| With the acceleration of China’s urbanization, decentralized sewage sources appeared in large numbers, such as new-built campus city, tourism resort, residential area around the city and expressway service area etc. The existing centralized sewage drainage network system is difficult to completely cover them. If laying the drainage network to take them into, the cost is too high. If discharging directly without treatment, it will cause pollution to the environment. So these swage should be decentralized and on-site treated, which is an important significance to non-point source pollution control, sewage treatment reuse and conservation of water resources. MBR(membrane bioreactor), as a new water treatment technology, has the following advantages, such as efficiency pollutant removal, small space occupation and fully automated system, which make significant advantages and good development prospects in decentralized sewage treatment.In this dissertation, decentralized sewage was treated by submerged plate ceramic membrane. The MBR was established. The flux characteristics of plate ceramic membrane MBR were inspected. The optimal operational conditions were determined. On the basis of that, the effect of MBR continuous treatment for swage was analyzed. And mechanism and control method of membrane pollution were studied.In the study of flux characteristics of plate ceramic MBR, under the experimental conditions which were MLSS=5000mg/L, SVI=75% of activated sludge and aeration of constant 25L/h to maintain cross flow velocity constant, the critical flux of membrane in MBR was 51.0L/m2-h. The choice of the initial flux had important implications to membrane fouling process. With the greater initial flux comes faster membrane fouling rate. After the formation of the filtration cake layer, the total resistance in the super critical flux operation was significantly greater than in the subcritical flux. When the initial flux was within the subcritical flux, the flux’s rate of decay was lower and the system could run a longer time with smaller resistance and lower energy consumption.In the study of decentralized sewage treatment by plate ceramic membrane, the optimal operational were determined that the initial flux was 42 L/m-h which was within the subcritical flux, the hydraulic remain time was 5.2h and the way of the effluent was 10min suction,2min pause. The results of decentralized sewage treatment by plate ceramic membrane showed that the average CODCr concentration of influent and effluent were 291mg/L and 27.75mg/L with a removal rate of 91%, the average ammonia nitrogen concentration of influent and effluent were 8.05mg/L and 0.62mg/L with a removal rate of 92.3%, TN, nitrate nitrogen, LAS and turbidity concentration of effluent were 1.373mg/L,0.683mg/L,0.5mg/L and 0.75NTU with removal rates of 85.66%,70.27%,96.20% and 98.83% respectively. The effluent could be directly reused as domestic miscellaneous water and landscape water.In the study of the mechanism and control method of membrane fouling, the membrane fouling resistance was analyzed after long term operation. The intrinsic membrane resistance Rm and the membrane pore adsorption & blocking resistance Rb were 2.54% of the total membrane resistance without growth as the filtration time went. The concentration polarization resistance Rcp and the filtration cake resistance Rc were 43.06% and 54.54% of the total membrane resistance. That showed a thick boundary layer in front of membrane and the thickening processing of filtration cake layer. And the system was running stable. Based on the Darcy law and Wiesner’s control theory of filtration cake resistance, the mathematical model expression of filtration cake resistance was derived as Rc (t)=(?)KctΔP/μ-R, which was proved to be in line with the actual rules based on experimental data. In the study of membrane cleaning method, using chemical immersion cleaning after sponge scrubbing,0.3% H2O2 and 0.2% NaCIO immersion cleaning had good effect with flux recovery rate of 94.8% and 92.2%. |
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