When the sewage treatment system failed at Vermont's busiest interstate highway rest area, "up from the ground came a bubblin'" something that was crude and smelly, but it wasn't oil. State officials had a serious problem that had to be corrected quickly.

They decided to install an innovative new system called the Living Machine. This system uses a series of tanks containing plants and other organisms to naturally clean wastewater.

The welcome center on I-91 in Guilford, Vt., was built in 1966. It was the first interstate rest area in Vermont and one of the first in the nation. It was originally designed to accommodate 30,000 people a year, but it immediately exceeded that number. By 1998, the rest area was serving more than 500,000 people a year.

Like most rest areas in Vermont, the Guilford center was built in an isolated area on poor soil.

"We didn't want to impact communities with noise and pollution, so rest areas weren't usually built near towns," explained Dick Foster, director of the Vermont Information Center Division of the state's Department of Buildings and General Services. This meant that the Guilford Center was located too far away to be hooked up to a municipal wastewater treatment system.

"The state didn't want to use prime agricultural or development land for rest areas, and as a result, we didn't have good soil in which to put the leachfield system," Foster added. By the 1970s, the Guilford center's leachfield system failed, and sewage could be seen bubbling out of the ground.

In 1985, the state started a program of connecting a rest area's wastewater to a municipal system when the rest area was rehabilitated. However, the cost of piping sewage from the Guilford center 11 kilometers (seven miles) to Brattleboro, the nearest community, was prohibitive.

The state tried other alternatives, including constructing two more leachfields at the rest area and installing microflush toilets that operated with compressed air and required very little water. Neither solved the problem.

"We often had 3,000 people come through the building in a single day and had toilets flushing every few seconds," Foster said. "The microflush technology was so touchy that the toilets were breaking down all the time." The breakdowns resulted in long lines of people waiting to use the restrooms, and complaints were made to the governor's office.

By the early 1990s, the operators of the welcome center were constantly dealing with swampy standing water, bad odors, and maintenance problems.

"We would have to close things up and call for emergency services from plumbers and septic services," said Wendy Randall, who has worked as an information specialist at the center for 19 years.

The state leased six portable toilets during the fall of 1996 to help deal with the influx of visitors during the busy foliage season, but these drew new complaints. State officials needed a solution that could be designed and built quickly for the next foliage season.

"We were looking for an alternative because we couldn't continue with that high level of frustration," said Foster. To further complicate matters, the welcome center was slated to be replaced by a newer facility in 2000, so the "quick fix" also needed to be low cost. Tom Leytham, an architect who had designed other rest areas in the state, suggested the concept of using a Living Machine to Foster.

"One day, Dick was in my office and said that the governor's office was getting calls on a daily basis complaining about the port-a-potties at the Guilford rest area," remembered Leytham. "I told him that I'd heard about Living Technologies, who had come up with a very elegant, simple solution that cleaned wastewater through a natural process involving plants." Leytham drove Foster to South Burlington, Vt., where Living Technologies had installed a Living Machine to treat municipal wastewater.

"I have a horticultural background and was impressed and started thinking about applying the technology to the Guilford Welcome Center," said Foster.

In December 1996, in response to an inquiry from state officials, Living Technologies proposed a sewage-to-reuse system to reduce flows to the leachfields by recycling treated wastewater back into the restrooms to flush toilets. The Living Machine could be installed to serve the existing facilities at the Guilford center, and because the system was a modular design, it could be moved to another rest area when the center was relocated.

In only eight months, the system was approved by the Vermont Agency of Natural Resources, funded by the Federal Highway Administration (FHWA) and Vermont Department of Buildings and General Services, and installed by Living Technologies. The Living Machine cost approximately $250,000, 90 percent of which was funded by FHWA and 10 percent by Vermont.

"FHWA is interested in innovative technologies, and we agreed that this rest area needed a creative solution that didn't fit normal parameters," said Mark Richter, an FHWA area engineer. "We also liked the fact that there would be an opportunity to use the system at another location."

"Living Machines are such a cost-effective alternative," said Foster. "Typically, the cost to connect to a municipal wastewater treatment plant can easily exceed a million dollars versus $250,000 for a Living Machine." The Living Machine was operating in time for the 1997 autumn foliage season.

On Nov. 1, 1999, it was decommissioned when a new Guilford Visitor's Center opened eight kilometers (five miles) north on I-91. The new center is hooked into Brattleboro's wastewater treatment system. Foster said the Living Machine is in storage now, but there are plans to install it next year to solve a similar wastewater problem at a rest area on I-89 in Sharon, Vt.

How the Living Machine Works

The Living Machine is a biological system consisting of a series of reactors housed in high-density polyethylene tanks. Each reactor has a different ecological environment designed for a specific treatment purpose. This ecological diversity includes plants, aquatic insects, snails, aquatic worms, and other flora and fauna.

Sewage from the rest area is treated to Vermont's reuse standards and recycled to the rest area as flush water in the toilets. The Living Machine was designed to treat wastewater from up to 4,300 visitors per day. Flows fluctuated with seasonal and weekend use, averaging 23,000 liters (6,075 gallons) per day and peaking at 3,785 liters (1,000 gallons) per hour.

At the Guilford Welcome Center, sewage flows to the center's existing septic tank. Here solids settle, and anaerobic bacteria feed on the waste. Septic tank effluent is then pumped into two treatment trains located inside a 168-square-meter (1,800-square-foot) double-glazed greenhouse.

The first treatment tanks in each train are closed aerobic reactors, which remove odors from the wastewater and metabolize the organic material as microbes consume the waste in the water. Aerators bubble air through the tanks, keeping their contents mixed and providing oxygen for waste-eating microorganisms.

Four open aerobic reactors are next. The surface of the wastewater in these aerated reactors are covered with vegetation. The roots of the vegetation provide living spaces and oxygen for the microbes consuming the waste.

The seventh tank is a clarifier in which microbial communities are separated from the treated water. Calm water in the clarifier allows the remaining biological solids to settle, and those solids are then pumped back to the septic tank for further digestion.

Ecological fluidized beds (EFBs) provide final "polishing" of the wastewater. These beds circulate the wastewater through different habitats that remove organic material and nutrients. The polished water is then disinfected with a hypochlorine solution, destroying pathogens. In the final step, the water is dechlorinated, and the reclaimed water is pumped to a holding tank to be reused to flush toilets in the rest area. Surplus water not needed for reuse is discharged to the existing leachfield.

On April 29, 1999, Living Technologies Inc. and the state of Vermont received the 1999 Engineering Excellence "Grand Award" from the American Consulting Engineers Council of Vermont for the Guilford Welcome Center Living Machine. The Living Machine was invented by Dr. John Todd, a founder and director of Living Technologies. The Living Machine has won numerous other environmental awards, including the Chico Mendes Memorial Award, Teddy Roosevelt Conservation Award, and Environmental Merit Award given by the U.S. Environmental Protection Agency.

Molly Farrell is a freelance writer living in Burlington, Vt. She specializes in business, law, and environmental issues.

Liz Van der Hoven is an engineer and Tedann Olsen is the marketing manager for Living Technologies Inc. in Burlington, Vt.