EPA/600/R-09/144

December 2009

Arsenic Removal from Drinking Water 

by Iron Removal and Adsorptive Media

U.S. EPA Demonstration Project at Stewart, MN 

Final Performance Evaluation Report

by

Wendy E. Condit

Abraham S.C. Chen

Lili Wang 

Anbo Wang

Battelle

Columbus, OH 43201-2693 

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, Ohio 45268 

National Risk Management Research Laboratory

Office of Research and Development

U.S. Environmental Protection Agency 

Cincinnati, Ohio 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 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 1-year U.S. 

Environmental Protection Agency (EPA) arsenic-removal technology demonstration project at the 

Stewart, MN, facility. The main objective of the project was to evaluate the effectiveness of Siemens’ 

Type II AERALATER® system for iron removal, as well as AdEdge Technologies’ Arsenic Package Unit 

(APU)-300 system for subsequent arsenic removal, whose effectiveness was evaluated based on its ability

to remove arsenic to below the new arsenic maximum contaminant level (MCL) of 10 μg/L. This project

also (1) evaluated the reliability of the treatment system for use at small water facilities, (2) determined 

the required system operation and maintenance (O&M) and operator skill levels, (3) characterized process 

residuals generated by the treatment process, and (4) determined the capital and O&M cost of the 

technology. 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 250 gal/min (gpm) treatment system consisted of an AERALATER® pretreatment unit and an arsenic 

package unit (APU)-300 arsenic removal unit. Used for iron removal, the 11-ft × 26-ft carbon-steel 

AERALATER® package unit was composed of an aeration tower, a detention tank, and a four-cell gravity 

filter in one stacked circular configuration. The effluent from the gravity filter was subsequently polished 

with AD-33 media, an iron-based adsorptive media developed by Bayer AG for arsenic removal. The 

APU-300 system consisted of two skid-mounted 63-in × 86-in fiberglass vessels configured in parallel. 

Each vessel contained 64 ft3 of pelletized AD-33 media supported by gravel underbedding. 

The treatment system began routine operation on February 2, 2006. Through the end of the performance 

evaluation study on February 28, 2007, the system treated approximately 20,441,000 gal of water with an 

average run time of 4.7 hr/day. The average daily demand was 52,418 gal. Water to the treatment system 

was supplied by two wells (Wells No. 3 and 4), each operating at an average flowrate of 191 and 184 

gpm, respectively, on an alternating basis. These reduced flowrates resulted in longer detention times (45 

to 46 min versus the design value of 34 min) within the AERALATER® detention tank and lower

hydraulic loading rates (2.0 to 1.9 gpm/ft2 versus the design value of 2.6 gpm/ft2

) to the gravity filter. The 

corresponding flowrates measured through the APU-300 system also resulted in longer empty bed contact 

time (EBCT) (5.4 min compared to the design value of 3.8 min) in each vessel. No significant 

operational or mechanical issues were experienced during the 1-year performance evaluation study 

period. However, 4 months after the end of the performance evaluation study, the operator reported 

biofouling of the AERALATER® filter that necessitated the use of chlorine to clean the filter media and 

re-injection of a previously selected, but later abandoned oxidant (sodium permanganate [NaMnO4]), to 

oxidize soluble As(III). 

The source water contained 31.4 to 56.4 μg/L of total arsenic, with soluble As(III) at an average 

concentration of 35.3 μg/L as the predominant species. To oxidize soluble As(III), NaMnO4 was selected 

due to the presence of elevated total organic carbon (TOC) (6.4 mg/L on average) and ammonia levels

(1.6 mg/L [as N] on average) in raw water. Based on February 2, 2006, data, 90% of soluble As(III) was 

oxidized to soluble As(V) when NaMnO4 was added prior to aeration. Soluble As(V) was then adsorbed 

onto and/or co-precipitated with iron solids, resulting in 57% soluble As(V) removal. The arsenic-laden 

iron solids were effectively removed by the gravity filter, achieving approximately 60% total arsenic and 

100% total iron removal. The remaining arsenic was present mostly as soluble As(V) at 26.4 μg/L (on 

average), which was subsequently removed by AD-33 media. The elevated soluble As(V) in the gravity 

filter effluent was most likely caused by the relatively high levels of pH (7.9 on average), competing 

anions (such as phosphorous [301 μg/L (as P) on average] and silica [25.1 mg/L (as SiO2) on average]), 

and TOC in source water. 
v

After one week of operation, NaMnO4 addition was inadvertently discontinued due to problems with the 

chemical feed pump. It was subsequently decided to operate the system without NaMnO4 addition due to 

the discovery of microbial-mediated As(III) oxidation processes and elevated manganese levels (e.g., 

127 μg/L on February 2, 2006) in the gravity filter effluent. The elevated manganese concentrations in 

the gravity filter effluent were attributed to the formation of colloidal MnO2 in the presence of TOC

(Knocke et al., 1991). Elevated manganese levels have been shown to be detrimental to AD-33 media

based on studies at other EPA demonstration sites, where high manganese loadings were found to coat 

and/or foul AD-33 media in the presence of chlorine (Oxenham et al., 2005). 

Without NaMnO4 addition, the total arsenic removal rate averaged 34%, and the iron removal rate was

100% across the gravity filter. The oxidation of Fe(II) was accomplished through aeration. It also was 

observed that the oxidation of soluble As(III) to soluble As(V) was occurring at a rate of over 94% across 

the gravity filter via naturally occurring microbial-mediated processes, with only 1.6 μg/L of soluble 

As(III) in the filter effluent (on average). Nitrification also was observed within the gravity filter, but was

not related to the microbially mediated processes as noted. The soluble As(V) concentration averaged 

26.4 μg/L after the gravity filter, which is comparable to the vendor’s design estimate of 20 to 27 μg/L of 

arsenic after the gravity filter and before the AD-33 adsorption system. Therefore, the arsenic removal 

rate without NaMnO4 was within the vendor’s design basis of 30% to 50% across the gravity filter. 

With or without the addition of NaMnO4, soluble As(V) remained above 10 μg/L in the gravity filter 

effluent, thus requiring further treatment with the APU-300 unit. The arsenic concentration in the APU300 system effluent was below 10 μg/L during the 1-year performance study. Based on compliance 

samples collected after the end of the study and average daily production values, the AD-33 media run 

length was estimated at 25,300 bed volumes (BV) of water, which was only 31% of the vendor-projected 

APU-300 capacity of 82,500 BV. As discussed above, the total arsenic-removal efficiency of the gravity 

filter was reduced from approximately 60% to 34% after discontinuing NaMnO4 addition, which shifted 

the burden of arsenic removal from the gravity filter to the downstream adsorption vessels. However, as 

mentioned above, the average concentration of soluble As(V) (26.4 μg/L) in the gravity filter effluent 

(without NaMnO4 addition) was close to the design basis of 20 to 27 μg/L in the influent to the APU-300 

system. Therefore, the reason for the discrepancy in run length was attributed, in part, to competition 

from elevated total phosphorous in the source water, which was not accounted for in the vendor’s runlength estimate. Biofouling in the adsorption vessels also might have contributed to the short run length.

AERALATER® backwash was manually initiated weekly by the operator. The APU-300 system was 

backwashed manually four times during the 1-year performance evaluation study. Approximately 

406,400 gal of wastewater, or 2% of the quantity of the treated water, was generated during the 1-year 

performance study from the AERALATER®. The AERALATER® backwash wastewater contained, on 

average, 87 mg/L of total suspended solids (TSS), 38 mg/L of iron, 343 μg/L of arsenic, and 57 μg/L of 

manganase, with the majority existing as particulate. The average amount of solids discharged per 

backwash cycle was approximately 5.5 lb, which was composed of 2.4 lb of elemental iron, 0.002 lb of 

elemental manganese, and 0.02 lb of elemental arsenic. In addition, 25,415 gal of wastewater were 

generated by the APU-300 unit, or 0.1% of the quantity of treated water. 

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

significant decrease in arsenic concentration from an average of 31.2 to 6.1 μg/L. The arsenic 

concentrations in the distribution system, however, were generally higher than those following the AD-33 

adsorption vessels. Desorption and resuspension of arsenic that previously accumulated on the 

distribution pipe surfaces was the probable reason for the higher concentration in the distribution system. 

Iron concentration in the distribution system was significantly reduced, while manganese levels appeared 

to remain the same after system startup. Both lead and copper concentrations in the distribution system 

were significantly lower than their action levels. 
vi

The capital investment for the system was $367,838: consisting of $273,873 for equipment, $16,520 for 

site engineering, and $77,445 for installation, shakedown, and startup. Using the system’s rated capacity 

of 250 gpm or 360,000 gal/day (gpd), the capital cost was $1,471 per gpm of design capacity ($1.02/gpd). 

This calculation did not include the cost of the building to house the treatment system. The O&M cost 

consisted primarily of the media replacement cost, which was estimated by the vendor at $41,370, to 

change out the AD-33 media. Media changeout did not occur during the performance evaluation period. 

The O&M cost is presented as a function of potential media run length in this report. 
vii

CONTENTS

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

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

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

FIGURES ................................................................................................................................................... viii

TABLES ...................................................................................................................................................... ix

ABBREVIATIONS AND ACRONYMS ..................................................................................................... x

ACKNOWLEDGMENTS ......................................................................................................................... xiii

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 ........................................................................................................... 7

3.1 General Project Approach............................................................................................................. 7

3.2 System O&M and Cost Data Collection ....................................................................................... 8

3.3 Sample Collection Procedures and Schedules .............................................................................. 9

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

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

3.3.3 Backwash Wastewater ..................................................................................................... 9

3.3.4 Distribution System Water ............................................................................................ 12

3.3.5 Residual Solids .............................................................................................................. 12

3.4 Sampling Logistics ..................................................................................................................... 12

3.4.1 Preparation of Arsenic Speciation Kits .......................................................................... 12

3.4.2 Preparation of Sampling Coolers ................................................................................... 12

3.4.3 Sample Shipping and Handling ..................................................................................... 13

3.5 Analytical Procedures ................................................................................................................. 13

4.0 RESULTS AND DISCUSSION .......................................................................................................... 14

4.1 Facility Description .................................................................................................................... 14

4.1.1 Source-Water Quality .................................................................................................... 17

4.1.2 Treated-Water Quality and Distribution System ........................................................... 19

4.2 Treatment Process Description ................................................................................................... 19

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

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

4.3.2 Building Construction .................................................................................................... 26

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

4.4 System Operation ....................................................................................................................... 28

4.4.1 AERALATER® Operations ........................................................................................... 28

4.4.2 APU-300 Operations ..................................................................................................... 29

4.4.3 Backwash Operations .................................................................................................... 29

4.4.4 Residual Management ................................................................................................... 31

4.4.5 Reliability and Simplicity of Operation ......................................................................... 31

4.4.5.1 Pre- and Post-Treatment Requirements ......................................................... 31

4.4.5.2 System Automation ....................................................................................... 32

4.4.5.3 Operator Skill Requirements ......................................................................... 32

4.4.5.4 Preventive Maintenance Activities ................................................................ 32

4.4.5.5 Chemical-Handling and Inventory Requirements ......................................... 32
viii

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

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

4.5.1.1 Arsenic .......................................................................................................... 33

4.5.1.2 Iron ................................................................................................................ 41

4.5.1.3 Manganese ..................................................................................................... 42

4.5.1.4 pH, DO, and ORP .......................................................................................... 43

4.5.1.5 Ammonia and Nitrate .................................................................................... 44

4.5.1.6 Other Water Quality Parameters ................................................................... 46

4.5.2 Backwash Wastewater Sampling ................................................................................... 46

4.5.3 Distribution System Water Sampling ............................................................................ 48

4.6 System Cost ................................................................................................................................ 51

4.6.1 Capital Cost ................................................................................................................... 52

4.6.2 Operation and Maintenance Cost................................................................................... 52

5.0 REFERENCES .................................................................................................................................... 56

APPENDIX A: OPERATIONAL DATA

APPENDIX B: ANALYTICAL DATA TABLES

FIGURES

Figure 3-1. Process Flow Diagram and Sampling Schedule and Locations ............................................ 11

Figure 4-1. Wellhead 3 at Stewart, Minnesota ......................................................................................... 14

Figure 4-2. Wellhead 4 at Stewart, Minnesota ......................................................................................... 15

Figure 4-3. Existing Chemical Addition Equipment at Stewart, Minnesota ............................................ 15

Figure 4-4. Existing Chemical Addition and Entry Piping with Flow Totalizer and Pressure 

Gauge at Stewart, Minnesota ............................................................................................... 16

Figure 4-5. A 65,000-gal Water Tower at Stewart, Minnesota ................................................................ 16

Figure 4-6. Schematic of AERALATER® and APU-300 Systems at Stewart, Minnesota ...................... 20

Figure 4-7. AERALATER® and APU-300 Systems at Stewart, Minnesota ............................................ 20

Figure 4-8. Schematic of Type II AERALATER® System ...................................................................... 24

Figure 4-9. Schematic of APU-300 System ............................................................................................. 25

Figure 4-10. Building with AERLATER® Tower, Backwash Sump, and Backwash Wastewater 

Holding Tanks at Stewart, Minnesota .................................................................................. 27

Figure 4-11. Off-Loading and Placement of AERALATER® Unit at Stewart, Minnesota ...................... 27

Figure 4-12. Instantaneous Flowrates Through Adsorption Vessels A and B .......................................... 30

Figure 4-13. Arsenic Speciation Results at Wellhead (IN), After Contact Tank (AC), After 

Filtration (AF), and After Vessels A and B Combined (TT) ............................................... 37

Figure 4-14. Total Arsenic Concentrations vs. Throughput ..................................................................... 39

Figure 4-15. Biogeochemical Cycle of Arsenic ........................................................................................ 41

Figure 4-16. Total Iron Concentrations vs. Bed Volumes ........................................................................ 42

Figure 4-17. Total Manganese Concentrations vs. Bed Volumes ............................................................. 43

Figure 4-18. Decreases/Increases in Ammonia/Nitrate Across AERALATER® Filter and AD-33 

Adsorption Vessels .............................................................................................................. 45

Figure 4-19. Comparsion of Total Arsenic Concentrations in Distribution System Water and 

APU-300 System Effluent.................................................................................................... 51

Figure 4-20. Media Replacement and O&M Cost for AERALATER® and APU-300 Systems at 

Stewart, Minnesota ............................................................................................................... 55
ix

TABLES

Table 1-1. Summary of Rounds 1 and 2 Arsenic- Removal Demonstration Sites ..................................... 3

Table 3-1. Pre-demonstration and Demonstration Study Activities and Completion Dates ...................... 7

Table 3-2. Evaluation Objectives and Supporting Data Collection Activities ........................................... 8

Table 3-3. Sampling Locations, Schedules and Analyses ........................................................................ 10

Table 4-1. City of Stewart, Minnesota, Water Quality Data .................................................................... 18

Table 4-2. Physical and Chemical Properties of AD-33 Media ............................................................... 21

Table 4-3. Design Specifications of Type II AERALATER® and APU-300 Systems ........................... 23

Table 4-4. Summary of Treatment System Operation at Stewart, Minnesota .......................................... 28

Table 4-5. Summary of Backwash Operations at Stewart, Minnesota ..................................................... 30

Table 4-6. Summary of Arsenic, Iron, and Manganese Analytical Results ............................................. 34

Table 4-7. Summary of Other Water Quality Parameter Measurements .................................................. 35

Table 4-8. AERALATER® Filter Backwash Wastewater Sampling Results ........................................... 47

Table 4-9. AERALATER® Filter Backwash Solids Total Metal Results................................................. 47

Table 4-10. APU-300 Adsorption Vessels Backwash Wastewater Sampling Results............................... 48

Table 4-11. Distribution System Sampling Results ................................................................................... 49

Table 4-12. Capital Investment Cost for Siemens and AdEdge Treatment Systems ................................. 53

Table 4-13. O&M Cost for City of Stewart, Minnesota Treatment System .............................................. 54
x

ABBREVIATIONS AND ACRONYMS

AAL American Analytical Laboratories

Al aluminum 

AM adsorptive media 

APU arsenic package unit

As arsenic

ATS Aquatic Treatment Systems

BET Brunauer, Emmett, and Teller Method

bgs below ground surface

BV bed volume(s) 

Ca calcium 

CAO chemolithoautotrophic arsenite oxidizer 

C/F coagulation/filtration

cfm cubic foot per minute 

Cl chlorine

CRF capital recovery factor

Cu copper 

DBP disinfection byproducts 

DO dissolved oxygen 

DOM dissolved organic matter

EBCT empty bed contact time

EPA U.S. Environmental Protection Agency 

F fluoride

Fe iron 

FedEx Federal Express

GCSP Greene County Southern Plant 

GFH granular ferric hydroxide 

gpd gallons per day 

gpm gallons per minute 

gph gallons per hour 

HAA5 haloacetic acids

HAO heterotrophic arsenite oxidizers

HIX hybrid ion exchanger 

H2SO4 sulfuric acid

hp horsepower 

ICP-MS inductively coupled plasma-mass spectrometry

ID identification

IX ion exchange 

kgal kilo gallons

KMnO4 potassium permanganate 

LCR (EPA) Lead and Copper Rule 
xi

MCL maximum contaminant level

MEI Magnesium Elektron, Inc.

MDH Minnesota Department of Health

MDL method detection limit

Mg magnesium 

μm micrometer

Mn manganese

mV millivolts

Na sodium 

NA not applicable 

ND not detected

NS not sampled

NSF NSF International

NTU nephelometric turbidity units

O&M operation and maintenance 

OIT Oregon Institute of Technology 

ORD Office of Research and Development

ORP oxidation-reduction potential 

P&ID process and instrumentation diagram 

Pb lead

pCi pico curie

psi pounds per square inch

PLC programmable logic controller

PO4 orthophosphate 

POE point of entry

POU point of use 

PVC polyvinyl chloride 

QA quality assurance 

QA/QC quality assurance/quality control 

QAPP Quality Assurance Project Plan

RO reverse osmosis

RPD relative percent difference

Sb antimony 

SDWA Safe Drinking Water Act

SiO2 silica

SMCL secondary maximum contaminant level

SO4 sulfate

STS Severn Trent Services

TCLP Toxicity Characteristic Leaching Procedure 

TDH total dynamic head 

TDS total dissolved solids

THM trihalomethanes 

TOC total organic carbon

TSS total suspended solids
xii

V vanadium 

VOC volatile organic compound
xiii

ACKNOWLEDGMENTS

The authors wish to extend their sincere appreciation to Mr. Michael Richards of the City of Stewart in

Minnesota. Mr. Richards monitored the treatment system and collected samples from the treatment and 

distribution systems on a regular schedule throughout this study period. This performance evaluation 

would not have been possible without his support and dedication. 
1

1.0 INTRODUCTION

1.1 Background 

The Safe Drinking Water Act (SDWA) mandates that 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 in order to reduce compliance costs. 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 was published in the Federal Register requesting 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 of the 115 candidate 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 from one to six proposals. In April 2003, an independent technical panel 

reviewed the proposals and provided its recommendations to EPA on the technologies it determined 

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. The community water system at the City of Stewart in Minnesota was one of those selected. 

In September 2003, EPA again solicited proposals from engineering firms and vendors for arsenicremoval 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 a maximum of four. Final selection of the treatment technology at sites receiving at least 

one proposal was made, again 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. 

Two technologies were selected for demonstration at the Stewart, MN, facility, including Siemens’ 

(formerly known as USFilter) Type II AERALATER® for iron removal, followed by AdEdge 

Technologies’ AD-33 adsorptive media for arsenic removal.
2

As of December 2009, 39 of the 40 systems were operational, and the performance evaluation of 34 

systems was completed. 

1.2 Treatment Technologies for Arsenic Removal

The technologies selected for the Rounds 1 and 2 demonstration host sites included 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 system modification. Table 1-1 summarizes the locations, 

technologies, vendors, system flowrates, and key source-water-quality parameters (including As, Fe, 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 costs 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 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 Siemens’ Type II AERALATER® and AdEdge Arsenic 

Package Unit (APU)-300 systems at Stewart, MN, during February 2, 2006, through February 28, 2007. 

The types of data collected included system operation, water quality (both across the treatment train and 

in the distribution system), residuals, and capital and O&M cost. 
3

Table 1-1. Summary of Rounds 1 and 2 Arsenic-Removal Demonstration Sites 

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

Newark, 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 Rounds 1 and 2 Arsenic-Removal Demonstration Sites (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 exchanger; 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 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

The Siemens AERALATER® and AdEdge Technologies AD-33 APU-300 units were installed and have 

operated at Stewart, MN, since February 2, 2006. Based on the information collected during the 1-year 

performance evaluation study from February 2, 2006 to February 28, 2007, the following conclusions 

were drawn relating to the overall objectives of the treatment technology demonstration study. 

Performance of the arsenic removal technology:

• Aeration was effective in oxidizing soluble iron, converting 100% of it to iron solids. 

However, aeration was only minimally effective in oxidizing soluble As(III), converting 

25.8% (on average) of soluble As(III) to soluble As(V) and particulate arsenic. 

• NaMnO4 was effective in oxidizing As(III), converting over 90% of soluble As(III) to soluble 

As(V) and particulate arsenic. Of the As(V) in the contact section of the AERALATER®, 

only 57% became attached to iron solids formed during the preoxidation step, presumably via 

adsorption and co-precipitation. The relatively low As(V) removal rate was most likely the 

result of the relatively elevated pH (i.e., 7.9), competing anions (such as 301 μg/L of total 

phosphorous [as P] and 25.1 mg/L of Si [as SiO2]), and total organic carbon [TOC] (6.4 

mg/L) in source water. 

• NaMnO4 addition resulted in elevated manganese levels in the gravity filter effluent, which 

were attributed to colloidal MnO2 formation in the presence of high TOC levels. 

• Upon discontinuation of NaMnO4 addition, naturally occurring microbial-mediated pathways 

were thought to be responsible for the oxidation of over 94% of soluble As(III) within the 

AERALATER® filter, leaving only 1.6 μg/L of soluble As(III) in the filter effluent. 

Nitrification also occurred within the gravity filter and AD-33 adsorption vessels. Oxygen, 

instead of nitrate, was believed to be the electron acceptor for the microbial-mediated As(III) 

oxidation processes observed. 

• The AERALATER® filter was highly effective in removing particulate matter. Without 

NaMnO4 addition, 34% of total arsenic was removed, compared to 60% removed with 

NaMnO4 addition. Aeration alone in the AERALATER® system was sufficient to 

accomplish complete iron removal. No particulate iron breakthrough was observed from the 

AERALATER® filter, suggesting adequate filter backwash frequency. 

• AD-33 media effectively removed arsenic to below 10 μg/L during the 1-year performance 

study. Based on compliance samples collected after the end of the study and average daily 

production values, the media run length was estimated at 25,300 bed volumes (BV), which 

was only 31% of the vendor-projected run length of 82,500 BV. Competition from 

phosphorous in source water might have contributed, in part, to the short run length. 

• Due to biofouling in the gravity filter and APU-300 system, the city used chlorine after the 

demonstration study to restore the hydraulic capacity of the gravity filter; NaMnO4 addition 

was re-started, along with a blending scheme to send only a portion of the gravity-filtertreated water to the APU-300 system. 

• The treatment system improved the water quality in the distribution system with considerable 

decreases in arsenic (from 31.2 to 6.1 μg/L) and iron (from 376 to 112 μg/L) concentrations. 

However, arsenic concentrations were higher in the distribution system than in the treatment 

plant effluent, suggesting desorption and resuspension of arsenic from pipe surfaces.

Required system operation and maintenance and operator’s skill levels: 
6

• Daily operation of the system did not require additional skills beyond those necessary to 

operate existing water-supply equipment. The daily demand on the operator was only 10 

min/day for routine operations. 

• Because the system was backwashed only once a week, manual backwash was acceptable to 

the plant operator. The time required was 31 min per backwash event.

• Biofouling, observed 4 months after the end of the study period, required using chlorine to 

clean up the gravity filter. NaMnO4 addition alone could not control biofouling and some 

periodic chlorination would be required. The high TOC and ammonia levels at the site 

limited the use of chlorine on a continual basis due to the potential for disinfection byproducts (DBP) formation. 

Characteristics of residuals produced by the technology: 

• Residuals produced by operation of the treatment system included only backwash wastewater 

from the AERALATER® gravity filter and the AD-33 adsorption vessels. The media was not 

replaced during the 1-year performance evaluation study. 

• The amount of wastewater produced was equivalent to about 2.1% of the amount of water 

treated (406,400 gal or 2% from the AERALATER® and 25,415 gal or 0.1% from the APU300 unit). 

• The amount of solids produced per filter backwash cycle was 5.5 lb, which included 2.4 lb of 

elemental iron, 0.02 lb of elemental arsenic, and 0.002 lb of elemental manganese. 

Cost-effectiveness of the technology:

• The capital investment for the system was $367,838: $273,873 for equipment, $16,520 for 

site engineering, and $77,445 for installation, shakedown, and startup. The building cost 

incurred by the City of Stewart was not included in the capital investment cost.

• Using the system’s rated capacity of 250 gpm, or 360,000 gpd, the capital cost was 

$1,471/gpm ($1.02/gpd) of design capacity. 

• Although not incurred during the 1-year performance study, the AD-33 media 

replacement cost would be the majority of the O&M cost for the system and was 

estimated to be $41,370. 
7

3.0 MATERIALS AND METHODS

3.1 General Project Approach

Table 3-1 summarizes the pre-demonstration and demonstration study activities and completion dates. 

Following the pre-demonstration activities, the performance evaluation study of the treatment system 

began on February 2, 2006. Table 3-2 summarizes the types of data collected and considered as part of 

the technology evaluation process. The overall system performance was evaluated based on its ability to 

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

across the treatment train. The reliability of the system was evaluated by tracking the unscheduled system 

downtime and the frequency and extent of repair and replacement. The plant operator recorded 

unscheduled downtime and repair information on a Repair and Maintenance Log Sheet. 

Table 3-1. Pre-demonstration and Demonstration Study Activities 

and Completion Dates

Activity Date

Introductory Meeting Held 08/30/04

Draft Letter of Understanding Issued 11/18/04

Final Letter of Understanding Issued 12/10/04

Request for Quotation Issued to Vendor 01/21/05

Vendor Quotation Received 03/15/05

Purchase Order Established 03/29/05

Letter Report Issued 03/09/05

Engineering Package Submitted to MDH 03/21/05

System Permit Granted by MDH 06/20/05

Building Construction Permit Granted 06/13/05

Building Construction Begun 07/01/05

APU-300 Unit Shipped/Arrived 09/06/05

AERALATER® Shipped/Arrived 09/16/05

System Installation/Shakedown Completed 01/18/06

Study Plan Issued 01/24/06

Performance Evaluation Begun 02/02/06

Building Construction Completed 02/09/06

Performance Evaluation Ended 02/28/07

MDH = Minnesota Department of Health. 

The O&M and operator skill requirements were evaluated based on a combination of quantitative data 

and qualitative considerations, including the need 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. The system staffing requirements were recorded on an Operator Labor Hour Log Sheet. 

The quantity of aqueous and solid residuals generated was estimated by tracking the volume of backwash 

wastewater produced during each backwash cycle and the need to replace the media upon arsenic 

breakthrough. Backwash wastewater was sampled and analyzed for chemical characteristics. 
8

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

Evaluation Objective Data Collection

Performance -Ability to consistently meet 10 μg/L of arsenic 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 for relevant chemical processes and health and 

safety practices

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

system operation

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

-O&M cost for chemical usage, electricity consumption, and labor

The cost of the system was evaluated based on the capital cost per gal/min (gpm) (or gal/day [gpd]) of 

design capacity and the O&M cost per 1,000 gal of water treated. This task required tracking the capital 

cost for the equipment, engineering, and installation, as well as the O&M cost for media replacement and 

disposal, chemical supply, electricity use, and labor. 

3.2 System O&M and Cost Data Collection 

The plant operator performed daily, weekly, and monthly system O&M and data collection following the 

instructions provided by the vendor and Battelle. On a daily basis (including Saturdays and Sundays), 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 contacted the Battelle Study Lead, who 

determined if the vendor needed to be contacted for troubleshooting. The plant operator recorded all 

relevant information, including the problems encountered, course of action taken, materials and supplies 

used, and associated cost and labor incurred, on a Repair and Maintenance Log Sheet. On a weekly basis, 

the plant operator measured several water quality parameters onsite, including temperature, pH, dissolved 

oxygen (DO), and oxidation-reduction potential (ORP), and recorded the data on a Weekly Onsite Water 

Quality Parameters Log Sheet. Weekly backwash data also were recorded on a Backwash Log Sheet.

The capital cost for the arsenic-removal system consisted of the expenditure for equipment, site 

engineering, and system installation. The O&M cost consisted of the expenditure for media replacement, 

electricity consumption, and labor. Electricity consumption was determined from utility bills. Labor for 

various activities, such as routine system O&M, troubleshooting and repairs, and demonstration-related 

work, were tracked using an Operator Labor Hour Log Sheet. Routine system O&M included activities 

such as completing field logs, ordering supplies, performing system inspections, and others as 

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

performing field measurements, collecting and shipping samples, and communicating with the Battelle 

Study Lead and the vendor, was recorded, but not used for the cost analysis. 
9

3.3 Sample Collection Procedures and Schedules

To evaluate system performance, samples were collected from the wellhead, across the treatment plant,

during backwash of Type II AERALATER® and AD-33 adsorption vessels, and from the distribution 

system. Table 3-3 provides the sampling schedules and analytes measured during each sampling event. 

Figure 3-1 presents a flow diagram of the treatment system along with the analytes and schedules at each 

sampling location. Specific sampling 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). Appendix A of the QAPP describes the procedure for arsenic 

speciation. 

3.3.1 Source Water. During the initial visit to the site, source-water samples were collected and 

speciated using an arsenic speciation kit as described in Section 3.4.1. The sample tap was flushed for 

several minutes before sampling; special care was taken to avoid agitation, which might cause unwanted 

oxidation. Table 3-3 lists analytes for the source-water samples. 

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

operator collected samples weekly, on a 4-week cycle, for onsite and offsite analyses. For the first week 

of each 4-week cycle, samples taken at the wellhead (IN), after the contact tank (AC), after 

AERALATOR® gravity filter (AF), and at the combined effluent of Vessels A and B (TT), were speciated

onsite and analyzed for the analytes listed in Table 3-3. For the next 3 weeks, samples were collected at 

IN, AC, AF, and after Vessels A (TA) and B (TB) and were analyzed for the analytes listed in Table 3-3. 

Over the 1-year demonstration study, two changes were made to the sampling schedules as follows:

• Before April 25, 2006, the monthly speciation sample at the TT location was 

collected from either the TA or TB sampling tap due to absence of a combined 

effluent sample tap at the time. 

• After December 18, 2006, the sampling frequency was reduced to monthly speciation 

sampling at IN, AC, AF, and TT locations through the end of the performance evaluation 

study. 

3.3.3 Backwash Wastewater. AERALATER® backwash wastewater samples were collected 

monthly by the plant operator. Grab samples were collected monthly from March 1, 2006, to August 23, 

2006. Because of the absence of a sampling tap on the backwash wastewater discharge line, grab samples 

were taken directly from the backwash wastewater discharge sump. One aliquot was collected as is and 

the other filtered onsite with 0.45-μm disc filters. Since September 20, 2006, composite samples were 

collected monthly, using a revised procedure to allow collection of more representative samples during 

backwash. A 1/40-horsepower (hp) recirculation submersible water pump was used to collect a 

slipstream of water from the backwash wastewater sump to a 50-gal container over the duration of 

backwash for filter cells 1 and 2, respectively. At the end of each backwash cycle, the content in the 

container was mixed thoroughly, and composite samples were collected and filtered onsite with 0.45-μm 

disc filters. Table 3-3 lists analytes for the backwash wastewater samples. 

The APU-300 system was backwashed manually four times during the performance evaluation study 

period, with one set of composite backwash wastewater samples collected. Tubing connected to the tap 

on the discharge line of each adsorption vessel directed a portion of backwash wastewater from each 

vessel at about 1 gpm into a clean, 32-gal container throughout the entire backwash. After the content in 

the container was thoroughly mixed, composite samples were collected and/or filtered onsite with 0.45-

μm disc filters. Table 3-3 lists analytes for the adsorption vessels backwash samples. 
10

Table 3-3. Sampling Locations, Schedules, and Analyses 

Sample Type

Sample

Locations

(a)

No. of

Samples Frequency Analytes 

Sampling

Date

Source Water IN 1 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,

Ra-226, Ra-228, TDS, 

TOC, alkalinity, and

turbidity 

08/30/04

Treatment Plant 

Water 

IN, AC, 

AF, TA, 

and TB

5 Weekly Onsite: pH, temperature, 

DO, and ORP

Offsite: As (total), 

Fe (total), Mn (total), 

P (total), SiO2, alkalinity, 

and turbidity 

Appendix B

IN, AC, 

AF, and TT

4 Monthly Same as weekly analytes 

shown above plus the 

following: 

Offsite: As (soluble), 

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

Mn (soluble), Ca, Mg, F, 

NO3, NH3, SO4, and TOC

Appendix B(b)

AERALATER® 

Filter

Backwash 

Wastewater

At 

backwash 

discharge 

sump

2 Monthly As (total and soluble), 

Fe (total and soluble), 

Mn (total and soluble), 

pH, TDS, and TSS

Table 4-8

AERALATER® 

Filter

Backwash 

Solids

At 

backwash 

discharge 

sump

2 Once TCLP metals and total Al, 

As, Ba, Ca, Cd, Cu, Fe, Mg, 

Mn, Ni, P, Pb, Sb, Si, V, 

and Zn

02/28/07

APU-300 

Backwash 

Wastewater

At 

backwash 

discharge 

line

2 Once As (total and soluble), 

Fe (total and soluble), 

Mn (total and soluble), 

pH, TDS, and TSS

01/17/07

Distribution 

Water

Three nonLCR 

residences

3 Monthly Total As, Fe, Mn, Cu, and 

Pb, pH, and alkalinity

Table 4-11(c)

(a) Abbreviation corresponding to sample locations in Figure 3-1: IN = at wellhead; AC = after contact 

tank; AF = after gravity filter; TA = after Vessel A; TB = after Vessel B; TT = after Vessels A and B 

combined; and BW = at backwash wastewater discharge line. 

(b) Sampling events before 04/25/06 were taken from TA or TB tap due to the absence of combined 

effluent sample tap.

(c) Four sampling events were performed before system startup.

LCR = Lead and Copper Rule; TCLP = toxicity characteristic leaching procedure
11

MEDIA 

VESSEL 

A

MEDIA 

VESSEL 

B

SLOW DRAIN

TO SEWER

INFLUENT

AERATOR

Weekly

Monthly

Stewart, MN

AERALATER®/AD-33® Technology

Design Flow: 250 gpm

DISTRIBUTION 

SYSTEM

KMnO4

(b)

Footnotes

(a) On-site analyses

(b) Switched to NaMnO4 prior to start-up

BW

IN

pH, TDS, TSS,

As (total and soluble),

Fe (total and soluble),

Mn (total and soluble)

TA TB

TT

TCLP

SS

DETENTION TANK

AC

GRAVITY FILTER

LEGEND

LEGEND

At Wellhead

AC After Contact Tank

Water Sampling Locations

IN

KMnO4

INFLUENT

Potassium Permanganate

Oxidation

Unit Process

Process Flow

Backwash Flow

SS

BW

AF After Gravity Filter

Backwash Sampling Location

Sludge Sampling Location

TA After Vessel A

TB After Vessel B

TT After Vessels A & B Combined

AF 

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg, F,

NO3, SO4, SiO2, P (total), NH3,

TOC, turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

BW

pH, TDS, TSS,

As (total and soluble),

Fe (total and soluble),

Mn (total and soluble)

MEDIA 

VESSEL 

A

MEDIA 

VESSEL 

B

SLOW DRAIN

TO SEWER

INFLUENT

AERATOR

Weekly

Monthly

Stewart, MN

AERALATER®/AD-33® Technology

Design Flow: 250 gpm

DISTRIBUTION 

SYSTEM

KMnO4

(b)

Footnotes

(a) On-site analyses

(b) Switched to NaMnO4 prior to start-up

BW

IN

pH, TDS, TSS,

As (total and soluble),

Fe (total and soluble),

Mn (total and soluble)

TA TB

TT

TCLP

SS

DETENTION TANK

AC

GRAVITY FILTER

LEGEND

LEGEND

At Wellhead

AC After Contact Tank

Water Sampling Locations

IN

KMnO4

INFLUENT

Potassium Permanganate

Oxidation

Unit Process

Process Flow

Backwash Flow

SS

BW

AF After Gravity Filter

Backwash Sampling Location

Sludge Sampling Location

TA After Vessel A

TB After Vessel B

TT After Vessels A & B Combined

LEGEND

LEGEND

At Wellhead

AC After Contact Tank

Water Sampling Locations

IN

KMnO4

INFLUENT

Potassium Permanganate

Oxidation

Unit Process

Process Flow

Backwash Flow

SS

BW

AF After Gravity Filter

Backwash Sampling Location

Sludge Sampling Location

TA After Vessel A

TB After Vessel B

TT After Vessels A & B Combined

AF 

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg, F,

NO3, SO4, SiO2, P (total), NH3,

TOC, turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a),

DO(a), ORP(a), As (total),

Fe (total), Mn (total), SiO2,

P (total), turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

pH(a), temperature(a), DO(a), ORP(a), 

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

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

Mn (total and soluble), Ca, Mg,

F, NO3, SO4, SiO2, P (total), NH3, 

TOC, turbidity, alkalinity

BW

pH, TDS, TSS,

As (total and soluble),

Fe (total and soluble),

Mn (total and soluble)

Figure 3-1. Process Flow Diagram and Sampling Schedule and Locations 
12

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

determine the impact of the arsenic treatment system on its water chemistry, specifically, the arsenic, 

lead, and copper levels. Prior to system startup from February to May 2005, four sets of baseline 

distribution water samples were collected from three residences within the distribution system. Following 

system startup, distribution system sampling continued monthly at the same three locations. 

The distribution system water samples were taken following an instruction sheet developed by Battelle 

according to the Lead and Copper Rule Reporting Guidance for Public Water Systems (EPA, 2002). 

First-draw samples were collected from cold-water faucets that had not been used for at least 6 hours to 

ensure that stagnant water was sampled. The sampler recorded the date and time of last water use before 

sampling, as well as the date and time of sample collection for calculation of the stagnation time. The 

samples were analyzed for the analytes listed in Table 3-3. Arsenic speciation was not performed on the 

distribution water samples. 

3.3.5 Residual Solids. Residual solids included backwash solids and spent-media samples. 

AERALATER® backwash solids samples were collected once on February 28, 2007, after the solids 

settled in the 32-gal backwash containers and the supernatant carefully decanted. The samples were airdried, acid-digested, and analyzed for Al, As, Ba, Ca, Cd, Cu, Fe, Mg, Mn, Ni, P, Pb, Sb, Si, V, and Zn. 

No backwash solids samples were collected during the backwash of the APU-300 unit, since the unit was 

only backwashed four times during the 1-year performance evaluation study. Because the adsorption 

media was not changed out during the performance evaluation study, no media samples were collected 

and analyzed.

3.4 Sampling Logistics

All sampling logistics, including arsenic speciation kits preparation, sample cooler preparation, and 

sampling shipping and handling, are discussed below.

3.4.1 Preparation of Arsenic Speciation Kits. The arsenic field speciation method uses 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 according to the procedures detailed in 

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

3.4.2 Preparation of Sample 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, colored-coded, 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, the sampling date, a two-letter 

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

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

labeled bottles for each sampling location were placed separately in a Ziplock® bag (each corresponding 

to a specific sample location) and packed in the cooler. When needed, the sample cooler also included 

bottles for the distribution system sampling.

In addition, all sampling- and shipping-related materials, such as disposable gloves, sampling instructions, 

chain-of-custody forms, pre-paid/pre-addressed FedEx air bills, and bubble wrap, were placed in each 

cooler. The chain-of-custody forms and air bills were completed except for the operator’s signature and 

the sample dates and times. After preparation, sample coolers were sent to the site via FedEx for the 

following week’s sampling event. 
13

3.4.3 Sample Shipping and Handling. After sample collection, samples for offsite analyses were 

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

custodian checked sample IDs against the chain-of-custody forms and verified that all samples indicated 

on the forms were included and intact. The Battelle Study Lead addressed discrepancies noted by the 

sample custodian with the plant operator. The shipment and receipt of all coolers by Battelle were 

recorded on a cooler tracking log. 

Samples for metal analyses were stored and analyzed at Battelle’s inductively coupled plasma-mass 

spectrometry (ICP-MS) laboratory. Samples for other water quality parameters were packed in separate 

coolers and picked up by couriers from American Analytical Laboratories (AAL) in Columbus, Ohio, and 

TCCI Laboratories in New Lexington, Ohio, both of which were under contract to 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 Section 4.0 of the EPA-endorsed QAPP (Battelle, 2003) were 

followed by Battelle ICP-MS Laboratory, AAL, and TCCI Laboratories. Laboratory quality 

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

of precision, accuracy, method detection limit (MDL), and completeness met the criteria established in the 

QAPP (20% relative percent difference [RPD], 80 to 120% percent recovery, and 80% completeness). 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 SP90M5 probe in the beaker until a 

stable value was obtained. 
14

4.0 RESULTS AND DISCUSSION

4.1 Facility Description

The water treatment system at Stewart, MN, supplies drinking water to approximately 600 community 

members. The water source is groundwater from two wells (Wells No. 3 and 4). Wellheads 3 and 4 are 

shown in Figures 4-1 and 4-2, respectively. The static water level of the wells ranges from 20 to 30 ft 

below ground surface (bgs). Each well is 8 in in diameter and extends to a depth of approximately 370 ft

bgs. Well No. 3 has a 50-ft screen length and is equipped with a 20-hp submersible pump with a capacity 

of approximately 350 gpm. Well No. 4 has a 52-ft screen length and a 15-hp submersible pump with a 

capacity of approximately 275 gpm. Prior to the performance evaluation study, the average daily demand 

was 52,420 gpd. Use of these two wells was alternated automatically based on the water tower level. 

Typically, each well ran for about 12,000 to 15,000 gal per cycle. 

The pre-existing treatment consisted of chlorination, fluoridation, and polyphosphate addition. 

Chlorination was accomplished with a gas chlorine feed system to provide chlorine residuals in the 

distribution system. The target residual level was 1.1 mg/L for total chlorine (as Cl2). The water also was 

fluoridated to a target level of 1.3 mg/L. Blended polyphosphates were added for iron sequestration and 

corrosion control. Figure 4-3 shows the chemical feed pumps and associated tanks within the pump 

house. Figure 4-4 shows the entry piping from Wells No. 3 and 4 and the tubing from the chemical feed 

pumps. As described in Section 4-2, the pre-existing equipment shown in Figures 4-3 and 4-4 was 

replaced with new equipment of similar sizes as part of the pre- and post-treatment. The treated water 

was stored in a nearby 65,000-gal water tower, as shown in Figure 4-5. 

Figure 4-1. Wellhead 3 at Stewart, Minnesota (near orange flag in center of photo)
15

Figure 4-2. Wellhead 4 at Stewart, Minnesota (in front of small brown shed)

Figure 4-3. Existing Chemical Addition Equipment at Stewart, Minnesota 
16

Figure 4-4. Existing Chemical Addition and Entry Piping with Flow Totalizer and 

Pressure Gauge at Stewart, Minnesota 

Figure 4-5. A 65,000-gal Water Tower at Stewart, Minnesota 
17

4.1.1 Source-Water Quality. Battelle collected source-water samples from Well No. 3 on August 

30, 2004 for detailed water quality characterization; Table 3-3 shows the analytes of interest. In addition, 

pH, temperature, DO, and ORP were measured onsite using a VWR Symphony SP90M5 handheld 

multimeter. The source water also was filtered for soluble arsenic, iron, manganese, uranium, and 

vanadium and speciated for As(III) and As(V) using the field speciation method modified by Battelle 

from Edwards, et al. (1998). Table 4-1 presents the analytical results from the source-water sampling 

event and compares them to historic data taken by the facility. 

The proposed treatment train for the City of Stewart included oxidation with potassium permanganate 

(KMnO4), iron removal using gravity filtration, and arsenic adsorption with AD-33 media. Several 

factors were anticipated to play a role in the pretreatment process for iron removal, including natural iron 

concentration, pH, turbidity, natural organic matter, ammonia, anions, and cations. Factors that may 

affect arsenic removal via adsorption include arsenic concentration, arsenic speciation, pH, and other 

competing anions. 

Arsenic. Total arsenic concentrations in source water ranged from 39.0 to 41.7 μg/L. Based on August 

30, 2004, sampling results from Well No. 3, out of 41.7 μg/L of total arsenic, 31.9 μg/L existed as soluble 

As(III), 1.0 μg/L as soluble As(V), and 8.8 μg/L as particulate As. Therefore, soluble As(III) was the 

predominating species (about 76%) in groundwater. The proposed treatment process was to use KMnO4, 

as originally designed, but was switched to NaMnO4 just before system startup by the city in order to 

oxidize soluble As(III) to soluble As(V) prior to iron removal and AD-33 adsorption. Oxidant addition

was discontinued after the discovery of a naturally occurring oxidation process developed within the 

AERALATER® filter (see detailed discussion in Section 4.5.1.1). Upon oxidation, soluble As(V) was 

removed via adsorption onto and/or co-precipitation with iron solids during the iron-removal pretreatment 

step. The remaining As(V) was then removed via adsorption onto the AD-33 media.

Iron and Manganese. In general, adsorptive media technologies are best suited to source water with 

relatively low iron levels (i.e., less than 300 μg/L, which is the secondary maximum contaminant level 

[SMCL] for iron). Above 300 μg/L, taste, odor, and color problems can occur in treated water, along 

with an increased potential for fouling of the adsorption system. The proposed treatment process at

Stewart, MN, relied on aeration and gravity filtration to remove elevated levels of iron in source water. 

This iron removal process also resulted in the removal of some As(V) in the water. Iron concentrations in 

source water ranged from 1,344 to 1,400 μg/L, which existed almost entirely as soluble iron. Total 

manganese in source water ranged from 24 to 27 μg/L, which was below the SMCL of 50 μg/L. 

pH. pH values of source water ranged from 7.7 to 7.8, which were near the upper end of the target range 

of 6.0 to 8.0 for optimal arsenic adsorption onto the AD-33 media.

TOC and Ammonia. The source water contained elevated levels of TOC (ranging from 6.8 to 7.2 mg/L) 

and ammonia (at 1.7 mg/L). To avoid the formation of DBPs and high chlorine consumption, the 

treatment process used NaMnO4, instead of chlorine, for As(III) oxidation. However, as mentioned 

above, oxidant addition was later discontinued because iron removal was accomplished through aeration 

and As(III) oxidation was attained via a naturally occurring process. 

Competing Anions. The adsorption of arsenic onto iron solids and AD-33 media also may be influenced 

by the presence of competing anions such as silica, sulfate, and phosphate. At the Stewart, MN, site, 

silica levels ranged from 24.0 to 26.6 mg/L (as SiO2) and sulfate levels ranged from <5 to 7.4 mg/L. 

These concentrations were low enough that they did not pose a significant problem for effective arsenic 

adsorption. The orthophosphate level was 0.02 mg/L; however, as discussed in Section 4.5.1.6, the total 

phosphorous 
18 

Table 4-1. City of Stewart, Minnesota, Water Quality Data , 

Parameter Unit

Source Water Historic Utility

Distribution

Water Data(c)

Utility

Data(a)

Battelle

Data(b)

Sampling Date Not Specified 08/30/04 10/16/01-10/18/04

pH S.U. 7.8 7.7 7.7–7.8

DO mg/L NS 2.2 NS

ORP mV NS -86 NS

Alkalinity (as CaCO3) mg/L(a) 415 424 410–420

Hardness (as CaCO3) mg/L(a) 230 246 <240

Turbidity NTU NS 7 <1–7.2

TDS mg/L NS 462 NS

TOC mg/L 6.8 7.2 6.7–6.8

Total N (Nitrate + Nitrite) mg/L NS NS <0.05

Nitrate (as N) mg/L NS <0.04 NS

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

Ammonia (as N) mg/L NS 1.7 NS

Chloride mg/L 6.5 7.2 6.3–6.8

Fluoride mg/L NS 0.4 0.5–4.0

Sulfate mg/L 7.4 <5.0 7.0–14.0

Silica (as SiO2) mg/L 24.0 26.6 23.0–24.0

Orthophosphate (as PO4) mg/L 0.02 <0.1 NS

As (total) μg/L 39.0 41.7 34.0–43.0

As (soluble) μg/L NS 32.9 NS

As (particulate) μg/L NS 8.8 NS

As(III) μg/L 39 31.9 NS

As(V) μg/L <0.1 1.0 NS

Fe (total) μg/L 1,400 1,344 1,200–1,500

Fe (soluble) μg/L NS 1,359 NS

Mn (total) μg/L 24.0 27.0 22.0–25.0

Mn (soluble) μg/L NS 28.0 NS

U (total) μg/L NS <0.1 NS

U (soluble) μg/L NS <0.1 NS

V (total) μg/L NS <0.1 NS

V (soluble) μg/L NS <0.1 NS

Na mg/L 87 87 84–89

Ca mg/L 46 56 44–48

Mg mg/L 28 26 26–29

Ra-226 pCi/L NS <1.0 NS

Ra-228 pCi/L NS <1.0 <0.77(d)

Gross-Alpha pCi/L NS NS 1.6–2.7(d)

Gross-Beta pCi/L NS NS <1.1–1.5(d)

Radon pCi/L NS NS 358–531(d)

(a) Provided to EPA for demonstration study site selection.

(b) Water from Well No. 3.

(c) Water from Wells No. 3 and 4 after chlorine, fluoride, and polyphosphate addition.

(d) Radiochemistry based on data collected from 12/14/92 through 10/18/04.

NS = Not Sampled; MDH= Minnesota Department of Health; TDS = total dissolved solids; 

TOC = total organic carbon.
19

level was elevated at 0.90 mg/L (as PO4) and could compete with arsenic for available adsorption sites 

onto iron solids and AD-33 media. 

Other Water Quality Parameters. Alkalinity, hardness, sodium, and total dissolved solids (TDS) levels 

in source water were all elevated. Alkalinity values ranged from 415 to 424 mg/L (as CaCO3); hardness 

values ranged from 230 to 246 mg/L (as CaCO3); and sodium and TDS concentrations (in the August 30, 

2004, sample) were 87 and 462 mg/L. Other water quality parameters, including nitrate, nitrite, chloride, 

fluoride, uranium, and vanadium, were below their respective detection limits or SMCLs. Radium was 

measured at less than the detection limit of <1.0 pCi/L. 

4.1.2 Treated-Water Quality and Distribution System. Historic water samples were taken from 

both Wells No. 3 and 4, but following chlorination, fluoridation, and polyphosphate addition; therefore, 

the analytical results obtained from the Minnesota Department of Health (MDH) are included in Table 4-

1 as distribution water data. These water samples were collected from residences, businesses (stores), city 

hall, and the treatment plant from October 16, 2001, through October 18, 2004. 

Historic arsenic levels detected within the distribution system ranged from 34.0 to 43.0 μg/L; iron levels 

ranged from 1,200 to 1,500 μg/L, and manganese levels ranged from 22 to 25 μg/L. These concentrations 

were similar to those measured in source water. Results of other water quality parameters measured 

historically also were very close to those found in the source-water samples collected by the facility and 

Battelle. 

The distribution system at Stewart, MN is supplied only by Wells No. 3 and 4. Water from Wells No. 3 

and 4 is blended within the distribution system and the 65,000-gal water tower. Based on the distribution 

system blueprint, the mains for the water distribution system are primarily constructed of 6-in to 8-in cast 

iron. Other connections within the distribution system include 3⁄4-in to 2-in galvanized iron, 2-in copper, 

and 2-in polyvinyl chloride (PVC) piping. Three locations were selected for both baseline and 

distribution system sampling after system startup. The locations were selected as part of the city’s 

historic sampling network for LCR. Compliance samples also included quarterly sampling for arsenic,

coliform, total chlorine residual, and fluoride and annual sampling for nitrate, volatile organic compounds 

(VOCs), trihalomethanes (THMs), haloacetic acids (HAA5), turbidity, TOC, alkalinity, and 

radionuclides. 

4.2 Treatment Process Description

The 250-gpm treatment system at Stewart, MN, consisted of pre-treatment for iron removal, followed by 

adsorption with AD-33 media for arsenic removal (Figure 4-6). This section provides a detailed 

description of the Siemens Type II AERALATER® system for iron removal and AdEdge APU-300 

system for arsenic adsorption. 

Due to elevated iron levels in source water, the adsorption system was preceded by a Siemens Type II 

AERALATER® system for iron (and some arsenic) removal via oxidation and filtration. Figure 4-7 

shows the 11-ft-diameter AERALATER® system, which is a packaged unit for oxidation, detention, and 

gravity filtration. The AERALATER® system included an aeration chamber, a detention tank, and four 

filter cells. The treatment processes were permanganate oxidation (with the oxidant added at inlet piping 

to the AERALATER® system), aeration, adsorption/co-precipitation of As(V) onto/with iron solids, and 

gravity filtration with anthracite and silica sand. The filtration media are approved for use in drinkingwater applications under NSF International (NSF) Standard 61. More details on the Siemens’ Type II 

AERALATER® system are provided below. 
20

Figure 4-6. Schematic of AERALATER® and APU-300 Systems at Stewart, Minnesota 

Figure 4-7. AERALATER® (left) and APU-300 Systems (right) at Stewart, Minnesota
21

The soluble As(V) that remained in the treated water after the AERALATER® system was further treated 

by the AdEdge APU-300 system. Designed for arsenic removal for small systems in the flow range of 10 

to 300 gpm, the APU series is a fixed-bed adsorption system. As groundwater is pumped through fixedbed pressure vessels, soluble arsenic is adsorbed onto the media, thus reducing the soluble arsenic 

concentration to below 10 μg/L MCL. The APU-300 adsorption system consisted of two 63-in-diameter, 

86-in-tall vessels configured in parallel (see Figure 4-7). Each vessel contained 64 ft3 of pelletized 

Bayoxide® E33 media (branded as AD-33 by AdEdge). This iron-based adsorptive media was developed 

by Bayer AG for the removal of arsenic from drinking-water supplies. Table 4-2 presents the physical 

and chemical properties of the media. The AD-33 media is delivered in a dry crystalline form and listed 

by NSF under Standard 61 for use in drinking water applications. AD-33 is available in both granular and 

pelletized forms. The pelletized media used at the Stewart, MN site is 25% denser than the granular 

media (35 vs. 28 lb/ft3

). Both media are reported by the vendor to have similar arsenic adsorption 

capacities on a per pound basis. After reaching its capacity, the spent media would be removed and 

disposed of as nonhazardous waste after passing EPA’s toxicity characteristic leaching procedure (TCLP) 

test. The media life depends on the arsenic concentration, pH, and concentrations of interfering ions in 

the influent water. 

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

Parameter Value

Physical Properties

Matrix Iron oxide/Hydroxide

Physical Form Dry pelletized media

Color Amber/rust

Bulk Density (lb/ft3) 35

BET Surface Area (m2/g)(a) 142

Attrition (%)(a) 0.3

Moisture Content (%) 5% by weight

Particle Size Distribution

(U.S. Standard Mesh) 14 × 18

Crystal Size (Å)(a) 70

Crystal Phase(a) α-FeOOH

Chemical Analysis(a)

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

 Note: BET = Brunauer, Emmett, and Teller Method. 

(a) For dry granular media. 

Data Source: Bayer AG. 
22

Table 4-3 presents design features of the treatment system at Stewart, MN. The major process 

components of the treatment system are described as follows:

• Intake. Source water was pumped from Wells No. 3 and 4 alternately, and fed into the entry 

piping of the Siemens Type II AERALATER® unit. The well pumps were turned on and off 

based on the low- and high-level settings of 23 and 27 ft of water, respectively, in the water 

tower.

• Oxidation. The original design called for the use of a 2% KMnO4 solution at a target dosage 

of 0.5 mg/L (as Mn) to oxidize As(III) and Fe(II). Before system startup, modifications were

made by the city to use a 20% NaMnO4 solution instead. The NaMnO4 solution was fed into 

the system with a 1 gal/hr (gph) electronic positive displacement metering pump. In addition 

to the metering pump with adjustable stroke length and speed, the chemical feed system 

included a 150-gal polyethylene day tank and a 1/3-hp propeller tank mixer. The addition of 

NaMnO4 was discontinued at the initial stage of the performance evaluation study (around 

February 14, 2006) because oxidation of As(III) was accomplished via naturally mediated 

processes without the use of any oxidant.

• Iron Removal. Siemens’ Type II AERALATER® was used as a pretreatment step for iron 

removal. Constructed of carbon steel, the 11-ft-diameter package unit was designed to allow 

oxidation, detention, and gravity filtration to all occur in a single unit. The system 

components were assembled in a stacked circular configuration, with an aeration chamber on 

the top, a detention tank in the middle, and four filter cells in the base (Figure 4-8). Details of 

these process components are described below: 

o Aeration. Air for the aluminum aeration unit was supplied by a 1⁄2-hp induced-draft air 

blower with a capacity of 855 ft3

/min (cfm) at a 3/8-in static pressure. The influent water 

was aerated as it passed over a network of 11⁄4-in PVC slats supported by a stainless-steel 

grid.

o Contact. The 11-ft-diameter by 11.5-ft-high steel detention tank provided 34 min of 

contact time to improve the formation of filterable iron flocs. The total detention time of 

34 min was based on the total volume of 8,550 gal in the detention tank, the freeboard 

above the filter, and the design flowrate of 250 gpm. 

o Filtration. The four filter cells sitting at the base of the circular unit had a total crosssectional area of 95 ft2

. Therefore, operating the system at the design flowrate of 250 

gpm would result in a hydraulic loading rate of 2.6 gpm/ft2

. The filtration bed in each

filter cell consisted of one each 12-in layer of 0.6 to 0.8 mm anthracite and 0.45 to 0.55 

mm sand, which were supported by a 14-in layer of gravel underbedding. A steel plate 

underdrain with media-retaining strainers was located under the gravel. 

o Backwash. The filter cells were backwashed manually once per week to remove filtered 

particles from the filter media (the system did not have automatic backwash capabilities). 

Each cell was backwashed individually at 285 gpm (or 12 gpm/ft2

) using filtered water 

from the other cells. To initiate the manual backwash, the influent valve on the first cell 

was closed and the corresponding backwash valve was opened. The backwash was 

continued until visual observation indicated that the backwash wastewater had reached a

“light straw” color. As a result, the duration of the backwash varied based on operator 

observations. Upon completion, the backwash valve was closed and the influent valve on 

the first cell was re-opened. The same procedure was followed for the remaining filter 
23

Table 4-3. Design Specifications of Type II AERALATER® and APU-300 Systems 

Parameter Value Remarks

Preoxidation

Oxidant 2% KMnO4 Changed to 20% NaMnO4 by city 

before system startup

AERALATER® System

Design Flowrate (gpm) 250 –

AERALATER® Diameter (ft) 11 –

AERALATER® Height (ft) 26

Aerator Cross-Sectional Area (ft2) 95 –

Detention Tank Size (ft) 11 D × 11.5 H –

Detention Tank Volume (gal) 8,550 Including freeboard above filter

Detention Time (min) 34 –

Media Volume (ft3) 190 24-in bed depth (12-in anthracite and 

12-in sand)

Hydraulic Loading Rate to Filter (gpm/ft2) 2.6 –

Backwash Flowrate (gpm) 285

Backwash Hydraulic Loading (gpm/ft2) 12 –

Backwash Frequency (time/week) 1 –

Backwash Duration (min) ~8 Variable based on visual observation

Wastewater Production (gal/filter cell) 2,250 Per vendor estimate

APU-300 Adsorbers

Vessel Size (in) 63 D × 86 H –

Cross-Sectional Area (ft2/vessel) 21.6 Based on 62-in inner diameter

Number of Vessels 2 –

Configuration Parallel –

Media Type AD-33 Pelletized media

Media Volume (ft3) 128 36-in bed depth or 64 ft3/vessel

Pressure Drop (psi) 4 psi Across a clean bed

APU-300 Service

Design Flowrate (gpm) 250 –

Hydraulic Loading (gpm/ft2) 5.8 –

EBCT (min) 3.8 –

Estimated Working Capacity (BV) 82,500 Projected by vendor, 1 BV = 958 gal

Throughput to Breakthrough (gal) 79,000,000 –

Average Use Rate (gal/day) 48,600 –

Estimated Media Life (month) 53 Estimated frequency of change-out at 

13.5% utilization

APU-300 Backwash

Pressure Differential Setpoint (psi) 10 –

Backwash Flowrate (gpm) 200

Backwash Hydraulic Loading Rate (gpm/ft2) 9.3 –

Backwash Frequency (per quarter) 1 Per vendor recommendations

Backwash Duration (min/vessel) 15 –

Fast Rinse Duration (min/vessel) 5 –

Wastewater Production (gal/vessel) 4,000 –
24

Figure 4-8. Schematic of Type II AERALATER® System (based on general 

arrangement drawing provided by Siemens) 

 

cells. All filter cells had to be backwashed on the same day to ensure consistent filter

performance. After all four cells were backwashed, the system effluent valve was reopened and the system returned to service. The backwash wastewater produced was

discharged to a sump and then drained by gravity to two backwash wastewater holding 

tanks before being pumped to the sewer system. 

• Adsorption. The AdEdge APU-300 system was fed by two 15-hp vertical end suction highservice pumps to provide pressurized flow to the water tower rated at 210 gpm at 145 ft total 

dynamic head (TDH). The high-service pumps were controlled to start and stop operations 

based on the water level in the AERALATER® detention tank. The APU-300 adsorption 

system consisted of two 63-in-diameter, 86-in-tall vessels configured in parallel, each 

containing 64 ft3 of pelletized AD-33 media supported by gravel underbedding. Figure 4-9 

shows the schematic of the APU-300 system. The adsorption vessels were constructed of 

composite fiberglass with a polyethylene liner and rated for 150 pounds per square inch (psi) 

working pressure. The system was skid-mounted and piped to a valve rack mounted on a 

polyurethane-coated, welded frame. The service, backwash, and media replacement are 

described in more detail below. 

 

o Service. Water flowed downward through the packed AD-33 media beds. Flow to each 

vessel was measured and totalized to record the volume of water treated. The pressure 

differential through each vessel also was monitored. Based on a design flowrate of 250 

gpm, the empty bed contact time (EBCT) for each vessel was 3.8 min, and the hydraulic 

loading to each vessel was approximately 5.8 gpm/ft2

.
25

Figure 4-9. Schematic of APU-300 System (Based on Process and 

Instrumentation Diagram Provided by AdEdge) 

 

o Backwash. Based on a set time period or a set pressure differential, the adsorption 

vessels were taken off-line one at a time for a manual backwash, using source water from 

the wells. The system was equipped with an automatic backwash trigger based on time 

or differential pressure, but this feature was disabled. The purpose of the backwash was 

to remove particulates and media fines built up in the beds and to uncompress the media 

beds. While one vessel was backwashed, the other vessel remained in service. Each 

vessel was backwashed at a flowrate of approximately 200 gpm (or 9.3 gpm/ft2

). The 

backwash wastewater generated was discharged to a sump and then drained by gravity to 

two 13,000-gal backwash wastewater holding tanks before being pumped to the sewer 

system. Each holding tank was equipped with a 3-hp submersible centrifugal sludge 

pump rated for 50 gpm at 20 ft TDH. 

o Media Replacement. During the performance evaluation study, the adsorption media 

was not exhausted, so the media was not replaced. When the AD-33 media arsenic 

removal capacity is exhausted, the spent media will be removed from the vessels and 

disposed offsite. Virgin media is then loaded back into each vessel. Based on the 

vendor’s estimate, the media will be changed out after treating approximately 79 million 

gal or 82,500 BV, given influent arsenic concentrations from 20 to 27 μg/L. 

• Post-Treatment Chemical Feed. After the APU-300 system, the treated water underwent

post-chlorination, fluoridation, and polyphosphate addition. Post-chlorination was carried out 

with a gas chlorine injection system, which consisted of two 150-lb chlorine gas cylinders, a 

digital, dual-cylinder scale rated for a capacity of 349 lb, a flow controller, and a 3-hp 

chlorine booster pump. Post-chlorination helped maintain a target total chlorine residual

level of 1.1 mg/L (as Cl2) in the distribution system. Fluoride was added at a target level of 

1.3 mg/L, using a 0.58-gph maximum capacity, electronic, positive-displacement metering 

pump and a 65-gal polyethylene storage tank. Blended polyphosphates were added with a 
26

0.58-gph maximum capacity, electronic, positive-displacement metering and a 50-gal 

polyethylene storage tank for corrosion control. 

4.3 Treatment System Installation

4.3.1 Permitting. The system engineering package, prepared by AdEdge and Bolton & Menk, 

Inc., included (1) a system design report and associated general arrangement as well as piping and 

instrumentation diagrams (P&IDs) for the Type II AERALATER® and APU-300 systems; (2) electrical 

and mechanical drawings and component specifications, and (3) building construction drawings detailing 

connections from the system to the entry piping and the city’s water and sanitary sewer systems. The 

engineering package was certified by a Professional Engineer registered in the State of Minnesota and 

submitted to MDH for review and approval on March 21, 2005. After MDH’s review comments were 

incorporated, the revised package was resubmitted on May 20, 2005. MDH issued a water supply 

construction permit on June 20, 2005, and system fabrication began thereafter. 

4.3.2 Building Construction. The city applied for building construction permit, which was issued 

on June 13, 2005. Building construction began on July 1, 2005, and was completed on February 9, 2006. 

The concrete block building had a 55.3-ft × 24.7-ft footprint with a sidewall height of 14 ft (see Figure 4-

10). The AERALATER® aeration tower protrudes through the building roof where two 16-in-diameter 

access hatches also were installed for adsorptive media loading. In addition to housing the treatment 

system, the building contains a fluoride room, a chemical room, a bathroom, and some office/laboratory 

space. Wastewater discharge is facilitated with a 4-ft × 2-ft × 2-ft (120 gal) underground sump that

empties by gravity into two 12,500-gal, pre-cast concrete holding tanks. Each holding tank is equipped 

with a 2-hp sump pump with a design capacity of 50 gpm for transferring backwash wastewater to the 

sanitary sewer system. 

4.3.3 System Installation, Shakedown, and Startup. Although building construction was 

ongoing, the site was prepared for delivery of the treatment systems by September 2005. Both units were 

shipped and arrived prior to roof construction to facilitate placement of the units in the building. The 

APU-300 system arrived on September 6, 2005, and the AERALATER® system arrived on September 16, 

2005. The vendor, through its subcontractor, off-loaded and installed the systems, including connections 

to the entry and distribution piping and electrical interlocks. Figure 4-11 shows the off-loading of the 

AERALATER® unit by crane. 

Subsequent to the treatment system delivery, construction work to finish the building and associated 

piping and electrical infrastructure continued through February 9, 2006. Siemens arrived onsite for 

mechanical checkout of the AERALATER® installation on January 4, 2006. AdEdge was onsite from 

January 4 to 11, 2006, for mechanical checkout of the APU-300 installation and startup activities, 

including hydraulic testing, media loading, initial backwashing, and system disinfection. After the 

bacteriological test results were received and passed, the systems began to operate manually, with the 

treated water sent to the distribution system starting on January 18, 2006. Manual operation of the 

systems continued until the city’s contractor completed the electrical wiring and control setpoints for the 

well pumps and high-service pumps. The operator began to record operational data on January 30, 2006. 

Battelle staff traveled to Stewart, MN to perform system inspections and operator training from February 

1 to 3, 2006, with the first set of treatment plant samples taken on February 2, 2006. A punch list was 

identified during the trip and later forwarded to AdEdge on February 16, 2006. The issues to be 

addressed included replacement of a headloss gauge on the AERALATER® system; installation of a 

combined effluent sample tap downstream of the APU-300 system and upstream of post-chlorination; 

disabling of the APU-300 system automatic backwash; calibration of flow meters for the APU-300
27

Figure 4-10. Building with AERALATER® Tower (top), Backwash Sump (bottom left), 

and Backwash Wastewater Holding Tanks (bottom right) at Stewart, Minnesota 

Figure 4-11. Off-Loading and Placement of AERALATER® Unit at Stewart, Minnesota 
28

System; and changes of combined flow totalizer programmable logic controller (PLC) programming for 

the APU-300 system. The vendor subsequently resolved these issues by August 2006.

4.4 System Operation

System operation data were tabulated and are attached as Appendix A. Key parameters are summarized 

in Table 4-4. From February 2, 2006, to February 28, 2007, the system operated for 1,821 hr, producing 

20,441,000 gal based on wellhead flow totalizer readings. The wells were operated on an alternating 

basis, with Well No.3 operating for 908 hr and Well No. 4 for 913 hr. The average daily demand was 

52,418 gal, and the average operation time was 4.7 hr/day. Given the full design capacity of 250 gpm 

(360,000 gpd), this represents an average hydraulic utilization rate of 15% on a daily basis. The system 

operation is discussed below in terms of the hydraulic performance of the AERALATER® and APU-300 

systems.

Table 4-4. Summary of Treatment System Operation at Stewart, Minnesota

Operational Parameter Values

Operational Period February 2, 2006 to February 28, 2007

Wellhead Operations Well No.3 Well No.4 Total

Total Operating Time (hr) 908 913 1821

Average Operating Time (hr/day) 2.33 2.34 4.7

Throughput (kgal) 10,421 10,020 20,441

Average Demand (gpd) 26,700 25,718 52,418

AERALATER® Iron Removal Operations Well No.3 Well No.4 Total

Average Flowrate [Range] (gpm)(a) 191 [100–217] 184 [127–248] –

Average Detention Time [Range] (min) 45 [39–86] 46 [34–67] –

Average Filtration Rate [Range] (gpm/ft2) 2.0 [1.1–2.3] 1.9 [1.3–2.6] –

Average ∆p across Filter (ft H2O) – – <1.5

Average Throughput Between Backwash [Range] 

(kgal)

– – 368 [138–739]

Average Run Time Between Backwash [Range] (hr) – – 33 [13–68]

Average Backwash Frequency [Range] 

(day/backwash)

– – 7 [3–15]

APU-300 Adsorption Operations Tank A Tank B Total

Throughput (kgal) 10,181 10,289 20,470

Throughput (BV) 21,264 21,489 21,377

Average Flowrate [Range] (gpm)(b) 88 [66–104] 88 [62–103] 176 [128–207]

Average EBCT [Range] (min) 5.4 [4.6–7.2] 5.4 [4.6–7.7] 5.4 [4.6–7.5]

∆p across tank/system (psi) 0 0 1 to 2

(a) Average flowrate based on readings of individual wellhead mechanical flow totalizers and hour meter.

(b) Average flowrate based on weekly readings of instantaneous flowrate from each vessel using digital 

paddlewheel flow meters. 

4.4.1 AERALATER® Operations. With an average flowrate of 188 gpm between the two wells, 

the AERALATER® system was run at approximately 75% of its full design capacity of 250 gpm. The 

flowrate to the AERALATER® system varied slightly, based on which well pump was operational. When 

Well No. 3 was operational, flowrate readings ranged from 100 to 217 gpm and averaged 191 gpm. At 

these flowrates, the detention times ranged from 39 to 86 min and averaged 45 min (compared to a design 

value of 34 min); the hydraulic loading rates to the filter ranged from 1.1 to 2.3 gpm/ft2

 and averaged 2.0 

gpm/ft2

 (compared to the design value of 2.6 gpm/ft2). When Well No. 4 was operational, the flowrate 

readings ranged from 127 to 248 gpm and averaged 184 gpm. This corresponded to a detention time of 
29

34 to 67 min (averaged 46 min) and a hydraulic loading rate of 1.3 to 2.6 gpm/ft2 (averaged 1.9 gpm/ft2). 

In general, the detention time was longer and the hydraulic loading rate was lower than the respective 

design values. 

During the 1-year performance study, 54 backwash events took place. The operator manually 

backwashed the AERALATER® system approximately once per week, with the number of days per 

backwash ranging from 3 to 15. During the filter run cycles, less than 1.5 ft of water head loss was 

measured across the filter media beds. The run times between two consecutive backwash events ranged 

from 13 to 68 hr, and the average run time was 33 hr. The throughput between two consecutive backwash 

events ranged from 138,100 to 739,000 gal, and the average throughput was 368,000 gal. The throughput 

to the filter varied, based on the amount of run time required to meet the water demand during the week. 

4.4.2 APU-300 Operations. The APU-300 system processed approximately 20,470 kgal, or 

21,377 BV of water, from February 2, 2006, through February 28, 2007, based on readings from the 

individual digital paddle-wheel flow totalizers installed on the effluent piping downstream from the 

adsorption vessels. In general, the throughput readings obtained via the paddle-wheel flow totalizers were 

consistent with those from the totalizers at the wellheads, with relative error within 2.1%, given the 

wellhead throughput and estimated backwash wastewater volume. Based on the readings for the 

individual vessels, Vessel A processed 21,264 BV (10,181,000 gal) of water and Vessel B processed 

21,489 BV (10,289,000 gal). 

Each week, the operator recorded the instantaneous flowrates through Vessels A and B based on the 

digital paddlewheel flow meter for each vessel. As shown in Figure 4-12, the flowrates through Vessels 

A and B were generally at the same level. The average flowrate was 88 gpm for both Vessels A and B, 

indicating balanced flow between them. According to the flowrates measured, the system operated at 

approximately 70% of its design capacity. The EBCTs for both Vessels A and B averaged 5.4 min, which 

is higher than the design value of 3.8 min. Throughout the performance evaluation study, the differential 

pressure across the adsorption system remained low at 1.0 to 2.0 psi, indicating effective particulate 

removal by the AERALATER® system. The four manual backwash events conducted during the 

performance evaluation study are discussed in detail below.

4.4.3 Backwash Operations. Both the AERALATER® and APU-300 systems required backwash. 

Because the AERALATER® system was used as pre-treatment to remove iron particles, it was

backwashed as often as once per week. The APU-300 system did not experience elevated differential 

pressures above the 10-psi setpoint; it was, therefore, backwashed only four times during the 1-year 

performance evaluation study. Both units used treated water for backwash. Table 4-5 summarizes key 

operational parameters related to system backwash for both systems. 

The 54 manual backwash events of the AERALATER® system generated approximately 406,400 gal of 

backwash wastewater, based on the readings obtained via the wellhead totalizer readings before and after 

backwash. The amount of wastewater produced represents 2% of the volume of water processed during 

this time period. The average backwash flowrate was 215 gpm, or 9.1 gpm/ft2

, which was about 25% 

lower than the design value of 285 gpm or 12 gpm/ft2

. The duration for each backwash event (for all four 

cells) ranged from 15 to 60 min and averaged 36 min, which is slightly higher than the vendor-provided 

value of 8 min/cell or 32 min/event. The backwash duration varied because backwash was manually 

controlled by the operator based on visual observations of the color of backwash wastewater. The 

backwash was discontinued when the backwash wastewater had reached a “light straw” color. The 

average amount of wastewater produced was 7,619 gal per backwash event, compared to 9,000 gal per 

event specified by the vendor. 
30

0

20

40

60

80

100

120

1/30/20062/13/20062/27/20063/13/20063/27/20064/10/20064/24/2006

5/8/2006

5/22/2006

6/5/2006

6/19/2006

7/3/2006

7/17/20067/31/20068/14/20068/28/20069/11/20069/25/200610/9/2006

10/23/2006

11/6/2006

11/20/2006

12/4/2006

12/18/2006

1/1/2007

Flowrate (gpm)

Vessel A

Vessel B

Figure 4-12. Instantaneous Flowrates Through Adsorption Vessels A and B

Table 4-5. Summary of Backwash Operations at Stewart, Minnesota 

Parameter Value

AERALATER® Backwash Operations

Total Number of Backwash Events 54

Total Volume of Backwash Wastewater Produced (gal) 406,400 

Average Frequency of Backwash [Range] (day) 7 [3–15]

Average Flowrate [Range] (gpm) 215 [157–387]

Average Hydraulic Loading Rate [Range] (gpm/ft2) 9.1 [6.6–16.3]

Average Duration [Range] (min) 36 [15–60]

Average Backwash Wastewater Volume [Range] (gal/event) 7,619 [3,600–12,400]

APU-300 Backwash Operations

Total Number of Backwash Events 4

Total Volume of Backwash Wastewater (gal)(a) 25,415

Average Backwash Wastewater Volume [Range](gal/vessel)(b) 2,963 [2,578–3,392]

(a) Backwash wastewater volumes, including fast rinse water.

(b) Calculations do not include Vessel A backwash that was initiated and then 

halted on February 2, 2006.

The recommended AD-33 media backwash frequency was once every 45 days. The system was equipped 

with an automatic backwash control that initiated backwash either by a 45-day time trigger or by a 

differential pressure trigger set at 10 psi across each vessel. Because of the process control configuration 

of the well pumps and high-service pumps, the automatic backwash feature was disabled. Per 

communication with the operator during the startup trip in February 2006, it was determined that there 

was no wiring connection between the APU-3 PLC and the city’s PLC that controlled the well pumps and 
31

high-service pumps. Therefore, if an automatic backwash was called for while the well pumps and highservice pumps were off, adequate flow would not be available to the APU-300 units to accomplish the 

backwash. For this reason, the automatic backwash capability was disabled in the PLC on February 2, 

2006, and the operator performed each backwash of the APU-300 unit with a manual trigger. The four 

manual backwashes occurred on February 2, February 22, and October 12, 2006, and on January 16, 2007 

as described below. 

The backwash on February 2, 2006, occurred during startup activities to confirm proper installation and 

setup of the system. During this event, it was noted that further adjustments were required to the PLC 

settings and to the backwash flowrate to meet design specifications. During the backwash of Vessel A, a 

higher than specified backwash flowrate of greater than 275 gpm (or 13 gpm/ft2

) was noted, along with 

visual observation of media loss discharged through the backwash line. Shortly after initiation of 

backwash, the operator throttled back the flowrate to approximately 181 gpm (or 8.6 gpm/ft2

), a value

below the design flowrate of 200 gpm (or 9.5 gpm/ft2

). It also was noted that the backwash and fast rinse 

time setpoints required adjustment in the PLC. Therefore, the backwash of Vessel A was halted after 28 

min to make these adjustments. The backwash time was changed from 1,200 sec (20 min) to 900 sec (15 

min) to match the design value of 15 min. The fast rinse time also was adjusted from 1,500 sec (25 min) 

to 180 sec (3 min) to be closer to the 5-min design value. During this backwash, Vessels A and B 

generated 4,668 and 2,979 gal of wastewater, respectively. The operator subsequently performed manual 

backwash events on February 22, 2006, October 12, 2006, and January 16, 2007 that generated 3,026, 

2,857, and 2,578 gal of wastewater from Vessel A, respectively, and 2,799, 3,392, and 3,116 gal of 

wastewater from Vessel B, respectively. Except for Vessel A on February 2, 2006, backwash produced 

smaller amounts of wastewater than the design value of 4,000 gal/vessel. During the 1-year system 

operation, backwash of the adsorption vessels produced 25,415 gal of wastewater, which represents

0.12% of the total amount of water processed. 

4.4.4 Residual Management. The residuals produced by the treatment system at Stewart, MN 

included backwash wastewater produced from the gravity filter and adsorption vessels. The wastewater

produced was discharged to the building sump, which emptied by gravity to two holding tanks before 

being pumped to the sanitary sewer. The total volume of wastewater produced was 431,815 gal, which 

represents a wastewater generation rate of approximately 2.1%. The AD-33 media was not exhausted 

during the 1-year performance evaluation study, so there were no residuals associated with spent media.

4.4.5 Reliability and Simplicity of Operation. No significant scheduled or unscheduled 

downtime was required during the 1-year performance evaluation study. The simplicity of system 

operation and operator skill requirements is discussed, including pre- and post treatment requirements, 

levels of system automation, operator skill requirements, preventive maintenance activities, and frequency 

of chemical/media handling and inventory requirements.

4.4.5.1 Pre- and Post-Treatment Requirements. Due to the high TOC and ammonia levels in source 

water, KMnO4, instead of chlorine, was originally selected to oxidize As(III) and Fe(II). However, prior 

to system startup, the operator indicated his preference of using liquid NaMnO4 instead of powdered 

KMnO4. Subsequently, a modification of the initial design was implemented by the city in December 

2005 to include the use of a 20% liquid NaMnO4 solution with a 1-gph chemical-metering pump. To 

achieve the target dosage, the chemical-metering pump operated with a 25% stroke and 2.5% speed

settings. Based on measurements with a calibration cylinder, these settings corresponded to a 0.092-gph

application rate, equivalent to only 9.2% of the pump’s maximum capacity. The pump size and low 

settings contributed to difficulties in controlling the NaMnO4 dose, and the pump appeared to have lost 

prime after February 2, 2006. Without NaMnO4 injection, it was observed that iron continued to be 

removed, presumably by aeration and that As(III) continued to be oxidized to As(V) via unidentified 
32

processes within the AERALATER® gravity filter (see Section 4.5.1.1). No post-treatment requirements 

existed related to the arsenic-removal system. 

4.4.5.2 System Automation. The wellhead and high-service pumps were automatically controlled by 

a PLC installed by the city. The AERALATER® system did not require significant automation other than 

the level sensors in the detention tank that controlled operation of the high-service pumps. The 

AERALATER® system did not include automatic backwash triggers, which could be added as a system 

upgrade. Because the system needed to be backwashed only weekly, the lack of automation for the 

gravity filter backwash was not a significant inconvenience. However, this lack of automation would 

likely be an issue at a site requiring more frequent backwash. As noted in Section 4.4.3, it was necessary 

to disable the automatic backwash capability of the APU-300 system. It was determined that there was no 

wiring connection between the APU-300 PLC and the city’s PLC that controlled the well pumps and 

high-service pumps. Therefore, if an automatic backwash was called for while the well pumps and highservice pumps were off, there would not be adequate flow to the adsorption vessels to accomplish the 

backwash. The city decided not to pursue a change to the control system and to manually backwash the 

adsorption vessels when required. 

4.4.5.3 Operator Skill Requirements. Under normal operating conditions, the daily demand on the 

operator was approximately 10 min for visual inspection of the system and recording on filed log sheets 

of operational data such as pressure, volume, and flowrate. The manual backwash operations required an 

average of 31 min of the operator’s time once per week. This is equivalent to approximately 1.7 hr of 

labor per week. The operator also performed routine weekly and monthly maintenance according to the 

users’ manual to ensure proper system operation. Normal operation of the system did not appear to 

require additional skills beyond those necessary to operate the existing water supply equipment. 

The state of Minnesota has five water operator certificate class levels (A, B, C, D, and E with A being the 

highest). The certificate levels are based on education, experience, and system characteristics, such as 

water source, treatment processes, water storage volume, number of wells, and population affected. The 

water operator for the City of Stewart has a Class C certificate. Class C requires a high school diploma or 

equivalent with at least 3 years of experience in operating Class A, B, or C system or a bachelor’s degree 

from an accredited institution with at least 1 year of experience in operating a Class A, B, C, or D system. 

4.4.5.4 Preventive Maintenance Activities. Recommended maintenance activities for the 

AERALATER® system include annual inspection of the aerator internals and slats to monitor iron buildup and perform cleaning if necessary; a complete interior inspection every 2 years by Siemens; and 

mechanical and electrical aerator blower checks if performance issues arise. Preventive maintenance 

tasks for the APU-300 system recommended by the vendor include monthly inspection of the control 

panel; quarterly checking and calibration of flow meters; biannual inspection of actuator housings, fuses, 

relays, and pressure gauges; and annual inspection of the butterfly valves. The vendor recommended 

checking the actuators at each backwash event to ensure that the valves were opening and closing in the 

proper sequence. Further, inspection of the adsorber laterals and replacement of the underbedding gravel 

were recommended to be concurrent with the media replacement. During the 1-year performance 

evaluation study, two relays that controlled the electrically actuated values on the APU-300 system were 

replaced, using spare relays in the PLC panel. No other significant repair and maintenance activities were 

reported during the period. 

4.4.5.5 Chemical-Handling and Inventory Requirements. No chemical-handling requirements were 

necessary because iron removal occurred by aeration, and because oxidation of As(III) to As(V) was 

occurring within the AERALATER® filter (see Section 4.5.1.1). Chemical handling of NaMnO4 was

required only initially from January 18 to February 2, 2006, during the system shakedown stage.
33

4.5 System Performance

The performance of the AERALATER® and APU-300 systems was evaluated based on analyses of water 

samples collected from the treatment plant, system backwash, and distribution system. 

4.5.1 Treatment Plant. The treatment plant water was sampled at six locations (IN, AC, AF, TA, 

TB, and TT) on 49 occasions (including three duplicate events) with field speciation performed during 13 

of the 49 occasions. Field-speciation samples were collected at the IN, AC, AF, and TT sampling 

locations monthly. Table 4-6 summaries analytical results for arsenic, iron, and manganese. Table 4-7 

summarizes results of the other water quality parameters. These tables include data from all 49 sampling 

occasions, except for those collected at AC, AF, TA, TB, and TT on February 2, 2006, when NaMnO4

was added. The February 2, 2006, results are included in Appendix B, which contains a complete set of 

analytical data. Results of the water samples collected throughout the treatment plant are discussed 

below. 

4.5.1.1 Arsenic. Figure 4-13 contains four bar charts showing the concentrations of total As, 

particulate As, soluble As(III), and soluble As(V) at the IN, AC, AF, and TT sampling locations for each 

speciation sampling event. Total arsenic concentrations in source water ranged from 31.4 to 56.4 μg/L 

with 27.6 to 44.0 μg/L existing as soluble As(III). Therefore, As(III) was the predominant species. 

Lower levels of soluble As(V) and particulate arsenic also were present, averaging 5.1 and 6.4 μg/L, 

respectively. Total arsenic concentrations measured during the performance evaluation study varied in a 

wider range than those measured historically (39.0 to 41.7 μg/L), as shown in Table 4-1. 

Arsenic Removal with NaMnO4 Addition. Upon completion of shakedown, the treatment system was 

operated with NaMnO4 addition for soluble As(III) and Fe(II) oxidation. However, the addition was 

disrupted due to loss of prime within 1 week after the first sampling and speciation event on February 2, 

2006, based on the measurements of solution level and consumption rate in the chemical day tank. 

For the sampling event on February 2, 2006, out of 52.3 μg/L of total arsenic in source water, 39.8 μg/L 

were present as soluble As(III). At 1,240 μg/L, iron existed almost entirely as soluble iron. The soluble 

As(III) and Fe(II) concentrations were decreased to 4.2 and < 25 μg/L, respectively, following NaMnO4 

preoxidation, aeration, and detention. About 0.51 mg/L of NaMnO4 (as Mn) was believed to have been 

added to source water based on the difference in total manganese concentrations between the IN and AC 

sampling locations. This amount was close to the stoichiometrically estimated dosage of 0.42 mg/L (as 

Mn) based on the February 2, 2006, source-water data. Therefore, the amount of NaMnO4 added should 

be sufficient to oxidize most, if not all, As(III) and Fe(II) in source water. It should be noted, however, 

that the NaMnO4 target dosage was estimated based mainly on the levels of soluble As, Fe, and Mn in 

source water (see data in Appendix B) and that the elevated TOC level at 6.7 mg/L could add to the 

oxidant demand (see Section 4.5.1.3). The As(V) thus formed, along with the pre-existing As(V), was 

adsorbed onto and/or co-precipitated with the iron solids formed during the preoxidation step, resulting in 

31.1 μg/L of particulate arsenic after the detention tank. 

The February 2, 2006, results also showed the presence of 17.0 μg/L of soluble As(V) after the detention 

tank, indicating incomplete As(V) removal by the naturally occurring iron in source water. The 

concentration ratio of soluble iron to soluble arsenic in source water was 26:1 on February 2, 2006, which 

was over the 20:1 target ratio for more effective As(V) removal via the iron-removal process (Sorg, 

2002). The relatively inefficient As(V) removal observed might have been caused by the relatively high 

pH value (8.2) and the presence in source water of competing anions (1.0 mg/L of total phosphorous [as 

PO4] and 27.6 mg/L of Si [as SiO2]) and TOC (6.7 mg/L). All could adversely impact the soluble As(V)

removal by natural iron solids. 
34 

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

Parameter

Sampling 

Location(a,c)

Number of 

Samples

Concentration (μg/L) Standard 

Minimum Maximum Average Deviation

As (total)

IN 49 31.4 56.4 44.8 7.1

AC 48 29.9 56.9 43.8 6.3

AF 48 19.8 42.7 29.0 5.2

TA 38 0.4 7.4 -

(b) -(b)

TB 36 0.3 9.2 -

(b) -(b)

TT 10 <0.1 9.8 -

(b) -(b)

As (soluble)

IN 13 34.1 48.9 40.4 4.7

AC 12 32.5 44.9 36.6 3.8

AF 12 21.9 37.4 28.0 3.9

TA 2 0.4 0.5 -

(b) -(b)

TB 0 NA NA NA NA

TT 10 <0.1 8.6 -

(b) -(b)

As (particulate)

IN 13 0.5 14.0 6.4 3.9

AC 12 <0.1 14.8 10.2 4.1

AF 12 <0.1 12.3 4.2 4.2

TA 2 <0.1 0.3 0.2 0.2

TB 0 NA NA NA NA

TT 10 <0.1 1.2 0.3 0.4

As (III) (soluble)

IN 13 27.6 44.0 35.3 5.6

AC 12 21.7 30.8 26.2 2.6

AF 12 <0.1 6.6 1.6 1.8

TA 2 0.6 1.7 -

(b) -(b)

TB 0 NA NA NA NA

TT 10 <0.1 1.1 -

(b) -(b)

As (V) (soluble)

IN 13 1.4 11.7 5.1 2.9

AC 12 6.1 23.2 10.4 4.2

AF 12 21.8 30.8 26.4 2.9

TA 2 <0.1 <0.1 -

(b) -(b)

TB 0 NA NA NA NA

TT 10 <0.1 7.5 -

(b) -(b)

Fe (total)

IN 49 993 1,491 1,188 110

AC 48 919 1,309 1,142 88.8

AF 48 <25 29.2 <25 3.2

TA 38 <25 337 <25 52.6

TB 36 <25 524 26.7 85.3

TT 10 <25 <25 <25 NA

Fe (soluble)

IN 13 412 1,335 922 283

AC 12 <25 68.5 <25 16.9

AF 12 <25 <25 <25 NA

TA 2 <25 <25 <25 NA

TB 0 NA NA NA NA

TT 10 <25 <25 <25 NA

Mn (total)

IN 49 19.6 44.3 23.6 3.5

AC 48 20.3 31.4 23.7 1.9

AF 48 21.9 47.8 27.5 5.7

TA 38 10.7 31.2 24.8 4.2

TB 36 7.2 33.2 25.8 5.2

TT 10 22.9 34.2 26.5 3.4

Mn (soluble)

IN 13 20.3 29.7 24.0 2.4

AC 12 20.3 25.6 23.4 1.7

AF 12 22.0 41.3 26.5 5.2

TA 2 17.5 26.0 21.8 6.1

TB 0 NA NA NA NA

TT 10 23.5 35.1 26.8 3.3 

(a) See Table 3-3. 

(b) Average and standard deviation not meaningful for arsenic breakthrough data.

(c) Not including results for AC, AF, TA, TB, and TT from the February 2, 2006, sampling event with NaMnO4

addition.

NA = not applicable.
35 

Table 4-7. Summary of Other Water Quality Parameter Measurements

Parameter

Sampling 

Location(a,b) Unit

Sample 

Count

Concentration Standard 

Minimum Maximum Average Deviation

Alkalinity 

(as CaCO3) 

IN mg/L 49 408 485 435 18.8

AC mg/L 48 410 487 436 19.3

AF mg/L 48 403 476 436 17.1

TA mg/L 38 400 474 431 18.1

TB mg/L 36 367 470 430 21.0

TT mg/L 10 416 469 438 20.0

Ammonia (as N)

IN mg/L 29 1.0 1.9 1.6 0.2

AC mg/L 28 1.1 1.9 1.6 0.2

AF mg/L 28 0.9 1.7 1.4 0.2

TA mg/L 19 0.6 1.4 1.1 0.2

TB mg/L 17 0.4 1.3 1.1 0.2

TT mg/L 9 1.0 2.3 1.2 0.4

Fluoride

IN mg/L 13 0.3 1.0 0.5 0.2

AC mg/L 12 0.3 0.6 0.5 0.1

AF mg/L 12 0.2 0.6 0.5 0.1

TA mg/L 2 0.4 0.4 0.4 0.0

TT mg/L 10 0.2 0.8 0.5 0.2

Sulfate

IN mg/L 13 <1 <1 <1 NA

AC mg/L 12 <1 <1 <1 NA

AF mg/L 12 <1 <1 <1 NA

TA mg/L 2 <1 <1 <1 NA

TT mg/L 10 <1 <1 <1 NA

Nitrate (as N)

IN mg/L 30 <0.05 <0.05 <0.05 0.0

AC mg/L 29 <0.05 0.1 <0.05 0.0

AF mg/L 29 <0.05 1.5 0.3 0.3

TA mg/L 19 <0.05 1.7 0.5 0.4

TB mg/L 17 0.2 1.6 0.5 0.3

TT mg/L 10 0.3 1.4 0.5 0.4

Total P (as P)

IN μg/L 49 80.9 350 301 40.9

AC μg/L 48 247 344 295 24.1

AF μg/L 48 89.3 158 112 13.2

TA μg/L 38 <10 246 26.4 40.1

TB μg/L 36 <10 336 33.0 55.0

TT μg/L 10 <10 111 37.2 32.8

Silica (as SiO2) 

IN mg/L 49 23.1 28.3 25.1 1.1

AC mg/L 48 23.1 28.2 25.0 0.9

AF mg/L 47 23.0 28.1 24.9 1.1

TA mg/L 38 23.3 28.3 25.1 1.0

TB mg/L 36 23.5 28.6 25.0 1.1

TT mg/L 10 23.7 27.0 25.2 1.0

Turbidity

IN NTU 49 4.1 15.0 6.5 2.0

AC NTU 48 7.1 15.0 9.2 1.5

AF NTU 48 0.3 8.3 0.9 1.1

TA NTU 38 0.2 2.2 0.8 0.4

TB NTU 36 0.2 3.5 0.9 0.7

TT NTU 10 0.4 1.3 0.8 0.3

TOC

IN mg/L 11 6.2 6.7 6.4 0.2

AC mg/L 11 6.2 7.0 6.5 0.3

AF mg/L 11 3.8 7.0 6.2 0.9

TA mg/L 1 6.1 6.1 6.1 NA

TT mg/L 9 3.1 6.7 6.1 1.2

pH

IN S.U. 46 7.4 8.2 7.9 0.2

AC S.U. 45 7.8 8.6 8.3 0.2

AF S.U. 45 7.7 8.9 8.1 0.2

TA S.U. 35 7.8 8.4 8.2 0.1
Table 4-7. Summary of Other Water Quality Parameter Measurements (Continued)

36

Parameter

Sampling 

Location(a,b) Unit

Sample 

Count

Concentration Standard 

Minimum Maximum Average Deviation

pH (Con’t) TB S.U. 33 7.9 8.4 8.2 0.1

TT S.U. 10 7.7 8.3 8.1 0.2

Temperature

IN °C 46 10.1 16.6 11.7 1.2

AC °C 45 10.1 13.8 11.4 0.9

AF °C 45 10.5 19.3 12.0 1.5

TA °C 35 10.6 14.3 12.0 1.1

TB °C 33 10.5 15.4 12.3 1.2

TT °C 10 10.8 13.5 11.9 0.7

DO

IN mg/L 45 0.5 2.2 1.2 0.5

AC mg/L 43 3.8 7.2 5.0 0.7

AF mg/L 43 1.6 4.9 2.6 0.8 

TA mg/L 33 1.5 6.2 2.7 0.9

TB mg/L 31 1.7 5.7 2.7 0.8

TT mg/L 10 2.2 6.8 3.0 1.4

ORP

IN mV 46 -36.6 404 216 129

AC mV 45 39.7 360 207 82.0

AF mV 45 36.6 386 186 78.0

TA mV 35 24.9 323 158 72.0

TB mV 33 23.5 321 150 68.8

TT mV 10 80.0 297 173 68.9

Total Hardness 

(as CaCO3) 

IN mg/L 13 200 238 218 13.0

AC mg/L 12 189 236 216 14.4

AF mg/L 12 206 242 219 10.3

TA mg/L 2 209 210 210 0.6

TT mg/L 10 205 247 222 13.3

Ca Hardness 

(as CaCO3) 

IN mg/L 13 88.2 127 112 10.6

AC mg/L 12 94.8 130 111 11.7

AF mg/L 12 97.2 134 113 10.0

TA mg/L 2 103 104 104 0.1

TT mg/L 10 95.2 137 115 11.5

Mg Hardness 

(as CaCO3) 

IN mg/L 13 94.0 118 107 8.6

AC mg/L 12 93.9 118 105 8.1

AF mg/L 12 92.7 117 107 6.6

TA mg/L 2 105 106 106 0.7

TT mg/L 10 94.9 119 107 6.9

(a) See Table 3-3. 

(b) Not including results for AC, AF, TA, TB, and TT from the February 2, 2006, sampling event with NaMnO4 addition.

NA = not applicable.
37 

Figure 4-13. Concentrations of Arsenic Species at Wellhead (IN), After Contact Tank (AC), 

After Filtration (AF), and After Vessels A and B Combined (TT)

Arsenic Speciation after Contact Tank (AC)

0

10

20

30

40

50

60

02/02/06 02/27/06 03/28/06 04/25/06 05/24/06 06/20/06 07/18/06 08/21/06 09/19/06 10/17/06 12/05/06 01/03/07 02/27/07

As Concentration (μg/L)

As (particulate)

As (III)

As (V)

Arsenic Speciation after Filtration (AF)

0

10

20

30

40

50

60

02/02/06 02/27/06 03/28/06 04/25/06 05/24/06 06/20/06 07/18/06 08/21/06 09/19/06 10/17/06 12/05/06 01/03/07 02/27/07

As Concentration (μg/L)

As (particulate)

As (III)

As (V)

Arsenic Speciation at the Wellhead (IN)

0

10

20

30

40

50

60

02/02/06 02/27/06 03/28/06 04/25/06 05/24/06 06/20/06 07/18/06 08/21/06 09/19/06 10/17/06 12/05/06 01/03/07 02/27/07

As Concentration (μg/L)

As (particulate)

As (III)

As (V)

Arsenic Speciation after Total Combined Effluent (TT)

0

10

20

30

40

50

60

02/02/06 02/27/06 03/28/06 04/25/06 05/24/06 06/20/06 07/18/06 08/21/06 09/19/06 10/17/06 12/05/06 01/03/07 02/27/07

As Concentration (μg/L)

As (particulate)

As (III)

As (V)
38

The results on February 2, 2006, also indicated that the gravity filter was highly effective in removing 

particulate matter, leaving only 2.7 μg/L of particulate arsenic and less than the detection limit of iron in 

the filter effluent. Also present in the filter effluent were 17.2 μg/L of soluble As(V) and 1.3 μg/L of 

soluble As(III). As expected, soluble As(V) in the filter influent was left essentially untreated. However, 

soluble As(III) concentrations were reduced from 4.2 to 1.3 μg/L across the filter bed. Conversion of 

soluble As(III) to soluble As(V) in the gravity filter also was observed during the subsequent sampling 

events after the addition of NaMnO4 had been inadvertently discontinued due to a pump issue. This 

unexpected finding is discussed in the following paragraphs. With NaMnO4 addition, the gravity filter 

achieved removal of approximately 60% total arsenic and nearly 100% total iron. 

Arsenic Removal Without NaMnO4 Addition. As noted above, after the sampling event on February 2,

2006, the NaMnO4 metering pump lost prime, thus inadvertently discontinuing NaMnO4 addition for 

soluble As(III) oxidation. The disruption of chemical addition was confirmed by both the lack of 

chemical consumption in the NaMnO4 day tank and the decrease in Mn concentrations in the AC samples 

taken after the detention tank starting from the second sampling event on February 14, 2006. 

As typified by the results of the first speciation event on February 27, 2006, since discontinuation of 

NaMnO4 addition, very little soluble As(III) conversion occurred via aeration, with 34.2 μg/L in source

water and 26.4 μg/L following aeration and detention. This observation was consistent with the general 

notion that aeration was not effective in oxidizing soluble As(III) (Ghurye and Clifford, 2001). 

Nonetheless, some soluble As(III) oxidation still occurred, with soluble As(V) concentrations increasing 

from 1.4 to 6.1 μg/L and particulate arsenic concentrations from 3.2 to 8.9 μg/L after aeration and 

detention. The amount of particulate arsenic formed via aeration was 5.7 μg/L (i.e., the difference of 3.2 

and 8.9 μg/L on February 27, 2006), compared to 22.6 μg/L (i.e., the difference of 8.5 and 31.1 μg/L) 

formed following NaMnO4 preoxidation and aeration on February 2, 2006. Note that the levels of soluble 

iron in the February 2 and 27, 2006, source-water samples were comparable at 1,159 and 855 μg/L, 

respectively. 

As discussed in the Design Manual for the Removal of Arsenic from Drinking Water Supplies by Iron 

Removal Process (Hoffman, et al., 2006), the use of a chemical oxidant and the point of chemical oxidant 

addition are critical to optimize arsenic removal via the iron-removal process. Research has shown that 

iron particles formed in the presence of soluble As(V), like the case of preoxidation with NaMnO4, had 

more capacity to remove soluble As(V) than pre-formed iron particles, as with the case of aeration. 

Edwards (1994) reported that pre-formed iron hydroxides only reached one-fifth to one-sixth of the

maximum adsorption density for iron hydroxides formed in the presence of soluble As(V). The 

differences in adsorption densities were attributed to certain mechanisms (i.e., strictly surface adsorption 

versus adsorption and co-precipitation). Lytle and Snoeyink (2003) also observed that arsenic removal 

was lower with pre-formed iron solids, as opposed to the ideal case of oxidizing both soluble Fe(II) and 

As(III) at the same time. Consequently, the oxidation of iron and arsenic should occur at the same time to 

achieve optimal arsenic removal.

The February 27, 2006, speciation results also showed that even without the use of NaMnO4, most soluble 

As(III) in the filter influent was oxidized to soluble As(V) within the gravity filter, with the soluble As(V) 

concentration elevated to 22.4 μg/L and particulate arsenic reduced to <0.01 μg/L in the filter effluent. 

The amount of soluble As(V) in the filter effluent suggested that a portion of the soluble As(V) formed in 

the filter, along with that already existing in the filter influent, was removed, presumably by attaching to

the iron solids accumulating in the filter. Removal of soluble As(V) also was observed during all but one 

(on February 27, 2007) subsequent speciation event, with removal rates ranging from 13% to 51% and 

averaging 26%. These soluble As(V) removal rates were lower than the 57% As(V) removal rate 
39

achieved on February 2, 2006, following NaMnO4 preoxidation. Adsorption of As(V) on pre-formed iron 

solids, as discussed above, probably explains why the removal rates were lower. 

The gravity filter was effective in removing particulate iron, as indicated by less than the MDL of iron in 

the filter effluent throughout the performance evaluation study (except for one sampling event on June 6, 

2006). The gravity filter removed approximately 59% of particulate arsenic, leaving only 4.2 μg/L (on 

average) in the filter effluent (Table 4-6). Because soluble As(III) was oxidized to soluble As(V) in the 

filter under natural conditions and due to elevated manganese levels in the filter effluent in the presence 

of high TOC, it was decided to continue the study without NaMnO4 addition (see Section 4.5.1.3). 

In summary, after the use of NaMnO4 was discontinued, the average soluble As(III) and soluble As(V) 

concentrations following the detention tank (AC) were 26.2 and 10.4 μg/L, respectively (Table 4-6). The 

average soluble As(III) level after the gravity filter (AF) decreased to 1.6 μg/L, and As(V) increased to 

26.4 μg/L. The aeration step in the AERALATER® unit converted approximately 26% (on average) of 

As(III) to As(V). Across the gravity filter, approximately 94% of As(III) was oxidized to As(V) via

naturally occurring microbial-mediated processes. As shown by Figure 4-14, approximately 34% (on 

average) of total arsenic was removed by the gravity filter, lower than the 60% from the single sampling 

event on February 2, 2006, with NaMnO4 addition. Arsenic exiting the gravity filter was removed by the 

AD-33 media in the APU-300 system. 

The arsenic breakthrough curves for the two adsorption vessels and the entire system are presented in 

Figure 4-14, with total arsenic concentrations plotted against throughput in BV at the IN, AC, AF, TA, 

TB, and TT locations. As expected, arsenic concentrations in the adsorption vessel effluent (TA, TB, and 

TT) increased gradually (except for one measurement at approximately 10,000 BV), with total arsenic 

concentrations measured below the MCL of 10 μg/L during the 1-year performance evaluation study. 

0

10

20

30

40

50

60

0 5 10 15 20 25

Bed Volume of Water Treated (x 1000)

As Concentration (μg/L)

IN

AC

AF

TA

TB

TT

As MCL = 10 μg/L

Figure 4-14. Total Arsenic Concentrations vs. Throughput
40

At the end of the study, the total arsenic concentration was 9.8 μg/L in system effluent (February 27, 

2007). The city took two more compliance samples after the end of the study, with total arsenic 

concentrations at 7.0 μg/L at around 22,400 BV on March 19, 2007, and at 11 μg/L at around 26,300 BV

on May 29, 2007. Extrapolating from the average daily production of 52,418 gpd, the arsenic 

breakthrough above 10 μg/L most likely occurred at 25,300 BV, which was only 31% of the vendor’s

projected capacity of 82,500 BV (Table 4-3). 

As discussed above, the total arsenic removal efficiency of the gravity filter was reduced from 

approximately 60% to 34% after stopping NaMnO4 injection, which shifted the burden of arsenic removal 

from the gravity filter to the downstream adsorption vessels. The vendor’s estimate of 82,500 BV was 

based on expected removal across the gravity filter of 30% to 50%, which would result in influent arsenic 

concentrations of 22 to 31 μg/L to the APU-300 treatment system. This design basis is comparable to the 

26.4-μg/L As(V) concentration from the filter effluent (without NaMnO4 addition). Therefore, the 

discrepancy observed in media run length would have been caused by factors such as competing ions (like

total phosphorous) in the source water, which were not accounted for in the vendor’s run-length estimate 

(see Section 4.5.1.6). 

Microbial-Mediated As(III) Oxidation. Since the NaMnO4 addition ended, soluble As(III) was 

unexpectedly oxidized to soluble As(V) in the gravity filter, apparently via certain natural pathways. 

Figure 4-15 shows the biogeochemical cycle of arsenic as it is transformed between the As(III) and As(V) 

states in the environment. This transformation often is mediated by microbial activities. Several 

researchers have reported the presence of As(III)-oxidizing bacteria in surface and groundwater 

(Oremland and Stolz, 2003; Battaglia-Brunet et al., 2002; Hambsch et al., 1995), with over 30 strains of 

microorganisms identified. These microorganisms are categorized in two groups (heterotrophic arsenite 

oxidizers [HAOs] and chemolithoautotrophic arsenite oxidizers [CAOs]) based on the pathways involved 

in arsenite oxidation. The term heterotroph means that the microbe uses organic carbon substrates for its 

biomass growth, while the term autotroph means that the microbe uses inorganic carbon (e.g. CO2) for its 

biomass growth. These two types of microorganisms oxidize As(III) through the following mechanisms

(Oremland and Stoltz, 2003): 

• Heterotrophic Arsenite Oxidizers. The HAOs primarily oxidize As(III) as a detoxification 

reaction that converts As(III) to As(V) at the cell membrane. This helps inhibit its entry into 

the cellular structure. This reaction does not create energy or biomass for the HAO microbe. 

• Chemolithoautotrophic Arsenite Oxidizers. The CAOs use As(III) as an electron donor to 

reduce oxygen or nitrate and use the energy to fix CO2 into biomass. The term 

chemolithoautotroph refers to the microbe that uses chemical reactions for energy (“chemo”) 

and uses inorganic electron donors (“litho”) to fix CO2 into biomass (“autotroph”).

Under a separate task order, researchers at EPA and Battelle observed similar naturally-occurring As(III) 

oxidation processes in a gravity sand filter following aeration at the Greene County Southern Plant 

(GCSP) in Beaver Creek, OH. Source water at the plant contained 45.9 and 2,280 μg/L of total arsenic 

and iron, both existing almost entirely in the soluble form. Upon aeration and filtration, As(III) 

concentrations were reduced from 37.2 μg/L (on average) in the filter influent to 1.2 μg/L (on average) in 

the filter effluent. As(V) removal across the filter bed was 77%, much higher than the 26% observed at 

the Stewart, MN facility without NaMnO4 preoxidation (Wang, 2006a). Higher As(V) removal at the 

GCSP was likely due to the lower pH value at 7.5, which is more favorable for As(V) adsorption onto 

iron solids, and the <10 μg/L of total phosphorous, which eliminated a source of competing species for 

As(V) removal. At the GCSP, the oxidation of As(III) occurred concurrently with nitrification in the 

filter bed, which converted almost 100% of the 1.2 mg/L of NH3 (as N) (on average) in the filter influent 

to NO3

-

 in the filter effluent (Wang, 2006a; Lytle et al., 2007). However, nitrification
41

CH2O

CO2

2 As (V)

2 As (III)

CH2O

CO2

O2,

Mn (IV),

NO3

–,

Fe (III)

4e– 4e–

Anaerobic

2H2

CH2O

CO2

2 As (V)

2 As (III)

CH2O

CO2

O2,

Mn (IV),

NO3

–,

Fe (III)

4e– 4e–

Anaerobic

2H2

Figure 4-15. Biogeochemical Cycle of Arsenic (Oremland et al., 2002) 

was determined not to be directly responsible for As(III) oxidation under an internally funded research 

project at Battelle. The results of this study will be further discussed under Section 4.5.1.5. 

At the Stewart, MN site, the average As(III) levels declined from 26.2 μg/L in the filter influent to 1.6 

μg/L in the filter effluent. The reduction of DO concentrations from 5.0 mg/L after aeration to 2.6 mg/L 

after the filter suggested that oxygen was the most likely electron donor in a biologically mediated 

process and that aerobic conditions persist throughout the filter. A portion of DO removal also might be 

attributed to the nitrification process that occurred, although this process was shown to be unrelated to the 

As(III) oxidation at the GCSP, as described below in Section 4.5.1.5. 

4.5.1.2 Iron. Figure 4-16 presents total iron concentrations measured across the treatment train. 

Total iron concentrations in source water ranged from 993 to 1,491 μg/L and averaged 1,188 μg/L, 

existing primarily in the soluble form at 922 μg/L (on average). The average soluble iron and soluble 

arsenic concentrations in source water corresponded to a ratio of 23:1, which was just over the 20:1 target 

ratio for more effective arsenic removal (Sorg, 2002). As discussed above, relatively high pH values 

and/or high concentrations of competing anion and TOC in source water might affect the arsenic-removal 

capacity of the natural iron solids.

Aeration alone in the AERALATER® unit was sufficient to accomplish complete Fe(II) oxidation. 

Soluble iron concentrations after aeration and the detention tank were <25 μg/L; complete conversion of 

soluble iron to particulate iron was achieved. The AERALATER® filter was effective in removing 

particulate iron, reducing the iron concentrations to be close to or below the MDL of 25 μg/L over the 1-

year study period. No particulate iron breakthrough was observed from the gravity filter, indicating 

adequate filtration rate and filter backwash frequency. 

Following the APU-300 adsorption vessels, iron levels remained at <25 μg/L, with the exception of one 

outlier taking place on July 25, 2006, when total iron (as particulate) appeared to break through from 

Vessels A and B at 337 and 524 μg/L, respectively. It was not clear what had caused the elevated iron 

concentrations observed. The system appeared to operate properly at the time, with differential pressure 

across the system remaining as low as 1 psi. On the subsequent sampling events, the total iron levels 

from Vessels A and B returned to <25 μg/L.
42

0

200

400

600

800

1,000

1,200

1,400

1,600

0 5 10 15 20 25

Bed Volume of Water Treated (x 1000)

Fe Concentration (μg/L)

IN

AC

AF

TA

TB

TT

Fe SMCL = 300 μg/L

Figure 4-16. Total Iron Concentrations vs. Bed Volumes

4.5.1.3 Manganese. Manganese concentrations in source water ranged from 19.6 to 44.3 μg/L and 

averaged 23.6 μg/L. Manganese existed primarily in the soluble form at an average concentration of 24.0

μg/L. Manganese removal is discussed below for treatment system performance, both with and without 

NaMnO4 addition. For the first sampling event on February 2, 2006, the NaMnO4 feed pump was 

operational and a total manganese concentration of 541 μg/L was measured after preoxidation, aeration, 

and detention. The total manganese concentration following the gravity filter (AF) was elevated at 127 

μg/L, existing entirely as soluble manganese. The presence of elevated soluble manganese in the filter 

effluent was unexpected, because the amount of NaMnO4 added was very close to the stoichiometric 

dosage of 0.42 mg/L (as Mn) for the February 2, 2006, source water, and should have been completely 

consumed and converted to MnO2 solids during the preoxidation step. 

The detection of “soluble manganese” was probably caused by the presence of high TOC levels in source

water. It is possible that the “soluble manganese” exiting the filter was present in the colloidal form that 

penetrated through the gravity filter and the 0.45-μm disc filters during speciation sampling. Researchers 

have reported that high levels of dissolved organic matter (DOM) in source water can form fine colloidal 

MnO2 particles not filterable by conventional gravity or pressure filters (Knocke et al., 1991). Similar 

observation also was made at another EPA arsenic demonstration site at Sauk Centre, MN, where 

elevated levels of “soluble manganese” up to 1,062 μg/L were observed following the contact tank and 

Macrolite® pressure filters as the KMnO4 dosage was progressively decreased from 3.8 to 1.4 mg/L (as 

Mn) due to concerns with overdosing. (Note that similar to the Stewart, MN system, permanganate was 

used for the Sauk Centre, MN system to preoxidize as much as 23 and 2,691 μg/L of As(III) and Fe(II), 

respectively, due to the presence of 4.0 mg/L of TOC.) At Sauk Centre, “soluble manganese” eventually 

was reduced to as low as 2.5 μg/L as the KMnO4 dosage was increased to 5.6 mg/L (as Mn). Increasing 

the KMnO4 dosage probably helped diminish the effect of DOM on Mn(II) oxidation and helped form

more filterable MnO2 particles (Shiao, et al., 2007). 
43

At Stewart, elevated manganese concentrations in the gravity filter effluent occurred only with NaMnO4

addition, which took place for about a week. The colloidal manganese present in the gravity filter effluent

was removed by AD-33 media, with its concentration reduced from 127 to 3.7 μg/L on February 2, 2006. 

Had NaMnO4 addition continued at the same dose rate as on February 2, 2006, the elevated colloidal 

manganese levels in the filter effluent could become an issue for media performance. At other EPA 

demonstration sites with pre-chlorination, such as Rollinsford, NH, elevated manganese levels were found 

to coat and foul AD-33 media (Cumming et al., 2009), resulting in early arsenic breakthrough and short 

media run length. The impact of elevated manganese levels on AD-33 media should be minimal because 

they occurred for only a very short duration. 

After the February 2, 2006, sampling event, when the NaMnO4 feed pump lost prime, manganese levels 

after the detention tank (AC) decreased significantly to those in raw water (e.g., at 21 μg/L by the next 

sampling event on February 14, 2006 [see Figure 4-17]). Total Mn levels exiting the AERALATER®

filter continued to be somewhat elevated relative to filter influent levels during most of the sampling 

events throughout the study. From February 14 to April 4, 2006, some manganese was removed by AD33 media, and the removal continued for approximately 3,400 BV. Since then, the effluent values have 

become equal to, or somewhat higher than, the influent values. These results suggest that AD-33 media 

had only a limited capacity for Mn removal (present as Mn2+ ions). As discussed in Section 4.5.1.1, the 

NaMnO4 addition was not resumed during the remainder of the performance evaluation study. 

0

50

100

150

200

0 5 10 15 20 25

Bed Volume of Water Treated (x 1000)

Mn Concentration (μg/L)

IN

AC

AF

TA

TB

TT

Mn SMCL = 50 μg/L

Peak = 541 μg/L at 700 

Bed Volumes 

Figure 4-17. Total Manganese Concentrations vs. Bed Volumes

4.5.1.4 pH, DO, and ORP. pH values of source water ranged from 7.4 to 8.2 and averaged 7.9. pH 

values increased slightly from an average value of 7.9 at the wellhead to 8.3 after the AERALATER®

filter. Aeration probably contributed to this increase in pH. DO levels averaged 1.2 mg/L in source water 

and increased to an average value of 5.0 mg/L after aeration. DO concentrations decreased by about 48% 

to an average value of 2.6 mg/L across the gravity filter. The aerobic biological processes responsible for 

As(III) oxidation and nitrification processes might have consumed some of the DO in the filter influent 
44

(Sawyer, et al., 2003). The average DO levels after the APU-300 system were 2.7 mg/L, essentially the 

same as those going into the adsorption system. ORP levels averaged 216 mV in source water and 207 

mV after aeration and the detention tank. Again, probably due to the biological processes, ORP readings 

decreased to 186 mV (on average) after the gravity filter. ORP levels averaged 173 mV in the combined 

effluent of the APU-300 system. 

4.5.1.5 Ammonia and Nitrate. Twenty-nine sampling events took place for ammonia and 30 for 

nitrate during the 1-year performance evaluation study. In source water, ammonia concentrations ranged 

from 1.0 to 1.9 mg/L (as N) and averaged 1.6 mg/L (as N); nitrate concentrations were consistently less 

than the MDL of 0.05 mg/L (as N). Following aeration and detention, ammonia concentrations remained 

essentially unchanged, although up to 0.3 mg/L (as N) concentration differences were observed between 

the IN and AC sampling locations. Nitrate concentrations also remained unchanged following aeration 

and detention, with all measurements less than 0.05 mg/L (as N), except for one outlier of 0.1 mg/L (as 

N) measured at the AC location on December 12, 2006. 

Figure 4-18 shows the decreases in ammonia concentration and increases in nitrate concentration across 

the gravity filter and AD-33 adsorption vessels versus volume throughput in bed volumes by the system. 

After treating 3,100 BV of water (or 69 days after system startup on January 18, 2006), some ammonia 

began to be removed by the gravity filter and AD-33 adsorption vessels. Decreases in ammonia 

concentration across the gravity filter ranged from 0 to 0.6 mg/L (as N) and averaged 0.3 mg/L (as N). 

Decreases in ammonia concentration across the AD-33 adsorption vessels ranged from 0 to 1 mg/L (as N) 

and averaged 0.3 mg/L (as N). Nitrate concentrations remained below 0.05 mg/L (as N) until 4,400 BV 

of water had been treated (or 97 days after system startup), and then started to increase. Increases in 

nitrate concentration across the gravity filter ranged from 0 to 1.5 mg/L (as N) and averaged 0.2 mg/L (as 

N). Increases in nitrate concentration across the AD-33 adsorption vessels ranged from 0 to 1.6 mg/L (as 

N) and averaged 0.3 mg/L (as N). The concentration changes between ammonia and nitrate across the 

gravity filter and AD-33 adsorption vessels appear to follow a stoichiometric relationship. 

The decreasing ammonia and DO concentrations and increasing nitrate concentrations indicate that 

nitrification was occurring within the gravity filter and AD-33 adsorption vessels approximately 69 to 97 

days into system operation. The 69-day timeframe was based on the observation of ammonia removal, 

while the 97-day timeframe was based on detectable levels of nitrate in the gravity filter effluent. 

Under the aerobic conditions in the AERALATER® filter, nitrifiers, including Nitrosomonas and 

Nitrobacters, can convert ammonia to nitrite and then to nitrate following the reaction equations (Sawyer 

et al., 2003) as follows: 

2NH3 + 3O2 = 2NO2

-

 +2H+ + 2H2O [Nitrosomonas] 

2NO2

- + O2 = 2NO3 [Nitrobacter] 

Through research efforts funded separately by EPA and Battelle, researchers have observed similar 

nitrification processes occurring in gravity filters at the GCSP in Beaver Creek, OH, that have a similar 

treatment train (i.e., aeration and gravity filtration) to the Stewart, MN, system (Lytle et al., 2007; Wang, 

2006). In addition, As(III) to As(V) oxidation also was observed, possibly through biologically-mediated

processes. Based on laboratory column tests conducted with filtered source water and filter media 

obtained from the GCSP, it was observed that As(III) oxidation continued to occur even after the 

nitrification processes had been completely inhibited by lowering the influent pH values to < 5.0 (Clark et 

al., 1977). This suggests that nitrification is not necessary for the microbial-mediated As(III) oxidation to 

occur (Wang et al., 2006). The same study also showed that, after the filter media in the column had been 
45 

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Bed Volume of Water Treated (x 1000)

Concentration (as N) Change across the Gravity Filter (mg/L)

Ammonia (Conc. at AF - Conc. at AC)

Nitrate (Conc. at AF - Conc. at AC)

Ammonia and Nitrate Concentrations Changes Across the Gravity Filter

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

Bed Volume of Water Treated (x 1000)

Concentration (as N) change Between TA and AF (mg/L)

Ammonia (Conc. at TA - Conc. at AF)

Nitrate (Conc. at TA - Conc. at AF)

Ammonia and Nitrate Concentrations Changes Across the Adsorption Vessel A

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

Bed Volume of Water Treated (x 1000)

Concentration (as N) Change Between TB and AF (mg/L)

Ammonia (Conc. at TB - Conc. at AF)

Nitrate (Conc. at TB - Conc. at AF)

Ammonia and Nitrate Concentrations Changes Across the Adsorption Vessel B

Figure 4-18. Decreases/Increases in Ammonia/Nitrate Across AERALATER® Filter 

and AD-33 Adsorption Vessels
46

sterilized with HgCl2, the pathways responsible for As(III) oxidation apparently were disrupted, thus 

allowing As(III) to break through from the column, with the same amount of As(III) measured in both the 

column influent and effluent. Furthermore, because significant nitrification was not observed for 97 days 

compared to 40 days for As(III) oxidation, it was very likely that oxygen, instead of nitrate, was the 

electron acceptor for the microbial-mediated As(III) oxidation process. As discussed above, there was a 

48% DO removal rate across the gravity filter, with approximately 2.6 mg/L of O2 in the filter effluent, 

suggesting the persistence of aerobic conditions through the filter. 

4.5.1.6 Other Water Quality Parameters. Alkalinity, fluoride, sulfate, silica, TOC, temperature, and 

hardness levels remained consistent across the treatment train and were not significantly affected by the 

treatment process (Table 4-7). TOC levels were elevated at 6.4 mg/L in source water, and no significant 

change was observed across the treatment train. Although high TOC levels might have contributed to the 

oxidant demand, they did not appear to have been adsorbed onto iron solids. The orthophosphate level in 

the source water was 0.02 mg/L (as PO4) based on historic sampling, and was not considered by the 

vendor as a factor impacting the media run length, which was estimated at 82,500 BV. However, the 

study results indicate that total phosphorus (as P) was present in source water at levels that lowered the 

effectiveness of arsenic removal in both the gravity filter and APU-300 treatment systems. Total P 

decreased from an average concentration of 301 μg/L (or 0.92 mg/L as PO4) in source water to an average 

concentration of 112 and 37.2 μg/L, following the AERALATER® filter and APU-300 system, 

respectively. Turbidity also decreased from 6.5 nephelometric turbidity units (NTU) in source water to 

<1.0 NTU after the AERALATER® filter and APU-300 system.

4.5.2 Backwash Wastewater Sampling. Table 4-8 presents the analytical results of 13 monthly 

backwash wastewater sampling from the two AERALATER® filter cells. pH values of the backwash 

wastewater ranged from 7.8 to 8.1 and averaged 7.9; TDS concentrations ranged from 378 to 468 mg/L

and averaged 423 mg/L; TSS concentrations ranged from 28 to 260 mg/L and averaged 87 mg/L. TSS 

levels appeared to decline after switching from grab to composite sampling, using a sump pump, on 

September 20, 2006. 

Concentrations of total arsenic, iron, and manganese ranged from 168 to 844 μg/L (averaged 343 μg/L), 

17 to 111 mg/L (averaged 38 mg/L), and 34 to 109 μg/L (averaged 57 μg/L), respectively, with the 

majority existing as particulate. Assuming that 87 mg/L of TSS (i.e., the averaged TSS) was produced in 

7,619 gal of backwash wastewater from the AERALATER® filter (Table 4-5), approximately 5.5 lb of 

solids would have been discharged during each backwash event. Based on the average particulate metal 

data (311 μg/L of particulate arsenic, 38 mg/L of particulate iron, and 34 μg/L of particulate manganese), 

the solids discharged would have been composed of 0.02 lb of arsenic (0.4% by weight), 2.4 lb of iron 

(43.6 % by weight), and 0.002 lb of manganese (0.04% by weight).

Backwash solids samples were collected on February 28, 2007, from both AERALATER® filter cells. 

The samples were analyzed for total metals; results are presented in Table 4-9. Arsenic, iron, and 

manganese levels in the solids averaged 0.94 mg/g (or 0.09%), 154 mg/g (or 15.4%), and 0.2 mg/g (or 

0.02%), respectively. Based on the backwash wastewater samples collected on February 28, 2007, the 

averaged concentrations of particulate arsenic, iron, and manganese were 206, 22,646, and 15.2 μg/L, 

respectively. Assuming that 79.5 mg/L of TSS (i.e., the averaged TSS in the backwash wastewater 

samples collected on February 28, 2007) were produced in 7,619 gal of backwash wastewater from the 

AERALATER® filter (Table 4-5), arsenic, iron, and manganese contents in the solids were calculated to 

be 0.26, 28.5, and 0.02%, respectively. While the calculated manganese content was equivalent to that 

based on the backwash solids analysis, the calculated arsenic and iron contents were about three and two

times higher, respectively. The degree of inconsistency is considered reasonable, considering that the 

results are from two independent sampling systems (wastewater and backwash solids). 
47

Table 4-8. AERALATER® Filter Backwash Wastewater Sampling Results

pHTDSTSSAs (total)As (soluble)As (particulate)Fe (total)Fe (soluble)Mn (total)Mn (soluble)pHTDSTSSAs (total)As (soluble)As (particulate)Fe (total)Fe (soluble)Mn (total)Mn (soluble)

No. Date S.U. mg/L mg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L S.U. mg/L mg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L

1 03/01/06(a) 8.1 426 92 209 NA NA 25,897 NA 69.2 NA 8.1 416 36 231 NA NA 28,765 NA 78.2 NA

2 03/22/06 8.0 432 104 255 23.2 232 31,173 33.5 48.8 26.8 8.0 422 46 176 26.8 149 18,262 37.8 42.2 26.3

3 04/12/06 8.0 428 28 215 28.5 187 18,889 25.8 41.2 28.1 8.0 420 38 168 30.2 138 16,691 47.8 42.9 25.3

4 05/31/06 8.0 454 130 654 29.6 624 55,791 245 70.0 19.5 8.0 436 260 844 26.7 817 73,492 143 86.4 19.0

5 06/28/06 7.9 430 214 835 39.7 795 110,886 206 109 24.3 8.0 404 122 538 30.9 507 69,635 158 103 24.3

6 07/26/06 7.9 428 126 456 38.3 417 52,912 76.7 64.9 24.0 7.9 426 100 403 59.1 343 50,511 133 64.2 24.6

7 08/23/06 7.9 468 144 585 43.1 542 73,364 127 74.8 22.7 7.9 432 127 495 27.3 468 67,266 78.4 70.1 21.5

8 09/20/06 7.9 454 54 290 29.9 260 28,455 57.7 41.6 22.5 7.9 464 28 194 27.3 167 19,399 78.3 64.9 26.5

9 10/25/06 7.8 422 54 284 32.5 252 29,772 40.7 44.5 24.2 7.8 418 66 272 29.4 242 30,779 58.3 41.5 22.1

10 11/29/06 7.8 432 60 235 28.4 207 21,541 63.0 40.5 24.5 7.8 418 60 288 28.7 259 27,079 65.7 40.3 21.5

11 01/03/07 7.9 392 50 200 33.3 167 24,234 43.2 42.7 22.5 7.9 402 65 214 33.7 180 28,184 52.5 58.2 22.4

12 01/17/07 7.9 382 58 209 25.1 184 22,112 66.8 37.1 20.5 7.9 378 50 193 29.5 164 20,386 43.6 33.6 21.6

13 02/28/07 8.0 422 71 230 39.4 190 21,075 41.5 39.8 25.6 8.0 402 88 251 29.3 222 24,328 70.3 38.7 22.6

Backwash Filter Cell No. 2

Sampling Event

BW1

Backwash Filter Cell No. 1

BW2

(a) Filtered samples were not collected by the operator.

 TDS = total dissolved solids; TSS = total suspended solids; NA = not analyzed

Table 4-9. AERALATER® Filter Backwash Solids Total Metal Results

Analyte Mg Al Si P Ca V Fe Mn Ni Cu Zn As Cd Sb Ba Pb

Filter Cell No. 1 33,005 318 1,091 19,347 96,155 2.43 162,397 182 10.5 3.3 214 1,310 <0.5 <0.5 4,082 <0.5

Filter Cell No. 2 24,141 132 <250 763 90,867 2.48 145,938 197 4.8 2.9 118 559 <0.5 <0.5 5,210 <0.5

Samples collected on February 28, 2007. 

Average compositions calculated from triplicate analyses.

Values in μg/g.
48 

During the 1-year performance evaluation study, the APU-300 adsorption vessels were backwashed four 

times using the treated water. One set of backwash wastewater samples were collected from the sample 

ports located in the backwash effluent discharge lines from each vessel on January 17, 2007. Table 4-10 

summarizes the analytical results. The backwash wastewater averaged at 7.9 for pH, 380 mg/L for TDS, 

54 mg/L for TSS, 201 μg/L for total arsenic, 21 mg/L for total iron, and 35 μg/L for total manganese. 

Soluble arsenic concentrations averaged 27.3 μg/L, which was higher than that in the treated water used 

for backwash. Therefore, desorption of arsenic from the adsorptive media might occur during backwash. 

Soluble iron concentration averaged 55.2 μg/L, which also was higher than that in the treated water (<25 

μg/L). In general, the results measured from Vessels A and B were consistent among one another. 

Assuming 5,926 gal of backwash wastewater generated from two APU-300 vessels (the average 

backwash wastewater generated per backwash event; see Table 4-5) and 54 mg/L of TSS (see Table 4-

10), approximately 2.7 lb of solids would have been discharged during each backwash event. Based on 

the average particulate metal data (174 μg/L of particulate arsenic, 21.2 mg/L of particulate iron, and 14.3 

μg/L of particulate manganese), the solids discharged would have been composed of 3.9 g of arsenic 

(0.32% by weight), 476 g of iron (39.6 % by weight), and 0.32 g of manganese (0.03% by weight).

Table 4-10. APU-300 Adsorption Vessels Backwash Wastewater Sampling Results

Sampling Event

pHTDSTSSAs (total)As (soluble)As (particulate)Fe (total)Fe (soluble)Mn (total)Mn (soluble)

Sample Location Date S.U. mg/L mg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L

Backwash Vessel No. 1 1/17/2007 7.9 382 58 209 25.1 184 22,112 66.8 37.1 20.5

Backwash Vessel No. 2 1/17/2007 7.9 378 50 193 29.5 164 20,386 43.6 33.6 21.6

4.5.3 Distribution System Water Sampling. Distribution system water samples were collected to 

determine if water treated by the arsenic removal system would impact the lead, copper, and arsenic 

levels and other water chemistry in the distribution system. Prior to system startup, baseline distribution 

water samples were collected on February 16, March 16, April 13, and May 18, 2005. Since system 

startup, distribution water sampling continued monthly at the same three locations until January 9, 2007. 

The samples were analyzed for pH, alkalinity, arsenic, iron, manganese, lead, and copper; Table 4-11 

presents the results.

The main differences observed between the baseline samples and samples collected after system startup 

were decreases in arsenic concentration at each of the three sampling locations. Arsenic concentrations 

were reduced from a pre-startup average of 31.2 to a post-startup average of 6.1 μg/L. In Figure 4-19, 

arsenic concentrations measured in the distribution system water were compared to those in the treatment 

system effluent. In general, total arsenic concentrations in distribution system water were higher than 

those in the treatment system effluent. Nonetheless, the concentrations in distribution system water were 

still below the MCL for all samples, except for the first sample collected at DS3. Desorption and 

resuspension of arsenic previously accumulated on the distribution pipe surface most likely are the 

reasons for higher arsenic concentration in the distribution system. 
49 

Table 4-11. Distribution System Sampling Results

Sampling Event

DS1 DS2

Stagnation Time pHAlkalinityAsFeMnPbCuStagnation TimepHAlkalinityAsFeMnPbCu

No. Date hr S.U. mg/L μg/L μg/L μg/L μg/L μg/L hr S.U. mg/L μg/L μg/L μg/L μg/L μg/L

BL1 02/16/05 9.0 7.6 436 27.0 337 21.4 0.8 130 8.5 7.6 414 37.2 1,317 23.2 19.8 0.5

BL2 03/16/05(b) 8.5 7.7 466 29.3 404 21.6 0.9 159 10.0(a) 7.5 433 37.1 548 23.0 <0.1 56.3

BL3 04/13/05 8.0 7.7 424 30.1 206 26.5 1.1 202 10.0 7.7 424 31.8 174 25.9 0.2 125

BL4 05/18/05 9.0 7.7 428 30.5 169 21.3 0.5 105 9.4(a) 7.9 428 33.8 193 21.4 <0.1 195

1 02/22/06 8.5 7.9 416 7.8 <25 10.7 <0.1 85.4 7.0 7.9 416 9.9 <25 11.7 <0.1 179

2 03/21/06 7.8 7.8 406 2.1 <25 20.9 <0.1 35.9 9.5 7.8 410 4.2 <25 18.0 <0.1 131

3 04/18/06 8.5 8.0 438 3.5 <25 26.4 0.1 70.4 9.5 7.9 438 4.1 62.8 22.9 <0.1 154

4 05/16/06 9.0 7.8 409 3.1 <25 26.9 <0.1 103 9.8 7.8 405 3.5 <25 28.2 <0.1 106

5 06/13/06 Homeowner did not collect sample 7.0 7.7 433 4.1 <25 30.2 <0.1 338

6 07/11/06 8.0 7.6 419 3.2 <25 24.9 <0.1 91.7 7.5 7.7 415 3.9 <25 23.2 0.4 292

7 08/15/06 9.0 7.7 413 5.2 <25 27.6 0.3 135 0.1(c) 7.7 400 5.6 <25 28.5 0.1 241

8 09/12/06 8.3 7.7 451 5.0 <25 25.4 0.3 138 6.5 7.7 446 4.9 <25 25.5 <0.1 144

9 10/10/06 7.5 7.6 444 6.6 <25 25.0 0.3 145 8.8 7.6 437 6.9 <25 27.4 0.2 344

10 11/07/06 9.0 7.7 443 7.2 <25 24.6 <0.1 83.2 10.0 7.7 425 8.5 <25 25.0 <0.1 345

11 12/12/06 8.0 7.4 426 9.0 <25 26.6 0.3 125 9.0 7.6 428 8.5 <25 26.1 <0.1 161

12 01/09/07 9.0 7.7 453 7.4 <25 22.2 0.2 128 8.7 7.8 440 7.3 <25 19.0 <0.1 316
50 

Table 4-11. Distribution System Sampling Results (Continued)

Sampling Event

DS3

Stagnation TimepHAlkalinityAsFeMnPbCu

No. Date hr S.U. mg/L μg/L μg/L μg/L μg/L μg/L

BL1 02/16/05 9.0 7.6 418 27.2 311 23.6 1.0 130

BL2 03/16/05(b) 8.5 7.7 433 29.8 197 20.1 0.5 143

BL3 04/13/05 8.0 7.7 446 29.7 427 25.7 1.4 162

BL4 05/18/05 8.3 7.7 428 30.4 230 22.3 0.5 118 1 02/22/06 9.8 7.9 420 17.8 <25 17.5 <0.1 103 2 03/21/06 8.0 7.9 419 9.9 250 20.2 0.4 177 3 04/18/06 8.8 7.9 434 4.7 249 25.3 0.3 222 4 05/16/06 11.5 7.7 405 4.7 <25 29.4 <0.1 184 5 06/13/06 8.0 7.6 429 3.7 203 30.1 <0.1 226 6 07/11/06 6.3 7.5 415 3.7 45.4 28.4 0.1 203 7 08/15/06 6.7 7.7 425 4.7 52.1 33.2 0.2 185 8 09/12/06 12.5 7.7 458 5.8 <25 29.6 <0.1 187 9 10/10/06 7.8 7.6 461 6.5 232 32.4 0.2 217

10 11/07/06 8.5 7.6 445 7.0 <25 28.3 <0.1 201

11 12/12/06 10.0 7.5 440 7.5 170 33.5 0.1 188

12 01/09/07 9.0 7.7 438 6.2 138 27.0 <0.1 208

(a)Estimate provided by the homeowner.

(b) DS1 sampled on 03/22/05.

(c) Not first draw sample.

Action levels: 15 μg/L Pb and 1.3 mg/L Cu. BL = baseline sampling; DS = 

distribution sampling
51

Measured pH values ranged from 7.4 to 8.0; alkalinity levels ranged from 400 to 466 mg/L (as CaCO3). 

Iron concentrations measured at DS1 and DS2 were <25 μg/L, except for one sample collected at DS2 on 

April 18, 2006. Iron concentrations measured at DS3 ranged from <25 to 250 μg/L and averaged 

116 μg/L, which was significantly higher than that measured at the system effluent (<25 μg/L). Some 

corrosion products might have been washed out of the distribution system during DS3 sampling. 

Manganese concentrations averaged 23.0 and 25.2 μg/L before and after system startup, respectively, 

which were similar to the levels in the treatment system effluent. 

The average lead level was 2.7 μg/L in the baseline samples and 0.2 μg/L in the samples taken after 

system startup; these concentrations were significantly lower than the action level of 15 μg/L. The 

average copper level was 127 μg/L in the baseline samples and 177 μg/L in the samples taken after 

system startup; these concentrations also were significantly lower than the action level of 1,300 μg/L. 

The treatment did not appear to impact the lead and copper levels in the distribution system.

0

5

10

15

20

0.0 5.0 10.0 15.0 20.0 25.0

Bed Volume of Water Treated (x 1000)

As Concentration (μg/L)

TA

TB

TT

DS1

DS2

DS3

As MCL = 10 μg/L

Figure 4-19. Comparsion of Total Arsenic Concentrations in Distribution System Water

and APU-300 System Effluent 

4.6 System Cost

The cost of the treatment 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 required tracking capital cost for the 

equipment, site engineering, and installation and the O&M cost for media replacement and disposal, 

replacement parts, chemical supply, electricity consumption, and labor. These costs do not include the 

building cost or instrumentation and control upgrades installed by the City of Stewart. 
52

4.6.1 Capital Cost. The capital investment for equipment, site engineering, and installation for the 

250-gpm treatment system was $367,838. The equipment cost was $273,873 (or 74.4% of the total 

capital investment), which included $125,555 for a Siemens Type II AERALATER® system; $126,482 

for a skid-mounted APU-300 system; $17,952 for ancillary equipment; and $3,884 for freight (as shown 

in Table 4-12). The Siemens’ Type II AERALATER® system included a 11-ft-diameter steel unit (which 

was composed of an aerator, a fan, a detention tank, and a four-cell filter for a total of $77,000); process 

valves and piping ($32,060); instrumentation and controls ($7,420); 190 ft3

 of sand ($8,400); and other

materials ($675). The APU-300 system included two skid-mounted fiberglass vessels ($45,360); process 

valves and piping ($19,460); instrumentation and controls ($20,860); 128 ft3 of AD-33 media ($32,000 or 

$250/ft3

); and $8,802 for other materials. 

The engineering cost included the cost for the preparation and submission of an engineering submittal 

package, including a process flow diagram of the treatment system, mechanical drawings of the treatment 

equipment, a schematic of the equipment footprint as discussed in Section 4.3.1, and attainment of the 

required state permit for implementing the system. The engineering cost was $16,520, which was 4.5% 

of the total capital investment.

The installation cost included the equipment and labor to unload and install the AERALATER® and skidmounted APU-300 systems, perform piping tie-ins and electrical work, and load and backwash the media

in both AERALATER® filter and AD-33 adsorption vessels (see Section 4.3.3). The installation was 

performed by AdEdge and a local subcontractor. The installation cost was $77,445, or 21.1% of the total 

capital investment.

The capital cost of $367,838 was normalized to $1,471/gpm ($1.02 per gpd) of design capacity, using the 

system’s rated capacity of 250 gpm (or 360,000 gpd). The capital cost also was converted to an 

annualized cost of $34,720/yr using a capital recovery factor (CRF) of 0.09439 based on a 7% interest 

rate and a 20-yr return period. Assuming that the system operated 24 hr/day, 7 day/wk at the design 

flowrate of 250 gpm to produce 131,400,000 gal/yr, the unit capital cost would be $0.26/1,000 gal. 

During the performance evaluation study, the system operated only 4.7 hr/day and produced an average of 

19,132,570 gal of water in one year (Table 4-4), so the unit capital cost increased to $1.80/1,000 gal at 

this reduced rate of use. These calculations did not include the building construction cost. 

4.6.2 Operation and Maintenance Cost. The O&M cost included items such as AD-33 media 

replacement and disposal, replacement parts, chemicals, electricity, and labor (see Table 4-13). During 

the 1-year study period, there was no chemical cost incurred because NaMnO4 addition was discontinued. 

There was no replacement-part cost incurred either because all parts were covered under a 1-year 

warranty. Although AD-33 media was not replaced during the 1-year study period, the media 

replacement cost would represent the majority of the O&M cost. The vendor estimate was $41,370 for 

replacing 128 ft3 media in the two APU-300 vessels. This cost includes new media, gravel underbedding, 

labor, travel, equipment rental, and freight. Although the vendor did not provide a cost breakdown for 

media profiling and disposal, such cost was assumed to be included in the total cost estimate. 

Because media replacement did not take place during the study, the cost per 1,000 gal of water treated 

was calculated as a function of projected media run length, using the vendor cost estimate (see Figure 4-

20). At the end of the performance evaluation study, the total arsenic concentration was 9.8 μg/L in the 

system effluent on February 27, 2007. Two more compliance samples were taken by the city after the end 

of the study, with total arsenic concentrations at 7.0 μg/L at about 22,400 BV on March 19, 2007, and at 

11 μg/L at about 26,300 BV on May 29, 2007. Extrapolating from the average daily production of 52,418 

gpd, the arsenic breakthrough above 10 μg/L most likely would occur at 25,300 BV, which was only 31% 
53

Table 4-12. Capital Investment Cost for Siemens and AdEdge Treatment Systems 

Description Quantity Cost

% of Capital 

Investment Cost

Equipment

Siemens Type II AERALATER®

11-ft-diameter Steel, Epoxy-Lined Unit, Including 

Aerator, Fan, Detention Tank, and Filter

1 $77,000 –

Filter Media (ft3) 190 $8,400 –

Process Valves and Piping 1 $32,060 –

Instrumentation and Controls 1 $7,420 –

Additional Sample Taps 1 $675 –

Subtotal $125,555 –

AdEdge APU-300 System

63-in-diameter Fiberglass Vessels on Skid 2 $45,360 –

AD-33 Media (ft3) 128 $32,000 –

Gravel Underbedding 1 $1,540 –

Process Valves and Piping 1 $19,460 –

Instrumentation and Controls 1 $20,860 –

Totalizer for Backwash Line 2 $2,422 –

1-Year O&M Support, O&M Manuals – $4,840 –

Subtotal $126,482 –

Ancillary Equipment

KMnO4 Feed System 1 $4,192 –

Booster Pumps 2 $6,580 –

Motor Controls/MCC/HOA for Pumps 1 $6,850 –

In-Line Mixer 1 $330 –

Subtotal $17,952

Freight

Freight–AD33 Media (lb) 4,460 $780 –

Freight–Filter Media (lb) 10,000 $680 –

Freight–System (lb) 26,000 $2,112 –

Freight–Ancillary Equipment 1 $312

Subtotal $3,884 –

Equipment Total – $273,873 74.4%

Engineering

Vendor Labor – $4,534

Vendor Travel – $2,480

Vendor Material – $98

Subcontractor Labor – $8,400

Subcontractor Travel $420

Subcontractor Material – $588

Engineering Total – $16,520 4.5%

Installation

Vendor Labor – $7,920

Vendor Travel – $3,800

Subcontractor Mechanical – $39,985

Subcontractor Electrical – $21,890

Subcontractor Other Labor – $3,850

Installation Total – $77,445 21.1%

Total Capital Investment – $367,838 100%
54

of the vendor-projected capacity of 82,500 BV (Table 4-3). The short media life corresponded to a high 

medial replacement cost of $1.71/1,000 gal (Figure 4-20). 

A comparison of the electrical bills before and after system startup was conducted to estimate the 

electrical cost. Before the treatment plant was installed, the utility bill totaled $3,643 from January 1 to 

December 31, 2005. After the treatment plant was operational, the utility bill totaled $5,125 from January 

1 to December 31, 2006. Therefore, the incremental electricity cost was approximately $0.08/1,000 gal. 

Electricity was used mainly for operating the AERALATER® unit.

Routine labor activities for O&M consumed 10 min/day for operational readings and 31 min/week for one 

manual backwash event. This is equivalent to 101 min/week (or 1.7 hr/week) on a 7 day/week basis. The 

estimated labor cost is $0.08/1,000 gal of water treated, based on this time commitment and a labor rate of 

$16.33/hr. 

Table 4-13. O&M Cost for City of Stewart, Minnesota Treatment System

Cost Category Value Assumptions

Volume Processed (kgal) 20,441 Through February 28, 2007

Media Replacement and Disposal

Media Cost ($/ft3) $250 Vendor quote

Total Media Volume (ft3) 128 Two vessels

Media Replacement Cost ($) $32,000 Vendor quote

Gravel Underbedding Cost ($) $1,650 Vendor quote

Labor, Travel, and Equipment Cost ($) $6,940 Vendor quote

Freight ($) $780 Vendor quote

Subtotal $41,370 Vendor quote

Media Replacement and Disposal Cost 

($/1,000 gal)

See Figure 4-20 Based on media run length at 10 μg/L 

arsenic breakthrough

Replacement Parts

Replacement Parts Cost ($) $0.00 Cost related to parts replacement was 

negligible during 1-year study period

Labor and Travel Cost ($) $0.00 –

Equipment Replacement Cost ($/1,000 gal) $0.00 –

Chemical Usage

Chemical Cost ($) $0.00 No chemicals required after NaMnO4

oxidation discontinued.

Electricity

Estimated Incremental Electricity Cost ($/yr) $1,482 Based on utility bills

Incremental Cost ($/1,000 gal) $0.08 Annual system throughput = 19,133 kgal

Labor

Average Weekly Labor (hr) 1.7 10 min/day, plus 31 min manual backwash

Annual Labor Cost ($/yr) $1,444 Average labor rate = 16.33/hr

Labor Cost ($/1,000 gal) $0.08 Annual system throughput = 19,133 kgal

Total O&M Cost/1,000 gal See Figure 4-20 –
55

$0.00

$0.25

$0.50

$0.75

$1.00

$1.25

$1.50

$1.75

$2.00

$2.25

$2.50

$2.75

$3.00

$3.25

$3.50

$3.75

$4.00

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Media Working Capacity, Bed Volumes (x1000)

Cost ($/1,000 gal)

O&M cost

Media replacement cost

Figure 4-20. Media Replacement and O&M Cost for AERALATER®

and APU-300 Systems at Stewart, Minnesota 
56

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Cumming, L.J., A.S.C. Chen, and L. Wang. 2009. Arsenic Removal from Drinking Water by Adsorptive 

Media. 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. 

Edwards, M. 1994. "Chemistry of Arsenic Removal during Coagulation and Fe-Mn Oxidation." 

JAWWA, 86(9): 64. 

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.” JAWWA, 90(3): 103-113. 

EPA. 2003. “Minor Clarification of the National Primary Drinking Water Regulation for Arsenic.” 

Federal Register, 40 CFR Part 141. 

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, D.C. 

EPA. 2001. “National Primary Drinking Water Regulations: Arsenic and Clarifications to Compliance 

and New Source Contaminants Monitoring.” Federal Register, 40 CFR Part 9, 141, and 142. 

Ghurye, G. and D. Clifford. 2001. Laboratory Study on the Oxidation of Arsenic III to Arsenic V. 

EPA/600/R-01/021. U.S. Environmental Protection Agency, National Risk Management 

Research Laboratory, Cincinnati, OH. 

Hambsch, B., B. Raue, and H.J. Brauch. 1995. “Determination of Arsenic(III) for the Investigation of 

the Microbial Oxidation of Arsenic(III) to Arsenic(V).” Acta Hydrochimica et Hydrobiologica, 

23(4): 166-172. 

Hoffman, G., D. Lytle, T.J. Sorg, A.S.C. Chen, and L. Wang. 2006. Design Manual. Removal of 

Arsenic from Drinking Water Supplies by Iron Removal Process. EPA/600/R-06/030. U.S. 

Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, 

OH. 
57

Knocke, W. R., J.E. Van Venschoten, M.J. Kearney, A.W. Soborski, and D.A. Reckhow. 1991. 

“Kinetics of Manganese and Iron Oxidation by Potassium Permanganate and Chlorine Dioxide.” 

JAWWA, 83(6): 80-87. 

Lytle, D.A., and V.L. Snoeyink. 2003. "The Effect of Dissolved Inorganic Carbon on the Properties of 

Iron Colloidal Suspensions." J. Water Supply: Res. and Tech. AQUA, 52(3): 165-180. 

Lytle, D.A., T. J. Sorg, C. Muhlen, L. Wang, M. Rahrig, and K. French. 2007. “Biological Nitrification in 

a Full-scale and Pilot-scale Iron Removal Drinking Water Treatment Plant.” J. Water Supply: 

Res. and Tech. AQUA, 56(2): 125–136. 

Oremland, R.S., S.E. Hoeft, J.M. Santini, N. Bano, R.A. Hollibaugh, and J.T. Hollibaugh. 2002. 

“Anaerobic Oxidation of Arsenite in Mono Lake Water and by a Facultative, Arsenite-Oxidizing 

Chemoautotroph, Strain MLHE-1.” Applied and Environmental Microbiology, 68(10): 4795-

4802. 

Oremland, R.S. and J.F. Stolz. 2003. “The Ecology of Arsenic.” Science, 300(5): 939-944. 

Oxenham, J., Chen, A.S.C, and L. Wang. 2005. Arsenic Removal from Drinking Water by Adsorptive 

Media. EPA Demonstration Project at Rollinsford, NH: Six-Month Evaluation Report. 

EPA/600/R-05/116. U.S. Environmental Protection Agency, National Risk Management 

Research Laboratory, Cincinnati, OH. 

Sawyer, C.N., P.L. McCarty, and G.F. Parkin. 2003. Chemistry for Environmental Engineering and 

Science. 5th Edition. McGraw-Hill Companies, Inc., New York, NY. 

Shiao, H.T., W.E. Condit, and A.S.C. Chen. 2007. Arsenic Removal from Drinking Water by Iron 

Removal. EPA Demonstration Project at Big Sauk Lake Mobile Home Park in Sauk Centre, MN. 

Six Month Evaluation Report. EPA/600/R-07/048. U.S. Environmental Protection Agency, 

National Risk Management Research Laboratory, Cincinnati, OH. 

Sorg, T.J. 2002. “Iron Treatment for Arsenic Removal Neglected.” Opflow, AWWA, 28(11): 15. 

Wang, L., W. 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. 

Wang, L. 2006. Long-Term Performance of Full-Scale Water Treatment Systems at Greene County, 

Ohio Evaluation of Treatment Technology for the Removal of Arsenic from Drinking Water. 

Letter Report for Contract No. 68-C-00-185, Task Order No. 20. U.S. Environmental Protection 

Agency, National Risk Management Research Laboratory, Cincinnati, OH. 

Wang, L., A.S.C. Chen, L. N. Tong, and A. Paolucci. 2006. Evaluation of As(III) Oxidation via 

Microbial-Mediated Processes. Report preapred under Battelle’s Internal Research and 

Development Program for Fiscal Year 2006, Columbus, OH. 
APPENDIX A

OPERATIONAL DATA
A-1

Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet 

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 01/30/06 07:35 NA NA NA NA NA NA No 92 282,600 590 91 275,090 575 0

Tue 01/31/06 07:00 1.1 12,800 194 0.0 0.0 NA Yes 92 288,114 602 91 280,488 586 0

Wed 02/01/06 07:30 3.9 44,400 190 2.1 23,900 190 No 92 318,183 665 91 309,822 647 0

Thu 02/02/06 06:30 2.0 23,000 192 1.7 19,800 194 Yes NA 337,773 705 NA 328,931 687 0

Fri 02/03/06 08:10 3.2 39,000 203 2.8 12,600 75 No NA 365,977 764 NA 355,460 742 7,647

Sat 02/04/06 08:15 1.8 21,700 201 1.5 37,300 414 No 92 384,714 804 91 372,554 778 7,647

Sun 02/05/06 08:50 2.0 22,700 189 1.9 21,500 189 No 92 406,021 848 91 391,931 819 7,647

Mon 02/06/06 08:15 2.0 23,700 198 1.8 20,500 190 No NA 426,860 892 NA 410,436 857 7,647

Tue 02/07/06 07:10 1.1 11,800 179 1.7 19,300 189 No NA 442,802 925 NA 424,496 887 7,647

Wed 02/08/06 08:35 1.9 22,900 201 1.7 20,000 196 No NA 463,684 968 NA 443,020 925 7,647

Thu 02/09/06 08:00 2.0 23,100 193 1.3 15,300 196 No NA 480,412 1,003 NA 457,596 956 7,647

Fri 02/10/06 09:10 1.7 20,300 199 2.6 28,300 181 No NA 502,250 1,049 NA 476,125 994 7,647

Sat 02/11/06 08:10 1.9 22,000 193 1.0 17,400 290 No 88 532,156 1,111 70 492,894 1,029 7,647

Sun 02/12/06 08:15 0.9 11,000 204 2.6 21,000 135 No NA 541,319 1,131 NA 507,614 1,060 7,647

Mon 02/13/06 07:15 1.8 22,400 207 1.9 22,200 195 No NA 563,172 1,176 NA 525,767 1,098 7,647

Tue 02/14/06 07:30 1.9 21,900 192 2.0 22,300 186 No NA 585,122 1,222 NA 544,109 1,136 7,647

Wed 02/15/06 07:30 1.7 20,800 204 1.1 12,200 185 No NA 601,420 1,256 NA 557,855 1,165 7,647

Thu 02/16/06 07:35 1.9 22,600 198 2.1 22,800 181 No NA 623,167 1,302 NA 576,526 1,204 7,647

Fri 02/17/06 08:00 0.9 11,500 213 2.6 21,600 138 Yes NA 639,994 1,337 NA 591,015 1,234 7,647

Sat 02/18/06 09:00 1.8 21,500 199 1.7 26,700 262 No NA 661,073 1,381 NA 609,618 1,273 7,647

Sun 02/19/06 08:30 2.0 23,000 192 2.0 22,100 184 No NA 682,816 1,426 NA 628,969 1,314 7,647

Mon 02/20/06 09:00 2.0 24,100 201 2.0 21,600 180 No NA 704,779 1,472 NA 648,622 1,355 7,647

Tue 02/21/06 08:00 1.8 22,300 206 2.2 23,900 181 No NA 726,872 1,518 NA 668,540 1,396 7,647

Wed 02/22/06 08:45 1.8 21,100 195 1.2 14,200 197 No NA 742,579 1,551 NA 682,802 1,426 7,647

Thu 02/23/06 07:30 1.8 21,100 195 2.4 27,400 190 No NA 763,415 1,594 NA 702,735 1,468 13,472

Fri 02/24/06 07:50 0.9 11,600 215 1.9 20,900 183 Yes NA 778,326 1,626 NA 717,060 1,498 13,472

Sat 02/25/06 08:15 2.8 34,000 202 2.0 22,300 186 No 82 797,262 1,665 78 735,356 1,536 13,472

Sun 02/26/06 09:30 1.7 20,700 203 1.5 16,600 184 No NA 814,936 1,702 NA 752,279 1,571 13,472

Mon 02/27/06 06:30 1.7 20,500 201 1.8 19,200 178 No NA 835,831 1,746 NA 772,329 1,613 13,472

Tue 02/28/06 10:15 2.0 23,900 199 1.9 22,100 194 No NA 856,567 1,789 NA 792,207 1,655 13,472

Wed 03/01/06 07:15 1.9 22,400 196 0.9 10,400 193 Yes NA 872,014 1,821 NA 806,985 1,685 13,472

Thu 03/02/06 08:15 1.9 21,800 191 2.7 31,400 194 No NA 971,158 2,028 NA 924,367 1,931 13,472

Fri 03/03/06 07:45 1.9 22,200 195 1.8 20,100 186 No NA 992,853 2,074 NA 945,645 1,975 13,472

Sat 03/04/06 08:30 1.4 16,800 200 1.7 19,200 188 No NA 1,000,897 2,090 NA 961,433 2,008 13,472

Sun 03/05/06 08:30 1.7 10,480 103 1.8 14,480 134 No 0 1,031,633 2,155 NA 983,608 2,054 13,472

Mon 03/06/06 06:40 2.2 33,620 255 1.7 26,320 258 No NA 1,054,674 2,203 NA 1,006,104 2,101 13,472

Tue 03/07/06 07:00 2.1 24,900 198 1.9 21,300 187 No NA 1,007,817 2,105 NA 1,029,016 2,149 13,472

Wed 03/08/06 08:00 2.0 23,200 193 1.8 21,100 195 No NA 1,100,817 2,299 NA 1,051,005 2,195 13,472

Thu 03/09/06 07:50 2.0 23,400 195 1.7 19,400 190 No NA 1,119,988 2,339 NA 1,069,653 2,234 13,472

Fri 03/10/06 07:30 1.9 21,900 192 1.1 12,700 192 Yes NA 1,140,465 2,382 NA 1,089,401 2,275 13,472

Sat 03/11/06 10:00 1.8 22,100 205 2.9 33,700 194 No NA 1,163,976 2,431 NA 1,112,105 2,323 13,472

Sun 03/12/06 09:15 1.4 16,800 200 2.1 22,500 179 No NA 1,181,234 2,467 NA 1,128,707 2,357 13,472

Mon 03/13/06 07:10 1.4 16,500 196 1.9 21,500 189 No NA 1,203,680 2,514 NA 1,150,212 2,402 13,472

Tue 03/14/06 06:30 1.8 21,700 201 2.0 22,100 184 No 103 1,226,174 2,561 98 1,171,717 2,447 13,472

Wed 03/15/06 07:45 1.7 20,500 201 1.0 11,200 187 No NA 1,242,433 2,595 NA 1,187,240 2,480 13,472

Thu 03/16/06 07:15 1.3 16,200 208 2.0 22,400 187 Yes NA 1,259,485 2,631 NA 1,203,462 2,514 13,472

Fri 03/17/06 07:50 3.6 44,000 204 2.0 21,500 179 No NA 1,291,047 2,697 NA 1,233,215 2,576 13,472

Sat 03/18/06 06:45 1.8 20,700 192 1.0 11,300 188 No NA 1,307,759 2,731 NA 1,248,624 2,608 13,472

Sun 03/19/06 07:30 1.6 20,300 211 2.1 23,600 187 No NA 1,330,633 2,779 NA 1,269,754 2,652 13,472

Mon 03/20/06 07:30 1.9 22,300 196 2.1 23,000 183 No NA 1,350,435 2,821 NA 1,291,692 2,698 13,472

Tue 03/21/06 07:00 0.9 10,800 200 1.9 21,500 189 No 104 16,886 2,856 103 16,535 2,732 0

Wed 03/22/06 10:00 1.8 21,700 201 2.1 22,800 181 Yes NA 40,391 2,905 NA 39,553 2,780 0

Thu 03/23/06 07:30 1.3 16,100 206 2.4 27,500 191 No NA 56,671 2,939 NA 55,448 2,814 0

Fri 03/24/06 07:30 1.8 19,700 182 1.8 20,000 185 No NA 79,796 2,987 NA 77,927 2,861 0

Sat 03/25/06 07:30 2.0 23,500 196 1.6 18,400 192 No 101 99,025 3,027 98 96,604 2,900 0

Sun 03/26/06 09:30 2.0 22,900 191 2.1 23,100 183 No NA 123,300 3,078 NA 120,078 2,949 0

Mon 03/27/06 07:30 2.0 23,000 192 1.1 12,700 192 No NA 144,965 3,123 NA 140,960 2,992 0

Tue 03/28/06 06:15 2.0 23,700 198 1.8 20,800 193 No 104 168,523 3,173 103 163,674 3,040 0

Wed 03/29/06 06:55 1.1 12,300 186 1.7 19,400 190 No NA 185,370 3,208 NA 179,924 3,074 0

Thu 03/30/06 08:30 2.0 23,400 195 1.8 20,000 185 No NA 208,268 3,256 NA 201,978 3,120 0

Fri 03/31/06 06:55 2.0 23,100 193 1.0 11,400 190 Yes NA 226,074 3,293 NA 219,063 3,155 0

Sat 04/01/06 11:30 2.6 30,700 197 2.7 31,400 194 No NA 254,724 3,353 NA 246,480 3,213 0

Sun 04/02/06 09:40 2.0 22,700 189 0.9 10,200 189 No NA 272,088 3,389 NA 263,018 3,247 0

Mon 04/03/06 07:30 2.1 23,800 189 1.9 21,300 187 No NA 295,966 3,439 NA 285,813 3,295 0

Tue 04/04/06 07:30 2.0 23,700 198 1.9 21,400 188 No 91 316,719 3,482 86 305,684 3,336 0

Wed 04/05/06 07:30 2.3 25,600 186 1.8 21,000 194 No NA 344,520 3,540 NA 332,196 3,392 0

Thu 04/06/06 07:10 1.1 12,300 186 1.8 19,600 181 Yes NA 361,684 3,576 NA 348,582 3,426 0

Fri 04/07/06 07:30 1.9 22,600 198 2.9 33,100 190 No NA 385,893 3,627 NA 371,649 3,474 0

Sat 04/08/06 07:00 1.7 21,000 206 1.0 11,400 190 No NA 403,723 3,664 NA 388,618 3,510 0

Sun 04/09/06 07:30 1.7 19,900 195 2.3 25,300 183 No NA 427,592 3,714 NA 411,311 3,557 0

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Totalizer

2

Week 

No.

1

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

3

7

6

5

4

8

9

10
Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet (Continued)

A-2

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 04/10/06 08:00 1.7 20,400 200 2.2 23,700 180 No NA 450,987 3,762 NA 433,564 3,603 0

Tue 04/11/06 07:30 1.8 22,700 210 2.2 24,000 182 No 86 474,931 3,813 83 456,451 3,651 0

Wed 04/12/06 07:30 1.0 11,200 187 2.0 22,200 185 Yes NA 493,225 3,851 NA 473,753 3,687 0

Thu 04/13/06 07:00 2.5 30,700 205 1.9 21,800 191 No NA 517,323 3,901 NA 496,698 3,735 0

Fri 04/14/06 07:00 1.5 18,400 204 1.9 17,500 154 No NA 523,009 3,913 NA 528,566 3,802 0

Sat 04/15/06 07:50 2.3 27,700 201 2.0 19,600 163 No NA 542,452 3,954 NA 559,093 3,866 0

Sun 04/16/06 10:30 1.9 22,100 194 2.2 24,600 186 No NA 567,273 4,005 NA 581,256 3,912 0

Mon 04/17/06 07:15 0.9 11,500 213 2.1 22,600 179 No NA 585,508 4,043 NA 598,270 3,947 0

Tue 04/18/06 06:45 2.6 30,700 197 2.5 28,800 192 No 99 611,098 4,097 95 622,415 3,998 0

Wed 04/19/06 08:00 2.5 27,400 183 2.2 24,700 187 No 94 639,417 4,156 90 649,110 4,054 0

Thu 04/20/06 07:30 2.1 24,600 195 1.4 16,300 194 No NA 660,342 4,200 NA 668,800 4,095 0

Fri 04/21/06 07:30 2.0 22,400 187 1.5 16,600 184 No NA 683,851 4,249 NA 691,123 4,141 0

Sat 04/22/06 08:00 2.2 24,700 187 1.9 21,400 188 No 81 706,158 4,295 98 712,438 4,186 0

Sun 04/23/06 08:00 1.1 12,400 188 1.8 20,900 194 No NA 725,593 4,336 NA 730,996 4,225 0

Mon 04/24/06 07:30 2.3 25,800 187 1.8 20,100 186 No NA 749,547 4,386 NA 753,989 4,273 0

Tue 04/25/06 09:30 3.2 34,700 181 1.8 21,100 195 No 89 778,661 4,447 85 782,073 4,331 0

Wed 04/26/06 07:30 2.3 25,400 184 1.8 20,900 194 No NA 802,861 4,497 NA 804,962 4,379 0

Thu 04/27/06 07:30 2.2 25,100 190 2.0 22,300 186 Yes NA 824,698 4,543 NA 825,800 4,423 0

Fri 04/28/06 06:50 1.8 21,700 201 2.5 27,800 185 No NA 847,633 4,591 NA 847,801 4,469 0

Sat 04/29/06 08:50 1.8 21,300 197 2.2 23,800 180 No NA 871,240 4,640 NA 870,491 4,516 0

Sun 04/30/06 10:00 1.8 21,200 196 2.3 25,300 183 No NA 895,354 4,691 NA 893,704 4,564 0

Mon 05/01/06 07:30 1.9 2,700 24 2.2 24,800 188 No 95 917,086 4,736 92 914,659 4,608 0

Tue 05/02/06 08:30 1.6 38,800 404 2.2 23,700 180 No 99 939,085 4,782 96 935,859 4,653 0

Wed 05/03/06 07:30 1.4 16,900 201 2.0 22,800 190 No NA 962,737 4,831 NA 958,668 4,700 0

Thu 05/04/06 07:30 2.0 23,800 198 2.1 22,900 182 Yes NA 986,918 4,882 NA 982,085 4,749 0

Fri 05/05/06 07:10 3.0 36,200 201 2.2 23,700 180 No NA 1,012,484 4,935 NA 1,006,893 4,801 0

Sat 05/06/06 09:00 2.1 24,100 191 2.0 23,000 192 No NA 1,036,423 4,985 NA 1,029,783 4,849 0

Sun 05/07/06 07:30 2.0 24,000 200 2.2 23,700 180 No NA 1,061,862 5,038 NA 1,054,119 4,900 0

Mon 05/08/06 07:30 2.4 28,500 198 2.1 23,500 187 No NA 1,086,995 5,091 NA 1,078,116 4,950 0

Tue 05/09/06 08:35 1.6 19,500 203 1.9 22,700 199 No 97 1,112,269 5,144 94 1,102,292 5,000 0

Wed 05/10/06 07:30 2.0 23,600 197 2.2 22,300 169 No NA 1,134,854 5,191 NA 1,123,876 5,045 0

Thu 05/11/06 07:10 2.0 23,900 199 2.1 23,200 184 Yes NA 1,159,259 5,242 NA 1,147,312 5,094 0

Fri 05/12/06 07:00 2.9 34,300 197 1.1 12,100 183 No NA 1,178,114 5,281 NA 1,165,472 5,132 0

Sat 05/13/06 06:00 1.8 20,300 188 1.9 22,600 198 No NA 1,197,538 5,322 NA 1,184,169 5,171 0

Sun 05/14/06 07:50 1.8 19,800 183 1.7 18,400 180 No NA 1,220,387 5,369 NA 1,206,143 5,217 0

Mon 05/15/06 08:10 2.0 23,000 192 2.0 24,100 201 No NA 1,244,073 5,419 NA 1,229,005 5,265 0

Tue 05/16/06 07:30 2.1 23,500 187 1.9 21,000 184 No 91 1,267,795 5,468 90 1,251,991 5,313 0

Wed 05/17/06 07:30 2.1 22,800 181 2.0 22,700 189 No NA 1,291,456 5,518 NA 1,274,925 5,361 0

Thu 05/18/06 07:30 2.0 22,700 189 2.1 23,700 188 No NA 1,315,427 5,568 NA 1,298,223 5,409 0

Fri 05/19/06 07:30 2.0 22,400 187 2.0 23,000 192 Yes NA 1,338,976 5,617 NA 1,321,122 5,457 0

Sat 05/20/06 07:45 1.0 11,600 193 3.7 42,000 189 No NA 1,361,859 5,665 NA 1,343,381 5,504 0

Sun 05/21/06 07:15 1.9 23,100 203 2.2 23,200 176 No NA 1,386,140 5,716 NA 1,367,029 5,553 0

Mon 05/22/06 07:45 2.6 30,000 192 3.1 35,100 189 No NA 1,419,448 5,785 NA 1,399,559 5,621 0

Tue 05/23/06 07:30 2.3 25,700 186 1.8 21,200 196 No NA 1,443,607 5,836 NA 1,423,099 5,670 0

Wed 05/24/06 08:00 3.0 33,300 185 1.9 21,000 184 No 88 1,468,540 5,888 86 1,447,450 5,721 0

Thu 05/25/06 07:00 2.1 23,100 183 2.0 22,400 187 Yes NA 1,482,626 5,917 NA 1,470,959 5,770 0

Fri 05/26/06 07:00 3.1 35,500 191 1.7 19,600 192 No NA 1,517,547 5,990 NA 1,495,225 5,821 0

Sat 05/27/06 07:30 3.3 36,500 184 2.0 22,300 186 No NA 1,545,234 6,048 NA 1,522,268 5,877 0

Sun 05/28/06 09:00 2.5 28,100 187 3.2 36,700 191 No NA 1,578,619 6,118 NA 1,554,878 5,945 0

Mon 05/29/06 09:30 2.8 31,200 186 2.0 22,700 189 No NA 1,608,016 6,179 NA 1,583,589 6,005 0

Tue 05/30/06 07:00 3.8 40,600 178 2.2 25,800 195 No 82 1,640,353 6,247 81 1,615,279 6,072 0

Wed 05/31/06 10:00 3.2 35,800 186 3.5 39,000 186 Yes NA NA NA NA NA NA 0

Thu 06/01/06 07:30 3.4 39,400 193 2.3 NA NA No NA 1,710,216 6,393 NA 1,683,814 6,215 0

Fri 06/02/06 07:00 3.1 36,300 195 2.7 NA NA No NA 1,743,905 6,463 NA 1,716,927 6,284 0

Sat 06/03/06 07:30 3.2 38,600 201 3.8 40,800 179 No NA 1,781,981 6,542 NA 1,754,425 6,362 0

Sun 06/04/06 08:30 3.6 42,600 197 5.8 62,000 178 No NA 1,838,375 6,660 NA 1,810,012 6,478 0

Mon 06/05/06 07:15 2.2 25,400 192 1.6 16,300 170 No NA 1,859,633 6,705 NA 1,831,041 6,522 0

Tue 06/06/06 07:15 2.7 32,000 198 3.7 40,100 181 No NA 1,896,516 6,782 NA 1,867,421 6,598 0

Wed 06/07/06 07:30 2.1 24,100 191 2.1 22,700 180 No NA 1,920,563 6,832 NA 1,891,195 6,648 0

Thu 06/08/06 08:00 3.1 37,100 199 3.5 38,300 182 No NA 1,956,062 6,906 NA 1,926,446 6,721 0

Fri 06/09/06 08:00 3.3 39,000 197 3.3 34,400 174 Yes 95 1,993,408 6,984 95 1,963,490 6,799 0

Sat 06/10/06 09:00 2.8 33,400 199 2.1 23,500 187 No NA 2,018,564 7,037 NA 1,988,497 6,851 0

Sun 06/11/06 09:00 2.0 23,500 196 2.1 23,600 187 No NA 2,042,466 7,086 NA 2,012,255 6,901 0

Mon 06/12/06 07:30 2.0 23,800 198 2.2 23,800 180 No NA 2,066,750 7,137 NA 2,036,415 6,951 0

Tue 06/13/06 07:00 2.4 29,500 205 2.3 24,900 180 No 95 2,092,388 7,191 96 2,061,868 7,004 0

Wed 06/14/06 07:10 2.9 33,000 190 4.1 43,700 178 No NA 2,133,607 7,277 NA 2,102,710 7,090 0

Thu 06/15/06 07:20 1.9 23,500 206 2.1 23,400 186 Yes NA 2,157,420 7,327 NA 2,126,215 7,139 0

Fri 06/16/06 07:00 2.2 23,700 180 2.6 30,700 197 No NA 2,180,588 7,375 NA 2,149,056 7,186 0

Sat 06/17/06 07:30 1.4 16,000 190 2.9 32,200 185 No NA 2,205,255 7,427 NA 2,173,412 7,237 0

Sun 06/18/06 07:45 3.6 39,800 184 2.3 25,900 188 No NA 2,238,756 7,496 NA 2,206,522 7,306 0

13

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

14

20

19

18

16

15

17

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Week Totalizer

No.

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

11

12
Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet (Continued)

A-3

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 06/19/06 07:30 1.2 13,500 188 1.9 19,600 172 No NA 2,256,658 7,534 NA 2,224,265 7,344 0

Tue 06/20/06 09:30 3.5 38,800 185 2.0 25,200 210 No 95 2,287,962 7,599 95 2,255,247 7,408 0

Wed 06/21/06 07:00 2.4 26,600 185 1.9 20,800 182 No NA 2,312,303 7,650 NA 2,279,162 7,458 0

Thu 06/22/06 07:00 2.8 29,700 177 3.0 33,700 187 Yes NA 2,344,847 7,718 NA 2,311,172 7,525 0

Fri 06/23/06 07:30 3.3 38,700 195 3.3 36,800 186 No NA 2,378,811 7,789 NA 2,344,822 7,595 0

Sat 06/24/06 09:30 5.3 38,500 121 4.5 48,600 180 No NA 2,423,121 7,882 NA 2,388,127 7,686 0

Sun 06/25/06 08:40 0.2 25,900 2158 2.1 22,600 179 No NA 2,448,429 7,934 NA 2,412,780 7,737 0

Mon 06/26/06 07:00 2.2 26,100 198 2.3 24,200 175 No NA 2,474,481 7,989 NA 2,438,009 7,790 0

Tue 06/27/06 07:30 2.9 34,900 201 2.2 24,000 182 No 94 2,501,625 8,046 92 2,464,389 7,845 0

Wed 06/28/06 07:30 2.2 25,000 189 2.6 27,800 178 Yes NA 2,531,793 8,109 NA 2,493,682 7,906 0

Thu 06/29/06 07:00 1.8 22,100 205 3.6 40,200 186 No NA 2,557,220 8,162 NA 2,518,338 7,958 0

Fri 06/30/06 07:00 2.1 25,000 198 7.9 87,300 184 No NA 2,616,173 8,285 NA 2,575,296 8,077 0

Sat 07/01/06 08:00 2.1 24,700 196 4.0 43,000 179 No NA 2,651,423 8,358 NA 2,609,067 8,147 0

Sun 07/02/06 08:00 3.3 40,000 202 2.4 25,400 176 No 94 2,681,050 8,420 92 2,637,568 8,207 0

Mon 07/03/06 07:00 2.1 23,500 187 3.1 32,600 175 No NA 2,714,077 8,489 NA 2,669,270 8,273 0

Tue 07/04/06 07:00 2.8 32,200 192 3.7 39,400 177 No NA 2,750,262 8,565 NA 2,703,977 8,345 0

Wed 07/05/06 07:00 3.1 36,400 196 3.4 36,100 177 No NA 2,786,863 8,641 NA 2,739,016 8,419 0

Thu 07/06/06 07:00 2.7 31,300 193 3.4 36,600 179 Yes NA 2,823,623 8,718 NA 2,774,146 8,492 0

Fri 07/07/06 07:30 4.4 51,900 197 4.4 45,800 173 No 85 2,865,948 8,806 81 2,814,596 8,576 0

Sat 07/08/06 07:00 3.5 41,900 200 3.4 35,400 174 No NA 2,908,966 8,896 NA 2,855,521 8,662 0

Sun 07/09/06 08:30 2.4 27,100 188 5.6 57,700 172 No NA 2,953,202 8,989 NA 2,897,540 8,750 0

Mon 07/10/06 07:30 5.3 61,700 194 2.6 27,600 177 No NA 2,998,101 9,082 NA 2,940,264 8,839 0

Tue 07/11/06 07:30 2.6 29,400 188 4.4 46,900 178 No NA 3,038,652 9,167 NA 2,978,660 8,919 0

Wed 07/12/06 07:45 4.4 50,700 192 7.7 77,400 168 Yes NA 3,105,202 9,306 NA 3,041,629 9,051 0

Thu 07/13/06 07:00 6.3 66,400 176 4.5 51,900 192 No NA 3,117,350 9,332 NA 3,091,457 9,155 0

Fri 07/14/06 07:30 3.3 36,100 182 3.4 36,800 180 No NA 3,156,849 9,414 NA 3,128,875 9,233 0

Sat 07/15/06 07:30 2.8 30,900 184 2.9 31,800 183 No 80 3,186,370 9,476 78 3,140,070 9,256 0

Sun 07/16/06 08:00 4.3 50,000 194 5.0 51,200 171 No NA 3,241,639 9,591 NA 3,192,592 9,366 0

Mon 07/17/06 07:30 3.0 33,600 187 2.1 24,400 194 No 93 3,268,449 9,647 91 3,218,007 9,419 0

Tue 07/18/06 07:30 3.6 38,100 176 5.8 63,500 182 No NA 3,320,042 9,755 NA 3,266,629 9,521 0

Wed 07/19/06 07:00 5.2 55,100 177 3.3 36,700 185 No 73 3,366,506 9,852 71 3,310,241 9,612 0

Thu 07/20/06 07:00 2.0 22,000 183 2.1 23,400 186 No 83 3,388,565 9,898 77 3,330,963 9,655 0

Fri 07/21/06 07:00 3.5 36,400 173 4.8 50,800 176 Yes 81 3,433,666 9,992 74 3,373,384 9,744 0

Sat 07/22/06 09:10 4.0 45,500 190 3.8 39,800 175 No NA 3,473,299 10,075 NA 3,410,821 9,822 0

Sun 07/23/06 10:10 3.2 36,500 190 3.2 32,500 169 No NA 3,506,408 10,144 NA 3,442,266 9,887 0

Mon 07/24/06 07:15 2.8 31,400 187 2.9 28,700 165 No 81 3,537,286 10,209 87 3,471,541 9,949 0

Tue 07/25/06 07:00 3.3 36,400 184 5.9 58,700 166 No NA 3,589,635 10,318 NA 3,520,970 10,052 0

Wed 07/26/06 06:20 2.8 33,400 199 4.0 42,400 177 Yes NA 3,626,432 10,395 NA 3,560,844 10,135 0

Thu 07/27/06 07:00 3.6 43,200 200 6.6 73,800 186 No NA 3,678,340 10,503 NA 3,616,274 10,251 0

Fri 07/28/06 07:00 4.3 49,700 193 6.7 70,800 176 No 82 3,734,103 10,620 89 3,675,770 10,375 0

Sat 07/29/06 08:15 4.2 50,300 200 5.7 59,800 175 No NA 3,789,942 10,736 NA 3,735,249 10,499 0

Sun 07/30/06 08:45 7.4 87,000 196 2.9 30,600 176 No NA 3,847,814 10,857 NA 3,796,925 10,628 0

Mon 07/31/06 06:30 2.6 32,600 209 4.6 48,500 176 Yes NA 3,887,370 10,940 NA 3,838,985 10,716 0

Tue 08/01/06 09:30 4.3 48,000 186 5.4 57,600 178 No 82 3,931,228 11,031 88 3,885,665 10,814 0

Wed 08/02/06 07:30 2.0 22,500 188 2.0 22,500 188 No NA 3,954,306 11,080 NA 3,910,153 10,865 0

Thu 08/03/06 07:45 4.0 43,800 183 2.1 24,200 192 Yes NA 3,987,471 11,149 NA 3,945,340 10,938 0

Fri 08/04/06 06:30 3.3 37,500 189 3.6 40,800 189 No NA 4,021,061 11,219 NA 3,980,997 11,013 0

Sat 08/05/06 10:00 3.4 37,700 185 2.1 23,400 186 No NA 4,050,664 11,281 NA 4,012,254 11,078 0

Sun 08/06/06 09:30 2.2 25,000 189 2.2 24,600 186 No NA 4,074,924 11,332 NA 4,038,023 11,132 0

Mon 08/07/06 07:00 2.3 25,600 186 2.2 25,200 191 No NA 4,099,546 11,383 NA 4,064,110 11,186 0

Tue 08/08/06 07:00 2.2 24,500 186 2.1 24,400 194 No NA 4,123,342 11,433 NA 4,089,310 11,239 0

Wed 08/09/06 07:00 2.4 26,600 185 3.3 36,700 185 No NA 4,152,384 11,493 NA 4,120,097 11,303 0

Thu 08/10/06 07:00 2.9 32,300 186 2.1 23,100 183 No NA 4,179,343 11,550 NA 4,148,629 11,363 0

Fri 08/11/06 06:45 3.1 33,800 182 2.0 23,600 197 Yes NA 4,206,219 11,606 NA 4,177,094 11,422 0

Sat 08/12/06 16:00 4.3 47,600 184 1.5 16,300 181 No NA 4,233,613 11,663 NA 4,206,006 11,483 0

Sun 08/13/06 18:00 3.3 37,400 189 3.4 37,600 184 No NA 4,270,098 11,739 NA 4,244,537 11,563 0

Mon 08/14/06 09:00 1.4 17,800 212 1.7 18,000 176 No 82 4,286,018 11,772 87 4,261,380 11,598 0

Tue 08/15/06 08:00 1.5 17,600 196 2.3 25,300 183 No 92 4,305,719 11,814 97 4,282,131 11,642 0

Wed 08/16/06 07:15 2.3 25,000 181 1.7 18,100 177 No NA 4,329,626 11,864 NA 4,307,316 11,694 0

Thu 08/17/06 07:45 3.0 36,100 201 4.2 45,600 181 No 90 4,366,564 11,941 96 4,346,263 11,776 0

Fri 08/18/06 07:00 2.3 24,200 175 1.7 19,800 194 Yes NA 4,389,862 11,989 NA 4,370,755 11,827 0

Sat 08/19/06 07:30 3.7 42,200 190 2.4 27,100 188 No NA 4,418,264 12,049 NA 4,400,660 11,889 0

Sun 08/20/06 08:30 1.6 18,400 192 2.8 30,400 181 No NA 4,442,142 12,099 NA 4,425,746 11,942 0

Mon 08/21/06 07:30 3.1 33,400 180 1.5 18,000 200 No NA 4,467,129 12,151 NA 4,451,964 11,996 0

Tue 08/22/06 07:00 1.7 19,900 195 2.7 29,000 179 No NA 4,491,132 12,201 NA 4,477,139 12,049 0

Wed 08/23/06 07:30 3.1 36,400 196 3.0 31,900 177 Yes NA 4,524,068 12,270 NA 4,512,252 12,122 0

Thu 08/24/06 07:30 3.1 34,500 185 2.0 22,500 188 No NA 4,547,599 12,319 NA 4,537,138 12,174 0

Fri 08/25/06 07:00 2.4 26,700 185 2.0 22,500 188 No NA 4,571,422 12,369 NA 4,562,312 12,227 0

Sat 08/26/06 11:00 3.5 39,300 187 2.7 30,600 189 No NA 4,605,023 12,439 NA 4,597,864 12,301 0

Sun 08/27/06 09:00 2.2 25,100 190 1.2 13,400 186 No NA 4,623,548 12,477 NA 4,617,376 12,342 0

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

21

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Week Totalizer

No.

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

22

27

25

23

24

26

28

29

30
Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet (Continued)

A-4

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 08/28/06 07:00 2.4 26,500 184 2.3 26,700 193 No NA 4,649,404 12,531 NA 4,644,690 12,399 0

Tue 08/29/06 07:00 2.4 26,300 183 3.0 33,300 185 No NA 4,679,093 12,593 NA 4,676,030 12,464 0

Wed 08/30/06 07:00 3.1 34,600 186 1.6 18,600 194 No NA 4,704,979 12,647 NA 4,703,289 12,521 0

Thu 08/31/06 07:00 1.5 17,900 199 3.1 32,300 174 Yes NA 4,729,638 12,699 NA 4,729,279 12,576 0

Fri 09/01/06 07:00 3.6 41,900 194 1.8 19,300 179 No NA 4,754,716 12,751 NA 4,755,705 12,631 0

Sat 09/02/06 10:00 1.9 22,500 197 3.8 40,500 178 No NA 4,783,164 12,811 NA 4,785,766 12,694 0

Sun 09/03/06 08:30 1.9 23,500 206 1.3 14,500 186 No NA 4,803,906 12,854 NA 4,807,442 12,739 0

Mon 09/04/06 16:20 3.1 36,800 198 3.9 41,200 176 No NA 4,842,202 12,934 NA 4,847,659 12,823 0

Tue 09/05/06 07:00 1.0 11,600 193 2.6 27,000 173 No 75 4,859,118 12,969 78 4,865,409 12,860 0

Wed 09/06/06 07:20 2.0 24,000 200 2.4 25,800 179 No NA 4,885,510 13,025 NA 4,893,021 12,918 0

Thu 09/07/06 07:15 2.1 25,000 198 2.3 25,600 186 No NA 4,910,069 13,076 NA 4,918,751 12,971 0

Fri 09/08/06 07:15 2.2 26,500 201 2.3 25,000 181 Yes NA 4,935,085 13,128 NA 4,944,965 13,026 0

Sat 09/09/06 09:30 3.8 43,900 193 2.1 23,100 183 No NA 4,960,553 13,181 NA 4,971,585 13,082 0

Sun 09/10/06 08:30 2.3 25,400 184 1.5 16,800 187 No NA 4,978,709 13,219 NA 4,990,503 13,121 0

Mon 09/11/06 07:30 2.3 25,500 185 2.5 28,300 189 No 92 5,004,872 13,274 95 5,017,808 13,178 0

Tue 09/12/06 07:30 3.2 37,100 193 1.4 15,900 189 No 90 5,030,173 13,327 74 5,044,147 13,233 0

Wed 09/13/06 07:30 2.3 27,000 196 2.4 25,700 178 No NA 5,058,919 13,387 NA 5,074,043 13,296 0

Thu 09/14/06 07:30 2.1 25,200 200 2.6 27,000 173 No NA 5,084,510 13,440 NA 5,100,619 13,351 0

Fri 09/15/06 07:30 2.1 25,000 198 2.6 27,500 176 Yes NA 5,110,226 13,494 NA 5,127,319 13,407 0

Sat 09/16/06 10:00 1.3 40,100 514 2.2 24,200 183 No NA 5,134,156 13,544 NA 5,152,109 13,459 0

Sun 09/17/06 08:30 4.2 25,200 100 2.3 25,300 183 No NA 5,158,965 13,596 NA 5,177,736 13,512 0

Mon 09/18/06 07:15 2.2 26,400 200 2.4 24,900 173 No NA 5,184,212 13,648 NA 5,203,764 13,567 0

Tue 09/19/06 07:45 2.8 33,500 199 2.4 25,600 178 No NA 5,213,280 13,709 NA 5,233,731 13,629 0

Wed 09/20/06 07:30 2.9 33,000 190 1.5 17,700 197 Yes NA 5,238,085 13,761 NA 5,259,243 13,682 0

Thu 09/21/06 07:00 2.4 25,800 179 3.3 37,500 189 No NA 5,264,714 13,817 NA 5,286,536 13,739 0

Fri 09/22/06 07:30 2.2 24,900 189 2.8 31,400 187 No 94 5,289,585 13,869 96 5,311,932 13,792 0

Sat 09/23/06 08:45 2.3 25,500 185 2.7 30,000 185 No 89 5,317,432 13,927 92 5,340,316 13,852 0

Sun 09/24/06 08:00 2.4 26,900 187 2.2 25,300 192 No NA 5,343,047 13,980 NA 5,366,361 13,906 0

Mon 09/25/06 07:30 2.7 29,100 180 2.2 24,400 185 No NA 5,372,295 14,041 NA 5,396,063 13,968 0

Tue 09/26/06 07:30 2.7 31,000 191 1.9 19,700 173 No NA 5,397,300 14,093 NA 5,421,417 14,021 0

Wed 09/27/06 07:30 2.5 27,400 183 1.9 22,500 197 No NA 5,421,918 14,145 NA 5,446,356 14,073 0

Thu 09/28/06 07:05 2.5 27,100 181 2.1 22,800 181 Yes NA 5,446,642 14,197 NA 5,471,373 14,126 0

Fri 09/29/06 08:30 3.0 34,800 193 2.5 26,500 177 No NA 5,469,349 14,244 NA 5,494,310 14,173 0

Sat 09/30/06 08:30 1.9 23,000 202 1.2 12,700 176 No NA 5,489,679 14,286 NA 5,514,713 14,216 0

Sun 10/01/06 08:30 1.9 23,000 202 2.5 26,400 176 No NA 5,514,331 14,338 NA 5,539,446 14,268 0

Mon 10/02/06 07:30 2.2 25,100 190 2.6 28,400 182 No NA 5,540,988 14,394 NA 5,566,197 14,324 0

Tue 10/03/06 07:30 2.0 23,700 198 2.6 26,600 171 No NA 5,566,147 14,446 NA 5,591,427 14,376 0

Wed 10/04/06 07:00 1.9 23,000 202 2.4 25,700 178 No NA 5,590,525 14,497 NA 5,615,854 14,427 0

Thu 10/05/06 07:30 2.1 24,200 192 3.0 31,900 177 No NA 5,616,794 14,552 NA 5,642,154 14,482 0

Fri 10/06/06 07:30 2.0 23,300 194 2.2 23,100 175 Yes NA 5,641,709 14,604 NA 5,667,047 14,534 0

Sat 10/07/06 08:15 3.2 39,100 204 2.3 24,400 177 No NA 5,667,122 14,657 NA 5,692,419 14,587 0

Sun 10/08/06 08:00 2.2 25,800 195 2.4 25,400 176 No NA 5,692,665 14,710 NA 5,717,853 14,640 0

Mon 10/09/06 07:30 2.3 26,200 190 2.4 25,400 176 No NA 5,718,486 14,764 NA 5,743,537 14,694 0

Tue 10/10/06 08:00 2.1 25,400 202 2.3 24,700 179 No NA 5,743,486 14,817 NA 5,768,379 14,746 0

Wed 10/11/06 07:30 2.8 31,800 189 1.6 17,100 178 No NA 5,767,870 14,867 NA 5,792,618 14,796 0

Thu 10/12/06 07:30 2.5 27,100 181 2.0 23,000 192 Yes 66 5,792,876 14,920 62 5,817,482 14,848 0

Fri 10/13/06 07:35 2.1 23,400 186 3.5 40,800 194 No NA 5,814,027 14,964 NA 5,839,531 14,894 0

Sat 10/14/06 09:00 2.8 30,400 181 2.0 21,800 182 No NA 5,842,318 15,023 NA 5,869,381 14,957 0

Sun 10/15/06 10:00 2.5 28,100 187 1.9 21,500 189 No NA 5,863,478 15,067 NA 5,891,781 15,004 0

Mon 10/16/06 07:30 1.4 14,600 174 2.0 23,200 193 No NA 5,884,786 15,112 NA 5,914,277 15,051 6,249

Tue 10/17/06 07:30 2.3 25,400 184 2.0 21,600 180 No NA 5,905,041 15,154 NA 5,935,705 15,095 6,249

Wed 10/18/06 07:30 2.3 25,800 187 1.2 13,800 192 No NA 5,926,979 15,200 NA 5,958,833 15,144 6,249

Thu 10/19/06 07:30 2.3 25,100 182 2.1 23,200 184 Yes NA 5,950,583 15,249 NA 5,983,698 15,196 6,249

Fri 10/20/06 07:30 3.7 43,800 197 1.0 12,000 200 No NA 5,969,846 15,289 NA 6,004,074 15,238 6,249

Sat 10/21/06 08:30 2.3 25,000 181 2.1 22,900 182 No NA 5,993,082 15,338 NA 6,028,582 15,289 6,249

Sun 10/22/06 09:30 2.4 26,300 183 2.0 22,600 188 No NA 6,014,351 15,382 NA 6,051,052 15,336 6,249

Mon 10/23/06 07:30 1.7 20,200 198 2.0 22,900 191 No 82 6,034,892 15,425 88 6,072,703 15,381 6,249

Tue 10/24/06 08:00 2.8 30,400 181 1.9 21,500 189 No 82 6,060,136 15,478 84 6,099,276 15,437 6,249

Wed 10/25/06 07:45 2.0 22,000 183 2.0 21,900 183 Yes NA 6,082,981 15,526 NA 6,123,298 15,487 6,249

Thu 10/26/06 07:45 3.3 37,000 187 2.0 22,100 184 No NA 6,108,243 15,578 NA 6,150,054 15,543 6,430

Fri 10/27/06 07:30 2.2 24,800 188 1.3 15,100 194 No NA 6,126,056 15,616 NA 6,168,942 15,582 6,430

Sat 10/28/06 08:30 2.2 24,400 185 1.9 21,500 189 No NA 6,149,901 15,665 NA 6,194,237 15,635 6,430

Sun 10/29/06 09:00 2.3 25,000 181 2.1 23,100 183 No NA 6,173,268 15,714 NA 6,219,037 15,687 6,430

Mon 10/30/06 07:30 2.3 26,000 188 2.1 24,100 191 No NA 6,197,559 15,765 NA 6,244,816 15,741 6,447

Tue 10/31/06 07:30 2.4 26,500 184 1.6 22,800 237 No 77 6,218,629 15,809 82 6,267,203 15,788 6,447

Wed 11/01/06 07:30 1.4 14,200 169 2.6 24,700 158 No NA 6,240,430 15,854 NA 6,282,890 15,820 6,447

Thu 11/02/06 07:30 2.2 24,700 187 1.1 12,400 188 Yes NA 6,247,805 15,870 NA 6,301,808 15,860 6,447

Fri 11/03/06 08:30 2.1 25,000 198 3.7 40,600 183 No NA 6,273,152 15,923 NA 6,328,679 15,916 6,447

Sat 11/04/06 09:00 1.0 12,300 205 2.3 24,400 177 No NA 6,290,878 15,960 NA 6,347,436 15,955 6,447

Sun 11/05/06 08:00 2.1 25,000 198 2.2 24,100 183 No NA 6,314,727 16,010 NA 6,372,691 16,008 6,447

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Week Totalizer

No.

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

32

40

31

33

39

34

36

38

37

35
Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet (Continued)

A-5

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 11/06/06 08:00 2.3 26,500 192 2.4 25,700 178 No NA 6,340,012 16,062 NA 6,399,479 16,064 6,447

Tue 11/07/06 07:30 2.8 33,400 199 2.3 24,300 176 No 91 6,365,280 16,115 97 6,426,258 16,120 6,447

Wed 11/08/06 07:00 1.9 22,900 201 2.5 26,000 173 Yes NA 6,390,768 16,168 NA 6,452,897 16,176 6,447

Thu 11/09/06 08:00 5.0 55,900 186 2.1 23,600 187 No NA 6,424,924 16,240 NA 6,489,356 16,252 6,447

Fri 11/10/06 08:00 2.3 25,600 186 2.2 25,400 192 No NA 6,449,596 16,291 NA 6,515,446 16,306 6,447

Sat 11/11/06 10:30 2.4 26,000 181 3.4 36,700 180 No NA 6,480,200 16,355 NA 6,547,814 16,374 6,447

Sun 11/12/06 10:30 2.3 25,800 187 2.2 24,600 186 No NA 6,504,631 16,406 NA 6,573,623 16,428 6,447

Mon 11/13/06 08:00 2.4 26,300 183 1.8 21,100 195 No NA 6,524,741 16,448 NA 6,594,873 16,472 6,447

Tue 11/14/06 08:30 2.4 26,500 184 2.7 29,900 185 No NA 6,554,910 16,511 NA 6,626,737 16,539 6,447

Wed 11/15/06 07:30 2.3 25,100 182 1.1 11,900 180 No NA 6,572,786 16,549 NA 6,645,596 16,578 6,447

Thu 11/16/06 07:45 1.7 19,900 195 2.1 23,100 183 No 79 6,590,890 16,586 84 6,664,733 16,618 6,447

Fri 11/17/06 07:30 2.1 23,700 188 2.0 20,000 167 Yes NA 6,612,353 16,631 NA 6,687,376 16,665 6,447

Sat 11/18/06 07:45 3.1 36,300 195 1.0 12,000 200 No NA 6,631,462 16,671 NA 6,707,501 16,707 6,447

Sun 11/19/06 07:45 2.3 25,100 182 2.2 23,700 180 No NA 6,653,106 16,716 NA 6,730,357 16,755 6,447

Mon 11/20/06 07:30 2.0 23,300 194 2.1 24,000 190 No 80 6,675,241 16,763 85 6,753,700 16,804 6,447

Tue 11/21/06 07:30 1.8 18,600 172 1.9 21,100 185 No NA 6,697,361 16,809 NA 6,774,971 16,848 6,447

Wed 11/22/06 07:30 2.4 26,300 183 1.1 11,800 179 Yes NA 6,715,751 16,847 NA 6,796,312 16,893 6,447

Thu 11/23/06 10:30 2.0 23,800 198 4.1 45,100 183 No NA 6,741,457 16,901 NA 6,823,364 16,949 6,447

Fri 11/24/06 06:00 1.0 11,500 192 2.1 22,700 180 No NA 6,759,689 16,939 NA 6,842,510 16,989 6,447

Sat 11/25/06 14:00 3.2 38,100 198 2.2 24,000 182 No NA 6,789,513 17,001 NA 6,873,854 17,055 6,447

Sun 11/26/06 05:00 1.0 11,500 192 1.3 12,800 164 No NA 6,801,400 17,026 NA 6,886,323 17,081 6,447

Mon 11/27/06 07:30 2.0 23,800 198 2.6 27,600 177 No NA 6,826,262 17,078 NA 6,912,404 17,135 6,447

Tue 11/28/06 07:00 1.5 17,900 199 2.3 24,800 180 No NA 6,844,536 17,116 NA 6,931,532 17,175 6,447

Wed 11/29/06 07:30 2.3 26,000 188 1.7 18,200 178 Yes NA 6,868,432 17,166 NA 6,956,573 17,228 6,447

Thu 11/30/06 07:30 3.4 39,400 193 1.2 13,300 185 No NA 6,886,644 17,204 NA 6,975,600 17,267 6,447

Fri 12/01/06 07:15 2.3 25,200 183 1.9 21,300 187 No NA 6,910,219 17,253 NA 7,000,183 17,319 6,447

Sat 12/02/06 08:30 2.5 27,000 180 2.0 22,200 185 No NA 6,931,555 17,298 NA 7,022,460 17,365 6,447

Sun 12/03/06 08:15 1.2 13,500 187 1.9 21,600 189 No NA 6,951,304 17,339 NA 7,043,023 17,408 6,447

Mon 12/04/06 07:30 2.5 27,300 182 2.3 24,500 178 No NA 6,974,963 17,389 NA 7,067,677 17,460 6,447

Tue 12/05/06 07:30 2.3 25,400 184 1.0 11,500 192 No NA 6,994,294 17,429 NA 7,087,749 17,502 6,447

Wed 12/06/06 07:30 2.8 31,400 187 1.0 11,700 195 No NA 7,015,027 17,472 NA 7,109,289 17,546 6,447

Thu 12/07/06 07:30 1.3 14,200 182 2.0 21,500 179 Yes NA 7,032,541 17,509 NA 7,127,515 17,585 6,447

Fri 12/08/06 07:30 3.5 39,800 190 1.4 16,400 195 No NA 7,051,448 17,548 NA 7,147,116 17,626 6,447

Sat 12/09/06 08:00 2.1 23,900 190 1.8 19,200 178 No NA 7,074,538 17,597 NA 7,171,010 17,675 6,447

Sun 12/10/06 09:00 1.9 21,800 191 2.0 23,200 193 No 80 7,093,470 17,636 82 7,190,628 17,716 6,447

Mon 12/11/06 07:30 2.0 19,900 166 2.1 22,300 177 No NA 7,116,957 17,685 NA 7,214,884 17,767 6,447

Tue 12/12/06 08:30 2.3 25,800 187 2.1 23,400 186 No 75 7,140,603 17,735 78 7,239,317 17,818 6,447

Wed 12/13/06 07:30 2.3 25,400 184 1.1 12,400 188 No NA 7,159,335 17,774 NA 7,258,613 17,858 6,447

Thu 12/14/06 07:30 1.6 18,100 189 2.1 23,200 184 Yes NA 7,176,913 17,810 NA 7,276,767 17,896 6,447

Fri 12/15/06 07:30 3.1 35,600 191 2.4 25,500 177 No NA 7,200,035 17,859 NA 7,300,620 17,946 6,447

Sat 12/16/06 08:45 1.9 23,300 204 1.3 13,800 177 No NA 7,220,901 17,902 NA 7,322,035 17,991 6,447

Sun 12/17/06 08:30 1.6 19,200 200 2.0 26,200 218 No NA 7,240,063 17,942 NA 7,341,717 18,032 6,447

Mon 12/18/06 07:30 1.7 19,300 189 2.8 24,500 146 No NA 7,264,327 17,993 NA 7,366,572 18,084 6,447

Tue 12/19/06 07:45 1.1 12,100 183 2.9 31,300 180 No NA 7,285,802 18,038 NA 7,388,564 18,130 6,447

Wed 12/20/06 07:45 2.0 24,300 203 1.7 18,100 177 No NA 7,303,537 18,075 NA 7,406,767 18,168 6,447

Thu 12/21/06 08:00 2.0 23,300 194 2.0 20,900 174 Yes NA 7,327,734 18,125 NA 7,431,556 18,220 6,447

Fri 12/22/06 07:00 1.3 13,900 178 3.2 36,100 188 No NA 7,346,710 18,165 NA 7,450,993 18,260 6,447

Sat 12/23/06 09:00 1.4 26,600 317 2.0 22,500 188 No NA 7,370,532 18,215 NA 7,475,324 18,311 6,447

Sun 12/24/06 09:00 3.4 25,800 126 1.1 11,700 177 No NA 7,388,756 18,253 NA 7,493,909 18,350 6,447

Mon 12/25/06 10:15 2.5 27,400 183 2.2 23,800 180 No NA 7,413,759 18,305 NA 7,519,454 18,403 6,447

Tue 12/26/06 07:45 1.2 13,000 181 2.0 22,600 188 No NA 7,431,065 18,341 NA 7,537,148 18,440 6,447

Wed 12/27/06 07:30 2.3 26,700 193 1.2 13,500 188 No NA 7,449,779 18,380 NA 7,556,249 18,480 6,447

Thu 12/28/06 07:00 2.3 25,000 181 1.9 22,000 193 Yes NA 7,473,442 18,430 NA 7,580,422 18,531 6,447

Fri 12/29/06 07:30 1.1 12,700 192 3.3 36,100 182 No NA 7,492,463 18,469 NA 7,599,831 18,571 6,447

Sat 12/30/06 07:00 2.1 24,500 194 1.2 32,700 454 No NA 7,510,508 18,507 NA 7,618,282 18,610 6,447

Sun 12/31/06 07:45 2.0 23,300 194 2.4 5,500 38 No NA 7,534,239 18,557 NA 7,642,535 18,660 6,447

Mon 01/01/07 08:00 1.1 13,300 202 2.5 26,000 173 No NA 7,558,362 18,607 NA 7,662,075 18,701 6,447

Tue 01/02/07 08:15 2.2 25,400 192 2.5 26,400 176 No NA 7,578,568 18,649 NA 7,687,901 18,755 6,447

Wed 01/03/07 07:30 2.1 24,000 190 1.3 13,700 176 Yes NA 7,596,685 18,687 NA 7,706,492 18,794 6,447

Thu 01/04/07 07:30 1.2 13,600 189 3.0 33,600 187 No NA 7,614,782 18,725 NA 7,725,065 18,833 6,447

Fri 01/05/07 08:00 2.6 28,100 180 2.0 22,500 188 No NA 7,639,143 18,776 NA 7,750,075 18,885 6,447

Sat 01/06/07 09:00 2.4 26,000 181 1.5 16,200 180 No NA 7,657,387 18,814 NA 7,768,803 18,924 6,447

Sun 01/07/07 09:30 2.3 25,400 184 1.8 19,500 181 No NA 7,681,237 18,864 NA 7,793,350 18,975 6,447

Mon 01/08/07 07:45 2.7 28,800 178 2.3 25,100 182 No NA 7,706,459 18,916 NA 7,819,370 19,030 6,447

Tue 01/09/07 07:30 1.1 14,300 217 2.1 23,200 184 No NA 7,725,499 18,956 NA 7,838,990 19,071 6,447

Wed 01/10/07 07:30 2.7 26,600 164 1.9 21,000 184 No 85 7,745,624 18,998 88 7,859,768 19,114 6,447

Thu 01/11/07 07:30 2.3 25,200 183 1.5 16,300 181 Yes NA 7,768,374 19,046 NA 7,883,250 19,163 6,447

Fri 01/12/07 08:00 1.3 11,200 144 4.1 46,300 188 No NA 7,791,514 19,094 NA 7,907,230 19,213 6,447

Sat 01/13/07 08:06 1.7 22,000 216 1.8 18,000 167 No NA 7,809,733 19,132 NA 7,926,089 19,252 6,447

Sun 01/14/07 07:30 2.3 26,000 188 2.3 24,900 180 No NA 7,834,171 19,183 NA 7,951,464 19,305 6,447

49

50

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Week Totalizer

No.

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

42

41

43

47

48

44

45

46
Table A-1. US EPA Arsenic Demonstration Project at Stewart, MN - Daily System Operation Log Sheet (Continued)

A-6

AERALATER

Gallon 

Usage

Gallon 

Usage

Hrs gal gpm Hrs gal gpm Yes/No gpm gal BV gpm gal BV gal

Mon 01/15/07 08:00 2.1 25,200 200 2.7 27,400 169 No NA 7,856,720 19,230 NA 7,974,918 19,354 6,447

Tue 01/16/07 08:30 2.0 23,200 193 3.3 25,200 127 No NA 7,882,406 19,284 NA 8,001,600 19,410 6,447

Wed 01/17/07 07:30 2.0 23,100 193 2.1 31,300 248 Yes NA 7,905,111 19,331 NA 8,026,114 19,461 6,447

Thu 01/18/07 07:00 2.8 34,000 202 1.9 19,800 174 No NA 7,923,716 19,370 NA 8,045,976 19,503 6,447

Fri 01/19/07 07:00 3.8 43,700 192 1.5 16,200 180 No NA 7,951,674 19,429 NA 8,075,798 19,565 6,447

Sat 01/20/07 07:00 2.3 25,500 185 2.1 23,400 186 No NA 7,975,078 19,477 NA 8,100,718 19,617 6,447

Sun 01/21/07 08:00 2.4 25,600 178 2.5 27,800 185 No NA 8,000,617 19,531 NA 8,127,937 19,674 6,447

Mon 01/22/07 08:00 2.4 26,600 185 2.2 24,500 186 No NA 8,025,044 19,582 NA 8,153,942 19,728 12,141

Tue 01/23/07 07:30 2.6 28,100 180 2.1 23,300 185 No NA 8,048,103 19,630 NA 8,178,516 19,780 12,141

Wed 01/24/07 07:30 1.6 18,100 189 2.0 22,700 189 No NA 8,066,929 19,669 NA 8,198,537 19,822 12,141

Thu 01/25/07 07:30 2.2 24,000 182 2.0 22,000 183 Yes NA 8,090,760 19,719 NA 8,223,881 19,874 12,141

Fri 01/26/07 07:30 2.5 26,700 178 2.9 33,300 191 No NA 8,113,365 19,766 NA 8,247,962 19,925 12,141

Sat 01/27/07 08:00 2.4 26,900 187 2.0 23,100 193 No NA 8,137,246 19,816 NA 8,273,380 19,978 12,141

Sun 01/28/07 08:00 2.9 31,000 178 1.6 12,500 130 No NA 8,159,132 19,862 NA 8,296,642 20,026 12,141

Mon 01/29/07 08:00 2.2 25,100 190 1.8 24,500 227 No NA 8,182,649 19,911 NA 8,321,656 20,079 12,141

Tue 01/30/07 07:30 2.3 25,400 184 2.2 25,000 189 No NA 8,206,499 19,961 NA 8,347,013 20,132 12,141

Wed 01/31/07 07:30 2.3 24,500 178 2.5 26,500 177 No NA 8,227,971 20,006 NA 8,369,902 20,179 12,141

Thu 02/01/07 07:10 1.6 18,000 187 1.8 21,800 202 Yes NA 8,248,826 20,049 NA 8,392,027 20,226 12,141

Fri 02/02/07 07:30 1.9 21,900 192 3.4 36,700 180 No NA 8,272,385 20,098 NA 8,417,008 20,278 12,141

Sat 02/03/07 08:00 1.9 22,700 199 2.3 24,200 175 No NA 8,293,484 20,143 NA 8,439,166 20,324 12,141

Sun 02/04/07 09:00 1.9 14,100 124 2.4 25,600 178 No NA 8,317,470 20,193 NA 8,464,709 20,377 12,141

Mon 02/05/07 07:30 2.1 33,100 263 2.2 24,300 184 No NA 8,338,083 20,236 NA 8,485,921 20,422 12,141

Tue 02/06/07 10:00 1.6 19,600 204 2.6 26,900 172 No NA 8,363,100 20,288 NA 8,512,083 20,476 12,141

Wed 02/07/07 08:00 2.4 27,500 191 2.3 25,000 181 No NA 8,387,479 20,339 NA 8,537,627 20,530 12,141

Thu 02/08/07 07:30 2.0 23,500 196 2.4 25,000 174 Yes NA 8,411,013 20,388 NA 8,562,223 20,581 12,141

Fri 02/09/07 07:30 1.7 18,500 181 3.2 35,900 187 No NA 8,430,179 20,428 NA 8,582,259 20,623 12,141

Sat 02/10/07 07:30 2.7 30,500 188 1.6 17,900 186 No NA 8,454,253 20,478 NA 8,607,397 20,675 12,141

Sun 02/11/07 07:30 1.7 19,900 195 2.1 24,400 194 No NA 8,473,187 20,518 NA 8,627,153 20,717 12,141

Mon 02/12/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Tue 02/13/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Wed 02/14/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Thu 02/15/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Fri 02/16/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Sat 02/17/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Sun 02/18/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Mon 02/19/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Tue 02/20/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Wed 02/21/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Thu 02/22/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Fri 02/23/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Sat 02/24/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Sun 02/25/07 00:00 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Tue 02/27/07 07:00 NA NA NA NA NA NA No NA 8,809,984 21,221 NA 8,976,131 21,446 12,141

Wed 02/28/07 07:00 1.8 20,500 190 2.0 21,200 177 Yes NA 8,830,297 21,264 NA 8,996,994 21,489 12,141

57

55

56

54

52

53

Cumulative 

Day of Bed Volumes

Week

Well 4

Backwash

Op 

Hours

Op 

Hours

Average 

Flowrate

Average 

Flowrate

Combined 

Backwash 

Week Totalizer

No.

Well 3

Vessel B

Service 

Totalizer

Vessel B 

Flow Rate

Vessel A

Service 

Totalizer

Vessel A 

Flow Rate

Date

Cumulative 

Bed 

Volumes

51

Highlighted columns indicate calculated values.

NA = data not available.
APPENDIX B

ANALYTICAL DATA TABLES
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-1

Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN

Parameter Unit

Bed Volume (103) BV - - - 0.7 - - - 1.2 1.1 - - - 1.5 1.4 - - - 1.7 - - - 2.2 2.1

423 432 427 432 421 442 417 438 421 419 419 419 419 414 422 413 434 418 419 410 427 419 419

- - - - - - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L 1.7 1.9 1.7 1.7 - - - - - - - - - - 1.0 1.1 1.1 1.1 - - - - -

Fluoride mg/L 0.3 0.3 0.3 0.3 - - - - - - - - - - 0.4 0.4 0.4 0.4 - - - - -

Sulfate mg/L <1 <1 <1 <1 - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L <0.05 <0.05 <0.05 <0.05 - - - - - - - - - - <0.05 <0.05 <0.05 <0.05 - - - - -

317 294 95.8 <10 304 275 89.3 <10 <10 294 289 106 <10 <10 290 306 101 <10 290 296 101 <10 <10

- - - - - - - - - - - - - - - - - - - - - - -

27.6 25.6 24.9 24.1 25.6 26.9 25.7 24.4 25.4 26.3 25.7 25.0 25.3 24.8 26.5 24.6 23.0 23.8 24.6 24.6 24.2 23.7 24.1

- - - - - - - - - - - - - - - - - - - - - - -

7.3 4.3 0.9 2.0 7.9 15 1.4 1.7 1.8 6.5 15 1.1 0.8 0.9 9.2 9.6 0.7 1.0 7.1 8.9 1.5 1.6 3.5

- - - - - - - - - - - - - - - - - - - - - - -

TOC mg/L 6.7 7.1 6.8 NA(a) - - - - - - - - - - 6.3 6.7 6.3 NA(a) - - - - -

pH S.U. 8.2 8.2 8.4 8.2 7.6 7.9 7.9 7.9 7.9 7.6 8.3 8.3 8.2 8.4 7.4 7.9 7.7 7.8 7.7 8.3 8.0 8.0 8.1

Temperature °C 11.4 11.8 12.4 10.9 11.4 11.4 12.4 13.1 13.4 12.9 10.5 11.7 12.1 12.2 10.6 11.5 11.9 12.5 10.5 10.1 11.6 11.8 11.4

DO mg/L 1.1 7.9 5.0 4.8 1.1 NA(b) NA(b) NA(b) NA(b) NA(b) NA(b) NA(b) NA(b) NA(b) 1.3 6.0 4.0 3.4 1.8 6.3 3.2 3.6 3.4

ORP mV -36.6 250 203 256 35.2 128 166 175 179 294 341 333 323 321 271 273 176 177 300 288 281 289 307

Total Hardness (as CaCO3) mg/L 211 209 206 214 - - - - - - - - - - 226 224 212 210 - - - - -

Ca Hardness (as CaCO3) mg/L 112 113 113 113 - - - - - - - - - - 109 110 105 103 - - - - -

Mg Hardness (as CaCO3) mg/L 98.9 95.4 93.6 101 - - - - - - - - - - 117 114 107 106 - - - - -

52.3 52.4 21.2 0.3 36.9 33.5 22.6 0.4 0.3 42.7 43.8 27.1 0.6 0.5 38.7 41.4 24.0 0.7 39.7 41.8 24.8 0.7 0.6

- - - - - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L 43.8 21.3 18.5 0.2 - - - - - - - - - - 35.6 32.5 24.4 0.4 - - - - -

As (particulate) μg/L 8.5 31.1 2.7 <0.1 - - - - - - - - - - 3.2 8.9 <0.1 0.3 - - - - -

As (III) μg/L 39.8 4.2 1.3 0.9 - - - - - - - - - - 34.2 26.4 2.0 1.7 - - - - -

As (V) μg/L 4.0 17.0 17.2 <0.1 - - - - - - - - - - 1.4 6.1 22.4 <0.1 - - - - -

1,240 1,202 <25 <25 1,144 1,044 <25 <25 <25 1,238 1,205 <25 <25 <25 1,193 1,192 <25 <25 1,202 1,185 <25 <25 <25

- - - - - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L 1,159 <25 <25 <25 - - - - - - - - - - 855 <25 <25 <25 - - - - -

29.4 541 127 3.7 21.3 21.0 47.4 10.7 7.2 24.5 25.4 47.8 14.2 11.2 24.3 26.5 40.5 17.1 24.3 31.4 37.2 18.2 20.1

- - - - - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L 29.7 118 138 3.6 - - - - - - - - - - 24.7 24.8 41.3 17.5 - - - - -

(a) TOC sample bottle broke during transit. (b) Operator recorded DO readings as percentage therefore no reading available. (c) TT sample tap is not present. Sample taken from individual vessel for speciation week. 

Fe (total) μg/L

Sampling Location AF TA

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

IN AC AF IN AC TB IN AC AF TA TB IN AC

02/02/06(c)

TB

02/27/06(c) Sampling Date 02/14/06 02/21/06

AF TA

03/06/06

IN AC AF TA TB

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-2

Parameter Unit

Bed Volume (103

) BV - - - 2.6 2.4 - - - 2.9 2.7 - - - 3.2 - - - 3.5 3.3

422 422 422 426 426 419 419 423 423 423 408 416 412 416 414 410 410 414 414

- - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L - - - - - - - - - - 1.7 1.7 1.6 1.4 - - - - -

Fluoride mg/L - - - - - - - - - - 0.4 0.4 0.4 0.4 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L - - - - - - - - - - <0.05 <0.05 <0.05 <0.05 - - - - -

296 281 105 <10 <10 313 315 116 <10 <10 80.9 304 117 <10 297 290 110 <10 <10

- - - - - - - - - - - - - - - - - - -

23.3 23.1 23 23.3 23.5 24.5 24.5 25.1 25.1 25.2 24.8 25 - 24.3 25.1 24.5 25.5 25.2 25.6

- - - - - - - - - - - - - - - - - - -

6.1 8.6 0.9 0.8 1.2 11 9.3 0.9 0.7 0.6 5.9 9.9 1 0.6 6.3 8.7 0.7 0.8 1.1

- - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.2 6.2 6.2 6.1 - - - - -

pH S.U. 7.9 8.2 8.1 8.1 8.1 7.9 8.3 8.1 8.2 8.2 8.1 8.3 8.3 8.3 8.0 8.4 8.2 8.2 8.2

Temperature °C 12.5 10.9 11.3 10.8 11.8 16.6 11.0 12.6 11.5 11.5 12.7 11.0 11.1 11.1 12.2 13.1 13.6 14.3 15.4

DO mg/L 1.1 6.2 3.1 3.9 3.4 0.8 5.7 2.2 2.4 2.7 0.6 5.5 4.9 4.7 0.5 5.2 1.6 2.4 1.9

ORP mV 284 291 268 212 188 216 237 249 168 154 281 266 195 158 8.9 146 148 140 146

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 229 213 206 209 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 117 107 102 104 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 112 106 103 105 - - - - -

49.3 48.4 30.3 0.6 0.7 37.2 38.9 25.0 0.5 0.5 36.5 41.4 30.2 0.5 37.1 37.6 25.2 0.5 0.5

- - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 36.0 33.3 29.2 0.5 - - - - -

As (particulate) μg/L - - - - - - - - - - 0.5 8.1 1.0 <0.1 - - - - -

As (III) μg/L - - - - - - - - - - 33.4 24.4 2.9 0.6 - - - - -

As (V) μg/L - - - - - - - - - - 2.5 8.9 26.4 <0.1 - - - - -

1,157 1,168 <25 <25 <25 1,155 1,139 <25 <25 <25 1,096 1,176 <25 <25 1,077 1,059 <25 <25 <25

- - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 412 <25 <25 <25 - - - - -

23.0 24.1 33.4 21.2 23.4 44.3 25.0 31.5 23.6 25.8 19.8 23.2 28.0 25.3 21.5 22.9 29.5 26.4 28.3

- - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 22.8 23.2 28.8 26.0 - - - - -

03/28/06

Fe (total) μg/L

AF TB Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

TA IN AC AF TA

04/04/06

IN AC AF TA TB

03/14/06 03/21/06

IN AC AF TA TB IN AC

Sampling Date

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-3

Parameter Unit

Bed Volume (103) BV - - - 3.8 3.7 - - - 4.1 4.0 - - - 4.4 - - - 4.8 4.7

440 440 448 440 435 435 444 440 444 431 423 415 431 427 421 420 432 412 412

- - - - - 448 435 431 440 444 - - - - - - - - -

Ammonia (as N) mg/L - - - - - - - - - - 1.6 1.4 1.3 1.0 - - - - -

Fluoride mg/L - - - - - - - - - - 0.5 0.5 0.4 0.4 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L - - - - - - - - - - <0.05 <0.05 0.2 0.3 - - - - -

294 265 94.8 <10 <10 287 289 113 11.5 <10 296 289 107 <10 264 254 97.0 <10 <10

- - - - - 289 291 113 10.9 <10 - - - - - - - - -

24.1 24.4 25.1 25.1 25.2 24.6 25.1 23.3 25.1 24.2 25.9 24.6 25.1 24.8 25.9 25.7 25.5 26.2 26.2

- - - - - 24.9 25.5 24.3 24.9 24.5 - - - - - - - - -

9.4 8.9 0.9 1.0 0.7 5.0 8.8 0.7 0.5 0.4 4.3 7.6 0.5 0.6 4.6 8.3 0.6 0.4 0.8

- - - - - 5.8 8.6 0.6 0.7 0.6 - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.2 6.2 6.3 6.1 - - - - -

pH S.U. 7.8 8.1 8.1 8.1 8.1 8.0 8.4 8.2 8.2 8.2 8.1 8.4 8.2 8.2 8.0 8.3 8.2 8.2 8.2

Temperature °C 13.0 11.5 12.9 14.0 14.1 14.2 12.7 13.3 13.8 13.3 12.6 12.1 13.8 11.7 10.2 10.3 10.5 10.8 10.8

DO mg/L 0.6 4.2 1.8 1.9 2.3 0.7 5.0 2.2 2.9 2.9 0.6 5.1 1.8 2.4 0.5 5.0 1.9 2.5 2.1

ORP mV 21.4 210 186 168 118 89.7 213 216 164 160 119 161 229 152 16.8 349 251 198 195

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 205 214 218 221 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 111 118 120 122 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 94.0 96.4 99.0 99.8 - - - - -

41.8 39.7 30.3 0.9 0.9 39.0 39.1 22.5 0.6 0.7 39.5 43.6 23.1 <0.1 36.6 36.1 30.8 0.7 0.9

- - - - - 38.9 39.6 22.5 0.6 0.7 - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 34.1 44.9 21.9 <0.1 - - - - -

As (particulate) μg/L - - - - - - - - - - 5.4 <0.1 1.2 <0.1 - - - - -

As (III) μg/L - - - - - - - - - - 27.9 21.7 <0.1 <0.1 - - - - -

As (V) μg/L - - - - - - - - - - 6.2 23.2 21.8 <0.1 - - - - -

1,175 1,179 <25 <25 <25 1,197 1,163 <25 <25 <25 1,181 1,277 <25 <25 1,088 1,063 <25 <25 <25

- - - - - 1,200 1,156 <25 <25 <25 - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 931 <25 <25 <25 - - - - -

23.1 24.2 31.9 30.5 33.2 23.3 23.8 28.5 27.9 30.2 24.0 27.7 30.4 34.2 22.2 22.6 29.6 28.2 32.3

- - - - - 23.6 23.8 28.2 28.5 30.6 - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 24.6 25.6 30.9 35.1 - - - - -

(a) Water quality measurements taken on 04/10/06.

05/02/06

IN AC AF TT IN TA TB

04/25/06

AC AF

04/11/06(a) 04/18/06

IN AC AF TA TB IN AC

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

AF TA TB

Alkalinity (as CaCO3) mg/L

Sampling Date

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-4

Parameter Unit

Bed Volume (103) BV - - - 5.1 5.0 - - - 5.5 5.3 - - - 5.8 - - - 6.2 6.1

410 419 423 423 410 422 434 426 409 422 414 423 423 419 424 420 420 400 367

- - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L - - - - - - - - - - 1.6 1.6 1.5 1.2 - - - - -

Fluoride mg/L - - - - - - - - - - 0.5 0.5 0.5 0.5 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L - - - - - - - - - - <0.05 <0.05 0.1 0.3 - - - - -

272 255 90.1 <10 <10 287 282 93.3 <10 <10 289 292 128 <10 292 278 114 25.3 26.7

- - - - - - - - - - - - - - - - - - -

25.5 26 25.9 26.3 26.3 26.3 26.8 25.2 26 26.2 25.2 24.5 24.9 25.2 24.5 24.4 24.2 24.5 24.1

- - - - - - - - - - - - - - - - - - -

4.1 8.3 0.7 0.6 0.7 5.5 8.1 0.6 0.4 0.7 4.9 9.1 0.7 0.7 4.3 9.7 0.6 0.4 1.0

- - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.3 6.3 6.5 6.6 - - - - -

pH S.U. 8.0 8.3 8.2 8.2 8.2 8.0 8.2 8.9 8.1 8.1 7.5 7.8 7.7 7.7 8.2 8.5 8.4 8.4 8.4

Temperature °C 11.8 11.0 11.0 10.6 10.5 11.0 10.8 11.1 10.9 11.5 12.6 11.6 19.3 11.7 10.9 11.5 11.2 11.4 11.5

DO mg/L 1.5 4.8 2.5 2.6 2.7 0.8 5.3 2.2 2.0 2.2 1.1 5.0 2.5 2.5 1.9 4.9 3.8 3.6 3.7

ORP mV 78.1 140 170 168 165 -1.4 140 119 112 117 71.3 248 386 150 265 340 308 300 297

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 200 189 217 222 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 101 95.0 109 110 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 98.8 93.9 108 111 - - - - -

35.5 35.9 21.5 0.7 0.8 40.3 40.1 21.2 0.5 0.7 45.2 47.2 38.7 1.1 35.7 33.6 19.8 0.7 0.9

- - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 41.8 33.7 26.7 1.0 - - - - -

As (particulate) μg/L - - - - - - - - - - 3.3 13.6 12.0 <0.1 - - - - -

As (III) μg/L - - - - - - - - - - 35.7 25.5 0.5 0.6 - - - - -

As (V) μg/L - - - - - - - - - - 6.2 8.2 26.2 0.3 - - - - -

1,027 1,081 <25 <25 <25 1,311 1,235 <25 <25 <25 1,057 1,019 <25 <25 1,063 983 <25 <25 <25

- - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 784 <25 <25 <25 - - - - -

21.0 24.5 29.7 31.2 32.9 25.1 25.7 28.5 30.7 32.0 20.3 21.8 25.1 29.4 20.3 20.3 21.9 24.6 26.4

- - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 20.7 20.3 22.0 28.7 - - - - -

(a) Operator turned off potassium permanganate pump after sampling event on 05/09/06.

05/30/06

AC AF TA TB IN AC AF TA TB

05/09/06(a)

IN AC AF TA TB

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 05/16/06

IN

05/24/06

IN AC AF TT

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-5

Parameter Unit

Bed Volume (103) BV - - - 6.8 6.6 - - - 7.2 7.0 - - - 7.5 - - - 8.0 7.8

422 435 431 435 422 429 416 433 454 441 454 416 425 421 421 417 417 417 417

- - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L - - - - - - - - - - 1.8 1.6 1.2 1.2 1.6 1.3 1.5 1.0 1.1

Fluoride mg/L - - - - - - - - - - 0.6 0.5 0.6 0.6 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L - - - - - - - - - - <0.05 <0.05 0.3 0.5 <0.05 <0.05 0.1 0.2 0.2

344 264 122 13.4 18.1 344 338 125 <10 14.7 318 312 123 14.9 289 288 115 14.2 17.3

- - - - - - - - - - - - - - - - - - -

25.7 25.5 25.4 26.1 26.1 27.0 26.8 26.9 27.1 27.0 28.3 26.1 26.6 27.0 26.8 26.1 26.2 26.7 26.5

- - - - - - - - - - - - - - - - - - -

15.0 9.9 0.7 1.2 1.1 6.2 8.5 0.6 0.5 1.0 7.6 8.5 0.9 0.9 4.6 8.8 0.7 0.6 0.8

- - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - NA(b) NA(b) NA(b) NA(b) - - - - -

pH S.U. 8.0 8.2 8.2 8.2 8.2 8.0 8.3 8.1 8.1 8.1 7.9 8.3 8.3 8.1 8.0 8.3 8.2 8.2 8.2

Temperature °C 10.9 12.1 11.4 11.3 11.2 11.4 10.6 11.2 11.6 12.6 11.2 11.0 11.2 11.4 10.1 10.4 11.0 11.6 11.5

DO mg/L 1.9 3.8 4.2 3.1 3.1 0.7 5.6 2.1 2.5 3.0 1.1 4.3 2.4 2.7 0.7 4.7 1.7 2.7 2.6

ORP mV 316 222 203 137 139 337 319 269 273 259 378 256 190 195 404 209 154 156 154

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 237 236 235 240 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 119 118 118 120 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 117 118 117 119 - - - - -

42.2 37.4 28.6 1.1 1.5 51.1 50.3 30.4 1.1 1.9 50.9 45.5 29.0 1.4 40.6 39.2 27.9 1.7 1.7

- - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 44.6 37.3 25.8 1.2 - - - - -

As (particulate) μg/L - - - - - - - - - - 6.3 8.2 3.2 0.2 - - - - -

As (III) μg/L - - - - - - - - - - 40.7 27.3 1.3 0.4 - - - - -

As (V) μg/L - - - - - - - - - - 3.9 10.0 24.5 0.9 - - - - -

1,491 1,037 27 <25 <25 1,104 1,111 <25 <25 <25 1,351 1,276 <25 <25 1,090 1,061 <25 <25 <25

- - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 1,335 68 <25 <25 - - - - -

23.0 21.6 27.6 27.2 30.6 23.5 24.1 26.5 28.2 29.2 25.5 25.3 25.5 28.3 23.8 24.2 26.5 29.0 30.4

- - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 26.1 25.2 24.7 27.6 - - - - -

(a) Operator no longer taking on-site oxidant measurements. (b) Sample analysis failed laboratory QA/QC check.

06/27/06

TA IN AC AF TA TB

06/06/06 06/13/06

IN AC AF TB IN AC AF TA TB

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 06/20/06(a)

IN AC AF TT

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-6

Parameter Unit

Bed Volume (103) BV - - - 8.6 8.4 - - - 9.2 8.9 - - - 9.6 - - - 10.3 10.1

431 419 419 410 406 427 423 423 419 423 439 447 439 416 421 421 425 421 417

- - - - - 419 419 419 423 419 - - - - - - - - -

Ammonia (as N) mg/L 1.2 1.2 0.9 0.7 0.9 NA NA NA NA NA 1.6 1.9 1.3 1.2 1.7 1.9 1.4 0.6 0.4

Fluoride mg/L - - - - - - - - - - 0.5 0.5 0.5 0.5 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L <0.05 <0.05 0.4 0.5 0.6 NA NA NA NA NA <0.05 <0.05 0.2 0.4 <0.05 <0.05 <0.05 0.7 1.6

288 288 101 <10 15.8 263 284 107 22.4 29.3 350 307 124 19.9 344 344 126 246 336

- - - - - 291 288 115 26.2 22.9 - - - - - - - - -

24.9 24.4 25.5 25.2 24.3 25.0 24.6 24.6 25.8 25.5 25.0 24.7 25.0 24.8 25.0 25.7 24.9 25.8 25.6

- - - - - 25.3 24.1 25.8 25.2 25.4 - - - - - - - - -

5.3 8.4 1.1 0.8 0.6 4.2 8.6 0.5 0.5 0.3 6.9 10.0 1.0 0.4 8.0 12.0 1.0 2.2 3.2

- - - - - 5.5 8.6 0.5 0.6 0.5 - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.4 6.6 6.5 6.5 - - - - -

pH S.U. 8.1 8.2 8.2 8.2 8.2 8.0 8.3 8.2 8.1 8.1 8.0 8.2 8.2 8.2 8.0 8.3 8.2 8.2(a) 8.2

Temperature °C 11.0 10.8 11.0 11.1 11.7 10.9 11.0 11.6 12.1 12.1 10.8 11.5 11.0 10.8 10.2 10.8 10.6 11.7(a) 11.5

DO mg/L 1.7 5.0 3.8 2.6 2.9 1.0 7.2 3.2 3.3 3.8 1.6 5.2 2.7 2.5 0.5 5.0 1.9 6.2(a) 5.7

ORP mV 311 170 166 140 134 163 172 236 229 179 343 288 261 264 371 267 156 137(a) 175

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 210 195 224 206 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 116 96.6 113 104 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 94.3 98.0 110 102 - - - - -

46.1 45.5 26.5 2.7 2.1 36.7 38.2 26.2 2.1 2.6 43.4 43.0 38.4 2.3 56.4 56.9 32.9 7.4 9.2

- - - - - 38.7 39.1 28.7 2.1 2.1 - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 39.4 33.9 26.1 3.0 - - - - -

As (particulate) μg/L - - - - - - - - - - 4.0 9.1 12.3 <0.1 - - - - -

As (III) μg/L - - - - - - - - - - 32.3 25.6 0.6 0.5 - - - - -

As (V) μg/L - - - - - - - - - - 7.0 8.3 25.6 2.5 - - - - -

1,321 1,305 <25 <25 <25 993 1,056 <25 <25 <25 1,197 1,230 <25 <25 1,312 1,309 <25 337 524

- - - - - 1,075 1,076 <25 <25 <25 - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 852 <25 <25 <25 - - - - -

25.8 26.1 26.1 27.7 27.5 20.9 21.5 23.1 25.1 26.0 23.2 24.7 23.6 26.4 23.9 25.0 26.1 26.9 27.5

- - - - - 21.9 22.5 24.5 25.2 23.0 - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 23.4 24.3 23.5 26.7 - - - - -

(a) Water quality measurements taken at sampling location TT.

(b) 07/25/06 TA and TB samples rerun with similar results for As, Fe, and Mn

AF

07/05/06

IN AC

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date

AF TA TB

07/11/06 07/18/06

IN AC AF TA TB IN AC AF TT

07/25/06

TA(b) TB(b) IN AC

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-7

Parameter Unit

Bed Volume (103) BV - - - 11.0 10.8 - - - 11.4 11.2 - - - 11.8 11.6 - - - 12.1

416 416 412 407 412 428 424 424 416 416 421 434 442 413 417 422 457 403 424

- - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L 1.9 1.6 1.2 1.0 1.0 1.9 1.6 1.7 1.1 1.2 1.4 1.7 1.7 1.0 1.2 1.8 1.8 1.2 1.0

Fluoride mg/L - - - - - - - - - - - - - - - 0.4 0.4 0.4 0.4

Sulfate mg/L - - - - - - - - - - - - - - - <1 <1 <1 <1

Nitrate (as N) mg/L <0.05 <0.05 0.4 1.7(a) 0.3 <0.05 <0.05 0.1 0.5 0.3 <0.05 <0.05 0.2 0.6 0.5 <0.05 <0.05 0.4 0.5

322 293 99.8 20.7 23.9 327 315 110 12.1 17.4 312 313 106 12.5 18.7 302 298 126 29.1

- - - - - - - - - - - - - - - - - - -

27.8 28.2 28.1 28.3 28.6 24.2 23.9 23.9 24 24.2 24.8 24.9 24.8 24.1 24.9 24.4 24.9 23.3 24.4

- - - - - - - - - - - - - - - - - - -

5.3 7.5 0.4 0.4 0.3 5.5 9.0 0.4 0.2 0.2 6.7 8.7 0.3 0.4 0.3 7.8 8.5 8.3 1.2

- - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - - - - - - 6.6 6.6 3.8(b) 3.1(b)

pH S.U. 8.1 8.3 8.2 8.2 8.2 8.0 8.3 8.2 8.2 8.2 8.1 8.4 8.2 8.2 8.2 8.1 8.3 8.2 8.2

Temperature °C 10.7 12.0 11.9 11.5 11.7 11.4 11.3 11.7 12.3 12.2 11.0 10.3 10.9 11.3 11.4 10.4 10.7 11.5 12.2

DO mg/L 0.6 4.4 3.1 2.1 2.2 1.1 4.0 1.6 1.5 2.0 1.4 4.4 1.8 2.3 2.1 0.8 4.9 2.1 2.4

ORP mV 111 95.9 108 88.7 83.9 56.1 118 103 94.5 99.7 130 64.5 59.9 65.8 73.7 268 191 113 89.6

Total Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - 226 224 219 219

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - 123 122 118 115

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - 103 102 101 105

52.3 44.1 27.3 2.8 3.3 56.0 51.1 36.1 3.0 3.4 38.0 38.5 27.9 2.0 2.4 54.0 53.1 36.1 2.8

- - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - - - - - - 46.2 40.5 29.2 2.5

As (particulate) μg/L - - - - - - - - - - - - - - - 7.8 12.7 6.8 0.4

As (III) μg/L - - - - - - - - - - - - - - - 44.0 30.7 0.7 0.7

As (V) μg/L - - - - - - - - - - - - - - - 2.2 9.7 28.6 1.8

1,121 1,070 <25 <25 <25 1,277 1,224 <25 <25 <25 1,196 1,157 <25 <25 <25 1,310 1,292 <25 <25

- - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - - - - - - 1,325 <25 <25 <25

22.3 22.9 24.9 25.2 26.2 24.3 23.8 24.1 24.8 25.4 22.3 22.5 24.4 22.9 24.3 24.5 24.8 23.8 25.9

- - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - - - - - - 24.0 23.9 24.2 25.9

(a) 08/01/06 TA sample was rerun with similar result for nitrate.

(b) Low effluent TOC levels. Results confirmed with laboratory.

AF TT

08/15/06 08/21/06

IN AC AF TA TB IN AC

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 08/01/06 08/07/06

IN AC TA TB IN AC AF TA TB

Total P (as P) μg/L

AF
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-8

Parameter Unit

Bed Volume (103

) BV - - - 13.0 12.9 - - - 13.3 13.2 - - - 13.7 - - - 14.1 14.0

474 476 456 474 460 436 438 441 438 443 434 439 453 448 443 440 454 440 433

- - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L 1.9 1.8 1.5 1.3 1.3 1.8 1.6 1.7 1.2 1.3 1.6 1.5 1.3 1.1 1.6 1.7 1.3 0.9 0.8

Fluoride mg/L - - - - - - - - - - 0.3 0.3 0.2 0.2 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L <0.05 <0.05 0.2 0.4 0.4 <0.05 <0.05 0.1 0.2 0.3 <0.05 <0.05 0.2 0.3 <0.05 <0.05 0.3 0.6 0.6

299 295 115 26.3 30.2 299 288 107 25.1 27.1 285 292 105 22.3 270 264 102 35.1 42.8

- - - - - - - - - - - - - - - - - - -

23.8 24.0 23.6 24.2 23.7 24.3 24.7 24.2 24.5 24.2 25.9 25.8 27 26.7 24.4 24.2 24.7 24.2 23.9

- - - - - - - - - - - - - - - - - - -

5.8 11.0 0.8 0.6 0.9 5.2 9.1 0.5 0.5 0.4 6.6 7.1 0.3 0.4 6.3 7.4 0.3 0.5 0.2

- - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.7 7.0 7.0 6.6 - - - - -

pH S.U. 8.1 8.3 8.2 8.2 8.2 7.7 8.4 8.2 8.2 8.2 8.0 8.4 8.2 8.2 7.9 8.1 8.2 8.2 8.2

Temperature °C 11.3 11.3 11.3 11.7 12.4 10.1 10.2 10.8 11.2 11.7 12.0 12.8 11.8 11.8 10.8 10.5 10.6 10.8 11.0

DO mg/L 1.6 4.0 2.6 2.3 2.4 0.7 5.9 2.0 1.9 1.7 1.3 4.5 2.5 2.2 1.2 4.5 1.7 1.9 2.2

ORP mV 230 123 77.2 76.1 83.7 337 193 199 104 103 -8.6 78.5 89.3 80 126 121 101 84.1 92.2

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 204 210 218 215 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 101 104 107 106 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 103 106 111 109 - - - - -

43.0 42.6 26.4 2.8 3.2 47.2 46.1 27.9 3.4 3.6 39.7 41.0 26.1 2.9 31.4 29.9 20.5 2.8 3.4

- - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 35.6 33.5 26.1 2.8 - - - - -

As (particulate) μg/L - - - - - - - - - - 4.1 7.5 <0.1 <0.1 - - - - -

As (III) μg/L - - - - - - - - - - 28.4 25.0 1.8 0.1 - - - - -

As (V) μg/L - - - - - - - - - - 7.2 8.5 24.4 2.7 - - - - -

1,187 1,162 <25 <25 <25 1,151 1,091 <25 <25 <25 1,030 1,045 <25 <25 1,108 1,080 <25 <25 <25

- - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 925 <25 <25 <25 - - - - -

24.9 24.7 23.8 25.3 25.6 22.7 22.2 23.6 24.6 25.5 19.6 20.3 23.2 22.9 21.5 21.8 24.0 25.8 26.1

- - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 20.3 20.3 23.6 23.5 - - - - -

IN AF TA TB

09/19/06 09/26/06

IN AC AF TA TB AC AF TT IN AC

09/05/06

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 09/12/06

IN AC AF TA TB

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-9

Parameter Unit

Bed Volume (103

) BV - - - 14.4 14.4 - - - 14.8 14.7 - - - 15.1 - - - 15.5 15.4

438 452 449 429 445 466 448 459 433 452 455 457 446 469 442 470 465 446 470

- - - - - 442 450 448 442 463 - - - - - - - - -

Ammonia (as N) mg/L 1.7 1.9 1.5 1.1 1.0 NA(a) NA(a) NA(a) NA(a) NA(a) 1.9 1.9 1.6 2.3(c) 1.5 1.5 1.3 1.1 1.1

Fluoride mg/L - - - - - - - - - - 0.5 0.6 0.5 0.5 - - - - -

Sulfate mg/L - - - - - - - - - - <1 <1 <1 <1 - - - - -

Nitrate (as N) mg/L <0.05 <0.05 0.3 0.7 0.6 NA(a) NA(a) NA(a) NA(a) NA(a) <0.05 <0.05 1.5(b) 1.4(b) <0.05 <0.05 0.2 0.5 0.4

322 326 124 43.2 49.1 325 329 117 34.6 42.2 347 341 131 52.5 331 321 123 43.7 49.4

- - - - - 339 340 122 39.7 43.1 - - - - - - - - -

24.3 25.0 24.5 24.6 24.3 25.3 24.4 25.3 24.8 25.2 24.3 25.0 24.4 25.1 23.1 25.2 25.1 25.0 24.8

- - - - - 25.9 24.7 25.0 25.9 24.1 - - - - - - - - -

4.4 8.9 0.3 0.5 0.6 7.1 9.2 0.7 0.4 0.5 7.1 11.0 1.2 1.1 7.5 9.5 0.9 1.5 1.1

- - - - - 6.9 9.8 0.9 0.6 1.0 - - - - - - - - -

TOC mg/L - - - - - - - - - - 6.7 6.7 6.9 6.7 - - - - -

pH S.U. 8.0 8.4 8.2 8.3 8.3 7.8 8.3 8.2 8.2 8.2 8.0 8.4 8.2 8.3 8.1 8.3 8.3 8.2 8.2

Temperature °C 10.8 10.7 11.0 11.2 11.3 11.0 10.5 10.8 11.2 11.5 11.9 12.1 13.4 13.5 12.9 11.6 11.6 12.2 12.6

DO mg/L 1.2 4.6 1.8 3.0 2.4 1.9 4.9 1.9 1.9 1.9 2.0 5.5 3.6 4.0 1.5 4.8 2.7 2.1 1.9

ORP mV 303 39.7 36.6 24.9 23.5 300 258 239 168 151 303 230 161 154 293 312 273 265 142

Total Hardness (as CaCO3) mg/L - - - - - - - - - - 206 211 211 205 - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - 88.2 94.8 97.2 95.2 - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - 118 116 114 110 - - - - -

51.6 52.3 31.0 3.7 4.2 54.9 49.7 29.7 4.4 4.8 53.4 52.6 32.6 5.6 56.2 54.1 37.7 5.4 5.9

- - - - - 54.0 50.1 31.2 4.4 4.8 - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - 39.3 37.8 29.9 4.9 - - - - -

As (particulate) μg/L - - - - - - - - - - 14.0 14.8 2.7 0.6 - - - - -

As (III) μg/L - - - - - - - - - - 27.6 27.1 1.3 0.9 - - - - -

As (V) μg/L - - - - - - - - - - 11.7 10.8 28.6 4.0 - - - - -

1,132 1,126 <25 <25 <25 1,273 1,168 <25 <25 <25 1,021 1,045 <25 <25 1,110 1,105 <25 <25 <25

- - - - - 1,262 1,120 29 <25 <25 - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - 478 <25 <25 <25 - - - - -

23.4 23.6 23.1 23.5 24.3 25.7 24.5 26.3 25.6 26.6 23.3 23.5 23.7 23.8 21.9 22.6 24.8 23.9 24.6

- - - - - 25.6 24.2 26.2 27.8 26.9 - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - 23.0 23.2 24.5 24.5 - - - - -

(a) Sample bottles not included in cooler per COC.

(b) Samples showed non-detect (<0.05 mg/L) during first analyses. Rerun values are reported. (c) Not able to rerun sample due to discard.

IN AC AF TA TB IN AC AF TA TB IN AC AF TT IN AC AF TA TB

10/03/06 10/10/06 10/17/06 10/24/06

Fe (total) μg/L

Mn (total) μg/L

Turbidity NTU

As (total) μg/L

Total P (as P) μg/L

Silica (as SiO2) mg/L

Sampling Date

Sampling Location

Alkalinity (as CaCO3) mg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-10

Parameter Unit

Bed Volume (103) BV - - - 15.8 15.8 - - - 16.1 16.1 - - - 16.5 16.5 - - - 17.1 17.2

463 456 460 469 465 457 447 462 470 466 445 443 445 433 435 474 474 476 442 436

- - - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L 1.5 1.5 1.0 1.0 1.0 1.6 1.5 1.4 1.2 1.2 1.6 1.7 1.5 1.1 1.2 1.6 1.7 1.2 1.2 1.1

Fluoride mg/L - - - - - - - - - - - - - - - - - - - -

Sulfate mg/L - - - - - - - - - - - - - - - - - - - -

Nitrate (as N) mg/L <0.05 <0.05 0.4 0.4 0.4 <0.05 <0.05 0.2 0.2 0.3 <0.05 <0.05 0.2 0.4 0.4 <0.05 <0.05 0.3 0.4 0.4

349 338 131 51.8 61.2 316 301 120 49.0 58.9 333 304 118 50.4 56.7 275 256 99.4 38.4 49.2

- - - - - - - - - - - - - - - - - - - -

23.5 24.3 24.2 24.5 25.1 23.8 24.9 24.5 25.3 24.1 24.8 24.7 24.8 24.7 24.4 24.2 24.2 23.8 24.9 24.5

- - - - - - - - - - - - - - - - - - - -

6.5 9.0 1.0 1.1 2.3 11.0 9.3 1.1 1.1 1.1 5.7 10.0 1.0 1.3 1.0 6.7 9.0 0.7 1.2 1.1

- - - - - - - - - - - - - - - - - - - -

TOC mg/L - - - - - - - - - - - - - - - - - - - -

pH S.U. 8.1 8.6 8.2 8.3 8.3 8.0 8.3 8.3 8.2 8.3 7.9 8.3 8.3 8.3 8.3 7.6 8.1 7.9 8.0 8.0

Temperature °C 11.2 10.6 12.4 12.4 12.7 12.1 12.2 13.0 13.6 14.3 13.8 13.8 13.9 14.1 14.6 11.1 13.0 13.1 12.2 12.3

DO mg/L 1.7 5.1 2.0 3.5 3.1 0.7 4.5 3.1 2.0 3.0 1.3 5.0 4.0 3.3 3.4 2.0 4.7 1.9 1.8 2.0

ORP mV 350 146 161 159 145 248 242 90.2 86.8 96.9 114 121 109 90.6 73.1 230 226 216 216 193

Total Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - - - - - -

Ca Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - - - - - -

Mg Hardness (as CaCO3) mg/L - - - - - - - - - - - - - - - - - - - -

49.1 46.2 28.9 4.3 5.0 52.8 50.3 37.4 5.0 6.1 53.5 50.4 33.1 5.6 5.8 41.6 38.5 25.7 4.0 4.9

- - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L - - - - - - - - - - - - - - - - - - - -

As (particulate) μg/L - - - - - - - - - - - - - - - - - - - -

As (III) μg/L - - - - - - - - - - - - - - - - - - - -

As (V) μg/L - - - - - - - - - - - - - - - - - - - -

1,227 1,189 <25 <25 <25 1,179 1,120 <25 <25 <25 1,255 1,162 <25 <25 <25 1,127 1,088 <25 <25 <25

- - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L - - - - - - - - - - - - - - - - - - - -

23.0 22.6 28.1 24.5 25.3 23.7 22.9 25.4 25.1 25.4 23.6 23.0 22.5 22.9 23.4 21.4 21.5 29.8 23.0 24.5

- - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L - - - - - - - - - - - - - - - - - - - -

TA TB

11/14/06 11/28/06

IN AC IN AC AF TA TB IN AC AF

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 10/31/06

AF TA TB

11/07/06

IN AC AF TA TB

Total P (as P) μg/L
Table B-1. Analytical Results from Long-Term Sampling at Stewart, MN (Continued)

IN = Influent, AC = after gravity filtration; TA = after tank A; TB = after tank B; TT = after combined effluent

NA = not available.

B-11

Parameter Unit

Bed Volume (103) BV - - - 17.5 - - - 17.7 17.8 - - - 18.0 18.1 - - - 18.7 - - - 21.3

449 455 447 439 457 448 442 446 432 469 461 457 455 455 485 487 463 469 445 445 447 450

- - - - - - - - - - - - - - - - - - - - - -

Ammonia (as N) mg/L NA(a) NA(a) NA(a) NA(a) 1.7 1.9 1.6 1.4 1.3 1.6 1.8 1.6 1.2 1.2 1.7 1.7 1.1 1.0 1.8 1.7 1.7 1.2

Fluoride mg/L 1.0 0.4 0.5 0.8 - - - - - - - - - - 0.5 0.4 0.4 0.5 0.6 0.5 0.6 0.6

Sulfate mg/L <1 <1 <1 <1 - - - - - - - - - - <1 <1 <1 <1 <1 <1 <1 <1

Nitrate (as N) mg/L <0.05 <0.05 0.7 0.7 <0.05 0.1 0.2 0.3 0.3 <0.05 <0.05 0.1 0.4 0.4 <0.05 <0.05 0.5 0.6 <0.05 <0.05 0.1 0.3

340 281 107 48.0 252 247 97.7 54.1 43.9 280 270 91.8 26.6 33.3 306 290 119 64.0 337 307 158 111

- - - - - - - - - - - - - - - - - - - - - -

24.0 23.6 23.4 23.7 24.4 24.9 24.0 24.2 24.1 26.1 25.4 26.0 24.6 25.3 25.1 25.2 24.8 24.8 24.6 24.6 24.5 25.1

- - - - - - - - - - - - - - - - - - - - - -

5.8 8.2 0.8 1.3 6.5 9.5 0.3 0.3 0.5 5.7 10.0 0.7 0.6 1.0 7.4 8.1 0.9 0.7 4.8 8.3 1.0 0.7

- - - - - - - - - - - - - - - - - - - - - -

TOC mg/L 6.4 6.3 6.3 6.4 - - - - - - - - - - 6.3 6.7 6.3 6.5 6.5 6.6 6.6 6.7

pH S.U. 7.9 8.2 7.9 8.0 7.9 8.2 8.0 8.0 8.0 7.8 8.2 8.0 7.9 8.0 7.7 8.1 7.9 7.9 7.6 7.8 7.8 7.7

Temperature °C 10.9 10.3 11.2 11.4 13.4 12.9 13.3 13.7 14.3 12.6 12.6 12.9 13.9 14.1 12.1 12.1 11.5 12.3 11.5 11.5 10.9 12.2

DO mg/L 2.0 5.0 2.7 2.3 0.8 5.4 2.4 2.3 2.8 1.1 4.5 3.2 2.1 2.6 2.2 5.5 3.6 6.8 1.0 4.3 3.2 2.4

ORP mV 295 252 235 201 346 93.4 89.1 78.6 84.8 215 171 133 105 114 361 360 299 297 389 186 169 143

Total Hardness (as CaCO3) mg/L 220 214 213 215 - - - - - - - - - - 226 226 213 227 238 235 242 247

Ca Hardness (as CaCO3) mg/L 108 118 121 120 - - - - - - - - - - 122 120 107 118 127 130 134 137

Mg Hardness (as CaCO3) mg/L 112 95.3 92.7 94.9 - - - - - - - - - - 104 106 106 110 112 105 108 110

52.9 52.2 33.3 5.7 41.1 42.1 28.3 5.9 4.9 42.6 41.2 33.5 4.6 5.2 53.5 53.1 32.8 5.8 48.6 46.4 42.7 9.8

- - - - - - - - - - - - - - - - - - - - - -

As (soluble) μg/L 43.3 38.0 28.9 5.3 - - - - - - - - - - 48.9 40.3 30.8 5.6 36.4 34.1 37.4 8.6

As (particulate) μg/L 9.5 14.3 4.4 0.4 - - - - - - - - - - 4.6 12.8 1.9 0.3 12.2 12.3 5.3 1.2

As (III) μg/L 36.8 26.9 0.9 0.6 - - - - - - - - - - 43.7 30.8 0.6 0.3 34.7 23.7 6.6 1.1

As (V) μg/L 6.6 11.1 28.0 4.7 - - - - - - - - - - 5.2 9.5 30.2 5.2 1.6 10.4 30.8 7.5

1,208 1,209 <25 <25 1,146 1,137 <25 <25 <25 1,298 1,224 <25 <25 <25 1,438 1,298 <25 <25 1,427 919 <25 <25

- - - - - - - - - - - - - - - - - - - - - -

Fe (soluble) μg/L 894 <25 <25 <25 - - - - - - - - - - 1,202 36 <25 <25 829 <25 <25 <25

23.2 23.9 25.0 24.2 22.4 22.4 23.0 24.4 22.8 23.8 23.2 25.1 23.8 24.1 24.3 24.2 22.5 24.7 22.7 23.5 25.4 25.5

- - - - - - - - - - - - - - - - - - - - - -

Mn (soluble) μg/L 24.3 23.4 26.0 25.8 - - - - - - - - - - 24.9 23.7 23.6 24.2 22.9 23.4 25.5 26.3

(a) Operator did not take ammonia samples on 12/05/06.

02/27/07

IN AC AF TT IN AC AF TT

01/03/07

Fe (total) μg/L

Sampling Location

Silica (as SiO2) mg/L

Turbidity NTU

Mn (total) μg/L

As (total) μg/L

Alkalinity (as CaCO3) mg/L

Sampling Date 12/05/06 12/18/06

IN AC AF TT TA TB

12/12/06

IN

Total P (as P) μg/L

IN AC AF TA TB AC AF