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	+ LSSC Home + ALS Highlights + Ground Research Activities + Controlled Environment Lab + Analytical Chemistry - Microbial Ecology		Advanced Water Recovery Biological Water Treatment Technology: Integrated Evaluation of Membrane Bioreactor Technology Overall Objective: Critical evaluation of the membrane bioreactor design (MBR) for treatment of spacecraft wastewater streams. Goal: Consistent, reliable production of a high quality effluent as a function of operating costs associated with mass, energy, and manpower. Wastewater is comprised of urine, atmospheric humidity condensate, and water used for hygiene purposes and represents the largest projected waste stream in crewed space systems. Wastewater production estimates range between 10 - 27 L person-1 day-1, depending on the extent of hygiene systems. Biological processes are used to treat the majority of terrestrial wastewater streams because they cost less than physical chemical systems. As part of advanced water recovery systems in crewed space systems, bioprocessing may also prove to be an efficient approach for reducing wastewater concentrations of organic and inorganic constituents. Microbial mineralization of surfactants to CO2 is the major organic transformation found in hygiene water, and the most important inorganic transformation is the microbial conversion of the high levels of ammonia found in urine to N2 gas via microbial nitrification/denitrification. Membrane biological reactors (MBR), resulting from the integration of membrane technologies with stirred tank reactors, warrant evaluation for biological treatment of wastewater during space flight due to their compact size, high effluent quality, low sludge production, and resiliency to perturbation. Linking nitrification and denitrification within the system is important to optimizing overall system performance because it will improve effluent water quality and reduce oxygen consumption. The first step in this effort, accomplished during the past year, was to define the operating conditions necessary to establish nitrification. The next step, the research focus this year, is to define the operating conditions necessary to allow for simultaneous nitrification / denitrification, under gravity dependent and independent (i.e., "bubble-less") aeration approaches. Given the importance of system reliability for space flight applications, the long term (6-9 month) performance of the optimized system will be evaluated next year with actual, rather than simulated, wastewater. Response of the system to perturbation, both in terms of variation in organic loading rate and the addition of antibiotics in the waste stream, will also be evaluated during all three years of the research effort. Analytical methods for characterization of organic components of the wastewater are being developed to evaluate the rate and pathway of degradation of major organic constituents (i.e., surfactants). Microbiological characterization is being performed to determine effects of different operating conditions on the spatial distribution of nitrifiers and denitrifiers as part of the effort to optimize the linkage of the processes within a single-stage reactor. Microbial risks associated the survival and growth of human-associated pathogens within the bioreactor are also being assessed. Performance Requirements Maximize desired outcomes Surfactant removal (biodegradation to CO2) Disappearance of parent molecule CO2 production Nitrification and Denitrification rate (conversion of NH4+ to N2) Minimize undesired products Surfactant biodegradation intermediates Microbial biomass Intermediate nitrogen compounds: N2O, NH3 Accomplishments: FY2002 - Initial MBR trials. Submerged separation membrane biological reactor Evaluated for treatment of a spacecraft wastewater analog. The aerobic MBR (a modified CSTR) had a 12 L working volume, submerged 0.2 µm membrane filter, 12.6 h hydraulic retention time (simulated 2 person crew), and infinite solids retention time. Simulated graywater contained a urine analog and two surfactants: disodium cocoamphodiacetate and sodium laureth sulfate (461 ppm of active ingredient, combined). Two MBR runs of 60- and 10-day durations were completed with different conditions (startup: 16 d vs. 3 d, pH control vs. none). Influent, effluent, and mixed liquor were analyzed for COD, BOD, TSS, surfactant concentration, and microbial load and activity. BOD removal averaged - 92% for each run with 100% surfactant degradation but no detectable nitrification. The food to mass (F/M) ratio decreased over time. Significant abiotic precipitation was problematic. The reactor pH was ~8.5 without pH control Conclusion: Surfactant decomposition is feasible with a small-scale MBR, although changes are needed to promote nitrification. FY2003 - Nitrification established. Simultaneous nitrification - denitrification attempted. A submerged membrane biological reactor (MBR) was evaluated for treatment of a spacecraft wastewater analog. The aerobic MBR (a modified CSTR) had a 12 L working volume, submerged 0.2 µm membrane filter, 48 h hydraulic retention time (simulated 2 person crew), and infinite solids retention time. Simulated graywater contained a urine analog and two surfactants: Disodium cocoamphodiacetate and sodium laureth sulfate (461 ppm of active ingredient, combined). Influent, effluent, and mixed liquor were analyzed for COD, BOD, TSS, surfactant concentration, and microbial load and activity. The MBR run was in excess of 180-day duration with varying process conditions. pH was controlled at 6.7 and 7.5 to establish significant nitrification, concomitant with aerobic surfactant biodegradation. Up to 80% nitrification when pH was controlled at 7.5 Nitrification was only ca. 30% at lower pH control points, i.e., 6.7, 6.0. BOD removal averaged - 92% for each run with 100% surfactant degradation. Membrane performance was exceptional. Phasic (18 h on, 6 h off) aeration was examined as a means of establishing concurrent nitrification and denitrification. No significant denitrification to N2 No surfactant biodegradation Adverse impact on nitrification. FY2004 - Gravity Independent Wastewater Bioreactor Development: Testing Simultaneous Nitrification/Denitrification in an Aerobic Rotational Membrane System (ARMS) Engineering trials with new reactor design Evaluation of reactor structural and operational integrity Pressure testing Tracer analyses (determination of hydraulic conditions) Install and validate monitoring and control systems Establishment of network connections Communication between sensors and hardware modules Sensor response and action to adverse conditions in reactor system Evaluate rotational membrane aeration unit Effects of mass transfer and mixing efficiency Structural integrity of module design Evaluate predenitrification fixed bed unit linked to membrane aerated nitrification module Develop test plan Develop kinetic data for linked units Membrane aeration rate on extent and fate of NH4 processing Rotation of membrane aeration modules Increasing loads of dominant organic constituents of urine, condensate Evaluate effects of biomass recycle on predenitrification module Prepare final report Evaluate simultaneous nitrification/denitrification in a membrane aeration module fed urine analog coupled to subsequent denitrification fixed bed fed high C/N waste streams (hygiene water, condensate) Construction and assembly of system Develop test plan Establish nitrification on urine salts analog Define kinetics of combined nitrification/denitrification on urine analog with dominant organic constituents, and effects of aeration rate, organic loading rate, HRT, rotation Initiate Preparation of Final Report Evaluate effects of supplemental electron sources on denitrification Develop test plan Conduct tests FY2005 will concentrate on long-term performance (6-12 month) with actual wastewater streams Staff: Principle Investigator: Jay Garland, PhD Co-Investigators: Tony Rector, bioengineer Mary Hummerick, microbiology Kristina Reid, microbiology Mike Roberts, PhD, microbiology Lanfang Levine, PhD, analytical chemistry Dick Strayer, PhD, microbiology Jan Bauer, analytical chemistry
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