On the STS-135 Space Shuttle mission, to be launched July 8, 2011, a forward osmosis bag (FOB) study will be conducted. At NASA Ames this summer, the ground truth testing is being conducted for results comparisons. The FOB technology is derived from a commercial product, the X-Pack water filter. Forward osmosis operates by utilizing an established concentration gradient across a semi-permeable membrane to move water molecules from one side of the membrane to the other. This concept is exploited to harvest drinking water from grey water sources such as urine, sea water, or vehicle water. In this experiment, potassium chloride (KCl) dissolved in water is used to simulate grey water. The KCl water is inserted into the FOB on one side of the membrane and highly concentrated sugar water is inserted on the other. The high concentration of sugar solutes creates a gradient that drives water molecules to pass through the membrane and enter the other side. The membrane properties prevent the solutes from diffusing, allowing only the water molecules to be harvested from the solution. The FOB efficiency is tested by use of a fluorescent dye marker in the sugar water side of the bag. The concentration of the dye decreases as more water diffuses across the membrane. The concentration of the dye is measured using a fluorometer and comparing intensity readings to intensity values of known concentrations. It is expected that the current system will retrieve 60% of the water from the grey water source. This concept could be used in space to provide drinking water in emergency situations
