Natural microbial populations in a water-based biowaste management system for space life support

AbstractThe 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 m2/m3 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

The influence of feed automatization on pH-fluctuations in urine processing trickling filters

With respect to crewed long-term space missions, closed-loop systems for resource management become increasingly important. Processing human wastes into plant-available nitrogen sources is a crucial part of ensuring food supply in space. This study describes a 90-day experiment in which trickling filters fitted with 6 L of lava rock (16-25 mm grain size), mussel shells as buffer material and a 28 L tank were fed with synthetic urine (SU) and observed with regard to their nitrogen conversion rates and pH stability. The filters were operated semi-continuously with a daily withdrawal of 500 mL processed SU and addition of 500 mL new SU. The processed urine was removed from the system with only one withdrawal for all filters. The addition was done at intervals that differed between the filters: the first filter triplet received 500 mL SU once a day, the second filter triplet received ten times 50 mL and the third filter triplet received 108 times 4.6 mL. Nitrogen conversion rates, measured as nitrate production/day, did not differ significantly between the filters. However, the pH fluctuations were reduced by the divided addition (\Delta pHminmax [triplet 1] \geq 1; \Delta pHminmax [triplet 2] \geq 0.7; for triplet 3 the measurement has not yet been completed; pHmeanmin [triplet 1] \sim pHmeanmin [triplet 2] \sim 3.8; pHmeanmax [triplet 1] \sim 5; pHmeanmax [triplet 2] \sim 4.5). We hypothesize that pH fluctuations with lower maximum values reduce the precipitation in the tank induced by the mussel shells. The measurements are ongoing

The influence of nitrogen concentration and precipitation on fertilizer production from urine using a trickling filter

Planetary habitation requires technology to maintain natural microbial processes, which make nutrients from biowaste available for plant cultivation. This study describes a 646 day experiment, in which trickling filters were monitored for their ability to mineralize nitrogen when loaded with artificial urine solutions of different concentrations (40, 60, 80 and 100% v/v). Former studies have indicated that increasing urine concentrations slow nitrogen conversion rates and induce growing instability. In the current experiment, nitrogen conversion rates, measured as nitrate production/day, did not differ between concentration levels and increasing instability was not observed. Instead, the buffering capacity of the mussel shells added as buffer system (∼75% calcium carbonate) increased with increasing concentrations of synthetic urine possibly due to the higher phosphate content. The intensified precipitation of calcium phosphates seems to promote carbonate dissolution leading to improved buffering. For space applications, the precipitation of calcium phosphates is not desirable as for the phosphate to be available to the plants the precipitate must be treated with hazardous substances. With regard to terrestrial agriculture the process-integrated phosphate precipitation is a possibility to separate the macronutrients nitrogen and phosphate without addition of other chemicals. Thus, the described process offers a simple and cost-effective approach to fertilizer production from biogenic residues like slurry

Food Production within a Container by Recycling Urine and Organic Waste

For long duration space missions fresh food and re-use of materials is mandatory. Also on Earth there are harsh or closed environments where fresh supply of food is not possible. Thus a highly efficient mobile and modular system for food production would be of great value. As test bed for further development of such a system a hydroponic plant area combined with a system for biological treatment of urine and organic waste, including water, air, light and power handling, were laid out in the framework of a Concurrent Engineering design study to be integrated into a high cube standard container. In this paper the study’s outcome i.e. configuration and input and output ratios are described

Bioassays for validation of ground-based microgravity simulators

Well defined and reproducible conditions are a prerequisite for platforms such as clinostats and Random Positioning Machines (RPM) in order to provide simulated microgravity and to prepare space-based experiments. To visualize potential non-gravitational cellular responses during microgravity simulation, we applied the dinoflagellate Pyrocystis noctiluca as a highly sensitive reporter organism. This organism responds to shear stress with detectable bioluminescence emission. Pyrocystis noctiluca was exposed to different microgravity simulations while varying operational modes. With cells in a RPM rotating around two axes with random velocities and directions, we observed significantly greater mechanical stress compared with clinostat experiments applying constant rotation around one axis. Thus, we conclude that in contrast to RPM, one axis clinorotation induces substantially less non-gravitational responses through shear forces. Therefore, we apply clinostats as our preferred and validated method for the simulation of microgravity in ongoing cellular experiments. Examples will be presented

Habitat Technology Research at DLR

For long duration space missions a closed-loop system which can re-use of materials is mandatory. Also on Earth there are harsh environments or overpopulated areas where a sustainable handling of given goods is indispensable. Addressing these challenges the German Aerospace Center (DLR) conducts research in various fields of habitat technology development, which will be illustrated within this paper. There are various complementary topics, such as coordination and funding of building blocks for Life Support and Energy Systems on behalf of the Federal Government, health and performance of astronauts, regenerative (e.g. bio-filter) and hybrid systems and plant and algae cultivation under closed environments, habitat research infrastructures and simulation as well as analogue testing experiments and spin-off potentials

C.R.O.P. – Combined Regenerative Organic food Production: Using Trickling Filters for Nitrate Production from Urine

The DLR Project C.R.O.P. generally aims to combine the utilization of all kinds of organic wastes with soilless plant cultivation. Within the project scientific work is divided into several research areas that are allotted to different groups. Our group is concerned with the waste management system, in which nutrients should be recycled to the highest possible degree. The core of the system is formed by microbial trickling filters in which organic matter is liquefied if needed, and converted into inorganic compounds. The resulting nutrient solution is intended for fertigation in greenhouse cultures in space and on Earth. In our testing facility at DLR the capability of the filters to convert urine into a nitrate containing solution is characterized. Each filter unit combines 30 l of liquid volume with 6 l of filter volume. Running the filters with diluted synthetic urine in different starting concentrations (7 %, 20 %) to simulate yellow water showed that the process of urea conversion as it occurs in the soil also worked in the filters. Even when nitrogen content far exceeded the concentrations usually found in wastewaters ammonia was turned over quickly and odour nuisance and toxicity were reduced to a minimum. Nitrate production occurred at rates of 45 g per day at a maximum, which corresponds to a urea degradation rate of 22.5 g per day. The use of the resulting solution as fertilizer is currently tested experimentall

C.R.O.P. – Combined Regenerative Organic food Production. A base for an easy to use system for wastewater reclamation

The basic idea of the project C.R.O.P. is to design a flexible waste processing system for all kinds of liquid and solid organic wastes. The system is envisioned to be combined with soilless plant cultivation for life support purposes during long-term space missions. The core of the C.R.O.P.-System is a microbial trickling filter which is inoculated with a diverse community of soil microorganisms. These are capable to degrade organic matter of all kinds into inorganic compounds, which can be taken up by plants. With regard to wastewater reclamation on Earth the C.R.O.P.-Filter can provide an easy to use and easy to maintain treatment plant for the processing of nitrogenous wastewater into nitrate fertilizer solutions for agricultural use. In our testing facility at the German Aerospace Center in Cologne a set of C.R.O.P.-Filters in operation are monitored regarding their long-term performance in nitrate production. It could already be shown that nitrification occurs in the filters. Ammonium is turned into nitrate so quickly that odour nuisance and toxicity are reduced to a minimum. The application of the resulting solution as fertilizer is currently tested