installation (figure 1). These risk factors are assessed through a set of questions based on the identified impact parameters that significantly influence Legionella occurrence (figure 2). The assessment considers both the hot water installation, including possible circulation, and the drinking water supply itself; that means it recognizes the potential for Legionella growth in lukewarm water pipes above 20°C. An overall risk assessment is determined by adding up the risk factors identified during the overall review of the domestic water installation. The purpose of the risk assessment is to identify specific areas where Legionella risks are present and opportunities for improving the installations, and it also includes considera- tions for supplementary temperature and biocide treatment. Through subsequent activation of these options, the overall risk can be reduced. In a pilot version, the tool has been tested on practical domes- tic water installations at KAB, a large Danish housing company representing 70,000 homes. Several numbers of properties were inspected and assessed, with a comparison to Legionella analysis from samples. The risk analysis and tests showed crit- ical conditions for one of the installations. Implementing an improvement measure involved installing a biocide system with hypochlorous acid (see later).
3a) The electric booster under test in lab
Electric booster unit ensuring temperature monitoring and optimal control.
The electric booster unit ensures monitoring and optimal control of the temperature of the domestic water installa- tion based on knowledge of Legionella growth and reduction from the literature search. Also, it can give an alarm if some of the temperature requirements are below the limit values and thus reduces the risk of using the hot water installation. Furthermore, it conducts a thermal heat treatment of 60°C of the water producer and the circulation, if present, when the control has calculated that there is a theoretical possibility that the Legionella content has doubled.
Figure 3: The electric booster tested in the lab for domestic hot water circulation. 3b) Complete control with attached sensors and cables
and low climate footprints, it is essential to focus on all poten- tial improvement opportunities, just as new knowledge and insight into the problems must be ensured. Tool for Legionella risk assessment The developed tool is based on the widely recognized and used method FMEA (Failure Modes and Effects Analysis) for assessing risks and opportunities for improvement of technical facilities. It has been further adapted to include impact parameters related to Legionella in domestic water installations. The tool aims to provide a simplified approach to reviewing and improving both existing and new domestic water installations.
Fel tt est: Single family house
CFU/L
12000
10000
Disinfec ti on at temperature 63 °C, fl ow 1 L per minute and for 20 minutes for all taps
Electric booster
8000
6000
4000
2000
0
04.05.22 13.06.22 13.06.22 14.06.22 23.08.22
30.02.23 06.09.22 12.10.22 26.10.02 16.11.22 14.12.22
Tap 1 Køkkenvask
Tap 2 Håndvask
Rather than relying on statistically based risk analysis, the tool considers risk factors associated with each component of the
Figure 4: Demo results (field test) of electric booster for a non-circulated hot water system.
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