Stakeholders must recognize the potential impact energy and water conservation measures can have on the growth of Legionella and other waterborne pathogens.

This review discusses the relationship between dissolved oxygen and Legionella growth. Growth of Legionella in building water systems is considered to pose a health risk and controlling it could benefit public health by reducing the number of healthcare and community acquired Legionnaires’ disease cases. Conditions known to encourage Legionella growth include low disinfectant concentrations, warm temperature, and water stagnation. Legionella is an obligate aerobe meaning its cellular respiration is inhibited under anaerobic conditions. Despite evidence from earlier published studies the importance of dissolved oxygen for the survival and growth of Legionella has received little attention from researchers and public health authorities. Modern measurement devices can reliably determine if dissolved oxygen concentrations in potable water and other building water systems are at levels capable of supporting Legionella growth or inhibiting its amplification. Removing dissolved oxygen from water can be achieved using gas transfer membrane contactors. Water with low dissolved oxygen levels interferes with Legionella’s cellular respiration by oxygen starvation, whereas disinfectants achieve the same effect by interfering with oxygen transport across the cell membrane. Ultimately, the same effect on Legionella growth may be achieved by reducing dissolved oxygen as treatment with oxidants, while avoiding the drawbacks of corrosion and disinfectant byproducts.

Legionella is the leading cause of waterborne disease outbreaks in the United States. Fortunately, there are many ways to prevent or mitigate Legionella growth in premise plumbing systems.