Edmonton adding orthophosphate at water plants to stay under new federal lead limit


To meet new lead concentration guidelines from Health Canada, Edmonton has begun to add orthophosphate at its two water treatment plants to create a protective coating inside lead service lines and plumbing that delivers drinking water.

The region’s water utility, EPCOR, notes that about 4,450 Edmonton-area homes have lead water service lines. About 46% of these homes may have lead levels that exceed the new guideline, which reduced the maximum acceptable concentration for lead in drinking water from 10 micrograms per litre to 5.

The decision to add orthophosphate was made by Edmonton City Council in 2019, the same year Health Canada adjusted its lead concentration threshold. Orthophosphate is a colourless, odourless member of the phosphate family considered to be the industry standard for treating lead corrosion in municipalities all over the world and in Canada.

On its website, EPCOR states that “nothing has changed overnight with Edmonton drinking water — it continues to be safe to drink. Lead in drinking water at the levels we have found in Edmonton is not an acute or immediate health risk. However, left unaddressed, longer-term exposure to lead in drinking water above the new guideline can have adverse health effects.”

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The last federal update also shifted the point of compliance from the municipal drinking water system to the taps where the water is accessed by residents and businesses.

“Considering that lead levels at the consumer’s tap may be significantly higher than levels at the treatment plant or in the distribution system, strategies to reduce exposure to lead will need to focus on controlling corrosion within the distribution and plumbing systems and on removing lead-containing components, such as lead service lines, from these systems,” states Health Canada’s guideline technical document on lead in drinking water.

City of Edmonton officials said that more than 300 high-priority homes where lead levels were highest have already seen lead service lines replaced. Those properties were determined to be over 25 micrograms per litre.

EPCOR has previously replaced only the utility portion of a lead service line, leaving the private portion in place; however, the utility has now agreed to remove both portions going forward.

EPCOR supplies water for much of the Edmonton region. It said the lead inhibitor will help mitigate any lead in Edmonton’s pipes, service lines, in-home plumbing, and old solder and brass fixtures, which have the potential to exceed Health Canada’s proposed guideline.

The addition of orthophosphate to the water supply may require businesses that rely on Edmonton’s water for manufacturing, food processing, petrochemical production, as well as commercial heating and cooling, to make adjustments to their own water processes. For instance, orthophosphate may change the type and amount of precipitate that deposits on commercial heat exchangers and cooling towers.


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