Research On Infiltration And Reuse Of Road Runoff By Artificial Soil Technology Jiaxing City

With the acceleration of urbanization in Jiaxing City, non-point pollution of roadrunoff caused serious pollution of urban rivers. As a result, water qaulity becomingdeterioration, the city that rich in water resources facing the embarrassment of watersupply shortage. In response to this situation, in order to alleviate non-point pollutionand reuse urban rainwater resources, This study made some research about rainfallcharacteristics in rainy season of the city, features of pollutants of road runoff,methods of enhancing infiltration permeability and purification permeability of clay,and scale, efficiency, feasibility of using soil percolation pond on the road rainwatertreatment. The main contents and conclusions are as follows:(1) Through analyzing the rainfall data of Jiaxing City, the study identified theaverage rainfall in rainy season （April to October） was750mm, and this trend isincreasing; Rainfall frequency was2.9day/event; The analysis shows that the mainrainfall pattern has two peaks, its frequency was33.6%, and these two peaks locatedin the middle and back of the storm.(2) The main pollutants of road runoff is COD, NH4+-N and SS. The averageconcentrations of COD is546mg/L, the average concentrations of NH4+-N is3.16mg/L, the average concentrations of SS is1050mg/L, and these three main pollutantsHave a high correlation.(3) The result of infiltration experiments showed that: the mixing soil has betterinfiltration permeability than clay after incorporating clay and fillers. Among8fillers,ceramsite and zeolite make more improvement of infiltration permeability of clay.NTF soil that Volume ratio is2:1:1has the best infiltration permeability. Theinfiltration coefficient is2.58m/d, that is3.9times than clay.(4) The result of purification experiments showed that: the mixing soil has betterpurification permeability than clay after incorporating ceramsite, zeolite, sand andmagnetite to clay respectively; On the other hand, the mixing soil has worsepurification permeability than clay after incorporating sawdust, nutshell and slag toclay respectively. NFZ soil has the best purification permeability on COD removal,the removal rate is91%. NTZ soil has the best purification permeability on TNremoval, the removal rate is67%. NTC soil has the best purification permeability onTP removal, the removal rate is96%. NFZ soil has the best purification permeabilityon NH4+-N removal, the removal rate is68%. NTF soil and NFZ soil have the best purification permeability on SS removal, the removal rate are98%. After comparison,NTF soil has the best comprehensive purification permeability to pollutants of roadrunoff. In addition, soil thickness has more influence on purification permeability thanratio of soil. NTF soil with a thickness of40cm has better purification performancethan soil with a thickness of30cm; However, NTF soil with different ratio (Volumeratio) has little disparity on purification performance.(5) The road of Jiaxing City which as long as193km can produce1.9×106m3runoff in rainy season. Collecting these runoff need to construct309pools which havevolume of150m3. There will be48%of rainwater resources used for flushing road,and31%of the rainwater resources for greening.(6) From economy aspect, the cost of construction and maintenance for rainwaterrecycling facilities is about6798million yuan, and annual earning is2163millionyuan. Theses facilities can work for30years, and recovering the cost will takes3years. From ecology aspect, reusing runoff of road by soil processing can intercept958tons of COD,7.4tons of TN,3.4tons of TP,5.9tons of NH4+-N and1267tons ofSS, may improve the water environment.