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A non-Steffen molasses was treated with sufficient barium hydrate to raise the pH from about 7.0 to 9.0. Besides adjusting the pH to the desired value, this treatment removed some of the sulfates present, thus preventing their crystallization on concentration. The viscosity of this molasses was determined a t 50" and 60" C. and over a concentration range from 76 to 80 per cent. The pH was then reduced to 7.2 by means of hydrochloric acid in one portion and sulfur dioxide in another. The viscosity of these two samples was determined over the same range. The results are given in Table IX. Table IX-Effect
of pH on Viscosity of Molasses VISCOSITY
PH 9.0
7 , 2 with HC1 7 . 2 with SOP
76% D. S.O Poises 2.04 2.07 2.08
1.14 9.0 1.15 7 . 2 with HCl 7 . 2 with Son 1.18 D. S. stands for dry substance.
78% D. S. Poises At 50° C. 3.50 3.53 3.55 At 60' C. 1.85 1.89 1.90
80% D. S.
Poises 6.34 6.41 6.50 3.15 3.21 3.27
It is seen that there is an apparent slight increase in the viscosity as the pH is lowered. The effect is small and is practically within the limit of error of the determination. It might well be accounted for by small errors in the determination of the dry substance. Discussion of Results
The viscosity of sirups made from a non-steffenizedmolasses is lower than the viscosity of a pure sugar solution of the same dry substance. This difference increases as the concentration increases and as the temperature decreases. This lowering in viscosity is due to the inorganic impurities present and is partially counteracted by the raffiose, which has a greater effect on viscosity than does sucrose.
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Sirups made from a steffenized molasses, as a rule, are higher in raffinose and lower in ash than are non-Steffen sirups. Consequently their viscosity is somewhat higher, but nevertheless it is lower than that of a pure sugar solution of the same concentration and temperature. Molasses resulting from the barium process for recovering sugar is extremely high in raffiose and correspondingly low in ash. Its viscosity is appreciably higher than that of either of the other types and is also higher than that of a corresponding pure sugar solution. I n general, it can be said that the viscosity increases as the raffinose increases and as the inorganic constituents decrease. The viscosity of saturated solutions at a given temperature increase as the purity of the sirup decreases (Tables I1 and V). This is because the solubility of sugar increases rapidly with decreasing purity. The viscosity of saturated solutions shows a decided minimum at some definite temperature, depending upon the purity of the sirup. Solutions of pure sugar show the minimum a t about 70" C., 75 purity sirups at 55" C., and 60 purity sirups at 45" C. Literature Cited (1) Bingham and Jackson, Bur. Standards, Sci. Paper %98. (2) Brown, "Handbook of Sugar Analysis," p. 310. (3) Brown, Sharp, and Nees, IND. ENG. CHEM.,20, 945 (1928). (4) Burkhardt, Z . Rubenzuckerind., 1874. (5) Fischer, 2. angew. Chem., 84, 153 (1921). (6) Fischer, Chem.-Ztg., 44, 622 (1920). (7) Gibson and Jacobs, J. Chem. Soc., 117, 473 (1920). (8) Green, Ibid., 98, 2023 (1908). (9) Hosking, Phil. Mag., 49, 274 (1900). (10) Kucharenko, Sucr. Belge, 46, 222 (1927); 47, 244 (1928). (11) Kucharenko, Planter Sugar M f r . , May, June, July, 1928. (12) Ladenburg, A n n . Physik, 28, 9 (1907). (13) Orth, Bull. assocn. chim. SUCY. dist., 29, 137 (1912). (14) Paine and Balch, IND.ENG.CHEM.,17, 240 (1926). (15) Powell, J. Chem. Soc., 105, 1 (1914). (16) Roubinck, Z . Zuckerind. Bbhmen, 38, 578 (1914). (17) Sheppard, J. IND.END.CHEM.,9, 523 (1917).
Thermophilic Digestion of Sewage Solids'*' I-Preliminary Paper Willem Rudolfs and H. Heukelekian NEWJERSEY AGRICULTURAL EXPERIMENT STATION, NEW BRUNSWICK, N. J.
HE role and importance of temperature in the digestion of sewage solids has been repeatedly emphasized during recent years. Attention has been called to the advantages of maintaining the temperature of digestion tanks a t approximately 20" C. during the winter months. The optimum temperature for digestion has been found t o be nearer 26-28' C., and higher temperatures up t o 37" C. have not shown further acceleration of the digestion. The bacteria known as thermophilic organisms have an optimum temperature range of 50" to 60" C. The group contains a variety of organisms some of which may grow a t both 37" and 55" C. (facultative thermophiles), while others only a t 55O.C. (obligate thermophiles). The bacteria that have an optimum growth range between 20' and 37' C. will ordinarily not be active a t 50-60" C. but they are not necessarily killed.
T
Presented before the Division of Water, 1 Received May 20, 1929. Sewage, and Sanitation at the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929. *Journal Series Paper of the New Jersey Agricultural Experiment Station, Department of Sewage Disposal.
The effect of high temperatures on the digestion of sewage solids has not been fully investigated. As early as 1875 Popoff (2) measured the rate of gas production from canal mud with temperatures as high as 50-55' C. He found that at the thermophilic range 38-55' C. the rate of gas production was faster than a t 16-22' C. When material incubated a t 50-55" C. was later digested a t 20-25" C., the evolution of gas stopped for 4 days. Coolhaas (1) studied the decomposition of salts of fatty acids and carbohydrates by thermophilic bacteria. At 60' C. a great number of salts of fatty acids were converted to methane and carbon dioxide when inoculated with canal mud. The minimum temperature for the thermophilic decomposition was found to be 45' C. and the maximum 69" C. The organisms were spore-forming types and were not the same as those active a t lower temperatures. Cabbage leaves inoculated with feces and incubated a t 60" C. gave more methane than a t 26" C. Out of 20 grams of dry cabbage leaves, 5.3 liters of methane were produced in 20 days. I n view of these results, it was considered of interest to
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period of initial inactivity a t 45" and 55" C., on the other hand, would indicate a period of biological adjustment in which the organisms typical of sludge digested a t lower temperatures were giving way to thermophilic organisms. Methods Once such a flora was established in the decomposing maFresh solids and ripe sludge were obtained from the Plain- terial, gasification proceeded rapidly and digestion was comfield plant, seeded in a ratio of 1 ripe sludge to 2 of fresh pleted in 18 to 20 days. The slightly more rapid rate of gasisolids on the basis of volatile matter, and digested in con- fication a t 55" C. indicates that the optimum temperature for stant-temperature incubators. Daily gas measurements thermophilic digestion is nearer 55" C. than 45" C. The were made, and solids and ash were determined both a t the yield of gas per gram of volatile matter in the fresh solids a t beginning and a t the end of digestion. The gas was analyzed 37", 45", and 55" C. was 804, 930, and 810 cc., respectively. The pH value of the seeded mixtures was a t no time below for carbon dioxide, oxygen, and combustible gases. p H values were determined during the course of digestion on a 7.1. Odors were a t times very strong. I n another series similar to the one just described] the reset of duplicates. sults reported above were checked. Thermophilic Digestion Experiments SLUDGE PRODUCED UKDER THERMOPHILIC CONDITIONS FOR FRESHSoLIDs-Unseeded fresh solids were incubated a t SEEDING-The above experiments indicated that with the ordinary ripe sludge there 37", 45", and 55" C. for 5 was an initial period of inmonths. Digestion a t 37" activity due to the establishC. was included for the purSewage solids, both seeded and unseeded, have been ment of the proper thermopose of c o m p a r i s o n . A digested at thermophilic temperatures in order to philic flora. It was thought moderate amount of gas was obtain information as to the rate of digestion and to a sludge produced that if produced a t 37" C., but a t the quantity and composition of the gas evolved. under thermophilic condi45" and 55" C. very little It has been shown that the digestion of fresh sewage tions was used for seeding, gas was produced throughsolids at temperatures of 45-55' C. is feasible. The the initial period of retardaout the period of incubation. time required for the digestion of seeded solids at this tion, and thereby the total T h e p H v a l u e of these temperature range is materially shorter than at the time of digestion, could be materials had reached the optimum (28' C.) for lower temperature digestion, m a t e r i a l l y reduced. Acn e u t r a l p o i n t within a provided the seeded sludge has been produced under cordingly, to the sludges obmonth, but still gasification thermophilic conditions. Unseeded solids do not tained from the previous exdid not take place. Within digest rapidly in the thermophilic range. The yield a definite quantity periment a month volatile-matter reof gas per gram of volatile matter is higher with therof fresh solids was added ductions of 21 and 10 per mophilic digestion, probably because of a greater (1:2 on basis of v o l a t i l e cent were obtained for the destruction of organic matter. The composition of m a t t e r ) and the mixtures materials incubated a t 45" the gas was 70 per cent combustible and 22 per cent were reincubated a t t h e a n d 5 5 " C., respectively. carbon dioxide, which corresponds to the gas compositemperature a t which the This reduction might be attion produced at lower temperatures. sludges were produced. t r i b u t e d to liquefaction. The rate of gas evolution Since there was no advanper gram of raw volatile tage to be derived from the incubation of fresh solids a t such high temperatures, attention matter per day is given in Figure 2. T i e materials incubated a t 37.5" C. had not gasified to any extent during the 19 days of was directed to the digestion of the seeded mixtures. FRESH SOLIDSAND RIPE SLUDGE-The rates Of gas produc- digestion. The large amount of gas recorded for the first day tion from the decomposition of seeded mixtures a t the three is due to the expansion of the air in the bottles and expansion temperatures indicated above are presented in Figure 1. At of the gas already entrained in the sludge. Apparently 37" C. gas evolution extended more or less uniformily over a 37" C. is above the optimum for the lower range of digestion period of 3 weeks, after which it decreased. At 45" C. gas temperature and not high enough for the thermophilic range. was evolved a t a very slow rate for 2 weeks, after which it Digestion a t both 45" and 55" C. was completed within 18-19 increased rapidly, reaching a peak within 22 days and drop- days, although gasification reached the peak 3 days earlier in ping to a low value again within 34 days. Incubation a t the mixture incubated a t 55" C. The initial period of re55" C. gave similar results as a t 45" C., except that the process tardation was reduced from 15 days to 5 days by the use of was hastened a few days. sludge produced under thermophilic conditions. The total The protracted gas evolution a t 37" C. would indicate that time of digestion was reduced similarly from 30-34 days to this temperature was beyond the optimum for non-thermo- 18-19 days. The reduction of volatile matter of the fresh solids a t 37", philic digestion and not high enough for the thermophilic range-hence its intermediate character. The prolonged 45", and 55" C. was 36.0, 51.5, and 58.0 per cent, respectively. digest sewage solids a t the thermophilic range and to obtain information as to the rate of digestion and the quantity and composition of the gas evolved.
450
INCUBATIOK
Day~ 7 8 9 11 13 20
Total
c.
50' C.
cot
CHI
%
CC.5
%
CC."
20:2 23.1 20.6 22.3 17.3
75.0 16.0 36.4 32.0 35.3
65:O 69.0
l8b:O 48.0 129.0 100.0 151.0
...
-_
194.7
Per gram volatile matter.
73.2 70.4 76.5
550
COa
__
613.0
CH4
%
cc.a
..
.. .. ..
..
24: 7 26.6 14.1
...
64.0 33.8 50.5
--
148.3
%
.. .. 66:7 67.9 81.0
c.
COa
cc.5
%
l72:O 86.0 290.0
27.2 23.4 23.0 19.7 22.2 16.3
... ...
__
548.0
CHI CC.0 79.0 15.2 15.3 26.0 20.7 35.4
191.6
% 61.4 66.0 70.0 64.7 69.5 82.5
CC.5 178.0 42.0 46.7 86.0
65.0 181.0
_-
597.7
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These figures give further proof that a t the termination of the experiment (19 days) the digestion at 37" C. was not complete while at 45" and 55" C. substantially greater reduction of volatile matter had taken place.
in this series, since no seed material produced at this particular temperature was available. The time required for complete digestion was the same as for the two other mixtures, although the peak of gas production came somewhat later. SEEDING WITH SLUDGE SUBJECTED TO SECOND THERMO- These results indicate that there is no well-defined optimum PHILIC DIGEsTIoN-8ince the subjection of ordinary sludge point of digestion a t the thermophilic range, but rather a to digestion under thermophilic conditions improved its range of 10" C. between 45" and 55" C. There are indiseeding value, i t seemed that a further improvement might be vidual characteristics a t the various temperatures, but the obtained by a second passage. It was thought that an en- total time of digestion is not materially affected. The differrichment of the numbers of the thermophilic organisms and ences in the type of digestion might be caused by the types of intensification of their activities might be induced by using organisms active a t the different temperatures. It is further the same sludge in digesting successively several different probable that the retardation observed a t 50" C. was caused batches of fresh solids under thermophilic conditions. b s the difference in the temDerature a t which the seed sludge w& produced and at which-the new mixture was incubateud. The yield of gas per gram of volatile matter in the fresh solids is generally higher in the thermophilic range than a t the non-thermophilic range, as will be seen from the figures given below: Temperature, C. Gas, cc. per gram raw volatile matter
cw7
Figure I-Gas
Production from Sewage Solids a t Different Temperatures
Accordingly, the sludges from the previous experiment were used for seeding a new batch of fresh solids. The sludge produced a t 45" C. was mixed with fresh solids and reincubated at 45" C. The one produced a t 55" C. was mixed similarly; half of it reincubated a t 55" C., the remainder a t 50" C. It was considered of interest to include the digestion at 50" C. in order to determine more accurately the optimum temperature within the thermophilic range. The digestion of 60" C. was omitted because it was considered to be beyond the optimum range.
20-30 45 50 55 550 877 750 850
The somewhat lower yield at 50" C. might be explained in the light of the suppositions made above. The carbon dioxide and combustible gases produced during the active period of gasification are given in Table I. The percentage of carbon dioxide was high (26 to 27 per cent) in the beginning and decreased gradually to about 15 per cent. Combustible gases, on the other hand, were comparatively low (60 to 65 per cent) in the beginning and increased to 75-80 per cent towards the end of digestion. The average percentages were practically constant-namely, 22.2 to 22.3 per cent for carbon dioxide, and 70.0 to 70.5 per cent for combustible gases. The percentage nitrogen, as determined by difference, was 7.2 to 7.8 per cent. There are, therefore, no differences in the composition of gas produced a t the different temperatures. The relationship noted above as to the decrease of carbon dioxide and increase of methane with the progress of digestion is identically the same as in the digestion a t lower temperatures. The average composition of the gas produced a t thermophilic range is also comparable with that a t lower temperatures. Discussion
It has been shown that the digestion of fresh sewage solids a t higher temperatures (45-55" C.) is feasible if certain conditions are fulfilled. In the f i s t place, it is best to start
mrs
Figure 2-Gas Production from Sewage Solids Inoculated with Material Produced under Thermophilic Conditions
I n Figure 3 are represented the daily gas-production values from materials incubated a t 45" and 55" C. The digestion of the mixtures seeded with sludge that had been subjected to thermophilic digestion a second time did not proceed faster than when the sludge has been digested once under thermophilic conditions. The digestion was completed in 19 or 20 days, as in the previous series. The initial lag period was not reduced beyond 5 days. At 45" C. the peak was attained in 11 days, whereas a t 55" C. it was more suppressed and prolonged. The highest gas production in any given day was 95 CC. per gram volatile matter. The gas-production curve for the material incubated a t 50" C. is not directly comparable
Figure 3-Gas Production from Sewage Sludge Reseeded with Material under Thermophilic Conditions
wherever possible with ripe sludge produced under ordinary temperatures, because fresh solids alone digest slowly, even a t high temperatures. It has been further shown that a "thermophilic" sludge is better for seeding than a sludge produced at lower temperatures. With a sludge produced under thermophilic conditions the total digestion time is 18 to 20 days. Within this period about 50 per cent reduction of
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volatile matter takes place with a higher yield of gas than would be obtained a t lower temperatures. The composition of the gas is not materially changed a t the higher temperatures. At about 28” C., which is considered to be the approximate optimum for lower temperature digestion, the time required to complete the digestion processes from a practical standpoint is about 30 days. If gas production is taken as an index and when it is considered that for practical purposes from 80 to 85 per cent of the gas is given off within 25 or 26 days so that a longer digestion period would be uneconomical, this number of days might also be used for comparison with the number required a t higher temperatures. The time required for complete digestion a t 45-55’ C. is from 18 to 20 days, whereas the time required for a gas production of 85 per cent of the total would under these conditions be from 14 to 15 days. The reduction in time is therefore considerable, but whether such a reduction would be economical depends upon several factors and local conditions. For instance, if in the neighborhood of a sewage plant factories are present which have an ample supply of exhaust steam which can be utilized a t practically no cost, the temperature of rather concentrated sludge could very well be raised. It should be kept in mind, however, that when the time of digestion is decreased an increase in the intensity of odors can be expected, because the same amounts of odor-producing substances must be decomposed in this shorter time. This necessitates, even more than under ordinary circumstances, adequate means of collecting and burning the gases. It might be expected that the heat loss from tanks operating
a t the higher temperature per unit of time and per unit of exposed surface is larger than from tanks operated a t lower temperatures. There are, however, two main factors which govern the economy of digestion in general-insulation of tanks and size of tanks. Insulation of digestion tanks is a problem for engineers which will be solved eventually, but if the insulation of low- and high-temperature digestion tanks is the same, the size of the tanks required for hightemperature digestion is materially less than for low-temperature digestion, because the digestion time a t 28” C. is a t least 30 days and a t 45-55’ C. about 15 days. This means that the size of the tanks can be cut in half while the total amount of gas produced is the same. Thus, even if the radiation is greater and the temperature required higher, sufficient gas is available to take care of these conditions. A more complete discussion of the digestion capacity required and economy of high-temperature digestion will be presented in a paper dealing with the digestion of daily additions of fresh solids. The early work of Popoff (.2) has been checked. The results are also in conformity with Coolhaas’ statement (1) that 45” C. is the minimum for thermophilic digestion, but his maximum temperature of 69” C. has been found too high. The yield of gas in 20 days per gram of dry cabbage leaves is reported to be 265 cc. Sewage solids are a much richer source of gas than material like cabbage leaves.
A Chemical Dictionary.
The author admits the possibility of errors of fact, omissions, etc. One such noted was the formation of chlorobutyrone by distilling butyrone with phosphoric anhydride. In spite of the above criticisms, the author has produced a book which represents many laborious hours of searching the literature and many more in attempting to re-state and re-define in simple modern terms the phenomena of science. The work will prove of invaluable assistance t o many students and scientific workers 3s a source of definitions of many obscure terms and many of the modern terms which have come into more or less general use without having been clearly defined, or, if defined, in a place not easily located. The author is t o be congratulated on the results of his labors and it is t o be hoped that all who use the book will cooperate with him in making i t possible to correct errors of fact, omissions, etc., in a future edition.-C. J. WEST
Containing the words generally used in chemistry and many of the terms used in the related sciences of physics, astrophysics, mineralogy, pharmacy, and biology with their pronunciation based on recent chemical literature. W. D. HACKH.790 pages. 100 tables. 232 illusBY INGO trations, P. Blakiston’s Son & Co., Inc., Philadelphia, 1929. Price, $10.00.
The scope of this work is defined by the author as follows: A chemical dictionary should state clearly and precisely the theories, laws, and rules; describe accurately the elements, compounds, minerals, drugs, vegetable and animal products; list concisely the important reactions, processes, and methods; mention briefly the chemical apparatus, equipment, and instruments; and, finally, should note the names of the investigators who have built up the science. As chemistry reaches into nearly every branch of human endeavor it should not forget to bring in the collateral vocabulary of physics, astrophysics, geology, minetalogy, botany, zoblogy, medicine, and pharmacy and, also, the pertinent jargon ofindustry, mining, and commerce.
Only continued use of the book will enable one t o decide how well the author has carried out this series of postulates. The author also states t h a t the terminology of Chemical Abstracts was taken as standard; yet we notice almost consistent use of such words as “chlorbenzene,” “iodaniline,” etc. ; and the abbreviation a for asymmetric, s for symmetric, and rfor racemic; the symbols for ortho, meta, and para are given as roman instead of italic letters. etc. It is unfortunate that this work, published in America, should not have adopted throughout the usage of Chemical Abstracts, which is being more and more recognized as the standard for chemical nomenclature. It seems t o the reviewer that the author has misunderstood the meaning of certain radicals; for example, he states that chlorobutyryl is the same as butyryl chloride : strictly speaking, chlorobutyryl should be the radical CH CH CH CO, containing a C1 in place of one of the H atoms. The same mistake is made with chlorocinnamoyl. One interesting feature of the work is the pronunciation of the words defined. While it may seem that this is carried to the extreme, in that such words as “fuel,” “fruit,” etc., have their pronunciations indicated, yet this will be of great value for the large number of words which always prove a stumbling block for the beginning student in chemistry, as well as for some of u s who are supposed to be well versed in the subject.
Literature Cited (1) Coolhaas, Cenlr. Bakt , Parasitenk., II Ab:., 75, 161 (1928). (2) Popoff, Arch ges. Physiol. (Pfluger’s),10, 113 (1876).
Sparking of Steel. B Y E. PITOIS. Translated and enlarged by JOHN D. GAT 89 pages. Chemical Publishing Co., Easton, Pa., 1929. Price, $2.00. The translation consists of two chapters and three appendixes. Chapter I sets forth the applications and technic of the art. It contains drawings and descriptions of the author’s apparatus for producing sparks under constant grinding pressure. Chapter I1 is devoted to verbal and photographic illustrations of the characteristic spark streams of carbon steels of varying degrees of hardness, cast irons, and alloy steels. In each plate is an insert freehand drawing by the author of typical sparks, or “bursts” as he terms them, several times magnified. Each kind of spark stream is vividly described, and the author frequently rises to poetic flights of imagery that are as scintillating as these fireflies of steel and emery. Appendix I gives the author’s method of spark photography. Appendix I1 shows phctcgraphs of incrustations formed by the impinging of spark-stream fragments on photographic plates. Appendix I11 treats of spark streams fcrmed in gases other than air The translator supplies Appendix IV, on “Spark Testing as It I s Conducted in the United States,” crediting his data to John A. Houtz. There are 24 pages of thoroughly practical details for grading steel by sparking. A portable grinder weighingonly 8 pounds, which is especially valuable in scrap classification, is illustrated. This novel book is cordially recommended to those interested in sparking.-CHARLES MORRISJOHNSON
