Long impractical and prohibitively expensive, desalting seawater has become cheaper as technology has improved in the past decade. The only drinking-water desalination plant built in New England so far has been a tiny one on Maine’s MacMahan Island, but as growing communities scramble for fresh water, desalination has begun to look more attractive.

Construction of a $40 million plant to purify salt water and deliver it to the city of Brockton could start as early as September. Hull residents will be asked this month for $280,000 to determine whether a desalting plant would lower the town’s soaring water rates, and Braintree has set aside $75,000 for a similar study this year. Seabrook, N.H., and several North Shore communities and groups also are interested in desalination plants.

“We are out of water; we are looking east,” said Robert Marquis, water superintendent for the town of Swansea, which recently notified the state that it wants to build a $16 million plant to desalinate water from the tidal Palmer River. “When there is a drought, you still have the ocean.”

More here.