Laurie LaPat-Polasko, PhD, QEP
Vice President, National Director of Remediation
Matrix New World Engineering
Dr. Laurie LaPat-Polasko is the National Director of Remediation for Matrix New World. She has more than 25 years of experience in groundwater and soil remediation and wastewater treatment. She combines her knowledge of microbiology with a background in civil engineering to develop cost-effective remediation solutions for sites impacted by organic and inorganic compounds. Laurie has managed numerous remedial investigations and feasibility studies for complex issues associated with surface water, groundwater and discharges from sewer systems. She has dealt with contaminants ranging from fluoride and arsenic to chlorinated solvents, 1,4-dioxane, explosives and fuel compounds. Laurie has been actively involved in numerous Superfund sites. She has taught graduate courses in water and soil remediation at Arizona State University. She has extensive experience working with USEPA and various county and city regulatory agencies across the US.
1,4-Dioxane: Biological Treatment
Evaluating In Situ Biodegradation of 1,4-Dioxane via Bioaugmentation with Pseudonocardia dioxanivorans CB1190
1,4-Dioxane (dioxane) is an emerging contaminant frequently detected at chlorinated solvent sites due to its use as a stabilizer. Although dioxane was once considered a recalcitrant compound, several microorganisms have been isolated that are capable of utilizing dioxane as a growth supporting substrate. In the current study, compound specific isotope analysis (CSIA) and quantitative polymerase chain reaction (qPCR) were performed to assess dioxane biodegradation at a TCE impacted site under native and enhanced bioremediation in the source zone.
At the study site, a shallow unconfined aquifer is impacted by PCE, TCE, 1,1,1-TCA, 1,1-DCE and the co-contaminant dioxane. Groundwater samples were periodically obtained for 2D-CSIA to quantify carbon (ï¤13C) and hydrogen (ï¤2H) isotope fractionation and evaluate dioxane degradation. An aerobic dioxane utilizing bacteria, Pseudonocardia dioxanivorans CB1190 (CB1190), uses dioxane monooxygenase (DXMO) to mediate the first step in dioxane metabolism while an aldehyde dehydrogenase enzyme (ALDH) catalyzes continued biodegradation of glycoaldehyde. qPCR assays targeting the DXMO and ALDH genes were periodically performed to evaluate the potential for metabolic biodegradation of dioxane. Based in part on qPCR results under initial site conditions, an in situ microcosm study was conducted to evaluate the feasibility of bioaugmentation with CB1190. The groundwater was monitored for hydrogeochemical properties to establish native conditions, which would impact biodegradation of dioxane.
Initial groundwater redox conditions were mildly anaerobic with evidence of reductive dechlorination of PCE and TCE to cis-DCE but limited production of vinyl chloride and ethene. Concentrations of the co-contaminant dioxane were approximately 3 to 5 mg/L in the source area and decreased to approximately 2 mg/L at a downgradient location. Consistent with the generally reducing conditions however, DXMO and ALDH genes were not detected in groundwater samples. Furthermore, dioxane ï¤13C (-31.1 to -30.6â€°) and ï¤2H (-51 to -47â€°) values did not provide evidence of dioxane degradation within the source area under the initial site conditions. To investigate the feasibility of bioaugmentation to promote dioxane biodegradation, Bio-Trap samplers were inoculated with the P. dioxanivorans CB1190 culture and deployed in source area monitoring wells with and without an oxygen source. Post-deployment DXMO (104 gene copies/bead) concentrations were comparable to pre-deployment concentrations demonstrating in situ survival of the CB1190 culture despite somewhat unfavorable redox conditions and suggesting bioaugmentation was feasible. This presentation will discuss the natural attenuation Bio-Trap in comparison to the Bio-Traps amended with CB1190 plus and minus an oxygen source and nutrients. In addition to the CSIA results, the key target genes associated with dioxane biodegradation and site geochemical data will be discussed.