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Chemical Additives that Prevent Pipes from Clogging may Release Harmful Bacteria

Water utilities that supply drinking water to residents in many cities across the country often add chemical softening agents in an effort to prevent mineral buildup in the pipes which if left unchecked can result in clogging. Now a new study shows that these chemical additives may increase the risk of harmful pathogens being released into drinking water as it weakens the grip that harmful bacteria, such as those that cause Legionnaires' disease, exert on the interior of pipes.

Biofilms similar to those found on the glass of home aquariums are common in water pipes that make up water delivery systems and attach themselves to the mineral scale that accumulates on the walls of the pipes. These biofilms mostly consist of harmless microbes that rarely cause disease.

Typical Rusted Water Pipe Typical Rusted Water Pipe

"The groundwater that supplies many cities may be high in magnesium and calcium," said Helen Nguyen, a professor of civil engineering and co-author of the study. "When combined with other elements, they can form thick deposits of mineral scale that clog up engineered water systems. Because of this, water treatment plants add chemicals called polyphosphates to dissolve the minerals to keep the scale buildup under control."

Another study conducted by co-author Wen-Tso Liu, a professor of civil and environmental engineering, shows that even when water utilities treat the water with antimicrobial additives, the bacteria that adhere to the mineral deposits on pipes can multiply to harmful levels in water that stagnates in indoor plumbing.

In this new study, which recently appeared in the scientific journal Biofilms and Microbiomes, a team of engineers from the University of Illinois show that anti-scaling chemicals added to the water system encourage growth of biofilms, causing them to become softer and thicker.

"Increased biofilm thickness means more bacteria, and the softening increases the chance that pieces will detach and foul the water supply under normal flow pressure," explains Nguyen. "Tap water is regulated by the Environmental Protection Agency up to the property line, not the tap. So, in buildings where water has been stagnating for a while, this could become a public health issue."

The top image shows a thin and stiff biofilm formed from untreated water, and the bottom image shows a thick and soft biofilm that formed as a result of polyphosphate treatment. The top image shows a thin and stiff biofilm formed from untreated water, and the bottom image shows a thick and soft biofilm that formed as a result of polyphosphate treatment.

The problem is really a catch-22 situation, as without the addition of an anti-scaling agent, scale will build up on the interior of water pipes, leading to clogging and a reduced flow. According to Nguyen, one solution would be to simply replace clogged pipes as and when necessary. But she points out that this would be extremely costly for both public water utilities and property owners considering the size of water network across the United States.

Nguyen suggests that rather than removing pipes, trying to eradicate all the microbes in the system or changing regulations, a more cost effective and appropriate solution will present itself with a clearer understanding of water chemistry. This study has provided more insight into the relationship between water chemistry and the communities of micro-organisms that exist in plumbing, and will help determine the most appropriate chemicals to use and the correct concentrations, said Nguyen.

The research team now plans to undertake related studies which focus on the effects that anti-corrosion chemicals have on biofilms as well as water quality, together with studies that look at how biofilms can be physically removed from pipes in-situ (i.e. without removing the pipes).

A Berkey water filter will filter out any dangerous bacteria that this may cause, and will help to protect you and your family.

Journal Reference

Yun Shen, Pin Chieh Huang, Conghui Huang, Peng Sun, Guillermo L. Monroy, Wenjing Wu, Jie Lin, Rosa M. Espinosa-Marzal, Stephen A. Boppart, Wen-Tso Liu, Thanh H. Nguyen. Effect of divalent ions and a polyphosphate on composition, structure, and stiffness of simulated drinking water biofilms. npj Biofilms and Microbiomes, 2018; 4 (1) DOI: 10.1038/s41522-018-0058-1

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