Evaluating RO performance with biological pretreatment of graywater Jason Crawley, W. Andrew Jackson, Todd Anderson, Lianfa Song and Audra Morse ABSTRACT Reverse osmosis (RO) is a treatment technology that may be used for the recovery of graywater terrestrially as well as the recovery of wastewater on board long duration, manned space flights. As with terrestrial RO applications, concentration polarization and membrane fouling lead to decreased productivity and increased energy demands with time. Physiochemical and biological pretreatment options can enhance the performance of the RO system; also, biological pretreatment has the advantages of low energy and consumable requirements as compared to other physiochemical pretreatment options. To determine the degree to which the incorporation of biological treatment enhances RO performance, a series of bench-scale experiments were performed. Observed resistances indicate that biological pretreatment alleviated the degree of non-reversible fouling while also improving the rate of permeate flux in a downstream RO process to further treat water. Results also indicated that enhanced urea hydrolysis, pH reduction, and carbon oxidation serve as the primary benefits of biological pretreatment of space-based graywater. The observations of this study may also benefit engineers considering the treatment of graywaters for terrestrial water-reuse applications. Jason Crawley W. Andrew Jackson Lianfa Song Audra Morse (corresponding author) Department of Civil and Environmental Engineering, Texas Tech University, Box 41023, Lubbock TX 79409–1023, USA E-mail: audra.n.morse@ttu.edu Todd Anderson Department of Environmental Toxicity, The Institute for Environmental and Human Health, Texas Tech University, Box 41023, Lubbock TX 79409–1023, USA Key words | flux, graywater, resistance, reverse osmosis, space INTRODUCTION As urbanization, droughts, and falling water tables continue to strain existing water resources, the need for creative water management practices will increase (Levine & Asano ; Maurer et al. ), and engineers and scientists must seek means to relieve stress on water supplies. One approach attracting attention is water reuse. Levine & Asano () go as far as to say that ‘society no longer has the luxury of using water only once’. By simply viewing wastewater as a valuable commodity with reuse potential rather than a sub- stance of little or no value, the amount of water available for use on the mission is vastly increased. Where you find mankind, you will also find water. Even as mankind travels beyond the confines of Earth, water will join in the travel. The same terrestrial challenges presented by water reuse also occur in spaceflight travel. For long duration space missions, the importance of wastewater recovery and reuse increases with mission duration ( Jones ). Recovery and treatment of wastewater to potable water standards provides a viable alternative to direct re- supply, due to the reduction in both mass and stowage demands. For the purposes of wastewater collection and treatment, one possible waste stream that can be generated based on the specific mission is the early planetary base wastewater (EPBW). The EPBW (Verostko et al. ) is composed of urine flush water, humidity condensate, and hygiene waste. The hygiene waste stream contains a large amount of surfactants, and the humidity condensate con- tains several organic compounds that account for a small majority of organic carbon in the EPBW. The urine waste stream provides the vast majority of nitrogen and organic 109 © IWA Publishing 2012 Journal of Water Reuse and Desalination | 02.2 | 2012 doi: 10.2166/wrd.2012.075 Downloaded from https://iwaponline.com/jwrd/article-pdf/2/2/109/375935/109.pdf by guest on 22 May 2020