Study On The Municipal Sewage Treatment With Submerged Membrane Bioreactor

The purposes of this article were to determine the optimal parameters and models of municipal sewage treatment with submerged membrane bioreactor(SMBR). Feasible methods to alleviate membrane fouling were established by analyzing the course of membrane fouling.Practical projects can be directed with the experiment results.On basis of design,installation and debugging,sequent experiments on municipal sewage treatment with SMBR had been planned and carried out.Thus the conclusions were listed as follows:When MLSS was 4000mg/L,DO was beyond 3mg/L and HRT was 6h in the experiment,the COD_cr,BOD₅,NH₃-N,TP and SS removal efficiency was 73.6%～88.1%,88.6%～93.5%,30.8%～98.5%,21.9%～83.3%and beyond 99%, respectively.The removal of COD_cr,BOD₅,NH₃-N and TP mainly depended on the biodegradation,but the effluent SS was almost zero due to effective rejection of the membrane module.With the study of raw water quality,MLSS,HRT and water temperature,it was therefore found that the concentration of effluent COD_crdeclined with the increase of the concentration of inflow COD_cr.The concentration of effluent COD_crwas beyond 50mg/L when the concentration of inflow COD_crwas beyond 350mg/L.The concentration of effluent COD_crgradually declined along with the increase of MLSS, till which up to 3200mg/L.Along with the increase of HRT,the influence of HRT on the removal of COD_crenhanced firstly and then declined.The removal efficiency of COD_crwas highest,the average removal efficiency was 87%when the HRT was among 8～9h.The removal of NH₃-N was greatly influenced by water temperature. The removal efficiency of NH₃-N declined gradually from 95%to 36.7%along with the water tempreture declined from 29℃to 8℃.Main factors affecting membrane fouling were analyzed with the way of grey relational analysis.The results showed that grey relational grade between operation parameters and membrane fouling in sequence from the biggest to the smallest was suction time,air-water ratio and suctiong suspended time.The optimum operation parameters were 10 minutes of suction time,4 minutes of suction suspended time and 30:1 of air-water ratio.Mass balance relationships were investigated in the SMBR for treating municipal sewage.Kinetic models of microorganism multiplication and optimum time for sludge-drainage were established based on Lawrence-McCarty mode and Pirt "maintenance" theory.The coefficient of contabescence K_d and the theoretical conversion yield y were calculated by linear regression method.The values of K_d and y measured for experiments with various solid retention times,were found to equal 0.087d^-1and 0.33mgVSS/mgCOD,respectively.By studying on the municipal sewage, the highest activated sludge Concentration and the optimum time for sludge-drainage were 3030mg/L and 37d,respectively.Visual windows were established in order to apply the kinetic models conveniently.The highest activated sludge concentration and optimum time for sludge-drainage were calculated conveniently with the visual windows.