Ultra Violet Filtration

Ultra Violet filtration is the use of Ultra violet rays to in-activate bacteria and hence ‘purify’ drinking  water for consumption.The use of Ultra Violet rays or UV is a natural phenomenon. The sun emits UV rays to act on water in rivers and lakes however in modern society our water is transported in pipe networks and so by mimicking the sun rays inside the pipe-work we can cleanse the water. Many manufacturers utilise a UV lamp in a quartz sleeve for protection and enclose it in a stainless steel chamber or reactor. These UV systems work very well and are mainly used as a ‘point of use’ treatment for water. It is important that if you purchase one and install it in your house or office that you disinfect the pipe-work so that the action of the UV lamp is effective and that the water is not re-contaminated after the lamp with bacteria that might be present in old pipework or ‘dead leg’ pipework. When disinfecting ensure you run all the taps in the house. More information on how the product is made and used can be found at www.tapandwaterfilters.com or follow this link to the UVEO product manufactured by Comap www.tapandwaterfilters.com/product/uveo-uv-lamp/

Much scientific research has been undertaken in recent years to show the benefits of this technology. The key issues with UV is the dose. The dose is dependent on how long the water is present in the chamber of UV rays and how much impurities are contained in the water. The strength of the lamp and number of lamps is also a factor. If is necessary to install a Pre-filter to ensure solid particles are not present in the UV chamber. High levels of iron and lime in the water can also adhere to the sleeve making the lamp ineffective. It is worth changing the lamp each year as most manufacturers only guarantee 9000 working hours on a lamp. The output fades with time effecting the dose.

Many different viruses and bacteria can be inactivated with UV lamps, E,Coli and larger protozoa such as Giardia can be inactivated with relatively low dose levels however Cryptosporidium may require higher doses. A good rule of thumb is to purchase and install a UV unit that has a minimum of 40mj/cm2. Comap wti and Trojan UV are two such companies that supply this standard of product. More information is available at

http://water.epa.gov/lawsregs/rulesregs/sdwa/mdbp/upload/2001_01_12_mdbp_alter_chapt_8.pdf

This report is by the US EPA and covers all the Technical aspects of Ultra Violet Radiation use.

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