By Jerry Ackerman / Special to Healthcare Facilities Today

Background

Legionnaires’ disease (LD) generated mainstream media attention and subsequent public awareness in 1976 during an outbreak of pneumonia at an American Legion convention held at the Bellevue Stratford Hotel in Philadelphia, Pennsylvania. In this one location, over 200 cases were reported and 34 people died from the disease.  Legionella “outbreaks” occur when two or more people become ill in the same place at about the same time: for example, patients in a hospital or guests in a hotel.  Hospital buildings have multiple complex water systems, and since many people staying in hospitals already have a suppressed immune system due to illness, it greatly increases their risk for Legionella infection.

Soon after the Philadelphia occurrence, the etiologic agent was identified as a fastidious gram-negative bacillus and named Legionella pneumophila. Although several other species of the genus Legionella were subsequently identified, L pneumophila is the most frequent cause (responsible for more than 90%) of human legionellosis cases and a relatively common cause of community-acquired and nosocomial (hospital or other building-acquired) pneumonia in adults. In children, L pneumophila is also an important, although relatively uncommon, cause of pneumonia. Hot water loops, which circulate hot water so that people can use it relatively quickly when taking a shower, are characteristic in hospitals and hotels.

Legionellosis refers to two distinct clinical syndromes: (1) Legionnaires’ disease, which most often manifests as severe pneumonia accompanied by multisystemic disease (often a dry, unproductive cough accompanied by severe headaches, malaise, and body aches with fever). These symptoms are typically onset 10 to 14 days after exposure. (2) Pontiac fever, which is an acute, febrile, self-limited, flu-like illness manifesting itself in 24 to 72 hours after exposure

The risk of human exposure to Legionella in buildings is greatest when the water in a cooling tower is untreated or under-treated.  The health, environmental, and economic risks associated with a Legionella outbreak at a facility is why Legionella prevention should be taken seriously.

Legionella in cooling towers

Legionella outbreaks have been linked to cooling towers, produce misters, ice machines, hot tubs, decorative fountains, and potable water used for showering. Cooling towers have received a disproportionate amount of attention as the vector of LD. In fact, there is a consensus in the scientific community that cooling towers are rarely the culprits. A specific cooling tower was often identified as a “point source” for aerosolized water droplets (i.e., water droplets entrained in a water vapor plume, which could be called a mist) that would potentially affect a whole neighborhood via drift. The more prevalent cause of LD is the potable water supply source, which provides numerous buildings in a neighborhood with amplified Legionella bacteria contaminated water. These droplets are often ingested to the lungs from the mist of a hot shower of potable water. 

A recent study of the South Bronx Legionella Outbreak of 2015 analyzes and documents this phenomenon (Sarah Ferrari, New York Legionella Regulations: Are They Missing The Boat?, Cooling Technology Institute, TP16-23, 2016). The undeniable conclusion is that the South Bronx Outbreak was not due to a cooling tower point source but rather the potable water supply.   

Legionella bacteria amplify to an infectious state between temperatures of 68°F and 120°F (20°C – 50°C) with optimum growth 95°F (35°C). Heat disinfection occurs at 160°F (71°C). 

The Legionella bacteria reside in a mature biofilm (i.e., a slime layer on immersed equipment surfaces). Amoebas ingest the Legionella bacteria and, when in these protozoa, the bacteria have perfect temperature, ample food source, and protection from biocidal chemicals. After a process termed amplification, the Legionella bacteria break through the amoeba’s membranes and discharge in huge numbers of infectious (also termed virulent or amplified) Legionella bacteria.

When these amplified bacteria are contained in the entrained water droplets as drift they are readily breathed into human lungs, and can cause LD. It is for this reason that cooling towers should never be installed next to air intakes or windows that may be opened.  

How do people get infected with legionellosis?

Legionellosis is a common name for one of the several illnesses caused by Legionnaires' disease bacteria (LDB). Legionnaires' disease is an infection of the lungs that is a form of pneumonia. A person can develop Legionnaires' disease by deeply inhaling water mist or aerosols contaminated with amplified LDB. LDB are widely present at low levels in the environment: in lakes, streams, and ponds. 

At low levels of contamination, the chance of getting Legionnaires' disease from a water source is very slight. Amplification causes the Legionella bacteria to become infectious and multiply in great number. Water heaters, cooling towers, and warm, stagnant water can provide ideal conditions for the growth of the organism. Stagnant water often occurs in “dead legs” where there is no flow or infrequent flow.

Scientists have learned much more about the disease and about LDB since it was first discovered in 1976. The following paragraphs help explain what is currently known about Legionnaires' disease.

It is estimated that in the United States there are between 10,000 and 50,000 cases each year. Most of them are sporadic cases not associated with outbreaks. Most people can fight off the disease, with infection rates being less than 5% or so of the general population. Mortality rates can be at 10 to 20%, with higher rates in hospital care settings with patients suffering from other health risk factors.

Some people have lower resistance to disease and are more likely to develop Legionnaires' disease. Some of the factors that can increase the risk of getting the disease include: organ transplants (kidney, heart, etc.); age (older persons are more likely to get diseases); heavy smoking; weakened immune system (cancer patients, HIV-infected individuals); underlying medical problems (respiratory disease, diabetes, cancer, renal dialysis, etc.); certain drug therapies (corticosteroids); and chronic consumption of alcoholic beverages.

Preventing amplification: The key to legionella risk management

System cleanliness (lack of microbial deposits and biofilms, the previously mentioned nutrient-rich matrix of microorganisms forming slime on surfaces in water-based equipment) plays an important role in Legionella control because Legionella flourish within biofilms in cooling towers (and domestic hot water systems). Biofilm Legionella and Legionella within protozoa (e.g., amoebas) are protected from concentrations of biocide which would kill or inhibit them if they were individually suspended in water. 

The dose level of Legionella that causes LD is unknown; therefore, biocides may not be effective in reducing Legionella bacteria to very low levels, still possibly above the unknown dose level. Cooling towers which spray water under pressure and create mists or aerosols can release the disease-causing bacteria to the atmosphere. Towers which pump water to distribution trays and cause large droplets or films of water to cascade over plastic fill cause far less whole water dissemination, and therefore, less exposure. The dose level of Legionella that causes LD is unknown. Therefore, biocides may not be effective in reducing Legionella bacteria to very low levels, still possibly above the unknown dose level.

Altering ambient temperature water (heating it, using it for cooling water) plays into the ecology of Legionella. Amoebas graze on the biofilm, which harbor Legionella bacteria. In this state Legionella are protected from chemical attack. If no biofilm is present, there is nearly no food source for amoeba populations. In water temperature between 68-120oF (20-50oC), Legionella hijack amoebas from the inside of the host organism and multiply rapidly inside them. Regardless of temperature, mature biofilm is required to support amoeba populations.

The Amplification Process. The takeover of the amoeba allows rapid reproduction of the Legionella, a process that eventually ruptures the amoeba. These highly infectious Legionella burst out of the amoeba and are thereby released into the water.

Transmission to Humans. An aerosol from amplified water must be produced. Common sources are showers, spas, cooling towers, and decorative water features. Infection requires deep inhalation of the aerosol to the aveolar region of the lungs. Once there, Legionella infect macrophases in the lung.

The essential path to Legionnaires’ disease in cooling towers occurs when mature biofilm feed the amoebas as the amplification of Legionella burst out of the amoeba, causing a release of virulent Legionella into the water. At this point, a heavy dose of chemicals (such as chlorine) has been a traditional method to stop this cycle, but this method often does not succeed. To compound the problem, a supersaturation of chlorine into the water pose an additional exposure of chlorine gas into the environment. In this way, threats to health via nosocomial illnesses can be compounded.

The point at which preventing the amplification of Legionella is best applied, therefore, is to eradicate the biofilm before it matures as an ample food source for amoebas. However, accomplishing this objective has been difficult. As the culprit, or ecosystem, for harboring bacteria, biofilm is structured to shelter microbes from harsh environments, such as the aforementioned chemical dosing. Tough polysaccharide slime prevents high chlorine doses from eradicating amoebas, and new pioneer microbes reestablish quickly. 

Compliance confusion regarding legionella control

Compliance guidelines or regulations vary from state to state and are sometimes vague or nonexistent. This ambiguity can be especially problematic for “a responsible person” being tasked to control the amplification of Legionella. The responsible person is described in this article as someone with the responsibility for managing and controlling any identified risks from Legionella bacteria to protect the health and safety of a building’s and its occupants’ environment. Therefore, compliance issues need to be addressed, such as: What laws or regulations need to be followed? Relevant federal, state, and local (e.g., county and municipal) compliance directives need to be identified.

Federal Compliance. Federal agency regulations and guidance can come from a number of organizations. The Occupational Safety and Health Administration (OSHA) offers guidance that is limited to defining steps to take after someone in the building has become infected. Ongoing investigation, mitigation, and monitoring efforts then follow, mired in anxiety. The Veterans Hospital Administration (VHA) offers a policy issued for the prevention of Legionellosis in VHA hospitals and clinics (VHA Directive 1061; 2014). 

The U.S. Environmental Protection Agency (EPA), through its Safe Water Drinking Act, regulates maximum contaminant levels (MCLs) for Legionella in potable water as zero (as with giardia and viruses). If a building water system (premise plumbing) tests positive, then the responsible person should take action with the local health department. An EPA non-regulatory document for more comprehensive guidance synthesizes multiple sources to consider. (EPA 815-D-16-001, Technologies for Legionella Control in Premise Plumbing Systems, Scientific Literature Review.

The Centers for Disease Control and Prevention (CDC) has developed health care infection protocols for diagnosing human disease. For prevention practices, the CDC references the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 188-2015 and ASHRAE Guideline 12-2000. The CDC has also developed a companion guide for ASHRAE Standard 188.

In summary, there are no federal regulations regarding operational Legionella prevention practices, although there is always the potential for OSHA fines for disregarding corrective actions and monitoring for Legionella amplification. Taken together, the federal documents do offer an outline for a standard of care.

State Compliance. State regulatory, protocol, or guidance issues vary greatly and are, in some states, nonexistent. 

For example, the Wisconsin Department of Public Health (DPH) issued a WI Protocol in 1987 as a disinfection procedure for cooling towers testing positive for Legionella. The protocol is no longer distributed.  In 2004, the state of California issued Legionella testing guidelines for power plant cooling towers. In 2005, South Dakota distributed an ornamental water feature guideline.

Guidelines for hospitals and other healthcare facilities have been issued in Maryland, Texas, New York, New Jersey, Louisiana, Nevada, and Utah. In 2015, the state of New York issued regulations under authority of the NY State code relating to healthcare potable water regulations. These regulations require building owners or operators to register, test, and file water treatment management plans for all cooling towers in the state. Other than the states of New York and California, there are no regulations for private-sector cooling towers with the exceptions of the healthcare sector of many states and the electrical power industry in California.

Local Regulatory Compliance. Local compliance documents are often spotty or nonexistent in many cases. Some such documents worthy of note include those of Allegheny County, Pennsylvania, which in 2014 issued revised guidelines for the healthcare sector covering potable water only. Also, in 2005 the city of Garland, Texas, issued an ordinance that requires testing of cooling towers for Legionella in multifamily dwellings.

In 2015, New York City ordinance and subsequent regulations require: (a) registration of all cooling towers, filing of a water treatment plan, and quarterly Legionella testing; (b) weekly biological monitoring, daily logging of system conditions, twice yearly cleaning, and definitive paper trail and audit procedures; and (c) restrictions to use only halogen products for ongoing water treatment.

Voluntary Compliance. The objective with voluntary compliance is to find out what accepted industry standards require. Such standards are provided by organizations such as ASHRAE, the American Society of Healthcare Engineering (ASHE), the Association of Water Technologies (AWT), and the Cooling Technology Institute (CTI).

ASHRAE standards pertain to Guideline 12-2000, Minimizing the Risk of Legionellosis Associated with Building Water Systems. (This document is currently undergoing update-and-review procedures.) ASHRAE Standard 188-2015, Legionellosis: Risk Management for Building Water Systems, is a continuous maintenance standard. CTI 148, Guideline Best Practices for Control of Legionella, is also currently undergoing update-and-review procedures.

AWT provides a Legionella 2003 Statement, and ASHE and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) distributed its Environment of Care (EC.02.05.01) in 2001.

All industry guidelines and standards are currently voluntary, except in New York State and New York City protocols, wherein limited portions of ASHRAE Standard 188 are referenced. The code cycle adoption of standards is usually for five years or more. However, it should be noted that local ordinance or state regulatory action can be immediate, especially when a Legionella outbreak occurs.

Risk management evaluations

To prevent Legionella amplification risks, what standard of care needs to be applied to avoid or mitigate legal entanglements? Adherence to the following standards aid in achieving this objective.

For hospitals and other healthcare facilities, the ASHE/JCAHO guidelines and ASHRAE Standard 188, Annex A, provide guidance to the standard of care for preventing Legionella amplification. 

For all other buildings (in the non-power sector), such as hotels, commercial offices, and university structures, adherence to ASHRAE Standard 188 offers the appropriate standard of care. For the petrochemical, heavy industry, and power sectors, CTI-148 provides the most relevant standard of care.

As previously noted, specific regulations are published for the state of New York and for New York City.

If an occupant (worker, guest, patient, etc.) is diagnosed with Legionnaires’ disease, the building owner or manager (or designated responsible person) needs to contact the local health department (not the CDC) and follow the ensuing guidance and instructions.  To preclude this event from ever happening, it is appropriate to sample and test for Legionella amplification. However, the cause of amplification should not be assumed, and no potable sources should be ignored. It is also wise to be aware of OSHA guidance on the notifications of others, disinfection, and ongoing surveillance and monitoring. Also, it is recommended that all actions taken be documented. 

Controlling bacteria populations and biofilm through physical water treatment

In the application and operation of IntegraClean 2.0TM with Wave 2.0TM, provided by Griswold Water Systems (GWS), superior results in controlling biofilm and bacteria have been achieved. The means by which amoebas grow, with ingested Legionella, were eliminated.

IntegraClean. GWS understood the water treatment challenge in preventing the amplification of Legionella and designed, developed, implemented, and produced the right solution. The GWS IntegraClean offer includes CleanSweep, with the Wave water treatment system, toroidal conductivity control, and blowdown system. CleanSweep is superior to standard filtration, especially under hard water conditions, because it does not re-suspend solids, thereby protecting cooling towers more effectively. The eductorless filtration system also has better zones of influence, resulting in superior basin cleaning. The WaveTM performs well on an energy-efficient sidestream because its electrodynamically generated signal is four times stronger than that of its competitors. InstAlert, always part of the WaveTM system ensemble, provides remote monitoring that transmits flow, conductivity, and cooling system operation information wirelessly. Cooling system conditions are tracked continually so that technician services can be readily dispatched, as appropriate.

CleanSweep. This component of the IntegraCleanTM suite moves settled solids carefully along the cooling tower basin floor in tranquil water and does not re-suspend the settled solids. The CleanSweepTM exit header sucks solids back to the separator, away from the chiller outlet. The component’s most important function is in protecting the chiller from solids, whereas most basin sweepers use eductors (nozzles) that stir up the settled solids, sending them to the chiller and thereby causing fouling to occur. Easily retrofitted on any cooling tower design, CleanSweepTM, when installed as part of IntegraClean 2.0TM, in removing solids in the most efficient and protective manner, allows for higher Cycles of Concentration (CoC) and thus less water use. (Note: Besides being a breeding ground for Legionella, biofilm is four times more insulating to heat transfer than mineral scale, thereby forcing more water use.)

Wave. With this component, the elegant use of physical properties is the core mechanism behind precluding biological growth, scale prevention, and corrosion control. The two means of limiting biological growth are encapsulation and electroporation. Through encapsulation, bacteria (being suspended particles) can become sites for precipitation and entrapped (drawn into) the ever-growing limestone-type powder. The bacteria are not killed but are limited in their ability to excrete wastes and obtain nutrients, rendering them incapable of reproducing. Through electroporation, the high frequency pulses of the WaveTM electric fields do not kill bacteria but damage the membrane walls by creating pores or holes in them. This condition weakens the bacteria (as they expend energy to repair the damage) and essentially inhibits their capability to reproduce.

The Wave 2.0 Process for Biofilm Destruction.  While chemical biocides do not easily penetrate biofilms, the Wave 2.0TM causes biofilms to not form to begin with or to to disintegrate if they are pre-existing. This effect is caused by three primary influences of the component. (1) It consistently controls bacterial population to low levels, avoiding the population surges and kills of bacteria common in chemically treated cooling towers. (2) It severely limits the availability of nutrient-rich, bio-debris to support biofilm. (3) As a result of these two influences, the biofilm disintegrates or falls apart from the nutrient limitation (i.e., the nutrient broth feeding the biofilm through its water channels is too thin).

IntegraClean 2.0 and Legionnaires’ disease prevention

The elimination of biofilm is the best way to prevent Legionella amplification. Simply stated, no biofilm leads to no amplification, which in turn leads to disease prevention. Biofilm in cooling water systems grows in low-flow areas, dead legs, stagnant piping, and sludge in cooling tower basins. IntegraClean 2.0 with basin sweeping protects heat transfer efficiency and basin cleanliness. It is also recommended that the responsible person rotate chiller room equipment, purge equalizers or slightly unbalance cooling tower basins to push water through, and cross-connect large headers to prevent shoulder season stagnation at low loads and flows.

Water management plan: Maintaining a high standard of care to prevent Legionellosis

ASHRAE Standard 188-2015, Legionellosis: Risk Management for Building Water Systems, can serve as a practical guidance document when developing a water management plan for a building. This standard provides a process to create a plan to prevent legionellosis. There are as many paths to compliance as there are buildings, and compliance is a voluntary initiative (with the exceptions of New York City and the state of New York). 

Griswold Water Systems (GWS) offers a customized water treatment plan, a document for executing a high standard of care, for its clients. The GWS IntegraClean 2.0TM, with CleanSweepTM and Wave 2.0TM, controls scale, corrosion, biological growth, and biofilm for water-based cooling systems. The water treatment recommends maintenance practices to ensure that the cooling tower is clean. Centrifugal separation is a good practice to achieve this objective. Operational practices are provided to avoid stagnant water in the cooling system (i.e., requiring no load circulation and rotation of redundant heat exchange equipment). Demonstrating the efficacy of this control strategy includes physical/visual inspections, periodic 9215B Total Bacteria Count (TBC) testing (not Legionella Buffered Charcoal Yeast Extract, or BCYE, testing), and confirming the absence of biofilm in a tower under Wave 2.0TM water treatment

Should Legionella testing be included in a water management plan? 

The answer to this question is not a simple yes-or-no matter. The BCYE culture test for legionella testing, although flawed, is an available means for such testing. Enumeration and speciation of Legionella is possible, but the process to arrive at these results is slow, requiring fourteen days in duration. The slowness in testing disqualifies BCYE as a process control. BCYE culture testing requires a professional-level skill, with subjective evaluations being made at each step of the testing process. The “quick” BCYE test reports all fifty species of the Legionella family as a group and not specifically the three or four species that cause the most disease. 

The Practical GWS Approach to Legionella Testing. The GWS Water Treatment Plan offers a comprehensive and detailed outline on how to deal with Legionella in cooling water. The company’s water treatment product Wave 2.0TM has a long-established track record of biofilm prevention and elimination, as can be judged by visual inspection and touch. However, there has not been a well-accepted testing method for quantifying the absence or presence of biofilm.

GWS now introduces a practical and accurate method for using bio-coupons to monitor the number of bacteria taking part in biofilm formation. The bacteria that adhere to water equipment surfaces (where biofilm can form) are called sessile bacteria. This method is economical, precise, and representative of conditions in an operating cooling system.

Accurately assessing the presence or absence of biofilm in a cooling system should be part of a responsible and effective Legionella risk management program.  Such testing has a better capability to assess the risk of Legionnaires’ disease than the current testing done for the presence of planktonic (freely suspended) Legionella bacteria. Planktonic Legionella bacteria enter a cooling system every day in the makeup water and from airborne contamination.  Such a testing program fits well within the guidelines of ASHRAE Standard 188.

In its water management plan, GWS offers this important test that will monitor, validate, and verify that a cooling system is being properly maintained by water treatment protocol and thus minimizes the risk of infectious Legionella being emitted from a cooling system. 

A flat bio-coupon will have a layer of biofilm on all its surfaces. Amplification of Legionella bacteria occurs within the biofilm and causes Legionella to multiply in large numbers and become infectious. A mesh bio-coupon has a greater surface area to host a biofilm and presents many more surface angles and crevices to which the bacteria can more easily adhere. A mesh bio-coupon is a more severe test of propensity for the formation of biofilm. 

After a precise cleaning procedure is applied to the biofilm coupons, the biofilm bacteria are released to the surrounding water.

The surrounding water, now containing the freely suspended bacteria, is now cultured by a traditional analytical procedure, and the results accurately converted from units of bacteria per unit volume of water (CFU/ml) to units of bacteria per unit of surface area (CFU/cm2). This distinction produces an accurate, reliable, and repeatable quantification of biofilm.

The flat bio-coupon may often report “non-detect” for a cooling tower free of mature biofilm.

The mesh bio-coupon is a truly severe test; therefore, one would not expect a report of “non-detect” even from a cooling tower free of mature biofilm, but rather expect very low values of CFU/cm2. A mesh bio-coupon producing actual numerical values of CFU/cm2 enables the analyst to monitor trends and diagnose the degree of cooling tower cleanliness, and therefore judge the likelihood of amplification taking place.

Previous attempts to measure sessile bacteria on a flat bio-coupon and report as CFU/cm2 have found that a typical value for a chemically treated system is about 100,000 CFU/cm2. Such a value was deemed acceptable and declared to represent a clean tower. However, the GWS method of physical water treatment has typically produced values of “non-detect” on flat coupons and single-digit values of CFU/cm2 on mesh coupons.

Flat and mesh bio-coupon testing is useful in quantifying the reduction of risk regarding Legionnaires’ disease and validating a clean, well maintained cooling system. Since biofilm is inextricably linked to amplification and therefore the presence of infectious Legionella bacteria, this test provides a useful quantifiable measure of freedom from mature biofilm capable of supporting amplification. 

Jerry Ackerman is a consultant for Griswold Water Systems.