Spacecraft Potable Water Monitor

Securing a supply of potable water is essential for human survival, and doing so aboard the ISS presents challenges distinct from terrestrial water safety challenges. Repeated recycling is the primary means of replenishing water aboard the ISS in order to minimize the need for costly re-supply of water. There is a critical need to continually monitor impurities in the water supply aboard the ISS in a manner that minimizes the sample volume. Existing technology can measure inorganic contaminants at concentrations established as safe in the Spacecraft Water Exposure Guidelines, but these methods are inappropriate for the ISS due to the required size and power of the equipment, the size of water sample required for testing, or some combination of these. Spectral Sciences, Inc. proposes to develop a novel water quality monitoring technology using x-ray fluorescence (XRF). In the proposed method, a small volume of water is diverted into a sampling chamber for XRF analysis, which takes place over a period of several minutes. XRF from the sample is detected by an energy-dispersive detector. The concentrations of contaminant elements in the sample are determined simultaneously from the fluorescence spectrum and compared to pre-determined threshold concentrations. After analysis, the water sample is returned to the main plumbing, and a warning is issued if any contaminant is present above the threshold concentration. This process would be entirely automated and require no crew interaction. The instrument would use commercially available parts common in portable XRF analyzers.

The International Space Station (ISS) water monitor will be a unique instrument with design elements that pertain primarily to ISS requirements. It will also serve as a prototype water quality monitoring system for future manned mission systems. It will be especially important for any planned long-duration missions. One prominent example would be a human mission to Mars. The proposed automated in-line heavy metal water supply monitor will operate continuously without the need for extractive sampling. The Phase I product consists of a laboratory-scale test unit and calibration curves for the analysis software. This will serve as the foundation for the engineering work which will take place as part of a Phase II effort.

This technology has potential non-NASA commercial applications for any instance in which a persistent automated analyzer for trace metals in water is required. Its advantage over current technologies (such as mass spectroscopy) is the reduction in required manpower. Potential applications include (1) screening soil and water in the neighborhood of landfills and industrial plants for toxicity, (2) the monitoring of industrial and nuclear facilities, (3) monitoring of hazardous waste transporters, (4) disaster management, and (5) damage assessment by first responders in the case of a spill or accident. We also see potential non-NASA usage for the developing world. Current environmental regulations are loose and as populations begin to demand clean water, instrumentation to monitor heavy metal content on-site without expensive, operator-intensive mass spectrometer equipment will be needed. Two examples of heavy metal pollution within the water supply of developing nations are wastewater generated from recycling of circuit boards and industrial manufacturing of printed circuits. Semiconductors and textiles processing is another source of heavy metal water pollutants.

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