._I /" ? , 4/_¢"
Final Report
DEVELOPMENT
AN ELECTROLYTIC
FOR WATER
IN APOLLO
OF
SILVER-ION GENERATOR
STERILIZATION
SPACEC...
N69-14494
21
Final Report
AN
IN
DEVELOPMENT
ELECTROLYTIC
FOR WATER
APOLLO
OF
SILVER-ION GENERATOR
STERILIZATION
SPACECRAFT...
CONTENTS
Section
I
2
5
APPENDIX A
INTRODUCTION
ANALYTICAL METHODS AND PROCEDURES
Colorimetric Determinations
Potentiometri...
I LLUSTRATIONS
Fi _u re
2-I
5-I
3-2
3-3
3-4
3-5
3-6
5-7
5-8
3-9
4-I
4-2
4-3
4-4
4-5
4-6
4-9
4-10
Spectronic 20 Used for An...
ILLUSTRATIONS (Continued)
Figure
4-11
4-12
4-13
4-14
4-15
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
5-1...
TABLES
Tab le
3-I
/4-I
4-2
4-5
4-/4
4-5
4-6
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
Design Data for Silver-Ion ...
TABLES (Continued)
Table
5-15
5-14
Silver Sensitivity of Test Organisms to Apollo Tank
Bladder Water {Static Tests with Si...
SUMMARY
An electrolytic water steril izer has been developed for control of
microbial contamination in the Apollo spacecra...
BIBLIOGRAPHY
I °
.
.
.
o
.
Investigation of Silver for Control of Microbial Contamination in
a Water Supply Subsystem_ Apo...
SECTION I
INTRODUCTION
The silver-ion generator was developed under Task 34 of the Phase II
Program Plan for sterilization...
SECTION 2
ANALYTICAL METHODS AND PROCEDURES
COLORIMETRIC DETERMINATIONS
The analytical procedure for the detection of silv...
Figure 2-I. Spectronic 20 Used for Analysis of Silver-Ion
Concentrations
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A fresh sample of the green dithizone solution was used each day to zero
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SECTION 3
ENGINEERING AND DESIGN
BASIC DESIGN CONSIDERATIONS
System Requirements
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DESIGN DATA FOR SILVER-ION GENERATORS
Dimension
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the original prototype unit (3-cc volume) would function more effectively.
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59804-2
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AIRESEARCHMANUFACTURINGDIVISION
Las Angeles Cahfarma
67-2158
Pag...
ANODE LEAD
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_p,NU_AC'_U ING D_VIS_ON
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PERFORMANCE CHARACTERISTICS
CELL PERFORMANCE
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Page 4-21
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Page 4-30
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BACTERIOLOGICAL TESTS
INTRODUCTION
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Nasa silver Apolo
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Nasa silver Apolo

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  • 1. ._I /" ? , 4/_¢" Final Report DEVELOPMENT AN ELECTROLYTIC FOR WATER IN APOLLO OF SILVER-ION GENERATOR STERILIZATION SPACECRAFT WATER SYSTEMS Apollo Applications Proqram 67-215g Junc, 1967 AIRESEARCH MANUFACTURING DIVISION Los Anleles , California Reproduced by NATIONAL TECHNICAL INFORMATION SERVICE U S Department of Commerce Springfield VA 2215]
  • 2. N69-14494 21 Final Report AN IN DEVELOPMENT ELECTROLYTIC FOR WATER APOLLO OF SILVER-ION GENERATOR STERILIZATION SPACECRAFT WATER SYSTEMS Apollo Applications Proqram 67-2158 June, 1967 Prcpared by (1. F. Albright R. Nachum M. D. Lcchtman Appr_vcd b) _ . v¢" _T t Prepared for National Manned Spacecraft Center Aeronautics and Space Administration Houston, Texas AIRESEARCH MANUFACTURING DIVISION Los Angeles,California REPRODUCED BY U.S. DEPARTMENT OF COMMERCE NATIONAL TECHNICAL INFORMATION SERVICE SPRINGFIELD, VA. 22161
  • 3. CONTENTS Section I 2 5 APPENDIX A INTRODUCTION ANALYTICAL METHODS AND PROCEDURES Colorimetric Determinations Potentiometric Measurements Atomic Adsorption ENGINEERING AND DESIGN Basic Design Considerations Control Ci rcuit Electrolytic Cell Design PERFORMANCE CHARACTERISTICS Cell Performance System Performance BACTERIOLOGICAL TESTS Int roduct i on Materials and Methods Results and Summary and BIBLIOGRAPHY MICROBIOLOGICAL BY Discussion Conclusions SENSITIVITY TO DISINFECTION IONIZED SILVER I-I 2-I 2-I 2-6 2-6 3-I 3-I 3-5 3-6 4-I 4-I 4-20 S-I S-I S-I 5-2 5-38 B-I A-J _ AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cal,forn,a 67-2t58 Page i
  • 4. I LLUSTRATIONS Fi _u re 2-I 5-I 3-2 3-3 3-4 3-5 3-6 5-7 5-8 3-9 4-I 4-2 4-3 4-4 4-5 4-6 4-9 4-10 Spectronic 20 Used for Analysis of Silver-lon Concent rat ions Calibration Curve for Analysis of Silver-lon Solution Influence of Total Silver Content of Sample on Possible Error Obtained in Analysis Theoretical Silver-lon Concentration as a Function of Current and Flow Rate Rate of Anodic Consumption as a Function of Operating Current Circuit for Control of Current in Electrolytic Silver-lon Generator Assembly Drawings for Laboratory Silver-lon Generators Used to Obtain Development Data Prototype Silver-Ion Generators Flight-Rated Water Sterilization Cell Power Supply System_ Flight-Rated Water Sterilization Cell Exploded View, Flight-Rated Water Sterilization Cell Outline Drawing, Part No. 133448 Amperage as a Function of External Control Resistance Variation in Current with Conductivity of Water Fluctuations in Effluent Concentration for the Large (150 cc) Silver-lon Generator Output Concentration as a Function of Flow Rate for Flight-Rated Silver-Ion Cell No. I (Flight Prototype Unit) Output Concentration as a Function of Flow Rate for Three Flight-Rated Water Sterilization Ceils Establishment of Equilibrium Between Generation and Deposition Rates Under Static (No-Flow) Conditions Predicted Cell Efficiencies Under Flow Conditions Schematic of Test Apparatus for Determination of Cell and Throughput Efficiencies View of Test Apparatus Used to Evaluate Cell and Throughput Efficiencies Effect of Stagnant Water Treatment on Throughput Efficiency of Aluminum Tubing 3-3 3-4 3-7 3-9 3-10 3-13 3-14 3-15 3-16 4-2 4-3 4-6 4-14 4-15 4-17 4-21 4-22 Z,-23 4-27 }_I AIRESEARCH MANUFACTURING DIVISION tos Angeles Ca1,1orn,a 67-2158 Page i i
  • 5. ILLUSTRATIONS (Continued) Figure 4-11 4-12 4-13 4-14 4-15 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 Schematic of Continuous Flow System of Reliability Tests 4-29 Views of Continuous-Flow System 4-30 Schematic of Simulated Apollo Waste Water System 4-33 Simulated Apollo Waste Water System 4-34 Wiring Schematic for Operational Control of the 4-35 Simulated Apollo Waste Water System Results of Static Tests Using Inoculated IE. coli] Sweat 5-8 Condensate and Silver Nitrate Solution Result of Static Test Using Inoculated IS. aureus) 5-I0 Sweat Condensate and Silver Nitrate Solution Systems Used for Testing the Bactericidal Effectiveness 5-11 of Silver-lon Generators Results of Static and Dynamic Tests on Kill Rate of E. coli 5-15 in Distilled Water Using Electrolytic Silver (Cell AT Results of Tests Using Inoculated (E. coli) Distilled 5-16 Water Through Silver-Ion Generators Results of Tests Using Inoculated (S. aureus) Distilled 5-19 Water Through a Silver-lon Generator (Cell A) Results of Static Tests Using Inoculated (E. coli) Distilled 5-20 Water Obtained from the Cyclic Accumulator Results of Tests Using Inoculated (E. coli) Distilled 5-21 Water Through Cell B and Cyclic Accumulator Results of Tests Using Inoculated (S. aureus) Sweat 5-27 Condensate Through Cell B and Cyclic Accumulator Results of Continuous Test Using Inoculated (E. coli] 5-31 Distilled Water Through the Apollo Waste Water Hold Tank Results of Continuous Test Using Inoculated (S. aureus) 5-33 Distilled Water Through the Apollo Waste Water Hold Tank Results of Static Tests Using Inoculated (E. coli) 5-36 Bladder Water and Silver Nitrate Solution Results of Static Tests Using Inoculated (S. aureus) 5-37 Bladder Water and Silver Nitrate Solution Summary of Static Tests with E. coli 5-41 Summary of Dynamic Tests with E. coli 5-42 Summary of _. aureus Tests 5-45 _ AIRESEARCH MANUFACTURING DIVISIONlos Angeles Cal_(_rn,a 6 7-2158 Page i i i
  • 6. TABLES Tab le 3-I /4-I 4-2 4-5 4-/4 4-5 4-6 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 Design Data for Silver-Ion Generators Typical Analyses of Silver-lon Generator Efficiencies Under Various Conditions Operating Tests for Flight Rated Water Sterilization (Silver Ion) Cells Silver Ion Concentrations Obtained in Small Prototype Cells Under Static Conditions Silver-lon Throughput Efficiencies for Aluminum Tubing Subjected to Various Treatments Adsorption of Silver by Polyisoprene Bladder (Analysis by Atomic Adsorption Typical Silver-lon Analyses at Various Sample Points in the Simulated Apollo Waste Water System Artificial Sweat Formula Silver Sensitivity of E. coli in Artificial Sweat (Static Tests with Silver Nitrate) Comparison of the Chemical Composition of Synthetic Sweat and Sweat Condensate Sensitivity of E. co]i to Silver in Sweat Condensate (Static Tests Using Silver N_trate) Sensitivity of S. Aureus to Silver in Sweat Condensate (Static Test Using Silver Nitrate) Tests of Electrolytically Produced Silver with E. coli (Static and Dynamic) Tests of Electro}ytically Produced Silver with S aureus Effect of Cyclic Accumulator on Kill Rate of E.coli (Static and Dynamic Tests) Silver Sensitivity of S. aureus in Sweat Condensate Through Cyclic Accumulator (Simulated Apollo Waste Water System Contamination of Effluents from Hold Tanks of Continuous and Simulated Apollo Waste Water Systems Contamination Levels for E. coli Under Continuous Flow Conditions (Simulated Apollo Waste Water System) Contamination Levels for S. aureus Under Continuous Flow Conditions (Simulated Apollo Waste Water System) 3-11 4-5 4-9 4-19 4-25 4-28 4-37 5-2) 5-3 5-5 5-7 5-9 5-13 5-17 5-22 5-25 5-28 5-30 5-32 _l AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahforma 67-2158 Page iv
  • 7. TABLES (Continued) Table 5-15 5-14 Silver Sensitivity of Test Organisms to Apollo Tank Bladder Water {Static Tests with Silver Nitrate) Summary of Bacteriological Tests 5-54 5-40 _ AtRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahfo,n,a 67-2158 Page v
  • 8. SUMMARY An electrolytic water steril izer has been developed for control of microbial contamination in the Apollo spacecraft. Individual units are self- contained and require no external power or control. The small size (2.5-in. diameter by 4 in. Iongj_ light weight (0.6 Ib)3 and absence of interface requirements make it possible to incorporate such sterilizers at various desirable locations in the potable water system or the waste water system. The sterilizer produces silver ions in concentrations of 50 ppb to more than 200 ppb in the water flow system_ the desired concentration being adjusted to the average water flow rate. After installation_ no maintenance is required. The unit can be neglected with no damage to the cell or the system_ since it becomes self-limiting if water flow is shut down. An external shunt is provided for on-off functions and monitoring of current flow. Probable life expectancy is 9000 hr without a change of batteries. Laboratory tests under simulated conditions have demonstrated essentially complete kill of Staphylococcus aureus and Escherichia coli within 8 hr, using initial bacterial concentrations greater than 5 x IO 5 organisms per ml. Methods for passivation of aluminum piping systems to minimize losses of silver ions by reduction have been developed. Elimination of system losses enhances bactericidal effectiveness_ decreases the required current_ and per- mits closer control over silver-ion concentrations in the water systems. CONCLUSIONS Adequate bacteriological control can be obtained within the water systems of the Apollo spacecraft by electrolytic generation of silver ions at concentra- tions of 50 to IO0 ppb. AIRESEARCHMANUFACTURINGDIVISIONt os Angeles CaldCrmld 67-2158 Page vi
  • 9. BIBLIOGRAPHY I ° . . . o . Investigation of Silver for Control of Microbial Contamination in a Water Supply Subsystem_ Apollo Applications Program_ AiResearch Manufacturing Co._ Los Angeles_ Calif._ Report No. 66-0810_ July 8_ 1966. Silver in Industry_ Edited by L. Addicks_ Reinhold Publishing Corp._ New York_ New York_ 1940_ pp. 401-429. Standard Methods for the Examination of Water and Waste Water_ 12th Edition_ 1965_ American Public Health Association_ Inc._ New York_ N. Y._ pp. 270-273. Snell and Snell_ "Colorimetric Methods of Analysis_ 3rd Edition Volume II_ D. Van Nostrand Co._ Inc._ New York_ N. Y._ 1961. pp. I-7 and 53-59. Public Health Service_ Drinking Water Standards_ U.S. Department of Health_ Education and Welfare_ Washington D.C. 3 1962. Slonim_ A. R._ et al_ "Potable Water Standards for Aerospace Systems 1967_" Life Support and Toxic Hazards Divisions_ Aerospace Medical Research Laboratories_ Wright-Patterson AFB_ Ohio. _ AtRESEARCH MANUFACTURING DIVISIONl_s Angeles Cahfo,n,a Page B- I
  • 10. SECTION I INTRODUCTION The silver-ion generator was developed under Task 34 of the Phase II Program Plan for sterilization of water systems in the Apollo Applications Program. The necessity of controlling microbial contamination and the require- ments for control were discussed in a previous report (Reference I). Silver ions in concentrations of 50 to I00 ppb, although nontoxic when ingested_ are an effective bactericide. The oligodynamic effects of silver have been known for a number of years (Reference 21. Since a sterilization unit for spacecraft water systems must operate in zero g, expend little power, and requireno elaborate controls, or expendables, the use of si Iver has many advantages over other possible sterilization techniques. It has previously been found (Reference li that silver plated on stainless steel provided the requisite concentrations, but silver-plated aluminum was not effective because the ionic activity of silver is suppressed by the much greater electrolytic solution pressure of aluminum. Exposed aluminum surfaces (anodic) and silver-plated aluminum Icathodici created electrolytic cells which effec- tively plated silver out of solution. This report covers the development of an electrolytic silver-ion generator. Electrolytic generation at the desired concentration levels (50 to IO0 ppbi is advantageous for the following reasons: Electrolytic silver provides effective bactericidal control. The silver-ion generator is self-contained, requiring no power from the spacecraft and no control system. The weight and volume of a single unit are such that several can be distributed throughout the water systems where required. The generator precisely meters silver ions with the water flow stream, the desired concentration being adjusted to the average flow. The generator is self-limiting if water ceases to flow. No maintenance is required, the generator being replaced if necessary. Life expectancy of 9000 hr is limited by battery life. No damage, aside from failure to sterilize the water, can occur to other spacecraft components if the generator should malfunction. _ AIRESEARCHMANUFACTURINGDIVISIONLo, Angekes Cahlorn,a 67-2158 Page I-I
  • 11. SECTION 2 ANALYTICAL METHODS AND PROCEDURES COLORIMETRIC DETERMINATIONS The analytical procedure for the detection of silver ions in quantities as low as 5 l_gm has been previously described (Reference I_. The procedure used throughout this investigation was essentially the same. Additional information can be found in Reference 3. The colorimetric method is extremely sensitive to impurities. The necessity for use of distilled water from the plant system rather than bottled distilled water has been previously pointed out (Reference I). Throughout the present investigation_ plant distilled water was used when possible. The procedure is a refinement of that employed in Reference 3, utilized for examination of waste water_ which is relatively complex because it necessi- tates eliminating ions other than silver ions from the solution. In the present investigation_ when silver was the only ion present in distilled water_ accuracy could be maintained and a larger number of samples could be analyzed by means of the refined procedure IReference I I. In those instances where other known ions Ichromate) or compounds (thiuram) were found to cause interference_ additional steps were employed which were found effective in eliminating the interference while preserving the rapidity of analysis. An initial estimate must be made of the concentration of silver in the sample so that the sample size can be chosen to yield 5 to 15 pgm of silver. Other metallic ions or organic materials which can be extracted by carbon tetra- -chloride and contribute to unwanted adsorption must also be absent. The sample is first acidified to a pH of approximately 0.8 by the addition of I cc of 5.5N H2S04 solution to each lO cc of sample. It is then shaken vigorously with a 5-ml solution of IO pg per ml dithizone in carbon tetrachIGride for one minute and the sample is set aside in a dark location until separation occurs. The water layer is decanted and discarded and the quantity of silver in the dithizone is determined by measuring the percentage of yellow light (620 mpl transmitted using a Bausch and Lomb Spectronic 20 Colorimeter (Figure 2-I). Percentage transmittance is related to the weight of silver in the dithizone using a calibration curve previously derived from standard silver nitrate solutions. Great care was required to reduce experimental error. The sample size was selected so as to avoid more than one dithizone extraction for each sample_ if possible. A new prescription bottle (4 to 16 oz) and cap was used for each sample to avoid reuse of glassware that had previously contained silver. Special precautions were taken with other glassware such as pipettesj burettes_ and graduated cylinders to avoid unwanted contamination. Standard silver nitrate solutions were stored in dark bottles that had been preequilibrated with the standard solutions for some weeks prior to storage. Since glass adsorbs silver_ such solutions were freshly made up if the solutions made earlier had been stored more than two or three months. Similarly_ samples were analyzed within minutes after acquisition to avoid losses of silver by adsorption on glassware. }_ AIRESEARCHMANUFACTURINGDIVISIONLOS Ang_,_es Ca_,forn,a 07-2158 Page 2-I
  • 12. Figure 2-I. Spectronic 20 Used for Analysis of Silver-Ion Concentrations I_l AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahfornla 67-2158 Page 2-2
  • 13. A fresh sample of the green dithizone solution was used each day to zero the colorimeter. Before analysis of each sample 3 the colorimeter was cali- brated with dithizone and pure carbon tetrachloride solutions. The dithizone solution undergoes color changes with light, so that it is necessary to store such solutions in the dark, to utilize them only as needed in a burette_ and store the calibrating solution in the dark when it is not in use. Since the light in the colorimeter also affects the dithizone solution_ it was necessary to discard and use fresh calibrating solution more than once a day when numerous analyses were made. Fresh dithizone solutions were made up when required by _nitially weighing 50 mg of dithizone dry crystal (Baker analyzed reagent) followed by appropriate dilutions with carbon tetrachloride. Minor errors (±I mg) in weighing might introduce considerable error in suc- cessive batches and cause a shift in the calibration curve. The curve used for converting transmittance to weiqht of silver in the sample is shown in Figure 2-2. Estimated error based on amount of silver in the sample is shown in Figure 2-3. Where possible the sample size was chosen so that it contained nearly IO _g of silver. This point on the graph could be calibrated with standard silver nitrate solution (IO0 ppb) when necessary to improve accuracy. The nature of the investigation_ however_ made it necessary to analyze various samples of different volumes containing unknown quantities of silver_ many of which could not be duplicated. Final results_ reported either as efficiencies or concentration_ do not indicate the amount of error in the analysis_which is a function of sample size used for the determination. When solutions other than distilled water--i.e._ sweat condensate_ fuel cell water_ or solutions containing bacteria--were analyzed_ it was necessary to check the effects of such solutions on dithizone in the absence of silver to ensure that unwanted adsorption of light had not occurred. Bacteria_ in particular_ seemed to have some effect on analysis of silver_ so that kill rates are reported as a function of theoretical silver ion concentration as well as measured concentrations which cannot be considered as accurate as those for distilled water. Hexavalent chromium_ used for coating aluminum tubes_ will cause a yellow shift in the dithizone solution. It was found that hexavalent chromium could be reduced to chromate ion by shaking the acidified water sample with a few drops of a 5-percent hydrogen peroxide prior to analysis. Chromate ion does not complex with dithizone. Tests of water from aluminum tubing treated with hexavalent chromium (Alumigold) indicated little or no chromium content in the effluent. Analyses of samples with and without peroxide treatment generally showed a slight increase in silver after the peroxide treatment_ which is the reverse of what is predicted if chromium interference occurred. This slight increase is apparently due to oxidation of collodial silver in the effluent_ which had previously been reduced in the aluminum tubing. Considerable trouble was encountered in using the colorimeter to analyze effluent from the Apollo potable water or waste water tanks. This was believed to be due to the presence of thiuram (dipentamethylene thiuram tetrasulfide) in the water that was leached from the bladder (polyisoprene) used for pressurization of the tank. A carbon tetrachloride (IO-ml) extract of the _ AIRESEARCH MANUFACTURING DIVISIONLO_ Angeles Cal,forf la 67-2158 Page 2-5
  • 14. 0 o.- r",, r'_ Z <_ r-,. t--'49 ,y- O O " I-- Z ,40 I O r-_ LI_ Z i... U') Z Z t._ 0 _ 0 I--- Z ¢Y" '_ I-" 0 0 0 0 0 0 0 o0 _D 0 00 ,0 0 0 _1 C_ I-- _1 k- 0 r 0 I > °_ 0 °-- c- O > L C 0 °_ rO 0 L ,B ,m -i I O_ °-- 33 NVJ_IINS NV_I .LN33_Bd Ir.AIIIII_TT AIRESEARCH MANUFACTURING DIVISION 67-2158 Page 2-4
  • 15. O ipj O O (:) 39V_I3AV 30 IN33W3d CWOWW3 378ISS0d O O O O i I I I I I I / / O cO ,O w __) Z p- l-- Z < I-" O Z w ILl 1:1. OID 4O ",,1" IN t- O QJ C1 E r0 O °B C >_ ¢- C O I,D I- ._ ._ £-- •_ O O O _.- I- O I-- hi C C O ,,4 I ¢M (11 I- :3 °_ 1.1... 6_ c_13A7i S 30 1HgI3M :IgV_I3AV (_ AIRESEARCH MANUFACTURING DIVISION O O 67-2158 Page 2-5
  • 16. tank effluent (150 mll) will turn yellow_ indicating that such impurities exist. This yellow color will disappear if the carbon tetrachloride is exposed to light overnight or will last indefinitely if it is kept in the dark. Since this yellow color [s extracted from a silver sample into the dithizone solution 3 it prevents accurate analysis of such solutions by colorimetric methods. Atomic adsorption was found to be effective for analysis of silver in the presence of thiuram and is further discussed. A partial colorimetric procedure was worked out_ however_ by which thiuram interference could be eliminated. It was found that adding a few drops of a potassium permanganate solution iI percent) to the acidified sample_ shaking_ and allowing about one minute for complete reaction_ followed by destruction of residual potassium permanganate with a few drops of hydrogen peroxide_ results in complete oxidizing of the thiuram_ and good analytical results can be obtained. The permanganate is a sufficiently strong oxidant to convert the sulfur in thiuram to sulfoxy com- pounds. Accurate silver analysis could be made using thiuram solutions obtained by soaking a portion of the bladder in distilled water. Effluent from the waste water hold tank_ however_ analyzed high_ indicating contamina- tion by the presence of other metallic ions. It is possible that such metallic ions could be eliminated by extracting the first dithizone solution with an aqueous ammonium thiocyanate solution (specific for silver)_ followed by destruction of the thiocyanate with perman- ganate. The resulting water solution containing only silver could then be extracted with fresh dithizone using the normal analytical procedure. Complete details for this modified procedure were not worked out, but the method described above would preserve the rapidity of analysis while extending the colormetric techniques to contaminated solutions. POTENTIOMETRIC MEASUREMENTS Attempts were made to set up an analytical procedure for silver ions in these low concentrations (50 to IO0 ppb) using a sulfide electrode (Orion Research_ Inc._ Cambridge_ Massachusetts) reported to be useful for the detec- tion of silver-ion concentrations down to IO ppb. Measurements agalnst a standard calomel electrode_ however_ indicated that the small shifts in potential difference encountered with concentrations below the parts per million level could not be measured accurately without exerting extreme care in control of pH_ temperature_ and aeration. Such techniques would not be practical for average analytical work. ATOMIC ADSORPTION Atomic adsorption was used to determine the silver ion concentration in bladder water effluent from the waste water tank. Silver adsorbed on the polyisoprene bladder was also analyzed by this technique. These analyses were performed by an independent analytical laboratory (Truesdai] Laboratories_ Inc._ Los Angeles). Results of such analyses are subsequently reported in Tables 4-5 and 4-6. These analyses are believed to be accurate. A control sample (standard silver nitrate solution) containing I00 ppb of silver_ sent for analysis at the same time_ was correctly analyzed. _ _ AIRESEARCH MANUFACTURING DIVISIONLas Angeles kalffnrn a 67-2158 Page 2-6
  • 17. P I SECTION 3 ENGINEERING AND DESIGN BASIC DESIGN CONSIDERATIONS System Requirements The potable water in the Apollo spacecraft is obtained from the fuel cell. The water flow rate is dependent on vehicle power requirements_ but essentially averages 7 cc per min. This water can be considered distilled but saturated with hydrogen. The waste water consists of excess potable water and condensate from the suit heat exchangers. The condensate flow rate averages between 2 and 4 cc per min and varies with work load. Desired silver-ion concentrations are 50 to I00 ppb. These levels ensure that ingestion of silver will not be injurious to human health (Reference 5). Previous tests have indicated such low concentrations are effective as bacteri- cides. However_ health standards are based on a minimum 25-year periodj so that it is safe to assume that higher concentrations up to 200 ppb would not be injurious for short intervals and could be utilized for more complete sterilization IReference 6). Electrode Reactions When the electrolytic silver-ion generator operates in a flowing water stream_ the silver ions are removed before deposition can occur at the cathode. The electrode reactions can be written as + Anode Ag - Ag + e Cathode H20 + e _ 0.5H2 + OH- Current requirements are low (15 _a or less)_ so that the internal.resistance of the cell is not excessive_ although distilled water is relatively noncon- ductive. Furthermore_ the amount of hydrogen produced is negligible_ so that the cathodic overvoltage is limited. The concentration of ionic silver (SO to I00 ppb) is within the solubility of silver oxide so that little or no precipitation occurs. Silver is more noble than other metals_ excluding gold and metals of the platinum series. An anode of high purity is therefore necessary to prevent introducing other metallic ions into the potable water stream. In the absence of an imposed potential_ silver is cathodic to most other metals. If the cathode were other than silver or a more noble metal_ a bucking potential would exist between the silver anode and the cathode. Such bucking potentials can be eliminated by using a silver cathode. Since no metal is being removed_ a composite cathode 3 in which aluminum is plated with silverj has been found effective for weight and cost reduction. When silver is used as a cathode 3 the internal resistance is reduced_ a more uniform __l AIRESEARCH MANUFACTURING DIVISIONlos A_ge_e_ Cahto_ma 67-2158 Page 3-1
  • 18. current density results_ the plating of unwanted silver under static conditions is facilitated_ and stable current levels can be maintained. Amperage Requirements If no losses occur by cathodic deposition or other means within the cell 3 the concentration in the effluent is a function of the silver ion generation rate and the water flow rate, and the three are interrelated by the equation G C -- p F where C = Concentration (_g/liter = ppb) G = Generation rate (_9/min] F : Water flow rate (liters/min) From Faraday's Law_ tile generation rate can be expressed as a function of current- G = 0.067 i_ where i = current (l_a). The current and_ consequently_ the generation rate, are constant 3 so the concentration in the effluent varies inversely with the flow rate. At an average flow of IO cc per min and a desired concentration of IO0 ppb_ the required amperage can be readily calculated as I&.9 l_a. Theoretical concen- tration as a function of flow rate and current is shown in Figure 3-I. Under no-flow or static conditions_ a limiting concentration will be reached in the cell where the deposition (or plating) rate equals the generating rate,so that the total quantity of silver in the water reaches an equilibrium level. Uniform concentrations and effective sterilization cannot be achieved in locations where rapid water surges exist if the surge volume exceeds the cell volume and no mixing or diffusion occurs downstream. Actual amperage requirements will be greater than theoretical_ to overcome losses of silver ions within the cell by deposition on the cathode 'and within the system downstream of the cells by reduction or adsorption. The rate of anodic loss of silver as a function of operating current is shown in Figure 3-2. The volumetric loss of silver from the anode during extended missions can be calculated from the density (I0.5 9m per cc). For missions to 90 days_ and at current levels up to 20 _a_ the dimensional changes for anodes (I/2-in. diameter by I/2 in. long) are negligible_ representing about 0.5 percent of the original diameter. Internal Cell Construction An electrolytic silver ion generator must be designed so as to ensure an even flow of water past the anode to remove all ionic silver. Any "dead" spots in the cell will accumulate silver ions. The higher concentration in this region will increase the solution conductivity and direct the current and ionic flow away from the main water stream. This condition becomes progressively worse as the silver-ion concentration increases. Operating efficiency is then reduced by preferred cathodic deposition. _] AIRESEARCH MANUFACTURING DIVISION(o_,AngelesCat,lotn_a 67-2158 Page 3-2
  • 19. m r_ =- 0 h- < t_ Z LLJ Z C3 0 400 58( 56( 540 520 500 280 260 240 220 ZOO 180 160 140 120 I00 80 60 i / / / / I// 2 / 4 / / / 6 / / 16 /t / / z / / z "I'-- / / / // ., 0 ._1 / / / / ,./ / / " ' ,// // 0 0 2 4 6 8 I0 12 O. 067 z, C- F Figure 5-1. 14 16 18 20 22 24 26 28 A-211458 s = OPERATING CURRENT_ _a Theoretical Silver-Ion Concentration as a Function of Current and Flow Rate _] AIRESEARCH MANUFACTURING DIVISION1o% A_eles iahfnrnla 67-2158 Page 5-5
  • 20. 5,0 >- (-,'3 0 -J i,I 0 2.8 2.6 2.4 2.'/ RATE OF ANODE CONSUMPTION AS A FUNCTION OF OPERATING CURRENT 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 / / / / / / / ANODIC LOSS_ MG/DAY / / / 2 4 6 8 OPERATING CURRENT_ #a / / = 0.0965 / A-28457 Figure 3-2. Rate of Anodic Consumption as a Function of Operating Current I" -_"Xl-t(:'_"i'm'EV")t AIRESEARCH MANUFACTURING DIVISION 67-2158 Page 5-4
  • 21. A similar situation can exist if concentration gradients form in the flowing water. Water flow is considered to be laminar so that no turbulence is available to dispense a gradient once formed. If the residence time in the cell is excessive_ such gradients can result from changes in conductivity of water flowing past the anode_ imperfections in the anode or cathode_ or from improper positioning of the anode in the true center of the cathode. Since current densities are very smaIl_ the current seeks the path of least resistance and follows the concentration gradient down the anode until the water leaves the cell. This nonuniform current density heightens losses by cathodic deposition and causes the concentration in the effluent to fluctuate. The silver-ion concentration is greatest at the cell exit_ and maximum losses due to cathodic plating can be expected in this region. Cathodic p)a_ing at the exit is minimized by keeping the cathode length less than the anode length and by drawing the water away from the cathode toward the anode as it leaves the cell. Overall cell losses are reduced by minimizing the cathodic area and the cell residence time. CONTROL CIRCUIT Basic Circuit Minor changes in silver-ion concentration are not detrimental and occur with fluctuations in water flow. Minor amperage variations will normally occur with changes in water conductivity within the cell. The maximum variation in current that can occur at any given current level can be limited by determining the internal cell resistance at the desired current level_ using water of both high and low conductivity_ and making the variation in resistance a fixed fraction of the overall resistance. This determines the required external resistance from which the battery voltage can be calculated. Fluctuations in output concentrations_ which can occur with changes in flow rate or pH_ are then fixed. The required circuitry reduces to a fixed control resistance of such magnitude that changes in internal resistance represent only a small fraction of the overall resistance_ with a battery of sufficient voltage to produce the required current. If the anode and cathode are shorted internally by a stray metallic path_ the cell becomes inoperative. The amperage then rises to the maximum value fixed by the control resistance and battery voltage. Interactions of Dissimilar Metals Aluminum and silver form an electrolytic cell in which the silver becomes the positive electrode (anode). Both silver electrodes_ i.e._ anode and cathode_ must be electrically isolated from the aluminum system which is considered to be the ground 3 to prevent undesirable electrical currents_ cor- rosion_ and plating out of silver ions. The use of silver-plated aluminum for a cathode is not detrimental if the silver coating is sufficiently thick so that no aluminum is exposed to the water (electrolyte). I_I AIRESEARCHMANUFACTURINGDIVISIONtos Angeles Cal,fnrn a 67-2158 Page 5-5
  • 22. To avoid complete electrical isolation of the cell; the silver anode is grounded through a high resistance (22 megohm).The current which would normally flow from the silver anode to the aluminum ground is then effectively nulled by current flowing from the battery to the anode. Corrosion of the aluminum portions of the cell is inhibited_ but the aluminum is maintained slightly anodic and tends to repel deposition or reduction of the ionic silver produced at the anode. By placing another resistor ( 22 meqohm) in parallel with ammeter correc- tions and/or a switch, a trickle current (about 0. I _a) always flows between the anode and cathode and the condition of zero current flow between anode and ground is maintained even if the cell is essentially in an of._f.fstatus. The cathode is completely insulated to avoid any contact with the ground. Cell design minimizes any interaction between the aluminum ground and the silver cathode. Battery Requi rements A regulated small current drain is required for extended periods up to six months. This dictates the use of a battery with a very stable voltage output. Mercury batteries (Malloy Duracell_ 4.2 v_ IO00 mAH) were used during laboratory testing. Flight units were equipped with a more stable silver oxide battery (Union Carbide_ Eveready No. 301_ I00 mAH_ 4.5 vl. These batteries_ rated at IO0 mAH_ will have a service life of more than one year under a continuous current drain of I0 I_a. Final Circuit A diagram for the overall circuitry is shown in Figure 3-3. With the exception that a variable resistor (0 to I megohm) was used to control amperage during developmental testing I this circuit was employed throughout for per- formance evaluation_ and is the one used in the final flight type units. After initial performance data were obtained (see Cell Performance)_ and possible variations in internal cell resistance were evaluated, a battery potential of 4.2 v (three 1.4-v Mercury batteries) was judged sufficient for practical purposes. For the flight units_4.5 v (three 1.5-v silver oxide batteries) were used. At current levels of IO i_a3 the amperage would vary between IO and 12 I_a so that variations in current due to conductivity changes would not exceed 20 percent. The final control resistors were selected on the basis of nominal flow rates of 3 cc per min for the condensate and 7 cc per min for the fuel cell water. This gives values of I megohm and 390 K ohms_ respectively. ELECTROLYTIC CELL DESIGN Electrode Construction Cathodes_ fabricated from aluminum_ were silver-plated to a depth of O.OOI in. In general_ electrical isolation and attachment of leads did not present any problem. _ AIRESEARCHMANUFACTURINGDIVISIONLOS Angeles Cah_,_n,a 67-2158 Page 5-6
  • 23. 22 MEG AMMETER AND SWITCH TERMINALS ( I CONTROL t SILVER-ALUMINUMINTERACTION I CURRENT WATER ANODE CATHODE (SILVER) BATTERYCURRENT m GROUND (ALUMINUM) (ELECTROLYTE) A-Z06_ Figure 3-3. Circuit for Control of Current in Electrolytic Silver- Ion Generator AtRESEARCH MANUFACTURING DIVISION Los Angeles Cahforma 67-2158 Page 3-7
  • 24. Anodes were fashioned from high-purity silver (99.999 percent or better 3 Electronic Space Products Inc. 3 Los Angeles _,mounted in teflon supports designed both to center the anode and to provide the required water distribution. Wire connections to the anode_ which are also within the water systemj were similarly fabricated from si Iver. Such connections were positioned upstream of the cathode so as to avoid any current flow between the thin electrical leads and the cathode_ which would result in deterioration of the leads and eventual cell failure. For test cells_ a jeweler's grade of silver wire was used and the connection to the anode was made by melting the wire to the anode. The wire was insulated with teflon tubing. For flight cells_a pure (99.999 per- cent) silver wire was used and the connection was made by crimping the wire to the anode. No insulation was used except where the wire passed through the container walls. Prototype Cell Design Three different test cell designs were evaluatedj the cells differing mainly in geometric configurations and volumetric capacity. Preliminary design drawings and photographs for each of the three different ceil designs can be seen in Figures 3-4 and 3-5. Design data are compared in Table 3-I. The first test cell_ designated the polycarbonate celIj was fabricated with a polycarbonate body and used to obtain preliminary performance data. It was later used with modifications in a continuous flow system. This cell did not include all of the design criteria previously set forth_ which were observed in later models. The second group of test cells_ designated as Prototype Cells A and Bj were built with aluminum bodies. The interior geometry_ later used for fabrica- tion of flight ceIls_ differed from the polycarbonate cell in that a shorter anode of larger diameter was employed. The anodic area was virtually unchanged_ but the cathodic area_ cell volume_ and_ consequently_ the residence time were reduced. Cell performance and efficiency should be enhanced_ but actual dif- ferences were difficult to detect. The improved design eliminated dead spots in the cell_ particularly at the entrance and the exit 3 and providecl for removal of water by drawing it away from the cathode. A third test cell_ designated as Prototype Cell 1503 was designed with an internal volume of 150 ml. The large cell volume provided the surge capacity and residence time necessary to obtain the requisite silver-ion concentration before discharge into the hold tank 3 when located downstream of the cyclic accumulators. This cell proved useful for obtaining deposition rate data. However_ silver-ion concentrations within the cell and exit concentrations were found to fluctuate considerably. Variations in effluent concentration could be traced to concentration gradients formed in the cell due to the large cell volume and small current density. Such gradients have been previously discussed. Redesign of the anode to provide several anodes in parallel was indicated_ but was not undertaken. If a water sterilization unit were positioned at the inlet to the cyclic accumulator_ where a more uniform water flow prevailed_ _ AIRESEARCH MANUFACTURING DIVISIONI 0s Angeles Cahforma 67-2158 Page 5-8
  • 25. POLYCARBONATE BLOCKS_ WATER FLOW ASSEMBLY WITH I ALUMINUMOR I II I ,LAssTUBE ' '_' F_pEvcV;E_;_BLE/TE DEFO°NO,N A(RTV SEALANT_ _ _I-_;VIMI;_? ;;BAE' CS;:_;R(_PLATEO) ,LOW MO%,E,;_:Eo IG,....... INITIAL DESIGN ANODE CATHODE (7-_-O_) POLYCARBONATE SILVER-ION CELL (ASSEMBLY DRAWING) Sl LI CONE RUBBER (1NSULATI ON) ALUMINUM CATHODE LEAD (SCREW)/ _ANODE LEAD (INSULATED) °°-W------_.. / _f?BS?:_ONNECTION I/4 IN. AN _ WATER FLOW FITTING _ F'_'J_ _ _Z_ _'_j NS_EuL:_I_DW_ToLTS / _v -- EXTERNAL SILICONE RUBBER ATEN_EON SUP P OR T YC/ATHODE- S ILVE R PLATED INSULATION A-le_sz PROTOTYPE SILVER ION CELL Aj B (ASSEMBLY DRAWING) WATER EXIT ALUMINUM END PLATE CATHODE CONNECTION (SCREW) 7 [_ /.- SIL lEONE RUBBER l , _,f// GASKETS USED IN THIS AREA II|............... ;c.'.Y.W.Y5............ ___J ITEFLOy CATHODE (ALUMINUM TUBE-SILVER PLATE) PROTOTYPE SILVER-ION CELL 150 (ASSEMBLY DRAWING) _- ANODE LEAD (INSULATED) 22-- -- ,_ WATER INLET A-ZUW,3_ Figure 3-4. Assembly Drawings for Laboratory Silver-Ion Generators Used to Obtain Development Data AIRESEARCH MANUFACTURING DIVISION los Angeles Cal,lornla 67-2158 Page 3-9
  • 26. /-°'::°-% ltt _'-......- _J., /,,J,,m,ji,m,i,,ii_l,m,l_,l,,,,_l,,l,,l,,i,_p,l,_,l,,i,k PROTOTYPE CELL A OR B POLYCARBONATE CELL PROTOTYPE CELL 150 F-7889 Figure 3-5. Prototype Silver-Ion Generators AIRESEARCHMANUFACTURINGDIVISION Los Ans_les California 67- 2158 Page 5- I 0
  • 27. TABLE 3-I DESIGN DATA FOR SILVER-ION GENERATORS Dimension Anode Diameter Length Effective area Cathode Diameter Length Effective area Electrode spacing Volume between electrodes Overall (cm) (cm) Cm (cm) (cm) (Cm 2 (cm) cm Polyca rbonate Cell O. 70 2.54 5.59 I .65 5.18 16.5 0.475 5.57 Prototype Ce] I_ A_B 1.20 I .27 4.79 I. 905 I .27 7.60 O. 555 2.18 _ volume assumed 3 cc due to other design factors. P rototype Cell 150 I . 20 9.55 56.0 4.75 8.26 I .25 I. 775 150 AIRESEARCH MANUFACTURING DIVISION tos AnReles Calrfornia 67-2158 Page 3- I I
  • 28. the original prototype unit (3-cc volume) would function more effectively. This arrangement was the one chosen. It was further advantageous in that a single cell design could be used for both the potable water system and the waste water system. Design and Construction of Anode Supports Anode support design is crucial for fabrication of a cell that will operate unattended for periods longer than six months at high efficiencies. Water flow paths through the ceII_ the position (centering) of the anode with respect to cathode_ and the possible formation of silver crystals within the cell are influenced by the design and materials of construction of supports. In the polycarbonate cell 3 shorting of the anode and cathode was found after about three months of operation. This was caused by a metallic silver sludge which had accumulated in a "dead" area at the exit. In the prototype cells_ such sludge at the exit was not noted_ but some small silver crystals were found on the teflon support at the entrance_ where maximum channeling of the water flow could be expected. Such crystal growth could not readily short the cell; but does point out the necessity for initial water distribution prior to flow across the anode. Teflon is utilized for a support material_ since it is nonconductive and can be readily machined. However_ in the machining of the teflon_ metallic particles_ particularly aluminum_ must not be permitted to become embedded in the teflon. Small_ electrically isolated_ virgin metal particles can serve as secondary cathodic sites_ act as a nucleus for silver deposition_ and support the eventual growth of large single crystals of silvebwhich reduces operating efficiency. Design of Flight-Rated Water Sterilization Units Three water sterilization units (Figures 3-6 through 3-I0_ Outline Drawing 1334481 were constructed using essentially the same internal design as that used for Prototype Cells A and B. The control circuit was the same as that noted previously (see Final Circuit). The battery (Union Carbidej Eveready_ No. 301) and the three required resistors (I/4 w ±5 percent) were incorporated into a receptacle on the unit. The battery connection and circuit board will be potted. Terminals_ in series with the current flow_ provide for on-off functions or for measuring the current. These terminals are normally shorted with the shorting plug provided when the cell is operating. Each cell is built as an integral unit; which simplifies installation or replacement. Values for the control resistors were selected to yield 85 to 90 ppb of silver at the cell exit at water flows of either 7 cc per min [potable water system) or 3 cc per min (waste water system). Some differences in current can be expected between various units having the same value for the control resistoo due to the tolerance of the resistor (±5 percent)jbut these are not critical. These flight units will undergo additional testing in the complete AAP system. I_ AIRESEARCH MANUFACTURING DIVISION Los An_ebes Cahfom,a 67-2158 Page 5-12
  • 29. 59804-2 Figure 3-6. Flight-Rated Water Sterilization Ceil AIRESEARCHMANUFACTURINGDIVISION Las Angeles Cahfarma 67-2158 Page 3-13
  • 30. ANODE LEAD RES CATHODE LEAD BATTERY F-7887 Figure 3-7. Power Supply System s Flight-Rated Water Sterilization Cell AIRESEARCH MANUFACTURING DIVISION Los Angeles C_hlom,a 67-2158 Page 3-14
  • 31. PLUG STORS BATT ERY CATHODE WATER INLET x ._!,_J" CATHODE INSULATION _ANODE WATER DISTRIBUTION _ ANODE SUPPORT F-7888 Figure 3-8. Exploded View_ Flight-Rated Water Sterilization Cell I_1 AIRESEARCH MANUFACTURING DIVISIONl_ Angeles CJhlornla 67-2158 Page 3-15
  • 32. 1 0.0 i ---q 'L a i k 'I i _0 O.- z- "L 0 0 _ I _U _n 4_ L_ 67-215B page 3"_6 _p,NU_AC'_U ING D_VIS_ON
  • 33. SECTION PERFORMANCE CHARACTERISTICS CELL PERFORMANCE Internal Cell Resistance The internal resistance of each of the three types of ceils (polycarbonate_ Prototype A and B, and Prototype 150) was obtained at different current levels by measuring the external resistance required to establish the current using a battery of known voltage (_.27 v) and a flow rate of distilled water (15 cc per minl sufficiently high to prevent a change in water conductivity in the cell during the measurements. Resistance was determined with a decade resis- tance box (General Radio Co._ Concord_ Massachusetts_ Type I_32-B_. The original polycarbonate cell was also tested with tap water Iassumed to be maximum conductivity) to observe the current variation with change in conduc- tivity of the water. Data are shown in Figures _-I and _-2. These curves directly establish the external control resistance required to obtain the desired current levels in flight units if the power supply is of similar voltage. Output Efficiencies Samples of effluent were obtained at constant flow rates during measured time intervals and analyzed for total silver. Analyses were made by colorimetric techniques using dithizone as a complexing agent for silver (see Analytical Methods). The ratio of weight of si Iver so measured to theoretical weight as established by Faraday's law constituted the cell efficiency. The concentration_ which is independent of the time interval 3 was calcu- lated from the ratio of total silver to measured sample volume. W C - V C = concentration (ppb = pg/liter) W = Weight of silver I_g) V = Volume of effluent (liter) For flow systems_ either intermittent or continuous_ the theoretical output can be established from the average flow and current by the equation given previously G C = F and compared with concentration obtained by analysis. Within the limits of experimental error when using distilled water_ cell output efficiencies were usually 90 percent or better of theoretical except at very low flow rates (2 cc per min or less). A number of different solutions _ AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahlo_n,a 67-2158 Pa ge z__ I
  • 34. N .If z o w z L_J I J 17 e_ ClN3_N3 o I _oo 0 0 0 oo O4 g o w g z l-- x g g g g 0"- U r- o_ "S C 0 C L. X LI..I 0 C 0 °_ U C r_ ffl m E I IlJ °I _] AIRESEARCH MANUFACTURING DIVISION Los Angeles Cah!ri,ma 67- 2 158 Page 4-2
  • 35. o_ N t q_ o 0 J I _J ,..,.. l..ul I'-- ,< I-- oO _D -,,.1" c_ 0 oo _D ",,1" _ 0 I-- ._1 _.1 e"_ rJ.N:I_ll:IrID I'-- I"-4 oo O_ oo cO g g oo g c_ oo 0 -i- 0 v" 0 Z la.l n,- ...I Z ,-,,.. LJJ l'-- X L_ (P .IJ 0 .IJ "> °_ "0 C 0 ¢- °_ c °-- C 0 °_ 4-1 °_ ! I- °_ AtRESEARCH MANUFACTURING DIVISION Los AnL_ele$Cahfc*rn,a 67-2158 Page 4-5
  • 36. were tested !recognizing the limitations of the analytical procedure) including distilled water_ sweat condensate_ fuel cell water_ hydrogenated wateoand a sodium carbonate solution [pH = 9.0)_ representative of a high pH. Typical values are tabulated in Table 4-I. Variations in efficiency were observedj but are possibly due to analytical error (see Analysesl. The short residence time in the small prototype cells precluded determina- tion of any minor fluctuations in concentration that could be present in the effluent. The sample required for analysis represented essentially an average concentration. Gross variations in concentration were found under flow condi- tions with the large cell (Prototype Cell I50)j since residence times on the order of 15 min or longer occurred3and sample size could be less than the internal cell volume. Such variations are shown in Figure 4-3. These fluctua- tions in output concentration indicate that the current density in the cell was not diffuse but localized in regions of high silver concentration. These regions then moved through the cell under the low flow conditions_ becoming more concentrated before eventually being discharged at the exit. When the cell was vibrated_ more uniform values for the effluent concentration were obtained3which approached predicted values (see cathodic deposition rates). Major losses within the silver ion cells could be attributed to plating on the cathode Imore prevalent at lower flow rate)_ adsorption at the aluminum outlet_ and possibly deposition of insoluble silver oxide at the anode. Although the silver ion concentrations are within the solubility limits of silver oxide (20.5 ppm) and silver chloride II.13 ppm) (Reference 2)j so that precipitation should not occur_ the electrode potential can apparently cause deposition of such compounds on the anode due to the higher mobility of the hydroxide and chloride ion which_ if present_ preferentially carry the current. Oxides were theorized to have formed by the dull appearance of the anode after us_although pH changes to 9.0 or better did not appear to have an appreciable affect on output efficiency. The presence of dissolved and gaseous hydrogen in the water had no effect on the generation of ionized silver in the tests performed. Theo- retically the ionization of hydrogen at the anode would proceed at a lower potential than silve_ but apparently the electrode overvoltage on smooth silver is sufficiently high to prevent loss in output efficiency by this means. Efficiencies of Flight-Rated Water Sterilization Cells Output concentrations of a flight prototype unit and three flight units were evaluated at different flow rates. These data are tabulated in Table 4-2 and shown graphically in Figures 4-4 and 4-5. Initial tests on the flight prototype unit were made at two different current levels by using an external resistance to augment the internal control resistance of the cell. The battery potential in this unit was determined to be 4.72 v. Tests on the three flight type units were made only at the current level as determined by the internal control resistances. When an ammeter was utilized in place of the shorting plug a theoretical concentration could be established _ AIRESEARCHMANUFACTURINGDIVISIONLOS Anl_e'le% Cahfo_n,a 67-2158 Page 4-4
  • 37. TABLE 4-1 TYPICAL EFFICIENCIES D*I_ Skl,er-I<,,, C,II $olutloM 7-ZI-_ mnl_cmrbonate D_stllled _ler ,,54 7-21.6 1 Polvc*rDon*te 11istillmd _ter 6._0 7-22-6 P_lvcerbon;te Dlstlllld _eter 1.72 7-?_-6 Polycorbo_ate Distilled _ter I,_ 7-Z5-6 Polycerbo_te Distilled _ter tO.] _-25-6 Polycarbonete Dlslll_ed _tmr I0.$ 7-25-6 Po)vclrbr,note Distilled weter 15.7 7-;_-6 Polyclrbonate 11_stilled wetlr 16.1 ;-26-6 Poly_orbonete Distilled _ter 16.11 7-_6-_ Po_ycarbonete Distfllmd _eter 16,5 0-_-66 Prototyp_ A Dbstllled _ter 16.05 11-_-66 Prototype A Distilled water 13.0 I-_-_ Prototype A Distilled _t0r 13.? D-_-O0 Prototype A Olstl Illd _te_ 9.1 11-_-66 Prototype A Distilled _tor 9._ S-_-_ Preset ype A O,$tllled _,_ter 9,1 S-5-6_ Prototype A O_stllled _ter 4.S 8-5-66 Prototype A O;stllled _llter _,O _-_-66 PrototyPe A Distilled _tor &. 75 |-5-66 Prototype A Distilled _tmr 6.67 S-5-66 Prototype A Distilled _eter 9.7_ D-5-66 P_ototype A Distilled w_ter 9.7] S-5-_ Prototype A Distilled _eter 973 S-5-66 Prototype A Distilled _ltor I_,0 S-5-66 Prototype A Distilled _tmr q4B 6-5-66 Protot_e A Distilled _eter t_.7 sIs-66 Prototype A Distilled _ter IO,O S-g-66 Prototype A Distilled =_lter iO.O 11o|-66 Prototypm A Distilled water I0.0 0-1S-6 Pr_totyp_ A 11_stllled _eter _7 O-lS-6 Prototype A Distilled _lter 9,6 S.lq-6 Prototype A Olstliled _Bter 51 9-Z_-6 Prototype A 11istl_led _ter 11,5 I-]0-_ Prototype A 11istilled walter 2.06 I-]_-6 Protot_e A Distilled water 2.01 2-2-67 Prototype A 11istIlled _ter 2.96 2-_-67 Prototy_ A Distilled _ter 2,06 2-2-67 Prototype _ 01stilled _lter 2._6 2-2-61 Prototype A 01stilled we ter 2.63 I-b-b7 Prototype A _l_CO_-pH = g,? 9,6 l-6-67 Prototype A Ne_CO_-pH : 9.7 q._ I-6-_7 Prototype A Distilled _lter 6.67 1-6-6T Prototype A 111st I I lad _lter 4.60 1-6-67 Prototype A S_et conden_ete 2,6 1-6-67 prototype A $_,_t condenslte 6. Z I-6-_7 Prototype A Sweet condensate _.9 1-6-67 Prototype A S_,eet condefllete 7. I 7 1o9-67 Prototype A Fuel cml) weter e 9,9 ANALYSES OF UNDER rlo_ mete, cu_m.t. 15 35 i5.30 15.55 15,55 15.60 15.55 15.70 15.10 15,05 15.05 52 5.25 5, 25 5.25 5,25 5. _'5 5.25 $.30 IO,O I0,1 10.O5 10.05 10.05 I0,00 I0,0 ¢ Om 0 16.2 16.Z _6.2 9._ 9.65 SO, i 12.5 6.2 6.2 66 6.6 6.6 20.0 20,0 16.I 16.8 20. 20,0 20.0 10.2 9.9 SILVER-ION GENERATOR VARIOUS CONDITIONS Cell I fflcioncy, Percent 91.2 I;6.9 7e.S 79,9 I01.0 99.1 t03,6 9|.6 91.6 I1,1 lO?.O IIi.O _16,0 IZO.O 105.0 125.0 104.0 O00,O ll_.O I I0,0 I07.0 100.0 99.0 It|.0 116.0 105.0 119.0 102.0 125.0 g1.0 91.0 97,0 99.0 110.0-- 12.O 94 ,O Q6.0 IO5.0 91.0 97,0 11.0 103.0 61.0 !nI,o 96.0 DI.O 92.0 g3,0 II_ rks !Cell IS fresh--excllsStve _lllver being Obtelned No eppreclmble chlmge eftem slverll months of : USe In testin 9 coil throughput efflclencles, Nigh currants used to Omsure presence of sufficient sliver for e_llysls. Tests _nd solutions were limited. 2 -6 -67 2 -6 -D 7 2-7-67 ;?-0-67 Prototype A Sledder _ter ee (Initial inelyll! indicated 2_ pt_b " Anolyses belo_ not corrected) Prototype A Slidder _tsr 10.5 10.15 I7,0 These enelysos subject to cm_sldorlble error due to Prototype A Dledder _tir I0._ 10.15 911,0 thlurem but Indlc0te c_ll output In the probe•co Prototype A Sledder _ter I0.2 10,1 105,0 of bladder _,_ter Tests o_ hydrogenated _ter _de under static conditions. Silver enDUe (12 m rod) and tithed• (7 w rod) Imrsed in beaker co•Seining • gitete_ distilled I ter. Test _s bubbled throu_ dispersion tube. COml_retlve tests Nde with nit ro_n end the absence of any _s flow. Results reported in sequence obtel_d, lnltlel inolyses Indlceted tree Io_Ic sliver on i_rsed el_trodes, 6-11-67 Velar only - not egltet_d 6-tS-67 Ueter only - eDit•ted 6-111-67 Veter only . eglt_ted &.i|-67 Hydrogenated water - _gitnted 6-10-67 flydrog_ted_lter - agltntod 4-10-67 Nitro9e_ted _ater - e11itmtod 6-iS-67 Nitro_tod weter - egit•ted 6-19-67 W•ter only - ogit_ted _-IQ-67 _ter only - egtt_ted (St=tic) 15 mlm test IO.O 115.0 15 mln test 10.0 109.0 15 mln test IO.O 90.0 I$ ml_ test lO.O 76,0 15 mln test I0.0 06,0 15 mln test 10.0 ' O&,O 15 mln test I0.0 15.0 15 mln test 10.0 73,0 15 mln test 10,0 73.0 No eppreclable effect noted on generetlon of sliver using different _ses or t ha ebsence of _s umder these toSS conditioms. Prop•big Io|ses by edsorptlon o_ gl•ss and/or cothodic deposition. eAllas-Chalmers Test No. S, =June 13, Iq)66. *e_eter colleEted from wmste water tlnk of silnulated Apollo system. F_] AIRESEARCH MANUFACTURING DIVISIONLOS Angeqe_ Cah_orma 67-2158 Page 4-5
  • 38. I J A3N3 I3IJ33 03 13 I(]3Hd_ ..Q r_ r, r-., O tl ee >- Z ,'Y' _: o c.) I-- ¢..) v ',0 ro I LI'*) :l_Z (_. O ¢'¢" Z Z ,:,":_ _: "'o _ogz o LLr_ 0 I Z ",0 0 '.0 I ?-., LLI TM I Z) t'_ Z 0 _f I I f y m,_ ! 0 O0 0 0 0 0 0 0 0 0 oo r,- wO u'_ _ _ c,J -- O O O O O O O (_, 00 r-,, ,O u_ o O ,,9 O o o o o O O N N o O J00 8 o O O O O ,() O '.,,1" O t_J O O Z w" I-- _J r- .I.J O 4- E O °-- f0 I- A_ r- L) L c 0 0 ._ c._ to i.. c c -1 t.g 4- c-- 4- 0 I c I- > (- ._ 0 cn .-- U o 0 Lr_ LLv I ",,1" OJ "s On °- lJ- 1N3 3_3 d rA3N3 13I'_33 AIRESEARCH MANUFACTURING DIVISION LosAngelesCahfolnla 67-2158 Page 4-6
  • 39. "0 ,0 h ! ! w Z m_ CD Z n.-" r._ I-4 O' mW r',, Z U.,li I'-- (.f), -i --0 ._1 -J ILl D O ,..u --I'-- o z r_ O. 0 Z .° (._ 0 (._) ILl 7- 'r'- fO I.-- ',0 O0 Z I • (D 0,,I O_ I -. I-- --t-- o. n-" I._ 0 ,n," Z ,_IZ .--I ZD 0 ,r",, LL. r_ (_) t._1 __1 LLJ (._ U_ 0 Z 0 H I-- r,," nn I'-- n," I'-- 6") / z ,,,,,,,0 w M-_ t-_ I-- Z r,_) L_ ILl F'- ._I l'-- X .=.I U.J 0 0 O 0 0 0 0 0 0 / / Z 0 I- n-' g Z _1 ..J L_ (.J ',0 ,0 ! ,0 ! 0,1 Z 0 I13 D Z / J / S J>- _ Z I-- w (_.) ca. _ n ill 0 o ;X 0 0 N 0 0 0 0 0 0 _ _ Z i.- ¢- 0 0 o _ _ 0 I'-- '_! (1) 0 _- o_ 0 m 0 z 0 0 0 t-- -- cd < _- 0 v) 00 ILl _-- 0 U_ _0 • Z 0 if3 -.-t o 0 0 0 0 0 0 0 0 Or, cO r_ _ u_ ,,,,I. J.N3D_I3d rAON31314"13 0 _1 AIRESEARCH MANUFACTURING DIVISIONLOSAngele_Cahfo?n,a 67- 2158 Page 4-7
  • 40. 0 0 0 0 0 0 0 0 0 -_' N 0 00 sO ,.1" oJ 0 oJ oJ r_l oJ ..... 1N39_3d CkDN3131333 0 0 N g 0 0 g O Z 0 0 0 0 0 0 0 0 c- 4-; Z c v P-4 I _. --7 °_ U- _ AIRESEARCH MANUFACTURING DIVISIONLosAngelesCahforma 67-2158 Page 4-8
  • 41. (/) _J ..J F-- <IZA OC Z O I-- (__ ,-_ _'_ U.I --J I, .._ I r," (j_ C) v I, 1,1 Z F'- N Z ,--4n" _-- ,,, n" U_ (3- r,- O ILl A V $.. E O I $- i --'- 0 r_ "0 c- Cl. 0 u') r_ I-- _rj r" tO 0 ¢} "-" o-- _ 4,J r" 0 0 , EE O I- O C_ r" ,_-.-. L I.. 2I_ IlJ e" Q.I U- U > U Z 0 E e- L. 0 I l I I I I I I I C_ ,,0 0 oO co u") 0 u'_ 0 M') -- -- c_J _c) re) (_, O, (_ ur} u') oJ oJ oJ u_ _ u_ 0 0 0 0 0 _r) u_ u') ',(3 '0 r,,- co co oC oC oC d oC oC oC oC r,,. r-. ,0 0 it-} 0 0 e,J -- od M'} -,,I- it) I I I I I -- (kl if) ..... I I I ,'," OC ,_" "" _ (_ _-) (o l.i. Li. m, l.m. _ OC _" I I I I I i, I, L.i- ..... I I I I I I I I I I I 4 "s > 4-_ C: 0 G) l=. _U :> (0 o- U o- ¢._.) 0 c'- 4=.¢ 0 G) 0 r- ot) •- 1.. r00 ),_ -- eJ > >.. O-- O +_ E r" >( O O I- v C_. C_. 0 _ m AIRESEARCH MANUFACTURING DIVISION LosA_eles C_hforn_a 67-2158 Page 4-9
  • 42. i C,J I ._J r_ u_ I=. E O _7 D.. .i-J L O C>.. L i :E O L r" C_ C J-_ 0 co i- L J 3: .-- _ O E _; h U > U v Z O_ E r0 C tO L tO ::I ".1" 4_ "O t- °_ t- O ¢.) I I i. O_ O_ O. E E E t_ tO > > > oI °i ._ O_ O_ O_ u3 u3 oO I I I I I I I I I I C_J 0 '0 U3 r'- r-- .... 0 0 0 0 0 0 .j j j .._ j .j .j .j .4 .j 0 0 -- 0,,I ..I" e_ e,J ,_ ,._ _ _ '4 ,4 ,,_ . . . I I n- ! I 0,.I I I I I I ! I I I IJ- If- i, Li- i, IJ.- l.i. i..i- Li- ' I I I I I I I I I I I I I I I I I C_J C,J C,J _I C'J C_J C'_ C_J @d .4=J i- U _J .-- "_ 0 "5 *°-- -- L m _ 0 _ m 11) c" U _ c" un _ °-- _ _ un 0 _ r- × 0 0 0 L E AIRESEARCH MANUFACTURING DIVISION LOS Angeles Cahforni_ 67-2158 Page 4- I0
  • 43. c,J _D E 0 ! L. 0 v (I. ri _,.__ •-- 0 _'--- 0"_ 4.a o- 0 • I- f_. c o II 0 _ LU _J o-- b- L. S -L=I "_ _ L _,...s °-- ! _.) C I0-- (_) • 0 E "-_ I.L U M_ U M') S d E I I I NN I I I ¢._ I I I _, {7, ".I" 0 ",,I" 0 0 W) -,I" 0 M") (_0 ,, • 0 0 u_ _'1 _ It) 0 0 0 C_ O_ oO oo oo cO _ u_ wC) oc oc oc ' d oc oc ' d oc d M') r'- _- 0 _ ,-,; ,_ _ _ _ ,_ .... Z I I I I I I I I I I i I I-- I I I I I I I I I I I I I_- ,Y' n," n" n,_ ,Y" ,Y' ,'.." n_ r." _ _ n." re') l,c) l.C) I¢_ I¢) _ I¢) _ l.c) h") I I I I I I I / I I I I I I I I I I I I I I I I % > C L U 0 > En E ,-- -(3 "_ 0J 4-1 73 O O E °-- _ I,- m • 0 _ m U 3 ¢- tO L m > °-- _ _,_ °-- 0 m L -- I1) 0-- 0 E _ oI r X @ 0 M e'_ 0 "_ _) L E _ m E-- _ AIRESEARCH MANUFACTURING DIVISIONLosAngelesCah(0_ma 67-2158 Page 4- I I
  • 44. °-- 0 c_I v od I i.u ,._I I-- c,,l u'} tO A m I{ '7 q. O7 r- io" L 0 0 A "_ ..C:: C" I I I _ I I I -- I I I • £0 U'} "Z J "-"0 _'--- 4=1 • I0 !_ m E II 0 0 0 o4 _ , 4 _ ,g , o: c_ -" , 0_ I-- l r,,.. _ _ , c; c; - , 4 _ _ , o,I o4 c_J O_ O_ O_ if) Lr) If) L L _L > :::0 .-- ,:I: C._ L. 0 0 0 0 0 0 _ c_ 0 0 0 0 _ c; c; c; ' c; d c; ' o. o. o. ...... d d d I m 0 E , o b_ u .,,I- r_- F_- 0 _ 0 0 0 ',0 -- _ 0 0 o o o _ -_ -_ _ _ _ _ _ ,d ,d ,d M _ ,2 _ ,Z .... d Z E 0 I I I I I I I I I I I I Z ............ I I | I I I I | I I ! I O. ;'_ r_, I_ I_. I_ r_, /_ i_ I_ P_ r_ i_ , , J, - _ - . . _ _ _ I I I I I I I I | I I I -1 % > 4_ I- t U tO L m o_ 7 °t- 4,J 2_ 0 ID U _ e-- m _ o_ _ _ m ";o 0 _ 0 0 ._ E .I::: X 0 0 L ¢7 (3 m _ E _ ell _ _j _ AIRESEARCH MANUFACTURING DIVISION Los An_el_s Cahforma 67-2158 Page _- 12
  • 45. "0 c r" 0 c_) I ",,1" ._/ c_ F-- L._ E _J II a_ r Q. +-J s- L. r" 0 c", ,- .4_ "..1" m 0", I I I fc) ('4 +ji I ,0 _I I.. Q s- _ D U E_ II 0,. 0 I 0 _0 ,4O 0 0 0 0"i o- t'-_ -- 0 I r_ .,.,1" 0 -- _ I • • • I U*) @, U") re) _ t" _.-._ 0 r0 Qj to z _ _ o-- L 0 0 u'_ _ u_ u'_ u_ u'_ re 0 E _'_ aJ LI_ U CO > U ",,1" '_ _ -,,1" CO CO _ _ CO 0O _0 oo C_l Z r-_ E ro I I I I I I I I I I I I i I I I i I i I I I I ! I I I I I I I I I I I % > s- s- "-s U t.. @ > t'- ,_ -i "0 •i_ 0 t*'- U m .-_'_ _ 0 m U _ f- r" 4-1 m _ m > m m 2t L 0 &l 0 _ e- X 0 0 0 IA3 "_ un 4-_ m AIRESEARCH MANUFACTURING DIVISIONlo, A_eles C311forn,a 67-2158 Page 4- 13
  • 46. z o I,.- <C p.. .=, (.J 230 220 ZlO 20O 190 180 170 160 150 140 120 I10 I00 90 8O 7O 6O 50 4O 50 20 CURRENT LEVELS: 9.5 - 9.8 _a 4.0 - 4.1 _a -- TESTED 1-31 TO 2-7-67 9 --THEORETICAL CURVES I0 0 0 4 b 8 I0 12 14 FLOW RATE., ML/MIN A-ZI4Sl Figure 4-4. Output Concentration as a Function of Flow Rate for Flight-Rated Silver-Ion Cell No.I (Flight Prototype Unitl AIRESEARCH MANUFACTURING DIVISION Los Angeles CallfOft_qa 67-2158 Page 4- 14
  • 47. Z3C 22C 2_0 200 190 180 170 160 150 J4o 130 _: 12C o II ¢_1 g to _" 90 -..1 N 80 70 60 50 40 30 20 I0 0 0 0 133448-I-I SERIAL NO. 37-RI (9.9 TO 9.5 l_a) /% 133448-I-I SERIAL NO. 37-R2 (10.2 TO 9.9 _al 0 133448-2-I SERIAL NO. 37-RI (4.3 TO 4.25 p.a) < TESTS WITH SHORTING PLUGS / TESTED 4-4 TO 4-7-67 T THEORETICAL CURVES 2 4 6 B I0 12 FLOW RATE, ML/MIN Figure 4-5. Output Three I0 ,,=, ac 14 A-2111& 52 Concentration as a Function of Flow Rate for FI ight-Rated Water Sterilization Cells AIRESEARCH MANUFACTURING DIVISION Lll_ An_e_eS ('allf+l_nd,_ 67-215E Page 4- 15
  • 48. from the known flow rate and amperage. However, the resistance of the ammeter [2.2 k ohm) reduced the current flow slightly. When only the shorting plug was used, the output concentration could be measured but a theoretical concen- tration could not be established, since no measurement of current was provided. Output concentrations in Table 4-2 reflect the use of both an ammeter and a shorting plug. Sample size was selected_ except as noted, to minimize analyt- ical error. These data are in good agreement with data obtained for the prototype ceils and indicate essentially 95 to IO0 percent output efficiency. Cathodic Deposition Rates In a well-constructed cell_ only silver ions can be produced at the anode, and the current is a measure of the weight rate of production. This silver must either be present in the effluent or redeposited on the cathode. Cathodic deposition rates can be obtained by analysis of the concentration of silver in the cell at various time intervals under no-flow (static) conditions. This deposition rate is a function of the instantaneous concentration and the generation rate, which can be considered constant. It was not practical to measure deposition rates with the original proto- type cells because of the small internal volume. Limiting concentrations are reached relatively rapidly_ the total weight of silver in the available sample precludes accurate analyses, and3since the overall water volume required for test purposes is more than double the true internal cell volume_ diffusion of silver introduces considerable error. Such rates were measured with the large cell (Prototype Cell 150) in which the overall volume of water analyzed did not differ appreciably from the true internal cell volume. The cell was operated under static conditions for various periods of time at different current levels, and the water in the cell was analyzed for total si Iver. Some changes in current were observed as the concentration increased_ but these changes were considered negligible for practical purposes. At high operating currents (30 to 40 I_a)_ it was necessary to break up concentration gradients and disperse the silver ions by vibrating the cell. Data obtained are plotted in Figure 4-6. These data were correlated by determining the constants in the equation dC I dt V [G - FC - C(a + bG)] which yields upon integration, C = F ÷ a +bGG [l - exp [- (F + av + bG)t] Nomenclature also is presented in Figure 4-6. I_] AIRESEARCHMANUFACTURINGDIVISIONLoc. Anep_es Calfforn,,_ 67-2158 Page 4-16
  • 49. 6 _I (IH91319 4V101 0 0 II II II II II I1 II II II "0 C C 0 C ,-- 0 _J .I o-- 4-J "I0 C _- 0 _J C_) (- I1/ t J_ _ o °-- 4.O ¢- 0 _ 0 m Q) ,d I °-- la_ ]_J AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahlom,a 67-2158 Page 4- 17
  • 50. The time constant V F+ a + bG is a function of the cell volume. Final equilibrium can be assumed to be established after five time constants. Note that in the absence of cathodic deposition the time constant reduces to the cell residence time. The concen- tration at equilibrium I_ = 51 is independent of the cell volume G C = eq F + a + bG In the above equations7 the constant a is not defined if the generation rate is zero or if the initial concentration is other than zero in the absence of an electric potential. The curves in Figure 4-6 represent the establishment of equilibrium at various current levels if the constants a and b are defined as a = 3.75 x I0 -_ liter/min b = 2.25 x I0 -_ liter/_g The curves so obtained fit the experimental data relatively closely being somewhat raised by the final equilibrium values. It is probable that the constants could be more precisely defined by reducing experimental error but this additional refinement is not considered necessary. Assuming variations in cell geometry have no appreciable influence_ the equations are applicable to the small (3-ml) silver-ion generators. The length of time required to establish equilibrium is directly proportional to the volume_but the final concentration is dependent only on the flow rate and generation rate. Attempts were made to verify predicted concentrations in the small cell under static conditions so that the validity of the constants for a different geometry could be established. Results (see Table 4-3) indicated either that diffusion into the surrounding (nongenerating) regions was sufficiently rapid to preclude accurate measurements or else that the constants are a function of the anode-to-cathode spacing. It is possible to estimatej however_ the total weight of silver which could accrue in the small celbassuming the water flow were shut down while the cell continued to generate silver ions. At I0 _a final concentration of 1267 ppb will be obtained. This is readily obtained from Figure 4-6 by dividing the equilibrium weight (190 _g) by the volume (0.150 liter) and noting that the final concentration is not a function of cell volume. If the cell volume were 3 ml2 representative of the small cellsj only 75 ml of water would be required to dilute this concentration to 50 ppb. Even if the final concentration or the volume of solution were three to five times this valuej _1 AIRESEARCH MANUFACTURING DIVISIONLOS AnReles Cahtorm_ 67-2158 Page 4-18
  • 51. I ILl .--I I-- Z 0 I-- ,.-,, Z 0 I'-- ILl Z ._1 ILl t..) Q.. F-- O O o_ _J ._J Z z i.-.4 oo O z O t--- F- z z O o Z O ._1 i-..4 co) t- O u O <_ 0j c-_ r_" I._ o_ E O L E r- O O _---. _..J re) r0 _ 0J c < 0 0 E c _ 0 E 0 °_ r- _ E tO rO C 0 r, I-- 0 t- O rO I.- .-- E C r_ 0 0 0 0 C_ r_ 0 0 0 0 r'_ -- _._ -- _.) c,,.J ....1- .<1" ,,0 _ .0 0 0 0 ,0 -- _C) I I 0 I _) -- O ! U E E > U t- I.. t_ °_ O C °-- _O O E O > °_ °_ 4-1 r0 O O °-- r0 ..O "10 4.J (13 ""-1 tO v __l AIRESEARCH MANUFACTURING DIVISIONLOS A_e)_'5 _,_lq_rn,J 67-2158 Page 4- 19
  • 52. the total weight of silver ions would still be insufficient to cause any health hazard on consumption. It is not necessary_ therefore_ to shut off the silver-ion generators during temporary no-flow conditions_ since downstream dilution will occur on start-up. It is also possible to calculate theoretical efficiencies at various flow rates and current levels from these equations. It is assumed that equilibrium is established in the cell at all times under flow conditions and that no concentration gradients exist. Such theoretical efficiencies are shown in Figure 4-7. Actual efficiencies are in good agreement with the theoretical predictions. For practical engineering purposes_the predicted values_ which represent the correlation of a large number of analyses_ can be considered more precise than scattered analyses obtained for individual cells operated at various currents and flow rates. SYSTEM PERFORMANCE System Losses I. Reduction in Aluminum Tubing When installed_ the water sterilization cells become part of an aluminum (I/4-in. OD) tubing system. The tubes are treated by an Alumigold process_ essentially a chromate treatment. Such tubing has a very high area-to-volume ratio (8.3 cm 2 per cm 3 for 0.030 wall) and losses by adsorption or by reduc- tion on aluminum surfaces in a few feet of tube length can become excessive unless proper precautions are observed. Losses through tubing of various lengths and treatment were examined using the experimental apparatus shown in Figures 4-8 and 4-9. Initial evaluation indicated that losses could exceed 90 percent within 30 ft of tubing length. The chromate treatment did not appear to enhance throughput efficiency. Such losses would severely limit the application of the water sterilization units and necessitate the precise location of the cell in the system. Furthermore_ the current level would have to be increased, to offset losses3and no control could be maintained on the silver ion concentration in the system. At low flow rates_ all the silver could be lost before it would be of any value as a bactericide. Various passivation methods for pretreatment of the tubes were examined. To be of any value_ a pretreatment procedure had to be applicable to the assembled system and not injurious to metals_ gaskets_ or polymeric materials in the system. Initially_ various weak oxidants such as nitric acidj phosphoric acid_ and sodium peroxide solutions were employedjbut appeared to have little effect. Inadvertently_ it was discovered that if the tubes were filled with water and then sealed offj the water soak provided an excellent method of passivation. Throughput efficiencies increased to 85 to 95 percent and silver-ion losses were negligible. The procedure appears equally applicable to aluminum tubes in an as-received condition or those treated with chromate solutions such as Iridite or Alumigold. I_ AIRESEARCH MANUFACTURING DIVISIONI os Ange)es Cahforn,_ 67-2158 Page 4-20
  • 53. 0 NIW/33 (3.L_'W_OlJ IN39_3d _ADN3IDI_33 7]39 AIRESEARCH MANUFACTURING DIVISION I (),,A_Re(e_ Cahfnrn,a 67-2158 Page 4-21
  • 54. REFILL AIR L _ VENT f- WATER FEED I ,_ (CONSTANT HEAD) / "_ TYGON " _ TUBING FLOW CONTROL VALVE _ _(BYPASS) TFST (ALUMINUM) INDICATES SAMPLE POINTS C = CONTROL I = CELL EFFICIENCY 2 = THROUGHPUT EFFICIENCY TYGON TUBING Z I SILVER l ION I C ELL I I lov ER FLOW TUBE IGRADUATED TUBE ( FLOW RATE ADJUSTMENT) 7 L_ I SAMPLE (OR) DRAIN A-Z$6_ Figure 4-B. Schematic of Test Apparatus for Determination of Cell and Throughput Efficiencies AIRESEARCH MANUFACTURING DIVISION LOS AnBeles_ Cahlorn_l 67-215B Page 4-22
  • 55. 59852-5 Figure 4-9. View of Test Apparatus Used to Evaluate Cell and Throughput Efficiencies Eli' J _l IRESEARCH MANUFACTURING DIVISIONLos Anse_es Cahforn+a 67-2158 Page z_-25
  • 56. If the system is filled with water and sealed off for four to seven days_ a pressure bui Idup will occur. This pressure rise occurs from the formation of hydrogen_ probably from the reaction of aluminum with water. Once this reaction has occurred_ the aluminum apparently loses the ability to reduce silver. In essence_ the active sites are oxidized. More than one treatment may be necessary before hydrogen is observed. Initial pressurization may be beneficial_ but has not as yet been thoroughly evaluated. Excessive oxidation of the aluminum surface (anodizing) could lead to adsorption of silver ions rather than reduction. Aluminum oxides are excel- lent adsorbents and very little area would be required for the small amounts of silver in solution. The effects of the above water treatment on anodized surfaces was not tested_ but preliminary tests indicated that such adsorption may take place. Additional investigations of the reactions involved were beyond the scope of this task and were not conducted. Throughput efficiencies for various tubes and treatment methods are given in Table 4-4. The increase in throughput efficiency by water treatment is shown in Figure 4-I0. It should be pointed out that the original tubing used in an as-received condition underwent passivation during initial evalua- tion of the performance characteristics of the Polycarbonate cell. The tubing underwent several days of testingj during which period_ although not sealedj it was left filled with stagnant water when not in use. The formation of bubbles in the water during these stagnant periods was noted3as was the grad- ual increase in throughput efficiency. The increased efficiencyj howeverj was thought to be due to other factors that were being evaluated at the time. 2. Adsorption on Polyisoprene Bladder (Water Tanks) The polyisoprene bladder contains sulfur compounds and was found to adsorb silver from solution in minute quantities. Analyses of the bladder material and water solutions in contact with the bladder were made by atomic adsorption techniques (see Table 4-5 and Analytical Methods and Procedures). Analyses of effluent from the waste water tank of the simulated Apollo system were similarly made after equilibrium had been obtained. Results of these analyses are sub- sequently reported (Table 4-6). Loss of silver within the Apollo water tanks by adsorption on the bladder will be a function of the rate at which such tanks are used and the stagnation periods between use. Effective sterilization was achieved during continuous testing I howeverj (see Bacteriological Tests) and such adsorption should not be detrimental. Continuous System Shortly after the first cells were fabricatedja continuous system was put on stream to obtain reliability data. (Figures 4-11 and 4-12.) Initiallyj Prototype Cell B was used to supply silver ions 3 but the modified polycarbonate cell was installed after two months. The effluent of the cell was fed through 4 ft of anodized aluminum tube after which it passed through a 50-ft coil of aluminum tube (Tube Coil A) before entering an aluminum hold tank (20-I volumej area-to-volume ratio = 0.19). At a flow rate of 7 cc per min_ the residence time in the hold tank was about 50 hr. A current of I0 _a was used for the first four monthsj but this was changed to 20 _a after initial evaluation of microbial contamination of the tank. (See Section 5.) __1 AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahlo_n,a 67-2158 Page 4-24
  • 57. TABLE 4-4 SILVER-ION THROUGHPUT EFFIC[ENClES FOR ALUHINUH TUBING SUBJECTED TO VAR[OUS TREATHENTS Cell M_lrriml C_Ps _ qna¢ ; nn TypP A HI _tL,r ,' 6061 plus ',,O52 B 5050 C 60_ I -o O 6061 -o E 6061-0 F-I 606 I-0 F-2 606 1-0 F-3 606 I-0 F-6 60(5 1-0 G 606 I-0 (1/I In. ,_la) H 606 I-O (UIId In llffv.a|lted tyItO_ between cyc| Ic accumulator and coil ]1 I Lenqth Trsted, ft 5O 5O 3O 30 16 30 7.5 7.5 7.5 7.5 10.3 7 Treatment mnd Re_erk_ As received (acetone rlnle) [ontinuo=_, Iystem (permInent Instellltlon) As received - Telted on continuous lylt_ [rldited - (Not rotated) Treated with AqNOs-tteemed-desorptlon noted |tripped and Inodl,ed Anodized and steamed Ste_d {2nd tl_) Pholphorlc Iced treltment (pH : 3.|) At received (acetone rln le ) Stignint water (let Inactive In syltem for 7 day,) Alumlgold (not rotated } Tested at midpoint o¢ coil Effluent of cmltlnuout lyttem (Input - 50 ppb) A|umlgO|d (nOt rotIted) Stlgnont _eter (copped off for 7 days - ga= noted) (Ulld |n simulated lyttem at connection bItWeen pump end Illver ion cell ) AlumlgoId (not rotated) - Nitric acid treitment (pH _,|) Al_lgo|d (rotated) - Not otherwiie triated (Ill L bol_) Itolnlnt water (tipped o(f for 5 dl¥1 - No ga*) Stagnant O.OIM Neego 4 (c=qP@ad off for Z days) Itil._t wirer (coIIped off for 4Z dlyl) Itripged - Not othorwlll treated Itatlmlflt wltor (copped off for b days - NO gol noted) NOt tilted - I/| In, tube Al_lgold (rotated) - Copped off for 6 dlyl - Ill noted (lnltlit ¢luih for I hr with dlmtllled _ltir) (and 9Ol build-u9 noted when tube retyped wtth itoinent _ter for additional 13 doyl) Tett Detej 66-67 T-IS tr, 7-Z6 1-23 to 2-2' I-I I-9 I-ll 9. I I-II 1-19 1-13 1-15 g-2 9-9 t-it 9-16 9-|5 IO-t 9-19 t-IO 10-3 10-6 9-1e 10-6 ... 9-16 NOT|: F|ow Rite, cc/mln 5 to 15 1 7 7 7 10 7 and I0 l0 I0 10 10 I0 I0 Y lO 10 10 I0 I0 I0 I0 I0 IO Avero|l Throughput Current, lfflclIncy_ _l percent l0 tO 15 15 -- iS I0 to I0 TO-15 I0 0 I0 0 10 >100 I0 Imd |0 _1 _ IS !0 I0 12 15 l= 90 lI It II II NOt Telted I8 |! 10 0 55 IO 60 $$ _ IS 60- O0 6S 60 91- IO0 90 to 95 Flret direct evldefl¢I that ita|_ent water triatmnt WlI beneficial I I I I AIRESEARCH MANUFACTURING DIVISION Los Angeles CahP[}rnla 67-2158 Page 4-25
  • 58. TABLE 4-4 (Continued) DP,iqnmtlnn H_{ er ; _ll LPnqth Type Tr,,_t Pd_ rt 60_ 1-0 7 806 1-0 _2 , I 60_ 1-0 7 606 1-0 7 60_51-0 21 b06 I-0 I I-0 II 606 _-0 8 b06 I-0 g Treatment end Remarks Alt,mlgold {rotated) - Capped off for & days - G4$ noted (Treated with O.001 m Naa 0a gfter treatment above) (Used in sim_lated Apo11o sy,tem as cnnnectl_n to waste tank outlet) Alumigold (rotated) - Treated with 0.001 m Na t Ot Alumtgold (rotated) - Not otherwise treated (see F-3) Capped off _ith distilled H_O for 7 d_y_ - NO gas noted Aiumigold (rot=ted) - Clpped off with N=O under _5 pslg N_ pressure - Pressure rise to _5 pslg Alumlgold (rot6ted) - Capped off with water - Gas noted Capped off wtth water for & months - Gas noted Alumigold (rotated) - Ftulhed with HIO- drted with N_ (Capped off 4 days wlthOut water) At uml_mld (rotated) - Flushed with HtO- Capped off & days with dlstll|ed wirer - NO geS noted Alumigold (rotated) - Flushed with HIO- fleme lned open _lth HlO Ifld flushed every 24 hr for 4 days (no gas bubbles notedt Alumlqold (rotated) - Flushed with H=O - Purged with c_tlnuous water flo_ of 2 cc/mln for & days Test Dlte_ 66-67 9-28 9-28 9-78 10-7 IO-._ IO-_ 2-21 IO-15 IO-15 10-15 IO- I_ Flow Ratep cc/mln I0 I0 I0 Io I0 6 I0 tO lO I0 Current_ _e 12 IZ 12 IZ 12 t2 I0 12 12 12 12 NOTE: Averlge Throughput Efficiency, percent 90 to 95 g to 20 gO - 60 g6 to g9 |7 to 95 63 67 6A 63 Alucfll num tubes fllhloned In coil form requl red rotltlon during t re0tment to ensure the Inside of the coil was thoroughly treated with chromate solutlocL AIRESEARCH MANUFACTURING DIVISION Los AngePes Cahtorn,a 67-2158 Page 4-26
  • 59. F- 5 L_ F-- C_ o -r I00 _(_ 9O 8O 70 70 f_ kJ F-4 50 4O 5O 20 J, M) D C D N I 0 0 A (AS I0 9 8 ) 7 D (AS REC'D) 6 5 5 tO 15 20 25 50 55 40 45 _0 55 TUBE LENGTH, FT REC'D) Figure 4-I0. Effect of Stagnant Water Treatment on Throughput Efficiency of Aluminum Tubing AIRESEARCH MANUFACTURING DIVISION Los Angeles Cahlornla 67-2158 Page 4-27
  • 60. tZ3 I ..J nt_ F-- r," r'_ .-J nn ',' Z Z CD t-- 0 0 _- 's- OD I- n,- ,c_ ._1 nn 0 _- ,iI Z 0 Z 0 - % Ln m -- c_°_ 0 ._ r_ _n 0 Z1 X 0 r- u_ 0 .-- 0 _ ._ r_ i-_ t- -- t_J 0 C_ .-_ _n r_ 0 0 0 _ E_ 0 0 e-- m ! Q EL t_ _'3 > t/) v 0 • -- 4-_ "-- × 0 0 _ "2" 0 t- -_ ct3 _ _ _._ 0 u_,-- 12, C 0 °-- r_ _ ,,._ 0 •-- L r_ -- 0 •-- C r_ X -- t- O _.) ,0 _0 t_ r_- (3_ I I 0 0 AIRESEARCH MANUFACTURING DIVISION LO_4n_elesCahtorma 67-2158 Page 4-28
  • 61. AIR REFILL L __-'_ V ENT J.JI"L._ /'-CONSTANT ______J_____Z/ HEAD WATER [--l-_J_ Y FLOW CONTROL_ VALVE =" SAMPLE POINTS (C = CONTROL) ROTAMETER 7 I V ENT (_ OVER FLOW HOLD TANK ALUMINUM ( 50 FT) COIL A-II_II Figure 4-II. Schematic of Continuous Flow System for Reliability Tests AIRESEARCH MANUFACTURING DIVISION LOS AnBe_e$ Calllormqa 6 7-2158 Page 4-29
  • 62. I= m n, ! 0 --3 C o_ C 0 o I nl I(_1 AIRESEARCH MANUFACTURING DIVISIONLOS An_,ele5, California 67-2158 Page 4-30
  • 63. Overall throughput'efficiency was about 50 to 60 percent of the theoretical. A concentration of 50 ppb could be obtained at the tank outlet with a theoret- ical input of 90 to I00 ppb. Flow rates could not be precisely maintained_and3 since the time required to insure equilibration in the tank was in excess of a week (IO days at 7 cc per min)_ the concentration in the tank effluent could not be directly correlated to the theoretical concentration at the time the sample was taken. The bulk of the silver ion losses appeared to be obtained initially in the cell(about 84 to 90 percent efficient) or through the tubing (75- to 85-percent efficient). Losses through the hold tank having a smaller area-to-volume ratio were about IO percent of the input. This system was not used for bacteriological testing 3 its value being restricted solely to long-term reliability tests. The polycarbonate cell shorted after about three months of operation (five months of testing). This was traced to cell design and has previously been discussed. Such shorting will not occur in the prototype cells. The system operated overall for a total of eight months. The high current (20 _a) used for the last four months of operation would not be necessary for flight unitsj but it provided an additional measure of cell reliability under extreme operating conditions. Simulated Apollo Waste Water System A more complete set-up was built to simulate conditions that could be expected within the Apollo waste water system. This system is the more com- plicated and is subject to interrupted and discontinuous water flows. No problems would be expected in the potable water system that are not also present in the waste water system. In the waste water system 3 a known source of bacterial contamination and growth is the suit heat exchanger and cyclic accumulators. Condensed moisture (sweat) is withdrawn from the heat exchanger by the cyclic accumulatorj from which it passes into the rest of the waste water system_ including the glycol evaporators and the waste water tank. Flow rates vary with physical activityj but are generally low 3 averaging approximately 3 ml per min. The cyclic accum- ulator (13S cc capacity) discharges at IO-min intervals with approximately 2 min required for a pressure drop after discharge before suction resumes. By interposing a silver-ion cell between the heat exchanger and the cyclic accumulator_ effective sterilization of bacteria cultures withdrawn from the heat exchanger can be achieved at the most uniform flow rate. The residence time in the cyclic accumulator also assures maximum kill before the water is moved into the remainder of the system. If the sterilization unit were located downstream of the accumulatorx a uniform silver-ion concentration could never be obtained with a small cellx because of the rapid discharge of a large liquid volume. I_ AIRESEARCH MANUFACTURING DIVISIONt os Angeles Cal_torma 67-2158 Page 4-3 1
  • 64. The simulated system IFigures 4-13 and 4-I/_ used an Apollo waste water tank and cyclic accumulator connected by two sections of aluminum tubing IAlumigold treated_ 14 ft total length] which had previously been subjected to stagnant water treatment and would effectively pass 90 percent or more of the silver ions. Metals such as stainless steel were incorporated so that any adverse effect of various metals that might be encountered in actual systems would be present in the simulated system. The heat exchanger output flow was simulated by a diaphragm pump (Lapp Pulsafeeder 3 Microflo Model LS-5). The pump flow could be adjusted between I and 65 m] per min and precisely maintained at the desired rate. Distilled water was fed to the pump from a polyethylene carboy (13-gal]_ which was agitated when inoculated with bacteria. The cyclic accumulator and the waste water tank require a gas pressure for operation of diaphragms and bladders. Tank nitrogen was used as a pressure source. The tank bladder was operated at a pressure of 16 to 17 psig and the cyclic accumulator at 50 psig. Appropriate relief valves were incorporated to avoid over-pressurization from either the pump or the nitrogen supply. Since only one water opening is available in the waste water tankj the inlet and the exit are identical. The tank was mounted on a scale 3 so that the weight of water in it at any time could be read. Overflow from the tank during discharge was regulated by a control valve and timer and could be discharged into a car- boy or drain as required. The assembly could operate continuously with no maintenance except for water and nitrogen make-up. A control panel incorporating two timers (Flexopulse 3 Eagle Signal Corp- oration 20-min and 20-hr dials) and related switches could be programmed in various ways so as to control the fill and dump cycles. A second set of in- stantaneous reset time delay timers (Industrial Timer Corp_ Series MTDj IS min and 3 min) was used to control the delay period between discharge of the cyclic accumulator and restart of the pump cycle. During discharge of the waste water tankj other operations were discontinued. A schematic of the control panel circuit is given as Figure 4-15. Tank input 3 as determined by pump settings and on-off periodsj was balanced against dischargej as determined by the control valve setting and time for dis- chargej so that the waste water tank was normally maintained between I/4 and 3/4 full, The time at which the tank discharged could be controlled manually--i.e.j at 24-hr intervals 3 if requiredj but during normal automatic operation discharge occurred at 16-hr intervals. Using these extended periods3better equilibrium could be obtained in the tank. Since tank capacity was 58 Ib of water_ it was necessary to feed at a rate of 8 cc per min to ensure a sufficient supply of water to the tank in the 16-hr interval. A normal cycle (switch arrangement No. I) consisted of the following: a. The pump operated for 8 min (Valves SIj S2j S3 closed). bo The pump shut off. Valves Sl and S3 opened for I0 sec 3 pressurizing the cyclic accumulator to 50 psig and dumping the contents to the waste water tank. _ AIRESEARCH MANUFACTURING DIVISION Los An_eqes Cahf_rna 67-2158 Page 4-52
  • 65. i_J _,_2,5sAIRESEARCH MANUFACTURING DIVISION Page 4-33LOS Ani_eles _lllOrnla
  • 66. LL | | l=: .i_1 >,, o'1 i_ (_ to lV3 to o o o. r0 E o-- V1 I ",1" I-- ::3 Q3 °_ LI. I_j AIRESEARCHMANUFACTURINGDIVISIONLOS Angeles Cahlom_a 67-2158 Page 4-34
  • 67. W a ,.5 I-" I ILl I- _- I-- .... | - I >- i_q ,o I -.I i,1 ,2,L... I.- Z oo i z_,--'-'('h,_ Z I.iJ 0 0.. 0 >- W .-J I'-- 0 n,- _ _ _.1 I-- o0 _ 0 Z _ O- 0 _ u') 0 _ I-- _.--_ I-- u') I--. _ ::) 0 <_ n-_ Z ,.-I _ O- -.r i.J ZZP I.L.I I I I I W I--" "_ --.Iql >- I'-- i,I 14..I I'-- I..1.1 I-- _ Z _ Z r_, 0 _ Z F-.-.I Z_ O 0 i I I I I 0 I-- I .. _" I _ '_' _ 0 0 i I ,_ _J __ m co u'_ u') I-.- F- I-- I-- r i I I I| ol I ..J 0 0 0 C o E m 0 °w In L r_ ..m 0 0 ¢_ 0 0 _'0 I- I:::: ,4 I I- 0") I_I AIRESEARCH MANUFACTURING DIVISIONLO_ An_Ie_ C_(Jotn,a 67-2158 Page Z,-55
  • 68. Co Valves Sl and $5 closed. Gas bled out of the cyclic accumulator. The time delay relay started to function to delay pump action for an additional IlO seconds. Supply tank agitator was actuated during this period if necessary. de The pump started. Supply tank agitator shut off. The pump could be operated for less than B min if necessary without upsetting the IO minute overall cycle. e. f. Upon waste water tank discharge solenoid valve $2 opened. Nitrogen pressure was available to the tank bladder at all times and forced water through the discharge control valve. Discharge occurred for 16 minutes. Power to the timers (other than T2OH) was off so the remainder of the system shut down. Upon completion of dischargej power was restored. The 20 minute Flexopluse Timer (T2OM) commenced operation at the point of interrup- tion. The time delay timer (TD3M) had reset so pump action was delayed an additional IIO seconds on the first start cycle after dis- charge. go A tank sample could be obtained at any time using the pushbutton provided. This pushbutton was also used to set the discharge control valve. Performance Analysis of Simulated Apollo System The system was initially operated with silver ion generation at various current levels so as to determine losses within the system. Samples were withdrawn at various sample points (See Figure 4-15). Results are shown in Table 4-6. Analyses of effluent from the tank could not be made using the colorimetric method;since the bladder releases a sulfur compound (thiuram) into the water in trace amounts which affects the color change (See Analyses). Such analyses were obtained by atomic adsorption from an independent laboratory (Truesdail Laboratories_ Inc. j Los Angeles). Recognizing the cyclic accumulator introduces rapid flow rates followed by stagnation periods of ten minutes in the aluminum tubing (14 ft) downstream of the accumulator before discharging to the tank the overall losses did not appear excessive. The system was primarily used to test the bactericidal effects of the silver on cultures of E coli and S aureus. Initially bacteriological tests were made using only the cyclic accumulator without passing the bacteria into the hold tank. Continuous tests were then made with both types of bacteria by passing inoculated water through the water sterilization celIj and cyclic accum- ulator and then into the hold tank. These tests lasted six days during which time the hold tank was discharged at 24-hour intervals and the effluent was sampled to determine residual contamination. Results of such tests are further presented (See Bacteriological Tests) but essentially complete kill was observed Bacteriological tests of inoculated sweat condensate were also made using only the cyclic accumulator since insufficient sweat condensate was available to fill the tank. 67-?158 _J AIRESEARCH MANUFACTURING DIVISION Page 4-36LOS Angekes Cahlorn,a
  • 69. ,0 I nn of) Z 0 "'l-- _j cs_ m >- _-cn u.l <C 0 to _j ,,, ._ >- _. Z z-_ <C"' I-- Z 0 ..J I _'- m," P-4 .J Z c_) Q- >- u3 L _0 E I.LI,_.._, cn _ r_ F--v cO c < "o __ r_ rO Lv 0 _ _'- u 0 E Z f- ._ E _ M- °- 0 E e'_ r" -- _ 0__--_0_--__--_ _0_ 0 ______----_---- _0_--_0____0--0-- _ _____0_--00_ O0000000000000000 O00000 ___--____ O0 _0 _0_ 0_0_0 _----N_------NII___ IIIIIIIII_IIIIIIIIIIII AIRESEARCH MANUFACTURING DIVISION LOSAn_e_esCal,torn,a 67-2158 Page 4-37
  • 70. SECTION 5 BACTERIOLOGICAL TESTS INTRODUCTION The second phase of this program_ to determine the efficiency of silver ions in decontaminating the Apollo water system has been completed. During this phase_ two microorganisms selected in the Phase I screening program_ Escherichia coli and Staphylococcus aureus_ were tested under additional simulated conditions. E. coli was chosen because of its relative sensitivity to silver and S. aureus because it is relatively resistant. E. coii_._ being very sensitive, served as an excellent test organism to examine silver under a variety of conditions_ since brief periods of time would suffice for experiments. As data accumulated for _. col._i_ the more resistant S. aureus was tested, and thus presented anticipated extremes of sensitivity to the various conditions under which the silver-ion generators were studied. As shown in the Phase I report_ a far more resistant organism is a sporulated bacillus--e.g., Bacillus subtilis var. niger. We have not included spores in this testing phase because anticipated levels are low and because the conversion of the spores into vegetative forms will result in an increased sensitivity to silver. MATERIALS AND METHODS The procedures for preparing test suspensions of the organisms and quantitation techniques are outlined in the screening report (Appendix). Two differential solid media were used: Mac Conkey agar (Difco) for E. col__i and Te]lurite-Glycine agar (Difco) for S. aureus. Artificial sweat was made up in double strength solutions_ then diluted with either sterile distilled water or silver solution. The resultant pH was usually 6.45. Oxygenation was performed as indicated in the screening report. Sweat condensate was generated by circulating air at approximately 90°F around a test subject in an enclosed suit as he walked 2 to 4 mph on a tread- mill. The moisture-laden air was then passed through a glycol heat exchanger_ and the condensate was formed by cooling the air to a dew point of 35°F. Con- densate was collected in sterile flasks and refrigerated until needed. Several samples of condensate were initially cooled in a dry ice chest until it was observed that carbon dioxide absorption reduced the pH to 5.3. When silver nitrate was added_ small quantities of a concentrated solution were used. When static bacteriological tests using silver nitrate were undertaken_ the requisite amount of silver could be precisely measured into the sample by dilution of standard silver nitrate solutions. Electrolytically produced silver-ion concentrations in this report are given as both (1) theoretical .silver concentrations based on the flow rate and amperage and (2) measured results using the dithizone colorimetric analytical procedure. Such analytical methods in the presence of bacteria are considered less accurate than analyses made for silver in distilled water only Csee Analytical Methods and Procedures). _ AIRESEARCH MANUFACTURING DIVISIONLOS Anl_ele_ Cahlom:a 67-2158 Page 5-1
  • 71. Therefore_ kill-rate data for electrolyt|cally produced silver are best com- pared on a theoretical basis. RESULTS AND DISCUSSION Effect of Artificial Sweat on Efficacy of Ionized Silver as a Bactericidal Agent This phase of the program was to use a human sweat simulant as suggested by NASA_ and to determine experimentally its effect 3 if anyj on the killing properties of ionized silver (AgN03). For the purpose of this study_ an arti- ficial sweat was put together on the formula obtained from NASA report N66-19642. Table 5-I gives the compounds and the amounts used to make the artificial sweat. TABLE 5-I ARTIFICIAL SWEAT FORMULA Compound mm/l Sodium chloride 2.106 Sodium lactate 1.568 (I.2 cc) Potassium chloride 0,448 Ammonium chloride 0.161 Urea 0.060 Distilled water I000 cc Escherichia coli B was used as a test organism throughout these studies_ since it is extremely sensitive to ionized silver and is therefore _n excellent indicator for any untoward effects of the artificial sweat on the efficacy of the ionized silver. Various concentrations of AgN03 were used I ranging from 50 ppb to 800 ppb. The methodology and procedures used for the actual testing_ platingj quantlta- tion, and cultural parameters are discussed in the screening report (Appendix). All tests were run at room temperature. The artificial sweat was made up in double-strength solutions and then diluted with either sterile distilled water or silver solution. Sterilization of the distilled water used to make up the artificial sweat solution assured sterility of the preparation_ even when the components added were not previously sterilized. Table 5-2 shows that silver concentrations above I00 ppb were not any more effective than I00 ppb_ probably due to binding of the silver by various components of the artificial sweat. Comparison of the percent kill in arti- ficial sweat with the percent kill obtained at similar pH values in distilled water shows that the latter diluent is considerably more effective as a suspending medium for the bactericidal properties of ionized silver. I_1 AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cahtornla 67-2158 Page 5-2
  • 72. oJ ! u_ .J re, I-- I-- IJJ _.1 I-- I-- Z ,'Y' :> -r i, 01.1') I-- _" u') _"-_ I-- I-- t-_ _.-_ _- Z I-- u.I L_ (.,-) ,__,. t- O U G) 0 v,.__ I i 0 "_ f- 0 U 000 0 _ _J }._ _.. t- _ 1- 0 ..C} 0 ,_D r'- _r) (-) _1 -,-I • ° °-- > 0 U °_ -_ --_ 0 57"_; _ °-- °-- _ 4.1 I" 0 0 °_ °_ t-- 0 I 0 0 0-- I u_ Lr) 000 × )< X 0 0 o..r if,) ¢._ I i I I I I I I I sol 0 0 O-- -- X X X ,,1" WZ) 0 I ,_ I c',J -._ rO 0 _ _ ,_ 000 X >( >( × ...T 0'_ 00 I,c) ,,0 ,0 I o,J 0,, o,,I 0000 I I I I I I I I I 000 00 0 -- oJ | ,0 I ° i",- I e_l ,0 000 X X >( ,z ,.: £ O0 o,I ".qr t- O °_ 0 m c × 0 000 oJ '-.._" _C) _r} ,0 I _0-_ r_- I it) O00-- X -_LOl 000 O--_rr) O0 0 0_ O_ 0_--_ 0_ _0 _ ld_d l_d 00--0 000 X XX X XXX O0 0 0_ O_ 0_--_ 0_ C_. II r_ II o.-r o-r- I I 0 ,0 0000 XXXX .... 00 0 o,J .-:r 0_--_ m ,.m 0 00 --,'_ 0 X-- X X ,0 X oO I O0 0 oJ .,,lr 0_--_ i i i i i I I I i I I i 0000 X X X X • • . , r'-.._ 0_ r'.- O0 0 c,J ".,nr I ,K_ Ln,n O0 00-- -- X X )'( × _0_ O0 0o,1",,1" 0_--_ II 0.-i- i 0 II II 0 0 o-r o-r I I 0 0 I 0 I ,4- 0 ° CLW:) (_ II _- 0 0 .-r ,.y- •,_ C)_v oJ I 0 AIRESEARCH MANUFACTURING DIVISION LOSAn_e_esCahgorma 67-2158 Page 5-5
  • 73. "ID I-" t- O m ! ill .--I r,m O l- .l_.l r O t- O .-- 'O © tY O (J °-- °l © l-- '.ill O IZ O --ID O "Q C_ II O O --I-- 'O r, u_ ! I I -- ! I ! I I I -- .I--' r" 0 L.) L r_ 0 °l °l _.- 0 '0 U _v 1,0 B +...' v 0000 00 IIII fill fill 0000 00_ O O O c_ "..I" O ,O-- c_ ,O I I 00 _ -- 0000 O O O C,.l ,,1" O ,O -- o,_ I ! 0 l _ _ _ l _ _ _ I _ _ # IOO--O X × X i 0 0 0 o,,I _.1" O ,O -- o,J I r, II o o -.l- co rl c,,4 i ,n _, o o o o-- -- x x × × -- o,, r. O ,o _r) • o . . O0 0 c_l ".q" O ..O -- O,l Old i _ O_ OO--O × 0 0 0 c_._ '-.1" E 0 I- ,4- i- °- u 0 I_ . O Q_,,O L ,_, O.. _ O u'_ -r" -- __ QO IN I O _J AIRESEARCH MANUFACTURING DIVISION 67-2 158 Page 5-4
  • 74. It should be realized that the sweat preparation used for the present study is artificial and is not a true example of humansweat, Manyof the trace elements normally found in humansweat and the residue of dead and lysed bacteria are not represented. Also2 a comparison of the chemical breakdownof artificial sweat and humansweat condensate as it comesout of the Apollo heat exchanger showssweat condensate to be almost devoid of the compoundsused to makeup the artificial sweat, Sweat condensate_ representative of the fluid obtained from the Apollo heat exchanger_ cannot therefore be considered to be actual human sweat and cannot be simulated by the artificial sweat formula used. Tests with these artificial sweat solutions were discontinued with NASA concurrence. Human Sweat Condensate as a Suspendin_ Medium for Ionized Silver (Static Tests) The results obtained using artificial sweat indicated a need for actual human sweat condensate to determine if such sweat condensate would be as detrimental to the efficiency of the silver ions. From Table 5-3 it is evident TABLE 5-3 COMPARISON OF THE CHEMICAL COMPOSITION OF SYNTHETIC SWEAT AND SWEAT CONDENSATE Concentration in mM/L PARAMETER SYNTHETIC SWEAT SWEAT I CO NDE NSATE 2 pH 6.1 - 6.6 7.08 Na 50 O. 02 8 K 6 O. 003 NH4 3 0.212 CI 45 0.020 Lactate 14 0.005 Urea I0 3 Bicarbonate 0 0.672 I. Formulation based on report by Johnson3 Phil3 and Sargent3 N66 19642. 2. Analyses performed at NASA_ MSC_ Houston 3. Analysis for urea not performed at time of report. I_I AIRESEARCH MANUFACTURING DIVISIONLOS Angeles Cal,torma 67-2158 Page 5-5

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