Apollo Experience Report Potable Water System

8/8/2019 Apollo Experience Report Potable Water System

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N A S A T E C H N I C A L N O T E

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F I LECOPY

APOLLO EXPERIENCE REPORT -POTABLE WATER SYSTEMby Richard L, Sauer and David J. C d e yMut2ned Spacecrafi CenterHouston, Texus 77058

M7344B3jNASA TN D-7291

N A T I O N A L A E R O N A U T I C S A N D S PA CE A D M I N I S T R A T I O N W A S H I N G T O N , D . C. JUNE 1 9 7 3


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2. Government Accession No.. Re r t No .N A G TN D-7291 IAPOLLOEXPERIENCEREPORTPOTABLE WATER SYSTEM4. Title and Subtitle

3. Recipient's Catalog No.

5. Report Date

7. Author(s)Richa rd L. Sau er and David J. Calley, MSC9. Performing Organization Name and Address

June 19736. Performing Organization Code

8. Performing Organization Report No .MSC-0750810. Work Unit No .9 14-50-95-27- 72

17. Key Words (Suggested by Author(s1)' Potable Wat er Microbiology' Sublimation Cooling 'Waste Water'Humidity Condensate ' Bacteriology'Membranous Bladder * BiocideWater-System Material

Manned Spacecraft CenterHouston, Texas 77058

18. Distribution Statement

2. Sponsoring Agency Name and AddressNational Aeronautics and Space AdministrationWashington, D. C. 20546

I .

11. Contract or Grant No.

19. Security Classif. (of this report) 20. Security Classif. (o f this page) 21. No. of Pages16one None

13. Type of Repor t and Period CoveredTechnical Note

22. Price$3.00

~ 14. Sponsoring Agency CodeI

5. Supplementary NotesThe MSC Dire ctor waived the use of the Interna tional Sys tem of Units (SI) fo r thi s Apollo Ex-perience Report because, in his judgment, the use of SI Units would impa ir the useful ness ufthe repor t or resu lt in excessive cost.6. AbstractA descript ion of the design and function of th e Apollo potable water system is presented. The com-mand module potable water is supplied as a byproduct of the fuel cells. The cel ls, located in these rv ic e module, function pri mar ily to supply elect rica l energy to the spacecraf t. The sour ce ofth e lunar module potable wat er is three storage tanks, which are filled before lift-off. The tech-nique of supplying the water in each of these cases and the problems associated with mater ialscompatibility ar e descr ibed. The chemical and microbiological quality of the water is reviewed,as are efforts t o maintain the water in a microbially safe condition fo r drinking and food mixing.

* For sale by the Nat i ona l Tech n i ca l In fo rmat iw Serv i ce , Spr ing f i e ld , V i rg i n ia 22151


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CONTENTS

Section PageSUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1DESCRIPTION O F THE APOLLO POTABLE WATER SYSTEM 2 .. . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . 2ommand and Service Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4unar Module

5ATER SYSTEM MATERIALS COMPATIBILITY . . . . . . . . . . . . . . . .5etallic Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Synthetic Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

CHEMICAL QUALITY O F WATER . . . . . . . . . . . . . . . . . . . . . . . . 7Water Source and Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . 7Fuel-Cell Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Water-Use Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

STERILIZATION O F THE POTABLE WATER SYSTEM . . . . . . . . . . . . . 8Medical Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Biocide Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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MICROBIOLOGICAL QUALITY OF WATER . . . . . . . . . . . . . . . . . . .Microbial Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance of Sterility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

CONCLUDING REMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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FIGURES

Figure12 Schematic of the LM water management system . . . . . . . . . . . .

Schematic of the CSM water management system . . . . . . . . . . . .

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APOLLO EXPERIENCE REPORTPOTABLE WATER SYSTEM

B y R i c h a r d L. S a u e r a n d D a v id J. Ca l l eyM a n n e d S p a ce c ra ft C e n t e rSUMMARY

The Apollo water-supply sy st em s and the water-quality problem areas in the sys-tems are described and discussed. The inflight water supply fo r the command moduleis a byproduct of the operat ion of the fuel cel ls designed fo r power generation in thespacec raft. The water produced in flight fo r crew us e is stored in a pressurized tankwhich is filled from a ground-facility water supply before lift-off and is replenished inflight as required. Because the re is no fuel-cell energy system in the lunar modulefrom which byproduct water can be obtained, water is loaded into storage tanks in th espacecraft before lift-off. The system sati sfi es the dual purpose of providing metabolicwater for the crewmen and water f or a sublimation cooling pro cess . In the commandmodule, a buffer and an inhibitor a r e added to the water to minimize metal corrosion.The metal corrosion is caused by severa l factors : the us e of ultra-high-purity water,the incompatibility of the chlorine biocide and the sys tem, the galvanic action resultingfrom the selection of d is si mi la r metal components, and the sur face imperfections inthe tubing used for system construction. Other related problems a r e the characteris-ti cs of the command module tank-bladder material, the presence of a metal dithiocar-bamate precipitate, and the re leas e of dissolved ga s fr om the water at the water-useports. The resolution of these problems is described. Accumulated preflight dataindicated t h a t a significantly sma ll er degree of corrosion and related problems existedin th e lunar module water system. A better system design and the u se of a less corro-sive biocide, in the lunar module water s y s t em , are reasonable explanations of thedifference i n problems noted in the command module and lunar module systems.

The NASA specifications for potable water require t h a t the water be ste rilethroughout the course of a mission. The us e of a biocide in the water system w a snecessary t o meet this requirement. Command module and lunar module data indi-cated adequate control of microbial growth exists when a proper biocide concentrationis maintained. Preflight data gathered on the command module water demonstratedthat sy stem st er ili ty cannot be maintained without an adequate biocide residual.

INTRODUCTION

1 m The water-supply sys tem s used in the Apollo Prog ra m and the water-quality prob-r e a s that developed in these sys tem s a re des cribed and discussed in this report.


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The complexity of the sys te ms and the requi rement to maintain drinking-water ste ril itycrea ted several unexpected problems.

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Essentially, th ree functions ar e served by the water-supply syst ems used in thecommand module (CM) and the lunar module (LM): generation and storage of a watersupply, transpor t of water to the por ts used by the crewmen fo r drinking and food prep-ara tion, and cabin cooling. Only the first and second functions are discussed in detailin thi s report. The principal difference between the CM and LM wate r sys te ms is inthe ini tia l function, which is water generation and storage. Water is generated by fuelcel ls in the CM; however, in the LM, all required water supplies ar e loaded in storagetanks before lift-off. Other differences between the two syste ms a r e that provisionsa r e made for chilling and heating of the wate r supply in the CM but not in the LM, anda portion of the LM water supply is used routinely fo r sublimation cooling of the LMcabin. In the CM, boiling of water is used only as a secondary o r supplementary cool-ing device in place of sublimation cooling.

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DESCR I P T I ON OF THE APOLLO POTABLE WATER SY STE MC o m m a n d a n d S e r v i c e M o d u l e

A schematic of the command and se rv ic e module (CSM) wate r management sys temis shown in figure 1. Water generated by the fuel cells, located in the ser vice module(SM), is transferred by means of a tube to a water-valve (control) panel. Fr om thewater-valve panel, wate r can be routed either to. the potable-water tank o r to the waste-water tank, and then to the food-preparat-ionunit after passirig thi-iiiigh a iieaier, or tothe drinking-water gun after passing through a chiller. If the potable-water tank is full,water is routed to the waste-water tank.Water system. - The water supply from the fuel cel ls is adjusted to 25 ps i and74" F and is conveyed to a hydrogen separato r, then to the water-cont rol panel (fig. 1).The active portion of the separato r consis ts of palladium-silver tubes. Hydrogen isdiffused from the water through the walls of the tubes and then vented into space. Themain controls on the water panel are two water-shutoff valves (one each for the potablewater and waste water systems), a shutoff valve that permits access to the waste watersystem, the chlorine-injection assembly, a control valve to the overboard dump, andtwo pressure-re lief controls. Fuel-cell water is supplied to both the potable-waterand waste-water tanks, and excess fuel-cell water is dumped overboard i f these tanksa r e filled. The potable water s ystem line (line 1, fig. 1) eads to the chlorine-injectionassembly, to a check valve, and to the potable-water tank. Water flowing out of thepotable-water tank (by means of a bypass line and check valve) can be transferred to

the chiller, heater, o r waste-water tank, o r dumped overboard. The chill er reduces, the water temperature fro m 76" F to approximately 45" F. The food-preparation unitconsists of a heater and two water-use ports, one f or hot water and the other for chilledwater. The heater has the capability to ra is e the water temperature to 154" F. A. 25-psi pressure is maintained in the potable water sys tem by applying oxygen to anexpansion bladder in the potable-water tank.

Waste water system. - Fuel-cell water can be supplied to the waste water systemonly i f the potable-water tank is filled. Water can be tr ans fer red from the waste-water


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Overboard SM sectorI -ump CM sector-1.2 Iblhr, minimum2.0iblhr. maximum

e hutoff valve-+q- Shutoff valve-@- Pressure-relief valve

-.- Waste +J-heck valve

Figure 1.- Schematic of the CSM water management system.tank by means of a se rvi ce line (line 2, fig. 1) leading to the overboard-dump orifice o rby means of another line (line 3, fig. 1) leading to two evaporators, which are second-ary heat exchangers for the CSM water/glycol cooling sys tem. Evaporated water isdischarged into space through an orifice. The se rv ice line rece ives humidity conden-sate fr om the pr es su re s uit s and fro m the CM atmosphere. The condensate is a secondsource of water fo r the waste water system.

Functional components. - The following key functional components a r e used in theCM water management system.Potable-water tank: The potable-water tank se rves two purposes: a water-storage container in ca se of fuel-cell fa ilur e and an equalization tank to provide waterduring peak-demand conditions when the water demand rate exceeds the fuel-cell pro-duction rate fo r brief periods. The cylindrical vessel holds a maximum of 36 poundsof water and is fabricated from 6061 aluminum alloy. An oxygen-filled polyisoprenebladder maintains a pressure of approximately 25 ps i in the tank and throughout thesys tem. The oxygen that keeps the bladder inflated is obtained from a common SMsupply that als o provides oxygen fo r metabolic consumption and for power generation.Because free hydrogen in the water diffuses through the bladder material , a low-rategas bleedoff is provided to prevent a buildup of diffused hydrogen, which could re su ltin an explosive hydrogen/oxygen mixture i n the oxygen plenum.Waste-water tank: The waste-water tank provides storage fo r water that can besupplied to the water evaporators in case of a fa il ure of the pr imar y cooling system

and operation to the potable-water tank.radiators . The tank holds a maximum of 56 pounds of water and is simil ar in design

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Water chiller : The chiller , which ha s a water-storage capacity of 0. 5 pound, re-duces the temperatur e of the water fr om 76" to 45" F fo r the drinking-water gun andthe food-preparation unit. The tubes of the heat exchanger in the chiller a r e made ofstainles s ste el (type 347), and all other components in the chill er a r e made of stainles ssteel (corrosion-resistant type 316L). Chilling is provided by the spacecraft wa ter/glycol cooling system.Food-preparation unit: The food-preparation unit tr an sf er s hot or cold water in1-ounce aliquots into dehydrated-food packages. The unit includes an ele ctr ica l hea terand two metering faucets. The heate r holds 2. 5 pounds of water and maintains thewater temperature at 154'" F. The heat er cons ists of a stainless-steel (type 347),corrosion-resistant re se rvoi r shell that contains copper (ASTM B 152-58) baffles andtubes.Drinking-water gun: A drinking-water gun is connected to the water system by70 inches of Viton flexible hose.Lines: A ll hard li nes in the system a r e fabricated f rom 0.25-inch-diameter

6061 aluminum tubing.Biocide: Sodium hypochlorite (NaOCl)w a s used as a biocide for the CSM watersupply system. The NASA potable-water specifications requir e that the minimumresidual chlorine concentration be 0. 5 mg/liter as chlorine.

Lunar ModuleThe LM water management system (fig. 2) differs in s ever al aspects from theCM system. The LM system is designed to supply drinking water and wate r f or sub-

limation cooling. The drinking-water gunprovides water fo r drinking and food prep-aration. However, no provisions a r e madefo r chilling o r heating potable wa ter onboard the LM. The sublimation unit isused as a heat exchanger to chill the cool-ing fluid for the cabin and various LMelec trical components.Three storage tanks, filled beforelift-off with deionized water, meet all

wate r demands. The la rg e stor age tank(tank I), which holds 400 pounds of water,is located in the LM descent stage. Thedescent-stage tank supplies all water forphase and during the surface-explorationphase. During the ascen t phase and theLM/CSM rendezvous and linkup phase, allwater requirements ar e met by the two

the LM during the lunar-orbit descent Check valve@ Pressure-relief

Figure 2. - Schematic of the LM watermanagement system.4


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40-pound water- storage tanks (tanks 2 and 3), which are located in the ascent stage.The LM descent st age is separated from the ascent stage before lift-off and remai nson the lunar surface. Storage tank 2 is used exclusively to supply water to the sublima-tion unit. A check valve prevents the tr ans fer of water fro m tank 2 to the drinking-water gun. Tank 3 provides drinking water and, i f required, supplies water to thesublimation units. Essentially, t h e entire LM water management s ystem is fabricatedfrom alodine-treated 6061 aluminum and 0.25-inch-diameter tubing. The following keyfunctional components are used in the LM water system.Water-storage tanks. - The three LM wate r-storage tanks a r e made of aluminum,and the water supply in these tanks is stored in sil as tic bladders. The space betweenthe bladders and the tank shell is pressuri zed with nitrogen at 45 psi.Sublimation units. - The sublimation units a r e heat exchangers t h a t chill the waterand glycol for t h e LM var ious components. Basically, the units consist of sin terednickel plates that form a ba rr ie r between the water (either liquid or solid) on one sideand the space vacuum on the other side. A thin ice film develops at the inner side of

the plates and sublimates and pas se s through the plat es into space.Disinfectants. - Iodine w a s selected as a disinfectant fo r the LM water manage-ment system because chlorine caused operating problems with the sublimation units.The NASA potable-water specifications r equ ire that the minimum residual iodine con-centration be 0. 5 mg/liter.

W ATE R S Y S T E M M A T E R IA L S C O M P A T I B I L I T YMetalI ic Components

Corrosion w as found initially at the following th re e points in the CM: the inlettube to the hea ter, the tube just in front of the connection to the hose of the drinking-water gun, and the section of tubing between the chlorine-injection point and the potable-water tank. An investigation revealed t h a t a pitting-type corrosion w a s occurringthroughout the sys tem. It w a s noted that pits occurred at points of s urface imperfec-tions in the 6061 aluminum tubing. Because of the corros ion, nickel, cadmium, andmanganese were pre sent in the water supply at leve ls in excess of the NASA cri te ri aexisting at t h a t time.It is believed that the corros ion w a s primarily attributable to the followingfactors.1. The use of ultra-high-pur ity water, which is corrosive by nature2. The incompatibil ity of the biocide with the system (for example, the capabilityof chlor ide ions to penetrate the passivating oxide layer formed on aluminum tubing)3. The selection of materi als fo r system fabrication

a. Dissimilar metals connected i n electromotive se ri es (for example, theinterconnection of aluminum and copper produces an electromot ive force of approxi-mately 2 volts)5


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b. Internal tubing- surface imperfections which provide sites for activelocalized corrosionTests indicated that fuel-cell water when combined with sodium hypochlorite andsodium dihydrogen phosphate (NaH PO ) at the concentration leve ls used in the space-

craf t produces considerable corro siv e action on aluminum. Nickel, cadmium, manga-nese, and (to a le ss er extent) other metals a r e released into the CM water supply as are su lt of corr osive activity and the attendant deterioration of the nickel- copper brazingand the aluminum-alloy tubing. In the CM, in addition to the problems that corros ionimpos es on maintaining sys tem integrity, corr osion also is a sink fo r biocide (chlorine)and results in a rapid loss of re sidual biocide. To solve the incompatibility problem,sodium nitra te was tested and found to be acceptable as a corrosion inhibitor.

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The interaction of iodine with aluminum has caused, to a significantly l es se r ex-tent, corrosion in the LM water system. The presence of nickel in sam ples taken fromthe ascent-tank u se po rt and the presence of cadmium in samples taken fr om thedescent-tank u se p ort are evidence of thi s corrosion. However, cor ros ion has provedto be of a minor nature, and inhibitors we re not deemed necessary.

Synthetic ComponentsIn the LM, a problem of rapid iodine depletion was found, caused by interactionbetween iodine and the silas tic membranous materia l used in the LM water tanks. Thepr im ar y cause of this depletion was the diffusion of iodine through the bladder mat er ial .Evidence indicates that the silastic bladder acts as a semipermeable membrane andthat t h e rate nf rr.err,brancperzieatiuii of t i e iodine in cr ea se s with increasing iodineconcentration and time of exposure of the bladder to iodinated water . To solve thepermeability problem, the following procedural changes were instituted for the loadingof the LM water tanks.1. Iodinated water was not placed in the tanks during ground-based testing.2. The loading of iodinated water into the tanks w a s delayed until the latest pos-sible time before launch.Interaction between the biocide and the membranous material in the LM has notcaused the objectionable ta st e and od or s as did the interact ion between the chlorine andthe original neoprene hose connecting the drinking-water gun to the wate r syst em in theCM. The extent to which chlorine-polyisoprene in teract ion affects the CM water ta st eand odor is unknown; however, organic precipi tat es have been found in the water syst em.The precipitate, a metal carbamate, was found to be a curing agent that was used in thepoly isoprene tank bladders.

GasesThe degassing of water at the us e por ts caused problems during flight becausethe quantity of gas in the water formed bubbles of sufficient si ze to inhibit dir ec t us eof the water for drinking o r food prepara tion. Techniques to perfo rm gas/liquid

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separa tion in ze ro- gravity conditions (such as bagging and centrifugation) we re noteffective. A hydrophobic/hydrophilic water/gas separator , which performed with rea-sonable su cc es s during the Apollo 11 mission, is being used along with the palladium-si lv er hydrogen separa tor that was used during the Apollo 12 and subsequent miss ions.The following a r e the two major so ur ce s of dissolved gas es i n the CM water.1. Hydrogen gas re leas ed from fuel-cell water as the water pass es through cas-caded pres sur es from 60 ps i (fuel cell) to 5 ps i (cabin atmosphere)2. Diffusion of oxygen, used as a pre ss ure balance in the water tanks, into thewater supply (Data on dissolved oxygen concentrations in the delivered fuel-cell watera r e not available. )Similar degassing problems have occurred at the us e por ts of the LM. The gasesa r e believed to have consisted ei ther of nitrogen diffused into the wate r supply fro m thebalancing plenum of the potable-water tanks or of entra ined air in the water supply atthe tim e of servicing. A so ur ce of dissolved gases that is common to the LM and theCM is ground-support-equipment water that is not degassed before being loaded onboard the spacecraft.

CHEMICAL QUALITY OF WATERWater Source and Serv ic in g

The water placed on board the spacecraft for the Apollo missions was drawn fr omthe re so ur ce s of the city of Cocoa, Florida, and w a s purified to ultrahigh quality at thelaunch site. The city water was filtered through particulate filters, charcoal filte rs ,and then through two mixed-bed ion-exchange units until the water had a resistivity of18 megohms. Then, the water w a s filtered through 0.22-micron bacteri al fi lt er s andwas loaded into a water-servicing unit for subsequent tra nsf er to the spacecraft.

The water was loaded into the servic ing units in a closed system that eliminatedexposure to the atmosphere. Once loaded, each servicing unit had the capability ofrec irculat ing water through the bacteri al filters. On-site measurement of the pH andele ctr ical conductivity was necessary to avoid atmospheric contamination of the highlypurified water. Sample containers were designed to prevent the entry of any extraneouscontaminants, and an anodized aluminum container (impregnated with Teflon) w a s foundto be satisfactory fo r this purpose.

Fuel-Cell WaterService module fuel-cell assembly. - The fuel cells are the only components inter-related with the water sys tem that are located in the SM.chambers, separat ed by porous-nickel electrodes, and contain concentrated potassiumhydroxide (KOH) liquid electrolyte. One of the chambers is filled with oxygen (cathode),and the other chamber is filled with hydrogen (anode);pre ss ure in both chambers ismaintained at 60 psi. Oxygen is diffused through the electrode into the hydrogen-filled

Fuel cel ls consis t of two

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chamber, wherein the two gase s react chemically to produce electri cal power to meetthe requi rements of the CSM. Extremely pure water is a byproduct of the chemical re-action. The fuel cells operate at approximately 410" F and 60 psi and produce water ata nominal rate of 1 . 2 lb/hr. The water-production rate depends on the power drawnfr om the cel ls and may incr ease fro m the nominal rate to as much as 2.0 lb/hr forbrief periods. Before fuel-cell water is tran sfer red to the CM, the water is cooled to74" F and the s ystem press ure is reduced to 25 psi.Chemical composition. - Chemically, the fuel-cell byproduct wat er is as pure asdistilled water, but the water is satu rated with hydrogen gas. The total dissolvedsolids in thi s water averages 0.73 mg/liter, and the average pH is 5.6.One problem associa ted with the fuel-cell wate,r is the reaction that appears tooccur between the storage-tank membranous bladder mate rial and the fuel-cell water.After chamber tests, analyses for total solids, turbidity, and part icula tes indicatedthat the water failed to meet these specifications because of the presence of a yellow,granu lar material. This mate rial was identified as Bis- (pentamethylenedithiacarba-mate) Ni (II) and w a s previously re fe rr ed to i n the discussion on synthetic componentsas a metal carbamate. It appea rs only after fuel-cell wate r has collected in the water-storage tank.

Wate r -Use Po r t sThe significant problems associated with the water-use port s of the CM and LMhave been rela ted to the failure to deliver adequate biocide levels, caused by int er-action with system components, and to the tra nsport tc th e use ports of dissuived ga sesI'mm the iuei cell and fro m the gas-pressurized wate r-storage tank. The attrition ofdisinfectant levels is directly rel ated to the problems of corrosion, the interaction ofdisinfectant with membranous mate rial s, and the presence of viable organisms , tastes,

and odors in the water. The pre sen ce of quantities of gas in the water supply trans -ported to the use po rts caused difficulty in the di rec t use of the port s to acquire drink-ing water or food-preparation water.

S T E R I L I Z A T I O N OF THE POT ABLE WATER SY ST EMMed ica l Req ui erne n s

The bacteriological cr it er ia used by the NASA fo r potable water s ystem s require sthe total absence of viable organ isms (sterility). The criteria do not specify indicatororganisms. The design char acte rist ics of the water system, possessing sever al poten-tial sources of contamination, offer little re st ra int preventing microbial entry andproliferation in the water. Little is known about the interrelationship between micro-organ isms and man in the spacecraft environment. In addition, a remote but realchance exists that fecal contamination of drinking water could occur. For these rea-sons, the NASA standard requi res that water in all spacecraft sys tem s be maintainedfree of viable organisms.

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In the development of biocide systems for the CM and LM, the size, weight, andpower requirement s of the systems were limited severely by the spacecraft design,which precluded the use (in the Apollo Program) of other than chemical tre atment f ordisinfection. With the implementation of chemical steril ization, it has been copfirmedthat the chemical s yst ems that were selected for u s e (chlorine in the CM, iodine in theLM) interac ted with metallic components and membranous mate ri al s in the water s y s -tem. A s a resul t of thes e interactions, problems of corrosion, taste, odor, and los sof residual biocide we re generated. Thus, the need for water-quality cr it er ia orientedtoward pres ervat ion of system integrity and the health and estheti c needs of the crew-men a r e evident.

Biocide AdditionSystem steril ization f or the CM. - Both preflight and inflight sys tem - sterili zat ionprocedures are used fo r the CM water system. Approximately 5 days before lift-off,the water sys tem of the CM is filled with deionized water containing 1 2 mg/liter sodiumhypochlorite as chlorine. Af t e r an exposure of 4 hours, the system is drained andflushed with water that has been deionized by means of a mixed-bed ion-exchange s y s -tem. Af t e r flushing, the system is filled with deionized water . Th ree hours beforelift-off, 20 cubic cen timete rs of sodium hypochloride (5000 mg/ li ter as chlorine) andsodium dihydrogen phosphate buffer (0.7 molar) ar e injected into the spacec raft system.Inflight ste rilization of the CM potable water system is performed in the followingsteps.1. Approximately 10 percent ullage is produced in the potable-water tank by(Thisithdrawing water through the drinking-water gun o r food-preparation unit.step is required in or der to permit a flow of fuel-cell water past the biocide-injectionpoint and into the potable-water tank. )2. A solution containing 1860 mg/l iter sodium hypochlorite as chlorine is injectedfrom a 20-cubic-centimeter ampule.3. The contents of a 20-cubic-centimeter ampule of sodium dihydrogen phosphatebuffer solution (0.297 molar) and sodium nitr ate corros ion inhibitor (0.217 mola r) isinjected.4. The injected solutions a r e flushed into the potable-water storage tank byflowing fuel-cell water past the chlorine-injection port and into the tank (fig. 1). Mostof the biocide and buffer passes the servi ce line branching point and is car ried into

the storage tank. However, a small fraction may remain in the injection tee or maybe diffused into the service line.5. After a 10-minute contact time, an ampule of water is withdrawn through theinjection point. As a result of withdrawal, a chlorine solution which may be in theservice line is pulled back into the main line where the chlorine can be tr an sf er redinto the stor age tank by the fuel-cell wate r.6. Before the water is used, an additional 20-minute period is required to allowthe biocide, buffer, and inhibitor to disperse in the potable-water tank.

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7. The sterilized water is withdrawn for consumption through the drinking-watergun and food-preparation se rv ice outlets.On seve ral occasions during the ea rl y Apollo flights, the crewme mber s reportedthat the water had a strong chlorine taste. In most instances, the difficulty was tr acedto a procedural error that occurr ed during the injection of the chlorine and buffer.When clea r and concise procedures were developed and used, the crewmembers hadno objection to the ta st e of the water.System steriliza tion for the LM. - Iodine was selected as the biocide for the LMwater management system because it was noted that chlorine caused operational prob-le ms with the sublimation units. The NASA potable-water specifica tions requi re theminimum residual iodine concentration to be 0. 5 mg/liter.Only preflight sterilization procedures a r e used on the LM wate r system. Ap-proximately 7 days before lift-off, the water management syste m is filled with a30-mg/liter iodine solution. A f t e r 1 hour, the syst em is drained and refil led with de-ionized water, to which a lO-mg/lite r iodine solution has been added. This solution

is left in the LM tanks and is used to supply water during the lunar mission.

MICROBIOL OGICAL QUAL ITY OF WATERM i c r o b i a l C o n t a m i n a t i o n

The problem of microbial contaminstinn in the w2k r s y s t em sf the C X has bee11related almost totally to preflight detection of aerobic organisms in the hot-water portand the drinking-water gun. Bacterial growth has been detected during the interva l im-mediately before a final chlorination before lift-off.Several types of organisms have been identified in cu lture s fr om the us e por ts(for example, Flavobacterium sp. , Staphylococcus epidermidis, Sarcinia-p. , andCorynebacterium sp. ). Flavobacterium sp. has been observed the most frequently andin the highest numFers. All of these s p e x e s have been detected before the preflightchlorine injection. Postflight sample s taken f rom the drinking-water gun consisten tlyhave had zero bacterial counts, and either ze ro o r nominal counts (20 organisms pe r

100 milliliters) have been recorded fo r sam ples taken from the hot-water port. Pre-flight and postflight testing of all sample por ts fo r coliforms, anaerobic bacteria, yeasts,and molds also resulted in a ze ro count. This condition can be attri buted to the 24-hourinflight chlorination schedule.

Samples of the LM water suppl ies can be taken only during the preflight periodbecause the LM stages are jettisoned in the course of the mission. Tests fo r coliforms,anaerobic bacteria, yeasts, and molds have been made on the LM water-supply samplesdrawn during the preflight period. Flavobacterium s p . has been found in a water supplyprepared for transf er to the LM; however, af te r iodgation, no org ani sms of any kindwere found in this water supply, either before o r after tra nsf er into the LM. Bacterialgrowth has not been obtained from any samples taken after preflight iodination proce-du re s have been completed.

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Maintenance of SterilityThe single common-use water disp ense r provided for the th re e Apollo crew-membe rs offers no protection from microbial transfer from crewman to crewman.The CM water dispenser is attached to a 70-inch-long Viton hose. The water in thehose has little or no residua l biocide a fte r remaining unused for extended periods.Consequently, bacterial growth may occur.It has been noted that maintenance of system ster il ity cannot be achieved in theabsence of res idua l biocide. Connections, valves, metering dis pensers and O-r ingsin water systems may harbor bacteria that rapidly recontaminate the water. Also,back contamination at use ports occurs. Bacterial growth in the water storage tankshas been unexpectedly rapid. During CM chamber te st s when no biocide was used,6bac teri al leve ls of to 6 X 10 organisms per 100 milliliters were found during the peri-od of time when the water w a s stor ed in the spacecraft. The source of the nutrient s tosupport this growth is unknown; however, the nutrients may be received from the tank-bladder mater ial, hose, o r other carbon compounds.

CONCLUDING REMARKSThe ove ral l performance of the command and se rv ice module and lunar modulewater sys tems has been good. Although design and operational difficu lties in the ApolloPr og ra m existed, the difficulties were not insurmountable despite the complex and un-conventional type of water system that is required fo r space travel. The design andoperational problems that we re experienced on the two water systems are of consider-able in te re st to industry , not only because of the uniqueness of the systems, but alsobecause of the technology that is being developed and applied to problem solving.The problems documented in this r epo rt have been successfully resolved in theApollo Pro gram. However, some concern exists that , as the timespan of space mis-sions is increased, problems that ar e potentially adver se over a comparatively shor tper iod of time may evolve into se rious problems during longer missions. During theApollo Pr og ra m, much of the technology w a s developed to meet future water-supplyneeds in spacec raf t. The information, equipment, and instrumentation developed inspacec raf t pro gra ms can be applied effectively to municipal, industri al, and privatewater- conservation prog rams. Technological advances described or cited in thisrep ort a r e found primaril y in the following general area s.1. Selection and evaluation of new types of water -system mat er ia ls

a. Metallics: Evaluation of corros ion resis tance of cer tain metal alloys,their physical chara cterist ics as watersystem components, and thei r compatibilitywith biocides.b. Nonmetallics: Endurance and permeability charac te ris ti cs of polymericmembrane mate ria ls; mate rial compatibility with water , gases, and biocides; andtaste and odor problems rela ted to material use.

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2. Selection and evaluat ion of water biocides3. Selection and evaluation of physical and chemical corr osion inhibitors4. The importance of sanitary-engineering concepts in the design developmentand testing phases of potable or multiuse water sys tem sIn recognition of the rapidly increasing need for new technology in modern water-supply management, a conscious effort will be made to make meaningful contributionsto modern ecology. It is the intent of the NASA to continue to design and develop high-quality potable-water use and recycle sys tem s fo r the space program.

Manned Spacecraft Cente rNational Aeronautics and Space AdministrationHouston, Texas, January 26, 1973914-50-95-27-72

12 NASA-Langley, 1973- 1 s-363

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Apollo Experience Report Potable Water System

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