Aquatic Consulting Services 3833 Lament Street 4C San Diego California 92109 Computer Modeling for Ozone System Sizing Alison Osinski, Ph.D. Aquatic Consulting Services 3833 Lament Street 4C San Diego, CA 92109 (619) 270-3459 Beth Hamil, Lan George, Paul French, Jennifer Engelmeier Del Industries 3428 Bullock Lane San Luis Obispo, CA 93401 (805) 541-1601
DEL Pro3 Size software was developed to provide the industry with a standardized method of sizing side stream (slip-stream), corona discharge ozone systems for swimming pools, spas, and recreational water features. An industry problem currently exists in which some manufacturers are significantly undersizing or oversizing ozone systems based on owner budget. This is leading to much confusion, and a perception by many that ozone "doesn't work". The software will allow manufacturers to compete equally in the marketplace. The end users will be able to select a system based on generator size and output, rather than being influenced by a charismatic salesperson only concerned with making the sale and pushing his or her product over the actual needs of the customer. They will be able to compare "apples to apples" when shopping for an ozone generating system. Informed consumers will hopefully be able to select a system that will meet their facility's needs, and that will achieve the goal of keeping the pool water properly sanitized and oxidized. DEL Pro3 Size software takes into consideration several factors which influence the amount of ozone that is needed to meet the needs of the facility, including: the facility type and pool location, the owner's motivation for wanting to install an ozone system, pool volume, the average daily bather load, and more importantly the bather load to water volume ratio, the temperature at which
the water is typically maintained, the flowrate and turnover time, and the type of filter media, filter area, and filter design flowrate. DEL Pro3 Size software also gathers information on the facility contact person, demographic information, the age of the facility, the chemical use profile of the pool including chemicals, the chemical feed system and controllers used. The software will flag items which are significantly out of range, so that pool owners can be alerted to problems that won't be improved simply by installing an ozone system. DEL Pro3 Size software is available in CD-ROM format and available for use on the IBM compatible PC platform. The target market for distribution of the software is architects, aquatic consultants, pool contractors/builders, and commercial aquatic facility owners. In the side stream, corona discharge method, the preferred method of generating ozone on-site for pool water treatment, air is first oxygen enriched then dried to prevent nitric acid from forming. The oxygen enriched, dried air is then sent past a di-electric or high voltage electrodes, which give off a bluish glow or "corona discharge". O2 is split into individual oxygen atoms which recombine into O,. The ozone is then injected through a venturi and transferred 3 into a side stream of water drawn off the pool water return line. Corona discharge ozone systems should also include the use of contact chambers and may include degassing units similar to those used in the larger and much more expensive European model ozone generation systems, to treat pool water and remove the ozone from the water prior to its entering the swimming pool.
The goal of side stream sizing is to achieve one complete turnover of water in a given period, or to cause all the water in the pool to be ozonated at a given percentage of side stream. Volume of the pool in gallons is divided by the time factor in minutes in a day, and then by the actual flowrate in gallons per minute. For example, a pool containing 95,000 gallons of water divided by 1,440 minutes in a day divided by a flowrate of 265 gpm (a typical 6 hour turnover rate), equals 0.248. Therefor, a minimum 25% side stream is required. The side stream is usually sized at between 25 and 33 percent, however, if you reduce the side stream, the dose concentration goes up inside the contact chamber. Ozone generator sizing is based on the formula " gallons per minute multiplied by 0.227 grams per gallon multiplied by 0.4 milligrams per liter equals grams per hour". DEL Pro3 Size software formula takes volume in gallons and divides by contact time in minutes, multiplies by the 0.227 conversion factor, then multiplies by an assigned motivational factor, temperature factor, location factor, and ozone factor (bather load divided by flowrate). Derivation of the 0.227 conversion constant for use in calculating ozone generator size is base on water flow rate, gpm times Xu. times ppm = grams per hour. Xu, equals grams per hour times minutes per gallon. X(i equals 60 minutes per hour times grams per gallon. 1 ppm is equivalent to 1 milligram per liter which equals 0.00379 grams per gallon. Therefor, X = 0.00379 grams per gallon times 60 minutes per hour, or X = 0.2271 grams per gallon.
The goal of contact chamber sizing is to achieve enough contact time between the ozone produced and water in the side stream to allow at least 4 minutes of retention of the side stream flow in a contact chamber, tower, or vessel, and an ozone dose of 1.6 ppm in the side stream when ozone is the primary oxidant. CT values of at least 1.6 are achieved when the concentration of ozone in milligrams per liter equals 0.4 for a time of 4 minutes. Flowrate in gallons per minute is multiplied by 4 minutes to determine the minimum size of the contact vessel in gallons. As can be seen when sizing ozone generating systems for different types of facilities with different user profiles and characteristics, it becomes obvious that one size does not fit all. Use Motivation Bather Load Per Day Water Temperature Volume Swim School Instruction 280 92 F 19,170 g Leisure Facility Recreation Water/ Air quality 1,500 83 F 274,828 g Therapy Pool Therapy 200 90 F 81,033 g Multi-Use Pool Recreation / Competition Water/ Air quality 500 84 F 240,700 g Spa Soaking 100 104 F 3,500 g Flowrate 320 gpm 1,145 gpm 644 gpm 668 gpm 116 gpm Location Outdoor Outdoor Bather Load : Water Volume 1:60 1:165 1:405 1:481 1:35 DEL Pro3 Size software will prepare and allow the customer to print out an individualized report recommending a generator size based on grams per
hour and pounds per day of ozone production, as well as the parts per million dose on main filtration. Side stream in gallons per minute and percentage of main flow are provided along with electrical specifications, oxygen feed gas flow, and cooling water requirements. Contact tank, degassing valve, ozone destruct, injector, booster pump and ambient ozone monitors models and sizes are also suggested. DEL Pro3 Size software development goals will be met when facility owners realize that proper sizing and installation of their corona discharge ozone generation system has led to easier to maintain, less costly, and better smelling, better tasting, and better quality pool water; and pass the word on to other potential customers.
1998 JSPSI Water Chemistry Symposium New Orleans, Louisiana DEL Proo Size Software Computer Modeling for Ozone System Sizing i Standardized method of sizing slipstream, corona discharge ozone systems for swimming pools, spas, and recreational water features Alison Osinski, Ph.D. Aquatic Consulting Services 3833 Umonl Street <C Sin Dtogo Crilfornk 92109 DEL Pro. Size Software i Takes into consideration: Facility type Motivation for wanting to install an 03 system Pool volume Average daily bather load Bather load:water volume ratio Water temperature Location of pool Flow rate and turnover time Filter media, filter area, filter design flowrate DEL Pro, Size Software i Also gathers information on: Contact persons Demographic information Chemical use profile Age of the facility Chemical feed system and controllers DEL Pro^ Size Software DEL Pro, Size Software i CD-ROM format i Will flag items that are significantly out of range i Target market for the software Architects Consultants Contractors/builders Commercial facility owners i Purpose: Standardization Prevent oversizing/undersizing of systems Provide a system that will meet the facility's needs Water will be properly sanitized - oxidized Manufacturer's will be able to compete equally End users will be able to select a system based on generator size compare "apples to apples" 1997 Alison Osinski, Ph.D. Aquatic Consulting Services
Side Stream Sizing i Goal: 1 complete turnover of water in the given period i How long it takes for all the water in the pool to be ozonated at a given % side stream Side Stream Sizing i Formula: Volume (gallons) + Time factor (minutes) + Flow rate (gpm) i Example: 95,000 gallons + 1440 minutes + 265 gpm = 0.248 = 25% side stream required Side Stream Sizing i Side stream % is usually sized at 25-33% i However, if you reduce the side stream, the dose concentration goes up inside the contact chamber O3 Generator Sizing Formula i Base formula: gallons/minute x 0.227 grams/gallon x 0.4 mg/l = grams per hour DEL Pro3 Size Software Formula Examples Volume (gallons) - Contact time (minutes) x 0.227 conversion factor x Motivational factor x O3 factor (bather load * flow rate) x Temperature factor x Location factor Use Motivation Bather Load Temp. F Volume Flowrate Location Swan Instruction 280 92 19,170 g 320 gpm 1.1 45 gpm Uv'isure Fadiity Rec Water/air quality 1.500 83 274,828 g Outdoor Tiia-,5py PC-d Therapy Rec/Comp 200 90 81. 033 g 644 gpm Multi-Use V* laquality 500 84 240.700 g 668 gpm Outdoor Spa Spa 100 104 3.500 g 116 gpm Load:Volume 1:60 1:165 1:405 1:481 1:35 12
Contact Time i Goal: 4 minutes of retention of the side stream flow in a contact chamber, tower, or vessel Ozone dose: 1.6 ppm in the side stream when ozone is the primary oxidant i Formula: Flowrate (gpm) x 4 minutes = gallons - size of contact vessel Conversion Factor for 0, i Derivation of the 0.227 conversion constant for use in calculating ozone generator size base on water flow rate gpm x X^ x ppm = grams/hour X^ = grams/hr x minutes/gallon X^ = 60 minutes/hour x grams/gallon 1 ppm = 1 mg/l = 0.00379 grams/gallon X = 0.00379 grams/gallon x 60 minutes/hour X = 0.2271 grams/gallon,
Aquatic Consulting Services 3833 Lament Street 4C San Diego California 92109 Pool Q & A What are some of the benefits of using ozone to disinfect pool water? What exactly is ozone anyway? Ozone is activated oxygen or O3. Ozone was named by C.F. Schoenbein in 1840, and its name is derived from the Greek word "ozein" which means "to smell". Ozone was first used for drinking water disinfection in 1893 in Oudshoorin, The Netherlands. Nice, France began disinfecting its public water supply in 1906 and still does today. Potsdam, New York was the first U.S. city to treat its drinking water with ozone. The largest ozone generation plant in the world is in Los Angeles. The L.A. plant can treat as much as 600 million gallons of water per day. Ozone is also use to treat air, and sewage. Pool disinfection with ozone has been common in Europe since the 1950's. A swimming pool ozone system was displayed at the 1939-1940 New York World's Fair. The first pool in the U.S. to use CD ozone to treat its water was the Lake Mohawk Cruiser Swim & Tennis Club in Byram, New Jersey. The system was installed in 1937 and is still in operation. Two common methods of producing ozone on-site for swimming pool and spa water oxidation and sanitation exist. In the ultraviolet light method of ozone generation, air is passed near special mercury vapor UV lamps made of quartz glass that produce light of a specific wavelength. Oxygen molecules, O2, are bombarded with UV rays and recombine into ozone, O3, but in very low concentrations. In the corona discharge method, the preferred method for pool water treatment, air is first dried to prevent nitric acid from forming. The dried air is then sent past a di-electric or high voltage electrodes, which give off a bluish glow or "corona discharge". O2 is split into individual oxygen atoms which recombine into O3. The ozone is then injected through a venturi and transferred into either a slip stream of water or directly into the pool water return line. Some corona discharge ozone systems also include the use of contact chambers and degassing units similar to those used in the larger and much more expensive European model ozone generation systems, to treat pool water and remove the ozone from the water prior to its entering the swimming pool. Ozone is an excellent oxidizing agent-thousands of times faster than chlorine or bromine at removing organic and inorganic contaminants and pathogens from the water. Organic contaminants such as perspiration, urine, creams, ointments, hair care products, cosmetics, nasal secretions, and creatine (a chemical normally found in blood and excreted into urine by the kidneys) are partially oxidized by ozone, reduced to nitrates, or flocculated and removed by 1997 Alison Osinski, Ph.D. Aquatic Consulting Services
the filters. Ozonated pool water will not foam, because ozone destroys foam causing organic compounds. Ozone will remove organic material before chlorine can react with the organics and help prevent the formation of carcinogenic substances called trihalomethanes (THM). No PCBs (polychlorinated biphenyls) form during ozonation, and ozone itself is not carcinogenic. Elite level competitive swimmers believe they can swim faster in an ozonated pool. Swim event times can drop because of the decreased friction resulting from more complete oxidation and increased oxygen levels in the water. Disease causing bacteria, waterborne viruses, yeasts, protozoa, cysts, parasites, spores, and amoebas can all be destroyed by ozone depending on the contact time and concentration of ozone in the water. Ozone is drawn to bacteria and explodes bacteria walls on contact Because ozone is only being generated when the pool water is circulating, and ozone leaves no residual for killing bacteria about to be introduced into the water, it must be used in conjunction with chlorine or bromine if continuous disinfection of pool water is desired. However, use of ozone results in a reduced halogen consumption. Less bromine or chlorine are needed to maintain the oxidation reduction potential (ORP), and lower halogen residuals are required. Ozone does not dry skin, or bleach swimmers' hair. For swimmers with halogen sensitivities, contact dermatitis problems and the resulting skin rashes will be reduced. Ozone helps prevent formation of chloramine compounds. Eye, sinus, mucous membrane and throat irritation from chloramines are eliminated. No objectionable odor is produced. Ozone is often described as smelling "like watermelons". Ozonated pools will only occasionally need to be shocked or superchlorinated. Ozone will floe paniculate matter increasing filter effectiveness, and the water will appear clearer, due to removal of finely suspended colloidal particles. Ozone does not contribute to the total dissolved solid (IDS) build-up, and may actually reduce the TDS because of particle coagulation. Therefor, less frequent draining and refilling of the pool is required. Ozone is safe and inexpensive to use once the generating system is installed. Since ozone is generated on-site, from oxygen in the air, as needed, there is less storage and transportation of large quantities of hazardous materials. Ozone in pool water is not explosive and is not flammable. Ozone injection lines are under vacuum. If a leak in an ozone line should occur, air would leak into system rather than ozone leaking into the air. Ozone helps remove metals which can discolor water and stain pool surfaces, prevents calcification, and softens the water. Ozone has no effect on ph or total alkalinity, so fewer chemicals are needed to adjust ph and water balance. Ozone destroys oils and converts them to carbon dioxide (CO?). The use of enzymes to remove oils is not necessary and bathtub ring formation at the waterline will be reduced. Proper installation of a quality ozone generation system will lead to easier to maintain, less costly, and better smelling, better tasting, and better quality pool water. 1997 Alison Osinski, Ph.D. Aquatic Consulting Services