Chlorine and Ozone, Which is More Efficient
The use of chlorine and ozone in water disinfection is prevalent throughout the modernized world. Both options allow us to take water that was previously thought unusable and to change it into potable water. These options allow us to eliminate chemicals, microorganisms and disease from water such as cholera, e-coli, cryptosporidium, giardia, enterovirus, and many more including metals. There are pros and cons to both treatment processes and we will go over them in the next few paragraphs.
Chlorine is the widest used process in water disinfection. Used by water municipals, as well as an emergency application by consumers and the like. When chlorine is added to water in one of its many forms, it easily bonds with other chemical substances and microorganisms found to be harmful to humans. After bonding, the chemicals can be dissipated out as gas, or destroyed by the acidic reaction of the new substances created. Two acids that come about when chlorine is added are HCl and HOCl. Both are very potent acids with a pH range of 1-4 (Reference 5).
There are drawbacks to chlorine being used to disinfect water supplies in mass quantities. In recent years the existence of DBP (Disinfection Byproducts) have led some to believe that maybe chlorine isn’t such a good disinfectant. DBPs come in two forms, HAAs (haloacetic acids) and THMs (trihalomethanes) (Reference 6). With these substances (one being chloroform) existing in the end product of drinking water, alternatives are coming forth; one of the main ones being the use of ozone.
Ozone is another long time water disinfectant. It has been used for about 100 years in the US and Europe just as chlorine has been. Ozone works similar to chlorine where it bonds with other chemicals, metals and other substances. Ozone works best with metal intrusions into water. Through oxidation, metals can be precipitated from water over a filter (Reference 4).
References: 1.) Pure and Applied Chemistry, Vol. 68, No. 9, pp. 1731-1735, 1996
2.) EPA Website- “Emergency Water Treatment”
3.) EPA Website- “Wastewater Technology Fact Sheet, Ozone Disinfection”
4.) BiOzone Corporation, “Ozone Drinking Water”
5.) Water Quality and Health Council, Groundwater Disinfection: Chlorine’s Role in Public Health
6.) Chlorine Chemistry Division: A New Perspective on Drinking Water Disinfection Byproducts
7.) Science Daily.com, “Drinking Tap Water Disinfected with Chlorine May Harm Fetus”
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