343 SYSTEMS: ENVIRONMENTAL CONTROL AND LIFE SUPPORT SYSTEM—SUPPORTING THE HUMAN ELEMENT OF THE ISS CHAPTER 19 43 kg (~95 lbs) of water. Cargo vehicles such as the HTV can also deliver water using CWCs, which are then stored until they are processed by the WPA. Similar containers are available on the Russian side. Additional wastewater comes from the Urine Processor Assembly (UPA) (Figure 7), which receives input from the Waste and Hygiene Compartment (WHC). A crew of six generates about 9 kg (20 lbs) of urine a day. Using flush water, the WHC sends the urine to the UPA (solids are retained in a tank to be disposed of later). Urine consists mostly of water but also contains many organic and inorganic waste products including urea, chloride, sodium, potassium, and creatinine. The urine is treated with a chemical, called pretreat, to prevent the urea from crystalizing and potentially plugging the plumbing lines. A filter also removes any particulates that are left behind. Once in the UPA, the urine is pumped to the distillate assembly where the temperature is raised and the pressure is lowered to cause water evaporation. This evaporated water is compressed back into liquid form and is passed along to the WPA for further processing. The remaining fluid, called brine, is sent to the Advanced Recycle Filter Tank Assembly (ARFTA) where multiple filters pull out any particulates as the brine is sent back to the distillate assembly where it joins with more pretreat urine and more water is pulled out. Accumulator To Potable Water Bus Delivery Pump Product Water Tank From Wastewater Bus Reject Line (Allows reprocessing) Mostly Liquid Separator (Removes air) O2 from ISS Low Pressure To Cabin To Cabin To/from Moderate Temperature Loop Microbial Check Valve (Provides isolation) Gas/Liquid Separator (Removes oxygen) Particulate Filter (Removes particulates) Multifiltration Beds (Removes dissolved contaminates) Reactor Health Sensor Regen. Heat Exchanger (Recovers heat) Reactor (Oxidizes organics) Pump Filter Wastewater Tank Preheater (Heats water to 275°F) Ion Exchange Bed (Removes Reactor by-products) Figure 8. Schematic of the WPA. Water is drawn from the wastewater tank and passes through a filter that separates gasses from the water since gravity isn’t present to facilitate natural separation. The water then passes through various filters including a heater to bake out impurities, a reactor to remove organics, and an ion exchange filter bed that will remove by-products of the organic reaction. Clean water is then stored in the product water tank. The WPA is a key component of the water system on the ISS (Figure 8). First, water that is stored in the wastewater tank passes through a centrifugal pump called the Mostly Liquid Separator (MLS) similar to that used in the CCAA to remove air from the water. The water then