Is Sediment a Risk Factor for Legionella Control?

Sediment can be an important factor in Legionnaire’s Disease prevention because it affects the growth of Legionella, the bacteria the causes Legionnaire’s Disease.

According to the National Center for Biotechnology Information in their article, “Ecology of Legionella Pneumophila Within Water Distribution Systems,” researchers investigated the influence of the natural microbial population and sediment (scale and organic particulates) found in water systems as growth-promoting factors for Legionella pneumophila. Their experiments showed that, among other factors:

• The concentration of sediment was directly related to the survival of Legionella
• The combination of sediment and environmental bacteria acted synergistically to improve the survival of Legionella
• The role of sediment in this synergistic effect was determined to be nutritional
• Sediment was found to stimulate the growth of environmental microflora, which in turn stimulated the growth of Legionella.

OSHA also notes the importance of sediment. When discussion water system maintenance and disinfection, they noted that “effective maintenance and visual inspections should prevent scale buildup, sediment, and gradual water organism accumulation on structural surfaces (i.e., biofouling)—processes that support Legionella growth.” Clean water is critical to water treatment effectiveness because water containing organic matter and dissolved solids in high concentrations will reduce biocide effectiveness.

Moreover, OSHA notes that “Water heaters maintained below 60°C (140°F) and that contain scale and sediment may foster Legionella growth. Large water heaters, such as those used in hospitals or industrial settings, frequently contain cool zones near the base where cold water enters. Scale and sediment accumulate in these cool zones where the temperature can provide ideal conditions for Legionella growth. Piping or plumbing altered or capped to prevent water flow (i.e., dead legs) and non recirculated plumbing lines may allow hot water to stagnate, conditions that also promote Legionella growth.””

The CDC also weighed in on the importance of sediment in their article, “What Owners and Managers of Buildings and Healthcare Facilities Need to Know about the Growth and Spread of Legionella.” Their list of factors that lead to Legionella growth include a variety of internal and external factors including scale and sediment and water stagnation. They state, “Maintaining and operating your building’s equipment effectively will help prevent biofilm, organic debris, and corrosion from contaminating your water system; all of these provide a habitat and nutrients for Legionella.”

Sediment must be considered in your Legionella control water management plan as well as any short-term and long-term Legionella control and mitigation measures. Contact Legionella Control Systems so we can assess your risk for Legionella as it pertains to sediment and others factors. Ideally, contact us before construction so that we can recommend preventative measures. If you are already at risk for Legionella, it is imperative that you contact Legionella Control Systems immediately.

Scale, biofilm, and water age are also important risk factors for Legionella. Learn about Legionella, scale and biofilm, as well as the effect of water age on Legionella.