Field testing hot water temperature reduction as an energy-saving measure – does theLegionellapresence change in a clinic's plumbing system?

Abstract

Legionella spp. represent a significant health risk for humans. To ensure hygienically safe drinking water, technical guidelines recommend a central potable water hot (PWH) supply temperature of at least 60°C at the calorifier. In a clinic building we monitored whether slightly lowered temperatures in the PWH system led to a systemic change in the growth of these pathogens. In four separate phases we tested different scenarios concerning PWH supply temperatures and disinfection with chlorine dioxide (ClO2). In each phase, we took 5 sets of samples at 17 representative sampling points in the building's drinking water plumbing system. In total we collected 476 samples from the PWH system. All samples were tested (culture-based) for Legionella spp. and serogroups. Additionally, quantitative parameters at each sampling point were collected, which could possibly be associated with the presence of Legionella spp. (Pseudomonas aeruginsoa, heterotrophic plate count at 20°C and 36°C, temperatures, time until constant temperatures were reached, and chlorine dioxide concentration). The presence of Legionella spp. showed no significant reactions after reducing the PWH supply temperature from 63°C to 60°C and 57°C, as long as disinfection with ClO2 was maintained. After omitting the disinfectant, the PWH system showed statistically significant growth rates at 57°C. PWH temperatures which are permanently lowered to less than recommended values should be carefully accompanied by frequent testing, a thorough evaluation of the building's drinking water plumbing system, and hygiene expertise.

Multi-criterion analysis of the effect of physico-chemical microbiological agents on Legionella detection in hotel water distribution systems in Crete

“…In general, it seems that it is agreed that a hot water temperature of <50°C is a risk factor for Legionella contamination, but there still seems to exist a controversy when it comes to the temperature range between 50°C and 60°C. There are studies that have suggested that contamination at temperatures between 50°C and 60°C or >60°C don't differ significantly and accept the guideline of >55°C (Volker and Kistemann, 2015), while others have pointed out the survival of a colonization of water distribution systems even at >60°C and hold temperatures as high as 57°C as a risk factor if water chlorination/hygiene is inadequate. Thus, these studies strictly suggest a temperature of over 60°C unless these other parameters can be regularly and closely monitored (Domenech-Sanchez et al, 2022).…”

Modelling of Consumption Shares for Small Wind Energy Prosumers

“…SB and WH capacities are deemed usable net values. Energy-associated factors, for instance, WH temperatures, are not evaluated and nor is the energy required to attain WH minimal temperature of 55 • C, to prevent reproducing Legionella bacteria [41]. Operating temperature is presumed to have been reached.…”

Simulation of Energy Exchange between Single Prosumer Residential Building and Utility Grid

“…Adding supercapacitors as levelling elements to decrease excess power from wind generator to batteries in our case is not used because of the small probability to increase maximum power allowed to batteries. Energy-related parameters such as WH temperature are not appraised, and neither is the energy necessary to reach WH minimal temperature of 55 • C, to avoid proliferating Legionella bacteria [36]. Operating temperature is assumed to have been attained, and the state-of-charge charge/discharge dependency is neglected.…”