Browsing by Author "Angle, Geoffrey"
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Item Developing Methods for Biofilm Control in Microgravity for a Water Recovery System(2020 International Conference on Environmental Systems, 2020-07-31) Velez, Yo-Ann; Carter, Donald; Nur, Mononita; Angle, GeoffreyBiofilm growth is a significant concern for NASA’s current and future water systems. The International Space Station (ISS) Water Processor Assembly (WPA) produces potable water from a combination of humidity condensate and urine distillate. After two years of operation, the WPA experienced a significant failure (clogged solenoid valve) due to biofilm growth in the waste tank that collects these two waste streams. The WPA waste tank now requires significant management to prevent biofilm from impacting downstream components. This issue is magnified for future NASA manned missions due to the need to place the vehicle’s life support system in a dormant state during uncrewed operations (e.g., when vehicle is in Mars orbit during surface mission). The urine distillate and humidity condensate are also expected to be an issue during dormancy, especially where these waste streams originate (the condenser in the Distillation Assembly of the Urine Processor) and the Water Separators that collects and delivers the humidity condensate removed from the atmosphere. To address these concerns, NASA is performing an ongoing research task to a) identify viable methods for inhibiting growth of biofilms, b) develop design solutions for implementing these various methods, c) perform a trade study to select methods (taking into account the design solutions), and d) evaluate effectiveness in ground test prior future missions This paper provides an overview of the current status on this effort.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 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.