WISCASSET — The Chewonki Foundation, an ecology-oriented school, used a natural solution to solve an environmental problem in its own backyard.

That solution, a new septic system that uses a man-made cattail marsh to treat waste, may offer options to other coastal landowners who want to replace their now disfavored overboard discharge systems.

The foundation installed the cattail system after discovering its old septic system couldn’t handle a planned expansion.

New employee housing at the school is near the head of a wetland that eventually empties into Montsweag Creek.

“We didn’t want to contribute to polluting the creek,” said Chewonki Executive Director W. Donald Hudson Jr.

So Chewonki hired environmental engineer Russell G. Martin to design a solution. It was approved by the state and installed recently by student volunteers, who spent a day laying a bed of rock into concrete basins, covering the rocks with mulch and planting cattail sprouts.

Solid wastes go into a traditional septic tank, but waste water, instead of flowing into a leach field, goes into the man-made cattail marshes.

Man-made marshes are not a new idea. They are being used to treat residential waste in California, Tennessee and South Dakota, Martin said. Chewonki’s is the first of its kind in Maine.

After the water is filtered by the cattails, it flows into a small leach field. The advantage is that the cattails allow Chewonki’s leach field to be half the size usually required to process waste from three houses.