UV water treatment's knowledge
1.The sensitivity of various pathogenic microorganisms in water to UV varies greatly, the order of uv water treatment which is: virus < bacteria < Cryptosporidium < Giardia.
2.Photoreactivation
UV achieves disinfection by destroying the genetic material nucleic acid in microorganisms, the most common of which are cyclobutane pyrimidine dimers and pyrimidine-pyrimidinone light products. But the UV damage of microorganism after UV irradiation can be reversed by visible light, which is called photoreactivation phenomenon.
UV dose and irradiation intensity can affect the photoreactivation rate. In practical applications, a large dose and intensity should be taken as much as possible to reduce the negative effects of photoreactivation.
3. Combination technology of UV and chemical disinfection
Chemical disinfection (e.g. chlorine, ozone, etc.) Because of the presence of residual disinfectant in the water body, the water body can remain sterilized for a long time. UV disinfection is a physical disinfection technology, similar to heating disinfection, if the source of pollution after disinfection, will be contaminated again. The solution to such problems depends on a combination of UV and chemical disinfection.
Although UV has a high rate of inactivation of various pathogenic microorganisms, especially anti-chlorine pathogenic bacteria such as Giardia and Cryptosporidium, UV disinfection technology does not have the ability of continuous disinfection. To solve this problem, a combination of UV and other disinfectants is usually used. The disinfectants are chlorine, chloramine and chlorine dioxide.
4.Advanced oxidation disinfection technology based on UV
In recent years, researchers have gradually begun to use advanced oxidation technologies based on UV for disinfection, such as UV-O3, UV-TiO2 and UV-H2O2. the main mechanism is to induce hydroxyl radicals with strong oxidation ability under uv irradiation in the 253.7 nm band. it cannot only kill bacteria, but also completely mineralize organic matter in water. it is a relatively new uv disinfection method.
5.Prospects
At present, the research on the application of UV technology in water supply treatment is very active at home and abroad, and there are many application examples.
Disinfection of drinking water:
At present, most of the simple evaluation of uv disinfection effect is based on the total number of escherichia coli and bacteria, especially the inactivation effect and influencing factors of cryptosporidium, giardia and algae should be discussed in the future; further in-depth research on the effect of uv and other disinfectants, especially the influence mechanism of various factors in the combined technology, so as to provide the basis for practical application of engineering.
Algae control:
uv has a good inactivation effect for algae, the test has shown that the technology can be used as a pretreatment to control high algae pollution of raw water. the inactivated dose of uv on different algae and the control of algae toxin and disinfection by-products in pretreatment should be systematically studied in the future; on the other hand, the study of uv pretreatment combined with other processes should be strengthened.
