Cameron Tapp

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OZONE for DISINFECTION

• Cameron Tapp
• ClearWater Tech, LLC.

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Ozone Basics

• History of Ozone
• How Ozone is Generated

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History of Ozone

• First discovered in 1840
• From the Greek word ozein, which means to
  smell
• 1886 Europeans recognize the ability of ozone
  to disinfect polluted water
• 1893 First full scale application using
  ozone for drinking water in Oudshoorn, Netherlands

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History of Ozone

• 1906 Ozone first used to disinfect drinking
  water in Nice, France
• 1915 At least 50 major ozone installations on
  line throughout Europe
• 1937 First commercial swimming pool to use
  ozone in the U.S.A.
• 1939 Ozone system displayed at the New York
  Worlds Fair as the future of water treatment
• 1940s Ozone first used in U.S.A. to disinfect
• municipal drinking water

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History of Ozone

• 1990s Ozone gains acceptance in a wide variety
  of applications
• - City of Los Angeles - 12,000 PPD
• - City of Dallas - 16,000 PPD
• - Also used to treat
• Waste water
• Bottled water
• Swimming pools spas
• Aquariums
• Cooling towers
• Soft drinks, breweries, wineries
• Food processing

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How Ozone is Generated
Ozone (O3)
Oxygen (O2)

O3

O1
O2
Some O2 molecules break apart
Ultraviolet Light or Corona Discharge
And reassemble with other O2 molecules to form
ozone
O3


O2
O1
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How Ozone is Generated

• Man replicates nature to produce ozone in two
  ways
• 1. By forcing oxygen or ambient air past
  an ultraviolet light source matching the
  ozone-producing wavelength of the suns rays
  
• (185 nanometers)

2. By sending a lightning-like spark (a
corona discharge) through an oxygen or dry
air flow
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How Ozone is Generated

• Ozone is highly unstable, and the action
  involved in killing the microorganisms it
  contacts causes it to revert back to its original
  state of biatomic oxygen (O2)

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How Ozone is Generated

• 1. Dried air or oxygen is passed through a gap
  between a glass dielectric and the anode

2. High voltage current is applied to the
anode, which arcs to the cathode. Air in the
gap is exposed to the
electrical discharge, converting a
percentage (1 to 14) of the oxygen to ozone
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What Ozone Does Not Do

• Ozone is incapable of oxidizing radon,
  methane or nitrite ion
• Below pH 9, ozone is incapable of oxidizing
  ammonia at any practical rate
• Ozone cannot practically oxidize any of the
  trihalomethanes, except very slowly

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What Ozone Does Not Do

• Ozone cannot oxidize chloride ion to produce
  free chlorine at any practical rate
• Ozone cannot oxidize calcium, magnesium,
  bicarbonate, or carbonate ions consequently,
  ozone cannot oxidize hardness or alkalinity ions

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What Ozone Does

• Disinfection
• Ozone kills bacteria, cysts etc. up to 3,125
  times faster than traditional methods
• Taste and Odor Control
• Ozone oxidizes the organics responsible for 90
  of taste and odor-related problems (e.g. tannin
  and color removal)

For Problem Water
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What Ozone Does

• Algae Control
• Ozone effectively kills plankton algae (e.g.
  ponds and water features)
• Oxidation
• Ozones high oxidation potential can remove many
  pesticide residuals (e.g. groundwater
  remediation)
• Preoxidation
• Ozones high oxidation potential can also
  precipitate iron, manganese, sulfide and metals
  more quickly than any other commonly used
  oxidants, aiding removal by direct filtration

For Problem Water
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Relative Oxidation Reduction Potential of
Oxidizing Species
Relative Oxidation Reduction Power
Oxidation Reduction Potential Volts
Species

• Fluorine 3.06 2.25
• Hydroxyl Radical 2.80 2.05
• Atomic Oxygen 2.42 1.78
• Ozone 2.07 1.52
• Hydrogen Peroxide 1.77 1.30
• Perhydroxyl Radicals 1.70 1.25
• Permanganate 1.67 1.22
• Hypochlorous Acid 1.49 1.10
• Chlorine 1.36 1.00
• Bromine .78 .57
• Based on chlorine as a Relative Oxidation
  Reduction Power of 1.00

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Oxidation of Typical Contaminants - Iron

• Divalent ferrous iron (Fe2) oxidizes to
  trivalent ferric iron (Fe3), which precipitates
  as ferric hydroxide
• Rapid reaction
• Best at pH over 7, preferably over 7.5
• Theoretical amount of ozone to oxidize 1mg/L
  Fe is .43 mg/L
• If complexed with organics, longer contact
  times and higher doses are recommended

For Problem Water
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Oxidation of Typical Contaminants - Manganese

• Divalent manganese (Mn2) oxidizes to
  tetravalent (Mn4), hydrolyzing to insoluble
  manganese oxydihydroxide
• Over oxidation will produce soluble
  permanganate ion (indicated by pink tint to
  water)
• Optimum pH range is 7.5 - 8.5
• Theoretical amount of ozone to oxidize 1 mg/L
  Mn is .87 mg/L

For Problem Water
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Oxidation of Typical Contaminants - Sulfide Ion

• Hydrogen sulfide ion is oxidized to soluble
  sulfate ion and insoluble
• sulfur
• Rapid reaction
• Theoretical amount of ozone to
• oxidize 1 mg/L sulfide ion is 1.5 mg/L

For Problem Water
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Oxidation of Typical Contaminants - Color

• Primarily composed of humic and fulvic acids
• No set dosage
• Complete color removal typically requires high
  dosages
• Filtration not always necessary

For Problem Water
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Sizing Basics

• Preoxidation system for iron, manganese and
  sulfide removal

Ozone Required To Treat
Stoichiometric Practical 1 PPM Iron
(Fe) Requires .43 PPM .5 -.14 PPM
1 PPM Manganese (Mn) Requires .88 PPM
1.5 - .6 PPM 1PPM Sulfide (S2) Requires
6 PPM 1.5 - .5 PPM
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Example Applied Dosage Calculation
Ozone Dosage Required for Iron/manganese
Removal (Water flow at 10 gpm with 1.3 PPM Iron
and .22 Manganese) Ozone Dosage Required
1.3 (Fe) X .43 (O3) .56 ppm
.22 (Mn) X .88 (O3) .19 ppm Ozone
Required .75 ppm Dosage added for
unknown demand .75 ppm Recommended Total
Ozone Dosage 1.50 ppm 1.50 (dosage) X
10 gpm X .012 X 19 3.42
g/h .012 is the constant for conversion from
gallons per minute (GPM) to pounds per day (PPD)
while 19 is the number of grams per hour in a
pound per day. In this example, 3.42 g/h is the
output of the ozone generator required.
Sizing Basics
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Factors That Affect System Performance

• Fluctuations in water temperature
• Changes in water contamination levels
• Changes in water flow rate
• Varying atmospheric conditions

Sizing Basics
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Mass Transfer Basics

• Definition The movement of molecules of a
  substance to and across an interface from one
  phase to another
• i.e. The amount (mass) of ozone that transfers
  from air, across the air-water interface and into
  water

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Mass Transfer Basics

• Factors affecting transfer of a gas into a
  liquid
• Pressure As pressure increases, more gas is
  forced into the liquid
• Temperature of the water/gas mixture At lower
  temperatures, ozone gas is more easily absorbed
  by the liquid. At higher temperatures, water
  tends to release gas rather than absorb it
• Bubble size As a gas is broken into more small
  bubbles, the total bubble surface area increases,
  enlarging the area for interaction between ozone
  and water
• Concentration of ozone in the carrier gas
  Increased concentration of ozone enhances the
  ability of ozone to be absorbed into water

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Ozone Contact Time

• The Contact Vessel
• An integral part of any ozone system
• Allows time for chemical reactions
  (precipitation) to occur
• Allows time for disinfection to occur
• Allows for ozone dissolution
• Allows for off-gassing of any remaining carrier
  gas and ozone not dissolved into the water

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CT Value Defined

• C the residual concentration of the
  disinfectant (expressed in mg/L) measured at or
  before the first point of consumption
• T The contact time (expressed in minutes)
  required for water to travel from the point of
  injection to the point where C is measured
• Example A 0.4 residual after 4 minutes of
  contact time will yield a value of 1.6
• (.4 x 4 1.6)
• Tables have been established to help determine CT
  values required for certain levels of
  disinfection at various water temperatures and pH
  readings

Contact Time
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• CT Values for Giardia Cyst Inactivation by Ozone
  
• (pH can be anywhere between 6 and 9) at
  various water temperatures
• (Source EPA, SWTR Guidance Manual, October,
  1990)
• Removal 0.5C 5C 10C 15C 20C 25C
• 33F 41F 50F 59F 68F 77F
• 0.5 log 0.48 0.32 0.23 0.16 0.12 0.08
• 1.0 log 0.97 0.63 0.48 0.32 0.24 0.16
• 1.5 log 1.50 0.95 0.72 0.48 0.36 0.24
• 2.0 log 1.90 1.30 0.95 0.63 0.48 0.32
• 2.5 log 2.40 1.60 1.20 0.79 0.60 0.40
• 3.0 log 2.90 1.90 1.40 0.95 0.72 0.48
• CT Values for Giardia Cyst Inactivation by Free
  Chlorine Water temperature at 20C (68F)
  at various pH readings
• Removal lt6.0 6.5 7.0 7.5 8.0 8.5 lt9.0
• 0.6 log 38 45 54 64 77 92 109
• 1.0 log 39 47 56 67 81 98 117
• 1.6 log 42 50 59 72 87 105 126
• 2.0 log 44 52 62 75 91 110 132
• 2.6 log 46 55 66 80 97 117 141

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Significant Points About CT

• Ozone kills bacteria very quickly and
  effectively on contact
• Viruses and cysts, respectively, require
  increasingly greater CT values. To maximize CT
  effectiveness, longer contact times should be
  emphasized over higher ozone concentrations
• Disinfectants for which CT values have been
  established
• Free Chlorine
• Chloramines
• Chlorine Dioxide
• Ozone

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Typical Installation
Surface water
Clarification
Residual Sanitizer Added
Ozone Contactor
Filtration
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Benefits of Ozone Use

• Generated on site
• No transportation, storage or handling
  challenges
• More powerful than chlorine
• Chlorines relative oxidation reduction power
• 1.00. Ozone 1.52.

• Reverts to oxygen leaving no telltale taste or
• odor to be removed
• Greatly simplifies water chemistry, control
• and convenience.

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Benefits of Ozone Use

• Creates no carcinogenic by-products, i.e.,
  trihalomethanes (THMs)
• New surface water treatment plants require
  ozone to meet modern THM regulations
• Ozones only by-product is oxygen
• Ozone is the only recognized disinfectant
  capable of practical inactivation of
  Cryptosporidium oocysts with CT requirements
  about 3 to 5 times those for Giardia cysts

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Large Commercial Ozone Plant
750 PPD
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Skid-Mounted Package Plant
650 PPD
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Installing Dielectrics
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Commercial Units
1 mgd Small Community Plant
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Disinfection Technology Comparison
ClearWater Tech, LLC
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Applicability of Disinfection Techniques
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Chlorine Advantages and Disadvantages

• Advantages
• Readily available
• Known technology
• Long half life
• Simplicity

• Disadvantages
• High CT values
• Highly toxic
• pH dependent
• Transportation issues

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Ozone Advantages and Disadvantages

• Advantages
• Low CT values
• No by-products
• Strongest oxidizer commercially available
• Generated on site
• Effective for THM control
• Effective against Crypto

• Disadvantages
• Capital cost
• Larger footprint
• Higher service and maintenance

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UV Advantages and Disadvantages

• Advantages
• High reliability
• No by-products
• Generated on site
• Effective against viruses and bacteria

• Disadvantages
• Initial capital cost
• No chemical residual
• Higher service
• requirements

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Conclusion

• No single water treatment method is the
  panacea for all types of water conditions.
  Typically, using the combined strengths of
  several methods will produce the best overall
  results.

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• Thank You