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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.

Computer models are currently being developed by NASA and major aerospace companies to characterize regenerative life support waste water reclamation bioreactors. Detailed models increase understanding of complex processes within the bioreactors and predict performance capabilities over a wide range of operating parameters. Bench-top scale bioreactors are contributing to the development and validation of these models. The purpose of the detailed bioreactor model is to simulate the complex water purification processes as accurately as possible by minimizing the use of simplifying assumptions and empirical relationships. Fundamental equations of mass transport and microbial kinetics were implemented in a finite-difference model structure to maximize accuracy and adaptability to various bioreactor configurations. The model development is based upon concepts and data from the available literature and data from the bench top bioreactor investigations.

Immobilized cell bioreactor (ICB) technology is being investigated under a multiyear, company-funded program to evaluate its applicability as a primary water processor for treatment of wastewater streams in a regenerative life support system (RLSS). Biological wastewater treatment methods may offer several advantages for long-duration space missions. Most contaminants found in life support wastewater can be aerobically converted by microorganisms to simple chemical molecules, such as carbon dioxide, water, ammonia, and nitrate. Thus, one unit could process several, possibly all, wastewater streams. This type of biochemical process can be operated at or near ambient temperature and pressure, requiring very little energy. In addition, bioreactor configurations are relatively simple. The objective of this paper is to describe two aspects of the ongoing ICB research: 1) performance stability over an extended time period, and 2) new reactor designs.