Tech Engineering professor Dietrich aids NASA water researchBy Lynn Nystrom
Spectrum Volume 19 Issue 22 - February 28, 1997
The space agency's cost of taking objects into space is about $5,000 a pound. Because one gallon of water weighs 8 1/2 pounds, this small amount alone equates to $42,500. That price makes for an expensive glass of drinking water.
If the astronauts want to have cost-efficient drinking water in the next space environment, the international space station, they will have to use recycled water. The trick will be to both purify the liquid and to make it appealing to the senses.
In the past, the space shuttle's daily operations provided for a continuous production of water as a byproduct from the hydrogen-oxygen fuel cells. Iodine was added to this H20 to act as a disinfectant and the result was drinkable water. But hydrogen-oxygen fuel cells will not be used in the controlled environment of the space station, so water will not be produced as a by product. An alternate source of drinking water will be needed for NASA's future space vehicles.
And when iodine is added to this recycled water for disinfection, the small molecules can react with it to produce "undesirable effects such as bad taste, unpleasant odor, and new chemicals that could have potential health problems," Dietrich said.
To help solve this problem, NASA, in conjunction with the Universities Space Research Association, conducted a nation-wide search to locate some experts in drinking water analysis and treatment. The agency selected Andrea Dietrich, a specialist in environmental chemistry and a member of Virginia Tech's civil engineering department, as one of its two visiting scientists in space life sciences. The selection allowed Dietrich to travel to the Johnson Space Center during the summer of 1996 to help evaluate the chemical composition and odor of recycled water for spacecraft drinking water.
Dietrich was joined at the Houston-based facility by J. Lawrence Katz, professor of biomedical engineering, Case Western Reserve University.
Dietrich said NASA should be able to collect recycled water for drinking from the space station's wash water and cabin condensation such as perspiration and humidity, as well as from urine.
In these forms of moisture, it is "fairly easy to remove the large molecules like detergents and salts," Dietrich said. "The challenge to producing good drinking water comes with trying to eliminate the small, water-soluble organic molecules that have only a few atoms."
And when iodine is added to this recycled water for disinfection, the small molecules can react with it to produce "undesirable effects such as bad taste, unpleasant odor, and new chemicals that could have potential health problems, "Dietrich said. The situation is not unlike what happens when chlorine is added to treat drinking water on earth. The major difference between iodine and chlorine use is that the effects of chlorinating drinking water have been well-researched because chlorine is so widely used, whereas iodine's application for potable water is limited and not well-researched.
Despite the problems, iodine-which is a solid at room temperature-remains the disinfectant of choice for the space station because NASA does not want to use liquids or gases in the zero gravity of space. "If a gas leak occurred inside the enclosed spacecraft, it could cause serious problems," she said.
The six weeks Dietrich spent at the space command center will be complemented by her continued work at Virginia Tech. She hopes to secure funding from the National Research Council (NRC) to continue her research.
NASA wants both chemically safe and pleasant-tasting water for the astronauts. So, in addition to performing chemical analyses, Dietrich has a team of graduate students who are trained to evaluate drinking water on the basis of its odor and taste. They plan to simulate the NASA conditions, using data Dietrich gathered while at the Johnson Space Center.
The best way to evaluate the sensory quality is to have humans test it, Dietrich said. As they do, the testers use words to describe the odor and taste of water, ranging from swampy to medicinal to fruity
"There is a bit of the chicken/egg theory. If we identify the chemical composition, then it is easier to do the sensory analysis. But, the human nose is often more sensitive than our scientific instrumentation. This sometimes means that a chemical can be detected by smell, but not by our instruments," she said.
After the particular compounds that have undesirable odors have been identified, then steps can be taken to control their presence, and the recycled drinking water would be more appetizing for the women and men who venture into space.