Expanding population, urbanization and the effects of climate change are forcing water-stressed cities to seek new sources of drinking water. The capture and recharge of urban runoff could expand the groundwater resources of cities while simultaneously providing flood risk mitigation. Unfortunately, urban stormwater contains a variety of pollutants (e.g., nutrients, toxic metals, trace organic contaminants and pathogens) that can compromise groundwater quality. Therefore, cost-effective technologies that provide a means of removing contaminants from urban runoff are essential to efforts to expand local water supplies. We have developed a pilot-scale Capture, Treat and Recharge (CTR) system that employs engineered geomedia to remove contaminants from urban runoff as it percolates into the grounds. The CTR system consists of an iron enhanced sand filter for phosphorous removal, a denitrifying woodchip bioreactor, and columns packed with different biochar- and manganese oxide-containing sand. After approximately 6 months of operation, the iron filter failed while the woodchip bioreactor continued to remove over 90% of the nitrate. A challenge test was conducted on the system after 8 months of conditioning with stormwater collected from a watershed in northern California. For the test, 50 µg L<sup>-1</sup> of a suite of representative organic contaminants was added to synthetic stormwater that closely mimicked the composition of water at the field site. During the challenge tests, hydraulic performance of the geomedia columns was stable and over 80% removal of trace organic compounds was observed. Analysis of samples collected from side-ports on the columns indicated that the biochar was more effective than the manganese oxide with respect to organic contaminant removal. Testing of the CTR systems realistic field conditions has improved this new technology and provided insight into its deployment at full scale.

Enhanced removal of nutrients and trace organic contaminants from urban runoff using biochar and manganese oxide-coated sand geomedia in capture, treatment, and recharge systems

255th National Meeting (2018)

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