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?
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