Drinking Water Microbiome Dynamics within Premise Plumbing and Point-of-Use Filtration Systems

Over the last several decades the frequency of drinking water associated disease outbreaks has remained constant while there has been a major shift from gastrointestinal diseases towards respiratory illnesses. This shift has been best associated with water quality changes within premise plumbing and at the point of use, indicating a need to better understand the microbiological dynamics of premise plumbing and at the point-of-use.

Examining the dynamics of tap water had revealed that overnight stagnation had led to significant bacterial growth, which was driven by chlorine residual decay. It was also found that with the natural variability with water usage there was a resulting variability in the stagnant water quality, where periods of high water use had lower microbial growth while periods of low water usage had high microbial growth.

In this work, carbon block filter systems used for point-of-use water treatment were used due to their popularity in usage. Here it was seen that there was a shift in the drinking water microbiome, which included a reduction in relative abundance of major tap water bacteria such as Mycobacterium, while some smaller tap water populations had grown significantly within the filter including Obscuribacterales, Reyranella, and Xanthobacteraceae. Subsequent studies had revealed that the carbon filter system yielded a more stable microbiome compared to tap water. This included a lack of impact from stagnation, as well as a more temporally consistent microbiome compared to tap water. When the carbon filter was examined, it was found that there was a significant bacterial growth. It was also found that the carbon filter was the dominant source for the filtered water microbiome, indicating that a biofilm had developed on these filters and that portions of this biofilm are sheared off into the drinking water. This was backed up by the major bacteria of filtered water having the function to build and export EPS molecules, indicating biofilm activity. There was an accumulation of heavy metals within the carbon filter, leading to heavy metal resistance in filtered water. This work has elucidated the factors driving the dynamics of the microbiome at the point of use.