Compared with conventional waste treatment systems,constructed wetland technology is simple operating and friendly maintaining.And it also has the superiority on cost and landscape value,etc.Substrate, such as slag or gravel,is one of the most important components in the building of constructed wetland system, and plays an important role in the removing process of some pollutants,such as phosphorus,in the constructed wetlands.But the removal of nitrogen by substrates is not high.Therefore,substrates have at...