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Few data are available on biodegradation rates of materials over the long-term (more than 30 days). This information is necessary to conduct trade studies (studies used to make selections between alternatives) comparing various degrees of biodegradation versus combining biodegradation with incineration for advanced life support (ALS) systems. This paper describes the extreme case in which solids are degraded only by biodegradation. Data on biodegradation of insoluble solids from inedible parts of tomato plants are fitted to single and double exponential decay models to obtain half-life estimates for these materials. The data were obtained from batch experiments of material degradation over a 128-day period using mixed microbial cultures including activated sludge and an inoculum of Phanaerochaete Chrysosporium, a fungus known for its ability to degrade lignin.

An aerobic pressurized bioreactor system to treat grey water under microgravity conditions has been developed. The treatment system consists of a packed bed bioreactor and an oxygenation device attached to an external re-circulation line. The membrane module provides bubble-free oxygen, at very high concentrations and transfer efficiency. Mass transfer characteristics of the oxygenation module have been studied. Oxygen mass transfer in water is described using a resistance-in-series model. A generalized mass transfer correlation that predicts the oxygen mass transfer coefficient has been developed. Experiments have been conducted to study the nitrification of grey water at various residence times.

This project investigates the effectiveness of a non-thermal diffuse plasma technology for destruction of environmental air contaminants in advanced life support (ALS) systems. A novel technique to generate large-volume, diffuse, non-thermal plasmas at ambient pressure with very low power consumption (∼ 10 Watts/cm3 plasma volume) has been developed. Plasma characteristics, chemistry, and contaminant destruction efficiency for benzene, toluene, and n-heptane are reported. The results of our research provide the basis for a self-sufficient, low-power, trace contaminant destruction technology that can potentially be a viable candidate in a respirable atmosphere revitalization system or a contaminant source control in ALS applications.

Nutrient recovery and biodegradation of inedible biomass is an integral part of an Advanced Life Support (ALS) system for space travel. This study investigates the mineralization and nitrogen recovery of hydroponically grown crops, namely, tomato, peanut, wheat and a 50:50 mixture of peanut and wheat. Shaker flask studies were conducted under various growth conditions of temperature and incubation times utilizing activated sludge and Phanerochaete chrysosporium (P. chrysosporium) inocula. Incubation temperature ranged from 25°C to 60°C and the flasks were monitored for nutrient recovery and solids reduction at 16, 32, 64 and 128 days. For the activated sludge systems, overall solids destruction during the 128 days of incubation ranged from 56% to 60% for the crops investigated. Similar results were found for the fungal systems indicating no substantial degradation enhancement.

Biological processing of grey water in space presents serious challenges, stemming mainly from microgravity conditions. Immobilized cell packed bed bioreactors (ICPB) have been used extensively for the treatment of wastewater on earth and can provide solutions to problems associated with microgravity. In this study two bench scale ICPB bioreactors were operated using synthetic grey water with the objective to develop a gravity independent system. Both reactors were packed with plastic flakes having a surface area of approximately 20 cm2/g, inoculated with activated sludge and fitted with an internal recirculation line to induce mixing and enhance oxygen transfer in the packed bed. One system was operated under ambient conditions with air supplied directly through a bottom port and the second was operated under 20 psi gauge pressure in order to achieve high dissolved oxygen concentration and overcome the problem of phase separation associated with microgravity conditions.