Increasingly, oil and gas companies in Alberta are receiving letters from the Alberta Energy Regulator (AER) to report on sulfolane use at their facilities and to investigate possible soil and/or groundwater impacts.
So, what is sulfolane and why it is now a contaminant of potential concern?
Sulfolane is an organosulfur compound that is highly soluble in water, with a reported solubility of 1,000 g/L
(Canadian Environmental Quality Guidelines). In its pure form, sulfolane is a clear, colourless liquid that is heavier than water. Sulfolane is a persistent contaminant in groundwater and is presumed not to breakdown easily in low oxygen/low nutrient
environments. Sulfolane moves with groundwater and because it is slightly heavier than water it will migrate downwards, often to bedrock. Many groundwater monitoring programs at sour gas plants are not designed to monitor effectively for contaminants that are denser than water. Sulfolane does not accumulate in the aquatic food chain, but is taken up by plants. Occupational exposure to sulfolane may be through vapour inhalation.
The most common uses of sulfolane are in aromatics extraction in the oil refining process, and in carbon dioxide (CO2) extraction in the natural gas sweetening process. Other uses include fractionalization of wood tars, insecticide production, pharmaceutical industry, as a curing agent in epoxy resins, and in the production of electronics and polymers.
Sulfolane has been widely released into the environment. It was historically under the radar because not all laboratories have the capabilities to analyze for sulfolane. A common problem with sulfolane detection is that remediation guidelines are often close to the laboratory detection limits.
Toxicity data and remediation guidelines are continually evolving. Internationally, Environment Canada is the most progressive regulatory authority in establishing environmental quality guidelines for sulfolane contaminated soil and groundwater. The United States Environmental Protection Agency (US EPA) issued a non-carcinogenic reference dose for sulfolane in 2012.
Below is a comparison of select recent soil and groundwater guidelines:
Based on recent studies, the Alberta Tier 1 groundwater guidelines will be lowered to 0.04 mg/L and soil guidelines will be adjusted accordingly.
Sulfolane does not volatilize from water or soil, nor does it readily adsorb to organic matter or soils. The primary attenuation mechanism appears to be biodegradation in an aerobic environment. There is a little information on viable approaches to remediation. Wide distribution and low cleanup levels add a level of complexity to practicable remediation. Treatability studies have demonstrated the most effective treatment options for groundwater sulfolane contamination are aeration and UV irradiation combined with chemical oxidation using hydrogen peroxide or sodium persulfate. Bio-treatment and in-situ chemical oxidation are commonly used methods for soil contamination remediation.
Understanding the nature of the technological challenges specific to sulfolane remediation is critical to managing its environmental liability. Ridgeline Canada Inc. has the expertise and capability to help you with sulfolane risk assessment, investigation, remediation, and reporting to regulators.