Study On Membrane Fouling In Dynamic Membrane Bioreactor Under The Synergistic Control Of Particulate Matter And Chitosan

Dynamic membrane bioreactor(DMBR)is a sewage disposal technology combining biological process of wastewater treatment and dynamic membrane filtration technology,which uses materials like certain pore sized non-woven fabrics and nylons as membrane base material to achieve the approximate filtering effect of microfiltration membrane through the biodynamic membrane formed in the process of the activated sludge filtration,and at the same time the organic matter in the wastewater can be degraded by the dynamic membrane microbial population.Membrane Fouling is inevitable in DMBR,therefore,much more study focuses on how to slow the membrane fouling through adding particulate matter to DMBR to improve sludge mixture than that of membrane fouling in dynamic membrane bioreactor under the synergistic control of particulate matter and chitosan.This study provided experimental basis for the engineering practice of dynamic membrane pollution control by delaying dynamic membrane fouling through the synergic control of particulate and chitosan.The experiment was conducted in a one-piece DMBR to further study the crucial problems that caused the dynamic membrane fouling.It mainly observed how the dynamic membrane fouling was affected with different membrane base materials,particulate matter,and when particulate matter and chitosan were applied synergistically.Also the reactor,sludge mixed liquor,mathematic model were analyzed to figure out how they worked in controlling membrane fouling.The research included:(1)By two parallel reactors,two different base-materials(non-woven fabric and nylon)were compared how they reacted to the operating characteristics,extracellular polymer(EPS)and the contamination cycle.It turned out,in non-woven fabric,the average COD,TN,NH4+-N,TP in the effluent water were 28.40,6.24,2.99,0.67(mg/L)while in the nylon it was 23.23,5.48,2.89,0.45 respectively.Furthermore,dynamic membrane on the surface of the nylon fabric could intercept the contaminant effectively to prevent osmosis to inner layer.As nylon was hydrophilic,it slowed down the accumulation of hydrophobic materials on the surface and formed a loose sludge layer,which prolonged the operation time of DMBR.(2)Two parallel DMBR experiments were conducted,with modified fly ash and powdered activated carbon,PAC added,to observe how the sludge mixture and the operation period were affected in the DMBR,and explore its mechanisms.The results showed that during the operation,in the DMBR with modified fly ash and PAC added,EPS increased from 28.66,27.85 to 100.4,67.5mg/g,Zeta potential declined from-6.3,-5.7 to-46.8,-30.0,the percentage of particles less than 10 microns was 0.92%,0.06%,and the viscosity grew from1.89,1.85 m.Pas to 2.92,2.35 m.Pas respectively.And in addition,in DMBR added with PAC,the operation time was prolonged 1/3 more than in that added with modified fly ash,PAC worked better than modified fly ash in postponing dynamic membrane fouling.Both PAC and modified fly ash had very good adsorption function,could absorb contaminants efficiently,and improve the sludge mixed liquor significantly.Dynamic membrane fouling was delayed due to the ?skeleton effect‘ of the two base-materials.(3)Chitosan and particulate matter were put to DMBR at the same time to study how effective they were in postponing dynamic membrane fouling.Mathematical model based on routine indexes and sludge performance indexes were established and the synergistic control of particulate matter and chitosan that took in membrane fouling was analyzed.The effluent quality in the reactor reached the standard A according to GB18918-2002 after both particulate and chitosan were added,and the TN,TP removal rate was 5%,10% higher than that with only particulate matter being added.EPS grew slowly and the polysaccharide contributed less than protein in DMBR pollution(rp=0.895,rp=0.992).The other indexes of sludge properties(pore,EPS,sludge properties,Zeta potential),after both particulate matters and chitosan were added,performed better than when particulate matter was added only.By establishing mathematical model,the results of analog computation showed that(when R~2=0.9943,R~2=0.9873 R~2=0.9869 R~2=0.9916)in the A/O-DMBR process,when particulate matter chitosan was added,it worked better in slowing down the clogging of the deposition layer of membrane fouling than when only particulate matter was added.