International Space Station Water Recovery System The Water Recovery System (WRS) aboard the International Space Station reclaims water from several sources, including humidity condensate, urine, and hygiene water. Extensive filtration and processing allow its reuse as drinking and wash water. However, incomplete water processing, resin failure, or leaching from metal coatings could lead to unsafe levels of metals in the crew drinking water. Trace toxic metals such as Cd, Ni, Ag, Zn, and Mn have been found in water samples from various expeditions at potentially dangerous concentrations and pose a significant threat to the crew. While Cd, Mn, Ni, and Zn are contaminants leached from the zinc coatings and stainless steel in the spacecraft water distribution lines and the humidity heat exchangers, Ag is added as a residual biocide to processed water. NASA has expressed a need to include measurement technologies to assure that the trace heavy toxic metal content of the water falls within acceptable limits and that the WRS and storage system are functioning properly for long-duration missions. A real-time sensor would allow the crew to quickly diagnose and resolve the metal contamination problems, thus protecting the health of the crew. Portable sensor for the determination of heavy metals in drinking water: Contamination of drinking water with various heavy metals is a world-wide problem. Successful development of a compact sensor for trace toxic metals in water would open the door to portable water analysis and water quality monitoring. Current techniques require the shipment of the sample back to a laboratory, which is cost-prohibitive and time consuming. This portable sensor would allow more frequent and more extensive water quality monitoring, which would lead to increased safety of drinking water worldwide and assurance that the metal contents of the water falls within acceptable limits for drinking water. Portable sensor for the determination of heavy metals in surface water, groundwater, and river water: Another potential application of this sensor is for the detection of heavy metals in environmental waters, where high heavy metal content can negatively affect various aspects of terrestrial and aquatic ecosystems.