INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
612
Vol. 42, No. 4
CONCLUSION
VI!.
Data Relative to Operation and Maintenance of a Refinery's Sewerage System" (Oil separation facilities and slop oil treatment equipment) Slop oil handled % of crude oil charge 2.00 Waste water trebted, gal. per barrel of crude oil charge 260 Sources of slop oil handled 29.5 Tank cleaning8 and bottoms, %, 44.0 Tank drawoffs t o the sewers, % Miscellaneous known sources drawn t o sewera, % 19.7 Miscellaneous unknown sources escaping to sewers, % 6.8 Distribution of operation and maintenance costs Operation labor, % 43.2 Maintenance and repair (labor and materials), % 20.0 Utilities, 9% 11.6 2.5, a Overhead and depreciation, 7; a All data are based on t h e 1945 annual average. The costs of waste treatment research, development, and process engineering equaled 37.0% of the total of the operating department's budget.
Table
ferent pilot plant investigations Imve bcwi carried on from 1!1-10 t u date, t,he current investigations are providing the most interesting and the most promising results. Typicai data from the operation of duplicate, single-stage, 6-inch di:amcter., &foot deep filters Iieing doused at. a rate of 15 million gallons pt:r a,cre per clay and bciiig followed by 2 hours' sediinent,atioii, are shown in Tahle 1'1. Plant wvastes from a fluid catnlyat cracking unit are being used :is t h e feed stock. Although no nutrient materials are being added, file efficiencies obtained are comp:ii.al)lc with those From sewagetreatment filters. It is interesting to note that the oil removnl .efficiencies are of the same order of magnitude as those for B.O.D. T o this date, there is no indioat,ion that oil contents up to and including 100 p.p.m. will iiavc any rctariling effect on B.O.D. removal. There is evidenrc that the prcsence of sulfides d l reduce R .O.D. efficiencies. Data obtained to datc show t1i:it :L significant part' of tlie oil feed t,o the filter is not osidieed. Tlie sludge accumulating in the effluent settling t,ank contains oil equivalent to about 31 7 0 of the oil-free solids content.. The data of Table V I indica hat the biological filter may have practical application as a tlcvice for improving thc qualit'y or refinery effluents.
Data relativc to the operation and maintenance ol a refinery's sewerage system, oil separation facilities, and slop oil treatment equipment are shown in Table VII. This table shows thc quantity and sources of slop oil that are handled and the relative costs of operating and maintaining the system. Operating personnel arc on duty around the clock every day of the year. They operate 8 separators draining directly to the Schuylkill River and 3 separators draining t,o plant sev,Ters. They also operate the slop oil treatment facilities, maintain the sewerage system, and keep abreast of activities in the rcfinery that may influence waste wvatcr quality. The foregoing discussions have dwelt on the problem of oil removal from refinery wast,es but have inferred that otlier problems of pollution abatement may esist. Ot,her problems do esist and in some cases may be of n greater magnitude and may bc more difficult and costly to solve than those of oil removal. However, tlie ot'her problems are generally susceptible to local solution, and so the satisfact,ory removal of oil from general plant effluents will continue t o be the industry's major pollution abatement prohlcni for some time to come. Oil removal is becoming more rlifficult continuously as new processes conducive to the formation of emulsions and nonseparnl)le suspensions continue t o be irist~nllrtlinside the refinery fenoc.. LITERATURE
CITED
(1) C a m p , T. R.. Pioc. Am. Soc. Civil Ilingrs., 71, S o . 4, 445-86 (1945). (2) Hart, SV. B., Sewuye W o r k s J . , 17, No. 2, 307-19, (1945). (3) W e s t o n , R. F., Proc. Ind. Waste Utilizetion Conj., P u d u e Unia., 1, 98-425 (1944). (4) V e s t o n , R. I?., ancl Hart, IT'. B., Water Works & S e w e m y e , 88, 208-17 (1941). (5) W e s t o n , R. F., M e r m a n , R. G., a n d D e M a n n , J. G., Proc. Arm, Water Conf., Engrs. SOC.West. Penn., 9, 151-70 (1948). (6) Weston, R. F., M e r m a n R. G., a n d D e h l a n n , J. G . , Scu:ogr; W o r k s J., 21, SO.2, 274-85 (1949). ~IECEIV Dccemher ED 12, 1040.
TREATMENT OF COMPRESSED YEAST WASTES WILLEM RUDOLFS ASTES from the imnufacture of nozeies a t the bottom and flow upof compressed Yeast a~ Cornward through a sludge blanket to peRutgers University, N e w Brunswick, N. J. posed predominantly of highly ripheral overflov weirs; a circular EUGENE H. TRUBNICK hopper-bottomed settling tank for reputrescible dissolved organic substances which require oxygen for slabiliaation tention and return of digester sludgcs; Anheuser-Busch, Inc., Old Bridge, N. J. in much the same manner as docs two 4-foot deer, trickling filters enuinncd domestic sewage. Spent nutrient, which with recirculating pumps; and a final settling tank for the collertion of filter sludge. comprises 15yoof the total volume of the IT astcs a t the ;InlieuscxrB.O.D. reductions of as high as 957% were obtaincd with t h o Husch yeast plant, has a biochemical oxygen demand (B.O.D.) digesters and 75yo with the trickling filters. The degree of value of 2000 t o 15,000 parts prr million (p.p.m.) and acpurification accomplished by each of the units could be contiolled counts for 70% of the pollution load of the combined wastes by varying operating conditions. Operating results indicate These wastes, which are typical of a great variety of soluble that certain factois influence the puiification processes signifiorganic industrial wastes, have bwn wcceisfull~treated for mol c cantly and that control of these factors can be utilized to achirvr than 5 years by a combination of anaerobic digestion ancl any desired degree of treatment. trickling filters. Tlic plant (Figure l), designed for flexibility of opwation, ronsists essentially of: two equalization tanks, one for the conDIGESTION centrated portions of the wastr and one for the dilute portions, Thc ripe sludge used as seed in the digesters has remained such as wash waters and cooling ~ a t e r s ~, h i c hprovide for conviable throughout the 5 years of operation; during this time not tinuous uniform flow to the treatment units; two steam heated only has it not been necessary to replenish sludge, but an average digrstrrs jn series, into whjeh the TI astcs arc introduced by means
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INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1950
613
removed to pounds applied remains constant within the range of detention of 1.4 to 3.7 days. In other words, within these limits the load, expressed in number of pounds applied, is the determining factor, regardless of the concentration of the raw waste or the rate of flow through the digesters.
Table
I. Relation between V o l a t i l e M a t t e r Loading and Removal Volatile Matter, Lb./Cu. Ft./Day Loading Removal 0.053 0.036 0.046 0.070
0.085 0.103 0.134 0.141 0.190
0.202 1
Figure 1.
0.220 0.334
TO SEWER
Waste Treatment Plant, Anheuser-Busch, Bridge, N. 1.
Inc.,
Old
Table
0.047 0.063 0.092 0.108 0.130 0.148 0.157 0.266
II. Relation between Organic Nitrogen Loading and Removal Organic Nitrogen, T,b /Cu. Ft./Day 1,oading Reinoval
of 55 cubic feet of wet sludge has been produced for every 1,000,0.003 0.002 000 gallons of waste digested. This was made possible by slow 0.006 0.005 0.007 0,006 acclimatization of the sludge a t the start of plant operations and 0.012 0,009 0.018 0.010 by careful control in avoiding excessive escape of sludge from thr 0.017 0.012 digesters. Since laboratory experimentation had shown that a minimum quantity of sludge equivalent t o 12% of the effective tank capacity was required for the supply of sufficient flora for purificaK tion, care was exerted to maintain more than this volume of I I 60 / n - L sludge a t all times. On the other hand, when the sludge volume Y exceeded 50% of the tank capacity, expansion occurred and t 40 resulted in excessive sludge carry-over with subsequent upsetting of the digestion process. The sludge volume is therefore maintained a t approximately 3391, of the total digester capacity. 20 Retention of sludge in the tanks is enhanced by the addition of s 100 p.p.m. sodium hydroxide to the raw waste. 0 The upward flow of the wastes through the sludge blanket is HOURS DIGESTION used as a means of establishing optimum distribution of the liquid through the sludge and of ensuring thorough contact of the seed Figure 2. Effect of Agitation o n Rate of Gasification and the substrate. It had been established in the laboratory that digestion mixtures, in which thorough contact was provided Peak digester efliciency of 95% B.O.D. reduction in the Lwothrough agitation, effected B.O.D. reductions and gas production stage systeni occurs at a loading of 0.1 pound per cubic foot per 30 and 26% greater, respectively, than were achieved with day as shown in Figure 6. I t appears that a t lower loadings the quiescent mixtures ( 4 ) . The rate of gasification was greatly applied material does not provide sufficient food for optimum accelerated, as shown in Figure 2. Furthermore, whereas quiesbiological activity, and a t higher loadings there is insufficient cent digestion mixtures could not handle daily volatile matter seeding t o handle the greater quantities of organic matter. Opcraloadings in cscess of 5% of the seed volatile matter, agitated tion as a one-stage system, mixtures could be loaded achieved by by-passing the a t rates greater than 20% " secondary tank, produces volatile matter per day. a peak efficiency of 85% As indicated in Figure 3, Compressed yeast wastes have been treated in a comB.O.D. reduction a t a the digester units were able pact plant comprising anaerobic digestion and trickling loading of 0.19 pound per to handle loads of 20 and filters, with resultant B.O.D. reductions of 80 to 98%, by cubic foot per day. The 30% volatile matter per means of careful control of the loading and other factors, apparently low optimum day. including, in the case of the digesters, acclimatization of loading of the two-stage By far the most signifithe seed sludge, maintenance of proper proportions of digestion, as compared t o cant factor influencing diseed and substrate, and provision for adequate contact one-stage, results from the gester performance is the .between the seed and substrate; and, in the case of the fact that the two digesters daily load applied to the trickling filters, maintenance of proper concentration are of equal volume and digesters. W h e t h e r t h e and a neutral pH value in the filter influent. Any desired that after the high degree loading is expressed in terms degree of treatment can be attained in either of the units of treatment accomplished of total solids (Figure 4), by control of the applied loading, so that loadihg is a usein the first stage the parvolatile matter (Table I), ful yardstick in evaluating plant performance, and a tially treated material organic nitrogen (Table 11), treatment plant can be designed on the basis of B.O.D. entering the secondary dior B.O.D. (Figure 5 ) , the reduction requirements. Maximum loadings attained gester represents a very number of pounds removed with either unit compare with results obtained in sewage is a function of the number low loading. It appears treatment under similar conditions. of pounds applied. The rethat the secondary digester lation of pounds of B.O.D. could therefore be some-
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
614
what smaller than the primary, but any reduction in size would be limited by hydraulic considcrations, in that too small a tank would involve excessively high over Holy rates that would mitigate effective retention of sludgc in thc cligesters.
Table
Ill. Effect OF Influent Concentration o n Trickling Filter
>is is the case with anaerobic digestion, the performance of the trickling filters is a, diwrt I > 25 function of the applied 13.0.11. at load, \Titha straight-line relationship between pounds of B.O.D. applied and pounds of R.O.D. removed, as shown in Figure 7. Recirculation a t a 1:l ratio docs not appear to improve thc performance of the filters; the rccirculated effluent apparently serves purely as a diluent. Daily loadings in excess of 8 pounds oC B.O.D. per cubic yard of stone were applied before any niarlred decrease in filter efficiency was observed. Extremely low loadings of 0.1 pound of B.O.D. pci cubic yard resulted in B.O.D. reductions as high as 75%. Over the loading range of 0.2 to 8.0 pounds of B.O.D. per cubic yard per day the filter efficiency decreases from 58 to 107, (Figurc 8 ) . Variation of the rate of surface application between 800,000 and 6,800,000 gallons per acre per day produced no significant variations in B.O.D. removal. Dilution of the trickling filter influent results in somewhat higher filter efficiencies a t constant loading. Vhen the materia.1 applied to the filters has a B.O.D. of 1100 p.p.m. the filter efficiency is 40%; when the intiuent is diluted to 170 p.p.m. the efficiency is increased t,o almost 6.501, (Table 111). A considerable amount of cooling wat,er a t a temperature of 80" F. and containing near-saturation qumt,itics of dissolved oxygen is discharged from the manufacturing process. I n view of the findings that the filters can handle dilute mastes more efficiently than they can the concentrated material and that variations in the rate of surface application do not affect performance a t a given loading, the cooling waters are included in the filler influent.
j
z s 0.3
,0.2 vi m1 -
~1
I
-
d
0
Recirculation 1:1 B.O.D.
B.O.D. raw, p ,p. rn
reduction,
B.O.D. raw,
reduotioil,
172 303 540
65 48
p.p.m. 184 200
58
660 811
51 44 47
1055 1308 1425
%
275
BO
316
370
432 802 1142
41 40
%
47 48
48 55 52 35 39
can be decided on the hasis of purifiostion rcquiremcnts. Thus it vvould be possible to t'reat the wastes by digestion exclusively, or on trickling filters only, or by a combination of the two units. .In over-all R.O.D. reduction of 857, is necessary to meet local requirements for dischargc of the Anheuser-Busch c:fRuents into the receiving stream. The t,otal load represented by t h c combined wmtes, in excess ol 9000 pounds of R.O.D. prr day, would require filters of too large a surface area, and for this reason it would not be economical to treat the wastes on trickling filters only. To treat the material by digestion, it would bo necessary, in avoiding too rapid a flow rate, t o load the digesters a t a rate considerably below the optimum, thereby sacrificing much of the potential efficiency of the digeshion process. The t,wo-process treatment scheme was therefore chosen as the most economical method as well as the one affording the most cornpa-t plant possible, The mastes flow from the manufacturing plant to the treatment unit through a dual sewer system; the highly concentrated spent nutrients and the more concentrated portions of the vash waters are digested, and the digester efflricnt, mixed Tyith the remainder of the process vvsstcs, cooling waters, and washings, is t,hen treat,ed o n the trickling filt distribution the digesters am loarlctl at, a rate of 0.1 pourd of B.O.D. per cubic foot per day a n d t,he fillers at a rate of 5 pounds o i B.O.D. per cubic yard per day. Over-all R.O.D. reductions vary froin SO to Y 8 ~ o 1vii.h an average reduction of BOYG; final effluents contain 24 to 174 p.p.m. B.O.D. with an a,verage of 120 p.1i.m. Gas production from the digesters avera,ges 7 . 5 cubic feet per pound of volatile matter added; this is equivalent to between 2.0 and 2.5 cubic feet of gas per cubic foot of total digester capacity per day.
After proper acclimatization of ripe seir-agc sludge as s e d , this material is capable of effectively removing lnrgc quantities of volatile matter and B.O.D. from a solublr organic type of in-
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B.O.D.
DISCUSSION
-
2 O.'
EFficiency
S o Recirculation
.
TRICKLING FILTER§
Vol. 42, No. 4
.IO 2 0 SOLIDS LOADINGS
.30
- LBS.
.40
.5D
/ CU F T / DAY
Figure 4. Relation between Solids Loading and Removal
.
Another factor influencing the efficiency of the filters is influent pH. Optimum B.O.D. removal occurs when the pH is 7.0. The efficiency deteriorates a t lower pH values, and below 6.0 the surface of the rock rapidly becomes coated with a heavy growth of wild yeast which clogs the filters. Clogging and lowered efficiency can easily be overcome by neutralization of the influent to p H 7.0 with a soluble alkali such as sodium hydroxide, and optimum efficiency can be maintained by p H eontrol. O P E R A T I N G RESULTS
The degree of purification attained by either the digesters or the trickling filters can be controlled by varying the load applied to the unit and by adjusting other conditions, such as concentration and pH. I n other words, the loading applied to a unit
8.O.D. LOADING
Figure 5.
-
LE%
/ CU. FT. / DAY
Relation between Removal B.O.D. Loading and
INDUSTRIAL AND ENG INEERING CHEMISTRY
April 1950 100
basis of these principles, it has been possible to maintain a high rate of digestion with no deterioration of seed and without replenishing sludge.
BO
BO
EO
F!
Y
b
3
615
3
40
40
d a
0
= 20
= eo
c 0
a
.os
0
.IO
LOADING
-
.I5
.ZO LBS. B.0.D.I OU. FT. I DAY
25
.30
Figure 6. Relation between B.O.D. Loading and Digester Efficiency
dustrial waste by digestion, as long as adequate amounts of seed sludge are effectively distributed through the substance being treated. B.O.D. reductions of as high as 95% have been achieved in a 2-day detention period, treating yeast waste with raw B.O.D. concentrations of up to 15,000 p.p.m. Maximum digester efficiency can be maintained by control of the load applied to the digesters. Since the percentage of B.O.D. reduction varies with the applied load, and since full scale operating results coincide with laboratory data (6),it is possible, on the basis of preliminary laboratory investigations, to design a digester on the basis of B.O.D. reduction requirements. Data on maximum allowable loading can readily be obtained for any B.O.D. reduction as required, and digesters can then be designed on the basis of that loading. Thus, the applied load can be used as an effective yardstick in evaluating digester performance in the treat-
c
0
2 O 4 8 0 D6I CU MI D 8 I D I Y1 LOADING-LBS. LOADING-LBS 8 0 D I CU I D I D I Y
Figure 8.
o0
Effect of Loading on Filter Efficiency
The straight-line relationship between B.O.D. loadings and removals that was observed with the digesters was also evidenced with the trickling filters. There is also L definite relation between filter loading and efficiency; this is of the same order as is experienced with shallow filters treating domestic sewage ( 1 ). The similarity of filter results with domestic sewage and with yeast wastes, which may also be extended to include results with other industrial wastes such as strswboard wastes ( 8 ) , a s well as the similarity of the results with quiescent digestion of yeast wastes and of sewage sludge, is highly interesting. It suggests that a given treatment operation is capable of performing a definite amount of work, and that the maximum possibilities of the process are the same regardless of the material being treated. In other words, if a waste is amenable to a particular type of treatment, the basic principles pf sewage treatment apply, regardless of the source of the waste, and the degree of purification to be achieved can, within limits, be anticipated. LITERATURE CITED
(1) Moore, W. A., Smith, R. S.,and Ruohhoft, C. C., Sewage Works J.,21, 31 (1949). (2) National Council for Stream Improvement, New York, N . Y . , Tech. Bull. 15 (1947). (3) Rankin, R. S., Sewage W o r k s J . , 20, 478 (1948). (4) Hudolfs, W., a n d Trubnick, E. H., Ibid., 21, 100 (1949). (5) Ibid., p. 294.
2
B.O.D. APPLIED-LBS. / CU.YD. I DAY
Figure 7. Relation between Filter Loading and B.O.D. Removal
ment of industrial wastes, just as detention time can be used in evaluating the performance of sludge digesters (5). Any desired degree of treatment can be obtained by control of the loading applied. The high degree of purification achieved with the digesters is attributed principally to the control of loading, and to the maintenance of adequate contact between the seed sludge and the materials being treated. Under quiescent conditions, in the laboratory, maximum digester loadings were of the same order as those in sewage sludge digestion. When steps were taken to distribute the wastes thoroughly throughout the sludge, both in the laboratory and in the large plant, loadings could be increased four- and fivefold. The various factors influencing the digestion are related to the question of proper balance between the organisms of the seed and the food material represented by the organic matter of the waste. First it is necessary that the organisms be properly acclimatized to the new source of food; then care must be taken that the food supply is sufficient for optimum utilization without being present in excess (this is reflected by the loading); and finally, the OPganisms must be kept in constant contact with the food material. By designing and operating the Anheuser-Busch plant on the
REOFJVED December 12, 1949. Journal series paper of the N.J . Agrioult u r d Experiment Station, Rutgers University, The State University of New Jersey, Department of Sanitation, New Brunswiok, N. J.
COURTESY INFILCO INC.
Accelator Used for Process-Water Clarification, Wheeling Steel Plant, Yorkville, Ohio. Stecl mills and metal proserrins plants use Accelator-treated water for rinsing metal parts after pickling or plating
