Compact System and Method for Treating Urine and Other Wastewater

Because resupply of commodities for long duration space missions would be prohibitively expensive and could take an extensive length of time to reach habitats in orbit around or on other planetary bodies, it is critical that astronauts have the ability to recycle and reuse local waste streams to provide resources such as clean water, fuel, and nutrients for growing plants. Scientists at Kennedy Space Center and the University of South Florida have developed a technology that addresses this critical mission need. The modular system design incorporates all wastewater streams and some food waste including urine water, hygiene water, humidity condensate, Sabatier water, fecal waste, laundry water, and organic food waste. These sources are fed simultaneously into the system, and a function-driven, sequential purification process occurs. The primary processes include carbon conversion, phase separation (solid/liquid/gas), disinfection, nutrient/salts management, and salts balancing to generate a clean water stream. The heart of the closed-loop bio-regenerative system is an anaerobic membrane bioreactor (AnMBR), which takes raw wastewater streams and utilizes an anaerobic microbial consortium to carry out the breakdown of the organic matter. An ultrafiltration membrane captures and destroys pathogenic bacteria and viruses. The AnMBR system generates a clean water stream containing fertilizer constituents which can be used to cultivate either microalgae (for food, pharma/nutraceuticals, fuel or bioplastics) in photobioreactors or crops in hydroponic systems. The system also generates methane and hydrogen gas which can be used for fuel (or conversion to bioplastics), and CO2 which can be used to support plant growth.

This invention is a system and associated method that is a two step process. It provides a contaminant treatment pouch, referred to as a urine cell or contaminant cell that converts urine or another liquid containing contaminants into a fortified drink, engineered to meet human hydration, electrolyte and caloric requirements. It uses a variant of forward osmosis (FO) to draw water from a urine container into the concentrated fortified drink as part of a recycling stage. An activated carbon pretreatment removes most organic molecules. Salinity of the initial liquid mix (urine plus other) is synergistically used to enhance the precipitation of organic molecules so that activated carbon can remove most of the organics. A functional osmotic bag is then used to remove inorganic contaminants. If a contaminant is processed for which the saline content is different than optimal for precipitating organic molecules, the saline content of the liquid should be adjusted toward the optimal value for that contaminant.

This approach allows water recycling, air treatment, thermal control, and solids residuals treatment and recycle to be removed from the usable habitat volume and placed in the walls of a radiation-shielding water wall. It also provides a mechanism to recover and reuse water treatment (solids) residuals to strengthen the habitat shell. Water-wall treatment elements are a much-enlarged version of the commercially available X-Pack hydration bag. Some water bags have pervaporation membranes facing inward that provide the capability to remove H0, C0, and trace organics from the atmosphere. Ideally the water wall is composed of a series of membrane bags packed as dry elements integrated into an inflatable habitat structure wall. After launch and deployment, it is filled with water and maintained as both a freshwater supply and radiation shield. As the initial water supply is consumed, the depleted treatment bags are filled with waste water and take on a dual role of active forward osmosis (FO) water treatment and water-wall radiation shielding.

The Surface-Adhering BioReactor (SABR) is a novel microbial cell cultivation platform that mimics the way vascular plants use transpiration to deliver nutrients to their cells. In this biomimetic platform, microbial cells are cultivated as immobilized cells on a porous substrate where transpiration is used to passively deliver water and nutrients as well as harvest and concentrate secreted biomolecules by the microbial cells. The SABR transports nutrients to microorganisms without using a pump. Instead, evaporation and the cohesive property of water are exploited to pull the nutrient medium through the device, with a high degree of control, on an as needed basis. It eliminates the hydrodynamic shear stress on the cells and decreases the working volume of water needed for cultivation by a factor of 25 compared to planktonic bioreactors. Furthermore, the transpiration mechanism allows for the concentration of secreted products in areas of relatively fast evaporation, thus providing a passive means of secreted product harvesting. By matching the time scales of nutrient medium delivery and product harvesting with the time scales of growth and product formation, minimal energy is wasted in bioreactor operation. Transpiration enables a passive cooling system for the cells where either externally imposed or internally generated heat due to cellular activity is mitigated, thus preventing overheating that can lead to decreased productivity or even cell death. This technology enables significant reductions in energy input for cultivating microorganisms.

Bacterial contamination of water systems used in microgravity is a major issue for NASA because biofilms can clog or interfere with water system functions and bacterial ingestion can be harmful to astronaut health. To address this problem, NASA innovators developed a microwave based technology to purify contaminated water by eradicating and eliminating bacteria that grows in systems that generate potable water, in equipment utilizing cooling loops and heat exchangers, and removing bacterial contamination that is present on a variety of surfaces. This decontamination system is chemical free and requires minimal to no consumables. Initial testing identified a specific microwave frequency band and exposure times for killing bacteria (Burkholderia cepacia) and biofilm. Test results show that exposing static water to microwave energy for 90 seconds can effectively kill waterborne bacteria and biofilm within a water filtration system. Additional testing, using a circulating water test bed, demonstrated that microwave energy at the selected frequency can effectively eradicate waterborne bacteria within 30 seconds. This technology could be further developed into a portable, lightweight system for use in remote locations as well as commercial space applications. The microwave decontamination system could also be added to existing water systems to extend the life of the system.