Living Machine

In 1997, the businesses located in the town center of Weston, MA were required to upgrade their sewage treatment system. The majority of these businesses, including the Omni supermarket and 30 others, chose a solar aquatic system that was later constructed by the Ecological Engineering Group. The natural waste treatment plant had tremendous advantages over other, traditional options. Who could refuse a cheaper, cleaner, odorless, aesthetically pleasing system that could treat all your waste?

Some businesses in Weston’s town center that are served by the treatment system

Located directly behind businesses on the main commercial street, and in front of natural wetlands, the bioremediation system is housed in a 70×40 foot greenhouse.
Sometimes referred to as a “living machine”, the center treats 4,000 to 5,000 gallons of sewage per day and has an upper limit of 7,000 gallons. Waste is treated to secondary or tertiary standards through natural wetland processes, using absolutely no chemicals. The resulting effluent could be used to irrigate plants, flush toilets, or be discharged to the surrounding wetlands.

The purification process

About 10% of contaminants are removed by 16 tanks of floating flora, including mint, watercress, primroses, water lilies, cherry tomatoes, celery, elephant ears, bamboo, papyrus and flowering ginger, as well as organisms such as snails and fish. These remove organic solids, nutrients, pathogenic bacteria and oxygen. With a greater biodiversity of organisms, it is possible to break down and remove more contaminants.

Many of the plant species used are not native to the Northeast, but survive due to the constant warm climate inside the greenhouse. The hot July day I visited, the greenhouse was 110 degrees F. Even when outside temperatures approach zero in the winter, the greenhouse only goes down to about 80 degrees F.

Elephant Ear, member of the Caladium genus

The remaining steps of treatment occur in the marsh on the opposite end of the greenhouse, containing five feet of rocks, where the water is leached through reeds and cattails. Oxygen is extracted and released as gas by microorganisms beneath the rocks. Next, ultraviolet light is used instead of chlorine to kill pathogenic organisms. The water is finally pumped into surrounding groundwater under the parking lot of the treatment center and local businesses.

The plants inside the greenhouse grow extremely quickly, so excess vegetation is trimmed and brought to the local compost heap in Weston. The CEO of Ecological Engineering Associates, Phil Henderson, explains that the treatment center “accelerates the rate at which nature would break down contaminants.” The whole process of treating sewage to tertiary quality takes around three days.

Making the Switch

When switching from the old waste treatment system, considerations included, cost, appearance and odor. The old waste treatment system cost 11 to 15 cents per gallon of waste treated, compared to the natural system, which costs merely 10 cents per gallon. This reduction in cost per gallon seems to be common after switching to natural systems. In Poughkeepsie, for instance, a newer reed bed operation costs 3 to 5 cents per a gallon, whereas the older mechanical systems cost 7 to 15 cents.

Weston’s solar aquatic system cost between $700,000 and $750,000 to build. Ten years after its construction, the treatment center is still in great shape; the pipes are going to be replaced for the first time in the near future.

Thanks to James for talking to us about the system during our impromptu visit. to the site

View Flickr Sideshow

For more information:
Ecological Engineering Group
FYI: Ecological Engineering Associates, Weston, MA owns the rights to John Todd’s Solar Aquatic patents. They do relatively small-scale greenhouse-based waste treatment systems.

John Todd’s Ecological Design
The squeaky-clean details of solar aquatics from Christian Science Monitor
Nature takes care of the dirty work

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