Facts about Drinking Water Disinfection and the Free Chlorine Conversion Process

Why is drinking water disinfected?

Disinfection of drinking water is critical to protecting consumers from disease-causing microorganisms, called pathogens, including bacteria or viruses. Disinfectants are very effective at inactivating (or killing) pathogens and have enormously benefited public health. For example, the incidence of typhoid fever was reduced by 1,000-fold in the U.S. in the last century by implementing the disinfection of drinking water.

Even with the advancements in drinking water disinfection practices and decreased incidence of diseases like typhoid fever and cholera in the U.S., disinfection of drinking water remains critical for public health. Failure to adequately disinfect water has led to high-profile illness outbreaks and deaths (for example, the 1991 Peru cholera epidemic and the 2000 Walkerton, Canada bacterial outbreak).

 

What are the drinking water disinfection requirements in Texas?

Public water systems are required to disinfect water prior to its entering the distribution system that carries it through pipes for delivery to consumers. Public water systems in Texas are also required to maintain a minimum amount of residual disinfectant throughout the distribution system to make sure levels of harmful microorganisms remain low. Treatment prior to distribution may utilize a number of different disinfectants, but a public water system is required to use either chlorine or chloramine in the distribution system.

 

What is chloramine?

Chloramine is a long-lasting disinfectant added to public drinking water for disinfection. It is formed by combining chlorinated water with small amounts of ammonia. It is commonly used for disinfection in many public water systems throughout Texas, the United States, and countries around the world.

 

Why does my public water system use chloramine?

Chloramine is an effective disinfectant and persists over a long period of time, particularly in areas with high temperatures. This makes chloramine useful in Texas’ large distribution systems, such as those of cities with numerous connections and in rural water systems with fewer connections spread out over a large geographic area. Chloramine typically produces lower levels of regulated disinfection by-products (such as total trihalomethanes (TTHMs) or haloacetic acids (HAA5) compared to free chlorine, because it is less reactive with naturally occurring organic matter that may be in the water.

 

What are disinfection by-products?

What are disinfection by-products?Disinfection by-products (DBPs) are formed when disinfectants such as chlorine and chloramines react with natural organic matter in drinking water. The U.S. Environmental Protection Agency (EPA) regulates some DBPs, such as total trihalomethanes (TTHMs) and haloacetic acids (HAA5) to minimize their health risks. A challenge faced in drinking water disinfection is to protect the public from waterborne diseases while reducing public exposure to DBPs.

 

Is chloramine safe?

Yes, water disinfected with chloramine is safe for drinking, cooking, bathing, and everyday use. The EPA, the Centers for Disease Control, and the World Health Organization have determined that chloramine is a safe disinfectant and that water disinfected with chloramine within regulatory standards has no known or expected adverse health effects.Chloramine, like chlorine, must be removed from the water prior to use in dialysis machines and can be harmful to fish and amphibians. However, proper filters and dechloramination products will address these concerns.

 

What is a free chlorine conversion (“chlorine burn”)?

A free chlorine conversion (also referred to as a “chlorine burn”) occurs when a water system that typically uses chloramine removes ammonia (needed to form chloramine) from the treatment process, and disinfects the water with only chlorine. Chlorine is more effective than chloramine at inactivating certain types of bacteria. Excess ammonia, which can accumulate in a chloramine-treated distribution system over time, is a source of food for specific types of bacteria that are harmless to people. These bacteria can make it difficult for public water systems to maintain a disinfectant residual, which means that microorganisms that are harmful to people can grow.The “chlorine burn” is a common practice by many public water systems throughout the country to reduce the number of the bacteria so that a satisfactory disinfectant residual can be maintained throughout the distribution system. Chlorine conversions can be used as a preventative strategy or to stop nitrification (the microbial process that converts ammonia and similar nitrogen compounds into nitrite and nitrate), which can diminish water quality. According to a 2016 EPA survey, 25 to 40 percent of the utilities that use chloramine reported using free chlorine burns to control nitrification1.Public water systems should notify their customers prior to a chlorine conversion, because changes in taste and odor may briefly occur.

 

Why is my water system conducting a free chlorine conversion?

A free chlorine conversion is typically conducted for two reasons:

1.  It is often conducted as a preventative maintenance measure to kill bacteria thatcan make the maintenance of disinfection residual problematic. A film can formin the distribution system piping that can contain bacteria which use ammonia asa food source. These bacteria in this film are harmless to people. When the watersystem stops adding ammonia, the bacteria starve. Therefore, a periodicconversion to free chlorine is effective for inactivating these types of bacteria inpiping with biofilm by interrupting the supply of ammonia and can help preventsubsequent issues from occurring.

2.  In rare occasions, if the distribution system receives a moderate to excessiveamount of ammonia over long periods of time, bacteria using ammonia as a foodsource can bloom and cause a loss of disinfectant residual. As a result, the watersystem may not be able to maintain the minimum required disinfectant residualin the distribution system, and may receive complaints regarding taste/odor.2.In rare occasions, if the distribution system receives a moderate to excessiveamount of ammonia over long periods of time, bacteria using ammonia as a foodsource can bloom and cause a loss of disinfectant residual. As a result, the watersystem may not be able to maintain the minimum required disinfectant residualin the distribution system, and may receive complaints regarding taste/odor.The conversion to free chlorine, in conjunction with increased flushing activities,assists in removing excess film from the distribution system and also starvesthese bacteria. The chlorine conversion helps the system return to anenvironment where the disinfectant residual can be maintained.

 

Are there any disadvantages to a free chlorine conversion?

Properly conducted free chlorine conversions can often cause the water to have a different taste and/or odor than when using chloramine for disinfection. Customers will likely be able to notice the difference, but there are no health effects associated with the change in taste/odor. Once the water system has returned to using chloramine as the disinfectant, the taste/odor of the water will return to normal.There may be an increase in the level of disinfection by-products being formed during this short time. Health concerns related to disinfection by-product formation are based on prolonged exposure, and the conversions typically only last two to four weeks at a time. Limited scientific studies following shorter-term exposure to disinfection by-products have been published that did not find any association between exposure and dermatitis (skin rashes).There have been a number of other studies that investigated maternal exposure to disinfection by-products and birth outcomes (such as small-for-gestational age infants) following shorter-term exposure to disinfection by-products2. Evidence in epidemiological studies looking at exposures to disinfection by-products above 80 ppb and pregnancy outcomes is mixed and limited by study shortcomings. Regulatory agencies worldwide continue to evaluate possible associations between disinfection by-products exposure and pregnancy outcomes. Reduction of disinfection by-products may be desirable, but it should never compromise effective disinfection.

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The original TCEQ General Information document can be found here: Facts about Drinking Water Disinfection and the Free Chlorine Conversion Process

Temporary Disinfectant Conversion from Chloramine to Free Chlorine
January 4, 2023

The Bell County Water Control & Improvement District #1 (BCWCID1), public water system, (PWS) ID TX0140016, and the City of Harker Heights, public water system, (PWS) ID 0140023, will temporarily convert the disinfectant in its water treatment process from chloramines to free chlorine. The conversion is scheduled to take place Wednesday, February 1, 2023 through Tuesday, February 28, 2023. This is the first annual conversion to be conducted as part of routine maintenance for the water transmission and delivery systems. Free chlorine conversion is an accepted and recommended step by the Texas Commission on Environmental Quality to help maintain water quality and minimize nitrification. During this period, you may experience taste and odor changes associated with the type of temporary disinfectant conversion.

Disinfection is a critical part of the water treatment process that keeps drinking water free of harmful microorganisms, such as bacteria and viruses. Disinfection involves a two-step process that first treats the water at the treatment plant and then chloramine disinfectant (chlorine + ammonia) is added to maintain water quality. During the temporary change, BCWCID1 will suspend adding ammonia and use free chlorine to keep water disinfected as it travels through pipes.

BCWCID1 and the City of Harker Heights are coordinating with Texas Commission on Environmental Quality (TCEQ) staff and local entities to implement a temporary disinfectant conversion to free chlorine to maintain the system and water quality. BCWCID1 and the City of Harker Heights continue to meet safe drinking water standards earning recognition from TCEQ as Superior Public Water Systems. The annual water quality reports are posted online at www.wcid1.org and www.harkerheights.com

Please share this information with all people who drink this water, especially those who may not have received this notice directly (i.e., people in apartments, nursing homes, schools, and businesses). You can do this by posting this notice in a public place or distributing copies by hand or mail.

If you have questions regarding this matter, you may contact:

Harker Heights Public Works Department at 254-953-5649
Mark Hyde, Public Works Director at 254-953-5641 or
David Mitchell, City Manager at 254-953-5600

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Press Release January 4, 2023

THE CITY OF HARKER HEIGHTS IS NOT UNDER A BOIL WATER NOTICE.

The City of Harker Heights receives its water from the Bell County Water Control & Improvement District No. 1 (WCID). WCID #1 is the regional water supplier for the following customers; City of Harker Heights, City of Killeen, City of Belton, City of Copperas Cove, Fort Hood, Bell County WCID #3 (City of Nolanville), Belton Outdoor Lake Recreation Area (BLORA) and the 439 Water Supply Cooperation.

WCID will convert its disinfection process from chloramines to free chlorine for a period of approximately one month beginning February 1, 2023 and will end on February 28, 2023.

Generally, there are no noticeable changes in water quality because of this temporary conversion. However, some individuals may notice taste and odor changes and a slight discoloration to the water.

WCID #1 currently uses chloramines (a combination of free chlorine and ammonia) to disinfect its drinking water supply prior to customer distribution. This is a reliable disinfection process that has been recommended by the Texas Commission on Environmental Quality (TCEQ) for systems predominantly treating surface waters, such as those in the Harker Heights water system.  It is standard industry practice to periodically convert chloramines back to free chlorine to improve and maintain the highest water quality standards in potable water distribution systems. In addition, the Environmental Protection Agency (EPA) and the TCEQ support this process as a necessary and effective measure for maintaining water quality.

The City will implement directional flushing, combined with routine water quality monitoring, as measures to maintain the highest water quality for customers during the conversion. Some discoloration may still make it into customer service lines despite the City’s efforts. Customers who experience discoloration should temporarily flush faucets, tubs, and toilets, until the water has cleared. Clothing should not be washed during times of discoloration to reduce the possibility of staining. Prior to washing clothing, customers may want to run a little water in a bathtub to check for discoloration.

Noticeable water quality changes associated with conversions are normally short lived and are not public health risks.

Customers can safely consume and use their drinking water as normal during the conversion period. However, dialysis patients should consult with their physicians prior to the conversion to ascertain whether pretreatment adjustments are necessary for their dialysis equipment. Most dialysis equipment has already been outfitted with charcoal filters that remove free chlorine and chloramines; however, customers should check with their doctor as a precautionary measure.

The City of Harker Heights has notified local hospitals and dialysis clinics in advance so that they can implement process changes if necessary.  Those conditioning water for fish or aquariums may also need to make changes to their water pre-treatment process.

The Texas legislature recently passed H.B. 872 which amended the Texas Utility Code to make utility customer information confidential by default. Residents do have the right to disclose your information under the Public Information Act to a specific person and / or to the public by completing a Request for Disclosure of Information Form and returning it to the Utility Administration Office. This form can be found on our website or obtained in the Utility Administration Office and returned by email to This email address is being protected from spambots. You need JavaScript enabled to view it., or by dropping off at 305 Miller’s Crossing, Harker Heights, TX 76548