SESSION 9

Utility Case Studies of On-Site Generated Sodium Hypochlorite

Amlan Ghosh

Jacobs Dr. Amlan Ghosh is a Water Process Engineer with Jacobs Engineering Group in Dallas, TX. He is a P.E. with 12 years of experience in all aspects of drinking water quality and treatment projects including process selection and optimization, process design, and bench- and pilot-scale studies. Specifically, Dr. Ghosh’s expertise lies in the areas of enhanced coagulation, granular activated carbon filtration, and use of advanced oxidants for disinfection. Dr. Ghosh serves on AWWA’s Inorganic Contaminants and Organic Contaminants Research Committees. Contact Information: Email: Amlan.ghosh@jacobs.com

Utility Case Studies of On-Site Generated Hypochlorite

Amlan Ghosh, Ph.D., P.E.

Water Treatment Committee SeminarFebruary 21, 2013

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Presentation Outline

• Regulatory Background• Selecting Disinfectants in a Security

Conscious Environment• OSG Case Studies:

• Design and Implementation Challenges• Operational and Maintenances Issues

• Lessons Learned

Regulations Related to Chemical Security

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Since 9/11 –• Bioterrorism Act• Patriot Act• Homeland Security Act

• SAFETY Act• Intelligence Reform Act• Chemical Facility Anti-Terrorism Act (CFATS)

Water utilities currently exempt from CFATS requirements

Concerns Remain with Chlorine Gas

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Selecting Disinfectants in a Security-Conscious Environment

• AWWA believes that choice of chemicals/ processes for disinfection at water utilities should remain a local decision

• AWWA published report “ Selecting Disinfectants in a Security-Conscious Environment” (2009)– Resource for utilities in making

appropriate disinfection choices– http://www.awwa.org/Resources/S

cienceTopics.cfm?ItemNumber=48752&navItemNumber=48910

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WITAF 519 Disinfection Selection Case Studies

Document water utilities’ processes and outcomes for selecting disinfection processes

Illustrate unique, site-specific considerations that underlie achieving the goals and meeting disinfection needs of each water system

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Summary of Decisions

Historical Disinfection Practice: Chlorine Gas

Convert to OSG HypochloriteContinue Using

Chlorine Gas

Convert to Bulk Delivered

Hypochlorite

Evaluate Disinfection

Options

Santa Clara, BoulderGreater Cincinnati, Phoenix, Denver Austin

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Summary of Decision Factors

Chlorine Gas◦ Fewer water

quality concerns◦ Lowest life cycle

costs◦ Higher system

reliability◦ Ease of

operations and maintenance

◦ Utility personnel experience and familiarity

Implementing double containment minimize chemical exposure risk

• Bulk Sodium Hypochlorite– Risk reduction

compared to chlorine gas

– Better system reliability compared to OSG

– Less operational complexity compared to OSG

– Similar life cycle costs compared to OSG systems

• On-site Generated Hypochlorite– Risk reduction

compared to chlorine gas

– Improved public perception

– Environmental sensitivity

– Chemical cost stability of NSF solar salt

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Conclusions from WITAF 519

Alternatives evaluation needs to be performed on a case-by-case basis◦ Unique, site-specific conditions may result in different outcomes

Chemical security risks need to be balanced with public health protection, water quality, and system performance

Choice of chemicals and disinfection processes should be a local decision, made by the utility

Evaluate On-Site Generation of Hypochlorite Solutions

Water Research Foundation Project # 4410

(Funded by Dallas and Arlington Water Utilities)

February 23, 2012In Partnership With

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WaterRF # 4410 Project Objectives

Conduct case studies on water utilities that have implemented OSG hypochlorite

Summarize design, operational, and economic information

Collect water quality contaminant data◦ Chlorite◦ Chlorate◦ Perchlorate◦ Bromate

Ten Case Study Utilities

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12

3

4

567

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1 – Louisville Water Company, KY2 – City of Tempe, AZ3 – City of Boulder, CO4 – Anchorage Water and Wastewater Utility, AK5 – Missouri American Water – St. Louis County, MO6 – Southern Nevada Water System7 – Des Moines Water Works, IA8 – Park Water Company, CA9 – Apple Valley Ranchos Water Company, CA10 – Albuquerque Bernalillo County Water Utility Authority, NM

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Overview of OSG Hypochlorite Systems at the Case Study Utilities

Utility Name OSG System ManufacturerNumber of

OSG Installations

OSG System Installed Capacity (lbs/day)

Louisville, KY Severn Trent -ClorTec 1 9,000

Tempe, AZ Severn Trent -ClorTec 2 4,500, 6,000

Boulder, CO MIOX Corporation 1 400Anchorage, AK Severn Trent -ClorTec 2 300, 360

Missouri American Process Solutions - MicrOclor 2 2,400, 3,700

Southern Nevada Siemens - OSEC 1 18,000

Des Moines, IA ETC - Klorigen 1 1,500

Park Water, CA Process Solutions - MicrOclor 7 20 - 60

Apple Valley, CA MIOX Corporation 14 10 – 50

Albuquerque, NM Severn Trent - ClorTec and Process Solutions - MicrOclor

32 40 – 6,000

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Information Collected from Case Study UtilitiesWater System Information

• Treatment facility capacity, treatment process details• Historical and current disinfection methods summary

OSG System Selection

• Decision drivers for selection of OSG hypochlorite• Economic factors (capital, O&M, life cycle cost)• Non-economic factors (operation, safety, water quality, etc.)

Implementation • Modification of existing plant processes• Location and space for new equipment• Need for temporary facilities for conversion

Operation and Maintenance

• Operation of electrolytic cells, softening system, heaters/chillers, etc.

• Maintenance/replacement of electrolytic cells/membranes• Staff training and (additional) labor requirements• Electrical consumption (total power requirements)• Salt consumption

Raw Materials • Salt quality, availability and reliability• Truck traffic for salt deliveries

OSG Product • Contaminants’ concentration change with storage• Oversizing OSG systems for production during off-peak

power rates

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Decision Drivers for OSG Hypochlorite Implementation

Safety concerns with chlorine gas

Cost of chlorine system upgrades or bulk hypochlorite

Solution strength stability of bulk hypochlorite

Water quality concerns with bulk hypochlorite

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OSG Hypochlorite System Costs Capital costs:

◦ Very specific to each facility profiled◦ Varied largely based on infrastructure improvements necessary at

facilities such as, new buildings, storage areas, pumping requirements, electrical requirements, ancillary equipment

◦ Dependent on chlorine use, design criteria, redundancy plans

O&M Costs:◦ Also very specific to utility◦ Dependent on availability and cost of solar/ food grade salt, and local

power costs◦ Some utilities decided to contract maintenance of system to

equipment provider or third party

Capital and O&M costs from one utility should not be extrapolated elsewhere

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Design and Operational Considerations

Safety and Ancillary Equipment◦ Rupture disks to prevent

over-pressurization◦ Heaters or chillers to

optimize efficiency and prevent system shutdown

Generation technologies are rapidly improving, so, future installations will overcome the challenges in past designs

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Materials of Construction◦ All parts in direct contact

with hypochlorite need to be of Teflon, or titanium, or other appropriate material

◦ Brine tanks, product storage tanks, and associated piping need to be appropriately designed to prevent leaks

◦ Protective coating needs to be applied to concrete floors and walls

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Salt Deliveries and Storage

Over-pressurized salt unloading from delivery trucks can cause salt blowout

Salt storage either outside or in a room isolated from generation equipment and rectifiers

When poor quality salt was used, scale built-up within electrolytic cells, generation efficiency reduced, and cell cleaning frequency increased

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Labor and Energy Requirements

Several utilities contracted maintenance to equipment supplier or a third party

Substantial energy required for system components

One utility noted that their system was not designed to operate continuously (24 X 7)

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High Strength (12%) OSG Considerations

High strength generation equipment is more complex

Consists of several sub-processes including low and high pH solutions

Materials of construction of equipment parts critical

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High Strength (12%) OSG Considerations

Substantial operator involvement and training necessary during start-up

Significant amount of laboratory analyses is necessary for maintaining and calibrating the generation equipment

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AWWA / WITAF 227 Study

PI: Ben Stanford, Hazen and Sawyer

Objectives:◦ Develop a wider data set from

different OSG systems and water qualities

◦ Examine chlorate, perchlorate, and bromate concentration between systems

◦ Examine temporal trends in concentration with a limited subset of systems

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Chlorate Concentrations in Product

Chlorate can be of concern depending on where future regulatory level is set

USEPA Health Reference Level is 210 µg/L

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Perchlorate Concentrations in Product

Perchlorate and bromate concentrations were quite low, and would not exceed current (bromate) and potential future (perchlorate) regulatory levels

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Conclusions Disinfection selection should be performed on a case-by-

case basis, and will result in unique, site-specific outcomes If OSG hypochlorite is selected, further evaluate

technology (low vs. high strength) and equipment supplier Majority of case study utilities with OSG hypochlorite are

satisfied with system Operation of OSG hypochlorite systems are relatively

complex, and significant operator training will be necessary Chlorate levels can be of concern, depending on where

future regulatory levels are set.

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Helpful Resources “Selecting Disinfectants in a Security-Conscious

Environment” (AWWA, 2009)◦ http://www.awwa.org/Resources/ScienceTopics.cfm?Item

Number=48752&navItemNumber=48910

Seidel et. al., “Selecting Disinfectants in a Security Conscious Environment: Six Utility Case Studies”, Journal AWWA, March 2011

WaterRF 4410: “On-Site Generation of Hypochlorite Solutions”

AWWA M65 Manual “On-Site Generation of Hypochlorite” (manuscript in preparation)

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Acknowledgements

Water Research Foundation Dallas and Arlington Water Utilities Participating Case Study Utilities Jacobs – Chad Seidel, Ph.D, P.E., David Haas, P.E. Hazen and Sawyer – Ben Stanford, Ph.D, P.E.

Thank You!

February 23, 2012

Amlan Ghosh, Ph.D, P.E.

amlan.ghosh@jacobs.com214-920-8077