1. OZONE for DISINFECTION
4/16/2017
OZONE for DISINFECTION
Cameron Tapp
ClearWater Tech, LLC.

2. Ozone Basics
• History of Ozone
• How Ozone is Generated

3. 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

4. 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

5. History of Ozone - City of Los Angeles - 12,000 PPD
• 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

6. How Ozone is Generated = + = + Ozone (O3) Oxygen (O2) O3 O1 O2 O3 O2
Ultraviolet Light or
Corona Discharge
Some O2 molecules break apart
And reassemble with other O2 molecules to form ozone = O3 O2 + O1

7. 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

8. 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)

9. High Voltage Electrode (Anode)
How Ozone is Generated
1. Dried air or oxygen is passed through a gap between a glass dielectric and the anode
Glass Dielectric
Stainless Steel
Sleeve
(Cathode)
High Voltage Electrode (Anode)
Gap
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

10. 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

11. 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

12. What Ozone Does For Problem Water • 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

13. What Ozone Does For Problem Water • Algae Control • Oxidation
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
For Problem Water

14. Relative Oxidation Reduction Potential of Oxidizing Species
Potential Volts
Relative Oxidation
Reduction Power
Species
Fluorine
Hydroxyl Radical
Atomic Oxygen
Ozone
Hydrogen Peroxide
Perhydroxyl Radicals
Permanganate
Hypochlorous Acid
Chlorine*
Bromine
*Based on chlorine as a Relative Oxidation Reduction Power of 1.00

15. 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

16. 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
• Theoretical amount of ozone to oxidize 1 mg/L Mn is .87 mg/L
For Problem Water

17. 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

18. 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

19. Sizing Basics
• Preoxidation system for iron, manganese and sulfide removal:
Ozone Required To Treat:
Stoichiometric Practical
1 PPM Iron (Fe++) Requires PPM PPM
1 PPM Manganese (Mn++) Requires PPM PPM
1PPM Sulfide (S2) Requires PPM PPM

20. 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 = (Fe) X .43 (O3) = .56 ppm
= (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 * X 19* = 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

22. Factors That Affect System Performance
• Fluctuations in water temperature
• Changes in water contamination levels
• Changes in water flow rate
• Varying atmospheric conditions
Sizing Basics

23. 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

24. 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

25. 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

26. CT Value Defined Contact Time
• 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

27. 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°C 5°C 10°C 15°C 20°C 25°C
33°F 41°F 50°F 59°F 68°F 77°F
0.5 log
1.0 log
1.5 log
2.0 log
2.5 log
3.0 log
CT Values for Giardia Cyst Inactivation by Free Chlorine: Water temperature at 20˚C (68˚F) at various pH readings
Removal < <9.0
0.6 log
1.0 log
1.6 log
2.0 log
2.6 log
3.0 log

28. 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

29. Typical Installation Clarification Ozone Contactor Filtration
Surface water
Clarification
Residual Sanitizer
Added
Ozone Contactor
Filtration

30. Benefits of Ozone Use • Generated on site
No transportation, storage or handling challenges
• More powerful than chlorine
Chlorine’s relative oxidation reduction power
= Ozone = 1.52.
• Reverts to oxygen leaving no telltale taste or
odor to be removed
Greatly simplifies water chemistry, control
and convenience.

31. 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

32. Large Commercial Ozone Plant
750 PPD

33. Skid-Mounted Package Plant
650 PPD

34. Installing Dielectrics

35. 1 mgd Small Community Plant
Commercial Units

36. Disinfection Technology Comparison
ClearWater Tech, LLC

37. Applicability of Disinfection Techniques

38. Chlorine Advantages and Disadvantages
• Readily available
• Known technology
• Long half life
• Simplicity
Disadvantages
• High CT values
• Highly toxic
• pH dependent
• Transportation issues

39. Ozone Advantages and Disadvantages
• 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

40. UV Advantages and Disadvantages
• High reliability
• No by-products
• Generated on site
• Effective against viruses and bacteria
Disadvantages
• Initial capital cost
• No chemical residual
• Higher service
requirements

41. 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.

42. Thank You