Customers may notice chlorine taste and odor in our water in March and early April due to an annual change in our disinfection process
You may notice some chlorine taste and odor in our drinking water in March and early April. This temporary change occurs annually because OWASA uses chlorine instead of chloramines for disinfection in March.
Chloramines are a compound of chlorine and ammonia which OWASA has used since 2002 for drinking water disinfection in months other than March.
In a system where water is normally normally disinfected with chloramines, the State requires that the utility use only chlorine for disinfection one month per year. As in past years, OWASA and several other utilities in the region have selected March for chlorine disinfection.
OWASA asks customers to be aware of the following:
- OWASA crews will release water from some fire hydrants in March. The purpose of this “flushing” of water mains is to ensure that water with chlorine goes through the entire water system.
- The flushing of water mains may cause some discoloration of OWASA drinking water because iron and manganese particles that have settled in water mains may be stirred up. Air bubbles, which can make water look milky, may also be in our water. Customers who notice discoloration or air bubbles are encouraged to run cold water through a bathtub faucet, etc. for about 5 minutes to clear up the water.
- OWASA uses special equipment and a chemical to neutralize the chlorine and ammonia in the water that is released during flushing so that it will not harm fish in streams and creeks.
- Customers with fish or amphibians in aquariums filled with OWASA water should continue to use chemicals as recommended by pet supply stores, etc. to neutralize chlorine and ammonia.
- Customers who use OWASA water for special purposes or processes involving careful control of water characteristics, such as kidney dialysis, are encouraged to get advice from an appropriate technical source such as a filter vendor or service company about whether and how to make adjustments to their use or filtration of OWASA water during March. With chlorine disinfection in March, OWASA expects that the pH of its drinking water at the treatment plant will be 7.1 to 7.3, compared to the pH of 8.1 to 8.3 in months with chloramine disinfection.
- OWASA will resume the use of chloramines for disinfection on April 1, 2011.
Customers are invited to contact OWASA with any questions or comments about the use of chlorine in March, the characteristics of OWASA drinking water, etc.
For more information:
Rachel Monschein, Water Treatment Plant Laboratory Supervisor, 537-4227; rmonschein@owasa.org
Ken Loflin, Water Supply and Treatment Manager, 537-4232; kloflin@owasa.org
Background information regarding disinfection with chloramines
In January, 2002, OWASA began using chloramines to disinfect drinking water. Disinfection with chloramines has improved the taste and odor and the overall quality of drinking water by reducing the levels of certain disinfection byproducts (please see additional information below). Before 2002, OWASA used chlorine in the form of sodium hypochlorite (bleach) for disinfection.
OWASA made the change from chlorine to chloramine disinfection in order to reduce the levels of certain disinfection byproducts which may be harmful at high levels over a lifetime. The disinfection byproducts, which result from the chemical reaction of chlorine with organic material, are called trihalomethanes (THMs) and haloacetic acids (HAAs). Small particles of organic material are naturally present in lake water.
In the Triangle region, water utilities including OWASA, the City of Durham, the City of Raleigh, the Town of Hillsborough and the Town of Cary use chloramines for disinfection except for one month of the year (March or a similar period), under normal conditions.