Children, the environment and cancer

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Specific environmental contaminants - VI

Chlorinated water

Alternatives to chlorination

Although chlorination is the traditional method of disinfection, there are a number of alternatives currently used along with chlorination that can result in lower levels of chlorination by-products in drinking water.

• Ozonation is a method of disinfection whereby ozone gas is added to water and an electric current applied. It has been used for a long time in parts of western Europe, and is very effective against microbes. It can create other potentially cancer-causing by-products, such as bromate, though these by-products can be removed with additional treatment. Ozonation is a good primary disinfectant, but not a good secondary disinfectant. Because this type of disinfection doesn’t last throughout the water delivery system to homes and businesses, another disinfectant (such as chlorine) must be used for secondary disinfection.  



• Ultraviolet (UV) light treatment is effective against most microbes, and is even more effective than chlorine against certain microbes such as Cryptosporidium. However, UV disinfection is less effective with murky water, must be carefully monitored to ensure it is working properly and can be costly to set up. Again, UV light treatment is a good primary disinfectant, but the effects don’t last while delivering water to homes and businesses.



• Chlorine dioxide is another chemical disinfectant that is effective against most microbes, but also creates disinfection by-products that may be harmful to human health, and can be more difficult to use than chlorine. It can be an effective primary disinfectant, but is not as good at maintaining disinfection during delivery of water to homes and businesses.



• Chloroamines are a group of chemicals that create much lower levels of harmful by-products than traditional chlorine. However, they can be expensive and difficult to use. Though they are effective against bacteria, they are not effective against certain other harmful microbes and therefore they are not good primary disinfectants. A different disinfectant has to be used at the water treatment plant. They are more stable throughout the water delivery system, and so may be a useful alternative to chlorine for secondary disinfection.

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