Review of Legionella in water systems

Bacteria such as Legionella occur naturally in freshwater. They are usually removed by water treatment and disinfection but can regrow in post-treatment water supply systems under certain conditions. The incidence of Legionella in conventional potable drinking water systems is well documented, but less is known about Legionella growth in alternative sources and recycled water. This research assessed and collated peer-reviewed reports about Legionella in potable, large-scale non-potable recycled wastewater and stormwater, and rainwater. A qualitative risk assessment framework was developed and applied to the domestic use of hot and cold rainwater, and the use of recycled stormwater. These risk assessments led to the conclusion that there is significant potential for Legionella growth in certain recycled water and rainwater systems and that further research is required before expanding the use of alternative water sources.