Groundwater resources have become seriously threatened due to improper use by industrial, municipal, and even public sectors. Widespread contamination of aquifer systems has jeopardized human health and the environment and methods for restoring these systems are needed. Biological and chemical in situ remediation, where contaminants are degraded within the natural system, has become the foremost technique for cleaning up affected sites. However, before in situ remediation can be implemented, studies of the sites' physical, chemical, and biological characteristics must be done. Physical aquifer models (PAM's) were constructed for use in evaluating groundwater remediation strategies in porous media. The PAM's offer a unique approach for work of this kind, the most important of which are opportunity for conducting large-scale transport experiments under controlled conditions, and maintaining geometric, dynamic, and reactive similitude. The PAM's consist of aluminum reactors, 4.00 m (length) x 2.00 m (width) x 0.20 m (height), supported by a steel framework. Reservoirs at each end of the reactor permit adjustment of hydraulic gradient across its length. An array of 40 fully-penetrating wells allows versatility in sampling, injection, or extraction of solutes. Experiments can be performed under confined or unconfined, steady-state or transient conditions where temperature, pressure, and hydraulic gradient can be controlled. Plumbing design, well design, sampling protocol, and media-packing procedure were developed and tested in dye and bromide tracer experiments. The results of dye experiments in a water-filled PAM demonstrated the effectiveness of the inlet and outlet port design and construction of the wells. This was evident through control of a symmetrical plume that developed within a uniform flow field. Protocols for sampling, injection, and extraction using the well array were also effective based on observed dye plume development and bromide concentration contour plots. A new approach for packing sand was used to create a statistically equivalent homogeneous and isotropic porous media. Results of bromide tracer experiments indicate that this condition of homogeneity and isotropy was achieved. The PAM's worked well for creating the desired experimental conditions needed for studying transport of solutes (non-reactive in this case) in porous media. Additional experimental work will be done to develop and expand more of their capabilities (e.g. transient flow, confined conditions, heterogeneic media) for which they were designed. Remediation strategies will be investigated using the developed PAM's and it is hoped that results obtained from these studies will be successfully applied to field situations. / Graduation date: 1993

Ph.D. / Environmental Science and Engineering / In the past decade, permeable reactive barriers containing zero-valent iron metal (FePRBs) have emerged as the most significant new technology for the treatment of groundwaters contaminated with chlorinated organic compounds and, more recently, other organic contaminants such as 2,4,6-trinitrotoluene (TNT). Principle issues relating to the design, implementation, and monitoring of FePRBs include the rates of contaminant transformation, the resulting distribution of products, and the potential changes in FePRB performance due to aging of the iron material. Each of these issues is, at its root, a problem of chemical kinetics. In this thesis, commonly observed kinetic expressions for contaminant transformation are derived. Analyses of the simplifications involved in these derivations indicate that the forms of the rate laws are correct (either exactly or approximately) over a wider range of conditions than previously expected and that reaction rates may respond in unexpected fashion to changes in concentrations of reacting species or iron loading. These theoretical developments are applied to experimental investigations of product distribution and FePRB longevity for the treatment of TNT contaminated groundwaters.

No description available.

Nanoscale zero-valent iron (NZVI) particles were encapsulated in calcium alginate capsules for application in environmental remediation. TCE degradation rates for encapsulated and bare NZVI were similar indicating no adverse effects of encapsulation on degradation kinetics. Microorganisms were separately encapsulated and used along with encapsulated NZVI and co-encapsulated in calcium alginate capsules. Batch experiments were performed to test the efficacy of the combined iron-Pseudomonas sp. (PpF1) system. The combined system removed 100% TCE over the first three hours of the experiment followed by 70% TCE removal post TCE re-dosing. Complete reduction of TCE was achieved by NZVI between 0-3 h and the second phase of treatment (3-36 h) was mostly achieved by microorganisms. Experiments conducted with co-encapsulated NZVI-D.BAV1 achieved 100% TCE removal. During the first three hours of the experiment 100% TCE removal was achieved by NZVI, and 100% removal was achieved post re-dosing where D.BAV1 accomplished the treatment. / Department of Civil Engineering, North Dakota State University

Batch and column experiments were performed to investigate the adsorption of bacteriophage MS-2 to silica at pH 5. Linear isotherm analysis of batch experiment data gave partition coefficient (KP) estimates of 270 cm³/g and 580 cm³/g for 4°C and 24°C, respectively. Breakthrough-type column experiments indicated that sorption and desorption were slow, as evidenced by a slow approach to breakthrough and tailing of the desorption limb. A non-equilibrium advection-dispersion model with all adsorption sites on the silica assumed to be kinetically controlled was used to model the column data. The model-generated parameters yielded Kp estimates 1000-fold smaller than those given by isotherm analysis and indicated that the time scale for desorption is on the order of 1-6 hours.

No description available.

No description available.

A pilot scale demonstration of a biological permeable barrier was conducted in a pentachlorophenol-contaminated aquifer at a wood preserving facility. A permeable reactor was constructed to fit within a large diameter well. Arranged in series, a cylindrical reactor 24" x 36" (0.61 x 0.91m) (diameter x height) was partitioned to provide three biological treatment zones. Pentachlorophenol (PCP) biodegradation was evaluated under several environmental conditions using a mixed microbial consortium supported on ceramic saddles. Imitation vanilla flavoring (IVF), a mixture of propylene glycol, guaiacol, ethyl vanillin and sodium benzoate, served as the electron donor. In the absence of exogenous substrate, PCP was not degraded in the inoculated permeable barrier. Substrate addition under oxidizing conditions also failed to initiate PCP removal. Anaerobic conditions however, promoted in-situ PCP degradation. PCP reductive dechlorination resulted in the transient production of 3,4,5-trichlorophenol through sequential ortho dechlorinations. Continued carbon reduction at the meta and para positions resulted in 3,4-dichlorophenol and 3,5-dichlorophenol production. Complete removal of all intermediate degradation products was observed. Reactor operation was characterized through two independent laboratory and field companion studies. Experiments were conducted to evaluate (1) the effect of supplemental electron donor concentration (IVF) and (2) the effect of sulfate, a competitive electron acceptor on PCP reductive dechlorination. Results from laboratory and field conditions were consistent. (1) In the presence of an exogenous electron donor, PCP degradation was independent of supplemental donor concentration (10, 25, 50, 100 mg COD/L). However, a comparatively slower rate of PCP degradation was observed in the absence of electron donor. (2) The presence of sulfate was not inhibitory to PCP degradation. However, compared to systems evaluated in the absence of sulfate, slower rates of PCP transformation were observed. Passive operation and low energy requirements, coupled with potential contaminant mineralization suggest that the biological permeable barrier is a highly effective tool for subsurface restoration. / Graduation date: 2000

Graduation date: 1995

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