A bioretention medium has considerable influence on the removal of pollutants, especially phosphorus pollutants. In this paper, the phosphorus adsorption properties of three bioretention media (sand, iron powder, and aluminum powder) are studied, and the effects of pH and ionic strength on the phosphorus adsorption are analyzed. Results show that the phosphorus adsorption isotherm can be well modeled by the Langmuir equation. The experimental results show the monolayer adsorption capacity of sand is the highest, while the iron powder the lowest. The pH of the solution has a considerable influence on the phosphorus adsorption of sand and iron powder, but has a minimal effect on aluminum powder.

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.