Naturally Wallace
             

Selenium Removal Wetland (Central Alberta, Canada)

Shell Projects and Technology wanted to explore the potential application of constructed wetlands for selenium removal in central Alberta. An assessment of wetland treatment technology for selenium removal at Shell’s Scotford upgrade facility was completed. Three principal selenium removal mechanisms were investigated: 1) Selenium volatilization. 2) Uptake of selenium into plant tissues and subsequent storage into accumulated sediments. 3) Chemical reduction of selenate or selenite to insoluble forms (elemental selenium or selenide).

The findings, based on available information, indicated that a treatment wetland at Scotford could remove a high percent of the projected annual selenium load and be a treatment alternative that would diversify Shell’s effluent management to enhance environmental compliance and reduce operating costs.

In order to quantitatively understand the nature of selenium dynamics at Scotford, the next phase of the project is to engage in a program of pilot testing to understand the importance, magnitude, and seasonality of the three major selenium removal mechanisms.



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