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ARSENIC RELEASE AND ATTENUATION PROCESSES IN A GROUNDWATER AQUIFER DURING ANAEROBIC REMEDIATION OF TCE WITH BIOSTIMULATION
Smith, S., R.R. Dupont, and J.E. McLean.
Groundwater Monitoring & Remediation 39(3):61-70(2019)
Lab tests were conducted to measure the amount of naturally occurring As released as a result of anthropogenic inputs of carbon used for TCE remediation. Large laboratory columns packed with TCE-contaminated aquifer solids from a site near Hill Air Force Base were fed with TCE-contaminated groundwater and biostimulated, bioaugmented, and monitored over 7.5 years. Columns were fed with either whey or 2 formulations of Newman Zone® emulsified oil, and a no-carbon addition control, to evaluate the biogeochemical changes that affect As solubilization. Columns were analyzed in 10.16-cm sections for pore water and sediment quality parameters. The whey treatment resulted in 52.9% of the total As in the solids leaching from the columns. The oil treatments promoted loss of 20.9% of the total As. Arsenic solubility was associated with strongly reducing conditions developed with whey addition, leading to the dissolution of crystalline Fe oxides and release of As. Arsenic was attenuated within the oil-treated columns and was associated with carbonates in the lower layers. A consequence of adding whey, resulting in the desired full dechlorination of TCE in this aquifer, is the mobilization of As in groundwater.
Groundwater Monitoring & Remediation 39(3):61-70(2019)
Lab tests were conducted to measure the amount of naturally occurring As released as a result of anthropogenic inputs of carbon used for TCE remediation. Large laboratory columns packed with TCE-contaminated aquifer solids from a site near Hill Air Force Base were fed with TCE-contaminated groundwater and biostimulated, bioaugmented, and monitored over 7.5 years. Columns were fed with either whey or 2 formulations of Newman Zone® emulsified oil, and a no-carbon addition control, to evaluate the biogeochemical changes that affect As solubilization. Columns were analyzed in 10.16-cm sections for pore water and sediment quality parameters. The whey treatment resulted in 52.9% of the total As in the solids leaching from the columns. The oil treatments promoted loss of 20.9% of the total As. Arsenic solubility was associated with strongly reducing conditions developed with whey addition, leading to the dissolution of crystalline Fe oxides and release of As. Arsenic was attenuated within the oil-treated columns and was associated with carbonates in the lower layers. A consequence of adding whey, resulting in the desired full dechlorination of TCE in this aquifer, is the mobilization of As in groundwater.
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