Arsenic remediation using constructed treatment wetlands

98 Pages·2016·3.35 MB·English

by  Matthew W. Gorr

The University of Toledo
The University of Toledo Digital Repository
Theses and Dissertations
2011
Arsenic remediation using constructed treatment
wetlands
Matthew W. Gorr
The University of Toledo
Follow this and additional works at:http://utdr.utoledo.edu/theses-dissertations
Recommended Citation
Gorr, Matthew W., "Arsenic remediation using constructed treatment wetlands" (2011).Theses and Dissertations. 576.
http://utdr.utoledo.edu/theses-dissertations/576
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A Thesis
entitled
Arsenic Remediation Using Constructed Treatment Wetlands
by
Matthew W. Gorr
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the
Master of Science degree in Biology

Dr. Daryl Dwyer, Committee Chair

Dr. Jamie Martin-Hayden, Committee Member

Dr. Alison Spongberg, Committee Member

Dr. Defne Apul, Committee Member

Dr. Patricia Komuniecki, Dean
College of Graduate Studies

The University of Toledo
May 2011
Copyright 2011, Matthew W. Gorr
This document is copyrighted material. Under copyright law, no parts of this document
may be reproduced without the expressed permission of the author.
An Abstract of

Wetland test cell characterization for the refinement of a conceptual model of arsenic
treatment wetlands

by

Matthew W. Gorr

As partial fulfillment of the requirements for the Master of Science degree in Biology

The University of Toledo
May 2011

The impact of arsenic contamination is globally evident in agriculture and
industry. Current methods for arsenic removal have several limiting factors that include
usage of large amounts of energy and production of a contaminant by-product.
Treatment wetlands are an alternative, sustainable method of contaminant removal
that are successful in removing organic contaminants from water, but have not yet been
used for arsenic remediation. In this study, small scale (0.57 m x 0.17 m x 0.17 m) test
cells were constructed to assess the ability of wetlands to remediate arsenic
contaminated water. We have proposed a conceptual model that envelops the
potential remediation processes, including soil, plants and microorganisms, within a
treatment wetland for arsenic removal. At the root of these processes is the flow of
water that transports arsenic-laden water to each component of the wetland. In this
experiment, my aim was to predict the transport of arsenate, the species of arsenic
with the greatest adsorption capacity, within the soil and water compartments of the
treatment wetland test cells. This will be accomplished with the following objectives:
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(1) use a bromide tracer test to characterize water movement within the test cells, (2)
characterize the ability of the soil to adsorb arsenate and (3) predict the fate of arsenate
in the cells using these data in an appropriate transport model. Test cells were
constructed with a sandy loam soil, packed to a field bulk density of 1.5 g cm-3. The
computer program, HYDRUS 2D, was selected as the model, because of its capacity to
simulate water and solute transport in soil, and its ability to be calibrated using the
obtained data. A tracer test using bromide and water samplers embedded within the
soil determined that the water was flowing to all the regions of the test cells. An
arsenate adsorption experiment to assess arsenate concentration using ICP-OES found
the soil was capable of adsorbing arsenate with a maximum capacity of 0.371 mg g-1.
The adsorption test obtained Langmuir values of K = 0.2585, η = 695.3 to use with
HYDRUS to model the water movement in the test cells with a close fit to the actual
data. Arsenic was predicted to reach the outlet of the cells in 50 days. This experiment
was the first to characterize water movement and predict arsenate transport through
treatment wetland test cells. Future work using these test cells would be done by
adding other that remove arsenate, e.g. plants. Data can also be used as a framework
to predict of arsenate transport within full scale treatment wetlands.
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For my wife, Kristina, and her love and patience.
Acknowledgements

First and foremost Dr. Daryl Dwyer, who was not just a thesis advisor but a mentor in my career
as a researcher.
Dr. Defne Apul, Dr. James Martin-Hayden, and Dr. Alison Spongberg for their consultation, time,
and patience with this project.
Dr. Jordan Rofkar, Deanna Bobak and Dr. Kris Barnswell for showing me the ropes, help in the
lab, and Sporcle.
Adam Waltz, Ryan Gorr, Marc Morandi, Kevin Keeler and William Gorr for help with construction
and data collection.
And my family, for their support, encouragement and food.

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Contents
Abstract iii
Acknowledgements iv
Contents v
List of Tables viii
List of Figures ix
1 Introduction 1
1.1 Arsenic, Problems and Solutions…………………………..............................................1
1.2 Arsenic in Nature…………………………………………………………………………………………….2
1.3 Arsenic Remediation in Practice Today……………………………………………………………3
1.3.1 Adsorbents……………………………………………………………………………………………3
1.3.2 Precipitates……………………………………………………………………………………………4
1.3.3 Membrane Filtration..……………………………………………………………………………5
1.4 Treatment Wetlands……………………………………………………………………………………….5
1.4.1 Compartmentalization of a Treatment Wetland for Arsenic Removal..6
1.4.2 Conceptual Model of Arsenic Treatment Wetlands……………………………..8
1.4.2.1 Hydrological Processes……………………………………………………………9
1.4.2.2 Media………………………..………………………………………………………….10
1.4.2.3 Biota………………………..……………………………………………………………11
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1.5 Experimental Aim and Objectives…………………………………………………………………12
1.5.1 Objective 1: Tracer Test……………………………………………………………………..12
1.5.2 Objective 2: Soil Characterization and Packing…………………………………..14
1.5.3 Objective 3: Predicting Arsenic Transport.....……………………………………..15
2 Methods 18
2.1 Test Cell Construction……………….…………………………………………………………………18
2.2 Soil Selection, Testing and Packing………………………………………………………………19
2.2.1 Soil Selection……………………………………………………………………….…………….19
2.2.2 Adsorption Test………………………………………………………………………….……..20
2.2.3 Soil Packing………………………………………………………………………….…….………21
2.3 Water Sampling…………….……………………………………………………………….…….………22
2.4 Tracer Test……………….…………………………………………………………….……………………23
2.5 Model……………………………………….………………………………………………………………….23
2.5.1 Program Inputs…………………………………………………………………………………….23
2.5.1.1 Geometry……………………………………………………………………….………..24
2.5.1.2 Domain Properties………………………………………………………….………..24
2.5.1.3 Initial Conditions…………………………………………………………….…………25
2.5.1.4 Boundary Conditions………………………………………………………..……….25
2.5.1.5 Flow and Transport Parameters..…………………………………….………..26
2.5.2 Simulation Stages………………………………………………………………………………….26
3 Results 29
3.1 Soil Analysis Results….……………….………………………………………………………………….29
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3.2 Tracer Test Results…………………….………………………………………………………………….31
3.3 Model Results……..…………………….………………………………………………………………….34
3.3.1 Stage one: Initial Simulation Using Only Flow and Dimension
Parameters……………………………………………………………………………………….…34
3.3.2 Stage Two: Calibrated HYDRUS 2D Using Tracer Test Data………………….35
3.3.3 Stage Three: Calibrated Model Used to Predict Arsenate Transport…….41
4 Discussion 44
4.1 Objective 1: Internal Sampling Successfully Characterized Water Flow ………..44
4.2 Objective 2: Soil Acted as a Good Adsorbent for Arsenate Removal……………..46
4.3 HYDRUS 2D was Capable of Modeling Water and Arsenic Movement at Small
Scale………………………………………………………………………………………………………………47
4.4 Conclusion…………………………………………………………………………………………..………..48
References 50
Appendix A Tracer Test Data for Small Scale Test Cells 58
Appendix B Large Scale Experiment 60
B.1 Large Scale Test Cell Methods.....………………………………………………………..………..60
B.2 Large Scale Test Cell Results………………………………………………………………………….67

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