Edition
Analytical Volume 3
Number 2
APRIL 15, 1931
Determination of Carbon in Sewage and Industrial Wastes' F. W. Mohlman and G. P. Edwards THESANITARY DISTRICTO F CHICAGO, CHICAGO,
ILL.
A modified chromic acid method for the determiThis work indicated to us that N VIEW of the fundamennation of carbon in sewage and trade waste has been we might modify their aptal importance of carbon studied. The determination, which can be completed paratus and procedure for use compounds in all probin about 3 hours, gives an accurate estimation of the in sewage work. lems of sewage treatment and strength of sewage or waste. This is particularly disposal, it isunfortunate that Methods of Carbon desirable for sewages or wastes high in carbon but low we have not had a satisfactory Determination in nitrogen. There is a constant ratio between the method for routine determinaorganic carbon and the 5-day oxygen demand in the tion of carbon in sewage and Carbon has usually been sewage and wastes used, supporting the theory that industrial wastes. The ease determined either by the dry the first stage of the oxygen-demand curve is a carbon and accuracy of the Kjeldahl combustion method or by the oxidation. There seems to be no relationship between method has made it possible wet combustion m e t h o d , the total carbon and the oxygen demand or between to accumulate a large amount using chromic acid. I n the the total nitrogen and the oxygen demand. of information concerning the dry method the sample must nitrogen comDounds in sewbe evaporated to dryness, age a i d was&, but the only determinations we have had which which is impracticable with large volumes of liquid, the resiare supposed to approximate the carbonaceous matter are due from which must be transferred from the evaporating the oxygen-consumed determination and the first stage of dish to the combustion boat. Not only is there this diffithe B. 0. D. test. It is, of course, true that neither of these culty but the carbon as determined will include carbonates. is an actual determination of total organic carbon, for they These unsatisfactory conditions and the time required and include other oxidizable substances such as sulfur, hydrogen, difficulty of the method have prevented itsuse. and inorganic reducing compounds. Notwithstanding this The chromic acid oxidation method has had occasional lack of a method for determining carbon, it has long been study but results have usually been found to be low, and also known that in the oxidation of sewage the carbon compounds difficulty has been encountered owing to liberation of sulfur are of more importance than the nitrogen compounds. The trioxide and free chlorine. I n the earlier work Schollenberger large amount of nitrogen in urea has no appreciable demand (3) showed that the sulfur trioxide fumes could be reduced for oxygen until hydrolyzed to ammonia. The nitrogen in by partial substitution of phosphoric for sulfuric acid. White ammonia is oxidized only slowly. It is therefore our belief and Holben (4) absorbed acid fumes in a U-tube filled with that if a satisfactory method for carbon could be perfected coarse glass wool drenched with 98.3 per cent sulfuric acid. the results would be correlated more closely with the actual Friedemann and Kendall demonstrated the importance of oxygen requirements of the sewage than any correlation high concentration of acid. I n our work we have added anpossible between the nitrogen and oxygen requirements. other precaution in absorbing in acid potassium iodide any Our attention was directed a year ago to some recent work free chlorine which may be liberated. on carbon determinations by Friedemann and Kendall (8). By taking advantage of these various improvements and Their work applied to materials of biochemical importance, suggestions we have developed apparatus and technic which such as, for example, urine, blood, tissues, and bacterial seem to give promise of a method of practical value for the culture media. I n their work they found that the usual determination of carbon in sewage and industrial wastes. difficulty encountered in obtaining complete oxidation by Description of Method chromic acid was caused by the presence of an excess of water in the sample. They demonstrated that the effect of The apparatus consists of a reaction flask, a Geissler tube large amounts of water could be compensated for by the use of larger amounts of sulfuric acid, and they show results of for absorbing free chlorine, and an absorbing system for oxidation approaching 100 per cent of the theoretical amount. carbon dioxide. The oxidizing agents consist of chromic, sulfuric, and phosphoric acid, as recommended by Schollen'Received November 19, 1930. Presented before the Division of berger. The carbon dioxide resulting from the reaction is Water, Sewage, and Sanitation at the 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930. absorbed by 0.1 N barium hydroxide, forming barium carbon-
I
120
ANALYTICAL EDITION
ate which is insoluble. The excess barium hydroxide is titrated with 0.1 N hydrochloric acid, using phenolphthalein as the indicator. Care must be taken during the titration to add acid slowly, with shaking, so that acid concentration will not be large enough locally to dissolve the precipitate. APPARATUS-A sketch of the apparatus is shown in Figure 1. Three tubes pass through the ground-glass stopper of the 300-cc. KjeIdahI flask, A , which is fitted with a condenser on the outside of the neck. Tube B, attached to the
rI
dahl flask with an absorption tower to hold 50 cc. of barium hydroxide. This size is more satisfactory for sewages and effluents containing small amounts of carbon. Air freed from carbon dioxide is obtained from a $foot (1.22-meter) glass tube, one inch (2.54 cm.) in diameter, filled with moistened soda lime of about equal proportions of 4 and 8 mesh. REAGENTS+) Chromic acid: 340 grams of chromic acid (CrOa) are dissolved in 400 cc. of hot carbon dioxidefree water and made up to one liter with 85 per cent phosphoric acid. (2) Sulfuric-phosphoric acid : equal volumes of concentrated sulfuric acid and 85 per cent phosphoric acid. (3) 0.1 N barium hydroxide. (4) 0.1 N hydrochloric acid. PROCEDURE-Asample containing 10 to 30 mg. of carbon is placed in the Kjeldahl flask and the flask connected to the apparatus. Then 75 cc. of standard barium hydroxide are added to the Erlenmeyer flask and the vacuum is turned on so that air passes through the tower at the rate of 100 to 200 bubbles per minute. Next, 10 cc. of chromic acid and 50 cc. of the phosphoric-sulfuric acid mixture are added through the separatory funnel. As recommended by Friedemann and Kendall, 2 cc. of concentrated sulfuric acid are added for each cubic centimeter of water present in the sample. The contents of the flask are gently heated until the mixture boils. Gentle boiling is continued for 2 hours. At the end of the digestion, the flame is removed and the vacuum turned off. The stopper at the top of the absorption tower is removed and the tower is washed with about 150 cc. of carbon dioxide-free water. The flask is removed and the excess barium hydroxide is titrated with the standard hydrochloric acid solution to obtain the value for total carbon. Blanks to correct for carbon dioxide in the apparatus and the reagents, and also for the carbon dioxide absorbed during the titration, should be run frequently. Table I-Carbon SAMPLE
separatory funnel, permits the addition of the oxidizing agents. Air, free from carbon dioxide, is drawn into the flask through tube C. Tube D leads from the Kjeldahl flask through the Geissler bulb, E, to the 300-cc. Erlenmeyer flask F. The absorption tower, G, containing glass beads which are held in place by a perforated porcelain plate, is connected to the Erlenmeyer flask. The tower is joined to the vacuum pump by the rubber tube with the clamp HI which regulates the flow of air through the apparatus. The vacuum pump draws carbon dioxidefree air through tube C into flask A . This air, with the carbon dioxide formed during the reaction, is drawn by way of tube D through the Geissler bulb, E. The Geissler bulb contains a saturated solution of potassium iodide, acidified with sulfuric acid to remove free chlorine liberated during the digestion. Then the air containing the carbon dioxide passes through flask F and the absorption tower which contains a definite volume of a standard solution of barium hydroxide. The carbon dioxide is absorbed by the barium hydroxide during the passage of the gas through the tower. The absorption tower is large enough to hold 75 CC. of barium hydroxide during operation. Apparatus of this size is best for carbon determinations of industrial wastes with high carbon content. Another set of apparatus used consists of a 500-CC. Kjel-
Determination in Pure Compounds THEORETICALDETERMINED CARBON CARBON
%
Gram 0.0147 0.0147 0.0147 0.0147
Gram 0.0153 0,0144 0.0147 0.0146 ‘
104 98 100 100
Sucrose
0.0144 0.0144
0.0143 0.0146
99.3 101.0
Asparagine
0.0096 0.0120 0.0120
0.00956 0.01186 0.01199
99.6 99.0 100
Sodium oleate
0.0157 0.0157 0.0157 0.0157
0,01527 0.01497 0.01529 0.01545
97.3 96.5 97.3 98.0
Filter paper
01344 0 01384
0,01335 0 01335
99.5 96.5
Potassium acid phthalate
Figure 1-Apparatus for the Determination of Carbon i n Sewage a n d Industrial Wastes
Vol. 3, No. 2
The free and combined carbon dioxide must be deducted from the total carbon in order to obtain the organic carbon. This may be done by first determining the carbon dioxide and then the organic carbon on the same sample, as follows: Another sample from the same source is placed in the Kjeldahl flask, the standard barium hydroxide added to the Erlenmeyer flask, and the apparatus connected. Two or three drops of the concentrated sulfuric acid are added through the separatory funnel and the contents of the Kjeldahl flask are slowly warmed. The sample is kept warm for an hour. The excess barium hydroxide, when titrated with hydrochloric acid, gives the amount of carbon dioxide and carbonate in the sample. A high concentration of acia and continued boiling may break down some of the organic matter, giving higher carbon dioxide results and correspondingly lower organic carbon, but it is probable that the carbon dioxide liberated in this way is small in comparison with total
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 15, 1931
Table 11-Raw ____
Se? ge from North Side Treatment Works
~~
CARBON SAMPLE Total
Organic
121
TOTAL NITROGEN
$:pD ORGANIC CARBONORGANIC CARBONTOTAL NITROGEN 200 c. TOTAL NITROGEN B. 0. D. B. D.
P. 9. m.
P. p . m.
P. fi. m.
Free COz plus carbonate
0.
1
100.8 96.6'3
P. p . m. 57.0" 52.8
43.8
11.2
74
4.9
0.74
0.151
2
100.8 94.4a
57.60 51.2
43.2
14.8
98
3.6
0.55
0.151
3
80.7 72.3a
37.2" 28.8
43.5
11.2
75
3.0
0.44
0.151
4
116.8 116. l a
56.50 55.8
60.3
15.6
84
3.6
0.66
0.186
5
182.4 198.98
62.3'' 78.2
120.3
14.4
185
4.9
0 38
0.078
6
121.2 117.60
70.2" 66.6
51.0
12.0 '
133
5.6
0.51
0.090
7
88.2 92.6"
27.45 31.8
60.8
12.4
60
2.4
0.50
0.206
8
110.5 99.70
59.75 48.9
50.8
14.8
100
3 0
0.54
0.148
9
148.2 151.6a
90.00 94.2
57.3
18 0
140
5.1
0.64
0.128
Av.
116.0
57.0
59.0
13.8
105
4.0
0.55
0.143
P. 9. m.
a Calculated.
Table 111-Activated
Sludge Emuent, North Side Treatment Works
ChRBON SAMPLE
TOTAL NITROGEN
5-DAu
$ :':'
ORGANIC CARBON,ORGANICCARBON TOTAL NITROGEN NITROGEN B. 0. D. B.0.D.
Total
Organic
Free COz plus carbonate
P. p . m.
P. 9. m. 10.30 11.4
P. 9. m.
P.P. m.
P. P. m.
58.5 59.6"
48.2
1.60
2.0
6.7
5.4
0.800
2
49.8 50.2a
11.6' 12.0
38.2
0.80
3.0
14.5
3.9
0.266
3
60.9 60.95
20.6" 20.6
40.3
1.04
6.0
19.8
3.4
a . 173
4
60.0 61.6n
14.2'' 15.8
45.8
2.60
8.0
5.8
5.0
0,868
5
54.4 53.6''
15.84 15.0
38.6
0.88
3.4
17.5
4.5
0.269
6
52.2 54.0a
10.0" 12.0
42.0
0.88
2.8
12.6
3.9
0.314
7
52.2 55.0"
14.40 17.2
37.8
1.68
5.7
9.4
2.8
0.294
8
47.5 49.70
7.30 9.5
40.2
1.00
2.3
8.4
3.6
0.435
Av.
55.0
41.4
1.31
3.5
11.8
4.1
0.426
1
13.6
TOTAL
" Calculated carbon, and that most of it may come from the carboxyl group (COOH), therefore not requiring oxygen for oxidation. The acidified sample from which the carbon dioxide, free and combined as carbonate, has been removed is treated with chromic, sulfuric, and phosphoric acid as described abqve, and the organic carbon is determined. The sum of the carbon dioxide and the organic carbon should, of course, equal the total carbon, as originally determined. Although a large quantity of sulfuric acid is necessary in the digestion of the large sample required when the carbon is low, it is the same amount recommended by Bauer and Deiss (1) for use in iron and steel analysis in the Corleis apparatus. They also recommend a 3-hour digestion period. Results
PURECOMPOUNDS-The carbon was determined in a few pure compounds, such as a soap, an amino acid, a carbohydrate, and an aromatic compound. Table I shows that the determined values were very close to the theoretical ones. The sodium oleate seemed to contain some impuriLies, as it was partially insoluble in alcohol. These analyses 'were made on dilute solutions (0.01 M ) of the compounds
in the manner mentioned above for total carbon. The samples were boiled for 2 hours. Friedemann and Kendall, working with smaller volumes of more concentrated solutions, found that the digestion of easily oxidizable substances, such as sugars, was complete in 30 minutes. Proteins required a longer digestion period, and substances difficult to oxidize, such as fats, required an hour. Certain compounds, such as stearic acid and carbazole, tended to creep upward and stick on the side and neck of the flask, giving low results. The large volume of sample required in our analyses seemed to make necessary a longer digestion period. Digestion was complete in 2 hours. SEWAGEAND EFFLuENTS-Table 11 gives the results Of analyses of nine samples of raw sewage obtained from the North Side Treatment Works, a sewage mainly of domestic origin. As mentioned before, the total carbon values were obtained from two determinations, the upper figure being the total carbon as determined, and the lower one the sum of the carbon-dioxide carbon and the organic carbon. The upper values for organic carbon are calculated by subtracting the carbon dioxide from the total carbon and the lower
ANALYTICAL EDITION
122
from J. Greenebaum Tanning Company
Table IV-Wastes CARBON SAMPLE
Vol. 3, No, 2
Total
Organic
Free COZplus carbonate
TOTAI, 5-DAy NITROGEN tb?'?'
ORGANICC A R B O N
ORGANIC
TOTAL NITROGEN
CARBON TOTAL NITROGEN B. 0. D.
B. 0. D.
P. Q. m.
P. Q. m.
P. Q. m.
P. 9. m.
Raw
946.8 952.3"
906.5" 912.0
40.3
182
1410
5.0
0.64
0.129
Settled
702 .' 1 660, O a
654.1" 612.0
48.0
167
1020
3.8
0.62
0.168
1035.1 1076.60
1000.3" 1044.8
34.8
247
1760
4.1
0.56
0.140
Settled
672.0 701.6"
584.8" 614.4
87.2
128
1410
4.6
0.42
0.091
Raw
768.0 808.5"
713.1" 753.6
54 ..9
187
1360
3.9
0.54
0.137
Settled
628.1 648.5"
573.0a 594.0
54.5
172
850
3.4
0.68
0,202
1400.0 1300.0"
1303.00 1203.0
97.0
339
2000
3.4
0.63
0.169
Settled
941.0 928.W
941.0" 928.6
0.0
259
1680
3 6
0.56
0.154
Raw
790.6 807.8"
709.1" 726.2
81.6
182
1090
3.9
0.66
0.167
Settled
704.4 723.30
667.7" 686.6
36.7
170
1120
3.9
0.60
0.152
Av.
859.8
806.4
53 5
203.3
1370
3.96
0.59
0.161
Raw
Raw
a
P. 9. m.
Calculated. Table V-Stockyards CARBON
SAMPLE
Total
Organic
Free COZplus carbonate
TOTAL NITROGEN
Wastes
{-.:!A.
ORGANIC CARBON
200 C.
ORGANIC CARBON
TOTAL NITROGEN B. 0. D.
TOIALNITROGEN 13.0. D.
P. Q. m.
P. fi. m.
P . p . m.
P. Q. m.
P. 9. m.
1
372.0 467.0'
279.6" 374.6"
92.4
51.2
620
6.4
0.52
0.083
2
188.9 183.6"
140.9" 135.6
48.0
16.0
262
8.6
0.53
0.061
3
413.3 411.4'
334.3" 332.0
79.0
51.2
590
6.5
0.56
0.087
4
248.4 253.2"
183.6" 188.4
64.8
24.8
295
7.5
0.63
0.084
5
207.6 191. o a
155.4' 139.4
51.6
25.6
237
5.7
0 62
0.108
6
484.2 497.30
428 50 441.6
55.7
56.0
580
7.7
0.77
0.097
7
139 2 144.0"
91.2a 96.0
48.0
16.0
I35
5.9
0.69
0.119
8
528.0 525.6"
470.4a 468.0
57.6
67.2
607
6.9
0.77
0.111
Av.
328.4
266.2
62.2
36.5
416
6.9
0.64
0.094
Calculated.
'
one is as determined. Total carbon in this sewage is made from 12-hour composite samples collected in sewers near up of about 50 per cent carbon dioxide, which is due partly the yards. The strength of the waste varies considerably to carbonates. This carbon undoubtedly has no oxygen depending upon the time and place of sampling. The ratio demand. There was no appreciable amount of nitrate- of nitrogen to carbon is lower than in sewage or tannery waste. Refinery wash water from the Corn Products Refining nitrite nitrogen. The results of analyses of activated sludge effluents from Company (Table VI) contains very little nitrogen although the North Side Treatment Works are shown in Table 111. the oxygen demand and carbon are high. The waste, colIt is interesting to note that the organic carbon is low as lected hot, contains little or no carbon dioxide. compared with the carbon dioxide and that the nitrogen is Relation of Organic Carbon to Other Determinations much lower in proportion to the carbon than in the raw sewTable VI1 shows the averages of carbon-nitrogen, carbonage. The 5-day oxygen demand is aIso lower in proportion B. 0. D., and nitrogen-B. 0. D. ratios for corn products, stockto the carbon than in the raw sewage. INDUSTRIAL WASTES-ReSUltS of analyses of tannery wastes yards, raw sewage, and tannery wastes. Although the carare shown in Table IV. These wastes were obtained from bon-nitrogen ratios vary from 3.96 to 42.7, the carbonan experimental treatment plant a t the J. Greenebaum Tan- oxygen demand ratios are quite constant, varying only from ning Company, a chrome tan factory. The values for carbon, 0.55 to 0.65, a maximum difference of 10 per cent from the nitrogen, and oxygen demand show the waste to be much mean of 0.61. This constant value indicates a relationstronger than raw sewage. The proportion of carbon to ship between the organic carbon content and the 5-day oxygen demand, supporting the theory that the first stage of the nitrogen, however, is about the same as for sewage. The analyses of stockyards wastes, shown in Table V, are oxygen-demand curve is a carbon oxidation. The activated
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 15, 1931
Table VI-Wastes
from Corn Products RefininQ - Comvanv - -
CARRON SAMPLE
Total
Organic
P. p . m.
123
TOTAL NITROGEN
Free COz plus carbonate
z;gfg, C.
ORGANICCARBOXORGANIC CARBON TOTAL NITROQEN TOTAL NITROGEN B. 0. D. B. 0. D.
~~~~
P. p . m.
P. 9. m.
P. fi. m.
1
310.2 301.4
P. p . m. 310.2 301.4
0.0
3.7
480
82.0
0 63
0.008
2
340.4 319.2
340.4 319.2
0.0
10.4
445
31.7
0.70
0.023
3
310.3 302.4
310.3 302.4
0.0
9.6
475
31.9
0.65
0.020
4
346.8 346.3
346.8 346.3
0.0
10.4
510
33.3
0.60
0.020
5
430.3 420.5
430.3 420.5
0.0
10.4
560
40.9
0.70
0.00s
6
383.3 406.2
383.3 406.2
0.0
14.0
620
2s.1
0.63
0.023
7
541.2 546.5
541.2 546.6
0.0
12.0
775
45.3
0.70
0.016
8
583.8 572.4
583.8 572.4
0.0
12.0
980
48.1
0.60
0.012
Av.
403.8
403.8
0.0
10.3
606
42.7
0.65
0.016
sludge effluent with a carbon-nitrogen ratio of 11.8 and a carbon-B. 0. D. ratio of 4.1 is in a different stage of oxidation and cannot be compared directly with the raw sewage or trade wastes. T a b l e VII-Comparison of Carbon-Nitrogen, Carbon-B. 0. D., a n d Nitrogen-B. 0. D. Ratios
Ratio organic carbon to nitrogen 42.7 Ratio organic carbon to 0.65 B. 0. D. Diff. fromaverage, % 6.6 RationitrogentoB. 0. D. 0.016 Diff. from average, 84.0
vo
6.9 0.64 5.0 0.094 6.9
4.0 0.55 10.0 0.143 41.5
3.96 0.59 3.2 0.151 49.5
14.4 0.61 6.1 0.101 45.5
As we would expect, we find no correlation between the values found for the nitrogen-oxygen demand ratios from
Effect of Light on Determination of Ethylene‘ J. Louis Oberseider and J. H. Boyd, Jr. THEATLANTIC REFINING COMPANY, 3144 PASSYUNK AvE.,PHILADELPHIA,PA.
THE course of the determination of ethylene in gaseous IatNatmospheric mixtures of paraffin and olefin hydrocarbons, separated pressure from cracked oils, inaccuracies may occur in the analysis because absorption in bromine water continues slowly after many passes if the apparatus is exposed to direct daylight or artificial light. To the knowledge of the authors, there is no mention of this phenomenon in standard texts (1, t?,3, 4) on gas analysis. The analyses were made in a modified Bureau of Mines Orsat apparatus. Acid gases and unsaturates, with the exception of ethylene, were absorbed in a 30 per cent caustic potash solution and an 87 per cent sulfuric acid, respectively. Ethylene was then determined by bubbling the gas three times through a Williams pipet containing a 33 per cent saturated solution of bromine water at an approximate 1 Received
November 29, 1930.
the sewage and trade wastes. These ratios vary from 0.016 to 0.151. The nitrogen-oxygen demand ratios for the different wastes seem to be similar only when the carbon-nitrogen ratios are similar. For instance, the nitrogen-B. 0. D. ratio for tannery waste is 0.151 and for raw sewage 0.143, whereas the carbon-nitrogen ratios are 3.96 and 4.0, respectively. The carbon-oxygen demand ratios are 0.59 and 0.55. When we compare corn products waste and raw sewage with carbonnitrogen ratios of 42.7 and 3.96, we find the nitrogen-oxygen demand ratios of 0.016 and 0.143, whereas the carbonoxygen demand ratios are 0.65 and 0.55. The total carbonoxygen demand ratios are not constant because of the variation in the free and combined carbon dioxide. Literature Cited (1) Bauer, O., and Deiss, E., “Sampling and Analysis of Iron and Steel,” p. 131, McGraw-Hill, 1915. (2) Friedemann, T. E., and Rendall, A. I., J . Biol. Chem., 81,45 (1929). (3) Schollenberger, C. J., J. IND. ENG.CHBM.,8, 1126 (1916). (4) White, J. W., and Holben, F. J., I b i d . , 17, 83 (1925).
rate 6f 15 cc. per minute, and subsequently through caustic potash solution to remove the bromine vapors. This should remove the ethylene from most gases, and repeating the operation should remove no more gas. With direct daylight shining on the apparatus, however, absorption continued even after making fifteen passes. By painting the Williams pipet black except for a narrow vertical strip, and shielding the buret from direct light, complete absorption was obtained after three or four passes. The cause of the continuous absorption in the presence of direct light is believed due to the well-known reaction between bromine and the heavier paraffin hydrocarbons. Some evidence in the support of this was obtained by passing a sample of n-butane through the bromine solution in the presence of direct light. Absorption was still taking place after ten passes. Using the shielded pipet no absorption took place. Literature Cited (1) Dennis, L. M., ”Gas Analysis,’’ MacMillan, 1920. (2) “Gas Chemist’s Handbook,” American Gas Assocn., 1922. (3) Parr, S. W., “The Analysis of Fuel, Gas, Water and Lubricants,” McGraw-Hill, 1922. (4) White, A. H., “Technical Gas and Fuel Analysis,” McGraw-Hill, 1920.
