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Information on the physical and chemical properties of human urine concentrates, including solute concentration, water concentration, specific heat, surface tension, dynamic viscosity, osmotic pressure, and density. The document also includes equations and tables to calculate various properties based on solute weight fraction and temperature.
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COMPOSITION AND CONCENTRATIVE
PROPERTIES OF HUMANURINE
MCDONNELLDOUGLASASTRONAUTICSCOMPANY - WESTERN DIVISION
1. Report No. 2. GovernmentAccessionNo. 3. Recipient'sCatalog No. NASA CR-l% 4. Title and Subtitle 5. ReportDate CON!?OSITION AND CONCENTRATIVE PROPERTIES HU"lOF WUtE^ July^^1971 6. PerformingOrganization Code 7. Author(s) 8. Performing Organization Report No. David F. Putnam (^) 10. DAC-61125-FWork Unit No. 9. Performing Organization NameandAddress McDonnell Douglas Astronautics Company Advanced Biotechnology and Power Department Huntington Beach, California 12. SponsoringAgencyNameandAddress National Aeronautics and Space Administration Washington, D.C. 20546 11. Contract or Grant No. NASI-~~S+ 13. Type of Report andPeriod Covered I ContractorReport
14. SponsoringAgencyCode 15. SupplementaryNotes 16. Abstract This report defines the composition of typical human urine and presents experimental data on its chemical, physical,. engineering and concentrative properties. The effects of chemical and electrolytic pretreatments used in aerospace applications for extraction of potable water are included. The results are presented in tables and plots of unsmoothed data, empirical equations, and tables of nominal values. Sample calculations and examples illustrating the consideration of these data in engineering design applications are included. 17. Key Words(Suggested byAuthor(s)) Urine water reclamtion Concentrative properties of human urine Water reclamtion Physical properties of urine Electrolytic pretreatment of urine 18. Distribution Statement
19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price*
For sale by the National Technical InformationService, Springfield, Virginia 22151
iv
variations in urine composition are presented in terms of refractive index, specific conductivity, pH, total dissolved solids, chemical oxygen demand (standard and rapid methods), total Kjeldahl nitrogen, and total organic carbon. The electrolytic pretreatment of urine is described, a mass balance is presented, a discussion of the electrochemistry of the process is given, and a typical composition of electrolyzed urine is listed. The physical pro-
solutes and 70 to140 degrees Fahrenheit. Both smoothed and unsmoothed data are presented in tables and plots, which are grouped together at the back of this report. The physical property data presented are the following:
soluteweightfractionsolute to^ waterratio
osmolalitypressure vapor
density osmolarity concentrationsoluteosmoticpressure waterconcentrationheat of vaporization heat of solutionitycosvis specificweightfractionheat of precipitatedsolids surfacetensionweightfraction of extractedwater specificconductivityrefractiveindex
H S HU
Lu
n
n. 0
I
p ::
= chemical oxygen demand (rapid method), g/J or mg/t.
urine = specificconductivity, m h o - c m - 1 o r pmho-cm'l = differential heat of vaporization of urine, BTU per pound of water evaporated = differential heat of vaporization of urine, BTU per pound of urine = differential heat of vaporization of water, BTU per pound of water evaporated
calculated from vapor pressure data and Raoult's Law
= number of moles of solvent = - ww 18
= numberof-moles of soluteparticles = - wsM
water = osmolarity, apparent g-moles of solute particles per liter of urine = v a p o r p r e s s u r e of urine concentrate, psia = v a p o r p r e s s u r e of pure water, psia
The composition of human urine has been studied by many investigators and the quantities of 158 different chemical constituents are summarized in the NASA BioastronauticsDataBook(Reference14).Theseconstituentsare broadly categorized as electrolytes, nitrogenous compounds, vitamins, hormones,organicacids,andmiscellaneousorganiccompounds.The 68 constituents that have individual maximum concentrations exceeding 10 m g / l are listed in Table I in decreasing order of concentration. These constituents add up to about 36,800 mg/f in typical urine. The remaining 90 compounds total approximately 2 5 0 mg/B.
For engineering analysis purposes in water reclamation technologies, an abbreviated list of compounds is in most cases more than adequate to charac- terize human urine. This is not to suggest that there is any substitute for using real urine in the development and testing of water recovery subsystems: rather, that it is convenient, and sufficiently accurate for most analyses, to use a simplified version of the real thing. An analog for real urine, consist- ing of 42 compounds, is presented in Table 11. The concentrations listed are considered to be typical, and are based on the information in Table I, the measurements presented elsewhere in this report, and the results of numer- ous chemical analyses of urine made over the last 10 years in the course of developing water recovery subsystems. The 42 out of 158compoundsin Table I1 account for over 98 percent of the total solute concentration in urine. For most analyses and calculations, Table I1 should serve as a convenient starting point to develop an even more simplified analog such as Table 111, which shows the major categories of (1) inorganic salts, ( 2 ) u r e a , ( 3 ) organic compounds, and (4) organic ammonium salts broken down into content of carbon,nitrogen,oxygen,hydrogen,andorganicsulfur.
Some measurements that help to broadly categorize urine are presented in Table IV. The measurements were made on 16 different batches of raw, unconcentrated, nonpretreated urine, each containing about 40 l i t e r s c o m - posited from 2 0 to 30 male subjects. The total dissolved solids (TDS) of the batches ranged from 24.8 grams per kilogram to 37. 1 grams per kilogram.
The measurements selected were considered to be the most significant available for broadly categorizing urine. In addition to the directly meas-
columns of nitrogen and carbon as determined by gas analysis in the elec- trolytic pretreatment process (see ELECTROLYTIC PRETREATMENT OF HUMAN URINE). The agreement between the two different methods of determination is close for nitrogen, but not s o close for carbon. The data
generally increasing trend with increasing TDS is apparent for each parameter except pH, there is considerable deviation from mean values. It is not known how much of the deviation is due to actual variations in the level of the measured quantities, and how much is due to interferences and side reactions involved in the method of measurement. The particular significance of each measurement is discussed below.
i'
Refractive Index (ni)
with a Bausch and Lomb refractometer calibrated for sodium yellow light relative to air. For a discussion of refractive index of aqueous solutions, see References 15 and16. For refractive index data on common binary solutions see References 16 and 17. The refractive index has been found to have a straight-line correlation (Figure 12) with solute weight fraction ( X ) for most species in binary solution. In addition, for many species the effects of solute weight fraction on refractive index are additive.
Specific Conductivity (k) Specific conductivity is a function of the ionic, species present in water. If the amount and identity of each ionic solute is known, then the specific conductivity of a solution can be calculated, as there is a definite relation- ship between ion concentration and specific conductivity for individual species. The specific conductivity, calculated for the urine listed in Table 11, assuming an activity coefficient of 0. 74 for each inorganic salt (Reference 17, p. D - 9 3 ) , is 18. 0 mmho-cm'l for the inorganic salts, and approximately
cm-1. This is very close to the values found in real urine (see Figure 2 ).
When both Equations (1) and (2) are balanced in respect to oxygen, then n = mta and the number of moles of CO produced in Equation (2) is equal to the number of oxygen atoms required in Equation (1). The results are r e p o r t e d a s g r a m s p e r liter of oxygen and are t e r m e d "C02D".
sented by the equation C2 H6 N2 02. The oxidation of this mixture by C 0 2 would be
Therefore,inthiscase, i f completeoxidationoccurred w i t h no interferences, the total organics in urine would be approximatelyequal t o 90180 x CO 2 D.
The efficiency of oxidation for a number of compounds as reported in Reference 18 i s as follows: Analyses of Known Solutions
Compound Acetic acid Benzoic acid Oxalic acid Glycine Urea p-Nitroaniline Phenol Sucrose Acetone Ethanol Methanol Ammonium hydroxide Ammonium chloride
CO,D, L m g / l Calcd 246 250 250 2 5 0 2 5 0 2 5 0 245 248 173 235 238 250 2 5 0
Found 239 248 2 44 248 2 50 2 44 2 16 2 15 145 2 00 205 2 04 2 74
Oxidation
Chemical OxygenDemand(COD)
Chemicaloxygendemandisoftenusedasindication of^ thetotalorganic content of water(Reference 19). It is a m e a s u r e of theamount of
I
dichromatethat is reducedbyoxidation of theorganics.Typical C O D valuesforthreeorganicmaterialsareasfollows:
Item COD Lactose (^) 0.84 g/g (Measured) Glucose (^) 1. 07 g / g (Theoretical, Reference 19) Potassium Acid Phthalate (^) 1. 1 8 g / g (Theoretical, Reference 19)
The oxidation of most organic compounds by dichromate is 95 to 100 p e r - cent of thetheoreticalvalue.However,ammonia,urea,benzene,toluene, and pyridine are among the compounds that are not oxidized by dichromate. Since urine contains large amounts of urea, ammonia and amines, its COD values would be expected to run considerably below the total organic content of urine, and the data presented in Table IV bear this out.
Total Kjeldahl Nitrogen (TKN) Total Kjeldahl nitrogen (Reference 19) measures organic nitrogen in the trinegative state and includes ammonia nitrogen. TKNwouldbe expected to measure essentially all of the nitrogen in raw urine. When the organics in rawurineareapproximatelyrepresentedbytheequation C H N 0 the total organics would be approximately equal to 9 0 / 2 8 x TKN.
Nitrate and nitrite nitrogen are not m e a s u r e d by TKN and are not present to any appreciable extent in raw urine. However, in electrolyzed urine there can be high levels of nitrate present, and in this case TKN does not indicate total nitrogen. Total Organic Carbon (TOC) The total organic carbon measurement was made with a Beckman Model 915 Total Organic Carbon Analyzer (see Reference 20). This instru- ment complies with the ASTM tentative method D2579-T for the determination of organic carbon in water and waste water. A small-size water sample is swept into a catalytic combustion tube (95OOC) where all carbonaceous m a t e r i a l is oxidized to carbon dioxide. After removal of the water vapor, the C 0 2 is introduced into an infrared analyzer sensitized to m e a s u r e COz. A parallel sample is then injected into a secondcombustiontube
By passing sufficient electricity through human urine, most of the dissolved organic compounds can be converted to hydrogen, oxygen, nitrogen, and carbon dioxide, which are outgassed, leaving behind a semipurified urine that contains primarily inorganic salts. These residual inorganic salts can be removed by electrodialysis to produce potable water. The com- plete water recovery process is termed electropurification and a typical
is approximately represented as follows: X 3 0 + 2 C 2 H6 N2 O2 t 11 H20 -. X304 t 17 Hz + 2N2 t 2 0 2 t 4C02 (4)
In this equation, X 0 represents the inorganic compounds in raw urine, C H N 0 representstheorganiccompoundsinrawurine,and X 3 0 4 represents the inorganic compounds in electrolyzed urine. X r e p r e s e n t s all atoms other than C, H, N, and 0 and is considered to have an atomic weight of approximately 30, which is about average for the composition of Table 11.
The mechanism for the overall electrochemical reaction is not known, However, it is felt that chemical reactions involving hypochlorite, chlorate, perchlorate, and perhaps both nascent chlorine and nascent oxygen are of prime importance. In actual practice, a batch of urine consisting of approxi- mately 4 liters is circulated through an electrolysis cell operating at a current density intherange 200 to 300 mA/cm until the TOG, COD, and TKN are each reduced-to less than 100 mg/L?. The transient behavior of the urineduringelectrolysisisshown in Figures 10,11, 1 2 , 13, 14 and15. These plots are estimates for the typical urine described in Tables 11 and 111, and are based on cornposited data from approximately 16 test runs. An estimate of the salts remaining after electrolysis is shown in Table V. Essentially all organic material is gone.Theorganicsulfur is converted to sulfate and most of the original chloride is converted to chlorate and perchlorate.Figures16, 17, 18 and 19 characterizeelectrolyzedurine in t e r m s of refractive index, specific conductivity, pH, and TDS respectively. Considerable deviation from mean values is evident.
2
Figures 10 through 15 give some insight into the dynamics of the organic removal process. In the first few minutes of e l e c t r o l y s i s there is an induc- tion period in which the chloride level drops about 10% (Figure 10). Conver- sion of chloride to hypochlorite according to the following reaction is indicated: Anode: 6C1- - 6e - 6 c l (5)
Cathode:6Nat t 6HOH t 6e - 6NaOH t 3H2 ( 6 )
Mixing: 6NaOH t 3C12-3NaOC1 t 3NaC1 t 3H20 ( 7 )
During the first 3 hours of electrolysis, the outgassing of oxygen is low (Figure 14), indicating that little if any excess water is being electrolyzed. The ratio of nitrogen to carbon (Figure 15) is higher than the average value for urine, indicating that urea and other high-nitrogen organics are being oxidized in preference to low- and zero-nitrogen organics such as the organicacids.ThefactthatCOD,whichdoesnotincludeurea,isdecreas- ing (Figure 10) indicates that other organics besides urea are also being oxidized. Th2 primary chemical reaction appears to be hypochlorite oxida- tion,which,forurea, is mainlyasfollows:
Oxidation: F12NCONH2 t 3NaOC 1 - C 0 2 t N 2 t 3NaC1 t 2H
Theoverallreaction,combiningEquations ( 5 ) , ( 6 ) , ( 7 ) , and ( 8 ) would be as follows:
Overallreaction: €12NCONF12 t I I 2 O - C 0 2 t N 2 t 3H2 ( 9 )
Between hour 3 and hour 4 the chloride level drops, indicating a higher concentration of hypochlorite and the preferential oxidation ofa new group of organiccompounds.Thedec.line inpII (Figures 10 and 15)indicatesthat ammonium ions are also being removed, leaving the organic acids unbuffered. By hour 4 the organic nitrogen ( T K N , Figure 1 0 ) has dropped to almost zero and the nitrogen to carbon ratio (Figure 15) is below the average value. The nitrogen compounds that renlain in solution a s z e r o TKN is approached
It probably does not involve the chlorate ion, which is not as good an oxidizer as hypochlorite.Also,nitrogencontinuestobeevolved(Figure 14) indica- ting the removal of unidentified residual nitrogen-containing compounds.
organic level falls to below 500 m g / l ( F i g u r e 10). Since nearly all of the chloride was converted to chlorate by the beginning of the fifth hour, the n. vs TDS data (Figure 12) indicate that chlorates are being converted to perchlorates by anodic oxidation as follows:
1
C103- t H 2 0 - 2e - C104- t 2HS
level is low enough that subsequent processing by electrodialysis produces water that meets all of the NAS/NRC chemical potability standards (Reference 24).
The physical properties reported in this section were determined for the mixed urine of 40 to 50 male subjects over a period of several months. Seven batches of urine, containing 19 liters per batch, were each concen- t r a t e d by evaporation to approximately 200 milliliters, at which point the liquors of similarly pretreated batches were mixed and concentrated further. The physical properties were measured at discrete intervals during the con- centrationprocess.TheunsmootheddataarepresentedinTable VI. Four different chemical pretreatments were investigated as follows:
0 H2S04 t C r 0 3 o H 2 S 0 4 t C r 0 3 + CuS 0 Ca(C10) .Electrolytic (see ELECTROLYTIC PRETREATMENT O F HUMAN URINE)
Pretreatments are used in most urine processing systems (References 2 and 2 5 ) to stabilize urine with respect to microbes, odors, and free ammonia. These four pretreatments are the most widely used. Physical property data were not obtained for untreated urine because bacterial action always devel- oped within the first few days of the one- to two-month period in which the progressive concentration of the urine and physical measurements were made. This bacterial action resulted in the decomposition of urea and the evolution of large amounts of ammonia.
Most of the physical properties are not sensitive to the first three pre- treatments, in which less than 10 g p e r l i t e r of chemical are involved. Only precipitate,viscosity,and pH arenoticeablyaffected.Theelectrochemical pretreatment which converts most of the organic material in urine to useful cabin gases has a noticeable impact on many of the concentrative properties, but not on vapor pressure and the other colligative properties.
Symbols are assigned in Table VI to each batch of urine, and these symbols are used consistently through this section. Deviations in the data can be readily determined from the individual plots that are presented in each section.
