CANNING INDUSTRY E. F. ELDRIDGE Engineering Experiment Station, Michigan State College, East Lansing,Mich.
b' b Most of the three thousand odd canneries of this
ninghasincreased butlittle; in fact therehasbemadecreasesince 1941, probably hecause of war restrictions. On the other hand, fruit-juice packed is up 400% in ten years. Canning factories are an outlet for farm products and for that reas-on are located in rural areas where soil and climatic wnditiqns are favorable for the g & t h of fruits and vegetables. In most of these sections factory operations are seasonal; and few operate the full twelve months. Many specializedoperations are limited to a few months each year.
eountry operate on a seasonal basis, packing either specialized or full-line products. The wastes from t h e operations consist largely of washings from the preparation of t h e products for canning. The volume and characteristics depend up6n t h e type of product packed and v a r y over a wide range. The material in the wastes eonsists largely of organic -lids io suspension and are objectionable heeause of conditions caused by their decokposition. Effective screening should be a eommon practice with all cannery wastes. This may h e followed by chemical precipitation, sedimentation, biological filtration, or lagooing, or a combination of these processes, depending upon the degree of treatment necessary. ?'he required treatment is establihed by gdvernmental agencies in each case.
SOURCES OF WASTES
The line operations of s cannery are adapted to the raw products. The so-called full-line canneries pack a large variety of both fruits and vegetables; usually each product has a different line of equipment, although some equipment, such as wokers and wolers, may he used on all Lines. Other factories may specialize in one or only a few products and, hence, have fewer lines and OMMERCIAI-canning is one of the country's most wideusually shorter seasons. spread and diversified industries and now includes many Because of the difference in raw products and wnsequent factypes of operations, such as dehydration, pickling, and freezing, tory operations, the problem of waste disposal is much more in addition to the original sterilimtion processes. The discussion complicated than it is in industries with more uniform conditions. which follows is limited to those operations in which food is preEach raw product produces a different wpte and requires special served in hermetically sealed containers (glass or tin) and sterivariations in methods of waste disposal. A n analysis of the lized by heat. waste problem in many cases involves a study of emh line indiThe art of canning is credited to Nicholas Appert of France. vidually. The three operations discussed in this paper are, in Appert 6rst preserved food in glass in 1804 and founded a cangeneral, typical of canning procedures and indicate the flow of nery, House of Appert, .which is still a famous organization in products and the sources of wastes. fiance. Tin containers for the preservation of food products TOMATO CANNING.Tomatoes are usually ready for harvesting were h t used by Peter Durand, an Englishman, in 1810.. Ezra about August 15, snd.the season lasts some six weeh. Figure 2 Daggett is believed to be the first calmer in the United States, and is a flow diagram of a tomato cannery showing the manufacture the Wm. Underwood Company of Boston, foupded in 1817, was of whole tomatoes and puree, and the recovery of seeds. The among the 6rsf canning,companies. The first Midwest cannery latter is not often a part of the process. was not established until 1860 when Thomas Duckwall built a The tomatoes are hauled to the cannery in hampers, weighed, small factory near Cincinnati for packing tomatoes. The soaked in ~r tank of water, snd passed through a washer. The Van Camp Company was establishd in Indianapolis in 1861,and 6rst waste from the process is the wash w&er and the dumps of ahout the same time companies were established in California for the preserving of fruits: the soak tank. The waste In the past Sighty' to contains soil, leaves, parts of the tomato, and some ninety years this industry has increased until, aocordjuice.and pulp. It is comparatively large in volume. ing to the last census, over three thousand canneries are rn After washing, the tomatoes are .moved along a now operating in the United picking table where culls are States; about 75% pack removed by hand. Usable f r u i t s a n d vegetables. tomattoes are scalded and Table I shows the number peeled. Those that are of casea of. the more 'imwhole and undamaged ,%re portant cannery products packed in cans, sealed, and packed in 1944. woked. The damqed toFigure 1 shows the trend matoes are trimmed to reof canning operations in the move spoiled portions and past ten yeass. Vegetable cores,. passed through the canning almost doubled, pulper, a n d t h e p u r e e 1942 1944 reaching a peak in 1942 and 1IS% wplaced in cans and woked. leveling off at about 155 -on cases. Fruit canFigure 1. Ten-Year Trend in Canning Operations If the seeds are .to be
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'
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619
[ N E E R I N G CHB; M I S T R Y
Val. 39, No. 5
.,Corn CANNERY. Figure 4 shows a typical flow diagram of
corn packing operations. The canning seawn is during August and September. T h e corn, as received at the cannery, is husked, sorted to remove defective ems, and xashed. The kernels are then removed and the wbs, husks, butts, and other discarded pasts p h d either in a silo or stack. The kernels are mixed with sugar and salt, packed in cans and cooked, cooled, and stored for shipment. About om third of the weight of the corn received at the cannery goes into the cans. The wastes from the process consist of the washings from the washer, floors, and equipment. They contain dirt, husks, silks, and a considerable amount of colloidal starch, soluble sugm, and other o r g d c compounds. OTHERPBODUCTS. Space will not be taken here to discuas the operations involved in the packing of the many types of v e w tables and fruits. The three processes presented are more or less typical of cannery methods and will serve to demonstrate the sources of wastes. It is evident from the flow sheets that the major wastes are produced as a result of the washing and prep% ration of the raw products for packing.' The silage juice and pea blancher wastes are notable exceptions. Once the products are prepared, very little material is wasted except &B a result of spillage around the can mer and an occasional broken em. VOLUME AND CONCENTRATION OF WASTES
Figure 2.
Flow Diagram of Tomato Cannery
separated, culls, peelings, and trimmings &lso go to a pulper. Discarded solid portions from the various operations are, as far as pcesihle, collected and hauled to a dump or spread on land. Juice from the ked separator contributes considerable organic matter to the waste. The periodic cleanup of flwm and equipment and the h a 1 cleanup at the end of the day are sources of a considerablevolume of waste. Thia waste is often more concentrated than the washer water, depending on the care used in the various operations of the factory. Normally considerable quantities of skins, pulp, and juice from the peeling and trimming tahles and from the can 6Uer wllect on the floor and are washed to the drain. PEACANNERY. Figure 3 shows a typical diagram of a pea cannery. The season far the pack is June and July, and usually lasts from six to eight weeks. The pea vines are hauled to vineries, usually located near the farms where the peas axe grown hut occaeionally connected with the cannery. The pods are removed at the vinery and the vines stored in stacks. Fermentation of the vines in the stacks produces a concentrated waste which varies in volume from 1.5 to 5.0 gallons per case of No. 2 cans packed, depending on the'amount of rainfall during the storage period. In the cannery the peas are screened and washed. The wash water is the first waste from the process. It is large in volume and contains soil, leaves, pods, and some starcby material from the pea. The peas are graded and blanched. The dumping of the blancher produces one of the most concentrated wastes from canning operations, with the exception of vinery juices, which are not usually considered a part of pea cannery operations. The blancher waste is high in temperature and contains h u h , partly cooked peas, and carbohydrates in the form of starches and sugars. The blanched peas are washed, hand-picked to remove ,d& colored peas and for6ign material, packed in cans, cooked, and stored for shipment. The rwsh water from the hlanohed pess and the wdh-up of floor and equipment contributes to the waste from the capnery.
The variation in the volume and concentration of wastes is wide, even from canneries packing the same product, To a much leaser degree there is variation within the same factory, depending on the condition of the raw product and on the extent of the pack. For instance, root crops collected during wet weather will contain much more soil and foreign matter than those collected during dry weather. Also, if the factory is operatiug at full capecity, the unit volume and concentration based on the pack will usually he less than that during pperation at partial capacity. ~
Table I. Vegetable and Fruit Pack in 1944a No. of Case
No. of Casea
3,832,800 14.818,wO 1.478.000 1,570.000 8,037,000 3,155,000
7 858 wo
Yewtablea AeParaeus Beans. green Beans. ysx Beans. lima Bmta C*r*Ota COIR Peas Pump!& and squash 8 'naoh &matoea whole Tomato ikca Tomato pur&
8:030:wO 683,000
4004wO 6:302'000 485:wo 14.035.000 4.801.000 10.104.000 1.418.000
25.982.m
30,131,000 2.127,wO 8W2000 22'577'000 26:487:wO 7.08?.000
2851000 45:116~000 7,957,000
Date furnished by National Canners' Asaodatian.
Table 11. Volume and Conaentration of Cannery Wastes WasteVol.,
Gal./Caae
etablaa %e*m,green BBSIY). yar Beam. lima Beets red Carrdt. Corn Corn ansi1e.ge Iiwor PeSE Pea *milage liquor Pioues Potatoas Spinach Tomatoes whola Tomatoea'snd ~ u r & Fruits A ricots CEmies Citrus fruit, seotions citrus fruit. ivice Gr.%W Pears V
42 26
60 25 23 25
Suawnded Solids. P.P.M.
..00 iiio 1830 980
I .
25
2860
B.O.D. P.P.M.'
B.O.D. Lb./C&
400 240 450
0.140 0.052
2500
0.188 0.520 0.213 0.025
2400
0:%4
1110 3000 27000
... ...
...
ilk
36000 3000
990 3500
16 7.5
190
950
570 2818
55 40 60 50
200 20 208 171 1050
750
0.250
1880 343
0.775 0.14%
51
310
450
2
... 20
...
...
220 0000
1.00 0.071
0.182
380 720
0.208 .
0: iSi
May 1947
I N D U S T R I A L A N D E N Q I N E E R I N G CHEMISTRY
621
tation type (4). During the last war, when material was not avrtilable for the construction of t r e s h e n t &mcturea, the National Canners' &ciation (6) cooperated in the development of methods of. broad irrigation and ponding. During this period fifty or more canneries adopted the system of ponding as a meem of relieving the streams of pollution. CANNERY WASTE TREATMENT
Fig-
3. Flow Diagram of Pea Cannery
There are several methods or cornbination of methods by meem of which w m e r y wastes m y be aucceddy treated for the m movd of polluting subst+ces. Selection of a method for a specific cannery depends on the type of products canned, the size nf operations, the length of sewn, surrounding areas (urban or rural), soil and climatic conditions, and the point of final dig posal. Perhaps the most important factor in this selection ia the latter, since it determines the degree of tredmebt nersssary. Many canneries are located in cities and bave acoass to municipal sewer syatema. Othera am located on small streams where even a small amount of pollution may pe undesirable. T h e 6rst item neoassary in making a sdection of methods is to determine the degree of treatment required. the method or combination is then selected which will give this treatment with the specilic was?. The following are the combinations adapted in general t o .ornery wastes: (1) screening, (2) screening and ch.ernid precipitation, (3)screening, chemical precipitatiou, and sand filter, (4) screening, chemical precipitation, and laiooning, (5) screening and biological filtration, (0) screening, biological filtration, and l w n i n g , and (7) screening and lagooning: ,
Table I1 was prepared from published reports (I, B,S,4 8)and from experience in the field. %me of the averages are based on large mass of data, especially those referring to the more common t w of cannery products (peas, tomatoes, corn, beets, and beans). The average values, howwer, should be used only as guides and should not be depended upon for the design of waste d i i p a l facilities. The unit used for the cornperison of the volume of waste and the pounds of biochemical oxygen demand (B.O.D.) ia one case of No. 2 cans (24 cans). When other size cans are packed, adjuatments must be made in 'the comparison. For dl practical purposes the values vary directly with the size of can, and the following tabulation gives this variation: 8
.
SCREENING
All canneries should be equipped with an @dent and ad+ quak wrean regardlw of whether further treatment of wastes in required. All wastes except the water from the boilern and coolers should be paeaed over this sereen. The wastes from some prcducts are d i i K d t to meen because of the presence of fine stringy fibers and thin skim. S q d wastea are psxticularly troublesome i n this connection. The
STREAM POLLUTION PROBLEM
The material contained in cannery wastes, with the exception of soil from the raw product, is largely organic. This organic metter will decompose through the agency of soil and water organisms. If these waste products are discharged to streams, ponds, or l&es, the deaomposition of the material is accompanied by a depletion of the oxygen content of the receiving water and, if wficient, may regult in the destruction of fish and aquatic life and the production of odors. The canning industry in general is cognisant of the undesirable esc€t' produced by cannery wastes diwharged to public waters, as evidenced by the interest of the National Canners' Association in this problem. This association has taken an active part in the investigations of waste treatment procesaes sponsored by state agencies, particularly in Wisconsin (6, 8),New York, and Ohia. The interest of the indwtw in the waste problem is indicated by the fact that, even as early as 1935,Wieconsin done had thirtyfour cannery waste treatment plants of the chemical precipi'
Figure 4.
Flow Diagram of Corn CBnnery
I
.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vd. 39, No.
S
cipitation for the treatment of waates under theee conditions,since results &re immediate, although the degree of removal is lees than that wssihle from a . urouerlv . -owrated biolomcal - -urocesa. Mist of the tre@ment plants-using chemical precipitation employ the 6ll-anddraw phciule. since it D r o ~ e sbetter wnditions for settling and-con&ntration of the eludge. Figure 6 shows the design recommended by the National Canners' Association (6)and employed at a considerable number of pea canneries in Wisconsin. The number of tanks required for the 6ll-anddraw process depends upon the waste flow. The minimum number is two. The capacity of each tank is based oh the following considerations: (Q) A %minute period is required for the addition of the ehemicds and flocculation. 6)A minimum ueriod of 2 hours is required for settling. (c) Oneto one and a hac hours are required for the drawinn of sludee and the discharge of the treated waste. (d) This means-that thecapacity must besuch as to allow 4 hours for the preceding operations of the tank or tanks out of service. When two tanks are used, each should have a capacity for 4 hours of maximum flow of waste. Considerable study has been made of the use of various cnltgulants for the flocculation of wastes from certain specialized canneries. However, in applying chemical treatment a study should be made at the cannery to determine the most effective chemical for the speciiic waste. The dosage required will vary throughout the period of treatment, and intermittent tests are necessarv for control of the DPoCeSS. Table 111 shows the averaee results chtained from &iilirs of chemical preciprtntion, most of which rere made in Wisconsin (.6.) . It will be uoted that lime is used in all case8. Sludge from the che itation p r m will dry OQ underdrained sand b 8. Usually the pack occurs during the no I, and sludge disposal is not a .h 19 rPwr< !%?A
.
....
Figure 5.
Screen for Removal of Lerge Solidi from Cannery Waste
rotary-type screen IS used in most factories, but experience in Michigan has favored screens of the vibrating type, since they clog less easily and the screenings are much drier. Figure 5 shows a small screen of this twe. A 40-mesh screen is most .. wmmonly recommended; however, If chemical precipitation is to follow the screen, a %mesh may be used. The capacity of the screen must be such as to handle the maximum rate of flow of that waste which is most difficult to screen. Manufacturers' specificitions must be wed in determining the siae. The use of'a screen .in most caes requires pumping, and the capacity of the pump must be equal to or less t h n that of the screen. The screenin@ sbould be continuously removed by means of a screw- or bucket-tvue .. conveyor to a loading.homer. .~ Srrapcr-type uonveym have uot proved datisfaetorg. The best type to KO I;. a combination of endless belt . with R vibratbrvecrccn nd bucket elevator.
S m . In those cases where the solide and B.O.D. obtruned by c reqmrements, applied t~ Hand IiILters. removal of B.O.D. hv a sand filter wnsistine of 6 inches of m'dvel with underdrain till overhyed with 18 inihes of sand with an dective size of 35 to 65 mm. The recommended rate of iiltration is 2 gallons per square foot per minute. The filter gives considerable trouble with clogging and should he equipped for hackwashing, using 6lter effluent for wash water and discharang backwash water to the raw waste.
Table 111. Coagulants for Treatment of Cannery Waste Product Packed Peas
LE300 7
Ferric d f + e Ferric chlonde Alum Ferrous s$fate Zino ohlmde Alum Ferric chloride
8 10 10 8 8
Corn
9
6
Tomatoea Ca?rots
Kraut
8 4 .
Chemical-
N?.IlE
7 7 6 8 10
Beats
-8eoond
GallOD@ 7
CHEMICAL PRECIPITATION
Many canneries operatmg on a few special products have such ahort 88awns that biological procasses are not adapted to the treatment of their wastes. Canneries packing peas, beets, wrn, tomatoes, and carrots me the most mmmon of these. The National Canners' Association has recommended chemical p r e
.
8
6
15
NOW
Ferroua sulfate Zinc chloride Ferrio sulfate Ferric chloride Fern- sulfate Zina ohloride NOW
' Alum None Ferroue sulfate Alum
Lb./1000 GallOD@ 1-3 1-3
B.0 D. Reduotmn.
%
33 38
2 4
46 47 75 36
...
38
43
7
46
3 3
2
4 10 3 8
46
85.
57
...
70 78 49 M 75
6
61
2
... 1
1
75
May 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
623
BIOLOOICAL. The chief limitation to the use of the biological filter for cannery waste treatment is the time required for the development of the filter flora. I n where chemicalWeatment does not give the required B.O.D. reduc: tion, it may be possible to build up the flora on a biological filter by means of the application of domestic sewage or river water to the filter media prior to the beginning of the pack. A recirculating type of filter similar to that recommended by the National Canners' Assooiation (6)is shown in Figure 7. The raw screaned waste enters a pump mell, where it is mixed with filtered waste from a settling tank. A pump having a capacity of six times the maximum rate of flow applies the waste to the filter. The filter consists of a E-foot bed of rock (3-4 inch) underdrained by ventilated tile lines or grid system. The volume of media should be such as to provide a loading factor of 1pound of B.O.D. per cubic yard per day. The waste from the .filter passes through a settling tank with a 1-hour detention period baeed on the pump capacity. Sludge from the settling tank is dried on sand
beds or Iwoned. Warrick (6) reports a removal of B.O.D. by the combined biological filterand settling tank for beet waste 70 to 75%, corn waste 80 to 85%. and tomato waste 83 to sS%. IlUIIGAl'XON AND WGOONMG
.
A detded study of the we of irrigation methods and'lagoons for cannery wastea mas d e by the Wisconsin State Board of Health and National Canners' Association (6)during the war period. The report of this work ChSified lagoons in four groups-namely, irrigation fields, untreated lagoons, chemically treated lagoom, and surface-treated lagoons. One desirable f e e ture of the hgmn method of disposal is that it completely eliminates stream pollution. Irrigation fields are satisfactory where soil is porous and will rapidly absorb the waste. One cannery in Iowa applied waste from the corn pack a t the rate of 4ooo gallon6 per hour per acre. The field was plowed with f m w s 42 inches wide a t the top, 18 inches deep, and 24 inches wide a t the bottom. The ridgea between the furmws were 42 inches wide. No objectionable odom were noticeable. Untreated storage lagoons c ~ l lbe used only if located 0.5 to 1 mile from dl babitation. An objectionable odor is produced by the deFigure composition of the waste in the lagoons and will result in complaints. Lagoons surfacetreated with oil or c h e m i d y treated with lime, sodium hydroxide, or creosote compounds were not satisfactory, according to Wisconsin experience, since these methods did not control the odors. The most satisfactory treatment of lagooned cannery maste to prevent odom is by the proper application of Sodium nitrate. Screened cannery waste or the a u e n t s from either chemical precipitation or biological filtration may he t w t e d with S o d i u m nitrate and Isaooned. if this eomhination fitdl the local conditions. This chemim-f-ishea oxygen for the aerobic decomposition of the organic matter in the initid stages and thus eliminates the production of intermediate reduced mmpnpounds which are re-
6.
Chemical Precipitation Plant for Cannery Waste (5)
sponsible for odors. It also stimuhtes the growth of oxygenproducing organisms and maintains an alkaline reaotion in the lagoon. Agricultural S o d i u m nitrate containing 98% NaN03 (54.7% available oxygen) is most commonly used. The waste is first screened and then pumped to the lagoon. The sodium nitrate may be disaolved in a drum and dripped into the pump sump. A auantitv sufficient to SUDD~V neeman, to satisfv ._ " the oxyeen " _ zO% of the M a y B.O.D.is neceasary for &ective oior controi. For example, Table I1 indicates that pea cannery waste has d average B.O.D. of 0.5 pound per case of No. 2 cans. To supply
ld
EFFLUENT
WEIR A IS SUFFICIENTLY LOWER THAN WEIR B TO ALLOW VOLUME OF WASTE EQUAL TO CAPACITY OF PUMP TO OVERFLOW INTO SUMP SEFORE ANY TREATED WASTE OVERFLOWS WEIR 0 TO OUTLET SEWER
ENLARGED YCTlON SHOWING WEIR ARQANGEMENT
Figure 7. BioIogical FUter and Settling Tank (5)
Estimated Cost of Cannery Waste Treatment
Table IV.
Traatment
G Iationper casea
0
20% of this B.O.D. will require 0.1 pound of oxygen or 0.183 pound of sodium nitrate per case (183 pounds per pack of 1wO oases). In order to be entirely effective, it is essential that the necessary m o u n t of chemical be added daily. This amount is determined by a pre-estimate of the pack for each day. Experience has indicated almost complete control of odors. The ponds should be shallow (3 to 5 feet deep) and have a capacity sufficient to hold 1.25 times the maximum waste volume for the 8eason. About 25% of the waste from the previous year should be held in the lagoon to furnish dilution and seeding org&mms. ' Storage lagoons should be constructed in tight olsy soil, if possible. The retaiaing dikea should be 7 to 10 feet in width WW8S the top, with an inner slope of 2112 horizontal to 1 vertical and an outer slope of 2 to 1. A freehoard of 3 feet is deairable. The outer slope should be planted to grm to prevent erosion. Since the inner slopes and lagoon bottom should be kept free of vegetable gmwth, i t m y be necessary to surface the m e r slope with stone. The dikes should be aonstructed to retain water. The rolled-iill type of construction is recommended where each layer is 0 inehes deep after rolling. The best type of soil for dike construction is a muture of clay, sand, and gravel. The inlet pipe should dis Crete or stone surf& to pre outlet pipe with locked va vided. COSTS
The following cost estimates were prepared from prewar experience,since the present rapidly changing prices do not allow estimates of value to be made. Table IV was prepared on the basis of a 1wO cases per day pack. In mast cams the cost will not increase in Dmportion to the pack. It is suggested tha(the factors at the bottom of Table IV be used to determine ooste for packs above loo0 cases per day. Operation values include labor, power, chemicals, and maintenance, but not depreciation and interest on investment. The type of pack d linfluence costs t o some extent. T h estimate ~4 made on experience with the canning of pem, corn, and beets.
$ 5.00
ACKNOWLEDGMENT
$3.10 7.60
1.60
sia.80 0.60
$lO.oOo
S 5.00
1.M)
The writer WI&W to acknowledge the assistance of L. F. Warrick, Wisconsin Department of Health, and N. H. Sanborn, National Canners' Association, from whom many of Dhe data and illustrstions contained in this paper were obtained.
0 80
~
Total Screen and lagoon B d v m nitrate Labor and hauling Power pump and ~creeo Maintenanae Total per day
Constmotion. Initial coat
$4.00 1.00 -
Toti Sareen and o h d d plant Chemic& lime and ooppem Labor and hauling Power pump, mreen. and prropdez Maintenance Total screen fdter Pnd nettline. t.nk Lab& and bauline. Power numn. screen and mrw-
C-
Vol. 39, No. S
INDUSTRIAL AND ENGINEERING CHEMISTRY
624
s7
10
$8,160
S3.30 4.00 1.00 0.60
$8.80 2WO
1 3 1.6 1.4 1.5 1.1 1.5 1.1 1.4
3MXl 1.5 2.1 1.8 1.8
1.2 1.8 1.2 1.Q
6WO
1.8 2.5 1.8 2.6 1.4
a.6
1.3 2.7
LITERATURE CITED
(1) Eldridge, E. F., "Industrid Waste Treatment Practice". pp. 147-73, New York, McGrsw-Hill Book CO., Inc.. 1942. (2) h o k e , A. W. "on, Pulley,G.N., N o h . A. J., and Goresline. R . E., Sauaye Wwka J., 13, 116 (1941). (3) U. 5. Public Hedth Service, Industriat Wash Guides. 1939. (4)Warriok, L. F.,Wder Wwka & S m q 81, ~ 346 (1934). (6) Warrick, L.F., McKee, F. J., Wirth. H. E., and Sanborn, N. H.. Natl. Canned Aaaoc:, Researoh Bull. 28-L (Dec. 1939).
(6) Wwiak, L. F., WisnieFki, T..F.. .ind Sanborn, N. H.. Ibid., 29-L (April 1946), ~. ;
...
PR~~NT before E D the Iqduatrial:Vfa+ Symposium at the 111th Mestins of the An;srcm C a s r r c ~Soormr, ~ Atlantic City, N. J.
