Efficient Treatment of Toxic Metal Contaminated Wet Scrubber Wastewater from Coal-Fired Power Plants

Data from EPA's Mercury Information Collection Request (ICR) reveals that soluble mercury (Hg) is captured in wet flue-gas-desulfurization (FGD) systems, such as those used in units burning bituminous coal. Furthermore, the use of selective catalytic reduction (SCR) for NOx control enhances the oxidation of Hg to the soluble ionic form, resulting in increased capture of Hg in the wet FGD system. Current state-of-the-art technologies for removing mercury from water are not cost-effective, as they produce large quantities of secondary waste or use expensive resins. This project will continue the development of a low-cost, nanoporous, inorganic-organic, hybrid-material-based sorbent (TFPAS) for the fast, efficient, and economic removal of mercury from wastewater. Preliminary laboratory column studies revealed a removal efficiency greater than 99.9% for Hg. In addition, the new sorbent removed more than 94% of the Se and As from surrogate FGD wastewater spiked with 267.3 ppb Hg, 7.22 ppm Se, and 251.1 ppb As throughout the tested period. Phase I will: (1) evaluate the the ability of the sorbent to remove of dissolved Hg, Se, and As from the surrogate and site FGD wastewater under dynamic flow conditions, using laboratory column experiments; (2) identify chemical and physical processes that may limit the long-term stability and reactivity of the sorbent in a treatment column; and (3) demonstrate the feasibility of regenerating the spent sorbent for reuse. Finally, laboratory column tests will be performed with FGD wastewater samples collected from coal-fired utility boilers equipped with both conventional wet FGD systems and forced-oxidized scrubber units. Commercial Applications and Other Benefits as described by the awardee: The novel nanoporus sorbent is expected to have a very high binding capacity for retaining large quantities of mercury ¿ which can be stripped off, allowing reuse of the sorbent. The overall waste management cost and waste disposal cost should be reduced.