Secondary Water Disinfection

There are a number of locations, including but not limited to healthcare facilities, where at-risk populations, waterborne pathogens and rigorous regulatory requirements intersect. Serious water borne infections have occurred at hospitals, nursing homes, ambulatory surgery centers, hotels, office buildings, assisted living facilities, and cruise ships.

Tap water is a documented source of infections, often traced to the presence of Legionella pneumophila, the causative agent of Legionnaire's Disease (LD), as well as Pseudomonas aeruginosa, Acinetobacter and Stenotrophomonas maltophilia.

Colonization of building water systems is closely associated with “biofilm”, a complex aggregation of microorganisms marked by the exceretion of a protective and adhesive matrix (slime).

Biofilm plays a key role in the proliferation of waterborne pathogens; it is ubiquitous in water environments and is found on most surfaces that are in prolonged contact with water, including the inside of both hot and cold water pipes in buildings. Municipal drinking water treatment processes do not kill all the microorganisms in the water, and do not prevent downstream development of biofilm.

 Legionella pneumophila reportedly colonizes approximately 70% of large plumbing systems.  Pseudomonas aeruginosa, the causative agent of pseudomonas pneumonia, is one of the most common pathogens in the health care environment, and is present in an estimated 40% of institutional water pipes. Infections in healthcare environments (nosocomial infections) associated with these organisms have a high mortality rate.

 Most waterborne nosocomial infections are associated with drinking the contaminated water or via inhalation and/or aspiration. An individual may inhale aerosols, fine sprays, mists or other microscopic droplets of water contaminated with pathogens (e.g., from a shower), providing direct access into the lungs. Aspiration may occur when choking or spontaneously during drinking, ingesting, and swallowing. Patients that have been recently intubated are at high risk of aspiration-based exposure because the process allows oral fluids and particles to by-pass natural gag reflexes and enter the respiratory tract and lungs instead of the esophagus and stomach.

 While relatively healthy people may contract waterborne infections, such as LD, the most susceptible people are over 55 years old, infants, cigarette smokers, those on immunosuppressive therapy and other atypical medical conditions.  Taken together, these groups constitute more than 25% of the population of the United States. In hospitals and long-term care facilities, the percentage of persons who are at risk is higher.

 There is a growing movement to bring drinking water systems under control.  The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recently issued its Standard 188P for “Prevention of Legionellosis Associated with Building Water Systems”.  This standard provides guidelines for building managers to test their water systems for Legionella and if necessary deploy remediation.  A copy of the Standard can be obtained at:  The U.S. Department of Health and Human Services recently published a guide for Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings.