Household plumbing systems are thriving with microorganisms, and engineers are focused on exploring these ecosystems to guarantee that clean water is accessible in residences.
Household plumbing is often home to various types of generally harmless microbes, yet there hasn’t been extensive documentation around the bacterial communities found in our homes.
The Safe Drinking Water Act mandates public water utilities to monitor water quality, but these assessments occur outside the boundaries of individual homes. Once water enters a house, the microbial communities can evolve and alter in ways that are often not checked or entirely understood.
Assistant professor Fangqiong Ling, who specializes in energy, environmental, and chemical engineering at Washington University in St. Louis, is determined to address this gap, along with her colleagues and students who are part of the school’s water quality research team.
In a paper released on December 10 in Nature Water, Ling and her team revealed findings from samples taken from bathroom faucets in eight homes in the St. Louis metropolitan area. They collected samples over a week to observe how different bacterial populations fluctuated. While there were common categories of bacteria across homes, they noted significant variations on the species level from one house to another.
“Every house has a distinct microbial signature,” Ling explained.
Since public tap water undergoes rigorous treatment and disinfection processes, the amount of microbial cells discovered was notably low, which presents another challenge for monitoring.
However, the microbes that do survive are resilient. The researchers expected to find genes linked to antibiotic resistance in these tap water microbiomes, and their predictions held true.
The use of a common disinfectant means that certain groups of microbes may develop resistance to that treatment. The researchers identified patterns of this “resistome” across different households. But what could explain the significant differences in microbial species?
Computer simulations indicate that microbes form their communities through both predictable and random processes, which may help explain the wide variety of species seen from home to home.
For household water, these processes might include the incidental timing of how microbes arrive in the household, their growth patterns, and several other factors that remain unclear.
This research strives to monitor, predict, and prevent the emergence of pathogenic bacteria and microbes that could cause diseases. Although such monitoring efforts are primarily developed for larger institutions like hospitals, they are limited in individual homes.
“Homes are where most of our water interactions occur, so we aim to study these environments,” Ling added.
While the researchers detected a few illness-causing pathogens in homes, this does not automatically imply that household water is unsafe—though this highlights the need for increased oversight from public health regulators, according to Ling.
Lin Zhang, a PhD student working with Ling and the lead author of the Nature Water paper, has initiated a community-based sampling project by enlisting high school students as “community scientists.” These students collected samples from around 100 households in the St. Louis area, which Zhang is now analyzing for her doctoral research.
While bacteria typically associated with plumbing are usually harmless, the antibiotic resistance genes they harbor can be transferred to more harmful pathogens when individuals are treated with antibiotics. As people frequently come into contact with these microbes during activities like bathing or using water, it is vital to understand the plumbing system’s microbiome and “resistome,” and how they interact with humans.
Meanwhile, Zhang appreciates her involvement in research that has the potential to benefit the local community while also engaging with students.
“I’m thrilled that we could show high school students a glimpse of real-world research and the scientific process,” she said. “This could inspire them to pursue careers in environmental engineering.”
Repairing the Pipes
This autumn, the Environmental Protection Agency introduced a rule mandating that municipalities replace lead pipes within the next ten years. This infrastructure upgrade could create opportunities for enhanced monitoring not just for metal contaminants but also for microplastics and microbial communities.
Dan Giammar, the Walter E. Browne Professor of Environmental Engineering, is leading several projects aimed at assessing and improving drinking water sources in the coming years.
“Monitoring changes in drinking water quality from the treatment plant to the tap can be troublesome,” Giammar remarked. “This innovative research offers new insights into the growth of microbes and their types present in household plumbing.”
As Ling and Zhang pursue more effective testing of home plumbing systems, many more questions are likely to emerge, for with microbial life, things are often not as they seem.
“The more homes we examine, the greater diversity we discover,” Ling noted. This research was funded by the McKelvey School of Engineering Startup Fund and a Ralph E. Powe Junior Faculty Enhancement Award from the Oak Ridge Associated Universities to F.L. The National Science Foundation, through its Chemical, Bioengineering, Environmental and Transport Systems Division, also provided partial support under award number 2047470 to F.L.