Forward Osmosis Bag (FOB) - 09.17.14
ISS Science for Everyone
Science Objectives for Everyone
The Forward Osmosis Bag (FOB) system is designed to convert dirty water into a liquid that is safe to drink using a semi-permeable membrane and a concentrated sugar solution. FOB looks at the forward osmosis membrane in a space flight environment and compares its performance against ground reference controls.
Science Results for Everyone
Hydration Technologies Inc (HTI), Albany, Ontario, Canada
Kennedy Space Center, , FL, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2011 - September 2011
Previous ISS Missions
FOB is a new payload, therefore there are no previous missions associated with it.
- Forward osmosis is the natural diffusion of water through a semi-permeable membrane from a solution of a lower concentration to a solution with a higher concentration. The semi-permeable membrane acts as a barrier that allows small molecules such as water to pass through while blocking larger molecules like salts, sugars, starches, proteins, viruses, bacteria and parasites.
- The Forward Osmosis Bag (FOB) investigation uses the osmotic pressure gradient across the membrane to produce a total flow of water through the membrane into the draw solution. Driven by an osmotic pressure gradient, forward osmosis does not require direct energy input. Forward osmosis is a low-resource water treatment technology that offers the advantage of high rejection of a wide range of contaminants than traditional membrane processes.
Buoyancy-driven convection and concentration polarization are known to affect membrane performance on Earth. Concentration polarization is the build up of a concentration gradient of solutes on the surface of the semi-permeable membrane. In 1 g environments temperature driven buoyancy effects tend to disrupt concentration polarization because buoyancy-driven mixing does not happen in microgravity. This suggests that the rate of "clean" water being transferred through the semi-permeable membrane is slower in microgravity. However, a reduction in concentration polarization may increase the rate of "clean" water being transferred. The FOB experiment determines which of these two are true and will aid in the advancement in water treatment technology in a microgravity environment.
Forward osmosis is a low-resource water treatment technology that can be ideal for spaceflight applications. It utilizes a semi-permeable membrane and a liquid osmotic concentrate to convert non-potable water into a liquid that is safe for consumption. Buoyancy-driven convection and concentration polarization are physical phenomena known to affect membrane performance in a unit gravity environment. Concentration polarization is the build up of a concentration gradient of ionic species, or other solutes, on the surface of the semi-permeable membrane. In 1 g environments temperature driven buoyancy effects tend to disrupt concentration polarization and minimize its effect. In microgravity this buoyancy-driven mixing does not occur. It is possible that if this happens the concentration gradients will build up to an extent that the process will not work or the production rate will be significantly reduced. Performance in a microgravity environment can be modeled, but is difficult to predict. The absence of buoyancy-driven convection in microgravity suggests that mass transport will be dominated by diffusion, slowing the rate of permeate production across the membrane. Conversely, a reduction in concentration polarization, as hypothesized by the Commercial Off The Shelf (COTS) device manufacturer, may increase the rate of permeate production.
A critical component affecting membrane performance will be the efficiency of membrane wetting during the initial charging of the FOB device. Some minimal air entrainment is expected in the non-potable “challenge” fluid. Two-phase fluids are prone to form non-homogeneous foams in microgravity that may inhibit membrane wetting or reduce the effective wetted surface area of membranes. This FOB membrane is highly hydrophilic and is expected to wet thoroughly even in the presence of a non-homogeneous foam.
As a part of the FOB-1 protocol, one set of three osmosis bags will be mechanically mixed/agitated by a crewmember while a second set of three osmosis bags will simply be charged with fluids and then remain quiescent. The hypothesis for testing in the FOB-1 experiment is that mechanical agitation will not affect the performance of the membrane as measured by membrane flux rate and/or wetted surface area after a six-hour exposure interval. Any detrimental effects of a non-homogeneous two-phase fluid contacting the membrane will be overcome by the highly hydrophilic nature of the membrane material.
The FOB hardware is comprised of five main components: the Forward Osmosis Bag, Input Storage Bag, Forward Osmosis Pump Syringe, Forward Osmosis Sampling Syringe and Osmotic Concentrate Syringe.
Forward osmosis technology has several potential applications for spaceflight. A small forward osmosis device could be incorporated into new long-exposure EVA suits in order to recycle metabolic wastewater (i.e., sweat and urine) into drinkable fluid. Determining the effect of mechanical mixing on membrane performance may help inform suit designers in the placement of a device to maximize permeate production. Suit elements that move freely, such as the legs, provide more mixing than the back for example.
A forward osmosis device similar to the existing COTS product could be incorporated into new return vehicles as a mass and volume-efficient method of providing crews with post-splashdown fluids. The existing lightweight COTS product can be tethered in seawater to produce a drinkable fluid. Current vehicle designs contemplate launching and returning only 2 kg of contingency water per crewmember.
A very near term application of the technology is its ability to extend existing non-potable water resources on the ISS in off-nominal situations. Currently, there are several broadly defined classes of water on the ISS including potable water, technical water, and wastewater. Potable water contains an effective concentration of a residual biocide and is intended for crew consumption. Technical water is used for processes such as oxygen generation. Wastewater is produced from multiple sources that may include humidity condensate, hygiene water, urine, flush water, and gray water. In the event that a resupply vehicle is delayed or the primary water-recycling system becomes nonfunctional, technical and/or wastewater from different sources can be treated for crew consumption using a forward osmosis device. The current COTS device can be reused for up to ten days. This provides a low mass alternative for the reduction of stockpiled water on the ISS and provides flexibility during off-nominal situations.
Hydration Technology Innovations (HTI), the manufacturer of the Forward Osmosis membrane used in NASA’s greywater recycling system, has used the same technology to create a lifesaving water filter. This filter is called the HydroPack, and will provide a clean, safe drink from any contaminated water source by simply dropping the product in water and leaving it to hydrate for ten hours. The Forward Osmosis membrane blocks all contaminants and provides an electrolyte enhanced drink that is beneficial to anyone in a water emergency situation.
This product has been successfully used in disaster relief efforts for the 2010 earthquakes in both Haiti and Chile and tested in the waters from the aftermath of Katrina. Most recently HTI conducted a research project on the HydroPack in a small village in Kenya, Africa. Ninety households in the flood prone village of Mudimbia took part in this ten-day project to prove the efficacy of the product as the better alternative to bottled water for the initial phase of disaster relief operations. The project was administered by the Kenya Water for Health Organization (KWAHO) and was closely observed by UNICEF, USAF and the Kenya Water Minister. The results so far have been outstanding. The people of Mudimbia found the HydroPack had a great flavor and was easy to use. The lab results showed that hydration levels improved through the test period and that there was no contamination in the produced drink.
One helicopter filled with HydroPacks is equivalent to sending 14 helicopters of bottled water. The logistical benefits combined with the new Kenya research project data illustrates that HydroPacks are the best solution for providing emergency hydration during the initial phase of disaster relief situations.
To learn more visit HTI’s Kenya Project Blog Water Division
The FOB experiment requires one crewmember to perform all activities including hardware set-up/initiation and sampling. These two activities are separated by a crew-untended period of approximately five hours. The FOB experiment requires digital downlink of images taken during operations. All FOB hardware is to be turned over to the NASA/KSC Payload Manager no more than 24 hours after return via STS-135.
The U.S. crewmember will remove all six of seven (seventh being a spare) FOB kits from the assigned middeck locker and transfer all items to a designated location to perform on-orbit operations. The flight experiment consists of charging each ‘challenge’ side of FOB with the contents of the Input Storage Bag (500 mL of KCl and 0.1 percent Methyl Blue Dye) using the Forward Osmosis Pump Syringe. All contents from the Input Storage Bag are to be transferred to the FOB utilizing the syringe pumping system. Then the U.S. crewmember will charge the ‘product’ side of FOB with 60mL of an osmotic concentrate consisting of fructose and glucose syrup using the Osmotic Concentrate Syringe. The U.S. crewmember will hand knead three Forward Osmosis Bags for approximately two minutes each to induce mechanical mixing. The remaining three Forward Osmosis Bags will not be hand manipulated. Upon completion of the FOB set-up initiation, all of the FOB hardware will be re-stowed in the middeck locker.
Once the FOB is charged, water is autonomously drawn through the membrane by the process of forward osmosis and collects in the ‘product’ side. After five hours, the U.S. crewmember will draw the treated product water into the Forward Osmosis Sample Syringe. Once all six Forward Osmosis Sample Syringes are filled, one syringe from each of the six Forward Osmosis Bags, the U.S. crewmember will return the six Forward Osmosis Bags and six Forward Osmosis Sample Syringes to the middeck locker to be stowed at ambient conditions until landing.
Flynn MT, Soler MP, Shull S, Broyan, Jr. JL, Chambliss JP, Howe AS, Gormly S, Hammoudeh M, Shaw H, Howard K. Forward Osmosis Cargo Transfer Bag. 42nd International Conference on Environmental Systems, San Diego, CA; 2012 Jul 15-19
Ground Based Results Publications
Flynn MT, Gormly S, Cath TY, Adams VD, Childress AE. Direct osmotic concentration system for spacecraft. International Conference On Environmental Systems, Chicago, IL; 2007
Gormly S, Flynn MT. Lightweight contingency urine recovery system concept development. International Conference On Environmental Systems, Chicago, IL; 2007 01-3037.
Edney S, Birmele MN, Roberts MS, Roberts MS. Evaluation Of A Passive Water Treatment Device for Contingency Liquid Recovery from Urine for Spacecraft Applications. 39th International Conference on Environmental Systems, Savannah, GA; 2009 01-2488.
Hydration Technology Innovations
Forward Osmosis Bag. Image courtesy of Monica Soler.
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Filling of Forward Osmosis Bag outer partition with ‘dirty’ solution from the Input Storage Bag using the Forward Osmosis Pump Syringe. Image courtesy of Monica Soler.
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Injection of Osmotic Concentrate into inner partition of Forward Osmosis Bag. Image courtesy of Monica Soler.
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NASA Image: S135E011546 - Mission specialist Rex Walheim uses the Forward Osmosis Pump Syringe to inject the Challenge Liquid into the Forward Osmosis Bag (FOB) during the FOB experiment on the Atlantis middeck (MDDK).
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