Annual Chlorine Maintenance

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Each year, the North Texas Municipal Water District (NTMWD) conducts its annual chlorine maintenance on its water transmission system and customer cities’ distribution systems for a 28-day period. The chlorine maintenance is a water system maintenance function as well as a water conservation measure. As a member city, Richardson receives its water from NTMWD.

The Texas Commission on Environmental Quality (TCEQ) allows water suppliers to perform a chlorine maintenance in order to maintain proper chloramine levels (required by the TCEQ) during the warm weather periods, thus conserving water.

The chloramines, a combination of chlorine and ammonia, are used to provide the disinfectant residual in the transmission and distribution systems as required by the TCEQ. Chloramines provide a longer lasting residual disinfection in the water pipelines and water storage facilities.

The chlorine maintenance does not affect water quality, and remains safe for use. Consumers who are sensitive to taste and odor changes in drinking water might notice a slight change during this period, however this palatability change does not alter the quality of the drinking water. For more information, visit www.ntmwd.com.

 

FREQUENTLY ASKED QUESTIONS

How does NTMWD treat drinking water?
NTMWD uses an industry-standard, multi-step process to treat water from lakes that make up all of our water supplies. This disinfection process eliminates bacteria, parasites and viruses through the combination of ozone, chlorine and chloramine (chlorine + ammonia) for disinfection. According to data provided by the Water Research Foundation, approximately 45 percent of the U.S. population is served by public water supplies using chloramine, a proven and effective method of maintaining water disinfection as it travels through systems and into homes and businesses.

Here is an overview of NTMWD treatment process:
First, chemicals are blended with lake water to remove large particles and sediment. Next, ozone is injected into the water as the primary disinfectant. Ozone is one of the fastest and most powerful disinfection processes available - 100 times more powerful that chlorine. Ozone is generated on-site by converting liquid oxygen into a gas using electricity. This is a state-of-the-art water process that is designed to ensure no ozone is released into the atmosphere. The addition of ozone at this stage eliminates bacteria and viruses and greatly reduces organic matter in the water. Using ozone reduces the amount of chlorine that is needed at the end of the disinfection process, thus reducing disinfection by-products and greatly improving water's taste and odor.

After the water is treated with ozone, it is further disinfected with free chlorine before it passes through a series of carbon filters. These filters use a purified form of carbon that further removes sediment and organic material. In addition, these carbon filters remove constituents from the water such as, nitrate, nitrite, metals and many other minerals and trace elements.

What is NTMWD doing to ensure Water Quality?
Ensuring water quality is a collaborative effort between the North Texas Municipal Water District (NTMWD) and our Member Cities and customers. Providing safe and reliable drinking water is a top priority, and hundreds of samples are monitored and tested each day to ensure that drinking water meets regulatory, health, and aesthetic standards set by the Texas Commission on Environmental Quality (TCEQ) and the Environmental Protection Agency (EPA).

NTMWD utilizes a multi-barrier approach to treat our surface water. The NTMWD water treatment process is considered state of the art, and is optimized to reduce organic material and the use of chlorine. In fact, the NTMWD has been recognized by the TCEQ’s Texas Optimization Program (TOP) for the superior performance of its treatment facilities in exceeding state and federal drinking water standards. More information on the TOP program can be found here: https://www.tceq.texas.gov/drinkingwater/swmor/top

The NTMWD disinfection process is designed to eliminate bacteria and viruses in the water and distribution system. The most commonly used disinfectants for water treatment are chlorine, chloramine (chlorine + ammonia) and ozone. NTMWD uses all three, and is one of the largest fully ozonated water treatment facilities in the world. By using ozone, the amount of chlorine needed during the treatment process is greatly reduced. As a result, the amount of disinfection by-products is also greatly reduced. However, ozone is not long-lasting disinfectant. The only disinfectants that are able to provide long-lasting disinfection in the distribution are chlorine and chloramine. There are no other alternatives. Chloramines are longer-lasting than chlorine, and allow water to remain disinfected to the far reaches of the distribution system. Also, the use of chloramines has been scientifically proven to reduce the formation of disinfection by-products. Therefore, the NTMWD uses chloramines to facilitate disinfection throughout the distribution system.

Why is this maintenance procedure necessary?
Studies by the Water Research Foundation have found that a periodic chlorine maintenance period is a preventative measure to reduce the potential of nitrification occurring in the distribution system during warmer temperatures. The chlorine maintenance, in conjunction with system flushing, is designed to remove any biofilm that may have formed since the last maintenance period. Chlorine must be used for this preventative maintenance because it is a stronger disinfectant than chloramine.

The temporary use of chlorine is a standard industry practice that is used to maintain water quality in the distribution system. This practice is considered safe and is utilized by water utilities that serve almost half of the U.S. population.

Is testing done during this period?
Routine monitoring of bacteria, disinfectant residuals, nitrate, nitrite and many other parameters occurs during the maintenance period at the treatment plant and in the distribution systems. Samples are collected by TCEQ licensed water operators and analyzed in appropriately accredited laboratories. NTMWD has performed process control monitoring at our treatment plant for trihalomethanes (THMs). The results for multiple samples have been less than 28 parts per billion (ppb) which is significantly lower than the EPA Maximum Contaminant Level of 80 ppb. The results of all testing are within federal and state guidelines. Our water remains safe to drink.

Where can I find more information?
More information about water treatment and the use of chlorine as a disinfectant, including free chlorine maintenance, can be found on the following websites:

TCEQ - https://www.tceq.texas.gov/drinkingwater/disinfection/nitrification.html
EPA - https://www.epa.gov/dwreginfo/chloramines-drinking-water
WRF - https://www.awwa.org/portals/0/files/resources/publicaffairs/pdfs/monocommkit.pdf
CDC - https://www.cdc.gov/healthywater/drinking/public/chloramine-disinfection.html
CDC - https://www.cdc.gov/healthywater/drinking/public/chlorine-disinfection.html

More information about NTMWD water quality, including test results is available on the NTMWD website at: https://www.ntmwd.com/water-quality-reports/

Why does NTMWD perform free chlorine maintenance?
The Texas Commission on Environmental Quality (TCEQ) allows water suppliers to perform a free chlorine maintenance to help minimize the need for water suppliers to flush water systems in order to maintain chloramine residual (required by the TCEQ) during the warm weather periods, thus conserving water.

What are chloramines?
The NTMWD utilizes chloramines, a combination of chlorine and ammonia, to provide the disinfectant residual in the transmission and distribution systems as required by the TCEQ. Chloramines provide a longer lasting residual disinfection in the water pipelines and water storage facilities.

Besides a water conservation measure, what are other advantages to free chlorine maintenance?
Free chlorine maintenance provides uniform water quality throughout seasonal changes in water temperature. It also aids in the reduction of disinfection byproducts.

Does free chlorine maintenance affect water quality?
Free chlorine maintenance does not affect water quality and remains safe for use.

Does the free chlorine maintenance cause the water to taste or smell different?
Consumers who are sensitive to taste and odor changes in drinking water might notice a slight change during this period, however this palatability change does not alter the quality of the drinking water provided to consumers.

During the free chlorine maintenance period, will the water in some neighborhoods in Richardson be affected more than others?
No. Any slight taste or odor issues during this period will happen throughout all water systems in the NTMWD service area.

For more information about the free chlorine maintenance please contact Denise Hickey, Public Relations and Water Conservation Manager at the NTMWD, at 972-442-5405.