NASA has found a way to recycle 98% of the pee and sweat that astronauts produce on the International Space Station.
Once recovered and treated, the water can then use for consumption, food preparation and brushing teeth. Achieving 98% total recovery - the previous figure was between 93 and 94% - is a milestone for low-orbit space exploration that seeks to provide basic supplies for astronauts, such as air, food and water, without the need for expensive resupply missions.
While the team acknowledges the idea of drinking recycled urine might make some people squeamish, they say the end result is far superior to what water treatment systems produce on the ground.
"The crew are drinking water that has been reclaimed, filtered and cleaned such that it is cleaner than what we drink here on earth."
Jill Williamson, NASA water subsystems manager, said, “The processing is fundamentally similar to some terrestrial water distribution systems, just done in microgravity.
"The crew is not drinking urine; they are drinking water that has been reclaimed, filtered and cleaned such that it is cleaner than what we drink here on earth. We have a lot of processes in place and a lot of ground testing to provide confidence that we are producing clean, potable water.”
Ideally, crew support systems need to recover close to 98% of the water that crews bring along at the start of a long journey. The space station’s environmental control and life support system (ECLSS) - a combination of hardware that includes a water recovery system - has demonstrated that it can achieve that goal.
This capability will be critical as humans travel deeper into space and resupply is not possible.
Christopher Brown of the Johnson Space Center, which manages the space station’s life support system, said, “This is a very important step forward in the evolution of life support systems.
"Let’s say you collect 100 pounds of water on the station. You lose two pounds of that and the other 98% just keeps going around and around. Keeping that running is a pretty awesome achievement.”
ECLSS collects wastewater and sends it to the water processor assembly (WPA), which produces drinkable water. One specialised component uses advanced dehumidifiers to capture moisture released into the cabin air from crew breath and sweat.
Another subsystem, the urine processor assembly (UPA), recovers water from urine using distillation and a brine processor. The BPA runs the brine produced by the UPA through a special membrane technology, then blows warm, dry air over the it to evaporate the water. That process creates humid air, which, just like crew breath and perspiration, is collected by the station’s water collection systems.
All the collected water is treated using specialised filters, then a catalytic reactor that breaks down any remaining trace contaminants. Sensors check the water purity and unacceptable water is reprocessed.
The system also adds iodine to the acceptable water to prevent microbial growth and stores it, ready for the crew to use. Each crew member needs about a gallon of water per day.
The systems have been carefully tested, not only to ensure that they perform as intended, but also to demonstrate that each is reliable and can operate long-term without a lot of maintenance or spare parts.
“The regenerative ECLSS systems become ever more important as we go beyond low earth orbit,” Williamson says. “The inability of resupply during exploration means we need to be able to reclaim all the resources the crew needs on these missions.
"The less water and oxygen we have to ship up, the more science that can be added to the launch vehicle. Reliable, robust regenerative systems mean the crew doesn’t have to worry about it and can focus on the true intent of their mission.”