Corn Products Manufacture ERIC M. VAN PATTEN and GEORGE E. McINTOSW American Maize-Products Co., R o b w , Ind.
methods. The program was accomplished by an investment of $850,000 in new equipment and by the isolation of all waste-bearing waters, the reuse of all process waters, the recovery of all solids possible, and the reduction of volatile organic matter. A 1% increase in over-all plant yields has helped to offset the expense incurred in this program.
American Maize-Products Co. is a producer of starches, sugars, sirups, and fermentation products from corn. The entire operation ie a wet milling process and lends itself easily to a high industrial waste problem. The company was able to reduce its industrial waste loadings considerably without resorting to. the usual waste disposal
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MERICAN Maize-Products Co. is a producer of corn prodIllinois vs. the State of Indiana et al. in the Supreme Court of ucts by the wet milling process. The plant of the comDany the United States. A definite program of procedure was outlined was built in 1907 in its present location in northern part of Hamin 1944 and was finally completedin September 1950; i t submond, Ind., largely because of the availability of an unlimited sequently resulted in the company's dismissal from the case on supply of water from Lake Michigan for cooling and process purNovember 6, 1950. For the past 9 months the total'trade waste poses and because of the availability of the lake for the discharge discharged by the company averaged 0.7 population equivalent of such water. During the past several years the company has per bushel of corn ground. Of this volume, wastes of essentially utilized as much as 15 million gallons of water per day. very dilute entrained sugar solids were discharged in cooling water Prior to the year 1940 there were no sewage facilities of any to Lake Michigan a t the rate of approximately 300 pounds per day. nature in the plant area. Consequently the entire plant effluent The balance was sewered to the Hammond sanitary system. was discharged into Generally speaking, Lake Michigan and the program was acequaled a t times as complished by the isoCORN ELEVATOR UNLOADING much as 350,000 perIationof all waste-bearCLEANING sons or 10 population ing water, the re-use of STORING equivalents per bushel bottling up of all procof corn processed. In ess water, the re1940 the Hammond covery of all solids posSanitary Board consible, and the reduction DRYING structed an interceptof considerable volatile ing sewer into the plant organic matter. The I ^""..,^ M I L L I N G AND ""ll"" SCREENING area for the purpose PRESSING company realized that of diverting sanitary they were not in a posiI TASL IN G sewage and industrial tion to attack the probPRESSING GLUTEN AND STARCH WD D R Y I N P waste to the modern lem as sanitary engiSEPARATION GLUTEN M E A L I O I L HEAL treatment plant of the n e e r s specializing in REFINED OIL district. The company w a s t e disposal, a n d CONVERTING then constructed therefore felt that this MAC0 sewerage facilities on method of approch its property and conwas the most feasible. nected the same with They hoped that imthe intercepting sewer. proved process operaSince then, the comtions and some inSUQAR pany has diverted all c r e a s e d solids yield CONVERTING CONVERTING of its sanitary scwage resulting from such a BLEACHING BLEACH I N G and a portion of its program would defray t r a d e w a s t e t o the a part of the heavy O R 1 NO1 NG 1 I treatment plant of the c a p i t a 1 expenditures C.S.U. DRYING district. This relieved attendant with watas I I I 1 I I the situation to Lake CORN SYRUP abatement. I t is becouuon s~~~~~~ SOLIDS STARCH Michigan considerably, lieved a t present that CRYSTALLIZING but the company conplant effluents are as SPINHINO DRYING tinued its program of good as can be obwaste abatement with tained under present purpose. In Septemconditions of developber 1944, the company ment in the industry. I FERMENTATION 1 BLEACHlNd agreed to make further However, i m p r o e v CONCENTRATIONS I L I improvements w h i c h ments under way a t the were incorporated in a plant should help mateLACTIC ACID stipulation filed in the rially in further reduccase of the State of Figure 1. Flow Sheet of Wet Milling Process for Corn tion of the bioloading.
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Liquid Industrial WasteThe Manufacturing Process Before reviewing in some detail the method and results of the abatement program of American bIaize-Products Co., a brief description of the 24-hour continuous wet milling process would be helpful
Table I.
Summary of 6-Month Survey of Lake Michigan System Loading
Source Feed house artery Feed house evaporators, condensate Starch department, filter water Oil refinery deodorizer a n d wash water Cooling water and miscellaneous Total Refinery artery Sugar a n d sirup evaporators, condensate Bone char wash water RIiscellaneous process water Cooling water e n d miscellaneous Total Lactic acid artery Evaporator condensate Spills and mash water Cooling water a n d miscellaneous Total e Grand total
Volume
Population Equivalent
200,000 120,000 1,200,000 5,480,000 7,000,000
9 0 , oooa 80,000 10,000 10,000 190,000
200,000 180.000 40,000 3,780,000 4,200,000
30,000 30.000 24,000 6,000 90,000
150,000 20,000 3,330,000 3,600,000 14,700,000
40,000 15,000 5,000 60,000
340,000 a 50,000 population equivalents due to entrained solids, 40,000 due t o volatiles.
The cleaned, shelled corn is steeped in a n eak solution of sulfurous acid. The corn (45,000-bushel daily grind) i-r then doubly milled by attrition and Buhr mills. This milled material is separated into the following fractions: starch, germ, proteinaceous solids, fibrous material, and soluble solids Devtiines, gums, and food starches are manufactured from the basic starch carried in water suspension and, in many instances, are chemically treated. (The filtrates from these slurries are mostly very dilute waters, the solids from which have very little commercial value although they represent a source of trade waste.) Corn sirup, sugar, devtrose, lactic acid, and many other products are manufactured from dilute water-starch suspension by acid hydrolysis or microbiological conversions. These dilute products must be concentrated before they are in a maiketable form and this concentration involves the use of elaborate vacuum evaporation equipment, the condensate from which is subject to dilute solids entrainment The proteinaceous material is either combined with the soluble solids and fibrous materia: or prepared directly as animal feed. The entire process is a met milling process and all materials are handled as slurries to the last manufacturing steps. Figure 1 shows a simplified ffow sheet of this wet milling process.
The Problem Outlined In January 1944, an extensive 6-month survey and study of' all Amaiao industrial waste was initiated with the following purposes in mind: 1. To classify the pollution load of the total industrial waste to all of its individual sources 2 To isolate and determine the source, basic characteristics, and magnitude of each source of waste. 3. To determine the seasonal fluctuations, if any, of the strength of the trade waste. 4. T o determine and develop methods to reduce and control the strength of these wastes. The problem was approached by setting up a unit of trained personnel within the research department, who were equipped and trained to gather analytical data on volumes, biochemical oxygen demand loadings, gravimetric solid loadings, and bacterial contamination as well as obtain basic information on the bioloading potentials of various organic matters subject to inclusion in the industrial waste. This unit also carried out funda484
mental work on possible pretreatment and process water reutilization practices applicable to the problem. Essentially, the sources of trade waste from the plant which were recognized were refinery bone char wash nater; entrained solids in the condensate from sirup and sugar evaporators in the refinery, entrained solids and volatiles in the feed house evaporators used for concentrating the steep water, process. and filtrate water: entrainment of lactic acid and calcium lactate in the lactic acid department evaporators: starch filtrate water from the starch washing operations; excess plant process aDd manufacturing water which was not economical to concentrate because of the low solids content; surface s e m r water and water from ffoor washing operations; inadequate equipment for handling spills and the occapional failure of process equipment; and oil refinery operations (deodorizer and wash water).
The Sewer System The plant is served internally by two discharge systrms-the Hammond system for the sanitary sewage and some industrial water and the Lake Michigan system for the cooling water and water-bearing negligible bioloading. In 1944 both systems were so laid out that industrial lvaste loading could easily be diverted from one system to the other. This was done by means of diversion chambers However all sanitary wastes were isolated so that there was no possible way for theii disposal into the Lake Michigan system. Two years ago a third system was added whereby a 10-acre lagoon could be used to protect the other two systems in cases of emergencies The Lake Michigan system IT hich handles the bulk of the ~1ater from the plant is comprised of three main arteries. The feed house artery handles the feed house evaporator cooling and condensate waters, the starch department filtrate and vacuum pump seal water. and the oil refinery deodorizer barometric downleg water and wash water. To the refinery artery are passed the corn sirup and sugar evaporator condensate and cooling water, bone char filters, wash and tempering water, floor washings and waste water from process equbment, and cooling Tpater from refrigerating equipment. The lactic acid artery consists of four departments. The lactic acid department handles the cooling and condensate water from evaporators, and the wash and process waters The dextrose department handles the cooling water. The corn siiup solids department handles the cooling and wash maters The boiler house handles the 1 Cooling water 2. Blowdown water 3. Filter back wash water With the establishment of this sewer system it was possible t o start the study of the actual loading, especially in the Lake Rfichigan system. Sampling as well as metei ing devices were installed a t strategic points. The 6-month study carried out in 1944 revealed the loading to the Lake Michigan sewer The results are presented in Table I. At that time the Hammond system was carrying only the domestic waste As a result of this study it was decided that the following program must be pursued if the agreement was to be met: 1. Reduce the solids entrainment losses in the glucose refinery evaporating equipment by the installation of new concentrating equipment or rebuilding the c>xistingequipment 2 Completely discard the feed house evaporators and install new equipment, allom-ing for additional evaporating capacity t o concentrate filtrate and wash water t h a t normally would be sewered-to the economic advantagc of the company. The new evaporators would have surface condensers so the condensate could be isolated from the cooling water 3. Install new starch filters whereby less -rash mater would be
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Liquid Industrial Wasterequired for washing the starch and a quality product would still be produced. 4. Devise means for limiting the amount of bone char wash water. 5. Completely revamp the concentrating equipment in the lactic acid department. 6. Isolate certain waste water, such as the acid or alkali water from boiling out the evaporators when they are cleaned. 7. Eliminate the sewering of all excess process water by either re-using or evaporating 8. Possible reduction of the volatile matter in the condensate from the steep water. On the basis of this study the company proposed a program for eliminating the industrial waste. First, all water-bearing organic and inorganic solids from the Lake Michigan system, except such traces of sugar solids not possible to separate from the refinery water, would be eliminated. Studies had shown that if the solids entrained from the evaporators did not exceed 10 grains per gallon, they would have anegligible effect on the bioloading of the cooling water when diluted in volumes from 10 to 15 million gallons. Only such low solids-bearing water as the bone char wash water would be diverted to the Hammond system (not to exceed a load of 5000 population equivalents per 24 hours). All condensates from the steep water evaporators would be diverted after they had been partially treated for reducing the bioloading to the Hammond system. Waters sewered to the Hammond system would be limited to a maximum volume of 600,000 gallons per 24 hours with a total bioloading not to exceed 14,000 population equivalents. With this program and commitment before them, the company started an intense rebuilding program late in 1944. Final delivery and installation of all the equipment was delayed by war shortages and postwar strikes until late 1949. During this period of rebuilding, a program was carried out whereby an entire new laboratory unit of three permanent employees under the direct supervision of the process chemists division was set up. This unit collected daily operational data on the entrainment losses and bioloading on all effluents leaving the plant, and checked all trade waste losses. Permanent sampling stations were installed throughout the plant with automatic sampling devices as well as temperature and metering equipment. Methods for re-use and bottling u p of waste bearing water were also developed. An intense educational program was initiated to inform the process workers from bottom rank to superintendents of the problem, and studies were made on ways of reducing the volatile loading of the steep water cond nsate. At the end of 1949 the total bioloading had been reduced to 2.9 population equivalents per bushel of corn processed or a reduction of 66% from 1944. However, the problems of further reduction of the volatiles in the steep water condensate; possible losses of materials .through floor drains; excess loading from the oil refinery; excess bone char wash water; and excess process water still confronted the company. The volatiles in the steep water condensate were reduced by aerating them with approximately 25,000 cubic feet per minute of air, the air being at atmospheric temperature. This treatment effected an average biochemical oxygen demand reduction of 53%--about 15,000 population equivalents. The temperature of the aerated condensate averaged 80" F. as opposed to an initial temperature of 140' F. This appreciable temperature reduction was another asset. -4n illustration of the condensate aerators is given in Figure 2. The air-scrubbed condensate effluent has a normal p H of 2.0 and is very corrosive. T o eliminate the hazard to sewer lines, boiler blowdown water and the sludge from the lime-alum water treatment plant were added to these condensates. This mixture raised the p H to a value of 5.0. Additional lime is fed to the
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Figure 2.
Feed House Condensate Air Scrubbers
water by a n automatic feeder to maintain a p H of 7.0 on the sewered condensate. The loading to the Hammond sewer system was also reduced by using approximately 10% of the air-scrubbed condensate water in place of fresh water for washing the high protein cake produced in the Mac0 department. The problem of the floor drains was solved by the complete elimination of all floor drains from the sewer system. Floor drains could serve as avenues for the process worker to dispose of spills without supervisory detection. The load from the oil refinery could not htk reduced without installing approximately $100,000 worth of equipment. Since this was a small department and the returns from it did not justify such an expenditure, the refining of oil was discontinued. The reduction of the excess bone char wash water was solved by the re-use of 10,000 gallons back in the refinery for washing filter presses. Sixty thousand gdlons are filtered and re-used as wash water for starch used in making glucose. The balance of 40,000 gallons is sent to the Hammond sanitary system. The sugar content of the hone wash water was reduced to less than 600 pounds per day by washing the filters longer-a sweetening-off process. The excess sweet water along n-ith other waste water from the department is concentrated for use in the feed. Again, water that normally went to the sewer was further re-used. The company had been using fresh water for flushing the sirup out of the bone char filters. The fresh water was replaced with the condensate from the second and third effects of the sirup and sugar evaporators. This condensate contained less than 170 p.p.m. of sugar solids but it was a change to conserve on fresh water and to save on heating the water as the condensate is a t a temperature of about 140" F. The problem of using more of the excess process water back into the system had to be approached cautiously because of the possibility of jeopardizing the quality of the finished products through the introduction of excess amounts of salts and solubles. American Maize-Products Co., like the rest of the companies in the industry, operates under a bottled-up system. I n this system fresh water enters the process only on the filters washing the starch, The filtrate water from the starch washes are worked back through the system and finally leave the process as the con-
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cootino WATERS
DOUNLEO WLTER
FROM CRYSTLLIZERS
ICE MACHINE
NASH PUMP SEAL YLTEl
AIR COMPRESSOR COOLING WATER
ICE MACHINE
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BmEX Om.
SYRUP REFIKERY
C O O L i N G WATERS
DOWNLEG WATER
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VLCUUM PUMP SEAL WATER
DOWNLEG WATERS
COHDENSER COOLING WATERS
CONDENSATE FROH 2ND EfFECT OF PEEBLES DOUBLE-EVAPORATOR
TURBINE COOLINO WATER
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MYERS
STEAM CONDENSATES
CONDENSATE CODLIN6 WATERS
QWNLEO WATER 6 CONDENSLTES
,STARCH
HASH PUHP SEAL WATER
CONDENSLTE OVERFLOWS
PUMP 1 COMPRLSSOR COOLING WATER
ZBollERnoUsF BLOW DOWN WATER
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SACKULSN FROM FILTERS
2
COOLING WATERS
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water; using special starch filtrates, formerly considered harmful to the bottled-up system, back in the system; constructing a large special starch filtrate holding tank for slowly metering those filtrates harmful to the system back to the feed house evaporators; discontinuing the production of special starches which produce filtrates containing salts harmful to animal feed in any quantity; and carefully scheduling all special starch processing and the use of metering devices. In addition to the above ~ r o b l e m ,corrections were made in some of the equipment. Starch filter vacuum pump seal water lines were found to prime intermittently, subjecting the Lake Michigan system to occasional shock loads of starch filtrate water. To make this system foolproof, it was necessary to install a catch-all system to prevent this priming situation. Steep water- and manufacturing water heaters in use proved unsatisfactory. There were times when the tubes w~ouldleak, discharging process water into the condensate and thus rendering the condensate unfit for the boiler house. A t such times the condensate was discharged to the Lake Michigan system causing a high bioloading. These heaters, three in number, were replaced. The floor drains from the lactic acid and corn sirup solids departments were bottled up, which required a rather elaborate collecting system and proved t o be more of a problem than had been anticipated. However, it has 1%-orkedout quite satisfactorily. At t,he onset of the industrial m s t e abatement program the company realized that the bacterial condition of the water discharged back to Lake Michigan would be an important factor and plans were made ultimately to effect a coliform bacterial kill in all water discharged back into the lake. This condition was not a part of any st,ipulation or agreement entered into by the company. All incoming raw lake water is now chlorinated a t a rate sufficient t.o maintain a free chlorine residual of 0.5 to 0.8 p.p,m. in all water discharged to Lake Michigan.
* ? COLLECTING
Figure 3.
Diagram of Lake Michigan Outlet
centrated steep water. The water balance in this system requires very careful control to avoid larger excesses which cannot be evaporated. Also, the separation of the starch from the gluten is dependent upon this balance as is the quality of the finished starch. After considerable research on this problem, all excess starch filtrates were eliminated from the sewer system by piping starch filtrate water to the wet dust collecting system, replacing fresh
Summary To dat,e the company has effected a reduct'ion in the total bioloading of it,s plant effluent from an average of 350,000 popula-
CHBIISTRY LAMRATORY S l H l ORLlNS
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P I L O T PLLNT FLOOR D R l l N S
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PROCESS WATERS TABLE WASH WLTERS SPECIAL STARCH FILTRATES
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M L L HWSE STEEP HOUSE
O R STARCH FLOOR DRAlXS
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OIL EXPDLERS
FaHWSE STEAM VAPOR TRAPS PAN BOIL CdUSTlC
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OUTS
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CURH STORAGE SYRUP REFINERY SUUP
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WASH WATER FROM PRESS CLOTHS
CONDENSATES SPAULDING PiiLClPlTATOR SLUDGE BOILER BLOW DOW L I V E FEEDfR
Figure 4.
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Diagram of Hammond Sewer Outlet
Figure 5. Diagram of Lagoon Outlet
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Liquid Industrial Wastes tion equivalents daily in 1944 t o a present average daily loading of 28,000 population equivalents, a reduction of 92%. Of the present total loading, an average of 20,000 daily population equivalents is being disposed of t o t h e Hammond Sanitary District treatment plant, A substantial part of this load t o Hammond is bone char wash water and steep water condensate. A plant improvement program t h a t is now well under way should reduce this load by 40%. In effecting the aforementioned 92% reduction in t h e industrial waste loading, t h e company has instituted control measures t o eliminate the human factor as much as possible, and thereby ensure normal steady control with better than average freedom from accidental shock loads. All possible avenues of trade wastes have been thoroughly surveyed and are under constant surveillance. The present setup for the disposition of the eflluent from t h e plant is illustrated by Figures 3,4,and 5.
of solids materials normally considered waste, and not by elaborate pretreatment or sanitary disposal techniques. American Maize has incurred direct benefits from this program in t h a t the company now experiences a 1% increase in over-all plant yields over what was once thought normal. Figured a t t h e present cost of corn this is roughly worth $175,000 a year. Of course the company has exceeded the dictates of the law of diminishing returns to obtain this yield increase but it does help t o support the overhead imposed by the over-all program. T h e company has had t o carefully control all phases of production planning t o make the waste abatement program work and this has proved a hidden asset, in t h a t all plant operations now run more smoothly and are under more uniform control. T h e general production worker has been well informed as t o the part he plays in waste abatement. H e has developed a genuine interest and the results are improved morale and closer operation control.
Acknowledgment
Conclusion To accomplish this appreciable reduction in trade wastes, the company has invested roughly $850,000. It has replaced equipment, which under normal conditions still possessed years of usefulness, and it has injected practices into the normal manufacturing processes, which at one time would have been considered hazardous t o h a 1 product quality. But, in general, it has accomplished its reduction in trade waste by the elimination and saving
The company has cooperated t o the fullest extent possible with the Hammond Sanitary District on the mutual problems and the company is deeply indebted t o Carl B. Carpenter, superintendent of the Hammond disposal plant for his sincere cooperation and help in solving a problem t h a t would have otherwise been far more difficult. RECEIVBID for review September 6, 1951.
ACCEPTEDJanuary 12, 1952.
DAIRY INDUSTRY H. G. HARDING, NatZond Dairg Research Laborator~es, Inc., Oakdale, Long Island, N. Y.
Since reduction of biochemical oxygen demand in dairy waste waters by waste prevention and waste saving is much more economical than subsequent waste treatment, much progress in this direction has been made by the dairy industry. Any of the well-known waste disposal processes used for city wastes can be used successfully for dairy wastes, but may easily become too costly as this industry has a low margin of profit. Therefore, a continuing search is under way for reliable, low cost, modified treatment
methods. Combined treatment with city wastes, where adequate capacity and an equitable cost distribution agreement can be obtained, is preferable to separate treatment. In small dairy plants, aerated flow equalization may provide sufficient treatment or a valuable pretreatment. The trend in thedairyindustryistousevariousmodifications of standard biochemical oxidation treatments in trickle filters or activated sludge systems. A satisfactory and economical method of excess sludge disposal is still lacking.
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higher milk volume during the spring and summer months than during the winter months; and the extremely rigid and sometimes contradictory state and municipal sanitary codes, which frequently do not permit the very things that would be most helpful in reducing plant losses. For instance, the exacting sanitary requirements make it necessary to take all equipment apart for cleaning every day. It was also pointed out t h a t the trend in the dairy industry is toward large manufacturing plants fully equipped to handle all by-products, although there still are a t present a large number of widely scattered small plants incompletely equipped t o handle by-products. The establishment of more large by-product plants which utilize all available waste products from nearby small plants will do much to reduce stream pollution. The industry was also marked by extreme efforts toward waste saving and waste utilization within the dairy plants. Another trend was toward the segregation of cooling waters for discharge t o rivers or storm sewers or for recirculation over cooling towers, and segregation of domestic wastes for treatment in septic tanks or
H E waste disposal problem of the dairy industry as it appeared in 1947 was reviewed (16)at the Industrial Wastes Symposium held during the spring meeting of the AMERICAN CHEMICAL SOCIETYt h a t year. Some of the features of the industry t h a t make the waste problem particularly difficult were discussed. These were and still are the great variety of products made, all producing wastes of different strength and composition; the extremely wide distribution of both the sources of raw materials-namely, the more than 4 million dairy farms in this country and the still more widely distributed ultimate consumers, which are the entire population of the country; the high nutritional value of dairy products, which is their greatest asset as a food and is also their greatest drawback from the point of view of pollution; the perishable nature of the products, which makes it necessary to avoid all possible delay in processing which might be caused by power failures or breakdown of processing or transportation equipment; the highly seasonal character of the industry which makes it necessary to provide a great deal of expensive extra equipment and extra labor to handle the 50%
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