Story highlights After the water is purified, the Charles River is a source for six local breweries

As recently as 1996, the river's raw sewage was severe enough that it failed state swimming standards

(CNN) Would you drink a beer originating in what used to be one of the most polluted rivers in the country?

In early August, Newton, Massachusetts-based water technology company Desalitech withdrew 4,000 gallons from Boston's Charles River. After purification, the water was delivered to six local breweries for a beer-making competition.

"The Charles River is one of the biggest icons of Boston. Being able to drink it is really tapping in one of the biggest symbols of the town," said Nadav Efraty, Desalitech's CEO. "Our company has reinvented the purification and reuse process in a way that enables us to almost completely eliminate the waste of water."

The company upgraded a traditional process called reverse osmosis to treat the water and clean it for reuse. Reverse osmosis uses special membranes to block salts and contaminants, producing purified water and a stream of concentrated pollutants.

Reverse osmosis systems typically operate around 75% water efficiency, wasting about 25 gallons for every 75 gallons of purified water, according to Efraty. For the Brew the Charles project, he said, there was 98% efficiency.

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