Soil Amendments for Removing Phosphorus, Metals, and Hydrocarbons

Andy Erickson, Research FellowSt. Anthony Falls LaboratoryApril 1, 2014

http://stormwater.safl.umn.edu/

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!

http://stormwater.safl.umn.edu/

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

http://stormwater.safl.umn.edu/

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 pollutantsChemical

• Vegetation uptake to capture or bacterial degradation to transform pollutants

Biological

http://stormwater.safl.umn.edu/

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), 485-497.

http://stormwater.safl.umn.edu/

18.4%

78.6%88.3%

0

100

200

300

400

Dis

solv

ed P

hosp

horu

s Co

ncen

trati

on (m

g/L)

Influent 100% Sand 0.3% iron 2% iron 5% iron

Experimental Results(Iron Enhanced Sand Filtration, SAFL)

Detection limit

n = 112 n = 336 n = 336n = 336 n = 112

http://stormwater.safl.umn.edu/

Iron Enhanced Filter (5% iron filings, Maplewood, MN)

Photo Courtesy: A. Erickson

http://stormwater.safl.umn.edu/

MN (Iron Enhanced) Filter(5% iron filings, Maplewood, MN)

Photo Courtesy: A. Erickson

2009-2011 Monitoring Data Total P Dissolved P

Average Inflow (μg/L, ppb) 111 16

Average Outflow (μg/L, ppb) 29 11

Percent of samples below detection (10 μg/L, ppb)

6% 70%

http://stormwater.safl.umn.edu/

Photos Courtesy: A. Erickson

Iron Enhanced Filter Trenches wet detention ponds (Prior Lake, MN)

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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)

http://stormwater.safl.umn.edu/

2010 Testing Data:Average Inflow Phosphate = 69.7 μg/L (ppb)

Average Outflow Phosphate = 18.7 μg/L (ppb)Average Reduction = 73.1%

Photos Courtesy: A. Erickson

MN Filter Trenches wet detention ponds (Prior Lake, MN)

http://stormwater.safl.umn.edu/

MN Filter Trenches (Prior Lake MN)

Photo Courtesy: A. Erickson

MN Filter Bioretention (Carver County, MN)

MN Filter Weir (Vadnais Heights, MN)

Photo Courtesy: W. Forbord

Photo Courtesy: VLAWMO and EOR

MN Filter Bioretention (Maplewood, MN)

Photo Courtesy: Barr Engineering Company

http://stormwater.safl.umn.edu/

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

http://stormwater.safl.umn.edu/

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.

http://stormwater.safl.umn.edu/

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

http://stormwater.safl.umn.edu/

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.

http://stormwater.safl.umn.edu/

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.

http://stormwater.safl.umn.edu/

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)

http://stormwater.safl.umn.edu/

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

http://stormwater.safl.umn.edu/

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Thank you for your attention!Questions?

Photo Courtesy: A. Erickson

For more information, contact: Andy Erickson (eric0706@umn.edu)