City working on ways to trim THM levels in drinking water

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This article was published 17/10/2012 (4999 days ago), so information in it may no longer be current.

Brandon’s water supply may have a higher than legal limit of trihalomethanes but it remains safe to drink, says Patrick Pulak, the city’s deputy director of engineering services and water resources.

“The standard that is in place for THMs (trihalomethanes) is a standard that minimizes health risks over a lifetime of 70 years,” Pulak said Monday evening. “We are just over that standard. It’s something we are working at bringing under the standard.”

A higher level of trihalomethanes was detected in the city’s water supply over three tests during the quarter, but Pulak said that was normal in most communities in Manitoba where surface water is used for drinking water.

“Seventy eight per cent of all water treatment plants in Manitoba that use a water body as a source for its water are not in compliance with the THM standard.”

Pulak had presented a mandatory quarterly report on the state of the city’s drinking water supply during Monday’s meeting. It stated that while water leaving the city’s water plant averaged 0.088 mg/L of THMs, below the legal limit of 0.1 mg/L of THMs, higher levels were detected at sample points elsewhere in the city.

One solution to lower THMs in drinking water has been to blend the surface source water with well water from a nearby aquifer, which dilutes the THMs to a more acceptable standard.

Similar results occur with drinking water tests from other communities along the Assiniboine River. In 2010, St. Lazare failed the turbidity and protozoa standard tests and posted a 0.120 mg/L level of THMs.

Elsewhere in Westman, Rapid City recorded a 0.203 mg/L level for THMs in 2010, while in Kenton, the THMs level was 0.204 mg/L in the same year. Pilot Mound’s drinking water contained 0.339 mg/L of THMs.

Winnipeg’s water supply, which originates from Ontario, was in compliance with the water regulations.

“The issue is organics in the water,” Pulak said. “The problem is it’s not something we can do year-round. Money is always an issue with any utility, and when you are trying to do improvements of this scale, it comes down to money. With the water treatment plant, we are developing a master plan to look at what things we need to do in the future to upgrade the facility and prioritize those improvements.”

Pulak said finding another groundwater source could also help, as the aquifer used to feed the existing wells does not have enough water supply over the course of the year to be the city’s primary water source on its own.

“This is not an operational issue, or an infrastructure issue,” Pulak said. “It’s just the type of water we use as a source.”

Pulak said he didn’t know how much it would cost to ultimately fix the problem because he didn’t know what can fix the problem permanently.

“We can dilute the water, but we don’t have enough of the water that can be a solution,” Pulak said. “Are there other sources of water we can go to? We don’t know that yet.”

» kborkowsky@brandonsun.com