Limited access to clean water due to natural or municipal disasters, drought, or contaminated wells is driving demand for point-of-use and humanitarian drinking water technologies. Atmospheric water capture (AWC) can provide water off the centralized grid by capturing water vapor in ambient air and condensing it to a liquid. The overarching goal of this dissertation was to define geographic and thermodynamic design boundary conditions for AWC and develop nanotechnology-enabled AWC technologies to produce clean drinking water.

Widespread application of AWC is currently limited because water production, energy requirement, best technology, and water quality are not parameterized. I developed a geospatial climatic model for classical passive solar desiccant-driven AWC, where water vapor is adsorbed onto a desiccant bed at night, desorbed by solar heat during the day, and condensed. I concluded passive systems can capture 0.25–8 L/m2/day as a function of material properties and climate, and are limited because they only operate one adsorption-desorption-condensation cycle per day. I developed a thermodynamic model for large-scale AWC systems and concluded that the thermodynamic limit for energy to saturate and condense water vapor can vary up to 2-fold as a function of climate and mode of saturation.

Thermodynamic and geospatial models indicate opportunity space to develop AWC technologies for arid regions where solar radiation is abundant. I synthesized photothermal desiccants by optimizing surface loading of carbon black nanoparticles on micron-sized silica gel desiccants (CB-SiO2). Surface temperature of CB-SiO2 increased to 60oC under solar radiation and water vapor desorption rate was 4-fold faster than bare silica. CB-SiO2 could operate >10 AWC cycles per day to produce 2.5 L/m2/day at 40% relative humidity, 3-fold more water than a conventional passive system.

Models and bench-scale experiments were paired with pilot-scale experiments operating electrical desiccant and compressor dehumidifiers outdoors in a semi-arid climate to benchmark temporal water production, water quality and energy efficiency. Water quality varied temporally, e.g, dissolved organic carbon concentration was 3 – 12 mg/L in the summer and <1 mg/L in the winter. Collected water from desiccant systems met all Environmental Protection Agency standards, while compressor systems may require further purification for metals and turbidity.

Terrestrial crude oil spills compromise a soil’s ability to provide ecosystem services by inhibiting plant life and threatening groundwater integrity. Ozone gas, a powerful oxidant, shows promise to aid in soil recovery by degrading petroleum hydrocarbons into more bioavailable and biodegradable chemicals. However, previous research has shown that ozone can change the soil pH and create harmful organic compounds.
The research objective was to determine the short-term ecological toxicity of ozonation byproducts on seed germination of three distinct plant types (radish, lettuce, and grass) compared to untreated and uncontaminated soils. We hypothesize that the reduction of heavy hydrocarbon contamination in soil by ozone application will provide more suitable habitat for the germinating seeds. The effect of ozone treatment on seed germination and seedling quality was measured using ASTM standards for early seedling growth in conjunction with a gradient of potting soil amendments. Ozonation parameters were measured using established methods and include total petroleum hydrocarbons (TPH), dissolved organic carbon (DOC), and pH.
This study demonstrated the TPH levels fall up to 22% with ozonation, suggesting TPH removal is related to the amount of ozone delivered as opposed to the type of crude oil present. The DOC values increase comparably across crude oil types as the ozonation dose increases (from a background level of 0.25 g to 6.2 g/kg dry soil at the highest ozone level), suggesting that DOC production is directly related to the amount of ozone, not crude oil type. While ozonation reduced the mass of heavy hydrocarbons in the soil, it increased the amount of ozonation byproducts in the soil. For the three types of seeds used in the study, these changes in concentrations of TPH and DOC affected the species differently; however, no seed type showed improved germination after ozone treatment. Thus, ozone treatment by itself had a negative impact on germination potential.
Future research should focus on the effects of post-ozonation, long-term bioremediation on eco-toxicity. By helping define the eco-toxicity of ozonation techniques, this research can improve upon previously established ozone techniques for petroleum remediation and provide economic and environmental benefits when used for soil treatment.

This study reports on the treatment of ammunition wastewater containing RDX (1,3,5-Trinitro-1,3,5-triazinane), HMX (1,3,5,7-Tetranitro-1,3,5,7-tetrazoctane), and the oxyanion co-contaminants nitrate (NO3-) and perchlorate (ClO4-) in a membrane biofilm reactor (MBfR), a Palladium (Pd)-coated MBfR (Pd-MBfR), and an abiotic Pd-coated film reactor (Pd-film reactor). A consortium of nitrate- and perchlorate-reducing bacteria, continuously fed with synesthetic ammunition wastewater featuring 4 mM nitrate and 0.1-2 mM perchlorate, formed robust biofilms on the membrane surfaces in the MBfR and Pd-MBfR. PdNPs with diameter 4-5-nm auto-assembled and stabilized on the surfaces of membrane and biofilm in MPfR and Pd-MBfR. Nitrate and perchlorate were rapidly reduced by the biofilms in the MBfR and Pd-MBfR, but they were not catalytically reduced through PdNPs alone in the MPfR. In contrast, RDX or HMX was recalcitrant to enzymatic degradation in MBfR, but was rapidly reduced through Pd-catalytic denitration in the MPfR and Pd-MBfR to form ‒N‒NHOH or ‒N‒H. Based on the experimental results, the synergistic coupling of Pd-based catalysis and microbial activity in the Pd-MBfR should be a viable new technology for treating ammunition wastewater.

The microalgae Scenedesmus have been regarded as a potential source for biofuel production, having up to ~30% of dry weight as lipids used for biodiesel fuel production. Electro-selective fermentation (ESF) is a novel approach that can selectively degrade proteins and carbohydrates while conserving lipids within algal cells, while simultaneously enhancing lipid wet-extraction and biohydrogenation. ESF is a combination of SF and Microbial Electrolysis Cell (MEC) technologies. Experiments reported here prove that ESF is an effective means of enhancing lipid wet-extraction by ~50% and achieving 36% higher lipid saturation conversion, compared to SF, over 30 days of semi-continuous operation. Anode-respiring bacteria (ARB) residing on the anode surface produced a current that led to increased rate of organic substrate utilization, protein degradation, and ultimately enhanced lipid extraction and biohydrogenation that converted unsaturated to saturated fatty-acids. Thus, ESF provides a promising method for enhancing lipid extraction for biofuel production.

While biodiesel production from photosynthesizing algae is a promising form of alternative energy, the process is water and nutrient intensive. I designed a mathematical model for a photobioreactor system that filters the reactor effluent and returns the permeate to the system so that unutilized nutrients are not wasted, addressing these problems. The model tracks soluble and biomass components that govern the rates of the processes within the photobioreactor (PBR). It considers light attenuation and inhibition, nutrient limitation, preference for ammonia consumption over nitrate, production of soluble microbial products (SMP) and extracellular polymeric substance (EPS), and competition with heterotrophic bacteria that predominately consume SMP. I model a continuous photobioreactor + microfiltration system under nine unique operation conditions - three dilution rates and three recycling rates. I also evaluate the health of a PBR under different dilution rates for two values of qpred. I evaluate the success of each run by calculating values such as biomass productivity and specific biomass yield. The model shows that for low dilution rates (D = <0.2 d-1) and high recycling rates (>66%), nutrient limitation can lead to a PBR crash. In balancing biomass productivity with water conservation, the most favorable runs were those in which the dilution rate and the recycling rate were highest. In a second part of my thesis, I developed a model that describes the interactions of phototrophs and their predators. The model also shows that dilution rates corresponding to realistic PBR operation can washout predators from the system, but the simulation outputs depend heavily on the accuracy of parameters that are not well defined.

This report investigates the mass-transfer kinetics of gas diffusion through an asymmetrical hollow-fiber membrane developed for the membrane biofilm reactor (MBfR) when it is used to microbiologically convert syngas (a mixture of H2, CO2, and CO) to organic products. The asymmetric Matrimid® membrane had superior diffusion fluxes compared to commercially available symmetric, three-layer composite and polypropylene single-layer membranes. The Matrimid® asymmetric membrane had a H2 gas-gas diffusion flux between 960- and 1600-fold greater than that of the composite membrane and between 32,000- and 46,800-fold greater than that of the single-layer membrane. Gas-gas diffusion experiments across the Matrimid® membrane also demonstrated plasticization behavior for pure CO2 and H2 gas feeds. In particular, a 10 psia increase in inlet pressure resulted in a 12-fold increase in permeance for H2 and a 16-fold increase for CO2. Plasticization was minimal for symmetric composite and single-layer membranes. Thus, diffusion fluxes were much higher for the asymmetric membrane than for the symmetric composite and single-layer membranes, and this supports the promise of the asymmetric membrane as a high-efficiency means to deliver syngas to biofilms able to convert the syngas to organic products. Gas-liquid diffusion was much slower than gas-gas diffusion, and this supports the benefit of using the MBfR approach over fermentation reactors that rely on sparging syngas.

Background
Syngas fermentation, the bioconversion of CO, CO[subscript 2], and H[subscript 2] to biofuels and chemicals, has undergone considerable optimization for industrial applications. Even more, full-scale plants for ethanol production from syngas fermentation by pure cultures are being built worldwide. The composition of syngas depends on the feedstock gasified and the gasification conditions. However, it remains unclear how different syngas mixtures affect the metabolism of carboxidotrophs, including the ethanol/acetate ratios. In addition, the potential application of mixed cultures in syngas fermentation and their advantages over pure cultures have not been deeply explored. In this work, the effects of CO[subscript 2] and H[subscript 2] on the CO metabolism by pure and mixed cultures were studied and compared. For this, a CO-enriched mixed culture and two isolated carboxidotrophs were grown with different combinations of syngas components (CO, CO:H[subscript 2], CO:CO[subscript 2], or CO:CO[subscript 2]:H[subscript 2]).
Results
The CO metabolism of the mixed culture was somehow affected by the addition of CO[subscript 2] and/or H[subscript 2], but the pure cultures were more sensitive to changes in gas composition than the mixed culture. CO[subscript 2] inhibited CO oxidation by the Pleomorphomonas-like isolate and decreased the ethanol/acetate ratio by the Acetobacterium-like isolate. H[subscript 2] did not inhibit ethanol or H[subscript 2] production by the Acetobacterium and Pleomorphomonas isolates, respectively, but decreased their CO consumption rates. As part of the mixed culture, these isolates, together with other microorganisms, consumed H[subscript 2] and CO[subscript 2] (along with CO) for all conditions tested and at similar CO consumption rates (2.6 ± 0.6 mmol CO L[superscript −1] day[superscript −1]), while maintaining overall function (acetate production). Providing a continuous supply of CO by membrane diffusion caused the mixed culture to switch from acetate to ethanol production, presumably due to the increased supply of electron donor. In parallel with this change in metabolic function, the structure of the microbial community became dominated by Geosporobacter phylotypes, instead of Acetobacterium and Pleomorphomonas phylotypes.
Conclusions
These results provide evidence for the potential of mixed-culture syngas fermentation, since the CO-enriched mixed culture showed high functional redundancy, was resilient to changes in syngas composition, and was capable of producing acetate or ethanol as main products of CO metabolism.

Nitrate (NO3- ) and selenate (SeO42-) are common contaminants found in mining wastewater. Biological treatment has proved successful using bacteria capable of respiring NO3- into nitrogen gas and SeO42- into Se°. The Membrane Biofilm Reactor (MBfR) utilizes biofilm communities on the surface of hollow-fiber membranes to transform oxidized water contaminants into innocuous reduced products. For this project, I set up two MBfRs in a lead and lag configuration to reduce NO3- [input at ~40-45 mg NO3-N/L] and SeO42- [0.62 mg/L], while avoiding sulfate (SO42-) [~1600-1660 mg/L] reduction. Over the course of three experimental phases, I controlled two operating conditions: the applied hydrogen pressure and the total electron acceptor loading. NO3- in the lead MBfR showed average reductions of 50%, 94%, and 91% for phases I, II, and III, respectively. In the lag MBfR, NO3- was reduced by 40%, 96%, and 100% for phases I, II, and III. NO2- was formed in Stage I when NO3- was not reduced completely; nevertheless NO2- accumulation was absent for the remainder of operation. In the lead MBfR, SeO42- was reduced by 65%, 87%, and 50% for phases I, II, and III. In the lag MBfR, SeO42- was reduced 60%, 27%, and 23% for phases I, II, and III. SO42- was not reduced in either MBfR. Biofilm communities were composed of denitrifying bacteria Rhodocyclales and Burkholderiales, Dechloromonas along with the well-known SeO42--reducing Thauera were abundant genera in the biofilm communities. Although SO42- reduction was suppressed, sulfate-reducing bacteria were present in the biofilm. To optimize competition for electron donor and space in the biofilm, optimal operational conditions were hydrogen pressures of 26 and 7 psig and total electron acceptor loading of 3.8 and 3.4 g H2/m2 day for the lead and lag MBfR, respectively.

Endocrine-disrupting chemicals (EDCs) are substances that disrupt the function of the endocrine system by blocking or mimicking hormones. Over the years, these substances have been identified as responsible for producing adverse reproductive effects in freshwater vertebrate populations. Freshwater vertebrates include reptiles, amphibians, and fish living in bodies of water such as lakes or streams and are exposed when concentrations of EDCs enter their habitats. With over 800 known or potential EDCs identified, ample studies can be conducted on the effects of EDCs on freshwater vertebrates; however, studies can be costly. Since studies are costly, I have developed a methodology to prioritize EDC studies. I analyzed ten EDCs to determine their impact on freshwater vertebrates. I specified four criteria and EDCs that passed all four criteria were considered significant. The four criteria I utilized were population decreases, routes of exposure, adverse reproductive effects, and environmental persistence. I analyzed research studies as evidence for the pass or fail of each criterion, where I considered the EDC "ambiguous" if there was not enough information to make a judgment. I then assessed the research available for each EDC. Only one EDC had adequate information to pass or fail each criterion. The one with adequate information passed all criteria. Two EDCs lacked adequate information for three of the four criteria, three EDCs lacked adequate information for two of the four criteria, and four EDCs lacked adequate information for one of the four criteria. I assessed the EDCs based on whether there was adequate information available in each criterion in order to provide researchers direction for future research endeavors. The results indicate either there is much research that remains to be conducted or that researchers are not making existing results of studies available. Companies producing EDCs that are released into the environment can use the information in this report as a basis for determining strategies to minimize the impacts of EDCs on freshwater vertebrates.