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Corona Discharge and
Vacuum Ultraviolet Ozone
Systems
Copyright. Prozone Pool Products. phone: 256-539-4570 fax: 256-539-4225
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Ozone and its Effects
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Ozonation
WHAT IS OZONE?
•Ozone is a form of energetic oxygen that has three atoms of
oxygen rather than the normal two.
Oxygen = 02
Ozone = 03
•Ozone is the most powerful disinfectant and oxidant which is
readily available
•Does not produce harmful by-products
•Generated on-site
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Ozonation
EFFECTS OF OZONATION
•Ozone performs two major functions in water that are normally
done by chlorine
Oxidation
Disinfection
Oxidation + Disinfection = Water Treatment

•Oxidation
– Oxidation is a process by which contaminants
(bather
load) are removed from water
•Disinfection
– Disinfection is the destruction of bacteria
and viruses
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Ozonation
Ozone and Oxidation
•In a typical pool, 70 to 90 percent of chlorine is used up in
oxidation of bather loading. This process creates byproducts
(combined chlorines) which can cause the following problems:
Chlorine
Odor
Eye Irritation
Skin Irritation
Hair Damage or Discoloration
Cloudy Water
Excessive Chlorine Consumption
•Ozone
oxidizes the bather loading reducing chlorine
consumption
•Ozone
oxidizes combined chlorines, creating free chlorine
and eliminating the problems listed above
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Ozone and Oxidation
Ozone Oxidation
Disinfection
Reacts with
Bather Loading
and Frees
Chlorine
Precipitation
Filterable
Compounds
•Reduced
Chlorine Use
•Clarified
Water
•Reduced
Combined Chlorines
•Chlorine
Effectiveness
Increases
•No
chlorine odor or Irritation
•Removes
Metals
Kills Bacteria,
Viruses
Precipitation
Filterable
Compounds
•Improved
Sanitation
Characteristics of Ozone
Chlorine
Oxidation Strength
Ozone
High
Highest
Disinfection Strength
High
High
Kill Time
Fast
Fast
Stability
Varies
Generate
On-Site
Organism Resistance
Yes
No
Major Byproducts
Chloramines,
No
Combined Chlorines
Staining Potential
No
Solubility
No
High
High
Stand Alone
Yes
No
pH Dependent
Yes
No
Chlorine Shock Equivalent
Yes
Yes
Algicidal Properties
High
Medium
Generating Ozone with Corona
Discharge
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Corona Discharge
Corona: High voltage, low current electrical discharge
across a discharge gap filled with gas (normally air or
oxygen). The gas becomes partially ionized, resulting
in a bluish glow.
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Corona Discharge
Translation: Air or oxygen is exposed to a high voltage field
which converts a portion (typically 1 to 5 percent)
of the air or oxygen to ozone.
Oxygen (O2)
Electrons
Oxygen (O2)
Ionized Oxygen (O- +O-)
Ozone (O3)
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Corona Discharge
In addition to ionizing oxygen to create ozone, the corona
process also breaks nitrogen bonds (in systems that are air fed
or do not use pure oxygen) creating nitrogen oxides.
Electrons
Oxygen (O2)
Ionized Nitrogen (N- +N-)
Nitrogen Oxides (NOx)
Electrons
Oxygen (O2)
Ionized Oxygen (O- +O-)
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Corona Discharge
Nitrogen Oxide Formation and Humidity: Air fed into corona
devices
should be extremely dry (dew point of -78 deg F, -61 deg C). In
systems that run on air only, nitrogen oxide production increases
with
increasing dew point (moisture content). Nitrogen oxides convert to
nitric acid in the presence of moisture. Nitric acid is extremely
corrosive.
Decreasing Ozone
Production
Formation of
Nitrogen Compounds
Increasing
14 deg F
Increasing Moisture Content
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Corona Discharge
Effects of Heat: Heat is detrimental to ozone production as it
inhibits formation of ozone and causes it to degrade faster.
Increased temperature also contributes to the problem of nitrogen
oxide formation.
Representative Sample of the Effects of Heat on
Ozone Production
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Ozone Generation with Corona Discharge
Corona discharge devices can be divided into two categories:
Type I Generators
•Use equipment to pretreat the feed air in order to remove nitrogen
(10 percent or less) and moisture (Relative Humidity of -78 deg F or better)
•Water or air is used to cool the ozone cell in order to keep it below 100 deg F
•Generate high concentrations of ozone and are generally found only in
commercial applications due to cost
Type II Generators
•Stripped down corona discharge devices
•No or limited provisions in place to control the environmental
factors which affect corona discharge ozone production
•Typically have erratic output, concentrations not comparable
with commercial grade units
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Corona Discharge Summary
•Humidity and heat are detrimental to ozone production and
require removal to maximize ozone generator performance
and limit the production of undesirable byproducts
•Clean air or oxygen free of contaminants and oil is required
•Generally, these issues are can only be controlled adequately
on on commercial grade equipment
•Production of nitric acid by small units without air preparation
Can cause damage and large pH variations in spas
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Corona Discharge Generator Types
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Corona Discharge Cell Designs
There are a variety of designs available for generating ozone
with corona discharge. The most common in the pool and psa
industry are:
•Surface Discharge (Only found on small spa type systems)
•Flat Plate Design (Commercial Systems Only)
-Single Dielectric
-Dual Dielectric (maximizes life and efficiency)
•Tubular Design (Used on spa and commercial Systems)
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Corona Discharge Cell Designs
Surface Discharge
•Generate a corona discharge above a ceramic plate
•Systems use ambient air and have rely on air flow for cooling
•System output declines as it heats up
•Use of unfiltered, humid air degrades performance
•Used only in small applications
•Low Reliability, performance decays over time
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Corona Discharge Cell Designs
Flat Plate Design
•Systems generate ozone when air or oxygen is passed through
the gap between enclosed flat plate electrode/dielectric (ceramic)
•Systems can utilize single ceramic or dual ceramic plates (use of
dual ceramics limits electrode erosion)
•Systems are air cooled (water cooling is an option)
•Oxygen is required for maximum performance
• Used in commercial systems
•Multiple cells for larger systems limit potential for
catastrophic failure
•High Reliability, Easy to Service/Replace
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Corona Discharge Cell Designs
Tubular Design
•Systems generate ozone when air or oxygen is passed through
concentric tubes, one of which is coated with a ceramic-interior
designs vary
•Oxygen and water cooling are required for maximum
performance
• Used in commercial systems (water cooled) and small systems
(air cooled)
•Capable of providing high quantities and concentrations of ozone
•Maintenance can be difficult
•Water cooling adds complexity in commercial systems
•Replacements can be costly
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Corona Discharge Systems
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
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Corona Discharge System Elements
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Corona Discharge System Elements
Oxygen Concentrator
Ozone Module
Boost Pump
Contactor System
Unit is Approximately 6 feet High
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Corona Discharge System Elements
Degas Valve
Contacting Loop
Contact/Degas Tank
Corona Unit
Venturi
Boost Pump
Oxygen Concentrator
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Feed Gas Preparation
•Feed Gas preparation normally consists of a:
-Compressor
-Oxygen Concentrator or Regenerative Drier
-Aftercooler for Compressed Air (Larger Systems)
-Air Filters and Oil Removal
-Safety Interlocks
•Smaller Oxygen Concentrators can be purchased with built in
compressors
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Feed Gas Preparation
Oxygen Concentrators
•The two main types used on pool installations are:
-Pressure Swing Adsorption (PSA)
-Rotary
•Oxygen Concentrators dry the air and can be used for this function
up to units which produce approximately 5 lbs/ozone per day
•Systems larger than 5 lbs/ozone per day require an Air Dryer prior
to the Oxygen Concentrator to ensure adequate performance and
system life
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Feed Gas Preparation-Oxygen Concentrators
•Rotary-Advantages
-Provide constant flow of oxygen
-Compact design
•Rotary-Disadvantages
-Operate at low pressure
-Mechanical parts are prone to failure
-Hard to replace/repair components
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Feed Gas Preparation-Oxygen Concentrators
•Pressure Swing Adsorption-Advantages
-Operate at higher pressures
-More robust system
-Easier to Service
-Larger systems available
•Pressure Swing Adsorption-Disadvantages
-Typically more complex
-Require surge tanks on larger units to provide steady output
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Contacting System
•There are a variety of ways to introduce ozone into water
•The most common ways in the United States use all or some of
the following elements:
-Venturi Injector
-Contacting Loops
-Contact Tanks
-Degassing Columns or Gas Separators
•In the United States, systems are normally installed in a bypass
configuration after the filter
•System Performance requirements have a large impact on
components selected
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Contacting Systems
•Contacting systems are designed to either mix the ozone
rapidly and promote oxidation reactions or to hit a specific
disinfection value (CT Value) which generates a residual of
ozone in the water
•Systems Designed for Oxidation
-Requires least ozone
-System typically includes Venturi, Contact Loop and a
Degasser
Also applicable for Vacuum Ultraviolet Systems
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Contacting Systems
•Systems Designed for Disinfection
-Designed to kill toughest disease causing organisms
(including cryptosporidium)
-May be required for some installations
-Requires highest amount of ozone
-Typically results in excess capacity
-Usually generates more off-gassing
-Contact system requires Venturi, optional Contact
Loop, Contact Tank and Degasser
Also applicable for Vacuum Ultraviolet Systems
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Corona Discharge System Elements
Type I Devices (Commercial Grade)
Ozone Destruction
•The Ozone Destruct portion of the system removes excess ozone
and or air
•Components include:
-Vent Valve
-Catalyst to Destroy Excess Ozone
-Water Traps
•System usually incorporates portions of the contact system to collect
excess ozone/air
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Vacuum Ultraviolet Ozone Generation
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Vacuum Ultraviolet Systems
Translation: Air or oxygen is exposed to ultraviolet light at
an ozone producing frequency (185 nm). Concentrations up to
1 percent can be produced. No nitrogen byproducts are
produced.
Oxygen (O2)
UV Light
Oxygen (O2)
Ionized Oxygen (O- +O-)
Ozone (O3)
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Characteristics of Vacuum Ultraviolet Systems
Low voltage operation
Little or no operator adjustment required
System can be installed, maintained and serviced by minimally trained service staff
Operation in any environmental condition
Easy installation, modular design
Rugged when properly designed
Readily configured for multiple injection points
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Ozone Generators
Vacuum Ultraviolet System Components
•Ozone Producing Lamp(s)
-Check lamp life
-Check output drop over life of system
-Check warranty
•Ballast
Electronic-Provide best performance and lowest energy consumption
Magnetic
•Housing
•Compressor or Air Pump (Used for Specific Installations and
Circumstances)
•Installation Kit
Proprietary and Confidential
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Vacuum Ultraviolet System Types
Proprietary and Confidential
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Equipment Types
Venturi Driven
•Relies on pressure differential created by the venturi in a bypass
installation to inject ozone into water
Compressor Driven
•Pressurizable lamp cartridges connected to diaphragm type air
compressors
•Used in bypass or direct injection installations
•Large systems will include contact loops, degassing systems, and
ozone destruct
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Compressor Driven Systems
Compressor driven systems are generally specified for:
•Commercial or Public Facilities (Pool and Spa)
•Heavily used or large residential pools
•Installations below water level, with non-adjustable jets, or with a
potential for high head pressures at the injection point
•Pools with infloor cleaners
Venturi Systems are typically used on:
•Residential Pools and Spas
•Small commercial facilities
•The use of a dedicated return in new residential construction is
recommended to ensure a venturi system can be used
Proprietary and Confidential
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Benefits of Compressor Driven Systems
•Higher output
•Injects ozone in to water under pressure, improving
effectiveness of ozone mixing
•Allows operation in a wider range of pressures and
hydraulic conditions
Proprietary and Confidential
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Venturi Systems
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Compressor Systems
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Large Compressor Systems
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Vacuum Ultraviolet Ozone
Installation
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Bypass Basic Installation
Venturi
Ozone
Generator
Ozone Generator
Extended Contact Distance
Saddle
or Tee
Pool
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Installation-Direct Injection
Compressor Only
Ozone
Injection
Extended Contact Distance
Ozone Generator
Saddle
Pool
or Tee
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Ozone Generators
Vacuum Ultraviolet
• Lower Cost
• Rugged
• Easy Operation
• Lower ozone concentration
• High Reliability
• Operation in almost any
environment
Corona Discharge
• High Ozone Outputs available
• High Ozone Concentrations
available
• Higher Cost up to 1 lb then lower
• More Complex
• Excellent performance when
properly applied
•May be required for large
applications
Proprietary and Confidential
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Safety and Regulatory Issues
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Sources of Ozone
•Undissolved ozone released at water surface
-Normal regulatory limit is .1 ppm
-UL (Spas) or NSF (commercial systems) testing certify
systems meet limit
-Typically controlled by limiting system output or by ozone
contact and/or destruct system
•Surface Discharge
-Flat Plate design only
-Does not generate substantial quantities, but levels can
be detected by smell
-Controllable by ventilation
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Sources of Ozone
•Natural Leakage
-Occurs as seals degrade or minor natural leaks
-Can be a problem depending on severity
•Line Breaks or Accidental Discharges
-Safety interlocks can limit
-Large systems may require emergency shutdown
-Respirators required by some states
-Vacuum ultraviolet units often allowed to substitute pressure
switches which shut of the unit in the vent of a pressure drop
(required for compressor systems only)
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Sources of Ozone
Air Detection Devices
•Multiple Types on Market
•Two basic types typically used: Low cost units which detect
ozone and similar oxidant; and expensive lab grade
equipment which detects ozone only, but is difficult to use
and uneconomical for many pool applications
•Low cost detectors can be set-off by chlorine and its
byproducts
•Background discharges from electrical equipment in the
plant room or atmospheric ozone can also cause false
alarms and unnecessary equipment shutdowns if
interlocked with equipment
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Installation Considerations
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Checklist
•Bather Loading
-Adjustment in sizing may be required if excessive
-Is system designed to meet a CT value or to act as a
primary oxidizer?
•Space Considerations-Is there enough space to install the
unit?
•Air Monitoring
-Are chemicals or electrical equipment in the plant room
which could cause erroneous readings?
-May not be required for vacuum ultraviolet units
•Look at Vendor Claims-ozone is not a stand alone
Product, chlorine is still required
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Installation Checklist
•Training
-Corona discharge units will require operator training
for: safety, operation and maintenance
-Vacuum ultraviolet units require less training
•Maintenance and Repair
-Review maintenance costs and cost of spares
-Check warranty and any warranty exclusions
-Check on service an support form vendor
-Consider a spares package to limit down time in the
event of a component failure
-Verify maintenance schedule (Daily, Weekly, Monthly,
Annual)
-Keep a maintenance log (corona systems)
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