Don't drink the sewage

IT DOESN'T TAKE a medical degree to know that drinking poop is bad for us. For centuries, we have protected ourselves from waterborne plagues by keeping human waste out of our water. Why, then, would the Environmental Protection Agency propose a new policy that would allow sewage treatment plants to discharge inadequately treated human waste into lakes, rivers, streams, and coastal waters?

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The Clean Water Act generally prohibits sewage treatment plants from discharging partially treated waste into our waterways. Sewage is normally treated by settling out solid materials, and then through a biological process that kills pathogens.

Both treatments are necessary to kill the full spectrum of viruses, bacteria, and parasites in sewage. Both are needed to minimize the risks to people downstream, and both are required by law.

The EPA's proposal would allow sewage to be dumped into waterways more often without biological treatment, which EPA calls ''blending" because the largely untreated sewage is mixed with treated sewage before it is discharged.

Many older communities, particularly in the Northeast and Great Lakes, have combined sewage and stormwater pipes. Heavy rainfall can overwhelm their sewage treatment capacity, leading to sewage spills. The Clean Water Act requires these communities to work toward a long-term goal of providing full treatment for sewage under all but extreme weather events.

The EPA's proposal would take them off course by allowing discharges of largely untreated, settled but not biologically treated sewage whenever it rains, rather than as an exception. In other words, this bad but occasionally necessary practice would become more widespread instead of increasingly rare.

Over the past 30 years we have identified many germs, such as cryptosporidium and giardia, that can infect us even if we drink a tiny number of them. By skipping full treatment, many will survive to infect us later.

Clear, scientifically credible information shows that blending sewage lets enough of these germs into our water so that the risks are increased. These pathogens can infect all of us, but are of particular concern to children, the elderly, and people with compromised immune systems.

No water treatment process is absolutely reliable at removing pathogens. Polluting drinking water sources with sewage is just increasing the odds that something will slip through the treatment plant to cause waterborne disease outbreaks. There is just no escaping the fact that blended sewage releases will increase the number of live, ready-to-infect-you pathogens in our drinking and recreational waters.

Sewage treatment not only protects our drinking water and swimming sites, it also protects businesses like the shellfish industry. Shellfish are filter feeders, and must be protected from human wastes or else they will concentrate human pathogens in their tissues. Sewage blending will increase shellfish bed closings, drive shellfish growers out of business, and increase the health risks to the population from eating shellfish.

The arguments for sewage ''blending" are short-sighted and not persuasive. The proponents of sewage blending are mainly focused on the cost savings they anticipate from using blending to further defer or avoid maintenance, or improvements, to their sewer and rainfall collection systems through this policy.

While I sympathize with these towns regarding finances, these infrastructure challenges should not be met by weakening public health protections. The Clean Water Act already allows sewage blending that cannot be avoided despite the use of best practices for maximizing treatment.

Instead of weakening requirements to upgrade and repair wastewater infrastructure, the problem should be met by dealing with the underlying needs to treat sewage and to channel rainwater in a responsible, cost-effective manner. The EPA's ''solution" effectively legalizes the problem and undermines three decades of progress in cleaning up lakes, rivers, and coastal waters.

Congress is about to vote on a measure that would block EPA from allowing sewage blending.

We should remind our elected officials that we want less, not more, sewage in the water.

Jeffrey K. Griffiths is an associate professor of public health and family medicine at Tufts University School of Medicine. He is a member of the US EPA's National Drinking Water Advisory Council and its Science Advisory Board.