Browsing by Author "Christenson, Dylan"
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Item Further Investigations into the Performance of Membrane- Aerated Biological Reactors Treating a Space Based Waste Stream(45th International Conference on Environmental Systems, 2015-07-12) Christenson, Dylan; Sevanthi, Ritesh; Baldwin, Daniel; Morse, Audra; Jackson, W. Andrew; Meyer, Caitlin; Vega, Leticia; Pickering, Karen; Barta, DanielMembrane aerated biological reactors (MABR) have proven in terrestrial testing to be a sustainable and robust technology for treating space based waste streams that prove challenging for conventional systems due to high concentrations of carbon and nitrogen. Biological pretreatment stabilizes the waste stream without the use of harsh chemicals and also provides several distinct advantages including: 1) the conversion of NH3 to N2(gas), a required atmospheric component, or NOx species that are easily rejected by evaporative or membrane systems; 2) the transformation of organic matter to increase the efficiency of desalinization processes and produce a more stable waste product (brine); 3) the production of metabolic water; 4) the reduction in pH that facilitates membrane and distillation processes and reduces the required consumables and increases the life span of the processes; and 5) the potential elimination of the current hazardous pre-treat chemicals thereby producing a brine from which water can be recovered more easily. Work at both Texas Tech University (TTU) and Johnson Space Center (JSC) using the Counter-diffusion Membrane Aerated Nitrifying Denitrifying Reactor (CoMANDR) design has shown the ability of these systems to provide consistent and efficient carbon removal (>90%) and nitrification (>60%) when treating a space based waste stream consisting of urine, flush water, hygiene and laundry water, and humidity condensate. However, several areas were in need of further investigation. These include the ability of the system to handle on production urine feeding and the impact of membrane density on performance. The study of on production urine feeding allows us to determine the versatility of MABR bioreactors to a range of mission scenarios. Our past work has also identified operational issues for high density membrane modules in which the spacing between membranes is reduced. These high density modules can increase gas transfer but suffer from flow short circuiting due to biofilm bridging. We evaluated this relationship by operating MABRs with a range of specific surface areas and treating an Early Planetary Base waste stream.Item Investigations into the Performance of Membrane-Aerated Biological Reactors Treating a Space Based Waste Stream(46th International Conference on Environmental Systems, 2016-07-10) Sevanthi, Ritesh; Christenson, Dylan; Jackson, William; Morse, Audra; Meyer, Caitlin; Vega, Leticia; Shull, SarahTwo demonstration size membrane aerated biological reactors (MABR) CoMANDR 1.0 and CoMANDR 2.0 have previously demonstrated their ability to stabilize an early planetary base (EPB) waste stream over operating periods of ~1 year. Biological stabilization includes oxidation (>90%) of dissolved organic matter to CO2, partial conversion of organic N to NOx-, and reduced pH. Biological stabilization has a number of advantages including: 1) elimination of hazardous pre-treat chemicals; 2) production of N2(gas); 3) production of metabolic water; 3) a low pH effluent that facilitates membrane and distillation processes; and 4) a effluent that produces a better quality and less hazardous brine for water recovery. Preliminary analysis suggests that water recovery systems that integrated biological treatment may trade favorably compared to all physical/chemical systems. However, previous systems have incorporated reactor geometries and membrane specific surface areas which are not flight compatible. The R-CoMANDR (rectangular Counter-diffusion Membrane Aerated Nitrifying Denitrifying Reactor) system was developed to evaluate the ability of the smaller footprint reactor treat the range of possible waste streams (e.g. ISS to EPB) as well as the potential to operate without a feed tank. Individual waste streams (e.g. urine, hygiene, laundry, humidity condensate) are directly fed to the reactor on production. We will present performance data and evaluate the new flight like system design compared to previous systems.Item Performance of a Full Scale MABR (CoMANDR 2.0) for Pre-treatment of a Habitation Waste Stream Prior to Desalination(44th International Conference on Environmental Systems, 2014-07-13) Sevanthi, Ritesh; Christenson, Dylan; Cummings, Elizabeth; Nguyen, Kevin; Morse, Audra; Jackson, W. AndrewRecycling waste water is a critical and crucial step to support sustainable long term habitation in space. Water is one of the largest contributors to the cost of space travel and the associated life support systems. In closed loop life support systems, membrane aerated biological reactors (MABRs) through biological reactions can reduce the dissolved organic carbon (DOC) and ammonia (NH3) concentration as well as decrease the pH of the waste water, leading to a more stable solution with less potential to support biological growth or promote carryover of un-ionized ammonia as well as producing a higher quality brine. We have previously demonstrated the successful performance over a 1 year period of a demonstration size MABR system, CoMANDR 1.0 (Counter-diffusion Membrane Aerated Nitrifying Denitrifying Reactor). This system was able to generally achieve DOC reductions of >90% and ammonium conversion rates of >50% over a range of loading rates. However, due to the very high specific surface area (SSA) (260 m2/m3) the system had poor hydraulic performance after one year of continual operation. The CoMANDR 2.0 system was developed to evaluate the impact of reduced specific surface area (200 m2/m3) as well as investigate the impact of low total air flow in to the system and forced hibernation periods (periods of no human habitation). The system was fed daily with un-stabilized wastewater composed of donated urine, ersatz hygiene water, humidity condensate, and laundry water. The liquid side system was continually monitored for pH, TDS, DO, and Temperature, and the influent and effluent monitored daily for DOC, TN, NOx, and NH4. The gas side system was continuously monitored for O2, CO2, and N2O was monitored intermittently in the effluent gas. Results support the ability of the system to effectively reduce organic carbon by over 90% and convert up to 70% of the total influent N to non-organic forms (e.g. NOx or N2). We have also demonstrated that for at least up to 4 weeks, CoMANDR may be placed in a recycle mode and can be brought back on line with no start up required supporting the ability to intermittently operate the system. Additionally, the system could handle low air and oxygen (80 mL/min) flow rates with a loading of 20 L/day and achieve high carbon removal.Item Rapid Start-up and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor(45th International Conference on Environmental Systems, 2015-07-12) Meyer, Caitlin E.; Pensinger, Stuart; Pickering, Karen D.; Barta, Daniel; Shull, Sarah A.; Vega, Leticia M.; Christenson, Dylan; Jackson, W. AndrewMembrane aerated bioreactors (MABR) are attached-growth biological systems used for simultaneous nitrification and denitrification to reclaim water from waste. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal and implementing a biologically-based water treatment system for long- duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the “start-up” duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to under two weeks, and that despite low ammonium removal rates, the MABRs are oversized.Item Results of the Alternative Water Processor Test, A Novel Technology for Exploration Wastewater Remediation(46th International Conference on Environmental Systems, 2016-07-10) Vega, Leticia; Meyer, Caitlin; Shull, Sarah; Pensinger, Stuart; Jackson, William; Christenson, Dylan; Adam, Niklas; Lange, KevinBiologically-based water recovery systems are a regenerative, low energy alternative to physiochemical processes to reclaim water from wastewater. This report summarizes the results of the Alternative Water Processor (AWP) Integrated Test, conducted from June 2013 until April 2014. The system was comprised of four (4) membrane aerated bioreactors (MABRs) to remove carbon and nitrogen from an exploration mission wastewater and a coupled forward and reverse osmosis system to remove large organic and inorganic salts from the biological system effluent. The system exceeded the overall objectives of the test by recovering 90% of the influent wastewater processed into a near potable state and a 64% reduction of consumables from the current state of the art water recovery system on the International Space Station (ISS). However, the biological system fell short of its test goals, failing to remove 75% and 90% of the influent ammonium and organic carbon, respectively. Despite not meeting its test goals, the BWP demonstrated the feasibility of an attached-growth biological system for simultaneous nitrification and denitrification, an innovative, volume- and consumable-saving design that does not require toxic pretreatment.