INDUSTRIAL A N D ENGINEERING CHEMISTRY
48
Since the observations indicate that the alcohol holds its acid tightly in the case of the methyl ester, that the glycol ester goes over to a mono-acid ester, and that the glycerol I O D I N E NUMBER C U R V E S FOR O X I D A T I O N OB B E T A - E L E O S T E A R I C ACID AND O F S E V E R A L O F I T S E S T E R S AT BZ'C
ACID
i TIME-HOURS
Figure 4
radical of the eleostearin decomposes (total acids rise from 91 to 97.5 per cent), it may be postulated that an important function of the alcohol valency is in determining the stability of the ester and preventing the @-eleostearicacid, with its long chain and ethenoid linkages, from condensing a t open bonds, which condensation is highly favorable to polymerization and colloidal aggregation. Even if the beta acid so released does not condense a t open bonds, these free, long chains would mesh with the ester polymers and, since
Vol. 20, No. 1
the acid is solid a t normal temperatures, would be of great assistance in gel formation, Under this hypothesis the oxidized methyl ester may be pictured with its condensation polymer having only the simpler acids condensed a t its open bonds and its quatre-polymer being more compact and regular than if these condensed acids had longer chains. The oxidized glycol ester may be visualized as the mono-acid ester with beta-acid chains condensed here and there a t its open bonds and a t the open bonds of the condensed acids, making possible a system composed of numerous highly complex polymers. Even though it is assumed that oxidized beta acid does not form condensation polymers, it may be pictured as giving rise to a gel by intermingling of the straight chains with oxidized and polymerized molecules which have changed in shape and size. The oxidized glycerol ester may be pictured as splitting off beta acid with subsequent decomposition of a portion of the glycerol as well as notable condensation of the beta acid at open bonds (hydroxyl rises from 3.75 to 7.21 per cent on liberation of total acids and 1.28 per cent water is given off during processing) Inasmuch as the condensation polymers of these long beta-acid chains are still linked to a considerable extent to glycerol radicals, a condition exists most favorable to polymer building and aggregation, thus precluding thoroughness of oxidation. I n brief, the end products of the esters and acids studied may be visualized, in the light of this work, as being tangles of long carbon chains deformed by oxidation and condensation. Acknowledgment The authors express their thanks to the Armstrong Cork Company for permission to publish the results of this investigation.
Odors and Sewage Sludge Digestion' I-Effect
of Sea Water on Hydrogen Sulfide Production2 Willem Rudolfs and P. J. A. Zeller AQRICULTURAL EXPERIMENT STATION, NEWBRUNSWICK, N. J.
EWAGE plants in the proximity of the seaboard
S
often produce strong hydrogen sulfide odors which are apparently due to unfiltered sea water. Sewage led directly into the sea produces also considerable odor a t the places of contact with sea water. Sometimes with high tides sea water backs into sewage-disposal plants located a considerable distance inland and has been reported to affect the digestion processes. Two types of materials may be involved, sulfates and sodium chloride. A number of treatment plants in the country receive comparatively large quantities of sulfates discharged by manufacturing processes and others are affected by salt water from mines or brine from industries. The studies reported in this paper were designed to throw light upon the following points: (1) Effect of the presence in sea water of sulfates (Ca and Mg), sodium chloride, and a combination of the two upon the rate of sludge digestion. 1 Presented before the Division of Water, Sewage, and Sanitation Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 9 Paper No. 365 of the Journal Series of the New Jersey Agricultural Experiment Stations, Department of Sewage Disposal.
( 2 ) Effect upon gas production caused by a possible retardation of the rate of digestion. ( 3 ) Effect upon the composition of the gas. (4) Relation between sulfate reduction and quantity of hydrogen sulfide present in the gas.
Experimental Procedure
Ripe sludge and fresh solids were mixed on the basis of dry volatile matter in the proportion of 1:l.Z. Analyses of fresh solids, ripe sludge, and sea water used are given in Table I. Table I-Analysis MATERIAL Ripesludge Fresh solids Sea water
of Material Used
PH
SOLIDS
ASH
7.5 5.7 8.0
7% 6.39, 6.14 2.74
21.3 78.4
7% 48.2
ALKACHLORIDES SULFATES LINITY P.p.m. P.p.m.P.p.m. 144 5200 129 770 116 48 1985 900 13,050
To these mixtures different quantities of sea water were added and the resultant mixtures analyzed (Table 11). All mixtures were brought to the same volume by addition of distilled water, and incubated at 20-22' C. Gas production was recorded daily and all the gas analyzed at intervals after being collected and stored over gas-saturated water. The mixtures were analyzed again after 44 days' incubation.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
January, 1928
of Mixtures at Beginning a n d End of Experiment SEA WATER CHLO- SUL- ALKAIN PH SOLIDSASH RIDES BATES LINITY B.O.D. SLUDGE % 70 P . p . m . P . p . m . P . p . m . P . p . m . Cc./L.
Table 11-Analyses MIXTURE
A
B C
D
BBOINNING
7.4 7.5 7.5 7.5
2 62 2.81 3.27 3.96
36.0 36.8 44.8 50.0
58 796 3635 7000
7.5 7 5 7.5 7.7
1.96 2.17 2.68 3.37
45.3 46.5 51.8 57.5
57 710 3410 6710
61 155 550 1020
1480 1420 1465 1520
2240 2000 1990 1870
1000
3.3 18.1 21.4
2805 2920 3280 3740
705 660 fi40
100 500
~..-14 8
0 100
500
*Ll"
A
B
C
D
(60
0
A
c D
No addition 500 cc. sea water 1000 cc. sea water
VOLATILE G i s PER MATTER GRAMVOLATILE REDUCTION MATTER 70 CC. 29 8 438 28 3 466 27 8 498
The percentage volatile-matter reduction of the treated mixtures was but slightly less than in the untreated mixture. This indicates some retardation of the digestion processes, but it is more definitely shown by the curves for daily gas production (Figure l ) , since the initial retardation has been overcome after the more prolonged period of digestion. I n the untreated material the peak of gas production occurred after 10 or 12 days, whereas with a medium amount of sea water this peak occurred after 17 days and with the largest amount of sea water after 18 days. Gas production from the untreated mixture increased rapidly from the beginning of incubation and was followed by a rapid decrease. The mixture receiving a medium amount of sea water started off with a higher gas production than the untreated mixture, followed during the first few days by a decrease and thereafter by a similar rise and fall as in the untreated mixture. The mixture with the largest quantity of sea water produced a still greater amount of gas during the first few days, but the peak comparable with those of the other mixtures was decidedly lower. The total quantities of gas produced from the different mixtures differed with the amounts of sea water added. However, the percentage methane in the gas was lowest from the mixture with the largest quantity of sea water (Figure 1). Effect of Chlorides
From a series of experiments with sodium chloride additions to ripe sludge-fresh solids mixtures the results of two mixtures are plotted in Figure 2 as an illustration of the retardation of digestion processes attributable to chloride. The mixtures were similar to those to which sea water was added and different quantities of sodium chloride were introduced. The two mixtures used for illustration received, respectively, nothing and 10 grams of sodium chloride per liter sludge mixture. Determinations and analyses were made a t weekly intervals. Although the retardation caused by the sodium chloride is not great, it was persistent and checks the slight retardation caused by sea water. It would seem, therefore, that the effect of sodium chloride and sea water on digestion is comparatively insignificant, provided sufficient ripe sludge is present to take care of the fresh solids-added. Sierp3 1
Tech. Gcmcindcblutt, 29 (1926-7).
concluded that only comparatively high salt concentration affects the rate of organic matter decomposition, and that small quantities of sulfates are not detrimental but larger quantities (1.07 grams per liter sludge as compared with 1.02 grams per liter in our mixture) were harmful. Purvis4 concludes that sludge decomposes very slowly when mixed with sea water, Although the writers' experiments indicate that retardation of decomposition occurs, it does not appear to be "very slow" with the comparatively large quantities of sea water added.
1000
The analyses a t the end of the experiment (Table 11) show that in every case digestion had progressed to the extent that the mixture could be pronounced as ripe sludge. Sludge could have been drawn earlier from A , C, and D, as indicated by the rate of gas production (Figure 1). There was no appreciable difference between the mixture with the smallest quantity of sea water and that which received no sea water. The percentage volatile-matter reduction and total amounts of gas produced after 44 days were as follows: MIXTURE
49
Hydrogen Sulfide Production
The amounts of sulfates added to the different mixtures varied from 5 to 48 mg. per gram volatile matter. All these sulfates disappeared in the course of digestion in addition to more than half the sulfates present in the original material (Table 111). The total amounts of hydrogen sulfide per liter sludge
36
10
z+
60
I2
50
DAYS 6 12 I8 24 30 36 4Z Figure 1-Daily Gas Production, Percentage M e t h a n e , a n d A m o u n t s of Hydrogen Sulfide in Different Mixtures
varied from 9.2 to 373 cc. according to the amounts of sulfates added. The mixtures receiving about 5 mg. sulfates per gram volatile matter produced the same amount of hydrogen sulfide in the gas per liter of sludge and the same quantity per gram volatile matter destroyed as the mixture without sulfate addition, owing to the fact that some hydrogen sulfide remains in solution in the liquid. Hydrogen sulfide in the gas varied from 0.08 to 4.83 per cent. None of the mixtures produced hydrogen sulfide in the gas during the first 14 days of incubation, although it was present in the liquid (Figure 1). Most of the hydrogen sulfide in the gas occurred during, and especially after, the peak of gasification had been reached. During the same periods of digestion nitrogenous matter is most actively decomposed. Although the percentage of hydrogen sulfide was comparatively small, odors were very strong. The percentage of hydrogen sulfide in the total gas pro4
Surreyor. 96, 277 (1926).
Vol. 20, No. 1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
50 SULFATE MIXTURE
Beginning
A
B C
D
1
SULFUR FROM SULFATE
HYDROGEN SULFIDE PRODUCED HzS O F TOTAL
PER G R A M DRY VOLATILE MATTER
Mg. 3.63 8.73 30.4 51.5
End
Beginning
Mg.
Mg.
1.37 0.28 1.40 1.50
1.21 2.91 10.13 17.17
Per liter sludge
End
Mg.
0.46 0.09
0.47
0.50
Mg. 0.38 0.38 2.93 15.53
duced from the mixtures with 500- and 1000-cc. additions of sea water was above the lethal dose; in fact, themixture with the largest quantity of added sulfates produced gas with hydrogen sulfide concentration of several times the lethal dose. The percentage sulfur of the total amounts of sulfates present in the original mixture recovered in the hydrogen sulfide of the gas produced varied from 0.65 to 5.62 (Table 111). The question arises as to what became of the rest of the sulfur since practically all the sulfates were destroyed. Part of it was present as hydrogen sulfide in solution in the mixtures, but more of it sublimated or precipitated out as elementary sulfur, forming a yellowish coat on the inside of the bottles. The same phenomenon has been observed in other experiments and a similar yellowish-white coating may be observed on plant and aquatic life in salt marshes subject to tides.' I n a sewage plant where the gases are not confined
Per gram volatile matter destroyed
cc.4
9.2 9.2 70.0 373,O
cc.
p
1
1.53 1.50 13.6 67 8
~
~
l
~ GAS ~ m
SULFUR
RECOVERED IN Has
cc.
%
%
25.1 6.96 24.7 66.5
0.12 0.08
2.86 0.65
0.83 4.83
1.58
5.62
sulfates were added, although at the end of the experiment no sulfates were present in the liquid. He concludes that, although all sulfates were destroyed, no hydrogen sulfide formed under strictly anaerobic conditions, but only when the sludge received sufficient air-via., H2S-formingbacteria are stimulated and the activities of H2S-oxidizing bacteria retarded. The experiments conducted by the writers were under anaerobic cond i t i o n s , no air was allowed t o enter the bottles for the duration of the experi400 ment', and hydrogen 40 sulfide was found not only in the liquid but 300 also in the gas pro- 30 duced. Summary
200
20
The digestion proc,o esses in ripe sludge100 fresh solids mixtures treated with sea water and sodium chloride A B C D were slightly retarded. The total quantities Figure 3-Sulfates Added a n d Hydrogen of gas produced from Sulfide Produced in Different Mixtures Sea water added: A = 0, B 250 cc., t h e d i f f e r e n t mixC = 500 cc., D = 1000 cc. tures varied with the amounts of sea water added, but the percentage methane was lowest in the gas produced from the mixtures with the largest amounts of added sea water. Practically all the sulfates added disappeared from the mixtures, but only from 0.65 to 5.62 per cent of the sulfur added in the form of sulfates was recovered in the gas as hydrogen sulfide. Hydrogen sulfide production was greatest during and after the peak of gasification had been reached. A large percentage of the sulfur of the sulfate added was changed to elementary sulfur.
-
Figure 2-Percentage Volatile Matter Reduction a n d A s h Increase of Mixtures Receiving S o d i u m Chloride
this sulfur precipitates against walls, goes off into the air, and some of it is carried out with the effluent. A thorough discussion of the sulfur cycle in sewage, including the effect of a variety of sulfates on digestion, hydrogen sulfide production, mercaptans, and other intermediate products will be published later. The relation between sulfates and hydrogen sulfide production, together with the percentage sulfur recovered in the gas, is shown graphically in Figure 3. It can be seen that the relation is direct as soon as more than 5 mg. sulfates per gram volatile matter are added. Sierpa was unable to find any hydrogen sulfide in the gas produced by mixtures of ripe sludge and fresh solids to which 5
Rudolfa, Pioc.
N. J .
M o S Q U i f O Exterminolion
Assocn., 1925.
The Siberian Chemical Industry Reports from the Chemical Division of the Department of Commerce indicate that lack of important consuming outlets has probably checked development of the Siberian chemical industry. Production is confined principally to basic products. Production of alkalies is little developed. There are two coal-tar plants, and ample raw material is available for a large wood chemical industry but a t present it is not of much importance. The tanning industry produces all kinds of leather, with glue as a by-product. Production of matches is concentrated in four plants. The fats industry makes vegetable oils from flax, hemp, cedar nut, etc. The soap-making plants represent the highest developed branch of the Siberian chemical industry. The silicate industries include cement plants, glass factories, a porcelain factory, and a number of small pottery plants. Some of the breweries and distilleries also produce acetic acid. The pharmaceutical industry is represented by a number of plants and laboratories. The radio-active ores are being worked in Turkestan.
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