Water disinfection is a process with which disease causing microorganisms are destroyed. Disinfection of drinking water prevents spreading of contagious diseases caused by microorganisms which are transmitted by drinking water. For this reason water disinfection is an urgent process to prepare drinking water. Disinfection of processed water prevents the damage which would be done by microorganisms entering the technological process of water.
There are several procedures of disinfection:
- Disinfection with chlorine gas;
- Disinfection with sodium hypochlorite;
- Disinfection with chlorine dioxide;
- UV disinfection;
- Disinfection with ozone.
CHLORINE GAS
Disinfection using chlorine gas is a bit older but most frequently used process and technology for water disinfection. Through centuries this kind of process has evolved to the extent to provide safety at a very high level. A vacuum process and some additional neutralisation of chlorine in the air contribute to its safety.
The gas comes under pressure from a gas bottle or from a tank to vacuum regulator, where vacuum is created which prevents leakage of gas in case of eventual faults in the pipelines. Afterwards, the dosing controller using electromagnetic valve and automatics doses an adequate gas quantity regarding the flow and the estimated chlorine residual in the pipeline.
SODIUM ?HYPOCHLORITE
Sodium hypochlorite is also known as a bleaching agent in the form of solution and it is dosed depending on the active chlorine content proportional to the flow and the estimated chlorine residual. It can be prepared on the dosing spot from NaCl by means of electrolysis. Most of the part sodium hypochlorite is delivered in drums.
CHLORINE DIOXIDE
Chlorine dioxide is a strong disinfectant which disinfects water using a different method as chlorine. Since it is explosive, we generate it on the dosing spot from NaClO2 and HCl. Even though operational and investment costs are a bit higher than the ones for chlorine disinfection, this process is being more widely used due to its insensitivity to pH which contributes to formation of less harmful side products. It does not react to ammonia.
UV DISINFECTION
UV disinfection is carried out without adding any substances into the water, thus it does not form any side products. UV radiation, which is generated by special illuminants, penetrates the cells of microorganisms and prevents their multiplication. UV disinfection is not suitable for water with high content of suspended articles, turbidity and dissolved organic compounds.
DISINFECTION WITH OZONE
Disinfection with ozone does not leave any side products. If dosed adequately and in timely manner it can be a highly efficient process. Since ozone is a highly reactive gas, it must be produced on the spot of dosing in special generators where strong electrical current splits the molecules of oxygen (O2) into individual oxygen atoms (O), which are then combined into the molecule of ozone (O3). The investment and operational costs are relatively high. Besides, operations and maintenance of this process is demanding as well.
