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Water Today Title November 25, 2017

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Virden MB, a tale of arsenic and new rules - 7/13/12

by Michel Ryan

The town of Virden in Southwest Manitoba has been under a water quality advisory since April 4th, 2012, due to levels of arsenic in the drinking water that exceed the Health Canada guidelines of 0.01 mg/L.

The town continues to face some water quality challenges despite making progress, and the advisory comes despite the town having invested approximately $1.8 million in water treatment facility upgrades in 2009, including two reverse-osmosis units. Yet, the town is in an area where naturally occurring levels of arsenic are exceptionally high, making this a particularly difficult and ongoing challenge for the town of Virden.

The irony of the situation here is that Virden has actually made dramatic improvements, but adjustments to the national guideline thresholds completely obscure those results. Situated in an area where arsenic naturally occurs in rocks and soil at exceptionally high levels, Virden has had to deal with arsenic in the water for a long time. As a result, according to the Town's Mayor Jeff McConnell, they have focused on adopting approaches that are "smart in the long-term and cost-effective".

Part of that strategy involved making Virden the site for a pilot project in 2004 that tested new means of removing arsenic from the water supply. According to a University of Waterloo civil engineering thesis on the experiments, those tests revealed that when a process call pre-oxidization is combined with either nano-membranes or reverse-osmosis processes, the capture of arsenic is dramatically improved. In some tests as much as 91% of arsenic was removed from the water.

While the town's staff will be getting back to the Water Chronicles with details on whether this pre-oxidization process is currently in use in Virden, a number of tangible results have been achieved according to Mayor McConnell.

Mayor McConnell told the Water Chronicles that since the upgrades in 2009, aesthetics of the water supply have improved dramatically, meaning that the water's colour, taste and smell are significantly better for residents. Additionally about 46% of arsenic parts per million have been removed from the water - that's going from 0.028 mg/L to 0.013 mg/L.

Had the national guidelines on arsenic levels remained where they were prior to 2006, this would have pushed Verdin well below the threshold for arsenic concentrations. But since Health Canada changed those guidelines to state that less than 0.010 mg/L is now acceptable, it seems as though the town's successes are being overshadowed.

As a point of comparison, the national guideline for Uranium is 0.020 mg/L - double the guideline for arsenic, and all guideline thresholds are based on lifetime exposure, meaning that the actual risks of developing complications due to drinking Virden's water are really quite low.

Mayor McConnell stressed that Virden works in close cooperation with the Office of Safe Drinking Water on these matters, "advising them on every step", and that despite the appearances generated by this latest advisory, "we are delivering safer water".

Related info
Health Canada Guidelines - Arsenic
Virden Advisory Notice
Town of Virden, MB
Treatment of Arsenic Contaminated Groundwater using Oxidation and Membrane Filtration - Kenneth Moore, U. Waterloo

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