Monitoring and analysis of pollutants removal efficiencies of typical rainwater projects in Beijing City

In order to compare the pollutant removal effects of different rainwater projects, the rainwater pollutant removal efficiencies of five measurements, including bioretention, grass swale, permeable concrete pavement, permeable brick pavement and vegetation brick pavement, were monitored. The results showed that the bioretention had high removal efficiencies on COD, SS, NH₃-N and TP, and the effluent water quality reached Class Ⅲ standard of Environmental Quality Standards for Surface Water (GB 3838-2002). Especially for COD and SS, the average removal rates reached 82.1% and 70.7%, respectively. Grass swale had a good removal effect on NH₃-N, with an average removal rate of 91.3%. However, TP concentration of effluent was higher than that of influent. The permeable brick pavement released NH₃-N, causing an increase of its concentration in the effluent. Comparing the three types of permeable pavements, the pollutant removal ability of the permeable concrete was the best comprehensively, and its average removal rates of COD, NH₃-N, TP and SS were 57.0%, 72.7%, 79.4%, and 82.2%, respectively. According to the monitoring results and literature reports comprehensively, it was found that bioretention and permeable concrete pavement had higher pollutant removal effects, and grass swale had outstanding performance in removing NH₃-N from rainwater. In the practical application of rainwater projects, appropriate measurement should be selected according to control objectives, costs and pollutant removal efficiency.