ENVIRONMENT and ENERGY
23
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
Continued on page 25 >>
www . plumbingafrica . co . za March 2017 Volume 23 I Number 1