how to measure residual chlorine in water

How to Measure Residual Chlorine in Water

Water industry professionals and water treatment facilities know the importance of measuring residual chlorine in water to ensure safe drinking water. Chlorine is a common disinfectant used to kill harmful microorganisms present in water. After the disinfection process, residual chlorine in drinking water acts as a protective agent to prevent recontamination from bacteria and other pathogens. In this article, we will discuss how to measure residual chlorine in water accurately.

What is Residual Chlorine?

Residual chlorine is the total amount of chlorine remaining in the water after the disinfection process. The level of residual chlorine is critical to ensuring the safety of drinking water for public consumption. The United States Environmental Protection Agency (EPA) recommends a minimum residual chlorine level of 0.2 mg/L or parts per million (ppm) for safe drinking water. The level of residual chlorine significantly affects the taste, odor and appearance of drinking water.

Why Measure Residual Chlorine?

Apart from ensuring safe drinking water for public consumption, measuring residual chlorine is vital for several reasons, which include:

1. Ensuring the effectiveness of the disinfection process: Measuring residual chlorine helps water facilities to determine if the disinfection process is effective. If residual chlorine levels are low, it may indicate that the disinfection process is not working correctly, and immediate corrective action is necessary.

2. Monitoring water quality: Measuring residual chlorine helps to monitor water quality by detecting the presence of harmful microorganisms in the water. It provides valuable information about the condition of the water distribution network.

3. Preventing contamination: Residual chlorine acts as a protective agent against recontamination of water from bacteria and other pathogens.

How to Measure Residual Chlorine in Water

Now that we understand the importance of measuring residual chlorine let's explore some methods of measuring it accurately.

Method 1: Test Strips

Test strips are an easy and convenient way to measure residual chlorine levels. They come in a vial and contain a reagent that reacts with residual chlorine in water. To measure residual chlorine using test strips, follow the steps below:

Step 1: Collect a sample of the water.

Step 2: Dip the test strip into the water and wait for the recommended time.

Step 3: Compare the color of the strip to the accompanying chart to determine the residual chlorine level.

Test strips are relatively inexpensive and require no special equipment or training to use. However, they may not be as accurate as other methods.

Method 2: Colorimeter

A colorimeter is a more precise method of measuring residual chlorine levels. It measures the intensity of color produced when a reagent reacts with residual chlorine. The higher the residual chlorine level, the more intense the color. To measure residual chlorine using a colorimeter, follow the steps below:

Step 1: Collect a sample of the water.

Step 2: Add a reagent to the water sample, which reacts with residual chlorine.

Step 3: Insert the sample into the colorimeter and wait for the device to measure the intensity of the color.

Step 4: Read the residual chlorine level displayed on the device.

Colorimeters are more accurate than test strips and provide digital readings. However, they are more expensive than test strips and require special equipment and training to use.

Method 3: Titration

Titration is a laboratory method of measuring residual chlorine levels. It involves the use of a chemical reagent called an indicator that reacts with residual chlorine. To measure residual chlorine using titration, follow the steps below:

Step 1: Collect a sample of the water.

Step 2: Add a titrant solution to the water sample, which reacts with residual chlorine.

Step 3: Add an indicator solution to the water sample to determine the end point.

Step 4: Record the volume of titrant solution used to reach the end point.

Step 5: Calculate the residual chlorine level using a formula.

Titration is the most accurate method of measuring residual chlorine levels. However, it requires specialized equipment and trained personnel to perform the test.

Conclusion

Measuring residual chlorine in water is essential to ensure safe drinking water for public consumption. Water treatment facilities and industry professionals need to use accurate testing methods to monitor residual chlorine levels. There are several methods available, including test strips, colorimeters, and titration. Each method has its advantages and disadvantages, but they all provide valuable information about water quality. With careful measurement, proper monitoring, and prompt corrective action, the safety and quality of drinking water can be ensured.