session 9 utility case studies of on-site generated sodium ... · 2/21/2013 · session 9 utility...
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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: [email protected]
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
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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.