Chlorine Burn Out in Water System Under Way

Posted on Tuesday August 31, 2021

The City of Holton Water Utility annually performs a free chlorine burnout of its potable water distribution system as well as hydrant flushing to maintain the integrity of the finished water supplied to its customers.  It is not uncommon during this burnout process for customers to notice a chlorine smell and or taste.  The water is safe for consumption.


This process is performed in order to maintain water quality.  If this maintenance is not performed in the water distribution system, the water will eventually lose all of its disinfection residual, which can cause water quality to degrade.


Throughout the duration of the burnout, the water disinfection process is changed from chloramines to free chlorine which is a stronger and faster-acting disinfectant. Flushing and chlorine burnouts are routine distribution system maintenance conducted by utilities with chloramine disinfection.


There are two common types of chlorine used in water treatment for disinfection purposes, combined chlorine (chloramines) and free chlorine. Chloramines are created by combining free chlorine with free ammonia.  A benefit of using chloramines is that they will retain disinfection residual longer in the distribution system and they do not promote a chlorine taste and or smell in the water. However, chloramines are not as strong of a disinfectant as free chlorine and it can allow certain types of bacteria to grow in the distribution system.  The natural occurring bacteria feed on the ammonia found in our finished water.  These bacteria are nonpathogenic and are of no health concern.  Nitrifying bacteria which naturally grow in any distribution system when using chloramines can become prolific in warm summer temperatures.  They will eventually cause water quality to degrade in the warmer summer months.


This is why water utilities across the nation perform an annual free chlorine burnout. The term burnout is used because free chlorine is a much more powerful disinfectant than chloramines.  Free chlorine oxidizes nitrifying bacteria and keep it in check.


Fire hydrants are used to flush the system to help remove sediment from the pipes and facilitate the change in disinfectant. At the end of the burnout, chloramines will be re-introduced and the system will return to normal operation at which time any chlorine smell and or taste should subside.