Emergent Macrophyte Emergent Macrophyte DensityDensity

In Constructed In Constructed Wetlands for Wetlands for Wastewater Wastewater TreatmentTreatment

Sophie Lagacé, Curtis Sophie Lagacé, Curtis Miller, and Robert Miller, and Robert

GearheartGearheart

Problem StatementProblem Statement

How How much plant material is there in a much plant material is there in a constructed wetland?constructed wetland?

How much surface do the plants offer How much surface do the plants offer for microbial growth?for microbial growth?

How much volumeHow much volume do they occupy?do they occupy?

Why are we interested?Why are we interested?

Design volume Design volume calculationscalculations

Growth surface Growth surface for for microorganismsmicroorganisms

Site ConditionsSite Conditions

Arcata Wastewater Arcata Wastewater Treatment Plant Treatment Plant Treatment marshes Treatment marshes Pilot marshesPilot marshes

Municipal wastewater Municipal wastewater effluent from oxidation effluent from oxidation pondsponds

Cattail-bulrush marshesCattail-bulrush marshes Dormant period (January)Dormant period (January)

Studied Plant SpeciesStudied Plant Species

Hardstem bulrush Hardstem bulrush (Scirpus (Scirpus acutus)acutus) Obligate wetland speciesObligate wetland species Usually 1-3m (3-10 ft) tallUsually 1-3m (3-10 ft) tall Stout, firm, gray-green round Stout, firm, gray-green round

stemstem Up to 30 mm (1¼ in.) at base, Up to 30 mm (1¼ in.) at base,

tapering to 2-4 mm (tapering to 2-4 mm (11//88--11//1616 in.) in.) at topat top

Little leaf and stem litterLittle leaf and stem litter

Studied Plant SpeciesStudied Plant Species

Wide-leaved cattail Wide-leaved cattail (Typha (Typha latifolia)latifolia) Obligate wetland speciesObligate wetland species Usually 1-3m (3-10 ft) tall Usually 1-3m (3-10 ft) tall Stout, smooth cylindrical stem Stout, smooth cylindrical stem

with spongy corewith spongy core 8+ alternate, elongated, 8+ alternate, elongated,

leaves per stem, > 12 mm (½ leaves per stem, > 12 mm (½ in.) widein.) wide

Accumulates leaf and stem Accumulates leaf and stem litterlitter

Field Work - IField Work - I

Select a location and Select a location and

note the species note the species

(monoculture plots)(monoculture plots)

Stake and mark a 1m x Stake and mark a 1m x

1m plot1m plot

Ten plots in all: five for Ten plots in all: five for

TyphaTypha, five for , five for ScirpusScirpus

Field Work - IIField Work - II

Cut stems to about 30-Cut stems to about 30-40 cm above water 40 cm above water level in and around the level in and around the plotplot

Remove the litterRemove the litter

Field Work - IIIField Work - III

Measure water depth Measure water depth

at each corner and in at each corner and in

center of plotcenter of plot

Count every stem Count every stem

within the plotwithin the plot

As a stem is counted, As a stem is counted,

cut it just above cut it just above

water levelwater level

Field Work - IVField Work - IV For two For two ScirpusScirpus plots, measure each stem’s plots, measure each stem’s

average diameter after cutting (round stems)average diameter after cutting (round stems) For two For two Typha Typha plots, measure each stem’s plots, measure each stem’s

maximum and minimum diameters after maximum and minimum diameters after cutting (elliptical stems)cutting (elliptical stems)

Pull five randomly selected stems of Pull five randomly selected stems of Scirpus,Scirpus, whole* whole*

Measure the diameter along the Measure the diameter along the ScirpusScirpus stems stems every 50 mm (2 in.), starting at the base and every 50 mm (2 in.), starting at the base and up to 1mup to 1m

**Typha stems were too decomposed to sample

CalculationsCalculations

Mean areal stem density for each speciesMean areal stem density for each species Mean stem diameter and cross-section for Mean stem diameter and cross-section for

each specieseach species ScirpusScirpus typical taper shape equation typical taper shape equation Wet area for varying water depth and stem Wet area for varying water depth and stem

density for each speciesdensity for each species Submersed volume for varying water depth Submersed volume for varying water depth

and stem density for each speciesand stem density for each species

ResultsResults

Plot 1 288 Plot 2 47Plot 3 152 Plot 5 42Plot 4 224 Plot 6 31Plot 7 148 Plot 9 42Plot 8 145 Plot 10 49Average: 191 Average: 42.2

Stem CountsBulrushes (Scirpus ) Cattails (Typha )

Areal Density: Stems per mAreal Density: Stems per m22

Stem Diameter and Cross-Stem Diameter and Cross-SectionSection

Scirpus acutus:Scirpus acutus: Maximum diameter along the stem Maximum diameter along the stem

varied between 20 and 30 mmvaried between 20 and 30 mm Typical diameter at water level: ~15 mmTypical diameter at water level: ~15 mm Typical cross-section at water level: Typical cross-section at water level:

190mm190mm22

Typha latifolia:Typha latifolia: Assumed constant cross-section along Assumed constant cross-section along

the stemthe stem Typical diameters at water level: 30mm Typical diameters at water level: 30mm

x 40mmx 40mm Typical cross-section at water level: Typical cross-section at water level:

1000mm1000mm22

ScirpusScirpus Typical Taper Shape Typical Taper Shape

Tapering of Scirpus Stems - Non-Linear Regression (4th Order Polynomial)

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

0.00 0.20 0.40 0.60 0.80 1.00

Height Along the Stem (m)

% o

f M

axim

um

Dia

mete

r

% of Maximum Width*

Nonlinear Regression

Wet Area: Wet Area: ScirpusScirpusas mas m22 of surface area per m of surface area per m22 of wetland of wetland

Stem Scirpus Stems per Square MeterDepth (m) 100 150 200 250 3000.25 1.71 2.56 3.42 4.27 5.130.30 2.05 3.07 4.09 5.11 6.140.35 2.37 3.56 4.74 5.93 7.110.40 2.68 4.02 5.37 6.71 8.050.45 2.98 4.47 5.96 7.45 8.940.50 3.26 4.89 6.53 8.16 9.790.55 3.53 5.30 7.07 8.83 10.600.60 3.79 5.68 7.58 9.47 11.370.65 4.04 6.05 8.07 10.09 12.110.70 4.27 6.41 8.54 10.68 12.820.75 4.50 6.75 9.00 11.25 13.500.80 4.72 7.09 9.45 11.81 14.170.85 4.94 7.42 9.89 12.36 14.830.90 5.16 7.74 10.32 12.90 15.480.95 5.37 8.06 10.74 13.43 16.111.00 5.58 8.37 11.16 13.95 16.74

Wet Area: Wet Area: TyphaTyphaas mas m22 of surface area per m of surface area per m22 of wetland of wetland

Depth Low Medium High(m) 30 40 500.25 0.82 1.10 1.370.30 0.99 1.32 1.650.35 1.15 1.54 1.920.40 1.32 1.76 2.200.45 1.48 1.98 2.470.50 1.65 2.20 2.750.55 1.81 2.42 3.020.60 1.98 2.64 3.300.65 2.14 2.86 3.570.70 2.31 3.08 3.850.75 2.47 3.30 4.120.80 2.64 3.52 4.400.85 2.80 3.74 4.670.90 2.97 3.96 4.950.95 3.13 4.18 5.221.00 3.30 4.40 5.50

Cattail Stems per sq. meter

Submersed Volume: Submersed Volume: ScirpusScirpus

as mas m33 per m per m22 of wetland of wetlandScirpus Stems per Square Meter Scirpus Stems per Square Meter

Stem Low Medium High

Depth (m) 100 150 200 250 300

0.25 0.010 0.015 0.020 0.025 0.0300.30 0.012 0.018 0.024 0.030 0.0360.35 0.014 0.021 0.028 0.035 0.0420.40 0.016 0.023 0.031 0.039 0.0470.45 0.017 0.026 0.034 0.043 0.0510.50 0.018 0.028 0.037 0.046 0.0550.55 0.020 0.030 0.039 0.049 0.0590.60 0.021 0.031 0.042 0.052 0.0630.65 0.022 0.033 0.044 0.055 0.0660.70 0.023 0.034 0.046 0.057 0.0690.75 0.024 0.036 0.048 0.059 0.0710.80 0.025 0.037 0.049 0.062 0.0740.85 0.025 0.038 0.051 0.064 0.0760.90 0.026 0.039 0.052 0.066 0.0790.95 0.027 0.041 0.054 0.068 0.0811.00 0.028 0.042 0.056 0.069 0.083

Submersed Volume: Submersed Volume: ScirpusScirpus

as % of volume in water columnas % of volume in water columnScirpus Stems per Square Meter

Stem Low Medium High

Depth (m) 100 150 200 250 300

0.25 4.0% 6.0% 8.1% 10.1% 12.1%0.30 4.0% 6.0% 8.0% 10.0% 12.0%0.35 4.0% 5.9% 7.9% 9.9% 11.9%0.40 3.9% 5.8% 7.8% 9.7% 11.7%0.45 3.8% 5.7% 7.6% 9.5% 11.4%0.50 3.7% 5.5% 7.4% 9.2% 11.1%0.55 3.6% 5.4% 7.2% 9.0% 10.7%0.60 3.5% 5.2% 6.9% 8.7% 10.4%0.65 3.4% 5.1% 6.7% 8.4% 10.1%0.70 3.3% 4.9% 6.5% 8.2% 9.8%0.75 3.2% 4.8% 6.3% 7.9% 9.5%0.80 3.1% 4.6% 6.2% 7.7% 9.2%0.85 3.0% 4.5% 6.0% 7.5% 9.0%0.90 2.9% 4.4% 5.8% 7.3% 8.7%0.95 2.8% 4.3% 5.7% 7.1% 8.5%1.00 2.8% 4.2% 5.6% 6.9% 8.3%

Submersed Volume: Submersed Volume: TyphaTyphaas mas m33 per m per m22 of wetland of wetland

Depth Low Medium High(m) 30 40 500.25 0.01 0.01 0.010.30 0.01 0.01 0.010.35 0.01 0.01 0.020.40 0.01 0.02 0.020.45 0.01 0.02 0.020.50 0.01 0.02 0.020.55 0.02 0.02 0.030.60 0.02 0.02 0.030.65 0.02 0.02 0.030.70 0.02 0.03 0.030.75 0.02 0.03 0.040.80 0.02 0.03 0.040.85 0.02 0.03 0.040.90 0.03 0.03 0.040.95 0.03 0.04 0.051.00 0.03 0.04 0.05

Cattail Stems per sq. meter

Wet AreaWet Area

Bulrush (Scirpus) Wet Area vs. Stem Depthby Stem Areal Density

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

0.00 0.20 0.40 0.60 0.80 1.00

Stem Depth (m)

Sp

ecifi

c S

urf

ace

Are

a (

m2/m

2)

Low 100

Medium 200

High 300

Cattail (Typha) Wet Area vs. Stem Depthby Stem Areal Density

-

1.0

2.0

3.0

4.0

5.0

6.0

0.00 0.20 0.40 0.60 0.80 1.00

Stem Depth (m)

Sp

ecifi

c S

urf

ace

Are

a (

m2/m

2)

Low 30

Medium 40

High 50

Submersed VolumeSubmersed VolumeBulrush (Scirpus) Submersed Volume vs. Stem Depth

by Stem Areal Density

0.00

0.02

0.04

0.06

0.08

0.10

0.00 0.20 0.40 0.60 0.80 1.00

Stem Depth (m)

Volu

me (

m3/m

2)

Low 100

Medium 200

High 300

Cattail (Typha) Submersed Volume vs. Stem Depthby Stem Areal Density

-

0.01

0.02

0.03

0.04

0.05

0.06

0.00 0.20 0.40 0.60 0.80 1.00

Stem Depth (m)

Volu

me (

m3/m

2)

Low 30

Medium 40

High 50

Implications for DesignImplications for Design

Emergent vegetation typically occupies 4 to Emergent vegetation typically occupies 4 to 10% of the available volume 10% of the available volume

Emergent vegetation stems typically offer 1.3 Emergent vegetation stems typically offer 1.3 to 10 mto 10 m22 of surface area for attached growth of surface area for attached growth per mper m22 of wetland (57,000 to 436,000 ft of wetland (57,000 to 436,000 ft22/acre!)/acre!)

Next question for research: Surface area and Next question for research: Surface area and volume of plant litter?volume of plant litter?