In an effort to reduce the weight of medical supplies that must be sent into space to support the Health Maintenance Facility (HMF) of the Space Station, a disposable cartridge (SWIS) is being developed which will purify the Space Station potable water to USP XXI(1) Water for Injection (WFI) quality. This water will subsequently be mixed with concentrates to reconstitute intravenous solutions such as Ringer's Lactate, which would be used in emergency situations for treatment of ill or injured crew members. The SWIS purification process train will consist of particulate prefiltration, carbon adsorption, mixed bed deionization, ultrafiltration, and sterilizing microfiltration. The present concept envisions a device that will be passive in nature, requiring only tap pressure as the driving force for filtration. The SWIS is being designed to produce at least 6 liters of WFI at a flow rate of 6 liters/hour. This paper presents performance data on removal capabilities for specific contaminants, namely, residual halogen (disinfectant, iodine), total dissolved solids (TDS), total organic carbon (TOC), bacteria, and bacterial endotoxin. In addition, design features of the cartridge will be discussed.