Pilot-study Of Microporus Aeration Oxidation Ditch For Municipal Wastcwater Treatmen

Oxidation ditch process is one of the widely used techniques in municipalwastewater treatment plants. Brush aeration, disc aeration and surface aerator are usedin oxidation ditch depended on shapes of ditch. They have high energy consumption andoxygen transfer efficiency is relatively low. However，The microporous aeration disc isless used in actual application of oxidation ditch which has low energy consumption andrelatively high oxygen transfer efficiency. In this study, a pilot-scale microporousaeration oxidation ditch was used to operating and adjusting tests (including starting ofbacterium tamed, technological adjusting and normal operating). In the pilot-scalemicroporous aeration oxidation ditch, this paper mainly analyzed biological nutrientremoval effects under low temperature conditions, also pollutant removal eficiency andenergy saving under low do, limited filamentous bulking conditions.(1) Test starting lasted40days under low DO concentration which dissolvedoxygen concentration was between0.5mg/L and0.9mg/L. In the late period of trialoperation, MLSS was stable at about4.0g/L, SVI was stable at about230mL/g, thesludge reflux ratio was50%and the average efficiency of COD, NH3-N, TN and TPremoval can reach91%,98%,79%and58%respectively. The pilot-scale microporousaeration oxidation ditch could achieve ideal removal effects and test starting wassuccessful.(2) Under low temperature condition, the pilot plant of COD removal efficiencywas nearly not affected, but the biological denitrification and phosphorus removal effectwere obvious affected, the effect would drop as the temperature falled. The lowest watertemperature which ensured the oxidation ditch pilot plant normal operation was11℃.When the water temperature was higher than11℃, the fall of water temperature would only affect the nitrification rate.(3) The DO concentration was maintained between0.5mg/L and0.9mg/L, and SVIvalue ranged between150mL/g to250mL/g, which could cause stable and sustainablelimited filamentous sludge bulking. During the test, the effluent average value of SSwas less than10mg/L, the average removal rates of COD, TP, NH3-N, TN in thepilot-plant could reach92.45%,96%,99.11%and82.14%respectively, and the effluentaverage value of pollutant had reached A level of discharge standard of pollutants formunicipal wastewater treatment plant.(4) Under low DO and limited filamentous sludge bulking, it could reduce theenergy consumption of oxidation ditch by ensuring that the average velocity ofoxidation ditch was more than0.15m/s. Maintaining the DO concentration was between0.5mg/L and0.9mg/L and limited filamentous sludge bulking could not only ensure thetreatment effect but also save50%aeration. Because gas supply equipment powerconsumption was dropped, the energy consumption of the pilot-scale microporousaeration oxidation ditch could be reduced.