The Science Behind NASA's Water Recycling: Astronauts Drink Purified Urine

As humanity prepares for extended space exploration missions, the need for sustainable water sources has become increasingly critical. During these missions, astronauts aboard the International Space Station (ISS) rely on advanced recycling methods to ensure a continuous supply of water, even resorting to the recovery of purified urine. This innovative approach not only supports astronaut health but also demonstrates a remarkable achievement in engineering and environmental sustainability.

Water is essential for various functions aboard spacecraft, including hydration, hygiene, temperature regulation, and protection against cosmic radiation. With extended missions planned beyond low Earth orbit, where resupply from Earth becomes impossible, NASA has developed robust systems for water reclamation. According to Jill Williamson, Environmental Control and Life Support System (ECLSS) water subsystems manager at NASA, "The regenerative ECLSS systems become ever more important as we go beyond low Earth orbit. The inability of resupply during exploration means we need to be able to reclaim all the resources the crew needs on these missions" (NASA, 2025).

The ISS employs a sophisticated ECLSS that recycles up to 98% of onboard wastewater, which includes urine, sweat, and cabin humidity. Christopher Brown from NASA's Johnson Space Center elaborated, "Let’s say you collect 100 pounds of water on the station. You lose two pounds of that, and the other 98 percent just keeps going around and around. Keeping that running is a pretty awesome achievement" (NASA, 2025).

Central to this water recycling process is the Urine Processor Assembly (UPA), which utilizes vacuum distillation to extract water from urine. Remaining brine is further processed by the Brine Processor Assembly (BPA). Williamson stated, "Before the BPA, our total water recovery was between 93 and 94 percent overall" (NASA, 2025). Now, with the BPA, NASA has achieved enhanced efficiency in water recovery systems.

The BPA employs membrane technology and dry air to evaporate residual water from urine brine. This humid air is then collected by dehumidifiers and sent to the Water Processor Assembly (WPA), which filters and purifies the water using a catalytic reactor. After rigorous testing for purity, the water is stored for use, with iodine added to prevent microbial growth.

Canadian astronaut Chris Hadfield has addressed public concerns regarding the safety of drinking recycled water. In a 2013 video, he reassured viewers, "Before you cringe at the thought of drinking your leftover wash water and your leftover urine, keep in mind that the water that we end up with is purer than most of the water that you drink at home" (NASA, 2013). This statement emphasizes the efficacy of the ECLSS in creating a self-sustaining environment aboard the ISS.

The water recovery improvements represent not just a convenience, but an essential requirement for human survival in space. As NASA reports, each astronaut consumes approximately one gallon of water daily, making these enhancements crucial for future missions aimed at exploring Mars and beyond (NASA, 2025).

In conclusion, the advancements in water recycling technology epitomize the ingenuity required for long-term human habitation in space. As we look toward the future of space exploration, the ability to reclaim and purify water from waste will be a cornerstone of sustaining human life off Earth. The success of these systems offers valuable lessons in resource management and sustainability that may one day be applied to environmental challenges on our home planet.