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Phosphorus Treatment – Advanced Removal Mechanisms & Amended Design for Stormwater BMPs. Scott Perry, CPSWQ. Nov. 17 th , 2011. Overview. Phosphorus Basics NPS Loads Stormwater BMP performance Ways to Increase Phosphorus Removal Advanced Removal Mechanism Amended BMP Designs
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Phosphorus Treatment – Advanced Removal Mechanisms & Amended Design for Stormwater BMPs Scott Perry, CPSWQ Nov. 17th, 2011
Overview • Phosphorus Basics • NPS Loads • Stormwater BMP performance • Ways to Increase Phosphorus Removal • Advanced Removal Mechanism • Amended BMP Designs • Things to Avoid
Phosphorus Basics • Essential nutrient for life • Cyclic between land & water • Limiting nutrient in freshwater
Phosphorus added Fisheries and Oceans Canada - 1973 Canadian Experimental Lakes Area # 226: • Plastic Curtain divides lake • Carbon & Nitrogen added to both sides • Phosphorus added to lower half
Lake Erie - Oct. 2010 Lake Erie – Sept. 2009 Lake Erie – Sept. 2008
Problem: • Excess Phosphorus in fresh water causes Eutrophication (over enrichment): • Algal blooms • Micro-toxins … Cyanobacteria • Hypoxia • Fish kills • Invasive species Lake Champlain AP & VPR News - 2010
Additional Issues : • Taste & odor problems • Fish & aquatic community • Recreational quality • Property values • Drinking Water Cost Charles River – Boston Metro
NPS Phosphorus Sources • Fertilizers • Animal & Pet Waste • Vegetation & Leaves • Detergents • Erosion & Sediment Loss • Hydrocarbons & Lubricants • Airborne Fallout: Dust, Pollen, Fossil Fuels • Waste Water (CSO / Septic)
Chesapeake Bay Watershed Relative Responsibility for Pollution Loads to the bay Sediment Nitrogen Phosphorus
Phosphorus Stormwater Loading by Land Use EPA Stormwater BMP Design Guide, 2004
Imperviousness Cover &Phosphorus Load Center for Watershed Protection - Schueler and Caraco 2001
Total Phosphorus (mg/L) % Tree Canopy USGS Water-Resources Investigations Report 99–4021 Phosphorus Load with Increasing % Tree Canopy
Total Phosphorus (mg/L) % Tree Canopy USGS Water-Resources Investigations Report 99–4021 Roadway Phosphorus EMC with Increasing % Tree Canopy
Sediment particle Total Phosphorus (TP) Partitioning • Particulate-Bound (PB) Phosphorus • Dissolved Phosphorus (DP) • Bio-available • “QUICK SUGAR” for Algal Blooms
Phosphorus Partitioning by Land Use TP = Particulate-bound phosphorus & Dissolved Phosphorus DP = Dissolved Phosphorus PB = Particulate-bound Phosphorus National Stormwater Quality Database New York State DEC, 2008
TSS Phosphorus in Stormwater
Typical Urban Stormwater BMPs designed to captures 80% TSS: Dissolved Phosphorus (DP) Particulate-bound Phosphorus (PB) + or Sediment particle 50% TP --- Dissolved (< 0.45-mircons) 50% TP --- Associated with TSS (sediment) 80% TSS capture X 50% (particulate-bound phosphorus) = 40% (TP) Removal
Range of Total Phosphorus (TP) % Removal per BMP Type Center for Watershed Protection, National Pollutant Performance Removal Database version3, Sept. 2007
Factors impacting Phosphorus Fate & Transport • Water chemistry conditions • pH • Alkalinity • Temperature / Seasonality • Redox potential • Particle charge • Concentration • Time / Maintenance frequency
Phosphorus Fate • Phosphorus speciation will shift • Examples • Runoff pH • Concrete Road > 7.0 vs Asphalt < 5.0 • Bottom of Lakes • Anaerobic activity / decaying organics
Absorption Adsorption Sorption • Combination of physiochemical interactions; • Adsorption - surface attachment • Absorption - internal attachment (sponge) • Ion Exchange - displacement of ions (Ca, Mg, Na) • Sorption Capacity --- mg/g Compared to soils … • Ion Exchange Capacity --- meq/100g
Sediment particle Methods to Increase TP removal & reduce variation
Sediment particle 1 - Increase TSS Removal • Achieve > 80% TSS Removal • Remove the most particulate-bound phosphorus • Silt-sized particles (Filtration) (63-microns) • Prevent Resuspension
TSS Particulate-Bound Phosphorus Silt & Clay
2 - Mitigate Phosphorus Speciation Shift • Prevent or mitigate anaerobic conditions • Maintenance (removal of decaying materials) • Catchbasins • Forebays • Wetlands • Underground Systems
3 - Runoff Reduction --- i.e. Infiltration Green Infrastructure • Reduce Impervious Cover and/or Impact • Maximize Infiltration • Maximize Evapotranspiration • Combine Technology with Green Infrastructure
Range of Total Phosphorus (TP) % Removal per BMP Type Center for Watershed Protection, National Pollutant Performance Removal Database version3, Sept. 2007
Sediment particle 4 - Target ALL Phosphorus (i.e. ... The Dissolved Phase too) Particulate bound Dissolved Phosphorus
Advanced Removal Mechanisms Practices that do not Infiltrate 100% • Engineer to Capture Dissolved Phosphorus • Amend & Design • Engineered Media • Displace conventional media or aggregate • Polish exfiltrating systems
Quantifying Engineered Media • Isotherm – • Best Case Maximum capacity? • Kinetics – • How fast can it be sorbed? • Breakthrough – • Volume of Pollutant/WQv treated? (maintenance) • Desorption – • Retaining DP … is the bond strong enough?
What is Breakthrough? Influent Effluent
Applications Amended Low Impact Development Surface Filters that Exfiltrate Sorption based Media
Applications Amended Surface Filters (sand filters / bioretention) Sorption based Media
Amended Pervious Pavements Applications Sorption based Media Under Drain PVC
7-inches of growth media Green Roof Research • Previous Research Observed: • Runoff Reduction • Increased Phosphorus Discharge
Green Roof Research • Previous Research Observed: • Runoff Reduction • Increased Phosphorus Discharge
Greenroof Study Findings • 2009 Runoff Reduction = 42% • 2010 Runoff Reduction = 53% • August - 77% versus October - 15% • NET EXPORTER of Phosphorus • TP discharged: ≈ 2 mg/L to ≈ 0.6 mg/L • Engineered Media … Exfiltration Treatment: • TP Reduction (87%): 1.18 to 0.16 mg/L • SRP Reduction (82%): 0.63 to 0.11 mg/L
Things to Avoid with “Sorption” Materials • Monitor the use of materials prone to desorption • Organics / Compost / Soils • Evaluate Material • Prevent leaching of other Toxics • pH, Heavy Metals • Slag, waste by-products
Things to Avoid with “Sorption” Materials Leaches Phosphorus
Summary • Urban Runoff is a significant Phosphorus contributor • Infiltration should be the first tool to combat • Exfiltration should treat Dissolved Phosphorus (DP) with an Engineered Media
Questions? Scott Perry 301-279-8827 sperry@imbriumsystems.com AP/Larry Dupont – Lake Champlain