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- All Subjects: Environmental engineering
- Genre: Masters Thesis
- Status: Published
Description
This study was designed to provide insight into microbial transport kinetics which might be applied to bioremediation technology development and prevention of groundwater susceptibility to pathogen contamination. Several pilot-scale experiments were conducted in a saturated, 2 dimensional, packed porous media tank to investigate the transport of Escherichia coli bacteria, P22 bacteriophage, and a visual tracer and draw comparisons and/or conclusions. A constructed tank was packed with an approximate 3,700 cubic inches (in3) of a fine grained, homogeneous, chemically inert sand which allowed for a controlled system. Sampling ports were located at 5, 15, 25, and 25 vertical inches from the base of the 39 inch saturated zone and were used to assess the transport of the selected microorganisms. Approximately 105 cells of E. coli or P22 were injected into the tank and allowed to move through the media at approximately 10.02 inches per day. Samples were collected intermittently after injection based off of an estimated sampling schedule established from the visual tracer.
The results suggest that bacteriophages pass through soil faster and with greater recovery than bacteria. P22 in the tank reservoir experienced approximately 1 log reduction after 36 hours. After 85 hours, P22 was still detected in the reservoir after experiencing a 2 log reduction from the start of the experiment. E. coli either did not reach the outlet or died before sampling, while P22 was able to be recovered. Bacterial breakthrough curves were produced for the microbial indicators and illustrate the peak concentrations found for each sampling port. For E. coli, concentrations at the 5 inch port peaked at a maximum of 5170 CFU/mL, and eventually at the 25 inch port at a maximum of 90 CFU/mL. It is presumed that E. coli might have experienced significant filtration, straining and attachment, while P22 might have experienced little adsorption and instead was transported rapidly in long distances and was able to survive for the duration of the experiment.
The results suggest that bacteriophages pass through soil faster and with greater recovery than bacteria. P22 in the tank reservoir experienced approximately 1 log reduction after 36 hours. After 85 hours, P22 was still detected in the reservoir after experiencing a 2 log reduction from the start of the experiment. E. coli either did not reach the outlet or died before sampling, while P22 was able to be recovered. Bacterial breakthrough curves were produced for the microbial indicators and illustrate the peak concentrations found for each sampling port. For E. coli, concentrations at the 5 inch port peaked at a maximum of 5170 CFU/mL, and eventually at the 25 inch port at a maximum of 90 CFU/mL. It is presumed that E. coli might have experienced significant filtration, straining and attachment, while P22 might have experienced little adsorption and instead was transported rapidly in long distances and was able to survive for the duration of the experiment.
ContributorsAcosta, Jazlyn Cauren (Author) / Abbaszadegan, Morteza (Thesis advisor) / Dahlen, Paul (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2017
Description
The study was to analyze the extent of bacterial transport in a two-dimensional tank under saturated conditions. The experiments were done in a 2-D tank packed with 3,700 in3 of fine grained, homogenous, chemically inert sand under saturated conditions. The tank used for transport was decontaminated by backwashing with 0.6% chlorine solution with subsequent backwashing with chlorine-neutral water (tap water and Na2S2O3) thus ensuring no residual chlorine in the tank. The transport of bacteria was measured using samples collected from ports at vertical distances of 5, 15 and 25 inches (12.7, 38.1 and 63.5 cm) from the surface of the sand on both sides for the 2-D tank. An influent concentration of 105 CFU/mL was set as a baseline for both microbes and the percolation rate was set at 11.37 inches/day using a peristaltic pump at the bottom outlet. At depths of 5, 15 and 25 inches, E. coli breakthroughs were recorded at 5, 17 and 28 hours for the ports on the right side and 7, 17 and 29 hours for the ports on the left sides, respectively. At respective distances Legionella breakthroughs were recorded at 8, 22 and 35 hours for the ports on the right side and 9, 24, 36 hours for the ports on the left side, respectively which is homologous to its pleomorphic nature. A tracer test was done and the visual breakthroughs were recorded at the same depths as the microbes. The breakthroughs for the dye at depths of 5, 15 and 25 inches, were recorded at 13.5, 41 and 67 hours for the ports on the right side and 15, 42.5 and 69 hours for the ports on the left side, respectively. However, these are based on visual estimates and the physical breakthrough could have happened at the respective heights before the reported times. This study provided a good basis for the premise that transport of bacterial cells and chemicals exists under recharge practices.
ContributorsMondal, Indrayudh (Author) / Abbaszadegan, Morteza (Thesis advisor) / Dahlen, Paul (Committee member) / Delgado, Anca (Committee member) / Arizona State University (Publisher)
Created2019
Description
Soil impacts from crude oil spills in the United States are regulated at the state level using the analytical group total petroleum hydrocarbons (TPH) as the primary regulatory metric. TPH concentration in soil is used to enforce and verify compliance with cleanup levels (CULs). While there are significant differences between states concerning TPH CULs based on land use, most states enforce an action level of 100 mg TPH kg⁻1. The most common standard method for quantification of TPH in soils is EPA Method 8015, which entails extraction of petroleum hydrocarbons by dichloromethane and analysis by gas chromatography with flame ionization detection (GC-FID). Using Method 8015 or similar methods, TPH is defined as the cumulative area of all peaks within a defined analytical range (typically C6-C36). A limitation of TPH standard methods is their lack of specificity for petroleum hydrocarbons (i.e., these methods can also detect and quantify compounds that are an inherent part of natural soil organic matter (SOM)). While the interference of SOM compounds with TPH quantification is known, documentation regarding the extent of this interference is almost absent in the peer-reviewed literature. In this thesis, 15 biogeochemically-diverse soils, uncontaminated by crude oil hydrocarbons, were sampled from geographically diverse locations and investigated in an effort to determine the concentration of SOM that registers as TPH. Solvent extractions using dichloromethane or n-pentane in conjunction with GC-FID analysis showed that all soils had detectable concentrations of TPH ranging from 160 to 2700 mg TPH kg–1. Based on the results from this study, it can be concluded that many soils have a higher apparent TPH concentration than most US state-level CULs. In addition, the data from this study show that soils with a lower pH and/or a higher organic carbon content also have higher concentrations of apparent TPH. Findings from this thesis show that uncontaminated soils have a significant apparent TPH concentration that would be considered part of the TPH originating from contamination and should be accounted for in the regulatory landscape.
ContributorsSundar, Skanda Vishnu (Author) / Delgado, Anca G (Thesis advisor) / Dahlen, Paul (Committee member) / Sihota, Natasha (Committee member) / Arizona State University (Publisher)
Created2020