Study On Diffuse Pollution And Street Dust Cleaning Measures In The Old Urban Area Of Chongqing

With the increasingly rapid urbanization and the continous improvement of the point source pollution in China, diffuse pollution has attracted more and more attention. Storm runoff washes the pollutants accumulated in the surface and the pipe network in sunny day into the natural water bodies during rainfall The sewer stormwater overflow with lots of pollutants and hith flow rate will bring serious harm to natural water bodies.The study basin located in the Funiuxi Street, Dadukou District, Chongqing City.The area is a typical zone of the old city. This study was conducted on the main road of street dust pollution, in order to understand the situation of street dust pollution experiment region. Characterization of stormwater runoff pollution in six underlying surface and a flood drainage of the area were studied. Finally, the removal of street dust of cleaning meathod in different street was investigated. The results are shown below.(1) Particle size distribution of street dust in the old urban area:150～300μm (35.53%)﹥75～150μm (24.68%)﹥300～1000μm (23.68%)﹥0～75μm (20.82%).The highest concentration TN and TP were residential area road,and TOC was branch way.Most of the samples of300～1OOOμm particles in street dust, nutrient pollutant content was the highest.﹤300μm particles showed that:the smaller grain size and the higher content. Distribution of nutrient pollution in different particle size street dust showed that: most of the samples of nutrients was﹤300μm particles.(2) Small particles of heavy metal content was the highest in most of samples, but it takes the least mass.﹥150μm particles of low heavy metal content, but more than150μm particles of heavy metal content in the highest. According to the analysis of heavy metals in street dust, The form of Cd, Cr and Ni were relatively stable, most were residue, Cu was the oxidation state of Zn, mostly weak acid extractable, reducible Pb was higher proportion in some sampling point.(3)The underlying surface rainfall runoff investigation showed that:the mean concentration of TSS,COD,TN and TP exceeded discharge standard of pollutants for municipal wastewater treatment plant. TSS and TP of Oil asphalt road were the highest, was2462.40±915.3mg/L、4.64±2.17mg/L. the highest COD concentration was on catering asphalt pavement, up to1579.63±733.87mg/L.The runoff concentration of Pb, Ni in all road were than the discharge standard of pollutants for municipal wastewater treatment plant.Cd, Cr and Zn of oil asphalt pavement were over the discharge standards,There was no underlying surface of Cu exceed the discharge standard.all the roof runoff,only TN concentration was over the surface water environment quality standard V(2mg/L), the other pollutants were low in the surface water environmental quality standard V or the city and town sewage treatment discharge standards Factory pollution.(4) Investigation of the combined floodway rainfall runoff showed that: most of pollutant concentration peak were ahead of runoff. all pollutants, in addition to N03"-N, the peak pollutant concentration appeared earlier than the peak of runoff flow, the concentration of pollutants formed in the early stage was higher than in the late stage,,runoff generally reached steady state in the late stage, the cumulative curve could be seen confluence for each pollutant drainage rain runoff present the phenomenon of first flush.(5) The correlation of the combined floodway runoff pollutant showed that:TP and six heavy metals are particulate form or adsorption TSS.COD and TP had significant positive correlation. So are the correlation between NH3-N and TP, as well as the correlation between NH3-N, TDN and TDP. NO3-N and other indicators show a negative correlation between the pollution behavior, different from other pollutants.(6) Study on street dust accumulation showed that, road street dust accumulation began to reach the peak after7sunny days. Study on the road cleaning method showed that, manual cleaning for small particle removal effect was the worst, street dust removal rate of the residential road and the courtyard was respectively30.21%,39.36%. Ordinary brush sweeping vehicle for large particle size (﹥300μm) street dust cleaning effect was well (80.91%), the diameter of the particle (﹤75μm) cleaning effect of street dust (41.54%) compared with the high pressure water gun cleaning mode was low. the overall removal rate is69.13%by Ordinary brush sweeping vehicle. The small particle size (﹤75μm) particle cleaning effect is best(76.84%) by high pressure water gun cleaning method, the removal rate of overall was up to76.84%.