Study On Pollution Characteristics And Pollution Reduction Technology Of Initial Rainwater Of Urban Roof

Flood disasters occur frequently all over the world,and urban waterlogging is serious.The main reason for the urban waterlogging is that the area of the impermeable surface and roof is increasing,resulting in changing in the natural underlying surface.The important means,controlling rainwater runoff and reducing emission,can alleviate urban waterlogging.Harvesting rainwater is one of the main measures to control the source and realize the low impact development mode in cities and towns.Areas of roof is large in urban.Roof rainwater has many advantages which the water head is high and it is easy to collect.Therefore,compared with ground rainwater,roof rainwater is easier to collect and utilize.Based on the continuous meteorological conditions and hydrological process,the cement roof with a slope of 2oand the steel roof with a slope of 20owere studied in this paper.The main detection indexes of water quality include pH,DO,EC,SS,TN,TP and COD_Mn.The water quality of initial rainwater,the middle term rainwater and the later term rainwater and the characteristics and changing regularity of roof rainwater pollution have been analyzed.Aiming at the serious problem of initial rainwater pollution of roof,the technology of rainwater pollution emission reduction of roof was put forward.The main conclusions are as follows:1.The runoff quality of roof rainwater is affected by roof property,sunny days before rain,air quality and air temperature.DO,EC,COD_Mn,SS and TP tended to be stable when rainfall was above 2mm,while TN tended to be stable when rainfall was above 3mm.The pollution degree of rainwater runoff of cement roof is more serious than that of steel roof.2.The pollution of initial rainwater of cement roof and steel roof is serious.25%of the initial runoff carried the pollution load varies from 29%to 65%,and 30%of the earlier runoff carried the pollution load vary from 35%to 68%.The initial scour degree of SS and TP is more obvious than that of COD_Mn and TN.The initial runoff of abandoned 2 to 3mm can remove 26.39%to 100%of the pollution load.Abandoning initial runoff vary from 2 to 3 mm,the pollution load varies from 26.39%to 100%can be removed.3.The concentration of TN,TP,and SS in initial rainwater of two kinds of roof is high,and the TN concentration exceeds the water quality standard of class?surface water.The TN of later rainwater of cement roof and steel roof can reach class?and class?surface water standards.The middle term and later rainwater can meet the standard of reuse water.4.The emission reduction model which include initial abandonment,middle term collection and late conservation was proposed in this paper.Compared with the traditional collection and utilization method of rainwater,it can abandon initial rainwater and reduce pollution load of urban runoff.At the same time,it can increase the rigid constraint on the source emission reduction of urban runoff,and improve the efficiency of utilization of rainwater resource.Figure[32]table[10]reference[84]...