Implementation of System-wide Chlorine Disinfection

The East Lyme Water and Sewer Commission is taking steps to implement permanent system-wide chlorine disinfection of the municipal water system. Improvements to the system were completed in June 2011. Chlorine disinfection has been recommended by the State Department of Public Health and will help to assure that safe drinking water is provided to the East Lyme customers.

Many public water systems add low levels of chlorine to their water supply for the purpose of killing or inactivating harmful microorganisms which can cause illnesses. This is also known as “chlorination” or “disinfection”.

Chlorine is also added for its “residual” properties. Chlorine remaining in the water supply, or added after disinfection is first done, is available to fight against potential contamination in water pipes and storage tanks that might enter through leaks and pipe breakages. This is called “secondary disinfection.”

The primary reason for adding chlorine to water is to make it safe to drink by killing or inactivating harmful microorganisms that can cause illness. People who work in public health consider the chlorination of water as one of the most important advances in the field of public health protection.

When chlorine is added to water, it reacts with organic matter that occurs naturally in the water. The compounds formed are called “disinfection byproducts (DBPs)” and have been known to be a potential health risk. The amount formed depends on the amount of chlorine used and the contact time between the organic substances and the chlorine. DBP levels are expected to be low for most groundwater systems (served by wells) such as in East Lyme because they generally have low levels of organic matter. Public water systems are also required to monitor for DBPs in drinking water to assure that their concentrations are within safe and allowable levels.

Consumers who are still concerned can reduce their exposure to DBPs by installing a carbon filter on their kitchen faucet or on the cold water line under the sink. It is important that these filters be changed in accordance with their instructions to avoid buildup of bacteria in the filter. Since some DBPs can evaporate into the air, windows can be opened or air vented to the outside when taking showers or baths to minimize exposure.

There are other methods used to kill microorganisms in drinking water. These include adding other disinfecting chemicals such as chloramines, chlorine dioxide or ozone. Ultraviolet light can also be used to disinfect water.

All disinfectants have advantages and disadvantages in how well they work and whether a residual is provided. The first three chemical disinfectants are more likely to be used at larger public water systems because they are more difficult to use. Ultraviolet light does not provide the additional benefits of “secondary disinfection”.

If you have further questions, please contact the Water Department at (860) 691-4104 or email

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