Water Disinfection With Ultraviolet (UV) Light
Water disinfection with ultraviolet UV technology is achieved by using UV-C rays with a wavelength of 254 nm. UV Lamp rays damage the DNA of bacteria, viruses and other microorganisms through “photooxidation”. All cell activities, including reproduction, of bacteria, viruses, etc., whose DNA is destroyed, cease and cell death occurs. With this method, disinfection is achieved.
Water disinfection, found in water and can multiply rapidly; It can be defined as the destruction of all pathogenic microorganisms (bacteria, spores, parasites) or the termination of their reproduction opportunities, including viruses, which pose dangers for humans, animals and even plant health.
With the Ultraviolet (UV) Device, water disinfection is achieved by using 254 nm wavelength UV-C rays. When UV-C rays come into contact with microorganisms, they damage their DNA through “photooxidation”. All cell activities, including reproduction, of a living thing whose DNA is destroyed, cease and cell death occurs.
Devices developed for ultraviolet (UV) water disinfection are equipped with a special Ultraviolet Lamp that produces UV rays with a wavelength of 254 nm. While the water to be disinfected flows through this device, it is exposed to intense UV rays and the microorganisms in the water become ineffective. The physical, chemical and microbiological properties of the water to be disinfected and the instantaneous water flow rate are the most important parameters in the selection of the Ultraviolet Device.
A properly designed and suitable Ultraviolet Device can provide safe water disinfection without creating undesirable side effects if the mounting point is determined appropriately. The device must have measurement/control equipment that warns the user on time. The necessary maintenance should be done for the continuity of the efficiency, and the Ultraviolet Lamp, which has completed its life, should be renewed on time.
MEASUREMENT OF DISINFECTION POWER: “UV DOSE”
We explained how microorganisms are inactivated by ultraviolet rays and that this technology can only be applied with the help of specially designed ultraviolet devices. However, at the point of practical application, the disinfection power of ultraviolet devices depending on the water flow should be given as a numerical value. This numerical value is called “UV dose” and its measure is “Joule/m2”.
THE UV DOSAGE THAT A UV DEVICE CAN SUBMIT TO WATER LOWERS AS THE WATER FLOW RISES AND RISES AS IT DECREASES.
For the correct selection of the ultraviolet UV device, it is necessary to know with which UV dose the targeted microorganism will be inactivated. The removal rates of various microorganisms depending on the UV dose are given in Table-1 below. For example, it can be seen from the table that the selected UV device should give at least 300 J/m2 UV dose to the water according to the water quality and peak flow rate at the point of use to provide 99.99% removal against the “Hepatitis A” virus. As additional information, studies have shown that it is possible to remove 99.99% of almost all pathogenic microorganisms with a UV dose of 400 J/m2. Therefore, to stay on the safe side in choosing a UV device, the UV dose should be at least 400 J/m2.
Table 1. Required Uv Doses for the removal of pathogens
|Pathogen Microorganism||Minimum UV doses for removal (J/m2 )|
|Escherichia coli O157:H7||15||28||41||56|
|Hepatitis A virus||55||140||220||300|
|Poliovirus Type 1||60||140||230||300|
|Coxsackie B5 virus||69||140||220||300|