Water Recycling In Space
NASA evaluates water purification system
A team from NASA at
Marshall Space Flight
Center in Huntsville, Ala
bama, is testing a system that will recycle all the water produced by astronauts aboard the intemational space station - including perspiration, shower and shaving water, even urine into fresh drinking water. NASA and its intemational partners are beginning assembly of the Space Station - a permanent, orbiting labora tory where astronauts will live and work year-round. Weight and storage limita tions will make continued recycling of water necessary, and even then, water
I
will be rationed.
A major series of tests at Marshall has been completed on the water recy cling system planned for the Space Sta tion and researchers are giving it high marks.
Eighty volunteers participated in the six-month study to evaluate the effi ciency of the system. Bach day approxi mately 20 of the volunteers would each complete an hour of activities - exer cising, eating, showering, washing their hands, shaving, brushing their teeth, and using the bathroom -in the test facility. On earth, water treatment plants use biological treatment to purify the water. Microorganisms metabolize and destroy contaminants. In contrast, the Space Station water recovery system uses physical and chemical processes to re move contaminants.
The Space Station Urine Processor uses distillation to evaporate and remove the more volatile components of urine, including the water. Less volatile and less desirable components remain as a liquid brine, which eventually has to be disposed of as waste. The Space Station Water Processor uses four technologies to purify the water. These technologies include particulate filtration, ion exchange, carbon adsorption, and catalytic oxidation. Fol lowing these steps, iodine is added as a microbial biocide, similar to the use of
chlorine in most municipal water sys tems. Last of all, the quality of the water is monitored to ensure the purifi cation process is working and water quality is acceptable. The system successfully recycled and purified the wastewater into potable water for 146 days, including the first 50
The water recycling system planned for the International Space Station recently completed a major series of tests at l\/larshall Space Flight Center In Huntsville, Alabama. Volunteers completed one-hour routines of daily activities in the test facility. The system collected and recycled all the water In the environment, including humidity from respiration, perspiration and microwave use; wastewater from showers, hand washes,shaves, toothbrushes and urine.
128 days in which the product water was recycled for use by the volunteers. This is significant because of the concern that contaminants not efficiently removed by the system would begin to accumulate after extended recycling. Of course, a significant measure of the system's success was the taste test. Test subjects said the water was very acceptable for drinking. There were no bad tastes or odours reported. • "The system was able to remove all microbial health hazards from the
water," said Monsi Roman,chief micro-
biologist for the Space Station life sup port system.
Viral test procedures for the system were developed as a cooperative effort by Marshall and the US EPA. During testing, a mixture of four viruses was added to the water. Only viruses capa ble of infecting bacteria were used so there was no risk to the volunteers par ticipating in the study. The water was then processed through the system. Test results show that the water processor is capable of removing all viruses present in the wastewater.
The processing system being devel oped for the Space Station can effi ciently recycle water containing a high concentration of contaminants. The less
water used, the higher the concentration of contaminants.
The system is claimed to be very ef ficient-10,000 times better than the av
erage water treatment plant. On board the Space Station, water will be rationed, so there will be a much higher concen tration of contaminants than dealt with
on earth.
For short-duration missions, it is not
necessary to recycle air, water or waste since sufficient quantities can be taken along. But with long-duration missions - such as Space Station or a venture to Mars-it is necessary to recycle as much as possible to reduce re-supply and stor age requirements. The Space Station water recovery system also could have applications for water processing on earth. One area where it might be applicable is in geo graphical areas where temperature is a factor, such as the basins of Antarctica
where biological processes do not work due to extremely cold temperatures. Physiochemical processes, like those used by the Space Station system,could work there.
Testing began in May 1990. The next stage of testing is scheduled to begin in mid 1998. After testing is complete,the system will be ready for integration into the habitation module, the living quar ters of the Space Station. For more information, circle reply card No. 145
Environmental Science & Engineering, March 1998