Operation of magnetically assisted fluidized beds in microgravity and variable gravity: experiment and theory.

The conversion of solid waste into useful resources in support of long duration manned missions in space presents serious technological challenges. Several technologies, including supercritical water oxidation, microwave powered combustion and fluidized bed incineration, have been tested for the conversion of solid waste. However, none of these technologies are compatible with microgravity or hypogravity operating conditions. In this paper, we present the gradient magnetically assisted fluidized bed (G-MAFB) as a promising operating platform for fluidized bed operations in the space environment. Our experimental and theoretical work has resulted in both the development of a theoretical model based on fundamental principles for the design of the G-MAFB, and also the practical implementation of the G-MAFB in the filtration and destruction of solid biomass waste particles from liquid streams.

Development of a microgravity-compatible reagentless organic acid and alcohol monitor (OAAM).

The development of a microgravity-compatible analyzer capable of quantifying organic acids in water is described. The analyzer employs "reagentless" solid phase acidification to convert organic acids to the volatile form followed by membrane separation and specific conductance detection to determine organic acids at concentrations between 0.005 and 40 mg/L. In the future, this technology will be extended to the detection of alcohols, which will be oxidized to form the corresponding organic acid and then determined using the same processes. An immobilized enzyme biocatalyst, alcohol oxidase, oxidizes alcohols to form an aldehyde. Oxidation to the corresponding organic acid is then completed over a heterogeneous catalyst. The combined organic acid and alcohol monitor (OAAM) will be utilized to determine levels of both analyte classes at various points within the water recovery system (WRS) baselined for the International Space Station (ISS). These data will improve water quality through enhanced process control, while allowing early diagnosis of potential problems. Grant numbers: NAG9-1081.

Next generation physico-chemical systems for water reclamation aboard spacecraft, lunar and planetary habitats.

The extent to which bioregenerative processes will be incorporated into future life support systems is not known. Until biologically based processes reach a higher state of readiness, more advanced physico-chemical systems will be required that are capable of reliable operation for long periods with a minimal resupply penalty by minimizing the requirement for expendables. Water reclamation systems must perform three primary functions: 1) removal of suspended solids, 2) removal of dissolved contaminants, 3) and control of microbial growth. In this article, regenerable physico-chemical systems capable of performing these tasks are discussed. These systems may be appropriate for near-term deployments such as a space station retrofit, a lunar outpost, or a Mars transit vehicle.

"Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification.

Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

Catalytically Active Regenerative Sorbent beds (CARS) for airborne contaminants.

The Pd on Al2O3 catalyst used in the projected Space Station's Trace Contaminant Control System (TCCS) catalytic oxidizer can be poisoned by volatile halogen-, sulfur-, and nitrogen-containing organic species. Catalytically Active Regenerable Sorbents (CARS) eliminate these problematic contaminants and the large carbon bed used for their elimination in a three-step process. Contaminants are conventionally adsorbed by the CARS bed. After saturation, the bed is connected to an off-line recirculation loop, filled with hydrogen, and then heated. At temperature, contaminants are hydrogenated on catalytic sites within the bed, forming simple alkanes and acid gases that are efficiently converted to innocuous salts in an in-line alkaline bed. The CARS bed is regenerated by this cycle and alkane gases are released to be safely oxidized in the catalytic oxidizer. A challenge mixture containing Freon-113, thiophene, trichloroethylene, Halon-1301, and dichloromethane at 1670, 75, 81, 68, and 83 mg/m3 was successfully treated using this technology, demonstrating the CARS feasibility.