UV Technology

What is ultraviolet radiation?

Ultraviolet, or UV light is invisible electromagnetic radiation covering the wavelengths bordering x-ray and visible light, within the 10-400 nm range. UV has become a widely accepted method of disinfection in various applications and media as it alters the DNA of micro-organisms, effectively eliminating them.

There are four UV categories:

  • Vacuum UV – wavelengths between 10-100 nm
  • UVC – wavelengths between 100 and 280 nm
  • UVB – wavelengths between 280 and 315 nm
  • UVA – wavelengths between 315 and 400 nm

UV as a disinfectant

The fact that UV is a powerful disinfectant has been known for centuries and today the technology is commonly used in a wide array of applications. When micro-organisms are exposed to UV within certain ranges inactivation occurs as the absorbed UV terminally damage their DNA inhibiting the reproductive ability.

UV provides an in-situ germicidal effect, only affecting the surface or media with which the rays are in direct contact unlike chemical agents. It does not produce any disinfection-by-products which are commonly formed when using chlorine, chlorine dioxide and some other chemical agents, it has no smell and does not affect the taste or color of liquids. Also, unlike chemical agents UV is not affected by the temperature or pH.

Parameters to consider for the optimization of micro-organism inactivation are primarily dosage and wavelength, (see table 1 for dosage requirements of specific micro-organisms). The absorbance of different wavelengths differs between organisms which is of importance when choosing UV source.

UV lamps

There are multiple types of UV lamps, the most common lamps are divided into two categories: low- and medium pressure lamps.

Low pressure lamps

These lamps emit UV at a set wavelength, 254 nm and are thus monochromatic. In relation to medium pressure lamps they have lower running temperatures, operate more efficiently, and have a longer lifetime. The single wavelength is oftentimes enough for disinfection of surfaces and airborne organisms, and the parameters regulating the dosage can be adjusted to necessary levels.

Medium pressure lamps

These are polychromatic lamps, meaning they emit a range of wavelengths within the 200-400 nm spectra, the actual span varies between lamps. Compared to low pressure lamps the wider span of emitted wavelengths provides more efficient inactivation of micro-organisms whose peak absorbance is not 254 nm. It should however be noted that medium pressure lamps consume more energy, have higher running temperatures and shorter lifetime.

Designing the UV system

Reactor design, such as its geometry, the selection and arrangement of lamps and quartz sleeves within the reactor, volumetric flows, the dimensioning of a ballast as well as auxiliary equipment are all imperative parts of the design in order to deliver a well-working solution.

In order to design a system, parameters such as flow rates, transmittance, micro-organisms to disinfect and to what grade, maintenance need, OPEX and CAPEX, environmental aspects and target media are some of the things that should be taken into consideration.

ConsiderationLow PressureMedium pressure
Process FlowBetter for intermittent flowNeeds constant flow
Water QualityNoYes
Lamp LifeYesNo
Energy UsageYes No
FootprintNo Yes
Fluid TemperatureNoYes

UV and Ozone

Ozone is generated naturally in two major ways: through corona discharges during thunderstorms and continuously through photolysis of the oxygen molecule in the upper atmosphere. Thus, the ozone layer is generated with UV-rays from the sun which are absorbed by oxygen molecules, providing protection against the harmful radiation.

When producing ozone artificially with the use of UV lamps, air or oxygen is exposed to UV radiation with a 185 nm wavelength. Paradoxically, UV can also be used to destroy ozone, this is achieved when ozone is exposed to 254 nm radiation.

Advanced Oxidation Process – UV and Ozone combined

The synergies of a well-designed UV and ozone treatment system renders hydroxyl radicals, an extremely powerful oxidant with more than double the oxidation potential of chlorine. This is the best-known type of Advanced Oxidation Process, AOP – suitable for the most demanding sanitation applications.

This can be done in two ways, either by using bichromatic lamps, producing and destroying ozone simultaneously in the presence of water or by introducing a source of ozone before a UV lamp within the right wavelength range.

Product parameters – radiance, dose, etc.

Ultraviolet dosage required for 99,99% reduction of organisms in µWs/cm2 at 254 nanometer
Bacillus anthracis – Anthrax8,700
Bacillus anthracis spores – Anthrax spores46,200
Bacillus magaterium sp. (spores)5,200
Bacillus magaterium sp. (veg.)2,500
Bacillus paratyphusus6,100
Bacillus subtilis spores22,000
Bacillus subtilis11,000
Clostridium tetani22,000
Corynebacterium diphteriae6,510
Ebertelia typhosa4,100
Escherichia coli6,600
Leptospira canicola – infectious Jaundice 6,000
Micrococcus candidus12,300
Micrococcus sphaeroides15,400
Mycobacterium tuberculosis10,000
Neisseria catarrhalis8,500
Phytomonas tumefaciens8,000
Proteus vulgaris6,600
Pseudomonas aeruginosa10,500
Pseudomonas fluorescens6,600
Salmonella entertidis7,600
Salmonella paratyphi – Enteric fever6,100
Salmonella typhosa – Typhoid fever4,100
Salmonella typhimurium15,200
Sarcina lutea26,400
Serratia marcescens6,160
Shigella dysenteriae – Dysentery4,200
Shigella flexneri – Dysentery3,400
Shigella paradysenteriae3,400
Spirillum rubrum6,160
Staphylococcus albus5,720
Staphylococcus aureus6,600
Staphylococcus hemolyticus5,500
Staphylococcus lactis8,800
Streptococcus viridans3,800
Vibrio comma – Cholera6,500
Mold spores
Aspergillius flavus99,000
Aspergillius glaucus88,000
Aspergillius niger330,000
Mucor racemosus A35,200
Mucor racemosus B35,200
Oospora lactis11,000
Penicillium expansum 22,000
Penicillium roqueforti26,400
Penicillium digitarium88,000
Rhisopus nigricans220,000
Chlorella Vulgaris22,000
Nematode Eggs92,000
Bacteriopfage – E. Coli6,600
Infectious Hepatitis8,000
Poliovirus – Poliomyelitis6,600
Tobacco mosaic440,000
Bakers yeast8,800
Brewers yeast6,600
Common yeast cake13,200
Saccharomyces carevisiae13,200
Saccharomyces ellipsoideus13,200
Saccharomyces spores17,600


  • Air disinfection
  • Water disinfection and wastewater treatment
  • Ultrapurification of water
  • Surface disinfection
  • Equipment disinfection
  • Food & beverage disinfection