Browsing by Author "Diaz, Angie"
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Item Effects of Surface Treatments on Stainless Steel 316 Exposed to Potable Water Containing Silver Disinfectant(49th International Conference on Environmental Systems, 2019-07-07) Li, Wenyan; Buhrow, Jerry; Diaz, Angie; Irwin, Tesia; Calle, Luz; Callahan, MichaelSilver has been selected as the forward disinfectant candidate for potable water systems in future space exploration. To develop a reliable antibacterial system that requires minimal maintenance, it is necessary to address relevant challenges to preclude issues for future missions. One such challenge is silver depletion in potable water systems. When in contact with various materials, silver ions can be easily reduced to its metallic state or form insoluble compounds. The same chemical properties that make silver a powerful antimicrobial agent also result in its quick inactivation or depletion in various environments. Different metal surface treatments, such as thermal oxidation and electropolishing, have been investigated for their effectiveness in reducing the depletion of silver disinfectant from potable water. However, their effects on the metal surface microstructure and chemical resistance have not often been included in the studies. This paper reports the effect of surface treatments on SS316 exposed to potable water containing silver ion disinfectants. Early experimental results showed that thermal oxidation, when compared to electropolishing, resulted in a thicker oxide layer and a compromised corrosion resistance of the SS316.Item Investigation into Simulated Microgravity Techniques Used to Study Biofilm Growth(51st International Conference on Environmental Systems, 7/10/2022) Diaz, Angie; Li, Wenyan; Irwin, Tesia; O'Rourke, Aubrie; Calle, Luz; Hummerick, Mary; Khodadad, Christina; Gleeson, Jonathan; Callahan, MichaelBacterial growth in liquid media in microgravity conditions is not well understood. Trends such as a shortened lag phase, longer log phase, slower growth rate, and a higher final population concentration have been noted but the underlying cause remains unclear. At the single cell level, it is predicted that bacteria are less gravity-sensitive than larger species. The effects on their immediate environment, including the lack of cell settlement and slower mass transfer of nutrients due to lack of density driven convection, could help explain the trends. Ground-based spaceflight analogs, or simulated microgravity devices, are often employed to achieve different attributes of weightlessness to study effects on bacterial growth. Though these technologies could isolate gravity�s role in various biological processes, they cannot replicate all its effects and underlying mechanisms. Hence, interpretation of results could be misleading, even if similar to spaceflight. In this study two common simulated microgravity devices were investigated to determine whether they could simulate relevant microgravity conditions for bacterial growth. A bioreactor, the high aspect ratio vessel (HARV), was used with dyes of different density mounted on a random positioning machine (RP machine) or a rotating wall vessel (RWV). The RP machine displayed higher mixing rates than the RWV. The RWV was further tested at different rotations per minute (RPM). The range to minimize effects of density driven convection (low speeds) or centrifugal forces (high speeds) was between a range of 15-20 RPM. These results will help inform the selection of simulated microgravity device as well as interpretation of subsequent biofilm growth results.Item Investigation of Biofilm Formation and Control for Spacecraft - An Early Literature Review(49th International Conference on Environmental Systems, 2019-07-07) Diaz, Angie; Li, Wenyan; Calle, Luz; Callahan, Michael; Irwin, TesiaBacterial biofilms are an important and often problematic aspect of life on earth and in space. Biofilms of opportunistic pathogenic bacteria can lead to severe and costly contamination problems that directly affect human health and long-term mission planning. Microbial contamination on board the International Space Station (ISS) continues to pose mission risks, both to crew health and hardware reliability. In order to optimize the design of future space exploration vehicles, a thorough understanding of biofilm formation and control technologies is needed to control the habitat’s microbial environment. This paper provides a literature review on microbial behavior, biofilm formation in spacecraft or simulated spacecraft environments, and the state of the art of biofilm prevention mechanisms.Item A Literature Review of Antifouling Surfaces and Treatments for Long-term Synergistic Biofilm Control(2020 International Conference on Environmental Systems, 2020-07-31) Diaz, Angie; Li, Wenyan; Irwin, Tesia; Calle, Luz; Callahan, MichaelBiofilm prevention and control are needed for spacecraft water storage and distribution systems for long duration exploration missions. One way of preventing biofilm formation involves the use of surface treatments. However, antifouling surfaces have a limited lifespan because microbes alter the surface properties and reduce their antifouling function over time. Surface treatment requires a maintenance strategy to extend the lifespan of the antifouling surface. This study aims to give an overview of state-of-the-art technologies for antifouling and maintenance methods that can be considered when developing Synergistic Biofilm Control (SyBiCo) method for spacecraft water systems.Item Literature Review of Disinfection Techniques For Water Treatment(2020 International Conference on Environmental Systems, 2020-07-31) Azim, Nilab; Diaz, Angie; Li, Wenyan; Irwin, Tesia; Calle, Luz; Callahan, MichaelWater treatment is a developing concern, both terrestrially and in spacecraft, as exploration missions extend in time and distance. Current biofilm control is limited for long-term applications. To optimize biocides for present and future space exploration vehicles, a thorough understanding of common and traditional disinfectant techniques is required. This review is focused on the three fundamental disinfection techniques: chemical, physical, and biological. Mechanisms, advantages, disadvantages, and specific properties of each major technique, as well as their studied effect on established biofilms, are also considered. This paper provides a general background on disinfectants and some information on effects on biofilms that can be useful to develop innovative ideas for state-of-the-art disinfection techniques for water treatment in specific environments, such as those currently posing mission risks as well as for future spacecraft water system development.Item Long-Term Survival of Bacteria under Dormancy Conditions: A Preliminary Review(50th International Conference on Environmental Systems, 7/12/2021) Li, Wenyan; Diaz, Angie; Irwin, Tesia; Calle, Luz; Velez Justiniano, Yo-Ann; Angle, Geoffrey; Johnson, Alexander; Callahan, MichaelBiofilm mitigation and biomass control can be challenging in wastewater processing systems, such as those onboard the International Space Station (ISS). Understanding bacterial behavior, under dormancy conditions, becomes critical as mission duration extends and long periods of dormancy become an integral state of the wastewater system. The objective of this review on the current state of knowledge on the long-term starvation and survival behavior of bacteria is to provide a useful insight for the ongoing long-term bacterial dormancy studies.Item Microgravity Effect on Bacterial Growth: A Literature Review(51st International Conference on Environmental Systems, 7/10/2022) Li, Wenyan; Diaz, Angie; Irwin, Tesia; Orourke, Aubrie; Calle, LuzGravity is a well-known, but little understood, physical force. It interacts with other physical environmental factors to impact the formation of today's Earth, and to contribute to biological variations between water and land species. It is also involved with cell differentiation process, and is responsible for setting the boundaries for life and keeping the cells small. With their simple structures and small sizes, microbes are expected to be less gravity sensitive than larger species. Nevertheless, various effects of space flight on bacterial growth have been reported, but the reports have been sometime inconsistent, and the underlying mechanism remains unclear to many. This paper summarize the systematic efforts to evaluate the effect of space flight on microbial growth, while highlighting the extracellular mass transfer mechanism: bacterial growth is a function of intracellular and environmental factors; the availability of the nutrients and the removal of metabolic by-products, through extracellular mass transfer, are the most important ones. Gravity results in cell settlement and induces density-driven convection within the fluid media, thus impacts the bacterial growth indirectly through the extracellular mass transfer process; where the immediate, direct influence of gravity might otherwise deem negligible.Item Mitigation of Biofouling in Plant Watering Systems Using AgXX, a Novel Surface Treatment(2023 International Conference on Environmental Systems, 2023-07-16) Irwin, Tesia; Li, Wenyan; Diaz, Angie; Hummerick, MaryThe development of plant growth systems with high yield and low maintenance for food production is a key focus area for NASA. One of the remaining technical challenges is keeping the plant watering systems clean without affecting plant growth, requiring consumables, or demanding crew time. Plant watering systems, such as the one onboard ISS, provide a nutrient rich environment for biofilm formation. Frequent maintenance is necessary to prevent biofouling, which currently requires crew time and mechanical means of cleaning. Better solutions are needed. The current ISS practices for biofilm mitigation in the water recovery and distribution system include the use of biocides (silver ion or iodine) along with regular maintenance (e.g. flushing, filter replacement). These biocide-based strategies could be problematic for plant watering systems, such as Ohalo, Exploration Garden, and APH, due to incompatibilities of the biocides with plants. We propose the application of AgXX, a novel antifouling surface treatment that meets the above requirements. This paper will report on an initial study that was completed to determine whether AgXX would be effective in a plant nutrient solution, and whether or not it would negatively impact plant growth in an aquaponics-type system.Item A Preliminary Modeling Study of Biofilm Accumulation in the Water Recovery System(2020 International Conference on Environmental Systems, 2020-07-31) Diaz, Angie; Li, Wenyan; Irwin, Tesia; Calle, Luz; Angle, Geoffrey; Velez Justiniano, Yo-Ann; Nur, Mononita; Callahan, MichaelBacterial biofilms are ubiquitous in wastewater systems on earth and in spacecraft, such as in the International Space Station (ISS) wastewater processing assembly (WPA), where they cause problems in the tank, solenoid valves, and pipelines. Downstream filter applications, tank cycling, and regular biocide water flushing have been used to control biofilm accumulation on board the ISS. Biofilm control is expected to be a challenge for long-term missions with a dormancy period of up to a year, as stagnant water systems are highly susceptible to biofilm growth. Flushing of the system with biocidal water has been proposed to avoid biomass problems for long-term missions. To validate the proposed flush method, a mathematical model, based on the metabolism maintenance rate of bacteria, is being developed to understand the current biofilm accumulation rate in the ISS WPA system and to calculate the biomass production rate under dormancy-like conditions. This method of quantification of biofilm can be applied as a function of nutrient inputs to guide the selection and optimization of biofilm mitigation approaches. The method can also be helpful in understanding, defining, quantifying, visualizing, and simulating the state of the water processing system during operation and after dormancy.Item Silver Foam as Long-Term Passive Biocide to Potable Water Systems(49th International Conference on Environmental Systems, 2019-07-07) Irwin, Tesia; Li, Wenyan; Buhrow, Jerry; Diaz, Angie; Calle, Luz; Callahan, MichaelSilver is being considered as the biocide for future exploration missions. Maintaining microbial control in spacecraft potable water storage and delivery systems is a significant challenge for long-duration human space exploration. The current electrolytic-based silver ion dosing system still has some challenges to be addressed and there is a need for a reliable passive silver biocide delivery mechanism. This paper describes the early stage development of a silver-based composite foam as an alternative silver dosing release technology, either to be used as a standalone, or in conjunction with the electrolytic-based systems to increase the overall system reliability. Composite foam, containing silver chloride nano particles, was synthesized and its structural properties and silver ion release rate are being optimized. This paper concerns the design, synthesis, and optimization of the silver composite foam.Item Silver Foam: A Novel Approach for Long-Term Passive Dosing of Biocide in Spacecraft Potable Water Systems -- Update 2022(51st International Conference on Environmental Systems, 7/10/2022) Irwin, Tesia; Li, Wenyan; Diaz, Angie; Calle, Luz; Callahan, MichaelA spacecraft water disinfection system, suitable for extended length space exploration, should prevent or control the growth of microbes, prevent or limit biofilm formation, and prevent microbiologically influenced corrosion. In addition, the system should have minimal maintenance requirements, be chemically compatible with all materials in contact with the water, be safe for human consumption, and be suitable to be shared across international spacecraft platforms and mission architectures. Silver ions are a proven broad-spectrum potable water biocide under investigation for future exploration missions. The competing technology for dosing silver ions in future water systems is based on actively dosing the ions via electrolytic production. Several challenges with this approach have prompted additional investigations into alternative dosing techniques. Control-release technology is an attractive option for developing a high-reliability passive silver dosing device. This paper describes the continued development of a nanoparticle/polyurethane (NP/PU) composite foam for the controlled release of silver ions, and is intended to build upon the 2021 International Conference on Environmental Systems (ICES) paper number 116. This paper provides the technical background and performance results (wash testing and ongoing long-term silver ion release testing) from the silver chloride (AgCl) NP/PU composite foams. The ultimate goal of the project is to develop a stable and reliable passive dosing silver ion release device for use in future spacecraft potable water systems.Item Silver Foam: A Novel Approach for Long-Term Passive Dosing of Biocide in Spacecraft Potable Water Systems – Update 2020(2020 International Conference on Environmental Systems, 2020-07-31) Irwin, Tesia; Li, Wenyan; Diaz, Angie; Calle, Luz; Callahan, MichaelA spacecraft water disinfection system suitable for extended length space exploration missions should prevent or control the growth of microbes, prevent or limit biofilm formation, and prevent microbiologically-influenced corrosion. In addition, the system should have minimal maintenance requirements, the effluent should be chemically compatible with all materials in contact with the water, be safe for human consumption, and suitable to be shared across international spacecraft platforms and mission architectures. Silver ions are a proven broad spectrum biocide and the chosen potable water biocide for future exploration missions. The leading technology for actively dosing silver in future water systems is based on electrolytic production. Several challenges remain with this approach which have prompted additional investigations into alternative dosing techniques. Control-release technology is an attractive option for developing a high-reliability passive silver dosing device. This paper describes the development of a nanoparticle (NP)/polyurethane (PU) composite foam for the controlled release of silver ions, and is intended to build upon the 2019 International Conference on Environmental Systems (ICES) paper of the same name. In this paper, the technical background and results from the updated nanoparticle (AgNPs)/PU composite foam synthesis and property testing is provided. The ultimate goal of the project is to develop a stable and reliable passive dosing silver ion release device for use in future spacecraft potable water systems.Item Silver Foam: A Novel Approach for Long-Term Passive Dosing of Biocide in Spacecraft Potable Water Systems – Update 2023(2023 International Conference on Environmental Systems, 2023-07-16) Irwin, Tesia; Diaz, Angie; Gooden, Jennifer; Hummerick, Mary; Li, Wenyan; Azim, Nilab; Essumang, Deborah; Callahan, MichaelA spacecraft water disinfection system that suitable for extended length space exploration, should prevent or control the growth of microbes, prevent or limit biofilm formation, and prevent microbiologically influenced corrosion. In addition, the system should have minimal maintenance requirements, be chemically compatible with all materials in contact with the water, be safe for human consumption, and be suitable to be shared across international spacecraft platforms and mission architectures. Ionic silver is a proven broad-spectrum potable water biocide under investigation for future exploration missions. The competing technology for dosing silver ions in future water systems is based on actively dosing the ions via electrolytic production. Several challenges with this approach have prompted additional investigations into alternative dosing techniques. Controlled-release technology is an attractive option for developing a high-reliability passive silver dosing device. This paper describes the continued development of a nanoparticle/polyurethane (NP/PU) composite foam for the controlled release of silver ions, and is intended to build upon the 2022 International Conference on Environmental Systems (ICES) paper number 97. This paper provides the technical background and performance test results of ongoing long-term silver ion release testing, microbial check valve (MCV) function, and disinfection function during system dormancy from the silver chloride (AgCl) NP/PU composite foams. The ultimate goal of the project is to develop a stable and reliable passive dosing silver ion release device for use in future spacecraft potable water systems.Item Silver Foam: A Novel Approach for Long-Term Passive Dosing of Biocide in Spacecraft Potable Water Systems � Update 2021(50th International Conference on Environmental Systems, 7/12/2021) Irwin, Tesia; Li, Wenyan; Diaz, Angie; Calle, Luz; Callahan, MichaelA spacecraft water disinfection system suitable for extended length space exploration should prevent or control the growth of microbes, prevent or limit biofilm formation, and prevent microbiologically influenced corrosion. In addition, the system should have minimal maintenance requirements, should be chemically compatible with all materials in contact with the water, be safe for human consumption, and suitable to be shared across international spacecraft platforms and mission architectures. Silver ions are a proven broad-spectrum biocide and the chosen potable water biocide for future exploration missions. The competing technology for dosing silver in future water systems is based on actively dosing silver via electrolytic production. Several challenges remain with this approach that have prompted additional investigations into alternative dosing techniques. Control-release technology is an attractive option for developing a high-reliability passive silver dosing device. This paper describes the development of a nanoparticle (NP)/polyurethane (PU) composite foam for the controlled release of silver ions, and is intended to build upon the 2020 International Conference on Environmental Systems (ICES) paper number 128. In this paper, the technical background and results from the updated silver chloride (AgCl) NP/PU composite foam properties and pre-treatment testing is provided. The ultimate goal of the project is to develop a stable and reliable passive dosing silver ion release device for use in future spacecraft potable water systems.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 An Updated Modeling Study on Nutrient Deprivation as a Biofilm Mitigation Strategy for Long Term Space Missions(50th International Conference on Environmental Systems, 7/12/2021) Diaz, Angie; Li, Wenyan; Irwin, Tesia; Calle, LuzSpacecraft wastewater processing systems are environments where bacterial biofilm growth can cause problems in daily operation. As crewed missions explore beyond the ISS to the Moon and Mars, long periods of system dormancy will be necessary, making biofilm control more challenging. Previously reported preliminary mathematical models of biomass growth, as a function of nutrient availability, were developed to understand the biofilm accumulation in the WPA system under daily operation and potential dormancy conditions. These models were since updated to reflect the effect of oxygen availability, as well as the tank cycling during daily operation. This paper describes the updated models and compares the influence of various nutrient and energy limitations on the biomass product, in order to provide insight on the nutrient deprivation strategy for biofilm mitigation.