Devon Frazier, Robin Wagner, Tao Huang, and Christine...
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Hydraulic Characterization of the Talking Water Gardens Wetland Devon Frazier, Robin Wagner, Tao Huang, and Christine Kelly. Chemical, Biological, and Environmental Engineering. Methods Tests were conducted to measure ammonia, nitrate, and tracer dye concentrations throughout the wetland during events spanning November 2011 to May 2012. The ammonia and nitrate concentrations were measured using a spectrophotometer at absorbance wavelengths of 700 and 490 nm, respectively. In-house assay results were compared to measurements recorded by ATI Wah Chang. Future nitrogen tests will use the ATI results. The tracer test added 450 g rhodamine WT (RWT) dye into the ATI Wah Chang influent water, shown in Figure 2. Water samples were collected in two-hour intervals for 64 hours at 11 locations. RWT concentrations were measured using a fluorospectrophotometer at an excitation wavelength of 530 nm and an emission wavelength of 595 nm. The first-order reaction rates of formation are shown in equations: (1) ammonia, (2) nitrite, and (3) nitrate. Differential equations, based on these reactions, were solved by MATLAB ODE45 function to predict concentrations of ammonia, nitrite, and nitrate in TWG. NH 3 = − 1 × NH 3 (1) NO 2 − = 1 × NH 3 − 2 × NO 2 − (2) NO 3 − = 2 × NO 2 − − 3 × NO 3 − (3) Figure 2 – A photograph showing the north influent point, where fluorescent tracer was added to the ATI Wah Chang influent. LGP4 Effluent 0 2 4 6 8 10 12 14 16 0 10 20 30 40 50 60 70 Rhodamine WT Concentration (μg/L) Time Elapsed (Hours) LM2 NLM2 CC WBM4 LGP4 NLM2 CC WBM4 LGP4 LM2 Figure 5 – A graph of RWT concentration versus time for the flow path highlighted in Figure 4, with color-coordinated weir sample locations. Parabolic curves are hand- drawn visual representations of peak concentrations for each sample location. Figure 4 – Map of the TWG showing the relative location of all 10 ponds. One of six flow paths is highlighted. The weirs connecting this path are circled. Results Figure 5 shows that the RWT concentration peaks could be detected using the described methods. The peaks follow expectations of a typical spike test and decrease in magnitude as the dye moves downstream. Samples collected closest to the wetland effluent have the most noise due to the merging of several flow paths and near-background concentrations. Figure 6 shows that a mathematical model based on reaction engineering can successfully predict dye concentration. Variables, such as residence time and pond volume, were updated to optimize the model output. Differences between the theoretical design and optimized volumes give an indication of where dead mixing zones are located, specific to each pond. Results from nitrogen studies in Table 1 show that overall ammonia and nitrogen levels are higher in May than in November. Vegetation, animal life, and warmer air contributes to a more active nitrification-denitrification cycle. This allows for a larger drop in ammonia and nitrate concentrations between influent and effluent locations. 0 Minutes 5 Minutes 1 Minute Figure 3 – RWT entering the wetland at the east oak influent point. The original dye concentration is 25 g/L. Background levels are 0.5 μg/L. Introduction The Talking Water Gardens (TWG) wetland was engineered by CH2M Hill to mitigate the thermal load of ATI Wah Chang and Albany WWTP effluents by 150 million Kilo-calories/day through evapotranspiration. 1 The wetland has a residence time of two days, via 10 ponds and 6 flow paths, to reduce effluent temperature up to 10 °F for a daily average of 12 MGD of water. The water is cooled to protect salmon migration routes along the Willamette River. Current work focuses on the dentrification of ATI Wah Chang water due to possible future regulation on the nitrogen-rich effluent. Figure 1 shows a pathway for nitrification-denitrification process. Recent studies indicate that the removal of nitrogen by Nitrosomonas and Nitrobacter species correlates to the concentration of carbon available in the water. 2 A refined hydraulic characterization of the wetland was needed to introduce carbon sources into targeted regions of TWG. Methods of characterization included nitrogen sampling and a fluorescent tracer study. Figure 1 – The desired nitrification-denitrification process in Talking Water Gardens. Carbon sources will increase the rate of transformation of nitrate into nitrogen gas, which is released into the atmosphere. Figure 6 – A graph of RWT concentration versus time for the LM2 weir, adjacent to the north influent. The points are experimental values from the tracer test in TWG and the line is a model generated in MATLAB by Tao Huang. Table 1 – Ammonia and nitrate concentrations at each TWG influent point and the final effluent. Samples were collected over two different seasons. The removal rate is higher in May than in November. 0 5 10 15 20 25 0 2 4 6 8 10 Rhodamine WT Concentration (μg/L) Time Elapsed (Hours) LM2 Experimental LM2-Model Background Level = 0.5 μg/L November Average May Average Ammonia [mg/L] Nitrate [mg/L] Ammonia [mg/L] Nitrate [mg/L] North Influent (LM2) 3.5 10.1 0.9 14 East Influent (EO3) 2.7 10 0.5 11 South Influent (SIP) 2.1 9.2 0.6 11.3 Final Effluent (LGP4) 1.7 8.8 <0.5 7.4 LM2 NLM2 CC WBM2 Map not to scale NH 3 NO 2 - NO 3 - N 2 Ammonia Nitrite Nitrate Nitrogen Gas Talking Water Gardens was designed by CH2M Hill and Kurisu International, Inc. The wetland is supported by the cities of Albany and Millersburg, OR and ATI Wah Chang. 1 Madison, Mark. Talking Water Gardens. Pacific Northwest Clean Water Association. Spring 2010. Pg 18-19. 2 Hart, Jeff. Evaluating the Rates of Nitrate Removal for a Nitrate Containing, Low Organic, Carbon Wastewater Interacting with Carbon-containing Solid Substrates. Oregon State University. March, 16, 2012. Special thanks to Phil Harding, Mark Dolan, Curtis Lajoie, Jimmy Beaty, Josh Marsh, Xiao-Yue Han, and the volunteers that assisted us during our 60+ hour sampling event. Acknowledgements Future Work The overall goal of the hydraulic characterization study is to optimize nitrogen removal from the wetlands. The MATLAB model will continue to be optimized with bench-scale and wetland experiments. Use of the model will allow researchers to see data from theoretical tests when resources are not available to conduct long-term investigations. Nitrogen removal in the Talking Water Gardens wetland will be optimized by locating dead zones and active volume. Previous research has determined the nitrogen removal abilities of various carbon- based materials , such as woodchips and biochar. 2 Dead zones will indicate where carbon should be placed in each pond to enhance TWG’s natural ability to remove harmful nitrogen-species.
Transcript of Devon Frazier, Robin Wagner, Tao Huang, and Christine...
Hydraulic Characterization of the Talking Water Gardens Wetland Devon Frazier, Robin Wagner, Tao Huang, and Christine Kelly. Chemical, Biological, and Environmental Engineering.
Methods
Tests were conducted to measure ammonia, nitrate, and tracer dye concentrations throughout the wetland during events spanning November 2011 to May 2012. The ammonia and nitrate concentrations were measured using a spectrophotometer at absorbance wavelengths of 700 and 490 nm, respectively. In-house assay results were compared to measurements recorded by ATI Wah Chang. Future nitrogen tests will use the ATI results. The tracer test added 450 g rhodamine WT (RWT) dye into the ATI Wah Chang influent water, shown in Figure 2. Water samples were collected in two-hour intervals for 64 hours at 11 locations. RWT concentrations were measured using a fluorospectrophotometer at an excitation wavelength of 530 nm and an emission wavelength of 595 nm. The first-order reaction rates of formation are shown in equations: (1) ammonia, (2) nitrite, and (3) nitrate. Differential equations, based on these reactions, were solved by MATLAB ODE45 function to predict concentrations of ammonia, nitrite, and nitrate in TWG.
𝑟NH3= −𝑘1 × NH3 (1)
𝑟NO2− = 𝑘1 × NH3 − 𝑘2 × NO2
− (2) 𝑟NO3
− = 𝑘2 × NO2− − 𝑘3 × NO3
− (3)
Figure 2 – A photograph showing the north influent point, where fluorescent tracer was added to
the ATI Wah Chang influent.
LGP4 Effluent
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70
Rh
od
amin
e W
T C
on
cen
trat
ion
(µ
g/L
)
Time Elapsed (Hours)
LM2
NLM2
CC
WBM4
LGP4
NLM2
CC
WBM4
LGP4
LM2
Figure 5 – A graph of RWT concentration versus time for the flow path highlighted in Figure 4, with color-coordinated weir sample locations. Parabolic curves are hand-
drawn visual representations of peak concentrations for each sample location.
Figure 4 – Map of the TWG showing the relative location of all 10 ponds. One of six flow paths is highlighted. The weirs connecting this path are circled.
Results
Figure 5 shows that the RWT concentration peaks could be detected using the described methods. The peaks follow expectations of a typical spike test and decrease in magnitude as the dye moves downstream. Samples collected closest to the wetland effluent have the most noise due to the merging of several flow paths and near-background concentrations.
Figure 6 shows that a mathematical model based on reaction engineering can successfully
predict dye concentration. Variables, such as residence time and pond volume, were updated to optimize the model output. Differences between the theoretical design and optimized volumes give an indication of where dead mixing zones are located, specific to each pond.
Results from nitrogen studies in Table 1 show that overall ammonia and nitrogen levels are
higher in May than in November. Vegetation, animal life, and warmer air contributes to a more active nitrification-denitrification cycle. This allows for a larger drop in ammonia and nitrate concentrations between influent and effluent locations.
0 Minutes 5 Minutes 1 Minute
Figure 3 – RWT entering the wetland at the east oak influent point. The original dye concentration is 25 g/L. Background levels are 0.5 µg/L.
Introduction
The Talking Water Gardens (TWG) wetland was engineered by CH2M Hill to mitigate the thermal load of ATI Wah Chang and Albany WWTP effluents by 150 million Kilo-calories/day through evapotranspiration.1 The wetland has a residence time of two days, via 10 ponds and 6 flow paths, to reduce effluent temperature up to 10 °F for a daily average of 12 MGD of water. The water is cooled to protect salmon migration routes along the Willamette River. Current work focuses on the dentrification of ATI Wah Chang water due to possible future regulation on the nitrogen-rich effluent. Figure 1 shows a pathway for nitrification-denitrification process. Recent studies indicate that the removal of nitrogen by Nitrosomonas and Nitrobacter species correlates to the concentration of carbon available in the water.2 A refined hydraulic characterization of the wetland was needed to introduce carbon sources into targeted regions of TWG. Methods of characterization included nitrogen sampling and a fluorescent tracer study.
Figure 1 – The desired nitrification-denitrification process in Talking Water Gardens. Carbon sources will increase the rate of transformation of nitrate into nitrogen gas, which
is released into the atmosphere.
Figure 6 – A graph of RWT concentration versus time for the LM2 weir, adjacent to the north influent. The points are experimental values from the tracer test in
TWG and the line is a model generated in MATLAB by Tao Huang.
Table 1 – Ammonia and nitrate concentrations at each TWG influent point and the final effluent. Samples were collected over two different seasons.
The removal rate is higher in May than in November.
0
5
10
15
20
25
0 2 4 6 8 10
Rh
od
amin
e W
T C
on
cen
trat
ion
(µ
g/L)
Time Elapsed (Hours)
LM2 Experimental
LM2-Model
Background Level = 0.5 µg/L
November Average May Average
Ammonia [mg/L]
Nitrate [mg/L]
Ammonia [mg/L]
Nitrate [mg/L]
North Influent (LM2) 3.5 10.1 0.9 14
East Influent (EO3) 2.7 10 0.5 11
South Influent (SIP) 2.1 9.2 0.6 11.3
Final Effluent (LGP4) 1.7 8.8 <0.5 7.4
LM2
NLM2
CC
WBM2
Map not to scale
NH3
NO2-
NO3-
N2
Ammonia
Nitrite
Nitrate
Nitrogen Gas
Talking Water Gardens was designed by CH2M Hill and Kurisu International, Inc. The wetland is supported by the cities of Albany and Millersburg, OR and ATI Wah Chang.
1 Madison, Mark. Talking Water Gardens. Pacific Northwest Clean Water Association. Spring 2010. Pg 18-19.
2 Hart, Jeff. Evaluating the Rates of Nitrate Removal for a Nitrate Containing, Low Organic, Carbon
Wastewater Interacting with Carbon-containing Solid Substrates. Oregon State University. March, 16, 2012.
Special thanks to Phil Harding, Mark Dolan, Curtis Lajoie, Jimmy Beaty, Josh Marsh, Xiao-Yue Han, and the volunteers
that assisted us during our 60+ hour sampling event.
Acknowledgements
Future Work
The overall goal of the hydraulic characterization study is to optimize nitrogen removal from the wetlands. The MATLAB model will continue to be optimized with bench-scale and wetland experiments. Use of the model will allow researchers to see data from theoretical tests when resources are not available to conduct long-term investigations. Nitrogen removal in the Talking Water Gardens wetland will be optimized by locating dead zones and active volume. Previous research has determined the nitrogen removal abilities of various carbon-based materials , such as woodchips and biochar.2 Dead zones will indicate where carbon should be placed in each pond to enhance TWG’s natural ability to remove harmful nitrogen-species.
