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Enhancing Rain Garden Design to Promote Nitrate Removal via Denitrification
Citation:
STANDER, E. K. AND M. BORST. Enhancing Rain Garden Design to Promote Nitrate Removal via Denitrification. In Proceedings, ASCE/EWRI 2008 Low Impact Development Conference, Seattle, WA, November 16 - 19, 2008. American Society of Civil Engineers (ASCE), Reston, VA, 1-10, (2008).
Impact/Purpose:
to share information
Description:
Recommendations for rain garden media design typically specify high sand content and low organic matter content to promote infiltration and avoid excessive ponding. This design is effective at infiltrating stormwater and removing solids, heavy metals, phosphorus, and some species of nitrogen; however, the aerobic and low carbon conditions inhibit denitrification, the microbial reduction of nitrate to nitrogen gas which is released to the atmosphere. As a result, rain gardens typically release nitrate in effluent. In this study, media enhancements that promote denitrification are tested for hydraulic properties in bench- and full-scale experiments. At the bench scale, media, with one and two layers of shredded, unprinted newspaper added as a carbon source for denitrification, will be tested for drainage properties. If drainage properties are acceptable, then full-scale, outdoor mesocosms containing three experimental treatments, high versus low organic matter content (as newspaper), presence versus absence of a saturated zone at depth, and large versus small mesocosm size, will also be tested for hydraulic properties. Infiltration rates and timing, flow rate, and volume of effluent will be measured following stormwater additions timed to coincide with high or low antecedent moisture conditions. Results will be used to design future nutrient removal studies.
