The Relationship Between The Water Depth Of Aeration Tank And The Effects Of Aeration In The Domestic Sewage Treatment Station Of Kunming Shipping Industrial District

In aerobic biological treatment,the supply of oxygen is a very important environmental condition.Therefore,aeration becomes a core part of the biological treatment.Currently, blasting aeration is widely used.The blowing machine provides the compressed air through the diffusers which were installed in the aeration tank by the air bubble form to the water of the aeration tank.The dissolved oxygen in the compressed air is necessary for biochemical reaction.At the same time play a role in stirring the mixture,and ensure the mixing of sewage and activited sludge in the state of suspension,and benefit activited sludge,water and air the three-phase full accessing,and ensure activated sludge full use of the dissolved oxygen in water to the decomposition of organic pollutants and containing N,P nutrition.So the effect of aeration enormously may affect the performance of biological treatment systems efficiency.In the meantime,aeration is also the process which extremely consumes high energy,thus it holds the very great proportion in the cost of the sewage treatment.In addition,in the biochemistry sewage treatment,the processing construction-aeration tank, water depth of it is also directly affecting the cost of the sewage treatment.Therefore,it is necessary to explore the relation between water depth of the aeration tank and the effects of aeration,and to seek water depth of the aeration tank is suitable,which causes the running of the aeration tank in the best conditions.And then enables the entire sewage treatment system to achieve higher processing efficiency,lower investment and the operating cost.Therefore,this subject takes the aeration tank which was installed the rubber diaphragm disk-shaped diffuser in the domestic sewage treatment station of Kunming Shipping Industrial District to launch the research as the foundation.The aeration tank is 7.5 meters deep and 7.2 meters depth.Aim at the research on the stabilization process of the aeration tank and its start-up,through the observation the characteristic of the activated sludge as well as the changes in the operation of the aeration tank,and analyzes the symbol of the process as well as completion,which is about the start-up on aeration tank;during the stable operation of the domestic sewage treatment station,test the indicators such as COD,BOD₅,SS,TN,TP periodicly,and then judge the removal rate of them in the aeration tank and their removal rate on the percentage of the total removal rate of them in the whole domestic sewage treatment station;then carries on the research about the relation between water depth of the aeration tank and the effects of aeration,and set up five monitoring points separately in two aeration tanks.In 1# aeration tank,the monitoring points are at the location of 6.7meters depth,4.7 meters depth,2.7 meters depth,1.2 meters depth and 0.2 meters depth separately,but in 2# aeration tank,the monitoring points are at the location of 6.7meters depth,5.1meters depth,3.4 meters depth,1.7meters depth and 0.2 meters depth separately. Through the research on changes in the law of the rate of oxygen transfer,MLSS,SV,SVI, the removal rate of COD and the removal of COD-sludge load in different water depths of the aeration tank,seek suitable water depth of such domestic sewage treatment station, which causes the running of the domestic sewage treatment station in the best conditions.At last,calculate the operating cost of the aeration system in this water depth of the aeration tank,and then compare it with the operating cost of the aeration system under the existing conditions.According to the above studies,which provide empirical data for the domestic sewage treatment station of Kunming Shipping Industrial District,as well as provide the reliable water depth,effective data and engineering practices for the design,construction and operation of similar domestic sewage treatment station.Through conducts the research on the stabilization process of the aeration tank and its start-up,the experimental result indicated that:Through the method cultivate activated sludge naturally,the activated sludge has been cultivated successfully for three and a half months and the fine bubble aeration tank could start up smoothly.At this time,the concentration of sludge in 1# and 2# aeration tank attains 1 288.8 mg/L and 2 275.0 mg/L respectively,and the biofacies in microscopic examination are abundant.The removal rate of NH₃-N in the earlier period of the start-up on the aeration tank is not high,due to the lower water temperature in the aeration tank.The change of pH and oxygen content of effluent of the aeration tank may reflect the process of organic oxidation and nitrification.The removal of COD and increment of DO as well as the removal of NH₃-N and increment of DO come into being obvious minus linear dependence,curvilinear equation being respectively y=-0.0128x+7.0376 and y=-0.053x+5.5073.The relevancy are respectively 0.8609 and 0.9082. The removal of NH₃-N and increment of pH also come into being obvious minus linear dependence,curvilinear equation being y=-0.0056x+0.1378.The relevancy is 0.8506.In the later period of the start-up on the aeration tank,the removal of COD and NH₃-N maintain relative stability,until the removal rate of COD and NH₃-N respectively achieved 78.4%and 75.7%,which symbolized the completion of the process that start-up on the aeration tank.In the stable operation stage of the domestic sewage treatment station,the average removal rate of COD,BOD₅,SS,TN andTP respectively are 84.9%,91.0%,86.6%, 69.2%and 72.6%,and in the aeration tank,the average removal rate of COD,BOD₅,SS,TN andTP respectively are 69.3%,67.0%,57.7%,26.1%and 79.8%,which separately account for the total removal rate of 51.0%,32.8%,38.9%and 21.6%,but the removal rate of TP in the aeration tank is higher than the total removal rate of TP in the wastewater treatment station.Through conducts the research on the relation between water depth of the aeration tank and the effects of aeration,synthesize and compare of the experimental result of the two aeration tanks,and then indicated that:the rate of oxygen transfer of each monitoring points gradually changes along with the water depth increase in a big way;aim at the aeration tank of 7.2 meters depth,in unit time the oxygen content of which is transferred to every layer of water along with the increase in water depth increases;the oxygen content which is transferred to the depth of 6.7 meters nearby water layer of 1# fine bubble aeration tank is the greatest,that is,1.32kgO₂/h,and in 2# fine bubble aeration tank the oxygen content which is transferred to nearby water layer of 6.7 meters depth is the greatest,that is,1.29kgO₂/h; between the depth of 4.7 meters and 5.1 meters,the concentration of sludge maintains the largest,correspondingly the number of microorganisms are most,which help the degradation of organic matter.Meanwhile in the scope of this water depth,the value of SV maintains the biggest,and the value of SVI in different water depths of the aeration tank are less than 100mL/g,which explained that the structure of the activated sludge is close,agglomerate, and the precipitability of the activated sludge is better.In addition,the removal rate of COD is also best.At the same time,under the condition that the value of SVI in different water depths of the aeration tank are relatively stable,the relation between the concentration of sludge and the value of SV are the linear relations,in 1# aeration tank,the curvilinear equation between SVI in different water depths and the concentration of sludge in different water depths is y=175.56x-1674.9.The relevancy is 0.945.However,in 2# aeration tank,the curvilinear equation is y=144.77x-851.47.The relevancy is 0.9194.But in 1# and 2# aeration tank,the change tendency of the removal of COD-sludge load are different,in 1# aeration tank,the trend is a further increasing before decreasing,but in 2# aeration tank,that is gradually increasing.The depth of 4.7 meters in 1# aeration tank,the value of the removal of COD-sludge load is the greatest,that is,0.56 kgCOD/kgMLSS·d.But in 2# aeration tank,in the depth of 6.7 meters,the value of the removal of COD-sludge load is the greatest,that is,3.1 kgCOD/kgMLSS·d.In summary,the final conclusions to be drawn are as follows:In the aeration tank which is 7.2 meters depth and was installed the rubber diaphragm fine bubble diffuser of the domestic sewage treatment station of Kunming Shipping Industrial District,between the depth of 4.7 meters and 5.1 meters,the effects of aeration are best.Supposes in the project the aeration tank were 5.0 meters depth,we compare it with the existing aeration tank,and in respect of the electricity cost we may save 36 000 yuan every year.The treatment costs of every cubic meters of water is 0.146 yuan.It proposes the fine bubble aeration tank of the domestic sewage treatment station of Kunming Shipping Industrial District to be 5.0 meters depth.