Ecology Vs. Engineering: A Clash of Values on a Mountain in Vermont

Just below one bank of condominiums at the Sugarbush ski resort near Warren, Vt., you can find three and sometimes four sewage-treatment systems being tested side by side. The story unfolding there is about more than the chemistry of sludge--it is about the mind-sets and values with which human beings attack environmental problems. It’s about, if you will, the Future Relationship of Human Beings, Technology and Nature on This Planet.

Sugarbush has spawned condominiums, restaurants, sports centers and other profitable sewage-producing entities, built essentially on bedrock. They are most heavily populated when temperatures are below zero, days are short and biological processes work slowly, if at all. This place is the ultimate test site for sewage-treatment schemes. Whatever works here will work anywhere.

And just about everything is being tested, because Sugarbush is desperate. Rice Brook, a small trout stream that drains the mountain, is contaminated in winter with ammonia from the Sugarbush leach field. The state hit the resort with a $50,000 fine and a moratorium on any further sewage hookups. If the problem isn’t fixed before next winter, the state could deny the resort a discharge permit, effectively shutting it down.

Sugarbush’s current sewage system is a collection of settling lagoons, which flow into a flocculator that adds aluminum to precipitate out phosphate, followed by a chlorinator, followed by a leach field. It is a sophisticated system of the traditional, land-intensive, out-of-sight out-of-mind variety. By Vermont’s strict standards, it doesn’t handle suburban-density housing on a cold mountainside.

The most high-tech alternative Sugarbush has tried is reverse osmosis. Sewage is shoved under pressure through a semi-permeable membrane. Water goes through; everything else stays behind. Reverse osmosis is Space Age sewage treatment at Space Age prices. It generates a concentrated “brine” of stuff that doesn’t go through the membrane. The company that sells you the system doesn’t tell you what to do with the brine. Sugarbush has decided that reverse osmosis is too expensive and too briny.

There are two remaining contenders. The first is a squat, square, windowless concrete structure with a sign at the entrance reading “DANGER CHLORINE GAS--turn fan switch on before entering.” Inside is a maze of pipes and dials, gas cylinders and reaction chambers. Bags of dry sodium hydroxide are piled up, each one stamped DANGER CAUSTIC. This is a break-point chlorine plant.

Across the driveway is an arched, plastic greenhouse. Inside, under a network of walkways, is a greenish pool with air bubbling through it. The pool is sewage, but the place smells good, like a greenhouse, humid and fertile. Pots of geraniums are in bloom; rafts of willow and eucalyptus float in the pool. At the far end is a lush marsh--bamboo and cattail, marsh marigold and swamp iris. This is a solar-aquatic plant, built by the Four Elements Corp. of Warren.

In the break-point chlorine process, effluent is made alkaline with sodium hydroxide and then blasted with chlorine gas. The chlorine oxidizes ammonia to nitrogen gas, which bubbles off into the atmosphere. Excess chlorine is inactivated with sulfur dioxide to produce sulfate and chloride. Then the whole business is filtered through activated carbon to remove any remaining chlorine.

This plant must handle ammonia levels 10 times higher than usual, so the chemicals are at very high concentration. The input chemicals are dangerous, and one possible byproduct, chloramine, is a carcinogen. If everything works right, at the end of the process 95%-99% of the ammonia is removed, and the effluent contains nothing worse than salt and sodium sulfate.

The break-point chlorine plant comes from a pipe-and-valve mentality: “What chemicals can we use to get rid of ammonia?” The solar-aquatic plant comes from an ecological mentality: “How does nature handle ammonia?” It sees sewage not as a waste to be rid of but as a resource to be cycled back into life. Nature handles ammonia by turning it into nutrient. Normal soils and waters are full of bacteria that transform ammonia into nitrate. Nitrate is taken up into plants, the plants are eaten by animals, the animals excrete ammonia again. That’s the nitrogen cycle, one of the planet’s great natural flows.

At the solar-aquatic plant, as raw sewage enters the greenhouse it flows first through a cylinder of nitrifying bacteria gathered from Vermont ponds. Then into the raceways where algae multiply in the water, taking up nutrients. Freshwater shrimp eat the algae. Bass and trout in aquaculture tanks at the purified end of the system eat the shrimp.

John Todd, of Ocean Arks International at Woods Hole, Mass., the research company for the system, lifts a corner of a Styrofoam float. It’s covered with snails and transparent globules of snail eggs. “Here are the hard workers of this place. They clean up the sludge. We drained the plant and found almost no sludge on the bottom.” The snails are also fed to the fish.

The river of effluent takes five days to wind from one end of the greenhouse to the other. When it reaches the end, it is filtered by the marsh. The plants there have commercial value (watercress) or pretty blooms (marsh marigold) or the ability to take up toxic substances (cattails, bulrushes). The iris roots produce a substance that kills Salmonella bacteria. The water coming out of the marsh tests about as pristine as Rice Brook--before Sugarbush.

The operators at the break-point chlorine plant have difficulty controlling it. The alkalinity has to be just right, chemicals have to be in exact relationship to each other. A mistake can produce a chemical excursion.

The greenhouse is not operator-intensive, but organism-intensive. With such a variety of species there are many biological pathways; some of them work on sunny days, some on cloudy, some when it’s hot, some when it’s cold--as in nature. The worst imaginable mistake might kill off some pathways, but it wouldn’t require an evacuation. Todd figures an acre of greenhouse would be needed for all the sewage of Sugarbush, and 120 acres for the city of Providence, R.I., where the Four Elements Corp. is planning a full-scale pilot plant. “That sounds like a lot of space, but it’s about the same as a traditional treatment system. And they’re not spaces you want to stay away from, like regular sewage plants. They’re beautiful, safe, productive.”

The greenhouses for Providence would not only treat sewage; they would house a business raising flowers, medicinal herbs and animals. The capital cost would be about one-third that of an equivalent sewage-treatment plant. Other solar-aquatic plants are being considered for Martha’s Vineyard and Santa Rosa, Calif. A simpler one, not glassed over and using only bacteria and water hyacinth to absorb nutrients, has operated in San Diego for years.

Most people involved in the tests are open-minded and interested in all the options. Everyone likes the solar-aquatic system, because it’s cheap and safe and pleasing. But it’s not a system you can set up or shut down quickly. It requires a kind of expertise not normal to civil engineers. It’s new and strange. The break-point system is expensive and hard to control, but it can go up quickly and it’s understandable to the world of sewage treatment.

The state of Vermont, its patience exhausted, recently told Sugarbush it had to comply by Nov. 1. Sugarbush thereupon decided to build a full-scale break-point chlorine system.

The story isn’t over yet. The town of Warren is not happy with all that chemistry and Sugarbush homeowners are balking at paying for the break-point system. The solar-aquatic plant will be tested for one more winter; even if it doesn’t remain at Sugarbush, the research will engender similar plants elsewhere.

Concrete block versus arched greenhouse. Pipes and chlorine tanks versus watercress and fish. The two systems are almost caricatures of each other and of engineering and ecological approaches to problem-solving. Those approaches are up against each other in every technical arena. Where shall we get our energy? The engineering answer is nuclear power, the ecological answer is solar power. How shall we dispose of garbage? Engineers: mass-burn incinerators. Ecologists: recycling. How shall we raise food? Engineers: agrochemicals and biotech. Ecologists: organic farming.

Maybe we have to make an ultimate choice between these mind-sets. Maybe we can and should embrace them both. Whatever the best choice is, we’re more likely to find it if we set up honest comparisons of real operations, side by side, tested fairly, like the tests at Sugarbush.