Changes in Groundwater Biogeochemistry Caused by Bioaugmentation Remediation in a Fractured Sedimentary Rock Aquifer
Monday, September 23, 2013: 3:45 p.m.
Thomas E. Imbrigiotta
,
U.S. Geological Survey, West Trenton, NJ
Scott R. Drew
,
Geosyntec Consultants, Ewing, NJ
Mary F. De Flaun
,
Geosyntec Consultants Inc., Ewing, NJ
Julie Kirshtein
,
U.S. Geological Survey, Reston, VA
Mary A. Voytek
,
U.S. Geological Survey, Reston, VA
Daniel J. Goode
,
U.S. Geological Survey, Exton, PA
Claire R. Tiedeman
,
U.S. Geological Survey, Menlo Park, CA
Allen M. Shapiro
,
U.S. Geological Survey, Reston, VA
An in situ bioaugmentation experiment to stimulate the degradation of chlorinated ethene compounds was initiated at the Naval Air Warfare Center in October 2008 by injecting emulsified soybean oil as an electron donor and a consortium of bacteria. Groundwater flow from the injection well is predominantly toward a pump-and-treat withdrawal well located about 45 meters (m) downgradient. Baseline geochemical conditions were established during the six months prior to injection by sampling 5-8 times for chlorinated ethene compounds, bacteria, inorganic geochemical constituents, and dissolved gases from the injection and withdrawal wells and from two multi-level observation wells located along the flow path. Following injection, the same constituents were monitored in the same wells 14-18 times over the next four years to assess the effects of the bioaugmentation.
From 2008-2012, substantial reductions (two orders of magnitude) were found in trichloroethene (TCE) concentrations in groundwater from the injection well and in one of the sampling intervals from the monitoring well 18 m downgradient, with lesser reductions (one order of magnitude) in one of the sampling intervals of the monitoring well 30 m downgradient. These sampling intervals are coincident with mudstone beds that are the primary conduits for flow between the injection and withdrawal wells. In water from these same sampling intervals, increased concentrations (1-2 orders of magnitude) of dechlorinating bacteria, cis-1,2-dichloroethene, vinyl chloride, ethene, and chloride were found, indicating that the decrease in TCE was primarily caused by reductive dechlorination.
Concentrations of lactic acid, one of the electron donors added, decreased to pre-injection levels in the injection well within two and a half years. Concentrations of acetic acid, a breakdown product of the soy bean oil, remained two orders of magnitude above pre-injection levels, in the same well, indicating that degradation of this electron donor may still be ongoing four years post-injection.
Thomas E. Imbrigiotta, U.S. Geological Survey, West Trenton, NJ
Thomas Imbrigiotta is a Supervisory Hydrologist with the U.S. Geological Survey. His research interests involve tracking of changes in groundwater geochemistry in fractured rock chlorinated solvent plumes during remediation, determining diffusion rates of contaminants from the primary porosity of fractured rock, and developing groundwater passive diffusion samplers.
Scott R. Drew, Geosyntec Consultants, Ewing, NJ
Scott Drew is a Senior Environmentatl Scientist with Geosyntec Consultants in Ewing, New Jersey.
Mary F. De Flaun, Geosyntec Consultants Inc., Ewing, NJ
Mary de Flaun is a Principal Environmental Scientist with Geosyntec Consultants in Ewing, New Jersey.
Julie Kirshtein, U.S. Geological Survey, Reston, VA
Julie Kirshtein is a Microbiologist with the U.S. Geological Survey in Reston, Virginia.
Mary A. Voytek, U.S. Geological Survey, Reston, VA
Mary Voytek is a Research Ecologist with the U.S. Geological Survey in Reston, Virginia.
Daniel J. Goode, U.S. Geological Survey, Exton, PA
Dan Goode is a Research Hydrologist with the U.S. Geological Survey in Exton, Pennsylvania.
Claire R. Tiedeman, U.S. Geological Survey, Menlo Park, CA
Claire Tiedeman is a Research Hydrologist at the U.S. Geological Survey, where her work involves characterizing and modeling flow and transport in fractured rock aquifers, calibrating and evaluating models of complex groundwater flow systems, and developing methods to evaluate prediction uncertainty. She is co-coordinator of USGS research on contaminant transport and remediation at the former Naval Air Warfare Center, and is co-author of the textbook Effective Groundwater Model Calibration: With Analysis of Data, Sensitivities, Predictions, and Uncertainty.
Allen M. Shapiro, U.S. Geological Survey, Reston, VA
Allen M. Shapiro is a Senior Research Hydrologist with the National Research Program of the U.S. Geological Survey in Reston, Virginia. His research focuses on the development of field techniques and methods of interpreting geologic, geophysical, hydraulic, and geochemical information in the characterization of fluid movement and chemical transport in fractured rock from meters to kilometers. Shapiro’s research has focused on a wide range of geologic environments, including crystalline and sedimentary rock, and carbonate aquifers that have undergone karstification. His research has been applied in issues of water supply, geotechnical engineering, waste isolation, and groundwater contamination and restoration.
