If short-term remediation does not have long-term effectiveness in eliminating legionella in your system, some facilities should consider continuous supplemental disinfection. However, the decision to add supplemental disinfection to your building water systems can be challenging. While a facility wants to reduce the risk of Legionnaires’ Disease, there are capital and ongoing maintenance costs. It also requires modification to plumbing systems, knowledge of EPA permitting and disinfectant levels, routine monitoring, and preventive maintenance activities.
Luckily, ChemREADY has experts that can walk you through the decision-making process, to see if this could be a good fit for your facility.
Several approaches can be considered for supplemental disinfection of potable water. There are many considerations for each solution to include required permitting, capital costs, availability of equipment, ongoing maintenance costs, EPA regulations, monitoring requirements, footprint of equipment, permitting timeline, water operator license requirements, and engineering constraints. Every state and municipality has different requirements and it’s important to understand those in order to make a decision.
Legionella supplemental disinfection should only be considered when shock disinfection and the water supply’s disinfection isn’t enough to continuously minimize the growth of Legionella bacteria along with other waterborne pathogens. There are a few common supplemental disinfection methods:
There are many continuous supplemental disinfection options available to end users. Each type of supplemental disinfection has advantages and disadvantages that are unique to every situation. The following list contains common supplemental disinfection methods:
Chlorination is a common disinfectant used in public water supplies and in supplemental disinfection. If your incoming water supply has low levels of disinfectant (<0.5mg/L), your facility has the potential for on-going issues with Legionella bacteria and other waterborne pathogens. Chlorination can be used to supplement the existing disinfectant in your water supply. Supplemental chlorination systems inject additional chlorine into the potable water, either the cold water supply or the hot water system.
The EPA drinking water limit for Chlorine (as Cl2) is 4 mg/L while most manufacturer’s recommend a control range between 0.5 to 3.0 mg/L
Advantages to using supplemental chlorination are:
Disadvantages of chlorination are:
Chlorine Dioxide (ClO2) is a versatile, broad-spectrum biocide, second only to ozone in biocidal efficacy. It selectively oxidizes biological pathogens while generating less disinfectant byproducts.
The EPA drinking water limit for Chlorine Dioxide (as ClO2) is 0.8 mg/L while most manufacturers recommend a control range between 0.1 to 0.7 mg/L.
Advantages of chlorine dioxide:
Disadvantages of chlorine dioxide:
Monochloramine
Monochloramine is one of the most effective disinfectants against Legionella, both in laboratory and field studies. Monochloramine is stable and has the ability to penetrate biofilm more effectively than chlorine, and has a wider pH working range than copper‑silver ionization and chlorine
The EPA drinking water limit for Monochloramine (as Cl2) is 4.0 mg/L while most manufacturers recommend a control range between 2.0 to 3.0 mg/L.
Advantages of monochloramine are:
Disadvantages of monochloramine are:
Ozone is created when Oxygen (O2) molecules are broken apart by an energy source into oxygen atoms and collide with an oxygen molecule to form an unstable gas, ozone (O3). Ozone is a very strong oxidant and disinfectant.
Advantages of ozone:
Disadvantages of ozone:
Copper-Silver Ionization
Copper-Silver Ionization was the original technology used in combatting Legionella bacteria. Copper-Silver Ionization is an electrolysis process that introduces positively charged copper and silver ions into the water supply through an electrical current. The positive ions bind to the negatively charged cell walls of bacteria, eliminating them through the process.
The EPA drinking water limit for Copper is 1.3 mg/L while most manufacturers recommend a control range between 0.2 to 0.8 mg/L. The drinking water limit for Silver is 0.1 mg/L while most manufacturers recommend a control range between 0.01 to 0.08 mg/L.
Advantages of Copper-Silver Ionization:
Disadvantages of Copper-Silver Ionization
Figuring out the best supplemental disinfection method can be a confusing and daunting task. If you feel your facility could benefit from the addition of a supplemental disinfection technology, contact our team of experts at ChemREADY today to discuss options.
