Researcher: Monochloramine Treatment Can Cause Harmful Levels Of Lead In Water

Using monochloramine to disinfect drinking water can cause harmful levels of lead in the water, a University of Missouri-Rolla (UMR) chemist concluded. According to a May 9 statement from the researcher, the disinfection process could have been behind the lead increase in Washington, D.C.'s drinking water in 2004.

With $150,000 in funding from the National Science Foundation, Dr. Jay A. Switzer, the Donald L. Castleman/Foundation for Chemical Research Missouri professor of Discovery in Chemistry at UMR, studied what happens when water districts switch from using free chlorine to disinfect drinking water to using monochloramine.

In 2004, officials in Washington, D.C., a city whose water district had recently switched to monochloramine as a disinfectant, discovered abnormally high levels of lead in several homes across the city -- some as high as 48,000 parts per billion (ppb). EPA stipulates an action limit of 15 ppb of lead for drinking water to be safe.

The rise in lead levels appeared to coincide with the water district's switch from the use of free chlorine to the use monochloramine to treat the city's water. This coincidence led researchers to explore its affect on lead in drinking water.

"You have to disinfect drinking water to kill pathogens or to inactivate them and what has traditionally been used is chlorine," Switzer said. "In the field they call this free chlorine. Basically they just bubble chlorine through the water and the practice has been very effective."

Effective, but not necessarily safe, the researcher said. Chlorine reacts with natural organic matter in the water and makes what are called disinfection byproducts. Of these byproducts, chloroform and other trihalomethanes are suspected to be carcinogenic.

In an effort to reduce the carcinogens in drinking water, EPA began exploring other disinfection options and found several advantages to monochloramine. While it isn't quite as good a disinfectant as free chlorine, it doesn't react with the natural organic molecules, so no trihalomethanes are formed. Plus, Switzer said, it lasts longer. "It's kind of a time-release disinfectant."

When chlorine is added to water, it produces hypochlorite and hypochlorous acid, which act as disinfectants. Free chlorine is still used in the water treatment plants as a primary disinfectant, but as a secondary or residual disinfectant, many plants bubble ammonia through the water to react with chlorine, which produces monochloramine.

To see if the switch to monochloramine in Washington, D.C., caused the elevated lead levels, Switzer and his research team deposited lead onto an electrochemical quartz crystal microbalance, a sensitive device capable of measuring masses to nanograms in a solution.

"You can deposit lead onto this device and put it into a beaker of simulated drinking water, then add a shot of monochloramine or chlorine and see what happens, then record the mass," Switzer said.

The researchers found that when monochloramine was added to the water, the lead almost completely dissolved into the water.

Switzer's team also tested lead deposits with chlorine. "We found that with chlorine, the lead gets coated with a lead dioxide, which passivates the lead and keeps it from dissolving." Passivate is to coat the surface of a metal with a substance that protects it against corrosion.

While homes are rarely constructed with lead pipes today, there are still several sources of lead along the path from the water district to a kitchen tap.

The water mains are usually made of plastic or cast iron with a service line running from the main to each home. In a lot of older houses, that service line is lead. Another source is brass alloys in water meters that contain lead. In houses, flow regulators, check valves, water meters and faucets -- even so-called lead-free brass faucets -- can contain up to 8 percent lead. Even copper pipes in many modern houses are soldered with lead solder.

When water treated with monochloramine passes this lead, the monochloramine dissolves the lead into the water. This could explain the lead increase in Washington, D.C.'s drinking water.

Now, Switzer is studying ways to disinfect water without producing harmful byproducts or leaching lead. One thing they're experimenting with is the occasional switch back to solely using free chlorine.

"What if you, periodically, just use chlorine to passivate the pipes," Switzer poses. "We'll be studying how long that passivity lasts, once the chlorine is introduced to the water supply."

Switzer will also explore the affects of monochloramine on copper pipes. Many cities whose water districts use the disinfectant are finding pin-hole perforations in their copper piping. Switzer hopes to determine if there is a correlation.

Jay A. Switzer: http://web.umr.edu/~jswitzer

This article originally appeared in the 05/01/2006 issue of Environmental Protection.

Download Center

  • Waste Management in 2021: Accelerate Your Success with Technology

    Join waste management experts on February 23rd for a live best practice session webinar. You’ll learn how to take your waste program to the next level with visual location, barcoding, and mobility. Register now.

  • Green Quadrant EHS Software 2021

    Reserve your copy of the new report by independent analyst firm, Verdantix, to get a detailed, fact-based comparison of the 22 most prominent EHS software vendors in the industry.

  • Your Guide to Environmental Metrics that Drive Performance

    Translating sustainability into action starts with implementing the right metrics to assess your environmental risk and performance. Learn how to design metrics that improve your decision-making process and drive enterprise performance.

  • 5 Keys to Best-in-Class Chemical Management

    Running a safe chemical program is challenging and complex: from knowing what's on-site to proper handling and disposal - all while navigating regulatory changes. Learn the best ways to mitigate chemical risk, get the most value out of your data, and gain buy-in for a chemical management solution.

  • Unpacking ESG: 6 Questions You Were Too Afraid to Ask

    Environmental and Sustainability experts from Arcadis and Cority answer 6 of the most pressing questions EHS professionals have about getting started with Environmental, Social, and Governance (ESG) reporting.

  • Industry Safe