ENVIRONMENT and ENERGY
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Risk management approaches to control legionella( continued)
Continuing from the March Plumbing Africa issue, this document describes risk management approaches and technologies for controlling legionella growth in premise plumbing systems. The information presented is based on the references reviewed during the preparation of this document.
By the Environmental Protection Agency
In addition to increasing energy use, increasing water temperature can increase scalding risks. For most adults, it takes 9 minutes for a seconddegree burn to occur at 49 ° C( 120 ° F), while at 51 ° C( 124 ° F) it takes 3 minutes( Moritz and Henriques, 1947). However, the assessment of scalding risk and selection of hot water temperatures should consider the susceptibility of people at higher risk of scalding, including young children, the elderly, the disabled, and those with sensory loss( HSE, 2014; VHA, 2014).
Installing automatic compensating mixing valves on outlets can be used to minimise the risk of scalding injury( HSE, 2014; WHO, 2007; ASHRAE, 2000). No scalding injuries were reported with the use of automatic compensating mixing valves over a period of 10 years in a hospital maintaining the temperature at 55 ° C( 131 ° F) throughout the premise plumbing system( Darelid et al., 2002). However, the blended water downstream of these mixing valves may allow legionella growth; facility managers may want to consider conducting a comparative risk assessment to determine where these valves can be used safely( HSE, 2014). The EPA WaterSense ® programme recommends using a showerhead and automatic compensating mixing valve that are marked with the same flow rate at a pressure of 45psi( additional information is available on EPA’ s website at http:// www3. epa. gov / watersense / docs / showerheads _ finalsuppstat508. pdf).
Changes in water temperature can affect the efficacy of disinfection treatment. Addition of treatment as part of a risk management approach programme of a building could have regulatory implications. EPA advises facility owners or operators who are considering adjustments to their premise plumbing system to consult with their water supplier and primacy agency for any specific considerations or requirements that may apply, including plumbing code requirements.
Environmental testing Environmental testing involves collecting water samples from the premise plumbing system and analysing for L. pneumophila or other hazards of concern, as well as for water quality parameters( pH, temperature, disinfectant residual) that may indicate efficacy of treatment performance and overall water quality. Environmental testing may be performed as part of an outbreak investigation to determine the source and stop transmission of the contaminant, or during implementation of a risk management legionella prevention plan, such as a WMP, HACCP or WSP( ASHRAE, 2015; AIHA, 2015; Kozak et al., 2013). Legionella testing data inform risk assessments and inspection, and maintenance programmes( Ditommaso et al., 2010).
Stout et al.( 2007) found that environmental monitoring followed by clinical surveillance proved to be effective in identifying previously unrecognised cases of hospital-
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www. plumbingafrica. co. za April 2017 Volume 23 I Number 2