Disinfection water treatment is not a stand-alone treatment but forms part of a number of water treatment processes. For municipal use it is used for the disinfection of drinking water and sometimes in sewage treatment to remove bacteria, viruses and protozoan parasites.
For industrial water systems, it is usually used to help generate ultrapure water and is implemented at the point of use in factories and plants. Disinfection also forms part of a process used for wastewater disinfection methods that treat industrial wastewater to standards for reuse.
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Veolia engineers are experts in ensuring the correct water disinfection treatment and management of surface and ground water.
We improve the performance and safety of drinking water treatment facilities by using first-in-class technologies and water disinfection additives. These are used to treat bacteria and micro-organisms and remove pesticides, arsenic, heavy metals and other substances hazardous to your health.
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Types of disinfection in water treatment
Disinfection can be achieved by either chemical or physical disinfectants. For chemical disinfection Veolia uses ozonation and chlorination; and for physical disinfection ultraviolet light (UV) is used.
Ozone Water Treatment (Ozonation)
When treating water to potable water status, after abstraction the water first undergoes the screening and filtration processes. This is followed by flocculation and sedimentation and sand filtration, before the water is disinfected using ozonation, the step just prior to activated carbon filtration. Ozonated water is not the last step in disinfection in drinking water treatment, but it is a necessary disinfection step.
Ozone is a form of oxygen (O²) with the molecular formula O³. It forms when oxygen in the air is exposed to the discharge of a powerful electric current through air.
For ozone disinfection drinking water, water is disinfected by using ozone to kill bacteria and viruses. Ozone gas, when mixed with water, also acts on organic matter by breaking it down into pieces, as well as improving both the water colour and taste.
Ozonation is popular as an onsite water treatment process because it is easier to work with than chlorine and, importantly, the gas used in the process can be generated onsite.
Disinfection of water by chlorine is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid. Adding chlorine or hypochlorite to water in order to kill certain bacteria and other microbes in tap water takes place after the activated carbon filtration process.
Chlorine is added as treated water leaves a water treatment plant and at various stages throughout the water supply system. This treatment prevents bacteria from growing as well as maintaining water quality as the water passes through the water mains.
Ultraviolet (UV) light is used as a method to inactivate micro-organisms by interrupting nucleic acids and disrupting their DNA, preventing replication. Usually used at the point of use, UV disinfection is utilised by industries like food & beverage and pharmaceuticals, which require ultrapure water disinfected at the point of entering the process to ensure zero contamination. There is no residual effect to the water and no disinfection by-products, which there are sometimes with both chlorination and ozonation.
UV radiation disrupts DNA and RNA polymerase at low doses while breaking down large organic molecules into smaller ionized components. These components are removed by high purity ion exchange resin beds downstream. Prior removal of organic ions optimises the effectiveness of this technology in water purification. Ultraviolet radiation is also used in photolysis to remove chlorine and chloramine species from the water.
Treatment of water with ultraviolet light is used to photo-oxidise organic impurities and/or inactivate micro-organisms. Photo-oxidation of organic impurities results in polar or charged species that can be removed by ion-exchange processes. Typically, the UV lamp forms part of a 'polishing' treatment loop including ion-exchange, through which water is repeatedly circulated to maintain quality.
Water with Total Organic Carbon (TOC) of less than 5 ppbC and bacteria at less than 1 CFU/ml can be achieved with ELGA products that use this approach. ELGA LabWater is a Veolia sister company that focuses on providing a reliable source of lab water that economically meets the required compliancy of all customers' scientific and medical applications.
Key benefits of UV disinfection
- No chemicals required
- No effects on taste and odour
- No corrosion problems
- Safe disinfection of drinking water
- Easy to operate and maintain