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Current Projects

Evaluation of Partitioning Electron Donors for Enhanced Bioremediation of Chlorinated Solvent Source Zones
Sponsor: National Science Foundation, Division of Earth Sciences: Hydrologic Sciences Program
Researchers: Natalie L. Cápiro (PI) and Kurt D. Pennell (co-PI)
Project ID: 1215837

Overall Project Objective:
Evaluate partitioning electron donors (PEDs) to enhance in-situ bioremediation of dense non-aqueous phase liquids (DNAPLs) trichloroethene (TCE) and tetrachloroethene (PCE).

Project Goals:

  • Determine if PEDs will have longer lifetimes in DNAPL source zones than currently used soluble electron donors.
  • Determine if PEDs will contribute to biologically enhanced dissolution (increased rate of dissolution due to microorganisms).

Abiotic batches set-up in glass vials
containing aqueous PED and NAPL.

Biotic batches set-up with varying
NAPL and PED concentrations.

Task 1: PED Screening and Identification

Objective: Identify possible PED candidates, measure their mass transfer rates, and determine if PEDs will support reductive dechlorination.
Approach: Three PED candidates were chosen; n-butyl acetate (nBA), isopropyl propionate (IPP) and 2-ethyl-1-hexanol (2E1H). A series of abiotic batches were performed to determine both the equilibrium NAPL-water partitioning coefficient (Knw) and NAPL-water effective rate of mass transfer (k). A series of biotic batches are in progress to determine if PED candidates will be used as electron donors in bioremediation.
Preliminary results: All PED candidates partition readily into the NAPL phase. Commercially available PCE/TCE to ethene dechlorinating consortium is able to degrade nBA for use as an electron donor.
Significance: PED candidates partition into the DNAPL phase and can provide a source of electron donor.


Task 2: PED Mass Transfer Utilization in Dynamic Systems

Sand packed column injected with NAPL
(dyed red).

Sand packed biotic column with emplaced
NAPL (dyed red of the left end) and 11
side ports used for sampling.

Objective: Measure PED partitioning under dynamic flow conditions.
Approach: Columns packed with Federal Fine Ottawa sand or Appling soil and imbibed with residual NAPL. Abiotic columns were used to determine the PED lifetime in the NAPL. Results were modeled and equilibrium partitioning coefficient, effective mass transfer and retardation factor were determined. Biotic columns will be used to evaluate the PED partitioning and utilization when microbes are present.
Preliminary results: A single PED injection could last up to 20 times the injected pore volumes in PCE and 100 times in TCE.
Significance: PED delivery could reduce the need for frequent or repeated electron donor injections, thereby improving the effectiveness of bioremediation at chlorinated solvent sites

Task 3: PED Evaluation in Heterogeneous Flow Conditions

2-D aquifer cell used to evaluate PED
delivery under heterogeneous flow
conditions and source zone architectures.

Objective: Evaluate PED technology to treat DNAPL source zones under heterogeneous flow conditions.
Approach: A 2-D aquifer cell will be packed with 40-50 or 20-30 mesh Ottawa sand with layers of lower permeability sand (100-140 mesh) to create a heterogeneous flow field. Microbes will be introduced through selected side ports and the spatial and temporal changes in local reductive dechlorination activity, substrate delivery and consumption, and aqueous geochemistry will be characterized via the analysis of side ports and effluent samples.
Significance: Results from this experiment will determine if PED delivery at the DNAPL:water interface will promote microbial colonization within ganglia and pooled DNAPL regions.

Task 4: Development and Evaluation of Mathematical Models to Describe PED Deliver and Utilization for Microbial Reductive Dechlorination

Objective: Mechanistically interpret experimental studies, and provide a means to predict and compare the performance of PEDs as a function of system parameters.
Approach: Mathematical models using a modified dual Michaelis-Menten model will be used to describe reaction kinetics of biotic batches. Code for Estimating Non-Equilibrium Transport Parameters from Miscible Displacement Experiments (CFITIM) as a part of Studio of Analytical Models (STANMOD) will be used to stimulate measured PED and nonreactive tracer effluent breakthrough curves from the abiotic columns. Biotic columns and aquifer cells will be simulated using MISER, a two-dimensional, finite element immiscible multiphase, multi-component simulator.
Significance: Models will be scaled to stimulate field-scale scenarios that may be able to predict the performance of PEDs at real world contaminated sites.

Awards, Presentations and Publications:

  • Sylvia, D. F., R. D. Meade, K. D. Pennell, N. L. Cápiro. "Partitioning Electron Donor Delivery for Chlorinated Solvent Bioremediation" UCOWR-NIWR-CAUHSI conference; Medford, MA. June 18-20, 2014.
  • Sylvia, D. F., K.D. Pennell and N.L. Cápiro. "Partitioning Electron Donor Delivery for Chlorinated Solvent Bioremediation" Gordon Research Conference; Environmental Sciences: Water; Holderness, NH, June 22-27, 2014.
  • Sylvia, D. F., K. D. Pennell, N. L. Cápiro. "Evaluation of Partitioning Electron Donors to Improve Chlorinated Solvent Source Zone Bioremediation" International Conference of Soils, Sediments, Water, and Energy; Amherst, MA. October 2014.

Project Team:

Natalie L. Capiro

Principal Investigator

Kurt D. Pennell


Danielle F. Sylvia

M.S. Student

Eimy Bonilla
Undergraduate Student

This material is based upon work supported by the National Science Foundation under Grant Number (#1215837). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.