Many water-stressed cities are considering projects involving the recharge of urban runoff to drinking water aquifers. Unfortunately, urban stormwater often contains contaminants (e.g., nutrients, trace organics, metals and pathogens). Many of the features typically employed in green infrastructure often fail to remove hydrophilic trace organic and metal contaminants. To overcome these existing treatment limitations, cost-effective sustainable technologies are needed to treat stormwater effectively prior to groundwater recharge. In previous research, we identified several different types of engineered geomedia capable of removing these contaminants under laboratory conditions. In this study, we present data from a pilot-scale sequential stormwater infiltration system that employs engineered geomedia to enhance the removal of trace organics and metals from stormwater at an urban site in Los Angeles, CA. 2-stage filters, consisting of 42 columns with an intermediate aeration step, were packed with different configurations of biochar and synthesized manganese oxide-coated sand. Two sets of columns were conditioned for 3 months with stormwater from a retention pond and an adjacent constructed wetland. After this conditioning period, a challenge test was conducted in which 50 μg L<sup>-1</sup> of a suite of representative organic contaminants and metals were added to the runoff. During the test, columns showed reliable hydraulic performance and geomedia amendments significantly enhanced (greater than 90%) the removal of both trace organics and metals compared to sand. Results also indicated that biochar was more effective than the Mn-coated sand for removal of most trace organic contaminants, while metal uptake was higher on the manganese oxide-coated sand. Testing novel stormwater treatment schemes under realistic field conditions improves urban stormwater treatment designs, decrease uncertainties associated with using infiltrated stormwater as a potential source of drinking water, and boost their implementation at full scale.

Enhanced removal of urban stormwater runoff contaminants using biochar and manganese oxide-coated sand geomedia in a sequential biofiltration system

2019 Fall National Meeting

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