| With the acceleration of urban processes and economic development,according to the current situation of water resources in China,the problem of water shortage will become more and more serious.Rainwater,as a special reusable water resource,has attracted wide attention.The purpose of rainwater reuse can be achieved by simply utilizing rainwater resources,mainly for landscape,greening,car washing,flushing and so on.At present,the engineering measures of rainwater resources mainly include green roofs,permeable pavements and bioretention tanks,and these engineering measures are all used the adsorption and infiltration of fillers for the removal of pollutants.Therefore,the filler layer is an important part of the engineering measures.Therefore,the analysis of pollutant composition and characteristics in rainwater,the study of the adsorption performance of filler,and investigation of the purification effect of infiltration system on rainwater have become the research hotspot of current rainwater resource utilization.In view of the shortage of water resources in China,based on the analysis of the characteristics of rainwater runoff pollution,this paper aims to construct a short-flow rainwater resource infiltration system to achieve the purpose of simple treatment and reuse of rainwater pollution.Choosing Chongqing Yuelai Guobo Center as the research area,the composition and pollution characteristics of pollutants in rainwater runoff were analyzed.Selecting simulated rainwater as treatment object,the adsorption performance and influencing factors of fillers such as activated carbon,zeolite,ceramsite and quartz sand were studied.The removal effect of different pollutants by rainwater infiltration system was investigated.A short-flow rainwater reuse system was constructed to treat actual rainwater pollution.Based on the experimental study,the system was enlarged to the engineering scale and economic analysis was carried out.The specific research contents and conclusions are as follows:1.The analysis of pollution characteristics of rainwater runoff in Chongqing Yuelai Guobo Center showed that the concentration of pollutants such as pH,SS,TN,TP,TFe and COD decreased continuously with the rainfall time,and finally tended to be stable.Rainwater runoff from greenbelt,roof and road was seriously polluted.The concentration of each pollutant exceeded the standard of GB/T 18921-2002"Water Quality for Landscape Environment".Direct discharge into accepted water environment will cause pollution.Therefore,it needs to be treated.The analysis of the initial flushing effect showed that there are different degrees of initial flushing effect in road,roof and green land rainwater runoff.The pollutants Fe,TP,TN,SS and COD carried by FF30-FF40 in road rainwater runoff are80%-84%,78%-88%,46%-54%,65%-74%and 84%-85%,respectively.The pollutants Fe,TP,TN,SS and COD carried by FF30-FF40 in roof rainwater runoff are 79%-81%、53%-64%、37%-51%、69%-89%、63%-74%.The pollutants Fe,TP,TN,SS and COD carried by FF30-FF40 in green land rainwater runoff are 38%-47%,55%-63%,63%-81%,58%-71%,69%-89%,respectively.2.The adsorption properties and influencing factors of activated carbon,zeolite,ceramsite and quartz sand were investigated.The experimental data were fitted by Langmuir and Freundlich isothermal adsorption model,adsorption kinetic model and intraparticle diffusion model.The adsorption of P and Fe on activated carbon,zeolite,ceramsite and quartz sand can be fitted by Langmuir and Freundlich isotherm adsorption models.The adsorption capacity of P was activated carbon(0.14 mg/g)>zeolite(0.09 mg/g)>ceramic(0.08 mg/g)>(0.06 mg/g);the adsorption capacity of Fe was activated carbon(0.79 mg/g)>Ceramsite(0.76 mg/g)>Zeolite(0.51 mg/g)>Quartz sand(0.26 mg/g).The adsorption of P by activated carbon and zeolite followed the pseudo-first-order kinetic model better,that is,physical adsorption was the dominant step,which was the rate control step;the adsorption of P by ceramsite and quartz sand followed the pseudo-secondary kinetic model better,that is,chemisorption was the dominant step,which was the rate control step.In addition,the adsorption of P and Fe by each filler could be divided into two stages and the intraparticle diffusion was the main rate control step.The adsorption capacity of each filler for P decreased with the increase of pH,while the adsorption capacity of Fe increased with the increase of pH.The acidic condition was favorable for the adsorption of P,and the alkaline condition was favorable for the adsorption of Fe.According to the actual water pH and the experimental results,the optimum pH is 7.0.With the increase of filler dosage,the removal rate increased first and then tended to be stable,but the unit adsorption capacity decreased.Considering comprehensively,the suitable dosage is 100 g/L.3.The optimal experimental results of infiltration system showed that hydraulic load had little effect on SS removal rate,while the removal rates of TP,TFe and COD decreased with the increase of hydraulic load.The optimal hydraulic load was 0.2747 m~3/m~2·h,and the filtration rate was1.38 L/h.At low pollution load,four single filler systems had an ideal effect on the removal of contaminants,that was,when the concentration of pollutants were COD(151.79 mg/L),TFe(0.98 mg/L),TP(0.64 mg/L)and SS(505.36 mg/L),the best removal effect could be achieved.The cumulative 100%particle size of 8(4 single and 4composite fillers)infiltration systems was obviously smaller than that of SS in inlet rainwater,indicating that the infiltration system intercepted most of coarse particles,but it could not remove the particles with diameter less than 16.19 um completely.Eight rapid infiltration systems had high removal efficiency for SS,TFe and TP in simulated rainwater,and canould effectively remove COD,but the removal efficiency of TN and NH4~+-N was not good.In general,the removal efficiency of pollutants by composite fillers infiltration system was better than these by single filler systems.The removal efficiencies of SS by 8 infiltration systems were not much different,all exceeding 90%.The removal efficiencies of COD by QZSC(Percolation column composition)system were the best,reaching 58.50%.The removal efficiencies of TP and TFe by QZSC system were the highest,86.38%and 85.96%,respectively.The removal efficiencies of TN and NH4~+-N by QZSC system were 60.24%and 89.78%,respectively.Generally speaking,QZSC composite fillers infiltration system is the most suitable one.Its removal rates of SS,TFe,TP,COD,TN and NH4~+-N can reach94.64%,85.96%,86.38%,89.03%,60.24%and 89.78%,respectively.The effluent quality of this system can meet the standard of surface water GB/T 18921-2002"Landscape Environment Water Quality",and can be directly recycled.4.A short-flow rainwater reuse infiltration system was constructed,and the performance of actual rainwater runoff pollution treatment was evaluated.The average removal rates of SS,TN,TP,COD and TFe by the short-flow rainwater reuse infiltration system were≥90%,80%,76%,90%and 90%,respectively.The effluent concentration fluctuated within the range of 10-20,1.0~2.5,0.1~0.2,10-20,and 0.9-1.4 mg/L,respectively.The effluent quality of the short-flow rainwater reuse infiltration system can met the standard requirement of surface water GB/T 18921-2002"Landscape Environment Water Quality",which can be used as water for landscape environment,and the purpose of rainwater resource utilization in this paper has been achieved.5.After enlarging the short-flow rainwater reuse infiltration system studied in the laboratory,the technology and economy analysis were carried out according to the construction project.The design of daily rainwater treatment scale was about 15 m~3,and the total annual treatment scale was about 5475 m~3.The price of treated rainwater was converted into the price of tap water.The calculation and analysis results showed that the cost of rainwater reuse was 2.35 yuan/m~3,the annual income of rainwater reuse project was 19.2million yuan/m~3,and the annual profit of rainwater reuse was 0.12 million yuan/m~3.Rainwater reuse has certain advantages in economy.Construction of rainwater reuse project is economically feasible,and the return is high during the recovery period.Rainwater reuse not only brings considerable economic advantages,but also contains huge indirect comprehensive benefits,mainly economic benefits,environmental benefits and social benefits.The pressure of rainwater discharge from municipal network has been reduced,the overall urban water environment has been improved,the economic burden and shortage of water resources have been alleviated,the living environment has been improved,and the sense of social harmony and happiness has been enhanced. |
PDF Full Text Request