The advantages of using UV light to kill aquatic infectious bacteria in wastewater treatment projects have been widely recognized. Sterilization is the main use of UV technology in the water and wastewater field. This skill is also used in many other ways, including ozone elimination, total organic carbon (TOC) reduction, liquid sugar disinfection, chlorine degradation, surface and air, and cooling tower disinfection. So what is the role of ultraviolet rays in sewage treatment?
1.Sterilization
Ultraviolet sterilization mainly uses ultraviolet light with a wavelength of 254 nanometers. Ultraviolet light of this wavelength, even under a small amount of ultraviolet projection dose, can damage the life center of a cell - DNA, thus preventing cell regeneration, and the loss of regeneration ability makes bacteria harmless, thereby achieving the effect of sterilization. Like all other UV applications, the size of this system depends on the intensity of the UV light (the intensity and power of the irradiator) and the touch time (how long the water, liquid, or air is exposed to the UV light).
2.Liquid sugar for disinfection
Liquid sugar is used in large quantities by most food and beverage manufacturers. Because sugar is a food that is easily used by bacteria, it is easy for bacteria to thrive. Plus, liquid sugar is opaque, so thorough sterilization is difficult. Ultraviolet light with a wavelength of 254 nanometers can be used to sterilize liquid sugar products. To compensate for the energy loss due to the viscosity and color formation of the liquid, many UV emitters need to be tightly packed into so-called "thin film" reactors. This tight combination of emitters delivers the very high doses of UV radiation required to effectively sterilize the liquid sugar. The energy output of its UV light is approximately 7 to 10 times that of conventional disinfection systems.
3.Eliminate ozone
In the industrial production of wastewater treatment engineering, ozone is often used to disinfect and purify water bodies. However, because ozone has a very strong oxidizing ability, the remaining ozone in the water may have an impact on the next process if it is not removed. Therefore, generally, the ozone-treated water must be left in the water before entering the main process flow. Ultraviolet light with a wavelength of 254 nanometers is very effective at destroying the remaining ozone, which can split it into oxygen. Although different systems require different scales, in general, a typical ozone elimination system requires about three times the amount of UV radiation that a traditional sterilization system requires.
4. Decrease in total organic carbon
In many high-tech and laboratory equipment, organic matter can hinder the production of high-purity water. There are many ways to remove organic matter from water, the more common methods include the use of activated carbon and reverse osmosis. Shorter wavelength UV (185 nm) is also effective in reducing total organic carbon (it is worth mentioning that these emitters also emit 254 nm UV, so they can be sterilized together). Ultraviolet rays with shorter wavelengths have more energy and are therefore able to break down organic matter. Although the reaction process of ultraviolet oxidation of organic matter is very complicated, its main principle is to oxidize organic matter into water and carbon dioxide by generating free hydrogen and oxygen with strong oxidation ability. Like ozone scavenging systems, this organic carbon-degrading UV system produces three to four times the UV radiation of conventional disinfection systems.
5.Degradation of residual chlorine
In municipal water treatment and water supply systems, chlorination is necessary. However, in the industrial production process of wastewater treatment projects, in order to avoid adverse effects on products, the removal of residual chlorine in water is often a necessary pretreatment. The fundamental method to eliminate residual chlorine is activated carbon bed and chemical treatment. The disadvantage of activated carbon treatment is that it requires constant regeneration and often encounters problems with bacterial growth. Both 185 nm and 254 nm wavelengths of UV light have been shown to effectively damage the chemical bonds of residual chlorine and chloramine. Although it requires a huge amount of UV energy to be effective, it has the advantage that this method does not require any drugs to be added to the water, does not require storage chemicals, is simple to repair, and also has the effect of sterilizing and removing organics.
