A `Living Machine' Purifies Waste
Faced with urgent sewage treatment need, Harwich, Mass., puts a special greenhouse to work
IN the world of nature, nothing goes to waste. That's the message you get when you step inside a warm, balmy greenhouse here at the edge of the town dump. Water hyacinths, willow trees, and watercress are living - in fact thriving - on truckloads of septic-tank waste, one of the most vile substances that human beings dump in the ground and like to forget about.
The town of Harwich, however, can no longer afford to forget. With an order form the state to close its septic lagoons next year and no government funds available to subsidize a new multimillion-dollar treatment plant, the citizens are bucking convention - and looking to Mother Nature for solutions.
Water plants and sunlight are the chief ingredients in this solar- aquatic system of purifying water invented by John Todd, founder of the Center for the Protection and Restoration of Waters in Falmouth, Mass. A nationally recognized ecological pioneer, Dr. Todd has worked with this technology for several years, attempting to treat waste water through ``living machines'' of bacteria, algae, higher plants, and fish. It's a process he claims saves money and energy and doesn't churn out the amount of sludge that huge treatment plants do.
While various ecological systems for treating sewage have sprung up during the last 10 years, mostly in the South and southwestern parts of the United States, Todd uses enclosed greenhouses, which enable his system to operate year-round in harsh northern climes.
A unique feature of the Harwich greenhouse is that it has the nasty job of treating ``septage'' (sewage from septic tanks), which is 30 to 100 times more concentrated than municipal sewage.
How to treat septage has become a critical matter on Cape Cod, where overdevelopment, sandy soils, and a high water table combine to increase the risk of ground-water contamination. In Harwich, the water table is a mere 25 feet below the two open-pit septage lagoons.
With Solar Aquatics, ``we've definitely taken a gamble,'' says Paula Champagne, health director of Harwich, which has a winter population of 10,000 that triples in the summer. But residents have overwhelmingly agreed to help pay for the prototype greenhouse, she says.
The project began last March and treats about 30 percent of the town's septage. This summer, the Massachusetts Department of Environmental Protection (DEP) will analyze the greenhouse's effectiveness and decide whether to grant a permit for a full-scale operation.
``If this works, it certainly would be a sizable breakthrough for towns in our population range,'' says Shirley Gomes, town selectman.
After ``honey wagons'' truck the septage from homes and businesses to the greenhouse, the gunk moves by gravity down through long rows of 600-gallon Plexiglas-like tanks. The aerated tanks are like giant washing machines, bubbling with bacteria, algae, and sludge-eating snails. Hyacinths float on the surface, and small trees form extensive root systems where microorganisms graze.
One tank cradles a blooming water iris. ``I found it floating on a Cape Cod pond,'' says Todd proudly, pushing back the greenery to reveal the specimen. ``Now it's a workhorse in this facility.''
The water then seeps through an engineered ``marsh,'' a narrow trough full of gravel, grasses, and small flowers. Another round of final ``polishing'' through more tanks and more marshes eventually produces water clean enough to put back into the ground, says Todd.
``This is Mother Nature at her best,'' says Phillip Henderson, chief executive officer of Ecological Engineering Associates, the private company that owns and operates the greenhouse. Solar Aquatics imitates nature's self-cleaning ability, only more quickly and thoroughly, he says.
The town currently pays Mr. Henderson's firm 15 cents for every gallon of water treated that meets a certain standard. Seated in the greenhouse, Henderson pulls out charts outlining various water-quality parameters set by the state. Several of the charts, though not all, show the greenhouse water averaging below government limits.
``The numbers aren't exactly where we'd like them to be,'' says Ms. Champagne. ``But what we've been achieving is far better than some of the old [conventional] plants in existence and even better than some of the newer plants,'' she says.
Henderson says construction and operation for the project have cost $500,000 for far. Based on the firm's projections, he says, capital costs for a full-scale operation ``should be a third to a half of what a conventional septage treatment plant would cost.''
The drawing card for town taxpayers, says Champagne, is that the greenhouse ``seems to be an environmentally pleasing approach and economically feasible. Those two stages generally do not go hand in hand.''
Town officials have considered a conventional plant, she says, but ``we did not feel that the state-of-the-art was advanced enough to treat waste and put it back into our sole-source aquifer ... without creating more problems, without using chemicals, and producing more byproducts and sludge.''
A new septage treatment plant in the nearby town of Orleans just opened last year, costing more than $15 million. Harwich will have to go the same route if Todd's method does not get the DEP's stamp of approval.
With a conventional plant, ``we know it would work. We know how to design them. This [greenhouse] system is new ... and the data to date has not been stable,'' says Brian Donahoe, director of the division of water pollution control at DEP. ``What happens if the greenhouse has an aberration [malfunction] or there's something in the septage that kills all the plants?''
Yet Harwich town officials remain hopeful. ``We realize we're going into pioneering territory for Massachusetts,'' says selectman Gomes, ``but you've got to look into the future. ... We've gone cautiously and carefully, although from the very beginning, we've been thoroughly impressed with what we saw.''
Though Mr. Donahoe says he doubts that this greenhouse technology could be adapted for use in densely populated urban areas, Henderson maintains that it can.
``We don't feel there are any limitations on the scope of possible projects,'' he says. The system is ``modular and can be scaled up,'' by adding on more greenhouses or developing separate clusters of them.
``There certainly is a remarkable interest out there for what we can provide.''