Production Operation And Optimal Control Of Improved A~2/O Bottom Aeration Oxidation Ditch In Alpine Region

Northeast of china belongs to alpine region, in winter, algae, fish andmicro-organisms growth slow, a significant decline in water self-purificationcapacity. Meanwhile, the operation of sewage treatment are also affected bylow-temperature environment, the treatment facilities were frozen, biologicaltreatment inefficiency, the effluent water quality is poor. In order to improve thesewage treatment efficiency and effluent water quality, the improved A2/O bottomaeration oxidation ditch was proposed to treating urban sewage in alpine region. Theprocess can operation in low-temperature, runs through alternating aerobic andanoxic, the organic matter in sewage water and sessile microorganisms hanging onthe filler, all these can enhance the comprehensive performance.Since improved A2/O bottom aeration oxidation ditch has the above advantages,take the actual operation of a sewage treatment in northeast china as the researchsubject, investigate the affect of temperature, internal reflux ratio and sludgeconcentration to the system processing, analysis the water quality of each reactionstage in bottom aeration oxidation ditch process, analysis the pollutant concentrationreduction law of each reaction stage. Use ASM2D model for simulate the bottomaeration oxidation ditch, calibration the model by a lot of monitoring date,optimization the operation parameters of bottom aeration oxidation ditch process.In winter, the temperature is low, the change range of air temperature in sewagetreatment is-31℃~5℃，the change range of water temperature is7℃~13℃.Temperature is an important factor to the removal efficiency of CODCr、BOD5、NH3-N、TN and TP, the removal rate decreases with decreasing temperature, theremoval efficiency of TN is poor in low-temperature.Investigate the water quality variation of bottom aeration oxidation ditchsystem in each stage under different control conditions, found that DO shows aupward trend in each reaction stage of the process, PH changes from7.35-7.42to6.81-7.02, CODCrremoval highest in anaerobic, reaching58.9%, stage of anoxic andaerobic was15.2%and14.5%, TP raised at first and then decreased. The effluent TPmaintained at0.48mg/L.Adjust the internal reflux ratio of bottom aeration oxidation ditch system, makeit at180%, in this condition, the removal efficiency of TN and TP achieve the bestsituation. The pollutants removal efficiency with the MLSS controlled in4500~5000is better than the MLSS in3500~4000. In order to study the operation of bottom aeration oxidation ditch process inalpine region, optimize the operating parameters, use ASM2D model, based on awof conservation of mass, conservation of energy and momentum conservation law,make the material balance equation of each reaction stage, and then made themathematical model of bottom aeration oxidation ditch process applied to alpineregion.