This presentation explores the issue of phosphorus in stormwater runoff, including what it is, where it comes from, and common phosphorous treatment practices.
2. Phosphorus: What is it and where does it come from?
How do we address Phosphorus in Urban Runoff?
Raising the bar on phosphorus removal the latest research
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and innovation
Agenda
3. Why do we care about Phosphorus?
Aren’t nutrients a good thing?
Phosphorus is usually the most limiting nutrient
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in freshwater systems
Too much of a good things makes watersheds
sick
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Sources of Phosphorus
Weathering of calcium phosphate minerals,
especially apatite
Anthropogenic (human) P is often much greater
than natural inputs of P in many watersheds
Common anthropogenic sources: agriculture,
wastewater, excess fertilizer, faulty septic
Wildlife can also contribute significant amounts
of phosphorus to local watersheds
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Forms of Phosphorus
Total P: Is most common measure of phosphorus
concentrations in runoff and watersheds. TP = DIP + DOP +
PP
We often measure both particulate and dissolved fractions of
phosphorus
o Dissolved P
o Ortho P
o Soluble Reactive P
TP is most commonly regulated
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Phosphorus in Lakes
Lake Productivity
Classification
Total Phosphorus mg/L
Ultra-oligotrophic <5
Oligotrophic 5-10
Mesotrophic 10-30
Eutrophic 30-100
Hypereutrophic >100
Phosphorus concentrations in untreated stormwater are often many times
higher than those in receiving waters!
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Phosphorus in Stormwater
• Phosphorus is often in both solid and soluble forms
• Solid phosphorus tends to be associated with finer particles
• Ratio of solid/soluble is often variable. Research suggests
50/50 split is a reasonable estimate (NYSDEC Chap. 10)
• Previously captured particulate can be leached as soluble P
11. Runoff Reduction
Preventing runoff from occurring or reaching receiving waters
eliminates all of the pollutants that would be carried by that
runoff
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Reduce runoff via LID site design concepts
Retain water onsite
o RWH
o Bioretention
o Pervious pavers
o Infiltration Systems
12. Removing Phosphorus With Treatment
Three primary mechanisms to removal Phosphorus from Urban
runoff:
Sedimentation Physical Filtration Reactive Filtration
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Sedimentation
Examples: Ponds, Vaults, Detention Systems, Hydrodynamic Separators
• Slow water down and allow solids to
settle
• Longer residence time = finer particles
captured
• Phosphorus removal often tied to
residence time
• No capture of dissolved/soluble P
• Leaching possible
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Physical Filtration
Examples: Screening, Media Filters, Sand Filters, Biofilters, Infiltration
• Physical barrier to solid particles
• Good control of TSS and attached
pollutants
• Good removal of particulate metals
and phosphorus
• No removal of dissolved/soluble
pollutants
• Leaching possible
• Longevity must be considered
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Reactive Filtration/ Processes
Reactive filtration media with an affinity for target pollutants,
organic matter,
• Often works in parallel with physical
filtration and/or sedimentation
• Target pollutant is bound to media via
adsorption, ion exchange etc.
• Effective removal of soluble/dissolved
pollutants
• Boosts overall pollutant load reduction
• Prevents leaching
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Bioretention Soil Mix Amendment
with Phosphorus-Adsorbing Sorbtive Media
Fleming College, Centre for Alternative
Wastewater Treatment
Ontario, Canada
Case Study 3
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Filterra Overview
Optimized media gradation
Functions as living biological system
Simple Maintenance
Consistent field removal of >60% TP
Can be deployed boxless
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PhosphoSorb Media
Lightweight, oxide coated, non
toxic, reactive media
Lab testing showed excellent
removal of dissolved P
TAPE and TARP field testing
showing >70% TP reduction
and excellent removal of DP
32. Fleming College
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Soil Mix Composition
Sand
Peat Moss
Sorbtive® Media AI 28x48
• High surface area phosphorus-adsorbing media
• Sand-like gradation
• Added to soil mix on volume basis, ranging 0% - 17%
Soil components mixed in buckets of 2 front-end loaders
33. Regulatory Challenges
NYSDEC 80% TSS, 40% TP threshold is essentially pass fail
Currently no review process in place to assign specific TP
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credit to BMPs
Limited value in achieving >40% TP without means of taking
regulatory credit
In load sensitive watersheds