Drinking water is treated at water treatment plants by transforming raw water into potable water. One step in water treatment is disinfecting the water to either kill or inactivate contaminants that can be harmful to humans.

Chlorine—a Common Form of Disinfection

Disinfection with chlorine is very common, but can react with organic matter that naturally occurs in water, causing disinfection byproducts (DBPs) to form. DBPs can be harmful to human health and are regulated by the U.S. Environment Protection Agency through the Stage I and Stage II Disinfectant/Disinfection Byproducts Rules.

Chloramines—an Alternative to Chlorine

Some water providers are now turning to chloramines to help reduce DBP formation. Formed by the reaction of chlorine and ammonia, chloramines have several advantages over chlorine:

• A more stable and longer lasting residual is provided in the distribution system
• Less DBPs are produced than from chlorine
• The swimming pool smell and taste is eliminated
• Chloramines' use can be more economical

The Correct Dosing for Chloramines

The correct dosing ratio is between four and five parts chlorine to one part ammonia. If not dosed correctly, chloramines can provoke taste and odor problems, or leave a distribution system without disinfection residual. Some characteristics in water quality can negatively affect lead and copper concentrations in the distribution system, especially if a distribution system contains older materials.

Choosing the Right Form of Ammonia for the Chloramination Process

Ammonia comes in liquid, dry, or gas forms and each has its own advantages and disadvantages for design, operations, and maintenance.

• Ammonia Gas
• Pros: Gas systems are smaller and more compact, and offers more storage space
• Cons: Pressurized gas could be a problem, as well as potentially effecting water quality
• Dry Ammonia
• Pros: Dry ammonia feed systems can include an automatic batching system. While one tank is in use, a second tank is mixing the dry ammonia and water
• Cons: Can be a labor intensive system to operate depending on the dosing requirements
• Ammonia Liquid
• Pros: Liquid ammonia feed systems are flexible, and can limit capital costs. Additionally, many forms of liquids are available for use
• Cons: Water quality and off-gassing are two issues that need to be investigated prior to selection

The Conversion Process

When ammonia feed equipment is installed and working properly, the water provider must flush the chlorinated water and introduce the chloraminated water into the system. The flushing program is necessary to avoid taste and odor problems when the two waters meet. All water customers should be notified of the change.

Protecting Our Health

When potable water providers are faced with DBP levels in excess of EPA limits, they may want to consider chloramines to help reduce DBP formation in the distribution system, providing healthier water.