Advanced Treatment Of Tail Water From Urban Sewage Plants By Myriophyllum Aquaticum-biofilm Membrane

The fast growing industrialization process has resulted in tremendous environmental problems.The wastewater treatment plants can be an obvious pollution of point source,due to the huge emissions of its tail water,discharging effluent containing contaminants of high concentration to the adjacent waters,which is one of the most recognized factors leading to the water eutrophication.Therefore,it is demanded to optimize the advanced treatment techniques,especially the most promising surface flow constructed wetlands.A combined treatment process of surface flow constructed wetland system of“Myriophyllum aquaticum-biofilm membrane”was conducted at a pilot scale in this study.This system was established to further the treatment of effluent from the wastewater treatment plants to enhance the quality of effluent and to simultaneously increase the spatial usage efficiency of the constructed wetlands and minimize the influences of environmental factors.Additionally,this pilot-scale experiment is to provide useful information as for the optimization of current advanced treatment techniques as well as development of novel ones.Through the test results of the system operation,some conclusions were reached as follows:1)At the mean temperature of 8 to 15℃and 23 to 30℃,the combined“Myriophyllum aquaticum-biofilm membrane”treatment reached the maximized removal efficiency of target contaminants from the synthetic wastewater effluent;2)With the increase of hydraulic retention time（HRT）,the combined“Myriophyllum aquaticum-biofilm membrane”treatment showed increased removal efficiency of nitrogen and phosphorus,and the HRT at 7.5 d was the most optimal condition for this experimented system;3)For the combined“Myriophyllum aquaticum-biofilm membrane”treatment,the rising environmental temperature led to the increment of removal of contaminants,such as ammonia（NH₄⁺-N）,total nitrogen（TN）and chemical oxygen demand（COD）,from the synthetic wastewater effluent,whilst the increased temperature lowered the removal efficiency of total phosphorus;4)At HRT=7.5 d,and the mean temperature at 8 to 15℃and 23 to 30℃,respectively,the combined“Myriophyllum aquaticum-biofilm membrane”treatment can remove 87.7%and 93.4%of ammonia,54.6%and 86.9%of total nitrogen,98.4%and89.5%of total phosphorus and 44.3%and 45.2%of COD from the synthetic wastewater effluent.