal efficiency of COD andammonia and lower membrane fouling were achieved in AGDMBR than in DMBR with the water turbidity at6,and the average removal rates of COD, ammonia nitrogen at91%,95%, respectively. In terms of the effect to membrane fouling by operating processparameters of AGDMBR system, the results showed that the flow rate and membranefouling time was positively correlated. The membrane flux lasted longest at the flow rateof20L/h and the best aeration rate was125-150L/h for the AGDMBR. AGDMBR systemwas better controlling membrane fouling which resulted from the deposit on membranepore than that of DMBR.