| The essence of activated sludge treatment is that microorganisms decompose pollutants in sewage and transfer them into sludge,resulting in a considerable amount of surplus sludge.Therefore,sludge reduction has become an urgent problem to be solved in the field of sewage treatment.Membrane bioreactor(MBR)combines the characteristics of activated sludge process and membrane separation technology,which has the advantages of low sludge load,small occupation area and high biomass.A~2O MBR is a new type of reactor with simultaneous denitrification and phosphorus removal,which is composed of anaerobic-anoxic-aerobic process combined with membrane separation technology.It has been widely used in the field of sewage treatment,but it still has the problem of high sludge yield.Metabolic uncoupling technology can coupling and destroy the respiratory chain of microorganisms and oxidative phosphorylation in sewage,and reduce the amount of microbial synthesis and the amount of residual sludge under the condition of degrading the same substrate.It has the potential to be widely used in the research of sludge reduction technology.In this study,the advantages of metabolic uncoupling technology and membrane separation technology were combined to study the sludge reduction,and the influence on membrane fouling was investigated at the same time.Subject adopts environment-friendly uncoupler3,3’,4’,5–Tetrachlorosalicylanilide(TCS),combined with A~2O MBR reactor,through the comparative study original A~2O MBR system with daily dosing(system 1),1 mg/L TCS A~2O MBR(system 2)under the same operating conditions of the sewage treatment efficiency,sludge reduction effect and membrane pollution,the main conclusions are as follows:(1)Adding TCS has little influence on the effluent quality of A~2O MBR system.By comparing the effluent water quality of the two system membranes,the removal rates of COD,ammonia nitrogen,TN and TP all showed a slight decrease,which decreased from91%,93%,70%and 77%to 90%,90%,60%and 70%,respectively.The effluent water quality indicators of this test,except TP,all reached the level A standard stipulated in the"Pollutant Discharge Standard for Urban Wastewater Treatment Plant";Since there is almost no sludge discharge in the process of system operation and the SRT is long,the TP removal effect of the two systems is not ideal.TP can be removed by chemical phosphorus removal method in the actual operation of sewage treatment plant.(2)TCS-A~2O MBR has a good sludge reduction effect.Compared with the undosed system 1,the MLSS of the dosed system 2 decreased to 2221mg/L,the average MLSS was about 2514mg/L,the sludge volume was reduced by about 25%,and the average MLVSS of the dosed system 2 was about 1722 mg/L.The MLVSS/MLSS values of the two systems showed an increasing trend,rising from 0.58 and 0.56 to 0.81 and 0.69,respectively,with the mean values being 0.72 and 0.64,respectively,indicating stable operation.The average SV of activated sludge in system 2 is 28%,and the flocculation and settling properties of activated sludge are slightly lower than those in system 1.The average sludge yield of system 1 was about 0.51 mg(MLVSS)/mg(COD),and that of system 2 was about 0.37 mg(MLVSS)/mg(COD),which decreased by about 27%compared with that of system 1.However,the addition of TCS would inhibit the aggregation and combination of bacteria in the mixed solution,reduce the particle size of sludge particles in the system,and cause certain influence on the settling performance of sludge floc.(3)Adding TCS will have certain influence on the biochemical properties of the system mixture and the filter cake layer on the membrane.TCS can promote the release of SMP and EPS in the mixture and filter cake layer of the A~2O MBR system to some extent,and the polysaccharide and protein contents of SMP and EPS in the system 2 were slightly increased compared with the system 1.At the same time,TCS will increase the total resistance of the membrane module,the resistance of the filter cake layer and the resistance of the membrane hole blocking,which will affect the membrane flux and membrane permeability and thus have a negative effect on membrane fouling.(4)Adding TCS has a certain negative effect on membrane anti-fouling ability.By monitoring the variation of the transmembrane pressure difference between the two systems,it can be seen that at the end of the first operating cycle of the membrane components of the two systems,system 1 has been running for 18 days,and system 2 has been running for 15 days.The recoverability of the membrane components of system 2after chemical cleaning is worse,and the growth rate of the transmembrane pressure difference is also faster.At the end of the test,the contaminated membrane filament was observed by scanning electron microscopy,and the surface of the membrane filament was clearly damaged and attached with pollutants.The contamination degree of No.2membrane filament was significantly higher than that of No.1 membrane filament.It can be seen that adding TCS can aggravate membrane fouling to some extent. |
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