Chemicals that keep drinking water flowing may also cause fouling

Civil and environmental engineering professor Helen Nguyen has found that water-softening additives may increase the risk of pathogen release into drinking water by weakening the grip that bacteria have on pipe interiors. Photo by L. Brian Stauffer

CHAMPAIGN, Ill. — Many city drinking water systems add softening agents to keep plumbing free of pipe-clogging mineral buildup. According to new research, these additives may amplify the risk of pathogen release into drinking water by weakening the grip that bacteria – like those responsible for Legionnaires’ disease – have on pipe interiors.

Biofilms, which are similar to the films that grow on the glass of fish tanks, are present in almost all plumbing systems and anchor themselves to mineral scale buildups in pipes. They are teeming with harmless microbial life and incidents of waterborne illness are rare.

“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.”

A recent study by co-author and civil and environmental engineering professor Wen-Tso Liu has shown that even with the addition of antimicrobial agents by water companies, the bacteria that grow on the mineral scale can reproduce to harmful levels in supplies that stagnate within indoor plumbing.

In a new study published in the journal Biofilms and Microbiomes, a team of University of Illinois engineers shows that the addition of anti-scalant chemicals cause the biofilms to grow thicker and become softer.

The team measured the thickness and stiffness of lab-grown biofilms using magnetomotive optical coherence elastography – a tool used to measure the strength of cancer tissues. The analytical method, developed by Stephen Boppart, a professor of electrical and computer engineering and study co-author, allowed the team to quantify the effect that polyphosphate has on the strength of biofilms.

To reproduce what happens in engineered plumbing systems, the team used PVC pipe and groundwater from the Champaign-Urbana area source to grow biofilms. They set up multiple scenarios with and without added polyphosphates. All scenarios produced biofilms, but the system that used polyphosphates grew a much thicker and softer biofilms than the others, the researchers said.

Editor’s notes:

To reach Helen Nguyen, call 217-244-5965; thn@illinois.edu.

The paper “Effect of divalent ions and a polyphosphate on composition, structure, and stiffness of simulated drinking water biofilms” is available online and from the U. of I. News Bureau. DOI: 10.1038/s41522-018-0058-1

Source: Illinois NEWS BUREAU

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Chemicals that keep drinking water flowing may also cause fouling
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Chemicals that keep drinking water flowing may also cause fouling
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CHAMPAIGN, Ill. — Many city drinking water systems add softening agents to keep plumbing free of pipe-clogging mineral buildup. According to new research, these additives may amplify the risk of pathogen release into drinking water by weakening the grip that bacteria – like those responsible for Legionnaires’ disease – have on pipe interiors.