Experimental Study On Membrane Bioreactor For Treating Initial Rainwater

With the growing problem of urban non-point source pollution,the harm has been deeply affected people's lives.Rainfall is a major way to cause non-point source pollution.The recycling of rainwater has a high social value,which can alleviate the urban water pressure and reduce the frequency of urban waterlogging.In this study,the stormwater runoff was treated by coagulation sedimentation and A/O-MBR process.The main contents were as follows:(1)During the study period,two rainwater sampling points were set up on the campus which were roof and pavement.It was found that there was obvious initial erosion in the process of rainfall,and the pollution of the rainwater was more serious in the early period.The rainwater quality was basically stable with the prolongation of the rainfall in a certain range.The CODcr and NH4+-N in runoff runoff are higher,and the turbidity and TP in rainwater runoff are relatively high.According to the correlation data analysis,it was found that the turbidity,CODcr and TP in rainwater runoff had obvious correlation.(2)The experimental results were analyzed by SPSS.The results showed that the influence degree of the five factors on the coagulation effect was in the order of coagulant dosage>stirring speed>Coagulant type>PAM dosage>Stirring time.The best experimental scheme of this experiment was as follows:the coagulant was PAC,the dosage of PAC was 30mg/L,the dosage of PAM was 0.2mg/L,the stirring speed was 30r/min,the stirring time was 10min.(3)It was found that,it has a higher rate of membrane flux and membrane pressure change rate under the 0.75L/min aeration than 1.5L/min aeration in A/O-MBR experiment.With the increase in aeration strength,the rate of membrane fouling decreased gradually.The rate of membrane contamination in pumping mode for 8 min was less than that in pumping mode for 9 min.The rate of contamination was increased with the increase of effluent efficiency.In the three initial fluxes,there was a lower membrane contamination rate in the initial flux of 22L/m2·h,with the initial membrane flux increases,the pollution rate gradually accelerated.(4)Through the analysis of membrane pressure and membrane flux,it was found that the main pollution resistance was concentration polarization and the pollution resistance inside the membrane,which accounted for 54.75%and 25.14%of the total resistance respectively.In the cleaning study of the membrane module found that the use of physical cleaning can make the flux recovery more than 80%;use pickling can be restored to 90%;and the use of sodium hypochlorite cleaning,the flux can be restored more than 95%.In the experimental period of more than 2 months of experimental study,it is recommended to use 8min stop 1.5min gas backwash 0.5min mode experiment.