Analyzers Provide Water Security in Space and on Earth
- Saturday, 01 January 2011
Resourcefulness is a key quality for living in space, and on the International Space Station (ISS), that means making the most of water supplies. In 2008, the installation of the Water Processing Assembly (WPA) onboard the ISS allowed the space station’s crew to do just that. The WPA purifies moisture from nearly every possible source—sweat, water vapor, wastewater, and even urine—for drinking and oxygen generation. Capable of producing 35 gallons of potable, recycled water a day, the system has reduced the need for water delivered to the ISS by over 1,000 gallons a year, saving significant payload costs in the process.
As with any drinking water, quality is a concern, particularly when that water has been recycled. This is an issue of particular interest in space, where ISS crewmembers would have to deal with any illness far from the nearest medical personnel and facilities. The WPA employs sensors that monitor water quality by measuring its conductivity, and rounding out the system’s quality assurance methods is a device developed for NASA by a private industry partner. That company has now made the technology available for ensuring the purity of water for consumption and industrial uses on Earth.
Known as a total organic carbon analyzer (TOCA), this device measures organic carbon levels in water, a key indicator of water quality, as carbon is present in most dangerous contaminants. Prior to the installation of the WPA, the ISS had a commercial TOCA onboard, but that technology did not fully satisfy NASA’s requirements. To develop a better solution to ensure the potability of the WPA’s recycled water, NASA contracted OI Analytical of College Station, Texas, in 2006. Working in conjunction with Wyle Laboratories, the company had proposed an advanced TOCA device that provided fast, effective monitoring of TOC levels while eliminating aspects of the technology that made it impractical for space applications.
The resulting Proto-flight Unit, or PFU1, proved to be the innovative breakthrough NASA needed to fully enable the WPA. Detection of TOC in water requires an oxidation process that standard TOCAs generate using either expensive, hazardous chemicals or through high temperature combustion—neither feasible for an environment like the ISS. OI devised an electrochemical solution to create oxidation using the water itself. By applying an electrical voltage to a composite electrode in the oxidation chamber of the analyzer, the TOCA breaks down the water sample, forming hydroxyl radicals that in turn break down any organic molecules into carbon dioxide and water. The analyzer’s infrared detector then measures the concentration of carbon dioxide to provide an accurate assessment of the water’s organic carbon content.
“The original prototype was at a level that allowed us to save two years in the development process,” says Gary Erickson, research and development manager for the TOCA project. This in turn allowed NASA to implement the WPA ahead of schedule. With the system’s recycling capabilities and now fully redundant safety measures, the ISS not only required fewer water deliveries, but it was also able to realize its full crew capacity—increasing from three members up to six.
OI recognized the potential for its NASA technology as a commercial solution. Adapting it for terrestrial use, the company now sells the electrochemical-oxidation device as its 9210e On-Line Total Organic Carbon Analyzer. The NASA-derived system provides a host of benefits for water quality applications ranging from municipal and industrial water treatment to feed water and condensate return in turbines and boiler systems.
“Essentially any place where large amounts of water are used, from the cleanest to the most contaminated, the need to measure organic carbon exists,” says Erickson, also market manager for the TOCA technology, “but the costprohibitive nature of the technology kept it from being mandated in a number of areas, and it kept commercial companies from utilizing the technology.”