Research On Pollution Characteristics And Treatment Countermeasures Of Runoff Based On Liuzhen Expressway In Guizhou Province

In China,the water pollution is still serious,the water environment protection is being strengthened constantly,and the research on the runoff pollution of expressway is urgently needed.Under these backgrounds,this paper research on pollution characteristics and treatment countermeasures of expressway runoff based on solving the water pollution of Liuzhen Expressway in Guizhou.The essential conclusions are described as follow:First,due to different influence factors in the research area,the concentrations of characteristic pollutants of expressway runoff were exhibited a great range of variation.The concentrations of highway runoff primary pollutants,such as SS、COD and Petroleum,seriously exceeded the first discharge standard of《Integrated Wastewater Discharge Standard》and the Class Ⅲ standard of《Surface Water Environment Quality Standard》.The concentrations of NH3-N、TP、Pb and BOD5 slightly exceeded the discharge standard,and most of pollutants concentrations exceeded the quality standards,they were defined as the secondary pollutants in expressway runoff.BOD5/COD was in range of 0.0317～0.1475,which means the expressway runoff was poor biodegradability.Second,the pollutants concentrations of expressway runoff showed exponential relationship with the duration of rainfall in each rain event,As the duration of rainfall went on,the concentrations of pollutants were generally decreased.However,this trend was not consistent with the influence of different rainfall periods and different rainfall characteristics.Firstly,as the duration of rainfall went on,the change rates of pollutants concentrations were generally decreased.Secondly,the decline rates of the pollutions concentrations caused by rainfall were positively correlated with the rainfall during the sampling period,the greater the rainfall went,the faster the decreased rate of pollutants concentrations would be.Moreover,the change trends of pollutants concentrations varied in different rainfall periods and different rain event,which were mainly affected by the rainfall and rainfall intensity during the sampling period.Third,based on the statistical data of the pollutants first flush effect(FFE),5.56%rain events showed non-FFE,32.29%occurred the weak FFE,and 62.15%occurred the medium FFE.The FFE of expressway runoff was obviously affected by rainfall intensity.The stronger the rainfall intensity presented,the more obvious the FFE would be.Fourth,a technical scheme of expressway runoff treatment was proposed in this paper,which included four system units:collection unit,pretreatment unit,runoff treatment unit and accident wastewater storage unit.According to the experimental evaluation of the implementation effect,the pollutants of runoff were greatly reduced after having been treated by the treatment facilities,which fully met the environmental requirements.The treatment facilities showed high a treatment efficiency for major pollutants such as SS,COD,petroleum,reaching 80.6%～92.4%,the remaining pollutants also presented a good treatment efficiency of 41.6%～80.1%,which accords with the design expectation.The pollutants increments in the river caused by runoff were very small,after the runoff had been treated by the treatment facilities.The single factor index of the river water quality was 0.03～0.70,which reached the quality standards and showed little detrimental influence on the water environment.