Synergistic Integration of Biological Pretreatment and Desalination for Enhanced Hybrid Wastewater Treatment in Life Support Systems

In this dissertation, we evaluate a potential hybrid system for long-term human space travel. Hybrid wastewater processing systems that include both biological pretreatment and desalination provide multiple benefits. This alternative is a low-cost and reliable process that can eliminate the need for hazardous chemicals and treat all proposed wastewater. This hybrid treatment system for recycling greywater and urine + flush water (U+F), consists of variable volume full-scale bioreactors, Reverse Osmosis (RO), and a distillation system. The main task for this study was to separate greywater from U+F, which could produce a high-quality, high-volume resource amenable to RO, while a distillation system desalinates the low-quality, low-volume U+F. However, to our knowledge, studies have yet to evaluate hybrid treatment systems for habitation wastewater. The Greywater MABR and RO system objectives were to evaluate 1) the greywater MABR and RO system effluent quality, 2) hollow fiber microporous membrane filtration modules (MFM) permeate quality, and 3) use the greywater MABR as an RO recycle tank. For the first task, the greywater MABR effluent was transferred to the RO system as a pulse once daily. The RO system operated in batch mode until 90% recovery, and the brine (10% of the influent) was drained to the distillation vessel. For the second configuration, three MFMs were installed in the MABR effluent zone to achieve better efficiency. Greywater MABR effluent was produced continuously and collected in the RO system recycle tank for further treatment. Thirdly, in this test point, the brine from the RO system returns to the greywater MABR. The second experiment was to evaluate the U+F MABR and the distillation system. System performance regarding processing capacity, rate, and water quality was evaluated. This research effort explored the impact of full nitrification (e.g., production of NO3- as end product) compared to nitritation (NO2- as end product), the impact of influent pH or the use of an in-line NH3 trap, and the ability to continuously process biologically stabilized wastewater without brine or salts removal. This dissertation provides data on the required sizing, RO permeate and distillate quality, and subsequent impacts on downstream polishing systems, as well as required consumables for hybrid systems that can be used to down-select promising architectures. Here, we report on the performance of each configuration and the required mass, volume, and consumable requirements. This work provides critical data to allow hybrid systems to be evaluated for partial gravity habitation systems and potentially increase the sustainability of human space habitation.