Soil Amendments for Removing Phosphorus, Metals, and Hydrocarbons Andy Erickson, Research Fellow St. Anthony Falls Laboratory April 1, 2014

Acknowledgements Collaborators: –John S. Gulliver (UMN) –Peter T. Weiss (Valparaiso University) –Multidisciplinary Technical Advisory Committee Partners: –UMN, LRRB, EPA/MPCA, CWL, BWSR, RWMWD, City of Prior Lake, PLSLWD, Scott WMO, Carver County, Dakota County, Wright County, VLAWMO, CLFLWD, CRWD, and others!

What’s in Urban Stormwater? Solids –inorganic, organic Nutrients –nitrogen, phosphorus, etc. Metals –copper, cadmium, zinc, etc. Deicing Agents –chloride, salts, etc. Hydrocarbons Bacteria/Pathogens Others

How do Soil Amendments Improve Water Quality? Better infiltration results in more water treated (less overflow) Better filtration results in more particles captured Physical Sorption or precipitation to bind dissolved pollutants Chemical Vegetation uptake to capture or bacterial degradation to transform pollutants Biological

Phosphorus Sorption with Iron Sand Filtration –Particulate capture > 80% Enhanced Sand Filtration –Steel wool increases dissolved phosphorus capture via surface sorption to iron oxide Photo Courtesy: A. Erickson Source: Erickson, A.J., Gulliver, J.S. and Weiss, P.T. (2007) Enhanced sand filtration for storm water phosphorus removal. Journal of Environmental Engineering- ASCE 133(5),

Experimental Results (Iron Enhanced Sand Filtration, SAFL) Detection limit n = 112n = 336 n = 112

Monitoring DataTotal PDissolved P Average Inflow (μg/L, ppb)11116 Average Outflow (μg/L, ppb)2911 Percent of samples below detection (10 μg/L, ppb) 6%70%

Filter Trenches around wet detention ponds (Prior Lake, MN) Normal Water Surface Elevation Drain tile Iron Enhanced Filter Water Level Control Weir Overflow Grate Drain tile Volume Treated by Trenches (Filter Volume)

Testing Data: Average Inflow Phosphate = 69.7 μg/L (ppb) Average Outflow Phosphate = 18.7 μg/L (ppb) Average Reduction = 73.1%

Designing for Phosphorus Capture with Iron As iron rusts, sorption sites for phosphorus are created, therefore: –Design Iron Enhanced Filter systems for watersheds with significant dissolved phosphorus fraction –Ensure the system is oxygenated to ensure iron oxides remain aerobic –Design systems with 8% or less iron by weight to prevent clogging

Metals sorption to Compost Source: Morgan, J. G., Paus, K. A., Hozalski, R. M., and Gulliver, J. S. (2011). "Sorption and Release of Dissolved Pollutants Via Bioretention Media." Project Report 559. St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN.

Expected Lifespan (Zinc at 10%) Source: Morgan, J. G., Paus, K. A., Hozalski, R. M., and Gulliver, J. S. (2011). "Sorption and Release of Dissolved Pollutants Via Bioretention Media." Project Report 559. St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN. Longer for Cadmium 12 inches

Rain gardens sustainably treat petroleum hydrocarbons in stormwater Petroleum Hydrocarbons are captured by sorption to organic matter Biodegradation prevents accumulation of petroleum hydrocarbons Source: LeFevre, G.H., Hozalski, R.M., and Novak, P.J. (2012). "The Role of Biodegradation in Limiting the Accumulation of Petroleum Hydrocarbons in Raingarden Soils." Water Research, 46(20), 6753–6762.

Phosphorus Leaching from Compost Source: Morgan, J. G., Paus, K. A., Hozalski, R. M., and Gulliver, J. S. (2011). "Sorption and Release of Dissolved Pollutants Via Bioretention Media." Project Report 559. St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN.

Other Amendments Alum (water treatment residual) & Hardwood Bark Mulch – Phosphorus sorption (A. Davis, Univ. of Maryland) Commercial products (various) Internal Submerged Zone for denitrification (W. Hunt, North Carolina State University)

Conclusions Dissolved Stormwater Pollutants are important –Approx. 45% of total concentration is dissolved Physical methods are not enough –Chemical and biological mechanisms can be used to capture dissolved fractions There are field-tested solutions! –Minnesota Filter (iron-enhanced sand)  phosphorus –Compost-amended bioretention  metals & petroleum hydrocarbons

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Photo Courtesy: A. Erickson For more information, contact: Andy Erickson