What is Ultra Violet Disinfection?
Ultra Violet disinfection (commonly abbreviated to U.V) is a well established, simple and safe technology, used for the purpose of disinfecting water without the use of chemicals. UV disinfection effectively renders Legionella, Salmonella, Ecoli and most other waterborne bacteria harmless, with no undesirable by-products to dispose of. UV disinfection works with a UV light penetrating the cell of microorganisms living in the water, halting their reproduction and rendering them harmless. The outer wall of bacteria and viruses differ in thickness. The thickness of their cell wall determines the amount of UV light exposure required to prevent their reproduction. The intensity of the light is measured in Joules per metre squared (J/m2 ). Drinking water applications require a dose of 400 J/m2. Rain water harvesting for grey water applications typically require a lesser dose.
UV treatment of water is an extremely effective low cost solution that kills most waterborne viruses and bacteria. UV disinfection does not result in any negative changes in the taste or odour of the treated water, so it is ideal for drinking water supplies in the private, community and business sectors.
How the system works
The water to be treated flows through the stainless steel radiation chamber and past the UV lamps. The UV lamps generate UVC light at a wave length of 254nm, which is particularly effective for the disinfection of water and destroys the DNA within the bacteria cells and viruses. The UV system is accurately controlled by modern electronics, whilst the UVC sensor (where fitted) monitors lamp ageing, the radiation intensity, the UV transmission of the water to be treated and any deposits formed on the quartz sleeve. Water passing through the system will be disinfected, but there is no residual effect. Due consideration must be paid to the overall design and installation of any system to ensure that contamination does not occur downstream of the unit. Two sample points should be provided prior to and after the unit for periodic testing.
The most important aspect when deciding on the choice or size of a UV system is determining the UV transmission of the water to be treated. This will differ depending on the maximum flow rate, type and origin of the water. Performance will be compromised if the maximum flow rate is exceeded. Where local site conditions are unpredictable, then additional control systems must be installed.
The quality and type of water source may make it necessary to pre-treat the source water before disinfection. Our technical team are available to offer free advice on a full range of water pretreatment including: sediment filtration, water softening and iron removal. A suitable sediment filter should always be installed prior to the UV unit to protect it from particulate matter and shadowing. Over time, the output of the UV lamp reduces with age. This means that typically, the UV lamp will need replacing on an annual basis. For most models, a UV intensity monitor is available separately to accurately monitor lamp output. This enables optimum performance to be maintained without unnecessary lamp replacement.
Note: It is recommended that isolating valves are fitted to either side of the unit and sufficient clearance should be left on at least one side of the unit to withdraw the lamp and quartz sleeve for maintenance purposes.