One of the highest priorities in Environmental Control and Life Support (ECLS) for longer missions is to recover and process wastewater to provide clean water. There is an important need for a total organic carbon (TOC) sensor to assure that the organic chemical content of water environment of the astronaut crew habitat falls within acceptable limits, and that the chemical life support system is functioning properly. For longer missions, water monitoring requires sensitive, fast response, online analytical sensors. Lynntech has successfully developed a novel regenerative TOC analyzer for real-time monitoring of water quality with an operational lifetime of 5 years with no maintenance required and no need to supply reagents. In addition, the TOC analyzer was flight-qualifiable and microgravity-compatible. This proposal concerns further development of the TOC analyzer as a compact online analytical sensor utilizing (i) electrochemical components producing two key elements in TOC analysis, acid and oxidant; (ii) photolysis/photocatalysis for the complete oxidation of organic carbons to carbon dioxide; and (iii) mesofluidic design. During the Phase I effort, the feasibility of the proposed system and approach will be demonstrated. A prototype will be designed, fabricated, tested, and delivered to NASA during the Phase II project.