Ozone is incapable of oxidizing radon, methane, and nitrates Below pH of 9, ozone is incapable of oxidizing ammonia at any practical rate Ozone can not practically oxidize any of the trihalomethanes except very slowly
What Ozone Does Not Do Ozone can not oxidize chloride ion to produce free chlorine at any practical rate Ozone cannot oxidize calcium, magnesium, carbonate, or bicarbonate ions; consequently, ozone can not treat hardness or alkalinity
What Ozone Does Well Disinfection Ozone kills bacteria, viruses, spores and cysts through a process called cellular lysis - an oxidation process in which ozone ruptures the cellular membrane of the micro-organisms and disperses the cytoplasm into solution. With bacteria such as E. Coli, streptococcus fecalis, and legionella pneumophila relatively low doses of ozone are required and inactivation occurs up to 3,125 times faster than chlorine.
What Ozone Does Well Disinfection: A 3-log (99.9%) reduction of viruses can be easily achieved with significantly lower CT values than for chlorine. Spores and cysts such as Giardia and Cryptosporidium can be inactivated with relatively high dosages of ozone. Crypto requires increasingly higher dosages of ozone for inactivation, currently with CT values 5 times that of Giardia. There is no established CT value for Cryptosporidium inactivation with chlorine.
What Ozone Does Well Taste and Odor Control Ozone oxidizes the organics such as tannins, unsaturated aldehydes, humic and fulvic acids, etc. responsible for 90% of taste and odor problems. Algae Control Ozone effectively kills plankton by oxidizing essential organic compounds that are part of the metabollic process.
What Ozone Does Well Oxidation Ozone’s powerful oxidation potential can remove a variety of man-made organic compounds including pesticides, VOCs, SOCs, and other micro pollutants. Pre-oxidation Ozone’s powerful oxidation potential can precipitate dissolved iron, manganese, and sulfide faster than any other commonly used oxidants, aiding removal by direct filtration
Benefits of Ozone Generated on site No transportation or storage required. More powerful than chlorine 100 times the oxidizing power of chlorine without the handling problems Reverts to oxygen leaving no telltale taste or odor to be removed Greatly simplifies water chemistry and control.
Mass transfer is the movement of molecules of a substance to and across an interface from one phase to another. i.e.: the amount of ozone that transfers from air, across the air-water interface and into water.
Mass Transfer Basics Factors affecting transfer of gas into liquid: Pressure: as pressure increases, more gas is forced into liquid. Temperature of the water/gas mixture: at lower temperatures, ozone gas is more easily absorbed into liquid. At higher temperatures, water tries to release gas rather than absorb it.
Mass Transfer Basics: Factors affecting the transfer of gas into liquid: Bubble size: as a gas is broken down into more and more smaller bubbles, the total surface area of the bubbles increase, thus increasing the surface area for interaction of ozone and water. Concentration of ozone in the carrier gas: at higher ozone concentration in the carrier gas, higher amounts of ozone are absorbed into the water.
Mass Transfer Basics Concentration of ozone in the carrier gas: Ultra violet ozone generators - 0.01% to 0.10% concentration by weight (0.10% concentration = 1,000 ppm) Corona discharge ozone generators - 1.0% to 6.0% concentration by weight (1.0% concentration = 10,000 ppm) The concentration of ozone gas is determined at a standard temperature of 68º F (20º C) and standard pressure of 1 atmosphere (14.7 psi).
Mass Transfer Basics Concentration of ozone in the carrier gas: At the same percentage of mass transfer efficiency, a CD ozone generator will deliver more ozone to the water than an UV ozone generator. Ozone concentration directly affects it’s ability to become soluble in water.
Mass Transfer Basics Concentration of ozone in the carrier gas:
Aeration vs. Venturi Injection Bubble diffusion Pressure in the system created by water column - relatively low pressures Taller tanks will increase system pressure. Large bubble size - smaller total surface area for ozone and water interface to occur Diffusion devices with smaller pore sizes are more likely to clog. Mass transfer efficiencies up to 75%, typically around 50%.
Aeration vs. Venturi Injection Venturi injection Differential pressure venturi injector technology utilizes water flow to create a vacuum to pull ozone gas into water. A turbulent interaction of the ozone gas and water occurs at the throat of the injector as the gas/water stream compresses, expands, and recompresses rapidly creating cavitation. Very fine bubbles are created allowing more total surface area for ozone and water interface to occur.
Aeration vs. Venturi Injection Venturi injection The back pressure at the outlet of the injector allows higher levels of ozone to dissolve into solution. Typically requires a 20 psi pressure differential. When properly sized, up to 99% mass transfer efficiencies can be achieved. Mazzei venturi sizing?
Water source Well water - generally very good quality; ozone used for pre-oxidation of dissolved metals including iron, manganese, and sulfides into filterable precipitate Wells with surface water intrusion - generally very good quality; ozone used for pre-oxidation of dissolved metals into filterable precipitate and disinfection, typically coliform bacteria Surface water - varying water quality; ozone used for primary disinfection, color, taste, and odor removal
Commercial Water Treatment Disinfection Independent of pH. Spores and cysts including Giardia, Cryptosporidium, etc. - sizing based on CT values, typically requires high dosages Currently, the EPA recognizes ozone as the only oxidant capable of Cryptosporidium inactivation - CT values 5 times that of Giardia Bacteria and viruses including coliform bacteria, E. Coli, Legionella, etc. - applied dosage of 1.5 mg/l recommended
Commercial Water Treatment Disinfection: the C.T. value concept C = the residual concentration of the disinfectant in mg/L measured at or before the first point of consumption T = the contact time required (in minutes) for water to travel from the point of injection to the point where C is measured the residual For example: A 0.4 disinfection residual after a 4 minute contact time (.4 x 4 = 1.6) will yield a CT value of 1.6.
CT Values for Giardia Cyst Inactivation by Ozone: At various water temperatures - pH can be anywhere between 6 and 8 (Source: EPA, SWTR Guidance Manual,October, 1990) Removal0.5°C5°C10°C15°C20°C25°C 33°F41°F50°F59°F68°F77°F 0.5 log0.480.3126.96.36.199.08 1.0 log0.970.630.480.320.240.16 1.5 log1.500.950.720.480.360.24 2.0 log1.901.300.950.630.480.32 2.5 log2.401.601.200.790.600.40 3.0 log2.901.901.400.950.720.48 CT Values for Giardia Cyst Inactivation by Free Chlorine: Water temperature at 20˚C (68˚F) at various pH readings Removal<6.06.57.07.58.08.5<9.0 0.6 log384554647792109 1.0 log394756678198117 1.6 log4250597287105126 2.0 log4452627591110132 2.6 log4655668097117141 3.0 log47576883101122146
Commercial Water Oxidation Best at pH over 7. Man-made organic compounds including pesticides, VOCs, SOCs, and other micro pollutants - applied dosage of 0.5 to 5.0 mg/l recommended Tannins, unsaturated aldehydes, humic and fulvic acids, etc. responsible for 90% of taste and odor problems - applied dosage of 1.5 mg/l recommended
Commercial Water Treatment Pre-oxidation: 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 applied ozone dosage to oxidize 1 mg/l of iron is 0.43 mg/l If complexed with organics, recommend doubling the applied ozone dosage and increasing contact time.
Commercial Water Treatment Pre-oxidation: Sulfide Hydrogen sulfide ion is oxidized to soluble sulfate ion and in-soluble elemental sulfur. Rapid reaction. Independent of pH. Theoretical applied ozone dosage to oxidize 1 mg/l of sulfide ion is 1.5 mg/l If complexed with organics, recommend doubling the applied ozone dosage and increasing contact time.
Commercial Water Treatment Pre-oxidation: Manganese Divalent manganese (Mn2+) oxidizes to tetravalent manganese (Mn4+), hydrolyzing to insoluble managanese oxyhydroxide. Optimum between pH range of 7.5 - 8.5. Theoretical applied ozone dosage to oxidize 1 mg/l of manganese is 0.88 mg/l. Over oxidation will produce soluble permanganate ion indicated by pink water.
Commercial Water Treatment Sizing an ozone system Based upon the amount of ozone required to completely react with the contaminants being treated in the water. Disinfection: spores and cysts - sizing based on CT values Disinfection: bacteria and viruses - 1.5 mg/l applied ozone dosage Oxidation: VOCs and SOCs - 0.5 to 5.0 mg/l applied dosage Oxidation: tannins - 1.5 mg/l applied dosage Pre-oxidation: iron - 0.43 mg/l applied dosage Pre-oxidation: sulfide - 1.5 mg/l applied dosage Pre-oxidation: manganese - 0.88 mg/l applied dosage
Commercial Water Treatment Sizing an ozone system Ozone systems are sized based on the principle of exact demand. To correctly size an ozone system, each contaminant and contaminant level must be accounted for. An accurate total ozone demand is important for sizing an ozone system. Ozone production is measured in grams per hour. The total ozone demand and water flow rate is needed to calculate for required ozone production.
Commercial Water Treatment Sizing an ozone system Ozone demand for each contaminant is calculated by multiplying the contaminant level by the applied dosage appropriate for that contaminant. By adding up the ozone demand for each contaminant, the total ozone demand can be found. A safety factor of 25% should be added to the total ozone demand.
Commercial Water Treatment Sizing an ozone system With the total ozone demand and water flow rate, the following equation is used to calculate for required ozone production: total ozone dosage X flow rate X 0.012 X 19 = grams per hour required ozone production Where 0.012 is the constant for conversion from gallons per minute to pounds per day, while 19 is the number of grams per hour in a pound per day.
Commercial Water Treatment Design considerations Recommend single pass ozone injection systems for all commercial water treatment applications - larger systems will use sidetream injection Sizing of sidestream pump is critical - oversize and take into consideration the presssure drop across the injector Minimum +5 psi required in the sidestream after injection and contacting to re-enter the main stream
Commercial Water Treatment Design considerations: contact vessels Contact vessels are an integral part of any ozone system. Allows time for chemical reaction to occur. Allows time for disinfection to occur. Allows for ozone dissolution. Allows for off-gassing of any carrier gas and ozone not dissolved into water
Commercial Water Treatment Design considerations for pre- oxidation and oxidation systems Importance of an accurate lab analysis. Recommend minimum 5 minutes contact time for pre-oxidation systems. Recommend 5 - 10 minutes contact time for oxidation systems. Pre-filtration may be required.
Commercial Water Treatment Design considerations for pre- oxidation and oxidation systems Ozone is not a stand alone water treatment tool, post filtration is required. Recommend activated carbon or multi- media filtration for pre-oxidation systems. Activated carbon filtration for oxidation systems. Residual sanitizer must be added for storage and delivery.
Commercial Water Treatment Design considerations for disinfection: Ozone is not a stand alone water treatment tool, pre and post filtration is required. Recommend multi-stage filtration levels down to 5 micron for pre- filtration and activated carbon for post filtration. Always exceed EPA recommended C.T. values. When meeting C.T. values, use lower ozone concentrations and higher contact times.
Commercial Water Treatment Design considerations for disinfection: When calculating for contact time, follow EPA guidelines for time credit - plug flow If oxidation or pre-oxidation is required in conjunction with disinfection, two complete ozone systems with two injection points and contact/de-gas systems is recommended. Residual sanitizer must be added for storage and delivery.
Commercial Water Treatment Design considerations for disinfection: Carcinogenic disinfection by-products may form when ozone is used in the presence of bromide ions - bromate and bromoform ions Difficult to treat after ozonation - some forms of activated carbon may have effective adsorption or chemical reduction capacities Low levels of ozone applied over long periods will minimize the formation of bromate ions.
Residential Wells Ozone is typically used when more than one contaminant is present. Typically used for pre-oxidation and oxidation. Maybe used for disinfection of bacteria and viruses that may be found in wells with surface water intrusion.
Typical Residential Well Water Treatment System
Typical Single Pass Ozone System OZD Vacuum Break Well Pump Ozone Generator Contact Tank Off-gas Vent Off-gas Destruct Pressure Tank Pressure Switch Multi-Media, Activated Carbon or Catalytic Carbon Filter Tank Well Pump Controlled by Pressure Switch Injection Manifold & Check Valve Assembly Water from Well Pump 120V Signal from Pressure Switch
Alpha Series Complete integrated component ozone systems - single pass treatment. OZD Vacuum Break Well Pump Ozone Generator Contact Tank Off-gas Vent Off-gas Destruct Pressure Tank Pressure Switch Multi-Media, Activated Carbon or Catalytic Carbon Filter Tank Well Pump Controlled by Pressure Switch Injection Manifold & Check Valve Assembly Water from Well Pump 120V Signal from Pressure Switch
POE Series Pressure Tank Pressure Switch Filter (optional) To Use Water Source (Well) Complete integrated skid mounted ozone systems - recirculated multi-pass treatment.
CWT Problem Water Ozone Demand Sizing Guideline Alpha Series Contaminants Iron (FE 2+) Manganese (Mn 2+) Sulfide (S 2-) Tannins PPM X X X X 0.43 0.88 2.20 1.50 PPM = = = = Ozone Dosage Required Safety Factor For Unknown Demand Total Ozone Dosage Required = = X PPM 1.25 PPM Contaminant Level (from water analysis) Ozone Dosage Required per PPM of Contaminant Ozone Dosage Required Recommended CWT Ozone Treatment Systems (based on dosage and flow rate): Dosage Rate1.0 - 2.0 PPM1.0 - 5.0 PPM1.0 - 8.0 PPM Flow Rate 10 GPM max 10 GPM max 10 GPM max Alpha ! Alpha II Alpha III
CWT Problem Water Ozone Demand Sizing Guideline POE Series Contaminants Iron (FE 2+) Manganese (Mn 2+) Sulfide (S 2-) Tannins PPM X X X X 0.43 0.88 2.20 1.50 PPM = = = = Ozone Dosage Required Safety Factor For Unknown Demand Total Ozone Dosage Required = = X PPM 1.25 PPM Contaminant Level (from water analysis) Ozone Dosage Required per PPM of Contaminant Ozone Dosage Required Recommended CWT Ozone Treatment Systems (based on dosage and flow rate): Dosage Rate1.0 - 10.0 PPM1.0 - 12.0 PPM1.0 - 15.0 PPM Flow Rate 10 GPM max 15 GPM max 15 GPM max POE10 POE15 POE20
Residential Wells ALPHA and POE series sizing notes Sizing based on dosage, residential applications only Maximum 10 gpm flow rate for ALPHA series and 15 gpm maximum flow rate for POE series Oxygen as an oxidizer Long contact times Assisted by media filtration Residual build-up through recirculation for POE systems Guidelines only - additional factors such as pH, temp, ORP, organic load, and other water impurities will affect ozone consumption
Residential Wells Design considerations for residential well treatment systems Importance of an accurate water analysis Draw down test required to get exact flow rate. Add 1.5 mg/l applied ozone dosage for disinfection of bacteria and viruses. Ozone is not a stand alone water treatment tool, post filtration is required. Recommend activated carbon or multi-media filtration for pre- oxidation systems. Activated carbon filtration for oxidation systems.
Factors that affect system performance Water temperature fluctuations Changes in water contaminant parameters Changes in flow rate Atmospheric conditions
Miscellaneous Ramblings Off-gas destruction Off-gas monitors Importance of monitoring for water quality using ORP or residual ozone monitors Automation capabilities
Miscellaneous Ramblings Importance of air prep The air we breath is composed of 78% nitrogen gas, 21% oxygen gas, and 1% other gases. When air is fed into the ozone reaction chamber, the oxygen and nitrogen molecules are split into atoms. The air we breath is humid (H2O is present). In a highly charged corona field, all molecules are split into atoms.
Miscellaneous Ramblings Importance of air prep The oxygen atoms combine into ozone molecules. The nitrogen, hydrogen, and oxygen atoms combine to form nitric acid. Nitric acid will destroy the reaction chamber from the inside out. Nitric acid will be introduced into the water.
Miscellaneous Ramblings Importance of air prep: air dryers Air is dried to -60 degrees F dewpoint using a molecular sieve material, most commonly silica gel. Nitrogen and oxygen atoms are still present but with the removal of moisture, the hydrogen atom is not introduced into the corona field. Ozone concentration: 1% by weight
Miscellaneous Ramblings Importance of air prep: oxygen concentrators High volumes of compressed air is pushed through a molecular sieve which removes nitrogen and water. Oxygen concentrations up to 95% are attainable. Minimum -100 degrees F dewpoint. Ozone outputs are tripled. Ozone concentration: minimum 3% by weight.