There is a place where recycling and attention to water consumption and waste are brought to the extreme, and it is not allowed to waste even a drop: it is the International Space Stationthe ISS, where astronauts can live for months without supplies. The food is (almost) exclusively brought by the earth, but thewaterfall used by astronauts is 98% purified Thanks to a system that transforms the urine and sweat of astronauts into drinking water. But how are the ISS exhaust waters treated in practice?
The first treatments to recycle water aboard the ISS
The space station is the result of a long collaboration between different national agencies: for this reason also theEnvironmental Control and Life Support System (Eclss), the complex system for maintaining livable conditions on the ISS, is actually a combination of different modules, implemented over the years.
To recycle the water, on the ISS there is a complex system for treatment of urine and drain waters. A first form of pretreatment Remove the gaseous substances and oxidizes liquids, using compounds such as TR-OSSID chrome and sulfuric acid. THE’oxidation It is a fundamental process for Eliminate the organic substances And the bacterial charge, a method used (usually with biological systems and longer times) also in wastewater treatments also on earth.
The next form is the so -called Hear (Urine Processing Assembly), a system designed by NASA that uses a very low atmospheric pressure to do evaporate the water by distillationobtaining a much more concentrated liquid called as a waste frost.
Over the years the system has required several tests to verify its operation in conditions of microgravityan environment in which liquids behave very differently than how they do on earth. The waste are pumped inside one rotating evaporation chambera system that allows you to adhere to the walls the reflua water that otherwise could spread in the instrument. At controlled temperature and pressures, most of the water contained in the wastewater can therefore evaporate and be aspirated towards a second part of the AIP, where it will be reinforced.
The experiments were conducted both on Earth and in actual microgravity conditions: a series of experiments was also conducted during the STS-107 Missionthe unfortunate last trip of the Space Shuttle Columbia disintegrated upon return to the atmosphere on February 1, 2003.
New recovery systems: the Processor Assembly solar on the ISS
These systems already allowed the recovery of over 90% of the water exhaust, but the high cost per kg to send loads in the space has pushed the research to further improve recycling skills.
The system Processor Assembly frosts (BPA) was made to extract a further fraction of water from the waste of the UPA system, bringing the overall recovery 98%.
A double membranemicroporous inside and composed of Ionomeri (polymers with electrically loaded sites) outside, allows you to retain waste and leave breathe water as humidity Outside: this will then be condensed and recovered by the heat exchanger of the Water Processor Assemblythe same that recovers the humidity generated by sweating and breathing by astronauts. Each membrane is able to filter up to 22 liters of frost in a cycle of 26 days. The double membrane is replaced and disposed of together with concentrated waste.
