Waste Sulfite Liquor-Sewage Mixtures ACTIVATED SLUDGE TREATMENT C. N. S-kWYER, University of Wisconsin, Madison, Wis. ASTE sulfite liquor having 10 per cent of dissolved solids normally contains from 3.5 to 5.0 per cent lignin and 2.0 to 3.5 per cent of carbohydrate matter. Because of this high content of organic matter, many methods for the production of more valuable products have been developed or postulated to utilize this source of raw materials. Due to competition from other sources of cheap and more concentrated raw materials, the applications of such developments have not been found economically feasible to any extent in this country. As a result, most of the waste sulfite liquor produced is wasted to the nearest watercourse. Much of the research on the utilization of such liquors has been pursued from the standpoint of improving the economy of the sulfite process, with little consideration given to decreasing the pollutional load. One notable exception has been the work of Howard and his colleagues, who developed a process ( 2 ) for by-product production and removal oi polluting materials. Using standard methods of water analysis ( I ) , early studies on the B. 0. D. removals accomplished by treatment of waste sulfite liquors with the Howard process showed that approximately 85 per cent of the pollutional load was removed. An investigation (at the Wisconsin State Laboratoryof Hygiene, 5 ) on the B. 0. D. of sulfite liquors treated by the Hciward process using a supplemented dilution water as recommended by Lea and Nichols (3, 4), showed that the residual B. 0. D. was many times greater than formerly determined. I confirmed this information by studying the B. 0. D. of corresponding liquors when mixed with domestic sewage. Similar results were obtained in a recent pollution survey a t Green Bay, Wis. ( 6 ) , in which aged river water, supplemented water, and standard dilution water were used. The results of the latter survey indicate that probably not more than 50 per cent of the B. 0. D. of waste sulfite liquor is removed by the Howard process, with 45 per cent removal a more likely figure. Thus, the pollutional load imposed by such wastes is still a problem of some concern. Because of the growing public demand that soinething be done to alleviate the conditions caused by the unrestricted disposal of waste sulfite liquors in the streams and rivers of Wisconsin, the responsible authorities decided to investigate the feasibility of treating such wastes by the standard biological methods of sewage treatment. The author was contacted by L. F. TTarrick of the Wisconsin State Board of Health with respect to making preliminary studies using the activated sludge process. The results of some of these investigations are presented here.
Sources of Materials and Methods Activated sludge used for starting the feeding experiments v a s obtained from the sewage treatment plant a t Madison. Sewage was collected once daily from the main piimping
station and represented a composite of the sewage from the whole city. Waste sulfite liquor treated by the Howard process was obtained from the Marathon Chemical Company. Raw waste sulfite liquor was obtained from the United States Forest Products Laboratory. The feeding experiments were conducted on a fill-and-draw basis in wide-mouthed bottles of 2-gallon capacity. Aeration was provided with diffused air in sufficient quantity to keep the activated sludge in suspension during the aeration period. The decision to work with waste sulfite liquor-sewage mixtures rather than with waste sulfite liquor alone was iduenced by a number of factors, the chief one being the advantage to be gained from the mineral substrate (nitrogen, phosphorus, etc.) which the sewage would provide. Mixtures of sulfite liquor and sewage containing as high as 20 per cent by volume of the waste were used. All sludges fed waste sulfite liquor and sewage were given mixtures containing one per cent of the waste during the first feeding, and the amount was increased one per cent a t each feeding until the desired concentration had been reached. The concentration of activated sludge was maintained near 2000 p. p. m. by wasting measured portions of sludge after every two feedings. Routine chemical analyses ( I ) were performed with the following modifications: ( a ) During the progress of the work it was found necessary in the determination of B. 0. D. t o use dilution water supplemented as recommended by Lea and Nichols (3) in order to get satisfactory results. ( b ) The Winkler method of determining dissolved oxygen was found most suitable on samples which had been incubated for 5 days a t 20" C.
Experiments on Waste Sulfite Liquor Treated by the Howard Process Howard process effluent was selected for the initial experiments rather than raw waste sulfite liquor because it was felt that the former would lend itself to biological treatment much more satisfactorily on account of its reduced content of lignin and lower B. 0. D. The Howard process effluent used had a 5-day B. 0. D. of 11,700 p. p. m. and a pH of 8.0 after adjustment with carbon dioxide neutralization. Sewage mixtures containing from 2 to 10 per cent of the waste were fed to separate portions of activated sludge. The B. 0. D. removals obtained exceeded 94 per cent with all concentrations below 8 per cent. The sludges which were fed mixtures containing in excess of 6 per cent of the waste eventually became too heaiy to be kept in suspension with normal amounts of air. The increased density of the sludges was found to be due to deposition of calcium carbonate in the activated sludge. This was apparently a result of the freeing of calcium ions during the biological oxidation and their precipitation by the carbon dioxide produced concurrently in the medium.
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INDUSTRIAL AND ENGINEERIKG CHEMISTRY
I n order to determine the optimum conditions for removing calcium from the Howard process effluent prior to feeding, a study of its removal by carbon dioxide precipitation was made. The results of this study are shown in Figure 1; P Lo the greatest removal of calZ 15 cium was effected when the p H of the liquor had been 3 10 lowered to about 8.4, and the 9 amount removed probably 9 5 did not exceed 20 per cent of the total amount present. The feeding of waste adPH justed to this optimum p H FIGURE 1. REMOVAL OF value did not minimize the CALCIUMFROM HOWARD difficulties encountered with PROCESSEFFLUENTBY CARBON DIOXIDE PRECIPI- heavy sludges. Complete removal of the calcium from TATION such liquors was accomplished Original calcium content of Howard process effluent, by precipitation with sodium 5.5 grams per liter. carbonate, but because of the prohibitive cost of this treatment from a commercial standpoint, no studies were made on liquors treated in such a manner.
z
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VOL. 32, NO. 11
supplemented dilution water ( 3 ) . The results are given in Figure 3 and show that the use of supplemented dilution water probably gave the more desirable results since the values obtained with i t increased in proportion to the concentration of sulfite liquor in the mixtures. The lower results obtained with the bicarbonate water on the mixtures containing the higher concentrations of sulfite liquor show the influence of some limiting factor. That the limiting factor is related to the lack of mineral elements is definitely shown by these data. Mixtures of sulfite liquor and sewage corresponding to the data shown in Figure 3 were fed to activated sludge and aerated for 22 hours. At the end of that period samples of the effluents were taken and analyzed for their B. 0. D., using bicarbonate and supplemented dilution waters. The results are given in Figure 4 and show that in the feed mixtures containing more than 10 per cent of waste sulfite liquor the effluents produced were so lacking in mineral elements that the residual food materials were only slowly oxidized biologically and low B. 0. D. values were obtained. With the supplemented dilution water, the biological oxidation proceeded unhindered, and much higher results were obtained. The data in these two figures show that the s u p
Feeding Experiments on a Magnesium-Base Waste Sulfite Liquor All waste sulfite liquor was neutralized with lime to p H values between 8 and 9 to allow precipitation and separation of sulfites as calcium sulfite before mixing the waste with sewage prior to feeding. The first supply of waste sulfite liquor obtained from the United States Forest Products Laboratory was a magnesium-base liquor having a &day B. 0. D. of 19,800. Shortly after the feeding of mixtures of this waste and sewage to the activated sludges was started, the sludges receiving more than 2 per cent of the liquor in their diet began to show a tendency to bulk. By the fifth day of the experiment the portions of sludge receiving more than 4 per cent of the waste in their diets settled so poorly that the experiments were discontinued. Settling-rate curves illustrating the bulking properties of the sludges fed on the various diets are shown in Figure 2. Very poor B. 0. D. removals were obtained with all of the bulking sludges.
Experiments on a Calcium-Base Waste Sulfite Liquor
30
10 SETTLING
TIME
40 IN
50
60
MIYUTES
FIGURE 2 . SETTLING CURVESOF ACTIVATEDSLUDGES AFTER 5 DAYSOF FEEDING ON DIETSCOSSISTING OF MIXTURES OF A MAGNESIUM-BASE WASTESULFITE L I Q U O R AND SEWAGE
A 50-gallon supply of a calcium-base waste sulfite liquor plemented dilution water had very little effect on the B. 0. D. was obtained from the United States Forest Products Laboraof sewage alone or mixtures of low concentrations of sulfite tory. The liquor had been used for processing Douglas fir liquor in sewage, but that its use was essential to obtain and had the composition shown in Table I. representative values in the higher concentrations; therefore Mixtures of sewage containing from 2 to 20 per cent of the all B. 0. D. determinations in the following work were obwaste were fed to activated sludge. B. 0. D. determinatained with supplemented dilution water. tions made on these mixtures using bicarbonate dilution Since the results from the B. 0. D. tests indicated that, water did not increase in proportion to the content of sulfite with mixtures of sulfite liquor and sewage containing in liquor in the mixture. This indicated that the content of excess of 6 or 8 per cent of the waste, the rate of biological mineral elements furnished by the sewage was not sufficient oxidation was limited by insufficient mineral elements, i t was in the higher percentage mixtures to satisfy t,he normal biological demands, and lower B. 0. D. values were obtained than would be expected on the basis of the lower concentraT A B L E I. COMPOSITION OF CALCIUM-BASE W.4STE SULFITE LIQUOR USEDIN ACTIVATED SLUDGE tions. I n order to prove this FEEDING EXPERIMEXTS indication, a duplicate set of Raw Neutralized Acidity samples was set up for B. 0. D. Solids, L?O N, p. p . m. Phosphorus B. 0. D., as CaO. p . p. m. Total Volatile NHl Organic Inorganic Organic p. p. m. determinations, one set using PH bicarbonate dilution water and 1.8 5500 6.15 4.52 0.0 42.5 0.0 0.0 12,800 one using Lea and Nichols’
NOVEMBER, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
constituents in the waste was considered. A study of these factors has been made in this laboratory and will be presented in a subsequent paper. With the discovery that only the portions of sludge receiving the lowest concentrations of waste sulfite liquor were capable of removing the majority of the B. 0. D. in a 12-hour aeration period, the sludges were placed on a once-daily feeding schedule. The sludges receiving sulfite liquor in their diets became noticeably heavier as the feeding progressed. The density of the sludges appeared to increase with increasing amounts of waste in the diet. After about 2 weeks of feeding, so much difficulty was encountered in keeping in suspension during the aeration period those sludges receiving more than 10 per cent of the liquor in their diets that they were discarded. The effluents produced from all sludges were highly colored and very little, if any, of the original color was removed. I n spite of this fact, good and uniform B. 0. D. removals were obtained with sulfite liquor concentrations as high as 10 per cent, as shown in Table 11; the removals of B. 0. D. varied from 93 to 95 per cent.
2600
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PER CENT OF W.S.L.
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14
16
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20
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FIGURE 3. FIVE-DAYB. 0. D. OF WASTESULFITE AS DETERMINED BY STANDLIQUOR-SEWAGE MIXTURES ARD METHODS AND BY THE USE OF LEA AND NICHOLS' SUPPLEMENTED DILUTION WATER
An appreciation of the stream pollution problem accompanying the pulping of wood by the acid bisulfite method can best be gained by consideration of a few facts. Approximately 5000 pounds of wood are required to produce 1 ton of paper pulp; thus about 3000 pounds or 60 per cent of the original wood is converted into soluble matter contained in the cooking liquor, and, in most cases, a t the end of the
decided to determine whether this limitation was also important in the rate at which activated sludge removed the B. 0. D. from such mixtures. Consequently, mixtures of sulfite liquor and sewage containing from 2 to 20 per cent of the waste were fed to activated sludges simultaneously. ACTIVATED SLUDGE After 6 hours of aeration the sludges were allowed to settle 30 minutes, and samples of the supernatant liquor were c 2 300 removed for B. 0. D. determinations. Aeration was con3 tinued for another 6 hours, and samples were again taken. c k 250 Samples were also taken in a similar manner a t the end of 24, L L 36, and 48 hours of aeration. The B. 0. D. data obtained 200 during this experiment are shown in Figure 5 . This figure shows that most of the B. 0. D. was removed from the d 150 mixtures containing less than 8 per cent of sulfite liquor 2 100 during the first 6 hours of aeration. With the concentrations 0 of waste above 10 per cent, the amount of B. 0. D. removed 50 during the first 6 hours of aeration was fairly uniform. I n those cases the amount removed during the second 6-hour o - " " ' 0 2 4 6 8 IO 12 14 16 18 20 period was also quite uniform but much less so than during the first period. It should be noted that in those cases where PER CENT OF W.S.L. IN SEWAGE MIXTURE considerable B. 0. D. remained after the first 6-hour aeration, FIGURE4. FIVE-DAYB. 0. D. OF EFFLUENTS FROM the rate a t which the B. 0. D. was removed during succeeding THE ACTIVATEDSLUDGE TREATMENT OF WASTESULperiods became gradually slower and slower. This slowing FITE LIQUOR-SEWAGE MIXTCRES,SHOWING THE Isup of B. 0. D. removal was attributed to certain limiting FLUENCE OF THE NATURE OF THE DILUTION WATERUSED factors which inhibited biological oxidation and was thought to be correlated with the TABLE11. B. 0. D. O F EFFLUENTS FROM THE ACTIVATED SLUDGE TREATXENT O F WASTE SULFITE B. 0. D. information obtained LIQUOR-SEWAGE MIXTURES, AERATED22 HOURS with bicarbonate and suppleW. S. L. in Av.B.0.D.Av.B.O.D. B. 0. D . on Various Days of Feeding Expt.: Sewage of Feed, Removal, mented dilution watersMixture, Yo 2nd 3rd 4th 7tha 14th P. P. RI. 70 namely, the lack of enough 23.0 22.4 430 2 19.5 18.3 18.4 mineral elements to satisfy 44.2 31.5 670 94.4 4 32.0 37.0 37.4 58.5 6 48.4 49.0 48.0 47.3 920 94.5 normal biological requirements. 85.3 8 68.0 68.5 73.0 74.0 1150 93.6 10 86.2 87.0 87.5 125.0 82.0 1400 93.2 I n addition, the possibility of a variation in the ease of oxi16-hour aeration period. dation of the different organic
2
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INDUSTRIAL AND ENGINEERING CHEMISTRY
2800
] 8.0. D. REMOVAL BY DILUTION WITH ACTIVATED SLUD
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FIGURE5. REMOVAL OF B. 0. D. FROM WASTESCLFITE LIQUOR-SEWAGE MIXTURESBY ACTIVATED SLUDGE CONCENTRATIOXS OF 2000 P. P. M.
cooking period the liquor and washings are diverted to some stream or river for ultimate disposal. About 3800 gallons of waste sulfite liquor, containing 10 per cent of dissolved solids and having a B. 0. D. approximately one hundred times greater than domestic sewage, are produced for each ton of sulfite paper pulp manufactured. The conversion of all components of the wood, except cellulose, to soluble substances results in making them especially susceptible to rapid biological assimilation and oxidation. The disposal of such enormous quantities of soluble organic matter into watercourses often results in the depletion of the dissolved oxygen supply, through increased biological oxidation, to levels below those which will support normal aquatic life. Such watercourses become devoid of fish and other desirable life. I n extreme cases the dissolved oxygen supply may be completely exhausted, and anaerobic conditions with accompanying putrefaction will result. The removal of potential B. 0. D.-producing substances from sewage or industrial wastes is accomplished by activated sludge in two major ways. Part of the organic matter is used to maintain normal metabolic functions and thus becomes biologically oxidized to the stable end products of carbon dioxide and water. Part of the energy released in this oxidation allows the utilization of the remaining food material to be used for synthesis of new tissue and for resultant growth. The rapid growth of activated sludge converts large quantities of unoxidized organic matter into a form which can easily be separated from the water; thus the removal of nearly all the polluting material is accomplished while only part of it is actually oxidized. The large amount of sludge produced in the activated sludge process of sewage treatment, as compared to the amount produced in trickling filter treatment, indicates that much less biological oxidation occurs in the activated sludge process to accomplish the same degree of purification.
VOL. 32, NO. 11
There appear to be a t least two possible explanations of why the calcium content of waste sulfite liquor treated by the Howard process cannot be materially reduced by carbon dioxide precipitation. They are: ( a ) Some of the calcium may be tied up in organic complexes which have an ion product less than the solubility product of calcium carbonate. ( b ) Some of the calcium may exist as calcium salts of organic acids; thus, when the calcium is precipitated as calcium carbonate, the organic acid released, in the absence of a buffer, causes the p H to drop to values below which calcium carbonate can form before much precipitation has occurred. Both of these factors are believed to be involved. The development of activated sludges with poor settling characteristics when fed on sewage mixed with sulfite liquor, which contains magnesium instead of calcium, may possibly be due to the inability of the organisms to substitute one element for the other in the synthesis of new tissues; but i t is more likely due to the physiological effects of the high concentrations of the magnesium ion on the orderly routine of the organisms present in the sludge. It has been shown in many ways, besides through logic, that the rate of biological oxidation is a function of the number of organisms which are in a position to utilize the available food supply. Since, a t the beginning of the determination of the 5-day B. 0. D. of wastes or sewages, only a relatively small number of living organisms are present in the presence of large amounts of available food, the first requirement of stabilizing the food material is that large numbers of organisms shall be produced through multiplication of those already present. If insufficient mineral elements are present, the rate a t which new growth can occur is restricted; as a result, less oxygen will be used during the period of incubation than otherwise because of this inhibiting factor. Low oxygen usage by such mixtures is interpreted incorrectly as meaning a low B. 0. D., when in reality the limiting factor is the restricted number of organisms present and the inability of such small numbers to utilize all of the food available in the time allotted. On the basis of the phosphorus and nitrogen requirements obtained with activated sludge treatment of W. S. L. mixtures, i t appears that a ratio of B. 0. D. to nitrogen to phosphorus of 45 to 3 to 1 is desirable; thus, if in a B. 0. D. bottle a depletion of 7 p. p. m. of oxygen can occur, i t would seem that the diluted waste in the bottle should contain 0.47 p. p. m. of ammonia nitrogen and 0.16 p. p. m. of phosphorus for optimum growth. The incorporation of such quantities of each in the dilution water v-ould appear to be part of the answer to the problem. Other elements, no doubt, are necessary and must be present to some extent, as Lea and Kichols (3) showed. On the basis of the data in Figure 5 showing the relative rates of B. 0. D. removal from waste sulfite liquor-sewage mixtures, i t might be concluded that the gradual slowing up in rate of B. 0. D. removal from the mixtures captaining in excess of 10 per cent sulfite liquor was due to a variation in ease of oxidation of the organic substances, with the easily oxidizable matter being removed first and the more difficult later. A study of the data will show the fallacy of such a conclusion. The 20 per cent mixture of sulfite liquor in sewage should contain approximately twice as much easily oxidizable matter as a 10 per cent mixture, and the B. 0. D. removal in 24 hours of aeration of the 20 per cent mixture should be comparable to that obtained in 12 hours of aeration of the 10 per cent mixture. That this was not true is shown by the data, since 83 per cent of the B. 0. D. was removed in 12 hours of aeration of the 10 per cent mixture, while only 64 per cent of the B. 0. D. was removed from the 20 per cent mixture in 24 hours of aeration. These data indicated, as did the B. 0. D. data in Figures 3 and 4, the importance of
INDUSTRIAL A4NDESGINEERIh-G CHEAIISTRY
NOVEMBER, 1940
the mineral substrate in determining the rate of biological oxidation.
Summary 1. Activated sludge treatment of sewage mixtures containing from 1 to 6 per cent of waste sulfite liquor treated by the Howard process resulted in B. 0. D. removals in excess of 94 per cent. Only slight reduction in the color of the waste was noted. JI7hen the sewage mixtures contained in excess of 6 per cent of the neutralized waste, the activated sludges became too heavy to be kept in suspension v i t h normal amounts of air. 2. Attempts to treat sewage mixtures containing a magnesium-base waste sulfite liquor with activated sludge resulted in the development of bulking sludges. 3. The determination of the 5-day B. 0. D. of sewage mixtures containing in excess of 2 per cent of waste sulfite liquor was found to require the use of a dilution water containing considerable quantities of nitrogen, phosphorus, and other mineral elements. The necessity of using such a supplemented dilution water in the determination of the B. 0. D. of effluents produced by activated sludge treatment of such mixtures was also shown. 4. Activated sludge treatment of sewage mixtures containing as much as 10 per cent of a calcium-base waste sulfite liquor gave B. 0. D. removals of 93 to 95 per cent. Very little color removal was accomplished during the aeration
1473
period. m i t h concentrations of sulfite liquor in excess of 10 per cent the activated sludges became too heavy to be kept in suspension during the aeration period. 5. The rate of B. 0. D. removal from waste sulfite liquorsewage mixtures by activated sludge treatment was rapid in the beginning but gradually decreased as the aeration period progressed. The slowing up in rate of B. 0. D. removal was found to be related to a lack of enough mineral elements to maintain normal rates of biological oxidation and metabolism.
Acknowledgment This research project was supported by a grant-in-aid from funds given the University of Wisconsin by the Wisconsin Alumni Research Foundation.
Literature Cited (1) Am. Pub. Health Assoc., Standard Methods of Water Analysis
(1936). (2) Howard, G. C., IND.ENG. CHEM.,22, 1184 (1930); 26, 614 (19x4). ~____,
(3) Lea a n d Xichols, Sewage Works J., 8 , 435 (1936). (4) Ibid., 9 , 34 (1937). ( 5 ) Nichols, RI. S.,Am. J . Pub. Health, 29, 901 (1939). (6) \Tis. State Board Health Rept. on Pollution Survey at Green Bay, \Vis., 1938-39 (1939). PREBESTED before the Division of Water, Sewage. and Sanitation Chemistry at t h e 99th Meeting of t h e -4merican Chemical Society, Cincinnati, Ohio.
K ALBFLEISCH'S ALCHEMIST Artist Unknown
T h e Bushwick Chemical Works of Martin Kalbfleisch's Sons (Charles H., Albert M., and Franklin H.), with their office at 55 Fulton Street, New York, in 1874 used a bill-head a t the upper left of which there appeared a lithographed drawing of the alchemis: which we bring as No. 119 in the Berolzheimer series of Alchemical and Historical Reproductions. ICis not known who made the original drawing, but undoubtedly the artist drew his inspiration from a painting by Teniers, probably No. 2 in the serics. However, he made one radical change in that h r has eliminated the salamander, crocodile, or fish, usually suspended from the ceiling, and has replaced i t by the owl, as the symbol of wisdom.
He may have been the same artist who made the original which was used in engraving the U. S. Internal Revenue "private medicine stamps" used on bottles of Barry's "Tricopherous", 1862-1883. The bill, t o Theo. H. Eaton & Son, is dated "Decem. 26, 1874" and covers: 3 Bbls. Blue S'itriol, 1083 Ibs., g3/& $101.53. The present price of blue vitriol, f . 0 . b. works, is 56 per pound. 50 East 41st Street New York, N. Y .
D. D. BBROLZHBIMBR
A list of the first 96 reproductions appcarcd in our January, 1939, issue, page 124. The list of rcproducrlons 97 to 108 appcarcd in January, 1940, page 134. An additional reproduction a p p c a r ~tach month.
