Ultraviolet: General Information

Ultraviolet radiation occupies the wavelengths between 100 nm and 400 nm in the electromagnetic spectrum, between visible light and X-rays.
It is subdivided into four bands: UV-A, UV-B, UV-C and V-UV.

UV-C provides the germicidal action associated with UV disinfection. The germicidal range is between 200 and 300 nm; the germicidal maximum occurs at 265 nm.

There are mainly two types of ultraviolet lamps – medium pressure and low pressure. The medium-pressure lamps cover the whole spectrum of ultraviolet light, from 100 up to 400 nm, and the low-pressure lamps emit radiation at 254 nm.

How UV rays work with microorganisms

Oxidation reactions occur at the disinfection frequencies with both low- and medium-pressure lamps due to radicals formed by the absorption of UV by chlorine. However, importantly, medium-pressure lamps promote additional oxidation, mostly due to V-UV below 230 nm, producing H2O photo-dissociation and direct photo-degredation reactions.

Photons of UV radiation are absorbed by adjacent thymine molecules in the DNA of the target organism, breaking the hydrogen bond with adenine and resulting in the formation of a dimer. This interferes with DNA replication and cell reproduction.
RNA and proteins exposed to UV radiation also take part in inhibition reactions within the cell structure.

With a sufficiently high UV dose, the amount of genetic disruption is such that the organism can no longer function and subsequently dies.

The degree of microbiological destruction depends mainly on two factors, namely, the contact time that the water is inside the reactor, and the intensity. The combination of these two factors is called the UV dose and is normally expressed in milijules/cm2.

All Oxicom equipment is designed so that at the end of the lamp’s useful life, the defined dose is guaranteed. That is to say, 60 mj/cm2 for the medium-pressure equipment and 30 mj/cm2 for the low-pressure equipment.