ENVIRONMENT and ENERGY
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may have an impact on the effectiveness of the treatment technologies discussed in this document, albeit not to the same degree. For example, chlorine and chlorine dioxide disinfectant residuals may be difficult to maintain as the water temperature increases due in part to faster reactions with organic materials or pipe surfaces. In contrast, temperature has little impact on the effectiveness of copper or silver ions. The pH of the finished water will impact the effectiveness of chlorine, monochloramine and copper ions, but it will have less of an impact on the effectiveness of chlorine dioxide and silver ions. Other physical parameters( such as turbidity) and chemical constituents( such as chlorides and dissolved organic carbon) can also affect the performance of specific technologies.
Ensuring proper maintenance is a priority for all of the technologies. Failures of technologies put in place to protect the occupants of buildings from exposure to legionella have resulted in outbreaks( CDC, 2013). Safety concerns also exist for most of the technologies( USEPA, 1999b, 1999c). The use of strong oxidants such as chlorine requires proper handling to avoid adverse health risks. The Stage 1 and Stage 2 Disinfectants and Disinfection Byproduct Rules( D / DBPRs) require regulated PWSs using chlorine, monochloramine and chlorine dioxide to maintain disinfectant and disinfection by-product( DBP) concentrations below the maximum residual disinfectant level( MRDL) and maximum contaminant level( MCL) to reduce risks from such exposure concerns( USEPA 2006b; USEPA, 1998).
Unless a legionella outbreak occurs, the decision to employ additional treatment is often difficult for facility owners or operators. Some facility owners or operators choose to install supplemental disinfection treatment systems as a preventative measure based on economic or insurance reasons. The detection of legionella bacteria in tap water samples from a building is likely the most common reason some facilities may choose to add treatment.
The CDC does not recognise a safe level of legionella and recommends certain preventative and corrective actions in health facilities that care for patients who are at higher risk for legionella infection( CDC, 2003). The CDC encourages facility owners or operators to develop and implement comprehensive water safety management plans( CDC, 2016; Garrison et al., 2015). Routine environmental sampling including monitoring for legionella can be performed as part of a building-specific water safety plan( CDC, 2016; ASHRAE, 2015; NYDOH, 2015); however, the CDC notes that there are knowledge gaps in how to use legionella test results as a measure of risk for disease transmission( Demirjian et al., 2015; Garrison et al., 2015). An environmental assessment of the various components of a facility’ s premise plumbing system can help determine vulnerabilities. These elements commonly include consideration of hot and cold water temperatures, proper service of heating components, water softeners, water fixtures( for example, showers), spas, water features, humidifiers and cooling towers. In combination with patient surveillance, the environmental assessment and a facility plan will assist in the overall evaluation and control of legionella risks( CDC, 2016; NYDOH, 2015; NYDOH, 2016).
Some limitations and uncertainties associated with the information presented in this document include:
• Some studies were conducted in PWS distribution systems; thus, some results may not be directly applicable to premise plumbing system environments. Likewise, some studies were performed under laboratory conditions that may not necessarily reflect‘ real life’ plumbing system conditions.
• The information on the infectious dose of legionella is limited due to difficulties in culturing the organism. Many factors can impact the infectious dose, such as the amount of legionella that has been inhaled, the vulnerability of the person, and the infectivity of the organism.
• Robust data on qPCR or culture counts in water that lead to disease outbreaks are not available.
• Further clarity is needed regarding the ecology of legionella to help inform the infectious dose question. Legionellae’ s capacity to colonise biofilms, grow inside protozoa, and enter a‘ viable but non culturable’ state increases the uncertainty associated with interpreting monitoring results.
Risk management approaches Background Risk management approaches refer to programmes that systematically apply risk management principles to reduce biological( including legionella), chemical and physical risks associated with premise plumbing systems. Different names are used throughout the literature to describe risk management approaches. Some examples of risk management approaches include water management programmes( WMP), hazard analysis and critical control point programmes( HACCP), and water safety plans( WSP). The HACCP concept was established in the early 1960s to ensure the safety of food from microbiological hazards for astronauts working in space( Mortimore and Wallace, 2015). Beginning in the mid-1970s, HACCP principles were applied to the food industry as a preventative approach for addressing biological, chemical and physical hazards. The process for using this approach in a water system was originally described within a food journal, Food Control, in 1994( Havelaar, 1994).
WSPs were developed by the WHO as a comprehensive risk management approach that uses multiple barriers based on HACCP to ensure public health protection from the source to the tap( WHO, 2011a, 2009, 2007 and 2005).
The American Society of Heating, Refrigerating and Air-Conditioning Engineers( ASHRAE) Standard 188 describes a risk management approach that establishes minimum legionellosis risk management requirements for premise
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www. plumbingafrica. co. za March 2017 Volume 23 I Number 1