Encyclopedia of Environmental Science and Engineering, Volume I and II

1252 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE

TABLE 3

Summary of Described ECLSS Technologies for Water Recovery

Technology Maximum Water

Recovery Rate %

Comments References

TIMES membrane filter 93 Max feed concentration 38%. 4,5

Original baseline system. Volatile can be a problem.

Lower production rate than VCD.

Vapor Compression

Distillation (VCD)

95+ Max feed concentration 60%. 4,6–11

Takes 50% power as TIMES, less susceptible to fouling, better

quality of product water. Volatiles can be a problem.

Reverse osmosis 95+ Poor removal of ionized gases. 12,13

Poor rejection of urea, acids, and ammonia.

Unibed filter Nearly 100 Low power consumption, lightweight, simple. 11,14–16

Filter bed units are expendable, must be replaced.

Wastestream must be of stable composition as filters are

designed for a specific, stable, known wastestream

composition.

Electrooxidation—Combined

Electrolysis and Electrodialysis

Nearly 100 Organic compounds are oxidised by electrolysis, and inorganic

salts are removed by electrodialysis.

7,17

High efficiency was achieved when polarity across the

electrodes was periodically reversed.

Final TOC levels of 1 ppm is achieved when treating raw urine.

Solution has to be spiked with an expendable electrolyte.

Supercritical Water Oxidation Nearly 100 Organics, and most atmospheric and trace contaminant gases are

completely oxidised.

18–20

Process can also oxidise many solid wastes. Inorganic salts and

metals produced have low solubility and precipitate out.

Mercury escapes into the vapor phase and must be removed by

ion absorption.

Electrodeionisation Nearly 100 Bacteria not completely removed. 21

Removes almost everything except silica.

Waste stream must be characterized for design of selective ion

exchange resins.

Best for removal of known ionized contaminants.

Air evaporation Nearly 100 100% water recovery from urine and numerous other feeds. 22

Consumables are required.

Use of solar collectors would reduce electrical power

requirements significantly.

Vapor Phase Catalytic

Ammonia Removal

95 Energy efficient due to system integration. 10,23

Bacterial growth in feed is suppressed, and vapor phase is a

barrier to non-airborne organisms and contaminants. High

temperatures destroy many micro-organisms.

Plant transpiration and water recovery Water vapor from unstressed plants had TOC of 1.4 ppm. 24–27

No data on results using actual wastewater.

Immobilised Cell or

Enzyme Bioreactors

No water

recovery

100 ppm phenol feeds were reduced to below detection limit of

10 ppb, i.e. 99 + % removal.

28–30

COD reductions of 95 + %, and urea reductions of 95–99% are

achieved.

Porous biomass support gives better results.

Fuel cell product water 100 Pure water, byproduct of power generation. 5

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