1995-07-01

Design of an Ultrafiltration/Reverse Osmosis Prototype Subsystem for the Treatment of Spacecraft Wastewaters 951738

Long duration missions in space will require regenerative processes to recover water for crew reuse. Membrane processes are attractive as a primary processor in water recovery systems (WRS) because of their design simplicity, low specific energy requirements, small size, and high water recovery. However, fouling has historically been regarded as a disadvantage of membrane-based processes. This fouling is often caused by micelle buildup on the membrane surface by high-molecular-weight organics (e.g., from soaps and laundry detergents).This paper describes a two-stage fouling-resistant ultrafiltration (UF)/reverse osmosis (RO) prototype subsystem, which was designed and constructed for a WRS in the Life Support Systems Integration Facility (LSSIF) at NASA Johnson Space Center (NASA/JSC). The first stage of the subsystem is a tube-side-feed hollow-fiber UF module that removes contaminants that tend to foul spiral-wound modules. The unique flow patterns in this module minimize the build-up of foulants on the membrane surface and allows the use of innovative system designs and operating modes that prevent fouling. The second stage is a spiral-wound RO module that removes the remaining contaminants.During testing, the prototype subsystem performed as designed, processing 92 liters (202 lb) of wastewater in 8 hours or less, at a water recovery of 94%. The prototype subsystem produced a permeate with less than 20 ppm total organic carbon (TOC).The design of the prototype UF/RO subsystem, the process flow diagram, and the control strategy used to obtain long term, reliable performance are described. Also, performance data for the UF/RO subsystem are presented.

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