Senior Project

Aquatech Solutions
1111 Engineering Drive
Boulder, CO 80302
May 1, 2015
Denver Water Department
1600 West 12th Avenue
Denver, CO 80204
Denver Water Department,
The attached Preliminary Design Report discusses several disinfection technologies that would
effectively serve Denver Water's future Ralston Treatment Plant and the design of an on-site generation of sodium
hypochlorite system only at the Ralston site that was selected using a multi-criteria decision matrix.
The following items are included in the preliminary design of the selected technology: the selection of the on-site
generation system manufacturer ClorTec® which will provide 6 independent OSG systems, the design of four high
density cross-linked polyethylene sodium hypochlorite tanks, a backup bulk delivery of sodium hypochlorite
system, a disinfection building layout including proper spacing and access roads, and a 20-year life cycle cost
assessment of the disinfection system resulting in a total present value of $27 million.
Aquatech Solutions would like your feedback of this report at your leisure. Any questions concerning
this report can be directed towards the Project Manager, Laura Meschke, laura.meschke@colorado.edu.
Aquatech Solutions has really enjoyed this entire experience and would like to thank you for all of the help you
have provided throughout this process. The team looks forward to receiving your feedback and hopes you will
consider our research and recommendations when making decisions regarding the future Ralston Treatment Plant.
Sincerely,
Aquatech Solutions

Preliminary Design of On-Site Generation of Sodium
Hypochlorite System at Denver Water’s Ralston
Treatment Plant
May 1, 2015
Laura Meschke
Cassidy Kuhn
Hali Hafeman
Fernando Monroy
Shaye Palagi

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TABLE OF CONTENTS
List of Figures ........................................................................................................................ 4
List of Tables ......................................................................................................................... 4
List of Acronyms.................................................................................................................... 5
List of Units ........................................................................................................................... 5
Team Member Roles and Acknowledgements........................................................................ 6
Laura Meschke: Project Manager .........................................................................................................................6
Cassidy Kuhn: Quality Control Manager ...............................................................................................................6
Fernando Monroy: Budget Manager ....................................................................................................................7
Hali Hafeman: Environmental Responsibility........................................................................................................7
Shaye Palagi: Social and Regulatory Responsibility ..............................................................................................7
Executive Summary ............................................................................................................... 8
1.0 Introduction .................................................................................................................. 10
1.1 Project Background....................................................................................................................................10
1.2 Existing Conditions.....................................................................................................................................11
1.3 Future Conditions ......................................................................................................................................11
1.4 Regulations................................................................................................................................................13
2.0 Alternatives................................................................................................................... 14
2.1 Chlorine Gas ..............................................................................................................................................14
2.2 Bulk Delivery of Sodium Hypochlorite........................................................................................................15
2.3 On-Site Generation of Sodium Hypochlorite for Use at the Ralston Site Only ............................................15
2.4 On-Site Generation of Sodium Hypochlorite for Delivery to All Plants.......................................................16
3.0 Selection Process ........................................................................................................... 17
4.0 Design of On-site Sodium Hypochlorite Generation........................................................ 19
4.1 Constraints and Considerations .................................................................................................................19
4.1.1 Salt Quality.................................................................................................................................................19
4.1.2 DBP and Bromate Formation .....................................................................................................................20
4.1.3 Safety of 0.8% Sodium Hypochlorite..........................................................................................................20
4.2 Process Overview.......................................................................................................................................20
4.3 Ralston Plant Design ..................................................................................................................................22
4.3.1 Injection Points ..........................................................................................................................................22

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4.3.2 Construction Phasing .................................................................................................................................23
4.4 Ralston Plant OSG Design ..........................................................................................................................24
4.4.1 Salt Storage Tanks......................................................................................................................................25
4.4.2 Rectifier......................................................................................................................................................25
4.4.3 Heat Exchanger ..........................................................................................................................................26
4.4.4 Water Softener ..........................................................................................................................................26
4.4.5 Brine Storage Tanks ...................................................................................................................................27
4.4.6 Electrolytic Cells.........................................................................................................................................28
4.4.7 Control Panel .............................................................................................................................................29
4.4.8 Hydrogen Gas Dilution...............................................................................................................................30
4.4.9 Sodium Hypochlorite Storage Tanks..........................................................................................................31
4.4.10 Pipe Network ...........................................................................................................................................32
4.5 OSG Building Design...................................................................................................................................33
4.6 Redundancy and Backup............................................................................................................................35
5.0 Cost Assessment............................................................................................................ 36
5.1 Capital Cost................................................................................................................................................36
5.2 Operation Cost...........................................................................................................................................37
5.3 Maintenance Cost......................................................................................................................................38
6.0 Conclusion..................................................................................................................... 38
7.0 References..................................................................................................................... 40
8.0 Appendix....................................................................................................................... 42
Appendix A: Decision Matrices ........................................................................................................................42
Original Decision Matrix......................................................................................................................................42
Updated Decision Matrix ....................................................................................................................................43
Appendix B: Material Balance around OSG system..........................................................................................44
Appendix C: Ralston Site Layout ......................................................................................................................47
Appendix D: Choosing the Size and Number of Brine and Salt Storage Tanks ..................................................49
Appendix E: Heat Exchanger Calculations ........................................................................................................50
Appendix F: Choosing the Sizes and Configuration of the ClorTec® High Output CT Series...............................52
Appendix G: Choosing the Hypochlorite Storage Tank Dimensions and Containment Area .............................54
Choosing the size and number of back-up bulk hypochlorite tanks...................................................................56
Choosing the containment wall configuration....................................................................................................57
Appendix H: Piping Specifications....................................................................................................................58

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Choosing the Appropriate Pipe Material ............................................................................................................58
Pipe Length Calculations.....................................................................................................................................58
Appendix I: Economic Costs.............................................................................................................................59
Capital Cost .........................................................................................................................................................59
Process Solution Inc Quote.................................................................................................................................61
Operation Cost....................................................................................................................................................65
Maintenance Cost...............................................................................................................................................66
TPV 20 year Lifecycle ..........................................................................................................................................67

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LIST OF FIGURES
Figure 1: Moffat Treatment Plant Filtration Room 1...................................................................................................11
Figure 2: Ralston Reservoir Site Location Overview ....................................................................................................12
Figure 3: City of Arvada Future Land Use Plan with Proposed Ralston Site ................................................................12
Figure 4: Typical Storage Tanks for Liquid Chlorine Gas..............................................................................................14
Figure 5: Bulk Hypochlorite Storage Tanks..................................................................................................................15
Figure 6: Map of Denver Water Plant Locations..........................................................................................................16
Figure 7: Water and Brine Preparation before Entering Electrolytic Cells ..................................................................21
Figure 8: Moffat Treatment Plant Process with Chlorine Injection Points ..................................................................23
Figure 9: Kinetico® Triplex Model Softeners................................................................................................................26
Figure 10: ClorTec® CT-1200 Series Electrolytic Cell....................................................................................................28
Figure 11: Sizing of Electrolytic Cell Systems...............................................................................................................28
Figure 12: ClorTec CT-Series Touchscreen Display Panel ............................................................................................29
Figure 13: Hydrogen Gas Blower .................................................................................................................................30
Figure 14: Disinfection Building Layout .......................................................................................................................34
Figure 15: Layers of Redundancy.................................................................................................................................35
LIST OF TABLES
Table 1: Original Criteria and Sub-Criteria Weights.....................................................................................................17
Table 2: Original Alternatives' Scores..........................................................................................................................17
Table 3: Final Criteria and Sub-Criteria Weights..........................................................................................................18
Table 4: Final Alternatives' Scores ...............................................................................................................................18
Table 5: OSG Manufacturer Details .............................................................................................................................24
Table 6: Capital Cost Breakdown.................................................................................................................................37
Table 7: Operations Cost Breakdown ..........................................................................................................................37
Table 8: Maintenance Costs Breakdown .....................................................................................................................38

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LIST OF ACRONYMS
AC alternating current
AWWA American Water Works Association
CDPHE Colorado Department of Public Health and Environment
CFATS Chemical Facilities Anti-Terrorism Standards
CPDWR Colorado Primary Drinking Water Regulations
DBP disinfection byproduct
DC direct current
EPA Environmental Protection Agency
FTE full time equivalent
GFRP glass fiber reinforced plastic
HDPE high-density polyethylene
HVAC heating, ventilating and air conditioning
LCD liquid crystal display
MCDM multi-criteria decision matrix
MCL maximum contaminant level
OSG on-site generation
OSG+ on-site generation plus delivery
PP polypropylene
UV ultraviolet radiation
LIST OF UNITS
Ca/mg hardness
ft3
cubic feet
°F degrees Fahrenheit
g/L grams per liter
gal gallon
gal/day gallon per day
gpm gallons per minute
kwh kilowatts hour
L liters
lb/day pounds per day
mg milligrams
MGD million gallons per day
ppm parts per million

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TEAM MEMBER ROLES AND ACKNOWLEDGEMENTS
Aquatech Solutions would like to thank Denver Water, especially Brett Balley, Andrea Song, Tim Curry and the team
at Moffat Treatment Plant for collaborative support and design guidance. Denver Water worked with Aquatech
Solutions to explore triple bottom line solutions, allowing us to narrow in on a beneficial design.
We are honored to have worked with our Technical Advisor, Amlan Ghosh, a leader in on-site generation system
knowledge. His experience and guidance were invaluable throughout the design process. Finally, none of our efforts
would have come to fruition without the leadership and encouragement of our Faculty Advisor, Chris Corwin. The
support of Professor Corwin not only made this senior design project possible, but helped us grow as young
environmental engineers.
Aquatech Solutions is composed of five senior undergraduate environmental engineering students at the University
of Colorado Boulder. The team ranges in areas of emphasis within the environmental engineering field with three
water quality specialists, one chemical processes engineer, and a member with experience in engineering for
developing communities. Aquatech Solutions' composition of differing experience gave the team a unique
perspective of the problem at hand.
LAURA MESCHKE: PROJECT MANAGER
Ms. Meschke oversaw all of Aquatech Solutions’ budgeting of time throughout the project and ensured the work of
all team members was geared towards efficient project completion. As the project manager, she assisted each team
member with their work whenever necessary. A majority of Ms. Meschke’s time was spent condensing previously
written documents into more concise summaries for needed background information. In addition, she was
responsible for assuring the quality of the overall project through various ways of organizing and editing.
CASSIDY KUHN: QUALITY CONTROL MANAGER
Mr. Kuhn analyzed DBP formation during and after hypochlorite generation, the materials used to store and pipe
the hypochlorite, and the sodium hypochlorite storage tank containment and failure design, including the back-up

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dilution panel sizing and manufacturer. He checked regulations specific to sodium hypochlorite generation for
compliance and analyzed the cost-benefit relationship for implementing a heat exchanger.
FERNANDO MONROY: BUDGET MANAGER
Mr. Monroy conducted cost estimates on the overall project which included capital cost, operation cost, and
maintenance cost under an ACCEi class III evaluation as well as a 20 year Total Present Value. Along with the cost
estimates Mr. Monroy designed a basic layout of the treatment plant and also created the OSG building layout on
Revit.
HALI HAFEMAN: ENVIRONMENTAL RESPONSIBILITY
Ms. Hafeman's time was spent investigating the effect of each disinfection alternative on the environment. As part
of her environmental responsibility role, she calculated the amount of CO2 emitted by each technology, and looked
into the possibility of alternative energy sources for the Ralston Plant. In addition to being the environmental
responsibility lead, Ms. Hafeman performed material balances on each technology, contributed to the selection of
the electrolytic cell, and designed the brine, bulk hypochlorite, and salt storage tanks.
SHAYE PALAGI: SOCIAL AND REGULATORY RESPONSIBILITY
Ms. Palagi led the investigation into how various disinfection technologies would impact the quality of life for both
operators and the surrounding community. As regulation is the first expression of a society’s concerns, she explored
relevant public health, zoning, and water treatment regulations. Ms. Palagi served as a design engineer throughout
the preliminary design phase of the project. She contributed on the selection of OSG manufacturer, electrolytic cell
size and configuration, and hypochlorite storage tank size and configuration. Ms. Palagi was a key team member in
the formulation of Aquatech Solutions’ layers of redundancy. She also contributed research and knowledge to the
team’s understanding of the water softener, rectifier, and hydrogen gas dilution blower.

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EXECUTIVE SUMMARY
All four of Denver Water’s Treatment Facilities, Foothills, Moffat, Marston and Recycle, currently use
chlorine gas as their primary disinfectant. Injecting chlorine gas into a water treatment process line is an extremely
effective disinfection technique because its addition to water creates hypochlorous acid, a compound with strong
disinfection capabilities. As compared to other disinfection technologies, the overall system encompassing the use
of chlorine gas is quite simple and therefore has very little capital, operational and maintenance costs. These two
facts are why Denver Water has successfully been using the chemical since the company’s birth in the early 1900s.
However, there is a significant disadvantage surrounding the chemical characteristics of chlorine gas. It is very
poisonous and can be fatal if inhaled, putting both operators and even the public in surrounding communities in
danger. The hazard posed by leaks, as well as the potential for terrorism, has caused a significant push to discontinue
an exemption from the Chemical Facilities Anti-Terrorism Standards allowing water treatment facilities to use the
dangerous gas in large quantities. For Denver Water specifically, the potential change has become an influential
factor in the design of their proposed new plant at their Ralston Reservoir location, as the plant should be within
regulations into the future once constructed. This new facility is being built due to the old age and physical
limitations in adaptability of new technology at Denver Water’s Moffat Treatment Plant. Functioning as a
replacement plant, the new Ralston Plant will have the same influent water and a similar flow rate to the Moffat
Treatment Plant.
Aquatech Solutions has proposed four possible disinfection technologies for the new site: continuing with
chlorine gas, bulk delivery of sodium hypochlorite, on-site generation of sodium hypochlorite for the Ralston Plant
only, and on-site generation of sodium hypochlorite for delivery to all of Denver Water plants. The team compared
these alternatives on a triple bottom line basis, economics, social, and environmental, with an added emphasis on
functionality within a multi-criteria decision analysis. The overall criteria weights were determined by the team
using knowledge gained from conversations with the client. Sub-criteria and their corresponding weights were
specifically chosen by Denver Water. Aquatech Solutions used a twenty-year life cycle cost assessment of each
technology to ultimately determine the scores given for the economics section of the matrix. Ratings within the
functionality, social, and environmental categories were chosen for each technology based on various calculations,
interviews with an assorted range of plant personnel, and information found in literature. The EnvisionTM
Sustainable Infrastructure Rating System was also applied to the different technologies even though many of its
criteria were not applicable due to the scope of this project.
The final scores tabulated by the decision matrix resulted in the following order from highest/best score to
lowest/worst: bulk delivery of sodium hypochlorite, chlorine gas, on-site generation of sodium hypochlorite for the
Ralston Plant only and on-site generation of sodium hypochlorite for delivery to all Denver Water plants. Aquatech
Solutions therefore suggested that Denver Water implement a bulk delivery of sodium hypochlorite system at their
new water treatment plant. Once Denver Water had appropriate time to review the alternatives assessment
presented to them by Aquatech Solutions, modifications to the decision matrix were required. Economic
considerations are not what Denver Water deems to be the most important deciding factor, as the team had
assumed earlier. Upon this realization, the multi-criteria decision matrix was updated to include new criteria weights
specifically set by the client. The restructured matrix gave new results in subsequent order from highest to lowest:
bulk delivery of sodium hypochlorite, on-site generation of sodium hypochlorite for the Ralston Plant only, on-site
generation of sodium hypochlorite for deliver to all Denver Water plants and chlorine gas. Even with this new
analysis, it was decided that Aquatech Solutions should move forward with the design of an on-site generation
system for only the Ralston Plant. This decision was made by the client in conjunction with the team and the Project

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Principle, Chris Corwin, Ph. D, P.E. due to the additional valuable information that could be gained by conducting a
preliminary design of an on-site generation system.
Before beginning the design of the on-site generation system, an overall site plan for the Ralston Treatment
Plant needed to be developed. In order to do so, the team studied the layout of the other Denver Water treatment
plants. Aquitech Solutions also collaborated with a team from the CVEN 3424 Water and Wastewater Treatment
class designing a 220 MGD water treatment plant. All of the gathered information was used to create an estimate
of the Ralston site layout. This map was extremely valuable for the design of the pipe system for the distribution of
sodium hypochlorite to the various injection points within the plant.
Aquatech Solutions researched six separate on-site generation system manufacturers before deciding on
the ClorTec® CT Series. The team chose to have six independent systems including two dual 2400 lb/day Cl2
equivalent systems and two 1000 lb/day Cl2 equivalent systems. With this set up, the plant would be able to create
the required amount of sodium hypochlorite for maximum flow with one of the systems down and enough for
average flow with four of the systems down. In order to store all of the generated sodium hypochlorite, four high-
density cross-linked polyethylene tanks would need to be installed within the disinfection building. The ClorTec®
systems and storage tanks have been designed to generate and hold enough hypochlorite to supply 1.6 days of
disinfectant while the plant is running at maximum capacity. A backup bulk delivery of 12.5 percent sodium
hypochlorite was also included in the design of the disinfection system. It is capable of supplying enough disinfectant
for one day at maximum flow through the use of a dilution panel. A disinfection building layout has also been
created, including individual component dimensions. This layout has been designed so supply trucks can drive
directly up to the salt tanks and dilution panel for easy unloading.
When conducting a preliminary cost estimate for this design, capital, operational and maintenance costs
were only considered for the on-site generation system itself. Capital costs included the price of the on-site
generation equipment, construction, and installation and totaled $17 million. Operational costs were determined
to equal $162,000 annually, which consisted of delivery, supplies, electricity, and labor expenses. The price of labor
and replacement materials for the overall maintenance cost associated with on-site generation results in a cost of
$380,000 annually. With all of these costs determined, Aquatech Solutions conducted a 20-year life cycle cost
analysis using a three percent interest rate to yield a total present value of $27 million. This total present value
yields $211/1,000 gallons of water treated, assuming an average flow of 46 MGD.
The team has really enjoyed this experience and learned a great deal about the engineering consulting and
professional process. Denver Water has been an extremely helpful client and provided beneficial feedback
throughout this entirety of this course. Aquatech Solutions has thoroughly enjoyed working with the company and
looks forward to possible correspondence in the future. The team hopes that Denver Water will consider their
research and recommendations contained in both the alternatives assessment and preliminary design report when
making future decisions about the Ralston Treatment Plant. Aquatech Solutions would like to thank everyone at
Denver Water for giving us the opportunity to participate and contribute to the Ralston Treatment Plant project.

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1.0 INTRODUCTION
1.1 PROJECT BACKGROUND
The City of Denver formed Denver Water after purchasing the Denver Union Water Company in 1918. As of now,
their three primary water treatment plants, Foothills, Moffat and Marston, plus an additional Recycle Plant, serve
1.3 million people. Each of the plants receive their water from various basins and reservoirs located throughout the
Rocky Mountains. Denver Water's proximity to its source results in an extremely high quality of water before it even
enters the plants, allowing the company to operate a strictly conventional treatment system at each of their drinking
water plants.
Denver Water's drinking water treatment plants have relied on the use of chlorine gas as their primary disinfectant
since the company's creation. Gaseous chlorine has historically been valued as a highly effective, yet economically
feasible method of disinfecting pathogens. However, concentrated chlorine gas is extremely poisonous and, if
procured by someone with malicious intent, could be used as a weapon. It would also pose as a severe threat to
plant operators if a leak was ever to occur. In fact, 779 injuries and two deaths have occurred in the past 15 years
resulting from chlorine gas accidents at chemical facilities across the country (Sinpatanasakul 2013). The Chemical
Facilities Anti-Terrorism Standards (CFATS) federally mandate that facilities managing high amounts of chlorine gas
must mitigate the vulnerability of the gas to terrorist attempts (Department of Homeland Security 2007). Water
treatment facilities have thus far been exempt from these regulations, but recent geopolitical concerns have called
for a stop to the exemption. This change to the CFATS is likely in the near future, which has motivated the American
Water Works Association (AWWA) to publish the report "Selecting Disinfectants in a Security Conscious
Environment," which outlines the steps involved when switching over to a new disinfection technology (Ghosh et al.
2012). Denver Water has therefore decided to research the feasibility of implementing a new disinfectant
technology into their systems.

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1.2 EXISTING CONDITIONS
Although security, safety, and legislative concerns are the
primary drivers for Denver Water's consideration of new
methods for disinfection, they are not the only issues.
Denver Water plans to build an entirely new treatment
facility to replace their Moffat Treatment Plant. Opened in
1937, the original Moffat infrastructure is still in use today,
including the building shown in Figure 1, but it has served
its useful lifetime. In addition to the continued use of the
original buildings, a collection of the equipment first
installed at the plant is still running and in practice. For example, the filters in Moffat Filter Room 1, pictured in Error!
eference source not found., are much shallower than the current filtration basins used in common practice.
Shallower filters must be backwashed more frequently causing extra work for operators that could be avoided if
updated. The new plant will be built at the Ralston Reservoir site shown in Figure 2 within the next 10 years, making
it an opportune time to consider other disinfection alternatives.
1.3 FUTURE CONDITIONS
The City of Arvada is the community abutting the site of the Ralston Plant from the east; the city owns much of the
encompassing land. Arvada’s future plans and goals have been taken into consideration as the host community,
while keeping in mind overarching needs of the entire Denver Water distribution system. The Arvada
Comprehensive Plan informs the City's detailed forecast, whereas the Denver Metro Vision 2035 Plan provides a
framework for regional goals and priorities. The Metro Vision plan stresses limiting the spread of urbanized land
and an increase in protected open space, revealing the City of Denver will be unsupportive of residential
Figure 1: Moffat Treatment Plant Filtration Room 1
http://www.denverwater.org/docs/Moffat_Filter_Plant.jpg

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development around the Ralston site. Restricting
residential areas around the plant is ideal for this
project, as it would distance community members
from potentially harmful chemicals in the event of
a leak. Figure 2 depicts the proposed site of the
Ralston Plant, situated to the northeast of Upper
Long Lake.
Figure 3, a close up of the Ralston property from the City
of Arvada Future Land Use Plan as of July 18th
2014,
reveals that the city is planning for the area just south of
the plant to eventually be low density residential and
mixed-use (City of Arvada 2014). The east side of
Highway 93 is all open space and parks, particularly
water-based recreation.
Denver is one of the fastest growing cities in the nation,
and although conservation efforts have succeeded in
managing demand, population growth and expansion
must be considered throughout the project. According to the Denver Metro Vision 2035 Plan, the current population
of 3 million citizens will grow to 4.5 million in the next 20 years (Denver Regional Council of Governments 2011).
Denver Water currently serves 43 percent of Denver’s population. If this percentage remains, they will be expected
to serve an extra 700,000 people in 2035. To meet these changes, Denver Water plans to increase the capacity from
185 million gallons per day (MGD) at the Moffat Plant now to 220 MGD expandable to 300 MGD at the future Ralston
Plant. Once built, it is projected that the Ralston Plant will average 46 MGD throughout the year, the current average
flow at the Moffat Plant.
Figure 2: Ralston Reservoir Site Location Overview
Figure 3: City of Arvada Future Land Use Plan with Proposed Ralston Site

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1.4 REGULATIONS
Pertinent state regulations that should be kept in mind when decided on a disinfection technology include the
Colorado Primary Drinking Water Regulations (CPDWR) and Colorado Water Quality Control Act. These documents
mandate that the new facility be required to pass the scrutiny of the Colorado Department of Public Health and
Environment (CDPHE) (CDPHE; Public Health Service Act 2002). Section 11.8 of the CPDWR outlines compliance
requirements for surface water treatment and monitoring: the treatment facility must maintain disinfection
sufficient to ensure that the total process achieves 4-log treatment of viruses and 3-log treatment of Giardia lamblia.
The concentration of the disinfectant residual must meet strict detection standards.
At the national level, drinking water quality is monitored by the Environmental Protection Agency, and within the
state through the Colorado Department of Public Health and Environment (CDPHE 2015; Public Health Service Act
2002). Although numerous regulations exist at both the federal and local level which set the standards for water
treatment and the effectiveness of disinfection, Aquatech Solutions expects neither major changes in potable water
quality policy nor significant variation in the treatment capability of the alternatives. Each technology can and will
disinfect the water to national standards. Additionally, shifting regulations due to western region water availability
and watershed management will not impact disinfection decisions and was not a concern. It is worth mentioning
that there exists a negative trend in water consumption in the Denver region. Denver Water is a strong advocate
for water conservation efforts, and so far efforts have been successful. Therefore, the most relevant regulations to
consider are those involving the management of treatment chemicals.
The Risk-Based Performance Standards Guidance for the CFATS lists eighteen compliance measures that Denver
Water will need to consider should the exemption currently provided to water treatment facilities be nullified
(Department of Homeland Security 2007). It is important to understand that the risk-based performance standards
are not an edict of exact numbers and specifications, but rather focus on how to create a secure environment. There
are numerous measures possible to increase the security of high-risk chemicals, many of which Denver Water
already takes, such as restricting personnel allowed on site. Should water facilities lose their exempt status from
the CFATS, the increased security requirements could come with increased cost.

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2.0 ALTERNATIVES
Aquatech Solutions chose four disinfection technologies to analyze in an alternatives assessment that was delivered
to Denver Water for consideration. The technologies that were examined are chlorine gas, bulk delivery of sodium
hypochlorite, on-site generation (OSG) for use at Ralston only and on-site generation for the delivery to all plants
(OSG+). The client had previously requested that the team explore other disinfection techniques. However, initial
research showed that these various options are unlikely to be beneficial for the water that will be treated at the new
plant. Cryptosporidium is not prevalent in the influent water to the plant, which is the major driver for using ultraviolet
radiation (UV). Because of this, the high cost of a UV disinfection system would not be merited (EPA 1999a). The
current Moffat Plant also does not have problems with trace organic contaminants; and, therefore the high cost for an
ozone disinfection system outweighs any other advantages the technology provides (EPA 1999b).
2.1 CHLORINE GAS
The use of chlorine gas as a disinfectant capitalizes on the
reaction that occurs when the chemical is injected into the
water process line. When the gas reacts with water, the
end result is hypochlorous acid, which acts as the primary
disinfecting agent. The gas is typically stored in steel
cylinders like those shown in Figure 4 before being
injected into the system. This technology has been used
at each of the Denver Water Treatment Plants since the
company’s birth. Implementing this system at the new plant would allow for consistency throughout all of their
plants. Operators would not need new training, allowing for a smooth transition once the new plant has been
constructed. The gas is also relatively inexpensive. However, this technology is still dangerous to the operators and
surrounding communities. There is also a good chance that in the coming years the water treatment plant
exemption from the CFATS will have ended.
Figure 4: Typical Storage Tanks for Liquid Chlorine Gas
http://www.beaumontenterprise.com/news/article/

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2.2 BULK DELIVERY OF SODIUM HYPOCHLORITE
The bulk sodium hypochlorite technology relies on
the delivery of 12.5 percent hypochlorite solution.
Once delivered, diluted, stored in tanks like those
shown in Figure 5, and injected into the water flow,
the chemical reacts with the water to form the
desired disinfectant hypochlorous acid and the by-
product sodium hydroxide. The combination is
commonly referred to as liquid bleach (White 2010).
There are many advantages to the implementation of
a bulk sodium hypochlorite delivery system. In contrast to hazardous chlorine gas, it is extremely safe for both
operators and the public (Michigan AWWA Research & Technical Practices Committee 2014). This technology has
low capital costs, but the salt itself is expensive, which leads to high operation and maintenance costs. By choosing
this technology, Denver Water would avoid future policy compliance issues if the CFATS were to be changed.
2.3 ON-SITE GENERATION OF SODIUM HYPOCHLORITE FOR USE AT THE RALSTON SITE ONLY
Three components are needed to successfully generate sodium hypochlorite on-site: salt, water and electricity. A
brine solution created from potable water and salt is sent through a series of electrolytic cells, which causes a
reaction that ultimately produces sodium hypochlorite. As compared to the previous two technologies, OSG is the
safest (Michigan AWWA Research & Technical Practices Committee 2014). The system is fairly independent of
outside forces because it does not require large amounts of salt truck deliveries. Similar to bulk delivery of sodium
hypochlorite, OSG would meet chemical standards even if regulations were to be changed in the future. OSG
Figure 5: Bulk Hypochlorite Storage Tanks
http://www.waterworld.com/content/dam.jpg

16
systems are expensive resulting in high capital costs, and the system additionally requires a large amount of
maintenance.
2.4 ON-SITE GENERATION OF SODIUM HYPOCHLORITE FOR DELIVERY TO ALL PLANTS
The on-site generation plus delivery alternative
capitalizes the same technology used in the previous
alternative, however it involves a much larger OSG
system. As stated in the alternative description
before, sodium hypochlorite would be generated at
the Ralston site from water, salt and electricity. The
difference is that enough sodium hypochlorite would
need to be generated in order to meet the demands
of all four Denver Water Plants. The generated
sodium hypochlorite would be delivered to the other
three plants, (locations shown in Figure 6), from
the Ralston site. There are currently no treatment
plants in the United States that use an OSG system at one plant and deliver the created sodium hypochlorite to other
locations. The key points presented earlier about the technology’s safety and compliance with possible future
regulations apply in this case as well. However, if Denver Water were to implement the OSG plus delivery alternative,
they would experience increased risk because the entire Denver distribution system would become entirely reliant
on one disinfectant source.
Figure 6: Map of Denver Water Plant Locations

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3.0 SELECTION PROCESS
To account for the unique constraints and objectives facing the client’s choice of selecting a disinfection technology
at the Ralston Plant, Aquatech Solutions coordinated with Denver Water to build a multi-criteria decision matrix
(MCDM) specifically tailored to the Ralston Plant. The matrix itself can be found in Appendix A.
Table 1: Original Criteria and Sub-Criteria Weights
For easy viewing, a subset of the matrix is provided in Table
1. The table displays the sub-criteria deemed worthy of
intensive review by the collaborative efforts of Aquatech
Solutions and Denver Water, and the weights assigned. The
weight is a reflection of how important a specific criterion
is to the ultimate decision facing Denver Water in their
selection of a disinfection system. Weights were also
assigned to the overall criteria by the team and influenced
by conversations with the client. Aquatech Solutions then
researched each alternative in terms of how appropriately it satisfied each criterion and assigned a rating accordingly
– ten reflects a positive outcome and zero a negative one. For example, the risk of exposure to a dangerous toxin
led to chlorine gas scoring a rating of two for the criterion of operator safety, whereas bulk delivery of sodium
hypochlorite scored a rating of 10, because it is a less dangerous alternative.
Table 2: Original Alternatives' Scores
Once each alternative was rated across each category, a final
score was calculated by the decision matrix. Scores are
illustrated below in Table 2. As shown below in the table,
bulk delivery of sodium hypochlorite scores the highest in the
MCDM and was therefore Aquatech Solutions'
recommendation for Denver Water.
Criteria Sub-Criteria Weight
Economic
0.4
Capital Construction Costs 7
Operation Costs 7
Maintenance Costs 3
Social
0.25
Operator Safety 10
Public Safety and Perception 7
Future Policy Compliance 7
Env.
0.1
CO2 Emissions and By-products 3
Functionality
0.25
System Reliability 10
Operational Complexity 7
Chemical Supply Reliability 7
Flexibility 5
Alternative Final Score
Chlorine Gas 124
Bulk Delivered Sodium Hypochlorite 152
OSG 114
OSG+ 112

18
Table 3: Final Criteria and Sub-Criteria Weights
All of the information gathered and analysis conducted was
then assembled into an alternatives assessment that was
given to Denver Water for review. The client provided
feedback on the report, which included the following
updates. Fiscal considerations are not Denver Water’s
highest priority. Safety and system reliability are the two
criteria that they consider the most important. This was not
previously reflected in the original decision matrix created
by Aquatech Solutions, but the matrix has since been
updated. The updated criteria weights are summarized in Table 3 and the full decision matrix can be seen in
Appendix A. These changes to the multi-criteria analysis yielded different overall alternative scores, which are shown
in Table 4.
Table 4: Final Alternatives' Scores
Even with the new overall criteria weights, bulk delivery of
sodium hypochlorite is the clear winner. However, through
talks with Denver Water and the approval from the Project
Principle, Chris Corwin, PhD, P.E., Aquatech Solutions has
decided to move forward with the design of an on-site
generation of sodium hypochlorite system for the Ralston
Plant only. The following report is a 30 percent preliminary design of this alternative.
Criteria Sub-Criteria Weight
Economic
0.25
Capital Construction Costs 7
Operation Costs 7
Maintenance Costs 3
Social
0.35
Operator Safety 10
Public Safety and Perception 7
Future Policy Compliance 7
Env.
0.05
CO2 Emissions and By-products 3
Functionality
0.35
System Reliability 10
Operational Complexity 7
Chemical Supply Reliability 7
Flexibility 5
Alternative Final Score
Chlorine Gas 125
Bulk Delivered Sodium Hypochlorite 179
OSG 140
OSG+ 130

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4.0 DESIGN OF ON-SITE SODIUM HYPOCHLORITE GENERATION
Producing sodium hypochlorite involves the combination of salt, water, and electricity in electrolytic cells (White
2010). Through the process of electrolysis, the added electricity propels a non-spontaneous reaction. The reaction
also results in the production of hydrogen gas, as shown in the reaction below.
𝑁𝑎𝐶𝑙 + 𝐻2 𝑂 + 2𝑒−
→ 𝑁𝑎𝑂𝐶𝑙 + 𝐻2
𝑆𝑎𝑙𝑡 + 𝑊𝑎𝑡𝑒𝑟 + 𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦 → 𝑆𝑜𝑑𝑖𝑢𝑚 𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 + 𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐺𝑎𝑠
Material balance relationships can be related to the amount of free chlorine required, based off flow rate and
dosage: for every pound of free chlorine needed, three pounds of salt, 2 kWh of electricity, and 15 gallons of water
can produce 15 gallons of 0.8 percent sodium hypochlorite (Woody 2009). See Appendix B for further clarification.
4.1 CONSTRAINTS AND CONSIDERATIONS
Although producing sodium hypochlorite is a rather straightforward process, ensuring high quality standards can be
very complex. Several considerations impacting water quality and operator safety are worth clarifying in detail.
4.1.1 SALT QUALITY
Impurities in salt have the potential to affect both the life expectancy of electrodes, by building up on the cell, and
bromate formation in the treated water (White 2010). Salt for OSG systems can come from seawater or mines; salt
from both sources is mixed with other minerals and requires recrystallization to be purified. The salt needs to be
99.7 percent pure dry weight Morton White crystal with low bromine content (Hooper 2005). Bromate
concentrations are regulated and have a maximum contaminant level (MCL) of 0.01 mg/L (Boal 2009). A direct
relationship exists between the salt quality, cell efficiency, and DBP formation. Therefore only the highest possible
quality salt should be used. Before being used in the OSG system, salt should be stored in a dry tank and out of
direct sunlight (Hooper 2005).

20
4.1.2 DBP AND BROMATE FORMATION
The potential for increased disinfection byproducts is a disadvantage of OSG. However, 0.8 percent sodium
hypochlorite produces less disinfection by-products (DBP) than the 12.5 percent solution used in a bulk sodium
hypochlorite delivery system. Dilute solutions can be stored for longer amounts of time because they take more
time to decompose. Granted authority through the Safe Drinking Water Act of 1996, the United States
Environmental Protection Agency (EPA) formulated rules to address public health concerns and balance the risks
between pathogens and disinfection byproducts. Under the Stage 1 DBP rules, bromate is regulated to a maximum
residual disinfectant level goal of zero and a maximum residual disinfectant level of 0.010 mg/L (EPA 1998). While
compliance is based on an annual average, any water treatment plant initiating an OSG system must be aware that
increased attention should be paid to monitoring bromate concentrations.
4.1.3 SAFETY OF 0.8% SODIUM HYPOCHLORITE
Although switching from using chlorine gas to common consumable raw materials lowers many safety concerns,
sodium hypochlorite is not a risk free chemical. Due to its oxidizing nature, sodium hypochlorite is an unstable and
corrosive chemical (White 2010). Caution must be taken to minimize the potential for the chemical to react. It
should be stored in plastic materials and not allowed to come into contact with metals (Solvay 2014). The
hypochlorite storage tanks should be kept secure with the use of containment walls. The walls and floor should also
be coated with epoxy to prevent concrete corrosion in the event of a spill (Solvay 2014). An emergency eyewash
and drench shower station should be installed nearby in case a spill were to occur.
4.2 PROCESS OVERVIEW
The water used to mix the brine solution created can be pulled directly from the water treatment process line once
it has been filtered. The water must first flow through a softener to reduce total hardness, preventing scale build
up on the cells (White 2010). After softening, some of the water is routed to the salt dissolver to prepare a
concentrated brine solution of approximately 300,000 mg/L (Casson and Bess 2006). In solution, NaCl dissolves into

21
Na+
and Cl-
ions. Metering pumps then pump the brine mixture to the electrolytic cells where it will dilute further
as it rejoins water from the softener as shown in Figure 7.
Figure 7: Water and Brine Preparation before Entering Electrolytic Cells (White 2010)
The electrolytic cell operates as a continuous-flow, steady-state, plug-flow type reactor (White 2010). A direct
current (DC) potential is maintained within the cell, therefore alternating current (AC) from the wall must flow
through a rectifier before power is sent to the generator. The cell consists of an elongated cylindrical clear holding
chamber and titanium electrode plate pairs (cathode and anode) (White 2010). The overall reaction occurs when
the cells electrolyze the brine solution by way of the following reactions (White 2010):
2𝐶𝑙−
→ 𝐶𝑙2 + 2𝑒− (𝐴𝑛𝑜𝑑𝑖𝑐 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)
2𝐻2 𝑂 + 2𝑒−
→ 2𝑂𝐻−
+ 𝐻2(𝐶𝑎𝑡ℎ𝑜𝑑𝑖𝑐 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)
2𝐶𝑙−
+ 2𝐻2 𝑂 → 𝐶𝑙2 + 𝐻2 + 2𝑂𝐻−(𝑂𝑣𝑒𝑟𝑎𝑙𝑙 𝐼𝑜𝑛𝑖𝑐 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)
2𝑁𝑎𝐶𝑙 + 2𝐻2 𝑂 → 𝐶𝑙2 + 2𝑁𝑎𝑂𝐻 + 𝐻2(𝑂𝑣𝑒𝑟𝑎𝑙𝑙 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)
𝐶𝑙2 + 2𝑁𝑎𝑂𝐻 → 𝑁𝑎𝑂𝐶𝑙 + 𝑁𝑎𝐶𝐿 + 𝐻2 𝑂 (𝑆𝑖𝑑𝑒 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)
3𝑁𝑎𝑂𝐶𝑙 → 𝑁𝑎𝐶𝑙𝑂3 + 2𝑁𝑎𝐶𝐿 (𝑆𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑆𝑖𝑑𝑒 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛)

22
Oxidation occurs at the anode to produce chlorine gas, while water is reduced at the cathode to produce hydroxyl
anions and hydrogen gas. The hydrogen gas is a byproduct of the reaction; for each pound of chlorine equivalent
produced, 7 ft3
of hydrogen gas is produced, which must be separated from solution and diluted before being
released to the atmosphere (Matthews 2010). The sodium and hydroxyl ions must first react to form sodium
hydroxide, and then sodium hydroxide can combine with chlorine gas to produce sodium hypochlorite solution
(White 2010). The secondary side reaction results in an unwanted byproduct, sodium chlorate, which can create
inefficiencies within the cell; this can be controlled by careful monitoring of brine temperature and concentration
(White 2010). Sodium hypochlorite is then sent to storage tanks before being used for disinfection.
4.3 RALSTON PLANT DESIGN
Before designing the OSG system itself, Aquatech Solutions felt it was important to have a good indication of what
the Ralston Plant could actually look like in terms of the process flow throughout the whole plant, as this could affect
building size, location and pipe length determinations. In order to create a rough estimate of the Ralston Plant
layout, the team analyzed layouts of Denver Water’s other plants currently in use, especially the Moffat Treatment
Plant. This research gave the team a good idea of where specific processes would be constructed. In order to
determine specific dimensions of the other conventional treatment techniques, Aquatech Solutions collaborated
with a team from the ongoing CVEN 3424 Water and Wastewater Treatment class designing a 220 MGD conventional
water treatment plant. All of the information collected, plus additional specific details needed for the OSG system
(for example, an access road for salt deliveries), was combined to create an overall site layout that will be used for
any subsequent calculations involving the plant as a whole. That site layout can be viewed in Appendix C. In the
future, Denver Water may expand the Ralston Plant to 300 MGD, therefore excess space has been provided for
treatment expansion.
4.3.1 INJECTION POINTS
The primary purpose for understanding the overall site layout is to gain the ability to consider locations of and
distances to disinfectant injection points. Aquatech Solutions received a schematic of the treatment process

23
currently used at the Moffat Water Treatment Plant, which depicts their chlorine injection points. That schematic is
shown in Figure 8.
Figure 8: Moffat Treatment Plant Process with Chlorine Injection Points
As can be seen, Denver Water injects disinfectant into the process line at three points: before rapid mix, before
filtration and after filtration. However, at the request of the client, Aquatech Solutions will be adding an injection
point before distribution, resulting in four sodium hypochlorite injection points. The exact location of those points
can be viewed on the overall site layout pictured in Appendix C.
4.3.2 CONSTRUCTION PHASING
Denver Water is extremely lucky in regards to the future construction of the Ralston Treatment Plant. With the
Moffat Treatment Plant still fully operational, there is some leeway when deciding how quickly the plant needs to
be built. They will be able to provide safe drinking water to the area served by this plant throughout the construction
process. Once the plant is built, Aquatech Solutions predicts that there will be issues surrounding the on-site
generation system when the plant begins running as it is unfamiliar to the operators. In anticipation of this, the
team has designed backup bulk delivery of sodium hypochlorite capabilities at the new site. If any issues with the
OSG system were to occur, the plant could smoothly switch over to the other disinfectant and work out the problem
without having to shut down. This backup system will be able to be used at any point during the plant’s lifetime as
well.

24
4.4 RALSTON PLANT OSG DESIGN
Aquatech Solutions compared six different OSG manufacturers in order to select the provider most capable of
meeting Denver Water’s needs. Various criteria were explored including production capability, electrical demand,
ease of use, and whether or not additional components, such as a softener, are included within the standard design.
Findings for each OSG manufacturer are summarized in Table 5. Aquatech Solutions ultimately selected ClorTec®, a
globally trusted and respected water treatment company. ClorTec® has been active in on-site generation since 1998
and have over 3,500 units in operation worldwide (Matthews 2010). Their experience will provide knowledge and
security to the Ralston Plant disinfection treatment system.
Table 5: OSG Manufacturer Details
Manufacturer Deciding Information
ClorTec® CT Series Trusted in the water treatment industry, leading OSG company. System
comes with many extra components including softener, hydrogen gas
dilution, rectifier, and hypochlorite storage tanks – allowing for fluid
connection between components. The CT Series is available in a wide
variety of OSG capacities, resulting in increased flexibility . Largest single
generator output is 3000 lb/day chlorine equivalence.
Klorigen™ M-Series OSG systems were not large enough; an unreasonable number would be
required to treat the Ralston Plant design flow rate.
Process Solutions, Inc: MicrOclor™ Excellent customer service with guaranteed next day field service, seven
days a week. Largest single generator output is 2400 lb/day chlorine
equivalence.
Miox RioGrande™ Well-designed systems, but fewer size options than ClorTec®, hindering
adaptability to the needs of the Ralston Plant. Wide (56.9 inches)
footprint compared to ClorTec® width of 14 inches per OSG system.
Pepcon ClorMaster® Poorly presented marketing material resulted in Pepcon appearing less
advanced, out of date, and less experienced than the competitors.
Siemens: OSEC® Although the Siemens system was operator friendly and elegantly
designed, the company is located in Germany, an unnecessary distance
compared to the adequate OSG providers located within the United
States.

25
4.4.1 SALT STORAGE TANKS
Aquatech Solutions has selected a distributor located in Salt Lake City to deliver the previously mentioned 99.7
percent pure dry weight Morton White crystal salt. Once delivered, it will be fed into the system at a rate of 16,513
lb/day (Severn Trent De Nora 2013). All tank calculations were completed using a maximum flow rate of 220 MGD.
Each salt storage tank will be constructed from high-density polyethylene (HDPE) material. It was assumed that a
minimum of 15 days of salt storage would be needed for continuous operation, which results in 247,698 pounds of
needed salt storage. The 15 day storage time was chosen as the design requirement because it is recommended for
plants that consume large amounts of salt, as it minimizes the number of deliveries needed (Casson and Bess 2006).
Salt will be delivered to the Ralston plant by blower truck, and each truck will have the ability to carry up to 20 tons
of salt. Each truck will measure eight to ten feet wide. Truck delivery space has been accounted for in the overall
site layout as shown in Appendix C. An auger system will be used to transport salt from the storage tanks to the brine
tanks. It was estimated that the optimal system would include two salt brine feed tanks, and three larger salt storage
tanks. The three salt storage tanks will each hold a volume of 10,094 gallons, and have a diameter of 9 feet and a
height of 21 feet. Assuming a minimum spacing of 3 feet between tanks, the total area of the salt storage tanks will
be 585 ft2
.
4.4.2 RECTIFIER
A rectifier converts AC, the standard current available from the electric grid, into DC, which is necessary for
electrolysis. The ClorTec® system comes with a rectifier capable of meeting the DC needs of the selected OSG system
as each independent OSG system has its own independent rectifier. The rectifier is rated for 100 percent continuous
duty at 104° F with a thyristor (also known as a silicon controlled rectifier, responsible for regulating voltage to the
load) designed for 200 percent load (Matthews 2010). The rectifier has the possibility of controlling the rate of
electrolysis by adjusting the amount of current supplied to the cells (White 2010). Rectifiers generate a significant
amount of heat, but the rectifiers accompanying larger ClorTec® systems are designed to exhaust hot air outside of
the room to minimize stress to the heating, ventilated, and air conditioning (HVAC) system and also come with
optional water cooler heat sinks (Matthews 2010).

26
4.4.3 HEAT EXCHANGER
Because the brine solution must be heated to temperatures ranging from 65° F to 80° F before being fed to the
electrolytic cells, a heat exchanger could be used to heat this feed brine as the newly generated hypochlorite solution
is cooled (Severn Trent De Nora 2013). AquaTech Solutions conducted a general cost savings analysis that indicated
a payback period of nine years, the details of which are shown in Appendix E. This payback period was not conclusive
enough to warrant a decisive recommendation regarding the use of a heat exchanger considering many assumptions
were used in the calculations. Namely, to what temperature the water is heated to within the desired range will
have a huge impact on the heat exchanger’s value, as will the true average temperature of the influent water. The
life expectancy of heat exchangers that use brine and hypochlorite solutions is also of importance, but there is not
much information available in literature. Therefore, AquaTech Solutions recommends that more detailed research
be conducted regarding the implementation of heat exchangers.
4.4.4 WATER SOFTENER
The included Kinetico® water softeners with the
ClorTec® system are designed for a recharge based
upon OSG usage, not time, and have an expected
resin life of ten years (Matthews 2010). Kinetico®
Hydrus Series water softeners are among the most
technologically advanced, decreasing waste
production and environmental irresponsibleness
(Kinetico® 2013). The water softeners require inlet
water at a pH of 6.5 to 8.5 and a temperature
between 65° and 80° F (Matthews 2010). Outlet
water has a hardness [Ca/Mg] of less than 10 ppm
(Matthews 2010). To meet the design flow, 82,575 gal/day, or 58 gpm will have to be processed through the
Figure 9: Kinetico® Triplex Model Softeners
http://www.flagcitywater.com/wpcontent.jpg

27
softeners to be used in making the brine solution. However, only 17,265 gal/day, or 12 gpm, is needed for the
average flow rate. Aquatach Solutions recommends the Hydrus Series Triplex H318sOD model to ensure robust
softening capability. As a triplet, the softeners are capable of treating 135 gpm even at low pressures, have a
regeneration time of 120 minutes, and are each 18 inches wide by 65 inches tall (Kinetico® 2013). By using the triplet
system, like the type shown in Figure 9, softening can continue even if one is down for maintenance and one is
undergoing regeneration. To increase efficiency, a hardness analyzer can be added in order to instantly indicate
hardness breakthrough and activate regeneration of the softener.
4.4.5 BRINE STORAGE TANKS
The ClorTec® on-site hypochlorite generation system comes with a brine tank and brine proportioning pump (Severn
Trent De Nora 2013). The brine solution entering the electrolytic cell will be three percent (30 g/L) salt concentration
(Casson and Bess 2006). Each brine tank will be constructed of high-density polyethylene (HDPE) material. The
design includes two salt brine feed tanks; the use of multiple brine tanks will ensure that if one tank has a leakage,
the system will continue to be functional. Each brine tank is designed to hold 16,515 lbs of salt - the amount of salt
required for one day of operation at a maximum 220 MGD flow rate. Fifteen days of salt storage are needed for
continuous operation, the remainder of salt would be located in the salt storage tanks described previously in this
report. The volume of each salt brine tank is estimated to be 2,329 gallon, with a diameter of 5 feet, and a height of
about 16 feet. Assuming a minimum spacing of 3 feet between tanks, the total area will amount to 209 ft2
.

28
4.4.6 ELECTROLYTIC CELLS
To meet the flow rate and dosage needs of the Ralston
Plant, Aquatech Solutions selected four ClorTec® OSG
systems: two dual systems, running 1,200 lb/day cells in
parallel like the system pictured in Figure , and two
singular 1,000 lb/day systems. The CT-1200 system is 102
inches long and the CT-1000 system is 90 inches long; both
are 24 inches wide, as shown in Figure . The plant will
operate off of six independent systems in total. Assuming
ten feet spacing between systems, it was determined that
the total footprint of the selected ClorTec® systems would
amount to 272 ft2
. Calculations detailing the selection of
the size and configuration of the ClorTec® high output CT
series OSG systems are outlined in Appendix F.
Figure 10: ClorTec® CT-1200 Series Electrolytic Cell (Matthews
2010)
Figure 11: Sizing of Electrolytic Cell Systems (Severn Trent De Nora 2013)

29
The clear body of each cell allows for easy visual inspection of the electrolytic process. Each electrolytic cell outputs
a dilute solution of 0.8 percent sodium hypochlorite through an oxidation reaction. A voltage is applied to the cell,
which generates a current that runs through the device and initiates reactions at the anode and cathode plates. All
oxidation reactions occur at the anode plate, and hydrogen gas is produced at the surface of the cathode plate (Boal
2009). Each electrolytic cell consists of vents that transport the hydrogen gas to a dilution blower. All oxidants
produced in the electrolytic cell exit the equipment at a pH of 9. Anode and cathode plate efficiencies can be
optimized by maintaining the water at a temperature between 40°F and 80°F, feeding high quality low-bromine salt
to the system, and monitoring the hardness of the incoming water (Casson and Bess 2006). Hardness must be kept
below 50 mg/L to minimize the likelihood of calcium and magnesium particles being deposited on the surface of
each plate. Anode and cathode plates will need to be washed with a hydrochloric or sulfamic acid wash every 1000
hours. The hydrochloric or sulfamic acid used should be low strength - approximately five to ten percent
concentration (Casson and Bess 2006). Each ClorTec® system includes an acid cleaning cart (Matthews 2010). The
cart will hold 30 gallons of acid and operates at a flow rate of upwards 40 gpm. It should be noted that each system
additionally allows for easy dilution and disposal of acid. Even with proper maintenance, the cells will need to be
replaced in 7-10 years, and the efficiency of the cells will decrease over the lifetime of the system.
4.4.7 CONTROL PANEL
ClorTec® CT-series OSG systems have an intuitively
designed operator interface. High output systems, such
as the size suggested for Denver Water, come with a
standard liquid crystal display (LCD) touchscreen,
shown in Figure. These screens can be optionally
upgraded to include a color LCD touchscreen industrial
computer with data storage and communication
capability (Severn Trent De Nora 2013). There will be
four control panels in total: each of the CT-2400 OSG
Figure 12: ClorTec CT-Series Touchscreen Display Panel (Matthews
2010)

30
systems has one touchscreen for the dual system and each of the CT-1000 systems has its own. The control panels
can be used to make precise adjustments in the operation of the electrolytic cells. For example, operators can use
the control panel to adjust voltage entering the cell in order to maximize cell performance.
4.4.8 HYDROGEN GAS DILUTION
The ClorTec® CT-series immediately
dilutes hydrogen gas out of the
hypochlorite storage tanks through use
of a blower depicted in Figure .
Although only small amounts of
hydrogen gas are produced, ClorTec®
prioritizes safety in hydrogen gas
management. The lower flammable
limit of hydrogen gas is 4 percent,
ClorTec® systems maintain hydrogen
gas concentrations below 25 percent
this limit, or less than 1 percent by
volume (Matthews 2010). The system has seven tiers of interlocks to serve as redundant protective devices: rupture
disk sensing, plant H2 sensing, inlet pressure switch and pressure reducing valve flow switch check, blower current
sensing, differential pressure sensing, and air flow sensing (Matthews 2010). Alarms will sound in the event of a
component failure. It is recommended that the vent stack is within 6 feet of the generator with a duct no longer
than 50 feet (Matthews 2010).
Figure 13: Hydrogen Gas Blower (Matthews 2010)

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4.4.9 SODIUM HYPOCHLORITE STORAGE TANKS
In determining the sodium hypochlorite storage capacity, several factors were considered. ClorTec®’s CT series
advocates for the design of hypochlorite tanks with two days’ worth of storage (Severn Trent De Nora 2013).
However, the AWWA recommends that hypochlorite solutions be stored as soon as it is created and only for one to
two days on the basis of perchlorate and chlorate formation (Stanford et al. 2011: 11). Recognizing that the Ralston
Plant will typically operate at less than a quarter of its capacity, AquaTech Solutions erred on the side of caution in
regards to DBP formation. Specifically, the hypochlorite tanks were designed for a storage capacity of 1.6 days when
operating at 180 MGD using the average chlorine dose of 3 mg/L. This storage capacity is sufficient to support the
proposed 24-hour bulk hypochlorite delivery time, which is further discussed later in this report.
The number of tanks used to hold this volume was modeled, in part, after the 180 MGD Crescent Hill Water
Treatment Plant in Louisville, Kentucky since it also uses six ClorTec® CT units; these on-site generators feed to four
hypochlorite storage tanks (Ghosh et al. 2012). Four tanks also allow for continued chemical supply during routine
acid washing and servicing of tanks as required by Section 5.1 of the CDPHE’s Design Criteria for Potable Water
Systems. Section 5.1 also outlines the requirement for a secondary containment wall in addition to the liquid level
monitors, tank covers and ventilation systems that come with the ClorTec® tanks. Therefore, the hypochlorite tanks
should be located within epoxy-coated containment walls that will have sufficient storage for complete failure of
two of the four tanks in the event of heavy equipment running into the side of two tanks. This containment area
will be sunken 4 feet below ground level and will also enclose the dilution panel equipment. Each hypochlorite tank
will hold 33,750 gallons when filled to the typical 85% of capacity volume for a total of 135,000 gallons of sodium
hypochlorite storage. The tank dimensions will be 18 feet wide by 21 feet tall. Calculations describing tank sizing
can be found in Appendix G.

32
4.4.10 PIPE NETWORK
The considerations used to establish the hypochlorite piping specifications included material, sizing, redundancy and
circulation, piping arrangements and state regulations. Several plastic-based piping materials were considered since
metallic ions can catalyze the decomposition of hypochlorite (Stanford et al. 2011). The main three plastic-based
piping materials used for sodium hypochlorite are glass fiber reinforced plastic (GFRP) with polypropylene (PP) lining,
HDPE, and PP pipes (Solvay 2014). GFRP with PP lining was chosen as the pipe material since it is cost competitive
with HDPE when installation is accounted for and it typically fails in a ‘weeping leak’ that can be repaired as opposed
to the catastrophic failure that is more common with HDPE (FRP vs HDPE 2015). Moreover, Section 4.4 of the
CDPHE’s Design Criteria for Potable Water Systems states that PVC, interior lining or otherwise, should never be
used for chlorination piping. Although PP piping is very cheap, it was discounted on the basis of its low fracture
toughness and since the benefit of its high breaking strain can be used within the lining of GFRP. For more
clarification, see Appendix H.
The pipe sizing was based on a typical in-pipe water velocity of 5 ft/s which, at the maximum hypochlorite generation
rate of 82,566 gal/day, which results in a minimum interior pipe diameter of 2.2 inches (Irrigation in the Pacific
Northwest 2015). Keeping in accordance with Section 5.1 of the CDPHE’s Design Criteria for Potable Water Systems,
this pipe diameter will be rounded up to 3 inches to accommodate for scale formation and minor variances in the
true pipe diameter. While most of the hypochlorite pipes will run within the facilities, Section 5.1 also mandates
that buried pipes running between buildings must be encased within a conduit to mitigate soil and groundwater
contamination. They must also be protected from freezing by burying the pipes below the frost line. AquaTech
Solutions proposes running two independent circulation lines from the sodium hypochlorite storage tanks to each
injection point and back again to ensure that plant operations can continue in the event of a major hypochlorite line
failure. This necessary redundancy means that the buried conduit will need to hold four 3” FRP with PP or PVC lined
pipes. The pipe sizing was based on a typical in-pipe water velocity of 5 ft/s (Irrigation in the Pacific Northwest 2015).
Using this water velocity at the maximum hypochlorite generation rate of 82,566 gal/day, a minimum interior pipe
diameter of 2.2 inches is needed.

33
The finished sodium hypochlorite needs to be distributed to four injection points throughout the plant: before rapid
mix, before and after filtration, and before distribution. This pipe network will consist of two parallel pipes, for
redundancy, travelling to each injection location from the OSG building. Once both pipes reaches the farthest point
in the network, they will circle back to the disinfection building. The ends result will be four pipes lined up next to
each other at all points along the line. Due to the location of the injection points, Aquatech Solutions recommends
constructing two of these networks. One is designed to travel from the disinfection building, through the filtration
building, to the raw feed, and the follows the same path back. The other line would reach from the OSG building to
the edge of the storage reservoirs at the entrance to the distribution system and then the reverse. Both of these
lines would need to be installed underground as they travel from building to building. Using the plant layout
developed, an estimate of total length for both of these lines has been made. For the rapid mix line, 600 feet of
total piping is needed, 72 feet of that being underground, for one pipe. Therefore 2,400 feet of piping will be needed
for the entire rapid mix network. For the distribution network, about 325 feet of entirely underground piping will
be required for an individual line, which gives a total of 1,300 feet. More detailed calculations surrounding these
pipe networks can be found in Appendix H.
4.5 OSG BUILDING DESIGN
Truck deliveries of salt are a routine part of the OSG and back-up bulk systems. The salt and bulk hypochlorite tanks
were placed along the same wall, as shown in Figure. A road will run adjacent to the wall to allow for easy material
unloading. In conversations with the project principal, Aquatech Solution learned the minimum dimension between
tanks of all types is three feet. For safety and ease of maintenance, the design incorporates a minimum of five feet
between all tanks. The salt and brine tanks, water softeners, rectifiers and electrolytic cells are all concentrated in
one area for ease of operation. To make the sodium hypochlorite, water will be pulled from the treatment line
directly after filtration and fed through the water softeners then mixed with salt in the brine tanks before entering
the electrolytic cells. Ten feet of space has been left between the each pair of electrolytic cells to allow access for
maintenance; forklifts will be able to easily maneuver between the pairs of cells. The dilution panel, bulk
hypochlorite storage, and 0.8 percent hypochlorite storage will be held in a distinct part of the building, dug four
feet lower to create a containment wall. The temperature of the hypochlorite room should be maintained relatively

34
cool at 60°F (Powell 2015). From the outside, the OSG building will appear to be a two story building. However, due
to the tall height of the hypochlorite tanks, the hypochlorite room will only have one story with high ceilings. The
generation room will have a main floor and a mezzanine for storage.
Figure 14: Disinfection Building Layout

35
4.6 REDUNDANCY AND BACKUP
Potentially millions of people will depend on the reliability and safety of the drinking water produced at the Ralston
Treatment Plant. To ensure Denver Water can meet the expectation of providing adequately disinfected water to
the people of Denver, multiple layers of redundancy have been considered throughout the system, which are
outlined in Figure .
Figure 15: Layers of Redundancy
The overall OSG system has six independent generators, each capable of continued operation even if others fail.
Aquatech Solutions designed the system to have the capacity to meet two standards (1) treatment requirements for
the maximum flow rate, 5,505 lb/day chlorine equivalence, with one system out of operation and (2) treatment
requirements for the average flow rate, 1,151 lb/day chlorine equivalence, with two systems out of operation.
However, even if the four largest systems lose functionality and only the two CT-1000 generators remain online, the
system would still be able to produce 2,000 lb/day chlorine equivalence, easily maintaining the capacity to disinfect
the average flow rate of water.
Next, there is security in the sheer size of the sodium hypochlorite storage tanks. At the maximum flow rate they
provide 1.6 days of storage, thus the tanks could be filled and reserved for an adequate amount of time for bulk
hypochlorite to be delivered. The plant will infrequently run at the design flow rate, yet the large storage capacity
means that with full storage tanks the plant could operate disinfection from the tanks alone for six days at average
flow. The storage tanks serve a dual role as they can also store hypochlorite diluted from delivered bulk hypochlorite.
A built-in dilution panel allows the plant to resort to the dependability of bulk delivery if needed. The dilution panel
Six
Independent
Generators
Large
Storage
Capacity
Dilution
Panel
Hydroelectric
Power
Connected to
the Electric
Grid
Connection
to Denver
Water
Distribution
Network

36
will dilute 12.5 percent sodium hypochlorite from a 500 gallon tank. A full tank has the capacity to serve just short
of a day at maximum flow and nearly 7 days at average flow (Force Flow 2015).
Denver Water hopes to power the Ralston Plant with hydroelectric power, capitalizing on the proximity and height
differential of the Ralston Reservoir. Generating independent power will give the plant a degree of preservation
from issues that may arise in the general power grid. However, the plant will remain connected to the electric grid,
and will retain the ability to buy electricity. Two options of stable electricity will protect the OSG system from
inoperability due to loss of power.
Finally, the Ralston Plant benefits from the connectivity of the entire Denver Water distribution network. If the
entire disinfection system were to fail, resulting in the closure of the Ralston Plant, other treatment plants within
Denver Water’s network have the capacity to continue providing clean drinking water to the people of Denver.
5.0 COST ASSESSMENT
Economic feasibility is not a main concern of Denver Water, but it was still weighted relatively high in the decision
matrix. The cost assessment conducted by Aquatech Solutions considered capital, operation and maintenance costs
under an ACCEI Class III evaluation. A 20-year lifecycle was also conducted for this system on a 3 percent interest
rate, which was calculated to be approximately $27.0 million for the OSG design specifically. The design resulted in
a production cost of $211/1000 gallons treated.
5.1 CAPITAL COST
The calculations for capital construction cost were based off of data gathered from various sources, which are shown
in Appendix I. This data included construction cost, cost of the OSG equipment and installation costs. In order to
determine the capital cost for the Ralston Plant, known OSG capital cost from other plants were graphed versus their
respective MGD. A trendline was then created that best fits the data. Based on that trendline and Denver Water’s
maximum MGD of 220, the capital cost was determined to be approximately $17.0 million as shown in Table 6.

37
Table 6: Capital Cost Breakdown
Aquatech Solutions contacted various companies for specific OSG
equipment costs; Process Solution Inc provided a quote for the design
flow of the Ralston Plant. This quote can be viewed in Appendix I. The
construction of an on-site hydroelectric power station was determined
to be economically advantageous. However, the on-site hydroelectric power station design is outside the scope of
this project, the capital cost for this system was not accounted for in the total capital cost of this project.
5.2 OPERATION COST
Table 7: Operations Cost Breakdown
Operation cost was calculated based on the cost of the supply, delivery,
electricity, and labor as shown in Table 7. Denver Water has asked Aquatech
Solutions to use an average MGD of 46 and an average chlorine dosage of 3
mg/L. Based on the average flow rate and the average dosage it was determined
that 1.3 million lbs of salt will be needed annually. Aquatech Solutions
determined that, on average, salt costs $0.12/lbs of chlorine. Delivery cost was
based on Univar’s delivery price of $130/tons. Labor cost was determined based
on a full time equivalence, which is a ratio of the total number of paid hours to
the number of working hours. Aquatech Solutions set one FTE as $150,000 which would be two full time employees
working 40 hours per week on the disinfection system. Labor cost was given a FTE ratio of 0.5 due to the fact that
the OSG system operates by itself, operators will have to do routinely checks on the cells, voltage and tanks. The
calculations for OSG building energy use were based off data gathered. The data gathered determined the amount
of energy required for the building for certain amounts of chlorine pounds required. A trendline was created that
best fit the data. Based on our trendline and amount of chlorine required per day the amount of energy required to
power the building was determined to be 147,000 kw-hr/yr. The OSG system will require 840,000 kw-hr/yr, therefore
the total amount of energy required for this design will be 987,000 kw-hr/yr. The Ralston site will have hydroelectric
Element Cost ($)
OSG System 2.5 Million
Total 17 Million
Element Cost ($)
Salt 50,410
Delivery 27,306
Labor 75,000
Energy 9,742
Total 160,000

38
power station that will provide more energy that is required for the OSG system. The total annual operation cost
was calculated to be $162,000 as shown in Appendix I.
5.3 MAINTENANCE COST
Table 8: Maintenance Costs Breakdown
Maintenance cost was based on the cost of labor and the cost
of materials as summarized in Table 8. Labor was given an
FTE ratio of 2.5 since there is more cleaning involved and
more equipment that may need to be repaired. Material cost
was based on data gathered from ClorTec®. The total
maintenance cost was calculated to be approximately $380,000 annually as shown in Appendix I.
6.0 CONCLUSION
The overall all goal of this project, made clear to Aquatech Solutions by the client, is that Denver Water wishes to
provide the best quality water to the public in a way that is both safe to the community and the operators at their
plants. As of now, the weekly shipments of chlorine gas that are brought to each of the Denver Water plants are
susceptible to terrorist attacks that could be disastrous to the surrounding communities. The poisonous gas also
poses a threat to the plant operators if a leak was ever to occur. In order to prevent these events from occurring,
Aquatech Solutions proposed three disinfection alternatives: bulk sodium hypochlorite delivery, on-site generation
of sodium hypochlorite, and on-site generation with delivery to all of Denver Water’s plants. In order to provide
Denver Water with the most valuable information possible, the team conceived the aforementioned design of an
on-site generation system for sodium hypochlorite. OSG, if implemented at the new Ralston Treatment Plant, would
uphold Denver Water’s objective of a safe way to disinfect their water. The technology is safe for both the operators
that would ultimately be handling the materials and the communities directly surrounding the plant.
Aquatech Solutions would again like to thank Denver Water for the opportunity to work on this project. It challenged
the team to think differently and develop solutions that have the possibility of impacting actual people. The real
Element Cost ($)
Labor 375,000
Materials 5,116
Total 380,000

39
world experience has better prepared each team member for professional careers. It has been a pleasure working
with everyone at Denver Water and Aquatech Solutions looks forward to seeing what becomes of this project.

40
7.0 REFERENCES
Boal, Andrew. "On-site Generation of Disinfectants." National Environmental Services Center. Vol 9. Issue 1. 2009:
4. Web.
Casson, L. and Bess, J. "On-site Sodium Hypochlorite Generation." Water Environment Foundation. 2006. Print.
Colorado Primary Drinking Water Regulations (5 CCR 1002-11). Colorado Department of Public Health and
Environment: Water Quality Control Commission. 2015. Print.
"FRP vs HDPE." Industrial Plastic Systems, Inc., 31 Oct. 2005. Web. 30 Apr. 2015.
Ghosh et al. "Evaluating On-Site Generation of Hypochlorite Solutions." Water Research Foundation. 2012: 27
pages. Print.
Hooper, John. “On-Site Generation of Sodium Hypochlorite Basic Operating Principles and Design Considerations.”
Proc. of Water Industry Engineers and Operators’ Conference, Bendigo. Sept. 2005. Print.
"Irrigation in the Pacific Northwest." Pipe Water Velocity and Minimum Pipe Diameter Calculator. Washington
State University, 1 Jan. 2015. 2015. Web.
Kinetico Commercial Water Systems. "Hydrus Series Water Softeners." 2013. Web.
Land Use Plan. Arvada Comprehensive Plan. City of Arvada. 2014. Print.
Matthews, M. "ClorTec Onsite Hypochlorite Generation Systems." Severn Trent Services. Ohio Section AWWA, 7th
Annual Conference. 2010. Presentation.
"Merlin Hypo Dilution Systems." Merlin Chemical Dilution Systems. Force Flow. 2015. Web.
Metro Vision 2035. Denver Regional Council of Governments. Feb. 2011. Print
Michigan American Water Works Association Research & Technical Practices Committee. Chlorine Disinfection: Use
Chlorine Gas, Buy Bulk Hypochlorite, or Generate Hypochlorite On Site?. April. 2014. Print.
Safety of Public Water Systems (Safe Drinking Water Act of 1974). Title XIV of the Public Health Service Act (42
U.S.C. 300f-300j-9). 2002. Print.
Section 550 of Appropriations Act of 2007. Chemical Facility Anti-Terrorism Standards. Department of Homeland
Security. 2007. Print.
Severn Trent De Nora. "ClorTec® On-site Sodium Hypochlorite Generation Systems - High Output CT Series - 450-
3,000+ lb/day." Severn Trent Services. 2013. Print.
Sinpatanasakul, Leeann. Chlorine Gas is a Major Risk across the Country, but Needn’t Be. Center for Effective
Government. 2013. Web.
“Storing Bleach (Sodium Hypochlorite).” Powell, Fabrication and Manufacturing Incorporated. 2015. Web. 28 April
2015.
Solvay Chemical International. "Technical Documentation. Sodium Hypochlorite - Storage." 2014. Print.

41
Stanford, Benjamin et al. "Chlorate, Perchlorate, and Bromate in Onsite-generated Hypochlorite Systems." Journal
- American Water Works Association 103.6 2011: 6, 11. Print.
United States Environmental Protection Agency. Stage 1 Disinfectants and Disinfection Byproducts Rule and
Interim Enhanced Surface Water Treatment Rule. 1998. Print.
United States Environmental Protection Agency. Wastewater Technology Fact Sheet: Ozone Disinfection. 1999b.
Print.
United States Environmental Protection Agency. Wastewater Technology Fact Sheet: Ultraviolet Radiation. 1999a.
Print.
White, Geo. Clifford. The Handbook of Chlorination: Fifth Edition. New Jersey: John Wiley & Sons, Inc. 2010. Print.
Woody, Jonathan. "Disinfection of municipal water systems through on-site hypochlorite generation." Saipan
Environmental Conference. 2009. Presentation.

42
8.0 APPENDIX
APPENDIX A: DECISION MATRICES
ORIGINAL DECISION MATRIX

44
APPENDIX B: MATERIAL BALANCE AROUND OSG SYSTEM
Hali Hafeman and Shaye Palagi
3/6/15
Characteristics of 0.8 percent Sodium Hypochlorite (White 2010):
 Density = 8.44 lb/gal
 0.067 pounds of available chlorine/gallon
Material balance relationships can be related to the amount of free chlorine required, based off of flow rate and
dosage: for every pound of free chlorine needed, three pounds of salt, 2 kWh of electricity, and 15 gallons of water
can produce 15 gallons of 0.8 percent sodium hypochlorite (Woody 2009).
𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
) = 𝑫𝒐𝒔𝒂𝒈𝒆 (
𝒎𝒈
𝑳
) × 𝑫𝒆𝒏𝒔𝒊𝒕𝒚 𝒐𝒇 𝑾𝒂𝒕𝒆𝒓 (
𝒍𝒃𝒔
𝒈𝒂𝒍
) × 𝑭𝒍𝒐𝒘 𝑹𝒂𝒕𝒆 (𝑴𝑮𝑫)
𝐶ℎ𝑙𝑜𝑟𝑖𝑛𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = 3 (
𝑚𝑔
𝐿
) × 8.34 (
𝑙𝑏𝑠
𝑔𝑎𝑙
) × 220 (𝑀𝐺𝐷)
𝐶ℎ𝑙𝑜𝑟𝑖𝑛𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐶ℎ𝑙𝑜𝑟𝑖𝑛𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = 3 (
𝑚𝑔
𝐿
) × 8.34 (
𝑙𝑏𝑠
𝑔𝑎𝑙
) × 46 (𝑀𝐺𝐷)
𝐶ℎ𝑙𝑜𝑟𝑖𝑛𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑯𝒚𝒑𝒐𝒄𝒉𝒍𝒐𝒓𝒊𝒕𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒈𝒂𝒍𝒍𝒐𝒏𝒔
𝒅𝒂𝒚
) = 𝟏𝟓 × 𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
)
𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (
𝑔𝑎𝑙𝑙𝑜𝑛𝑠
𝑑𝑎𝑦
) = 15 × 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 82,575 (
𝑑𝑎𝑦
)
𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (
𝑑𝑎𝑦
) = 15 × 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 𝐷𝑒𝑚𝑎𝑛𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 17,265 (
𝑑𝑎𝑦
)
𝑵𝒂𝑪𝒍 𝑹𝒆𝒒𝒖𝒊𝒓𝒆𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
) = 𝟑 × 𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
)

45
𝑁𝑎𝐶𝑙 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = 3 × 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑁𝑎𝐶𝑙 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 16,515 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑁𝑎𝐶𝑙 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = 3 × 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑁𝑎𝐶𝑙 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 3,453 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑾𝒂𝒕𝒆𝒓 𝑹𝒆𝒒𝒖𝒊𝒓𝒆𝒅 (
𝒅𝒂𝒚
) = 𝟏𝟓 × 𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
)
𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (
𝑑𝑎𝑦
) = 15 × 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 82,575 (
𝑑𝑎𝑦
) = 58 (
𝑚𝑖𝑛𝑢𝑡𝑒
)
𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (
𝑑𝑎𝑦
) = 15 × 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑊𝑎𝑡𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 17,265 (
𝑑𝑎𝑦
) = 12 (
𝑚𝑖𝑛𝑢𝑡𝑒
)
𝑷𝒐𝒘𝒆𝒓 𝑹𝒆𝒒𝒖𝒊𝒓𝒆𝒎𝒆𝒏𝒕 (𝒌𝑾𝒉) = 𝟐 × 𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
)
𝑃𝑜𝑤𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (𝑘𝑊ℎ) = 2 × 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑃𝑜𝑤𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 11,010 (𝑘𝑊ℎ)
𝑃𝑜𝑤𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (𝑘𝑊ℎ) = 2 × 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝑃𝑜𝑤𝑒𝑟 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 2,302 (𝑘𝑊ℎ)
𝑺𝒐𝒅𝒊𝒖𝒎 𝑯𝒚𝒑𝒐𝒄𝒉𝒍𝒐𝒓𝒊𝒕𝒆 𝑷𝒓𝒐𝒅𝒖𝒄𝒆𝒅 (𝒈𝒂𝒍𝒍𝒐𝒏𝒔) = 𝑯𝒚𝒑𝒐𝒄𝒉𝒍𝒐𝒓𝒊𝒕𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒅𝒂𝒚
)
𝑆𝑜𝑑𝑖𝑢𝑚 𝐻𝑦𝑝𝑜𝑐ℎ𝑙𝑜𝑟𝑖𝑡𝑒 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 82,575 (
𝑑𝑎𝑦
)
𝑆𝑜𝑑𝑖𝑢𝑚 𝐻𝑦𝑝𝑜𝑐ℎ𝑜𝑟𝑖𝑡𝑒 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 17,265 (
𝑑𝑎𝑦
)
𝑯𝒚𝒅𝒓𝒐𝒈𝒆𝒏 𝑮𝒂𝒔 𝑷𝒓𝒐𝒅𝒖𝒄𝒆𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
) = (
𝟏
𝟑𝟓
) × 𝑪𝒉𝒍𝒐𝒓𝒊𝒏𝒆 𝑫𝒆𝒎𝒂𝒏𝒅 (
𝒍𝒃𝒔
𝒅𝒂𝒚
)

46
𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐺𝑎𝑠 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = (
1
35
) × 5,505 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐺𝑎𝑠 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝑀𝑎𝑥 𝐹𝑙𝑜𝑤 = 157 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐺𝑎𝑠 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 (
𝑙𝑏𝑠
𝑑𝑎𝑦
) = (
1
35
) × 1,151 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)
𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝐺𝑎𝑠 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑑 @ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐹𝑙𝑜𝑤 = 33 (
𝑙𝑏𝑠
𝑑𝑎𝑦
)

47
APPENDIX C: RALSTON SITE LAYOUT

49
APPENDIX D: CHOOSING THE SIZE AND NUMBER OF BRINE AND SALT STORAGE TANKS
Hali Hafeman
4/19/15
Aquatech Solutions used case studies from Ghosh et al. (2012), and data calculated in the alternatives assessment
to calculate the number of brine and salt storage tanks that will be needed for the on-site generation system. It was
determined through material balance calculations that the Ralston Plant will consume a total of 16,513 lb/day of
salt. Detailed calculations and explanations of equations used can be found in appendix A. Although ClorTec®
recommends seven days as the minimum amount of salt storage time, Aquatech Solutions designed the system to
hold 15 days of salt storage. Aquatech Solutions chose 15 days because it was suggested by other sources to be an
adequate amount of storage time for salt, and Aquatech Solutions wanted the tanks to have the ability to hold the
maximum salt requirement (Casson and Bess 2006). In 15 days the Ralston Plant uses 247,698 lb of salt. The storage
tanks were consequently designed to hold a total volume of 29,700 gallons. Aquatech Solutions used case studies
from Ghosh et al. (2012) to determine a sufficient number of brine and salt storage tanks for the Ralston Plant. A
case study from Anchorage Water and Wastewater Utility in Alaska revealed that the 35 MGD Alaskan plant uses
three 3000 gallon salt storage tanks and two 100 gallon brine tanks. Aquatech Solutions modeled the salt and brine
storage design after this case study. Brine tanks were constructed to hold one day of salt, and the salt storage tanks
were designed to hold the remainder of salt. It was additionally assumed that each tank would only be filled up 85
percent of the way full. Volumes for the salt storage and brine tanks (8580 and 1980 gallons respectively), were
therefore multiplied by a factor of (1/.85). Dimensions of tanks were estimated using the calculated volume for each
tank type, as well as the equation for the volume of a vertical cylinder. Optimal diameters and heights were chosen
for each tank by taking into consideration that a minimum ceiling height would be roughly 25 feet tall. The total
footprint was calculated by assuming a minimum 3 feet spacing between tanks.

50
Design Specifications Salt Storage Tanks Brine Tanks
Number 3 2
Volume (gal) 10094 2329
Diameter (ft) 9 5
Height (ft) 21 16
Total Footprint (ft2
) 585 209
APPENDIX E: HEAT EXCHANGER CALCULATIONS
Cassidy Kuhn & Fernando Monroy
4/28/2015
The purpose of these calculations is to assess the economic feasibility of using a heat exchanger with the influent
and effluent to the electrolytic cells. This cost comparison was based on a fixed head heat exchanger and the
following assumptions were made.
Assumptions
𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝐵𝑟𝑖𝑛𝑒 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑅𝑎𝑤 𝑊𝑎𝑡𝑒𝑟) = 𝑇𝑐1
= 50℉
𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑃𝑜𝑠𝑡 𝑂𝑆𝐺 = 𝑇ℎ1
= 72.5℉
𝛥𝑇𝑐2
= 6℉
𝑇𝑐2
= 58.25℉
𝑇ℎ2
= 64.25℉
𝐹𝑃(𝑂𝑝𝑒𝑟𝑎𝑡𝑖𝑛𝑔 𝑢𝑛𝑑𝑒𝑟 100 𝑝𝑠𝑖) = 𝐹 𝑀 = 𝐹𝐿 = 𝐹𝑇 = 1
𝑐 𝑃 = 𝑐 𝐵
The temperature of the brine solution was approximated and based on typical river temperatures in Colorado while
the temperature of the hypochlorite post-OSG was assumed to be equal to the temperature that the brine solution
is fed in at. This brine feed temperature was averaged over the range that was provided by ClorTec (Severn Trent
De Nora 2013). In determining the log mean temperature difference, the hot and cool effluent streams were

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