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Prevent Tragedy With Disinfection Programs

By: Robert S. Miller, CWT

Founder and President, Earthwise Environmental

Complications from Legionnaire’s disease are linked to the recent death of a 37-year-old Chicago Transit Authority electrician following possible exposure to stagnant water from a Chicago ‘L’ train washing system.

The waterborne Legionella pathogen that causes typically treatable but potentially fatal Legionnaire’s disease is found in domestic drinking water systems, cooling towers, evaporative condensers and decorative fountains. Other contained systems like vehicle washing equipment are also at risk. A May 2008 public Legionnaires’ outbreak was linked to a self-serve carwash in Australia and two Albany, NY bus washing system employees who contracted the illness in August 2007, according to industry trade reports.

The media has widely reported the CTA tested water samples from the two facilities and found no Legionella. The CTA confirms it notified 800 employees at the two facilities about potential for contracting the disease.

The specific strain of bacteria responsible for causing Legionnaires’ disease is Legionella pneumophila. This serious illness results in fatality rates ranging from five to 30 percent of all cases, according to the Centers for Disease Control and Prevention (CDC). Individuals with weak immune systems are most susceptible. Risk heightens for those middle-aged and older, for smokers, those with chronic lung disease and for those whose immune systems are suppressed by cancer, kidney failure, diabetes or AIDS.

Commonly found in water-cooled heat transfer systems and domestic hot water systems, Legionella exposure through aerosol or misting of contaminated water - showers, produce misters and cooling tower drift - leads to individual and sometimes widespread illness. Symptoms include high fever and flu-like symptoms following airborne exposure to contaminated water.

Testing for Legionella bacteria is not required by law and impacts reporting of medically-diagnosed Legionnaire cases. An estimated 8,000 to 100,000 cases are contracted annually according to confirmed cases and estimates from sources including the CDC, the U.S. Department of Labor Occupational Safety and Health Administration (OSHA) and industry experts.

So-called “dead legs” in plumbing systems allow scale and bio build-up and support growth of Legionella bacterial colonies. Systems that mix hot and cold create ideal Legionella growth environments. Proven effectiveness varies for common techniques to disinfect water systems for Legionella organism control. Individual water system managers are encouraged to weigh effectiveness, implementation cost, potential for plumbing corrosion and environmental impact. Employees should also be trained to recognize the symptoms of Legionella.

Thermal Heat/Flush - Water temperature raised to as high as 160ºF for up to 30 minutes to sterilize systems. Chemical-free, commonly-used method requires no additional equipment. Labor intensive and can prove ineffective for long-term Legionella infestation management. Can damage older pipes and creates potential for scalding.

Shock (Hyper) Chlorination - Chlorine injected into water distribution system. Initial shock chlorination levels approach 50 ppm, and taper off to create 2ppm to 5ppm chlorine cycle. Chlorine decomposes rapidly at elevated water temperatures; Legionella re-colonization can occur in as little as one to two weeks during continuous chlorination following the shock. Highly corrosive to plumbing (can be offset in part with silicate corrosion control). Places facility employees handle stored chemicals or implement disinfection at risk for exposure to chlorine byproduct Trihalomethane (THMs, linked to several types of cancer).

Chlorine Dioxide - Chlorine Dioxide (CIO2) is EPA-approved for potable water disinfectant use under CFR Par 141-National Primary Drinking Water Regulation. Commonly used in Europe, CIO2 is a gas generated by either chemical or electrolytic means and distributed throughout the water distribution system. The powerful oxidant kills Legionella and other bacteria. CIO2 readily decomposes in drinking water and residuals decrease as water system temperatures rise, making this treatment approach difficult in hot water systems. CIO2 is corrosive to plumbing infrastructure and creates byproducts including chlorate and chlorite; field testing for EPA maximum limits is required.

Copper-Silver Ionization - Latest advance in disinfection methods dissolves and distributes small amounts of copper and silver ions throughout water systems to eradicate bacteria. Continuous eradication metallic ion unit is required. Highly effective in eliminating Legionella, particularly in recirculation hot water systems, according to research and monitoring of hospital-implemented systems by Janet F. Stout, Ph.D., University of Pittsburgh special pathogens laboratory director and an international expert on waterborne pathogens. According to Stout, the only disinfection modality to fulfill all four hospital evaluation criteria currently proposed for by experts is:

1) Demonstrated ability of Legionella eradication with laboratory assays (in vitro)

2) Anecdotal experiences in individual hospital Legionnaire’s outbreak prevention

3) Controlled studies in individual hospitals

4) Validation from multiple hospitals over prolonged time period

There are no blanket remedies for Legionella eradication programs. The facility team must evaluate the effectiveness and ultimate costs of various available technologies.

Water treatment experts recommend a complete mechanical and system evaluation of plant operations, from sampling to data analysis, to determine the best fit of technology, products and services. For a chemical approach, specialists should determine the custom blend that best meets facilities’ water treatment needs.

NOTE: For more information about the leading role of Bensenville, IL-based Earthwise Environmental in Legionella eradication and prevention, visit Earthwise Environmental’s Web site at www.earthwiseenvironmental.com.

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