Special and highly efficient low-pressure lamps with a strong radiation peak at 254 nm (nanometres) are used for UVC water disinfection. This is not to be confused with the turquoise-blue light component often shown, which these emitters also emit. The wavelength of 254 nm is very close to the absorption maximum of biological cells, which is around 260 nm. This radiation is absorbed in the cell nucleus of the organisms - more precisely in the DNA or RNA - resulting in a lasting photochemical change, so that the genetic material of the exposed cells is damaged. After sufficient exposure, the microbes are no longer able to repair the photochemical changes - this is referred to as dimerisation or dimer formation - cell division stops and they ultimately die.

UVC water sterilisation - if it can be used - is practically always the most cost-effective disinfection method in direct comparison. It requires little energy, no additives are added to the water, the taste, consistency or odour of the medium is not altered and ultimately no undesirable decomposition products are produced. As nothing is added to the water (UVC disinfection is a purely physical method), there is also no risk of corrosion or decomposition of components in a pipework system.

Yes, of course. However, handling UVC systems is subject to the same safety regulations as handling a kitchen knife. A kitchen knife is ideal for chopping onions, but you can also injure yourself if you handle it incorrectly. It is very similar with UVC systems: UVC rays are absorbed by exposed cells and damage them. For this reason, people should not look into a luminous UVC source without protection! However, as UVC rays are very high-energy and short-wave, they do not penetrate solid materials, solid clothing or normal glass panes or acrylic glass panels. Even a large pair of safety goggles reliably protects the eyes.

The areas of application for UVC water sterilisation are very diverse. Intuitively, one thinks of municipal and/or private drinking water treatment. However, the range of applications for UVC systems is much wider! In all areas in which water is used for cooling, cleaning or humidification or in areas in which water is circulated - e.g. ornamental fountains - there is a need to disinfect water. This is because biology is omnipresent and multiplies naturally. However, this poses a considerable problem, especially for recirculated media, which is why disinfection measures must be taken. Whether it is simply to protect the consumer, to ensure product hygiene and shelf life or to ensure the economic operation of a facility and prevent sludge, algae and mould growth. In all these areas of application, UVC disinfection systems - whether as photoreactors or in the form of immersion lamps - are a reliable, environmentally friendly, very cost-effective and highly effective device.

Water is very often recirculated, especially in industrial applications. Whether in the form of cooling or washing processes, water is always recirculated and reused. However, such recirculation processes inevitably lead to soiling and contamination of the medium, meaning that it has to be treated. UVC technology ensures effective and reliable disinfection to prevent the unwanted growth of germs of any kind. Whether pathogens such as bacteria, viruses or protozoa or even mould spores carried in the water, UVC devices ensure very energy-efficient disinfection without chemically changing the composition of the water. In cooling systems in particular, it is important that the chemical consistency of the water is not altered. This is easily possible with UVC systems and thus contributes to the resource-saving use of the precious element of water.

Basically, almost any liquid medium can be treated with UVC, even oils and emulsions. However, handling such liquids requires considerable expertise, as UVC radiation sources consist of a quartz glass tube and UVC rays are absorbed very quickly. Think, figuratively speaking, of your own sunglasses and the mishap if you touch the glass with oily or creamed fingers. The same applies to the quartz tube of a UVC emitter. If this is wetted by an oily emulsion, the measurable UVC yield of the emitter drops drastically, as oils and fats have a maximum absorption power at a wavelength of 254 nm. This also applies to other dissolved and undissolved additives in a liquid medium, whereby ‘the medium is clear’ is of no significance here. Nevertheless, in technical applications, aqueous media with additives can be treated with UVC in the same way as UVC units are frequently used in the food industry to disinfect brines, whey and permeates.

In principle, both processes are justified and should not be seen as an ‘either/or’ relationship. UVC disinfection is an active process that inactivates and thus kills microorganisms in the water; a filter, on the other hand, is a passive element, a collector whose degree of separation depends on the pore density and thus particle size. The finer the pore density, the higher the degree of separation, but the greater the pressure loss. Even microorganisms can be retained with appropriate filters, although the problem here is that the filters quickly become clogged. There are no such problems with UVC treatment, as there is no pressure loss, but also no retention of unwanted suspended matter or particles. There are two different approaches to treating water.

This can be answered very briefly and succinctly with NO. For marketing reasons, UVC LEDs are often advertised today with the characteristics of LEDs from the lighting industry, but this is misleading and usually false. The most powerful high-power LEDs today initially generate around 100 mW_uvc @ 350 mA under laboratory conditions and have an energy efficiency of approx. 5 %. In comparison, a conventional UVC low-pressure lamp achieves 18,000 mW_uvc @ 225 mA under the same conditions and has an energy efficiency of 40 %.

The reason for the low yield is the semiconductor material aluminium gallium nitride (AlGaN), which is required for very high frequencies, a typical reverse voltage of ~7 V for LEDs and the high heat development of up to 90° C. The mandatory cooling of such high-power LEDs prevents the formation of high-density LED arrays; homogeneous irradiation of high-intensity surfaces is therefore not possible. In addition, the higher the temperature of an LED, the shorter the expected service life/useful life. Very short-wave LEDs with 260 nm, for example, exhibit a power loss of up to 50 % after just 300 operating hours. In other words: the shorter the wavelength, the worse the energy balance, performance and service life!

Considering the poor recyclability of LEDs, which use materials such as antimony, arsenic, chromium, copper, gallium, gold, indium, iron, lead, nickel, phosphorus, silver and zinc, as well as the environmentally harmful mining of the rare earths required for their manufacture, such as europium (Eu), terbium (Tb) and yttrium (Y), the ecological advantages of LEDs, which are so readily claimed, quickly melt away.

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