Why chlorine residual is so important
It is imperative that public water systems maintain the minimum chlorine residual in ALL active areas of the distribution system at ALL times.
How is chlorine used to disinfect drinking water?
Bacteria, viruses, and other potentially harmful organisms can thrive in the water mains, services lines, and pipes underground that deliver water to your home. This is especially true in the summer months, when old, cracked pipes combine with the warm, moist environment underground to provide a breeding ground for bacteria, including legionella (the cause of Legionnaire’s disease). To kill these organisms, water systems add a disinfectant, typically chlorine, directly to the water system.
What is a chlorine residual and how does it protect residents?
Water departments start by adding chlorine at certain points in the water system. This chlorine is then carried to the rest of the system as the water flows from one part to the next. Chlorine, however, decays quickly over time. As the chlorine interacts with organic material, metals (such as iron particles), and nitrates in the water, it gets “used up,” and no longer is available for disinfection. Chlorine residual measures the amount of chlorine effectively “left over” and available for disinfection at any given point in the water system. The most important components to control the growth of bacteria in water distribution systems are maintenance of a disinfectant residual, limitation of biodegradable organic material and corrosion control.
A detailed explanation can be found on the CDC’s website here.
Why do states set minimum chlorine residuals?
The minimum chlorine residual is a drinking water safety standard. As noted above, the measure of free chlorine residual measures the amount of chlorine actually available to disinfect the water in the distribution system. If the amount of residual chlorine is too low, then there is effectively nothing left to kill harmful bacteria, viruses, or organisms in the water. This can, at minimum, result in foul-smelling, bacteria-laden water, or at worse, lead to the proliferation of fatal pathogens through the drinking water.
What is Illinois’s minimum chlorine residual?
Illinois requires the free chlorine residual to be at least 0.5 mg/L in all parts of the distribution system at all times. This means that no matter where or when the water department tests the water in the distribution system, it should be above 0.5 mg/L. Sycamore currently only tests for chlorine residual at four sites, which can be found on the following map.
What is water age and how does it impact water quality?
Water age refers to the time it takes for water to travel from a water source to consumers. The longer the time it takes, the more likely the water quality will deteriorate. Many factors can increase water age, but it is primarily influenced by the flow of the water through the system. Narrow pipes, dead end water mains, broken valves, and old, corroding infrastructure will contribute to increased water age. Sycamore has all of these factors, so it unsurprisingly has water age issues, as detailed in the 2019 Master Water Plan (p. 3-17) commissioned by the city. Increased water age can lead to other problems, particularly increased corrosion and sediment, foul smelling water, discoloration, and low chlorine residuals. More information can be found here.