Bacteria in tap water can multiply when a faucet is left unused for a few days, such as when a house is vacant for more than a week, according to a recent study by University of Illinois engineers. The study proposes a new method to show how microbial communities, including those responsible for diseases such as Legionnaires' disease, can collect in the sanitation systems of homes and public buildings.
The results are published ISME Journal: Multidisciplinary Journal of Microbial Ecology
Fresh tap water teems with harmless microbes, and water that sits in pipes for a few days can contain millions of bacteria. Although cases of water infection from indoor plumbing are rare, the new model can help health authorities assess drinking water quality.
"Previous studies relied on the reproduction of the conditions of a stagnant sanitary system in a laboratory environment," said co-author and civil and environmental professor Wen-Tso Liu. "We were able to collect samples in a real situation."
It is important to determine where in the waterworks water samples come from to determine the source of microbes. Since it is not possible to remove water directly from the piping without tearing pipes and breaking down walls, the researchers have found another way to determine the sample locations.
The team collected tap water samples from three closely guarded dorm buildings during a school break. In the prevention of contamination by sanitation or sampling equipment from the outside, they have taken samples from the sink before closing the building. while the water was fresh from the city supply; and after the water had been in contact with the inner pipes for a week.
"We performed a variety of analyzes, including tests to determine the concentration of bacteria in the samples before and after building closure," Liu
The laboratory results showed that after stagnation, the samples were taken at the end of the day next to the faucets containing the highest concentrations of bacteria. The team also found that bacteria levels decreased significantly as the distance between the tap and the pipeline increased. None of the samples in the study contained microbial species or cell concentrations that pose a risk to public health.
"Our results suggest that the increase in bacteria in the stagnant samples is due to something that occurred in the indoor installations, the source of the outskirts and in pipe sections closest to the faucets," Liu said.
Bacteria that live in tap water exist in two communities ̵
The researchers determined the city's water biofilm composition by studying the internal parts of the water, routinely collected during the water utility's exchange program. Liu worked with the municipal water company to collect discarded water meters for nearly four years and to give the team a large amount of city biofilm data.
By combining pre and post stagnation data, the biofilm of the city has "control." Using data and information from building plans, the team developed a model to test water quality in almost every building.
"We only need two samples – one before stagnation and one after – and we can see how large the microbial growth is inside the inner tubes, and we can do this now without destroying property," Liu said.
The study also found that bacterial concentrations are highest in the first 100 milliliters of conduction. Liu recommends that people run some taps for some time before using the water after they have been away for a few days, and discuss the council with U. of I. Facilities and Services and others at a campus workshop in October 2017.
"It's in stark contrast to what we learned about water conservation, but I just think of it as another basic sanitary step," Liu said. "We've made it a habit to wash our hands, and I think we can make it a habit to use the faucet for a few moments before we use it."
Although the microbial communities in this study did not pose a health risk, this method could be used in such cases, the researchers said.
"Communities have and will continue to invest in green infrastructure that emphasizes water conservation," Liu said. "If indoor installations were contaminated with harmful bacteria, it could lead to unforeseen public health problems if buildings remain free for more than a few days."
The desire to reuse and recycle water is unlikely to disappear soon, Liu said. "How do we deal with the problem when we combine it with water conservation practices? If we seek green practices, our engineers, public health organizations, scientists and municipal water companies must work together cooperatively."