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Constructed Treatment Wetlands
for
Stormwater Management
An Overview of The Technology
and Two Case Studies
Constructed Treatment Wetlands
for
Stormwater Management
An Overview of The Technology
and Two Case Studies
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What Is AConstructed Wetland?
What Is AConstructed Wetland?
Saturated Substrates
Definition:A designed and man-made complex of:
Emergent and Submergent Vegetation
Mircobes
Water
Physical, Chemical and Biological ContaminantRemoval Processes that Emulate a Natural WetlandSystem
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Types of ContaminantsTreated
Types of ContaminantsTreated
l Nitrate
l Ammonial Phosphate
l Coliform Bacteria
l Total Suspended Solids (TSS)
l Oil and Greasel Benzene, Ethylbenzene, Toluene and Xylenes (BTEX)
l Chlorinated Solvents
l Polynuclear Aromatic Hydrocarbons (PAH)
l Heavy Metals (iron, lead, zinc, chromium, cadmium, nickel, silver, cooper and manganese
l Alcohols, Glycols
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Rip-Rap PlantingSubstratePlantingSubstrate
Rip-Rap
Water Level
HydraulicGradient
EffluentCollection System
Water Level
To ReceivingSystem
EffluentCollection System
InfluentDistribution
SystemTo Receiving
System
Treatment Media(gravel, sand, soil)
InfluentDistribution
System
OutflowControl
Structure
Treatment Media(gravel, sand, soil)
InflowControl
Structure
OutflowControl
Structure
InflowControl
Structure
Conceptual CTW SubsurfaceFlow Systems
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55
1515
44
33
22
11
00
Typical Construction Costs
CONSTRUCTEDWETLANDS
CONSTRUCTEDWETLANDS
LAGOONSLAGOONS
CONVENTIONALTREATMENT
SYSTEMS
CONVENTIONALTREATMENT
SYSTEMS
$PER
GALLONPERDAY
$PER
GALLONPERDAY
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Anatomy of a Typical CW ProjectAnatomy of a Typical CW Project
ll Work ElementsWork Elements–– Waste stream Characterization AnalysisWaste stream Characterization Analysis–– Treatability White PaperTreatability White Paper–– Site SelectionSite Selection–– Bench Testing (Optional)Bench Testing (Optional)–– Pilot TestingPilot Testing–– FullFull--Scale DesignScale Design–– Construction OversightConstruction Oversight–– Performance EvaluationPerformance Evaluation
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Case Study No. 1 Williamsburg, Virginia
Case Study No. 1 Williamsburg, Virginia
•• Treat surface water runoff into an impoundment Treat surface water runoff into an impoundment impacted by landfill leachateimpacted by landfill leachate
•• COCs: Zinc, Iron and Acidity COCs: Zinc, Iron and Acidity
•• Typical Zinc influent: 800 mg/LTypical Zinc influent: 800 mg/L
•• Treatment Target Treatment Target –– 2.0 mg/L2.0 mg/L
•• Flow range: 100,000 to 150,000 gpdFlow range: 100,000 to 150,000 gpd
•• CTW was retrofitted into the existing impoundmentCTW was retrofitted into the existing impoundment
•• Designed to treat runoff from 100Designed to treat runoff from 100--year storm eventyear storm event
•• 100100--year operational design lifeyear operational design life
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Site PlanSite Plan
Flow into the CTW
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0.1
1
10
100
1000
10000
1/26/9
92/2
5/00
4/30/0
1
6/26/0
2
Zn (m
g/L
)
Effluent Zinc Concentrations: Jan. 1999 to Sept 2002CTW Performance Data: Zinc InInfluent Zinc Concentrations: Jan. 1999 to Oct. 2002
Avg. 70 mg/L
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0
5
10
15
20
25
30
35
1/26/9
9
2/25/0
0
4/30/0
1
6/26/0
2
Zn (m
g/L
)Effluent Zinc Concentrations: Jan. 1999 to Sept 2002
CTW Performance Data: Zinc OutEffluent Zinc Concentrations: Jan. 1999 to Oct. 2002
Hurricane Floyd
Uncontrolled
Operator Release
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Case Study No. 2 Glen Cove, New York
Case Study No. 2 Glen Cove, New York
•• Treat stormwater runoff into Cedar Swamp Creek and Treat stormwater runoff into Cedar Swamp Creek and Mill PondMill Pond
•• COCs: Sediment, Nitrogen and Phosphorus COCs: Sediment, Nitrogen and Phosphorus
•• High flow = 1,280 cfs (575,000 gpm)High flow = 1,280 cfs (575,000 gpm)
•• Project also included:Project also included:
ØØEnhancement of degraded wetlandsEnhancement of degraded wetlands
ØØAesthetic improvement to central area of Glen CoveAesthetic improvement to central area of Glen Cove
ØØEducational and recreational opportunitiesEducational and recreational opportunities
ØØEnhancement of wildlife habitatEnhancement of wildlife habitat
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Cedar Swamp Creek Site PlanCedar Swamp Creek Site Plan
Forebay: mitigate velocity and promote sedimentation
Marsh: pollutant removal
Micropool: collect, polish and discharge water back into the existing creek
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Cedar Swamp Creek
10 ft x 8 ft Culvert
GL
E NC
O VE
AVE
.
PRATT BLVD.
GLE
N COVECREEK
GLE NS
T.
HENDRICKAVE.
RTE. 107
R TE.10 7
CHARLESST.
L.I.R
. R.
300 ftCity of Glen Cove,New York
PedestrianPath
Micropool
Forebay
Mill Pond
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Forebay During ConstructionForebay During Construction
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Forebay and MarshForebay and Marsh
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Mill Pond Interpretive SignsMill Pond Interpretive Signs
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FundingFundingl To encourage environmental and economically sound
development, the New York Department of State (NYDOS) awarded the City of Glen Cove a grant under the Long Island Sound Coastal Management Program to develop the Glen Cove Creek Revitalization Plan.
l A second NYSDOS grant was awarded through the NYS Environmental Protection Fund to the City of Glen Cove to study the feasibility of creating a stormwater treatment system to improve water quality and eliminate and/or reduce siltation in Mill Pond and Glen Cove Creek, and ultimately Hempstead Harbor.
l As part of the Charles Street road extension/upgrade and the incorporation of a pedestrian path into the project design, the Department of Transportation covered all construction costs via the Transportation Equity Act