Beneficial Bacteria Up in ARMS
After a hard day of work, nothing feels better than a long, hot shower.
In space, though, water is far too important to spend on such luxuries. Carrying fresh water into space takes up valuable cargo space and weight. On board the International Space Station and during Space Shuttle missions, NASA has to conserve as much water as possible.
One way to maximize water usage is to collect, clean and reuse wastewater from the sink, shower, the Shuttle's fuel cells, and even from urine and condensation.
"We're trying to move toward a biological treatment method -- using bacteria to help cleanse the water," explained Tony Rector, a bioprocess engineer with Dynamac, the Life Services Support contractor at NASA's Kennedy Space Center in Florida. "An efficient biological treatment method would require much less mass and energy than the physical and chemical water treatment processes used now on the Shuttle and the Station."
One such research project underway at KSC's Space Life Sciences Lab is the Aerobic Rotational Membrane System (ARMS), part of the Center's Resource Recovery research.
Inside the clear plexiglass ARMS reactor vessel, 115 tubes, called membranes, deliver gaseous oxygen to a community of bacteria. But believe it or not, this is a good thing! Fed by the oxygen, thin films of beneficial bacteria, called biofilms, grow across the membranes' surface and help cleanse the water.
Image to left: Bioprocess engineer Tony Rector monitors the Aerobic Rotational Membrane System (ARMS) in the Resource Recovery lab at Kennedy Space Center. His hand rests at the top of the reactor vessel. Inside, a series of 115 rotating membranes stretches to the bottom. Credit: NASA/KSC
Biological treatment reactors aren't anything new, but there's something unique about the one at KSC.
"The novelty is that membranes are rotating," Rector said. "Rotation increases our chance of developing biofilms, because as the membranes move, the bacteria are exposed to more of the contaminants they thrive on. As a result, we'll waste less oxygen and use all the space in the reactor, reducing the need for a larger reactor." Ultimately, this innovation could lead to a system that will clean water while freeing up precious cargo space.
Wastewater is pumped in a constant stream from the bottom of the reactor vessel. As the membranes sweep through the water, the bacteria break down and destroy contaminants. As the water emerges from the top of the vessel, chemical characteristics such as pH and the amount of oxygen concentration are monitored and compared to the condition of the water before it entered the vessel.
Because of the limited storage space available, each Space Station crewmember is rationed two liters of water per day. By comparison, the average Earth-bound American uses about 227 liters, or 60 gallons, daily.
"In space, the waste stream is more highly concentrated than it is on Earth, because so much less water is used," he explained. "So whatever system we end up with needs to be able to handle that increased contaminant load."
Image to right: Astronaut Susan J. Helms, Expedition Two flight engineer, sits in front of a large amount of water temporarily stored in the Unity node aboard the International Space Station.
Previous studies have proven that systems similar to ARMS, but without the rotating mechanism, are robust enough to handle the high concentration of contaminants. Now, scientists are trying to learn more about the effects and benefits of the rotating membranes.
No biological treatment reactors have flown in space yet, but the technology has been extensively ground-tested. Researchers like Rector are trying to improve them to the point that they can also be used for new, gravity-dependent initiatives, such as bases on the Moon or on Mars.
"At the moment, we're focusing on the immediate needs of the Station and the Shuttle in the microgravity environment. But looking ahead, we're thinking of ways to adapt to projects that NASA's vision
calls for," Rector explained with a smile. "We're looking ahead."
NASA's John F. Kennedy Space Center