Chlorine Testing

What Is Chlorine?

Chlorine is a naturally occurring element found in gaseous form at room temperature. The highly reactive nature of chlorine means it is usually bound with other elements, such as sodium chloride (salt). A strong oxidizing agent, Chlorine deactivates microorganisms by breaking through the cell membrane.

What Is Chlorine Used For?

Chlorine was first added to drinking water systems in the 19th century to combat diseases such as cholera. Since then chlorine has been widely adopted as a disinfectant across multiple applications, including in swimming pools and for washing food produce. As with all disinfectants, monitoring of residuals and dosing is important to ensure that levels are not too high or low.

Chlorine levels are routinely monitored to ensure that water is free of harmful bacteria. However, because it is very sensitive to pH and temperature, both those parameters must be tested and carefully controlled to achieve optimum performance.

Chlorine In Drinking Water

Most drinking water is treated with chlorine to prevent harmful bacteria causing illness in humans and animals. Whether added as free chlorine or a combined chlorine depends very much on how quickly the water is to be consumed and the potential for disinfection by product formation.

To learn more about controlling chloramination in drinking water, click here.

Chlorine In Food And Beverage

Chlorine is widely used as a sanitizer in the food and beverage industry due its relatively low cost and efficacy at preventing produce cross-contamination. Used across all the main applications and processes, chlorine remains the most popular sanitizer in the food and beverage industry.

Chlorine is a popular disinfectant in poultry processing. It is inexpensive, requires a relatively short contact time with pathogens and is extremely effective in killing Campylobacter and Salmonella. To find out more read our article What Role Does Disinfection Play in Poultry Processing in the US? 

Chlorine used in fresh produce washing is usually generated from using sodium hypochlorite, calcium hypochlorite, or through the onsite generation of chlorine gas directly into aqueous solution.

Chlorine In Wastewater

Chlorine is often used at the end of a wastewater treatment process to ensure no harmful bacteria are discharged back into the environment. However, the chlorine added must then be removed before discharge to ensure that aquatic life is not harmed.

Chlorine In Pools And Spas

Chlorine in the most common disinfectant used in pools and spas. Like drinking water, the aim is to add enough chlorine to maintain a free chlorine residual in the presence of relatively high contamination levels without adding so much that you form harmful disinfection by products.

For more information about managing chlorine levels in your pool and spa download our Pool Chemistry Guide or Spa Chemistry Guide.

Contact us for more information

What Equipment Is Used For Chlorine Testing?

Palintest offers a wide range of equipment for chlorine testing ranging from simple visual tests such as test strips and comparators, to advanced digital testing with our photometers and Kemio Disinfection.

Kemio Disinfection is ideal for monitoring sanitisers in the food and beverage industry. It delivers unbeatable accuracy as well as being extremely user friendly. To find out why Kemio performs better than drop count in poultry processing read our support article.

Depending on your application or regulatory needs, we offer a wide range of solutions to suit your application. View our products or contact our team to find out more.

People Also Ask

What is free chlorine?

Free chlorine has the highest disinfection efficacy and usually exists in water as hypochlorous acid (HOCl) or the hypochlorite ion (OCl – ), with the proportion of each dependent upon the pH of the sample.

To learn about the difference between free and combined chlorine, click here.

What is total chlorine?

Total chlorine is the sum of free chlorine and combined chlorine, or chloramines, which have weaker disinfection properties. When chlorine comes into contact with molecules containing nitrogen, it reacts to form a chloramine. Chloramines and free chlorine together are referred to as total chlorine.

To learn about the difference between free and combined chlorine, click here.

Why should I measure free chlorine?

Free chlorine and combined chlorine have different disinfection potential. Free chlorine has a stronger sanitizing potential and therefore the presence of free chlorine residual gives an indication of the sanitizing potential of your wash water. We recommend the level of free chlorine is set to ensure sufficient disinfection and must be monitored separately from total chlorine.

What level of free chlorine should I use?

This is dependent on the application for which you are using the chlorine. Contact your local regulator for more advice about how much chlorine you should be using in your system.

For information about chlorine levels in pools and spas, see our Pool Chemistry Guide or Spa Chemistry Guide

What are the disinfection by products (DBPs) of chlorine?

When chlorine interacts with natural organic matter in the water, disinfection by-products (DBPs) called trihalomethanes (THM) are formed. These substances can have adverse health and environmental effects and need to be monitored.

What is the impact of diluting the test sample?

Methods requiring dilution introduce potential error. For example, a 1 in 100 dilution magnifies any measurement error on the 1 mg/L by 100 times. For systems with high frequency of tests, and a variation in operator experience, errors are inevitable and magnified during dilution. Our Kemio technology includes a high range chlorine sensor, which reduces the need for dilution. In addition where dilution is required, a dilution factor can be added to the test to do the calculations for the operator.

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