Vapor Compression Distillation Subsystem Evaluation: Microbiological Analysis of System Hardware, Pretreatment Solutions and Product Water 891551

In this study, the Vapor Compression Distillation Subsystem (VCDS), a candidate system to recover water from pretreated urine for Space Station Freedom, was operated and its hardware, urine pretreatment solution, brine solution, in-line and product tank water sampled for microbiological analysis, Bacterial populations were enumerated and isolates identified. Also, experiments were conducted to determine survivability of Klebsiella pneumoniae in urine pretreatment solution. Bacteria were cultured from all samples tested; the largest populations obtained from product tank water. Bacteria recovered from urine pretreatment and brine solutions were identified as Bacillus spp.; likely due to survival of bacterial spores. Klebsiella pneumoniae. Bacillus spp. and Pseudomonas spp. were recovered from post operative VCDS hardware. Also, Klebsiella pneumoniae was isolated from water collect from the in-line sampling port and product tank. It appears that bacteria, especially those that produce spores or extracellular polymeric substances (capsules) survive pretreatment and VCDS operation. These results support the hypothesis that bacteria revert to a viable but nonculturable phase; a possible adaptive strategy to the urine pretreatment, as in the case of Klebsiella pneumoniae. It is concluded that under the conditions used to test the VCDS, acceptable product water was not realized.


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