PLAINFIELD, N.H. — 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.