Development of a sensor to detect select trace toxic heavy metals (Ag, Cd, Mn, Ni, and Zn) in water is proposed. Using an automatic side-stream sampling technique, this compact, electrochemical sensor will use small volumes of water and detect metals in the low parts-per-billion range. The novel coupling of a high-performance novel electrode material, microarray electrode geometry, and a highly sensitive sensing algorithm allows for a sensor with low detection limits and excellent specificity. Additionally, the sensor will show long-term repeatability and reliability, while requiring minimal maintenance or user calibration time. The sensor and its components have been engineered to function in a microgravity environment and for easy integration with the Water Recovery System. Giner will partner Johnson Space Center to ensure the ability of the sensor to detect trace metals in a range of reclaimed water samples and determine the appropriate concentrations. This sensor will detect trace heavy metals in water in near real-time, allowing for timely response and resolution to water contamination problems.