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The effluent, or ‘broth’ output of bioreactors fed Advanced Life Support (ALS) solid wastes contains suspended particulate material composed of undigested waste residues and microbial cells. ALS crop scientists have required the removal of particulates from these solutions before they can be used to recycle soluble crop nutrients, also contained in the effluents, to hydroponic crop growing systems. A two-stage filtration system was designed and evaluated with different membrane filtration elements. The first stage, prefiltration, was designed to remove large particles (μm to mm range). The key study factors for prefiltration were: (1) filter bag pore size – 50 vs. 5 vs. 0.5 μm- and (2) rinse solution - none, de-ionized water, and simulated graywater). Between 22 to 30% of the liquid was retained by the pre-filters and retained solids, indicating the necessity of introducing a rinsing step to better recover soluble crop nutrients.

This paper will describe the screening and development of absorbents for HFC-134a in the chemical/mechanical heat pump. The absorbents must have low volatility, low melting point, high solubility for HFC-134a vapor, high heat of mixing with HFC-134a, suitable vapor pressure/temperature concentration characteristics when mixed with HFC-134a, low toxicity, low flammability, and thermal stability. A screening procedure was used to select approximately 15 absorbents for experimental evaluation. Measurement of the key physical and thermodynamic properties of the absorbent/HFC-134a mixtures, such as vapor pressure/temperature/concentration properties, materials compatibility, and thermal stability, is described. From these measurements, activity coefficients, enthalpy of mixing, and entropy of mixing of the liquid solution were determined.