DRINKING WATER QUALITY IN NORTHERN MEXICO AND ARSENIC TREATMENT WITH IRON

254 Pages·2005·1.89 MB·English

DRINKING WATER QUALITY IN NORTHERN MEXICO AND ARSENIC
TREATMENT WITH IRON IMPREGNATED GAC
by
Jorge Christian Navarro Aragon

A Thesis Presented in Partial Fulfillment
of the Requirements for the Degree
Master of Science

ARIZONA STATE UNIVERSITY
December 2005
DRINKING WATER QUALITY IN NORTHERN MEXICO AND ARSENIC
TREATMENT WITH IRON IMPREGNATED GAC
by

Jorge Christian Navarro Aragon

has been approved

November 2005

APPROVED:

___________________________________________________________________, _C_h_a_ir_

________________________________________________________________________

________________________________________________________________________
Supervisory Committee

ACCEPTED:

____________________________________
Department Chair

____________________________________
Dean, Division of Graduate Studies

ABSTRACT
Drinking water samples were collected from over 400 sites throughout northern
Mexico along the US border to evaluate water quality. Detectable chlorine residuals
(>0.05 mgCl /L) were present in 80% of the samples indicating at least a minimal level of
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protection for microbial disease. Laboratory analysis of anions, dissolved organic carbon
(DOC), and metals were used to assess the exposure of Mexicans to potentially
dangerous chemicals in the drinking water. The median nitrate concentration was 1 mg
NO -N/L. Approximately 6% of the samples contained fluoride above the USEPA MCL
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of 4 mg/L. Most of the water samples contained low DOC concentrations (<1 mg/L),
indicative of ground waters which are the most prevalent source of drinking water in
northern Mexico. The main focus of this project was arsenic occurrence. Arsenic is
classified as a human carcinogen (prone to cancer of the bladder, lungs, skin, kidney,
liver, and prostate). The states of Sonora and Chihuahua had the highest arsenic
concentrations (30 to >200 µg/L). Approximately 30% of the samples contained arsenic
above the current USEPA MCL and WHO recommended level of 10 µg/L, but only 4%
were above the current Mexican standard of 50 µg/L. In addition, analyses for 20 other
metals were conducted and all these inorganics were below regulatory levels with the
exception of uranium and lead in very limited number of samples.
A second investigation focused on technical feasibility of using iron-oxide
impregnated GAC (Fe-GAC) composites as adsorbents of arsenic and organics. Batch
experiments and rapid small scale column studies (RSSCTs) were conducted in different
water sources to evaluate ~25 formulations of Fe-GACs. Isotherms conducted in model
solutions demonstrated that Solmetex composites have the highest arsenic adsorption
capacity. Freundlich isotherm model indicated a range of qo values of 0.25−1.1
µgAs/mg-dry adsorbent (at C = 10μg/L, C = 100μg/L and pH = 7). Isotherms and
e o
RSSCTs indicated that Fe-GACs could remove arsenate (As V), methyl terbutyl ether
(MTBE) and benzene from Scottsdale ground water. However MTBE and benzene
reduced the arsenic adsorption efficiency of the media approximately 40% (revised at C
e
= 10μg/L) in RSSCTs. Additional RSSCTs showed high removal (q = 0.46 and
o
0.63µgAs/mg-dry adsorbent) for ASU samples and low removal (q = 0.06 and
o
0.08µgAs/mg dry-adsorbent) for the aerogel-GAC and Clemson composites.

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ACKNOWLEDGEMENTS
Drinking Water Quality in the US-Mexico Border Region was funded by Southwest
Center from Environmental Research and Policy project # W-0319. American Water
Works Association project # 3079 supported Aerogel and Iron-Oxide Impregnated
Granular Activated Carbon Media. First I would like to thank Dr. Paul Westerhoff for his
faith on me in working on these projects and his guidance through all the research work. I
would also like to thank Drs. John Crittenden and Paul C. Johnson, members of my
committee that contribute in this project with their knowledge and important input. Peter
Goguen was also a valuable person in this work for his assistance with the instrumental
equipment used in the CEE laboratories. Thanks to Tom Collela who helped me several
times while working in the Environmental Lab with the GFAA instrument. Special
mention for Mario Esparza–Soto who worked with me during the first part of this project
transmitting part of his lab and field experience to me. Thanks to Mohhamad
Badruzaman who assisted me with his knowledge about arsenic treatment in water, lab
work, time and patience. Also I want to name the rest of the research group who always
was there for me to guide me and support me to reach this goal. Andrew Baumgardner,
Troy Benn, YoungII Kim, Naeem Ahmed, Wontae Lee, Bai Yang Chen, Bo Song, Darla
Gill, Steve Aqcuafreda and many others in the Civil and Environmental Department.

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TABLE OF CONTENTS
Page
LIST OF TABLES............................................................................................................x
LIST OF FIGURES.......................................................................................................xiv
CHAPTER
1. INTRODUCTION..........................................................................................1
2. BACKGROUND............................................................................................5
2.1. Arsenic Occurrence in North America....................................................5
2.2. Arsenic Adsorption onto Iron Hydroxides.............................................12
2.3. Composite-GAC Adsorbents.................................................................14
3. EXPERIMENTAL METHODS....................................................................20
3.1. Sampling Strategy..................................................................................20
3.1.1. Sampling Sites in Mexico.............................................................20
3.1.2. Sampling Procedure for Scottsdale Well Sites.............................22
3.2. Iron (Fe)-Granular Activated Carbon (GAC) Materials........................23
3.2.1. Material Characterization..............................................................24
3.2.2. Spectroscopic Characterization.....................................................27
3.3. Stock Solution Preparation for Experiments..........................................31
3.4. Batch Arsenic Adsorption Experiments.................................................31
3.5. Rapid Small Scale Column Studies (RSSCTs)......................................35
4. ANALYTICAL METHODS........................................................................40
4.1. Sample Preservation...............................................................................40
4.2. Glassware Cleaning Procedure..............................................................41
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CHAPTER Page

4.3. Arsenic Analysis by Graphite Furnace Atomic Adsorption (GFAA)....41
4.4. Metals Analysis by Inductively Coupled Plasma Mass Spectrometer
(ICP-MS) Procedure...............................................................................48
4.5. Ion Chromatography Analysis...............................................................49
4.6. Gas Chromatography Analysis..............................................................50
4.7. Chlorine Residual Measurements..........................................................51
4.8. Other Measurements..............................................................................51
5. DRINKING WATER QUALITY IN THE US-MEXICO BORDER .........54
5.1. Non-Metallic Constituents.....................................................................56
5.2. Arsenic Occurrence................................................................................65
5.3. Other Trace Metal Occurrence...............................................................77
5.4. Summary and Conclusions ...................................................................80
6. ARSENIC ADSORPTION BY IRON-GAC MEDIA IN BATCH
TESTS...........................................................................................................83
6.1. Kinetic Tests..........................................................................................83
6.2. Screening Tests......................................................................................85
6.3. Isotherms in Model Solutions and Ground Waters................................90
6.4. pH Effects..............................................................................................97
6.5. Silicon (Si ) and Vanadium (V) Effect..................................................99
6.6. Co-Adsorption of Organic Chemicals and Arsenic.............................101
6.7. Summary .............................................................................................105
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CHAPTER Page

7. ARSENIC REMOVAL BY IRON-GAC MEDIA IN COLUMN
STUDIES....................................................................................................109
7.1. Fe-GAC Media Performance...............................................................109
7.2. Effect of EBCT....................................................................................112
7.3 Comparison of Fe-GAC Composites....................................................116
7.4. Concurrent Arsenic and Organic Removal..........................................118
7.5. Summary..............................................................................................121
8. DISCUSSION.............................................................................................123
8.1. Batch and RSSCT Adsorption Capacities............................................123
8.2. Effects of pH and Ion Competition......................................................132
8.3. Material Properties...............................................................................133
9. SUMMARY AND FUTURE WORK........................................................141
9.1. Water Quality in USA-Mexico Border Region...................................141
9.2. Arsenic Removal by Iron-GAC media................................................144
REFERENCES.............................................................................................................152
APPENDIX
A PRELIMINARY BATCH TESTS BY AEROGEL-GAC MEDIA............157
B AEROGEL-GAC FOR ARSENIC AND URANIUM REMOVAL...........175
C FINAL ISOTHERMS FOR COMPARISON OF FE-GAC MEDIA.........180
D STANDARDS CALIBRATION CURVE FOR MTBE-BENZENE ........195
E ANALYTICAL DATA OF WATER SAMPLES IN MEXICO................201
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CHAPTER Page

F BATCH ISOTHERM TESTS DATA.........................................................210
G RSSCT EFFLUENT DATA.......................................................................227

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