Paramount to controlling the introduction of contaminants into the potable water system is the ability to accurately and consistently monitor the quality of spacecraft potable water. The collection and in-flight microbiological analysis of Shuttle potable water is necessary to evaluate the operation of hardware and the growth of microorganisms in a 0-g environment.
Flight evaluations of this hardware are required since there is no information concerning the complete integration of microbial potable water testing procedures in a 0-g environment. Although KC-135 testing has demonstrated the fluid transfer capabilities of the Microbial Capture Device (MCD), concern still exists over the ability of the bacteria to adhere to the MCD in 0-g.
The findings from this investigation will help determine and direct the need for redesign of water sampling hardware and microbial procedures for future routine application on long-duration missions.
STS-70: The kit was used successfully. Water containing bacteria grew in zero gravity as well as on the ground. Sterile water was processed successfully on orbit without contamination. The galley water contained bacteria, thus allowing a performance check of direct enumeration in flight. Two problems were encountered in flight, (1) separation of the luer fitting from the MCD and (2) the in ability to process the expected amount of water (only 50-70% of the expected sample volume was pulled across the filter). The first problem has been corrected by manufacture of a custom MCD fitting. The second problem appears to be associated with the syringe pump, The syringe pump has been altered, but not tested in flight.
STS-94: DT0-677 was successfully completed on this mission. The objective of DT0-677 was to test the ability of the hardware to transfer fluid from the sample bag across the MCD to the waste bag. On a previous flight (STS-70) only 50-70 % of the expected volume was transferred. After STS-70 the syringe pump was modified to enhance fluid transfer in microgravity. DT0-677 on STS-94 confirmed the successful modification of the syringe pump in that 95-102% of the expected volume was transferred.