Ozone water treatment has many applications including sewage treatment, supplying treated water for nuclear power plants, aquaculture and the food industry. Europe has been using ozone water treatment on a large scale for decades and the practice of using ozone is gaining popularity in the United States. The process of ozone treatment in home drinking water systems is similar to that used in municipal water treatment plants, but on a smaller scale.
Identification
Ozone is a colorless gas capable of oxidizing many organic and inorganic compounds in water. It consists of three oxygen atoms. Ozone generators dissociate oxygen (O2) molecules with high-voltage electricity running across a dielectric or non-conductive gap. These separated atoms then collide with another oxygen molecule creating ozone gas (O3) according to the Environmental Protection Agency site.
Process
Ozone produced by the generator is injected into a contact chamber, called the reactor, where the water is infused with the gas. These components come in a large range of designs. They may be fine bubble diffusers, deep u-tube reactors, turbine contactors or spray contactors. Their primary function is efficient ozone distribution through the water to be treated. Ozone works as a powerful oxidant by destroying bacterial cell walls known as lysis. According to Lenntech's site, the damaged walls allow for the intrusion of ozone that further destroys the nucleus, enzymes, RNA and DNA of the cell.
Advantages
The U.S. Environmental Protection Agency states ozone is a more effective disinfectant than chlorine because it requires a considerably shorter contact time. As ozone decomposes, the only residual is dissolved oxygen. Ozone does not create undesirable by-products like trihalomethane (THM), produced by chlorine. The process of ozone treatment oxidizes iron, sulfides and manganese and its potential as a biocide is not affected by water pH levels. As a disinfectant, ozone effectively eliminates a range of bacterial, viral, fungal and protozoan pathogens. Lenntech states that although giardia and cryptosporidium are resistant to conventional chlorine use, ozone treatment can successfully deactivate these amoebic cysts.
Disadvantages
According to the EPA site, among the disadvantages of ozone use is the initial cost of equipment being greater than other methods. In addition, the cost of energy for ozone generation is high. Ozone is very toxic and corrosive. Since ozone has a residual time of minutes, unlike chlorine that endures for hours, there are no benefits of continued disinfection throughout your home.
Considerations
According to the State of Connecticut website, proper maintenance and monitoring in home applications is essential because ozone generators have the potential to create toxic gases. Since ozone gas is unstable and dissipates into the atmosphere as oxygen quickly after its creation, ozone generators must be located at the point of use. Chlorine may still be the most desirable means of water treatment due to the high cost of equipment and low residual times of ozone disinfection.
References
- United States Environmental Protection Agency: Wastewater Technology Fact Sheet Ozone Disinfection: Description
- Clear Water Tech: Use of Ozone in Recirculating Aquaculture Systems: Ozone Application System specifications
- Lenntech: Ozone Disinfection Disinfection Mechanism
- U.S. Environmental Protection Agency: EPA Guidance Manual: Alternate Disinfectants and Oxidants: 3.7.1 Advantages and Disadvantages of Ozone Use: April 1999
- Lenntech: Ozone Disinfection Resistant Microorganisms
- The Official State of Connecticut Website: Private Drinking Water in Connecticut: Other Considerations
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