Frank Butterworth, Technical director at water hygiene, treatment, and equipment specialist, Goodwater, discusses the various strategies that have been used over the years to combat the growth and proliferation of Legionella in healthcare water systems. He particularly focuses on the advantages, in combating the bacterium, of monochloramine as a secondary disinfectant in buildings’ water systems, compared with using other chlorine-based disinfectants.
Legionellae are ubiquitous bacteria which can be present in water systems and can cause respiratory illnesses. Various strategies have been used to combat these bacteria over the years, but most disinfectants have drawbacks, such as corrosion/material compatibility issues, or toxic by-products. Monochloramine has been presented as a promising solution. In this article I will explain the chemical properties of monochloramine that make it stable and less corrosive than other chlorine-based disinfectants, its ability to penetrate biofilms, and its long-term residual disinfectant properties. I will also highlight the importance of controlling ammonia formation rates when using monochloramine as a supplemental disinfectant. Finally, the article will emphasise the importance of choosing the right disinfectant, and the location of installation, to ensure effective control.
Legionellae can be present in both natural and artificial water environments, and can survive under a range of environmental conditions. Their ability to colonise artificial water systems poses a serious concern for public health, as they can cause a range of pneumonic and nonpneumonic respiratory illnesses collectively referred to as legionellosis.
There are a number of strategies available to combat Legionella and protect water systems, but most of them – while having acknowledged disinfectant power – can also be responsible for significant sideeffects, both on water system conditions (corrosion) and on human health, due to the potential generation of toxic disinfection by-products (DBPs). Monochloramine can be considered one of the best solutions available, both due to its ability to reach and kill bacteria by penetrating biofilm, and to maintain its effectiveness in low-flow systems over extended periods, even at the extremities of the system.
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