Study On The Application Of Constructed Wetland In The Advanced Treatment Of Sewage

At present,China's sewage treatment technology has made great progress,but the quality of China's water environment is still not optimistic,and the water pollution situation is still grim.With the introduction of the "Water Pollution Prevention Action Plan" and the increasingly stringent local requirements,the upgrading of sewage treatment plants will become the only way.Therefore,in order to improve the environmental quality of the water body,after the traditional sewage treatment process,an advanced sewage treatment process is added to improve the effluent quality.At present,the advanced treatment technology of sewage is still based on physical and chemical methods,chemical methods and biological methods.As an ecological treatment method,constructed wetland belongs to biological method and enters people's field of vision with its unique treatment method.It has good research prospects and development potential.This paper summarizes the types,composition,decontamination mechanism,advantages and disadvantages,and main application areas of constructed wetlands through literature review and field research.And completed the on-site research on the artificial wetland advanced treatment system of three sewage treatment plants,namely the artificial wetland of an industrial park sewage treatment plant in Guang'an City,the artificial wetland of a medium water treatment project in Chengdu,and the constructed wetland of a wetland park in Chengdu.The COD,ammonia nitrogen and TP of the inlet and outlet water of three typical wetland systems were tracked and monitored,and the purification effect was analyzed.The results show that the constructed wetland system can effectively improve the water quality of a sewage treatment plant in an industrial park in Guang'an,the water from a domestic sewage treatment plant in Chengdu,and the water quality of a polluted river in Chengdu.According to the "Emission Standards for Pollution of Municipal Wastewater Treatment Plants"(GB18918-2002),the water quality of Grade A and the water quality of Class V are upgraded to Class III water quality of Surface Water Environmental Quality Standard(GB3838-2002),and the water output is stable.The COD removal rates of the three wetlands were 40%,60%,and 60%,respectively;the ammonia nitrogen removal rates were40% or more,50% to 70%,and 70%,respectively;the TP removal rates were 45%,70%,and 60%,respectively.This paper separately monitors the autumn and winter of the wetland of the constructed wetland of a sewage treatment plant in an industrial park in Guang'an and the wetland of a wetland park in Chengdu,and a constructed wetland in a water treatment project in Chengdu in summer,autumn and winter,and analyze the purification effect of each season.The purification effect of COD and ammonia nitrogen is greatly affected by seasonal changes,and the purification process of TP is less affected.The overall COD removal effect of the three constructed wetland projects decreased with the decrease of temperature,which reached the lowest in winter,38%,60%,60% respectively.In terms of TP removal rate,the three wetland projects showed a trend of decreasing quarter by season,but the overall change was not significant,and the highest removal rates were 68%,72%,and 67%,respectively.In this paper,three important elements affecting the effluent effect of constructed wetland are analyzed in combination with three constructed wetland advanced treatment projects:wetland plants,wetland substrates and wetland microorganisms.However,the effects of the three parts are different.The main functions of the wetland plants are oxygen supply,the root system provides the space for the microorganisms to attach,and the substrate of the wetland system is stabilized;the role of the matrix is mainly to adsorb phosphorus,provide growth carriers for plants and microorganisms,improve wetland hydrodynamics through reasonable grading,filter SS in wastewater,and further reduce the load for its microbial treatment and avoid blockage of the core bed;.The change of temperature directly affects the growth and activity of plants and microorganisms in the wetland,and then affects the purification effect of the wetland system.The technology can be used for the inferior V natural water body,low-concentration domestic sewage,and the direct purification of the treated water from the first-grade A-standard urban sewage treatment plant or some low-concentration industrial wastewater.The key is to screen suitable plant types,filler types and grading for water quality and quantity,and reasonable countermeasures when the temperature is low in winter.