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Hollow fiber membrane reactors (HFMBRs) may be used for biological wastewater treatment, and may be integrated with NASA's current research developments. The goal of this paper is to (a) evaluate the effect of mass transfer and hydrodynamics in a microporous HFMBR and (b) appropriateness of HFMBRs for use in space applications. Even though bubble-less aeration was not achieved by the use of microporous membranes, mass transfer within the HFMBR was found to increase after biofilm formation. Conversely, convective flow dominated transport within the system. Despite the high treatment efficiency obtained by the HFMBR, due to the bioreactor size, configuration and membrane spacing within the HFMBR, the bioreactor was not a suitable option for application under microgravity conditions. Even though developing a system with more favorable system hydrodynamics would aid in treatment efficiency, the use of a microporous HFMBR is not a recommended option to meet NASA's needs.

A modified membrane-aerated biofilm reactor (mMABR) was constructed by incorporating two distinct biofilm immobilization media: gas-permeable hollow fiber membranes and high surface area inert bio-media. In order to evaluate the mMABR for space flight applications, a synthetic ersatz early planetary base (EPB) waste stream was supplied as influent to the reactor, and a liquid loading study was conducted at three influent flow rates. On average, percent carbon removal ranged from 90.7% to 93.1% with volumetric conversion rates ranging from 25 ± 3.3 g / m3 d and 95 ± 13.4 g / m3 d. Simultaneous nitrification/denitrification (SND) was achieved in a single reactor. As the liquid loading rate increased from 0.15 mL/min to 0.45 mL/min, the volumetric denitrification rates elevated from 27 ± 3.3 g / m3 d to 65 ± 5.2 g / m3 d. Additionally, it was found that nitrification and denitrification were linearly related with respect to both percent efficiency and volumetric reaction rates.

Microbial control in closed environmental systems, such as those of spacecraft or proposed base missions is typically limited to disinfection in the potable water system by a strong chemical agent such as iodine or chlorine. However, biofilm growth in the environmental system tubing threatens both the sterility of the potable water distribution as well as operational problems with wastewater systems. In terrestrial systems, biofilm has been recognized for its difficulty to control and eliminate as well as resulting operational problems. In order to maintain a potable water source for crew members as well as preventing operational problems in non-sterile systems, biofilm needs to be considered during system design. While biofilm controls can limit biofilm buildup, they are typically disruptive and cannot completely eliminate biofilm. Selenium coatings have shown to prevent initial biofilm attachment as well as limit attached growth on a variety of materials.

When compared to physical and chemical processes for wastewater treatment in space, the benefits of biological systems include reduced storage and handling of waste material, lower energy requirements and plant growth system compatibility. An advanced membrane reactor (AMR) was constructed to treat ammonium-rich simulated wastewater. The effluent pH was approximately 6.3, and ammonium and TOC reduction rates were greater than 60 percent and 99 percent, respectively. The experimental results demonstrate that this technology may be suitable for space applications. However, the long-term performance of these systems should be investigated.

Hollow fiber membranes aerate wastewater without bubble formation by separating the liquid and gases phases with a semi-permeable membrane. These membranes have shown to successfully create aerobic conditions within a biological reactor. This research investigated the effect of long term usage and biofilm growth on membrane's ability to transfer oxygen to solution. Results show that oxygen transfer across the membrane decreased significantly compared to unused membranes in areas of high biofilm growth while low biofilm growth showed only slight decreases.

Bioreactor studies and microcosm experiments were conducted to determine the degradation potential of a commercial cleansing formulation. With the possible replacement of the current cleansing formulation under consideration (Ecolab whole body shampoo containing Igepon TC-42™ as an active ingredient), determination of the degradation characteristics of the alternative formulation is necessary. The commercial formulation currently being evaluated is a modified version of Pert Plus® for Kids (PPK). The degradation potential of the PPK and main surfactant Sodium Laureth Sulfate (SLES) was determined in a packed bed denitrifying bioreactor. Results from the bioreactor studies led to the development of stoichiometric relationships to help predict and monitor SLES degradation. In addition to the degradation rates of Ecolab, the PPK formulation, as well as the four leading constituents contained in the PPK formulation was determined under denitrifying conditions in microcosm studies.

The purpose of this study was to evaluate the viability of treating wastewater through edible plant hydroponics. After the harvest in the hydroponic experiment (32 day study period), plant yield for edible biomass (corresponds to the harvested leaves) in wastewater and hydrosol (control) were 0.131 kg/m2 and 0.104 kg/m2, respectively. Potassium, TDS, and TN showed decreasing trends in hydrosol and wastewater during the experiment. Nitrification was observed in the wastewater unit with a significant increase (92.5%) in nitrate mass. Nitrite and ammonium mass in wastewater decreased with time, while hydrosol had negligible amounts of nitrite and ammonium during the study period. Calcium and magnesium masses decreased in the control and increased in wastewater. Wastewater showed a decrease in the mass of TOC (19.7%), while the hydrosol had negligible mass with respect to TOC.

Biological pre-treatment of early planetary/lunar base wastewater has been extensively studied because of its predicted ability to offer equivalent system mass (ESM) savings for long term space habitation. Numerous biological systems and reactor types have been developed and tested for treatment of the generally unique waste streams associated with space exploration. In general, all systems have been designed to reduce organic carbon (OC) and convert organic nitrogen (ON) to nitrate and/or nitrite (NOx -). Some systems have also included removal of the oxidized N in order to reduce overall oxygen consumption and produce additional N2 gas for cabin use. Removal of organic carbon will generally reduce biofouling as well as reduce energy and consumable cost for physiochemical processors.