Study Onapplication Of A~2 OA-MBR Process In Municipal Wastewater Treatment

With the eutrophication issues becomes increasingly serious, denitrogen and phosphorus removal of sewage treatment becomes an important research subject in this field. In recent years, Membrane bioreactor (MBR) process has attracted more attention with its excellent quality effluent, small area and low sludge production rate. The traditional technology(Anaerobic/Anoxia/Oxic,A~2O) and membrane separation technology has been combined to form an effective MBR process (A~2O-MBR) for denitrification and phosphorus removal. Anaerobic/Anoxia/Oxic/ Anoxia-Membrane Bioreactor (A~2OA-MBR) process has been constructed by increasing an anoxic phase after the oxic phase.This study has focused on the second project of a municipal wastewater treatment plant in Wuxi, which used A~2OA-MBR process. A~2OA-MBR process has been monitored and analysed in terms of the pollutant removal efficiency, the kinetic parameters as well as membrane pollution control and operation cost. In addition, the effluent of the A~2OA-MBR process was treated by ozonation, and the effect of disinfection, decoloring and further removal of the difficult degradable organics has been researched. The main conclusions are obtained as followed.A~2OA-MBR system has achieved high removal efficiencies of pollutants, the concentrations of COD, TN, NH4+-N and TP in the effluent were far lower than the grade A standardsregulated in GB18918-2002 of China. The removal rates of COD, NH4+-N and TP basically over 90%, and TN around 83%, respectively.The kinetic parameters of the activated sludge in oxic tank were obtained for A~2OA-MBR system. KdH(Heterotrophic decay rate) was 0.141/d, while KdA(Autotrophic decay rate) was 0.238/d. YH(Yield coefficient for heterotrophic biomass) was 0.543gVSS/gCOD, and YA(Yield coefficient for autotrophic biomass) was 0.285 gVSS/gCOD. vmS (Maximum removal rate for COD) was 1.78 gCOD/(gVSS·d), and Ks (Half saturation coefficient for COD) was 24.27 mgCOD/L. vmN(Maximum removal rate for ammonia) was 0.124gN/(gVSS·d), while KN (Half saturation coefficient for ammonia) was 2.525mgN/L.In a word, the kinetic parameters would provide basic information and scientific foundation for MBR's engineering design and operation management in the future.Meanwhile, the results show that cleansing periodically could control membranepollution of A~2OA-MBR system. In addition, the energy consumption was 0.65 kWh per cubic wastewater treatment. The blowers in the oxic tank and membrane tank were the major high-energy-cost equipments. MBR process would reduce the energy consumption by improving the structure and running mode of the membrane module.The results show that ozone has a higher removal efficiency of TOC, UV254, color, the total bacterial count and the total coliform groups in the MBR effluent. And the removal rates were 43.7%, 64.2%, 96.4%, 99.9% and 100%, respectively. The results of 3D fluorescence spectra show that the main organic substances of the different effluent in the plant were protein substances and humic substances, and the fluorescence intensity weakened gradually as the ozone reacting time was extended. Ozone could significantly remove the organic substance.