Immobilized microbial cell bioreactor technology is being investigated under a company-funded program to evaluate its applicability as a primary water processor for treatment of wastewater streams in a regenerative life support system. Incorporating biological wastewater treatment methods, as either a primary processor or a trace contaminant polisher, may offer several advantages over use of physicochemical processing methods alone, for long-duration space missions. Most contaminants found in a life support wastewater stream can be biologically converted to simple molecules. This occurs at near ambient temperature and pressure, requiring very little energy. In addition, bioreactor configurations are relatively simple, compared to physicochemical processes. One of the major benefits of using an immobilized cell bioreactor as a primary processor in a regenerative life support system is that such a unit could process several, and possibly all, of the wastewater streams. This would then require only trace contaminant polishing methods, depending on the end use of the water.The immobilized bioreactor technology described in this paper was initially developed and applied in treatment of complex industrial wastewater streams. Adapting this technology for use in a regenerative life support system involves selection of specific microorganisms adapted to the expected waste streams. Development of process configurations which optimize volume, weight, power, and other consumables will also be required.Efforts to develop and test an immobilized cell bioreactor for use as a primary wastewater processor have been initiated, using a simulated feed containing contaminants found in several life support wastewater streams. A consortium of enriched aerobic microorganisms was immobilized onto various supports in packed bed reactor configurations; these reactors were then operated in a continuous process mode. Bioreactor performance in preliminary bench-scale experiments, as a function of reactor geometry, support material, pH, and hydraulic retention time (HRT), is presented.PREVIOUS SHORT-DURATION U.S. space missions have depended upon open-loop life support systems. Space Station Freedom will take the first steps toward recycling valuable life support resources, with partial closure of the air and water loops. Developing regenerative systems which are capable of recycling essential life support resources, in order to reduce dependence on resupply of consumables from Earth has been identified as a critical technology need.(1)*The objective of this paper is to discuss the application of an immobilized cell bioreactor as a primary wastewater processor in a regenerative life support system. This technology has been utilized terrestrially for a variety of applications, including treatment of groundwater and industrial wastewater. Adapting this technology for use in a regenerative life support system involves selection of specific microorganisms adapted to the expected wastewater streams. The major components of these waste streams are very different from those of either industrial or groundwater effluents studied to date. In addition, optimum reactor and process configurations which minimize volume, weight, power, and other consumables will need to be developed. Initial investigations involve the treatment of simulated wastewater by aerobic immobilized cell bioreactors. Preliminary results of these bench-scale experiments are presented.