The squeaky-clean details of solar aquatics

By , Special to The Christian Science Monitor

With the smell of a freshly tossed garden salad and the glassy look of a botanical museum, this Massachusetts wastewater treatment plant will amaze you. It's a greenhouse that turns 4,000 gallons of sewage into sparkling water each day.

The system is known as solar aquatics, a process that replicates nature's cleansing action by which plants and microbes purify waste. After years of pilot projects and toiling under skepticism, solar aquatic facilities are sprouting up not only in the US, but around the world.

They're also gaining ground on traditional wastewater treatment facilities that can be concrete eyesores with rank lagoons that neighborhoods balk at and city councils dread.

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The three-year-old plant here in the center of Weston, a small town 15 miles from Boston, serves about 30 businesses. Inside the 70-by-40 foot greenhouse, 16 gravity-fed tanks brew sewage with the help of floating flora. Mint, watercress, primroses, water lilies, cherry tomatoes, and celery, suck up contaminants. Even a few fish and snails help out.

Phil Henderson, chief executive officer of Ecological Engineering Associates (EEA), which owns and operates the greenhouse, strolls between the tanks pulling back greenery billowing over the sides. "Not sure how these got here," he says, pointing to the tomatoes. "Don't worry," he smiles, "we don't eat them."

Aerated from the bottom of the tank to blend the muck, microbes gradually break down the organic matter as it flows through the process. While the flora only absorbs about 10 percent of the contaminants, their roots provide ideal living conditions and attachment sites for microorganisms.

After flowing through the tanks, the sewage is further polished in a man-made marsh in the back of the greenhouse. On top of five feet of rocks sits the marsh where water leaches through the reeds and cattails. Microbial organisms clinging to rocks beneath the marsh pull oxygen off the remaining nitrates in the water, releasing it as gas. In the final stage, the water is pumped into a natural wetland behind the greenhouse.

The plant in Weston has the capacity to handle 25,000 gallons of sewage, which is a mere drip compared with most sewage treatment plants, but the benefits are numerous. Thanks to this process, businesses in this white-steepled town are better off.

Before the greenhouse was built (right off main street), businesses pumped their wastewater into holding tanks behind their back doors, because the high water table didn't allow for septic systems.

The waste then had to be hauled away, Mr. Henderson says, for 11 to 15 cents per gallon. Now, businesses pay 10 cents per gallon to have Ecological Engineering Associates purify it. "There is progressively increasing interest in natural systems," says Mr. Henderson. "It's an alternative technique that should be looked at and used." There are several advantages:

*It produces half or less as much sludge than most industrial plants, which is hauled away only three times a year, much less than municipal facilities.

*Most residents would rather have a greenhouse next to them than a traditional treatment plant.

*It is a great learning tool for students and the community.

Henderson says several groups a month visit, from graduate students in land planning to chemistry classes. The facility in Bear River, Nova Scotia, attracted 8,000 tourists in its first year.

Solar aquatics isn't a quaint New England phenomenon. EEA has a plant in La Paz, Mexico, one in Metz, France, and several more plants in Canada.

A new plant has recently been approved for an environmentally sustainable community in Fredericksburg, Va., that will handle 1 million gallons a day and serve 4,000 households.

Living Technologies, another wastewater treatment facility in Burlington, Vt., has installed large systems around the world, from a 10,000 gallons per day (gpd) facility for the National Audubon Society in southwest Florida to a large system that handles more than 200,000 gpd at a pet-food processing plant near Sao Paulo, Brazil.

Despite the eco-friendly aspects of solar aquatic facilities, several factors inhibit their development across the country - mainly a reluctance to break away from traditional technology.

Henderson says that "consulting engineers are well versed in conventional wastewater treatment plants." When alternative methods such as solar aquatics are proposed, "you end up with a lot of different opinions." He also says city planning systems are rooted in bureaucracy. This makes it difficult for some communities to embrace new wastewater treatment technology.

"The decision process to build a wastewater treatment facility is very lengthy and very tedious," says Henderson. But it can be less expensive to build than traditional facilities.

Bruce Strong, operations manager at the Weston plant, said the greenhouse operation here cost between $700,000 and $750,000 to build.

Other ecological wastewater treatment plant operators agree that the industry has yet to be fully accepted because of the adherence to traditional systems.

"It's so new, it's hard to get people living in a bureaucracy to look outside the box," says Tedann Olsen, Marketing Manager at Living Technologies, which has more than 20 systems worldwide. "It's the way earth has been purifying wastewater forever. Some get it right away, some don't want to bother," she says.

(c) Copyright 2000. The Christian Science Publishing Society

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