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News Release from: Berson UV-techniek | Subject: Medium pressure UV
Edited by the Processingtalk Editorial
Team on 03 April 2003
Bugs killed by medium pressure UV stay
dead!
Bacteria and many other micro-organisms contain enzymes that can repair UV-damaged DNA, a process known as 're-activation': research shows this does not occur with medium pressure UV disinfection
Some of the enzymes need visible light to perform the repairs ('photo-reactivation'), while others can do so without light (known as 'dark repair') Photo-reactivation is generally quicker than dark repair, but both of these phenomena pose obvious problems for operators of UV disinfection plant
This article was originally published on Processingtalk on 17 Jun 2003 at 8.00am (UK)
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Medium pressure UV for Wastewater Treatment plant
A paper presented at the International UV Association describing the importance of an accurate dose when designing UV disinfection for wastewater treatment, received a very positive response
Recent research on the process, however, has produced interesting new developments.
When comparing photo-reactivation of E.coli DNA after exposure to UV wavelengths emitted by low and medium pressure lamps, independent researchers have shown that the DNA underwent extensive repair following exposure to UV from low pressure UV lamps, but virtually none following exposure to UV from medium pressure lamps.
The researchers concluded that it was the broad UV output of medium pressure lamps, between 185-400nm, that has this desirable effect.
By emitting UV over a wide range of the UV spectrum, medium pressure lamps appear to damage other intercellular molecules, such as enzymes, in addition to DNA.
It is this damage which seems to permanently inactivate the cell DNA repair mechanisms.
Low pressure UV lamps, on the other hand, produce only a single UV peak at 254nm which only affects DNA.
These preliminary results have serious consequences for operators of low pressure UV disinfection systems.
If, following exposure to low pressure UV lamps, micro-organisms are capable of recovering, operators need to seriously consider upgrading to medium pressure technology.
By providing permanent microbial deactivation, medium pressure UV offers peace of mind, something low pressure UV does not do.
Applications affected by these findings are wide-ranging and include municipal drinking water, bottled water, rinse or wash water in the food industries, wastewater and effluent, fisheries and swimming pools.
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