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A Place in Maine Where Desalinated Water is Nothing New
by Stephen Hochbrunn, NEIWPCC
In researching the desalination article for IWR, I occasionally encountered newspaper reports that mentioned a place in Maine, MacMahan Island, as the site of New England’s only drinking water desalination plant. But details were lacking. Where was this place? And what were they doing there?
After a dozen phone calls, I got the man with the answers on the other end of the line. Peter Schuerch, MacMahan Island’s superintendent, said yes, they were desalinating seawater and happily drinking it, and yes, he’d show me around if I was interested. I imagine he’d made the same offer to other curious callers, who never made the trip. I took him up on it.
Located about 14 miles from the city of Bath, in a cluster of islands just off Maine’s southern coast, MacMahan Island was easy to get to—until the final segment of the trip. A half-mile of water separates the island from the nearest road, so I hitched a ride on a boat piloted by an island resident who’d gone for groceries. MacMahan Island is a seasonal community, and there are no stores there. No cars either. Schuerch, a big man with a humble manner, met me at the landing in a golf cart, and we drove up to the desalination plant.
Actually, the word “plant” implies a place considerably bigger and less rustic than what exists on MacMahan Island. Inside a small, cramped wooden building are two Matrix reverse osmosis desalination units, each capable of producing 4,000 gallons of fresh water a day. But on the island, they don’t need that much, so Schuerch limits the units’ operation to about eight hours a day, generating roughly 1,800 gallons between the two of them. Seawater is pumped up to the plant via a pipeline that begins with an intake in the waters right next to a boat dock. At the plant, the water passes through a filtration system that screens out sediment, seaweed, and anything else pulled up the pipe. The filtered but still salty water is then forced through the RO membranes. There’s no disinfection done, no chemical pretreatment. Schuerch said it’s not necessary.
“We’re required by the state to test the water once a month, and we’ve never had a problem,” he said. “The water in the desal units is under about 900 pounds of pressure per square inch, and any impurities are removed. It’s almost like kidney dialysis, but on a bigger scale.”
Until it’s needed, the water is stored in large tanks next to the desalination building. When water usage creates a demand, the desalinated product is blended with fresh water pulled up by the island’s two wells, and that blend is piped out to the island’s approximately 40 homes. The well water alone used to be enough, but Schuerch said that was before the state decided in 1998 to put a stop to the island’s practice of flushing toilets with salt water and discharging the wastewater at sea. The state’s decision created the need for septic systems on the island—and more fresh water.
“We could have dug more wells, but that would have meant digging about 320 feet through ledge,” Schuerch said. He began exploring the option of desalination, and the more he looked, the better it sounded. In 1999, he bought the first of the Matrix units for about $24,000. He oversaw the building of the plant and pipeline, and the installation of the pumps. It was, he said, a lot of work, but with the dry summer that year, the system proved its worth immediately.
“The wells on these islands ran dry,” he said, “and we were the only ones with fresh water. That was a good thing.”
You might expect that islands in any ocean, faced with limited means of getting fresh water, would be ideal locations for desalination systems, and in fact many communities in the Caribbean adopted desalination years ago. But along the island-studded Maine coast, Schuerch stands alone in his embrace of the technology. Desalination has made water more expensive on MacMahan Island; the rate rose from 30 cents to 50 cents a cubic foot when the RO system went online. But nobody was complaining on the day I visited. One woman said residents marvel at what Schuerch has done, at how good a teacher he is to the young men who help maintain the desalination plant. Another resident, Lucy Melvin, invited me into her home to test the water for myself. She had told me it tasted “perfectly fine,” and she was right.
In September, two months after my visit, Schuerch and his small maintenance crew performed one final cleaning of the desalination system’s filters and membranes, treated them with chemicals designed to limit bacterial growth, added antifreeze to the equipment, and then shut the system down for the season. Most residents had already left the island and returned to their mainland homes for school and work and everyday life. In July, they will return for another summer on their cherished island in Maine. Schuerch and his water will be waiting.