title: Natural microbial populations in a water-based biowaste management system for space life support.
abstract: The reutilization of wastewater is a key issue with regard to long-term space missions and planetary habitation. This study reports the design, test runs and microbiological analyses of a fixed bed biofiltration system which applies pumice grain (16-25 mm grain size, 90 m(2)/m(3) active surface) as matrix and calcium carbonate as buffer. For activation, the pumice was inoculated with garden soil known to contain a diverse community of microorganisms, thus enabling the filtration system to potentially degrade all kinds of organic matter. Current experiments over 194 days with diluted synthetic urine (7% and 20%) showed that the 7% filter units produced nitrate slowly but steadily (max. 2191 mg NO3-N/day). In the 20% units nitrate production was slower and less stable (max. 1411 mg NO3-N/day). 84% and 76% of the contained nitrogen was converted into nitrate. The low conversion rate is assumed to be due to the high flow rate, which keeps the biofilm on the pumice thin. At the same time the thin biofilm seems to prevent the activity of denitrifiers implicating the existence of a trade off between rate and the amount of nitrogen loss. Microbiological analyses identified a comparatively low number of species (26 in the filter material, 12 in the filtrate) indicating that urine serves as a strongly selective medium and filter units for the degradation of mixed feedstock have to be pre-conditioned on the intended substrates from the beginning.
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Gravitational Biology, Linder Hoehe, 51147 Cologne, Germany. Electronic address: gerhild.bornemann@dlr.de.
authors.forename: Gerhild
authors.initials: G
authors.lastname: Bornemann
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Gravitational Biology, Linder Hoehe, 51147 Cologne, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Waßer
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Gravitational Biology, Linder Hoehe, 51147 Cologne, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Tonat
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Radiation Biology, Linder Hoehe, 51147 Cologne, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Moeller
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Radiation Biology, Linder Hoehe, 51147 Cologne, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Bohmeier
authors.affiliation: German Aerospace Center, Institute of Aerospace Medicine, Gravitational Biology, Linder Hoehe, 51147 Cologne, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hauslage
mesh_terms: D018441:Biofilms; D005374:Filtration; D008021:Life Support Systems; D009566:Nitrates; D009584:Nitrogen; D012987:Soil; D014865:Waste Disposal, Fluid; D062065:Wastewater; D014867:Water; D018508:Water Purification
chemical_list: D009566:Nitrates; D009584:Nitrogen; D012987:Soil; D062065:Wastewater; D014867:Water
keywords: Biofilter; Life support; Nitrification; Nutrient recycling; Urine; Waste management