Reclaimed Water and Legionella: Do water reuse and water recycling create a risk for Legionnaire’s Disease?

Reclaimed water, sometimes referred to as water reuse, water recycling, or water reclamation, is water that has been treated and reused for purposes such as irrigation, industrial processes, and environmental restoration. Water reuse can provide alternatives to existing water supplies and is growing in importance in the U.S. because it can improve water security and sustainability. If you utilize reclaimed water, it should be part of your water management program.

Examples of reclaimed water usage include:

• Irrigation in parks and golf courses
• Toilet operation
• Industrial process water for manufacturing facilities, power plants, petroleum refineries, paper mills, and factories
• Construction dust control or surface cleaning
• Construction processes
• Agricultural irrigation
• Decorative fountains operation

The EPA does not require or restrict any reuse, leaving regulatory authority to the states. However, this does not mean that water reuse is without risk and should be considered as part of your Legionella risk assessment.

A study in the Frontiers of Environmental Science and Engineering noted that residual pathogens in recycled water have been frequently reported, and are identified as the primary source of health risks for wastewater reuse. This is important because many of the uses noted above tend to produce significant amounts of aerosols which can lead to Legionella inhalation and Legionnaire’s Disease. The study, “Aerosol exposure assessment during reclaimed water utilization in China and risk evaluation in case of Legionella,” specifically noted that people exposed to aerosols containing pathogens could develop illnesses.

The study examined three scenarios:

• People walking on a sidewalk where road cleaning is taking place
• People walking in a park where an irrigation system is being used
• People passing by a decorative fountain.

The results found the following annual infection probability for the populations exposed to Legionella in the three scenarios:

• 0.0764 for the road cleaning
• 1.0000 for the park irrigation
• 0.9981 for the fountain

These were markedly higher than the threshold recommended by World Health Organization. Therefore, it is important that recycled water be included in your Legionella testing and control strategies.

If you have not considered the risks of reclaimed water in your water management program or reviewed your program recently, contact Legionella Control Systems. We can help you identify your waterborne pathogen risk factors and create a plan to minimize your risk. We can also help you with your Legionella risk assessment, Legionella testing, Legionella remediation, and everything else you need to control Legionella.