Study On Treatment Of Urban Landscape Water By Using Combined Multi-layered Biological Filter And Constructed Wetland

With the development of urbanization in China,the landscape function of urban surface water has been paid more attention.But pollution of urban landscape water is widespread.The landscape water is difficult to be treated by conventional wastewater treatment processes because of its natural openness,low concentration and unreasonable carbon/nitrogen（phosphorus）ratio.In this study,a combined process of multi-layered biological filter and constructed wetland was applied to treat the urban landscape water（river water and simulated landscape water）.The results show that there is significant purification effect of the combined process on polluted landscape water.With the multi-layered biological filter hydraulic loading of 2.40 m³·m^-3·d^-1,the constructed wetland hydraulic loading of 0.25 m³·m^-2·d^|（-1）,NH₄⁺-N,TN,TP and COD_Cr concentration in influent are 0.70¹.46,0.73¹.82,0.087⁰.126 and 15.50²0.10 mg·L^-1,average concentrations in effluent are 0.52,0.77,0.039 and 13.4 mg·L^-1,respectively,corresponding to the pollutant removal rate of 53.67% 42.05%,56.10%,and 30.19%,which could meet the Ⅲ,Ⅲ,Ⅱ and Ⅱ standards specified in China’s environmental quality standards for surface water（GB3838-2002）.Constructed wetland could achieve the best treatment effect if using gravel/zeolite composite filler and with reeds.Plants can increase the pollutant removal efficiency up to 11%.On the basis of the above experiments,the effects of simulated closed landscape water were studied under different treatment cycles,and the influence of seasons was discussed.Under the best condition of 14-day cycle in spring,NH₄⁺-N,TN,TP and COD_Cr concentration in influent are 4.31,14.61,0.530 and 57.8 mg·L^-1,average concentrations in effluent are 0.81,5.73,0.060 and 5.0 mg·L^-1,respectively,corresponding to the pollutant removal rate of 81.16%,60.78%,91.35% and 89.35%,and NH₄⁺-N,TP and COD_Cr could meet Ⅲ,Ⅱ and Ⅰ standards specified in China’s environmental quality standards for surface water（GB3838-2002）.14-day is the best cycle period to improve the quality of water in winter.The removal rates of NH₄⁺-N,TN,TP and COD_Cr are 15.38%,46.77%,43.46% and 84.53%.In winter,21-day cycle is the best cycle to remove NH₄⁺-N and TP;14-day cycle is the best cycle to remove the organics;7-day cycle is the best cycle to remove TN.