How uv works - Ultraviolet Data
Summary
Ultraviolet (UV) light is a form of radiation that has germicidal properties, meaning it can deactivate harmful bacteria, viruses, and other microorganisms. UV light works by disrupting the genetic material of these organisms, preventing them from reproducing and causing infection. UV light can be used to disinfect water, air, and surfaces in order to prevent the spread of harmful bacteria and viruses. UV light can be a safe and effective way to disinfect your environment and protect your health.
UNDERSTANDING ULTRAVIOLET RADIATION IN WATER OR LIQUIDS
Ultraviolet Radiation:
Ultraviolet (UV) light is invisible radiation within a range of the solar spectrum. UV is similar to the wavelengths that are produced by visible light, but much shorter. UV radiation is measured in millionths of a millimeter, i.e., Angstrom units (one Angstrom unit wave-length equals one hundred-millionth 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 nanometers) 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. Our systems can also supply an 1849A (185NM) ultraviolet lamp that produces ozone (03) disinfection residuals, and in most cases this lamp interchanges with our standard 2537A ultraviolet lamp.
Complete sterilization is not necessary for the production of potable water. However, the water must conform to the drinking water standards of the EPA 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 groups 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 at 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 microwatt 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.
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 our UV water purifier is installed. Pre-filtration 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. 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. It will be noted that at 56.6 F (12C) the lamp will be only 22% efficient in generating bactericidal radiation. Our systems use only high intensity ultraviolet lamps inside a high-transmission clear fused quartz jacket so that an optimum temperature of 104 F (40C) 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. It is recommended that spare ultraviolet lamps be kept on hand at all times, and that accurate records be kept of lamp use and replacement. The ultraviolet 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 ultraviolet liquid 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 make-up (absorption coefficient) of the liquid to be treated.
(c) Ultraviolet energy level required for microorganism destruction.
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 micro-organisms 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.
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 one of our technical staff.
APPLICATION DATA
185 NANOMETER ULTRAVIOLET LIQUID TREATMENT
GENERAL:
Organic carbon, which is measured as total organic carbon (TOC), is one of the many impurities present in water. This impurity is found in water as either particulate organic matter, such as debris of vegetable and animal origin, microorganisms, and oily material, or in the form of soluble organic matter, such as fatty acids, organic acids, and nitrogenous matter (proteins, peptides and amino acids, sugars, dissolved organic gases such as methane, and synthetic organic compounds).
It may be desirable to reduce or totally eliminate the TOC impurity in a water system. For example, in the manufacture of high density semiconductor devices the defect density correlates with the level of TOC in a pure water system. Or, in the situation where groundwater has been contaminated with synthetic organic compounds, it may be necessary to reduce the TOC level while the removal of other impurities in the water is unnecessary. For these water treatment requirements, the selection of a 185 nanometer (NM) wavelength ultraviolet purifier may be the optimal choice.
185 NM ULTRAVIOLET SYSYTEMS:
The following information relates to ultraviolet systems as manufactured by Double Star and Aqua Azul Corp.
The Historical purpose of UV disinfection systems are to produce germicidal ultraviolet light (energy) for the destruction of microorganisms such as bacteria, viruses, and molds. Ultraviolet light in the spectral region of 200-300 NM is extremely effective, with a wavelength of 265 NM being the most destructive to microorganisms. Low-pressure mercury vapor UV lamps generate the greatest energy at a wavelength of 254 NM, or very close to the optimum germicidal wavelength.
Ultraviolet lamps internally generate both 254 NM and 185 NM wavelengths UV light. A 254 NM lamp tube is constructed of quartz material with a metal oxide, which absorbs 99.9% of the 185 NM wavelengths. However, if the lamp tube material is pure fused quartz containing no metal oxide, the lamp generates both wavelengths.
The total UV energy output of the 185 NM (or TOC reduction) lamp consists of approximately 85% 254 NM UV energy, 7% 185 NM energy, and 8% other wavelengths, thus the 185 NM lamp retains 254 NM microbiological destruction capacity.
Although the 185 NM wavelength energy of the TOC reduction lamp is on 7% of its total energy output, the 185 NM wavelength energy has the unique capability to destroy organics by oxidation of the organic to carbon dioxide gas. The extent of the TOC reduction is dependent on UV purifier sizing (expressed as dosage level units in microwatt-seconds per centimeter squared). TOC reduction is also dependent on the type of organics present and other factors such as the temperature, turbidity, and other particulate matter and UV absorbing compounds in the liquid.
It should be noted that the 185 NM UV lamp produces ozone, but very little of the ozone enters the water stream. Most of the ozone is trapped and dissipates in the air space between the outside surface of the UV lamp and the inside surface of the quartz sleeve which shields the UV lamp from the water stream. The lamp socket boots must be constructed of ozone resistant material instead of the standard EPDM rubber.
APPLICATIONS:
The following are applications for TOC reduction UV purifiers:
TOC reduction in pure water streams - 185 NM UV purifiers can be sized to reduce TOC in a water stream from an inlet of 50 – 250 ppb to a product value of 30 ppb or less. Note that in this application the TOC reduction UV purifier should be placed prior to a demineralizer, since the reduction of non-ionized organics to ionized carbon dioxide will degrade pure water resistivity.
TOC “burst” reduction after regeneration of demineralizers - 185 NM UV purifiers can be installed on the recirculated rinse line of a freshly regenerated demineralizer to reduce the characteristic 24-hour TOC sluffage of 200 ppb to less than the inlet value when the demineralizer is placed in line.
TOC reduction in contaminated groundwater - 185 NM UV purifiers can be sized to reduce TOC in groundwater from an inlet of 5-10 ppm to a product value of 2 ppm or less.
Hydrogen peroxide additive - The addition of small quantities of hydrogen peroxide injected in conjunction with the UV purification equipment can enhance the 185 NM organic oxidation effect.
The sizing of TOC reduction UV equipment is dependent on many variables, thus no set flow rating can be stated. Experience has shown that TOC reduction equipment operated at normal capacities can reduce TOC levels by up to 50%. A UV purifier sized at 30% of its normal flow ratings can dramatically reduce TOC levels in a water stream. For TOC reduction of less than 10 ppb, the UV purifier must be specifically sized for individual water stream parameters. We at Double Star welcome the opportunity to discuss your TOC reduction requirements.
UV Information Ultraviolet Data
