Research Of Intercepting And Treatment Technology For First Flush Rainwater From Urban Road

Quality of rainwater from urban roads in different functional areas was investigated in Changzhou and effect of specific pipeline storing technology combined with CFD model for the first flush runoff in a labortarty-scale.Additionally,a design of specific pipeline storing technology was undertaken for an urban road in Changzhou in order to intercept first flush rainwater,and a pre-evaluation for technology performance was carried out in this study.Simultaneously,the treatment efficiency of pressureless hydrocyclone separation technology treating rainwater from urban road was studied in a labortarty-scale.The event mean concentrations?EMC?of rainwater runoff from urban roads under different rainfall types were in order of heavy>moderate>light and were in order of commercial>residental>industrial for different functional areas.Particles in road runoff were predominantly fine particles?<75?m?.COD and TP had a good correlation with SS in road runoff.The relatively obvious secondary flush phenomenon happened in road runoff of moderate rain and light rain.A certain initial flushing effect of road runoff was found in Changzhou.Curves of M?V?could be fitted by mathematical models,and values of R² were all not less than 0.978.Then,about 5 mm of initial runoff depth removal in eastern China?Changzhou?was suggested for first flush capturing device design.Water intercepting means of specific pipeline storing technology applied in separate system of road drainage are equipped with tubular well.High hydraulic slope,low liquid level of tube well,small pipe diameter and proper launder of specific pipeline storing technology are benificial for reducing impact in pressure flow.Additionally,specific pipeline storing technology was designed,such as rain mouth,pipe diameter,pipe material,pipe grade,other parameters?spare length,connecting pipe,etc.?.Evaluation index was defined with intercepting ability and emptying time.Maintenance and management method from three aspects of source,transportation and ending were suggested in this study.Simulated results of geometric model established by CFD were well fitted to practical experiment conditions,and changes of tube hydraulic parameters could be visual performanced.Removal ratio of SS was the highest by pressureless hydrocyclone separation technology,which was basically in 20-30%and followed by COD and TP,and convert cutting sizes were in 33-85?m.Optimal combinations of small main diameter pressureless cyclone separator were 0.8 m of feeding height,45°of inner cone distance and medium split ratio,while Optimal combinations of big main diameter pressureless cyclone separator were 1.0 m of feeding height,15°of inner cone distance and medium split ratio.Separating effect of pressureless cyclone separator was better in low concentration inlet and particle size had no significant effect in separation.Pressureless cyclone separator could be regarded as rapid processing unit or pretreatment unit of combination process in practical use.Service area of initial charge of rainwater storage demonstration project in Hengtanghe west road is 15000 m²,and length of specific pipeline is greater than 1 km.Intercepting with tube well of specific pipeline storing technology is applied.Specific pipeline's initial rainwater in specific pipeline is flowed into Hengtanghe sewage pumping station in sunshine day.About 551 mm road runoff depth is intercepted by this project during the year,which is 34.5%of annual rainfall,and intercepting volume of initial rainfall is 782.5 m³.Evaluation results of pollution index method showed that pollutant impact by road rainwater runoff in service area polluted surrounding river,and main pollutants were SS and COD.Pollutant loads reduced by this demonstration project are estimated that SS,COD,TN,TP and NH₃-N are 1337.4 kg/a,1262.1 kg/a,60.8 kg/a,3.7 kg/a and 15.3 kg/a,seperately.