Degree Granting Department
Civil and Environmental Engineering
Sarina J. Ergas
bioremediation, calcium polysulfide, community-level physiological profiling, remedial amendment, Shewanella oneidensis MR-1, surfactant
The chemical and physical processes controlling contaminant fate and transport in the vadose zone limit the options for application of many remedial technologies. Foam delivery technology (FDT) has been developed as a potential solution to overcome these limitations for remediating subsurface and deep vadose zone environments using reactive amendments. Although there are many advantages to utilizing FDT for treatment in the deep vadose zone, little information is available on how the addition of these surfactants and remedial amendments affect the indigenous microbial communities in the deep vadose zone as well as the impact of biological transformations of surfactant-based foams on remediation efforts. The purpose of this study was to develop a rapid method for assessment of microbial communities in contaminated subsurface environments. This research was divided into two phases: (1) assess the toxicity of proposed FDT components on a single bacterial species, Shewanella oneidensis MR-1; and (2) determine the effects of these components on a microbial community from the vadose zone.
In Phase I, S. oneidensis MR-1 was exposed to proposed FDT components to assess potential growth inhibition or stimulation caused by these chemicals. S. oneidensis MR-1 cultures were exposed to the surfactants sodium laureth sulfate (SLES), sodium dodecyl sulfate (SDS), cocamidopropyl betaine (CAPB), and NINOL 40-CO, and the remedial amendment, calcium polysulfide (CPS). Results from this phase revealed that the relative acute toxicity order for these compounds was SDS>>CPS>>NINOL40-CO>SLES≥CAPB. High concentrations of SDS were toxic to the growth of S. oneidensis MR-1 but low concentrations were stimulatory. This benchtop system provided a capability to assess adverse microbial-remediation responses and contributed to the development of in situ remedial chemistries before they are deployed in the field.
For Phase II, sediments from the BC Cribs and Trenches (BCCT) area of the Hanford Site, WA, were characterized before and after exposure to potential FDT components. First, the phylogenetic and metabolic diversity of sediment from the BCCT was assessed by sequencing the microbial community and measuring the metabolic activity. The sediment was also incubated with various concentrations of SDS, CAPB, and CPS. Phylogenetic analysis detected phylotypes from the Alpha-, Beta-, Delta-, and Gammaproteobacteria, and Actinobacteria. Unlike the S. oneidensis MR-1 studies conducted in Phase I, the surfactants and CPS stimulated the metabolic activity of the native microbial communities. The observed stimulation could be caused by sorption of the chemicals to the sediment particles, or utilization of the surfactants by the microbial communities. These findings emphasize the importance of monitoring microbial activity at remediation sites in order to determine short and long term efficacy of the treatment, compliance with regulatory mandates, and act as an early warning indicator of unintended changes to the subsurface.
Scholar Commons Citation
Bailey, Kathryn Lafaye, "Assessing the Microbial Consequences of Remediation: Surrogate Microbial Screening and Native Metabolic Signatures in Tc(VII) Contaminated Sediments" (2012). Graduate Theses and Dissertations.