EPA/600/R-11/027 

March 2011 

Arsenic Removal from Drinking Water by Adsorptive Media

U.S. EPA Demonstration Project at 

Covered Wells in Tohono O’odham Nation, AZ

Final Performance Evaluation Report

by

Ryan J. Stowe* 

Abraham S.C. Chen** 

Lili Wang** 

*

Battelle, Columbus, OH 43201-2693 **ALSA Tech, LLC, Columbus, OH 43219-0693 

Contract No. 68-C-00-185 

Task Order No. 0029 

for 

Thomas J. Sorg 

Task Order Manager 

Water Supply and Water Resources Division

National Risk Management Research Laboratory

Cincinnati, OH 45268 

National Risk Management Research Laboratory

Office of Research and Development

U.S. Environmental Protection Agency 

Cincinnati, OH 45268 
ii

DISCLAIMER

The work reported in this document was funded by the United States Environmental Protection Agency 

(EPA) under Task Order 0029 of Contract 68-C-00-185 to Battelle. It has been subjected to the Agency’s 

peer and administrative reviews and has been approved for publication as an EPA document. Any 

opinions expressed in this paper are those of the author(s) and do not, necessarily, reflect the official 

positions and policies of the EPA. Any mention of products or trade names does not constitute 

recommendation for use by the EPA. 
iii

FOREWORD

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the nation’s 

land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to 

formulate and implement actions leading to a compatible balance between human activities and the ability 

of natural systems to support and nurture life. To meet this mandate, EPA’s research program is 

providing data and technical support for solving environmental problems today and building a science 

knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect 

our health, and prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation 

of technological and management approaches for preventing and reducing risks from pollution that 

threaten human health and the environment. The focus of the Laboratory’s research program is on 

methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems; remediation of contaminated sites, 

sediments and groundwater; prevention and control of indoor air pollution; and restoration of ecosystems. 

NRMRL collaborates with both public and private sector partners to foster technologies that reduce the 

cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions to environmental problems by developing and promoting technologies that protect and improve the environment; 

advancing scientific and engineering information to support regulatory and policy decisions; and providing the technical support and information transfer to ensure implementation of environmental regulations 

and strategies at the national, state, and community levels.

This publication has been produced as part of the Laboratory’s strategic long-term research plan. 

It is published and made available by EPA’s Office of Research and Development to assist the user 

community and to link researchers with their clients.

Sally Gutierrez, Director

National Risk Management Research Laboratory
iv

ABSTRACT

This report documents the activities performed and the results obtained from the arsenic removal 

treatment technology demonstration project at Covered Wells in Tohono O’odham Nation, AZ. The main 

objective of the project was to evaluate the effectiveness of AdEdge Technologies’ (AdEdge) AD-33 

media in removing arsenic to meet the new arsenic maximum contaminant level (MCL) of 10 μg/L. 

Additionally, this project evaluated 1) the reliability of the treatment system (Arsenic Package Unit 

[APU]), 2) the required system operation and maintenance (O&M) and operator skills, and 3) the capital 

and O&M cost of the technology. The project also characterized the water in the distribution system and 

residuals produced by the treatment process. The types of data collected included system operation, water 

quality (both across the treatment train and in the distribution system), process residuals, and capital and 

O&M cost.

The treatment system consisted of two 36-in × 72-in composite vessels in parallel configuration, each 

containing approximately 19 ft3 of AD-33 pelletized media. AD-33 is an iron-based adsorptive media 

developed by Bayer AG and marketed under the name of AD-33 by AdEdge. The treatment system was 

designed for a flowrate of 63 gal/min (gpm) (31.5 gpm per vessel) and an empty bed contact time (EBCT) 

of 4.5 min. Over the performance evaluation period, the actual average flowrate was 29.5 gpm for Vessel 

A and 30.6 gpm for Vessel B, based on readings from the flow meter/totalizer installed on each 

adsorption vessel. The average EBCT was 4.8 min for Vessel A and 4.7 min for Vessel B. 

Each of the two wells had its own chlorination system that consisted of a storage tank, a chemical feed 

pump, and an injector. The chemical feed pumps were tied to the well pumps, which operated on an 

alternating basis, and would start injecting sodium hypochlorite (NaOCl) solutions only when the well 

pumps turned on. The pre-existing chlorine addition systems were configured for prechlorination and 

could not be feasibly converted to post-chlorination as called for in the design since the predominate 

arsenic species was As(V) (>90%) and oxidation of As(III) (average concentration of 0.5 μg/L) was not 

needed. The prechlorination system was used to maintain a target free chlorine residual of 1.0 mg/L (as 

Cl2) or less in the distribution system for disinfection. 

As part of the water treatment system, a Destin North Bay carbon dioxide (CO2) pH adjustment/control 

system was used to adjust pH values of raw water from as high as 8.4 to a target value of 7.0. Due to 

several operational issues, the Destin North Bay system was replaced with an AdEdge CO2 pH 

adjustment/control system approximately five months into the study. The AdEdge system consisted of a 

control panel/cabinet and a "Venturi style" injector. The control panel/cabinet contained components 

such as an "Inlet" solenoid valve, a non-venting single stage pressure regulator, a manual loop controlled 

by a needle valve, an automatic loop controlled by a Burkert pH controller and solid-state SensorX in-line 

pH probe, a rotameter, an "Outlet" solenoid valve, and a check valve. CO2 was injected downstream of 

the chlorination injection point. 

The treatment system began regular operation on February 13, 2008. From February 13, 2008, through 

the end of the performance evaluation study on March 19, 2010, the treatment system operated for a total 

of 3,353 hr, treating approximately 11,686,000 gal (or 41,148 bed volume [BV]) of water. The average 

daily operation time was 4.38 hr/day and the average daily demand was 15,276 gal/day (gpd). 

Total arsenic concentrations in raw water ranged from 29.0 to 38.6 μg/L and averaged 34.9 μg/L. Soluble 

As(V) was the predominating species, ranging from 33.3 to 36.4 μg/L and averaging 32.4 μg/L, based on 

the results from six speciation sampling events. At the end of the performance evaluation study on March 

19, 2010, total arsenic levels in the treated water were 0.6 and 0.4 μg/L following Vessels A and B, 

respectively. (Note that treatment plant water sampling continued on June 15, September 29, and 
v

November 3, 2010, with arsenic concentrations increasing from 1.2 to 4.2 and then to 3.3 μg/L following 

Vessels A and from 0.7 to 3.2 and then 3.0 μg/L following Vessel B. By November 3, 2010, the 

treatment system had treated approximately 60,000 BV of water.) Concentrations of silica and 

phosphorus, which could interfere with arsenic adsorption by competing for adsorption sites, averaged 

26.2 mg/L (as SiO2) and were less than the method detection limit (MDL) of 10.0 μg/L (as P), 

respectively, in raw water. Concentrations of iron, manganese, and other ions in raw water were not high 

enough to impact arsenic removal by the media.

Comparison of the distribution system sampling results before and after operation of the system showed a 

significant decrease in arsenic concentration (from an average of 36.5 to an average of 0.9 μg/L). Arsenic 

concentrations in the distribution system were somewhat higher than those in the system effluent, 

probably caused by redissolution and resuspension of arsenic particles. Lead and copper concentrations 

appeared to have elevated somewhat after operation of the system; however, the elevated levels were 

significantly under their respective action levels.

The capital investment cost of $115,306 included $86,018 for equipment, $12,897 for site engineering, 

and $16,391 for installation. Using the system’s rated capacity of 63 gpm (or 90,720 gpd), the capital 

cost was $1,832/gpm (or $1.27/gpd) of design capacity. The capital cost also was converted to an 

annualized cost of $10,884/yr using a capital recovery factor (CRF) of 0.09439 based on a 7% interest 

rate and a 20-year return period. At a 100% use rate, the unit capital cost would be $0.33/1,000 gal. At 

the actual use rate, the unit capital cost increased to $1.89/1,000 gal. 

The O&M cost included only the cost associated with the media replacement and disposal, CO2 and 

chlorine usage, electricity consumption, and labor. Although media replacement did not occur during the 

performance evaluation study, the media replacement cost would have represented the majority of the 

O&M cost. Media replacement and O&M cost per 1,000 gal of water treated was estimated and plotted 

as a function of the projected media run length to the 10 μg/L arsenic breakthrough. 
vi

CONTENTS

DISCLAIMER .............................................................................................................................................. ii

FOREWORD ............................................................................................................................................... iii

ABSTRACT ................................................................................................................................................. iv

APPENDICES ............................................................................................................................................ vii

FIGURES .................................................................................................................................................... vii

TABLES ..................................................................................................................................................... vii

ABBREVIATIONS AND ACRONYMS .................................................................................................... ix

ACKNOWLEDGMENTS ........................................................................................................................... xi

1.0 INTRODUCTION ................................................................................................................................. 1

1.1 Background ................................................................................................................................... 1

1.2 Treatment Technologies for Arsenic Removal ............................................................................. 2

1.3 Project Objectives ......................................................................................................................... 2

2.0 SUMMARY AND CONCLUSIONS .................................................................................................... 5

3.0 MATERIALS AND METHODS ........................................................................................................... 6

3.1 General Project Approach ............................................................................................................. 6

3.2 System O&M and Cost Data Collection ....................................................................................... 7

3.3 Sample Collection Procedures and Schedules .............................................................................. 7

3.3.1 Source Water ................................................................................................................... 9

3.3.2 Treatment Plant Water ..................................................................................................... 9

3.3.3 Backwash Wastewater/Solids and Spent Media .............................................................. 9

3.3.4 Distribution System Water .............................................................................................. 9

3.4 Sampling Logistics ...................................................................................................................... 10

3.4.1 Preparation of Arsenic Speciation Kits .......................................................................... 10

3.4.2 Preparation of Sampling Coolers ................................................................................... 10

3.4.3 Sample Shipping and Handling ..................................................................................... 10

3.5 Analytical Procedures ................................................................................................................. 10

4.0 RESULTS AND DISCUSSION .......................................................................................................... 12

4.1 Facility Description and Pre-existing Treatment System Infrastructure ..................................... 12

4.1.1 Source Water Quality .................................................................................................... 13

4.1.2 Distribution System ....................................................................................................... 15

4.2 Treatment Process Description ................................................................................................... 15

4.3 System Installation ...................................................................................................................... 26

4.3.1 Permitting ...................................................................................................................... 26

4.3.2 Building Preparation ...................................................................................................... 26

4.3.3 Installation, Shakedown, and Startup ............................................................................ 26

4.4 System Operation ........................................................................................................................ 27

4.4.1 Operational Parameters .................................................................................................. 27

4.4.2 Residual Management ................................................................................................... 29

4.4.3 CO2 pH Adjustment System .......................................................................................... 29

4.4.4 System/Operation Reliability and Simplicity ................................................................ 31

4.5 System Performance ................................................................................................................... 33

4.5.1 Treatment Plant Sampling ............................................................................................. 33

4.5.2 Backwash Wastewater Sampling ................................................................................... 41

4.5.3 Distribution System Water Sampling ............................................................................ 41

4.6 System Cost ................................................................................................................................ 44
vii

4.6.1 Capital Cost ................................................................................................................... 44

4.6.2 Operation and Maintenance Cost................................................................................... 45

5.0 REFERENCES .................................................................................................................................... 47

APPENDICES

Appendix A: OPERATIONAL DATA

Appendix B: ANALYTICAL DATA

FIGURES

Figure 4-1. Fenced-In Area Around Well No. 1 and Pressure Reducing Valve Vault ........................... 12

Figure 4-2. Future Location of Arsenic Treatment System .................................................................... 13

Figure 4-3. Process Flow Diagram for APU System at TOUA .............................................................. 17

Figure 4-4. Process Flow Diagram with Sampling Schedules and Locations ........................................ 18

Figure 4-5. Chlorine Addition System at TOUA .................................................................................... 20

Figure 4-6. Overview of Destin North Bay CO2 pH Adjustment System .............................................. 21

Figure 4-7. Destin North Bay CO2 Gas Flow Control System for pH Adjustment ................................ 22

Figure 4-8. Process and Instrument Diagram of AdEdge CO2 pH Adjustment System ......................... 23

Figure 4-9. AdEdge CO2 pH Adjustment System Control Panel............................................................ 24

Figure 4-10. AdEdge APU Arsenic Adsorption System........................................................................... 25

Figure 4-11. New Treatment Building with 15,000 gal Storage Tank (left)............................................. 27

Figure 4-12. System Instantaneous and Calculated Flowrates ................................................................. 29

Figure 4-13. System Pressure Readings.................................................................................................... 30

Figure 4-14. Differential Pressures Across Vessels A and B ................................................................... 30

Figure 4-15. Concentrations of Various Arsenic Species at IN, AP, TA, and TB Sampling 

Locations .............................................................................................................................. 37

Figure 4-16. Total Arsenic Breakthrough Curves ..................................................................................... 39

Figure 4-17. pH Values Before and After Adjustment ............................................................................. 41

Figure 4-18. Comparison of Arsenic Concentrations in System Effluent and Distribution System ......... 43

Figure 4-19. Media Replacement and Other Operation and Maintenance Cost ....................................... 46

TABLES

Table 1-1. Summary of Round 1 and Round 2 Arsenic Removal Demonstration Locations, 

Technologies, and Source Water Quality ............................................................................... 3

Table 3-1. Predemonstration Study Activities and Completion Dates .................................................... 6

Table 3-2. Evaluation Objectives and Supporting Data Collection Activities ........................................ 7

Table 3-3. Sampling Schedules and Analytes ......................................................................................... 8

Table 4-1. Water Quality Data for Tohono O’odham Nation, AZ ........................................................ 14

Table 4-2. Physical and Chemical Properties of AD-33 Media (a) ......................................................... 15

Table 4-3. Design Specifications of AdEdge APU System ................................................................... 19

Table 4-4. System Punch-List/Operational Issues ................................................................................. 27

Table 4-5. Summary of APU System Operation ................................................................................... 28

Table 4-6. Summary of Analytical Results for Arsenic, Iron, Manganese, Uranium, and 

Vanadium ............................................................................................................................. 33

Table 4-7. Summary of Water Quality Parameter Sampling Results .................................................... 35
viii

Table 4-8. Distribution System Sampling Results ................................................................................. 42

Table 4-9. Capital Investment Cost for APU Arsenic Adsorption System ........................................... 44

Table 4-10. Operation and Maintenance Cost for APU Arsenic Adsorption System ............................. 45
ix

ABBREVIATIONS AND ACRONYMS

Δp differential pressure

AAL American Analytical Laboratories

AM adsorptive media 

APU arsenic package unit

As arsenic

ATS Aquatic Treatment Systems

BET Brunauer, Emmett, and Teller 

bgs below ground surface

BV bed volume 

Ca calcium

C/F coagulation/filtration process 

Cl chlorine

CO2 carbon dioxide 

CRF capital recovery factor

Cu copper 

CWRWS Covered Wells Regional Water System

DO dissolved oxygen 

EBCT empty bed contact time 

EPA U.S. Environmental Protection Agency 

F fluorine 

Fe iron 

gpd gallons per day

gph gallons per hour 

gpm gallons per minute 

HDPE high-density polyethylene 

HIX hybrid ion exchanger 

hp horsepower 

ICP-MS inductively coupled plasma-mass spectrometry

ID identification

IHS Indian Health Services

ISFET Ion Sensitive Field Effect Transistor

IX ion exchange 

LCR Lead and Copper Rule 

lph liter per hour

MCL maximum contaminant level

MDL method detection limit

MEI Magnesium Elektron, Inc.
x

ABBREVIATIONS AND ACRONYMS (Continued)

Mg magnesium 

Mn manganese

mV millivolts

Na sodium 

NaOCl sodium hypochlorite 

NSF NSF International 

O&M operation and maintenance 

OIT Oregon Institute of Technology 

ORD Office of Research and Development

ORP oxidation-reduction potential 

P phosphorus 

PID Proportional Integral Derivative

PO4 phosphate 

POU point of use

psi pounds per square inch

PVC polyvinyl chloride 

QAPP Quality Assurance Project Plan

QA/QC quality assurance/quality control

RO reverse osmosis

RPD relative percent difference

scfh standard cubic foot (feet) per hour

SDWA Safe Drinking Water Act

SiO2 silica

SMCL secondary maximum contaminant level

SO4

2- sulfate

SS stainless steel

STS Severn Trent Services

TCLP toxicity characteristic leaching procedure

TDS total dissolved solids

TOC total organic carbon

TOUA Tohono O’odham Utility Authority 

U uranium 

V vanadium 
xi

ACKNOWLEDGMENTS

The authors wish to extend their sincere appreciation to the Tohono O’odham Utility Authority (TOUA) 

for its support to this demonstration project. Mr. David Saddler, Water Manager, and his staff provided 

logistical support before and during the performance evaluation study. Ms. Myrt McIntyre of TOUA’s 

Water Quality Control Laboratory monitored the treatment system and collected samples from the 

treatment and distribution systems throughout this study period. This performance evaluation study 

would not have been possible without their efforts. 
1

1.0 INTRODUCTION

1.1 Background 

The Safe Drinking Water Act (SDWA) mandates that the U.S. Environmental Protection Agency (EPA) 

identify and regulate drinking water contaminants that may have adverse human health effects and that 

are known or anticipated to occur in public water supply systems. In 1975 under the SDWA, EPA 

established a maximum contaminant level (MCL) for arsenic at 0.05 mg/L. Amended in 1996, the 

SDWA required that EPA develop an arsenic research strategy and publish a proposal to revise the 

arsenic MCL by January 2000. On January 18, 2001, EPA finalized the arsenic MCL at 0.01 mg/L (EPA, 

2001). To clarify the implementation of the original rule, EPA revised the rule text on March 25, 2003, to 

express the MCL as 0.010 mg/L (10 μg/L) (EPA, 2003). The final rule required all community and nontransient, non-community water systems to comply with the new standard by January 23, 2006. 

In October 2001, EPA announced an initiative for additional research and development of cost-effective 

technologies to help small community water systems (<10,000 customers) meet the new arsenic standard, 

and to provide technical assistance to operators of small systems to reduce compliance cost. As part of 

this Arsenic Rule Implementation Research Program, EPA’s Office of Research and Development (ORD) 

proposed a project to conduct a series of full-scale, onsite demonstrations of arsenic removal 

technologies, process modifications, and engineering approaches applicable to small systems. Shortly 

thereafter, an announcement published in the Federal Register requested water utilities interested in 

participating in Round 1 of this EPA-sponsored demonstration program to provide information on their 

water systems. In June 2002, EPA selected 17 out of 115 sites to host the demonstration studies. 

In September 2002, EPA solicited proposals from engineering firms and vendors for cost-effective arsenic 

removal treatment technologies for the 17 host sites. EPA received 70 technical proposals for the 17 host 

sites, with each site receiving one to six proposals. In April 2003, an independent technical panel 

reviewed the proposals and recommended to EPA the technologies they determined to be acceptable for 

the demonstration at each site. Because of funding limitations and other technical reasons, only 12 of the 

17 sites were selected for the demonstration project. Using the information provided by the review panel, 

EPA, in cooperation with the host sites and the drinking-water programs of the respective states, selected 

one technical proposal for each site. 

In 2003, EPA initiated Round 2 arsenic technology demonstration projects that were partially funded with 

Congressional add-on funding to the EPA budget. In June 2003, EPA selected 32 potential demonstration 

sites, including the Covered Wells site in the Gu Achi District of the Tohono O’odham Nation in Arizona. 

The Covered Wells site is operated by the Tohono O’odham Utility Authority (TOUA), which is charged 

by the Nation to provide services, including water/wastewater, electric, telephone, cellular, propane, and 

internet to customers in the Nation. 

In September 2003, EPA again solicited proposals from engineering firms and vendors for arsenic 

removal technologies. EPA received 148 technical proposals for the 32 host sites, with each site 

receiving from two to eight proposals. In April 2004, EPA convened another technical panel to review 

the proposals and provide recommendations to EPA; the number of proposals per site ranged from none 

(for two sites) to four. At the site receiving at least one proposal, the final selection of the treatment 

technology was made through a joint effort by EPA, the state regulators, and the host site. Since then, 

four sites have withdrawn from the demonstration program, reducing the number of sites to 28. AdEdge 

Technologies’ (AdEdge) AD33 Arsenic Removal Technology was selected for demonstration at the 

TOUA site in April 2004. 

 
2

As of July 2010, 39 of the 40 systems were operational, and the performance evaluation of all 39 systems 

was completed.

1.2 Treatment Technologies for Arsenic Removal

The technologies selected for the Rounds 1 and 2 demonstration host sites include 25 adsorptive media 

(AM) systems (the Oregon Institute of Technology [OIT] site has three AM systems), 13 coagulation/

filtration (C/F) systems, two ion exchange (IX) systems, 17 point-of-use (POU) units (including nine 

under-the-sink reverse osmosis [RO] units at the Sunset Ranch Development site and eight AM units at 

the OIT site), and one process modification. Table 1-1 summarizes the locations, technologies, vendors, 

system flowrates, and key source water quality parameters (including arsenic, iron, and pH) at the 40 

demonstration sites. An overview of the technology selection and system design for the 12 Round 1 

demonstration sites and the associated capital cost is provided in two EPA reports (Wang et al., 2004; 

Chen et al., 2004), which are posted on the EPA Web site at 

http://www.epa.gov/ORD/NRMRL/wswrd/dw/arsenic/index.html. 

1.3 Project Objectives

The overall objective of the arsenic demonstration program is to conduct full-scale arsenic treatment 

technology demonstration studies on the removal of arsenic from drinking-water supplies. The specific 

objectives are to:

• Evaluate the performance of the arsenic removal technologies for use on small systems. 

• Determine the required system operation and maintenance (O&M) and operator skill levels. 

• Characterize process residuals produced by the technologies. 

• Determine the capital and O&M cost of the technologies.

This report summarizes the performance of the AdEdge AM system at the Covered Wells site in Tohono 

O’odham Nation, AZ, from February 13, 2008 to March 19, 2010. The data collected included system 

operation, water quality (both across the treatment train and in the distribution system), and capital and 

preliminary O&M cost. 
3

Table 1-1. Summary of Round 1 and Round 2 Arsenic Removal Demonstration 

Locations, Technologies, and Source Water Quality

Demonstration

Location Site Name Technology (Media) Vendor

Design 

Flowrate 

(gpm)

Source Water Quality

As 

(μg/L)

Fe

(μg/L)

pH

(S.U.)

Northeast/Ohio

Wales, ME Springbrook Mobile Home Park AM (A/I Complex) ATS 14 38(a) <25 8.6

Bow, NH White Rock Water Company AM (G2) ADI 70(b) 39 <25 7.7

Goffstown, NH Orchard Highlands Subdivision AM (E33) AdEdge 10 33 <25 6.9

Rollinsford, NH Rollinsford Water and Sewer District AM (E33) AdEdge 100 36(a) 46 8.2

Dummerston, VT Charette Mobile Home Park AM (A/I Complex) ATS 22 30 <25 7.9

Felton, DE Town of Felton C/F (Macrolite) Kinetico 375 30(a) 48 8.2

Stevensville, MD Queen Anne’s County AM (E33) STS 300 19(a) 270(c) 7.3

Houghton, NY(d) Town of Caneadea C/F (Macrolite) Kinetico 550 27(a) 1,806(c) 7.6

Buckeye Lake, OH Buckeye Lake Head Start Building AM (ARM 200) Kinetico 10 15(a) 1,312(c) 7.6

Springfield, OH Chateau Estates Mobile Home Park AM (E33) AdEdge 250(e) 25(a) 1,615(c) 7.3

Great Lakes/Interior Plains

Brown City, MI City of Brown City AM (E33) STS 640 14(a) 127(c) 7.3

Pentwater, MI Village of Pentwater C/F (Macrolite) Kinetico 400 13(a) 466(c) 6.9

Sandusky, MI City of Sandusky C/F (Aeralater) Siemens 340(e) 16(a) 1,387(c) 6.9

Delavan, WI Vintage on the Ponds C/F (Macrolite) Kinetico 40 20(a) 1,499(c) 7.5

Greenville, WI Town of Greenville C/F (Macrolite) Kinetico 375 17 7827(c) 7.3

Climax, MN City of Climax C/F (Macrolite) Kinetico 140 39(a) 546(c) 7.4

Sabin, MN City of Sabin C/F (Macrolite) Kinetico 250 34 1,470(c) 7.3

Sauk Centre, MN Big Sauk Lake Mobile Home Park C/F (Macrolite) Kinetico 20 25(a) 3,078(c) 7.1

Stewart, MN City of Stewart C/F&AM (E33) AdEdge 250 42(a) 1,344(c) 7.7

Lidgerwood, ND City of Lidgerwood Process Modification Kinetico 250 146(a) 1,325(c) 7.2

Midwest/Southwest

Arnaudville, LA United Water Systems C/F (Macrolite) Kinetico 770(e) 35(a) 2,068(c) 7.0

Alvin, TX Oak Manor Municipal Utility District AM (E33) STS 150 19(a) 95 7.8

Bruni, TX Webb Consolidated Independent School 

District

AM (E33) AdEdge 40 56(a) <25 8.0

Wellman, TX City of Wellman AM (E33) AdEdge 100 45 <25 7.7

Anthony, NM Desert Sands Mutual Domestic Water 

Consumers Association

AM (E33) STS 320 23(a) 39 7.7

Nambe Pueblo, NM Nambe Pueblo Tribe AM (E33) AdEdge 145 33 <25 8.5

Taos, NM Town of Taos AM (E33) STS 450 14 59 9.5

Rimrock, AZ Arizona Water Company AM (E33) AdEdge 90(b) 50 170 7.2

Tohono O'odham 

Nation, AZ

Tohono O’odham Utility Authority AM (E33) AdEdge 50 32 <25 8.2

Valley Vista, AZ Arizona Water Company AM (AAFS50/ARM 200) Kinetico 37 41 <25 7.8
4

Table 1-1. Summary of Round 1 and Round 2 Arsenic Removal Demonstration

Locations, Technologies, and Source Water Quality (Continued)

Demonstration

Location Site Name Technology (Media) Vendor

Design 

Flowrate 

(gpm)

Source Water Quality

As 

(μg/L)

Fe

(μg/L)

pH

(S.U.)

Far West

Three Forks, MT City of Three Forks C/F (Macrolite) Kinetico 250 64 <25 7.5

Fruitland, ID City of Fruitland IX (A300E) Kinetico 250 44 <25 7.4

Homedale, ID Sunset Ranch Development POU RO(f) Kinetico 75 gpd 52 134 7.5

Okanogan, WA City of Okanogan C/F (Electromedia-I) Filtronics 750 18 69(c) 8.0

Klamath Falls, OR Oregon Institute of Technology POE AM (Adsorbsia/ARM 200/ArsenXnp) 

and POU AM (ARM 200)(g)

Kinetico 60/60/30 33 <25 7.9

Vale, OR City of Vale IX (Arsenex II) Kinetico 525 17 <25 7.5

Reno, NV South Truckee Meadows General 

Improvement District

AM (GFH/Kemiron) Siemens 350 39 <25 7.4

Susanville, CA Richmond School District AM (A/I Complex) ATS 12 37(a) 125 7.5

Lake Isabella, CA Upper Bodfish Well CH2-A AM (HIX) VEETech 50 35 125 7.5

Tehachapi, CA Golden Hills Community Service 

District

AM (Isolux) MEI 150 15 <25 6.9

AM = adsorptive media process; C/F = coagulation/filtration; HIX = hybrid ion exchange; IX = ion exchange process; RO = reverse osmosis

ATS = Aquatic Treatment Systems; MEI = Magnesium Elektron, Inc.; STS = Severn Trent Services

(a) Arsenic existing mostly as As(III).

(b) Design flowrate reduced by 50% due to system reconfiguration from parallel to series operation. 

(c) Iron existing mostly as Fe(II).

(d) Withdrew from program in 2007. Selected originally to replace Village of Lyman, NE site, which withdrew from program in June 2006.

(e) Facilities upgraded systems in Springfield, OH from 150 to 250 gal/min (gpm), Sandusky, MI from 210 to 340 gpm, and Arnaudville, LA from 385 to 770 gpm. 

(f) Including nine residential units.

(g) Including eight under-the-sink units.
5

2.0 SUMMARY AND CONCLUSIONS

AdEdge’s APU treatment system with AD-33 pelletized media was installed and has operated at the 

Covered Wells site in Tohono O’odham Nation, AZ since February 13, 2008. Based on the information 

collected during the system evaluation period, the following summary and conclusion statements are 

provided. 

Performance of the arsenic removal technology for use on small systems:

• AD-33 media effectively lowered arsenic concentrations to 0.6 and 0.4 μg/L following 

Vessels A and B, respectively, after treating 11,686,000 gal (or 41,148 bed volumes [BV]) of 

water, based on a total media volume of 38 ft3 (19 ft3 per vessel). 

• The operation of the treatment system significantly lowered arsenic concentrations from 36.5 

to 0.9 μg/L (on average) in the distribution system. Although lead and copper levels in the 

distribution system were slightly elevated after the system was put into service, the 

concentrations were significantly below their respective action levels. 

Required system O&M and operator skill levels:

• The operator typically spent over an hour to visually inspect the system, record operational 

parameters, and change out carbon dioxide (CO2) cylinders. Additional time and effort were

required to troubleshoot the problems associated with the CO2 system. 

• Some operational issues were encountered during operation of the Destin North Bay 

and AdEdge CO2 pH adjustment systems. Primary issues involved a leaking 

manifold, a malfunctioning pneumatic flow control valve, a faulty pH meter display, 

a faulty solenoid, and a faulty check valve.

• Operation of the system did not appear to require additional skills beyond those 

necessary to operate the existing water supply equipment, with the exception of the 

CO2 and pH control portion of the system. The CO2 system required additional 

operator training and safety awareness. 

Process residuals produced by the technology: 

• The pressure differential (Δp) measured across the media vessels remained low during

system operation. Therefore, no backwash was required or performed throughout the 

performance evaluation study. 

Cost-effectiveness of the technology:

• Based on the system’s rated capacity of 63 gpm (or 90,720 gal/day [gpd]), the capital cost 

was $1,830/gpm (or $1.27/gpd) of design capacity. 

• Media replacement and disposal did not occur during the performance evaluation

study; however, the cost to change out both vessels (38 ft3 AD-33 media) was 

estimated to be $18,405, which included the replacement media, spent media 

disposal, shipping, labor, and travel.
6

3.0 MATERIALS AND METHODS

3.1 General Project Approach

Following the predemonstration activities summarized in Table 3-1, the performance evaluation study 

of the AdEdge arsenic removal system began on February 13, 2008, and ended on March 19, 2010 (note 

that treatment samples continued to be collected and analyzed on a quarterly basis after the study had 

been ended). Table 3-2 summarizes the types of data collected and considered as part of the technology 

evaluation process. The overall performance of the system was determined based on its ability to 

consistently remove arsenic to below the arsenic MCL of 10 μg/L through the collection of water samples 

across the treatment plant, as described in the Study Plan (Battelle, 2006). The reliability of the system 

was evaluated by tracking the unscheduled system downtime and the frequency and extent of repair and 

replacement. Unscheduled downtime and repair information was recorded by the plant operator on a 

Repair and Maintenance Log Sheet. 

Table 3-1. Predemonstration Study Activities and Completion Dates

Activity Date

Introductory Meeting Held December 7, 2004

Project Planning Meeting Held February 18, 2005

Draft Letter of Understanding Issued February 25, 2005

Final Letter of Understanding Issued March 11, 2005

Request for Quotation Issued to Vendor March 11, 2005

Vendor Quotation Received by Battelle September 7, 2005

Purchase Order Completed and Signed October 5, 2005

Letter Report Issued February 16, 2006

Final Study Plan Issued May 5, 2006

Building Construction Completed March 2007

Treatment System Shipped and Arrived March 2007

System Installation Completed January 7, 2008

System Shakedown Completed January 7, 2008

Performance Evaluation Begun February 13, 2008

O&M and operator skill requirements were assessed through quantitative data and qualitative 

considerations, including needs for pre- and/or post-treatment, level of system automation, extent of 

preventive maintenance activities, frequency of chemical and/or media handling and inventory, and 

general knowledge needed for relevant chemical processes and related health and safety practices. 

Staffing requirements for the system operation were recorded on an Operator Labor Hour Log Sheet. 

The cost of the system was evaluated based on the capital cost per gpm (or gpd) of design capacity and 

the O&M cost per 1,000 gal of water treated. This task requires tracking the capital cost for equipment, 

site engineering, and installation, as well as the O&M cost for media replacement and disposal, CO2 and 

chlorine consumption, electrical power usage, and labor. Data on O&M cost were limited to CO2

consumption, electricity usage, and labor because media replacement did not take place during the 

performance evaluation study. 
7

Table 3-2. Evaluation Objectives and Supporting Data Collection Activities 

Evaluation Objectives Data Collection

Performance -Ability to consistently meet 10 μg/L of arsenic MCL in treated water

Reliability -Unscheduled system downtime 

-Frequency and extent of repairs including a description of problems, 

materials and supplies needed, and associated labor and cost

System O&M and 

Operator Skill 

Requirements

-Pre- and post-treatment requirements

-Level of automation for system operation and data collection 

-Staffing requirements including number of operators and laborers

-Task analysis of preventative maintenance including number, frequency, and 

complexity of tasks

-Chemical handling and inventory requirements 

-General knowledge needed of relevant chemical processes and health and 

safety practices

Residual Management -Quantity and characteristics of aqueous and solid residuals generated by 

system process

System Cost -Capital cost for equipment, engineering, and installation

-O&M cost for media replacement, electricity usage, and labor

3.2 System O&M and Cost Data Collection 

The plant operator performed daily, biweekly, and monthly system O&M and data collection according to 

instructions provided by the vendor and Battelle. On a regular basis, the plant operator recorded system 

operational data, such as pressure, flowrate, totalizer, and hour meter readings on a Daily System 

Operation Log Sheet, and conducted visual inspections to ensure normal system operations. If any 

problem occurred, the plant operator would contact the Battelle Study Lead, who determined if the vendor 

should be contacted for troubleshooting. The plant operator recorded all relevant information, including 

problem encountered, course of action taken, materials and supplies used, and cost and labor incurred on 

the Repair and Maintenance Log Sheet. Every other week, while collecting samples, the plant operator 

measured pH, temperature, dissolved oxygen (DO), and oxidation-reduction potential (ORP), and 

recorded the data on an Onsite Water Quality Parameters Log Sheet. Approximately three months after 

the start of the study, DO and ORP measurements were discontinued due to difficulties with the 

equipment encountered by the operator. 

The capital cost for the arsenic removal system consisted of the cost for equipment, site engineering, and 

system installation. The O&M cost consisted of the cost for chemical usage, electricity consumption, and 

labor. CO2 consumption was tracked by the number of CO2 cylinder change-outs. Electricity

consumption was tracked through an onsite electric meter. Labor for various activities, such as routine 

system O&M, system troubleshooting and repair, and demonstration-related work, were tracked using an 

Operator Labor Hour Log Sheet. The routine O&M included activities such as completing field logs, 

replacing empty CO2 cylinders, ordering supplies, performing system inspections, and others as 

recommended by the vendor. The demonstration-related work, including activities such as performing 

field measurements, collecting and shipping samples, and communicating with the Battelle Study Lead 

and vendor, was recorded, but not used for the cost analysis. 

3.3 Sample Collection Procedures and Schedules

To evaluate the performance of the system, samples were collected from the wellheads, across the 

treatment plant, from the backwash discharge line, and from the distribution system. Table 3-3 provides 

the sampling schedule and analytes measured during each sampling event. Specific sampling
8

Table 3-3. Sampling Schedules and Analytes

Sample 

Type

Sampling

Locations(a)

No. of 

Samples Frequency Analytes

Sampling

Date

Source 

Water

Well No. 1 and 

Well No. 2

2 Once during 

initial site 

visit

Onsite: pH, temperature, 

DO, and ORP

Offsite: 

As (total and soluble), 

As(III), As(V), 

Fe (total and soluble), 

Mn (total and soluble),

U (total and soluble), 

V (total and soluble), 

Na, Ca, Mg, Cl, F, NO3, 

NO2, NH3, SO4, SiO2, 

PO4, turbidity, alkalinity, 

TDS, and TOC

12/07/04

Treatment 

Plant Water 

(Speciation)

IN, AP, and TT 3 Before 

05/28/08:

once every 8 

weeks; 

After 

05/28/08:

once every 3 

to 4 months

Onsite: pH, temperature, 

DO(b), ORP(b), and total 

and free Cl2

(c)

Offsite: 

As (total and soluble), 

As(III), As(V), 

Fe (total and soluble), 

Mn (total and soluble), 

U (total)(d), V (total)(e), 

Ca, Mg, F, NO3, SO4, 

SiO2, P, turbidity, and 

alkalinity

04/01/08, 05/28/08, 

10/07/08, 03/17/09, 

07/14/09, 11/17/09 

Treatment 

Plant Water 

(Regular)

IN, AP, TA, and 

TB

4 Before 

05/28/08:

3 times in 

one 8-week 

cycle; 

After 

05/28/08:

monthly

Onsite: pH, temperature, 

DO(b), ORP(b), and total 

and free Cl2

(c)

Offsite: 

As (total), Fe (total)

(f), 

Mn (total)(f), U (total)(d,f), 

V (total)(e), SiO2

(f), P(f), 

turbidity(f), and 

alkalinity(f)

02/13/08, 04/15/08, 

04/29/08, 05/12/08, 

07/08/08, 07/30/08, 

09/02/08, 11/18/08, 

12/16/08, 01/20/09, 

02/17/09, 04/15/09, 

05/20/09, 06/16/09, 

08/18/09, 09/15/09, 

10/20/09, 12/15/09, 

01/19/10, 02/16/10, 

03/16/10

Distribution 

System 

Water

Three LCR 

residences within 

distribution 

system

3 Monthly(g,h) pH, alkalinity, As (total), 

Fe (total), Mn (total), Pb, 

and Cu

Baseline and 

monthly sampling:

see Table 4-8 

(a) Abbreviations in parentheses corresponding to sample locations shown in Figure 4-4. 

(b) Measurement discontinued after 05/28/08. 

(c) Except IN location.

(d) Measurement discontinued after 09/02/08.

(e) Measurement added on 09/02/08. 

(f) Measurements discontinued after 11/17/09.

(g) Four baseline sampling events performed from October 2005 to January 2006 before system startup. 

(h) Sampling frequency reduced to quarterly after system startup in February 2008.

DO = dissolved oxygen; LCR = Lead and Copper Rule; NA = not applicable; ORP = oxidation-reduction 

potential; TDS = total dissolved solids; TOC = total organic carbon
9

requirements for analytical methods, sample volumes, containers, preservation, and holding times are 

presented in Table 4-1 of the EPA-endorsed Quality Assurance Project Plan (QAPP) (Battelle, 2004).

3.3.1 Source Water. During the initial site visit on December 7, 2004, one set of source water 

samples was collected from each of the two supply wells (i.e., Wells No. 1 and No. 2) and speciated using 

an arsenic speciation kit (see Section 3.4.1). Sample taps were flushed for several minutes before 

sampling; special care was taken to avoid agitation, which might cause unwanted oxidation. Analytes for 

the source water samples are listed in Table 3-3. 

3.3.2 Treatment Plant Water. During the performance evaluation study, the plant operator 

collected water samples across the treatment train for onsite and offsite analyses. Battelle’s Study Plan 

(Battelle, 2006) called for biweekly sampling at the wellhead (IN), after chlorination and pH adjustment 

(AP), after Vessels A and B (TA/TB), and/or after effluent from Vessels A and B combined (TT). 

Speciation was performed once every 8 weeks, with samples taken at IN, AP, and TT and analyzed for 

the analytes listed under “speciation” in Table 3-3. The other three sampling events collected samples at 

IN, AP, TA, and TB and analyzed for analytes listed under “regular” in Table 3-3. This sampling 

schedule was followed only briefly from April 1 through May 28, 2008. Since then, treatement plant 

water samples were collected monthly for a total of 21 times, including four speciation events collected 

once every 3 to 4 months. 

Over the course of the performance evaluation study, the sampling schedule was changed several times as 

presented below: 

• After May 28, 2008, onsite measurements were modified to include only pH, temperature, 

and total and free chlorine; DO and ORP measurement were discontinued. 

• On September 2, 2008, uranium (total) was deleted from the list of analytes due to low levels 

present in raw water. Meanwhile, vanadium (total) was added to the list of analytes. 

• After the November 17, 2009, sampling event, speciation sampling was discontinued and 

regular, non-speciation sampling was modified to include only arsenic (total), vanadium 

(total), and the aforementioned water quality measurements.

 

3.3.3 Backwash Wastewater/Solids and Spent Media. Because the system did not require 

backwashing during the performance evaluation study, no backwash residuals were produced. Further, 

because media replacement did not take place, media samples were not collected. 

3.3.4 Distribution System Water. Samples were collected from the distribution system to 

determine the impact of the arsenic treatment system on the water chemistry in the distribution system, 

specifically the arsenic, lead, and copper levels. From October 2005 to January 2006, prior to the startup 

of the treatment system, four monthly baseline distribution sampling events were conducted at three 

residences located within the distribution system. Following the startup of the arsenic adsorption system, 

distribution system sampling continued on a quarterly basis at the same three residences until October 20, 

2009, when it was discontinued. 

The three residences selected were included in the Lead and Copper Rule (LCR) sampling in the past. 

The baseline and quarterly distribution system samples were collected following an instruction sheet 

developed according to the Lead and Copper Monitoring and Reporting Guidance for Public Water 

Systems (EPA, 2002). The date and time of the last water use before sampling and the date and time of 

sample collection were recorded for calculation of the stagnation time. All samples were collected from a 

cold water faucet that had not been used for at least 6 hr to ensure that stagnant water was sampled. 
10

Analytes for the baseline samples coincided with the quarterly distribution system water samples as 

described in Table 3-3. Arsenic speciation was not performed for the distribution system water samples.

3.4 Sampling Logistics

All sampling logistics including preparation of arsenic speciation kits and sample coolers, and sample 

shipping and handling are discussed as follows. 

3.4.1 Preparation of Arsenic Speciation Kits. The arsenic field speciation method used an anion 

exchange resin column to separate the soluble arsenic species, As(V) and As(III) (Edwards et al., 1998). 

Resin columns were prepared in batches at Battelle laboratories in accordance with the procedures 

detailed in Appendix A of the EPA-endorsed QAPP (Battelle, 2004). 

3.4.2 Preparation of Sampling Coolers. For each sampling event, a sample cooler was prepared 

with the appropriate number and type of sample bottles, disc filters, and/or speciation kits. All sample 

bottles were new and contained appropriate preservatives. Each sample bottle was affixed with a preprinted, color-coded, and waterproof label, consisting of the sample identification (ID), date and time of 

sample collection, collector’s name, site location, sample destination, analysis required, and preservative. 

The sample ID consisted of a two-letter code for the specific water facility, sampling date, a two-letter 

code for a specific sampling location, and a one-letter code for designating the arsenic speciation bottle (if 

necessary). The sampling locations at the treatment plant were color-coded for easy identification. For 

example, red, orange, yellow, blue, and green were used to designate sampling locations for IN, AP, TA, 

TB, and TT, respectively. The prelabeled bottles for each sampling location were placed in separate ziplock bags and packed in the cooler. 

 

When appropriate, the sample cooler was packed with bottles for the three distribution system sampling 

locations. In addition, all sampling- and shipping-related materials, such as latex gloves, sampling 

instructions, chain-of-custody forms, prepaid UPS air bills, and bubble wrap, were included. Except for 

the operator’s signature, the chain-of-custody forms and prepaid UPS air bills had already been completed 

with the required information. The sample coolers were shipped via FedEx to the facility approximately 

1 week prior to the scheduled sampling date. 

3.4.3 Sample Shipping and Handling. After sample collection, samples for off-site analyses were 

packed carefully in the original coolers with wet ice and shipped to Battelle. Upon receipt, the sample 

custodian verified that all samples indicated on the chain-of-custody forms were included and intact. 

Sample IDs were checked against the chain-of-custody forms and the samples were logged into the 

laboratory sample receipt log. Discrepancies noted by the sample custodian were addressed with the plant 

operator by the Battelle Study Lead. 

Samples for metal analyses were stored at Battelle’s inductively coupled plasma-mass spectrometry (ICPMS) laboratory. Samples for other water quality analyses were packed in separate coolers and picked up 

by couriers from American Analytical Laboratories (AAL) in Columbus, OH and Belmont Labs in 

Englewood, OH, both of which were under contract with Battelle for this demonstration study. The 

chain-of-custody forms remained with the samples from the time of preparation through analysis and final 

disposition. All samples were archived by the appropriate laboratories for the respective duration of the 

required hold time and disposed of properly thereafter. 

3.5 Analytical Procedures

The analytical procedures described in detail in Section 4.0 of the EPA-endorsed QAPP (Battelle, 2004) 

were followed by Battelle ICP-MS, AAL, and Belmont Labs. Laboratory quality assuarnce/quality 
11

control (QA/QC) of all methods followed the prescribed guidelines. Data quality in terms of precision, 

accuracy, method detection limits (MDLs), and completeness met the criteria established in the QAPP 

(i.e., relative percent difference [RPD] of 20%, percent recovery of 80% to 120%, and completeness of 

80%). The QA data associated with each analyte will be presented and evaluated in a QA/QC Summary 

Report to be prepared under separate cover upon completion of the Arsenic Demonstration Project. 

Field measurements of pH, temperature, DO, and ORP were conducted by the plant operator using a 

VWR Symphony SP90M5 Handheld Multimeter, which was calibrated for pH and DO prior to use 

following the procedures provided in the user’s manual. The ORP probe also was checked for accuracy 

by measuring the ORP of a standard solution and comparing it to the expected value. The plant operator 

collected a water sample in a clean, plastic beaker and placed the Symphony SP90M5 probe in the beaker 

until a stable value was obtained. The plant operator also performed free and total chlorine measurements 

using Hach chlorine test kits following the user’s manual.
12

4.0 RESULTS AND DISCUSSION

4.1 Facility Description and Pre-existing Treatment System Infrastructure

The Tohono O’odham Nation’s Covered Wells Regional Water System (CWRWS) serves the 

communities of Lower Covered Wells and Upper Covered Wells (Covered Wells), located approximately 

20 miles northwest of Sells, Arizona in the Gu Achi District of the Tohono O’odham Reservation. The 

CWRWS has a total 64 of connections, serving a population of 310. The facility operates approximately 

10 hr/day with an estimated daily demand of 36,000 gpd. The water system is supplied by two 8-in 

diameter wells (Wells No. 1 and No. 2), which operate on an alternating basis at approximately 60 gpm. 

Wells No. 1 and No. 2 are installed to a depth of 755 ft below ground surface (bgs) and screened from 

605 to 745 ft bgs. The static water level is approximately 610 ft bgs. The pump is set at 692 ft bgs in 

each well. Figures 4-1 and 4-2 are photographs of the fenced-in area surrounding Wells No. 1 and No. 2, 

respectively.

The existing water facility was comprised of the following: two 8-in diameter wells each equipped with a 

30-horsepower (hp) submersible pump and a pressure reducing valve in a vault, one 88,000-gal above 

groundwater storage tank located approximately 9 miles from the well site, and 45,589 ft of 6-in water 

line. Chlorination with a sodium hypochlorite (NaOCl) solution was the only pre-existing treatment, 

which was accomplished by injecting the solution at the point of entry using a chemical metering pump 

for a target free chlorine residual level of 1 mg/L (as Cl2) or less. The metering pump was set based on 

the system flowrate. The proposed arsenic removal system was placed in between Wells No.1 and No.2 

(Figure 4-2). 

 

Figure 4-1. Fenced-In Area Around Well No. 1 and Pressure Reducing Valve Vault
13

Figure 4-2. Future Location of Arsenic Treatment System 

(Well No. 2 in a Fenced-in Area in the Background)

4.1.1 Source Water Quality. Source water samples from Wells No. 1 and No. 2 were collected and 

speciated on December 7, 2004. The results are presented in Table 4-1 and compared to those taken by 

the facility and Indian Health Services (IHS) for the EPA demonstration site selection. 

Arsenic. Total arsenic concentrations in source water ranged from 26.0 to 37.0 μg/L. Based on the 

December 7, 2004 sampling results, of the 31.8 to 33.1 μg/L of total arsenic, 30.1 to 32.7 μg/L existed as 

As(V) and up to 0.7 and 1.2 μg/L existed as particulate arsenic and As(III), respectively. Therefore, 

As(V) was the predominating arsenic species in source water. 

Iron. Iron concentrations in source water ranged from less than its detection limit of 25 μg/L to 240 μg/L. 

In general, adsorptive media technologies are best suited to sites with relatively low iron levels (e.g., less 

than 300 μg/L of iron, which is the secondary maximum contaminant level [SMCL] for iron). With 

concentrations greater than 300 μg/L, taste, odor, and color problems can occur in the treated water, along 

with an increased potential for fouling of the adsorption system components with iron particulates.

pH. The source water pH was relatively high, with values ranging from 7.7 to 8.4. The pH of the water 

was adjusted to a target value of 7.0 using CO2 prior to adsorptive media to increase its adsorptive 

capacity and prolong its run length. CO2 was also less corrosive than mineral acids, such as H2SO4,
14

Table 4-1. Water Quality Data for Covered Wells Site in Tohono O’odham Nation, AZ 

Parameter Unit

Facility 

Data(a)

IHS 

Data(b)

Battelle

Data

Date -- NA 12/08/03 12/07/04

Well -- NA NA Well No. 1 Well No. 2

pH -- 7.7 8.4 8.2 8.2

Temperature °C NA NA 21.5 21.5

DO mg/L NA NA 4.3 4.3

Total Alkalinity (as CaCO3) mg/L 150, 140* 150 150 150

Hardness (as CaCO3) mg/L 27 32.0 39.1 39.6

Turbidity NTU NA NA 0.2 0.5

TDS mg/L NA NA 214 248

TOC mg/L NA 0.5 <0.7 1.0

Nitrate (as N) mg/L NA NA 1.1 1.2

Nitrite (as N) mg/L NA NA <0.01 <0.01

Ammonia (as N) mg/L NA NA <0.05 <0.05

Chloride mg/L 17, 21* 6.9 20.0 21.0

Fluoride mg/L NA NA 0.6 0.6

Sulfate mg/L 23, 23* 33.0 23.0 23.0

Silica (as SiO2) mg/L 24* 22.7 25.7 27.1

Orthophosphate (as PO4) mg/L <0.065* ND <0.06 <0.06

As (total) μg/L 26, 34* 37.0 31.8 33.1

As (soluble) μg/L NA NA 31.1 33.9

As (particulate) μg/L NA NA 0.7 <0.1

As(III) μg/L NA ND 1.0 1.2

As(V) μg/L NA 37.0 30.1 32.7

Fe (total) μg/L 228*, 29* 240 <25 <25

Fe (soluble) μg/L NA NA <25 <25

Mn (total) μg/L 4* ND 0.6 1.1

Mn (soluble) μg/L NA NA 0.3 0.5

U (total) μg/L NA NA 8.0 7.4

U (soluble) μg/L NA NA 8.1 7.6

V (total) μg/L NA NA 32.2 30.7

V (soluble) μg/L NA NA 34.2 31.2

Na (total) mg/L 76, 72* 78.9 77.5 75.0

Ca (total) mg/L 11, 10* 9.1 11.7 11.4

Mg (total) mg/L 2* 2.2 2.4 2.7

(a) Data provided by Facility unless otherwise noted.

(b) After Farley, 2004. 

*EPA analytical results 

DO = dissolved oxygen; NA = not available; ND = not detected; TDS = total dissolved 

solids; TOC = total organic carbon

and when the treated water depressurized after exiting the adsorption vessels, some CO2 may degas, 

thereby raising pH values of the treated water and reducing its corrosivity to the distribution piping.

Competing Anions. Arsenic adsorption can be influenced by the presence of competing anions such as 

silica and phosphate. Analysis of source water indicated that silica levels ranged from 22.7 to 27.1 mg/L 

and that orthophosphate levels were less than the detection limit (i.e., <0.06 mg/L). The effect of silica on 

arsenic adsorption was monitored closely during the demonstration study. 
15

Other Water Quality Parameters. Nitrate levels in source water ranged from 1.1 to 1.2 mg/L (as N), 

which were far below the MCL of 10 mg/L (as N). Nitrite levels were below the MDL of 0.01 mg/L (as 

N). Chloride, fluoride, sulfate, manganese, and TDS were below their respective SMCLs. TOC levels 

were <0.7 mg/L for Well No. 1 and 1.0 mg/L for Well No. 2. 

4.1.2 Distribution System. The distribution system at Covered Wells is supplied by two wells 

(Wells No. 1 and No. 2) that operate on an alternating basis. Water from each well is stored in a 88,000-

gallon aboveground storage tank, which is located approximately 9 miles from the well site. The mains 

for the water distribution system are constructed primarily of 6-in C900 polyvinyl chloride (PVC). 

Copper piping is used in some of the connections to the distribution system. Three locations, which are 

part of the historic LCR sampling network, were selected to provide a good representation of the 

distribution system for both baseline sampling and quarterly sampling after the system startup. 

4.2 Treatment Process Description

The AdEdge arsenic package unit (APU) is a fixed-bed, down-flow adsorption system used for small 

water systems with flowrates up to 75 gpm. The system uses Bayoxide® E33 media, an iron-based 

adsorptive media developed by Bayer AG, for the removal of arsenic from drinking water supplies. Table 

4-2 presents physical and chemical properties of the media. The Bayoxide® E33 media is delivered in a 

dry granular form and is listed by NSF under Standard 61 for use in drinking water application. For this 

site, Bayoxide® E33 was supplied in pelletized form, which has a density of 35 lb/ft3

. 

Table 4-2. Physical and Chemical Properties of AD-33 Media(a)

Physical Properties

Parameter Value

Matrix Iron oxide composite

Physical form Dry pellets

Color Amber

Bulk Density (lb/ft3) 35

BET Area (m2/g) 142

Attrition (%) 0.3

Moisture Content (%) <15 (by weight)

Particle size distribution (U.S. Standard mesh) 10 × 35 

Crystal Size (Å) 70

Crystal Phase α – FeOOH

Chemical Analysis

Constituents Weight (%)

FeOOH 90.1

CaO 0.27

MgO 1.00

MnO 0.11

SO3 0.13

Na2O 0.12

TiO2 0.11

SiO2 0.06

Al2O3 0.05

P2O5 0.02

Cl 0.01

(a) Provided by AdEdge. 

BET = Brunauer, Emmett, and Teller
16

As groundwater is pumped through fixed-bed pressure vessels, dissolved arsenic is adsorbed onto the 

media, reducing its concentration to below the 10 μg/L MCL. When the effluent arsenic concentration 

reaches 10 μg/L, the spent media is removed and can be disposed of as non-hazardous waste if it 

successfully passes the EPA’s toxicity characteristic leaching procedure (TCLP) test. The media capacity

is dependent upon arsenic species and its concentration in influent water, empty bed contact time (EBCT), 

influent pH, and concentrations of interfering ions in the water. During the performance evaluation study, 

the need for media replacement was never required. At the end of the study, arsenic concentrations in

Vessels A and B effluent were 0.6 and 0.4 μg/L, respectively. 

The APU system at TOUA consisted of two pressure vessels (i.e., Vessels A and B) operating in parallel. 

Figure 4-3 shows a simplified process flow diagram of the treatment system. The system sat on a covered 

concrete pad, which provided sufficient space for the modular treatment system and booster system

consisting of one 5,000-gal intermediate storage tank and three booster pumps. Figure 4-4 is a 

generalized process flow sampling diagram of the system that illustrates sampling locations and 

parameters analyzed during the demonstration study. Table 4-3 presents key system design parameters.

The key process steps and major components of the water treatment system include:

(a) Intake. Raw water was pumped from Wells No. 1 and No. 2 to the APU treatment system 

via 6-in PVC pipe. 

(b) Prechlorination. The original design called for post-chlorination since As(V) was the 

predominant species. Due to the location of the chlorine injection point (i.e., at each 

wellhead) and the associated cost required to relocate the injection point to the end of the 

treatment train, a decision was made to keep the pre-existing chlorination setup. The chlorine 

addition system was used to oxidize any As(III) in source water to As(V), while providing the 

needed chlorine residuals for disinfection. Each well had its own NaOCl addition system (see 

Figure 4-5), which consisted of a ProMinent Concept Plus Model 704 pump with a maximum 

capacity of 1.03 gal/hr (gph) or 3.9 L/hr (lph), a chlorine injection tap, a 30-gal chemical feed 

tank (containing a 2% NaOCl solution, which was diluted down from 12.5%), and a control 

relay box for chlorine pump control. Chlorine addition was synchronized with the well 

pumps and consumption was monitored by measuring the solution level in each feed tank. 

The metering pumps were set for a target free chlorine residual level of 1 mg/L (as Cl2) or 

less.

(c) pH Adjustment. The raw water had high pH values (i.e., 8.4) that had to be lowered to a 

target value of 7.0 to enhance arsenic adsorption. A CO2 automatic pH adjustment/control 

system manufactured by Destin North Bay in Niceville, FL was initially used for pH 

adjustment, but was later replaced with a system produced by AdEdge. Figure 4-6 presents a 

schematic diagram of the original system, which was designed to introduce gaseous CO2 into 

water using an in-line CO2 injector. The four major components of the system, as shown in 

Figure 4-7, included a non-glass pH probe, a pH controller, a gas flow control panel, and a 

CO2 injector, all of which are further explained below: 

o The non-glass pH probe was a Honeywell Durafet III Electrode mounted inline with an 

integral 50-ft cable, which was connected to a Honeywell pH controller. This probe was 

more durable than its glass counterpart and utilized an ion sensitive field effect transistor 

(ISFET), a miniaturized semiconductor chemical sensor, for a fast response. 

o The pH controller was a Honeywell controller with dual 4 to 20 milliamp outputs, two 

alarm relays, NEMA-4X enclosure, panel-mounting hardware, and an infrared 

communications port. The pH controller required 110 V power. 
17

Figure 4-3. Process Flow Diagram for APU System at TOUA
18

Figure 4-4. Process Flow Diagram with Sampling Schedules and Locations 

MEDIA 

VESSEL 

A

MEDIA 

VESSEL 

B

INFILTRATION GALLERY

INFLUENT

(WELL 1 or 2)

Once Every 8 Weeks (Before 05/28/08)

Once Every 3 to 4 Months (After 05/28/08)

Sells, AZ

AdEdge APU w/ Bayoxide® E33 

Design Flow: 63 gpm

DISTRIBUTION SYSTEM

Footnote

(a) On-site analyses

BW

TA TB

TT

SS

pH ADJUSTMENT –

CO2 INJECTION

IN

LEGEND

INFLUENT Unit Process

IN

BW Backwash Sampling Location

SS Solid Sampling Location

Process Flow

Backwash Flow

TT Total Combined Effluent

TB After Vessel B

TA After Vessel A

Water Sampling Locations

LEGEND

IN At Wellhead

AP After pH Adjustment

AP

Pre-Chlorination

BOOSTER PUMP STATION WITH

5,000-GAL INTERMEDIATE STORAGE TANK

pH(a), temperature(a),

Cl2 (free and total)(a), As(total 

and soluble), As(III), As(V), Fe 

(total and soluble), Mn (total and 

soluble), U (total), V(total), Ca, 

Mg, F, NO3, SO4, SiO2, P, 

turbidity, alkalinity

pH(a), temperature(a), 

Cl2(free and total)(a), As (total), 

Fe (total), Mn (total), U (total), 

V(total), SiO2, P, turbidity, 

alkalinity

pH(a), temperature(a),

Cl2(free and total)(a), As(total 

and soluble), As(III), As(V), Fe 

(total and soluble), Mn (total and 

soluble), U (total), V(total), Ca, 

Mg, F, NO3, SO4, SiO2, P, 

turbidity, alkalinity

pH(a), temperature(a),

As(total and soluble), As(III), 

As(V), Fe (total and soluble), Mn 

(total and soluble), U (total), 

V(total), Ca, Mg, F, NO3, SO4, 

SiO2, P, turbidity, alkalinity

pH(a), temperature(a), 

Cl2(free and total)(a), As (total), 

Fe (total), Mn (total), U (total), 

V(total), SiO2, P, turbidity, 

alkalinity

pH(a), temperature(a), 

As (total), Fe (total), Mn (total), 

U (total), V(total), SiO2, P, 

turbidity, alkalinity

3 Times in One 8-Week Cycle

(Before 05/28/08)

Monthly (After 05/28/08)
19

Table 4-3. Design Specifications of AdEdge APU System

Parameter Value Remarks

Prechlorination (Pre-existing)

Target Free Chlorine Residual Level (mg/L [as Cl2]) <1.0 Using NaOCl solution

CO2 pH Adjustment

Total Usage (lb CO2/day) 5.6 Reducing pH from 8.2 to 7.0

Injection Rate (scfh) 6.1 –

No. of 50 lb Cylinders Used per Month 3 to 4 –

Adsorption Vessels

Vessel Size (in) 36 D × 72 H –

Cross-Sectional Area (ft2/vessel) 7.1 –

No. of Vessels 2 –

Configuration Parallel –

Underlying Gravel Bulk Density (lb/ft3) 100 Gravel composed of 1⁄4-in × 1/8-in quartz

Underlying Gravel Quantity (lb/vessel) 450 900 lb in both vessels

Media Quantity (lb) 1,330 Media bulk density 35 lb/ft3

Media Volume (ft3/vessel) 19 38 ft3 in both vessels 

Media Bed Depth (in) 32 –

Pressure Drop (psi) 4 Across a clean bed

Service

Design Flowrate (gpm) 63 System maximum flowrate 75 gpm

Hydraulic Loading (gpm/ft2) 4.4 –

EBCT (min) 4.5 Based on design flowrate

Estimated Working Capacity (BV) 51,000 –

Throughput To Breakthrough at 10 μg/L (gal) 14,484,000 1 BV = 284 gal

Average Use Rate (gal/day) 22,500 Based on 7 to 8 hr of daily operation at 

50 gpm

Estimated Media Life (months) 21 –

Backwash

Pressure Differential Setpoint (psi) 10–15 –

Backwash Flowrate (gpm) 64 –

Backwash Hydraulic Loading (gpm/ft2) 9.0 –

Backwash Frequency (per month) 1 On as needed basis

Backwash Duration (min/vessel) 15 –

Filter-to-Waste Flowrate (gpm) 64 –

Filter-to-Waste Duration (min/vessel) 5 –

Wastewater Production (gal/event) 2,560 Both vessels combined

o The CO2 gas flow control panel adjusted the CO2 gas injection rate in response to the pH 

controller signal to maintain the setpoint of 7.0. The pressure regulator inside the panel 

was set at 100 psig and the instrument regulator was set at 20 psig. The CO2 pH control 

system was designed to feed 6.1 standard ft3

/hr (scfh). The average CO2 use rate was 

estimated to be 5.6 lb/day based on a 63 gpm flowrate and the source water quality. The 

gas supply included up to four 50-lb cylinders to provide a one-month supply of CO2. 

o The in-line CO2 injector used the “Venturi effect” to provide CO2 gas mixing with the 

water stream. The assembly included the injector, a check valve, a metering valve, and a 

5-ft long stainless steel (SS) flexible hose. The CO2 injector was installed on the well 

pump discharge piping where the piping comes onto the treatment system slab. 
20

Figure 4-5. Chlorine Addition System at TOUA

Several issues, such as malfunctioning components and leaks in the manifold, were 

encountered immediately after installation of the Destin North Bay system in January 2008. 

By early July 2008, AdEdge replaced the original system, at no additional cost, with one that 

was designed and built by AdEdge. The problems associated with the Destin North Bay 

System are further discussed in Section 4.4.3. Figure 4-8 shows a process and instrument 

diagram of the AdEdge pH adjustment system and photographs of the control panel are 

presented in Figure 4-9. Details concerning operation and components of the replacement 

AdEdge CO2 pH adjustment system are described below: 

o Gas supplied by the two 50-lb CO2 cylinders entered the control panel through an inlet 

solenoid valve, which was controlled by a logic circuit that allowed CO2 gas to enter the 

panel only if a signal was received by the control panel when the well pump was on. 

o From the inlet solenoid valve, CO2 gas flowed to a non-venting single stage pressure 

regulator mounted inside the control panel, by which gas pressure supplied to the 

remainder of the panel components and ultimately to the injector was further reduced and 

controlled. An “Inlet Pressure” gauge mounted on the control panel indicated the gas 

pressure supplied to the upstream side of the pressure regulator.

o After the panel-mounted pressure regulator, the CO2 gas flow path was split into a 

manual adjustment loop and an automatic adjustment loop depending on which mode, 

automatic or manual, was selected. When the manual valve was opened, CO2 gas flowed 

through the valve to a needle valve, by which the operator could control the gas flow 

delivered to the injector. When the automatic valve was opened, CO2 gas proceeded 
21

Figure 4-6. Overview of Destin North Bay CO2 pH Adjustment System

 
22 

 

 

Figure 4-7. Destin North Bay CO2 Gas Flow Control System for pH Adjustment

(Clockwise from top left: non-glass inline pH probe; 

Honeywell pH controller; gas flow control panel; Venturi injector) 

through the valve to a proportional solenoid valve. The valve was automatically 

controlled via the proportional integral derivative (PID) functionality of the Burkert 8205 

pH controller, which was connected to a solid state SensorX in-line pH probe mounted 

approximately 25 ft downstream of the injection point. The manual and automatic flow 

paths were brought back together and CO2 gas flow proceeded through a panel mounted 

rotameter, by which the operator could gauge and record relative gas flow to the injector. 

The rotameter reading was a relative reading only, since the meter was calibrated for air 

and not CO2. 

o An “Outlet Pressure” gauge mounted on the control panel measured the delivery pressure 

of CO2 gas at the outlet of the panel. CO2 gas flowed to an outlet solenoid valve, which 

was controlled by the same logic circuit as the inlet solenoid valve, allowing CO2 gas to 

flow only when the well pump was on. CO2 gas then flowed from the outlet solenoid 

away from the panel through a check valve and a submicron filter to the injector. The 

injector from the original system, which employs the “Venturi effect”, was used with the 

new pH adjustment system. Failure of the outlet solenoid valve and check valve occurred 

during the performance evaluation period leading to problems with the pH adjustment 

system. The problems experienced and the corrective actions taken are explained in 

further detail in Section 4.4.3. 
Figure 4-8. Process and Instrument Diagram of AdEdge CO2 pH Adjustment System

23
24

Figure 4-9. AdEdge CO2 pH Adjustment System Control Panel

(d) Adsorption. The APU system consisted of two 36-in × 72-in composite vessels configured

in parallel, each containing 18.5 ft3

 of pelletized E33 media supported by a gravel underbed. 

The vessels had a 6-in flange opening on the top of the vessel for loading media and assessing 

vessel contents. A 2-in Fleck control valve (Fleck Model 3150) was used on each vessel to 

allow the vessel to operate independently. Each valve had a 3200NT timer for electronic 

programming, which allowed for setting custom parameters such as backwashing frequency, 

external notifications for alarm conditions, and accommodating other inputs and outputs. 

Water entered the system through 2-in piping and flowed in parallel through the vessels. 

Water in each vessel flowed from the upper distributor downward though the media where 

treated water was collected at the bottom through a slotted hub and lateral assembly. The 

treated water then traveled up through the riser piping in the vessel before it exited at the 

outlet of the Fleck control valve. 

All piping on the APU system was Schedule 80 PVC. The inlet line to each control valve 

contained a diaphragm valve for isolation followed by a Y-strainer to prevent particulates 
25

from entering the controller. Ball valves were located on each outlet line from the controllers 

also for isolation. Based on a design flowrate of 63 gpm, the EBCT for each vessel was 4.5

min and the hydraulic loading to each vessel was 4.4 gpm/ft2

. Figure 4-10 shows the APU 

system along with the booster station (left) and CO2 pH adjustment system (center

background). 

Figure 4-10. AdEdge APU Arsenic Adsorption System

• Backwash. Backwashing was performed with raw water and initiated in one of three ways: 

(1) automatically based on the number of days since the last backwash (once every 30 to 45 

days as recommended by the vendor); (2) automatically based on reaching a high pressure 

differential (typical setpoint of 10 to 15 psi); and (3) manually by depressing the backwashing 

selector switch. The system was designed to backwash one vessel at a time while the second 

vessel remained in service. During a backwash, each vessel underwent 15 min of an upflow 

wash followed by 5 min of a downflow rapid rinse, both at a flowrate of 64 gpm. Each 

backwash event (both vessels combined) would produce 2,560 gal of wastewater, which was 

directed to a modified evaporation/transpiration bed consisting of four infiltration chambers 

covered with gravel.

The differential pressure and timer triggers were disabled during the entire performance 

evaluation period allowing backwash to only occur manually. Due to minimal pressure drop 

across the vessels and low levels of arsenic in the treated effluent, routine system 

backwashing was not performed. Pressure drop and arsenic concentrations across the vessels 

were monitored regularly.
26

On August 18, 2009, during sample collection by the operator, Vessel A went into backwash. 

The operator noticed an unfamiliar value on the display screen of the control valve during the 

backwash and made note of it. Battelle contacted the vendor the following day to determine 

what triggered the vessel to automatically engage into a backwash. The vendor informed

Battelle that the value the operator recorded indicated the valve programming had been reset, 

possibly by a power surge. The vendor walked the operator through the valve reprogramming steps on September 2, 2009, making certain to disable the timer and differential 

pressure triggers for backwash. To engage a backwash, the operator would have to do it 

manually by depressing the selector switch on the control valve.

• Media Replacement. Based on the analytical results from the final sampling event on March 

16, 2010, total arsenic concentrations in the treated water were 0.6 and 0.4 μg/L for Vessels 

A and B, respectively. The total arsenic concentration in the combined effluent did not

exceed the MCL of 10 μg/L; therefore, the media was not replaced during the study period. 

Based on the estimate provided by the vendor, breakthrough of arsenic at 10 μg/L was 

expected to occur after treating approximately 14,484,000 gal (51,000 BV) or 21 months of 

system operation assuming an estimated daily throughput of 22,500 gal. 

4.3 System Installation 

The installation of the APU system was completed by AdEdge on January 7, 2008. The following briefly 

summarizes some of the predemonstration activities, including permitting, building preparation, and, 

installation, shakedown, and startup. 

4.3.1 Permitting. Because the Tohono O’odham Nation is governed by Tribal Sovereignty and 

IHS performed the work related to site engineering and system/building tie-ins, the issuing of permits was 

not required. Instead, the vendor provided IHS and TOUA with the system layout, footprint, and 

electrical requirement for all system components to facilitate the facility’s building design and 

construction. 

4.3.2 Building Preparation. A new structure was designed and funded by IHS and constructed by 

TOUA to house the treatment system and other necessary components (i.e., pH adjustment system and 

booster system). The new structure consisted of a 10 ft × 12 ft concrete slab covered by a 20 ft × 20 ft 

ramada shelter enclosed on the sides with corrugated metal panels. A fence was constructed around the 

building and 5,000 gal storage tank for the booster system for additional security. Figure 4-11 shows the 

new building and storage tank. 

4.3.3 Installation, Shakedown, and Startup. The treatment system arrived onsite in March 2007, 

but installation was delayed due to construction upgrades being made to the well site, which were not 

completed until December 2007. The vendor was onsite for the system installation and shakedown during 

the week of January 7, 2008. Onsite activities included hydraulic testing, media loading, freeboard 

measurements, and media backwash along with the installation and shakedown of the CO2 pH adjustment 

system. The vendor returned to the site the week of February 4, 2008 to train the operator and put the 

system online. Battelle was onsite on March 31 and April 1, 2008, to inspect the system and provide 

training to the operator for sampling and data collection. As a result of the system inspection, a punch-list 

of items was identified. Table 4-4 summarizes the items identified and corrective actions taken. In 

addition, these problems are discussed in detail in Section 4.4.3. 

 
Figure 4-11. New Treatment Building with 5,000 gal Storage Tank (left) 

27

Table 4-4. System Punch-List/Operational Issues

Item 

No.

Punch-List/

Operational Issues Corrective Action(s) Taken Resolution Date

1 Well pump hour meter not 

provided for each well

Not in request for quotation (RFQ)

to vendor; two hours meters 

purchased from AdEdge and 

installed by TOUA

07/07/08

2 CO2 regulators not functioning 

properly

Two new CO2 regulators sent to site 

by AdEdge

05/15/08

3 Sample tap not installed at 

combined effluent location (TT)

Sample tap supplied by AdEdge and 

installed by TOUA

06/08

4 pH controller display not 

working

Destin North Bay CO2 pH 

adjustment unit replaced with new 

unit designed and installed by 

AdEdge.

07/10/08

5 Pneumatic flow control valve 

malfunctioning

6 CO2 manifold leaking

4.4 System Operation

4.4.1 Operational Parameters. The operational parameters for the system performance 

evaluation were tabulated and are attached as Appendix A. Key parameters are summarized in Table 4-5. 

From February 13, 2008, through March 19, 2010, the system operated for a total of 3,353 hr. Due to a 
28

Table 4-5. Summary of APU System Operation

Operational Parameter Value

Performance Evaluation Study Duration 02/13/08 to 03/19/10

Number of Days System Operating (day) 765

Cumulative Operating Time (hr) 3,353

Average Daily Operating Time (hr) 4.38

Throughput (gal) 11,686,000

Throughput (BV)(a) 41,148

Average (Range) of Instantaneous Flowrate (gpm) Vessel A

29.5 (9.4-52.8)(b,c)

Vessel B

30.6 (20.1-54.2)

Average (Range) of EBCT per Vessel (min)(d) Vessel A

4.8 (2.7-15.1)(b,c)

Vessel B

4.7 (2.6-7.1)

Average (Range) of System Inlet Pressure (psi) 9.0 (5.0-18.0)

Average (Range) of System Outlet Pressure (psi) 5.1 (2.0-10.0)

Average (Range) of Δp Across System (psi) 4.0 (0.0-14.0)

Average (Range) of Δp Across Vessel A (psi) 2.4 (0.0-10.0)

Average (Range) of Δp Across Vessel B (psi) 2.7 (0.0-9.0)

(a) Calculated based on 38 ft3 of media; 1 BV = 284 gal.

(b) Not including two outliers on November 23, 2009.

(c) Not including values from April 30 to May 20, 2009; flowmeter not functioning.

lack of hour meters on the well pumps since system startup until July 8, 2008, the system operating time 

during this period was estimated based on the average daily operating time of 4.38 hr/day from July 8, 

2008, through the end of the performance evaluation study. 

Figure 4-12 compares calculated flowrates at each wellhead with instantaneous and calculated flowrates 

through each vessel. Calculated flowrates were obtained by dividing incremental volumes recorded by a 

totalizer by respective incremental operating times recorded from the well pump hour meter. 

Instantaneous flowrates were recorded by the operator from a flow meter. Because the wellheads did not 

have flowmeters, no instantaneous flowrates were recorded. Calculated flowrates for Wells No. 1 and 

No. 2 averaged 59.9 and 60.3 gpm, respectively. The flowrate through each vessel was consistent at 

approximately 30 gpm with slight fluctuations being observed periodically. The exceptions occurred 

during the period when the vessel totalizers were not operating correctly, such as from April 30, 2009, 

through May 20, 2009, for Vessel A. Excluding the data collected during this period and an outlier 

recorded on November 23, 2009, also for Vessel A, an average instantaneous flowrate of 29.5 gpm was 

calculated for Vessel A and 30.6 gpm for Vessel B. Since the vessels were configured in parallel, the 

flow through each vessel should have been one-half (i.e., 30 gpm) of the total flow from the wellhead. 

At the end of the study, the system had treated 11,686,000 gal of water based on the totalizers installed on 

the vessels. This amount is comparable to the 11,627,700 gal recorded from the well head totalizers. The 

amount of water treated was equivalent to 41,148 BV based on the 38 ft3 of media in both vessels (19 ft3

per vessel). Based on the instantaneous flowrates to the vessels, the average EBCT was 4.8 min for 

Vessel A and 4.7 min for Vessel B, which were very close to the design value of 4.5 min as presented in 

Table 4-3. 
29

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

2/2/2008 4/22/2008 7/11/2008 9/29/2008 12/18/2008 3/8/2009 5/27/2009 8/15/2009 11/3/2009 1/22/2010 4/12/2010

Flowrate (gpm)

Date

Well No. 1 Calculated Flowrate

Well No. 2 Calculated Flowrate

Vessel A Instantaneous Flowrate

Vessel A Calculated Flowrate

Vessel B Instantaneous Flowrate

Vessel B Calculated Flowrate

Figure 4-12. System Instantaneous and Calculated Flowrates

 

Pressure readings of the APU system were monitored at the system inlet and outlet, while only 

differential pressures (Δp) were monitored across the vessels. Throughout the duration of the 

performance evaluation period, system inlet and outlet pressure readings averaged 9.0 and 5.1 psi, 

respectively. The average Δp across the system was 4.0 psi. Δp readings ranged from 0 to 10 psi and 

averaged 2.4 psi across Vessel A and from 0 to 9 psi and averaged 2.7 psi across Vessel B. Due to low 

differential pressures across the system and vessels, no media backwash was performed during the 

performance evaluation study. Figure 4-13 presents system pressure readings at the inlet and outlet along 

with calculated differential pressures. Figure 4-14 presents differential pressures across Vessels A and B.

4.4.2 Residual Management. No residuals were produced because neither backwash nor media 

replacement was required during the evaluation period. 

4.4.3 CO2 pH Adjustment System. As described in Section 4.2, pH adjustment using a CO2 gas 

flow control system was a process component. During system startup in early February 2008, problems 

with regulators on the CO2 gas cylinders were observed. Leaks were detected in the SS hoses that 

connected the regulators on the CO2 cylinders to the pH adjustment system. In addition, the low pressure 

side (delivery pressure) of one of the regulators continually read 150 psi. The problems with the 

regulators persisted until the vendor sent a new set of regulators to the site on May 15, 2008. Since then, 

TOUA had to have one of the regulators rebuilt twice and the other once. Rebuilding the regulators has 

kept them functioning properly throughout the evaluation period. 
30

0

2

4

6

8

10

12

14

16

18

20

03/18/08 06/06/08 08/25/08 11/13/08 02/01/09 04/22/09 07/11/09 09/29/09 12/18/09 03/08/10

Pressure (psi)

Date

System Inlet Pressure

System Outlet Pressure

System Differential Pressure

Figure 4-13. System Pressure Readings

0

1

2

3

4

5

6

7

8

9

10

11

01/13/08 04/02/08 06/21/08 09/09/08 11/28/08 02/16/09 05/07/09 07/26/09 10/14/09 01/02/10 03/23/10

Pressure (psi)

Date

Vessel A Differential Pressure Vessel B Differential Pressure

Figure 4-14. Differential Pressures Across Vessels A and B
31

A number of operational issues arose during the use of the Destin North Bay CO2 pH adjustment/control 

system. On May 2, 2008, the operator reported that the display on the Honeywell pH controller was no 

longer working. After contacting the manufacturer, it was confirmed that there was a batch of pH 

displays malfunctioning and that they would replace the display free of charge. Also on May 2, 2008, a 

leak from the connection between the stainless steel piping and pneumatic flow control valve was 

observed. On May 9, 2008, the CO2 manifold was found to not be functioning properly. Because of 

concerns over the operational issues, the vendor proposed on May 30, 2008, to replace the Destin North 

Bay system with a new CO2 pH adjustment system designed and assembled by AdEdge. The new system 

was installed by the vendor on July 10, 2008. 

On September 16, 2008, the operator noticed water in tubing in the system control panel, which, 

according to the vendor, was caused by a malfunctioning check valve and a malfunctioning solenoid 

valve on the outlet line to the injector. The operator reported again on October 28, 2008, the presence of 

water in the same tubing and that the system was no longer able to adjust the pH to below 7.1 based on 

the display on the pH control panel. After checking with the vendor for the status of replacement part 

shipment, it confirmed that one three-way solenoid valve and two check valves had been shipped on 

November 7, 2008. The replacement parts were apparently lost during shipping and had to be resent. On 

December 10, 2008, the operator received one shipment with one three-way solenoid valve, but no check 

valves. On December 11, 2008, the operator reported continuing presence of water in the tubing even 

after the installation of the new three-way solenoid. By January 15, 2009, the rotameter on the system 

control panel stopped working and water had leaked out of the tubing connections into the control panel. 

In addition, the pH would not go below 7.6 based on the display on the pH control panel. It must be 

noted, however, that pH measurements by a field pH meter during this period continued to show 

acceptable pH values as presented in Appendix B (e.g., 7.2 and 7.0 following Vessels A and B, 

respectively, on November 18, 2008, and 6.9 and 7.0 on December 16, 2008 [see Figure 4-17 in Section 

4.5.1]). The differences observed between the field and inline pH measurements are further discussed in 

Section 4.5.1. 

On February 16, 2009, an engineer was dispatched by the vendor to the site to fix the pH adjustment 

system. An additional solenoid valve was installed on the outlet line and the malfunctioning check valve 

was replaced. Water was drained from the system control panel and the delivery pressure was increased

to approximately 80 psi. When the vendor left the site, the pH display was reading 7.0. No additional 

issues with the pH adjustment unit were experienced after the onsite visit. 

4.4.4 System/Operation Reliability and Simplicity. Operational irregularities experienced during 

the demonstration study were almost entirely related to the pH adjustment system (as discussed in Section 

4.4.3), vessel flow meters/totalizers, Y-strainers, and chlorination addition system. 

On April 30, 2009, the paddlewheel in the Vessel A flowmeter/totalizer stopped rotating due to solids 

buildup, which was cleaned off by the operator on May 27, 2009. Quarterly checking and cleaning of

paddlewheels were incorporated into the routine maintenance schedule. Problems also were experienced 

with the Well No. 2 flowmeter, which stopped working on September 1, 2009. After troubleshooting and 

cleaning by the Water Department, the meter was placed back into service approximately two weeks later.

Starting on September 30, 2009, higher-than-usual differential pressures (i.e., ≥ 4 psi) were observed 

across both vessels and had continued to increase to approximately 10 psi within three weeks. The cause 

of the pressure increase was determined to be accumulation of sediment in the Y-strainers located on the 

inlet lines to the valve controller on each vessel. Four new strainers were therefore purchased to allow the 

operator to rotate the strainers on a quarterly basis. The dirty strainers were removed and cleaned for the 

next changeout. 
32

On October 20, 2009, the operator noticed that chlorine residuals across the system were uncharacteristically low. Upon further inspection, the operator found that there was a hole in the line leading to the 

injector. The line was repaired and the NaOCl solution was replenished. No further difficulties were 

encountered with the chlorine addition systems during the study. 

The system O&M and operator skill requirements are discussed below in relation to pre- and posttreatment requirements, levels of system automation, operator skill requirements, preventive maintenance 

activities, and frequency of chemical/media handling and inventory requirements.

Pre- and Post-Treatment Requirements. Two pre-treatment processes were required at the Covered 

Wells site, i.e., pH adjustment and prechlorination. CO2 was used to lower pH values of raw water from 

as high as 8.4 to a target value of 7.0 to maintain effective arsenic adsorption by AD-33 media. The CO2

injection point and inline pH probe used to monitor and control pH were installed downstream of the 

chlorine injection point. O&M of the pH adjustment system required routine system pressure checks and 

regular changeout of 50-lb CO2 cylinders. The operator also recorded daily pH readings from the inline 

probe and CO2 gas flowrates from the rotameter on the control panel. The use of CO2 for pH adjustment 

also required safety training for and awareness by the operator, due to potential hazards. 

For prechlorination, the existing chlorination system at each well was utilized to maintain a target free 

residual level of 1.0 mg/L (as Cl2) or less. Since the original chlorine system was used, no additional 

maintenance or skills were required for its operation. The operator monitored chlorine tank levels and 

measured residual chlorine levels at different locations across the treatment train. 

System Automation. The system was fitted with a valve controller on each vessel, which was capable of 

performing automatic backwash when triggered. All backwash triggers, however, were disabled to allow 

for better management of backwash events. The system also was equipped with an automated CO2 gas 

flow control system, which included a liquid CO2 supply assembly, a pH control panel with automatic 

and manual models, a CO2 “Venturi style” injector, and an inline pH probe located downstream of the 

injection point. 

Operator Skill Requirements. The skill requirements to operate the system demanded a higher level of 

awareness and attention than the previous system. The system offered increased operational flexibility, 

which, in turn, required increased monitoring of system parameters. The operator’s knowledge of the 

system limitations and typical operational parameters were key to achieve system performance objectives. 

The operator was onsite typically one to two days a week and spent approximately 1.5 hr/day to perform 

visual inspections and record system operating parameters. The basis for the operator skills began with 

onsite training and a thorough review of the system operations manual; however, increased knowledge 

and system troubleshooting skills were gained through hands-on operational experience. 

Preventive Maintenance Activities. Preventive maintenance tasks included periodic checks of flow 

meters and pressure gauges and inspection of system piping and valves. Checking the CO2 cylinders and 

supply lines for leaks and adequate pressure also were performed. Typically, the operator performed 

these duties while onsite for routine activities. 

Chemical/Media Handling and Inventory Requirements. NaOCl was used for prechlorination; the 

operator ordered chemicals as done prior to the installation of the APU system. CO2 used for pH 

adjustment was ordered on an as-needed basis. Typically, four 50-lb cylinders were used per month. The 

CO2 cylinders were delivered to TOUA by the CO2 supplier and then transported to the site 

approximately 20 miles by the operator. Empty cylinders were returned to the CO2 supplier for reuse.
33

4.5 System Performance

The system performance was evaluated based on analyses of water samples collected from the treatment 

plant, backwash, and distribution system. 

4.5.1 Treatment Plant Sampling. Table 4-6 summarizes the analytical results of arsenic, iron, 

manganese, uranium, and vanadium concentrations measured at the five sampling locations across the 

treatment train. Table 4-7 summarizes the results of other water quality parameters. Appendix B 

contains a complete set of analytical results through the performance evaluation study. Treatment plant 

water samples were collected on 28 occasions (including one set of duplicate samples collected during 

the November 18, 2008 sampling event), with field speciation performed during six of the 28 occasions at 

IN, AP, TA,TB, and TT sampling locations. Sampling at the TT location occurred only four times due to 

the absence of a TT tap until June 2008. The results of the water samples collected throughout the 

treatment plant are discussed below.

Table 4-6. Summary of Analytical Results for Arsenic, Iron, Manganese, Uranium, 

and Vanadium

Parameter

Sampling 

Location

Sample 

Count

Concentration (μg/L) Standard 

Minimum Maximum Average Deviation

As (total)

IN 28 29.0 38.6 34.9 2.2

AP 28 26.6 39.4 34.9 2.9

TA 27(a) <0.1 1.2 0.5 0.3

TB 28 <0.1 1.3 0.5 0.3

TT 4 <0.1 1.1 0.5 0.4

As (soluble)

IN 5(b) 33.7 36.8 35.0 1.2

AP 6 34.2 36.2 35.4 0.9

TA 6 <0.1 1.1 0.5 0.4

TB 6 0.2 1.0 0.4 0.3

TT 4 0.2 1.1 0.5 0.4

As 

(particulate)

IN 5(c) 0.3 2.0 1.2 0.8

AP 6 <0.1 2.9 1.5 0.9

TA 6 <0.1 0.5 0.1 0.2

TB 6 <0.1 0.3 0.1 0.1

TT 4 <0.1 0.3 0.1 0.1

As (III)

IN 6 0.1 1.0 0.5 0.3

AP 6 0.1 1.1 0.5 0.3

TA 6 <0.1 1.1 0.5 0.3

TB 6 <0.1 1.0 0.4 0.3

TT 4 0.3 1.0 0.5 0.3

As (V)

IN 5(d) 33.3 36.4 34.5 1.2

AP 6 34.0 35.9 35.0 0.8

TA 6 <0.1 <0.1 <0.1 -

TB 6 <0.1 <0.1 <0.1 -

TT 4 <0.1 <0.1 <0.1 -

Fe (total)

IN 24 <25 60 <25 12.5

AP 24 <25 32 <25 6.3

TA 24 <25 77 <25 13.8

TB 24 <25 <25 <25 -

TT 4 <25 <25 <25 -
Table 4-6. Summary of Analytical Results for Arsenic, Iron, Manganese, Uranium, 

and Vanadium (Continued)

34

Parameter

Sampling 

Location

Sample 

Count

Concentration (μg/L) Standard 

Minimum Maximum Average Deviation

Fe (soluble)

IN 6 <25 <25 <25 -

AP 6 <25 <25 <25 -

TA 5(e) <25 <25 <25 -

TB 6 <25 <25 <25 -

TT 4 <25 <25 <25 -

Mn (total)

IN 24 0.1 2.8 0.7 0.9

AP 24 <0.1 3.0 0.7 0.7

TA 24 <0.1 2.1 0.3 0.5

TB 24 <0.1 1.3 0.1 0.2

TT 4 <0.1 <0.1 <0.1 -

Mn (soluble)

IN 6 <0.1 3.2 0.7 1.2

AP 6 <0.1 0.4 0.2 0.1

TA 6 <0.1 2.7 0.5 1.1

TB 6 <0.1 <0.1 <0.1 -

TT 4 <0.1 0.1 <0.1 0.0

U (total)

IN 7 7.0 8.3 7.7 0.4

AP 7 7.0 8.4 7.7 0.4

TA 7 <0.1 <0.1 <0.1 -

TB 7 <0.1 <0.1 <0.1 -

TT 0 - - - -

V (total)

IN 20 23.5 38.1 32.2 3.4

AP 20 25.2 39.7 32.5 3.6

TA 19(f) <0.1 6.2 1.6 2.0

TB 20 <0.1 3.7 1.4 1.5

TT 4 <0.1 3.7 1.2 1.4

One-half of detection limit used for samples with concentrations less than detection limit for 

calculations. 

(a) One outlier (i.e., 31.8 μg/L) from 08/18/09 omitted. 

(b) One outlier (i.e., 22.0 μg/L) from 04/01/08 omitted. 

(c) One outlier (i.e., 14.6 μg/L) from 04/01/08 omitted. 

(d) One outlier (i.e., 21.9 μg/L) from 04/01/08 omitted.

(e) One outlier (i.e., 78 μg/L) from 05/28/08 omitted.

(f) One outlier (i.e., 31.8 μg/L) from 08/18/09 omitted.

Arsenic. Figure 4-15 contains three bar charts showing concentrations of particulate arsenic, soluble 

As(III), and soluble As(V) at the IN, AP, TA, and TB sampling locations. Speciation results at the TT 

location were not presented in the figure because they were very similar to those at the TA and TB

locations. Speciation results at the IN location from the April 1, 2008 sampling event contained outliers 

and were omitted from Figure 4-15. 

Total arsenic concentrations in raw water ranged from 29.0 to 38.6 μg/L and averaged 34.9 μg/L. Soluble 

As(V) was the predominating species, ranging from 33.3 to 36.4 μg/L and averaging 32.4 μg/L. Soluble 

As(III) also was present in source water, although very low, ranging from 0.1 to 1.0 μg/L and averaging 

0.5 μg/L. Particulate arsenic concentrations also were low, ranging from 0.3 to 2.0 μg/L and averaging 1.2 

μg/L. The arsenic concentrations measured were consistent with those collected previously during source 

water sampling (Table 4-1). 
Table 4-7. Summary of Water Quality Parameter Sampling Results 

Parameter

Sampling 

Location Unit

Sample 

Count

Concentration Standard 

Minimum Maximum Average Deviation

Alkalinity 

(as CaCO3) 

IN mg/L 24 144 156 150 4.1

AP mg/L 24 140 156 148 3.9

TA mg/L 24 134 201 155 15.1

TB mg/L 24 139 196 159 15.9

TT mg/L 4 146 192 174 21.4

Fluoride

IN mg/L 6 1.1 1.2 1.1 0.0

AP mg/L 6 1.0 1.4 1.1 0.2

TA mg/L 6 1.0 1.2 1.1 0.1

TB mg/L 6 1.0 1.2 1.1 0.1

TT mg/L 4 1.0 1.1 1.0 0.1

Sulfate

IN mg/L 6 22.2 24.8 23.8 1.0

AP mg/L 6 21.6 24.6 23.6 1.1

TA mg/L 6 21.4 27.1 23.7 2.2

TB mg/L 6 20.5 28.1 24.0 2.9

TT mg/L 4 21.3 23.8 22.4 1.1

Nitrate

(as N)

IN mg/L 6 1.2 1.3 1.2 0.0

AP mg/L 6 1.1 1.8 1.3 0.2

TA mg/L 6 1.2 1.2 1.2 0.0

TB mg/L 6 1.2 1.2 1.2 0.0

TT mg/L 4 1.2 1.2 1.2 0.0

P 

(as P)

IN μg/L 24 <10 <10 <10 0.0

AP μg/L 24 <10 <10 <10 0.0

TA μg/L 24 <10 <10 <10 0.0

TB μg/L 24 <10 <10 <10 0.0

TT μg/L 4 <10 <10 <10 0.0

Silica 

(as SiO2) 

IN mg/L 23 24.4 27.8 26.2 1.1

AP mg/L 23 24.5 27.5 26.2 0.9

TA mg/L 23 18.7 32.6 26.9 3.0

TB mg/L 23 20.7 33.8 27.3 2.9

TT mg/L 4 26.6 34.7 31.5 3.8

Turbidity

IN NTU 24 0.1 1.9 0.5 0.5

AP NTU 24 0.1 2.2 0.6 0.7

TA NTU 24 <0.1 2.3 0.5 0.7

TB NTU 24 <0.1 2.0 0.5 0.6

TT NTU 4 <0.1 0.3 0.1 0.1

pH

IN S.U. 20 7.8 8.4 8.0 0.2

AP S.U. 20 6.5 7.9 6.9 0.3

TA S.U. 20 6.4 7.5 6.9 0.3

TB S.U. 20 6.2 7.6 6.9 0.3

TT S.U. 3 6.6 7.1 6.9 0.3

Temperature

IN °C 11(a) 26.2 34.1 30.6 3.0

AP °C 11(a) 27.4 33.7 31.8 2.0

TA °C 11(b) 26.8 34.0 31.9 2.3

TB °C 11(b) 27.2 34.4 32.3 2.1

TT °C 2(c) 30.6 34.7 32.7 2.9
Table 4-7. Summary of Water Quality Parameter Sampling Results (Continued)

Parameter

Sampling 

Location Unit

Sample 

Count

Concentration Standard 

Minimum Maximum Average Deviation

Dissolved 

Oxygen (DO)

IN mg/L 1 3.7 3.7 - -

AP mg/L 1 3.1 3.1 - -

TA mg/L 1 3.0 3.0 - -

TB mg/L 1 3.4 3.4 - -

TT mg/L 0 - - - -

OxidationReduction 

Potential 

(ORP)

IN mV 2 225 243 234 12.3

AP mV 2 287 303 295 11.5

TA mV 2 289 321 305 23.1

TB mV 2 320 351 336 21.5

TT mV 0 - - - -

Free Chlorine 

(as Cl2) 

IN mg/L 9 0.0 0.1 0.0 0.0

AP mg/L 15 0.1 2.2 1.5 0.5

TA mg/L 15 0.0 2.1 1.5 0.5

TB mg/L 15 0.0 2.2 1.4 0.6

TT mg/L 3 1.1 2.1 1.7 0.5

Total Chlorine 

(as Cl2) 

IN mg/L 9 0.0 0.1 0.0 0.0

AP mg/L 16 0.0 2.1 1.4 0.6

TA mg/L 15 0.0 2.1 1.5 0.5

TB mg/L 15 0.0 2.2 1.4 0.5

TT mg/L 3 1.1 1.9 1.6 0.4

Total 

Hardness 

(as CaCO3) 

IN mg/L 7 29.7 47.3 37.5 5.7

AP mg/L 7 32.9 48.8 38.7 5.2

TA mg/L 7 33.4 94.5 52.2 28.6

TB mg/L 7 30.9 93.0 50.5 27.2

TT mg/L 4 37.5 86.7 61.0 25.8

Ca Hardness 

(as CaCO3) 

IN mg/L 7 21.3 36.2 27.4 4.9

AP mg/L 7 23.5 37.3 28.3 4.6

TA mg/L 7 23.2 67.8 37.3 20.6

TB mg/L 7 21.2 66.1 35.6 19.4

TT mg/L 4 27.2 60.0 42.5 17.5

Mg Hardness 

(as CaCO3) 

IN mg/L 7 8.4 11.1 10.1 1.0

AP mg/L 7 9.4 11.4 10.4 0.7

TA mg/L 7 9.2 27.4 14.8 8.1

TB mg/L 7 9.5 26.8 14.9 7.9

TT mg/L 4 10.3 26.7 18.5 8.4

One-half of detection limit used for samples with concentrations less than detection limit for calculations.

(a) Nine outliers all at 25.0°C on 05/28/08, 07/08/08, 10/07/08, 11/18/08, 12/16/08, 02/17/09, 

04/15/09, 09/15/09, 01/19/10 omitted. 

(b) Eight outliers all at 25.0°C on 07/08/08, 10/07/08, 11/18/08, 12/16/08, 02/17/09, 04/15/09, 

09/15/09, 01/19/10 omitted. 

(c) One outlier at 25.0°C on 10/07/08 omitted. 

Because most arsenic was present as soluble As(V), oxidation with chlorine was not required. After 

chlorination, As(III) concentrations exhibited little change. Free and total chlorine residuals were 

monitored at the IN, AP, TA, TB, and TT locations to ensure that the target chlorine residual level was 

properly maintained for disinfection purposes. Measurements at the IN location were discontinued after 

the September 15, 2009 sampling event. Total chlorine levels at the AP location ranged from 0.0 to 

2.1 mg/L (as Cl2) and averaged 1.4 mg/L (as Cl2); free chlorine levels ranged from 0.1 to 2.2 mg/L (as 

Cl2) and averaged 1.5 mg/L (as Cl2) (Table 4-7). The total and free chlorine measurements from 
37

 

Figure 4-15. Concentrations of Various Arsenic Species at IN, AP, TA, and TB Sampling Locations 

0

5

10

15

20

25

30

35

40

5/28/2008 10/7/2008 3/17/2009 7/14/2009 9/15/2009

As Concentration (μg/L)

Date

Arsenic Species at the Inlet (IN)

As (Particulate) As(III) As(V)

0

5

10

15

20

25

30

35

40

4/1/2008 5/28/2008 10/7/2008 3/17/2009 7/14/2009 11/17/2009

As Concentration (μg/L)

Date

Arsenic Species after Chlorination and pH Adjustment (AP)

As (Particulate) As(III) As(V)
38

Figure 4-15. Concentrations of Various Arsenic Species at IN, AP, TA, and TB 

Sampling Locations (Continued) 

0

5

10

15

20

25

30

35

40

4/1/2008 5/28/2008 10/7/2008 3/17/2009 7/14/2009 11/17/2009

As Concentration (μg/L)

Date

Arsenic Species after Tank A (TA)

As (Particulate) As(III) As(V)

0

5

10

15

20

25

30

35

40

4/1/2008 5/28/2008 10/7/2008 3/17/2009 7/14/2009 11/17/2009

As Concentration (μg/L)

Date

Arsenic Species after Tank B (TB)

As (Particulate) As(III) As(V)
39

July 30, 2008, were omitted from all sampling locations due to the uncharacteristically high levels 

measured. The total and free residual chlorine levels measured at the TA,TB, and TT locations were very 

similar to those at the AP location, indicating little or no chlorine demand through the AD-33 vessels.

As shown by the samples taken during the last sampling event on March 16, 2010, after treating 

approximately 41,000 BV of water, total arsenic concentrations following Vessels A and B were still as 

low as 0.6 and 0.4 μg/L, respectively. Based on the vendor’s estimate, total arsenic breakthrough at 

10 μg/L would occur at 51,000 BV (or 14,484,000 gal). Figure 4-16 presents total arsenic concentrations 

at the IN, AP, TA, and TB locations plotted against bed volumes. 

0

5

10

15

20

25

30

35

40

45

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000

As Concentration (μg/L)

Bed Volume

Total As vs. Bed Volume

At Wellhead (IN) After chorination & pH Adjustment (AP) After Tank A (TA) After Tank B (TB)

Figure 4-16. Total Arsenic Breakthrough Curves (1BV = 284 gal)

Iron and Manganese. Iron and manganese were analyzed through November 17, 2009. The average

total iron concentration in raw water was less than the MDL of 25 μg/L (Table 4-6). Average total iron 

concentrations across the treatment train also were below the MDL. Total manganese levels in raw water 

were low, ranging from 0.1 to 2.8 μg/L and averaging 0.7 μg/L. Manganese existed primarily in the 

soluble form prior to chlorination, after which manganese existed mostly as particulate. Total manganese 

levels were reduced to an average of 0.3 and 0.1 μg/L following Vessels A and B, respectively.

Uranium and Vanadium. Uranium was detected in the initial source water samples collected by Battelle 

on December 7, 2004 (Table 4-1) and its levels were monitored through September 2, 2008. Total 

uranium concentrations in the raw water ranged from 7.0 to 8.3 μg/L and averaged 7.7 μg/L. Total 

uranium levels were reduced to below the MDL of 0.1 μg/L following each adsorption vessel. Since 

uranium levels in the raw water were always below their MCL of 30 μg/L and levels in the treated water 
40

were continually below the MDL, uranium analysis was discontinued in favor of vanadium analysis. 

Total vanadium levels in raw ranged from 23.5 to 38.1 μg/L and averaged 32.2 μg/L. Total vanadium 

concentrations averaged 1.6 and 1.4 μg/L after Vessels A and B, respectively. Currently, there is no 

MCL for vanadium. 

Competing Anions. Phosphorus and silica, which might influence arsenic adsorption, were measured at 

the five sampling locations across the treatment train through November 17, 2009, when the list of 

analytes was reduced to only include arsenic and vanadium. Phosphorus was below its MDL of 10 μg/L 

for all sampling events during the evaluation period. Silica concentrations in the raw water ranged from 

24.4 to 27.8 mg/L and averaged 26.2 mg/L. Little silica removal by the adsorption vessels was observed 

during the study. 

Other Water Quality Parameters. As shown in Table 4-7, pH values of the raw water varied from 7.8 to 

8.4 and averaged 8.0. pH values following CO2 injection for pH adjustment at the AP location varied 

from 6.5 to 7.9 and averaged 6.9, which is just below the target value of 7.0. Figure 4-17 shows the pH 

of the well water before and after pH adjustment by CO2 as measured by the operator with a field pH 

probe during sampling events. For comparison, pH readings recorded from the inline pH probe, which 

was connected to the pH controller on the control panel, were plotted alongside the measurements made 

by the operator. pH values of the adjusted water, as measured by the inline probe, ranged from 5.5 to 8.5 

S.U. and averaged 7.1 S.U., which is somewhat higher than that measured with a field pH probe. The 

discrepancies observed might have been caused by instrumentation errors, being that the field pH probe 

used by the operator was calibrated before each use and that the inline pH probe connected to the pH 

controller was calibrated twice during the entire study period. Nonetheless, the higher pH values 

measured with the field pH probe were to the contrary of those observed at two other arsenic 

demonstration sites where CO2 also was used for pH adjustments (Cumming et al., 2009; Williams et al., 

2010). Lower pH values measured at these sites were thought to be caused by CO2 degassing during 

sample collection and analysis. 

Alkalinity, reported as CaCO3, ranged from 144 to 156 mg/L and averaged 150 mg/L in raw water. As 

expected, alkalinity after pH adjustment and adsorption remained relatively unchanged at 148 to 159 

mg/L (on average), since CO2, instead of mineral acids, was used for pH adjustment. 

Hardness. The treatment plant water samples were analyzed for hardness only on speciation events. 

Total hardness, reported as CaCO3, ranged from 29.7 to 47.3 mg/L and averaged 37.5 mg/L in raw water. 

Total hardness existed primarily as calcium hardness. Total hardness levels remained relatively 

unchanged from IN to the AP sampling location. On March 17, 2009 and July 14, 2009, significantly 

elevated total hardness levels (approximately 2-3 times the average concentration at IN and AP) were 

observed at TA, TB, and TT for unknown reasons. Slightly elevated total hardness levels at TA, TB, and 

TT also were also seen on November 17, 2009. Due to the elevated levels on the aforementioned 

sampling dates, the average total hardness increased to 52.2, 50.5, and 61.0 mg/L following Tank A, 

Tank B, and TT, respectively. The hardness levels at TA, TB, and TT from the remaining four sampling 

events were somewhat lower or similar to the concentrations at IN and AP. 

Sulfate concentrations in raw water ranged from 22.2 to 24.8 mg/L and averaged 23.8 mg/L. After pH 

adjustment and adsorption, sulfate levels remained unchanged at 23.6 to 24.0 mg/L (on average). 

Fluoride results ranged from 1.0 to 1.2 mg/L and averaged 1.1 mg/L following both treatment vessels.

The results indicated that the adsorptive media did not affect the amount of fluoride in water after 

treatment. 
41

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

01/28/08 04/17/08 07/06/08 09/24/08 12/13/08 03/03/09 05/22/09 08/10/09 10/29/09 01/17/10 04/07/10

pH (S.U.)

Date

Raw Water pH Adjusted Water - By Field pH Probe pH Adjusted Water - By Inline pH Probe

AdEdge CO2 pH Adjustment 

System Installed on 07/10/08

Figure 4-17. pH Values Before and After Adjustment

Due to difficulties experienced by the operator with the equipment, DO was measured only once while 

ORP was measured twice. On May 28, 2008, both measurements were discontinued. DO levels ranged 

from 3.0 to 3.7 mg/L throughout the treatment train. ORP readings averaged 234 mV in raw water, but 

increased to an average of 295 mV after chlorination. 

4.5.2 Backwash Wastewater Sampling. Backwash was not performed during the performance 

evaluation study.

4.5.3 Distribution System Water Sampling. Prior to the installation/operation of the treatment 

system, four baseline distribution system water samples were collected from three residences, previously 

used for LCR sampling, on October 19, 2005, November 22, 2005, December 14, 2005, and January 24, 

2006. Following startup of the treatment system, distribution system water sampling continued on a 

quarterly basis at the same three locations, with samples collected from July 2008 through October 2009. 

Table 4-8 summarizes the results of the distribution system sampling. 

The most noticeable change in the distribution system samples since the system began operation was a 

decrease in arsenic concentration. Baseline arsenic concentrations averaged 35.6, 37.3, and 36.6 μg/L for 

the first draw samples at the DS1, DS2, and DS3 sampling locations, respectively. After the performance 

evaluation study began, arsenic concentrations at DS1, DS2, and DS3 averaged 0.5, 1.5, and 0.7 μg/L, 

respectively. Although arsenic concentrations in the distribution system were low, there were three 

sampling events ( i.e., July 8, 2008, April 15, 2009, and October 20, 2009) when the arsenic levels in the 

distribution water were higher than those in the system effluent. It is surmised that some redissolution 
42

 Stagnation Time pH Alkalinity As Fe Mn Pb Cu Stagnation Time pH Alkalinity As Fe Mn Pb Cu Stagnation Time pH Alkalinity As Fe Mn Pb Cu

No. Date hrs S.U. mg/L μg/L μg/L μg/L μg/L μg/L hrs S.U. mg/L μg/L μg/L μg/L μg/L μg/L hrs S.U. mg/L μg/L μg/L μg/L μg/L μg/L

BL1 10/19/05 7.0 8.1 158 30.6 <25 1.5 <0.1 36.6 8.9 7.9 158 31.7 <25 2.3 <0.1 4.3 8.2 7.9 158 30.4 <25 1.9 0.1 81.8

BL2 11/22/05(a) 13.3 8.0 154 36.5 <25 1.3 0.1 22.2 12.5 8.1 145 39.5 <25 1.1 0.1 12.8 8.0 8.1 150 40.3 <25 0.9 0.2 1.6

BL3 12/14/05 NA 8.3 154 34.2 <25 0.9 <0.1 9.0 NA 8.2 150 36.3 <25 2.0 0.3 4.0 NA 8.2 145 34.2 <25 0.8 <0.1 10.6

BL4 01/24/06 10.3 8.2 154 41.0 <25 0.6 <0.1 8.2 8.0 8.1 154 41.6 <25 0.3 <0.1 9.1 7.0 8.3 154 41.3 <25 0.1 <0.1 1.2

1 07/08/08 7.2 7.0 163 1.2 <25 1.1 0.3 260 9.0 7.0 160 1.4 <25 0.7 0.7 220 9.5 6.8 147 0.5 <25 0.4 2.9 283

2 10/16/08(b) NA NA NA NA NA NA NA NA 8.3 7.3 157 0.5 <25 0.2 0.5 166 7.0 7.2 155 0.4 <25 0.2 1.8 39.5

3 01/20/09 9.0 8.2 142 0.3 <25 <0.1 0.7 34 7.5 7.5 158 0.4 <25 <0.1 0.3 156 7.0 8.0 158 0.6 <25 0.2 0.5 138

4 04/15/09(c) 9.5 7.0 152 0.3 <25 0.2 2.4 99.6 7.8 7.1 161 4.0 <25 0.2 0.4 145 NA NA NA NA NA NA NA NA

5 07/14/09(d) 7.3 6.8 158 0.2 <25 0.1 2.0 74.8 NA NA NA NA NA NA NA NA 7.0 6.8 162 0.5 <25 <0.1 1.8 124

6 10/20/09(e) NA NA NA NA NA NA NA NA 7.3 7.5 148 1.3 <25 0.7 0.5 169 7.0 7.3 154 1.3 <25 0.5 1.1 78.2

Sampling

Event

Tautolo #0020-409-52600 Saraficio #0020-409-51200

DS2

 1st draw

LCR LCR

 1st draw

LCR

1st Draw

DS1 DS3

Johnson #0020-409-50200

Table 4-8. Distribution System Sampling Results 

(a) DS2 sampled on 021/21/05. 

(b) DS1 not available for sampling on 10/16/08.

(c) DS3 not available for sampling on 04/15/09.

(d) DS2 not available for sampling on 07/14/09.

(e) DS1 not available for sampling on 10/20/09.

BL = baseline sampling; NA = not available. 

Lead action level = 15 μg/L; Copper action level = 1,300 μg/L

Alkalinity measured in mg/L as CaCO3. 
43

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000

As Concentration (μg/L)

Bed Volume (BV)

After Vessel A (TA)

After Vessel B (TB)

DS1

DS2

DS3

Figure 4-18. Comparison of Arsenic Concentrations in System Effluent and Distribution System 

and/or resuspension of arsenic particles might have occurred in the distribution system. Figure 4-18 

shows arsenic levels in the system effluent and distribution system plotted against BV.

Lead concentrations ranged from less than the detection limit of 0.1 to 2.9 μg/L, with none of the samples 

exceeding the action level of 15 μg/L. Copper concentrations ranged from 34.1 to 283 μg/L, with no 

samples exceeding the 1,300 μg/L action level. Measured pH values ranged from 6.8 to 8.2 and averaged 

7.2, which were 0.3 units higher than the average pH value immediately after the adsorption vessels. 

Higher pH values in the distribution system might be due to CO2 degassing. Compared to an average

value of 8.1 before the treatment sytem became operational, the lowered pH values appeared to have 

some effects on the lead and copper concentrations in the distribution system. Lead and copper 

concentrations were observed to increase slightly after the system was put into service. Before the system 

was put into service, lead levels averaged <0.1, 0.1, and 0.1 μg/L at DS1, DS2, and DS3, respectively, 

while copper levels averaged 19.0, 7.6, and 23.8 μg/L, respectively. After the system was put into 

service, lead levels averaged 1.4, 0.5, and 1.6 μg/L, respectively, and copper levels averaged 117, 171, 

and 133 μg/L, respectively. 

Alkalinity levels exhibited no change, with concentrations ranging from 142 to 163 mg/L (as CaCO3). 

Total iron concentrations were always less than the MDL of 25 μg/L for all distribution sampling events, 

including baseline sampling. Total Mn concentrations in the distribution system samples were typically 

low, ranging from <0.1 to 1.1 μg/L.
44

4.6 System Cost

System cost is evaluated based on the capital cost per gpm (or gpd) of the design capacity and the O&M 

cost per 1,000 gal of water treated. The capital cost includes the cost for equipment, site engineering, and 

installation. The O&M cost includes the cost for media replacement and disposal, electrical power use, 

and labor. 

4.6.1 Capital Cost. The capital investment for equipment, site engineering, and installation of the 

treatment system was $115,306 (see Table 4-9). The equipment cost was $86,018 (or 75% of the total 

capital investment), which included $48,715 for the skid-mounted unit, $18,402 for the CO2 pH control 

system, $13,861 for the AD-33 media ($365/ft3

 or $10.42/lb to fill two vessels), $992 for the gravel 

underbedding, $1,339 for additional sample taps and totalizer/meters, and $2,709 for shipping.

The site engineering cost was $12,897, or 11% of the total capital investment. Because an engineering 

plan or a permit submittal package was not required for the Covered Wells site, the engineering cost 

represents a small fraction of total capital cost.

The installation cost included the equipment and labor to unload and install the skid-mounted unit, 

perform piping tie-ins and electrical work, load and backwash the media, and perform system shakedown 

and startup. The installation cost was $16,391, or 14% of the total capital investment. 

Table 4-9. Capital Investment Cost for APU Arsenic Adsorption System

Description Quantity Cost

% of 

Capital 

Investment

Equipment Cost

APU Skid-Mounted System 1 $48,715 –

CO2 pH Control System 1 $18,402 –

AD-33 Media 38 ft3 $13,861 –

Gravel Underbedding – $992 –

Sample Taps & Totalizer/Meters(a) – $1,339 –

Shipping – $2,709 –

Equipment Total – 86,018 75

Engineering Cost

Vendor Labor 73 hr $6,967 –

Vendor Travel 2 day $1,008 –

Subcontractor Labor – $4,594 –

Subcontractor Travel – $329 –

Engineering Total – $12,897 11

Installation Cost

Vendor Labor 60 hr $7,256 –

Subcontractor Labor – $9,135 –

Installation Total – $16,391 14

Total Capital Investment – $115,306 100

(a) Additional taps and totalizer/meters for study purposes. 

The total capital cost of $115,306 was normalized to the system’s design capacity of 63 gpm (90,720 

gpd), which resulted in $1,830/gpm of design capacity ($1.27/gpd). The capital cost also was converted 

to an annualized cost of $10,884/yr using a capital recovery factor (CRF) of 0.09439 based on a 7% 

interest rate and a 20-year return period. Assuming that the system operated 24 hours a day, 7 days a 
45

week at the system design flowrate of 63 gpm to produce 33,112,800 gal of water per year, the unit 

capital cost would be $0.33/1,000 gal. Because the system operated only 4.38 hr/day at approximately 60 

gpm on average (see Table 4-5), producing an estimated 5,755,320 gal of water annually, the unit capital 

cost increased to $1.89/1,000 gal at this reduced rate of use.

4.6.2 Operation and Maintenance Cost. The O&M cost included the cost for items such as 

media replacement and disposal, CO2 usage, electricity consumption, and labor (Table 4-10). Although 

media replacement did not occur during the performance evaluation study, the media replacement cost 

would have represented the majority of the O&M cost and was estimated to be $18,405 to change out the 

media in both vessels. This media changeout cost would include the cost for media, the gravel 

underbedding, freight, labor, travel, spent media analysis, and media disposal fee. This cost was used to 

estimate the media replacement cost per 1,000 gal of water treated as a function of the projected media 

run length to the 10 μg/L arsenic breakthrough (Figure 4-19).

The chemical cost associated with system operation included the cost for NaOCl for prechlorination and 

CO2 gas for pH adjustment. NaOCl had already been used at the site prior to the installation of the APU 

unit for disinfection purposes. The presence of the APU system did not affect the use rate of the NaOCl 

solution. Therefore, the incremental chemical cost for chlorine was negligible. During the performance 

evaluation period the 50-lb CO2 cylinders were replaced a total of 91 times, or once every eight days. 

Each changeout cost $38.74, which included the replacement and delivery charges. The CO2 cost for the 

study period was $3,525 or $0.30/1,000 gal of water treated. 

Table 4-10. Operation and Maintenance Cost for APU Arsenic Adsorption System

Cost Category Value Assumptions

Estimated Volume Processed (gal) 11,686,000 During 765-day study period; equivalent to 

5,576,000 gal annually 

Media Replacement and Disposal Cost

Media Replacement ($) $13,861 $365/ft3 for 38 ft3 

Labor, Travel, Freight, & Disposal ($) $4,544

Media Replacement and Disposal 

($/1,000 gal)

See Figure 4-19 Based upon media run length at 10-μg/L 

arsenic breakthrough

CO2 Cost

CO2 Cost ($) $3,525 Based on cost of CO2 cylinders (50-lb) for pH 

adjustment

Unit CO2 Cost ($/1,000 gal) $0.30

Electricity Cost

Electricity ($/1,000 gal) $0.05 Includes power used by the booster pumps

Labor Cost

Average Weekly Labor (hr) 2.3 1.5 hr/visit, 1.5 visit/week (on average)

Labor through Study (hr) 251 109 week through study

Labor Cost ($) $5,522 Labor rate = $22.00/hr

Unit Labor Cost ($/1,000 gal) $0.47

Total O&M Cost/1,000 gal See Figure 4-19 Media replacement cost (based upon media 

run length at 10-μg/L arsenic breakthrough) + 

$0.30 (CO2 cost) + $0.05 (electrical cost)+ 

$0.47 (labor cost)

Comparison of electrical bills supplied by TOUA prior to system installation and since startup indicated 

an additional 3,304 kWh per year was required to run the system. The cost of the additional electricity 
46

was $299.75, which included the power necessary to run the three booster pumps. The electrical cost 

associated with the operation of the system was calculated to be $0.05/1,000 gal of water treated. 

Under normal operating conditions, routine labor activities to operate and maintain the system consumed 

1.5 hr/day, 1 to 2 days per week, or 2.3 hr/week (on average). The labor cost incurred during the 

performance evaluation study was $5,522 or $0.47/1,000 gal of water treated. This estimation assumed 

that maintenance and operational procedures were consistently performed through the completion of the 

performance evaluation study. 

Figure 4-19. Media Replacement and Other Operation and Maintenance Cost 

$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

$5.00

$5.50

$6.00

$6.50

$7.00

$7.50

$8.00

$8.50

0 10 20 30 40 50 60 70 80 90 100

Media Working Capacity, Bed Volumes (x1000)

Cost ($/1,000 gal)

O&M cost

Media replacement cost

Note: One bed volume equals 38 ft3 (284 gal)
47

5.0 REFERENCES

Battelle. 2004. Revised Quality Assurance Project Plan for Evaluation of Arsenic Removal Technology. 

Prepared under Contract No. 68-C-00-185, Task Order No. 0029, for U.S. Environmental 

Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH. 

Battelle. 2006. Final System Performance Evaluation Study Plan: U.S. EPA Demonstration of Arsenic 

Removal Technology at Covered Wells, Tohono O’odham Nation, Arizona. Prepared under 

Contract No. 68-C-00-185, Task Order No. 0029 for U.S. Environmental Protection Agency, 

National Risk Management Research Laboratory, Cincinnati, OH. 

Chen, A.S.C., L. Wang, J.L. Oxenham, and W.E. Condit. 2004. Capital Costs of Arsenic Removal

Technologies: U.S. EPA Arsenic Removal Technology Demonstration Program Round 1. 

EPA/600/R-04/201. U.S. Environmental Protection Agency, National Risk Management 

Research Laboratory, Cincinnati, OH. 

Edwards, M., S. Patel, L. McNeill, H. Chen, M. Frey, A.D. Eaton, R.C. Antweiler, and H.E. Taylor. 

1998. “Considerations in As Analysis and Speciation.” J. AWWA, 90(3):103-113. 

EPA. 2001. National Primary Drinking Water Regulations: Arsenic and Clarifications to Compliance 

and New Source Contaminants Monitoring. Fed. Register, 40 CFR Parts 9, 141, and 142. 

EPA. 2002. Lead and Copper Monitoring and Reporting Guidance for Public Water Systems. 

EPA/816/R-02/009. U.S. Environmental Protection Agency, Office of Water, Washington, DC. 

EPA. 2003. Minor Clarification of the National Primary Drinking Water Regulation for Arsenic. 

Federal Register, 40 CFR Part 141.

Farley, D. 2004. Preliminary Arsenic Feasibility Study: A Study to Evaluate and Recommend Options 

for Reducing Arsenic Levels in Drinking Water on the Tohono O’odham Nation, Indian Health 

Services, Sells, AZ.

Cumming, L.J., A.S.C. Chen, and L. Wang. 2009. Arsenic Removal from Drinking Water by Adsorptive 

Media, U.S. EPA Demonstration Project at Rollinsford, NH, Final Performance Evaluation 

Report. EPA/600/R-09/017. U.S. Environmental Protection Agency, National Risk Management 

Research Laboratory, Cincinnati, OH. 

Wang, L., W.E. Condit, and A.S.C Chen. 2004. Technology Selection and System Design: U.S. EPA 

Arsenic Removal Technology Demonstration Program Round 1. EPA/600/R-05/001. U.S. 

Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, 

OH. 

Williams, S., A.S.C. Chen, and L. Wang. 2010. Arsenic Removal from Drinking Water by Adsorptive 

Media, U.S. EPA Demonstration Project at Webb Consolidated Independent School District in 

Bruni, TX, Final Performance Evaluation Report. EPA/600/R-10/040. U.S. Environmental 

Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH. 

 
APPENDIX A

OPERATIONAL DATA
A-1

Table A-1. EPA Arsenic Demonstration Project at Covered Wells in Tohono O’odham Nation, AZ - Daily System Operation Log Sheet

Inst. 

Flowrate

Incremental 

Volume

Bed 

Volume 

Average 

Flowrate

Inst. 

Flowrate

Incremental 

Volume

Bed 

Volume

Average 

Flowrate

Well # 1 

or 2 hr gal gpm hr gal gpm gpm gal no. gpm gpm gal no. gpm Inlet Outlet A B

1 02/13/08 NA NA 0.0 NA NA 0.0 NA NA NA 0 0 0.0 NA 0 0 0.0 NA NA NA NA

02/20/08 13:31 NR 0.0 NA NA 0.0 NA NA NA 35,920 253 NA NA 35,098 247 NA NA NA NA NA

02/21/08 11:18 2 0.0 NA NA 0.0 NA NA 30.3 6,848 301 NA 28.4 6,837 295 NA NA NA 1.3 2.0

02/22/08 12:47 NR 0.0 NA NA 0.0 NA NA NA 7,046 351 NA NA 6,991 345 NA NA NA NA NA

02/25/08 15:00 2 0.0 NA NA 0.0 NA NA 30.0 13,444 445 NA 31.2 13,103 437 NA NA NA 0.0 1.5

02/27/08 10:00 NR 0.0 NA NA 0.0 NA NA NA 11,926 529 NA NA 11,542 518 NA NA NA NA NA

02/28/08 13:00 2 0.0 NA NA 0.0 NA NA 29.3 9,798 598 NA 31.0 9,584 586 NA NA NA 0.0 0.0

03/03/08 15:35 2 0.0 NA NA 0.0 NA NA 27.2 24,162 769 NA 31.2 23,474 751 NA NA NA NA NA

03/07/08 14:32 2 0.0 NA NA 0.0 NA NA 29.3 31,496 990 NA 31.2 30,514 966 NA NA NA NA NA

03/10/08 13:53 NR 0.0 NA NA 0.0 NA NA NA 20,122 1,132 NA NA 19,721 1,105 NA NA NA NA NA

03/12/08 14:20 2 0.0 NA NA 0.0 NA NA 30.3 21,931 1,287 NA 31.6 21,707 1,258 NA 9 NA 5.0 5.0

03/13/08 10:31 NR 0.0 NA NA 0.0 NA NA NA 1,577 1,298 NA NA 1,532 1,268 NA NA NA NA NA

03/14/08 11:02 NR 0.0 NA NA 0.0 NA NA NA 6,453 1,343 NA NA 6,389 1,313 NA NA NA NA NA

03/17/08 9:45 NR 0.0 NA NA 0.0 NA NA NA 20,274 1,486 NA NA 19,947 1,454 NA NA NA NA NA

03/18/08 10:22 NR 0.0 NA NA 0.0 NA NA NA 6,978 1,535 NA NA 6,937 1,503 NA NA NA NA NA

03/19/08 9:42 NR 0.0 NA NA 0.0 NA NA NA 2,354 1,552 NA NA 3,296 1,526 NA NA NA NA NA

03/20/08 14:38 1 0.0 NA NA 0.0 NA NA 36.4 8,636 1,612 NA 30.7 8,542 1,586 NA NA NA NA NA

03/24/08 10:15 NR 0.0 NA NA 0.0 NA NA NA 26,196 1,797 NA NA 26,082 1,770 NA NA NA NA NA

03/27/08 13:05 1 0.0 NA NA 0.0 NA NA NA 20,815 1,943 NA NA 20,035 1,911 NA NA NA NA NA

03/31/08 9:26 NR 0.0 NA NA 0.0 NA NA NA 26,914 2,133 NA NA 25,972 2,094 NA NA NA NA NA

04/01/08 10:25 2 0.0 NA NA 0.0 NA NA 29.3 7,248 2,184 NA 31.4 7,447 2,146 NA NA NA 3.0 5.0

04/04/08 10:25 NR 0.0 NA NA 0.0 NA NA NA 19,874 2,324 NA NA 21,480 2,297 NA NA NA NA NA

04/07/08 9:03 NR 0.0 NA NA 0.0 NA NA NA 17,185 2,445 NA NA 13,841 2,395 NA NA NA NA NA

04/11/08 11:36 NR 0.0 NA NA 0.0 NA NA NA 26,330 2,630 NA NA 26,146 2,579 NA NA NA NA NA

04/15/08 10:35 1 0.0 NA NA 0.0 NA NA 35.5 14,924 2,736 NA 31.6 14,579 2,682 NA 13 8 2.5 2.5

04/17/08 15:27 1 0.0 1,320 NA 0.0 53,210 NA 32.3 27,467 2,929 NA 34.1 26,725 2,870 NA 13 9 2.5 4.0

04/21/08 10:58 2 0.0 25,070 NA 0.0 79,450 NA 30.2 25,444 3,108 NA 32.1 24,891 3,045 NA 12 8 2.5 2.5

04/23/08 11:44 1 0.0 42,240 NA 0.0 91,490 NA 30.9 14,987 3,214 NA 32.9 14,352 3,146 NA 12 8 2.5 2.5

04/28/08 15:15 1 0.0 95,770 NA 0.0 115,180 NA 32.2 40,104 3,496 NA 32.7 40,351 3,430 NA 12 7 3.0 5.0

04/29/08 10:15 2 0.0 98,990 NA 0.0 116,390 NA 31.6 2,090 3,511 NA 27.0 1,969 3,444 NA 9 9 2.5 2.0

05/02/08 12:16 1 0.0 116,110 NA 0.0 140,540 NA 32.2 21,686 3,664 NA 34.4 20,637 3,590 NA 12 8 2.5 4.0

05/05/08 9:45 2 0.0 134,390 NA 0.0 157,300 NA 30.6 18,374 3,793 NA 30.5 17,761 3,715 NA 12 8 6.0 4.0

05/06/08 15:02 1 0.0 134,520 NA 0.0 171,620 NA 31.2 8,137 3,850 NA 30.5 7,675 3,769 NA 12 8 7.0 4.0

05/08/08 10:50 1 0.0 152,960 NA 0.0 180,000 NA 35.7 14,532 3,953 NA 34.7 14,117 3,868 NA 12 8 2.0 2.5

05/12/08 12:40 2 0.0 174,770 NA 0.0 219,380 NA 33.3 30,676 4,169 NA 31.5 29,496 4,076 NA 10 5 0.0 1.0

05/16/08 14:20 1 0.0 196,040 NA 0.0 232,150 NA 31.4 17,365 4,291 NA 30.2 16,733 4,194 NA 9 4 1.0 2.5

05/19/08 14:36 2 0.0 227,840 NA 0.0 271,210 NA 31.9 35,648 4,542 NA 29.0 34,219 4,435 NA 8 4 2.5 3.0

05/22/08 10:30 1 0.0 249,540 NA 0.0 282,290 NA 36.0 17,736 4,667 NA 31.0 17,177 4,556 NA 14 10 2.5 2.5

05/27/08 11:00 2 0.0 272,060 NA 0.0 315,300 NA 31.0 28,592 4,868 NA 30.8 27,256 4,748 NA 10 6 2.0 2.5

05/28/08 13:05 1 0.0 277,550 NA 0.0 337,140 NA 33.9 14,025 4,967 NA 30.2 13,502 4,843 NA 11 7 2.0 5.0

06/02/08 9:04 1 0.0 325,240 NA 0.0 356,230 NA 33.1 34,344 5,209 NA 33.8 32,940 5,075 NA 12 8 2.0 5.0

06/04/08 10:50 2 0.0 340,740 NA 0.0 375,030 NA 29.0 18,521 5,339 NA 30.4 17,689 5,199 NA 11 7 2.0 3.0

06/09/08 15:30 1 0.0 371,280 NA 0.0 427,630 NA 33.0 45,040 5,656 NA 31.0 43,622 5,506 NA 10 5 2.0 5.0

06/13/08 11:52 2 0.0 402,610 NA 0.0 457,990 NA 27.3 28,971 5,860 NA 30.3 27,974 5,703 NA 10 5 2.0 0.0

06/16/08 14:00 2 0.0 421,540 NA 0.0 492,170 NA 30.0 27,549 6,055 NA 29.5 26,482 5,890 NA 15 5 2.0 2.0

06/20/08 15:03 2 0.0 445,450 NA 0.0 535,650 NA 29.9 34,938 6,301 NA 28.4 33,558 6,126 NA 8 5 2.0 2.5

06/25/08 15:00 1 0.0 477,400 NA 0.0 593,160 NA 35.0 47,183 6,633 NA 31.0 45,585 6,447 NA 8 4 10.0 7.0

06/26/08 12:20 2 0.0 480,920 NA 0.0 595,940 NA 31.0 2,081 6,647 NA 29.0 1,981 6,461 NA 9 6 9.5 2.0

21 07/01/08 13:53 2 0.0 510,040 NA 0.0 665,130 NA 30.7 49,946 6,999 NA 27.5 47,898 6,798 NA 9 6 5.0 2.5

07/07/08 12:20 2 0.0 556,950 NA 0.0 711,700 NA 28.1 48,692 7,342 NA 31.1 46,734 7,128 NA 5 3 4.0 2.5

07/08/08 12:08 1 0.0 556,990 NA 0.0 729,330 NA 30.7 9,602 7,410 NA 29.9 9,275 7,193 NA 10 6 4.0 3.0

07/14/08 14:47 2 7.0 583,750 63.7 17.0 791,340 60.8 31.1 44,530 7,723 30.9 31.5 42,747 7,494 29.7 10 5 2.0 2.0

07/16/08 16:00 1 9.8 594,780 65.7 22.3 810,290 59.6 52.8 16,296 7,838 33.5 54.2 15,634 7,604 32.2 NA NA 9.0 8.0

07/18/08 11:45 2 10.9 598,910 62.6 25.2 820,990 61.5 30.1 7,221 7,889 30.1 31.3 6,933 7,653 28.9 9 5 9.0 2.5

24 07/25/08 11:50 1 17.5 624,380 64.3 44.5 891,650 61.0 31.4 49,507 8,238 31.9 30.9 47,550 7,988 30.6 10 8 2.5 2.5

07/28/08 11:10 2 20.0 633,730 62.3 52.7 921,860 61.4 27.7 19,887 8,378 31.0 29.5 19,090 8,122 29.7 10 8 0.0 2.0

07/30/08 NA 2 24.9 653,050 65.7 59.9 947,730 59.9 29.0 22,701 8,537 31.3 28.2 21,743 8,275 29.9 9 5 1.0 2.5

26 08/06/08 9:42 1 32.3 681,710 64.5 83.0 1,032,480 61.1 34.7 57,903 8,945 31.6 33.6 55,557 8,667 30.4 12 8 2.0 2.5

08/11/08 14:35 2 36.2 696,520 63.3 98.9 1,090,530 60.8 28.4 36,954 9,205 31.1 27.6 35,317 8,915 29.7 9 5 0.0 1.0

08/13/08 16:00 2 38.5 704,490 57.8 104.2 1,109,990 61.2 27.8 14,360 9,307 31.5 29.8 13,718 9,012 30.1 10 4 0.0 1.0

08/15/08 9:05 1 40.8 717,100 91.4 107.1 1,120,540 60.6 28.1 11,175 9,385 35.8 29.8 10,669 9,087 34.2 9 5 2.5 1.0

08/18/08 13:15 1 55.0 769,630 61.7 107.1 1,120,540 0.0 33.2 26,895 9,575 31.6 30.8 25,746 9,268 30.2 10 5 3.0 4.0

08/22/08 15:00 1 63.5 798,360 56.3 116.0 1,153,310 61.4 28.5 31,779 9,799 30.4 30.6 30,539 9,483 29.3 9 5 2.5 2.5

27

28

18

19

20

22

23

25

12

13

14

15

16

17

6

7

8

9

10

11

2

3

4

5

Average 

Flowrate

Vessel A Vessel B

Pressure 

Differential for 

Vessel (psi)

Cum. 

Hours 

Well

Cum. 

Volume

Cum. 

Hours 

Well

Cum. 

Volume

Average 

Flowrate

Week No. Date Time

Well 

Running 

Well No. 1 Well No. 2 Instrument Panel

System Pressure 

(psi)
A-2

Table A-1. EPA Arsenic Demonstration Project at Covered Wells in Tohono O’odham Nation, AZ - Daily System Operation Log Sheet

Inst. 

Flowrate

Incremental 

Volume

Bed 

Volume 

Average 

Flowrate

Inst. 

Flowrate

Incremental

Volume

Bed 

Volume

Average 

Flowrate

Well # 1 

or 2 hr gal gpm hr gal gpm gpm gal no. gpm gpm gal no. gpm Inlet Outlet A B

08/26/08 14:25 1 70.4 823,450 60.6 122.2 1,175,720 60.2 32.5 24,423 9,971 31.1 30.8 23,374 9,648 29.7 11 5 2.0 2.5

08/29/08 12:15 NA NA NA NA NA NA NA 30.8 16,509 10,087 NA 33.3 15,784 9,759 NA 10 4 2.0 2.5

09/02/08 10:32 2 85.2 877,370 60.7 135.7 1,224,150 59.8 27.9 35,387 10,336 20.8 29.7 33,755 9,997 19.9 10 4 1.0 2.0

09/04/08 14:50 1 89.1 891,860 61.9 138.2 1,234,170 66.8 30.0 12,140 10,421 31.6 31.1 1,599 10,008 4.2 10 5 2.0 2.5

31 09/10/08 15:15 1 98.7 926,760 60.6 145.9 1,270,070 77.7 29.7 33,866 10,660 32.6 30.4 42,316 10,306 40.8 10 5 1.0 2.5

32 09/15/08 12:30 1 107.9 960,140 60.5 154.6 1,294,270 46.4 30.9 32,223 10,887 30.0 29.0 30,730 10,523 28.6 8 4 2.0 4.0

09/22/08 10:00 2 115.2 986,300 59.7 169.5 1,348,560 60.7 30.3 40,837 11,174 30.7 29.8 39,165 10,798 29.4 8 4 2.0 1.0

09/25/08 10:15 1 119.5 1,001,820 60.2 176.3 1,373,380 60.8 31.2 19,800 11,314 29.7 29.4 19,053 10,932 28.6 8 4 2.0 2.5

34 10/01/08 12:40 1 137.7 1,068,040 60.6 183.7 1,400,240 60.5 30.6 48,473 11,655 31.6 27.1 46,620 11,261 30.4 10 5 2.0 2.5

10/06/08 10:47 1 144.5 1,092,500 60.0 191.8 1,429,890 61.0 31.2 27,743 11,851 31.0 31.8 26,853 11,450 30.0 12 8 1.5 2.5

10/07/08 11:00 2 145.3 1,095,140 55.0 199.3 1,457,100 60.5 31.1 15,610 11,961 31.3 25.9 15,113 11,556 30.3 9 5 1.0 1.5

36 10/15/08 14:37 1 156.5 1,135,090 59.4 218.4 1,526,840 60.9 30.8 55,395 12,351 30.5 31.1 53,108 11,930 29.2 10 7 2.0 2.5

10/22/08 9:21 2 167.7 1,174,710 59.0 232.5 1,578,470 61.0 28.7 47,133 12,683 31.0 29.5 45,211 12,249 29.8 9 5 2.0 2.5

10/24/08 15:00 2 171.6 1,188,610 59.4 236.9 1,594,630 61.2 31.3 15,048 12,789 30.2 29.3 14,406 12,350 28.9 9 4 0.0 2.0

38 10/28/08 13:49 2 179.6 1,216,850 58.8 241.5 1,611,410 60.8 29.7 23,294 12,953 30.8 29.8 22,420 12,508 29.7 8 4 2.0 2.0

39 11/05/08 15:24 1 193.3 1,265,620 59.3 257.4 1,671,140 62.6 31.2 55,911 13,346 31.5 31.4 53,758 12,887 30.3 18 5 1.0 2.5

40 11/14/08 9:27 2 210.1 1,326,340 60.2 268.5 1,710,270 58.8 29.9 50,220 13,700 30.0 26.6 48,191 13,226 28.8 8 4 0.0 0.0

41 11/18/08 9:46 1 215.6 1,345,370 57.7 278.0 1,744,730 60.5 29.5 28,308 13,899 31.5 28.7 27,190 13,417 30.2 10 7 1.0 1.0

43 12/02/08 14:31 1 235.8 1,417,120 59.2 307.5 1,852,180 60.7 30.6 91,524 14,544 30.7 29.2 88,256 14,039 29.6 10 5 1.0 2.5

44 12/10/08 13:53 1 247.3 1,458,240 59.6 320.1 1,898,280 61.0 30.1 43,984 14,854 30.4 29.3 42,417 14,338 29.3 11 5 1.5 2.5

45 12/16/08 9:33 1 256.6 1,490,860 58.5 327.0 1,923,440 60.8 31.9 30,197 15,066 31.1 29.8 29,858 14,548 30.7 10 5 1.0 2.5

46 12/26/08 14:50 2 274.4 1,555,830 60.8 339.2 1,966,920 59.4 30.7 55,153 15,455 30.6 28.6 52,687 14,919 29.3 10 5 1.5 2.5

47 12/31/08 9:15 2 286.6 1,593,650 51.7 347.2 2,001,500 72.0 31.7 36,984 15,715 30.5 30.1 35,870 15,172 29.6 10 5 1.0 2.0

48 01/07/09 14:05 1 295.1 1,631,470 74.2 358.0 2,036,100 53.4 32.1 37,088 15,976 32.0 31.7 35,667 15,423 30.8 10 6 2.5 3.0

01/13/09 11:35 1 304.0 1,661,860 56.9 371.9 2,087,330 61.4 30.6 41,441 16,268 30.3 31.8 39,888 15,704 29.2 14 10 2.5 2.5

01/16/09 13:05 2 314.1 1,697,880 59.4 372.9 2,093,600 104.5 30.0 21,762 16,421 32.7 29.0 20,884 15,851 31.4 10 6 2.0 2.5

49 01/20/09 8:54 2 320.1 1,722,340 67.9 377.9 2,110,150 55.2 29.9 20,775 16,568 31.5 28.9 19,966 15,991 30.3 10 8 1.0 2.0

01/26/09 15:25 1 330.7 1,758,240 56.4 384.9 2,136,140 61.9 32.1 31,504 16,790 29.8 30.0 30,204 16,204 28.6 12 8 2.0 2.5

01/30/09 16:00 1 335.8 1,776,480 59.6 390.9 2,159,670 65.4 27.5 21,074 16,938 31.6 33.6 20,152 16,346 30.3 8 4 5.0 3.0

51 02/04/09 12:15 1 344.7 1,809,160 61.2 397.9 2,182,040 53.3 31.0 27,922 17,135 29.3 30.1 27,729 16,541 29.1 10 6 2.0 3.0

53 02/17/09 8:48 2 361.6 1,868,860 58.9 416.9 2,251,340 60.8 29.1 65,833 17,598 30.6 27.1 63,277 16,987 29.4 13 10 0.5 2.0

03/03/09 11:05 1 382.0 1,945,620 62.7 436.9 2,324,110 60.6 29.7 71,654 18,103 29.6 28.6 69,244 17,475 28.6 8 4 2.0 2.0

03/06/09 13:22 NA NA NA NA NA NA NA 30.7 12,635 18,192 NA 28.7 12,193 17,560 NA 8 5 2.5 2.5

56 03/10/09 11:12 1 389.3 1,959,750 32.3 446.9 2,364,550 67.4 29.8 20,407 18,336 19.7 26.7 19,594 17,698 18.9 11 8 2.0 2.5

57 03/17/09 9:35 2 399.5 1,992,250 53.1 NA 2,401,840 NA 30.7 36,613 18,593 NA 27.2 35,269 17,947 NA 11 7 2.0 2.5

03/25/09 15:30 1 409.5 2,025,260 55.0 472.9 2,456,970 35.3 31.0 44,624 18,908 20.7 32.0 43,068 18,250 19.9 10 4 2.5 2.5

03/27/09 14:40 2 413.0 2,037,470 58.1 476.9 2,468,790 49.3 29.9 12,765 18,998 28.4 30.0 12,338 18,337 27.4 10 5 2.0 2.5

03/31/09 11:50 2 419.5 2,060,490 59.0 480.9 2,485,070 67.8 28.9 20,021 19,139 31.8 29.5 19,323 18,473 30.7 8 4 2.0 2.5

04/03/09 12:40 1 424.5 2,076,940 54.8 484.9 NA NA 31.6 16,516 19,255 30.6 29.0 16,048 18,586 29.7 8 5 2.5 3.0

60 04/08/09 9:44 NA 431.6 2,103,650 62.7 490.9 2,523,020 63.3 29.0 25,372 19,434 32.3 26.8 24,603 18,759 31.3 10 6 2.5 2.5

04/15/09 12:10 1 442.3 2,141,950 59.7 502.9 2,565,390 58.8 31.0 42,696 19,734 31.3 30.9 41,131 19,049 30.2 12 9 2.5 3.0

04/17/09 14:50 2 446.3 2,155,780 57.6 505.9 2,576,260 60.4 31.0 10,886 19,811 25.9 29.6 10,561 19,123 25.1 8 4 2.5 3.0

04/27/09 15:45 1 465.6 2,223,690 58.6 518.9 2,622,890 59.8 29.4 59,584 20,230 30.7 29.0 57,560 19,529 29.7 10 6 2.5 3.0

04/30/09 14:21 1 475.0 2,258,180 61.2 522.9 2,639,250 68.2 0.0 20,426 20,374 25.4 30.2 24,883 19,704 30.9 8 4 2.5 2.5

05/06/09 14:45 2 488.4 2,304,510 57.6 533.9 2,677,790 58.4 0.0 0 20,374 0.0 30.6 42,268 20,002 28.9 8 2 2.5 2.5

05/08/09 14:42 2 496.3 2,319,690 32.0 538.9 2,682,570 15.9 NA NA NA NA NA NA NA NA NA NA NA NA

65 05/15/09 14:00 1 & 2 510.6 2,386,040 77.3 548.9 2,732,020 82.4 0.0 0 20,374 0.0 29.8 66,530 20,470 45.6 8 4 2.5 2.5

66 05/20/09 11:42 1 522.1 2,429,060 62.3 554.9 2,753,120 58.6 0.0 0 20,374 0.0 31.9 29,776 20,680 28.4 10 6 5.5 5.5

67 05/29/09 12:20 2 538.7 2,485,080 56.2 569.9 2,809,130 62.2 26.1 17,238 20,496 9.1 28.2 58,098 21,089 30.6 8 4 2.0 2.0

06/01/09 14:04 1 545.4 2,507,590 56.0 577.9 2,837,600 59.3 28.7 26,566 20,683 30.1 30.5 34,644 21,333 39.3 7 4 2.0 2.0

06/05/09 15:40 1 552.1 2,531,040 58.3 581.9 2,851,990 60.0 30.5 18,776 20,815 29.2 29.7 12,023 21,418 18.7 8 6 2.5 3.0

69 06/10/09 15:30 1 560.1 2,560,140 60.6 591.9 2,888,560 61.0 30.5 31,768 21,039 29.4 27.2 32,738 21,648 30.3 9 5 2.5 2.0

70 06/16/09 10:03 1 570.3 2,596,230 59.0 600.9 2,922,230 62.4 29.0 33,955 21,278 29.5 31.6 35,193 21,896 30.5 8 4 2.5 2.5

06/24/09 10:10 1 593.5 2,681,800 61.5 611.9 2,961,950 60.2 31.2 60,908 21,707 29.7 30.0 62,901 22,339 30.7 9 5 2.5 2.5

06/26/09 15:15 1 599.3 2,700,630 54.1 619.9 2,993,310 65.3 29.8 24,162 21,877 29.2 30.9 24,876 22,514 30.0 8 4 2.5 2.5

72 07/01/09 15:10 2 612.1 2,745,910 59.0 633.9 3,041,900 57.8 28.9 46,497 22,204 28.9 29.3 47,904 22,851 29.8 8 4 2.5 2.5

73 07/10/09 10:30 1 644.1 2,861,840 60.4 660.9 3,142,420 62.0 29.0 108,190 22,966 30.6 28.9 107,545 23,609 30.4 8 5 2.0 2.5

74 07/14/09 9:33 1 662.1 2,923,750 57.3 672.9 3,185,300 59.6 26.3 51,610 23,330 28.7 30.1 50,326 23,963 28.0 11 8 2.0 2.5

07/20/09 12:00 2 NA 2,987,720 NA NA 3,276,230 NA 29.8 79,227 23,888 NA 30.2 74,964 24,491 NA 6 4 2.0 2.0

07/24/09 15:00 1 686.1 3,014,270 18.4 713.9 3,337,620 25.0 31.4 44,503 24,201 11.4 28.1 42,381 24,790 10.9 6 4 0.0 0.0

76 07/29/09 10:45 2 696.1 3,048,460 57.0 733.9 3,409,340 59.8 31.8 56,252 24,597 31.3 29.2 53,501 25,166 29.7 7 4 0.0 1.0

77 08/07/09 14:45 2 722.1 3,141,180 59.4 774.9 3,561,350 61.8 30.0 126,416 25,487 31.4 30.4 120,484 26,015 30.0 7 4 2.0 2.0

61

63

64

68

71

75

37

48

50

55

58

59

29

30

33

35

Week No.

Instrument Panel

Cum. 

Hours 

Well

Cum. 

Volume

Average 

Flowrate

Cum. 

Hours 

Well

Cum. 

Volume

Average 

Flowrate

Vessel A Vessel B

Date Time

Well 

Running 

Well No. 1 Well No. 2

System Pressure 

(psi)

Pressure 

Differential for 

Vessel (psi)
A-3

Table A-1. EPA Arsenic Demonstration Project at Covered Wells in Tohono O’odham Nation, AZ - Daily System Operation Log Sheet

Inst. 

Flowrate

Incremental 

Volume

Bed 

Volume

Average 

Flowrate

Inst. 

Flowrate

Incremental

Volume

Bed 

Volume

Average 

Flowrate

Well # 1 

or 2 hr gal gpm hr gal gpm gpm gal no. gpm gpm gal no. gpm Inlet Outlet A B

78 08/13/09 14:45 1 739.1 3,201,820 59.5 798.9 3,647,560 59.9 32.5 74,813 26,014 30.4 30.0 71,185 26,516 28.9 8 5 2.0 2.5

08/17/09 14:50 2 749.1 3,237,550 59.6 819.9 3,726,500 62.7 29.5 57,378 26,418 30.8 31.1 55,823 26,909 30.0 6 4 0.0 2.0

08/18/09 10:25 1 750.1 3,241,750 70.0 822.9 3,738,650 67.5 29.2 8,593 26,479 35.8 30.8 8,286 26,968 34.5 5 4 0.0 0.0

08/21/09 10:02 1 758.1 3,271,410 61.8 834.9 3,780,990 58.8 31.7 36,538 26,736 30.4 32.2 17,450 27,090 14.5 8 4 2.0 2.5

80 08/26/09 9:45 2 770.1 3,315,340 61.0 853.9 3,833,140 45.7 30.4 58,651 27,149 31.5 29.8 74,761 27,617 40.2 7 5 0.0 2.5

81 09/01/09 15:13 1 790.1 3,384,910 58.0 874.9 3,833,180 0.0 30.9 74,656 27,675 30.3 31.9 71,975 28,124 29.3 8 4 2.0 2.5

09/08/09 11:45 2 808.1 3,450,680 60.9 902.9 3,833,640 0.3 30.8 84,960 28,273 30.8 27.4 81,126 28,695 29.4 7 4 0.0 2.0

09/10/09 10:39 2 814.1 3,472,230 59.9 909.9 3,833,140 -1.2 31.1 24,093 28,443 30.9 30.0 23,134 28,858 29.7 10 5 0.0 2.0

09/15/09 9:30 1 829.1 3,524,770 58.4 923.9 3,833,140 0.0 31.5 55,099 28,831 31.7 29.6 52,164 29,225 30.0 9 4 2.5 3.0

09/18/09 9:55 2 836.1 3,549,980 60.0 931.9 3,833,640 1.0 30.3 28,097 29,029 31.2 29.3 26,550 29,412 29.5 9 4 0.0 2.0

09/21/09 9:52 1 845.1 3,583,380 61.9 942.9 3,833,680 0.1 31.3 37,616 29,294 31.3 31.4 35,529 29,663 29.6 8 7 2.5 2.5

09/24/09 13:10 NA NA NA NA NA NA NA 32.9 40,279 29,577 NA 29.8 37,702 29,928 NA 10 4 2.0 2.5

85 09/30/09 10:00 2 875.1 3,694,100 61.5 968.9 3,841,740 5.2 26.9 63,970 30,028 19.0 32.3 62,619 30,369 18.6 8 4 4.0 4.0

10/05/09 15:00 2 891.1 3,749,490 57.7 985.9 3,904,700 61.7 28.4 49,339 30,375 24.9 34.8 69,111 30,856 34.9 8 4 5.0 5.0

10/07/09 11:00 1 898.1 3,775,150 61.1 994.9 3,938,680 62.9 24.2 23,728 30,542 24.7 34.1 36,343 31,112 37.9 8 4 5.0 5.0

10/14/09 11:00 1 917.1 3,843,400 59.9 1015.9 4,016,050 61.4 18.1 47,058 30,874 19.6 44.1 97,247 31,797 40.5 10 4 6.0 7.0

10/16/09 11:10 2 921.1 3,856,490 54.5 1023.9 4,045,750 61.9 9.5 8,889 30,936 12.3 44.9 33,031 32,029 45.9 12 4 9.0 9.0

10/19/09 9:30 2 931.1 3,892,180 59.5 1032.9 4,074,470 53.2 9.4 10,229 31,008 9.0 46.9 51,011 32,388 44.7 18 4 9.0 9.0

10/20/09 10:32 2 936.1 3,908,360 53.9 1036.9 4,089,010 60.6 11.0 32,599 31,238 60.4 40.2 29,982 32,600 55.5 17 4 8.5 8.0

89 10/26/09 13:48 1 950.1 3,961,280 63.0 1058.9 4,172,410 63.2 33.8 67,234 31,712 31.1 32.9 65,845 33,063 30.5 7 4 2.0 2.5

90 11/04/09 9:45 2 974.1 4,048,590 60.6 1086.9 4,274,680 60.9 34.3 97,271 32,397 31.2 29.5 92,446 33,714 29.6 6 4 2.0 2.5

11/09/09 10:35 2 985.1 4,087,620 59.1 1105.9 4,345,590 62.2 29.0 55,672 32,789 30.9 28.5 51,829 34,079 28.8 7 3 2.5 2.5

11/12/09 15:28 1 995.1 4,123,480 59.8 1114.9 4,377,360 58.8 32.2 34,733 33,033 30.5 30.8 33,328 34,314 29.2 8 4 2.0 2.5

11/16/09 10:30 1 1005.1 4,162,690 65.4 1127.9 4,426,370 62.8 31.2 43,532 33,340 31.5 31.0 41,625 34,607 30.2 8 4 2.0 2.0

11/17/09 9:12 1 1007.1 4,166,950 35.5 NA NA NA 31.5 8,366 33,399 NA 32.7 8,014 34,664 NA 10 5 2.5 2.5

11/19/09 15:05 2 1014.1 4,173,210 14.9 1135.9 4,499,880 153.1 32.2 24,206 33,569 26.9 28.9 22,960 34,825 25.5 8 4 2.0 2.5

11/23/09 13:15 2 1018.1 4,208,650 147.7 1150.9 4,508,610 9.7 0.0 3,579 33,594 3.1 30.9 33,078 35,058 29.0 6 4 2.0 2.0

11/25/09 12:20 1 1021.1 4,226,370 98.4 1158.9 4,513,070 9.3 31.2 8,335 33,653 12.6 28.5 15,214 35,165 23.1 6 4 2.0 2.5

11/30/09 9:50 2 1035.1 4,267,520 49.0 1167.9 4,570,030 105.5 30.4 43,514 33,959 31.5 29.1 43,016 35,468 31.2 6 4 2.5 2.5

12/04/09 11:25 1 1044.1 4,302,160 64.1 1179.9 4,616,770 64.9 31.4 39,267 34,236 31.2 29.3 39,064 35,743 31.0 7 4 2.0 2.5

12/08/09 9:26 2 1055.1 4,341,080 59.0 1187.9 4,644,540 57.9 31.2 32,116 34,462 28.2 29.7 32,214 35,970 28.3 7 4 2.5 2.5

12/11/09 10:10 1 1064.1 4,374,550 62.0 1193.9 4,667,040 62.5 30.9 27,558 34,656 30.6 29.9 27,925 36,167 31.0 6 4 2.0 2.5

12/14/09 14:15 2 1077.1 4,420,850 59.4 1196.9 4,677,880 60.2 28.9 26,544 34,843 27.7 20.1 26,918 36,356 28.0 6 4 2.0 2.5

12/15/09 8:52 1 1080.1 4,432,280 63.5 1197.9 4,679,790 31.8 27.5 7,077 34,893 29.5 31.5 7,188 36,407 30.0 10 5 2.5 2.5

12/21/09 10:45 1 1099.1 4,501,290 60.5 1208.9 4,720,090 61.1 31.7 52,494 35,263 29.2 30.4 52,596 36,777 29.2 9 4 2.5 2.5

12/24/09 12:00 2 1109.1 4,540,340 65.1 1213.9 4,740,310 67.4 29.6 28,265 35,462 31.4 29.1 28,361 36,977 31.5 6 4 2.0 2.5

12/28/09 10:00 1 1126.1 4,603,770 62.2 1217.9 4,754,820 60.5 32.1 36,399 35,718 28.9 29.4 36,531 37,234 29.0 7 4 2.5 2.5

12/31/09 12:04 1 1135.1 4,639,310 65.8 1223.9 4,776,990 61.6 31.4 28,507 35,919 31.7 29.7 28,821 37,437 32.0 7 4 2.5 3.0

01/06/10 12:01 1 1159.1 4,722,520 57.8 1231.9 4,804,120 56.5 33.2 55,173 36,307 28.7 30.8 54,735 37,823 28.5 8 4 2.5 3.0

01/08/10 9:05 2 1162.1 4,734,300 65.4 1237.9 4,826,900 63.3 31.9 17,194 36,428 31.8 29.2 16,825 37,941 31.2 10 4 2.5 2.5

01/11/10 11:10 1 1172.1 4,769,500 58.7 1242.9 4,845,970 63.6 33.1 27,727 36,624 30.8 30.0 27,067 38,132 30.1 8 4 2.0 2.5

01/15/10 15:10 2 1185.1 4,817,990 62.2 1248.9 4,866,570 57.2 31.3 34,442 36,866 30.2 28.9 33,692 38,369 29.6 9 4 2.5 2.5

01/18/10 11:10 1 1192.1 4,843,800 61.5 1252.9 4,883,160 69.1 29.8 20,730 37,012 31.4 28.9 20,695 38,515 31.4 6 4 2.5 3.5

01/19/10 9:10 1 1193.1 4,845,400 26.7 1256.9 4,897,180 58.4 33.0 7,820 37,067 26.1 28.5 9,794 38,584 32.6 6 5 2.5 3.0

01/22/10 11:00 1 1200.1 4,873,380 66.6 1263.9 4,921,620 58.2 32.0 24,765 37,242 29.5 29.5 22,608 38,743 26.9 6 4 2.5 3.0

01/25/10 10:30 1 1206.1 4,893,040 54.6 1270.9 4,950,360 68.4 29.4 23,236 37,405 29.8 32.6 22,835 38,904 29.3 7 4 2.5 3.0

01/29/10 13:30 1 1213.1 4,918,680 61.0 1279.9 4,981,220 57.1 31.5 27,781 37,601 28.9 30.3 27,143 39,095 28.3 6 2 2.0 2.5

02/01/10 14:00 1 1223.1 4,957,880 65.3 1280.9 4,985,110 64.8 31.8 21,967 37,756 33.3 28.9 21,736 39,248 32.9 6 3 2.0 2.5

02/03/10 10:30 1 1227.1 4,969,930 50.2 1286.9 5,006,090 58.3 31.1 16,937 37,875 28.2 31.0 15,993 39,361 26.7 8 4 3.0 2.5

02/05/10 12:40 1 1232.1 4,988,450 61.7 1291.9 5,026,220 67.1 32.1 19,658 38,013 32.8 29.9 18,758 39,493 31.3 6 4 2.5 2.5

104 02/09/10 14:30 2 1246.1 5,039,940 61.3 1294.9 5,038,010 65.5 30.1 32,676 38,244 32.0 31.2 31,445 39,714 30.8 9 6 2.0 2.5

02/16/10 9:45 2 1261.1 5,095,530 61.8 1308.9 5,090,230 62.2 33.0 52,832 38,616 30.4 29.0 52,108 40,081 29.9 6 4 2.0 2.5

02/19/10 9:45 1 1267.1 5,118,600 64.1 1315.9 5,114,590 58.0 30.3 23,680 38,782 30.4 31.1 23,165 40,244 29.7 7 4 2.5 2.5

106 02/23/10 14:20 1 1275.1 5,144,480 53.9 1325.9 5,152,680 63.5 32.0 32,476 39,011 30.1 30.6 32,378 40,472 30.0 7 4 2.5 3.0

03/02/10 10:25 2 1290.1 5,198,800 60.4 1342.9 5,213,340 59.5 31.0 56,710 39,410 29.5 27.0 55,504 40,863 28.9 6 4 2.5 2.5

03/05/10 11:00 2 1290.1 5,199,160 NA 1356.9 5,265,170 61.7 31.2 25,184 39,588 30.0 30.5 24,977 41,039 29.7 6 4 2.0 2.0

03/08/10 13:00 2 1300.1 5,231,970 54.7 1361.9 5,284,870 65.7 30.6 26,336 39,773 29.3 31.7 26,121 41,223 29.0 7 4 1.5 2.0

03/12/10 10:00 1 1306.1 5,255,270 64.7 1370.9 5,316,910 59.3 31.4 27,970 39,970 31.1 31.3 27,444 41,416 30.5 7 4 2.5 2.5

109 03/19/10 15:20 1 1330.1 5,340,610 59.3 1382.9 5,361,790 62.3 30.9 65,246 40,430 30.2 30.3 63,903 41,866 29.6 6 5 2.5 2.5

NOTE : 

(a) Bed volume = 19 cu.ft. (142 gal) for Vessel A, 19 cu.ft. (142 gal) for Vessel B, or 38 cu.ft. (284 gal) total for two vessels.

NR = Not Running; NA = Not Availble.

Flowrate readings on each vessel are instantaneous. 

102

103

105

107

108

96

97

98

99

100

101

88

91

92

93

94

95

79

82

83

84

86

87

Cum. 

Hours 

Well

Cum. 

Volume

Average 

Flowrate

Vessel A Vessel B

System Pressure 

(psi)

Pressure 

Differential for 

Vessel (psi)

Week No. Date Time

Well 

Running 

Well No. 1 Well No. 2 Instrument Panel

Cum. 

Hours 

Well

Cum. 

Volume

Average 

Flowrate
APPENDIX B 

ANALYTICAL DATA
B-1

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ 

Parameter Unit

Bed Volume 103 - - 0.0 0.0 - - 2.2 2.1 - - 2.7 2.7 - - 3.5 3.4 - - 4.2 4.1

145 146 158 172 149 147 143 139 155 151 151 153 145 147 165 165 151 151 147 147

- - - - - - - - - - - - - - - - - - - -

Fluoride mg/L - - - - 1.2 1.0 1.2 1.2 - - - - - - - - - - - -

Sulfate mg/L - - - - 23.3 24.0 27.1 26.8 - - - - - - - - - - - -

Nitrate (as N) mg/L - - - - 1.3 1.2 1.2 1.2 - - - - - - - - - - - -

<10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

- - - - - - - - - - - - - - - - - - - -

NA (b) NA (b) NA (b) NA (b) 27.7 27.5 25.0 20.7 24.7 25.1 25.0 24.6 24.7 24.7 26.9 26.7 26.6 26.0 26.2 26.1

- - - - - - - - - - - - - - - - - - - -

1.4 1.9 1.9 2.0 1.9 0.6 0.4 0.5 1.0 0.9 0.8 0.8 0.6 1.0 1.4 2.0 0.5 0.6 0.9 0.8

- - - - - - - - - - - - - - - - - - - -

pH S.U. 8.1 6.8 6.4 6.2 NA NA NA NA NA NA NA NA NA NA NA NA 8.1 7.2 7.1 7.0

Temperature °C NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 31.1 32.6 32.9 33.0

DO mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 3.7 3.1 3.0 3.4

ORP mV NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 243 287 321 351

Free Chlorine mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Total Chlorine mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Total Hardness mg/L(a) - - - - 39.0 38.3 35.2 33.8 - - - - - - - - - - - -

Ca Hardness mg/L(a) - - - - 28.0 27.3 25.2 23.9 - - - - - - - - - - - -

Mg Hardness mg/L(a) - - - - 11.1 10.9 10.0 9.8 - - - - - - - - - - - -

35.6 35.1 1.0 0.9 36.6 35.3 0.1 0.1 33.4 34.8 <0.1 0.2 36.4 36.7 0.2 0.2 37.3 36.0 1.0 0.8

- - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - 22.0 34.2 <0.1 0.2 - - - - - - - - - - - -

As (particulate) μg/L - - - - 14.6 1.1 <0.1 <0.1 - - - - - - - - - - - -

As (III) μg/L - - - - 0.1 0.1 <0.1 <0.1 - - - - - - - - - - - -

As (V) μg/L - - - - 21.9 34.0 <0.1 <0.1 - - - - - - - - - - - -

49 <25 <25 <25 <25 <25 <25 <25 60 <25 <25 <25 <25 32 37 <25 <25 <25 <25 <25

- - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - <25 <25 <25 <25 - - - - - - - -

1.3 0.7 0.5 0.3 0.3 0.2 0.2 <0.1 2.8 0.3 <0.1 <0.1 0.5 1.2 0.7 0.2 0.2 1.1 <0.1 <0.1

- - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - 0.3 <0.1 <0.1 <0.1 - - - - - - - - - - - -

7.0 7.0 <0.1 <0.1 7.9 7.7 <0.1 <0.1 8.3 8.4 <0.1 <0.1 7.9 7.9 <0.1 <0.1 7.8 7.5 <0.1 <0.1

- - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - -

(a) As CaCO 3 (b) Silica not measured on 02/13/08.

Sampling Date 02/13/08 04/01/08 04/15/08 04/29/08 05/12/08

TB

Alkalinity mg/L(a)

Total P (as P ) μg/L

AP TA TB IN AP TA TB IN AP TA TB IN Sampling Location IN AP TA TB IN

V (total) μg/L

Fe (total) μg/L

Mn (total) μg/L

U (total) μg/L

Silica (as SiO2) mg/L

Turbidity NTU

As (total) μg/L

AP TA
B-2

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ (Continued)

Parameter Unit

Bed Volume 103 - - 5.0 4.8 - - 7.4 7.2 - - 8.5 8.3 - - 10.3 10.0 - - 12.0 11.6 11.8

156 149 145 149 147 145 145 143 147 149 149 151 148 146 151 146 146 144 144 146 146

- - - - - - - - - - - - - - - - - - - - -

Fluoride mg/L 1.1 1.4 1.2 1.2 - - - - - - - - - - - - 1.1 1.1 1.0 1.1 1.1

Sulfate mg/L 24.8 23.7 25.0 28.1 - - - - - - - - - - - - 23.7 24.3 24.2 23.1 23.8

Nitrate (as N) mg/L 1.2 1.8 1.2 1.2 - - - - - - - - - - - - 1.2 1.2 1.2 1.2 1.2

<10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

- - - - - - - - - - - - - - - - - - - - -

26.9 27.0 26.4 26.0 27.8 27.2 28.4 28.2 26.5 26.7 27.1 27.2 26.7 26.7 27.0 26.9 27.0 26.8 26.8 26.5 26.6

- - - - - - - - - - - - - - - - - - - - -

0.6 0.1 0.1 0.1 0.2 0.1 0.2 0.1 0.2 0.2 0.1 <0.1 0.1 0.2 <0.1 <0.1 0.2 0.3 0.1 <0.1 0.3

- - - - - - - - - - - - - - - - - - - - -

pH S.U. NA NA NA NA 8.1 6.6 6.6 6.6 8.1 7.1 7.1 7.1 NA NA NA NA 8.2 7.1 7.1 7.1 7.0

Temperature °C NA NA NA NA 25.0 25.0 25.0 25.0 32.9 32.6 32.9 33.1 NA NA NA NA 25.0 25.0 25.0 25.0 25.0

DO mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

ORP mV 225 303 289 320 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Free Chlorine mg/L - NA NA NA - NA NA NA - 6.3 (c) 7.6 (c) 7.8 (c) - NA NA NA 0.0 1.8 2.0 2.1 2.1

Total Chlorine mg/L - NA NA NA - 0.0 0.0 0.0 - 6.7 (c) 6.7 (c) 7.2 (c) - NA NA NA 0.0 1.7 1.9 2.0 1.8

Total Hardness mg/L(a) 39.3 39.3 34.5 31.3 - - - - - - - - - - - 34.6 37.3 36.9 36.4 37.5

Ca Hardness mg/L(a) 28.3 28.5 25.3 21.8 - - - - - - - - - - - - 25.1 27.1 26.9 26.4 27.2

Mg Hardness mg/L(a) 11.0 10.9 9.2 9.5 - - - - - - - - - - - - 9.5 10.2 10.0 10.0 10.3

36.9 37.6 0.3 0.3 33.6 33.9 0.2 0.2 35.6 36.0 1.1 0.7 35.0 36.8 0.5 0.3 35.7 36.5 0.9 0.6 0.6

- - - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L 35.3 36.0 0.3 0.3 - - - - - - - - - - - - 33.7 34.5 0.4 0.3 0.2

As (particulate) μg/L 1.6 1.6 <0.1 <0.1 - - - - - - - - - - - - 2.0 2.1 0.5 0.3 0.3

As (III) μg/L 0.5 0.4 0.4 0.4 - - - - - - - - - - - - 0.4 0.4 0.4 0.4 0.4

As (V) μg/L 34.8 35.6 <0.1 <0.1 - - - - - - - - - - - - 33.3 34.0 <0.1 <0.1 <0.1

<25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25

- - - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L <25 <25 78 <25 - - - - - - - - - - - - <25 <25 <25 <25 <25

0.4 0.3 <0.1 <0.1 1.3 0.6 <0.1 <0.1 0.3 0.4 <0.1 <0.1 0.2 0.2 <0.1 <0.1 0.2 0.4 <0.1 <0.1 <0.1

- - - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L 0.3 0.4 2.7 <0.1 - - - - - - - - - - - - 0.2 0.2 <0.1 <0.1 <0.1

NA NA NA NA 7.8 7.8 <0.1 <0.1 NA NA NA NA 7.5 7.5 <0.1 <0.1 - - - - -

- - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - 30.2 30.2 0.1 <0.1 29.4 30.4 0.7 0.4 0.4

- - - - - - - - - - - - - - - - - - - - -

(a) As CaCO 3 (b) All metals re-analyzed on 08/28/08 from TB

(c) Uncharacteristically high levels

Sampling Date

Sampling Location

Alkalinity mg/L(a)

Total P (as P ) μg/L

Silica (as SiO2) mg/L

Mn (total) μg/L

U (total) μg/L

V (total) μg/L

Turbidity NTU

As (total) μg/L

Fe (total) μg/L

05/28/08 07/08/08 07/30/08 09/02/08 10/07/08

IN AP TA TB (b) IN AP TA TB IN AP TA TB IN AP TA TB IN AP TA TB TT
B-3

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ (Continued)

Parameter Unit

Bed Volume 103 - - 13.9 13.4 - - 15.1 14.5 - - 16.6 16.0 - - 17.6 17.0 - - 18.6 17.9 18.3

145 145 156 156 147 147 145 145 144 140 140 142 149 147 151 158 148 146 195 193 189

145 148 156 159 - - - - - - - - - - - - - - - - -

Fluoride mg/L - - - - - - - - - - - - - - - - 1.2 1.1 1.0 1.0 1.0

Sulfate mg/L - - - - - - - - - - - - - - - - 23.7 23.5 21.4 20.5 21.3

Nitrate (as N) mg/L - - - - - - - - - - - - - - - - 1.3 1.1 1.2 1.2 1.2

<10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

<10 <10 <10 <10 - - - - - - - - - - - - - - - - -

25.1 25.7 26.9 27.3 25.0 25.2 25.1 25.4 24.4 25.5 23.0 23.3 26.0 25.9 28.6 27.1 25.2 25.2 31.4 32.0 34.7

25.6 25.9 25.9 27.7 - - - - - - - - - - - - - - - - -

0.1 0.2 <0.1 0.2 0.2 0.2 0.1 0.1 0.2 0.3 <0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.1 <0.1 <0.1 <0.1

0.1 0.1 <0.1 <0.1 - - - - - - - - - - - - - - - - -

pH S.U. 8.0 6.9 7.2 7.0 7.9 6.9 6.9 7.0 NA(d) NA(d) NA(d) NA(d) 8.1 7.0 7.1 7.1 8.4 6.9 7.5 7.4 NM

Temperature °C 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 NA (d) NA(d) NA(d) NA(d) 25.0 25.0 25.0 25.0 26.6 28.9 30.3 31.4 NM

DO mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

ORP mV NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Free Chlorine mg/L 0.0 2.2 2.1 1.9 0.0 1.7 1.8 1.9 NA(d) NA(d) NA(d) NA(d) 0.0 2.1 2.0 2.2 0.1 1.6 1.6 1.5 NM

Total Chlorine mg/L 0.0 2.1 2.0 1.8 0.0 1.6 1.7 1.8 NA(d) NA(d) NA(d) NA(d) 0.0 2.1 2.1 2.2 0.1 1.6 1.6 1.3 NM

Total Hardness mg/L(a) - - - - - - - - - - - - - - - - 47.3 48.8 93.6 93.0 86.7

Ca Hardness mg/L(a) - - - - - - - - - - - - - - - - 36.2 37.3 67.8 66.1 60.0

Mg Hardness mg/L(a) - - - - - - - - - - - - - - - - 11.1 11.4 25.8 26.8 26.7

37.9 38.2 0.5 0.5 36.3 35.1 0.7 0.5 37.7 35.6 0.4 0.4 32.3 33.0 0.7 0.9 37.1 39.1 0.2 0.2 <0.1

38.6 37.6 0.5 0.4 - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - - - - - - - 36.8 36.2 0.3 0.3 0.2

As (particulate) μg/L - - - - - - - - - - - - - - - - 0.3 2.9 <0.1 <0.1 <0.1

As (III) μg/L - - - - - - - - - - - - - - - - 0.4 0.3 0.4 0.3 0.3

As (V) μg/L - - - - - - - - - - - - - - - - 36.4 35.9 <0.1 <0.1 <0.1

<25 <25 <25 <25 30 28 77 <25 <25 <25 <25 <25 <25 <25 <25 <25 31 <25 <25 <25 <25

<25 <25 <25 <25 - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - - - - - - - <25 <25 <25 <25 <25

0.3 <0.1 <0.1 0.1 2.6 1.3 2.1 0.2 1.0 <0.1 <0.1 <0.1 0.2 0.5 <0.1 0.1 1.8 0.8 <0.1 <0.1 <0.1

0.3 0.2 <0.1 <0.1 - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - - - - - - - 3.2 0.4 <0.1 <0.1 <0.1

- - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

35.5 36.6 0.5 0.5 33.2 32.5 0.7 0.5 31.9 30.5 0.5 0.5 27.5 28.6 0.8 0.9 33.2 31.8 0.5 0.5 0.3

34.2 36.6 0.5 0.5 - - - - - - - - - - - - - - - - -

(a) As CaCO 3 (d) pH, temperature, free chlorine & total chlorine not measured

Sampling Date

Sampling Location

Alkalinity mg/L(a)

Total P (as P ) μg/L

Silica (as SiO2) mg/L

Mn (total) μg/L

U (total) μg/L

V (total) μg/L

Turbidity NTU

As (total) μg/L

Fe (total) μg/L

11/18/08 12/16/08 01/20/09 02/17/09 03/17/09

IN AP TA TB IN AP TA TB IN AP TA TB IN AP TA TB IN AP TA TB TT

 

 
B-4

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ (Continued)

Parameter Unit

Bed Volume 103 - - 19.7 19.0 - - 20.4 20.7 - - 21.3 21.9 - - 23.3 24.0 23.6 - - 26.5 27.0

148 150 161 161 155 150 155 155 154 156 156 158 151 151 201 196 192 154 154 152 154

- - - - - - - - - - - - - - - - - - - - -

Fluoride mg/L - - - - - - - - - - - - 1.2 1.2 1.0 1.1 1.0 - - - -

Sulfate mg/L - - - - - - - - - - - - 24.8 24.6 22.3 23.5 22.7 - - - -

Nitrate (as N) mg/L - - - - - - - - - - - - 1.2 1.2 1.2 1.2 1.2 - - - -

<10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

- - - - - - - - - - - - - - - - - - - - -

27.4 27.0 32.6 31.7 27.3 26.7 28.9 28.8 26.5 27.1 26.1 25.8 26.7 27.2 32.1 33.8 34.3 26.3 25.9 25.9 25.8

- - - - - - - - - - - - - - - - - - - - -

0.5 0.3 0.3 0.6 0.3 1.4 0.1 0.2 0.7 2.2 2.3 0.8 0.2 0.1 0.1 0.4 <0.1 0.7 0.2 0.4 0.4

- - - - - - - - - - - - - - - - - - - - -

pH S.U. 8.3 6.9 7.2 7.2 8.2 6.9 6.8 6.8 7.8 6.8 6.8 6.8 7.9 7.9 7.1 7.1 7.1 8.1 6.9 6.9 7.0

Temperature °C 25.0 25.0 25.0 25.0 31.4 33.3 33.5 33.8 32.0 32.1 33.3 33.2 33.7 33.7 34.0 34.4 34.7 34.1 32.4 30.9 32.1

DO mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

ORP mV NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Free Chlorine mg/L 0.0 2.1 2.0 2.2 0.0 1.5 1.6 1.5 0.0 0.8 1.0 0.8 NA 1.7 1.7 1.8 1.9 NA NA(e) NA(e) NA(e)

Total Chlorine mg/L 0.0 2.1 2.1 2.2 0.0 1.5 1.6 1.5 0.0 1.0 1.0 1.0 NA 1.8 1.8 1.9 1.9 NA NA(e) NA(e) NA(e)

Total Hardness mg/L(a) - - - - - - - - - - - - 39.1 40.4 94.5 87.0 79.8 - - - -

Ca Hardness mg/L(a) - - - - - - - - - - - - 29.3 30.2 67.1 61.1 55.1 - - - -

Mg Hardness mg/L(a) - - - - - - - - - - - - 9.8 10.2 27.4 25.8 24.6 - - - -

31.4 31.7 0.6 0.4 35.6 39.4 0.5 0.5 33.8 26.6 <0.1 <0.1 35.7 37.2 0.6 0.5 0.4 32.2 32.6 31.8 1.3

- - - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - - - 34.0 35.7 0.5 0.4 0.3 - - - -

As (particulate) μg/L - - - - - - - - - - - - 1.8 1.5 <0.1 <0.1 <0.1 - - - -

As (III) μg/L - - - - - - - - - - - - 0.4 0.4 0.5 0.5 0.5 - - - -

As (V) μg/L - - - - - - - - - - - - 33.6 35.3 <0.1 <0.1 <0.1 - - - -

<25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 <25 28 <25 <25 <25 <25 <25 <25 <25

- - - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - - - <25 <25 <25 <25 <25 - - - -

0.3 0.3 <0.1 <0.1 0.3 0.8 0.1 0.2 0.2 0.2 <0.1 0.2 0.2 3.0 <0.1 <0.1 <0.1 2.6 1.9 1.7 1.3

- - - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - - - 0.2 0.2 <0.1 <0.1 0.1 - - - -

- - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

27.9 27.6 <0.1 <0.1 33.6 34.8 0.5 0.5 35.1 35.2 0.6 <0.1 34.4 35.2 0.1 <0.1 <0.1 33.3 32.9 31.8 0.2

- - - - - - - - - - - - - - - - - - - - -

(a) As CaCO 3 (e) Operator did not have chlorine kit at time of sampling

Sampling Date

Sampling Location

Alkalinity mg/L(a)

Total P (as P ) μg/L

Silica (as SiO2) mg/L

Mn (total) μg/L

U (total) μg/L

V (total) μg/L

Turbidity NTU

As (total) μg/L

Fe (total) μg/L

04/15/09 05/20/09 06/16/09 07/14/09 08/18/09

IN AP TA TB IN AP TA TB IN AP TA TB IN AP TA TB TT IN AP TA TB
B-5

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ (Continued)

Parameter Unit

Bed Volume 103 - - 28.8 29.2 - - 31.2 32.6 - - 33.4 34.7 34.0 - - 34.9 36.4 - - 37.1 38.5

156 156 154 152 148 142 134 190 156 147 159 174 168 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

Fluoride mg/L - - - - - - - - 1.1 1.1 1.1 1.0 1.1 - - - - - - - -

Sulfate mg/L - - - - - - - - 22.2 21.6 21.9 21.7 21.9 - - - - - - - -

Nitrate (as N) mg/L - - - - - - - - 1.2 1.2 1.2 1.2 1.2 - - - - - - - -

<10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

26.1 26.2 26.2 26.2 24.6 24.5 18.7 29.3 27.7 27.1 29.5 30.9 30.3 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

0.6 2.1 2.1 1.1 1.3 0.8 0.7 0.2 0.1 0.5 0.3 0.2 <0.1 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

pH S.U. 7.9 7.0 7.0 6.9 8.0 6.6 7.2 7.6 7.9 6.6 6.8 6.8 6.6 8.0 6.6 6.6 6.6 8.0 6.5 6.5 6.5

Temperature °C 25.0 25.0 25.0 25.0 32.5 32.5 34.0 34.4 26.5 30.5 29.0 30.7 30.6 29.4 27.4 26.8 27.2 25.0 25.0 25.0 25.0

DO mg/L NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

ORP mV NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Free Chlorine mg/L 0.0 1.0 0.9 1.0 NA 0.1 0.0 0.0 NA 1.1 1.1 1.1 1.1 NA 1.7 1.4 1.4 NA 1.8 1.8 1.7

Total Chlorine mg/L 0.0 1.1 1.0 1.0 NA 0.0 NA NA NA 1.1 1.1 1.1 1.1 NA 1.6 1.3 1.4 NA 1.8 1.8 1.8

Total Hardness mg/L(a) 33.1 34.0 33.4 30.9 - - - - 29.7 32.9 36.9 41.5 40.2 - - - - - - - -

Ca Hardness mg/L(a) 23.3 24.1 23.2 21.2 - - - - 21.3 23.5 25.9 28.8 27.8 - - - - - - - -

Mg Hardness mg/L(a) 9.8 9.9 10.2 9.7 - - - - 8.4 9.4 11.0 12.7 12.4 - - - - - - - -

29.0 31.0 0.1 0.2 34.2 35.2 0.1 0.8 35.8 35.5 1.2 1.2 1.1 33.2 33.9 0.4 0.3 33.8 31.7 0.5 0.4

- - - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - 35.4 36.0 1.1 1.0 1.1 - - - - - - - -

As (particulate) μg/L - - - - - - - - 0.4 <0.1 0.1 0.2 <0.1 - - - - - - - -

As (III) μg/L - - - - - - - - 1.0 1.1 1.1 1.0 1.0 - - - - - - - -

As (V) μg/L - - - - - - - - 34.4 34.9 <0.1 <0.1 <0.1 - - - - - - - -

<25 <25 <25 <25 <25 27 <25 <25 <25 <25 <25 <25 <25 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - <25 <25 <25 <25 <25 - - - - - - - -

0.1 0.4 <0.1 <0.1 0.3 2.0 <0.1 0.1 0.3 <0.1 <0.1 <0.1 <0.1 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - <0.1 0.1 <0.1 <0.1 <0.1 - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - -

23.5 25.2 <0.1 <0.1 28.5 28.8 1.3 3.6 38.1 39.7 4.2 3.0 3.7 34.6 34.6 3.1 2.0 35.0 35.6 4.7 3.0

- - - - - - - - - - - - - - - - - - - - -

(a) As CaCO 3

Sampling Date

Sampling Location

Alkalinity mg/L(a)

Total P (as P ) μg/L

Silica (as SiO2) mg/L

Mn (total) μg/L

U (total) μg/L

V (total) μg/L

Turbidity NTU

As (total) μg/L

Fe (total) μg/L

09/15/09 10/20/09 11/17/09 12/15/09 01/19/10

IN AP TA TB IN AP TA TB IN AP TA TB TT IN AP TA TB IN AP TA TB

 
B-6

Table B-1. Analytical Results from Treatment Plant Sampling at Covered Wells in Tohono O’odham Nation, AZ (Continued)

Parameter Unit

Bed Volume 103 - - 39.0 40.5 - - 40.0 41.4

- - - - - - - -

- - - - - - - -

Fluoride mg/L - - - - - - - -

Sulfate mg/L - - - - - - - -

Nitrate (as N) mg/L - - - - - - - -

- - - - - - - -

- - - - - - - -

- - - - - - - -

- - - - - - - -

- - - - - - - -

- - - - - - - -

pH S.U. 7.9 6.6 6.9 6.9 NA NA NA NA

Temperature °C 26.2 33.5 32.9 32.5 NA NA NA NA

DO mg/L NA NA NA NA NA NA NA NA

ORP mV NA NA NA NA NA NA NA NA

Free Chlorine mg/L NA 1.5 1.5 1.5 NA 1.1 0.6 1.2

Total Chlorine mg/L NA 1.5 1.6 1.6 NA 1.3 0.7 1.3

Total Hardness mg/L(a) - - - - - - - -

Ca Hardness mg/L(a) - - - - - - - -

Mg Hardness mg/L(a) - - - - - - - -

33.1 29.7 0.6 0.3 34.4 34.6 0.6 0.4

- - - - - - - -

As (soluble) μg/L - - - - - - - -

As (particulate) μg/L - - - - - - - -

As (III) μg/L - - - - - - - -

As (V) μg/L - - - - - - - -

- - - - - - - -

- - - - - - - -

Fe (soluble) μg/L - - - - - - - -

- - - - - - - -

- - - - - - - -

Mn (soluble) μg/L - - - - - - - -

- - - - - - - -

- - - - - - - -

32.0 31.2 6.2 3.7 33.4 32.6 5.2 3.3

- - - - - - - -

(a) As CaCO 3 (f) bed volume from 03/12/10

Sampling Date

Sampling Location

Alkalinity mg/L(a)

Total P (as P ) μg/L

Silica (as SiO2) mg/L

Mn (total) μg/L

U (total) μg/L

V (total) μg/L

Turbidity NTU

As (total) μg/L

Fe (total) μg/L

02/16/10 03/16/10(f)

IN AP TA TB IN AP TA TB