Study On Optimized Operation Of Double-channel Oxidation Ditch Under The Low-Load Operation Conditions

A sewage treatment plant in Dujiangyan,Chengdu,uses double ditch type oxidation ditch to treat domestic sewage.In actual operation,due to low influent load and large influent water fluctuation,the operation of sewage treatment plant deviates from the design condition.In order to solve the operation mode of double ditch oxidation ditch under different influent conditions,optimize the operation conditions and save the energy consumption of the sewage treatment plant,this paper studied the process optimization operation method of the double ditch oxidation ditch.The design flow of the sewage treatment plant is 30000m3/d.Through the assessment of water intake and water quality in the last two years,it is found that the average influent concentration of COD in the wastewater treatment plant is 125mg/L,which is lower than the water quality of the design,and the influent load fluctuates greatly.The average influent concentration of ammonia nitrogen is 12.5mg/L,and the fluctuation is small.According to the different load of COD,this paper reconstructs the appropriate operation mode of oxidation ditch to adapt to different influent load.Analyzing the operating conditions of oxidation ditch during stable influent period,this paper checked the operating parameters of the oxidation ditch in actual operation.Further,under different influent loads,this paper analyzed the mixed transport process in the oxidation ditch and the variation of the concentration of pollutants in the oxidation ditch.And determined the different operating modes of the oxidation ditch.The results of the study show that:(1)The working conditions of the sewage treatment plant can be divided into three kinds according to the different COD load,which are full load condition,actual stable condition and low load operating condition,and three working conditions account for 10%,70% and 20% of the total time respectively.The operation modes of double ditch oxidation ditch under three working conditions were determined respectively.(2)This study calculated and analyzed the nitrification and denitrification characteristics of oxidation ditch at different inlet loads,and determined the distribution of nitrification time and denitrification time of oxidation ditch under different load,the operation mode and running time of brush the aerator and the propelling machine in the oxidation ditch and the operation mode of the sludge reflux pump.Therefore,the oxidation ditch can run stably,the effect of nitrogen and phosphorus removal is improved,and the energy consumption is reduced.(3)Comparing the power consumption of the rotary brush aerator and the sludge reflux pump before and after the optimization,combining the energy consumption analysis of the actual operation of the sewage treatment plant,it is concluded that the overall energy consumption of the double ditch oxidation ditch can be reduced by 9.8% after the optimization of the working condition.