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Gustav Zhuravlev
Gustav Zhuravlev

Cooling Tower Institute Blue Book Pdf



Despite the absence of federal regulations or laws that could broadly control the presence of Legionella in water systems, there are local and state regulations that attempt to do just that. Likewise, agencies of the federal government have certain enforceable policies that affect buildings under their control. This section discusses the policies of the U.S. Department of Veterans Affairs and the Centers for Medicare & Medicaid Services (CMS), as well as New York City and State regulations for Legionella control in cooling towers and in certain healthcare facilities. Plumbing and building codes can also significantly impact control of Legionella amplification and transmission in buildings and can be widely enforced, but only at certain times during the life of a building.




cooling tower institute blue book pdf



The first regulation in the United States to require registering and monitoring cooling towers for Legionella was enacted in 2005 in Garland, Texas, for cooling towers associated with multifamily housing; it was later revised to include hotels and places of accommodation (Whitney et al., 2017). The ordinance was simple and implemented at low cost to the health department, resulting in a decrease in the number of contaminated cooling towers over time. All testing was required to be independent of those responsible for maintenance.


As of April 2019, approximately 6,100 cooling towers were registered in NYC and about 11,000 in New York State (including NYC). Currently, results from the NYC Legionella sampling are not publicly available, but this will change in October 2019. Cooling tower data for New York State are publicly available.4 Both the city and state programs have seen progress in implementation and adherence to the existing regulations. For New York State, rates of cooling tower compliance with current regulations increased from 30 percent in 2017 to 67 percent in 2018. In NYC, the cooling tower registry has been invaluable in providing real-time information for Legionnaires' disease cluster response. Promptly locating cooling towers and having a history of operations and maintenance records has provided valuable information for identifying potential sources and evaluating risk. Additional benefits of the regulations include:


The proportion of cooling towers testing positive for Legionella in samples collected by the department is typically less than 30 percent and has remained relatively stable in the first two years of implementation of the regulations.


ASHRAE 188 considers individual types of water systems, from the potable water system to cooling towers and evaporative condensers, spas, fountains, and aerosol-generating misters. There are some peculiarities for each type of water system, and the standard states that details are given in ASHRAE Guideline 12 (ASHRAE, 2000). The standard also covers requirements for designing building water systems, such as documenting potential hazards in all major water systems, as well as documentation of all the water systems themselves upon installation, including what was built and where, what materials were used, and corresponding manuals. Detailed instructions for commissioning, including flushing and disinfection, have to be provided.


Similar to other guidance documents, AIHA (2015) is based on risk assessment, but it tends to be more descriptive. It specifically calls for Legionella samples to be collected (to be assayed via the culture method) from selected water systems on an ongoing basis to determine the effectiveness of control strategies and identify potential hazards. AIHA (2015) recommends that, although PCR techniques can be used as a complementary analysis, they should not replace culture-based methods. Table 5-1, taken from the guidance document, provides levels of Legionella that can be thought of as action levels to compare to routine sampling results. For all water system types (except cooling towers), a measured concentration below 1 CFU/mL (1,000 CFU/L) is considered to be at the detection limit. Between 1 and 10 CFU/mL (1,000 to 10,000 CFU/L), Legionella amplification could be possible. A sample above 10 CFU/mL (10,000 CFU/L) indicates that amplification has occurred, and action needs to be taken (for cooling towers, the document suggests that 100 to 1,000 CFU/mL [105 to 106 CFU/L] is indicative of possible amplification). These values mirror those of the Occupational Safety and Health Administration (OSHA), which used to suggest guidelines for Legionella to assess the effectiveness for water system maintenance but no longer does.6


NSFI standard 453 (NSFI, 2017) provides minimum practices for treating, operating, and maintaining cooling towers to avoid Legionella growth. The standard uses the terms program (all the conducted activities) and plan (the documentation of the program) and adheres to the bulleted list of risk management elements discussed previously.


Standard 453 requires treatment of cooling towers with an oxidizing biocide as well as maintenance of pH, corrosion control, scale and deposit control, and conductivity. Startup procedures for cooling towers are outlined, including initial startup and after a system shut-down. Routine inspection, service, and maintenance are outlined, including weekly, quarterly, and when there is an issue. Cycles of concentration are a key operating parameter for cooling towers that need to be monitored, managed, and documented.


Monitoring of biocides is required as part of standard 453, as is testing for heterotrophic plate counts and Legionella. If concentrations of Legionella are less than 10 CFU/mL (10,000 CFU/L), no action is needed. If concentrations are between 10 and 100 CFU/mL (10,000-100,000 CFU/L), then the entire program must be reviewed and on-line remedial treatment is needed. Between 100 and 1,000 CFU/mL (105 to 106 CFU/L), a visual inspection is also required (in addition to the above) to determine whether full draining and repair are required. Greater than 1,000 CFU/mL (106 CFU/L) requires off-line remedial treatment, and the standard describes the conditions for completely shutting down the cooling tower. This standard will be superseded by NSFI standard 444, which, when released, will cover all building water systems, not just cooling towers.


Four laws in the Netherlands were revised to include Legionella spp., in each case following an outbreak. For the first Legionella outbreak, in 1999, a hot tub on display in Bovenkarspel was found to be the source of the bacteria, resulting in more than 200 cases of Legionnaires' disease with 32 fatalities (den Boer et al., 2002). This outbreak led to the addition of regulations to the Drinking Water Act, the Hygiene and Safety Act, and the Safety at Work Act. In 2006, a second outbreak caused by a contaminated cooling tower in Amsterdam led to the creation of new regulations in the Environmental Protection Act. Legionella is the only pathogen in premise plumbing to be a target of Dutch regulations.


The Environmental Protection Act applies to wet cooling towers only. Like the previous two Acts, it requires a risk assessment and management plan that includes treatment and monitoring. Technical guidelines are also available to help guide the creation of such plans. However, no specific treatment is required as long as an effective method is used. Similarly, the monitoring requirements are loose, with no specific threshold above which action must be taken and no recommended frequency of monitoring. This Act does not require that the consultant creating the risk management plan be certified, but the plan must be updated when cooling tower operations change or the surroundings change. The Act requires all cooling towers built after 2010 to be registered; currently, about one-third of all towers are registered.


The federal German Emissions Control Act and technical guidance cover every open cooling tower. They have similar requirements for a management plan, monitoring, and concentration thresholds above which action must be taken.


All of Germany has to comply with the regulations, and compliance is high because building owners can be punished by law for not complying. Implementation of the regulations in large cooling towers and most building water systems is now broad, although the implementation is not as widespread for small cooling towers. The sewage regulations are only being enforced in North Rhine Westphalia. In general, the government tries to educate water consumers about Legionella by posting information on every public health department's website. If monitoring data are above the action level for a large apartment building, the building owner has to inform the occupants. As a result, people have become much more aware of Legionella. There are also guidelines for the homes of immunosuppressed people.


England's regulations for Legionella management have evolved from two pages of guidance in 1980 to hundreds of pages today. The primary impetus for creating regulations was the 1985 outbreak of Legionnaires' disease at Stafford Hospital. Engineering guidance was then developed for cooling towers and evaporative condensers. In 1991, the Health and Safety Commission published the Approved Code and Practice for the Prevention of Legionellosis. In 1998, there was specific guidance for hot- and cold-water systems. In 2000, everything was combined into one guidance called L8, in which there are various levels of documents: laws, regulations, approved codes of practice, and technical guidance.


The monitoring requirements for cooling towers are quarterly sampling for Legionella spp. with a target of less than 100 CFU/L. Heterotrophic plate counts have to be less than 10,000/mL. For hot- and cold-water systems, Legionella tests are not required, although they are recommended if biocide failure has occurred, if there are high-risk individuals in the building, where biocides are used as the primary control and not high temperature, or if a case of Legionnaires' disease has been associated with the premises. At concentrations above 100 CFU/L and 1,000 CFU/L, certain actions have to be taken. More stringent requirements for monitoring of healthcare facilities and for spas and pools exist as well.


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