In a final step, to rid the water of the remaining organic contaminants, it flows through a high-temperature catalytic oxidation process. The water is heated, and oxygen is injected to oxidize the contaminants to either carbon dioxide or other gases that can more easily be removed. And for good measure, NASA adds iodine to the water to keep microbes at bay.

To make sure that it works properly, the system will continually collect samples of the drinking water and send them back to Earth for testing on future shuttle missions.

The system is the first to purify urine in space; the Russians have a similar, but smaller, water processing system that is only able to treat the water derived from humidity in the cabin.

The new system is part of a plan to expand the number of crew members that can adequately live on the ISS without heavily relying on supplies from Earth. Once the space shuttles retire--currently scheduled for 2010--the shuttle replacements will have limited payload capacity.

The water treatment system is a small but fundamental part of NASA's ISS makeover. NASA also sent new crew living quarters and exercise equipment.

Bagdigian says that the engineers are already looking ahead to how the water system could work farther out in space. "We are making plans to establish a permanent presence on the moon," he explains. "This new hardware will give us the operational experience with regenerative life-support systems so we know what works well, and what parts we can improve."