Study On Removal Of Phthalate Acid Esters From Sewage Treatment Plant Tailwater By Constructed Wetland

Phthalate acid esters（PAEs）are often used as plasticizers in industry,agriculture and daily necessities.PAEs are inevitably released into the atmosphere,water,soil and sediment during the production,use and disposal stages,which pose a serious threat to the ecological environment and human health in the form of environmental hormone pollutants.At present,the removal effect of PAEs in domestic sewage by urban sewage treatment plants in China is limited,and it is easy to cause secondary pollution to the ecological environment after the tail water is discharged into the natural water body.As an ecological treatment process,constructed wetland plays an important role in the deep purification project of tail water of sewage plants.In this paper,Jiaxing urban sewage treatment plant and the supporting constructed wetland were selected as the research object,and the purification effect of the supporting constructed wetland on the tail water of the sewage treatment plant was detected and analyzed;the effects of zeolite,volcanic stone,medical stone and limestone on three PAEs:Bis（2-ethylhexyl）phthalate（DEHP）,Di-n-butyl phthalate（DBP）and Dimethyl phthalate（DMP）were compared The removal efficiency of PAEs,total nitrogen（TN）,COD_Cr,total phosphorus（TP）and ammonia nitrogen（NH₄⁺-N）in continuous flow constructed wetland and sequencing batch constructed wetland was studied by indoor simulation experiment,and the differences of microbial community structure in two sets of constructed wetland simulation devices were investigated and analyzed,so as to provide theoretical support and reference for further purification of PAEs in wastewater treatment plant tail water by constructed wetland Scientific basis.The main research results are as follows.（1）The target pollutants of constructed wetland tail water purification were determined.The results show that the removal efficiency of DBP,DEHP and DMP PAEs by constructed wetland is not obvious,and the effluent concentration is relatively high,the removal rate is less than 14.96%,the average concentration of PAEs is 1166.67 ng/L,and the average concentration of total nitrogen in constructed wetland effluent is 9.53 mg/L,exceeding class V water standard of environmental quality standard for surface water（GB3838-2002）.（2）The adsorption effects of different matrix fillers on three PAEs at different initial concentrations were investigated.The experimental results of adsorption kinetics of DBP,DEHP and DMP on zeolite,medical stone,volcanic stone and limestone show that the increase of initial concentration of PAEs can promote the adsorption process.With the increase of initial concentration,the adsorption capacity of the four materials for PAEs increases,and the removal rate decreases gradually The adsorption intensity of three PAEs was DEHP>DBP>DMP.（3）The removal efficiency of conventional pollutants by constructed wetlands under different operation modes was compared and analyzed.The optimal removal rates of four conventional pollutants were 52.28%～82.34%for SCW and 0.16%for CCW The results show that the optimal removal rates of four conventional pollutants are 35.56%～78.41%when the COD/TN ratio of influent increases,and the removal rates of TN by SCW and CCW increase by 28.12%and 16.18%respectively.（4）The effects of PAEs removal by constructed wetlands under different operation modes were compared and analyzed.The results showed that the best removal rates of three PAEs were 66.22%～82.9%for SCW and 47.83%～76.41%for CCW at 36 h:12 h and 0.24 m³（m²·d）.（5）The microbial community structure and dominant population in two constructed wetlands filled with zeolite and volcanic stone were compared and analyzed.The results showed that the microbial community structure of SCW and CCW had low similarity,and the microbial community richness and biodiversity of SCW were higher than that of CCW.Therefore,the artificial wetland with zeolite and volcanic stone as fillers and sequencing operation mode was conducive to the growth of aerobic microorganisms and promoted the degradation of PAEs under the action of aerobic microorganisms.（6）The horizontal subsurface flow constructed wetland uses zeolite and volcanic stone as the wetland substrate,and has good removal effect on PAEs in the tail water of sewage treatment plant through sequencing batch operation;increasing the influent cod can further reduce the total nitrogen concentration in the tail water of sewage treatment plant and improve the removal rate of PAEs.