ENV-09-23 A Coordinated Approach to Achieving NPDES Permit Compliance

Description:

To implement water quality standards, parts-per-billion (ppb) and parts-per-trillion (ppt) limits were established for selenium and mercury, respectively, at the Suncor Energy Commerce City, Colorado, refinery. As water quality based limits became law in the 1990s, the refinery initiated a broad, coordinated approach that capitalized on stakeholder engagement, dialogue, and cooperation with regulatory agencies, while using technical evaluations to assess future limits, applicable technologies, and compliance options. The most significant effort began in year 2000, when the refinery and several neighboring dischargers in Colorado‘s Sand Creek watershed launched a multi-year effort to review potential impacts of the new standard and develop rational selenium stream standards. In parallel to these watershed-based activities, the refinery commenced several iterations of sampling and evaluation to identify sources and forms of selenium and mercury in refinery wastewater. As a result, the Suncor refinery discovered that selenium is concentrated in the sour water stripper bottoms—suggesting intermediate stream treatment. However, mercury was found to be ubiquitous in refinery wastewater streams—indicating end-of-pipe treatment. Because selenium levels have been regulated for years, over a dozen technologies for selenium removal have been evaluated through bench- or pilot-scale studies. However, since mercury has only recently claimed regulatory attention, it has been evaluated only over the last three years, focusing primarily on filtration and membrane investigations. As expected, there are no easy solutions. Both significant capital costs and the creation of residual streams requiring disposal present formidable challenges. Suncor continues to engage the State and the U.S. Environmental Protection Agency (EPA) in discussions of the appropriateness of water quality standards for selenium and mercury as well as the current limitations of technology. The most recent consideration— sustainability—focuses on the net environmental benefit tempered by energy use, carbon footprint, and other negative societal effects. By continuing to conduct regulatory discussions in parallel with evaluation of treatment alternatives—in alignment with sustainability goals, Suncor anticipates ultimately achieving cost-effective, sustainable solutions that comply with environmental regulations.