Browsing by Author "Jackson, Andrew"
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Item Analysis, occurrence, and fate of per- and polyfluoroalkyl substances (PFAS) in pesticides and grocery store produce(2023-12) Yang, Zhao; Guelfo, Jennifer; Jackson, Andrew; Anderson, ToddEvaluating per- and polyfluoroalkyl substances (PFAS) in foods and pesticides presents challenges due to diverse matrices and a lack of standard methods. Prior studies implemented universal methods on different food samples and one-size clean-up methods on pesticide samples, which may yield an underestimation in PFAS concentrations. The objectives were to screen and optimize PFAS extraction methods for matrices, including foods and commercial pesticides, considering internal standard recoveries of 50-150% and matrix spike recoveries of 70-130%; apply optimized method to examine PFAS occurrence in dietary foods and commercial pesticides; exposure assessment based on detections in foods was performed to compare with new released reference doses (RfDs); total PFAS in pesticides were quantified through total oxidizable precursor (TOP) assay and combustion ion chromatography (CIC) techniques; a two-site kinetic model was utilized for simulating long-term applications of PFAS-impacted pesticides on field soil and plants. PFAS were detected in 16/22 food produce with concentrations ranging from 41 ng/kgdw (perfluorobutane sulfonate; washed green beans) to 2680 ng/kgdw (perfluorohexane sulfonate; radish). Concentrations of perfluorooctanoic acid (PFOA) in carrots, lettuce, radish, and canned green beans yielded median exposure intake (EI) values of 0.026-0.240 ng/kgbw-day, which exceeded the EPA RfD (0.0015 ng/kgbw-day). A total of 6 PFAS were detected in the 4/6 pesticide formulations at concentrations of 40 ng/L (6:2 fluorotelomer sulfonate, malathion) - 39123 ng/L (6:2 fluorotelomer sulfonate; spiromesifen). Increases in perfluoroalkyl carboxylates after TOP suggested unknown PFAS may be present in spiromesifen and imidacloprid formulations. Nontargeted MS analysis of these formulations tentatively identified 2 additional PFAS (CAS Nos. 376-27-2 and 2681-00-7) in imidacloprid. CIC analysis of pesticides resulted in 80% recovery of total organic fluorine in matrix spike samples. Simulated model results showed that long-term application of PFAS-impacted pesticides would not be considered as a significant PFAS source for detected PFAS in field soil and plants. But long-term application of current PFAS-impacted pesticides would impact groundwater concentrations. The findings provide a more accurate PFAS profile in diverse matrices, identify potential dietary exposure risks, and shed light on PFAS fate and transport in the environment. These works will be valuable for risk assessment and regulations of PFAS usage.Item Development and standalone testing of a gravity dependent biological reactor(2020-12) Harkins, Christian David; Jackson, Andrew; Millerick, Kayleigh; Gray, EvanLong-duration human spaceflight relies upon recovery of potable water from the wastewater produced during interplanetary missions. For long-term human missions to Mars, a recovery of greater than 98% of potable water from wastewater is the goal of wastewater treatment. This research project demonstrates the use of a Membrane Aerated Biological wastewater Reactor (MABR) as a means to effectively treat space based wastewater to conditions necessary for direct reuse treatment through an Integrated water Recovery Assembly (IRA) in order to produce potable water without the need for chemical stabilization and extensive post distillation treatment as conducted on the International Space Station (ISS). The newly developed system is composed of a gravity dependent MABR (referred to as gMABR or MABR throughout) that serves as the collection tank for all waste streams (ISS, Early Planetary Base (EPB), and Transit) and removes dissolved organic carbon (DOC). This new system also stabilizes the organic Nitrogen (N) by biologically oxidizing it to Nitrogen Oxides (NOx-), which reduces the pH of the waste stream. The IRA as an independent treatment option is incompatible with free Ammonia (NH3) and cannot remove some low molecular weight organics. Integrating the two systems provides a sustainable water recovery system. The research objective is to demonstrate that a MABR can operate with variable volume, allowing on-demand loading and production of effluent compatible with the IRA. The project team designed a MABR for EPB wastewater. The system contains a 0.123 m3 tank containing four self-contained independent membrane modules with a specific surface area of 8.82 m2. The MABR receives wastewater (laundry, shower, hygiene, and urine) as generated during the 16-hour wake cycle, and continuously receives humidity condensate (HC). The system discharges the accumulated volume (~14.8L) once per day, prior to the wake cycle. The system was continuously operated for 16 months. During its operation, the MABR was monitored for pH, dissolved oxygen (DO), DOC, total nitrogen (TN), and NOx, daily and less frequently for total ammonium. The MABR system was tested for loadings of one and 1.25 crew-day of an EPB wastewater with both pulse and continual feeding regimes. The reactor removed 76.6% of the TOC reduction and oxidized 51.8% of the organic N. The treatment provided wastewater with a pH of less than five. There was no clear impact of continuous versus pulse feeding on reaction rates or treatment efficacy.Item Development of a Hybrid Integrated Water Recovery Assembly for Exploration Habitats(48th International Conference on Environmental Systems, 2018-07-08) Finger, Barry; Jackson, Andrew; Pasadilla, Patrick; Zimmerman, BrittanyParagon Space Development Corporation® (Paragon) and our partner Research Institution Texas Tech University (TTU) are developing a game changing spacecraft habitat wastewater recycling system that integrates 1) the TTU Membrane Aerated Biological Reactor (MABR), 2) Nafion Membrane Water Purification (NWP) distillation technology, and 3) Gas-phase Trace Contaminant Removal (GTCR) to realize a low-mass, low-volume, closed-loop, sustainable, and ultra-reliable water recycling and purification system. It is the coupling of these three well-developed and understood processes that is novel and offers a significant advantage over state of the art (SOA) spacecraft water processing systems. When fully developed, the Integrated water Recovery Assembly (IRA) will reduce the need for hazardous chemical pretreat and potentially eliminate the need for aqueous-phase treatment now used to reach potable standards. Further, IRA will reduce waste generation and increase material recycling by converting carbon, hydrogen, and nitrogen species into useful products such as H2O, N2, and CO2 (which can be further processed to recover O2). IRA will be less complex, require far fewer consumables, be more robust, and more sustainable than SOA systems. This paper summarizes the results of work completed during the initial development phase where a subscale demonstrator was manufactured and tested. A preview of the ongoing development and testing of a full-scale demonstrator will also be provided.Item Effects of polycyclic aromatic hydrocarbons in urban stormwater on receiving sediment(2019-08) Athanasiou, Dimitrios; Reible, Danny; Jackson, Andrew; Anderson, Todd A.; Uddameri, VenkateshUrban stormwater runoff has long been identified as a major influence to the contamination of receiving water bodies and sediment. The episodic nature of storms combined with the imperviousness of urban surfaces, lead to stormwater discharges laden with high levels of solids-associated polycyclic aromatic hydrocarbons (PAHs). These compounds pose a concern due to their toxicity, mutagenicity and carcinogenicity, and many of them have been placed on USEPA Priority Pollutant List. The core objective of this study was to determine the physical, chemical and biological characteristics of stormwater runoff form a mixed use urban watershed and determine the distribution and bioaccumulation potential of its effects on the receiving sediment. Historically, stormwater assessment has been focused on loads rather than impacts on sediments and different sampling approaches were needed to characterize those impacts. The experimental approach involved a 2-year sampling plan in Paleta creek at Naval Base San Diego (NBSD) involving a variety of sampling approaches including intensive sampling of individual storms, water and sediment collection before and after the winter rainy season and settling traps collecting depositing sediments throughout the storm season. Storm runoff samples from 2 storms in January 2016 were collected and size fractionated. Receiving sediments were monitored with water column, sediment and sediment trap measurements. Porewater passive samplers and both in-situ and ex-situ bioaccumulation studies using bent-nose clams (Macoma Nasuta) were conducted in cooperation with US Navy personnel to assess the response of the receiving benthos. Total Organic Carbon (TOC) and Black Carbon (BC) contents were measured to better understand the source of the depositing solids as well as to link PAHs in sediments to their bioaccumulation potential. Sediment and tissue was extracted by pressurized liquid extraction (PLE), storm samples were liquid-liquid extracted (LLE) and final analysis was carried out by HPLC-FLD and GC-TQMS. In preparation for the sediment sampling, a study of PLE was conducted in order to develop an in-house method that would allow us to process large amounts of sediment samples in an efficient and accurate way and, in particular, extract PAHs effectively from weathered and high BC sediment samples. The combination of size fractionated stormwater loads with sediment traps were identified as the most effective monitoring tools to assess sediment recontamination. Analysis of stormwater samples showed most of the PAHs were associated with large particles in runoff and led to rapid near field deposition and sediment recontamination. SEM imaging confirmed the presence of large BC-rich particles in the near field traps. However, bioavailability was limited as indicated by bioaccumulation studies suggesting that sediment recontamination assessment should also be coupled with assessment of bioavailability. Porewater concentrations were also shown to correlate well with the observed bioaccumulation suggesting that either bioassays or porewater assessment could characterize bioavailability for PAHs. Parent and alkylated PAH ratios allowed stormwater from this watershed to be separated from sediments settling in areas away from the stormwater discharges.Item Evaluating the influence of capping materials on composition and biodegradation activity of benthic microbial communities: Implications for designing bioreactive sediment caps(2020-08) Pagnozzi, Giovanna; Reible, Danny D.; Millerick, Kayleigh; Jackson, Andrew; Anderson, ToddSediment contamination by polycyclic aromatic hydrocarbons represents a chronic environmental issue and challenges remediation practices. Capping placement contains contamination and minimizes risk of exposure to the benthic community. Biotransformation within sediment caps has the potential to degrade toxic compounds improving efficiency of the remedy. However, little is known about biodegradation within sediment caps. The goal of this work was to elucidate the impact of capping materials on composition and activity of benthic microbial communities using naphthalene as a model contaminant. Specific aims were to: i) summarize current literature and identify gaps of knowledge; ii) examine how biogeochemistry influences the biodegradation of naphthalene in different capping amendments; iii) describe the role of adsorption/desorption and biodegradation processes; iv) ultimately identify capping materials that can promote biodegradation. Microcosms were prepared containing capping materials (sand, organoclay, and activated carbon), sediment enrichments, naphthalene, and terminal electron acceptors. Results and multivariate analyses showed that microbial community shifts were significant with respect to both capping amendments and biogeochemistry for all geochemical conditions examined. Microorganisms linked to PAH biodegradation were enriched under appropriate electron accepting conditions, and the increased abundance positively correlated between genera, suggesting the formation of biodegrading consortia. Under oxic conditions, biofilm formation, naphthalene decay and biomarker levels increased with activated carbon, and naphthalene exerted a strong selective pressure in all systems except clay, where attached growth was not enhanced. Activated carbon stimulated naphthalene biodegradation that would otherwise not occur under strictly sulfate reducing conditions, and mineralization corresponded with enrichment of genera that biodegrade naphthalene (Geobacter and Desulfovirga spp.). Results of this study showed that capping materials influence indigenous microorganisms and can stimulate biodegradation under highly reducing conditions, ultimately providing recommendations for designing bioactive caps.Item Investigations into the Fate and Occurrence of Chlorate in the Environment: Implications for Oxy-Chlorine Species on Mars and Earth(2018-05) Brundrett, Maeghan; Jackson, Andrew; Anderson, Todd; Horita, Juske; Reible, Danny; Yan, WeileClO3- occurrence, production, and post depositional transformation has significant implications to our understanding of chlorine (Cl) cycling and potential biogeochemical reactions on Earth and Mars. However, little information is known on the natural isotopic composition of ClO3- and the post-depositional processes that can reduce ClO3- in the environment. The objective of this study was to develop a method to measure the stable isotope composition (δ18O, δ17O and δ37Cl) of ClO3- and to determine the isotopic composition of ClO3- in natural desert salt accumulations that have been studied previously for NO3- and ClO4-. We also determine the potential abiotic transformation of ClO3- by Fe (II)-bearing minerals, similar to known reactions between NO3- and Fe (II) minerals. Additionally, ClO3-, nitrate (NO3-), and ClO4- were evaluated for use as electron acceptors in comparison to oxygen (O2) by comparing oil transformation and mineralization in mesocosms consisting of oiled salt marsh sediment from an area impacted by the BP Horizon oil spill. The isotopic composition of oxyanions can be used to evaluate their production mechanisms and post-depositional alteration. The process of ClO3- purification and analysis of δ18O, δ 17O and δ37Cl is problematic, but has recently been resolved by adapting previously published methods for ClO4-. Competitive anions (e.g. NO3-, Cl-, ClO4-, and SO4-2) are removed through a series of processes including biological reduction, solid phase extraction, and anion or cation exchange and for the first time we report the natural isotopic composition of ClO3- from Death Valley and the Atacama Desert. As the presence of iron-derived minerals has been established in Antarctica, Martian soils, and chondrite meteorites, batch experiments were conducted by reacting four Fe (II)-bearing minerals (wustite, siderite, magnetite, and green rust) with ClO3- at various pH (4.5, 6.5, 8.9). Chlorate reduction was rapid and generally ClO3- was quantitatively converted to Cl-, establishing a previously unknown abiotic reaction that could reduce ClO3-. In order to determine the potential biotic reduction of oxy-anions during oil transformation, mineralization rates were determined by measuring CO2 production and δ13C of the produced CO2 and compared to transformation evaluated by measuring the alkane/hopane ratios over a 4 month period. Oil mineralization was greatest for the aerated treatments and least for the perchlorate amended. Results of this study will increase our understanding of production and surface reactions that produce and transform oxy-chlorine compounds.Item Long Term Biological Treatment of Space Habitation Waste Waters in a One Stage MABR: Comparison of Operation for N and C Oxidation With and Without Simultaneous Denitrification(48th International Conference on Environmental Systems, 2018-07-08) Sevanthi, Ritesh; Salehi Pourbavarsad, Maryam; Morse, Audra; Jackson, Andrew; Callahan, MichaelAerobic biological stabilization has been previously demonstrated for full size MABR’s (CoMANDR 1.0, CoMANDR 2.0, and R-CoMANDR) over operating periods of ~1 year. These systems have successfully treated a variety of possible habitation waste streams including an ISS (urine + flush and humidity condensate) and Early Planetary Base (EPB) wastewater (urine, flush water, hygiene wastewater, and laundry). Biological stabilization has a number of advantages including: 1) elimination of hazardous pre-treat chemicals; 2) production of NOx species (that can be easily rejected by evaporative or membrane systems); 3) elimination of volatile organic constituents; 4) a low pH effluent that facilitates membrane and distillation processes; and 5) an effluent that produces a better quality and less hazardous brine for water recovery. Previous work has primarily evaluated aerobic operation in which organic carbon and nitrogen is converted to CO2 and NOx-, respectively. An alternative to aerobic operation would be to include anoxic operation to promote denitrification and production of N2 gas. This allows for production of make-up gas as well as reduces the O2 demand and can increase ammonia oxidation efficiency. We evaluated the operation of a full scale (2 crew/day) MABR operated to perform oxidation of organic carbon and nitrogen with and without simultaneous reduction of oxidized N to N2 gas, simultaneous nitrification denitrification (SNDN). The system was challenged with a variety of space habitation wastewaters ranging from an ISS composition to a possible EPB waste stream under both continuous and on-production feeding modes. The system has been operated for over 2.5 years. We report on an overall comparison of aerobic oxidation and SNDN operational regimes to evaluate the system with the best overall attributes to support recycling of space habitation waste streams.Item PFAS Fate and Transport: Passive Sampling, Plant Uptake, and Trophic Transfer(2022-12) McDermett, Kaylin; Jackson, Andrew; Anderson, Todd; Guelfo, JenniferPer- and poly-fluoroalkyl substances (PFAS) are a group of anthropogenic, highly recalcitrant organic compounds consisting of thousands of individual species that are of increasing importance as environmental contaminants. Although PFAS have been in widespread use since the 1940s, several PFAS have recently become contaminants of concern for various health and environmental organizations, including the United States Environmental Protection Agency (US EPA). Recent studies have attempted to gain a better understanding of the toxicity and behavior of PFAS in ecosystems around the world, but there are still many knowledge gaps surrounding PFAS fate and transport in the environment following release or exposure. This dissertation focuses on evaluating PFAS fate and transport through a series of unique, laboratory experiments: First, a high-resolution, diffusive equilibrium passive sampler prototype was designed and deployed to better understand PFAS diffusion mechanisms in subsurface saturated media. Over a deployment period of 28 days, concentrations of several PFAS inside the samplers reached equilibrium with porewater (sampler concentration > 90 percent of porewater concentration). Next, the bioaccumulation potential for PFAS to soil invertebrates was evaluated through a laboratory-scale exposure experiment. This study focused on two different consumption pathways in a population of crickets (Acheta domesticus): individuals consuming PFAS-contaminated alfalfa and individuals consuming PFAS-spiked drinking water. Alfalfa accumulation of PFAS and subsequent consumption by the crickets resulted in overall similar tissue concentrations to the crickets who consumed PFAS-spiked water directly and indicates that source concentration (water) may be an important factor in assessing bioaccumulation of PFAS in organisms. Lastly, PFAS distribution in an agricultural water re-use scenario was evaluated through a field study to investigate potential PFAS exposure by using treated effluent wastewater for irrigation activities. Results indicate that treated effluent re-use may not pose a high risk of exposure to ecosystems for some PFAS, but there are other PFAS present in the effluent water which may need to further study before accurately estimating risk to the environment. Overall, the work presented in this dissertation helps to better understand PFAS fate and transport in a variety of scenarios that are critical to understand if we aim to reduce the risk of PFAS exposure to the environment or human populations.Item Quantification, Transformation and Recovery of Per and Poly Fluoroalkyl Substances (PFAS) during In situ Treatment of Impacted Soils(2022-12) Guelfo, Jennifer; Crimi, Michelle; Reible, Danny; Jackson, AndrewPer- and polyfluoroalkyl substances (PFAS) are persistent man made organic compounds used in a variety of products and applications such as aqueous film forming form (AFFF), food packaging, pesticides, and oil and water repellent coating. Application of AFFFs in fire training and emergency response sites is one of the primary sources of PFAS contamination to soil and groundwater. AFFF formulations include anionic, zwitterionic and cationic PFAS. Depending on the manufacturer and year of production, they may contain PFAS produced by either electrochemical fluorination (ECF) or fluorotelomerization. Whereas perfluoroalkyl substances such as perfluoroalkyl acids (PFAAs) do not degrade in the environment, polyfluoroalkyl substances (precursors) transform to terminal PFAAs by biotic and abiotic activity. Stronger sorption of cationic and zwitterionic polyfluoroalkyl substances in source zone soils, combined with slow biotransformation to PFAAs can represent a long-term source of PFAAs to the saturated zone. The objective of this work was to evaluate the potential for in-situ chemical oxidation (ISCO) and biosparging to enhance transformation of stronger-sorbing PFAS to more mobile, terminal PFAAs so that total PFAS can more readily be recovered during pump and treat remediation of AFFF impacted groundwater. Design, implementation, and monitoring of PFAS remediation approaches evaluated herein relies on the ability to evaluate the composition and concentration of total PFAS in soil and groundwater. This study utilized target analysis, total oxidizable precursors (TOP) assay, suspect screening coupled with semiquantitative (SQ) concentration estimates, and two soil extraction techniques to optimize estimation of total PFAS concentration in environmental media. Results showed applying the TOP assay followed by SQ analysis on post TOP samples may result in more representative of total PFAS concentration. However TOP is a bulk assay, so when project objectives include evaluation of the individual PFAS present, suspect screening with SQ analysis can be used to determine the individual PFAS present and estimate their concentrations. Extraction techniques were applied on 3 AFFF impacted soils, and results showed the comprehensive extraction approach led to 35% higher total PFAS concentration and improved extraction of cationic/zwitterionic suspect PFAS in one soil. However, the acidic solvent used in the comprehensive approach resulted in higher matrix effects which impacted estimation of PFAS concentrations using suspect screening with SQ analysis. So overall, it was determined that there was not an advantage to routine application of the comprehensive extraction method to all PFAS-impacted soils. Once sample preparation and analytical techniques were finalized, the present study applied chemical oxidation to treat AFFF impacted soils using batch and column experiments with the objective of evaluating precursor degradation and total PFAS mobilization using persulfate. Results of both batch and column experiments suggested that persulfate pre-treatment could be used as an effective flushing technique to enhance total PFAS recovery from impacted soils during groundwater extraction. Results of batch and column experiments were consistent, but column studies using two AFFF impacted soils were conducted to confirm batch experiment results under more field relevant conditions. Whereas nearly complete precursor transformation was seen in batch systems treated with heat activated persulfate, columns treated with the same approach showed partial precursor oxidation, suggesting that ISCO parameters such as oxidant dosage and number of oxidation pulses needs to be optimized for each site. Batch and 1-D column test were also used to evaluate the effect of oxygen infusion on precursor biotransformation of precursors to PFAAs and any resulting changes to PFAS mass transport in groundwater. Batch tests were conducted on an AFFF impacted soil, and oxygen was sparged directly into a soil water slurry. Results showed faster degradation of precursors in oxygen sparged reactors resulted in faster desorption of PFAS in aqueous phase in relative to control reactors. In order to evaluate change in PFAS mass transport during in-situ biosparging, columns packed with two AFFF impacted soils were injected with oxygen sparged artificial groundwater (AGW). Due to the gas permeability of the column tubing, DO concentrations in column influent were lower than in the directly sparged batch reactors, however, DO in air sparged columns was still higher than ambient control columns. Analysis of effluents showed no change in total PFAS recovery due to biosparging. However, analysis of PFAS remaining column soils after experiments were completed showed that less PFAS mass was retained in oxygen sparged columns and suggesting that higher oxygen concentration might result in more biotic or abiotic precursor transformation. Findings of this study set the stage to scale this techniques up to pilot and eventually field scale approaches that can be used to improve the efficiency of remediation of PFAS-impacted groundwater. Specifically, current treatment techniques that are capable of PFAS destruction rely on extraction of groundwater and ex situ treatment, so techniques investigated herein may be beneficial to improve the efficiency of the PFAS extraction process. Specifically, it may reduce the duration of pumping required for effective total PFAS extraction, thus lowering the time, energy, and cost associated with pumping and remediation system maintenance. Although results suggested that ISCO had was more effective in transforming and mobilizing PFAS, this technique may not be appropriate at all field sites due to factors such as the potential for altering subsurface geochemistry. In such situations, biosparging may still be considered, although this method needs further evaluation to establish potential as a flushing approach. Results herein also have important implications for legacy sites where these approaches have been applied to remediate co-occurring contaminants such as chlorinated solvents and hydrocarbons. At these sites, it is possible that unintentional precursor transformation and PFAA mobilization occurred, which highlights the importance of understanding detailed site history when evaluating and prioritizing PFAS-impacted sites.Item Semi-conductive materials for engineered bioremediation: From surface properties to microbial diversity(2021-12) Redwan, Asef Mohammad; Millerick, Kayleigh; Jackson, Andrew; Gray, Evan; Yan, WeileEngineered bioremediation has gained attention in recent years as a speedy and efficient option for environmental pollution control. Solid materials can speed up in situ bioremediation processes because they offer a platform for microbial attachment and immobilization, and serve as electron donor and energy source, acceptor, and/or redox mediator to promote biological reaction rates. These materials can impact microbial community composition, behavior, and growth. This work evaluates anaerobic bacterial responses to two different semi-conductive materials used in subsurface remediation, granular activated carbon (GAC) and zerovalent iron (ZVI), with the goal of elucidating relationships between material properties and microbial activity. GAC studies investigate the influence of solution chemistry and surface oxidation treatments, mimicking natural weathering processes, on Geobacter sulfurreducens strain PCA’s ability to colonize GAC and utilize the material as a solid-phase electron acceptor. Results show that surface oxidation most significantly affects PCA catabolism at elevated pH, compared to neutral or acidic pH conditions. Effects of GAC oxidation are most pronounced for highly weathered GAC under growth conditions. However, similar improvements in respiration and biological growth rates are not observed using a freshwater sediment-derived enrichment consortia containing PCA and active sulfate reducers. These findings provide evidence that increased GAC oxidation promotes enrichment of Geobacter under unfavorable aqueous conditions (high pH) only if strong reductants (sulfide) are absent. ZVI studies compare the impact of sulfidated and non-sulfidated ZVI particles on bacterial culture Desulfovibrio desulfuricans and sulfate-reducing enrichment culture AMR-1. Experiments with D. desulfuricans show that sulfidation of the particles can significantly (p < 0.05) decrease rates of sulfate reduction, but the extent to which respiration rates decline depends upon whether ZVI is pure and nanoscale (nZVI) or mesoscale with impurities (Peerless). When AMR-1 is present, non-sulfidated nZVI enriches Archaea, yet sulfidated nZVI does not promote methanogenic growth. Both sulfidated and non-sulfidated Peerless particles suppress methanogens and maintain the richness and diversity of the consortia. Our results indicate that ZVI source material may be more influential than surface sulfidation on the enrichment and behavior of sulfate-reducing bacteria. Overall, this work shows that tailoring surface properties of semi-conductive materials can influence microbial enrichment and biotransformation reactions under appropriate environmental and microbial conditions. These findings address critical knowledge gaps related to microbial responses to material amendments, critical frontiers in establishing solid-phase amendments as an effective and reliable bioremediation strategy.Item Sodium Chloride Removal from International Space Station Wastewater Brine to Generate Plant Fertilizer(50th International Conference on Environmental Systems, 7/12/2021) Irwin, Tesia; Diaz, Angie; Li, Wenyan; Lunn, Griffin M.; Koss, Lawrence; Wheeler, Raymond; Callahan, Michael; Jackson, Andrew; Calle, Luz M.Water is a critical resource for human exploration beyond low earth orbit. There are two general mechanisms for wastewater recovery. The current practice on the International Space Station (ISS) is vapor compression distillation, which requires a significant amount of consumables and has a water recovery rate of around 75%. An alternative approach is a biological water processor (BWP), integrated with a forward osmosis secondary treatment system (FOST). The integrated system is expected to recover 95% of the initial wastewater volume. The remaining 5% is lost as a concentrated brine. For a closed-loop water recovery system, all nutrients should be recovered and reused. For far-term life support, plant systems will be introduced to grow in situ foods, as well as to regenerate O2 and remove CO2 from cabin air. To do so will require a continuous flow of nutrients or fertilizer. The wastewater brine provides a rich source of nutrients for plants, but its high sodium content presents a challenge for most food crops. Direct recycling of urine to crops for life support was tested in Bios-3 (Russia) and resulted in salinization of growth systems. Halophytic plants have been tested with high Na inputs but their yields are low. A thermal swing process has been proposed to separate NaCl from other salts in wastewater for use as plant fertilizer. The paper reports the initial proof of concept testing results, which showed that the thermal swing process is a promising approach for NaCl reduction from wastewater, as well as the tasks planned for further development.Item Surface Modification of Commercial Zero Valent Iron (ZVI) for Degradation of Chlorinated Ethenes(2018-05) Islam, A.S.M. Syful; Yan, Weile; Millerick, Kayleigh; Jackson, AndrewIt has been shown in several recent studies that sulfidation enhances the reactivity of nanoscale zero-valent iron (nZVI) for dechlorination of chlorinated ethenes. The majority of these studies have been carried out using lab synthesized nZVI particles via borohydride reduction method. Sulfidation of commercially available zero valent iron (ZVI) has scarcely been studied. Given the widespread application of commercial ZVI products (e.g., ZVI granules, filings or powder) in remediation field installations, the use of sulfidation to enhance the reactivity of commercial ZVI in degrading chlorinated contaminants is of growing interest to remediation researchers and practitioners. To address this necessity, the effects of sulfidation on dechlorination performance of five different commercial ZVI particles were assessed using trichloroethene (TCE), tetrachloroethene (PCE), and cis-1,2-dicchloroethene (cis-DCE) as model contaminants. Alfa Aesar iron powder (spherical, <10 micron, 99.9+% (metals basis)), BASF Carbonyl Iron Powder (CIP) OM and CC grade, HEPURE Ferox-PRBTM zero valent cast iron powder, and Peerless zero valent cast iron were employed in this study. They were referred to as AA, B-OM, B-CC, HPR, and PLES, respectively. Sulfidation of ZVI was done either by soaking particles in sulfur precursor solutions (referred to as “direct sulfidation”), or by pre-washing the particles in diluted hydrochloric or acetic acid before mixing with sulfur precursor solutions (referred to as “sulfidation”). Sodium thiosulfate was used to prepare sulfur precursor solutions, and S/Fe molar ratio was fixed at 0.05 for all the batch experiments. As a control, as-received ZVI materials or those washed in acid solutions without further exposure to sulfur amendments were prepared as well. The chemically treated ZVI particles were reacted with model contaminants in batch reactors with headspace. The headspace of the batch reactors was sampled periodically to quantify parent compounds, reaction intermediates, and products. Results of the batch experiments indicated that sulfidation of commercial ZVI significantly enhanced TCE reduction rates compared to the respective as-received ZVI products (i.e., no acid washing and/or sulfidation treatments). The apparent mass normalized pseudo-first-order TCE degradation rate constants of sulfided AA, B-CC, HPR, and PLES ZVI particles were 1.77, 1.02, 0.682, and 6.29 x 10-5 L/g-min respectively, which were 53.2, 54.3, 4.6, and 118 folds higher respectively than that of the untreated particles. TCE reduction rate constant for B-OM was 2.39 10-5 L/g-min, which was 1.9 folds higher compared to direct sulfidation. TCE degradation by all five ZVI yielded similar products including ethene and ethane as dominant products. No chlorinated intermediate was detected, except that very small amount of cis-DCE was detected during TCE degradation by sulfided and direct sulfided B-OM, and sulfided AA particles. Compared to significant improvements in TCE dechlorination rates, PCE and cis-DCE dechlorination rates were enhanced to smaller extents by the sulfidation of commercial ZVI used in this study. Mass normalized pseudo-first-order PCE degradation rate constants of sulfided AA, B-OM, and HPR ZVI particles were 2.74, 1.65, and 2.46 x 10-6 L/g-min, respectively, and cis-DCE degradation rate constant of sulfided AA, B-OM, and HPR ZVI particles were 1.33, 0.76, and 0.21 x 10-6 L/g-min, respectively. In the last part of this study, the effect of metal impurities on ZVI reactivity for the degradation of PCE and cis-DCE was also evaluated. Experimental results showed that copper amended particles enabled higher degradation rates for both PCE and cis-DCE compare to unamended ZVI. Nickel amended ZVI increased PCE removal rate, but was ineffective for cis-DCE. Manganese amendment did not show any improvement in removal of either PCE or cis-DCE. Lastly, sulfidation was conducted on Cu-amended B-OM ZVI for PCE degradation. Data revealed that sulfur is able to poison the catalytic effect of Cu and significantly slow down PCE reduction. Therefore, the effect of sulfidation on reactivity of commercial ZVI is selective to the type of contaminants and importantly, depends on their chemical compositions and nature of impurities, which are strongly affected by their manufacturing routes.Item The multipactor effect in rectangular waveguides(2021-05) Shaw, Zachary Charles; Neuber, Andreas A.; Dickens, James C.; Joshi, Ravindra P.; Jackson, AndrewThe multipactor effect is studied at length in rectangular waveguide geometries akin to WR-284. A test section utilizing a plug and play method was designed and implemented in order to carry out measurements with multiple test gaps. While many studies implement the use of global detection methods, usually in the form of phase and/or power monitoring, this test cell utilizes both local and global detection methods. An electron multiplier tube is used as the local detection method in order to view electron multiplication events with ns resolution in order to better understand the effects multipactor has on high Q structures. Multipactor was measured at 2.85 GHz with input powers fed into the test section ranging from single kW to MW. Measurements are reported for 'as processed' copper samples, as well as said samples undergoing an in situ bakeout. Comparison of measurements post bakeout coincided with literature in the desorption of surface contaminants contributing to an increase in secondary electron yield fi rst crossover point as compared to its 'as processed' counterpart. While lower thresholds for the multipactor effect were found for the samples, the reported data suggests that there is no theoretical upper limit in rectangular waveguide geometries due to the propagating modes electric fi eld distribution. As power was increased far past the requirements for first order multipactor, a temporal separation of the forward power detuning signal from the electron growth signal was observed, suggesting that at high power levels multipactor conducive regions shift towards the broadside walls of the waveguide, due to the field distribution of the dominant TE10 mode.Item A Two-Stage Biological Reactor for Treatment of Space Based Waste Waters(48th International Conference on Environmental Systems, 2018-07-08) Salehi Pourbavarsad, Maryam; Sevanthi, Ritesh; Ducon, Daniela; Morse, Audra; Jackson, Andrew; Callahan, MichaelPrevious works on Membrane Aerated Biological Reactors (MABR) CoMANDR 1.0, CoMANDR 2.0, and R-CoMANDAR have demonstrated their ability to stabilize various space based waste streams over operating periods of ~1 year. Biological stabilization includes reducing the pH, conversion of organic N to NOx- and oxidation of dissolved organic matter to CO2. These processes produce a more stable waste product (brine), facilitate distillation processes, and enable evaporative or membrane based systems. An alternative to aerobic operation would be to include anoxic operation to promote denitrification and production of N2 gas. This results in a reduced O2 demand and increases ammonia oxidation efficiency. Denitrification can be accomplished in either a single reactor (Simultaneous Nitrification Denitrification) or in a two-stage system with separate aerobic and anoxic reactors. We evaluated the performance of both architectures in pilot scale systems (1-2 crew/d). Each system was continuously operated for over 2 years during which they processed a variety of habitation waste streams including ISS (International Space Station), Transit, and EPB (Early Planetary Base) in both a continuous and on production feed mode. Here we report the results of the two stage system. Results indicate that the two stage system can successfully remove organic carbon, lower pH and convert organic N to N2 gas. Organic carbon and organic N oxidation reaction rates for the two stage system are similar to past studies for single stage aerobic systems. The two stage system is more complex and requires an additional pump. While no maintenance was required on the system during the nearly two year period of operation, the packed bed did produce N2 gas for many operational test points. The performance and comparison of operational conditions are detailed below.Item Use of Alternative Water Sources(Texas Department of Transportation, 2005-10) Rajagopalan, Srinath; Morse, Audra; Fedler, Clifford; Jackson, Andrew; Jayawickrama, PriyanthaItem WRC Newsletter (Oct 2001)(Water Resources Center, 2001-10) Jackson, Andrew; Thompson, David; Morse, Audra; Crabtree, Greg; Rainwater, Ken