Chemical Characterization of U.S. Lab Condensate

Approximately 50% of the water consumed by International Space Station crewmembers is water recovered from cabin humidity condensate. Condensing heat exchangers in the Russian Service Module (SM) and the United States On-Orbit Segment (USOS) are used to control cabin humidity levels. In the SM, humidity condensate flows directly from the heat exchanger to a water recovery system. In the USOS, a metal bellows tank located in the US Laboratory Module (LAB) collects and stores condensate, which is periodically off-loaded in about 20-liter batches to Contingency Water Containers (CWCs). The CWCs can then be transferred to the SM and connected to a Condensate Feed Unit that pumps the condensate from the CWCs into the water recovery system for processing. Samples of the condensate in the tank are collected during the off-loads and returned to Earth for analyses. This paper reports the results from the chemical analyses of LAB condensate samples returned on Shuttle and Soyuz flights from STS-100/6A through Soyuz 10. The results show organic levels have regularly exceeded Russian proposed limits for the amount of organics that can be removed by the condensate recovery system. Efforts to lower the organics by reducing the number of crew personal hygiene and payload items containing volatile organics have had mixed success. There were also high levels of zinc and nickel in the initial condensate samples. The source of these metals appears to be the condensing heat exchangers in the LAB.