Legionella Supplemental Disinfection

When short-term Legionella remediation doesn’t provide long-term effectiveness in eliminating bacteria from your water systems, it may be time to consider continuous supplemental disinfection. Deciding to add supplemental disinfection to your building’s water systems can be complex. While the goal is to reduce the risk of Legionnaires’ Disease, there are associated capital and ongoing maintenance costs. Additionally, it requires modifications to plumbing systems, knowledge of EPA permitting and disinfectant levels, routine monitoring, and preventive maintenance.

Fortunately, ChemREADY has experts who can guide you through the decision-making process, helping you determine if supplemental disinfection is the right solution for your facility.

Types of Secondary Disinfection

There are several approaches to consider for supplemental disinfection of potable water. Each solution has unique considerations, including required permitting, capital costs, equipment availability, ongoing maintenance expenses, EPA regulations, monitoring requirements, equipment footprint, permitting timelines, water operator license requirements, and engineering constraints. It’s crucial to understand the specific requirements of your state and municipality before making a decision.

Legionella supplemental disinfection should only be considered when shock disinfection and the primary water supply disinfection aren’t sufficient to continuously minimize the growth of Legionella bacteria and other waterborne pathogens. Here are some common supplemental disinfection methods:

Legionella Treatment
  • Chlorination: Chlorination is widely used in public water supplies and for supplemental disinfection. If your incoming water supply has low disinfectant levels (<0.5mg/L), your facility may be at risk for ongoing Legionella bacteria issues. Supplemental chlorination systems inject additional chlorine into the potable water, either in the cold water supply or the hot water system. The EPA drinking water limit for chlorine (as Cl2) is 4 mg/L, with a recommended control range between 0.5 to 3.0 mg/L.
    • Advantages:
      • Readily available and cost-effective
      • Effective against bacteria, viruses, and other organisms
      • Easily monitored for disinfectant levels
      • EPA-certified for drinking water disinfection
    • Disadvantages:
      • Limited penetration of biofilm; oxidizes quickly on contact with bacteria
      • Potentially creates harmful disinfectant byproducts when reacting with organic materials
      • Can degrade piping materials over time
      • Less effective in hot water systems due to dissipation
  • Chlorine Dioxide: Chlorine Dioxide (ClO2) is a versatile, broad-spectrum biocide, second only to ozone in biocidal efficacy. It selectively oxidizes biological pathogens while generating fewer disinfectant byproducts.
    • Advantages:
      • More effective than chlorine as a disinfectant, with fewer byproducts
      • Effective at low concentrations and does not cause odor or taste issues in drinking water
    • Disadvantages:
      • Requires on-site generation due to transportation difficulties
      • Higher capital costs for equipment installation
      • Short shelf life and rapid decomposition
      • Requires strict safety measures due to the explosive nature of chlorine dioxide gas
  • Monochloramine: Monochloramine is highly effective against Legionella, both in laboratory and field studies. It is stable and penetrates biofilm more effectively than chlorine, with a wider pH working range than copper-silver ionization and chlorine.
    • Advantages:
      • Effectively penetrates biofilm and maintains longer stay times in water
      • Does not dissipate in hot water like chlorine and chlorine dioxide
      • Less corrosive to plumbing with fewer disinfection byproducts
    • Disadvantages:
      • Requires on-site generation using ammonia and chlorine, with associated capital costs
      • Monitoring of free ammonia is necessary to prevent increased corrosion in systems
      • Cold water application can affect dialysis, fish tanks, and nitrification in water
  • Ozone: Ozone is created when oxygen (O2) molecules are broken apart by an energy source, forming ozone (O3). Ozone is a powerful oxidant and disinfectant.
    • Advantages:
      • More effective than chlorine in destroying bacteria and viruses
      • Requires only a short contact time to be effective
      • Decomposes rapidly, leaving no harmful residuals
    • Disadvantages:
      • High capital and maintenance costs make it less competitive for smaller facilities
      • Requires a highly skilled maintenance team and constant monitoring
      • Very corrosive, requiring corrosion-resistant piping materials
      • High energy requirements
  • Copper-Silver Ionization: Copper-Silver Ionization was the original technology used to combat Legionella bacteria. This electrolysis process introduces positively charged copper and silver ions into the water supply through an electrical current, eliminating bacteria by binding to their negatively charged cell walls.
    • Advantages:
      • Effective in both cold and hot water applications
      • Not affected by pH levels up to 9.00
      • Long stay-times in both cold and hot water, making it a good long-term solution
    • Disadvantages:
      • Effectiveness drops to 10% at pH levels above 9.00
      • High dissolved solids can cause silver to precipitate, reducing disinfection effectiveness
      • High capital costs for system installation

Legionella Disinfection Solutions

Choosing the right supplemental disinfection method can be challenging. If you believe your facility could benefit from a supplemental disinfection technology, reach out to our experts at ChemREADY today to discuss your options.

FAQ for Legionella Supplemental Disinfection

What is Legionella Supplemental Disinfection?

Legionella Supplemental Disinfection refers to the continuous disinfection methods used to prevent Legionella bacteria from growing in water systems when short-term remediation is not effective. This process helps reduce the risk of Legionnaires’ disease by maintaining ongoing protection.

When should a facility consider supplemental disinfection?

Facilities should consider supplemental disinfection when shock disinfection and the water supply’s existing disinfection are insufficient to continuously minimize the growth of Legionella and other waterborne pathogens.

What are the common methods of supplemental disinfection?

The most common methods include chlorination, chlorine dioxide, monochloramine, ozone, and copper-silver ionization. Each method has its own advantages and disadvantages based on factors such as cost, effectiveness, and maintenance requirements.

What are the advantages of using monochloramine for Legionella control?

Monochloramine is effective in penetrating biofilm, does not dissipate in hot water, and is less corrosive compared to chlorine. It also produces fewer disinfection byproducts, making it a safer choice for long-term use.

How can ChemREADY assist with Legionella supplemental disinfection?

ChemREADY’s experts can guide you through the decision-making process, helping you determine the best supplemental disinfection method for your facility. They provide support in understanding EPA regulations, equipment needs, and ongoing maintenance.