Evaluation of an Aeration Module for Microbial Environmental Control Life Support System (mECLSS) Integration with ECLSS

Space habitats utilize Environmental Control Life Support Systems (ECLSS) to produce continuous supplies of potable water from waste streams. The approach to ECLSS of the last two decades on the International Space Station (ISS) has been to inactivate microbial popula-tions with chemical or radiative biocides to enable physical-chemical processes to convert wastewaters to water that meets potable requirements. This approach enables high water clo-sure rates, but creates operational challenges: biofilm blockages, odors, incomplete carbon cycle closure, and hazardous brines. Metabolic emissions from the human crew contain re-duced carbon and nitrogen compounds that serve as substrate (food) for bacteria. Despite biocidal inactivation strategies, unmanaged aqueous bacterial populations remain active at niche locations in the ECLSS subsystems. The only managed biological processes on ISS are the experimental plant growth chambers which provide the optimal environments for photo-synthetic reactions but are not integrated into ECLSS. This paper provides technical back-ground on an engineering aeration technology to support beneficial microbial respiration in habitat wastewaters. An engineered technology to control and utilize microbial growth is de-fined as a microbial Environmental Control Life Support System (mECLSS). A potential lo-cation for introducing mECLSS with minimal engineering configuration changes is as far upstream as possible to lower the biofilm forming potential of microbial substrates in down-stream segments. An aeration module (AM) using gas-permeable tubes would provide ade-quate dissolved oxygen to biologically stabilize the organic load in condensate prior to physical-chemical processes. The AM would contribute to future ECLSS by preventing un-controlled biofilms and by increasing the capacity of the current WRS to process condensate when cabin air concentrations of VOCs are elevated. The AM would also provide a critical first step in adding a bioregenerative component to the ISS ECLSS air and water systems.