According to the EPA, more than 26 million households in the U.S. rely on septic systems to treat their wastewater. That’s more than one in five. Septic systems are most prevalent in New England, but they’re also pretty common in the southeast and northwest. And there's a reason for that: they’re a relatively low cost option for small communities.
But, in places like Cape Cod, it’s become obvious that there are some major drawbacks, like excess nitrogen flowing from septic systems into nearby estuaries and bays, causing algae to bloom out of control, and disrupting the natural balance of plants and fish. There is also increasing concern about so-called contaminants of emerging concern, such as pharmaceuticals and household chemicals that may be able to mimic or interfere with hormones.
“These impact the environment at very low concentrations, down in the nanogram levels,” said George Heufelder, director of the Massachusetts Alternative Septic System Test Center.
Despite the drawbacks, Heufelder says septic systems are here to stay. He doubts that Cape Cod, for instance, will ever sewer more than half of homes. And he’s okay with that.
“We’re finding that if we can use the natural soil system that is there by redesigning what we do, we can achieve rather high levels of removal – higher than treatment plants,” said Heufelder. “Some compounds, such as fire retardants, are going to persist anyway. But when we treat them in soil-based systems, we see some dramatic reductions.”
Since 1999, the Massachusetts Alternative Septic System Test Center has been trying out ways to improve septic systems. One simple change they’re testing is having the wastewater enter the system closer to the soil surface. That seems to help with reducing both nitrogen and pharmaceuticals, which are digested by the microbes that naturally live in the shallow soil level.
Another promising advance they’re testing is pretty low-tech: wood chips. A layer of sand and sawdust added to a standard septic system leach field significantly cuts the amount of nitrogen that escapes into the environment.
“The wood chips actually provide a carbon source for denitrification,” explained Heufelder. “A wood-based layer shuts the air off and the bugs - the bacteria – use it as a carbon source to denitrify the wastewater before it hits the groundwater.”
There are still details to work out – whether the wood chips would be water-saturated, or not, and how that would affect their longevity. There’s also a question of space. Heufelder says they’re experimenting with a boxed system that might work in small spaces.
These relatively low cost, simple tweaks to septic systems could have big ramifications. Beyond that, though, Heufelder says we need to change our attitudes toward wastewater - stop thinking about it as something to be put out of our minds, and start recognizing it as the lifeblood of entire ecosystems within our septic systems.