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Water Today Title October 21, 2020

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Update 2018/3/14
Persistent Organic Contaminants


This story is brought to you in part by Waterloo Biofilter Systems

By Cori Marshall

Perfluorooctane Sulfonate (PFOS), according to the Health Canada (HC) document Perfluorooctane Sulfonate (PFOS) in Drinking Water, is "a man-made compound that does not occur naturally in nature." Further "it is no longer manufactured, imported, sold, (or) offered for sale in Canada, but is still found in the environment because of its extremely persistent nature."

The compound was generally "used for water, oil and/or stain resistance on surface and paper-based applications." It also had a use in fire-fighting foams.

There has been no evaluation of the carcinogenicity of the compound, though "some cancer effects were observed in humans after exposure to PFOS, but no clear links could be made due to various study limitations." Studies that have had rats exposed to the substance for long periods of time, have observed tumours in the liver, thyroid, and mammary glands. The lowest level of exposure in animal testing had observed effects on the immune system as well as "changes in serum lipid levels."

There is no production or sale of PFOS in Canada, how are Canadians exposed?

The HC document explains that exposure can occur "through its presence in food, consumer products, dust, and drinking water." Exposure to PFOS through drinking water is the least likely though it "can increase in individuals living in areas with contaminated water." Typically, the compound makes its way into drinking water from the discharge from industrial facilities and wastewater treatment plants.

The maximum acceptable concentration (MAC) for PFOS in Canada is 0.0006 mg/L (0.6µg/L).

Once it is detected in drinking water how is it dealt with? HC said that "granulated activated carbon (GAC) can achieve treated water concentrations of PFOS below the proposed MAC."

We contacted Calgon Carbon, a manufacturer of products that can be used to treat the presence of PFOS in drinking water.

Leo Zappa, Director of Sales, Municipal Business Unit for Calgon Carbon, informed us that the company was "established in 1942, and is a global leader in the manufacture and distribution of innovative coal, wood, and coconut-based activated carbon products." He added that the company "provides purification solutions for more than 700 distinct applications including drinking water, wastewater, pollution abatement, and a variety of industrial and commercial manufacturing processes."

Calgon Carbon research "has discovered that bituminous-coal based GAC, manufactured via a process called 'reagglomeration', is highly effective for removal of FPOS and other PFAS compounds from drinking water," Zappa said.

"GAC works through a process called 'adsorption,' where the unwanted compounds adhere to the internal surface area of the activated carbon particles," Zappa explained. Further "a single gram of GAC has a surface area of about 1,000 metres square, allowing for the removal of a large number and variety of contaminants."

Zappa underlined that "testing and installations have repeatedly shown that this type of GAC removes PFOS to below the limit of detection of the compound (< 2µg/L)."

PFOS is a global contaminant, and Zappa informed WaterToday that "GAC is used all over the world." As for Calgon Carbon itself, it "has a presence in North and South America, Asia, and Europe (where it is known as Chemviron)," Zappa said.

Zappa said that "Calgon Carbon has installations all over the United States that are treating PFAS, with more than 45 large equipment installations and over 1,000 Point-of-Entry Treatment (POET) systems."

Currently, there are no Calgon Carbon installations in Canada that treat the compound. The company's carbon products are "complemented by world-class (...) ultraviolet (UV) light purification and disinfection systems and service capabilities as well as diatomaceous earth and perlites," Zappa said.


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