Scott Kahle Explores Chloramination and How to Optimize the Process

Chloramination can be a complex topic, but our own Scott Kahle, Vice President of Process Analyzers and Monitoring, breaks it down and explains the benefits and challenges of monitoring at every stage to optimize the process.

In-Situ: Scott, tell us how the chloramination process was developed?

Scott: Around the turn of the last century, scientists discovered that chlorine added to water dissipated quickly but when natural ammonia was present, chlorine lingered, and bacteria didn’t form as easily.

In the early 1930s, some cities in the U.S. began putting ammonia in treated water so the chlorine would last longer, resulting in safe drinking water all the way to people’s taps.

In the 1970s, carcinogenic disinfection byproducts, specifically trihalomethane and haloacetic acid, were discovered in drinking water. The Safe Drinking Water Act was created in 1975, putting limits on byproducts.

In the same decade, chloramines started being used as a secondary disinfectant to meet disinfection byproduct requirements. Chloramines are a group of compounds that contain chlorine and nitrogen. They are less volatile than chlorine and provide a better protection against bacterial regrowth in systems.

The process of treating water with chloramines is called chloramination. It is now widely used in municipalities in the US. and Canada.

In-Situ: What are the advantages of chloramination over other disinfection processes?

Scott: Other disinfection processes involve complete organic material removal and require more manpower. Chloramination is a lower-cost process and results in better-tasting drinking water with little to no odor. Currently, more than 1,500 utilities use chloramination in the United States.

In-Situ: And what about breakpoint chlorination?

Scott: Breakpoint chlorination is the technique of removing combined chlorine by adding free chlorine, adhering to the breakpoint curve.

The breakpoint curve has four zones that are vital to the chloramination process:

Zone 1: Where the initial chlorine demand is met and chlorine is oxidizing

Zone 2: When chloramines are forming up to an approximate ratio of 5:1

Zone 3: When no free ammonia is available for reaction and dichloramines and trichloramines are formed

Zone 4: When free chlorine is being created and for every 1.0 mg/l of chlorineadded, the residual will increase 1.0 mg/l.

It’s critical to follow the breakpoint curve during zone two when monochloramines are formed. Keeping the chlorine feed stable and adjusting ammonia levels will keep the water free from microbes and keep di and trichloramines from being created.

Following the breakpoint curve is a balance, but adhering to it will keep the water from having undesired taste or odor.

In-Situ: What are the challenges of chloramination?

Scott: There are four primary challenges:

• It’s important to maintain the correct level of disinfectant to ensure safe water.

• You need to add enough ammonia to be in the right zone of the breakpoint curve.

• You also need to avoid adding too much ammonia to minimize potential for nitrification in the distribution system. It’s really a balancing act of having enough ammonia but not too much.

• You need a reliable on-line analysis system that gives you continuous information to control the chloramination process.

In-Situ: How do ChemScan analyzers help with chloramination?

Scott: Our analyzers measure multiple parameters including monochloramine, free ammonia, total ammonia and total chlorine, which helps operators know where they are in the breakpoint curve. It’s difficult for

an operator to get stable and accurate ratios with manual measurement, as it requires many measurements as well as manual analysis. Our equipment provides operators with timely chemistry measurements to optimize the process.