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CSIR-CEERI Mercury-Free Plasma UV- Lamp, makes water purifiers free from deadly Mercury

21 Aug 2017

Water is the elixir of life. Safe drinking water is the basic need of all human beings but in many developing countries, generally, water that is available is impure and contaminated with bacteria, viruses, salts and various organic compounds. This impure water produces many waterborne diseases, which kill over 3 million people worldwide and seriously sicken hundreds of million each year according to WHO estimates. Existing technologies for water purification include mechanical filtration, reverse osmosis (RO), distillation, Ultraviolet (UV) disinfection, chlorination and Ozonation.

Each of these technologies suffers from various limitations.  Out of the existing water purification technologies UV disinfection has been known to be the most efficient method. It does not cause any side effects on health and also any chemical by products if proper dose is used.  The sterilization effects of UV radiation are well-known, and low-pressure mercury vapor lamps are being used for water purification at domestic and industrial levels. These are produced billions in number per year worldwide. The low pressure UV lamps contain ~5-50 mg of mercury per lamp whereas low pressure high output lamps contain ~26-150 mg of mercury per lamp, and medium pressure lamps contain ~200-400 mg of mercury per lamp. As a consequence, at the end of the lamp life a considerable amount of “undesirable” toxic waste is generated. Besides this the major problem with the currently available mercury based UV lamps is that they can sometime lead to catastrophic explosion and the toxic mercury mixing with water can cause serious health problems. There are many other problems with the present mercury based UV-lamp technology including start-up time, filament failure, sleeve breakage, dimensional restrictions and non- repairability. The Principle of operation used is the Dielectric barrier based electrical gas discharge.

CSIR-CEERI scientists have very recently developed a mercury-free plasma UV lamp with a novel structural design and an optimized gas mixture that produces strong spectral bands peaking at wavelengths 253 nm and 172 nm along with a weak band peaking at wavelength 265 nm, which are highly useful for water sterilization. This invention alleviates most of the problems of mercury lamps by virtue of its unique design and the composition of active discharge elements. As a result it is able to produce the desired VUV/UV wavelengths for the deactivation of bacteria and viruses most efficiently – without the use of mercury.

The developed mercury-free plasma UV lamp technology can replace UV light sources used in household water purifier systems, storage/sewage/waste water treatment plants, municipality water treatment plants. Further, application specific systems can be developed for sterilization of food, medical equipment, surfaces, ill skin conditions, air-conditioners and air fresheners for hospitals, titanium coated toilet sterilization in trains, water supply in trains and buses, portable water purifiers for soldiers, outdoorsmen, farmers, etc. It can capture significant market of UV disinfection.

The use of UV light for disinfection has been practiced for more than 30 years, but only in the last decade has the technology expanded from a niche market to hold a significant share of the disinfection equipment market.

Though access to safe drinking water is still a distant dream for millions in the developing world, CSIR is steadily developing technologies for providing clean drinking water for the millions who are still grappling with water woes.

{Feature has been uploaded by CSIR (Unit for Science Dissemination), Ministry of Science & Technology, New Delhi}.

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