Bioreactor technology for waste water reclamation in a regenerative life support system (RLSS) is currently being developed by a team of NASA and major aerospace companies. To advance this technology, several activities are being performed concurrently; these include conducting small-scale studies and developing computer models.Small-scale studies are being performed to characterize and enhance the bioprocesses occurring within the bioreactor. New bioreactor configurations have been investigated which improved total organic carbon degradation as well as nitrification, the polishing step which converts nitrogenous wastes into forms that are easily removable from the water. Small-scale studies have also been performed using an activated sludge reactor demonstrating that TOC reduction and nitrification can occur in a single reactor.Computer models have been developed to guide the laboratory studies and to assist in full-scale system design. These models have provided a method to investigate performance-limiting factors and to improve future designs. An example of this is how the “detailed” Immobilized Cell Bioreactor (ICB) computer model was used as a design tool for the improved parallel-plate, four-person ICB designed for the Hybrid Regenerative Water Recovery System (HRWRS) program at NASA Johnson Space Center (JSC) in support of upcoming closed environmental tests. Additional modeling activities included investigating nitrification and decreasing run time, particularly for very thin biomass layers.