Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays.
Ultraviolet radiation covers the wavelength range from 100 to 380 nanometers. The disinfection process uses wavelengths in the UVC range from 240 to 280 nanometers, while the oxidation process uses the wavelengths down into the VUV range below 200 nanometers.
A 185 nm lamp is also referred to as an Ozone lamp. This lamp produces 185 nm in addition to the 254 nm. These lamps are used for applications like TOC reduction and other disinfection projects that require the oxidizing properties of the 185 nm lamp.
"VH" germicidal lamps generate energy at 185nm in addition to the 253.7nm line. This UV emission produces abundant amounts of ozone in air. Ozone is an extremely active oxidizer, and destroys microorganisms on contact. Ozone also acts as a deodorizer. One of ozone's advantages is that it can be carried by air into places that the UV radiation cannot reach directly. When using the 185 nm lamps, ensure that the room is well ventilated.
185 nm photons are absorbed by ambient air. Oxygen molecules (O²) are dissociated into two oxygen atoms (O+O), forming ozone (O³) by collision with an oxygen molecule. Ozone is chemically very aggressive and is used as a strong oxidizer in so called Advanced Oxidation Processes (AOP).
High energy photons emitted by low pressure mercury discharge lamps are able to decompose many chemicals. By means of direct photolysis organic bonds are broken as a result of photon absorption. Photons with a wavelength of 254 nm can split such bonds like O-H, C-H, C-C and C-O. 185 nm photons break even higher energetic bonds like C=C and O-O. The energy equivalent of the VUV radiation (185 nm) is, however, not high enough for the strong C=O bond.
UV LIGHT - SPECIALTY APPLICATIONS
UV LIGHT - UV Destruction of sulfate reducing bacteria (SRB)
In well drilling, bore drilling and fracking applications, Sulfate Reducing Bacteria (SRB), can become a problem. SRB (sulfate reducing bacteria) is introduced into the water supply while drilling, boring or fracking. The water that is used to drill the holes interacts with the bacteria in the gas, the bacteria uses water as energy and then multiplies. The water is re-used and re-circulated an as it travels through the drilling machine the bacteria eats the metal.
In addition to the introduction of SRB, the SRB will continue to cause problems with the wastewater discharge. Glasco UV uses UV disinfection for SRB. Systems are designed using a higher dosage than drinking water. A dosage of > 80 mJ is applied to reduce the SRB.
Ultraviolet disinfection technology uses UV light to target and disable disease causing microorganisms (pathogens). Over 100 years ago, scientists discovered that if you exposed pathogens to UV light, their reproduction was limited. The UV light used, resided in the UVC range of the light spectrum. Specifically, they discovered that light in the 254 nanometer (nm) range was the most effective.
When water pathogens are exposed to UV light, their cells become damaged and this damage inhibits reproduction. The UV light, produced by a special lamp damages the cell’s DNA and RNA and once damaged, they are unable to replicate. This physical process renders them harmless. The amount of damage is a result of the intensity of the UVC output multiplied by the time the water is exposed to the light. The applied dosasge is commonly referred to as microwatts and is often expressed as mJ/cm2. Doses of 40,000 microwatts (40 mJ) are accepted for water disinfection.