Meeting Part-per-Trillion Mercury Limits for Power Plant Wastewater

摘要

This paper reviews options available to power plants to comply with low part per trillionmercury limits on wastewater discharge. Such limits are being driven by both waterquality-based effluent limits (especially in the Great Lakes region), as well astechnology-based limits (proposed Effluent Limitation Guidelines for the industry).These limits pose a challenge to most commercially available treatment technologies.This paper documents results of full-scale testing of treatment technologies to removemercury to low part per trillion levels from flue gas desulfurization (FGD) wastewater.This paper also describes lessons learned from case studies of plants that havereported improved mercury removal over time through treatment plant optimization. Thisincludes a discussion of the mercury-removal levels achieved, factors that affectmercury removal, and design and operations issues and lessons learned in optimizingtreatment for mercury removal. Technologies evaluated include physical/chemicaltreatment including organosulfide addition and anaerobic biological treatment. Theeffect of mercury particle size on removal is evaluated. This provides insights onwhether removal performance is due to mercury solubility or the ability to removeparticulate mercury (either mercury in particulate matter that is formed in the FGDabsorber or precipitated in treatment).