Washing wastewater

Not all pollutants are waste products. Some can be recycled as… depollutants!

Catherine Mulligan, a professor at Concordia University and Director of the Concordia Institute for Water, Energy and Sustainable Systems, is currently developing a method for the treatment of wastewater that uses industry-produced CO₂.

Catherine Mulligan thought of capturing the CO₂ and injecting it into the wastewater.

Industries generally treat their wastewater through a process called "aerobic digestion" whereby oxygen is added to bacteria which then decompose the pollutants. This "cleaning" method is widely used and has been tried and tested. However, it produces a large volume of biological sludge which must then be decontaminated, a highly energy-intensive process.

As the same industries produce CO₂ – a greenhouse gas –, Catherine Mulligan thought of capturing the CO₂ and injecting it into the wastewater. In an anaerobic process, i.e. in the absence of oxygen, bacteria will consume the CO₂ and decontaminate the industrial effluent. In addition to reducing the level of harmful CO₂ in the atmosphere, the process creates a value-added product: methane, which could be used to power generators!

Together with her research partner, FPInnovations, Mulligan took wastewater samples from pulp and paper plants in Trois-Rivières and Matane to test her "cleaning" method in the laboratory. The results are promising: the method successfully breaks down the pollutants in the water while generating less biological sludge, removing the CO₂ dissolved in the water and producing useable biogas.

Mulligan hopes to soon begin testing her concept on a large scale, with the goal of creating a "highly sustainable" method for the treatment of wastewater and air.