Identifying Corrosive Water, A Step Forward Against Lead Contamination

Without a doubt, the biggest story in the world of water treatment this year has been lead contamination. Since a state of emergency was declared in Flint, MI, last year, the public and water quality professionals have been on high alert for the contaminant and have found it in communities from coast to coast.

Nearly every instance can be traced to a single cause. When corrosive water passes through the nation’s network of lead drinking water pipes, it brings the poisonous substance into homes with it. It’s not known exactly how many of the country’s pipelines consist of lead, but it’s now apparent that a significant portion of its water is corrosive.

A study of 27,000 wells nationwide conducted by the United States Geological Survey (USGS) demonstrated that 25 states have groundwater with high or very high potential to be corrosive. 

This first national-scale study was prompted by the contamination in Flint, which can be traced back to a decision by government officials to switch water supplies to a more corrosive source, a principal investigator of the study told Water Online.

“The USGS study relied on groundwater quality data collected by the USGS as part of various studies [from 1991 to 2015],” an investigator said. “The USGS relied upon two indicators of corrosivity that had been previously reported on in literature. Values of the indicators were computed at all locations where the USGS had sufficient data. Maps were then prepared and data were summarized on a state-by-state basis.”

The USGS map indicates one of four levels for potentially corrosive groundwater for every state, from low prevalence to very high prevalence. States at risk stretch down the East Coast from Maine to Florida, travel through the south to the Texas border, and include Washington, Oregon, and Hawaii.

The two indicators used to determine what water can be considered “potentially corrosive” were the Lanelier Saturation Index, measuring the degree of saturation of calcium carbonate, and the Potential to Promote Galvanic Corrosion, based on the chloride-to-sulfate mass ration and alkalinity.

While the maps resulting from this study will be particularly helpful to those who depend on private wells that don’t have government-appointed guardians testing them for lead, public water utilities and treatment plants that do regularly test can glean some useful information as well.

“Managers of public utilities might find the maps helpful in understanding the characteristics of untreated groundwater in their areas as compared to other areas,” an investigator said.

Municipal water operations that find they do pull corrosive groundwater need to consider a variety of treatment strategies.

As a scientific information agency, the USGS does not make explicit recommendations about risks that it detects or information it uncovers. This study, however, provides background information necessary to combat a problem that we are all too familiar with.

“Our intent is to provide relevant, reliable information about this topic at a broad scale,” said an investigator. “Interested individuals, organizations, and water suppliers can use this information in considering whether to undertake additional investigations about the quality of their source water. As warranted, they can work with appropriate local, state, and federal partners to ensure safe drinking water supplies.”