Legionella Control Programs

Effective Legionella Control Requires an Effective Biofilm Control Program

Outbreaks in Legionnaires’ Disease such as the one in the South Bronx in August 2015 highlight the importance of having an effective Legionella Control Program. Legionella bacteria grow in biofilms in building water systems, where they are protected from the disinfecting action of oxidizing and non-oxidizing biocides.

The importance of biofilm control is highlighted in the following excerpt from Biofilms: The Stronghold of Legionella Pneumophila by M. Adbel-Nour, C. Duncan, D.E. Low and C. Guyard (Toronto); Int. J. Mol. Sci. 2013, 14, 21660-21675.


The evidence from decades of scientific research is very clear. Legionella pneumophila resides primarily in biofilms in building and industrial water systems.

Priscilla Declerck’s article, Biofilms: the environmental playground of Legionella pneumophila (Society for Applied Microbiology and Blackwell Publishing Ltd, Environmental Microbiology, 12, 557-566) summarizes several research studies involved with the mechanisms and factors that affect the biofilm life cycle of L. pneumophia. Declerck notes:

For further reading on Legionella in biofilms see “Replication of Legionella pneumophila in Biofilms of Water Distribution Pipes”, by Priscilla Declerck, Jonas Behets, Anca Margineanu, Vincent van Hoef, Brenda DeKeersmaecker, and Frans Ollevier. Microbiological Research 164 (2009) 593-603.

These articles illustrate that in order to deliver effective Legionella control, it is absolutely essential that your biocide program effectively controls biofilms!

AMSA’s BCP 1015 (DTEA II®) is a field-proven organic deposit penetrant/dispersant which has been used with oxidizing and non-oxidizing biocide programs for more than 18 years to provide an effective Biofilm Control Program in industrial water systems.

BCP® 1015 has been used effectively in the hyper-halogenation Wisconsin Emergency Protocol for Legionella cleanup and control, and can be used subsequent to cleanup and disinfection in an ongoing maintenance program with biocides to control biofilm buildup throughout the cooling system. See Legionella case study.


ASHRAE Standard 188-2015: Legionellosis: Risk Management for Building Water Systems

A key document from ASHRAE that establishes minimum Legionellosis risk management requirements for building water systems was published in June of 2015 (ANSI/ASHRAE 188-2015). Many government buildings and municipalities concerned with Legionella control are mandating building managers follow the guidelines outlined in this document.


Four important documents cite the importance of using a “dispersant” in conjunction with biocides for clean-up and control of Legionella.
Cooling Tower Institute (CTI) WTB-148 (2008)
Legionellosis Guideline: Best Practices for Control of Legionella

“Legionella pneumophila grows within biofilms and within protozoa acting to shield L. pneumophila from concentrations of biocides that would otherwise kill or inhibit L. pneumophila when freely suspended in water.”

“Emergency Disinfection Procedure:

  1. Add a biocide sufficient to achieve 25 to 50 ppm of free residual halogen.
  2. Add an appropriate biodispersant (and antifoam if needed).
  3. Maintain 10 ppm free residual halogen for 24 hours…
  4. Drain the system…
  5. Refill the system and repeat (the treatment)…
  6. Inspect after the second drain-off.
  7. If a biofilm is evident, repeat the procedure.
  8. When no biofilm is obvious, mechanically clean the tower fill, tower supports, cell partitions, and sump.”
OSHA Technical Manual, Section III Chapter 7
Section III, Chapter 7. Legionnaires Disease

Clean and disinfect the entire cooling system including attached chillers and/or storage tanks (sumps) following the “Wisconsin (Emergency) Protocol” , as follows:

  1. “Shock” treat cooling tower water at 50 ppm free residual chlorine.
  2. Add dispersant.
  3. Maintain 10 ppm chlorine for 24 hours.
  4. Drain system.
  5. Refill and repeat steps a through d.
  6. Inspect system for visual evidence of biofilm. If found, repeat steps a through d.
CDC Procedure for Cleaning Towers infected with Legionella
  1. Add fast-release, chlorine-containing disinfectant in pellet, granular, or liquid form, … to achieve initial free residual chlorine of 50 mg/L
  2. Add dispersant simultaneously with or within 15 minutes of adding disinfectant.
  3. After adding disinfectant and dispersant, continue circulating the water through the system. Add chlorine as needed to maintain FRC at > or = 10 mg/L for 24
  4. Drain the system. Refill system with water and repeat procedure
Legionella and the Prevention of Legionellosis (2007)
  1. Add fast-release, chlorine-containing disinfectant in pellet, granular, or liquid form, … to achieve initial free residual chlorine of 50 mg/L
  2. Add dispersant simultaneously with or within 15 minutes of adding disinfectant.
  3. After adding disinfectant and dispersant, continue circulating the water through the system. Add chlorine as needed to maintain FRC at > or = 10 mg/L for 24
  4. Drain the system. Refill system with water and repeat procedure

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