Difference Between Free And Total Chlorine
Introduction
Chlorine is a commonly used chemical in the water treatment industry to disinfect swimming pool water and drinking water supplies. When it comes to maintaining water quality, it is crucial to understand the difference between free and total chlorine. Both play an essential role in water disinfection, but their measurements indicate different aspects of water quality.
What is Chlorine?
Chlorine is a strong oxidizing agent that effectively kills bacteria, viruses, and other microorganisms in water. It is added to water supplies in different forms, such as chlorine gas, sodium hypochlorite, or calcium hypochlorite, to ensure water safety.
Free Chlorine
Free chlorine refers to the amount of chlorine available in the water to effectively kill microorganisms. It exists in various forms, including hypochlorous acid (HOCl) and hypochlorite ion (OCl-), depending on the pH level of the water. Hypochlorous acid is more effective against microorganisms than hypochlorite ion.
Testing for free chlorine helps determine the cleanliness of the water and its ability to destroy harmful pathogens. It should be maintained within a specific range, typically 1-3 parts per million (ppm) in swimming pools and 0.2-0.5 ppm in drinking water supplies, to ensure optimal water disinfection.
Total Chlorine
Total chlorine measures the combined amount of free chlorine and combined chlorine (also known as chloramines) in the water. Combined chlorine is formed when free chlorine reacts with nitrogen-bearing compounds such as ammonia, urine, or sweat. Chloramines give off a strong odor and can cause eye and skin irritation.
The presence of combined chlorine indicates the incomplete elimination of microorganisms and points to the need for additional chlorine or shock treatment to restore water quality. It is important to note that high levels of combined chlorine can also contribute to the formation of disinfection byproducts (DBPs), which can be harmful to human health.
Testing Methods
To measure free chlorine levels accurately, one can use a colorimetric test kit or a digital chlorine tester. These tests are generally based on the color change of specific chemical compounds in the presence of free chlorine.
The measurement of total chlorine is usually done by subtracting the value of free chlorine from the value of total chlorine. Some advanced digital testers can directly measure both free and total chlorine without any calculation.
Conclusion
In summary, understanding the difference between free and total chlorine is crucial for maintaining water quality and ensuring effective disinfection. Free chlorine levels indicate the availability of chlorine to kill microorganisms, while total chlorine accounts for both free chlorine and combined chlorine. By regularly testing and maintaining appropriate chlorine levels, waterborne illnesses can be prevented, and overall water safety can be ensured.
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Difference Between Free And Total Chlorine
