Study And Application Of Constructed Wetland Tailwater Treatment Technology In Southern China

As a kind of ecological treatment technology,constructed wetland technology has the advantages of simple structure,low cost of infrastructure and operation,easy operation and management,and more and more attention has been paid to the improvement of water environment,especially in the tailwater treatment of urban sewage treatment plant.However,the sewage treatment technology of the tailwater constructed wetland has not yet formed a set of mature and reliable technical system,especially the selection and design of the process of the constructedwetland need further improvement.On the basis of relevant materials,combining with the experience in the design work of ecological engineering in recent years and the case of Dongyang sewage treatment plant tailwater constructed wetland project,the selection of process,substrates and wetland plants for different types of wastewater treatment plants are made.It is hoped that it can provide references for the application and popularization of tailwater constructed wetlands.The tailwater constructed wetland mainly includes 3 process links,such as pretreatment,wetland treatment,post treatment and so on.According to the water quality conditions and requirements,land area,construction conditions and so on,the wetland process is rationally selected and combined,and the specific process design and layout are carried out.In this paper,6 kinds of commonly used process combinations and their applicable conditions,such as contact(ecological)oxidation + vertical(horizontal)subsurface flow constructed wetland,coagulant sedimentation + vertical(horizontal)subsurface flow constructed wetland,were summarized.If ammonia nitrogen is removed,the downlink vertical subsurface constructed wetland process which is beneficial to nitrification can be considered.If the total nitrogen is removed,the process combination for denitrification can be used:downlink vertical subsurface vertical subsurface flow constructed wetland,vertical subsurface flow current horizontal subsurface flow wetland,horizontal subsurface flow vertical subsurface flow Artificial wetland.The commonly substrates in constructed wetland are sand,zeolite,slag,volcanic rock and ceramsite.It is necessary to consider the factors such as price,transportation distance,pollutant removal requirement and land area.Generally,the proportion of ceramsite,zeolite,volcanic rock and slag can be properly increased under the conditions of economic conditions,in order to increase the void ratio and improve the removal effect of nitrogen and phosphorus.In the selection of wetland plants,we should first select the local plants with strong pollution resistance and good decontamination effect,and then combine them with the constructed wetland types.Generally,surface flow constructed wetlands should choose shallow root scattered and shallow root tufted wetland plants,such as Canna,reed,Amur grass,and weilgrass,and horizontal and vertical subsurface constructed wetland should choose deep root tufted and deep rooted scattered wetland plants,such as windmill grass,reed bamboo,flower Ye Luzhu,Zizania grass and papyrus.Elephant grass,cattail,calamus,pickerelweed,Shuicong,Thalia etc.The rationality and effectiveness of "contact(ecological)oxidation +ecological treatment + vertical(horizontal)subsurface flow constructed wetland"combined process were analyzed and verified through the monitoring data of water quality in the case of Dongyang sewage treatment plant tail water constructed wetland project,and the problems needed to be paid attention to the design and management of the process were also carried out.The analysis and discussion..