Bioretentions can remarkably improve the rainwater quality. Though iron and aluminum as fillers in bioretentions can remove nitrate nitrogen, its adsorption mechanism is not clear yet and was rarely studied. This paper takes sand, iron powder and aluminum powder as the research objects to study the adsorption characteristics of nitrate nitrogen in the bioretention with different pH values and different ionic strength. The results show that aluminum powder has the highest the adsorption capacity. Langmuir adsorption isotherm equation and the quasi-secondary kinetic model are adopted to analyze the experimental data.

Ammonia nitrogen is one of the important pollutants in urban rainfall. Though iron ions and aluminum ions as a filler for plant retention system have a good effect on the removal of ammonia nitrogen, their adsorption characteristics was rarely studied. This paper uses different media (sand, iron powder, aluminum powder) with different pH values and ionic strengths in the Bioretention system to study the adsorption mechanism of ammonia nitrogen in an artificial rainwater. The result shows that Langmuir isothermal adsorption model is more in line with the ammonia nitrogen adsorption process, and the sand has the best adsorption capacity among three samples. Effect of pH values on adsorption kinetics is also studied.