Study on Nitrogen and Phosphorus Treatment in Storm Runoff by Subsurface Constructed Wetland

A simulation of storm runoff treatment with three types of subsurface flow wetlands(SFS) of the pilot-scale bed of blank plant,Phramites communis and Zizania caduciflora was studied.The three types of wetlands' removals of nitrogen and phosphorus and their abilities to withstand shock loadings were investigated.The results show that the subsurface flow wetlands can control the nitrogen and phosphorus concentrations in storm runoff effectively and can strongly withstand shock loading,and that the Phragmites communis of the three SFS techniques preformes the best of all.Using the Phragmites communis,the removal rates of TP,TN reach 92% and 63% respectively when the storm recurrence interval is 5 years and the treatment system area occupies above 3.7% of the catchment area.When the runoff load increases,the treatment system area occupies below 2% of the catchment area and the TN and TP removal rates of using the Phragmites communis bed are 38.6% and 52.6% respectively and that of using the blank plant are 36.3% and 42.7%.At the same HRT averages and compared to previous similar studies,the shock loading can now decrease systematic nitrogen and phosphorus removal.TN and TP removal rates can decrease by about 10% and 15%.