Clear blue water

A water treatment system that zaps impurities using pulsed ultraviolet (PUV) light will make its debut in the UK early next year.

Its developers claim PUV technology allows the system, called LSi, to disinfect water more efficiently and without the risk of mercury contamination posed by other UV light sources.

LSi is the first commercial result of five years’ research by US water technology specialist LightStream, which hopes that industrial users, utilities and even local swimming pools will embrace PUV as a risk-free way of killing pathogens in everything from effluent waste to drinking water.

LightStream will deliver its first LSi units in January, and said early orders include several from UK industrial companies.

UV purification is already gaining ground over alternatives such as chlorination, currently the subject of growing anxiety over claims that harmful by-products are created by the process.

Standard UV disinfection is carried out using hundreds, or even thousands, of lamps. These operate continuously at temperatures of up to 600 degrees C, combining to deliver a massive dose of UV to the water.

The lamps use mercury vapour which is contained under high pressure inside them. If a burst occurs the mercury is released into the water, sparking a major contamination alert.

PUV emits light from a single lamp pulsing at 30Hz, with each pulse transmitting power at a peak rate of 6MW to the water rushing past it.

The PUV lamp contains inert xenon gas instead of mercury, is not under pressure and works at a low temperature.

LightStream vice-president Josh Lanier said that PUV has been used for disinfecting food packaging.

‘It occurred to us that PUV has unique applications for water, and that is why we saw the technology as very helpful,’ he said.

According to Lanier, PUV is also a far more exact method of providing UV light because it is a single source rather than many. ‘It can produce exactly the UV dose the controller wants it to. There’s no guessing or estimating involved, which inevitably happens when you’ve got a large number of lamps,’ he said.

The first generation of PUV systems will treat up to 160m3 of water per hour, and LightStream expects early users to be industrial companies that need to clean up waste water before it leaves their site.

Lanier said larger units able to handle up to 800m3 would begin appearing by the end of next year, propelling PUV towards the capacities required by major water utilities. He hopes PUV systems will eventually be in use ‘everywhere, right down to the local pool’.

PUV’s disinfectant qualities may apply to more than just water. Lanier said R&D is underway into possible use of the technology for air purification, although this is still at an early stage.

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