Now you can love -- and drink -- that once-dirty water

A view of the Charles River from Cambridge.David L. Ryan/Globe Staff

Nearly 300 people took a dip in the Charles River last week, a feat once considered harmful to your health. And last year, Harpoon actually made beer with water from the river.

Now for the latest challenge: Brew the Charles.

Six Massachusetts breweries will compete to brew the best beer at HUBweek this September using, you guessed it, our beloved once-dirty water.

Newton-based global water purification company, Desalitech, treated the water for Harpoon Brewery’s Charles River Pale Ale for last year’s HUBweek and will also be treating the water for this year’s competition.

The company will withdraw a limited amount of water from the Charles in early August, treat it, and deliver the potable water to the local breweries.

Desalitech’s purification system uses technology that combines simple filtration with traditional reverse osmosis. In a traditional reverse osmosis system, only a portion of the water is treated as it passes through membranes -- fine filters with very small holes -- and a lot is wasted.

With this system, the water is passed through the system repeatedly until all of it is clean.

Nadav Efraty, the chief executive of Desalitech, said the beer contest was a novel way to raise awareness of a limited resource and new technology.

“We think this competition is a very good opportunity to show the public what modern water technology can do, even turning it into something fun, like good beer,” Efraty said.

HUBweek is a creativity and innovation festival, a collaboration among The Boston Globe, Harvard, MIT, and Massachusetts General Hospital.

The breweries competing include Cape Ann Brewing Company from Gloucester, Castle Island Brewing Company from Norwood, Harpoon Brewery from Boston, Idle Hands Craft Ales from Malden, Ipswich Ale Brewery from Ipswich, and Samuel Adams from Boston.

The only rule is to use the now-clean Charles River water. There will be two awards, one from the public, which can vote for its favorite beer, and the second from a panel of experts that will decide the champion on Sept. 30.

Efraty said the water from the Charles is relatively easy to treat. As for the Harpoon beer from last year?

“It tasted... just like beer,” he said.

Tickets cost $25. A portion of proceeds from ticket sales will go to the Charles River Conservancy’s Swimmable Charles program.