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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