Ultraviolet (UV) Disinfection - Technical Information

Factors to be considered in water or liquid purification

Ultraviolet Radiation: Ultraviolet (UV) light is invisible radiation within a range of the solar spectrum. UV is similar to the wave-lengths that are produced by visible light, but much shorter. UV radiation is measured in millionths of a millimeter, i.e., Angstromunits (one Angstrom unit wavelength equals one hundred-millionths of a centimeter), and like visible light, it primarily has a surface effect. Within the UV radiation spectrum, there are three main groups.

Ultraviolet lamp radiation of 2537 Angstrom units (or 254 namometers) wavelength must hit the microorganism to inactivate it, and each microorganism must absorb a specific amount of energy to be destroyed.

Proteins and nucleic acid, which all microorganisms contain as their main constituents, absorb UV radiation energy. After absorption, the UV energy destroys or inactivates the DNA (deoxyribonucleic acid), thus preventing the microorganisms from reproducing.

Sterilization of water implies that all life, i.e. bacteria, mold virus, algae, and protozoa are destroyed. Table I gives the absolute amount of UV necessary to kill many of the common types. We can also supply an 1849A (185nm) UV lamp that produces ozone (03) disinfection residuals, and in most cases this lamp interchanges with our standard 2537A UV lamp.

Complete sterilization is not necessary for the production of portable water. However, the water must conform with the drinking water standards of the Public Health Service or those of the agency governing your supply. Normally, the water must contain less than 2.2 coliforms per 100 ml to be considered safe to drink. The coliform group of microorganisms are generally associated with fecal matter and indicate that pathogenic (disease-causing) organisms, such as typhoid, may be present. As will be explained later, a different sizing formula must be used for purification if 100% sterilization is required.

Energy and Exposure: The germicidal spectrum of the ultraviolet wavelength is from 2000 to 3000 Angstroms, with the peak of 2537 Angstroms. The total UV energy emitted from all sides of the UV lamp is expressed in watts. The total exposure of the liquid is expressed in microwatt-seconds per square centimeter, which is a product of energy, time, and area. The same number of micro-watt seconds per square centimeter can be accomplished with a short exposure at a high intensity of UV or a long exposure at a low intensity of UV. Table II gives the UV energy data on the high intensity ultraviolet lamps used in purifiers.

Transmission: The amount of energy available to any microorganism from a given ultraviolet source is dependent on the UV transmission of the liquid. The transmission is dependent on the depth of the liquid and the absorption coefficient of the liquid. The absorption coefficient is dependent on the quantity and types of dissolved and suspended matter in the liquid. Generally, iron salts and organic matter have the greatest effect on absorption, while alkali salts (such as common salts) do not absorb these radiations. The physical requirements of less than 10 NTU of turbidity, 15 TCU of color, and 0.2 ppm of iron should be met before a water purifier is installed. Prefiltration of all suspended matter to at least 5 microns in size is recommended for all private water supplies, as the efficiency of the purifier is determined by the transmission of the water or liquid.

Table III illustrates the percent of transmission of the ultraviolet for water of various absorption coefficients. The absorption coefficient of the average tap water varies between 0.12 and 0.07 with highly polished DI or distilled water at 0.008 and cloudy water from a private source, such as a pond, well, or spring, at 0.50 or less. The absorption coefficient of the liquid to be purified must be known for proper sizing.

Other Factors Affecting Ultraviolet Purification: The ultraviolet output of the UV lamp is also dependent upon the primary voltage output and the lamp wall temperature. Table IV shows the effect of line voltage on UV output, and Table V shows the effect of temperature. It will be noted that at 56.6F (12 C) the lamp will be only 22% efficient in generating bactericidal radiation. We use only high intensity UV lamps inside a high-transmission clear fused quartz jacket so that an optimum temperature of 104 F (40 C) can be obtained for 100% UV output. The liquid does not come in contact with the lamp.

Another factor that must be considered is the useful life of the UV lamp. The performance of the various types of lamps is indicated in Table II. It is recommended that spare ultraviolet lamps be kept on hand at all times, and accurate records be kept of lamp use and replacement. The ultraviolet lamps output gradually decreases over the life of the lamp, and the lamp must be replaced as indicated by hours of use or by a UV monitor.

Sizing of Ultraviolet Liquid Purification Equipment: The various factors that must be considered were discussed above. Assuming a proper voltage source, the purifier can be sized properly if the following are known.

(a) Peak flow rate required in gpm, gph, gpd or m3/h.

(b) Transmission and physical makeup (absorption coefficient) of the liquid to be treated.

The Public Health Service requires that UV disinfection equipment have a minimum UV dosage of 16,000 uW sec./cm sq. (microwatt-seconds per square centimeter). Our purifiers are manufactured in standard sizes from 1 to 2600 gpm to impart a dosage of 30,000 uW sec./cm sq. All significant waterborne pathogenic microorganisms are destroyed by under 10,000 uW sec./cm sq. Industrial high purity water may require higher radiation levels depending on the type of microorganism to be destroyed.

Suggested flow rates of the various models with different liquid transmission are indicated in figures 1 and 2. If 100% sterilization is required, the flow rate through the purifier can be computed, depending on the energy level required. For a particular problem or application, consult our technical staff.

MOLD SPORES
Aspergillus flavus (yellowish green) Aspergillus glaucus (bluish green) Aspergillus niger (black) Mucor ramosissimus (white gray) Penicillum digitatum (olive) Penicillum expensum (olive) Penicillum roqueforti (green) Rhizopus nigricans (black)	99000 88000 330000 35200 88000 22000 26400 220000
ALGAE
Chlorelia vulgaris (algae)	22000
PROTOZOA
Nematode eggs Paramecium	92000 200000
VIRUSES
Bacteriophage (E. coli) Hepatitis virus Influenza virus Pollo virus (Poliomyeiitis) Rota virus Tobacco masaic virus	6600 8000 6600 21000 24000 440000
YEAST
Baker's yeast Brewer's yeast Common yeast cake Saccharomyces var. ellipsoideus Saccharomyces sp	8800 6600 13200 13200 17600

TABLE II
Technical Data on High Intensity Mercury Vapor Ultraviolet Lamps Use for Air and Water Purification
Lamp No.	Lamp Length	Arc Length	Lamp Watts	Rated Life (HR)	UV Output (Watts)	Intensity (Microwatts per CM Sq.)***
						Through Air		Through Water**
						At 1"	At 3"	At 1"	At 3"
8060	17"	14"	16.0	9000	5.3	8800	3400	7040	3920
8090-OZ	17"	14"	16.0	9000	5.3	8800	3400	7040	3920
5340	33"	30"	39.0	9000	13.8	8800	3400	7040	3920
5360-OZ	33"	30"	39.0	9000	13.8	8800	3400	7040	3920
9410	61"	60"	65.0	9000	26.7	8800	3400	7040	3920
6780-OZ	61"	60"	65.0	9000	26.7	8800	3400	7040	3920
Output of 2537 Angstroms with new lamps at 80 F, still air, ambient With an absorption coefficient of 0.10 **UV lamp intensity at 2537 Angstrom units wavelength at a given distance. Variations in voltage, temperature and tube material will cause the lamp output to vary. The intensity through water is based on a 0.10 absorption coefficient.

TABLE V
Relative percent output of 2537A radiation at various UV lamp temperature
Temperature		Output	Temperature		Output
F^{^{^o}}	C^{^{^o}}		F^{^{^o}}	C^{^{^o}}
56.6 60.8 68.0 75.2 82.4 89.6 96.8	12 16 20 24 28 32 36	22% 30% 40% 53% 68% 85% 95%	104.0 111.2 118.4 125.6 132.8 140.0 147.2	40 44 48 52 56 60 64	100% 98% 93% 85% 75% 66% 58%

Uses and Applications of UV Purifiers
Application	Explanation
Air conditioning and heating	10,15,16
Apple and fruit storage	5,16
Ampoules, bacteriological, biological enzyme laboratories	8,15,16
Bakeries, bread, cakes, pies, candy mfg.	1,2,8,15,16
Barber shops	16
Beverage plants (soft drinks), syrups, chocolate concentrates, flavoring extracts, coffee & tea concentrates, maple sugar & syrup, cider plants	1,2,3,6,8,15,16
Blood banks & donor agencies	1,8,15,16
Bottle water plants	1,4,8,15,16
Breweries	1,3,8,15,16
Butter processing	1,3,5,8,15,16
Canning	1,3,5,8,15,16
Cheese processing & packaging plants	1,3,5,8,15,16
Chicken, turkey and game farms	13,16
Cosmetics	1,2,3,8,15,16
Dairy products, ice cream	1,2,3,8,15,16
Drug & pharmaceutical mfgrs., vitamin products, chemical plants	1,2,3,8,15,16
Eggs, canned, frozen, dried	1,3,8,15,16
Electroplating & mirror plants	8,9,15,16
Electronic Equipment Manufacturing Plants	8
Farms	1,5,13,14,16
Food products, fruit juices, fresh/frozen	1,2,3,8,15,16
Homes	12,13
Hospitals, sanitoria, institutions, nursing & convalescent homes	1,2,3,8,10,12,13,14,15,16
Hotels, motels and camps	12,13,16
Meat packing, fish and other food plants	1,3,5,11,13,16
Mines, lumber camps, oil refineries	8,10,13,14,15,16
Nylon & synthetic fiber manufacturers	1,6,8
Office and factory	13,16
Paper mills	1,8,10,15,16
Packaging	1,3,5,13,16
Photograph film and paper manufacturers	8,10,15,16
Potable water treatment plants	13,16
Rest Rooms	13,16
Restaurants	12
Schools, auditoriums, theaters, public buildings, office buildings, factories	1,3,11,13,15,16
Sewage plants	3,8,10,13,14,15,16
Swimming Pools	14,16
Vegetable washing	1,5,15,16
Wineries	1,2,6,8,15,16

EXPLANATIONS (List of applications for water or liquid purifiers)
1.	Purify final rinse water in holding and blending tanks, cans, bottles, pipe lines, heat exchanges and all other types of equipment and containers, floors, walls, tables and other working areas, to flush out foreign matter and idsinfecting solutions without introducing water-borne bacteria which may re-contaminate the surface or product.
2.	To provide uncontaminated water for making simple (sugar) syrup so as to avoid fermentation and costly spoilage. Also for making various other aqueous solutions in which bacteria contamination would cause spoilage.
3.	To provide germ-free make-up water used to reconstitute powered milk; to add to syrups for carbonated or still beverages, or to add other ingredients where a percentage of water is present in the end product. Thus, by eliminating micro-organisms, the purity, freshness and flavor of the products are safeguarded and shelflife is extended.
4.	To purify the bottle spring, well or other water prior to bottling, to destroy invisible algae and all types of microorganisms which would otherwise cause obnoxious odors, tasts, and cloudiness. This eliminates costly returns, loss of customers and sales, by safeguarding the purity, freshness and tastes.
5.	Sterilize wash water for butter, cottage cheese and all other curd cheeses, smoked meats and other foods without introducing water-borne contaminants which later develop unsightly mold, foreign odors and taste, reduce butter-score and result in losses.
6.	Special purifiers are available for treating susceptible liquids, including pharmaceuticals, liquid sugar, chemicals, various solutions and wines, to destroy budding yeast cells, bacteria, mold and algae so as to prevent fermentation and other spoilage. Any micro-watt seconds per square centimeter intensity can be delivered.
7.	To use in the preparation of yeast culture, to prevent contamination of pedigreed yeast, to assure consistent, pedigreed quality, unaltered flavor and safeguarding of purity, freshness and keeping qualities; also in the preparation of any unprocessed products containing water.
8.	Eliminate slime and fouling of mineral beds inall types of water treatment equipment. It prevents frequent shutdown for de-contamination procedures and provides the best, and most economical, method of obtaining bacteria-free, de-ionized water. The first chamber purifies the water before it enters the de-ionizer, this prevents bacteria, mold, yeast or algae settling on the resins. The second chamber irradiates the water after it leaves the de-ionizer to assure purified water in the event of internal contamination from the resins.
9.	As a final, germ-free rinse for flushing electronic and other parts, without introducing contamination which may later cause fouling or product loss.
10.	Purify cooling water for heat exhangers, etc., also spray-washing water and process water recirculated for other purposes. To eliminate odors, ocntamination from water-borne bacteria, algae, slime, etc., & prevent algae build-up in pipe lines, cooling towers & clogged spray nozzles.
11.	To provide germ-free water for making ice incorporated in frankfurters, bologna and other smoked meats, also in other foods and beverages.
12.	To provide germ-free water for recirculation in swimming pools with a reduction of up to 80% of chlorine and other chemical previously required. This means that the extrememly small amount of chlorine recommended is at an unobjectionable level where it is also easy to maintain, and swimming is a pleasure. This small amount of chlorine acts as a bleach-booster to maintain the water crystal clear, while the ultra-violet purifier is constantly discharging germ-free water into the pool. An algaecide should be used periodically to prevent any microscopic spores from adhering to the sides and bottom of the pool, preventing them from entering the U.V. purifier, where they are destroyed.
13.	To deliver purifed, germ-free water by guaranteed 99% bacteria destruction in water distribution systems without the use of chlorine and without imparting any foreign taste, odor, corrosive or allergenic properties to the water. Cost of processing is the world's lowest - up to 30,000 GPH purified for only one kilowatt of current - costing only pennies a day!
14.	To bacteriologically purify the final clear effluent, without the use of chlorine, from sewage treatment equipment or plants. At least 99% bacterial destruction is accomplished at high flow rates. The high cost of chlorinators, chemicals, supervision and constant testing are eliminated at a substantial savings.
15.	To destroy at least 99% of all organisms in the water and sewage effluent from food, beverage, pharmaceutical plants, abattoirs, public conveyors, planes, ships, etc., after the water is rendered relatively free of turbidity, solids and excess color.
16.	A) Permanent or portable utra violet ozone fixtures for mold, bacteria and odor control. B) Direct U.V. radiation with permanent handing hood or wall mounted fixtures or portable U.V. air purifiers for sterilization of air, surfaces or products. To prevent air-borne bacteria or mold contamination on foods, meats, vegetables, fruits, products, tables, walls, wrappers, packages, cans, bottles, overns, coolers, caps, etc., shielding used for human and animal protection from direct U.V. radiation. C) Indirect U.V. radiation with ceiling or wall fixtures to sterilize the room air and eliminate the spread of air-borne infections among humans and animals. Safe for humans and animal occupancy due to special construction. No protective clothing, face masks or shields required unless placed below eye level. Proven effective in hospital rooms, operating rooms, nurseries, offices, cafeterias, restaurants, schools, motels, hotels, hallways, coolers, holding rooms, stables, pens, incubators, hatcheries, brooder rooms, laying houses and veterinaries. D) Direct and indirect radiation in special shielded cabinet for the sterilization of glasses, cans, utensils, instruments, caps, bottles, containers, conveyor belts, fillers and processing equipment. Special fixtures and cabinets for special applications. E) High intensity germicidal radiation fixture for air conditionig and heating system ducts for 98% destruction of air-borne bacteria and communicable diseases. Special equipment for odor control. Prevents the dangers of drawing in bacteria and germs in a closed system...heating or cooling them and redistributing them to toher rooms or areas. Proven effective in hospitals, nurseries, offices, restaurants, schools, etc.

General Information on Ultraviolet Purification
1.	The peak germicidal wavelength of the ultra-violet spectrum is 2537 angstrom and its intensity is expressed as micro-watts per square centimeter, a product of energy and area, or micro-watt seconds per square centimeters, a product of energy, time and area. Germicidal ultra-violet is invisible to the human eye.
2.	Germicidal ultra-violet must contact the micro-organisms to kill them. Therefore, the water or liquid must be clear to be purified, and a prefilter is recommended if the water does not meet USPHS physical standards and chemical requirements.
3.	Humans and animals must be protected from direct radiation of ultra-violet lamps, however, can safely congregate in areas or rooms treated with indirect radiation. Special shields are not required. Ultra-violet will not penetrate through glass or plastic and regular eye glasses are sufficient protection for looking at the bare ultra-violet lamp for a short period of time.
4.	The 1849 angstrom wavelenth of the ultra-violet from our special ozone lamps produces activated oxygen in free air (0₃) and (H₂O₂) hydrogen peroxide in water. This is commonly referred to as OZONE and is an excellent odor oxidizer and bactericide. Ozone can be used to supplement the 2537 A. wavelength on hard to get places. Safe for humans and animal if used as directed.
5.	All ultra-violet lamps have a useful operating life expressed in hours, and must be replaced as directed for effective results. We manufacture U.V. Monitors for the measurement and metering of ultra-violet germicidal radiation output.

All known micro-organisms are destroyed with proper exposure to ultra-violet radiation in the 2,000 to 3,000 Angstrom Unit (1) range.

Most water-borne pathogenic (disease-causing) Micro-organisms are destroyed with under 10,000 Microwatt seconds per square centimeter.

Some typical examples are noted below:

Micro-Organism	Disease	MW Sec./CM2
Salmonella typhosa	Typhoid fever	4,100
Salmonella paratyphi	Enteric fever	6,100
Shigella disenteriae	Dysentery	4,200
Shigella flexneri	Dysentery	3,400
Vibro comma	Cholera	Approx. 6,500 (2)
Leptospira spp.	Infectious jaundice	6,000 (2)
Poliovirus	Poliomyelitis	Approx. 6,000 (3)
Virus of infectious hepatitis	Infectious hepatitis	Less than (8,000) (4)
Our purifiers provide in excess of 30,000 MW sec/cm2 of ultra-violet energy.

General Notes
1.	Angstrom unit: A unit of wavelength 1/1,000,000,000 of a centimeter.
2.	This estimate is based on the similarity of these organisms to others and is probably of the same order of magnitude.
3.	Based on American Journal of Hygiene (1951) Dic, G.W. 53:131
4.	Since viruses in general are more susceptible to U.V. radiation than bacteria, this estimate is based upon work done with bacteriaophage.

Relative Percentage Output	UV Lamp Output Relative to Reactor Water Temperature

	Water Temperature Degrees F

TABLE I
Ultraviolet Energy Levels at 2537 Angstrom Units Wavelength required for 99.9% Destruction of Various Microorganisms UV Energy in Microwatt- seconds per Square Centimeter
BACTERIA
Agrobactrrium tumetaciens Bacillus anthracis Bacillus megaterium (vegetative) Bacillus megaterium (spores) Bacillus subtilis (vegetative) Bacillus subtilis (spores) Clostridium tetani Corynebacterium diphtheriae Escherichia coli Legionelia bozemanii Legionelia dumoffii Legionelia gormarii Legionelia micdadei Legionelia longbeachae Legionelia pneumophia Leptospira interrogans (infectious jaundice) Mycobacterium tuberculosis Neisseria catarrhalis Proteus vulgaris Pseudomonas aeruginosa (laboratory strain) Pseudomonas aeruginosa (envir. strain) Rhodospirillum rubrum. Salmonelia enteritidis Salmonelia paratyphi (enteric fever) Salmonelia typhimurium. Salmonelia typhosa (typhoid fever) Sarcina iutea SSerratia marcescens Shigelia dysenteriae (dysentery) Shigelia flexneri (dysentery) Shigelia sonnei Staphylococcus epidermidis Staphylococcus aureus Staphylococcus faecalis Streptococcus hemolyticus Streptococcus iactis Veridans streptococci Vibrio cholerae	8500 8700 2500 52000 11000 58000 22000 6500 7000 3500 5500 4900 3100 2900 3800 6000 10000 8500 6600 3900 10500 6200 7600 6100 15200 6000 26400 6200 4200 3400 7000 5800 7000 10000 5500 8800 3800 6500

TABLE III
Relative percent output of 2537A for water absorption coefficients*
Absorption Coefficient	Transmission		Absorption Coefficient	Transmission
	At 1"	At 3"		At 1"	At 3"
0.008 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11	99% 95% 92% 90% 88% 87% 85% 82% 81% 80% 78%	95% 87% 80% 74% 68% 64% 59% 55% 50% 46% 44%	0.12 0.15 0.16 0.17 0.18 0.20 0.25 0.30 0.35 0.40 0.50	75% 72% 70% 68% 65% 60% 56% 54% 50% 40% 30%	40% 34% 29% 28% 25% 23% 16% 11% 8% 5% 2%
*As a measured percent of transmission with GL-100 monitor. (Note: Monitor meets US Bureau of Standards Requirements.)

TABLE IV
Effect of line voltage on UV output, relative percent of 2537A*
PRIMARY VOLTS	OUTPUT
90 95 100 105 110 115 120 125	68% 73% 78% 84% 90% 96% 102% 108%
*Optimum=118 VAC/60 HZ