Abstract: To evaluate pollutants removal efficiency and dynamic feature of nitrogen and phosphorous removal in a constructed wetland in Rongcheng,Shandong Province,water samples collected from Jan.1999 to Dec.2003 were analyzed.The results showed that the constructed wetlands could effectively reduce output of SS(suspended solids) by 71.8?8.4%,BOD(biological oxygen demand) by 70.4?9.6%,COD(chemical oxygen demand ) by 62.2?10.1%,and fecal coliform by 99.7%.However,the removal efficiency of nitrogen (40.6?15.3%) was relative low,and phosphorous (29.6?12.8%) had the least reduction efficiency.Nitrogen reductions displayed seasonal variations.The least efficient nitrogen reduction happened during Jan.to Mar.(23.0?11.6%),while the most efficient reduction happened during Jul.to Sept.(50.7?12.4%).Seasonal variation of phosphorous reductions was not as obvious as that of nitrogen.The nitrogen reduction efficiency increased from 2001 to 2003.Phosphorous reduction efficiency did not change on the whole from 2001 to 2002,but decreased a little in 2003.

Key words: Veterinary medicines, Ecotoxicology, Environmental impact