Behind a 108-year-old New Windsor house is a new way of treating household sewage -- two 20-by-20-foot beds of bulrushes.
If the system works, water leaving it will be clean enough not to pollute wells nearby and may be cleaner than water leaving a standard septic tank.
That could be an important feature in Carroll County, where about 27,400 households rely on wells for drinking water and 28,700 use septic systems to dispose of waste.
David T. and Barbara Duree, owners of the house, turned to the "constructed wetlands" system after their cesspool failed last autumn. Raw household waste flowing into the ground threatened to pollute well water in the area, but the Durees couldn't install a conventional septic tank because their land failed health department percolation tests.
Mr. Duree was concerned about the public health aspects.
"Failed [septic] systems have a public health factor. They can contaminate irrespective of boundaries. Your system can contaminate your well or your neighbor's," he said.
Mr. Duree, a marketing consultant, and biologist Dale Gray, who helped modify and install the constructed wetlands system, formed a consulting partnership called Innova Ltd. to advise others about the wetlands system.
"We think we've got a winner here," Mr. Duree said. "If most of us did this, we'd need fewer public systems."
The Tennessee Valley Authority (TVA), whose engineers developed constructed wetlands, will mail design specifications on request. The design is not patented, although the TVA is seeking a patent on new technology for introducing oxygen into the system.
The estimated $5,000 Mr. Duree spent on his wetlands system is about twice the cost of a standard septic tank. He said the wetland was cheaper to create than a sand mound, another alternative sewage disposal system that filters waste through sand.
The TVA has about seven years of experience with large-scale constructed wetlands in Alabama, Tennessee and Kentucky.
"The question is still out there [on] how well they're going to work," said Leslie Behrends, team leader at the TVA's constructed wetlands research facility in Muscle Shoals, Ala. "Preliminary data show they do a real good job in removing suspended solids and biological oxygen demand. The thing they're not doing especially well is removing phosphorus and ammonia."
The new technology of adding oxygen is expected to remove phosphorus and the ammonia that is released from nitrogen in the sewage, Mr. Behrends said.
Mr. Duree's system, which began operation Saturday, is the fourth such wetland in Maryland.
The Maryland Department of the Environment doesn't have data yet from two systems in St. Mary's County and one in Charles County, said Jay Prager, head of the department's innovative and alternative on-site sewage disposal section.
In the Durees' system, wastewater from the house goes into a lined bed where it seeps through layers of rock to the potato-like roots of the bulrushes. Microbes in the bulrushes remove the pollutants.
After three to five days, the water goes into the second bed, where it percolates through layers of soil and gravel into the ground.