Principle Of Biological Denitrification Of A～2C Oxidation Ditch And Research On Its Application In Municipal Wastewater Treatment Plant

With the development of industry and agriculture, the environment pollution is more and more serious. It is important way of preventing the water from being polluted and eutrophication to control the amount of the nutritional substance such as nitrogen and phosphor flowing into water. In the national standard the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant issued in 2002, the discharge of total nitrogen, ammonia and total phosphor are specified, so it is more and more significant and necessary to choose the process and technology with good efficiency of denitrification when it comes to decision of the wastewater treatment process.According to the requirements of outlet water quality parameters and removal of nitrogen and phosphor, the thesis researched and analyzed the process of removal of nitrogen and phosphor adopted by many wastewater plants, integrated their process characteristics, brought forward the biological treatment process of A²C Oxidation Ditch, so as to improve the efficiency of biological denitrification and assure the outlet water quality parameters can meet the discharge standard. A²C Oxidation Ditch process has the predominances of the A²O and Carrousel Oxidation Ditch, and good performances of biology denitrification, and it actualized the recirculation of the process water without power, so that the operation cost was lowered.The operating of the A²C Oxidation Ditch plant indicates it can meet the capacity of designed scale, all buildings match the design requirements, and it has the high efficiency of denitrification and removal of organic substance, and the outlet water quality meets or excels the design standard. Furthermore, the treatment effect and operation is stable. It's the suitable process for removal of nitrogen and phosphor in municipal wastewater treatment plant.It is more reasonable to design A²C oxidation ditch as the dynamic method and the control factor of sludge retention time; Sludge retention time is 20d, which meets the requirements of organism oxidation, sludge partly stability and nitrification of ammonia; Sludge loading rate is 0.14kgBOD₅/MLSS.d, which is reasonable by and large; The equipments of aeration and mixture (push flow) in the oxidation ditch is reasonable and meet the function requirements; The dissolved O₂ in anoxic zone (A²) keeps 0.45—0.7mg/L so that the denitrification process has appropriate O₂ concentration (0.5mg/L); and the dissolved O₂ in Aerobic Zone keeps 1.6—5.1mg/L in order to satisfy the aerobic environment of biological degradation and ammonia nitrification; the dissolved O₂ in the oxidation ditch is distributed as gradient along the water flow, part zone has much lower concentration of O₂(≤0.5mg/L, anoxic state), so the denitrification function can be implemented.