OZONE for
DISINFECTION
Cameron Tapp
ClearWater Tech, LLC.
Ozone Basics
• History of Ozone
• How Ozone is Generated
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
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
World’s Fair as the future of water treatment
• 1940s: Ozone first used in U.S.A. to disinfect
municipal drinking water
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
•
How Ozone is Generated
Ozone (O3)
Oxygen (O2)
O2
Ultraviolet Light
or
Corona Discharge
+
Some O2
molecules
break apart
O2
O1
=
O3
And reassemble with other O2
molecules to form ozone
+
O1
=
O3
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 sun’s rays
(185 nanometers)
2. By sending a lightning-like spark
(a ‘corona discharge’) through an
oxygen or dry air flow
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)
How Ozone is Generated
High Voltage
Electrode (Anode)
Stainless Steel
Sleeve
(Cathode)
Gap
Glass
Dielectric
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
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
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
For Problem Water
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 odorrelated problems (e.g.: tannin and color
removal)
What Ozone Does
For Problem Water
• Algae Control
Ozone effectively kills plankton algae
(e.g.: ponds and water features)
• Oxidation
Ozone’s high oxidation potential can
remove many pesticide residuals (e.g.:
groundwater remediation)
• Preoxidation
Ozone’s high oxidation potential can
also precipitate iron, manganese,
sulfide and metals more quickly than
any other commonly used oxidants,
aiding removal by direct filtration
Relative Oxidation Reduction
Potential of Oxidizing Species
Species
Fluorine
Hydroxyl Radical
Atomic Oxygen
Ozone
Hydrogen Peroxide
Perhydroxyl Radicals
Permanganate
Hypochlorous Acid
Chlorine*
Bromine
Oxidation Reduction
Potential Volts
Relative Oxidation
Reduction Power
3.06
2.80
2.42
2.07
1.77
1.70
1.67
1.49
1.36
.78
*Based on chlorine as a Relative Oxidation Reduction Power of 1.00
2.25
2.05
1.78
1.52
1.30
1.25
1.22
1.10
1.00
.57
For Problem Water
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
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
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
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
Sizing Basics
• Preoxidation system for iron,
manganese and sulfide removal:
Example Applied
Dosage Calculation
Ozone Dosage Required for Iron/manganese Removal
(Water flow at 10 gpm with 1.3 PPM Iron and .22 Manganese)
Sizing Basics
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.
ClearWater Tech, LLC Problem Water Ozone Demand Sizing Guideline
Contaminants
PPM Contaminant
Level (From
Water Analysis)
Ozone Dosage Requi red
Per PPM of Contaminant
Ozone Dosage
Requi red
Ir on (FE 2+)
Manganese (Mn 2+)
Sulfi de (S 2-)
PPM
PPM
PPM
X
X
X
0.43 PPM
0.88 PPM
2.20 PPM
=
=
=
0 PPM
0 PPM
0 PPM
Tani ns
PPM
X
1.50 PPM
=
0 PPM
Ozone Dosage Requi red
=
0 PPM
Safety Factor For Unknown Demand
X
Total Ozone Dosage Requir ed
=
Re com m ende d Cle ar Wate r Te ch Ozone Tr e atm e nt Sys te m s (bas e d on dos age and flow rate ):
Dosage Rat e
Flow Rate
POE 10
1.0 - 10. 0 PPM
10 GPM max
POE 15
1.0 - 12. 0 PPM
15 GPM max
POE 20
1.0 - 15. 0 PPM
15 GPM max
Note # 1:
POE series are skid mounted recirculat ion sy stems.
Note # 2:
Add 1. 5 PPM ozone dose f or disinf ection.
Note # 3: These are guideli nes only! Other factors such as pH, temperature, ORP, or ganic l oad, and other
water impuri ties wi ll affect ozone consumpti on.
1.25
0 PPM
Sizing Basics
Factors That Affect
System Performance
• Fluctuations in water temperature
• Changes in water contamination
levels
• Changes in water flow rate
• Varying atmospheric conditions
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
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
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
CT Value Defined
• C = the residual concentration of the
Contact Time
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
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
0.5 log
1.0 log
1.5 log
2.0 log
2.5 log
3.0 log
0.5°C
0.48
0.97
1.50
1.90
2.40
2.90
5°C
33°F
0.32
0.63
0.95
1.30
1.60
1.90
10°C
41°F
0.23
0.48
0.72
0.95
1.20
1.40
15°C
50°F
0.16
0.32
0.48
0.63
0.79
0.95
20°C
59°F
0.12
0.24
0.36
0.48
0.60
0.72
25°C
68°F
0.08
0.16
0.24
0.32
0.40
0.48
77°F
CT Values for Giardia Cyst Inactivation by Free Chlorine:
Water temperature at 20˚C (68˚F) at various pH readings
Removal
0.6 log
1.0 log
1.6 log
2.0 log
2.6 log
3.0 log
<6.0
38
39
42
44
46
47
6.5
45
47
50
52
55
57
7.0
54
56
59
62
66
68
7.5
64
67
72
75
80
83
8.0
77
81
87
91
97
101
8.5
92
98
105
110
117
122
<9.0
109
117
126
132
141
146
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
Typical Installation
Surface water
Clarification
Residual Sanitizer
Added
Ozone Contactor
Filtration
Benefits of Ozone Use
• Generated on site

No transportation, storage or handling
challenges
• More powerful than chlorine
 Chlorine’s 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.
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
 Ozone’s 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
750 PPD
Large Commercial Ozone Plant
650 PPD
Skid-Mounted Package Plant
Installing Dielectrics
Commercial Units
1 mgd Small Community Plant
ClearWater Tech, LLC
Disinfection Technology
Comparison
Applicability of Disinfection Techniques
CONSIDERATION
Size of plant
Applicable le ve l of tr e atm e nt
pr ior t o dis inf e ction
Equipm e nt r e liability
Pr oce s s cont rol
Re lat ive com ple xity of
t echnology
Safe t y conce r ns
Tr ans por tat ion on site
Bacte r icidal
Vir ucidal
Oxidat ion
Cl2
all s ize s
all le ve ls
good
w e ll de ve lope d
s im ple t o
m ode r ate
ye s
s ubs tant ial
good
poor
m ode r ate
O3
all s ize s
UV
s m all t o m e dium
s e condar y
s e condar y
f air to good
f air to good
de ve loping
com plex
no
m ode r ate
good
good
good
de ve loping
s im ple t o
m ode r ate
no
m inim al
good
good
no
Hazar dous by-pr oducts
ye s
none e xpe cte d
no
Pe r sis te nt r e s idual
long
s hort
none
Contact t im e
long
m ode r ate
s hort
no
ye s
no
Contr ibut e s diss olve d oxyge n
Re act s w it h am m onia
Color r e m oval
ye s
ye s ( high pH only)
no
m ode r ate
ye s
no
Incr e ase d dis s olve d s olids
ye s
no
no
pH de pe nde nt
ye s
O&M s e ns it ive
Cor ros ive
m inim al
ye s
s light (high pH)
no
high
m ode r ate
ye s
no
Chlorine
Advantages and Disadvantages
Advantages
• Readily available
• Known technology
• Long half life
• Simplicity
Disadvantages
• High CT values
• Highly toxic
• pH dependent
• Transportation
issues
Ozone
Advantages and Disadvantages
Advantages
Disadvantages
• Low CT values
• Capital cost
• No by-products
• Larger footprint
• Strongest oxidizer
• Higher service and
commercially available
maintenance
• Generated on site
• Effective for THM control
• Effective against Crypto
UV
Advantages and Disadvantages
Advantages
Disadvantages
•
•
•
•
• Initial capital cost
• No chemical
residual
• Higher service
requirements
High reliability
No by-products
Generated on site
Effective against
viruses and
bacteria
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.
Thank You