Throughout history, the contaminants in source waters have changed, as has our understanding of what is safe and what is not. The introduction of chlorine in the early 20th century, combined with filtration, dramatically reduced waterborne disease in the United States and has made the American water supply one of the safest in the world. But these technological advances have caused people to question the importance of protecting source lands. “The bargain made by some communities of a century ago was to trade source water protection for a future reliance on water treatment. The wisest choice is to marry the two together whenever possible,” according to Dr. Jeffrey Griffiths, Director, Graduate Programs in Public Health, Tufts University School of Medicine.

Some of the treatment challenges faced by suppliers drawing from intensively used source lands include:

• Emerging Contaminants
• New Contaminants are Difficult to Monitor
• Spikes in Pollutant Loads
• Changing Standards

Emerging Contaminants

The threat to public health from emerging contaminants presents the most compelling reason to protect drinking water sources. Emerging contaminants are contaminants that are either new to the environment (new diseases or chemicals) or have only recently been identified as potential health threats.

New Contaminants are Difficult to Monitor

“It is difficult to know what new contaminants might be in the watershed that could make it to the treatment facility, and therefore what treatment process will be most effective at safely removing them,” explains Chris Crockett, Manager of Philadelphia Water Department’s Source Water Protection Program. “From a public health perspective it is prudent to manage and protect the source area to the degree possible to prevent contaminants from reaching the raw water source in the first place.”

Spikes in Pollutant Loads

Spikes in pollutant loads are caused by the accumulation of pollutants in the watershed over time and the transport of those pollutants to waterways during rainfall or snowmelt. These pollutants are eventually flushed into a receiving body of water, such as a lake, reservoir, or large river via stormwater runoff or storm sewer overflows. Because spikes usually occur during heavy rains, and because the pollutants accumulate throughout the watershed and over a period of time, it is very difficult to accurately target sources and measure the impact of pollution on water quality and public health.

Changing Standards

From the passage of the Safe Drinking Water Act to present day, the EPA has continued to identify compounds with the potential to cause cancer and other adverse health effects, and has set maximum contaminant levels in drinking water for each substance. The establishment of such standards has dramaticlly improved the quality of drinking water in this country. However, “as any analytical chemist knows, what you see depends on what you look for,” says Lynn Roberts, a professor of environmental chemistry at Johns Hopkins University. Clearly, there are contaminants in our source waters that we are not currently monitoring, and that we may not be treating.