Wetlands Ecology in the Lake Erie Basin

Overview

• What is a wetland?

• Case study

• Types of treatment wetlands

• Wetlands for water quality

• Important variables in wetland design

• Management after construction

Case Study

Wolf Creek Watershed

Maumee BayMaumee Bay SP Lodge

Beach advisories due to high coliform counts…..

• Coliform bacteria: Rod-shaped, gram-negative organisms which ferment lactose with the production of acid and gas when incubated at 35-37°C.

• Coliforms are generally not the cause of sickness, but are easy to culture. Their presence indicates that other pathogens of fecal origin may be present.

• Escherichia coli (E. coli), is an example of a coliform bacterium. Found in the intestine of warm-blooded animals. Most E. coli strains are harmless, but some can cause serious food poisoning.

• E coli’s ability to survive outside the body makes them an ideal indicator to test environmental samples for fecal contamination

0

10

20

30

40

50

0 200 400 600 800 1000

5

4

3

2

1

0

E. coli from Rain Flush(Berger Ditch, Maumee Bay SP, Aug 24, 2001)

Time (minutes)

E.

coli

, F

lush

Co

nd

itio

ns

(Th

ou

san

ds

cfu

/100

ml)

E.

coli

, B

ackg

rou

nd

Co

nd

itio

ns

(Th

ou

san

ds

cfu

/100

ml)

Source: University of Toledo/Lake Erie Center, June 2003

Recreational use (primary contact) is impaired if the mean fecal coliform content exceeds 1000 CFU/100ml (for no less than five samples/month)

Maumee Bay 2004: E. Coli

High E. coli in Maumee RiverSettle out in shipping channelLow E. coli levels between CDF & parkHigh E. coli levels at Berger DitchLow E. coli levels at other ditches

Design considerations for E. coli removal

…..go to the literature (case studies)

• Ecological Engineering

• Wetlands Ecology and Management

• Wetlands

• Environmental Science and Technology

Source: Hull and Assoc. 2007

Source: Hull and Assoc. 2007

Wetland Design Considerations for

E. coli Removal• Retention time

– Longer retention promotes removal

• Aquatic macrophytes– Planted systems have higher removal efficiency

• Substrate conditions– Gravel works better than sediments

• Water depth– Shallow systems remove more E. coli

• UV light– High UV (summer) kills E. coli

Overview

• What is a wetland?

• Case study

• Types of treatment wetlands

• Wetlands restoration for water quality

• Important variables in wetland design

• Management after construction

In-stream constructed wetlands

Rain gardens

After Kadlec and Knight (1996)

Soil cross section of a surface and a sub-surface flow wetland

Surface water

Sand, soil or gravel

Overview

• What is a wetland?

• Case study

• Types of treatment wetlands

• Wetlands restoration for water quality

• Important variables in wetland design

• Management after construction

What can be treated?

• Municipal wastewater

• Mine drainage

• Stormwater runoff, non-point-source pollution

• Landfill leachate

• Agricultural wastewater (dairy, swine, feedlot)

How can wetlands transform pollutants in runoff?

• Sedimentation (including filtration, adsorption, and precipitation)

• Volatilization

• Microbial decomposition

• Uptake by plants

Water Quality

Organic Carbon Export from Wetland-dominatedWatersheds Compared with Non-wetland Watersheds

0

4

8

12

16

0 50 100 150 200 250

Annual Runoff (cm)

Exp

ort

(g C

m-2 y

r-1)

Wetland-dominatedWatersheds

Non-WetlandWatersheds

Summary of effectiveness data for constructed and natural wetlands (after Strecker et al. 1992)

Total Suspended Solids (TSS)

Ammonia (NH3)

Total Phosphorus

(TP)

Lead (Pb)

Zinc (Zn)

Constructed Wetlands – Median Removal Rate (%)

80 44 58 83 42

Coefficient of Variation (%) 28 49 48 56 39

Natural Wetlands – Median Removal Rate (%) 76 25 5 69 62

Coefficient of Variation (%) 62 168 1,900 67 47

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60

80

100

0 20 40 60 80 100

Removal of P from wastewater by several wetlandsP

rem

ove

d (

%)

P loading (g m-2 yr-1)

> 25 years ofwastewater applied

< 2 years of wastewater applied

Removal of N from wastewater by several wetlandsN

rem

ove

d (

%)

N loading (g m-2 yr-1)

0

20

40

60

80

100

0 100 200 300 400 500

< 5 years of wastewater applied

> 25 years ofwastewater applied

Potential drawbacks of diverting runoff into natural wetlands

• Changes the hydrology!

• Eutrophication (inorganic nutrients and organic matter)

• Habitat loss (herbicides)

• Ecotoxicological effects (trace metals, organochlorines)

• Pathogenic effects (coliform bacteria and other agents)

Houghton Lake treatment wetland (Michigan) where treated sewage has been applied to a natural peatland since 1978.

a & b. Visually-affected area in 1998 (vegetation changes)

c. Dissolved inorganic nitrogen levels in inflow and outflow

d. Ditto for total phophorus

Overview

• What is a wetland?

• Case study

• Types of treatment wetlands

• Wetlands restoration for water quality

• Important variables in wetland design

• Management after construction

Design requires attention to…

• Hydrology (“First, get the water right”)– drawdowns, rates of inflow/outflow, detention times,

groundwater recharge

• Basin morphology– gentle slopes (6:1 or better) to maximize the littoral

zone, (wetland plants)

– multiple inflow locations and avoid flow channelization

– variety of deep and shallow areas

• Chemical loading– loading graphs, retention rates, empirical models

• Soil physics and chemistry– organic content, soil texture, depth and layering

• Wetland vegetation– establishment, growth form, species

Overview

• What is a wetland?

• Case study

• Types of treatment wetlands

• Wetlands restoration for water quality

• Important variables in wetland design

• Management after construction

After wetlands are constructed and wastewater has been applied, management may include:

• Plant harvesting– harvest multiple times per growing season.

• Wildlife habitat– ancillary goal, but often welcomed

• Mosquito and pathogen control– adjusting hydrology, introducing chemical or biological

control agents

• Water-level management– pulse stability

• Sediment dredging– expensive; also removes seed bank and rooted plants.

Best done during drawdown

New UT treatment wetlands(aka “rain gardens”)

Honors rain garden

Lot-10 rain garden

Carolyn Edwards Memorial Rain Garden (July 2010)

Carolyn Edwards Memorial Rain Garden – July 2010

Carolyn Edwards Memorial Rain Garden – July 2010

May Sue Cave Honors Rain Garden (July 2010)