UV-teknik
Termen tryck som används för att beskriva UV-systemen nedan hänvisar till typen av kvicksilverlampa som används i UV-systemet och trycket på gasen inuti lampan, inte trycket i vattnet som behandlas. Medium-lampor har ett kontinuerligt uteffektspektrum som sträcker sig från 200 till 400 nm, där spektrumet är unikt för varje tillverkare. Lågtryckslampor- producerar två smala UV-utgångslinjer, en vid 185 nm och en vid 254 nm. 185 nm-linjen producerar ozon i luft och filtreras bort för många applikationer genom att välja rätt kvarts som används för att tillverka lampan.
Medium pressure. Medium-pressure systems have been used primarily for water disinfection for many years. These systems typically have a stainless steel chamber that fits in-line with the plumbing and has the lamp located perpendicular to the flow. This makes for a compact system which can be retrofitted to existing plumbing. The controls and ballast are typically housed in a cabinet nearby. The technology does, however, have some drawbacks when compared with low-pressure units. Medium-pressure systems use more energy, have a shorter lamp life and operate at a much higher lamp surface temperature (up to 1,600 degree /2,912 degree F ) than a comparable low-pressure system.
Low pressure – conventional. The most recognizable UV systems in use today are systems that utilize low-pressure mercury lamps. These units are typically constructed in a stainless steel pressure vessel with the lamps installed parallel to the water flow. Chamber diameter, the number of lamps and the lamp length determine the capacity of the equipment. With minor improvements, this design has been in place for over 50 years. A major drawback to this design (as well as the medium pressure systems discussed above) is the fact that stainless steel absorbs about 80 percent of the UV light that impinges on its surface. This greatly increases the number of lamps and energy consumption required to achieve the desired level of UV treatment, which has added to the market perception that UV treatment carries a high operating cost.
Earlier attempts to reduce operating costs. There have been a number of attempts to improve the performance of UV systems by replacing the stainless steel-walled chambers with designs that overcome the inherent lossy (dissipation of electrical energy) nature of conventional chambers. A number of designs use an external reflector made of aluminum. Aluminum has a much higher level of reflectivity of UV (generally 80 to 90 percent or more) than stainless steel. In one such design, the flow tube is in the center, with lamps and parabolic reflectors surrounding the flow. This design provides an improved reflection of the UV, however, most of the UV is outside the flow of water, limiting the overall efficiency. Another drawback is that the systems can get quite large for higher flows.
Andra system använder egenskapen att ljus som faller in på en yta i en mycket ytlig vinkel reflekteras nästan helt. Dessa system har lamporna i ena eller båda ändarna av ett långt flödesrör, så att det mesta av UV-ljuset som når flödesrörets yta reflekteras tillbaka i vattnet. Att introducera ljuset effektivt i det långa flödesröret från dess ände är en av utmaningarna som begränsar effektiviteten hos denna kammardesign.
