491 Environmental Microbiology and Legionella: Managing Building Water Risks with Dr. Rajiv Sahay

Reliable Legionella results begin long before a sample reaches the laboratory. Dr. Rajiv Sahay of Sahay Scientific Services explains how building conditions, field collection practices, and laboratory methods influence the quality—and usefulness—of the data water professionals receive.

Building Water Conditions Shape the Risk

Modern buildings rely heavily on controlled mechanical systems, yet water can remain an overlooked part of the indoor environment. Stagnation, low flow, dead legs, temperature, pH, disinfectant residuals, corrosion, and accumulated organic material can all influence biofilm development and microbial activity.

Dr. Sahay cautions against solving one problem while creating another. Raising a disinfectant concentration without considering system materials, water chemistry, and occupant health can introduce secondary risks. Instead, water professionals need enough data to balance microbial control with the operational realities of the system.

Better Samples Begin in the Field

Sample quality depends on what happens at the collection point. Dr. Sahay recommends recording temperature and pH when the sample is taken, selecting a collection technique suited to the water body, and avoiding unnecessary sediment or debris.

He also explains how gloves, hands, bottles, and sampling equipment can introduce cross-contamination. Aseptic handling, clean barriers, appropriate disinfection, and complete chain-of-custody documentation help the laboratory connect its findings with actual field conditions.

What Happens Inside the Laboratory

Dr. Sahay walks listeners through three testing pathways: non-culture methods, traditional culture, and molecular diagnostics such as PCR. Culture remains the reference method discussed for isolating and confirming Legionella, while molecular testing can provide faster screening information.

The conversation also follows a sample through filtration, preparation, inoculation on BCYE media, incubation, preliminary identification, and confirmation. This context helps water professionals understand why laboratory turnaround times and reported results vary by method.

Reading Results With the Right Context

A nondetect does not necessarily establish that an entire water system—or even the full sample bottle—contains no Legionella. It means the laboratory did not detect the organism in the analyzed portion under the method's detection capability.

That distinction reinforces the central lesson: usable field data, representative sampling, appropriate laboratory methods, and informed interpretation must work together.

Listen to the full conversation above. Explore related episodes below. Stay engaged, keep learning, and continue scaling up your knowledge!

Connect with Dr. Rajiv Sahay 

Phone: (727) 488-4001 

Email: rajiv_sahay9@hotmail.com 

Website: Environmental Services Consulting  

LinkedIn: Dr. Rajiv Sahay, FIAS, CIAQP | LinkedIn  

Sahay's Scientific Services: Overview | LinkedIn 

Guest Resources Mentioned  

Presentation – Legionella Unveiled: Safeguarding Water Systems in a Changing World by Dr. Rajiv Sahay 

Environmental Microbiology 3rd Edition by Ian Pepper (Editor), Charles P. Gerba (Editor), Terry Gentry (Editor) 

Bergey's Manual of Systematic Bacteriology: Volume One : The Archaea and the Deeply Branching and Phototrophic Bacteria 2nd Edition by David R. Boone (Editor), George M. Garrity (Editor), Richard W. Castenholz (Editor) 

Bergey's Manual of Determinative Bacteriology. Eighth Edition by R. E. Buchanan (Editor), N. E. Gibbons (Editor) 

CDC Legionella water management program overview 

CDC Legionella prevention resources: https://www.cdc.gov/legionella/index.html

CDC ELITE Program (Environmental Legionella Isolation Techniques Evaluation) 

EPA (Legionella-related publications and resources) 
ASHRAE Standard 188 (Legionellosis risk management)  

Scaling UP! H2O Resources Mentioned 

AWT (Association of Water Technologies) 

Scaling UP! H2O Academy video courses 

Submit a Show Idea 

Rising Tide Mastermind 

Scaling UP! H2O Legionella Resources Library 

Water You Know with James McDonald

Today's definition is an organophosphorus compound containing a direct carbon-phosphorus bond that is commonly used in water treatment for corrosion control and threshold scale inhibition. Can you guess the word or phrase?

2026 Events for Water Professionals 

Check out our Scaling UP! H2O Events Calendar where we've listed every event Water Treaters should be aware of by clicking HERE. 

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