WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 1253
contaminants may also encourage the growth of bacteria in
the water storage and transport system. This is especially
true when urine, with its heavy load of organic compounds,
is treated and recycled. The specified maximum contaminant
level for unidentified organic compounds is in the ppb range.
Only about 70% of the organic content of urine distillate has
been identified, hence it is difficult to design compound-
specific removal techniques.
Oxidizers have been used to stabilize urine, but the use of
such compounds produces many volatile organic compounds.
Urine distillate obtained after such treatment was found to
have a TOC content of 25–30 mg/L and a high ammonia con-
centration. When non-oxidizing compounds were used for
pretreatment the TOC cotent was 8–10 mg/L and the ammonia
concentration was lower. Certain of the processes described
above are very effective in removing these organic compounds
and ammonia, and hence require less pretreatment.
Post-treatment methods of polishing the product water
are required after the main processes described above. Both
multifiltration and UV assisted ozone oxidation reduced the
TOC by over 90%. Reverse osmosis also achieved over 90%
reduction of TOC and ammonia.^34 The post-treatment tech-
nique required depends upon the process used to perform the
main water recovery.Finished Water Quality MonitoringIn order to avoid contamination the processed water is con-
tinuously monitored for the levels of certain key parameters
which are indicative of the water quality for the desired appli-
cation. This is necessary to detect any loss of performance
in the processing equipment, such as subsystem failure, or
exhaustion of a consumable component in the system.PLANNED TERRESTRIAL USE OF ECLSSAttempts are being made to utilize ECLSS technology at the
South Pole station. The proposed system is designed to recy-
cle water and to grow plants, and later fish, for food at the
South Pole. The Antarctic winter lasts some nine months,
and the South Pole station is completely isolated during that
time. Even emergency medical evacuations are very difficult
and rare. A major supply problem is the need to transport
some 240,000 gallons of diesel fuel to the station during the
short 14 week summer flying season. The proposed ECLSS
will reduce the amount of fuel needed. The system will be
built in stages, and will ultimately include a waste processing
facility. It will include some physical/chemical processing
technology, particularly for the feed liquid to the plant grow-
ing facility. Experiments are being conducted to evaluate
high yield varieties of edible crops. Experiments are planned
to utilize wind power, solar obviously not being available
during the Antarctic night.^35 This facility may prove more
useful for evaluating possible terrestrial uses than many of
the space studies, as the equipment is designed for normal
gravity, with less emphasis on minimizing volume and weight,and maintenance requirements can be more relaxed than
those for the space station.SUMMARYIn summary, the systems described have high rates of water
recovery, and remove or destroy a wide variety of contami-
nants. The technologies developed may have terrestrial appli-
cations. The emphasis on weight and volume saving that is
such a major part of the NASA evaluation process may not
apply to the same extent for terrestrial uses. Hence the produc-
tion of reliable systems utilizing the principles tested by NASA
should be relatively easy. It is not likely that the recycling of
urine will be needed for many, if any, terrestrial uses, thus
removing one of the most stringent NASA-imposed require-
ments for water recovery. Power efficiency, particularly in an
integrated water recovery system, may be worth paying a high
financial price for, in certain specialized needs. The present
NASA system uses only 2 W per hour per kg of water recov-
ered.^2 For some of the systems described it will be necessary
to determine the composition of the contaminants in the waste
stream as accurately as possible, in order to design and test the
system. The requirements in possible terrestrial applications
will vary tremendously according to the specific application.
Recycling of urine is unlikely, but recycling of hygiene water
is more likely. The make-up potable water may come from an
original stored supply or low volume natural supply source.
It may be possible to use metabolic wastes as input to a pro-
cess for producing sterile fertilizer for plants, thus recovering
water and reducing the volume and possibly the toxicity of the
wastes generated. The water recovered from transpiration has
potential for use as a potable water supply.
A major problem is that the conventional soap seriously
affects some of the processes developed for space applica-
tions. They have all been designed to process wastewater
which does not contain foaming cleansers. Hence any tech-
nology that is being considered must be tested with conven-
tional cleaning products.
Other possible applications for ECLSS technologies may
be to clean up well defined industrial waste streams. Several
of the basic technologies can provide the capability to both
concentrate and treat contaminants, and produce near-potable
water as a bonus. As the basic technologies have been devel-
oped for space, it should be simple to produce mobile or
package (skid-mounted) unites for industrial applications.
It must be remembered that the hardware developed for the
space program has been designed to handle the waste from a
small number of people, and will probably have to be made
much larger for most likely terrestrial applications.REFERENCES- Mitchell, K.L., et al., Technical Assessment of MIR-1 Life Support
Hardware for the International Space Station, Structures and Dynamics
Laboratory, George C. Marshall Space Flight Center, NASA TM108441,
March 1994. - Craig, C., R. Davenport, and M. Plam, Water reuse in space, Worldwater,
February, 1996, pp. 11.
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