alum gave an oil removal of 94%, the final effluent from the recirculation unit containing 12 p.p.m. oil. The results given in Table I1 were obtained using an APT chamber design for flotation, while the results given in Table I were obtained using a vertical flow chamber. A comparison between the recirculation runs with 10 cubic feet of air input per hour indicate no significant difference, the vertical flow chamber showing removals of 64% and the API chamber removals of 62% for the averages. No correlation between PI-I and oil removal mas indicated in the runs in which air was used without chemicals. As shown in Table I1 the data indicate that the unit will separate considerable more oil than is considered separable as determined by the susceptibility to separation (STS) test B.ATCII T E S T S
For the batch tests using the portable flotation kit the results can be considered qualitative since the air input could not be measured. The principal purpose in presen ting these data is to show that the kit can be used to make exploratory tests to determine the effectiveness of flotation as a method of tieating industrial wastes. In the data s h o m in Table I11 the removals obtained on the tests using the final effluent from an iiPI separator were somewhat lower than those obtained in the continuous flow pilot plant even with the much higher chemical dosage that was used, The best results, using the batch method with chemical addition, were obtained rThen the waste undergoing treatment was primary influent to an AU'I separator. The samples for these tests were taken as the waste was discharged over the influent weir to the separatoi. In this case oil removals of about 85% were indicated. The results of this preliminary investigation of the application of air flotation to refinery waste waters indicate that the flotation process warrants consideration. The pilot plant data show that considerably more oil removal can be obtained in flotation treatment of a separator effluent than is indicated by susceptibility to separation tests, One of the prinripal advantages of the process is the relatively short detention time (15 minutes) required in
the flotation chamber to effect separation. Variations in chemical composition of wastes from different refineries and even within one refinery are proof that there is no such thing as a typical refinery waste, but use can be made of a portable flotation kit, similar to the one described, for survey purposes a t a particular refinery. The results of such surveys n-ill form a basis for further study of pilot plant or prototype operation and design. ACKNQWLEDG3PENT
The author wishes to acknowledge the cooperation of Roy N. Giles, Robert J. Auatin, and George M. Brooks of the Standard Oil Co., Whiting, Ind., in providing facilities for conducting these studies, and in making the analytical determinations. Acknowledgment is made, also, to Leo Schumann, Oliver Tucker, Carlton rind, Weld Conky, and William Throop of the Chain Belt Co., bIilTvaukee, \Vis., who participated in the design of the pilot plant and portable flot,ation equipment', and who assisted in the operation of these units. LITERATURE CITED
( I ) =Ishley, J. H., Wuter & Sewage W o r k s , 97, 297 (19.50). (2) Barry, A. I., Chem. Eng., 58, 107 (1951). (3) D'Arcy, N. A, Jr., Proc. Am. Petroleum Inst., 31M (111) (1951). (4) Easton, P., and Baum, R., T a p p i , 33, 301 (1950). (5) Eliassen, R., and Schulhoff, H. R., Sewage W o r k s J . , 16, 287 (1 944) (6) Farrell, L. S.,Water 6: Sewage Works, 100, 171 (1953). (7) Fisher, A. J., Food Inds., 15, 87 (July 1943). ~
(8) Gaudin, A. bI.,"Flotation," 1 s t ed., New York, McGraw-Hill Book Co., 1932. (9) Gibbs, F. S., Water 6: Sewage Works, 97, 241 (1950). (10) Hansen, C. A , and Gotaas, H. B., Sewage Works J . , 15, 242 (1943). (11) (12) (13) (14)
Hopper, 6 . H., J . Am. Water Works Assoc., 37, 302 (1945). Hopper, S. H., arid McCowen, M. C., Ibid., 44, 719 (1952). Logan, R. P., Sewage W o r k s J . , 21, 799 (1949). Newe, >I., Schmidt, J., and Szniolis, d.,Gaz, Woda i Tech. S a n k (Poland) 25, 176 (June 1961): abstract Sewage and Ind. Wastes, 24, 1203 (1952).
RECEIVED €or review April 16, 1953.
Treatment of Petroc eractivated Slu
ACCEPTEDJuly 3 , 1953
ical
J
E. R. STRONG AND RICHARD HATFIELD Southwest Research Institzhte, Sun Antonio, Xes.
SI"""
3 the summer of 1948, Southwst Research Institute has cooperated with the Celanese Corp. of America in a study of the waste waters discharged by their Chemcel plant a t Bishop, Tex. The plant produces by diiect oxidation of petroleum hydrocarbons such synthetic organic chemicals as acetic acid, acetone, acetaldehyde, formaldehyde, pa1 nformaldehyde, methanol, propanol, butanols, and propylene glycol. As a result of this method of operation, vmtei contaminated by the process is discharged a t a rate of flow of 400 to 700 gallons per minute. This process waste water has an organic fraction which is composed of traces of the compounds produced by Chemcel as well as intermediates and other by-products resulting from side reactions A typical analysis is presented heren ith. At present process waste is being disposed of by solar evaporation i n carefully constructed ponds that cover 375 acres (3). Celanese has studied numerous treatment methods in an effort to find one
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that might require less land and yet be as economical as solar evaporation. I n 1949 they began a pilot plant study to investigate the ability of the trickling filter in treating the process waste water, and Ragan (6) published a progress report on the results obtained. SouthFest Research Institute joined Celanese Corp. of America in the filter study after it was already in progress, first to perform the necessary biochemical analyses and later t o
TYPICAL AXALYSIS biological oxygen demand, ZOO C., p . p . m . Chemical oxygen demand, p . p . m . Immediate oxygen demand Total suspended solids Formaldehyde, p.p.in. Other orgmic compounds
g-%ay
INDUSTRIAL AND ENGINEERING CHEMISTRY
4.5 11,000 30,000
nil
nil 6000
traces
Vol. 46, No. 2
-Petroleum
Wastes-
w h i l e investigating the application of the activated sludge process to a toxic high oxygen-demanding petrochemical waste, it was found that by increasing the returned sludge rate, maintaining an unusually high concentration of suspended solids in the aeration basin, and by using a heavy recirculation rate of treated effluent, B.O.D. could be removed with excellent efficiency at applied loads many times greater than those handled by domestic sewage plants. B.O.D. removal efficiencies were 99 and 80% for loads reaching 183 and 365 pounds per day per 1000 cubic feet of aeration volume, respectively. Because of its apparent extraordinary performance, the modified process was named the “superactivated” sludge process. Further study is needed to completely establish the merits of the process. This paper is a progress report giving laboratory data and the initial results obtained with a pilot plant application.
cooperate in guiding the study. The data indicate that a threestage high rate trickling filter system with an over-all B.O.D. loading of about 1 pound per cubic yard per day (37 pounds per day per 1000 cubic feet) would produce an effluent with a B.O.D. concentration as low as 5 p.p.m. in which the fish could live. However, a plant of this type would be extremely expensive both from the standpoint of capital investment and operating cost. Research to improve the operations of the filter and to find a less expensive method is continuing. Results obtained by Southwest indicated that the process waste water might be treated satisfactorily by catalytic oxidation, but operating costs would be excessively high. When i t appeared that the toxic process waste water could be treated biologically on trickling filters, Southwest began a laboratory study to investigate the potentialities of the activated sludge process. This paper is a progreEs report giving laboratory data and the initial results obtained with a pilot plant activated sludge system.
container utilized with both types of aeration chambers was a 4500-ml. aspirator bottle equipped with a glass stopcock a t the outlet. A one-hole stopper was placed in the top of this bottle with a section of fine capillary tubing extending through it to the bottom of the bottle. The total daily feed volume used in essentially all experiments was approximately 4300 ml. After this volume of liquid was added to the feed chamber, the stopcock wa5
PROCEDURE AND APPARATUS
The experimental work was divided into three phases each requiring a different type of apparatus. First, laboratory batchwise feeding tests Fere conducted to develop a culture of acclimated organisms. Secondly, laboratory continuous feeding tests were made to determine the practicability of the process. Thirdly, pilot plant investigation was begun to obtain design data. Laboratory Batchwise Feeding Tests. The laboratory batchwise feeding tests were conducted in 1-gallon clear glass bottles using small carborundum diffusers as aerators. The volume of reactants waa maintained a t 3 liters. Air rate was maintained constant a t about 1 cubic foot per hour per gallon of mixed liquor. At the beginning of each feeding cycle, the air flow was stopped, and the sludge was allowed to settle. Then, 2 liters of the supernatant were discarded, 2 liters of diluted waste (tap aTater and raw waste) added, and aeration started again. In some cases, the tap water was eliminated from the feed, and only the concentrated waste portion was added following the discarding of a corresponding volume. Laboratory Continuous Feeding Tests.
The two general types
of continuous feeding units used in this study are shown pictorially in Figure 1. One type is shown schematically in Figure 2. Originally, suction flasks were used as aeration chambers and uarborundum diffuser bulbs served as aerators. Whereas these units performed satisfactorily, they demanded considerable attention. Sludge particles tended to plug the exit air and effluent vents. This caused a pressure in the system, and usually its sudden release resulted in a loss of a large portion of the reacting mixture. The glass aeration chambers were replaced with open metal vessels. A perforated metal or saran tube extending lengthwise on one side of the bottom of these vessels served as an aerator. This gave a longitudinal rolling motion to the sludge similar to that obtained in an activated sludge plant. The feed
February 1954
Figure 1. Laboratory Continuously Fed Activated Sludge Units adjusted so that the rate of feeding was approximately three ml. per minute. Once this rate was carefully adjusted it would usually remain unchanged during a 24-hour period which would empty the contents of the feed chamber. The effluent from these aeration units flowed into a bottle or any other open vessel of suitable volume which served as settling basins. The settled sludge was returned to the aeration basin twice a day. In some tests, the raw waste to be fed was combined with a portion of the effluent discharged the previous day in preparing the 4300 ml. of total feed volume. This, in a sense, constituted recirculation. I n other tests, the raw waste to be fed was diluted to 4300 ml. with tap water. Effluent was discarded in the latter case. Applied B.O.D. load was varied by changing the volume of raw waste fed and/or by using different sized aeration vessels. However, essentially all the experiments were performed with 1- or 2liter aeration chambers. During operation, air rate was maintained a t about 1 cubic foot per hour per gallon of mixed liquor. Pilot Plant Aerator. The pilot plant activated sludge plant constructed and operated a t the Celanese Chemcel plant is shown diagrammatically in Figure 3.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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The raw feed tank was fabricated from two 55-gallon diums into which the raw feed and, if necessary, diluent could be pumped daily. The feed was withdrawn through a manually operated valve and fed at a reasonably uniform rate to the aeration chamber.
basin. At that point a constant head weir was used to control the rate of recirculation. Sludge and associated effluent thus recirculated entered the aeration basin in the same gctneral region as the incoming raw waste. Brief f l o ~diagrams of the vaSious types of oontiiiuously fed systems used in laborator), and/or pilot plant study $\re given in Figure 4. Addition of Nutrients. The process waste \vat \\-a*t1c:void of nitrogen and contained a negligible amount of phosphorue. These necessary nutrient constituent's were supplenirnteti i)y the addition of ammonium nitrate and diammonium phosphate in quantities such that, the B.O.D. to nitrogen raiio was 20: I , and the B.O.D. to phosphorus ratio was 7 5 : 1. These a,rnouni!: have been found to be sufficient,, and subsequent work will iriclutie a deterruinatmionof the actual nutrient requirements.
,
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