Packed-Bed Reactors as Model Systems for Simulating Shallow Subsurface Flow and Sediment Microbial Dynamics

Sediment-packed traps were deployed at the Oak Ridge National Laboratory-Field Research Center (ORNL-FRC), a well-characterized Superfund site where contamination in sediment and groundwater (i.e., heavy nitrate and pH disturbances) leads to distinctive microbial communities. The sediment traps were placed at three locations known to have different pH and nitrate contamination profiles. Resident microbial communities were allowed to develop in the traps, after which they were transferred back to the laboratory and used to inoculate up-flow packed bed reactors (PBRs). Each PBR was designed to mimic field-relevant attributes of the original system, including particle size, sediment type, as well as the nutrient conditions, pH, and groundwater flow rate. The PBRs were run for four months, with media samples collected every three weeks for microbial composition analysis. At the end of the experiment, reactors were disassembled, and samples were taken for microbial community composition.