Stormwater Symposium

Oral

393836 - Laboratory Experiments of Abiotic Capture of Nitrate from Urban Runoff and Agricultural Tile Drainage

Thursday, June 7
10:30 AM - 12:00 PM
Location: Greenway AB
Co-Authors: John Gulliver, Minneapolis, MN – University of Minnesota; Bill Arnold, Minneapolis, MN – University of Minnesota

When in excess, nitrate can have devastating effects on marine environments such as hypereutrophication and hypoxia. Nitrate from urban runoff and agricultural tile drainage is often soluble and considered unreactive via ion exchange and sorption. Thus, most stormwater treatment practices are designed for denitrification to capture nitrate, requiring storage of captured stormwater, anaerobic conditions, and residence time for bacterial conversion of nitrate to nitrogen gas. Laboratory experiments reveal, however, that two granular activated carbons (GACs) captured soluble inorganic nitrate from synthetic stormwater, likely via ion exchange. Experiments also revealed that nitrate removal was reduced due to competition with other ions such as (bi)carbonate. In addition, some nitrate captured during loading experiments was released from the GAC during a “clean” water rinse, suggesting the nitrate is loosely attached to the GAC. Despite these limitations, the abiotic capture of nitrate has distinct advantages compared to denitrification for stormwater treatment, including 1) no reliance on denitrification bacterial community, 2) no need for anaerobic conditions, 3) less contact time with the media (~15 minutes), and 4) less storage volume required and thus smaller treatment practices. These advances could result in more capture of nitrate from urban runoff and agricultural tile drainage within smaller footprints, resulting in more cost-effective protection of natural resources.

Andy Erickson


St. Anthony Falls Laboratory

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