Search Results

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.

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.

This research is based on the hypothesis that recycling biofilm can provide the required carbon to increase biological denitrification of the carbon limited early planetary base wastewater. Recycling biofilm may offer significant advantages including a reduction in solid waste from biological wastewater processors, increased N2 return to cabin air, a reduction in TDS loading to the RO system, and increased alkalinity to drive further nitrification. The results of the study indicate that denitrification rate did increase due to the addition of lysed biofilm derived from the nitrification reactor. However, there was a simultaneous large release of additional ammonium. Further work will be required to understand the magnitude of the ammonium release and overall benefits of the process.

The objective of this study was to investigate the potential of membrane-aerated bioreactors as long term microgravity compatible nitrifying biological water processors (BWP). A small-scale (1/20th) replica of the water recovery system (WRS) at JSC has been operated and extensively analyzed at Texas Tech University (TTU) for the last 3 years. The current nitrifying tubular reactor at JSC and TTU has experienced difficulty in maintaining efficiency and low maintenance. In an attempt to increase the efficiency of the biological portion of the WRS, a membrane-aerated bioreactor (MABR) was constructed and operated using the same parameters as the TTU-WRS in August 2003. The MABR is downstream of an anaerobic packed bed and is designed to promote nitrification (NH4 → NOx). The MABR achieved a percent nitrification of 61% and 55% for recycle ratios of 10 and 20, respectively.

Simulated wastewater, known as early surface mission wastewater, treated in previous experiments at JSC and TTU included urinal flush water, shower water, humidity condensate, oral hygiene water, and hand wash water. In reality, there is a difference between the early surface mission wastewater and the International Space Station wastewater. The ISS does not have a shower or hand wash, which contributes approximately 59 percent of the make-up water treated. The average influent ammonia concentration in the simulated wastewater treated by the TTU water reclamation system frequently exceeds 500 mg/L. Removal of the shower make-up water in simulated wastewater will result in a significant increase in the ammonia concentration, resulting in higher influent pH values and ammonia concentrations that may be inhibitory. Biological treatment technologies have suitably treated the diluted waste stream but a more concentrated waste stream may present a greater challenge.

The objective of this study was to evaluate the treatment efficiency and reliability of a small-scale (1/20th) replica of the JSC biological treatment system over an extended period of time (18 months of operation). The two biological reactor components were an anaerobic packed bed for denitrification and an aerobic tubular reactor for nitrification. A recycle line (20X) linked the two biological reactors. Effectiveness of the biological system to treat a waste stream (1 L/day) containing water, urine, and soap (Igepon T42) was quantified by monitoring total nitrogen and organic carbon. Distribution of nitrogen in the effluent was measured and consisted of ammonium, nitrite, and nitrate. Daily concentrations of total nitrogen in the influent varied greatly. The system achieved 50% removal of total nitrogen and 80% removal of the influent organic carbon. The results indicate improved treatment effectiveness and resiliency with time.

This research compared the nutrient content of the Biological Water Processor (BWP) effluent at JSC with acceptable nutrient ranges for general hydroponic NFT-solutions. Evaluated nutrient-components were NO3-N, P, K, Ca, Mg, Fe, Mn, Zn, B, Cu and Mo. Compared to Cooper's and Molyneaux's solution (Jones, 1997) BWP-nutrient concentrations were low for Ca, Mg, Fe and B. Compared to the NFT-solution used at KSC (Wheeler et al., 1997), the BWP-effluent showed higher contents of P, K, Zn, Cu and Mo and lower contents of N, Ca, Mg, Fe and B. This indicates that the BWP-effluent could support NFT-plant production.