Chemical-free super-oxygenated water that is affordable and sustainable … it sounds like a health or sports drink marketing dream. But this isn’t bottled for human consumption. Instead, super-oxygenated water is a bioremediation solution to clean up contaminated groundwater and impacted soil, and it comes with its own set of compelling selling points.
Super-oxygenated water (SOW) has significant advantages over other methods that have been used for groundwater remediation at sites contaminated with petroleum hydrocarbons – such as former fuel storage facilities. For industries such as oil, gas and transport, this offers a cost-effective, natural approach to clean up hydrocarbon contamination in groundwater aquifers and reduce risks to human health and the environment.
Originally developed by a remediation team in Montreal at Golder Associates, which is now integrated with WSP as one company, the SOW approach has been used by Golder since 2004 in Canada, and more recently has been further enhanced and used successfully for projects in Australia, the United States, South America and Europe.
Building on the successes with remediating hydrocarbons in the oil and gas sector, SOW is now being applied to other contaminants and is being embraced by other sectors. It offers a solution for each sector in which the residual presence of petroleum hydrocarbons presents challenges (such as manufacturing, mining and government).
What Is SOW and How Does It Work in Bioremediation?
When described in technical terms, the process may sound complex – but, really, it’s a simple, elegant enhancement to a natural environmental process. No added ingredients, just oxygen and nutrients. No nasties, just enhancing naturally occurring microbes.
Bioremediation is a proven approach by which oxygen stimulates microorganisms to break down organic contaminants into simple, safe end products. However, in an area of contaminated groundwater (a petroleum hydrocarbon plume), the geochemistry of the groundwater is mostly without oxygen (anaerobic) because the available oxygen has been consumed by microbes in the process of metabolizing the undesirable organic compounds into carbon dioxide, methane, water, inorganic salts and cell matter – a process known as biodegradation.
To enhance biodegradation and speed up the metabolism of organic compounds, more oxygen is needed. SOW is injected into the groundwater aquifer via injection wells, creating a zone of high concentrations of dissolved oxygen – giving the bugs more oomph to do their thing.
High-purity oxygen is dissolved into potable water or extracted groundwater within either a pressurized aeration tower or pressurized chamber (venturi process). Both methods are very effective, as more than 90 percent of the oxygen injected (as SOW) is transferred into the groundwater aquifer. The method can produce oxygen concentrations of up to 40–50 mg/L, which is five to six times the natural dissolved oxygen concentration of groundwater.
Is it too good to be true? Not at all – but as with any technology, SOW does have some limitations. For example, SOW may be of limited use in low-permeability or shallow aquifers, so a good conceptual site model is required to understand these limitations and uncertainties.