Monochloramines vs. Copper-Silver Ionization (CSI): Which is Better for Legionella and Waterborne Pathogen Control for Potable Water?

When it comes to controlling Legionella and other waterborne pathogens in building water systems, both monochloramines and copper-silver ionization (CSI) are widely used methods for long-lasting disinfection ideal for larger, complex, potable water systems. Each has its own strengths and weaknesses, and the best choice often depends on the specific circumstances of the water system, water quality, the level and type of pathogen control required, and regulatory or environmental concerns. Both methods benefit from a multi-barrier approach including filtration, UV and temperature and stagnation control. Here’s a comparison of the two approaches:

Monochloramines for Legionella Control

Monochloramines are a combination of chlorine and ammonia used as a disinfectant in water systems. This method is well known for its stability and effectiveness in complex water systems.

Pros:

• Residual Effect: Monochloramines provide longer-lasting disinfection than oxidants like chlorine and chlorine dioxide, allowing them to travel farther through the water distribution system to reach distant parts of plumbing for up to two weeks.
• Effective Against Biofilms: Monochloramines penetrate and disrupt biofilms, the slimy coatings that harbor Legionella bacteria and protect them from disinfectants.
• Fewer By-products: Monochloramines produce fewer harmful by-products than other oxidizers such as trihalomethanes (THMs) and haloacetic acids (HAAs), which are linked to health risks.
• Broad Based Pathogen Control: Monochloramines attack a wide variety of waterborne pathogens.

Cons:

• Disinfection By-products: Though they produce fewer byproducts than some other oxidants like chlorine, harmful by-products are still created, which are linked to health risks.
• NTM: NTM, a hard-to-kill and common waterborne pathogen, has been shown to be more prevalent in systems treated with monochloramines.
• Sensitive to Water Quality: The efficacy of monochloramines can be influenced by factors such as temperature, suspended solids, organic matter, and pH which may reduce its effectiveness in controlling pathogens.
• Slower-Acting: Monochloramines are slower to act than other oxidants like chlorine and Mixed Oxidant Systems. They require a longer contact time to kill pathogens, which can be a disadvantage in situations that demand rapid disinfection of hard-to-kill organisms.
• Requires Chemicals: Two chemical precursors, Chlorine and Ammonia, are required to be delivered and safely handled and monitored for the production of monochloramines. 

Best Use Cases:

• Large, complex water distribution systems in which maintaining residual disinfectant is critical for controlling Legionella and biofilm.
• Broad-based pathogen control where many pathogens are being controlled, such as in acute healthcare facilities.

Copper-Silver Ionization (CSI) for Legionella Control

Copper-silver ionization (CSI) uses the antimicrobial properties of copper and silver ions to target Legionella and other bacteria. This method is particularly effective for controlling biofilms and gram-negative bacteria and is often used in healthcare facilities.

Pros:

• Residual Effect: Copper silver ionization provides longer-lasting disinfection than all the oxidants, including monochloramines, allowing it to travel farther through the water distribution system and remain effective even when water is stagnant in piping systems for up to two months.
• Effective for Biofilm Control: CSI is highly effective at disrupting biofilms, where Legionella and other pathogens thrive. This makes it an ideal choice for systems prone to biofilm formation, such as hospitals and buildings with large, complex plumbing systems.
• Non-Corrosive: CSI does not corrode pipes like monochloramines and other chemical disinfectants, which is an advantage in maintaining the integrity of plumbing systems.
• Chemical Free with No By-products: CSI does not use chemicals nor does it produce harmful disinfection by-products (DBPs), making it an environmentally friendly option.
• Temperature Independence: Unlike oxidizers such as monochloramines and chlorine dioxide, water temperature has no effect on the efficacy of copper silver ionization.

Cons:

• Slower Action: Similar to monochloramines, copper silver ionization works more slowly than chemical disinfectants like mixed oxidant solution or chlorine dioxide.
• Water Chemistry Sensitivity: The effectiveness of CSI changes based on water conductivity, pH and hardness levels.
• Initial Cost: Installing a copper silver ionization system can have a higher initial cost compared to monochloramine systems.
• Narrow-Based Pathogen Control: Though CSI is very effective against biofilm and Legionella, less is known about its ability to control other waterborne pathogens.

Best Use Cases:

• Healthcare settings and large facilities that require the longest-term residuals in the water to control biofilm and Legionella and other gram-negative bacteria, even during times of low water use and stagnation.
• Buildings with large, complex plumbing systems that benefit from CSI’s non-corrosive, temperature independent properties where the focus is Legionella mitigation.

Which is Better?

For all facilities, a multi-barrier approach that combines methods such as monochloramines or CSI, paired with filtration, ultraviolet disinfection and temperature and stagnation control with automatic balancing and flushing will provide the best overall protection against Legionella and other waterborne pathogens.

The choice between monochloramines and copper-silver ionization largely depends on the specific needs of the facility as well as design of plumbing system and water chemistry. Both are ideal for large, complex building systems and the mitigation of Legionella and biofilm.

• Monochloramines have an edge for broader based disinfection of other waterborne pathogens when the focus is on more than Legionella.
• Copper-silver ionization has the advantages of a longer residual effect and no disinfection byproducts.

For the best results, call the engineers at Legionella Control Systems, Inc. for expert consulting on the best systems for combating Legionella at your facility.