W WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE INTRODUCTION DRINKING WATER QUALITY STANDARDS Environmental Control and Life Support System (ECLSS) is the NASA terminology for the systems which allow people to exist and work in confined spaces and in uninhabited locations and hostile environments These systems supply air, water, temperature and humidity controls to enable personnel to survive and work under hostile conditions The purpose of this paper is to review the various devices that have been developed for the recovery and reuse of liquid wastes in spacecraft and space stations, and their possible terrestrial applications NASA has very strict standards for water consumed on the shuttle, and even stricter standards for the proposed space station This is logical, as the water on the space station will be continuously recycled, and hence the astronauts will be exposed to this water for an extended duration Table lists the present potable water standards for the shuttle and Space Station Freedom (SSF), and compares these to the existing EPA potable water standards The SSF hygiene water standards are also shown in the table These standards were established early in the program.3 In order that hardware designers should have constant reference solutions to use when testing their equipment, NASA found it necessary to determine the compositions of urine and wastewater that would be produced on the space station Hence NASA analyzed average urine composition, and determined a chemical model for urine, which could be made up and used to test recycling equipment Similarly, a chemical model formula for hygiene water, i.e., water used for personal washing, laundry, and food preparation, was derived These model compositions for urine and wastewater were then used to test individual items of hardware and complete processing systems However, the final evaluation tests must include the processing of urine and wastewater obtained from volunteers living in a closed test environment A SHORT HISTORY OF U.S SPACECRAFT ECLS SYSTEMS The U.S spacecraft ECLS systems have grown in capabilities and complexity as the spacecraft have grown and the duration of their missions has been extended Initial systems were almost completely open loop, with only CO2 removal in a closed loop There was no recycling of water or wastes On the Orbiter, water is not recycled, but is vented overboard Air is recycled Solid wastes are returned to the earth This system will be changed as the Orbiter is reconfigured for longer duration missions Due to the high cost of transporting fresh water and oxygen into orbit, the space station is designed to operate in an almost completely closed loop mode Only solid body waste and trash will be returned to the earth Air and liquid wastes will be recycled Regenerative systems have been evaluated by NASA for the different functions of the ECLSS (Figure 1).1 A partial list of the various technologies is given in Table The emphasis is on purification and recycling the air and wastewater streams for atmosphere revitalization and water recovery and management The high cost of transporting mass into orbit, approximately $22,000/kg, causes NASA to place a premium on low weight, low volume, high efficiency, and low maintenance requirements.2 TECHNOLOGIES TESTED FOR USE IN THE ECLSS Various technologies were tested and/or evaluated for the ECLSS systems, with the emphasis on the water and air revitalization systems Less attention has been paid to the treatment of solid waste, as this will only be required for long space voyages and for long term inhabitation of stations on the moon and planets A number of water recovery and waste management systems have been tested for application in the space station These systems have been evaluated by comparing them to the baseline technology that was originally 1242 © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1242 11/18/2005 1:29:10 PM C023_001_r03.indd 1243 ECLSS Temperature and Humidity Control (THC) Refrigerator/ Freezers FIGURE O2/N2 Pressure Control Vent & Relief O2/N2 Storage O2/N2 Distribution Experiment Support Contingency Gas Support EVA Support Atmosphere Revitalization (AR) CO2 Removal CO2 Venting Trace Contaminant Control Major Constituent Monitoring Trace Contaminant Monitoring O2 Generation CO2 Reduction (SCAR) Fire Detection and Suppression (FDS) Fire Detection Fire Suppression Water Recovery and Management (WRM) Waste Management (WM) Waste Storage & Return Fecal Urine Waste Processing Processing Combined Potable/Hygiene Urine Collection and Processing Pretreatment Online Water Quality Monitoring EVA Support Fuel Cell Water Transfer/Storage Contamination Recovery Experiment Support Water Distribution Water Venting Space Station Alpha Environmental Control and Life Support System (ECLSS) Functions Source: Ref WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE Air Temperature Control Humidity Control Air Particulate Control Ventilation Intermodule Ventilation Avionics Air Cooling Atmosphere Control and Supply (ACS) 1243 11/18/2005 1:29:11 PM © 2006 by Taylor & Francis Group, LLC 1244 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE selected for the space station The original baseline system was the Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES) This was replaced by a new baseline subsystem which is a combination of multibed filtration (Unibed) and Vapor Compression Distillation (VCD) These baseline systems along with many other promising technologies are described below In all cases urine is pretreated immediately upon collection to minimize bacterial growth and possible damage to collection and handling equipment In addition to inhibiting bacteria, the treatment is intended to control ammonia, stabilize dissolved solids to prevent precipitation, and allow the overall subsystem to function in a zero-gravity environment Present pretreatment comprises the injection of either Oxone TABLE ECLSS Technologies Used or Evaluated ECLSS Subsystem Category Atmosphere revitalisation Used/Evaluated Technology Used LiOH Used Molecular sieve Used Sabatier reactor Used Static feed water electrolysis Evaluated Solid amine fixed bed Evaluated Liquid sorbent closed loop Evaluated Bosch system Evaluated Algal bioreactor Evaluated Growing green plants Used Activated charcoal Used Catalytic oxidiser Used Trace Contaminant Removal Particulate filters Used* Vapor compression distillation Used Water recovery and management Chlorine Used Sodium hypochlorite injection Used Iodine injection Used Heat sterilisation Used Fuel cell by-product water Evaluated* Unibed filter Evaluated* TIMES membrane filter * Evaluated Reverse osmosis Evaluated* Electrodialysis Evaluated* Electrooxidation Evaluation* Supercritical water oxidation Evaluation* Electrodeionisation Evaluation* Air evaporation Evaluation* Vapor phase catalytic ammonia removal Evaluation* Immobilized cell or enzyme bioreactors Evaluation* Plant transpiration and water recovery Temperature and humidity control Used Condensing heat exchangers Used Water cooled suits Atmosphere control and supply Used Compressed gas storage Used Cryogenic gas storage Waste management Urine stored in bags Used Feces stored in bags Used Urine vented Used Feces stored in bags and vacuum dried Used Urine stored in tank and vented Used * Used Feces stored in bags and compacted Described in this paper © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1244 11/18/2005 1:29:11 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 1245 TABLE Water Quality Standards Comparison QUALITY PARAMETERS PHYSICAL PARAMETERS TOTAL SOLIDS (mg/L) “COLOR, TRUE (Pt/Co units)” CONDUCTIVITY TASTE (TTN) Shuttle Potable EPA Current SSF Potable — — — SSF Hygiene — to 10 500 100 500 15 15 15 15 Reference only — — — — N/A ODOR (TON) 3 3 PARTICULATES (max size—microns) — — 40 40 pH TURBIDITY (NTU) DISSOLVED GAS (free @ 37°C) Reference only 11 None at AT 6.5–8.5 6.0–8.5 5.0–8.5 — (see Note 1) N/A FREE GAS (@ STP) — — (see Note 1) Note INORGANIC CONSTITUENTS (mg/L)(see Notes and 5) — — — — ALUMINUM — 0.05 — — AMMONIA — — 0.5 05 ARSENIC — 0.05 0.01 BARIUM — 1 CADMIUM 0.01 0.01 0.005 0.005 0.01 CALCIUM — — 30 30 CHLORINE (Total—Includes chloride) — 250 200 200 CHROMIUM 0.05 0.1 0.05 COPPER 1.00 1.00 IODINE (Total—Includes organic iodine) Reference only — 15 0.05 1.00 15 IRON 0.3 0.3 0.3 LEAD 0.05 0.05 0.05 MAGNESIUM — — MANGANESE 0.05 0.05 0.05 0.05 MERCURY 0.005 0.002 0.002 0.002 NICKEL 0.05 0.1 0.05 NITRATE (NO3-N) — 10 10 10 POTASSIUM — 340 340 SELENIUM 0.01 0.05 0.01 SILVER 0.1 0.1 0.05 SULFATE — 250 SULFIDE — — 0.05 0.05 ZINC 5 5 BACTERICIDE (mg/L) 50 250 0.3 0.05 50 0.05 0.01 0.05 250 — — — RESIDUAL IODINE (minimum) Reference only — 0.5 0.5 RESIDUAL IODINE (maximum) Reference only — AESTHETICS (mg/L) — — CATIONS — — — 30 — — N/A ANIONS — — 30 N/A CO2 (see Note 1) — — 15 N/A (continued) © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1245 11/18/2005 1:29:11 PM 1246 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE TABLE (continued) QUALITY PARAMETERS MICROBIAL Shuttle Potable EPA Current SSF Potable SSF Hygiene None Viable — — — BACTERIA (CFU/100 mL) — — — — TOTAL COUNT — — 1 ANAEROBES — — 1 COLIFORM — 1 ENTERIC — — — — VIRUS (PFU/100 mL) — — 1 YEAST and MOLD (CFU/100 mL) — — 1 — — — — RADIOACTIVE CONSTITUENTS (pCi/L) ORGANIC PARAMETERS (mg/L) (See Note 2) NRC LIMITS — (see Note3) — TOTAL ACIDS — — 500 500 CYANIDE (total including organic cyanides) — — 200 200 HALOGENATED HYDROCARBONS — 0.1 (THM)* 10 10 TOTAL PHENOLS — — 1 TOTAL ALCOHOLS — — 500 500 10000 TOTAL ORGANIC CARBON (TOC) Reference only — 500 UNCHARACTERIZED TOC (UTOC) — — — — (see Note 4) — — 100 1000 ORGANIC CONSTITUENTS (mg/L) — — — — (see Notes and 5) — — — — Note 1: No detectable gas using a volumetric gas vs fluid measurement system This excludes CO2 used for aesthetics purposes Note 2: MCLs considered independently of others Note 3: The maximum contaminant levels for radioactive constituents in potable and personal hygiene water shall conform to Nuclear Regulatory Commission (NRC) regulations (10CFR20, et al.) These maximum contaminant levels are listed in the “Federal Register Vol 51, No: 6, 1986, Appendix B, Table Note 4: Total organic carbon minus identifiable organic contaminants Note 5: MCLs for others, if found, will be established as necessary * THM = Trihalomethanes SSF = Space Station Freedom Source: Ref (a potassium monopersulfate compound) combined with sulfuric acid, or hypochlorite (bleach) before distillation Thermoelectric Integrated Membrane Subsystem (TIMES) This was the original baseline water recovery subsystem for the space station (Figure 2) Wastewater is heated to 66ЊC in a heat exchanger, and is then pumped through bundles of small diameter hollow Nafion fiber membranes in the evaporator module The Nafion allows only water, gases, and small neutral molecules to pass through The pressure on the exterior of the membrane is reduced to 17 kPa (2.5 psi) to assist in both transport through the membrane, and subsequent evaporation The water vapor is then condensed, and the latent heat of condensation is conducted to the input heat exchanger The TIMES system was found to produce poorer quality water than the VCD.4,5 Vapor Compression Distillation (VCD) The VCD process involves spreading a thin film of the wastewater on the inside wall of a thin-walled rotating drum under low pressure, typically about 4.8 kPa (0.7 psi) The VCD is shown in Figure 3, and in-depth discussions may be found in Refs 4, and 6–11 The system operates at 35ЊC which is slightly above ambient temperature Heat is applied to the outside of the wall causing the thin film of water to boil The vapor is extracted from the drum interior and compressed by a pump The compressed vapor is then condensed on the exterior wall of the drum The compressed vapor condenses at a higher temperature than that at which it had originally evaporated The latent heat of condensation thus supplied the heat required to evaporate the original feed water in the inside of the drum The unevaporated brine, heavily loaded with contaminants, is recycled back to the inflow stream, or passed to another subsystem © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1246 11/18/2005 1:29:11 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE Membrane Evaporator Thermoelectric Regenerator Wastewater Heat Exchanger Purified Water FIGURE Hollow Fiber Membranes Thermoelectric Elements Waste water 1247 Waste water Water Vapor Condenser Latent Heat Schematic diagram of the TIMES (Thermoelectric Integrated Membrane Subsystem) Source: Ref Reverse Osmosis (RO) Reverse osmosis is a process in which pressure is applied to a concentrated solution which is on one side of a semipermeable membrane The pressure forces the molecules of solvent through the membrane to the pure solvent or more dilute solution on the other side Greater concentration differential between the two solutions on either side of the membrane require greater pressure A test unit containing a bundle of tubes, capable of operating at up to 4140 kPa (600 psi), was evaluated When wash water containing soap was processed a soap gel film formed on the membrane surfaces.12 Reverse osmosis is a candidate for producing high quality water A combination of several systems, including RO, produced water that met National Committee for Clinic Laboratory Standards.13,14 Multifiltration (Unibed) The multifiltration system comprises a heat sterilization unit to kill microorganisms, followed by a series of progressively finer particulate filters down to 0.5 microns to avoid particulates clogging the sorbent beds.15 The water then enters the Unibeds which remove the dissolved contaminants The Unibed is a single replaceable unit which utilizes a set of beds of different sorptive materials arranged in a specified optimum sequence (Figure 4) The beds are designed to remove specified types and amounts of contaminants from a known waste stream in such a way that all the beds are exhausted at the same time A sequence of Unibeds of identical design, each comprising three five-tube replaceable subunits, may be used Unidentified compounds are generally removed by a mixture of several types of activated charcoal and nonionic sorbents near the outlet from the bed Microbial control to avoid bacterial fouling of the various beds is achieved by iodinated resin beds at the inlet and outlet of each Unibed Detailed discussions of the system may be found in Refs 11, and 14–16 Electrooxidation—Combined Electrolysis and Electrodialysis Electrodialysis alone removes ions more efficiently than does reverse osmosis (RO); however, when combined with electrolysis the organic compounds are oxidized in the electrolysis and the inorganic salts are removed by the electrodialysis.7 A combined electrolytic and electrodialytic cell is illustrated in Figure No chemicals are used Low voltages are used to avoid unwanted side effects such as the production of chlorine, or the formation of insoluble salts Various types of electrode materials have been tested Efficiency was increased considerably when the polarity across the electrodes was periodically reversed This procedure is termed Periodic Reverse Pulsed Electrolysis (PRPE) The process has theoretical advantages over RO, as increasing the brine concentration improves the conductivity, and hence the efficiency of the process Electrooxidation effectively kills bacteria in the feed.17 Supercritical Water Oxidation (SCWO) Wastewater is heated to a temperature of 650ЊC under pressures of 250 atmospheres When water is above its critical point, its properties as a solvent change Organic compounds which are insoluble at normal temperature and pressure become soluble The addition of sufficient oxygen then leads to the complete oxidation of these compounds Most atmospheric gases and trace contaminant gases are also soluble in supercritical water, and will also be oxidized The process also has the potential © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1247 11/18/2005 1:29:11 PM 1248 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE Condenser Compressor Motor Evaporator Outer Shell FIGURE Rotating Drum Cross section of a VCD (Vapor Compression Distillation) still Source: Ref for oxidizing much of the organic solid wastes produced on the space station.18 Inorganic salts are produced when human metabolic wastes are subjected to supercritical water oxidation These salts have very low solubility in supercritical water and precipitate out, and thus can be removed.19 Metals are also precipitated out, with the exception of mercury, which carries over in the vapor phase, and has to be removed by ion adsorption.20 Electrodeionisation Feed water moves through an ion exchange resin bed which selectively removes certain ions from the water Simultaneously, the resin is regenerated by the action of an electric field imposed upon the resin bed.21 A schematic process diagram may be found in Ref 21 Bacteria are not completely removed It appears that this process works best to remove ionic contaminants It is a candidate for the production of reagent grade water Both benchtop and industrial capacity units are available Air Evaporation A system with a heat pump and solar collectors for evaporative heat was tested The system is capable of 100% water recovery from numerous types of contaminated sources The wastewater is pretreated with a chemical solution to prevent decomposition and bacterial growth It is then pumped through a wick filter to remove particles, in a series of pulses The timing of the pulses is such that the liquid from one pulse is distributed along the wick by capillary action before the next pulse arrives A heated air stream evaporates the water from the wick, leaving the solids behind When the wick is full of solids, it is dried and replaced by a new wick The air and vapor stream passes through a condensing heat exchanger and then through a water separator to extract the free water from the stream and test it for quality It is then transferred to the post-treatment filter section and thence to the main water storage and distribution system The wick system can be sterilized by heating it to 121ЊC while in a dry state.22 Vapor Phase Catalytic Ammonia Removal (VPCAR) Neither pre-treatment nor post-treatment of the feed and product water are required The high temperature employed also destroys microbes to a very great extent.23 The present design utilizes the thin film evaporation technique of the VCD process in a rotating disk evaporator, combined with catalytic reactors for vapor phase chemical reactions The ammonia and volatile hydrocarbons which are evaporated along with the water vapor are oxidized to innocuous gases by catalytic chemical reactions carried out in the vapor phase The overall system schematic is shown in Figure 6.10,11 The vapor from the VCD boiler passes over two catalytic beds The first bed operates at a temperature of about 250ЊC, to oxidize organic volatiles to CO2 and water, and ammonia to NO and water The second bed operates at 450ЊC and reduces the NO to N2 and O2 The O2 produced is more than sufficient for first bed usage The vapor is recycled to maximize O2 utilization This high temperature vapor or steam supplies the © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1248 11/18/2005 1:29:11 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE TOP OF UNIBED PROCESS FUNCTION +30 US Mesh Coarse Filtration Turbidity Removal -30 US Mesh Fine Filtration Turbidity Removal MCV Iodinated Resin Iodinated SBA Anion Iodine Injection Microbial Control Dowex-1 Dowex-1 SBA Anion Absorption Cleansing Agents Organic Scavenging Ion Exchange Reduction Inorganic Salts Adsorption 1249 TOC Removal/Reduction Diatomaceous Earth Coarse Diatomaceous Earth Fine MEDIA TYPE DIRECTION OF FLOW Mixed Bed Resin Mixed Resin SAC/SBA Carbon/Adsorbent Silicalite Mixture Weak Base Anion MCV Iodinated Resin BOTTOM OF UNIBED FIGURE Adsorbant Section Methacrylic Weak Base Gel Type Resin Iodinated SBA Anion Ion Exchange Weak Organic Acids Iodine Injection Reduction Organic acids Microbial Control Multifiltration unibed schematic and process details Source: Ref 15 heat to evaporate the feed, condensing to form the product water The residual concentrated feed, or brine, is sent to a supercritical water oxidizer (SWCO) to remove the remaining contaminants Bacterial growth is suppressed because bacteria not thrive in the concentrated brine due to the buildup of both toxic compounds and of heavy metals in the brine The vapor phase provides a barrier to non-airborne micro-organisms.10 Plant Transpiration and Water Recovery The use of plants to produce clean water by transpiration is being examined by NASA It is believed that plants can process wastewater, and transpire it with minimal contaminants However, any volatile contaminants must be removed first, so that they cannot evaporate directly from the wastewater into the air The type of pretreatment required will depend upon the waste steam being treated Plant nutrients will have to be added to the water Preliminary experiments using only a plant nutrient solution indicated that the amount of total organic carbon (TOC) in transpired water vapor from unstressed plants was very low, about 1.4 mg/L in the water that was collected in condensers outside the plant chamber Water collected in the plant chamber had higher TOC values, averaging 2.5 mg/L Stressed plants transpired water with TOC values of up to mg/L The average TOC level of tap water was 1.6 mg/L Insect infestation stressed the plants, causing higher TOC levels in the transpired water It was not clear if any of the increased TOC was derived from the insects themselves There are many questions about the feasibility of using a compact growth facility to treat the wastewater These questions need to be examined carefully © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1249 11/18/2005 1:29:11 PM 1250 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE Electrolysis + Electrodialysis Bleed to waste RO Brine Stream Cation Exchange Membrane Anion Exchange Membrane Positive Electrode RO Recycle Stream Negative Electrode Brine Drain FIGURE Electrooxidation—combined electrolytic and electrodialytic cell Source: Ref Discussions on these and related topics may be found in Refs 24–27 Immobilized Cell or Enzyme Bioreactors Immobilized microorganisms convert contaminants into simpler molecules at near ambient temperatures The immobilized cells can treat a wide variety of contaminants This technology is under development, but it may have significant terrestrial uses.28–30 These biological systems require little energy, and may leave little waste residue Prototype reactors were tested using a packing of diatomaceous earth When tested with feed containing 10 and 100 mg/L phenol in an oxygenated solution, they were able to produce an effluent with phenol content below the detection limit of 0.01 mg/L The report did not say what organisms were used, nor how they were arranged for the test.30 Immobilized microbial cell bioreactors have been used in industrial wastewater treatment applications In a comparative test processing feed from a coal tar plant, a reactor using a porous polymeric biomass support achieved effluent phenol levels 100 times lower than those achieved by a commercial bioreactor utilizing a nonporous polyethylene support Similar results were observed for minor contaminants, and the sludge output was about 20% of that from the nonporous system A bioreactor test using a consortium of enriched aerobic microorganisms immobilized in packed bed reactors was conducted, utilizing a simulated wastewater feed A porous polymeric biomass support was used in the reactor Influent concentrations were nominally 600 mg/L COD, and 1000 mg/L urea COD reductions of 95% or more, and urea reductions of 95–99% were achieved when using hydraulic retention times of 24 or 48 hours Effluent total suspended solids ranged from to mg/L.28 Tests have shown that low-molecular weight, polar, nonionic contaminants can be removed from solution by immobilized enzymes which catalyze the oxidation of various organic compounds, such as alcohols, aldehydes, and so on, to organic acids, for subsequent removal by ion exchange Hence existing ion exchange technology (multifiltration Unibeds) can be © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1250 11/18/2005 1:29:12 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 1251 OXYGEN TO AIR REVITALIZATION SUBSYSTEM N2, CO2 & H20 VAPOR PHASE CATALYTIC AMMONIA REMOVAL UNIT (VPCAR) URINE & FLUSH New VPCAR Processor HYGIENE & WASH WATER POTABLE WATER VENT GASES VPCAR BRINE RESIDUAL INORGANIC SOLIDS SOLID WASTE SLURRY (IF DESIRED) Heavy Liquids Processor SCWO SCWO PRODUCT WATER OXYGEN SUPERCRITICAL WATER OXIDATION UNIT (SCWO) FIGURE Schematic flow diagram of integrated water reclamation system utilizing a combination of VPCAR unit and SCWO unit Source: Refs 10 and 11 made more effective The enzymes are bound to support, usually, a silica-based material, which is in a form that makes it easy to utilize in a Unibed Specific enzymes are used depending upon the compound or class of compound, to be removed These Unibeds have to include iodine removers at the inlet, and iodinating resin beds at the outlets to maintain bacterial control in the water supply system of the spacecraft.29 Fuel Cell Product Water When hydrogen and oxygen are combined in a fuel cell to produce electric power, pure water is also produced This system was used in both the Apollo and Orbiter spacecraft.5 Urine and wastewater can be electrolyzed to produce hydrogen and oxygen, thus providing a closed loop system (see Electrooxidation above) COMPARATIVE PERFORMANCE OF TECHNOLOGIES Many promising technologies for wastewater treatment and water recovery aboard the space station have been described briefly Their performance levels vary depending upon the characteristics of the wastewater feed The performance levels and the basic features of each system are compared in Table WATER QUALITY CONTROL A major problem in these regenerative systems is bacterial contamination and biofilms forming on the internal surfaces of the water supply system These biofilms are the result of colonies of bacteria forming on the surface They occur even in nutrient-limited environments Biofilms accelerate corrosion and are difficult to remove, or to prevent from forming.31 Pathogenic bacteria have been shown to survive in sterile water and at elevated temperatures for many hours.32 This bacterial contamination poses both health and long term mechanical problems in any recycling system Adequate continuous sterilization procedures and equipment will be required in any recycling system A high concentration of micro-organisms is found in shower water, reinforcing the necessity of ensuring the disinfection of the recycled potable water supply A special soap is used for all washing on the Orbiter and is proposed for use on the space station, which reduces foaming and consequent problems in the recycling process.33 Great care is taken to avoid the possibility of contamination due to cross connection of wastewater and processed water systems Pre- and Post-Treatment of Recycled Water Pre- and post-treatment of water is generally necessary in order to obtain the desired water quality after the treatment of recycled water NASA concentrated much of its research effort on distillation processes The combination of distillation and ion exchange is quite successful in removing inorganic contaminants but is less successful in removing volatile organic contaminants These volatiles must be removed to avoid their accumulation to toxic levels Organic © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1251 11/18/2005 1:29:12 PM 1252 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE TABLE Summary of Described ECLSS Technologies for Water Recovery Technology TIMES membrane filter Maximum Water Recovery Rate % 93 Comments Max feed concentration 38% References 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 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 © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1252 11/18/2005 1:29:12 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 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 compoundspecific 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 concentration 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 technique required depends upon the process used to perform the main water recovery Finished Water Quality Monitoring In order to avoid contamination the processed water is continuously monitored for the levels of certain key parameters which are indicative of the water quality for the desired application 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 ECLSS Attempts are being made to utilize ECLSS technology at the South Pole station The proposed system is designed to recycle 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 growing 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, 1253 and maintenance requirements can be more relaxed than those for the space station SUMMARY In summary, the systems described have high rates of water recovery, and remove or destroy a wide variety of contaminants The technologies developed may have terrestrial applications 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 production 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 requirements 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 W per hour per kg of water recovered.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 process 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 applications They have all been designed to process wastewater which does not contain foaming cleansers Hence any technology that is being considered must be tested with conventional 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 developed 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 © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1253 11/18/2005 1:29:12 PM 1254 WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE Sauer, R.L., R Ramananathan, J.E Straub, and J.R Shultz, Water Quality Program Elements for Space Station Freedom, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991 Society of Automotive Engineers, Warrendale, PA, pp 1–21 Wieland, P.O., Designing for Human Presence in Space: An Introduction to Environmental Control and Life Support Systems, George C Marshall Space Flight Center, NASA RP-1324 1994 Miernik, J.H., B.H Shah, and C.F McGriff, Waste Water Processing Technology for Space Station Freedom: Comparative Test Data Analysis, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 229–239 Howard, S.G and J.H Miernik, An Analysis of Urine Pretreatment Methods for Use on Space Station Freedom, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 157–166 Herrman, C.C and T Wydeven, Physical/Chemical Closed-loop Water Recycling for Long Duration Missions, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 233–245 Zdankiewicz, E.M and J Chu, Phase Change Water Recovery for Space Station—Parametric Testing and Analysis, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 669–679 Noble, L.D Jr et al., Phase Change Water Recovery for the Space Station Freedom and Future Exploration Missions, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 145–158 10 Noble, L.D Jr et al., An Assessment of the Readiness of Vapor Compression Distillation for Spacecraft Wastewater Processing, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 271–282 11 Flynn, M.T et al., Water Reclamation Technology Development for Future Long Range Missions, Proceedings of the 22nd International Conference on Environmental Systems, Seattle, WA, July 13–16, 1992, Society of Automotive Engineers, Warrendale, PA, pp 1–9 12 Ray, R.J et al., Membrane-Based Subsystem for Very High Recoveries of Spacecraft Waste Waters, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 645–659 13 Highsmith, A et al., Evaluation of Water Treatment Systems Producing Reagent Grade Water, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990 Society of Automotive Engineers, Warrendale, PA, pp 113–117 14 Carrasquillo, R.L et al., ECLSS Regenerative Systems Comparative Testing and Subsystem Selection, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 213–228 15 Colley, C.D., Functional Description of the Ion Exchange and Sorbent Media Used in the ECLSS Water Processor Unibeds, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 175–188 16 Putnam, D.F., W.F Michalek, and T Van Pelt, Space Station Hygiene Water Reclamation by Multifiltration, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 189–194 17 Hitchins, G.D et al., Electrooxidation of Organics in Waste Water, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 179–188 18 Hall, J.B Jr., and D.A Brewer, Supercritical Water Oxidation: Concept Analysis for Evolutionary Space Station Application, In Proceedings of the 16th Intersociety Conference on Environmental System, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 733–745 19 Armellini, F.J and J.W Tester, Salt Separation During Supercritical Water Oxidation of Human Metabolic Waste: Fundamental Studies of Salt Nucleation and Growth, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 189–203 20 Swallow, K.C et al., Behavior of Metal Compounds in the Supercritical Water Oxidation Process, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 205–210 21 Highsmith, A.K et al., Water Quality after Electrodeionisation In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 90–96 22 Morasko, G., D.F Putnam, and R Bagdigian, Air Evaporation Closed Cycle Water Recovery Technology—Advanced Energy Saving Designs, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 681–690 23 Budininkas, P., F Rasouli, and T Wydeven, Development of a Water Recovery Subsystem Based on Vapor Phase Catalytic Ammonia Removal, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 661–667 24 Macier, B.A., Quality Assessment of Plant Transpiration Water, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 1–4 25 Janik, D.S and J.J DeMarco, Engineering Testbed for Biological Water/ Air Reclamation and Recycling, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 1–7 26 Ray, R.J et al., Water Vapor Recovery from Plant Growth Chambers, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 89–97 27 Blackwell, C.C et al., Options for Transpiration Water Removal in a Crop Growth System Under Zero Gravity Conditions, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 15–18 28 Petrie, G.E and M.S Nacheff-Benedict, Development of Immobilized Cell Bioreactor Technology for Water Reclamation in a Regenerative Life Support System, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 179–191 29 Jolly, C.D., L.J Schussel, and L Carter, Advanced Development of Immobilized Enzyme Rectors, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 109–117 30 Miller, G.P et al., Using Biological Reactors to Remove Trace Hydrocarbon Contaminants from Recycled Water, In Spacecraft Water Quality, Proceedings of the 21st International Conference on Environmental Systems, San Francisco, CA, July 15–18, 1991, Society of Automotive Engineers, Warrendale, PA, pp 99–107 31 Richardson, J.C et al., Bacterial Selectivity in the Colonization of Surface Materials from Groundwater and Purified Water Systems, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 101–111 32 Kundsin, R and R.E Perkins, Survival of Mycoplasmas and Ureaplasmas in Water and at Elevated Temperatures, In Proceedings of the 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9–12, 1990, Society of Automotive Engineers, Warrendale, PA, pp 97–100 © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1254 11/18/2005 1:29:12 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 33 Verostko, C.E et al., Results on Reuse of Reclaimed Shower Water, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 635–643 34 Putnam, D.F., G.V Colombo, and C Chulien, Pre- and Post-Treatment Techniques for Spacecraft Water Recovery, In Proceedings of the 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14–16, 1986, Society of Automotive Engineers, Warrendale, PA, pp 627–634 35 Straight, C.L et al., The CELSS Antarctic Analog Project: A Validation of CELSS Methodologies at the South Pole Station, In Proceedings 1255 of the 23rd Intersociety Conference on Environmental Systems, Colorado Springs, CO, July 12–15, 1993, Society of Automotive Engineers, Warrendale, PA, pp 1–11 ROBERT G ZACHARIADIS SYED R QASIM The University of Texas at Arlington © 2006 by Taylor & Francis Group, LLC C023_001_r03.indd 1255 11/18/2005 1:29:13 PM ... possibility of contamination due to cross connection of wastewater and processed water systems Pre- and Post-Treatment of Recycled Water Pre- and post-treatment of water is generally necessary in order... 1:29:12 PM WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE 33 Verostko, C.E et al., Results on Reuse of Reclaimed Shower Water, In Proceedings of the 16th Intersociety Conference on Environmental Systems, ... Suppression Water Recovery and Management (WRM) Waste Management (WM) Waste Storage & Return Fecal Urine Waste Processing Processing Combined Potable/Hygiene Urine Collection and Processing Pretreatment