HR: 0800h
AN: B31A-0970    [Abstracts]
TI: A Continuous Flow Column Study of Anaerobic PCE Transformation With the Evanite Culture and Hanford Aquifer Solids
AU: * Semprini, L
EM: lewis.semprini@orst.edu
AF: Department Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: Behrens, S
B31A-0970 AF: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 United States
AU: Azizian, M
B31A-0970 AF: Department Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: Sabalowsky, A
B31A-0970 AF: Department Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: Dolan, M
B31A-0970 AF: Department Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: Ruiz-Hass, P
B31A-0970 AF: Department of Chemistry, Oregon State University, Corvallis, OR 97331 United States
AU: Ingle, J
B31A-0970 AF: Department of Chemistry, Oregon State University, Corvallis, OR 97331 United States
AU: Spormann, A
B31A-0970 AF: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 United States
AB: Anaerobic reductive dehalogenation of tetrachloroethene (PCE) and trichoroethene (TCE) is a promising technology for the in situ treatment of high concentration source zones in contaminated aquifers. Continuous flow column studies were performed where a mixed dehalogenating culture (Evanite culture) that contains Dehalococcides-like microorganisms was bioaugmented into aquifer solids from the Hanford DOE site. Studies conducted prior to bioaugmentation showed PCE transport was retarded due to sorption onto the aquifer solids. Upon bioaugmentation and with continuous lactate addition, PCE (10 mg/L) was transformed to cis-dichloroethene ( cis-DCE), and enhanced transformation of sorbed PCE was observed. Prolonged production of cis-DCE was associated with iron reducing conditions, while eventual vinyl chloride (VC) reduction to ethene was associated with sulfate reducing conditions. Microbial processes included lactate fermentation to acetate and propionate, iron reduction, sulfate reduction, and reductive dehalogenation, with reductive dehalogenation utilizing 2 to 3% of the electron donor addition. PCE was completely transformed to ethene within a hydraulic residence time of one day. Upon competition of the column tests spatial samples of aquifer solids were analyzed using molecular methods and solids were used in batch microcosm activity tests. Dehalococcoides sp. 16S rRNA gene copy numbers dropped from ~ 74% of total Eubacterial 16S rRNA genes in the original inoculum, to about 0.5 to 4% through out the column, consistent with the estimates of electron donor utilization for dehalogenation reactions. Microcosm tests showed most of PCE transformation activity at the entrance of the column, consistent with the Dehalococcoides sp. 16S rRNA gene copy numbers being highest in that area. Roughly 20% of the Dehalococcoides sp. population in the column possessed a vcrA gene for the respiration of VC to ethene. The vcrA-positive subpopulation decreases to about 5% towards the column outflow, while VC microcosm activity tests show fairly constant rates of VC transformation across the column. The column studies demonstrated that complete transformation of PCE to ethene can be obtained over short spatial and temporal scales.
DE: 1094 Instruments and techniques
DE: 1831 Groundwater quality
DE: 1895 Instruments and techniques: monitoring
DE: 4894 Instruments, sensors, and techniques
SC: Biogeosciences [B]
MN: Fall Meeting 2005