Add Products to the Cart to Obtain Instant Discounts!

Chlorimation and the false Free Chlorine residual

December 06, 2016 0 Comments

Chlorimation and the false Free Chlorine residual

Chloramination is often used as a disinfectant method when there is a large distribution network, as it provides a more prolonged disinfection compared to free chlorine.

Chloramines are usually formed by adding ammonia to water containing free chlorine (HOCl- or OCl-, depending on the pH) in a particular ratio (usually chlorine:ammonia 5:1). When the reaction takes place, three kinds of inorganic chloramines can be formed; monochloramine; dichloramine and trichloramine. Which form is predominant within the solution is dependent on the chlorine:ammonia ratio, the pH of the solution and the contact time. The ideal pH value for the production of monochloramines in this reaction is 8.4.

The Problem

 

Traditionally, DPD (N,N Diethyl-1,4 Phenylenediamine) chemistry has been used to monitor free chlorine and chloramines. This can lead to confusion within the distribution network as the DPD method for determining free chlorine can suffer interference from monochloramine. This is known as 'breakthrough' and is when monochloramine breaks into the free chlorine fraction. The rate of breakthrough is affected by pH and temperature and is often witnessed as a slow increase in the free chlorine value, whilst not affecting the total chlorine reading.

At Palintest, DPD tablets are controlled so that they do not suffer excessive breakthrough when testing chloramine solutions, however some interference (<5%) still exists. The utility used an online monitoring system based on the DPD colorimetric method and frequently found fluctuations in their free chlorine measurements, which they suspected were related to breakthrough.

 

The Solution

The ChloroSense instrument uses a patented electrochemical method known as chronoamperometry, combining an instrument and disposable sensors for the simultaneous measurement of free and total chlorine. When the sensor is immersed in the test solution, chlorine will react with the reagents on the free chlorine electrode and chlorine and chloramines (total chlorine) will react with the reagents on the total chlorine electrode.

 

The Results

The ChloroSense was used alongside a DPD colorimetric on-line system on an hourly basis over two days within their distribution network, to determine the performance of two methods in the chloraminated water.

The graph shown below demonstrates that both the ChloroSense and the online DPD based method gave similar total chlorine readings across the test period around the expected 1.5 mg/L dose.

TOTAL CHLORINE

 

FREE CHLORINE

Conclusion

With high levels of ammonium (NH4) and free chlorine being dosed into the network, the utility expected to see a low free chlorine residual and a total chlorine response of approximately 1.5 mg/L. The on-line DPD method struggles to monitor the free chlorine residual accurately whilst performing well when testing total chlorine.

The ChloroSense results show that breakthrough is not an issue with the chemistry used on the sensor. Free chlorine residuals are monitored as below 0.05mg/l over the two day testing period. The total chlorine results show the ChloroSense matches on the on-line analyser.

In summary, for applications where chloramination is being used, using DPD chemistry to monitor free chlorine residuals can be difficult - a skilled operator is called for. For applications where breakthrough is an issue, ChloroSense can provide the solution.

 


Also in Blog

Advanced Cooling Tower Management: Enhancing Efficiency with Lakewood Model 140
Advanced Cooling Tower Management: Enhancing Efficiency with Lakewood Model 140

February 28, 2024 0 Comments

View full article →

Optimizing Cooling Tower Performance: Understanding Efficiency, Maintenance, and Water Quality Management
Optimizing Cooling Tower Performance: Understanding Efficiency, Maintenance, and Water Quality Management

February 28, 2024 0 Comments

Implementation of the Lakewood 3175 controller in cooling tower systems, emphasizing its significant role in enhancing operational efficiency, reducing chemical usage, and mitigating issues related to corrosion and deposition. It highlights the controller's ability to automate the management of water conductivity, ensuring optimal water quality and system performance. Examples and hypothetical calculations are provided to illustrate the controller's benefits, including water savings, cost reductions in chemical treatments, and energy efficiency gains through the prevention of scale buildup and corrosion. The Lakewood 3175 controller is presented as a strategic tool for achieving a more sustainable, efficient, and cost-effective cooling tower operation, demonstrating the value of advanced technology in industrial water management.

View full article →

Revolutionizing Water Analysis: Everything You Need to Know About the Kemio KEM10DIS
Revolutionizing Water Analysis: Everything You Need to Know About the Kemio KEM10DIS

April 19, 2023 0 Comments

The Palintest Kemio KEM10DIS is a highly accurate, fast, and easy-to-use water analysis device that offers several advantages over other methods. Its portability and wide measurement range make it ideal for use in a range of applications, from drinking water to industrial process water. With its patented Dual-Field technology and fast results, the Palintest Kemio KEM10DIS can help to improve the efficiency of water treatment processes and reduce the risk of contamination. Compared to other methods, the device is highly accurate and easy to use, making it accessible to a wide range of users. By following the simple procedure outlined above, users can quickly and easily obtain accurate results for a range of parameters, helping to ensure the safety and quality of water for various applications.

View full article →