Legionella Control at Reduced Hot Water Temperatures with Copper and Silver Ionisation

Laura Schotte News item

A recent study as published in the American Journal of Infection Control indicates that Legionella pneumophila can be controlled in water systems at reduced hot water temperatures with copper and silver ionisation. Not only are Legionella bacteria completely under control, but considerable energy savings and reduced carbon emissions are also apparent.

Copper and Silver Ionisation (CSI)

The Department of Health in the United Kingdom recommends Legionella control by maintaining hot and cold water temperatures at > 55°C and < 20°C respectively. Such temperature control can result in the following concerns and/or risks; 1) engineering control to prevent the high risk of scalding, 2) maintenance of > 55°C water requires a high energy consumption, 3) temperature control does not treat other water borne bacteria, and 4) temperature control often fails to control the Legionella bacteria. Especially the latter results in a requirement for other control methods, such as copper and silver ionisation (CSI). CSI was chosen in this particular case for its efficacy, reliability, energy savings, carbon reduction, and cost minimisation. But also as a result of an estimation by the United Kingdom’s Green Investment Bank that installing energy efficiency measures could cut back on the National Health Service’s (NHS) energy usage by 20%.

Case Study

The present study was conducted at a new health care building in a pediatric hospital in the United Kingdom and covers a six year timespan starting in September 2011. Here, CSI was employed as the primary control method for Legionella bacteria. Traditional temperature control to treat Legionella bacteria as described above was not employed during the study period. The CSI systems were set to treat the water supply with the minimum required levels of Copper (Cu) at > 0.2 mg/l and Silver (Ag) at > 0.02 mg/l. The ion levels automatically adjusted to any variations in flow rates and water quality. The CSI systems were checked once a month and water samples were taken from the CSI systems, tanks and outlets during the study period (total of 23 tapping points per month). These were analysed for Cu and Ag ion levels and Colony Forming Units (CFUs).

Safety and Savings

Throughout the six year study period, Legionella bacteria were not detected in any of the 1,598 samples taken. Aside from this tremendous control of the Legionella bacteria in the pediatric hospital, the usage of CSI also resulted in significant energy savings. If CSI had not been employed, three of the five tanks would have had to have been heated to 65°C instead of 45°C. As this was unnecessary thanks to the CSI systems, the pediatric hospital saved 33% on its energy usage (Table 1). Not only did the lowering of the temperature result in energy savings, it also facilitated a reduction in the building’s carbon emissions; with an estimate of 22.3 metric tons of CO2e per year.

The Complete Package

Where previous studies have already indicated the insufficiency of temperature control for Legionella treatment and the effectiveness of CSI for such treatment, regardless of temperature, the present study truly provides a complete overview of the combination of these benefits thanks to correct CSI management.

Efficacy, reliability, energy savings, carbon reduction, and cost minimisation can all be realised with the help of copper and silver ionisation systems. Contact us here for more information.

Hot water temperature reduction (hot water at 45°C and 65°C)

Tank

Tank water temp (°C) (new building) ∆T Tank water temp (°C) (traditional) ∆T Annual energy use (kWh) 45°C

Annual energy use (kWh) 65°C

1

45 27 65 48 34,421

61,089

2

45 27 65 48 35,691

61,089

3

45 27 65 48 35,691

61,089

4

60 48 65 48 27,370

27,370

5

60 48 65 48 27,370

27,370

Total 160,543

238,005

ΔT is the change in temperature from the cold storage water tank (17°C).