Study On The Operating Characteristic Of Submerged Membrane Bioreactor

In order to investigate the operating characteristics of SMBR (Submerged Membrane Bioreactor), we took the hollow fiber membrane as the core, artificial sewage as the study object, designed and operated a membrane bioreactor device (SMBR),which content was 19 liters. Then we studied the influence effect of sludge concentration, dissolved oxygen concentration, the hydraulic retention time and inspected the main factors of membrane fouling. Test confirmed when we used SMBR process to treat wastewater, we could get a good removing efficiency and stable effluent quality. To overcome the shortcomings of SMBR that was easy to be plugged in the treating high concentration wastewater, at the end of experiment, a biological contact oxidation reactor was constituted to composite the hybrid submerged membrane bioreactor. The operating characteristics were studied initially. The result showed:(1) The turbidity of the effluent water was between 0.6 and 6.5NTU, the average turbidity was 3.3NTU. This value met the requirements of the "Miscellaneous city water quality standards";(2) Submerged membrane bioreactor system was not appropriate to run in the high loading condition. In low loading, effluent water was stable, and COD value was under 20 mg/L. far lower than the water quality standard;(3) In SMBR, NH3-N removal was correlative with the influent loading and dissolved oxygen concentration of reactor. To get a good NH₃-N removal, dissolved oxygen concentration should be in 2mg/L and influent loading should not be too high.(4) As the concentration of the sludge increased, the dissolved oxygen concentration was decreased. When the sludge concentration was less than 7500mg/L, the concentration of dissolved oxygen was higher, and when the sludge concentration was above 7500mg/L, the concentration of dissolved oxygen was lower;(5) The efficiency of SMBR was hardly affected by the influent water's quality and quantity. The SMBR system had the strong fighting capabilities to withstand the impact loading;(6) The sludge concentration was the important factor of the membrane fouling. When the sludge concentration was higher, oxygen transfer coefficient decreased. At the same air-water ratio, the resistance by EPS (Extracelluar Polymers) increased, fouling accelerated.(7) Compared the permeability of membrane cleaned using acid and alkali method, membrane permeability increased by 3-4 times after alcohol immersion. The membrane cleaning cycle could be extended about six times.(8) In the membrane bioreactor system, the characteristics of microbial growth was also an important factor of the fouling of hollow fiber membrane. The microbial growth characteristics could be controlled through the sludge loading and the dissolved oxygen concentration. The most appropriate sludge concentration was 0.01-0.3 kgCOD/kg (MLSS).d and the most appropriate concentration of dissolved oxygen was 1.0⁴.0mg/L.