New RIVM research has shown that it is plausible that employees of waste water treatment plants and local residents run a higher risk of legionella. By inhaling small water droplets in the air, they may become infected with the legionella bacteria. That bacterium can cause veteran disease (severe pneumonia).
A step in the water purification process is aeration, whereby air is blown through the waste water. “This creates very small water droplets that can spread over a large area,” says RIVM’s Petra Brandsema on Radio 1. “Legionella can grow in the waste water and the bacterium can then ride along in those very small water droplets to the environment.”
An earlier study by the RIVM had already shown that 81 water treatment plants in the Netherlands give an increased risk of spreading the legionella bacteria. They are now being advised, pending further research, to take (temporary) measures to prevent the spread of the pathogenic bacteria. For example, by covering the water tanks during aeration and forcing employees to wear masks, for example.
More research needed
In 2018 there were nearly 600 patients with legionella pneumonia in the Netherlands, almost twice as many as five years earlier. In 2017 and 2018 it appeared that a number of patients were infected by exposure to legionella bacteria from two waste water treatment plants (WWTPs) in Boxtel and Son. The models showed that legionella was probably spread over a distance of approximately 6 kilometers from Son’s AWZI. That is why an investigation was launched into all wastewater treatment plants in the Netherlands.
A total of 775 installations were identified. At 69 industrial waste water treatment plants and at 12 sewage treatment plants, the risk of spreading the legionella bacterium appeared to be increased.
Measures had already been taken at some of these riskier wastewater treatment plants to prevent the bacteria from spreading. It is still unclear whether these measures work sufficiently. According to RIVM, additional research is needed to determine which permanent adjustments in waste water treatment plants can prevent the possible spread of legionella.
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