David Sedlak

David Sedlak. (Photo by Daniel McGlynn)

Q&A: Lead, chloramines and drinking water safety

Conditions leading to widespread lead poisoning in Flint, Michigan are not unique to the troubled Rust Belt city. In recent decades, many cities have made the switch from chlorine to chloramine for water treatment; this can, without proper management, release toxic lead from old pipes directly into drinking water.

Here in California, the city of Stockton drew pointed criticism from environmental activist Erin Brockovich for making the switch in January. But as civil and environmental engineering professor David Sedlak explains, some of that fear may be misplaced.  Sedlak, who co-directs the Berkeley Water Center and directs Berkeley’s Institute for Environmental Science and Engineering, has also published a book, Water 4.0, which details the past, present and future of urban water systems.

Why are chloramines added to drinking water? And how widely are they used?
In the 1960s, people learned that the chlorine that we were adding to our tap water to protect us from waterborne pathogens was reacting with organic matter to produce a class of chemicals known as disinfection byproducts. These byproducts can cause cancer, miscarriages or other health effects. So water utilities spent a lot of time trying to figure out how to minimize the formation of disinfection byproducts while still protecting people from waterborne pathogens, and one of the solutions they found was replacing chlorine with a family of compounds known as chloramines. If you add a small amount of ammonia to the water when you add the chlorine, you create something called chloramines, which don’t react with water to produce disinfection byproducts. Starting in the 1980s and 1990s, many cities in the United States switched from chlorine to chloramines. We did that here in the East Bay in 1998.

In Stockton and elsewhere, what risks are associated with chloramines?
Chloramines are used in many cities around the country without incident, but under some conditions, switching from chlorine to chloramines can mobilize lead from lead-containing drinking-water pipes and solder in household plumbing. This was observed in Washington, D.C. about ten years ago, and led to a problem similar to what we saw in Flint recently. But these cases appear to be quite rare. The engineers who operate water systems are now aware of this phenomenon and have taken steps to prevent the mobilization of lead. It’s now one of the risks that people think about when they switch from chlorine to chloramines. In the case of Stockton, it wasn’t considered as big a risk as it might have been in the East Coast or Midwest, because fewer drinking-water pipes in California are made of lead, as our water systems developed in the latter part of the 20th century. The type of water that you’re putting through the pipes also makes a difference.

So we can also get a sense of the local risk level based on the composition of the water?
Water engineers have a good understanding of the composition of the water and know how to manage the water to minimize the chance that lead would dissolve. They can add small amounts of a compound called polyphosphate, which can prevent the lead from dissolving. The way I understand it, the managers of the Flint water system didn’t take some of the normal steps to prevent the dissolution of the lead from the pipes.

Is this something that the East Bay Municipal Utility District, for instance, would monitor?
Our local water utilities in California do a good job paying attention to conditions that might result in the mobilization of lead, and they collect samples from consumer taps to test whether or not lead is dissolving. Every city that has lead pipes has a potential risk that has to be managed if they’re unwilling to spend the money to pull all the lead pipes out and replace them.

Moving to your Water 4.0 concept and perhaps a more ideal solution, can you paint a picture of the future of water treatment?
Here in California, we have less concern about leaded pipes and decaying infrastructure, and more concern about the quantity of water available to us, and how we’re going to survive in the future if we experience extended droughts. California’s cities are starting to invest in new types of water sources — potable water recycling is being planned in San Jose and San Diego, and it is already an important water resource in Orange County.   Seawater desalination is underway in Carlsbad, and in Los Angeles, they’re capturing storm water and using it to recharge the aquifer. All of these are new types of water, which are going to present new challenges for the operators of water treatment plants.

Update 6/20/16: The text has been changed to correct the suggestion that the Flint water crisis was due in part to a switch from chlorine to chloramines for disinfection. Flint did not make the switch, and its problems have been unrelated to chloramines.


Topics: Civil engineering, Environment, Health