At EAI, we are deeply committed to protecting human health and safety through proper water management. Our Total Water approach encompasses cutting-edge expertise across all aspects of cooling tower, boiler, and potable water treatment to fully safeguard your systems. We lead with integrity in everything we do, from comprehensive site evaluations to transparent recommendations tailored to your facility’s needs.

Legionella risk assessments are a critical component of water management programs aimed at controlling the risk of Legionnaires’ disease. Conducting periodic risk assessments enables facilities to identify conditions that could allow Legionella growth and amplification in their water systems. Unchecked, Legionella bacteria can multiply and spread via water droplets, potentially causing deadly outbreaks if people inhale contaminated aerosols.

The importance of Legionella control was made clear after the 1976 outbreak in Philadelphia that gave Legionnaires’ disease its name. This outbreak at an American Legion convention led to over 200 cases and over 30 deaths after Legionella amplified extremely in the hotel’s cooling tower and contaminated its water distribution system.

This article will show how to conduct a legionella risk assessment.

Identifying Risk Factors

Pinpointing aspects of cooling tower systems and their surrounding environments that could promote Legionella growth is imperative to mitigate risk. These risk factors encompass the water systems themselves, operational practices, and ambient conditions around the cooling equipment. Thoroughly analyzing and addressing these items enables facilities to formulate targeted water treatment regimens and physical interventions to stem Legionella amplification.

Cooling Tower System Components Prone to Legionella Growth

Certain pieces of cooling equipment tend to foster Legionella proliferation more readily than others. Areas to scrutinize closely include:

• Cooling tower basins: Stagnant water and biofilms offer prime harborage
• Fill pack: Provides ample surface area for colonization
• Drift eliminators: Susceptible to biofilm accumulation
• Water distribution piping: Biofilms and sediment foster growth

Environmental Conditions Favoring Proliferation

Ambient factors around cooling systems can also accelerate Legionella amplification:

• Warm water temperatures (77°F – 108°F)
• Stagnation and low flow areas
• High humidity levels
• Exposure to soil and organic material

Cooling towers are particularly susceptible to harboring legionella bacteria because the temperature range they typically operate at is perfect for Legionella growth.

Operational Practices That May Increase Risk

Deficient operational practices can engender Legionella as well:

• Infrequent or inadequate disinfection
• Failure to routinely clean and flush water systems
• Lack of equipment inspections and maintenance
• Improper chemical treatment

Careful ongoing analysis of these numerous risk parameters is requisite to address the unique conditions permitting Legionella amplification in each facility.

Conducting the Risk Assessment

Performing a successful Legionella risk analysis requires properly scrutinizing facility water systems, sampling to confirm extent of hazards, and delineating appropriate control measures based on results. Risk assessments should systematically progress through inspection, testing, data analysis, and definition of action thresholds.

Site Inspection and System Analysis

Thoroughly inspect the cooling tower system and all connecting water lines. Document locations prone to stagnation, sedimentation, biofilm build-up, and temperature fluctuations. Review maintenance logs and operational practices for deficiencies. Identify potential environmental risk factors.

Sampling and Testing Methods

1. Culture-Based Testing: Use certified laboratories to test water samples via culture-based assays. This allows quantitative analysis and Legionella species identification.
2. Rapid Testing Methods: Alternately, portable test kits can rapidly detect Legionella antigen levels at the point of use. However, these presence/absence tests do not speciate or enumerate bacteria and are not an EPA approved testing methodology for compliance.

Interpreting Test Results and Establishing Action Levels

Compare testing results at each location to proposed maximum thresholds based on risk level. Components testing over this allowable limit require intervention. Define and implement customized disinfection, cleaning, or system modifications per component to control Legionella to acceptable parameters.

Conscientious assessment, measurement, analysis, and response tailoring provides the scaffolding for successful water management programs that control Legionella hazards. Understanding what to do when something goes out of bounds is just as important. If you have a positive Legionella, it doesn’t mean it’s the end of the world. What it means is that you now have a little extra work to do.

By following a structured approach to risk assessments, facilities can ensure their water systems are safe and compliant, protecting both their occupants and their reputations.

EAI’s Legionella risk assessments incorporate our signature Total Water methodology centered on environmental responsibility and technical excellence. Our holistic perspective and exacting protocols equip facilities to confidently maintain compliance. Work with us to implement customized water treatment regimens, equipment modifications, testing programs, and training procedures that control risk while optimizing efficiency, sustainability, and peace of mind. We remain your trusted partner at every step of responsible cooling tower management.