WATER RECLAMATION: URINE PRETREATMENT AND PHASE CHANGE PROCESSING


Current phase change technology for the reclamation of water from urine and other brines is represented by two processes: the Air Evaporation System used aboard the Mir, and Vapor Compression Distillation (VCD) to be used aboard ISSA. These two systems and methods of urine pre-treatment are discussed below. More information on two related systems, Thermoelectric Integrated Memebrane Evaporation Subsystem (TIMES), and the Wick Evaporator are provided under Advanced Life Support Systems (ALSS).


VAPOR COMPRESSION DISTILLATION

 

Vapor Compression Distillation (VCD) is the process selected for primary treatement of urine aboard ISSA. The process uses a thin walled rotating drum. Contaminated water enters the drum and coats its surface as a thin layer. Water is evaporated from the surface of the drum. The water vapor loaded air is first compressed and then condensed on the opposite side of the drum. Compression allows the water to liquify at a higher temperature than that at which it was originally evaporated. The condensed urine distillate flows out of the system. The latent heat of vaporization is reclaimed in the condenser and conducted across the rotating drum where it energizes the evaporation of more contaminated water. The process produces a urine distillate and a brine. Energy requirements for this process are in the range of 77-110 W-hr/kg.


 


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Author: Tugrul Sezen
sezen@nas.nasa.gov

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