Nav: Home

Keeping lead out of drinking water when switching disinfectants

January 22, 2020

About 80 percent of water systems across the country use a disinfectant in drinking water that can lead to undesirable byproducts, including chloroform. There is an alternative, but many cities have been afraid to use it.

That's because in 2000, when the water authority in Washington, D.C., switched from free chlorine to chloramine, the nation watched as levels of lead in drinking water immediately shot up. They stayed up for four years while scientists determined the problem and implemented a solution.

In other cities that used free chlorine, Washington's experience had a chilling effect; many have put off switching disinfectants, fearing their own lead crisis.

They may soon be able to safely make the switch, thanks to research from the McKelvey School of Engineering at Washington University in St. Louis. Researchers found that adding orthophosphate to the water supply before switching to chloramine can prevent lead contamination in certain situations.

The results of the study were published in Environmental Science & Technology.

Because of its malleability and longevity, lead was the preferred material for service lines, the pipes that deliver water from a water main to homes, for the first half of the 20th century. As the pipes corrode in the presence of free chlorine, a certain type of lead, PbO2, can build up on their interior surfaces.

That buildup typically isn't a problem. In fact, so long as free chlorine is being used as a disinfectant, the PbO2 is actually a positive, according to Daniel Giammar, the Walter E. Browne Professor of Environmental Engineering at Washington University. This form of lead has a low solubility so it stays in a solid form on the pipes, instead of in the water.

PbO2 is not always so benign, however. "There is a potential risk because the solubility is only low if you keep using this type of chlorine," Giammar said.

Switching to a different disinfectant such as chloramine -- the mixture of chlorine and ammonia that Washington switched to in late 2000 -- causes the lead to become water soluble. The PbO2 then dissolves quickly and releases lead into the water system.

In Washington, researchers determined that adding a particular phosphate, called orthophosphate, to the system would create lead phosphate. This new material was also low solubility, so again, the lead material began to line the walls of the pipes instead of dissolving into drinking water.

"But forming the new, low-solubility coating takes time," Giammar said. In the case of Washington, "the lead concentrations took months to come down."

The solution had been identified and implemented, but residents continued to deal with lead in their water for months. "Our overarching question was, 'Would they have had a problem if they had implemented the solution before they made the chlorine switch? What if they added orthophosphate before, as a preventative measure, and then they switched the disinfectant? Would they have had a problem?'"

Recreating Washington water

To find out, the researchers had to recreate 2000 in their lab. "We had to recreate the crisis, then watch the crisis happen and watch our proposed solution in parallel," Giammar said. They sourced lead pipes, then recreated Washington water.

First author Yeunook Bae, a PhD student in Giammar's lab, looped the water through a six-pipe system with free chlorine for 66 weeks to get the lead scales to form. Once they approximated those found in Washington, the pipes were divided into a study group and a control group.

Researchers then added orthophosphate to the water in three of the pipe systems, the study group, for 14 weeks.

Then, as the Washington water authority had done, researchers switched from free chlorine to chloramine in all six systems, looping the water through the pipes for more than 30 weeks.

The lead on the pipes that did not receive orthophosphate became soluble, as it had in Washington, leading to high lead levels in the water. In the pipes to which orthophosphate was added, "levels went from really low to still quite low," Giammar said.

The experimental setup was designed to let researchers remove small sections of pipe without disturbing the system. That allowed them to see just how quickly the switch to chloramine affected the system.

The regulatory level set by the EPA for lead in drinking water is 15 micrograms of lead per liter of water.

Within five days of the switch, lead levels in the control pipes -- those without orthophosphate -- rose from five to more than 100 micrograms/liter. During the subsequent 30 weeks, levels never fell below 80 micrograms/liter.

In water treated with orthophosphate, levels remained below 10 micrograms/liter for the duration of the experiment.

The Washington University team also learned something else: Because of the high levels of calcium in Washington's water, adding orthophosphate did not result in a pure lead phosphate, but a calcium lead phosphate.

This surprise points to the uniqueness of each situation. Those who oversee water systems and are concerned about switching disinfectants can not only benefit from this study, according to Giammar, but also from their own studies, tailored to their specific water and environmental conditions.

Nevertheless, this finding can help guide decisions in the roughly 80 percent of American water systems that are still using free chlorine, including Chicago and New York City.

"Our next big step," Giammar said, "is making sure places that are thinking about switching disinfectant know that the option is there to do it safely."
The McKelvey School of Engineering at Washington University in St. Louis promotes independent inquiry and education with an emphasis on scientific excellence, innovation and collaboration without boundaries. McKelvey Engineering has top-ranked research and graduate programs across departments, particularly in biomedical engineering, environmental engineering and computing, and has one of the most selective undergraduate programs in the country. With 140 full-time faculty, 1,387 undergraduate students, 1,448 graduate students and 21,000 living alumni, we are working to solve some of society's greatest challenges; to prepare students to become leaders and innovate throughout their careers; and to be a catalyst of economic development for the St. Louis region and beyond.

Washington University in St. Louis

Related Drinking Water Articles:

Natural contaminant threat to drinking water from groundwater
Climate change and urbanisation are set to threaten groundwater drinking water quality, new research from UNSW Sydney shows.
Fresh clean drinking water for all could soon to be a reality in Pakistan
A fresh, clean water supply will be a reality in Pakistan, particularly in South Punjab, following the announcement of an international partnership spearheaded by the Pakistan government, alongside other key stakeholders, and driven by the University of Huddersfield.
Keeping lead out of drinking water when switching disinfectants
Researchers at the McKelvey School of Engineering at Washington University in St.
Solar power with a free side of drinking water
An integrated system seamlessly harnesses sunlight to cogenerate electricity and fresh water.
'Liquid forensics' could lead to safer drinking water
Ping! The popular 1990 film, The Hunt for Red October, helped introduce sonar technology on submarines to pop culture.
Progress in hunt for unknown compounds in drinking water
When we drink a glass of water, we ingest an unknown amount of by-products that are formed in the treatment process.
Arsenic in drinking water may change heart structure
Among young adults, drinking water contaminated with arsenic may lead to structural changes in the heart that raise their risk of heart disease.
Not drinking water associated with consuming more calories from sugary drinks
This study examined how drinking water was associated with the amount of calories children, adolescents and young adults consume from sugar-sweetened beverages, including sodas, fruit drinks and sports drinks.
Not drinking water may boost kids' consumption of sugary beverages
Kids and young adults who drink no water throughout the day may consume twice the amount of calories from sugary drinks than those who drink water, according to Penn State researchers.
Drinking water sucked from the dusty desert air
An inexpensive hydrogel-based material efficiently captures moisture even from low-humidity air and then releases it on demand.
More Drinking Water News and Drinking Water Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Clint Smith
The killing of George Floyd by a police officer has sparked massive protests nationwide. This hour, writer and scholar Clint Smith reflects on this moment, through conversation, letters, and poetry.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at