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Composting is a biological solid waste treatment technology with potential use in the management of organic solid wastes generated within advanced life support (ALS) systems, such as planetary bases with extensive plant production. Composting can serve to decrease mass, volume and water content, as well as stabilize and sanitize waste materials. Composting may also serve as a pre-treatment system prior to aqueous extraction (for nutrient recovery) or incineration. Additionally, the compost produced may serve as a nutrient-rich plant growth substrate. Each of these treatment objectives exerts different compost quality requirements. It is necessary to accurately determine the processing time required for the specified treatment objectives prior to system design and analysis. For example, waste stabilization will require less processing time than production of composts suitable for plant growth.

In this paper we explore the stoichiometry and kinetics of nitrification reactions (ammonia oxidation to nitrite and nitrite oxidation to nitrate) and the use of fixed film and/or suspended growth bioreactors for treatment of wastewater in Advanced Life Support Systems. While the main focus of the paper is on the development of a model for predicting the theoretical performance of nitrifying reactors, in particular, the JSC designed slug-flow nitrifying bioreactor, it also provides a broader view of the potential benefits of using controlled bioreactors. This broader view is based on two assumptions. First that bioreactors are robust systems that respond in predictable, and generally positive, ways to alterations in system loads. Second, that bioreactors can be made more robust and controllable than the physical-chemical reactors commonly selected for use in space flight.

The growth of Swiss chard in compost, Mars regolith simulant, and mixtures thereof, was studied for application in Advanced Life Support (ALS) systems, particularly Mars/lunar based operations. The purpose was to begin characterizing a sustainable biomass production method based on compost derived from inedible biomass. Compost would serve both as a means of recycling plant nutrients while improving the physical qualities of regolith as a plant growth medium. An outpost’s cropping area could be expanded by blending a minimal amount of compost (scarce, initially imported resource) and a maximal amount of regolith (plentiful local resource), consistent with adequate crop yields. Swiss chard was selected for the study as it is an ALS crop candidate for which there are little data.

The use of air treatment biofilters for the control of trace air contaminants in advanced life support (ALS) systems is currently being investigated by the Waste Processing and Resource Recovery team of the New Jersey - NSCORT (NASA Specialized Center of Research and Training). Ammonia (NH3) was selected as a model compound because it presents special challenges to the sustained operation of a biofilter; additionally, ammonia' is a contaminant of concern to ALS. The special challenges that NH3 removal presents to biofilter operation are due to (dynamic changes in the biodegradation environment which result from the accumulation of ammonia and its metabolic (biotransformation) products. This accumulation degrades the quality of the environment eventually limiting and eliminating the desired biological activity. This paper contains inform&ion on the development of a mathematical model for a nitrifying biofilter.

Distant and/or long-term missions, particularly Mars and lunar bases, will require a high degree of regenerative systems utilization. Bio-regenerative systems inherently lend themselves to integrative application, and can serve multiple processing functions in Advanced Life Support (ALS) systems. Striving for maximal use of bio-regenerative systems can reveal possibilities and relationships difficult to conceptualize within the context of a “unit process” methodology common to physico-chemical (P/C) systems. The required regenerative functions of biomass production and solid, liquid, and air processing are discussed, and a potential integrated ALS system scenario including “soil'based” plant production is developed to illustrate potential ramifications of biological (and P/C) system integration.

The use of biofilters for the control of air contaminants in Advanced Life Support (ALS) systems is currently being investigated by the Waste Processing and Resource Recovery research team of the New Jersey - NSCORT (NASA Specialized Center of Research and Training). Ammonia (NH3) was selected as a test air contaminant as it presents special challenges to the sustained operation of a biofilter. Ammonia loading to the ALS atmosphere will likely be from waste treatment (biological treatment of human, plant and food wastes) and food processing operations. This NH3 has the potential of causing adverse effects on plant growth and humans.

A current study is investigating the feasibility of using air treatment biofilters to remove ethylene from atmospheres of Advanced Life Support (ALS) systems for spacecraft or planetary habitat environments. Ethylene was selected as the contaminant because: 1) it partitions poorly in water, thus challenging the limits of biofilter performance; and 2) it is a plant growth regulator that can adversely affect plant growth even at concentrations as low as 40 parts per billion (ppb). Thus control of ethylene in a biomass production chamber (BPC) is of direct concern. In laboratory scale studies ethylene was removed from air to below a target level of 20 ppb, with 4 ppb being the lowest exit concentration observed. This performance (<20 ppb) was observed for 12 days, with exit concentrations gradually increasing to 70 - 100 ppb by day 55. The decreased level of performance was apparently due to nutrient (nitrogen) limitation.

Biological treatment technologies used in removing air pollutants are reviewed from the perspective of an Advanced Life Support System (ALSS). These are based on the capability of microbial communities to biodegrade complex and variable mixtures of organic and inorganic compounds, typically to innocuous end products. The technologies considered are biofilters, biotrickling filters and bioscrubbers, with emphasis on biofilters. Theoretical design aspects are outlined. Different bed media (matrices) are described. A list of compounds treated successfully, solely or in complex mixtures, is provided. A brief summary of our current research on the removal of ethylene and ammonia (model compounds) through biofiltration is included.