Geochemical investigations of metals release from submerged coal fly ash using extended elutriate tests

Abstract

a b s t r a c tA storage pond dike failure occurred at the Tennessee Valley Authority Kingston Fossil Plant that resulted in the release of over 3.8 million cubic meters (5 million cubic yards) of fly ash. Approximately half of this material deposited in the main channel of the Emory River, 3.5 km upstream of the confluence of the Emory and Clinch Rivers, Tennessee, USA. Remediation efforts to date have focused on targeted removal of material from the channel through hydraulic dredging, as well as mechanical excavation in some areas. The agitation of the submerged fly ash during hydraulic dredging introduces river water into the fly ash material, which could alter the redox state of metals present in the fly ash and thereby change their sorption and mobility properties. A series of extended elutriate tests were used to determine the concentration and speciation of metals released from fly ash. Results indicated that arsenic and selenium species released from the fly ash materials during elutriate preparation were redox stable over the course of 10 d, with dissolved arsenic being present as arsenate, and dissolved selenium being present as selenite. Concentrations of certain metals, such as arsenic, selenium, vanadium, and barium, increased in the elutriate waters over the 10 d study, whereas manganese concentrations decreased, likely due to oxidation and precipitation reactions.Published by Elsevier Ltd.

Impact assessment of dredging to remove coal fly ash at the Tennessee Valley Authority Kingston Fossil plant using fathead minnow elutriate exposures

“…These dredges pumped the ash from the river bottom through a pipeline into an ash recovery ditch, where the heavier ash particles that settled rapidly were removed by a mechanical excavator for disposal. The remaining water and suspended ash flowed into a sluice channel and mixed with plant process water, then flowed into an ash settling pond that overflowed into a stilling pond for final effluent polishing, and finally was discharged back to the Emory River [2].…”

Bioaccumulation of metals in three freshwater mussel species exposed in situ during and after dredging at a coal ash spill site (Tennessee Valley Authority Kingston Fossil Plant)

“…As long as residual ash exists in the Emory River (or downstream), the potential for changes in metal binding and/or changes in speciation leading to differing leaching dynamics exists. Previous work, including studies focused on the Kingston spill site, have shown that river conditions play a major role influencing the bioaccumulation of metals known to be present in coal ash (Ruhl et al 2010;Bednar et al 2010;Ruhl et al 2009;Deonarine et al 2013;Liu et al 2013). Therefore, it is recommended that a holistic long-term monitoring plan be utilized to fully understand the longterm impacts of this spill and minimize risk.…”

“…However, the removal of contaminated sediments also comes with significant challenges, including the re-suspension of potential contaminants, measuring effects, and potential changes in metal speciation (Bednar et al 2010;Rowe et al 2002;Gustavson et al 2008). Given the volume of the ash spilled (4.1 million m 3 ), the volume of contaminated sediments dredged (more than 2.6 million m 3 ), and the fluctuations in Emory River discharge during dredging (50-70,000 cfs), issues related to the physical disruption of ashassociated sediments were a concern at the Kingston Fossil spill site.…”

“…As unfortunate as the spill was, it provided an opportunity to directly study the impact of coal fly ash in a large lotic system where the amount of downstream transport of ash was also being investigated and monitored (TVA 2010b). Previous research on the Kingston spill has provided insight on the contaminants of concern from multiple perspectives including sediment biogeochemistry, metal speciation, and metal bioaccumulation across multiple organisms (Ruhl et al 2010;Bednar et al 2010;Ruhl et al 2009;Otter et al 2013;Deonarine et al 2013;Bartov et al 2012;Liu et al 2013;Beck et al 2013;Souza et al 2013). Otter et al (2012) showed elevated concentrations of arsenic and selenium in various tissues of multiple fish species at ash-associated sites compared to reference sites.…”

“…The release impacted terrestrial areas, the adjacent Emory River, and downstream river locations due to ash transport in the river channel (TVA 2009;Bednar et al 2010).…”