Zeolite amended bioretention media improves nitrogen removal from stormwater

Abstract

Bioretention cells alleviate stormwater toxicity by permeation through soil media. Amending bioretention materials may result in increased chemical pollutant removal while maintaining hydraulic properties. Zeolite was tested in bioretention media for zinc, copper, phosphorus, ammonium, and nitrate removal from synthetic stormwater in a column study. Ecolite did not improve metal or phosphorus removal; however, significantly lower effluent concentrations of ammonium (p < .001) and nitrate (p = .014) were measured compared with the standard media. The standard media averaged a 70% reduction in ammonium concentration, while mixtures containing 10 and 20% Ecolite per volume averaged 86 and 87% reduction, respectively. All media leached higher nitrate concentrations than the influent stormwater. Ecolite significantly increased the saturated hydraulic conductivity by up to 55% (p < .001). The inclusion of Ecolite in bioretention cells may be practical in areas with nitrogen-impaired watersheds.