April 2005 Mechanical Engineering Departments: Tech Focus, Pt. 2

This section was written by
Associate Editor Gayle Ehrenman.

Fluid Handling
and Fluid Power

Water Wonders

Columbus never would have discovered the New World, if his crew didn't have enough water to drink. Similarly, man won't make it to Mars without enough potable water. But NASA is working on solving that particular problem.

Researchers at NASA Ames Research Center at Moffett Field, Calif., have developed a water recycler that can turn wastewater into potable water. The washing machine-size device can run for three years without needing maintenance or resupplying, according to Michael Flynn, principal investigator for the NASA Ames Advanced Water Recycling Development Lab.

The system uses fully regenerative technology, according to Flynn. "You just provide electricity, and turn it on. It runs three years without human intervention," he said.

Researchers at NASA Ames Research Center have developed a water recycler that can convert 13.2 pounds per hour of wastewater into drinkable water. Water Reuse Technology Inc. is building the unit.

The unit, which is being developed with Water Reuse Technology Inc. of Garden Valley, Calif., uses distillation technology to turn wastewater and urine into drinkable water.

"The process is analogous to how the water cycle works," Flynn said. The device, which is officially called the Vapor Phase Catalytic Ammonia Removal system (or the equally tongue-twisting VPCAR), heats the waste stream to create vapor. The vapor passes through a platinum catalytic reactor, which converts its organic content into CO₂ and O₂.

Ammonia in the vapor is converted to nitrous oxide. In a second Rosidium-based reactor, the nitrous oxide is converted to nitrogen and oxygen. The vapor passes through five phases before it condenses to form a liquid that is suitable for drinking.

A preliminary engineering development unit can recycle 13.2 pounds per hour, or about one gallon, of wastewater into drinkable water.

"If we were going to Mars tomorrow, this is the water treatment system astronauts might well use," Flynn said. "This unit can enable a six-person crew to shower, wash clothes and dishes, drink water, and flush toilets over three years without resupply," he said.

Flight validation is the next step in testing the system, according to Flynn. A micro-gravity compatible version of VPCAR is being tested in parabolic aircraft at the Johnson Space Center.

Prize Targets Arsenic

The National Academy of Engineering has established the Grainger Challenge Prize for Sustainability. The competition will award a $1 million prize for the development of a community- or household-scale water treatment system to remove arsenic from contaminated drinking water.

Arsenic-contaminated drinking water is a particular problem in South Asia and China. The World Health Organization estimates that more than 50 million people in the Asia region drink arsenic-laced groundwater.

"Different solutions are required in the developing world, and the solution has to work in the field," said Alden Henderson of the U.S. Agency for Toxic Substances and Disease Registry in Atlanta.

Arsenic-contaminated drinking water is a major problem in Bangladesh, where between 8 million and 12 million people rely upon shallow tube wells, according to the World Health Organization. These tube wells, which provide a cheap, low-tech way of accessing groundwater, were built with international aid to provide an alternative to bacteria-tainted surface water. Unfortunately, these wells frequently tap into aquifers contaminated by arsenic from natural sources.

Arsenic poisoning is a slow, painful process that can result in death.

The Grainger Challenge Prize criteria state that the system should provide a rural community of approximately 1,000 residents with 7.5 liters per person daily of potable water.

The system must have a low lifecycle cost and must be robust, reliable, easily maintainable, socially acceptable, and affordable. As a sustainable technology, the system must also be within the manufacturing capabilities of a developing country and must not degrade other water-quality characteristics or introduce pathogens.

The prize, which is being financed by the Grainger Foundation of Skokie, Ill., will be awarded in February 2007.