A new advisory from the Manitoba government is cautioning the public about elevated levels of manganese in nearly a third of the province’s private residential wells.
The May-issued evaluation from Manitoba Conservation and Climate found that 56% of residential wells recently sampled above the 0.02 mg/L aesthetic objective for manganese, while 34% were above the new 0.12 mg/L manganese health standard.
Prior to 2019, the national guideline for manganese contained an aesthetic objective only, the province noted in its advisory.
Manganese, a naturally-occurring element, exists in Manitoba as a result of groundwater coming into contact with rocks or soils containing manganese. The element can stain laundry or plumbing fixtures, but can also be harmful for infant brain development when ingested through drinking water, which often appears dark in colour.
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“Private well owners are responsible for testing and, if necessary, treating their water to ensure it is safe to drink and for other domestic uses,” Manitoba officials stated in their advisory. “All wells should be tested to ensure there are no manganese concerns,” the document added.
Well water should be tested for manganese every three to five years in areas known to have elevated concentrations, according to provincial recommendations. The only way to know if well water contains manganese is to have a water sample tested by a laboratory accredited by the Standards Council of Canada or the Canadian Association for Laboratory Accreditation.
Manitoba officials said they obtained the well data from results of groundwater samples collected through regional groundwater quality surveys. Additionally, the government used its provincial observation well sampling program, as well as data collected through the regulation of public and semi-public water systems in Manitoba.
To treat well water, the province recommends that water treatment devices should be certified to meet applicable NSF International /American National Standards Institute standards.
“Although there are currently no treatment units certified specifically for manganese reduction, there are several treatment technologies that can be effective for manganese removal at the residential scale,” the Manitoba advisory noted.
Recommended treatment devices for manganese include greensand filters and ion exchange filters, but reverse osmosis (RO) membrane filters are not recommended for point-of-entry treatments as they have potential to clog.
A map of the distribution of manganese in groundwater samples is available from the Manitoba government website.