[Limestone and pyrite-limestone constructed wetlands for treating river water].

Polluted river water was treated with limestone and pyrite-limestone subsurface horizontal constructed wetlands.The aims were to know the performance of two wetlands on removal of common pollutants,especially nitrogen and phosphorus,and analyze the actions of these minerals.The relationship between hydraulic retention time and purification performance of two constructed wetlands was studied.The optimal hydraulic retention time for pollutant removal was about 3 d,The average removal efficiency of COD,TN and TP were 51%,70% and 95%,respectively.With same influent and hydraulic loading,the average removal efficiency of COD,NH4+ N,TN and TP were 53.93%,82.13%,66%,50.9%,and 51.66%,77.43%,72.06%,97.35% for limestone and pyritelimestone constructed wetlands,respectively.There were few differences between limestone and pyrite-limestone wetlands on COD removal,but the nitrogen and phosphorus removal of pyrite-limestone constructed wetland was higher than that of limestone constructed wetland.The phosphorus removal of pyrite-limestone wetland was more efficiency and stable,not affected by temperature.