Air Biofilter Design and Integration in ALS Systems: Effect of Inlet Gas Carbon and Nitrogen Properties 2003-01-2562

To decrease consumable usage by current physico-chemical (P/C) air Trace Contaminant Control Systems (TCCS), there is an increased focus on developing regenerative TCCS technologies for long duration missions. This potentially includes reducing the need for disposable activated charcoal canisters (which pre-treat air prior to thermal catalytic treatment) as well as decreasing catalyst regeneration/replacement from eventual (and predictable) poisoning. Biofiltration is a low-energy, bio-regenerative air treatment technology capable of removing a variety of air contaminants and may substantially reduce loading to subsequent P/C TCCS components, thereby decreasing consumable usage.

The design, operation and integration of biofilters are tightly coupled with waste stream characteristics. In particular, the inlet gas carbon to nitrogen ratio (C:N) will directly affect whether the system eventually becomes limited through nitrogen depletion or excess. As the C:N ratio may vary greatly with the specific waste stream and/or integration scenario, a primary objective of this study is to develop a fundamental understanding of the effect of the gaseous C:N ratio on biofilter performance to facilitate both biofilter design and the maintenance procedures required for long-term operation. Laboratory experimentation is currently investigating carbon and nitrogen removal under variable C:N inlet gas ratios, and determining the necessary biofilter matrix conditions and design needed for sustained operation. A total of four biofiltration reactors (14L working volume), utilizing perlite as the matrix, are designed to allow individual control of the C:N loading rates. Methane, ethanol and ammonia are utilized as the carbon and nitrogen gas constituents as they are major contaminants in spacecraft. Along with preliminary data from this work, integration issues are presented that address the incorporation of biofilters in different potential mission scenarios in order to facilitate technology assessment and identify future research needs.