Aromatic hydrocarbons represent a large class of environmental contaminants that have a broad range of structures, physicochemical properties, and toxicities. Arising from the burning of organic matter, particularly fossil fuels, they are both widespread and abundant in all environmental compartments. Both monoaromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAHs) are...
CisCis-Dichloroethylene (ciscis-DCE), 1,1,1-Trichloroethane (1,1,1-TCA), and 1,4-Dioxane (1,4-D) are chlorinated solvents used as solvents and degreasers in industrial cleaning agents that have become common groundwater contaminants. To develop an effective treatment method for these compounds, polyvinyl alcohol (PVA) and sodium alginate (SA) hydrogel beads were co-entrappcapsulated with Rhodococcus rhodochrous Strain ATCC...
Chlorinated solvents are a class of widespread groundwater contaminants that are toxic, carcinogenic, and difficult to remediate at low concentrations. 1,4-dioxane, a suspected carcinogen, is often a co-contaminant found in mixtures of chlorinated solvent plumes. In-situ bioremediation methods of degrading these chemicals through aerobic cometabolism have shown promise. Permeable Reactive...
1,4-Dioxane (dioxane) and cis-dichloroethylene (cDCE) are compounds commonly found in industrial cleaning and degreasing agents that are frequently present as groundwater contaminants. In an effort to develop a more effective treatment method for these compounds, hydrogel beads were fabricated with either gellan gum or a combination of polyvinyl alcohol (PVA)...
As access to potable water grows scarce, there is an increasing reliance on alternative drinking water sources, namely groundwater (WHO, 2018). Chlorinated solvents, such as 1,1,1-trichloroethane (TCA) and 1,2-cis-Dichloroethene (cisDCE) are some of the most ubiquitous groundwater contaminants spread throughout the US. 1,4-dioxane (1,4D) was used primarily in the late...
Mixtures of 1,4-dioxane (1,4-D) and chlorinated aliphatic hydrocarbons (CAHs) are common and hazardous groundwater contaminants that can be challenging to address with traditional remediation strategies. Bioremediation through aerobic cometabolism has the potential to be an effective in-situ treatment strategy for these contaminants. Rhodococcus rhodochrous strain ATCC 21198 is capable of...
The cometabolic ability of Burkholderia vietnamiensis G4 grown on aromatic substrates was first assessed by resting suspended cells, and subsequently for cells encapsulated with and without slow release compounds (SRCs). In Chapter 3, benzyl alcohol was assessed as a food-grade growth substrate for promoting cometabolism of trichloroethene (TCE), via the...
Chlorinated solvents are common groundwater pollutants that often exist as mixtures resulting from the use of multiple solvents and their transformation into chlorinated daughter products. These sites are often co-contaminated with the solvent stabilizer 1,4-dioxane (1,4-D), which is not treated by traditional chlorinated solvent remediation techniques. Both 1,4-D and chlorinated...
Chlorinated aliphatic hydrocarbons (CAHs) like trichloroethene (TCE) were mostly used to replace drying cleaning fluids which contained hydrocarbons like benzene, and were highly flammable. Through improper disposal, storage, and spills, TCE and its downstream products, like cis-dichloroethene (cDCE) and vinyl chloride (VC), leached into groundwater and threaten human and environmental...
1,4-dioxane and chlorinated aliphatic hydrocarbons (CAHs) such as trichloroethylene (TCE) and 1,1-dichloroethene (1,1-DCE) are hazardous compounds commonly found in soil and groundwater. Bioremediation through aerobic cometabolism is a potential option for the remediation of these contaminated sites. The purpose of this study was to examine the use of different primary...
Methods were developed for the co-encapsulation of slow release compounds (SRC) with viable microbial cells in alginate and gellan gum hydrogel beads, for the in-situ aerobic cometabolic treatment of groundwater contaminated with mixtures of 1,4-dioxane and chlorinated aliphatic hydrocarbons, which will be referred to as contaminants of concern (CoC). The...
Methanotrophic bacteria are promising means of producing value-added products as they have the ability to transform methane under atmospheric temperature and pressure. Efforts to develop methanotrophs to produce value-added products are hoped to incentivize a decrease in methane flaring operations. The data collected during this study was used to inform...
Despite decades of cleanup efforts, chlorinated solvents are some of the most common groundwater and subsurface contaminants of the industrialized world. These compounds include chlorinated ethenes (CEs) such as trichloroethene (TCE) and chlorinated methanes (CMs) such as carbon tetrachloride (CT). Dehalococcoides mccartyi belongs to a class of microorganisms called organohalide-respiring...
Stream chemistry studies conducted in the forested Watershed 1 of the HJ Andrews Experimental Forest show a contribution of CO2 from the hyporheic zone. Hyporheic CO₂ concentrations, measured as pCO₂, have a seasonal trend as well as a responsiveness to storm events. Concentrations are highest at the end of the...
1,4-dioxane, a probable human carcinogen at low (< 1ppb) concentrations, has emerged as a groundwater contaminant due to its historical use as a stabilizer for the chlorinated solvent 1,1,1-trichloroethane. Aerobic cometabolism, the use of a primary substrate to induce the production of microbial enzymes that fortuitously degrade other compounds, is...
The ability of Mycobacterium sp. ELW1, a novel microbe capable of alkene oxidation, to co-metabolize phenanthrene (PHE) was studied. ELW1 was able to completely co-metabolize PHE, at different concentrations below its water solubility limit, in an aqueous environment. The alkene monooxygenases in ELW1, used to initiate oxidation of PHE, were...
Carbon tetrachloride (CT) and chloroform (CF) were transformed in batch reactor experiments conducted with anaerobic dechlorinating cultures and supernatant (ADC+S) harvested from continuous flow reactors. The Evanite (EV-5L) and Victoria/Stanford (VS-5L) cultures capable of respiring trichloroethene (TCE), 1,2-cis-dichloroethene (cDCE), and vinyl chloride (VC) to ethene (ETH) were grown in continuous...
Two methanotrophs, M. trichosporium OB3b and M. buryatense 5GB1, were encapsulated using two methods to investigate the potential of methane conversion for biofuel production. Ca-alginate and low melt agarose were used to immobilize the methanotrophs for batch and continuous flow column testing. Varying protein concentrations, residence times, and immobilization methods...
Trichloroethene (TCE) is a common groundwater contaminant. Bioremediation, or the enhancement of natural microbial processes for the transformation of toxic compounds in soil and groundwater, is an effective solution to this widespread problem. The organisms that transform TCE in the subsurface are sensitive to environmental conditions, especially to the presence...
Bioremediation of chlorinated ethenes by the augmentation of contaminated soils with microorganisms is a proposed method of reducing contaminant concentrations in groundwater. To determine the viability of using ELW-1 or R. rhodochrous for groundwater remediation, kinetic analyses of transformation rates must be performed. The focus of this research was to...
Silver nanoparticles are increasingly being incorporated into consumer products due to their broad-spectrum antimicrobial properties. The resulting influx of silver nanoparticles into wastewater may pose a threat to bacteria involved in biological wastewater treatment. Ammonia-oxidizing bacteria, which convert ammonia to nitrite in the first step of nitrification, are highly sensitive...
The inhibitory effects of Corexit 9500A, Alaska North Slope Crude oil (ANSC), and mixtures of the two on the ammonia-oxidizing bacteria, Nitrosomonas europaea, and the ammonia-oxidizing archaea, Nitrosopumilus maritimus, were investigated. Corexit 9500A was found to be minimally toxic to both microorganisms with concentrations of 2000 and 3000 ppm yielding...
The rising demand on freshwater resources emphasizes the benefit of biogeochemical processes that maintain clean water by removing pollutants such as excess nitrogen. The most sensitive step in the removal of nitrogen from waterways is the oxidation of ammonia, a part of nitrification, which is carried out by ammonia oxidizing...
Tetrachlorethene (PCE) and trichloroethene (TCE) were common solvents used in the 1970’s that are now frequently observed groundwater contaminants. One method of remediating these contaminants is in-situ bioremediation that uses a dechlorinating microbial population. The microbial population performs the sequential reductive dechlorination of PCE and TCE to cis-1,2-dichloroethene (c-DCE), vinyl...
The inhibitory effects of (Ag⁺) and silver nanoparticles (Ag NP) 3-5 nm in diameter (stabilized with polyvinylpyrrolidone (PVP)) and 20 nm (stabilized with citrate) on nitrification rates of the model ammonia-oxidizing bacteria (AOB) Nitrosomonas europaea were investigated. Experimental solutions contained HEPES buffer and ammonia (NH₃) in the presence and absence...
Due to the effective antimicrobial properties of silver nanoparticles they represent a significant proportion of all consumer-‐related nanomaterials. The introduction of silver nanoparticles from these products into domestic and industrial wastewater streams poses potential complications for biological treatment systems. A critical component of biological treatment that is extremely sensitive to...
Identifying the inhibition of ammonia oxidizing bacteria (AOB) by emerging organic contaminants is crucial due to the importance of AOB in wastewater treatment, the widespread use of antibacterial agents such as triclosan (TCS) in consumer products, and the sensitivity of N. europaea to inhibitors. Triclosan inhibition of nitrification by AOB...
Radon-222 gas has unique properties allowing it to be used as an indicator for the
presence of organic phase liquids in the saturated zone. It naturally occurs in soils. It is
radioactive, making quantitative detection straight forward. A noble gas, it is chemically
inert and does not react with aquifer...
Continuous-flow and batch experiments were conducted with a column reactor
system containing Hanford aquifer material in order to evaluate the potential of in-situ
bioremediation of carbon tetrachloride (CT) at Hanford. The effectiveness of benzoate
and acetate as primary substrates was considered. Nitrate and sulfate were potential
electron acceptors. Transport experiments...
A mix-culture of methanogenic and sulfate-reducing bacteria was capable of degrading trichloroethylene (TCE) to dichloroethylene (DCE). The culture was incubated under anaerobic conditions within a soil sample taken from Gilbert-Mosley site, Wichita, Kansas. To stimulate the growth of indigenous bacteria, a carbon and energy source was added in this microcosm...
Persistence of Non aqueous phase liquids (NAPLs) in the subsurface at residual
saturations eventually contributes to undesirable groundwater contamination. Proper
characterization of subsurface NAPL, its location, composition and distribution, is
essential for the chosen remediation technology to be effective. It is also desirable to
assess the performance of remedial actions...
Batch microcosm studies were carried out to screen for microorganisms from the
subsurface of Hanford DOE site that could cometabolically transform chloroform (CF)
under aerobic conditions. The potential need for CF bioremediation at the Hanford site
has resulted from the large release of carbon tetrachloride (CT) to the subsurface, of...
At Site-300, Lawrence Livermore National Laboratory (LLNL), CA,
trichloroethene (TCE) is present along with tetraalkoxysilanes such as tetrabutoxysilane
(TBOS) and tetrakis(2-ethylbutoxy) silane (TKEBS), as subsurface contaminants.
Intrinsic transformation of TCE to cis-dichloroethene (c-DCE) was observed in the
groundwater at locations co-contaminated with TBOS or TKEBS. Attenuation of TBOS
and TKEBS...
Laboratory scale microcosm studies were conducted using site specific groundwater and aquifer solids to assess the feasibility of stimulating indigenous microorganisms in-situ to biologically transform Trichloroethylene (TCE) and its lesser chlorinated daughter products dichloroethylene (DCE) and vinyl chloride (VC). Three different treatments were conducted to determine the best approach for...
This microcosm study demonstrated the enhanced anaerobic transformation of vinyl chloride (VC) to ethylene. A previous microcosm study from Point Mugu site showed the accumulation of VC due to the slow transformation step of VC to ethylene. To overcome the rate-limiting step, two laboratory experiments tested the effect of trichloroethylene...
This research focuses on the anaerobic transformation of trichloroethylene (TCE) that is occurring in the subsurface of the Evanite site in Corvallis, OR. Two anaerobic studies were conducted to investigate the effects of microbial communities in the presence of different electron donors during the anaerobic degradation of trichlorofluoroethylene (TCFE), and...
A method is described for determining the partition coefficient, K, for radon gas
distributed between an aqueous phase and an organic solvent. The method uses
sequential extractions of radon into equal volume aliquots of organic solvent. The
radon-laden organic liquid is then counted on a liquid scintillation analyzer with alpha-beta...
The 1,1-dichloroethene (1,1-DCE) cometabolic transformation abilities of indigenous and bioaugmented microorganisms were compared in microcosms constructed with groundwater and aquifer solids from the Moffett Field site, CA. Microbial community structure in the microcosms and possible community shifts due to 1,1-DCE transformation stress was evaluated by terminal restriction fragment length polymorphism...
This study investigated the use of radon-222 as an in situ partitioning tracer for quantifying nonaqueous phase liquid (NAPL) saturations in the subsurface. Laboratory physical aquifer models (PAMs), field experiments, and numerical simulations were used to investigate radon partitioning in static (no-flow) experiments and in single-well, 'push-pull' tests conducted in...
The goal of this research was to mathematically simulate the ability of bioaugmented microorganisms to aerobically cometabolize a mixture of chlorinated aliphatic hydrocarbon (CAH) compounds during in-situ treatment. Parameter values measured from laboratory experiments were applied to the transport model with biotransformation processes included. In laboratory microcosm studies, a butane-grown,...
Laboratory and modeling studies were performed with a mixed-anaerobic-culture obtained from the Evanite site in Corvallis, Oregon. The culture completely transforms trichloroethene (TCE) to cis-dichloroethene (c-DCE), vinyl chloride (VC), and finally to ethene. Acetylene inhibition studies were used to examine the culture's microbial activities. Kinetic studies determined the half-saturated constant...
The aerobic transformation of TCE and cis-DCE by a tetrabutoxysilane-grown microorganism (Vancheeswaran et al., 1999) led to the investigation of novel substrates, including benzyl alcohol, for promoting cometabolism. The culture grew on carboxylic compounds and alcohols, but did not grow on formate, methanol, methane, propane, butane, ethylene, benzene, toluene, or...
This thesis focused on using microcosms to better understand the aerobic cometabolic processes of TCE and cis-DCE transformation that occurred during a Cometabolic Air Sparging (CAS) demonstration at McClellan Air Force Base. The microcosms were created with groundwater and aquifer materials from the demonstration site. Concentrations of compounds in the...
This study evaluated the potential of the aerobic Mycobacterium strain JS6O to grow on a variety of organic acid substrates, and the possible effects an organic acid would have on the degradation rate of vinyl chloride (VC). A series of batch growth tests were designed to determine the time it...
Halogenated organic compounds have had widespread and massive applications in industry, agriculture, and private households, for example, as degreasing solvents, flame retardants and in polymer production. They are released to the environment through both anthropogenic and natural sources. The most common chlorinated solvents present as contaminants include tetrachloroethene (PCE, perchloroethene)...