The British Columbia town of Osoyoos has been adding chlorine to several of its water supply wells to dissolve manganese ahead of concerns that Health Canada may revise acceptable levels for the mineral in drinking water later this year.
While low levels of manganese have few known effects on human health, at concentrations exceeding 0.15 mg/L, the mineral stains plumbing fixtures and laundry and causes undesirable tastes in water.
Adding chlorine to the water forms a solid and produces cloudy water that resembles tea.
Osoyoos officials said they were advised that a new federal maximum allowable concentration for manganese could be .12 parts per million. The town’s current affected wells sit at about .135 parts per million.
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“It’s always been an issue here and we’re working towards it,” Steve Underwood with True Consulting Ltd. told the Town’s Committee of the Whole. “It’s going to be a problem to comply.”
A True Consulting Ltd. report to presented to the Committee of the Whole meeting on February 19. said the town’s manganese particles settle in reservoirs and coat the walls of the distribution piping, creating an environment for bacterial growth that gets stirred up when the system is drained or flushed.
In a memo to municipal officials from Osoyoos director of Operational Services, Jim Dinwoodie, it was noted that the elevated levels of manganese in the water supply make it necessary to remove the manganese prior to treatment with chlorine.
In 2014, Osoyoos piloted a new manganese removal technology at two of its six approved wells, which did successfully eliminate manganese from the water sampled.
True Consulting Ltd. suggested options for the development of a water treatment program for Osoyoos. They involve treating certain wells at a centralized treatment facility ($12 million) or converting the water supply to surface water obtained directly from Osoyoos Lake ($24 million).
“Your chances for a grant will be really high with this expected change in regulation,” Underwood told the committee.
The report also states that B.C.’s Interior Health Authority has concerns about the town’s number of positive coliform tests, which have also prompted Osoyoos Public Works to flush the system and treat with chlorine.
“The Town of Osoyoos will be exploring various water treatment options during upcoming Capital Budget discussions to ensure our water system remains and continues to be compliant with the Canadian Drinking Water Protection Act,” officials wrote in a recent public notice.
