Study On The Operation Of Improved Carrousel Oxidation Ditch Aeration Condition

In the urban sewage treatment plant,the aerobic biological treatment method is generally used,the activated sludge process is widely used,and the oxidation ditch process is the improvement of the traditional activated sludge process.Because the oxidation ditch process is stable,the treatment facility is simple,the effluent quality is good,and has the anti impact load capacity and so on.Oxidation ditch process has become the first choice for many small and medium sized urban sewage treatment plant,it is widely used in domestic sewage and industrial sewage treatment at home and abroad.The improved Carrousel oxidation ditch has added the anaerobic and anoxic zone on the front end of the traditional Carrousel oxidation ditch process,which has better effect of nitrogen and phosphorus removal.Aeration equipment in the oxidation ditch plays a key role in the biological treatment of wastewater,the concentration of dissolved oxygen will affect the effect of sewage treatment,so it is very important to determine the suitable aeration conditions.In this paper,a modified Carrousel oxidation ditch sewage treatment plant in Chongqing as the research object,The influent water quantity and water quality,aeration condition and the corresponding sewage treatment effect during the initial operation stage of the sewage treatment plant are analyzed;Field test is carried out at the middle operation stage of wastewater treatment plant,The effect of different aeration conditions on the sewage treatment are studied and discussed,and determine the suitable aeration condition of the sewage treatment plant in the middle operation stage;On the basis of analysis of initial and middle stage aeration condition of the sewage treatment plant,Suggestions are put forward on the aeration condition of full load operation period.The main research results are as follows:Sewage treatment plant at the initial operation stage water inflow is less,wastewater pollutant concentration is lower than design value;when the water inflow is 380m³/d²01m³/d,open one aerator,aeration time around 5 hours,sewage treatment plant effluent quality meet the standard;It is found by calculation that actual operation of the aeration time is higher than the theoretical aeration time,the aeration system has the problem of prolonged aeration time and high energy consumption.The result of sewage treatment plant operation test of different aeration conditions of middle stage show that the distribution of dissolved oxygen concentration in the oxidation ditch is significantly different in the five aeration conditions,and the difference of the sewage treatment effect is also great.From working condition one to working condition five,the average value of dissolved oxygen at the test point of each section in the oxidation ditch aerobic zone of 0.5m water depth are 0.13mg/L,0.21mg/L,0.6mg/L,1.05mg/L and 1.47mg/L;while 2m water depth are 0.04mg/L,0.08mg/L,0.47mg/L,0.8mg/L and 1.24mg/L;and 3.5m water depth are 0.03mg/L,0.06mg/L,0.36mg/L,0.65mg/L and 0.91mg/L respectively.The fluctuation of dissolved oxygen concentration in the upper layer of the oxidation ditch is more severe,While at the bottom of the oxidation ditch is relatively far away from the aeration machine,the effect of aeration machine on the dissolved oxygen concentration is smaller than the upper layer.From the sewage treatment plant in the middle operation stage of the sewage treatment effect of field test,from working condition three to working condition five,the dissolved oxygen concentration in oxidation ditch increases,its sewage treatment effect is also improved.Under the working condition of opening two aeration machines,the dissolved oxygen concentration of each section in oxidation ditch aerobic zone,working condition two is slightly higher than working condition one,the sewage treatment effect of working condition two is slightly better,but effluent COD,NH4₊^-N,TN and TP are not up to standard.Under the condition of opening three aeration machines,the effluent COD and TP concentration under the operation of working condition three have reached the standard,but the concentration of NH4₊^-N and TN is not up to the standard.Working condition four and five of the sewage treatment effect is good,the effluent COD,TP,NH4₊^-N and TN are able to reach the standard.The effect of dissolved oxygen concentration in oxidation ditch on the removal of NH4₊^-N and TN is greatly,while the effect on the removal of COD and TP is smaller.Determined by the test of sewage treatment plant medium-term operation phase,in the middle operation stage,when the water inflow is about 3500m³,influent COD concentration is at the range of 200mg/L²50mg/L,NH4₊^-N is 16mg/L³0mg/L,TN is 25mg/L⁴3mg/L,and TP is 1mg/L⁴mg/L.the working condition four is suitable for the aeration condition of middle operation stage.While working condition four with respect to working condition five,the energy consumption of sewage treatment can be reduced by 0.04 k W·h/m³.By testing and calculating,the problem of aeration capacity of aeration equipment in wastewater treatment plant is determined.The existing aeration equipment can not meet the requirement of the sewage treatment in full load operation stage.It is recommended that the sewage treatment plant should change aeration equipment at once.If the medium-term operation stage use condition four operating mode,sewage treatment plant should select at least three inverted umbrella surface aerator that oxygenation capacity in 14.2kg O₂/h above;if in the equipment maintenance and easy repairment point of view,aeration equipment two open,one standby,sewage treatment plant in full load operation stage select inverted umbrella surface aerator that oxygenation capacity in 17.7kg O₂/h above is suitable.If the existing aeration equipment can not be replaced in time,it can be considered in oxidation ditch in the downstream position of each aeration machine,adding three aeration devices of oxygenation capacity in 3.8kg O₂/h above respectively.And from the perspective of optimizing the new aeration equipment,expanding the diameter of the impeller,increasing the number of blades and adding the impeller these three schemes are put forward,The optimization and improvement of aeration equipment need to be further improved.