Stormwater runoff has been implicated as a major source of excess nutrients

to surface waters, contributing to the development of eutrophic conditions.

Bioretention, a promising technology for urban stormwater pollution treatment, was

investigated to determine if an aluminum-based water treatment residual (WTR)

amended bioretention soil media (BSM) could adsorb phosphorus to produce

discharge concentrations below 25 μg/L.

 Batch, small column, and vegetated column studies were employed to

determine both the optimal BSM mixture and media performance. Media tests

demonstrated P adsorption proportional to WTR addition. Final selected

experimental media consisted of 75% sand, 10% silt, 5.8% clay, 5.2% WTR, and

3.4% bark mulch (air dry mass basis).This media showed excellent P removal relative

to a non-WTR-amended media. Whereas the control media leached P (71.1%

increase in mass), the experimental media adsorbed 85.7% of the P mass applied,

displaying a cumulative effluent EMC of 16.1 μg/L, below the 25 μg/L goal.