Browsing by Author "Jackson, Andrew W."
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Item Advantages and disadvantages of microporous membranes in a hollow fiber bioreactor for space applications(Texas Tech University, 2005-08) Ruiz Careri, Maria Noel; Morse, Audra N.; Jackson, Andrew W.Texas Tech University (TTU) works in conjunction with NASA to develop a wastewater recovery system robust enough for use on long term-space missions. Biological treatment has been the primary focus at TTU, with specific thrusts in developing a biological treatment system that may be operated with minimal crew maintenance and low energy and mass requirements. Hollow fiber membrane bioreactors (HFMBRs) may be used for biological wastewater treatment, and may be integrated with NASA’s current research developments. The goal of this research is to (a) evaluate the effect of mass transfer by the use of microporous membranes and their application for microgravity conditions; (b) compare the effect of membrane type and configuration on treatment efficiency to previous literature values; and (c) determine the amount and distribution of biofilm growth within the reactor. Therefore, the objective of this research was accomplished using a microporous HFMBR. From the experimental studies performed for this thesis it was found that the HFMBR exhibits promising use in space applications. Maximum nitrification efficiency at low loading rates and high HRTs were accomplished using the HFMBR. Therefore, characteristics such as, suitable bioreactor size and the efficiency obtained during its operation, the HFMBR offer a potential for NASA’s needs; nonetheless, developing a system with more favorable system hydrodynamics would aid to improve treatment efficiency in a HFMBRItem Application of passive sampling technology in HOCS contaminated sediment management and remediation(2018-12) Yan, Songjing; Reible, Danny D.; Chen, Chau-Chyun; Jackson, Andrew W.; Marston, JeremyPassive sampling technology is an emerging approach of using sorbents to obtain freely dissolved concentrations of target compounds in air or aquatic environment. This research focuses on using passive sampling technology to determine and monitor hydrophobic organic contaminants (HOCs) in sediment porewater using solid phase micro-extraction (SPME) with polydimethylsiloxane (PDMS) fibers. The traditional way to obtain porewater concentrations is to convert bulk sediment concentrations. Compared to conventional techniques, passive sampling technology has several advantages. It’s efficient and easy to process. It has less impacts on the surroundings and it can provide lower detection limits. More importantly, passive sampling method can directly obtain sediment porewater concentration which is regarded as a good indicator of bioaccumulation and chemical activity. Therefore, it is essential for risk management. In addition, passive samplers have the capability to capture the concentrations that change over time and don’t need to be corrected for organic carbon or lip species on a temporal or spatial scale. Due to the above advantages, passive sampling approach is a promising method to monitoring pollutants in aquatic environment, especially in contaminated sediment management and remediation. In this dissertation, three applications of passive sampling technologies in HOCs contaminated sediment management were explored based on in situ pilot studies. The SPME PDMS method was employed at two different polychlorinated biphenyl (PCB) contaminated sediment sites, Hunter’s Point Navy Shipyard (San Francisco, CA) and Columbia Slough (Portland, OR). The spatial representativeness of passive sampling method was explored and compared with bulk sediment measurement by developing spatial semivariogram models. The SPME PDMS fibers were used to monitor the concentration change with time after application of activated carbon to the sediment surface as an in situ treatment at the Hunter’s Point site. The ability of passive sampling to assess site transport conditions was also explored. An analytical model was developed to estimate groundwater upwelling velocities and effective diffusion coefficients using the rate of release of performance reference compounds. The results indicate that passive sampling approach is a viable and promising tool for evaluating exposure and risk of HOC contaminated sediment management, the effectiveness of in situ remediation and for characterizing site transport characteristics.Item Assessing effects of oxidizer characteristics on composite reaction kinetics(2013-12) Mulamba, Oliver K.; Pantoya, Michelle; Chaudhuri, Jharna; Ekwaro-Osire, Stephen; Anderson, Todd A.; Jackson, Andrew W.Enhancing the performance and efficiency of energetic materials is what helps to keep our military on the forefront of cutting edge weapon research and advancements. Whether it’s increasing the energetic output, improving burn rates or decreasing sensitivity, the ability to tailor materials to a specified goal provides a foundation for continued improvements. This body of work investigates and assesses the effects of oxygen scavenging additives, varying molecular composition, and fragmental reactions on the reaction kinetics and thermal behaviors of different energetic compositions. Closing the gap between practical and theoretical heat of combustion values requires innovative strategies for exploiting reaction kinetics. One potential strategy forcing reaction between Al and CuO, bypassing environmental oxygen is shown here to improve heat of combustion measurements significantly. Results reveal that using hafnium hydride additives at 10 mass% enhanced the heat of combustion of Al+CuO by 12%. The transition of this equilibrium based observation to a non-equilibrium fast heating setup is also investigated using plate deformation tests. Exploding bridge wire heads (EBW) initiated by a capacitive discharge unit (CDU) are used to dent plates and the deformation energies are estimated to observe the effects of varying composites in a non-equilibrium setting. The presence of HfH2 showed improved deformation energies for Al+CuO in the 10%.mass HfH2 range. Taking polytetrafluoroethylene (PTFE) varying in chain lengths and molecular weight combined with the exothermic surface chemistry of the alumina passivation shell presents results based on very tailorable parameters. Experimentation was performed using simultaneous thermal analysis (STA) that covers both heat flow and mass loss. Flame speeds were also tested and required the use of an altered Bockmon tube method. Results showed a pre-ignition reaction (PIR) with longer chained PTFE samples and not with the shorter chained PTFE samples. The PIR is attributed to fluorine dislodging the hydroxyls from the alumina (Al2O3) surface and forming Al-F structures on the surface of Al2O3. Composites exhibiting the PIR correspondingly result in significantly higher flame speeds. The PIR surface chemistry may contribute to promoting the melt dispersion mechanism (MDM) responsible for propagating energy in nano Al reactions.Item Assessment of stormwater metals on receiving water sediment recontamination(2020-08) Drygiannaki, Ilektra; Reible, Danny D.; Jackson, Andrew W.; Yan, Weile; Dawson, John A.Contaminated sediments serve as the sink and source of contaminants, and pose one of the most difficult and cost-effective remediation challenges. Continued metal inputs from stormwater discharges may result in significant discharges into receiving waters and remediating sediments; presenting a challenge from both regulatory and assessment perspective. Metals, like cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), nickel (Ni), and the metalloid arsenic (As), are non-degradable and toxic, posing biological risks by accumulation on living organisms entering the food chain. Stormwater sources are difficult to understand due to the poor characterization of the irregular, event-driven inputs, and the difficulty of managing these diffuse sources of large volumes. Effective means of evaluating the significance of stormwater inputs is particularly important when examining the long-term effectiveness of sediment remedial efforts. This dissertation presents improved approaches for assessing the impact of metals in stormwater on receiving sediments at Paleta Creek in San Diego Naval Base, USA. First aim of the study presents the stormwater assessment and characterization and the exploration of useful indicators for associating metal discharges to sediment recontamination. Second goal presents the evaluation of seasonal storm effects to biologically available metals and biota accumulation in sediments as well as to bulk sediment chemistry. Intensive stormwater and receiving waters sampling was coupled with sediment trap and seasonal sediment core collections, ex situ bioassays, and porewater passive sampling via DGTs during the wet and dry seasons. The first part identified that the most successful indicators of stormwater impacts on sediment recontamination were the size segregated stormwater discharges both in water and on suspended solids, total (>0.45 μm), sand (>63 μm), coarse silt (20-63 μm), fine silt (5-20 μm), clay (0.45-5 μm), as well as the dissovled phase (<0.45 μm) combined with sediment traps in the receiving waters. The stormwater concentrations, characterized by particle size distribution, provided the potential of the discharged mass and resulting deposition on sediments. The sediment traps provided an indication of the short-term sediment deposition and recontamination resulting from the storm events. The comparison of these various indicators allowed the estimation of the proportion of sediment recontamination likely due to stormwater and the proportion that might be caused by other sources, including resuspension of sediment in the receiving waters. Among the metals studies, Cd was clearly associated with large (>63 µm) particles and was found to settle quickly into locations immediately downstream. Cu, however, was associated with a range of particle sizes and was found in all sediment traps, even those located with some distance from the stormwater discharge. Other constituents, like Pb, Zn, Ni, Hg, and As, showed behavior intermediate to these two extremes suggesting both stormwater and other sources were likely important for these metals. In the second part, the synthesis of multiple lines of evidence successfully evaluated the biota accumulation due to contamination of sediments by stormwater heavy metals. The metal uptake in Macoma nasuta in bioaccumulation assays using sediments collected after the storm seasons were reduced with statistical certainty relative to pre-storm season samples for all measured metals, Cd, Hg, Cu, Pb, Zn, Ni, and the metalloid As; suggesting deposition of stormwater contaminants in low bioavailable forms. Similar reductions were observed after the storms in porewater of sediments measured by DGTs for all measured metals. Interestingly, sediment recontamination as indicated by stormwater loads and bulk chemistry of the receiving sediments did not indicate biological impacts as indicated by bioaccumulation. Moreover, the bulk sediment chemistry did not correlate with bioaccumulation with the exception of Pb. Analysis of the metal biota accumulation and DGT measured porewater concentrations showed statistically significant positive correlations (p<0.05, α=0.05) for most metals; suggesting that porewater concentrations can successfully indicate metal availability. In conclusion, sediment recontamination should be assessed by the combination of size-segregated stormwater discharges and settling traps to identify short term deposition resulting from those storms. Any observed sediment recontamination should also be subjected to bioassays or other bioavailability assessments because bulk sediment recontamination may not lead to negative impacts on benthic organisms.Item Bioaccumulation and correspondent biochemical response of lumbriculus variegatus by exposure to fullerenes (C60)(2012-05) Wang, Jiafan; Cobb, George P.; Anderson, Todd A.; Maul, Jonathan D.; Jackson, Andrew W.; Hope-Weeks, Louisa J.Nanotechnology is one of the most popular and promising technologies in this era. It has been developed from a novel concept to an integral aspect of product advancement. Engineered nanomaterials (NMs) have been massively produced and applied into groups of products, such as automotive, defense, aerospace, electronics and computers, energy production, environmental, food production, agriculture, housing and construction, medical devices, pharmaceuticals, personal care, cosmetics. In 1985, a spherical carbon allotrope fullerene (C60) was discovered by Kroto et al. It is a foundational carbon based NM, widely applied into products due to its physical and chemical properties. However, the likelihood of direct C60 release into the environment has increased due to its applications. In recent decades, research associated with potential C60 environmental and human health risks has been emphasized. However, environmental risks of C60 are not fully understood. This research evaluated the bioaccumulation and correspondent catalase (CAT) activity change in Lumbriculus variegatus exposed to C60. With the challenge to quantify C60 in our experimental matrix, a normal shaking method was developed in this study to extract C60 effectively. Recovery results revealed 90.7 ± 4.5 % efficiency using silanized glass vessels. With relatively low cost of the supplies, this method was applied throughout the subsequent bioaccumulation study. Since few studies have emphasized C60 uptake by organisms in the environment, bioaccumulation factors have not been determined for C60 to L. variegatus. With no mortality observed in the concentration range of 0.05 to 11.33 mg C60 / kg dry weight sediment, biota-sediment accumulation factor (BSAF) was determined. For C60 aggregates in micro-size ranges (µ-C60), BSAF was 0.032 ± 0.008 at day 28, while a negligible (0.003 ± 0.006) BSAF was associated with the bigger C60 aggregates (bulk-C60). In comparison, BSAF of pyrene at day 28 (1.62 ± 0.22) was measured as a reference to determine C60 accumulation risk in the environment. Results demonstrated a lower potential for C60 accumulation in L. variegatus than pyrene. However, size effect for C60 suggests smaller aggregates can increase the accumulation in living organisms. Although C60 shows little accumulation risk in the environment, biological response corresponding to C60 exposure was observed. CAT activity was evaluated after both C60 and pyrene exposure to L. variegatus. Results illustrated a significant CAT activity change (p=0.034) at day 14 for worms exposed to C60 aggregates. This elevation was associated with the highest C60 body residue (199 ± 80 µg/kg worm tissue). Worms exposed to pyrene showed no significant CAT activity change while 600-fold higher body residues were found as compared to C60. This suggests that L. variegatus is more susceptible to C60 even through accumulation risk is relatively low. Furthermore, the relationship between C60 body residues and increased CAT activity was analyzed in linear regression to predict biological risk to L. variegatus from exposure to C60. NMs also include other compounds besides C60, such as carbon-nanotubes (CNTs) and metal-based nanoparticles. Current research has demonstrated some potential environmental and human health risks from exposure to NMs due to their special properties. In order to prevent future adverse effects from nanotechnology, an integrated governance approach that is based on scientific research and life cycle assessment is suggested to formulate effective NMs regulation. Advanced scientific research, general public education and engagement, application of well defined agenda-setting theory in public policy are all important norms in this approach to push sustainable NMs management and to prevent any unfriendly accident due to NMs exposure. In sum, this research adds to the knowledge of C60 effects on aquatic invertebrates (Lumbriculus variegatus). Governance approach suggestion is summarized and helpful in a proactive NMs management to not only aquatic ecosystems but also human health.Item Chronic toxicity of perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA) to northern bobwhite (Colinus virginianus)(2018-08) Thompson, William; Anderson, Todd A.; Jackson, Andrew W.; Crago, JordanThis project’s primary objective was to characterize any adverse impacts of two perfluoroalkyl acids (PFAAs) to birds, with growth, development, and survival as the primary endpoints. PFAAs are a class of persistent, anthropogenic pollutants used in a wide variety of products for their non-reactivity, including in aqueous firefighting foam (AFFF). This study evaluated if chronic exposure at environmentally relevant concentrations could alter the health and reproductive fitness of adult birds and any negative impacts in ovo exposure may have on their offspring through maternal deposition into eggs. Secondary endpoints included examining how much accumulation of the target chemical occurs in liver tissue and how the body burden of PFOA and PFHpA, the two target PFAAs of this study, are altered by egg deposition. Furthermore, this project attempted to assess how much of the target chemical was present in egg yolk and how much juvenile quail retain after one month of growth. Chronic toxicity of the two target compounds was tested using Northern Bobwhite (Colinus virginianus) as the model species. Adult birds were exposed to drinking water containing nominal concentrations of 20 ng/mL, 1 ng/mL, and 0.1 ng/mL of the target chemical over the course of study (90 days). Juvenile bobwhite offspring were assessed for 30 days to determine any potential fitness effects from in ovo exposure. Residue analysis was conducted on adult and juvenile liver tissue as well as on eggs. Neither PFHpA or PFOA reduced hatching success, reproduction, or adult or juvenile Northern bobwhite survival at 1.860 or 1.745 µg/kg/day, respectively. However, it did appear that chromic ingestion of PFOA (1.745 µg PFOA/kg/day) may significantly increase weight of hatchling birds after one week, an effect observed in other vertebrates. Furthermore, residue analysis confirmed that female birds do reduce their body burden of both PFOA and PFHpA through deposition to eggs. In addition, some non-significant patterns of liver damage were identified in adult birds following chronic exposure.Item Comprehensive trade study of bioreactors and advancement of membrane-aerated biological reactors for treatment of space based waste streams(2012-03) Kubista, Kyle; Jackson, Andrew W.; Morse, Audra N.Biological processes offer an alternative approach to treatment of waste streams for water recycling during long term space missions. The combination of biological pretreatment with downstream physiochemical processes may be able to produce potable water at a lower equivalent system mass (ESM) compared to systems composed of only physiochemical processes. Several biological configurations exist for the removal of carbon and nitrogen. To date, no studies have comprehensively evaluated the relative ESM of each system. The configurations evaluated include: 1) membrane aerated biological reactor for simultaneous nitrification/denitrification, 2) membrane aerated biological reactor for nitrification in sequence with a packed-bed reactor for denitrification and organic carbon removal, 3) a pre-carbon oxidation reactor followed by a membrane aerated biological reactor for nitrification, and 4) an extended membrane aerated biological reactor for nitrification and aerobic carbon oxidation. We report on the systems, analysis and results including a detailed discussion of the inputs of the ESM analysis, methodology for determining reactor size and mass, and the implications of each system on downstream processing and reliability. Ongoing development of microgravity compatible biological reactors is essential to develop full scale flight ready technology. Recently, the first full scale membrane aerated biological reactor (MABR) was developed and evaluated. Despite several shortcomings, the reactor laid the groundwork for future development. To further develop the full scale MABR, a counter-diffusion membrane aerated nitrification denitrification reactor, a new upgraded MABR (CoMANDR) was designed to overcome the limitations experienced by the first generation. The first generation was limited primarily by its ability to transfer oxygen to the bulk liquid and inability to make repairs due to inaccessibility to the various chambers. CoMANDR is designed to overcome oxygen transfer limitations by using a submersible membrane module (SMM) with a pressurized lumen and additional membranes (to provide increased surface area). The SMM has the ability to be completely removed from the bulk liquid chamber allowing for ease of maintenance and repair. Along with the SMM, features like unidirectional gas flow patterns, offset liquid influents, and additional membranes are incorporated into CoMANDR to address the limitations experienced in the first generation. CoMANDR has been designed, constructed and is expected to meet treatment efficiencies of 90 % dissolved organic carbon removal, 70 % nitrification, and 50 % denitrification. CoMANDR will treat mass loadings of 34 g-C/d and 44 g-N/d at a hydraulic loading rate of 40 L/d. The reactors use silicone membranes to provide surface area for bacterial attachment and to supply oxygen to the bacteria. The membranes are the most important feature of MABRs because they provide a unique biofilm stratification that allows for higher removal efficiencies. The counter-diffusion of oxygen and substrate to the bacteria create optimum biofilms. MABR technology has been studied for over 10 years and has recently been designed for full scale applications. The first full scale model experienced oxygen transfer limitations. The next full scale application intends to operate under liquid pressure and lumen pressure (conditions that have not been investigated). This paper investigates benefits of switching to thin walled membranes (1.3 mm thick) from the previously used 2.24 mm thick membranes. The thin walled membranes cannot maintain structural integrity under elevated liquid pressure. Also, the thin membranes only slightly increase the oxygen transfer rate. The thick wall membranes are recommended for the optimization of the new full scale MABR, (CoMANDR).Item Determination of groundwater velocity in-situ by using passive samplers at sediment water interface(2011-05) Ponnada, Phani; Jackson, Andrew W.; Rainwater, Ken A.Contaminated bottom sediments are one of the major sources of contaminants in surface water. The contaminants may originated from human activities, enter the subsurface environment through waste disposal, spills, and land application of chemicals. These contaminants get transported through the porewater and may enter the surface water from the bottom sediments. Establishment of effective remediation systems and protection of public health rely on the ability to estimate the mass flux of the contaminants to surface water. The mass flux is a function of porewater velocity, retardation factor, and degradation coefficient. In this research, passive sampler (peepers) were used to determine the groundwater velocity insitu when the mass flux of the contaminants to surface water was low. This study suggested that the ability of the samplers to accurately capture produced tracer profiles depends on the velocity of the flow and equilibration time of the peeper. Low velocities allowed greater time for the sampler to equilibrate, approaching steady state with the pore water. The sampler was able to serve as a tracer source but was not able to provide a large enough flux of tracer to allow downstream locations to approach the source concentration. Regardless, steady state profiles developed rapidly, likely due to the rapid increase in area available for diffusional flux with distance from the source and the limited flux of source from the sampler cell. A sensitivity analysis indicated that, as expected, diffusional transport dominated at very low velocities and that the source dimensions were the critical determinant of the tracer concentration profile shape. Overall, these studies suggest that it may be possible to differentiate groundwater velocity, but that samplers with very low depths would be required (<0.5cm).Item Environmental fate studies of Fullerene C60: Sorption to soil, desorption from soil, biodegradation and plant uptake(2010-08) Narasimhan, Raghavendhran A.; Anderson, Todd A.; Jackson, Andrew W.; Cobb, George P.Buckminster fullerene (C60) is the most representative among all fullerenes. It has been widely studied for its potential applications. Because its use in the medical, electronic, and materials industries is ever expanding, its release into the environment is inevitable. Studying the environmental fate of C60 fullerene is essential in order to better assess its potential for exposure to aquatic and terrestrial organisms. Our goal was to determine the basic environmental fate processes for C60 including sorption to soil, desorption from soil, biodegradation, and uptake into plants. Information on the fate of C60 in the environment and its potential transport to other trophic levels were critical data gaps that we addressed. Aqueous suspensions of 14C-labeled C60 were prepared by two methods 1) extended mixing in water and 2) solvent exchange with THF. The aqueous suspensions of 14C60 were characterized using a filtration experiment. It was observed that the aqueous suspension produced by extended mixing in water did not have aggregates in the nanometer range, whereas a majority (~60%) of aggregates in the aqueous suspension prepared by solvent exchange was in the nanometer range. The aqueous solution prepared by solvent exchange was used for all subsequent fate studies. Sorption and desorption parameters in three different soil types (sandy loam, silt loam, and a loam) were studied using the batch equilibrium method. Koc values for sandy loam (3684.8 mL/g) and silt loam (3719.65 mL/g) showed the expected consistency, while the Koc value for C60 in the loam was dramatically higher (10083.4 mL/g). Desorption from these soil types was determined as a percentage of the sorbed C60. We found maximum desorption from sandy loam (85% at 24 h). The loam and silt loam showed around 35% C60 desorption at 24 h. Plant uptake experiments in sand and a hydroponic substrateshowed very low uptake of C60 (< 10%). 14C60 was distributed in the root > tuber > stem > leaf. Biodegradation of C60 in the sandy loam and the silt loam was monitored for more than a year. No mineralization of C60 was observed. Our results on some basic environmental fate parameters for C60 have helped to fill data gaps related to the potential for fullerene nanomaterials to impact the environment. As is the case in nanomaterials research, there are some uncertainties in the results we obtained owing to the ability of C60 to aggregate and subsequently behave as a particulate.Item Experimental studies and mathematical modeling of simultaneous nitrification/denitrification in membrane-aerated biofilm recators(2010-12) Landes, N; Jackson, Andrew W.; Morse, Audra N.; Moore-Kucera, Jennifer; Long, KevinMembrane-aerated biofilm reactors (MABRs) have emerged as a potential nitrogen removal technology for high-strength, nitrogen dominant waste streams (TOC:N<1, NH4+ > 500mg/L). In particular, the unique properties of a MABR are well suited for extreme and/or isolated environments with carbon limited wastes such as a lunar habitation scenario. Among many other features, the ability of MABRs to degrade carbonaceous and nitrogenous pollutants concomitantly via simultaneous nitrification and denitrification (SND) in a single-stage vessel has posed this technology as a well-suited candidate for space-based water reuse applications. Relatively untouched by current MABR research, nitrogen dominant waste streams have been deemed outside the range for significant SND in a MABR without the supply of exogenous consumables; however, experimental research has not been conducted in order to confirm or disprove this hypothesis. The goal of this current work was to explore the performance limits of treating a space-based waste stream with the MABR technology using experimental studies and mathematical modeling efforts. The experimental studies entailed investigating the performance of a traditionally designed MABR and a modified MABR (mMABR). The mMABR combined oxygen permeable membranes in tandem with inert attachment media theoretically supporting nitrification on the former and denitrification on the latter. The traditionally designed MABR reported average carbon and total nitrogen (TN) removal rates as high as 0.33 g-C/m2-d and 0.14 g-N/m2-d, respectively, whereas the mMABR achieved mean carbon and TN removal rates reaching 0.26 g-C/m2-d and 0.22 g-N/m2-d, respectively. The most notable difference between the two reactors was the ability of the mMABR to support denitrification, which was attributed to the mMABRs combination of co- and counter-diffusion biofilms. The mathematical modeling study aimed to identify the inherent differences that could be propagated by the range of assumed nitrification and denitrification biochemical pathways for one-dimensional membrane-aerated biofilm models. The overarching conclusion reached as a result of this study was that mathematical simulation results vary based upon the assumed biopathway applied to the model. The results of this study were used to understand the underlying processes that occurred during the MABRs treatment of a space-based waste.Item Exposure of contaminants to small mammals collected near a low-level radioactive waste site in the Amargosa Desert, Nye County, NV(2018-08) Cleary, Ryan S.; Anderson, Todd A.; Presley, Steven M.; Jackson, Andrew W.Abstract The Beatty, Nevada low-level radioactive waste (LLRW) site was established in 1962 and has since transitioned to US Ecology, Inc., a company responsible for the conversion of hazardous inorganic wastes to non-hazardous, delisted residues. Throughout the years, this site has been responsible for the storage and disposal of liquid radioactive waste, volatile organic compounds, and polychlorinated biphenyls (PCBs). In an effort to identify contaminant presence and movement from the immediate disposal site to ecosystems in the surrounding areas, a study was developed to asses concentrations of per- and polyfluoroalkyl substances (PFAS), PCBs, various heavy metals, and tritium. To complete this assessment small mammals, insects, vegetation, and soil samples were collected from the area directly surrounding the LLRW site and a reference site located approximately 3 kilometers south of the LLRW site. Samples underwent analysis via LC-MS/MS, GC-MS, ICP-MS, and liquid scintillation spectroscopy depending on analyte of interest. Small mammal tissues showed varying concentrations of PFAS, PCBs, several heavy metals, and tritium. A restricted sample size of insects allowed for analyses of PFAS and PCBs which were both present at low concentrations. PCBs were the primary contaminant found in soil samples, with traces of PFAS and tritium. Little data were obtained from vegetation samples due to the complex matrix of the plant species (creosote bush). These data suggest that various anthropogenic contaminants may be moving from the LLRW to the surrounding areas but additional analyses are necessary to confirm this along with the pathways through which contaminants in this hyper-arid environment move.Item Heterogeneous production of perchlorate and chlorate by ozone oxidation of Cl-(2011-08) Wang, Sixuan; Jackson, Andrew W.; Anderson, Todd A.ABSTRACT Perchlorate (ClO4-) is proved to be of atmospherically produced, it found to be widely spread in environment although in a low concentration. Studies had demonstrated atmospheric ClO4- formation and mechanism of ClO4- formation by UV irradiation and ozone oxidation of Cl- and oxy-chlorine species. They also analyzed environmental condition impacts on perchlorate formation. However, little information is known about ozone oxidation of dry Cl-. This study mainly focused on factors that impact ClO4- formation through ozone oxidation of chloride in the dry condition. Reaction time, mass of initial Cl-, reactor surface area, humidity in the reactor, and the physical form of Cl- are factors that been systematically evaluated in this experiment. The mass of ClO4- formed in the reactor increased roughly linearly (R2 = 0.98; R2 = 0.83) with respect to reaction time. ClO4- mass did not consistently vary with an increase in Cl- mass while ClO3- increased 3 order of magnitude (0.043 μg- 37.93 μg) over the 4 order range of Cl- masses reacted. ClO4- formed mass in the humidity system was similar with it produced in the dry system, however, ClO3- mass increased by 2 orders of magnitude in humidity system compared to dry system. The increase of glass surface area could increase the production of ClO4- in this experiment, it seems like glass tube surface could act as catalyst to accelerate ClO4- formation. ClO4- mass produced by HCl gas was relatively the same with it produced by NaCl salts, so, Cl physical phase do not have impact on ClO4- production.Item Occurrence, distribution, and speciation of arsenic in the Southern High Plains aquifer system(2010-12) Venkataraman, Kartik; Rainwater, Ken A.; Jackson, Andrew W.; Ridley, Moira K.Significant levels of arsenic have been detected in the groundwater of the Southern High Plains. The potential sources include atmospheric deposition, the use of agricultural defoliants and natural subsurface geochemical interactions. To identify the source of arsenic, groundwater and soil samples were collected from sites spread over 18 counties in the Southern High Plains. Total arsenic and its inorganic species were quantified along with commonly occurring and related cations and anions such as iron, manganese and sulfate. Correlation studies were conducted to understand the variation of arsenical species with related parameters. A geochemical modeling tool, MINTEQ was used to predict the speciation of arsenic and compare these results with lab analyses. The distribution of arsenic in the soil profiles tested indicated a positive correlation with depth. The highest concentrations were found close to the water table while the upper soil layers had low to non-detect concentrations. In the groundwater samples, arsenic concentration and speciation varied significantly between sites. As (III) was found to be the dominant species in over 80% of the samples. MINTEQ speciation forecasts compared favorably with a majority of the groundwater analyses. Very little evidence of atmospheric deposition exists and the sources of arsenic are likely anthropogenic land sources in the shallow subsurface and natural geologic processes in the deeper subsurface.Item Optimization of DGT methyl mercury recovery, bank leaching assessment and evaluation of stabilization efforts on mercury fate and transport in freshwater systems(2018-08) Vrtlar, Tea; Reible, Danny D.; Jackson, Andrew W.; Yan, Weile; Ridley, Moira K.Bioavailable mercury (Hg) in the environment is methylated by bacteria to form methyl mercury (MeHg) a bioaccumulative acute neurotoxin. The ability to quantify Hg and MeHg in sediment pore water may allow for better understanding of mercury mobility, bioavailability and toxicity in the environment. Flooding events in South River, VA have been associated with leaching of pore water total mercury from the contaminated river banks, creating a potentially significant source of mercury to the system. In this research the mobility and availability of Hg in these river banks is assessed through diffusion gradient in thin film (DGT) devices to measure pore water Hg and MeHg. This research had four main specific objectives. The first objective was to improve the recovery of MeHg from the DGT devices to ensure quantitative recovery. The second objective was to apply DGTs to measure Hg from the pore water leaching from river banks in the South River during inundation/drainage cycles associated with storm events and the associated potential for methylation by assessing redox conditions and MeHg during these cycles. The third objective was assessment of the ability of stabilization and capping of the river bank to reduce Hg flux. The cap was composed of layers of biochar as a Hg sorbent as well as sand and armoring material. The final objective was to predict long term effects of storm events and bank leaching with and without the stabilization and capping. Studies were done to improve the recovery of MeHg from the DGT resin, resulting in method for extraction of MeHg that improves currently used poorly reproducible extraction recovery in 1-56% range to a reproducible recovery of 91±9%. Field sampling was done at the Constitution Park and North Park in 2015 during baseline conditions as well as during bank drainage after inundation by a storm event. The results demonstrated that storm event associated leaching introduced an order of magnitude increase in pore water total mercury due to drainage from contaminated banks. Stabilization of the bank and placement of a composite cap led to reduction of pore water concentrations and likely Hg fluxes by 1-2 orders of magnitude, depending on the initial level of contamination at different locations. Lastly, the inundation and drainage cycle was simulated using a commercial finite element package, COMSOL®. The simulations demonstrated that leaching predominately (90%) occurs near the bank-water interface and allowed estimation of leaching/seepage fluxes. These results were used to simulate long term chemical containment performance of the composite cap during regular 3 and 6 ft flood events for the next 100 years using CapSim®, a modeling environment designed to simulate contaminant transport at the sediment-water interface. The composite cap was predicted to be effective in reducing the pore water concentration and Hg flux at the cap-water interface by more than 93.5% compared to that estimated without a cap layer in place. The maximum Hg flux associated with the flood events was approximately 0.6 µg/cm^2/yr in the period of 30 to 100 years after the cap implementation.Item PRELIMINARY ASSESSMENT OF CHLOROBENZENES FATE AND TRANSPORT IN SEDIMENT ENVIRONMENT(2016-08-15) Nomaan, Mohammad; Reible, Danny D.; Jackson, Andrew W.Chlorobenzenes are omnipresent environmental pollutants due to their widespread use as a chemical intermediate and solvent. Sediment from a specific site was characterized for monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene and 1,2,4-trichlorobenzene contamination. Adsorption of Chlorobenzenes on commercially available sorbents such as activated carbon (AC), biochar, and organophilic clay were investigated for their potential use for in-situ management and active capping of Chlorobenzene-contaminated sediment. The results show that sorption on AC follows the Freundlich isotherm model whereas, organophilic clay, and biochar exhibit linear sorption properties. AC was found the most sorbing compared to biochar and organophilic clay by about two and four orders of magnitude, respectively. In addition, AC was most affected by natural organic matter (NOM) fouling; the effect of NOM on biochar and organophilic clay was minimal. Data from these studies were used to simulate Chlorobenzenes flux under existing field conditions, as well as, the performance of caps amended with AC, biochar, and organophilic clay. The modeling was done for diffusion control, diffusion-advection (Darcy’s velocity 1 cm/day) and tidal flow system (tidal cycle 12 hours 25 minutes with maximum tidal flow of 100 cm/yr). The effect of bioturbation was also considered. Simulation results suggest that the system with the presence of diffusion-advection is the most critical in terms of flux breakthrough from caps. Only AC amended caps were found to be effective to contain the contaminants for considerable amount of time. The breakthrough time for 15 cm AC layer with 15 cm sand on top and 50% AC amended sand cap is simulated to be about 100 years.Item Sustainable resource recovery in closed loop system(2018-12) Sevanthi, Ritesh; Jackson, Andrew W.; Morse, Audra N.; Millerick, Kayleigh; Anderson, Todd A.; Poch, JohnDemands on water supplies and carbon dioxide emissions are increasing due to population growth. Water scarcity has led to an increasing need for robust waste-water treatment technologies that can be integrated into water reuse systems. Long term space habitation is currently limited by the frequency at which resources can be delivered. Loop closure through regenerative processes is a method to greatly reduce resupply needs. Resources currently reused on the International Space Station (ISS) are limited to water and air revitalization. The technologies used are based on physical and chemical processes some of which are expendable and non-regenerable. Non-regenerable processes require significant supply of the active material to replenish those lost in regeneration. The expansion of human presence in space necessitates a reliable, sustainable, carbon dioxide adsorption system and water source. Water is a critical life support element, representing at minimum, 65% of the daily mass input for crew members. A reliable water source is essential for space habitation. Water recovery allows mission duration to be uncoupled from a dependence on initial water resources or resupply scenarios. However, current water recovery systems require a significant use of consumable resources such as hazardous chemicals needed for urine stabilization. These systems also yield toxic end products that create additional challenges regarding storage or disposal. In contrast, biological treatment uses living cells to recycle energy harnessed from the oxidation of compounds in waste water for cell growth and maintenance, which can result in a sustainable process. Membrane aerated biological reactors (MABRs) provide an efficient and sustainable alternative process for treating a space-based waste stream. Research on the use of biological waste water treatment for space habitation has culminated in the development of the rectangular Counter-diffusion Membrane Aerated Nitrifying Denitrifying Reactor (rCoMANDR) and a graphene based carbon dioxide removal technology at Texas Tech University (TTU). This work demonstrates the ability to treat space-based waste streams using a microgravity compatible biological reactor. We have demonstrated the continuous operation of the reactor over almost 3 years. The CoMANDR system was able to operate in both an oxic mode and anoxic mode. Both modes were able to achieve carbon and nitrogen oxidation although in the anoxic mode performance was reduced and reaction rates were smaller. The anoxic mode did allow for increased reduction of oxidized nitrogen through denitrification. CoMANDR was also able to operate without the need for a feed tank by accepting waste-waters as they are produced with no reduction in efficiency. The system required little if any maintenance although bio-solids did accumulate over the operational period. The system does require O2 as a consumable but at a relatively low rate compared to human consumption. The system also produces some N2 gas, which is a useful product, and CO2, a contaminant that must be removed. In order to efficiently remove CO2 without consumption of resources and in a manner that would facilitate its use as a resource by producing a more concentrated waste gas, graphene based adsorbents were evaluated. Joule heating / electric swing adsorption (ESA) was evaluated as a mode of regeneration. Pristine graphene films and reduced graphene oxide (rGO) aerogels were both tested for their ability to remove CO2. The amount of CO2 captured by graphene films and rGO aerogels was at the upper range of carbon adsorbents and was found to be stable over multiple samples and multiple cycles of adsorption and electrical current stimulated desorption. The use of similar graphene based adsorbents in space-based systems could provide a lower mass adsorbent and more efficient regeneration method.Item The impact of biological pretreatment on reverse osmosis performance in space flight applications(2007-12) Crawley, Jason; Morse, Audra N.; Jackson, Andrew W.; Song, Lianfa; Anderson, Todd A.RO is a treatment technology likely to be used for the recovery of wastewater on board long duration, manned space flights. As with terrestrial RO applications, concentration polarization and fouling lead to decreasing productivity and increasing energy demands with time. These problems are further complicated in a closed loop environment that demands a high level of recovery and quality. Physiochemical and biological pretreatment options can enhance the performance of the RO system. Physiochemical pretreatment is not always desirable in the application of long duration space flight because the transport and stowage of consumables can be cost prohibitive. Also, the transport and stowage of hazardous materials such as strong acids and bases is not desirable. Biological pretreatment is a low energy option that requires only a limited supply of consumables. Additionally, biological pretreatment is a proven terrestrial technology that is well understood. To determine the degree to which the incorporation of biological treatment enhances RO performance, a series of bench scale experiments were performed. The RO performance was measured in terms of permeate flux decline, solute rejection, and flow resistances. A mass balance and observed solute concentrations also helped to determine the fate of selected solutes. The gel layer model was used to evaluate the permeate flux for each of the experiments. Observed resistances also indicate that biological pretreatment alleviates the degree of fouling. Results indicate that enhanced urea hydrolysis, pH decrease, and carbon oxidation serve as the primary benefits of biological pretreatment.Item Uptake, distribution, and fate of RDX and MNX in dark green bulrush plants(2009-05) Sanka, Sameera; Jackson, Andrew W.Constructed wetlands are emerging as a promising technology for remediation of water contaminated with low RDX concentrations. A study on the ability of dark green bulrush (Scirpus atrovirens), a wetland plant, to uptake RDX will help to find its utility in constructed wetlands. In this study RDX uptake in actively growing bulrush was evaluated over a sixteen week period at different RDX exposure levels (0.5, 1, 3 mg/l). Plant samples along with influent water, effluent water, and final soil samples were analyzed for RDX, MNX, TNX and DNX. After 16 weeks of exposure and sacrificing 7 of the 9 sets of plants, exposure to RDX was discontinued. The remaining two sets of plants were sacrificed at weeks 19 and 22. RDX concentration in plants substantially decreased during the period of no exposure. About 97% of the RDX concentration in the top third and 75% in bottom and middle thirds of the leaf was lost during the six weeks of cessation to RDX exposure. RDX uptake in mature bulrush was also evaluated over a six week period at 1 mg/l exposure concentration. RDX was detected at higher concentrations in the top third of the leaf when compared to middle and bottom thirds in actively growing as well as in mature bulrush. MNX was detected in 99% of plant and soil samples. DNX and TNX were detected in few bottom thirds of the leaf and root portions of the bulrush in very low concentrations (0.003 to 0.03 mg/kg), but were very rarely detected in other samples. MNX uptake in mature bulrush was also evaluated over a five week period at 0.5 mg/l exposure concentration. Unaccounted MNX in the treatment systems of bulrush exposed to 0.5 mg/l MNX was around 59% compared to unaccounted RDX of 19, 23 and 38% respectively for 0.5, 1, 3 mg/l RDX exposure treatment systems. No bleaching or necrosis was observed during the course of the experiment in any of the plants. The results are suggesting that RDX exposure up to 3.0 mg/l does not have any adverse effects on bulrush. RDX accumulation in actively growing bulrush increased with time but in mature bulrush RDX accumulation remained more or less constant.Item Utilization of nitrogen from surface and subsurface applied wastewater(2012-12) Francis, Richard; Fedler, Clifford B.; Jackson, Andrew W.; Zartman, Richard E.A pilot test was conducted to determine the difference in nitrogen removal between surface and subsurface applied wastewater systems in soil columns topped with Bermuda grass (cynodon dactylon). Six columns were set up, three with water applied to the surface, and three with water applied in the subsurface through a positive-displacement pump. The concentration of nitrogen was kept uniform within the system with variable loading rates to ensure leaching occurred. The water added and the water leached were tested with HACH(R) test-n-tube kits for total nitrogen, ammonia, and nitrate-N concentrations. A statistical analysis was performed to determine if there were any significant differences in the concentrations of these constituents in the effluents between the two systems. The analysis showed that there was virtually no difference (Pr>F = 0.657) between the two systems in regards to percent of nitrogen removed from the system. The test also showed that subsurface applied systems performed marginally better that surface applied systems in total nitrogen and nitrate-N concentrations in the effluent. There were also virtually no differences (Pr>F = 0.209) in the total Kjeldahl Nitrogen concentrations in the plant tissue.