Legionella Control with Efficient Water Conditioning

Early Spring is a good time for facility operators to prepare their building water systems for the warm months ahead, and to consider safe and sustainable ways to prevent legionella, which forms in numerous water systems besides cooling towers. Legionella is not a new strain of bacteria, but with continuous improvements in the efficiencies of systems and building practices, these bacteria could be more difficult to control in some areas that chemicals have difficulty reaching.  HydroTech Solutions is a distributor of HydroFLOW, that provides electronic water conditioning to control bacteria, scale and corrosion in water systems. HydroFLOW controls legionella and algae in cooling towers, potable water systems and water heaters with a frequency that extends throughout a water system.

Chemicals should be used in water systems according to regulations, and when used with HydroFLOW the volume of chemical use is reduced between 50%-75%, and water purging/ blowdown is decreased by more than 50% in most cases. HydroFLOW reduces chemicals, water and energy use as a sustainable water management technology for water systems of any size.

Legionnaires outbreaks have occurred with some frequency recently, and after considerable time and review, ASHRAE approved the 188 standard for legionella in 2015 called ANSI/ASHRAE 188-2015, “Legionellosis: Risk Management for Building Water Systems.” The Legionella risk reduction strategy set forth in 188-2015 is to implement a water management plan for building water systems including cooling towers, evaporative condensers, whirlpool spas, ornamental fountains, misters, atomizers, air washers, humidifiers, and other devices that release water droplets.

A management plan would be required for potable plumbing systems only in buildings that have any of the following: (a) multiple housing units with a centralized hot water system; (b) more than 10 stories; (c) housing for occupants over the age of 65; (d) health care for patients staying longer than 24 hours; or (e) an area housing or treating persons at especially high risk of contracting Legionnaires' disease.

ASHRAE 188-2015 is consistent with the World Health Organization, Veterans Health Administration, and the U.S. Environmental Protection Agency (EPA) about the essential components each water management plan should include:

  • A list of the water management plan team members. Teams typically consist of 10 or fewer people who oversee the program and make decisions about it. Many others are needed to implement the plan.
  • A brief description of the building water systems, with flow diagrams. Salient information should be included for all of the building water systems, not just the ones prone to Legionella growth and transmission. Simple line flow diagrams should show where water is received, processed, and used.
  • Analysis of the building water systems. Commonly referred to as hazard analysis, this is a brief explanation as to why each water system does or does not present a significant potential for Legionella growth and transmission and, for those that do, whether it is a location at which Legionella control measures can be applied.
  • Control measures. Only what is actually done to water systems will reduce Legionnaires' disease, so control measures are the most important part of any Legionella water management plan. The team must come up with a specific list of control measures for each building water system. ASHRAE gives a framework for the team to fill in, stating that procedures must be included, as applicable, for new construction, equipment siting, start-up and shutdown, inspections, maintenance, cleaning, disinfection, monitoring (e.g., temperatures, disinfectant levels), and water treatment. The team must also write out steps for responding to Legionnaires’ disease should a case occur despite the prevention efforts.
  • Each control measure must be monitored to determine whether it is performed to the standard, called a control limit, designated in the plan. If the control limit is not met, then corrective action must be implemented. The monitoring procedure, monitoring frequency, control limit, and corrective action must be listed for each control measure.
  • Documentation and communication procedures. Draft number five of 188-2015 instructs the team to “establish documentation and communication procedures for all activities of the program.”
  • Verification procedures. The team, or a designated “verification person,” must review documentation to ensure the plan is being implemented.
  • Validation. The effectiveness of the plan in controlling Legionella must be validated. Testing water systems for Legionella provides the most direct feedback on Legionella control. Legionella testing is discussed as a validation option in 188-2015 but is not required.

HVAC contractors and others that provide services on or near cooling towers should take reasonable measures to protect themselves from Legionnaires’ disease, and many building operators have initiated legionella testing programs on a schedule to monitor levels of bacteria in water systems.

Water systems that are determined to require Legionella control measures require designers to provide documentation, diagrams, and instructions for monitoring and control of legionella, and should note locations of equipment access (and note inadequate access), filling and draining, flushing, sampling, temperature monitoring, treatment, no flow and low flow areas, possible cross connections between potable and non-potable systems, and outside air intakes.

Preventive measures for legionella have been specified in ASHRAE 188-2015: Locate cooling towers to minimize transmission of drift to people; for example, as far as reasonably possible from building openings, outside air intakes, parking lots, and sidewalks. Also, avoid locating cooling towers near sources of contamination such as kitchen exhausts that make water treatment for microbial control even more challenging.

Legionella prevention and mitigation should be a part of every facility manager’s standard operating procedures, and while chemicals have traditionally been at the forefront of control, more sustainable methods can be used that complement chemical applications while reducing their volume and cost.

HydroFLOW installs in minutes and operates 24/7 without balancing dosages or concentrations.  HydroFLOW neutralizes bacteria, biofilm and algae throughout a water system while controlling scale, which reduces another set of chemicals that require balancing. Sustainable water management is good for people, budgets and it improves operations.


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