Design and Performance Characterization of Roadside Bioretention Systems

Abstract

In the current study, three roadside bioretention systems with different configurations were constructed to investigate their pollutant removal efficiency in different rainfall recurrence intervals. The bioretention systems (referred as units) (unit A: 700 mm height material without submerged zone; unit B: 400 mm height material with 300 mm submerged zone; unit C: 400 mm height material without submerged zone) were used to conduct the rainfall events with uniform 120 min rainfall duration for 2-, 5-, 10-, 15-, and 30-year recurrence intervals. Results reveal that the gradual increase of rainfall return period would have negative effects on TN and NH4+-N removal. The higher filler layer may increase pollutant removal efficiency. Setting a submerged zone could improve the CODMn and TN removal compared to TP and NH4+-N removal. The values for comprehensive reduction rate of pollutant load in the three bioretention systems were recorded as follows: 64% in SS, 50%~80% in TP, 69% in NH4+-N, and 28%~53% in NO3-N separately. These results provide greater understanding of the design and treatment performance of bioretention systems.