Eutrophication, caused by phosphate, can be detrimental both for the aquatic environment and human health. This research aims to provide deep knowledge about the adsorption properties of low-cost Fe/Mg layered double hydroxide modified biochar (LDHBC) for removal of phosphate from aqueous solution. Firstly, Fe/Mg layered double hydroxide (LDH) was synthesized by mixing FeCl3 and MgCl2. 6H2O salts in water, followed by NaOH treatment (coprecipitation method). For LDHBC, FeCl3, and MgCl2. 6H2O salts were dissolved in water, and Douglas fir biochar was added to the salts mixture to make a slurry, followed by NaOH treatment. The surface chemistry and elemental composition of both adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, and TEM. Adsorption ability of LDH and LDHBC was studied by pH effects, kinetics, and the highest capacity for the analyte.

Petroleum spills cost large sums of money to remediate, which has resulted in the use of more in-situ technologies, including chemical oxidation, as cost effective alternatives to traditional methods of remediation. There are numerous case studies documenting the success of hydrogen peroxide as an in-situ oxidizer in that regulated BTEX concentrations were lowered below target cleanup levels. Little information is available; however, regarding the behavior of petroleum hydrocarbons post injection of hydrogen peroxide or what chemical derivatives may be produced as a result of the oxidation process. Laboratory protocols have been employed to yield data regarding the behavior of BTEX specifically, and all volatile gasoline constituents in general, over a period of time post injection of hydrogen peroxide. The results of the data indicate variations in petroleum compound behavior are predicated on the concentration of hydrogen peroxide, the degree of contamination, and the presence of a soil matrix.

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Included in this file is a CD drive titled "Chapter Three: Supporting Information" with a 00:40 second long animation. For best quality, view in VLC, not Quicktime Player. / <p>Groundwater contamination by dense non-aqueous phase liquids (DNAPLs ), such as chlorinated solvents, continues to be a significant environmental problem. When released to the subsurface, either due to improper disposal or accidental release, DNAPLs can form complex source zones whose geometry is largely controlled by the geological heterogeneity of the subsurface. These source zones are composed of disconnected, immobile blobs or ganglia trapped by capillary forces (referred to as DNAPL residual) between high-saturation regions located at permeability interfaces (referred to as DNAPL pools). The slow dissolution of DNAPL pools can result in the contamination of groundwater for time periods on the order of decades to centuries.</p> <p>The common conceptual model used in the investigation of DNAPL-contaminated sites is based primarily on the mass transfer from DNAPL to the surrounding aqueous phase in the saturated zone. However, the presence of a discontinuous gas phase above a DNAPL pool can significantly affect the mass transfer from the pool through repeated, spontaneous expansion and mobilization of the gas phase. This mechanism has not been included in the common conceptual models.</p> <p>The goal of this research was to develop a quantitative understanding of discontinuous gas phase expansion and mobilization above a DNAPL pool. This goal was addressed using a combination of small-scale and intermediate-scale laboratory experiments. Small-scale, no-flow vial experiments were used to measure the expansion of single gas bubbles above DNAPL pools, and provide the basis for the development of an analytical model to assess the effect of expansion by multi-component partitioning on the mass transfer from DNAPL pools. Small-scale flow cell experiments were used to measure spontaneous expansion rates in porous media, and provide visual data concerning the distribution of the gas phase. Small-scale air injection experiments were used to characterize the gas flow. Finally, an intermediate-scale flow cell experiment was used to provide larger-scale data concerning the transient distribution of the gas phase, and measure the effect of spontaneous expansion and mobilization on the aqueous-phase DNAPL constituent concentrations.</p> <p>The combined results of these experiments established a detailed conceptual model for the spontaneous expansion and mobilization of a discontinuous gas phase above a DNAPL pool. In this conceptual model, spontaneous expansion of a discontinuous gas phase above a DNAPL pool occurs due to multi-component partitioning, and depends on the concentrations of both the volatile DNAPL and the other dissolved gases. This expansion is more likely to occur, and will be faster, in shallower systems (i.e. lower hydrostatic pressures) containing coarser media (i.e. lower capillary pressures), more volatile DNAPL, and higher concentrations of other dissolved gases (i.e. higher partial pressures). Mobilization of the expanding gas will occur as discontinuous gas flow in most sands, where the repeated trapping and coalescence of gas clusters can allow rapid, large-scale vertical transport of the gas phase. This discontinuous gas flow can produce macroscopic gas fingers composed of multiple, discrete gas clusters. These macroscopic fingers can reach substantial heights above the pool surface, but the growth occurs predominantly at the pool's leading edge due to the stripping of other dissolved gases. This expansion and mobilization can significantly affect the mass transfer from the DNAPL pool if the gas phase is in direct contact with the pool surface; or if the gas phase is close to the pool surface, covers a large fraction of the pool, and the groundwater flow is sufficiently slow. The partitioning of DNAPL constituent from the mobilized gas phase to the aqueous phase well above the pool surface can also change the spatial distribution of aqueous-phase DNAPL constituent concentrations, increasing them above those that are expected based on theoretical calculations for strictly DNAPL-water systems, even at elevations where the concentrations are expected to be zero. The increased concentrations well above the pool surface can appear as short-duration events in the presence of a sustained gas phase, due to the partitioning of DNAPL constituents from the gas to the aqueous phase during multi-component mass transfer. The results of this research provide the necessary basis to begin incorporating this fundamental mechanism into the conceptual and mathematical models used for DNAPL-related research, the investigation ofDNAPL-contaminated sites, and the design and application of DNAPL remediation technologies.</p> / Thesis / Doctor of Philosophy (PhD)

The Deepwater Horizon (DWH) blowout, in the Gulf of Mexico, heavily contaminated miles of sandy beaches. Previous experience of petroleum contamination has shown that oil residues can persist in the sediments for decades. Biodegradation is the major mechanism of remediation regarding petroleum hydrocarbons. There is an urgent need to evaluate the competent indigenous microbial biomass in contaminated sediments if the risks posed by toxic oil residues, for the coastal ecosystem, are to be minimized. We report a field investigation during December 2010 and January 2011 regarding measurement of microbial activity in a sandy beach at the Bon Secour National Wildlife Refuge in Alabama. One transect of wells for sampling was installed in the beach; starting with multiport one, being most landward and thought to be least exposed to oil residue and ending with multiport four being the most seaward and exposed to the open waters of the Gulf of Mexico. Sediment samples were collected from different depths purposely chosen from above, inside, and below the oil layers for microbial analysis. Dissolved oxygen (DO) measurements were obtained and temperature was recorded while collecting the oxygen measurements. Pore water samples were collected for nutrient content and were monitored using the multiport sampling wells. Moisture content was analyzed from the sediments extracted at various depths at each well. pH and salinity were also analyzed for their contributing affect on the microbial community. Grain size distribution analyses were conducted on samples collected at all wells and at multiple depths to characterize the field study location. Results show that the bacterial biomass, as measured by Adenosine-5-triphosphate (ATP) and numbers of alkane and polycyclic aromatic hydrocarbon (PAH) degraders determined by Most Probable Number (MPN), are consistently higher in the sediment layers where oil had been detected. A very good correlation was observed among the relative abundance of bacteria in the different samples using MPN and ATP measurements. As expected, ATP based estimates of the microbial populations were two orders of magnitude higher than the alkane and PAH numbers determined by MPN, which reflect the non-cultivability of most environmental bacteria. The lower concentrations of PAH degraders than alkane degraders that were observed in this study are consistent with other studies, even though both populations are lower than in studies involving fresh oil trapped in beach or wetland sediments. PAHs (aromatics) are notoriously more resistant to biodegradation than alkanes, therefore allowing a lower number of biomass to grow using them. The overall smaller size of the bacterial numbers could be explained by the naturally occurring low-organic content of beach sand. On the other hand, this may be due to the highly weathered nature of the oil or it could reflect some other limitation. / Civil Engineering