A Primary Study On The Non-point Source Pollution Load Control At The East Coast Of The Dianchi Lake

In recent years, pollution in the Dianchi Lake basin is still very serious. Non-pointsource pollution from rainfall runoff is the main source of pollution in Dianchi Lake.Chenggong district is located in the east bank of Dianchi Lake; it will become the newcenter of administration, culture and education. And it will also be a center of socialservice and international logistics. Thus, with the rapid development of urbanizationChenggong, the pollution caused by urban storm runoff will become more serious, andit leads to heavier pollution load of Dianchi Lake. Therefore, controlling urbannon-point source pollution of Chenggong district becomes necessary. Kunming built themain canal sewage in order to cut down the pollution load of Dianchi Lake. The maincanal sewage has huge volume; pollution load can be regulated and stored to increasethe efficiency of the main canal of the sewage. It is a effective method for quantitativestudies on urban non-point source pollution in Chenggong by using model simulation.Meanwhile, using non-point source pollution model of main canal along the east bankcan discuss the pollution condition of the canal, inlet of sewage plant and inlet ofrainwater station, and it can provide the theory basis for optimizing operation. On theother hand, measuring water quality, morphology distribution, settling performance andparticle size distribution of pollutants on monitoring points of city underlying surfacecan provide the theory basis for pretreatment facilities of water quality.Comparing wildly used models which were used for water quality simulation,SWMM is chosen for consummating mechanism, detailed output.non-point source pollution model of main canal along the east bankis built basedon SWMM by dividing285subcatchments, generalizing369junctions,400conduitsand1outfalls, and setting14hydrological and hydraulic parameters and16waterquality parameters(each pollution indicatior). The validation results showed that eventrainfall pollution load, and peak concentration were close to the monitoringobservations, with low mean deviation of16%and17%, respectively, which indicatingthat the model has a good reliability and precision in another aspect.On the other side, under the circumstance of designed rainfall and practicalrainfall, the water quantity and quality of abouchements along main canal wereanalyzed. The factors that affect the time interval between flow peak and pollutantsconcentration peak in storm water pipe was studied.(area of underlying surface and the length of main pipe were the related factors). As for the sewage main canal outlet,rainfall all bring low concentration load(each pollution indicators) to sewage plant. Thepollutant concentration(SS、COD、TN、TP) will below the designing rage for a longperiod, but it will also be much higher than designing rage for a period.On the other hand, there were two monitoring point, one monitoring point is undercombined system, and the underlying surface was the old city zone of chenggong.Another monitoring point is under separate system, and the underlying surface was thenew city zone of chenggong. Under the condition of rainfall, precipitation and waterquantity were measured. And water samples of each monitoring points were taken backfor laboratory analysis. The morphology distribution, settling performance and particlesize distribution of pollutants was studied. It can be concluded from both monitoringpoints that, under many rainfalls, SS have a good correlation to other pollution index.And SS can represent the water quality to some extent. For monitoring point of separatesystem: the form of TN, COD were mainly dissolved, but the TP was in particle state.And concentration of COD in monitoring point of separate system reach Class2standard of Discharge standard of pollutants for municipal wastewater treatment plant.And after sedimentation, concentration of COD reaches Category B, Class1standard.，the concentration of TN,TP can reach Category A,Class1standard. The rainwaterwhich reaches the standard can be discharge directly without treatment. And it alsoconclude that, particle diameter distribution rage from20to80μm has a strongenrichment effect towards TP and COD. And this section of particle diameter leadsmore attention.