Everything You May Want to Know About Free Chlorination

Wednesday 5 September Everything You May Want to Know About Free Chlorination


Port St. Lucie Utility Systems prides itself on providing the highest quality of safe drinking water for our community. All of Port St. Lucie’s water treatment facilities are regulated by the Florida Department of Environmental Protection (FDEP) and the Environmental Protection Agency (EPA), and operated under stringent construction, operating, and maintenance standards to protect both human health and the environment.

Maintaining a Vast Water Distribution System

We operate an extensive distribution system which provides water for 75,000 customers through more than 1,200 miles of water main. Maintaining and protecting that system is vital. Chlorine is by far the most commonly used drinking water disinfectant in all regions of the world. Today, about 98 percent of U.S. water treatment systems use some type of chlorine disinfection process to help provide safe drinking water. The U.S. Environmental Protection Agency (EPA) requires treated tap water to contain a detectable level of chlorine to protect against germs as it flows from the treatment plant to consumers’ taps.

The Centers for Disease Control and Prevention (CDC) sites, “the U.S. Environmental Protection Agency (EPA) allows drinking water treatment plants to use chloramine and chlorine to disinfect drinking water. Water system pipes develop a layer of biofilm (scum) that makes killing germs more difficult. Water providers may temporarily switch from chloramine to chlorine disinfection to help remove this scum layer.”

The Port St. Lucie Utility Systems Department utilizes chloramines, a blend of ammonia and free chlorine as a disinfectant to prevent the creation of trihalomethanes (THMs—a potential carcinogenic), which are caused by free chlorine alone reacting with total organic carbon (TOC), and are naturally occurring compounds found in decayed plant material in the water. A small portion of the water produced in the City comes from its lime softening treatment facility that is not capable of removing all organics (TOC) found in the shallow aquifer. Much of the water produced comes from the Floridan aquifer, which is treated by the City’s two reverse osmosis treatment facilities. These facilities provide a more advanced type of treatment that removes the majority of TOC in the water supply.

Our goal is to add just enough ammonia to react with the chlorine to create chloramines and keep free, available ammonia out of the distribution system, as that keeps a food source for bacteria out of the system. Over a period of time, a bio film forms on the interior of the distribution piping causing nitrification, which in turn breaks down the disinfection quality in the water.

Port St. Lucie Utility Systems’ NELAC (National Environmental Laboratory Accreditation Conference) certified laboratory personnel collect a minimum of 120 bacteriological samples throughout our service area each month to assure that our customers are receiving the highest quality of drinking water. The samples are tested to monitor chlorine residuals and detect any presence of microbiological contaminants throughout the entire system. A preventative measure (free chlorination) was recommended because we were experiencing certain areas in the service area where additional flushing of fire hydrants was needed to keep the chlorine residuals at an acceptable level. Exercising the common practice of free chlorination is a nationwide industry standard because it is an effective preventative measure. This temporary free chlorination process removes the biofilm from the pipes and is removed from our distribution system via flushing of hydrants.

Why Free Chlorinate?

Free chlorination of our vast water distribution system is currently underway. We are temporarily modifying the disinfection process between August 21 and September 3. Port St. Lucie Utility Systems has not conducted a free chlorination operation since August 2018, which is a testament to our ability to maintain our outstanding water quality. Martin County Utilities, West Palm Beach Public Utilities, City of Fort Lauderdale, and Miami-Dade Water Department are just a few of our many neighboring utilities who conduct free chlorination annually or as they deem necessary.

The Florida Department of Environmental Protection (FDEP) sites in their Disinfection Byproducts Requirements the following, "The definition of 'normal operating conditions' include any routine maintenance practices. An event such as a chlorine burn, a switch from chloramine to chlorine, is considered to be part of normal operations of a system for periodic maintenance. A water line break or other disruptive event which is outside the control of the facility is considered non-normal operation condition. The length of chlorine burns should be kept to a maximum of 21 days. Whenever possible, systems should try to optimize processes using guidance such as AWWA manual 'A Guide to the Implementation and Use of Chloramines'."

The American Water Works Association (AWWA) states, “chloramines are widely used to maintain a disinfectant residual in water distribution systems. However, chloraminated distribution systems can promote the growth of nitrifying bacteria, an undesirable condition known as nitrification. Many chloraminated systems minimize the potential for nitrification by converting from chloramines to free chlorine on a periodic basis. The concept behind this switch is that free chlorine will oxidize any ammonia present in the distribution system, thus removing the food source for nitrifying bacteria, and will reduce the number of nitrifying bacteria.”

Our Promise

Port St. Lucie Utility Systems will continue to work closely with FDEP and our other regulatory agencies to maintain and provide a safe and clean water supply for our customers through the use of preventative maintenance and industry-wide best practices. Water is essential for life and it is essential for this utility to continue to provide clean, safe, great-tasting drinking water our customers can trust.


1. Florida Department of Environmental Protection
Memorandum: Clarification of Rile 62-550.822 Disinfection Byproducts (DBP) Requirements

2. American Chemistry Council

2. American Water Works Association

3. Centers for Disease Control and Prevention

4. Port St. Lucie Utility Systems 2022 Water Quality Report


For more information, contact:
Port St. Lucie Connection Support