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chlorine residual monitoring

by:BOQU     2023-04-25

Chlorine Residual Monitoring: A Must for Safe Drinking Water

Water is considered the most essential need for humans, and we depend on it for many activities, including drinking, hygiene, and cooking. However, safe drinking water is not always available to everyone, and in many regions, waterborne diseases are still a significant public health concern. Therefore, safe water management practices are essential, including treating the water before distribution. One of the most commonly used disinfectants is chlorine, and monitoring chlorine residuals is critical to ensure safe water distribution.

What is Chlorine Residual?

Chlorine residual refers to the amount of chlorine remaining in the water after the adequate disinfection period has passed. In other words, it is the leftover chlorine that can still kill any pathogens that might still be present in the water. Chlorine residual is necessary to ensure that the water remains safe for human consumption, and an insufficient amount of chlorine residual can lead to waterborne diseases. Therefore, monitoring chlorine residual is paramount to confirm that the disinfection process is effective, and the water quality remains safe.

Why is Chlorine Residual Monitoring Important?

1. Safety: Keeping the water safe for human consumption is the primary driving factor behind chlorine residual monitoring. By measuring the amount of residual chlorine present in the water, it is easy to determine whether the water is safe for drinking or not.

2. Compliance: In many countries, there are regulations and standards on the amount of residual chlorine that should be present in the water. Chlorine residual monitoring ensures compliance with the regulatory requirements, and it is useful to identify any departure from the standard.

3. Efficiency: Monitoring chlorine residual is an efficient way to evaluate the effectiveness of the disinfection process. It helps to detect any potential issues early and ensures the proper maintenance of equipment and systems.

4. Early Detection: Detecting any decline in chlorine residual levels early enough can prevent cross-contamination from occurring.

How is Chlorine Residual Measured?

The most common method of measuring residual chlorine is known as the colorimetric method. This method involves the use of reagents that react with the chlorine residual to produce a color, and the intensity of the color is proportional to the amount of chlorine present. Additionally, there are devices that measure chlorine residual using electrochemical sensors that detect changes in the current as it passes through the water.

Challenges of Chlorine Residual Monitoring

While chlorine residual monitoring is critical to ensuring safe drinking water, it comes with many challenges, including:

1. Testing Frequency: Depending on regulatory requirements, the frequency of chlorine residual monitoring may differ from one facility to another. Some facilities are required to test their water hourly, while others may test less frequently.

2. Turbid Water: Turbid or cloudy water can interfere with the chemical reaction used in colorimetric testing. As a result, it may lead to false readings of chlorine residuals.

3. Sensor Calibration: Electrochemical sensors require regular calibration to ensure accurate chlorine residual readings. Any failure to calibrate the sensors could affect the accuracy of the results.

4. Human Error: The use of reagents and chemicals in the colorimetric method makes it prone to human error, leading to false readings. It is therefore essential to train staff involved in chlorine residual monitoring and limit human error where possible.


Chlorine residual monitoring is essential for safe drinking water distribution, and it helps to ensure that the water quality is not compromised. It also helps to keep facilities compliant with regulatory standards and ensures the efficiency of disinfection methods. While there are challenges associated with chlorine residual monitoring, leveraging technology and training staff can help mitigate some potential issues. Adequate chlorination and monitoring of chlorine residual levels are a vital part of water disinfection, and it is clear that it must be taken seriously to prevent waterborne diseases.

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