| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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horizons Living Machines Like a concrete metropolis, massive gray buildings, giant egg-shaped sludge digesters, and dark tunnels fill San Francisco's Oceanside Water Pollution Control Plant. The monotone of the high-tech and high-cost sewage plant is somewhat relieved by what appears to be an elevated, sky- blue dumpster overflowing with foliage that occupies one corner of the site. Upon closer look, I see that the structure is a trailer bed surrounded by a metal catwalk and containing two rows of square cells, each full of water and plants such as duckweed, iris, papyrus, water hyacinth, river birch, willow, and bald cypress. This horticultural hodgepodge, assisted by an array of unseen microbes and other organisms, can clean up to 15,000 gallons per day of the City's domestic wastewater and storm runoff as a substitute for the final phase of the plant's conventional treatment. It's a Living Machine, "half engineered artifact and half wild nature," according to ecological designer John Todd, who nearly ten years ago conceived the idea of a natural engine to clean water, grow food, regulate climate, even repair damaged habitats. The cogs in this machine consist of hundreds of species--from microbes, to plants, to vertebrates--linked together in a fabricated food web. Unlike anything born of the Industrial Revolution, Living Machines have the potential to organize, repair, and reproduce themselves. They offer a cheaper, cleaner, chemical-free alternative for containing and removing high- strength waste. "The real world is not made up of magic bullets, but of symphonies of organisms," Todd told an enthusiastic capacity crowd last October at the Bioneers Conference in San Francisco. "There is a new kind of relationship that humans can have with life forms that can turn the tragedy of the twentieth century around." The Oceanside Plant experiment was one of several works-in-progress highlighted by Todd, president of Ocean Arks International in Falmouth, Massachusetts. Living Machines currently operate in 13 states and seven countries, with several more being developed by non-profit Ocean Arks and engineered and built by Burlington, Vermont-based Living Technologies, Inc. and a few other companies. "Basically, it's just alchemy, throwing in a bit of this and that to see what works," says Michele Hallahan, who ran the Oceanside Living Machine for two years starting in December 1994 and kept tabs on its evolving, engineered ecology. Hallahan seeded the system from time to time with water from local vernal pools and streams to add a dose of microbial critters. Pretreated sewer water, diverted before chlorination, is gravity-fed into the eight-foot-deep tanks, or cells. The cells then convert ammonia in the wastewater to nitrate and ultimately to nitrogen gas that will be recycled to the atmosphere. The cells also remove remnant phosphate and pathogenic coliform bacteria. Five cells treat the water aerobically, and the final two complete the process without oxygen. A pump at the base of the first five cells circulates air and selects for the nitrifying bacteria that will convert nitrogen into a reusable form. Bacteria cling to either pebbles of pumice or plastic netting inside each cell. A porous rock such as pumice provides a large amount of surface area in a small volume to maximize microbe density while leaving spaces for gas to escape. The plants, their roots suspended in the water without any anchoring soil, help with nutrient uptake and gas exchange.In the anaerobic cells at the end of the line, nitrogen gas bubbles up to the surface, choked with water hyacinth. The last cylinder contains, to my eye anyway, clear, clean water. The Living Machine also supports a pair of adjacent tanks full of fathead minnow (donated by the plant's bioassay lab), mosquitofish, and a few koi carp. Clams scattered on the bottom remove unwanted bacteria, such as Cryptosporidium, and parasites. The fish and mollusks help buffer the system and keep the water from getting too acidic for the plants and other inhabitants. The Oceanside Plant processes anywhere from 25 million to 65 million gallons of wastewater per day, which is then pumped into the Pacific. Although the Living Machine handles less than 1/1,000th as much water--a drop in the bucket of San Francisco's sludge--the output can be reused for irrigation or other purposes and meets state water-quality standards for swimming pools. The average discharge from the plant into the ocean contains 31 milligrams per liter of ammonium, but the Living Machine reduces that figure by 90 percent. The Oceanside Plant cost $220 million to design and build; the price tag for the prototype Living Machine was around $120,000. Although the Oceanside Living Machine had been planned as a three-year experiment, the project prematurely folded last December after Congress gutted the Environmental Protection Agency's budget for innovative programs. It continues to reside at the treatment plant and operate at a minimal life-support level, while Ocean Arks seeks a new industrial home for the facility.
Perhaps the best demonstration of the technology's power comes from Chattanooga Creek, Tennessee, where coal-tar contaminants in the creekbed from the manufacture of munitions, pesticides, and creosote have been making people ill. In 1992, the local community turned to Ocean Arks to conduct a lab experiment with the highly toxic waste. After 60 days of filtering through a pilot Living Machine, two- thirds of the compounds, including DDE and aldrin, were largely removed from the water. Five years later, the Environmental Protection Agency (EPA) remains undecided on how to proceed with clean-up and may opt for just dredging and burning the Chattanooga waste. Although EPA has recognized Todd's inventiveness--he received their first Chico Mendes Memorial Award and the 1996 Merit Award--the agency has yet to embrace his invention. Todd's recent Living Machines have created case studies in combating commercial waste. Working with such environmentally aware companies as Ben & Jerry's and The Body Shop, Ocean Arks and Living Technologies have built systems to reduce the levels of fats, grease, and oils in water left over from making ice cream and cosmetics. Three years ago, when the M&M-Mars chocolate plant in Waco, Texas faced exorbitant off-site waste disposal fees, they purchased a Living Technologies design featuring a marsh-like reed bed to remove and compost biosolids at the factory. The facility paid for itself in saved disposal costs within two years. A similar set-up at the Ethel M chocolate plant near Las Vegas, Nevada treats all the factory waste, removes odors that could contaminate the confections, and reuses the water for landscape irrigation. Todd plans to investigate the potential for Living Machines to grow marketable products, such as flowers, fish, or trees, while they perform the primary task of waste reduction. He also hopes to convince the pet food industry to try his technology, and negotiations are underway with one company in Australia. By harvesting fish in Living Machines that treat their wastewater, pet food manufacturers could grow one of the main ingredients of their product, relieving natural fish populations and the guilt of pet owners. Beyond clearing some corporate consciences, Ocean Arks has begun focusing most of its current efforts on restoring damaged environments. After Flax Pond in Harwich, Massachusetts, a popular swimming and fishing spot and a source of irrigation for Cape Cod's cranberry bogs, was closed in the mid-1980s due to pollution, Ocean Arks deployed a "replacement wetland": a sun- and wind-powered raft that cycles 100,000 gallons of pond water through nine ecological cells. Three cells harbor microbes to break down the contaminants, and the other six cells, containing typical marsh plants and animals, filter water that then returns to the pond. Since the Lake Restorer began operation in 1990, beaches have reappeared, oxygen in the water has increased, and the biodiversity of bottom-dwelling invertebrates has blossomed. Although pollutants from the adjacent landfill and septic waste basin continue to leach into the pond from contaminated groundwater, the pond is again safe for swimming and fishing. Todd believes that such floating restorers could solve pollution problems for a fraction of the cost of dredging, the main alternative. Future restorers may help bring back some of Cape Cod's depleted eelgrass and shellfish beds on salt ponds, and a large-scale raft may one day clean up Oakland's Lake Merritt. By returning it to an industrial ecosystem or releasing it into nature in a benign form, Living Machines turn waste into a resource. They follow one of the first principles of ecological design, namely that everything is either food or energy. "Why should sludge be put on landfills," asks Todd, "when it can be put into food chains?" Blake Edgar is Associate Editor of California Wild. |
Spring 1997
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