EPA 440/1-73/028
DEVELOPMENT DOCUMENT FOR
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
AND NEW SOURCE PERFORMANCE STANDARDS
FOR THE
GRAIN PROCESSING
SEGMENT OF THE
GRAIN MILLS
POINT SOURCE CATEGORY
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
DECEMBER 1973
-------
Publication Notice
This is a developemnt document for proposed effluent limitations
guidelines and new source performance standards. As such, this
report is subject to changes resulting from comments received
during the period of public comments of the proposed regulations.
This document in its final form will be published at the time the
regulations for this industry are promulgated.
-------
DEVELOPMENT DOCUMENT
for
PROPOSED EFFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
GRAIN PROCESSING SEGMENT OF THE
GRAIN MILLS POINT SOURCE CATEGORY
Russell Train
Administrator
Robert L. Sansom
Assistant Administrator for Air and Water Programs
Allen Cywin
Director, Effluent Guidelines Division
Robert J. Carton
Project Officer
December 1973
Effluent Guidelines Division
Office of Air and Water Programs
U. S. Environmental Protection Agency
Washington, D. C. 20U60
Protection Ae«oy
-------
AGENCY
-------
ABSTRACT
This document presents the findinqs of an extensive study of th- qrain
milling industry by the Environmental Protection Agency for the purpose
of developing effluent limitations guidelines. Federal standards of
performance, and pretr^atment standards for the industry, to implement
Sections SOU, 306, and 3')7 of the "Act."
Effluent limitations guiielines contained in this document set forth thf
dpqr^e of effluert reduction attainable through the apnlication of ^h0
bf-st practicable contr >l technology currently availanl<= and th:- degree
ot effluent reduction attainable through the application of the fc^st
available technology economically achievable which must be achieved uy
existing point sources by July 1, 1977 and July 1, 1983, respectively.
The Standards of Performance for new sources contained herein set forth
the degree of effluent reduction which is achievable through th-
application of the best available demonstrated control technology,
processes, operating methods, or other alternatives.
Separate effluent limitations guidelines are described for the follcwino
subcitegories cf the grain milling point source category; corn w~~
milling, corn dry milling, normal wheat flour milling, bulgur whear
flour milling, normal rice milling, and parboiled rice processinq.
Treatment technologies are recommended for the four subcategories wit 1;
allowable discharges: corn wet milling, corn dry milling, bulgur wheat
flow milling, and parboiled rice processing. They are generally
similar, and may include equalization, and biological treatment followed
by clarification. In order to attain the 1983 limitations additional
solid removal techniques will be necessary. The standards of
performance for new sources are the same as the 1983 limitations.
The cost of achieving these limitations are described. The highest
costs are in the corn wet milling subcategory. For a typical corn wet
milling plant with a grind of 60,000 bu/day, the investment cost for the
entire treatment system to meet the 1977 limitations is $2,5<4U,000. An
additional $288,000 will be necessary to install the solids removal
techniques to meet the 1983 standards. The economic impact of th0
proposed effluent limitations guidelines and standards of performance
are contained in a separate report entitle "Economic Analysis of
Proposed Effluent Guidelines-Grain Milling Industry."
Supportive data and rationale for developments of the proposed effluent
limitations guidelines and standards of performance are contained in
this report.
ill
-------
TABLE OF CONTENTS
SECTION page
I Conclusions 1
II Recommendations 3
III Introduction 5
Purpose and Authority 5
Summary of Methods 6
Source of Data 7
General Description of Industry 8
Production Processes 17
Waste Water Considerations 27
IV Industry Categorization 31
Factors Considered 31
V Water Use and Waste Water Characterization 35
Introduction 35
Corn Wet Milling 35
Corn Dry Milling 54
Wheat Milling 56
Rice Milling 57
VI Selection of Pollutant Parameters 59
Major Control Parameters 59
Additional Parameters 60
VII Control and Treatment Technology 63
Introduction 63
Corn Wet Milling 63
Corn Dry Milling 73
Wheat Milling 74
Rice Milling 75
VIII Cost, Energy, and Non-Water Qaulity Aspects 77
Representative Plants 77
Terminology 77
Cost Information 78
Non-Water Quality Aspects 85
IX Effluent Reduction Attainable Through the Ap- 87
plication of the Best Practicable Control
iv
-------
Technology Currently Available - Effluent
Limitations Guidelines
Introduction 87
Effluent Reduction Attainable Through the 87
Application of Best Practicable Control
Technology Currently Available
Identification of Best Practicable control 88
Technology Currently Available
Rationale for the Selection of Best 90
Practicable Control Technology Currently
Available
Restraints on the Use of Effluent Limitations Guidelines
95
X Effluent Reduction Attainable Through the Ap-
plication of the Best Available Technology 97
Economically Achievable - Effluent Limita-
tions Guidelines
Introduction 97
Effluent Reduction Attainable Through the 97
Application of the Best Available Tech-
nology Economically Achievable
Identification of Best Available Technology 98
Economically Achievable
Rationale for the Selection of the Best 99
Available Technology Economically
Achievable
XI New Source Performance Standards 103
Introduction 103
New Source Performance Standards 103
Rationale for the Selection of New Source 104
Performance Standards
XII Acknowledgments 107
XIII References 109
XIV Glossary 113
Conversion Table 115
-------
FIGURES
NUMBER page
1 The Corn Wet Milling Process 18
2 The Corn Dry Milling Process 21
3 The Wheat Milling Process 23
4 The Bulgur Process 24
5 The Rice Milling Process 26
6 The Parboiled Rice Process 28
7 Basic Milling Operations in a Typical
Corn Wet Mill 37
8 Finished Starch Production in a Typical
Corn Wet Mill 38
9 Syrup Production in a Typical
Corn Wet Mill 39
10 Effect of Wet corn Milling Plant Age on
Average BOD5 Discharged 47
11 Quantity of Waste Water Discharged by
Corn Wet Milling Plants 49
12 Average BODJ Discharged as a Function of
Corn Wet Mill Capacity 50
13 Average Suspended Solids Discharged as a
Function of Corn Wet Mill Capacity 51
14 Average BOD5 Discharged as a Function of
Waste Water Volume 52
15 Average Suspended Solids as a Function of
Waste Water Volume 53
vi
-------
TABLES
NUMBER Page
1 Uses of Corn Grown in the United States 9
2 Composition by Dry Weight of Yellow Dent Corn 10
3 Corn Wet Milling Companies and Plants 12
U Bulgur Mills - Locations and Estimated Capacities 14
5 Parboiled Pice Milling Companies 16
6 First and Second Effect Steepwater Condensate
Waste Water Characteristics 40
7 Finished Starch Production, Waste Water
Characteristics 41
8 Individual Process Waste Loads, Corn Wet Milling 42
9 Corn Syrup Cooling, Waste Water Characteristics 43
10 Total Plant Raw Waste Water Characteristics,
Corn Wet Milling 44
11 Waste Water Characteristics Per Unit of Raw
Material, Ccrn Wet Milling 46
12 Waste Water Characteristics, Corn Dry Milling 55
13 Waste Water Characteristics, Bulgur Production 56
14 Waste Water Characteristics, Parboiled Rice
Milling Processing 57
15 Effluent Reduction Attainable Through the Appli-
cation of Best Practicable Control Technology
Currently Available 88
16 Effluent Reduction Attainable Through the
Application of Best Available Technology
Economically Achievable 98
17 New Source Performance Standards 104
vii
-------
SECTION I
CONCLUSIONS
The segment of the grain milling industry that is covered ir. thir7
document (Phase I) has been classified into six subcategories. Thi?
categorization is based on the type cf grain and manufacturing process.
Available information on factors such as age and size of plant, product
mix, and waste control technologies does not provide a sufficient basi?
for additional subcategorization.
The subcategories of the grain milling industry are as follows:
1. Corn wet milling
2. Ccrn dry milling
3, Normal wheat flour milling
4. Bulgur wheat flour milling
5. Normal rice milling
6. Parboiled rice processing
-------
SECTION II
RECOMMENDATIONS
The recommended effluent limitations for the waste water parameter? of
significance are summarized below for the subcategories of the gr^in
milling industry covered in this document. These values represent the
maximum average allowable loading for any 30 consecutive calendar days.
Excursions above these levels should be permitted with a maximum daily
average of 3.0 times the average 30-day values listed below.
The effluent limitations to be achieved with the best practicable
control technology currently available are as follows:
BD
§usp_ended_Solids
Corn wet rrilling
Corn dry milling
Normal wheat flour
milling
Bulgur wheat flour
milling
Normal rice milling
Parboiled rice
milling
0.893
0.071
0.0083
0.140
50.0
4.0
0.625
0.062
35.0
3.5
no discharge of process wastes
0.5 0.0083 0.5
no discharge of process wastes
0.014
0.080
0.008
pP
6-9
6-9
6-9
Using the best available control technology economically achievable
the effluent limitations are:
BOD
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Eulgur wheat flour
milling
Normal rice milling
Parboiled rice
milling
0.357
0.0357
0.0050
0.070
20.0
2.0
0.179
0.0179
10.0
1.0
no discharge of process wastes
0.3 0.0033 0.2
no discharge of process wastes
0.007
0.030
0.003
pH
6-9
6-9
6-9
6-9
The recommended new source performance standards correspond, in all
instances, to the limitations defined above for the best available
control technology economically achievable.
-------
SECTION III
INTRODUCTION
PURPOSE ANC AUTHORITY
Section 301 (b) of the Act requires the achievement by not later than
July 1, 1977, of effluent limitations for point sources, other than
publicly cwned treatment works, which are based on the application of
the best practicable control technology currently available as defined
by the Administrator pursuant to Section 30^ (b) of the Act. Section
301 (b) also requires the achievement by not later than July 1, 1983, of
effluent limitations for point sources, other than publicly owner!
treatment works, which are based on the application of the best
available technology economically achievable which will result in
reasonable further progress toward the national goal of eliminating 1-h^
discharge of all pollutants, as determined in accordance with
regulations issued by the Administrator pursuant to Section 304 (t) of
the Act. Section 306 of the Act requires the achievement by new sources
of a Federal standard of performance providing for the control of the
discharge of pollutants which reflects the greatest degree of efflu^n*-
reduction which the Administrator determines to be achievable through
the application of the best available demonstrated control technoloay,
processes, operating methods, or other alternatives, including, where
practicable, a standard permitting no discharge of pollutants.
Section 304(fc) of the Act requires the Administrator to publish within
one year of enactment of the Act, regulations providing guidelines for
effluent limitations setting forth the degree of effluent reduction
attainable through the application of the best practicable control
technology currently available and the degree of effluent reduction
attainable through the application of the best control measures and
practices achievable including treatment techniques, process and pro-
cedure innovations, operation methods and other alternatives. The
regulations proposed herein set forth effluent limitations guidelines
pursuant to Section 304 (b) of the Act for the grain milling source
category.
Section 306 of the Act requires the Administrator, within one year after
a category of sources is included in a list published pursuant to
Section 306 (b) (1) (A) of the Act, to propose regulations establishing
Federal standards of performances for new sources within such
categories. The Administrator published in the Federal Register of
January 16, 1973 (38 F. R. 1624), a list of 27 source categories.
Publication of the list constituted announcement of the Administrator's
intention of establishing, under Section 306, standards of performance
applicable to new sources within the grain milling source category,
which was includedd within the list published January 16, 1973.
-------
SUMMARY OF METHODS USED FOR DEVELOPMENT OF THE EFFLUENT LIMITATIONS
GUIDELINES AND STANDARDS OF PERFORMANCE
The effluent limitations guidelines and standards of performance pro-
posed herein were developed in the following manner. The point source-
category was first categorized for the purpose of determining whether
separate limitations and standards are appropriate for different
segments within a point source category. Such subcategorizat.ion was
based upon raw material used, product produced, manufacturing process
employed, and other factors. The raw waste characteristics for each
subcategory were then identified. This included an analysis of (1) the
source and volume of water used in the process employed and the sources
of waste and waste waters in the plant; and (2) the constituents
(including thermal) of all waste waters including toxic constituents and
other constituents which result in taste, odor, and order, and color in
water or aquatic organisms. The constituents of waste waters that
should be subject to effluent limitations guidelines and standards of
performance were identified.
The full range of control and treatment technologies existing within
each subcategory was identified. This included an identification of
each distinct control and treatment technology, including both inplanr
and end-of-process technologies, which are existent or capable of being
designed for each subcategory. It also included an identification in
terms of the amount of constituents (including thermal) and tne
chemical, physical, and biological characteristics of pollutants, of th°
effluent level resulting from the application of each of the treatment
and control technologies. The problems, limitations and reliability of
each treatment and control technology and the required implementation
time was also identified. In addition, the nonwater quality
environmental impact, such as the effects of the application of such
technologies upon other pollution problems, including air, solid waste,
noise and radiation were also identified. The energy requirements of
each of the control and treatment technologies were identified as well
as the cost of the application of such technologies.
The information, as outlined above, was then evaluated in order to
determine what levels of technology constituted the "best practicable
control technology currently availabler" "best available technology
economically achievable" and the "best available demonstrated control
technology, processes, operating methods, or other alternatives." In
identifying such technologies, various factors were considered. These
included the total cost of application of technology in relation to the
effluent reduction benefits to be achieved from such application, the
age of equipment and facilities involved, the process employed, the
engineering aspects of the application of various types of control
techniques, process changes, nonwater quality environmental impact
(including energy requirements,) and other factors.
-------
SOURCES OF DATA
The data for identification and analyses were derived frcm a number of
sources. These sources included published literature, previous EPA
technical publications on the industry, a voluntary information
retrieval form distributed to the Corn Refiners Association and to ether
grain millers, information contained in Corps of Engineers discharge
permit applications, and on-site visits, interviews, and sanplina
programs at selected grain milling facilities throughout the United
States. A more detailed explanation of the data sources is giver trlow.
All references used in developing the guide lines for effluent
limitations and standards of performance for new sources reported herein
are included in Section XIII of this document.
During this study the trade associations connected with the grain
milling subcategories covered by this study were contacted. These
associations are listed below:
Milling_subcategorv.
Wet Corn
Dry Ccrn
Normal Wheat Flour
Bulgur Wheat Flour
Rice, Normal & Parboiled
Association
Corn Refiners Association, Inc.
American Corn Millers Federation
Millers National Federation
Assoc. of Operative Millers
National Soft Wheat Millers Association
Protein Cereal Products Institute
Rice Millers Association
These associations were informed of the nature of the study and their
assistance was requested. Subsequently a voluntary data retrieval form
was made available to them and also to individual plants. This form is
shown in Table . The completed forms provided a more detailed source
of information about the various plants including manufacturing
processes, data on raw materials and finished products, waste
characterization and sources, waste treatment, and water requirements.
All of the existing plants in the corn wet milling, bulgur wheat flour
milling, and rice milling subcategories were covered. Based on the 1971
Directory of the Northwestern Millers there are 126 corn dry mills
listed. The plants contacted comprise 70-75 percent of corn processed
by the corn dry milling industry. An unknown percent of the normal
wheat flour milling industry was contacted. A summary of the plants who
responded and those forms with usable data are shown below.
Retrieval Forms
Industry
Corn Wet Milling
Corn Dry Milling
Wheat Milling "
Eulgur Milling
Rice Milling:
Ordinary Process
Parboiled Process
Retrieval Forms
Returned with
UsableData
16
9
47
6
29
28
5
15
4
20
2
9
8
2
-------
RAPP applications to the Corps of Engineers for discharges together with
computerized FAPP data, supplied by EPA, were also used as a source of
data. These data included the identification of the plant, the number
of waste discharge points, the volumes of discharge, and the character
and quantity of waste. The number of sources included in the FAPP
applications was seven in the corn wet milling industry, two in the
normal wheat milling industry, and one in the parboiled rice industry.
Plant visits provided information about the manufacturing process, the
distribution of water, sources of wastes, type of equipment used,
control of water flows, in-plant waste control, and effluent treatment.
A total of eleven plants were visited in the following subcategories:
Industry Tota1_P1 ant s visited
Corn Wet Milling 5
Corn Dry Milling 1
Normal Wheat Flour 1
Bulgur Wheat Flour 1
Parboiled Rice 3
In addition to the above, several plants in each category were contacted
by telephone for information on the industry and waste handling.
Detailed data were obtained during these conversations consisting of raw
material description, flow rates, waste quantities, and waste treatment.
Plant sampling of each industry subcategory was provided at a total of
eight plants with emphasis focused on plants having typical waste loads
and waste treatment facilities. The sampling program provided data on
the raw and treated waste streams. It also provided verification of
data on waste water characteristics provided by the plants.
Industry Total Plants^ Sampled
corn Wet Milling 4
Corn Dry Milling 1
Bulgur Milling 1
Parboiled Rice Milling 2
GENERAL DESCRIPTION OF THE INDUSTRY
The cultivation, harvesting, and milling of grains dates back to the
beginning cf recorded history. Wheat was first cultivated in Asia,
later became prominent in Europe, and was introduced to the United
States by the colonists in the early 1600's. Similarly, rice originated
in Asia thousands of years ago and was brought to this country in the
mid 1600's. Corn or maize is the only one of the three major cereal
grains that is indigenous to this country, and was cultivated by the
Indians long before Columbus discovered America.
-------
The cereal arains, sc-called because they can be used as food, inclule
barley, corn, grain sorghum, millet, oats, rice, rye, and wh^at. This
report, however, only covers the milling of the three principal grains,
namely, corn, wheat, and rice.
Corn
With an annual agricultural yield of about 140 million metric tons (5.5
billion bushels), the United States is easily the largest corn producer
in the world. About 80 percent of the corn crop is used as animal feed,
as shown in the accompanying table. Some eight percent of the corn is
milled into various products and the remainder of the crop is used for
table and breakfast foods, alcohol, and other industrial products or is
exported.
Table 1
Uses of Corn Grown in the United states
Percent of total corn_prQduction
Feed 77.3
Export 14.0
Wet milling 5.7
Dry milling 2.2
Alcohol 0.8
Seed 0.3
Breakfast food 0.2
Corn is milled by either dry or wet processes, and the production
methods and final products of each are distinctly different. Corn dry
milling produces meal, grits, and flour while the principal products of
corn wet rrilling are starch, oil, syrup, and dextrose.
Corn_Wet_Millin2-
The corn wet trilling industry is an American development and originated
with the commercial extraction of starch from corn in 1842, at a time
when the greatest source of starch was from wheat and potatoes. Starch
from the corn wet trilling process now accounts for 95 percent of the
American starch output.
The first corn wet mills were segregated to produce either finished
starch or corn syrup. Not until the turn of the century was a combined
mill developed to produce both starch and syrup. Many of the present
milling companies had their beginning at about this time as most of the
existing milling plants were consolidated.
Today, twelve companies operate 17 plants in seven states with a total
corn grind cf over seven million metric tons per year (275 million
bushels per year). A list of the companies and plants is given in Table
3. Of these plants, eight were put into operation since 1949, utilizing
-------
newly developed equipment and methods of operation -to provide better
products, higher yields, and less waste. The older plants meanwhile,
have incorporated new process procedures and replaced nearly all
equipment with more efficient machinery providinq cleaner operating
conditions and increased yields with reduced odors, wastes, and water
usaqe. The raw material for corn wet millinq is the whole kernel. Most
of the qrain, primarily hybrid yellow dent corn, comes from the midwest
or Corn Belt reqion of the country. The composition of yellow dent corn
is qiven in Table 2.
Table 2
Composition by Dry Weiqht of Yellow Dent Corn
Percent
Carbohydrates
Protein
Oil
Fiber
Ash
80
10
U.5
3.5
2.0
The standard unit of measure cf corn in the United States is the tushel
(25.1 kq) and plant size is measured by the number of bushels of corn
processed per day. Wet millinq plants receive the corn kernels at 10 to
25 percent moisture. The standard bushel is defined, for purposes of
this repcrt, as 25.4 kq (56 Ibs) corn at 15.5 percent moisture. The 17
corn wet mills in this country ranqe in size from about 380 to 3050
kkq/day (15,000 to 120,000 SBu/day).
CORN <
STEEPING
k.
f
CORN OIL
EXPELLING
AND REFINING
1
WE
SE
4-
STEEPWATER
>
GERM
IT MILLING
D STARCH
.PAR AT ION
HULLS
GLUTEN
r
FEED
DRYING
^ CORN OIL
WATER
+
STARCH
STA
MODI
^ANIMAL ™
T FEED
BCH
ING,
FYING
~M<
SYRUP
HYDROLYSIS
AND REFINING
REGULAR AND
MODIFIED STARCHES
CORN SYRUP
' & DEXTROSE
CORN WET MILLING
The corn wet milling can be considered as three basic process
operations, namely millinq, starch production and syrup manufacturinq as
shown in the accompanying schematic diagram. The initial wet millinq
10
-------
sequence separates the basic components of the corn kernel into starch,
germ, gluten, and hull. The individual process operations include
steepinq, grinding, washing, screening, centrifugation, and flotation.
Following the basic milling and separation operations, the product
slurry may be dried, modified and then dried, or converted +:o corn syrun
or dextrose. In processing the starch slurry from the wet mill inn
operations, the fractions are proportioned between the starch finishim
and corn sweeteners departments. The supply of starch distributed to
each will depend on daily and seasonal fluctuations controlled by ~h"
economic situation and, ultimately, customer demand and competition.
Products from the dry starch operations may be classified as regular
(unmodified) and modified starches. The purpose of modification is *:o
change the resultant starch characteristics to conform to the specific
needs of the industry using the product. Starch modifications are
accomplished, generally, by chemically treating the raw starch slurry
under closely controlled conditions. In the corn sweetener department,
the starch slurry is hydrolyzed to corn syrup and dextrose.
The finished products of starch and corn sweeteners resulting from the
corn wet milling process, as well as the secondary products, have many
uses in the home and industry. A portion of the finished products are
used directly in the home, but the bulk of the products are distributed
among industrial users. Food products account for 1/U to 1/3 of th<~-
total starch and starch converted products. The list of industrial uses
includes, in descending order of quantity: paper products, food
products, textile manufacturing, building materials, laundries, and
other miscellaneous applications.
Corn Dry Milling-
Ccrn dry milling differs in almost all respects from wet milling, except
in the raw material used. The grinding or dry milling of corn oredat^^
wet milling by hundreds of years. Today, a little over two percent of
the total ccrn production is processed by the dry millers.
There are approximately 126 corn dry mills throughout the country,
although most are located in the midwestern Corn Belt, ranging in siz-
from very small millstone operations to large modern mills with capa-
cities up to about 1500 to 1775 kkq/day (60,000 to 70,000 SBu/day.) The
larger plants process about 90 percent of the corn in the dry milling
segment of the industry.
Most small millers are distinguished from the larger plants in both
production methods and finished products. Specifically, the small mills
usually grind the whole kernel and produce only ground whole corn meal.
These small mills use little, if any, water and will not he discussed
further in this report.
The larger irills employ a number of production steps designed to
separate the various fractions of the corn, namely the endosperm, bran,
and germ. The primary oroduction sequence is shown on thu-
-------
Table 3
Corn Wet Milling Companies and Plants
American Maize-Products Company
250 Park Avenue
New York, New York 10017
Plant: Hammond, Indiana 46326
Anheuser-Busch, Inc.
P.O. Box 1810 Bechtold station
St. Louis, Missouri 63118
Plant: Lafayette, Indiana 47902
Cargill, Inc.
Cargill Building
Minneapolis, Minnesota 55402
Plants: Dayton, Ohio 45414
Cedar Rapids, Iowa 52401
Clinton Ccrn Processing Company
Division of Standard Brands, Inc.
Clinton, Iowa 52732
Plant: Clinton, Iowa 52732
Corn Sweeteners, Inc.
P.O. Box 1445
Cedar Rapids, Iowa 52406
Plant: Cedar Rapids, Iowa 52406
CPC International Inc.
International Plaza
Englewood Cliffs, New Jersey 07632
Plants: Argo, Illinois 60501
Pekin, Illinois 61555
North Kansas City, Missouri
Corpus Christi, Texas 78048
Dimmitt Corn Division
Amstar Corporation
Dimmitt, Texas 79027
Plant: Dimmitt, Texas
79027
Grain Processing Corporation
Muscatine, Iowa
Plant: Muscatine, Iowa 52761
The Hubinger Company
Keokuk, Iowa 52632
Plant: Keokuk, Iowa
52632
National Starch and Chemical
Corporation
750 Third Avenue
New York, New York 10017
Plant: Indianapolis
Indiana 46206
Penick and Ford, Limited
(Subsidiary of VWR United
Corporation)
Cedar Rapids, Iowa 52406
Plant: Cedar Rapids, Iowa
A. E. Staley Manufacturing
Company
Decatur, Illinois 62525
Plants: Decatur, Illinois
62525
Morrisville, Penn-
sylvania 19067
-------
accompanying diagram. The corn is first cleaned and then tempered to a
moisture content of about 21 percent. The germ and bran are separated
from the endosperm in a series of grinding/ sifting, classifying, and
aspirating operations. In an additional step, corn oil is mechanically
extracted from the germ. The final products of a typical corn dry mill
include corn meal, grits, flour, oil, and animal feed.
WATER
WATER
CORN-
DRYING,
T F SIFTING
BRAN I GERM
ANIMAL
FEED
I CORN MEAL,
~ GRITS, FLOUR
^ OIL
T EXTRACTION
1 SPENT
1 GERM
ANIMAL
FEED
w CORN
r OIL
CORN DRY MILLING
Wheat
Wheat production is now the largest of any cereal grain in the world.
The United States produces about 38 million metric tons (1.5 billion
bushels) and is second only to Russia in total production. In this
country, about 40 percent of the wheat is milled into flour and the
remainder is used for breakfast foods, macaroni products, animal feed,
alcohol production, and ether more limited markets.
The milling of wheat in the United States is handled by over two hundred
plants of various sizes and ages, scattered across the country. There
are several types of wheat and various grades of each type available to
the wheat miller. In some mills, other grains are milled using similar
operations. Different kinds of wheat or regulated blends of wheat are
mixed at the mills, together with various additives. These products are
formulated to customer specifications to meet the required qualities for
final use.
Preparation of wheat into ground flour or granular products is
fundamentally a dry milling process. Other similar grains such as rye
and durum, not detailed separately in this report, are milled by
comparable processes. Some variations may be found in the cleaning
process and in the milling and separation based on the prime product
requirements.
Wheat milling, shown below, begins with cleaning with water or air. The
wheat is then tempered to about 17 percent moisture and milled in roller
mills. The germ and bran are separated from the flour by sifting.
WATER
WHEAT •
STORAGE
CLEANING
k
f
k
f
MILLING &
SIFTING
IGERM
[BRAN
FLOUR
MILLFEED
WHEAT MILLING
13
-------
A special process of particular significance to this study, is the
production of bulgur shown in the next diagram. Bulgur is wheat that is
parboiled, dried, and partially debranned for use in either cracked or
whole grain form. Bulgur is produced primarily for the Federal
Government as part of a national effort to utilize surplus wheat for
domestic use and for distribution to underdeveloped countries as part of
the Foods for Peace program. There are five bulgur mills in this
country ranging in size from about 145 to 408 kkg/day (3200 to 9000
cwt/day). The companies, plant locations, and estimated capacities are
given in Table 4.
WATER
WHEAT
BULGUR
MILLFEED
BULGUR PRODUCTION
Table 4
Bulgur Mills - Locations and Estimated Capacities
Archer Daniels Midland Co.
Shawnee Mission, Kansas 66207
Plant: Abilene, Kansas
Burrus Mills Division
Cargill, Inc.
Dallas, Texas 75221
Plant: Dallas, Texas
California Milling Corporation
Los Angeles, California 90058
Plant: Los Angeles, California
Fisher Mills, Inc.
Seattle, Washington 98134
Plant: Seattle, Washington
Lauhoff Grain Company
Danville, Illinois 61832
Plant: Crete, Nebraska
227
145
5000
3200
204
408
272
4500
9000
6000
14
-------
Pice
The unique nutritional and chemical qualities of rice makes it one of
the world's most important food products. In the United States, i-t- is
used in numerous products and in many forms including (in descendinq
order) :
Direct table food
Brewing
Breakfast cereals
Soups, canned foods, baby foods
Crackers, candy bars, and others
Production of rice is scattered throughout the world with the greatest
crop concentration in Asia and nearby island areas. Although; the United
States produces only a small percentage of the total crop, it is the
world's largest exporter. The cultivation of rice in the United States
began around 1635 in South Carolina. Rice is now produced in thirteen
states with an annual grain production over 3.8 million metric tons in
1972 (8.5 billion pounds). Texas, Arkansas, Louisiana, and California
produce 97 percent of this total. There has been a gradual decline in
the number of rice companies, and a corresponding decline in the number
of mills operated. In 1973 there were 36 companies in the United States
operating 42 rrills.
Milling of rice differs from ether cereal milling in that the product is
the whole grain rather than flour or meal. The milling sequence, shown
in the accompanying diagram, begins with the cleaning of the rough rice
and removing the inedible hulls by passing the grain through shelling
devices or hullers. Aspirators then separate the loosened hulls from
the resultant brown rice which, in turn, is milled to remove the coarse
outer layers of bran and germ using machines called pearlers. The bran
and germ are separated from the milled rice and the final white rice
product is sized, enriched with vitamins and minerals, and packaqed.
Fice hulls, bran, polish, and small pieces of the grain may be sold sep-
arately or combined into so-called millfeed for animals. The average
yields for ordinary rice milling are:
Percent
Whole grain white rice 54
Broken grain rice 16
Hulls and waste 20
Bran 8
Rice polish 2
VITAMIN
MINERALS
RICE—M CLEANING I—M MILLING
SEPARATION -l-k WH°LE GRAIN RICE
JBRAN
GERM
RICE POLISH
BROKEN GRAIN RICE
MILLFEED
ORDINARY RICE MILLING
15
-------
Parboiling rice has been practiced in foreign countries for years and
differs significantly from ordinary rice milling. The manufacturing
process was introduced in the United States in 19UO. At present, there
are six known parboiled rice plants in this country, as given in Table
5, four in Texas, one in Arkansas, and one in California. The purpose
of parboiling rice is to force some of the vitamins and minerals from
the bran into the endosperm. The product also has superior cooking
qualities and is more impervious to insect damage in storage.
Table 5
Parboiled Rice Milling companies
Blue Ribbon Rice Mills, Inc.
Box 2587
Huston, Texas 77001
Comet Rice Mills, Inc.
Box 1681
Houston, Texas 77001
P&S Rice Mills, Inc.
Box 55040
Houston, Texas 77055
Rice Growers Association of California
111 Sutter Street
San Francisco, California 9410U
Plant: Sacramento, California
Riceland Foods
Box 927
Stuttgart, Arkansas 72160
Uncle Ben's, Inc.
Box 1752
Houston, Texas 77001
The manufacturing process, shown below, begins with careful clean-
ing of the rice. The rice is then parboiled by soaking in water
and cooking to gelatinize the starch. Procedures for soaking and
ccoking are carefully controlled to produce suitable product pro^-
perties and yields. After cooking, the water is drained and the
parboiled rice is dried before milling in the same manner employed
for ordinary rice milling.
RICE
WATER
VITAMIN
MINERALS
CLEANING
k
T
PARBOILING
k
w
k
w
WACTFV^TFR "'»!
-------
PRODUCTION PROCESSES
The production methods used in milling the various grains differ
significantly in most cases as summarized earlier in this section. ^h0
following discussion provides a more detailed description for each
industry subcategory of the processes used in milling.
Corn_Wet_Milling
Storage_and_Cleaning-
Corn wet milling, shown in Figure 1, begins with the delivery to the
plant of shelled corn, normally No. 3 grade or better. The corn is dry
cleaned to remove foreign materials, stored, and dry cleaned a second
time prior to entering the main production sequence.
Steeping, the first step in the process, conditions the grain for
subsequent milling and recovery of corn constituents. This process
softens the kernel for milling, helps break down the protein holding the
starch particles, and removes certain soluble constituents.
The steeping process consists of a series of tanks, usually referred to
as steeps, and might be termed a batch-continuous operation. Each steeo
holds about 51 to 152 kkg (2000 to 6000 SBu) of corn, which is submerged
in continuously recirculating hot water (about 50 degrees C). Sulfur
dioxide in the form of sulfurous acid is added to the incoming water to
aid in the steeping process.
As a fully-steeped tank of corn is discharged for further processing,
fresh corn is added to that steep tank. Incoming water to the total
steeping system is derived from recycled waters from other operations at
the mill, and is first introduced into the tank with the oldest corn (in
terms of steep time) and passes through the series of steeps to the
newest batch cf corn. Total steeping time ranges frcm 28 to 48 hours.
Steep_water_Eva£or at ion-
Water drained from the newest corn steep is discharged to evaporators as
so-called light steepwater containing about six percent of the original
dry weight of the grain. On a dry weight basis, the solids in the
steepwater contain 35 to 15 percent protein and are recovered for
addition to feeds. Such recovery is effected by concentrating the
steepwater to 30 to 55 percent solids in triple effect evaporators. The
resulting steeping liquor, or heavy steepwater, is usually added to the
fibrous milling residue which is sold as animal feed. Some steepwater
may also be sold for use as a nutrient in fermentation processes.
Milling-
The steeped ccrn then passes through degerminating mills which tear the
kernel apart to free the germ and about half of the starch and gluten.
The resultant pulpy material is pumped through liquid cyclones or
flotation separators to extract the germ from the mixture of pulp,
17
-------
SHELLED CORN
STORAGE AND
CLEAING
ST EEPW ATER
ST EEPW ATER
E V APORAT ORS
STEEPWATER
CONCENTRATES
HULL
GLUTEN
FEED DRIERS
FEEDS
STEEP TANKS
DEGERMINATORS
GERM SEPARATORS
GRINDING MILLS
WASHING SCREENS
CENTRIFUGAL
SEPARATORS
STARCH
WASHING MIHIS
1
I
I
I l 1
! STARCH
"* MODIFYING J
STARCH DRIERS
CORN SYRUP
DRY STARCHES
DEXTRIN
ROASTERS
D E X T R I N S
GERM
*
WASHING S ORfINC
OF URMS
OIL EXTRACTORS
SYRUP & SUGAR
(ON V! R10R5
1
R E F 1 N
N G
DRUM or SPRAY
DRIERS
SUGAR
CRVSTAIUHRS
CORN SYRUP SOUDS
CENTRIFUGALS
DEXTROSE
FIGURE 1
THE CORN WET MILLING PROCESS
18
-------
starch and gluten. The germ is subsequently washed, dewatered, dri^d,
the oil extracted, and the spent germ then sold as ccrn oil meal.
The product slurry passes through a series of washing, grinding, and
screening operations to separate the starch and gluten from the fibrous
material. The hulls are discharged to the feed house where they are
dried and used in animal feeds.
At this point, the main product stream contains starch, gluten, and
soluble organic materials. The lower density gluten is then separated
from the starch by centrif ugation, generally in two stages. A hiah
quality gluten of 60 to 70 percent protein and 1.0 to 1.5 percent
solids, is then centrif uged, dewatered, dried, and added to the animal
feed. The centrifuge underflow containing the starch passes to starch
washing filters to remove any residual gluten and solubles.
Starch_Producti.on-
The pure starch slurry can now be directed into one of three basic
finishing operations, namely ordinary dry starch, modified starches, and
corn syrup and sugar. In the production of ordinary pearl starch, th-
starch slurry is dewatered using vacuum filters or basket centrifuges.
The discharged starch cake has a moisture content of 35 to <42 percent
and is further thermally dewatered by one of several different types of
dryers. The dry starch is then packaged or shipped in bulk, or a
portion may be used to make dextrin.
Modified starches are manufactured for various food and trade industries
for special uses for which unmodified starches are not suitable. For
example, large quantities of modified starches gc into the manufacture
of paper products, serving as binding for the fiber. Modifying is
accomplished by treating the starch slurry with selected chemicals such
as hydrochloric acid to produce acid-modified, sodium hypoclorite to
produce oxidized, and ethylene oxide to produce hydroxyethyl starches.
The treated starch is then washed, dried, and packaged for distribution.
Since most chemical treatments result in a more water soluble product,
waste waters from the washing of modified starches may contain a large
concentration of BOD_5. In addition, because of the presence of residual
chemicals, and dissolved organic materials, these waste waters often
cannot be reused and must be discharged to the sewer.
In most corn wet mills, about 40 to 70 percent of the starch slurry is
diverted to the corn syrup and sugar finishing department. Syrups and
sugars are formed by hydrolyzing the starch, partial hydrolysis
resulting in corn syrup and complete hydrolysis producing corn sugar.
The hydrolysis step can be accomplished using mineral acids or enzymes,
or a combination of both. The hydrolyzed product is then refined, a
process which consists of decolorization with activated carbon and
removal of inorganic salt impurities with ion exchange resins. The
refined syrup is concentrated to the desired level in evaporators and
ccoled for storage and shipping.
19
-------
The production of dextrose is quite similar to that of corn syrup, the
major difference being that the hydrolysis process is allowed to go to
completion. The hydrolyzed liquor is refined with activated carbon and
ion exchange resins to remove color and inorganic salts, and the product
stream is concentrated to the 70 to 75 percent solids range by
evaporation. After cooling, the liquor is transferred to crystallizing
vessels where it is seeded with sugar crystals from a previous batch.
The solution is held for several days while the contents are further
cooled and the dextrose crystallizes. After about 60 percent of the
dextrose sclids have crystallized, they are removed from the liquid by
centrifuges, dried, and packed for shipment. A smaller portion of the
syrup refinery is devoted to the production of corn syrup solids. In
this operation, refined corn syrup is drum or spray-dried to generate
corn syrup solids, which are somewhat more convenient to use than the
liquid syrup.
The corn dry milling process is shown in Figure 2 and begins with Grade-
No. 2 or better shelled corn as the raw material. After dry cleaning,
some mills wash the corn to remove any remaining mold. Waste waters
from the washing operation normally go to mechanical solids recovery,
using dewatering screens or settling tanks. The solids from this
operation are added to the hominy feed and the spent wash water is
discharged frcm the plant.
Tempering, the first process operation, raises the moisture content of
the corn tc the 21 to 25 percent level necessary for milling. The corn
passes through a degerminatcr that releases the hull and germ from the
endosperm and the product stream is dried and cooled in preparation for
f ractionation.
Fractionaticn comprises a series of roller mills, sifters, aspirators,
and separators. The product stream first passes through corrugated
roller mills or break rolls and then to sifters. This process may be
repeated several times and, after the separation of the germ and hulls,
the fine product stream goes to reduction mills to produce corn flour.
Corn grits and meal are removed earlier in the fractionating sequence.
The separated germ goes to oil expelling operations, where approximately
10.7 to 1U.3 kg/kkg (0.6 to 0.8 Ibs/SBu) of oil are recovered from the
ccrn.
A few of the larger mills further process the grits, meal, and flour
through expanders and/or extruders. Such processing is not an integral
part of the basic milling sequence and is not practiced by most small
and mediurr sized mills.
Wheat, Milling
Wheat milling has been subdivided into two segments, normal flour
milling and bulgur production. The production methods differ con-
siderably and are discussed separately in the following paragraphs.
20
-------
CORN
^
r
WASHING &
DE WATER ING
'
RECEIVING
STORAGE &
DRY CLEANING
1
TEMPERING
SOLIDS
RECOVERY
^
. I
WASTEWATER
SOLIDS
TO FEED
DEGERMING
DRYING &
COOLING
HULLS
MILLFEED
GERM
OIL EXPELLING
& EXTRACTING
CORN OIL
MILLING &
SIFTING
I l COP
J ' 4
CORN GRITS
MEAL
REDUCTION
MILLING
CORN FLOUR
FIGURE 2
THE DRY CORN MILLING PROCESS
21
-------
N o r ma 1_F 1 g ur _M i 1 1 i ng -
The wheat milling process, presented in Figure 3f starts vvith dry,
matured, graded, sound, and partly cleaned wheat seed. Grain, as
needed, is moved from storage to the cleaning house for final cleaning
prior to milling. It is here that other seeds, grains, arid foreign
matter such as sticks, stones, and dust are removed. The type of
equipment and sequence of steps in the cleaning operation, as well as
the extent of cleaning, may vary between mills. As a final cleaning
step, a few mills use a water wash following air cleaning. The wash
adds about one percent moisture to the original wheat and is believed to
reduce microbiological contaminants. The excess water from washing is
removed by centrifugal force. Prior to grinding, the wheat is tempered
and conditioned by adding water under carefully controlled conditions to
bring the moisture content up to desired levels, usually 15 to 20
percent. The amount and method of moisture addition, soaking time,
temperature, and conditioning time will vary for different grades of
grains and individual rrill procedures.
After tempering, the wheat is ready for milling, which is normally
performed in two sets of operations. The first, or break system,
comprises a series of corrugated rolls, sifters, and purifiers. This
milling operation breaks open the bran. The mixture of free bran,
endosperm, germ, and bran with adhering endosperm are scalped over
sifters. The scalped fractions of endosperm go into purifiers for
separation and grading.
The second, or reduction, system consists of a series of smooth roller
mills to reduce the granular middlings (endosperm) from the first system
to flour. After each reduction, the product is sifted to separate the
finished flour, germ, and the unground endosperm. The latter is sent
back to reduction rclls for further processing. At the end of the
milling operation, the discharged flour is treated with a bleaching
agent to mature the flour and neutralize the color. Depending upon its
end use, the flour may be blended or enriched. It is then directed into
storage hoppers prior to packaging or bulk shipping.
Millers may vary the milling procedures used in the different steps
described above. Flour emerges at several points in the process and may
be kept separate or the various streams combined. The products from the
individual mills differ in type and quantity of flour produced. By-
products from the milling industry consist primarily of the wheat germ,
shorts, bran, and unrecovered flour. These byproducts, know as
millfeed, are generally used as animal and poultry feed additives.
Of the various processes in the manufacture of bulgur, the most familiar
is a continuous mechanized system which is herein described and shown in
Figure 4. As a first step, the wheat is thoroughly cleaned and graded
by conventional cleaning processes to remove loose dust, dirt, and
chaff. The wheat enters a washer which also raises the moisture
content. From the washer, the wheat is conveyed to the top of the first
22
-------
WATER
WASTEWATER
MILLFEED
WHEAT
RECEIVING
STORAGE &
DRY CLEANING
EAT
4ING
L
1 |
r^
TEMPERING
BREAKER
BRAN
SIFTER
I
PURIFIER
REDUCING
ROLL
GERM
SIFTER
ADDITIVES
BLEACHING &
ENRICHING
FLOUR
WATER
STEAM
FIGURE 3
THE WHEAT MILLING PROCESS
23
-------
WHEAT
RECEIVING
STORAGE &
DRY CLEANING
WATER
WASTEWATER <
WATER
STEAM
STEAM
BRAN
MILLFEED
WASHING
SOAKING
PRESSURE
COOKING
DRYING
COOLING
POLISHER
GRINDING
SIFTING
ENRICHING
& BLENDING
BULGUR WHEAT
FIGURE 4
THE BULGUR PROCESS
MEAL & FLOUR
24
-------
of a series of soaking or tempering bins where the grain is conditioned
as it progresses continuously through each bin from top entry to bottom
of discharge. Water and live steam are added to the grain between each
bin as it travels along a transfer conveyor from the bottom of the first
bin to the top of the second. The process is repeated for the next bin
with a progressively higher moisture content and temperature. Time,
percent moisture, and temperature are all important variables and
require clcse control during this soaking sequence.
Upon leaving the bottom of the last tempering bin, the wheat enters a
pressurized steam cooker where the starch in the kernel is gelatinized.
The cooked wheat is discharged to a series of two continuous dryers, the
first for the removal of surface moisture and the second to reduce the
moisture content to 10 to 11 percent.
Variations to the general procedures outlined above occur between
manufacturing plants. Conventional grain milling procedures, similar to
those used in normal flour production, follow the drying operations.
The dried wheat is conveyed to a polisher (pearler or huller) follcwed
by a series of grinders and sifters, which separate the fines and bran
from the granular finished product. The combined by-products, approxi-
mately 10 percent of the raw materials, are disposed of as animal feed
while the bulgur is packed in 100 Ib bags for shipment.
Rice_Millin2
The raw material for rice milling may be one of several varieties of
rice, which are normally classified as long grain (such as Bluebelle and
Bluebonnet), medium grain (such as Nato and Nava) , and short grain (such
as Pearl). Each variety is graded according to U.S. Department of
Agriculture standards. In this country, the long grain rice is
preferred.
Normal rice milling is a dry process operation and is described herein
only to contrast it with parboiled rice production. The latter adds a
cooking or parboiling step ahead of the conventional milling sequence.
Norma1_Rice_Mi11ing-
The production operations, shown in Figure 5, begin with the cleaning of
the rough rice. Shaker screens and aspirators are used to remove
foreign materials, hulls, and chaff. The cleaned rice is then dehulled
in roller shellers or hullers with the loosened hulls removed by
aspirators. Rough rice that is not dehulled is separated from the brown
rice in a paddy machine, or separator, and returned to a second set of
shellers.
At this point, brown rice may be removed as a finished product or
processed through the complete milling operation. Calcium carbonate is
added as an abrasive to help in removing the bran from the rice in the
pearlers. In some cases, water is added to the brown rice to aid in the
removal of tightly adhering bran layers and improve the adhesion of the
calcium salt to the kernel. The pearlers remove most of the bran with
25
-------
ROUGH RICE
DRAFT
RECEIVING
STORAGE &
DRY CLEANING
SHELLER
HULLS
BRAN &
RICE POLISH
BRAN
r VITAMIN
SEPARATOR
1
1
PEARLER 1
|
BRUSH
S& 1
TO MILLFEED MINERALS
ADDITION
TRUMBLE
BROWN RICE
RICE POLISH
TO MILLFEED
SCREENINGS
SECOND HEADS
SCREEN &
SEPARATOR
RICE FLOUR
MILLING
WHITE RICE
RICE FLOUR
FIGURE 5
THE RICE MILLING PROCESS
26
-------
some kernel breakage occuring. Some plants use pearlers in parallel as
a one-break operation while some have twoand three-break systems to
reduce breakage. Air through the pearlers removes the loose bran to a
central bran bin and also cools the rice to reduce stress cracks.
Additional processing in a brush machine removes the remaining loose
bran.
Rotating horizontal drum trumbles are used to polish the rice. The rice
is coated in the trumbles with talc and water, or glucose water, to fix
the remaining bran to the kernels, which are then dried with warm air to
produce the desired luster. Rice enriching is accomplished by adding
vitamins and minerals, along with water, ahead of the trumbles.
Finally, the whole and broken rice kernels are separated to meet product
standards.
Farboiled^JRice-
Parboiled rice production begins with basic rice cleaning in shakers and
aspirators. Precision graders are added in parboiled rice cleaning to
remove the immature small grains and the rice that has been dehulled in
handling.
The parboiling process, as presented in Figure 6, may involve several
variations, only one of which is discussed in this report. A measured
amount of cleaned rough rice is dumped into the steeping tanks, which
are then sealed. A vacuum is applied to remove most of the air in the
hulls and the voids to allow water to penetrate into the kernel faster.
Hct water (70 to 95 degrees C) containing sodium bisulfite as a bleach-
ing agent is added to cover the rice and the tank is pressurized to
about 7.8 atm. The water is heated and recirculated to maintain close
temperature control. When the grain moisture content reaches about 32
percent, the tank is drained and the rice is discharged into a cooker
heated with live steam to gelatinize the starch. The parboiled rice is
then dried and cooled before milling.
Besides steeping water discharge, waste waters may be generated from
barometric condensers en the dryer vacuum system and from wet scrubbers
on the other dryers. Steepwater is not reusable for steeping because of
the color pick-up, which would discolor the rice.
In parboiled rice milling, machines called whiteners are used in series
with pearlers to loosen the bran. Otherwise, the milling process is
essentially the same as for normal rice.
WASTE WATER CONSIDERATIONS IN INDUSTRY
Of the four subcategories of grain milling covered in this report, only
corn wet milling generated large quantities of waste waters. Water use
in the corn wet mills ranges from about 3785 to 189,000 cu m/day (1 to
50 mgd) . Large quantities of BOD5_ and suspended solids are discharged
in the waste water, and hence, waste waters from these mills potentially
constitute major sources of pollution. At the present time, only six
27
-------
HOT WATER
ROUGH RICE
RECEIVING
STORAGE
DRY CLEANING
X
STEEP
TANKS
• WASTE WATER
STEAM
COOKER
DRYER
COOLER
HULLS
BRAN &
RICE POLISH
TO MILLFEED
SHELLER
WHITENER
PEARLER
BRUSH
TRUMBLE
SCREEN &
SEPARATOR
PARBOILED RICE
FIGURE 6
THE PARBOILED RICE PROCESS
28
-------
corn wet mills discharge directly to receiving waters. Three of these
provide biological treatment, one is constructing a treatment plant, and
the fifth will be discharging to a new municipal system now under
construction. The sixth discharges only once-through barometric
condenser water. The remainder discharge untreated or, in at least four
cases, pretreated waste waters to existing municipal treatment
facilities.
There are two potential sources of waste waters from corn dry mills,
namely corn washing and car washing. Corn washing has been a standard
operation at many, but not all, mills while car washing is practiced
infrequently and only at some mills. The quantities of waste waters are
relatively small, compared to corn wet mills, ranging up to perhaps 900
cu m/day (2UO,000 gpd), but the wastes typically have high suspended
solids and BOD_5 concentrations. Most corn dry mills now discharge their
waste waters to municipal systems.
Ordinary wheat milling usually generates no process waste waters. A few
mills wash the wheat and some infrequently wash cars. Bulgur mills
produce a small quantity of waste water, 38 to 113 cu m/day (10,000 to
30,000 gpd) from the soaking and cooking operation. These waste waters
contain moderately high levels of BOD5 and suspended solids. All of the
five bulgur mills in the country are believed to discharge these wastes
to municipal systems for treatment. Normal rice milling does not use
any process waters, hence no process waste waters. Parboiled rice does
generate some waste waters from the parboiling or steeping operation, up
to about 760 cu m/day (200,000 gpd). These waste waters are high in
dissolved BOD, but low in suspended solids. At least five of the six
rice parboiling plants discharge these wastes to municipal system.
29
-------
SECTION IV
INDUSTRY CATEGORIZATION
The Phase I study of the grain milling industry covers the primary
milling of the three principal cereal grains, namely, corn, wheat, and
rice. After considering various factors, it was concluded that the
industry should be categorized into several discrete segments for
purposes of developing effluent limitations. These subcategories are as
follows:
1. Corn wet milling
2. Corn dry milling
3. Normal wheat flour milling
U. Bulgur wheat flour milling
5. Normal rice milling
6. Parboiled rice milling
FACTORS CONSIDERED
The factors considered in developing the above categories included:
1. Raw materials
2. Finished products
3. Production processes or methods
4. Size and age of production facilities
5. Waste water characteristics
6. Treatability of wastes
Careful examination of all available information indicated that two of
these factors, specifically raw materials and production processes,
provided a meaningful basis for categorization, as summarized in the
ensuing paragraphs.
Bgff.^ Mater ia Is
Clearly, one basis for segmenting the industry would be the three
different raw agricultural products used, specifically corn, wheat, and
rice. The three grains have very distinct physical and chemical
characteristics. As described below, they also produce distinct raw
waste water characteristics. Accordingly, raw materials were selected
as one basis for subcategorization.
Finished^Productg
The finished products from the milling of the different grains are quite
distinct. corn milling products range from corn meal and grits to
starch and syrup. Wheat milling produces flour for baking and other
purposes and the specialty product, bulgur. Finally, rice milling
31
-------
yields ordinary and parboiled rice for direct human consumption. The
wide variety of finished products, however, especially from corn
milling, make further segmentation based on finished products
impractical. In a broad sense, the categorization does reflect the
finished products inasmuch as each subcategory generates different
product lines. The finished products, however, are not themselves basis
for subcategorization.
jProduction_Processes
While siirilar in some respects, the production methods used in milling
form an excellent basis for subcategorizing the industry. The most
marked differences in production processes are the techniques used in
corn wet trilling. These highly sophisticated physical, chemical, and
biological processes are completely different from most process
operations in dry corn, wheat, and rice mills.
Ery corn and ordinary wheat milling employ somewhat similar processes.
Both require cleaning, tempering, milling, and mechanical separation of
the products although slightly different equipment is used. Eulqur
wheat milling differs considerably from ordinary flour milling in
production method, thereby providing a basis for further subdividing
wheat milling.
Rice milling involves distinctly different techniques and equipment than
ether grain milling operations. Moreover, parboiled rice requires
several additional production steps, thereby justifying further
subdivision of rice milling into normal rice milling and parboiled rice
production.
Size_and_A3e_of_ProductJ.on_Facilities_
There appears to be little rationale for subcategorization based on size
or age of milling facilities. Certainly there is no correlation between
large and small mills considering the entire industry as one group. For
example, a large corn wet mill has nothing in common with a large rice,
wheat, or dry corn mill. Similarly, no relationship can be established
for age of plant for the industry as a whole.
Within any of the subcategories defined previously, it must be
acknowledged that relationships may exist between size or age of
production facilities. However, with the information developed in this
study no correlations could be established between waste characteristics
and size or age of plants.
Waste_Water_Characteristics
The waste water characteristics from the several types of grain mills do
differ to some degree, wet corn mills typically generate large volumes
of wastes containing large total amounts of BOD5 and suspended solids,
the concentrations of which depend on the quantities of once-through
contact cooling waters.
32
-------
Corn dry mills discharge much smaller waste water quantities with high
EOD5 and suspended solids levels. Parboiled rice mills generate amounts
of waste water that are comparable to corn dry mills and with a hiqh
dissolved BODJ5 content. Suspended solids levels, however, are quitf. low
in rice milling wastes. Finally, bulgur milling generates srrall
quantities of moderately strong wastes.
In summary, while the waste water characteristics do differ, sometimes
significantly, these differences are adequately reflected by the ether
factors mentioned above.
Treat abi].itY_of_Wastes
All of the waste waters from the grain milling operations covered by
this document are amenable to physical and biological treatment systems
of the same general type. In general, the fundamental design criteria
will be similar and treatability is not a satisfactory means for
subcategorization.
33
-------
SECTION V
WATER USE AND WASTE WATER CHARACTERIZATION
INTRODUCTION
Process water use and waste water discharges vary markedly ir. the
industry subcategories covered by this document, ranging from extremely
high uses and discharges in the corn wet milling segment to virtually no
process waste waters in ordinary flour and rice milling. Ey far the
largest water users and hence, the greatest waste water dischargers are
the corn wet mills. The very nature of corn wet milling processes is
different from other segments of the grain milling industry. In effect,
these plants are large chemical complexes involving, as their name
implies, wet production methods.
Dry corn and normal wheat milling may employ water to clean the incoming
grain, although many plants, particularly the wheat mills, use
mechanical methods for grain cleaning. Bulgur and parboiled rice
manufacturing techniques require water for steeping or cooking and
hence, generate modest quantities of process waste waters.
This section presents a detailed discussion of water use, individual
process and total plant waste water characteristics, and factors that
might influence the nature of the waste waters generated. The
information presented has been collected from state and federal
regulatory surveys, Corps of Engineers permit applications, industrial
sources, literature, and the results of a series of sampling visits to
selected plants in each industrial subcategory. The source of data are
described in more detail in Section III. Moreover, the sampling program
provided limited information on the waste water characteristics from
individual plant processes, particularly in the corn wet milling
subcategory.
In general, information on waste characteristics from cooling water and
boiler blcwdown and water treatment plarvt wastes has been excluded from
the following discussion. These auxiliary activities are common to many
industries and the individual practices at any given plant usually do
not reflect conditions that are unigue to the grain milling industry.
The types of treatment employed for cooling water systems, boiler feed
water, and process water vary widely throughout the industry and depend
on such factors as raw water characteristics, availability of surface or
city water, individual company preferences, and other considerations not
related to the basic nature of the industry. Separate guidelines for
auxiliary wastes common to many industries will be proposed by EPA at a
later date,
CORN WET MILLING
Water Use
35
-------
For clarity in presentation, the basic corn wet milling operations have
been divided into three process water and waste water flow diagrams,
Figures 7, 8, and 9. These diagrams cover the basic milling operation,
starch production, and syrup refining, respectively.
The modern wet corn mill, in many respects, is already a "bottled up"
plant, compared to its ancestors of 50 to 75 years ago. Historically,
this segment of the industry has succeeded in reducing the fresh water
consumption per unit of raw material used in the basic production
operations exclusive of cooling waters. The waste waters from one
source are now used as makeup water for other production operations.
Fresh water, recycled process waste waters, and discharged waste waters
are shown on the attached diagrams. Recycled process waste waters are
identified by the symbol "PW" to distinguish them frcm waste waters that
are sewered.
Fresh water enters the overall corn wet milling production sequence
primarily in the starch washing operations. This water then moves
ccuntercurrent to the product flow direction back through the mill house
to the steepwater evaporators. More specifically, the process waste
waters frcm starch washing are reused several times in primary starch
separation, fiber washing, germ washing, milling, and finally as the
input water to the corn steeping operation. The principal sources of
waste waters discharged to the sewer from this sequence of operations
are modified starch washing, and condensate from steepwater evaporation.
Additional fresh water is used in the syrup refinery. Although practice
varies within the industry, fresh water may be introduced in starch
treating, neutralizing, enzyme production, carbon treatment, ion
exchange, dextrose production, and syrup shipping, as indicated in
Figure 9. In some plants, evaporator condensate is used to supply many
of these fresh water requirements, particularly in carbon treatment and
ion exchange regeneration. Other process waste waters are used in mud
separation, syrup evaporation, animal feeds, and corn steeping.
Total water use in this subcategory varies from less than 3785 cu m/day
up to 190,000 cu m/day (1.0 mgd to 50 mgd) depending, in large measure,
on the types of cooling systems employed. Those plants using once-
through cooling water have much higher water demands than those using
recirculated systems, whether they be surface or barometric condensers.
The water use per unit of raw material ranges from about 0.0067 to
0.0745 cu m/kkg of corn grind (45 to 500 gal/MSBu). Those plants that
predominantly use once-through cooling water will have total water use
values of about 0.045 cu m/kkg of grind (300 gal/MSBu). This number
should be contrasted with the several plants that use recirculated
cooling water almost exclusively, where the total water use values are
about 0.0075 cu m/kkg (50 gal/MSBu). Information is not available on
the water use by individual production processes since these vary from
plant to plant. Company preferences, type of equipment, product mix,
and other factors all influence the water use in terms of both the
individual processes and the total plant.
36
-------
UJ
z
cc
o
u
u
a.
(0
Z
o
cc
ui
Q.
o
o
O
<
STEEP
WATER
/^
J« J
1
gjxvm ONHOOO . ^j~
3iVSN3QNOO dOdVA ^ii
37
-------
00
o u
£2
1°
d
I
Ul
DC
O
O
o
I BJ -
Bs a I-*F-->S
.
Ul
z
u. g
U
O
O
flC
Q.
O
Ul
X
(A
Z
Uu
38
-------
UJ
o
o>
Ul
cc
a
z s
ii
Si
o
o
o
o
cc
a.
a.
cc
(O
39
-------
Waste_Water^Characteristics_gf Individual Product! on^Processes
As indicated in the preceding discussion on water use, many process
waste waters that were discharged to sewers years ago, are now recycled
back into the process. This section is concerned only with those wastes
that are generally discharged to the sewer as shown previously in
Figures 7, 8 and 9. Major wastes included are those from steepwater
evaporators; starch modifying washing, and dewatering; syrup refining
(cooling, activated carbon treatment, and ion exchange regeneration) ;
syrup evaporation; and syrup shipping.
The condensate from steepwater evaporation constitutes one of the
several major waste water sources in a corn wet mill. Normally, triple-
effect evaporators are used with either surface or barometric
condensers. Vapors from each of the first two effects passes through
the subseguent effect before being discharged to the sewer. For those
systems using surface condensers, the condensate from the third effect
is sewered. In the case of barometric condensers, the third effect
condensate becomes a part of the barometric cooling water discharge and
hence, is greatly diluted. Limited data on characteristics of the waste
discharges from the first and second effect evaporators were acquired
during the sampling program and are presented in Table 6. Selected
samples taken from the barometric cooling waters serving the third
effect evaporator, indicate much lower waste concentrations, as
expected. BOD5_ levels ranged from 10 to 75 mg/1 with typical values
reported by industry in the range of 25 mg/1.
Table 6
First and Second Effect Steepwater Condensate
Waste Water Characteristics
Range j
~
EOD5 723 - 93U
COD 1095 - 1410
Suspended Solids 10 - 28
Dissolved Solids 110 - 292
Phosphorus asP 0.5- 0.7
Tctal Nitrogen as N 2.U - 2.6
pH 3.0-3.5
Surface condensers will generate essentially the same total quan-
tity of waste constituents, but in a much smaller volume of water.
To reduce waste water flows, several plants presently recirculate
barometric cooling water and only discharge the blowdown from the
cooling tower to the sewers. Measurements of the blcwdown from
such a system at one plant indicated a BOD5 of about 440 mg/1 and
a suspended solids content of 80 mg/1.
Data from a previous study for the Environmental Protection Agency
40
-------
(Table 7) indicate that steepwater evaporation systems usinq oncf—
through cooling water generate about 4.5 to 13.4 cu m/kkq (30 to
90 gal/SEu) of process wastes. Recirculating cooling water syst^mf,
on the other hand, generate about 10 percent of this flow, namely
0.6 to 0.9 cu m/kkg (4 to 6 gal/SBu) .
Additional data from the same study related waste characteristics
to raw material input and indicated a BOD5 range of 0.9 to 2.9 kg/kkq
(0.05 to 0.16 Ibs/SBu) and a COD range 1.1 to 3.2 kg/kkg (0.06 to
0.18 Ibs/SEu) .
Modified_Starch Production-
In many, if net most, corn wet mills the waste from the production
of modified starches represents the largest single source of con-
taminants in terms of organic load. Limited samples taken at two
mills indicated very high BOD, COD, and dissolved and suspended
solids, as indicated in Table 7.
Table 7
Finished Starch Production
Waste Water Characteristics
Ran ge x_ rmj /1
EOD5
COD
Suspended solids
Dissolved solids
Phosphorus as P
Tctal nitrogen as N
pH
These very high-strength wastes are highly variable in both composition,
flow and biodegradability. Information from earlier studies on the
waste characteristics relative to raw material input is summarized in
Table 8.
It is important to note that the production of modified starches varies
not only from plant to plant, but from day to day and week to week in
any given plant. Moreover, the nature of the waste water generated from
starch modification depends on the particular starches being
manufactured. For example, mild oxidation with sodium hypochlorite
generates a lower dissolved organic load than highly oxidized starch
production. No correlation has yet been established between the types
and amounts of starches being produced and the waste loads from this
operation.
gyrup gef inery-
In most mills, waste waters are discharged from several operations in
the syrup refinery. Most of these waste waters are generated by the
series of operations generally referred to as syrup refining, which
3549
8250
918
9233
25
32
4.
-
-
-
-
-
-
2-
3590
8686
2040
16211
63
41
5
41
-------
ra
S
0)
•p
ra -iH
cu to S
rH 0)
f O -P
O) O Q)
cd o
3 o
to
13
•H
rH
O
to
rH
cd
-P
O
EH
CD ra
H -H
0 H
W O
to to
•H
Q
PP
J3
to
H
s
CM
^
CM
h
,k
\^
h
r3
pq
»=H
ra
rH
^0
•>*
C1^
^
o
CM
CM
§
iH
d
,it
,!*
\
h
O
C^\
1
-
2 0
Q
0
O
Q
5
pq
fe
H
P»H
pq
J5-
"\
ra
H
to
H
1
0
MD
ty
r^M
^
~\
ft
PS
m
,ci
1-1
CM
c^\
1
H
rH
s
rH
ci
ITN
ft
,i£
^
^
b
^
PQ
\^
to
rH
d
h(
.
CM
Q\
•
o
o
^
jj
^v
^.^
"
g
^*
c^\
iH
A
0
ra g
ra
0.
£
P.
hi
F
7
-p
o
ct
F
^
•H
-P
cd
ft
cd
CD
cu
-p
cti
ft
CD
0)
•P
to
'
1
O
ci
I — 1
ir\
•
0
CM
0*
1
1
O
H
CM
O
-i-
CM
^0
•
O
A
o
ho
-p
cd
1
•a
•a
CD
CD
Q
C'N
ci
rH
UA
O
CM
O
O
CM
O
i — 1
~^-
•
0
1
CM
0
1
1
O
CM
.
O
-*J-
o
o
LTN
CM
CM
O*
£v_
•
C'A
A
o
o
I
FJ
•H
«H
CD
H
•H
O
8
ir\
CM
ci
to
to
^
-sf
1
t^
S
0
\£)
rH
£v-
^D
•
to
CM
Q
•
rH
O
s
1
o
D-
•
O
rH
|
C^N
CM
O
s
o
O
1 — 1
t~-
0
H
1
to
rH
O
IfN
ci
1 — 1
ITN
•
c*-
1
H
ho
FJ *
•H O
CM 0)
•H
ebo
F)
•H
Xi 41
o ra
[3 g
+o
co
tio fl
PH C
!s'H.
J-l 43
FH
ft C(J
d co
p!i
CO
o
IfN
O
rH
O
to
ITN
-^J-
•
O
rH
0
CM
KA
C^\
•
O
o
LT\
H
j^
•
CM
UA
CM
C^-
C^
•^
" bo
s
41
O
g
0
u~\
S
in
0^
j
H
rH
O
-J-
s
MJ
H
*
\Q
|
I-f
H
0
H
ir\
•
cv
o
r'A
•
H
8
CM
CM
O
co
Q
*"
CM
rH
Q
^
r^
B
rH
O
to
-t
i-H
O
QN
*
o
C*A
CM
^j.
•
0
o
bo
Fi
•H
ft
ft
•H
ra
ft
^
ra
g
0
o
O
CM
CM
W
o ra
-B
ra
to ft
O 2
Q
42
-------
includes activated carton and ion exchange treatment. Typically, ~^'"
so-called sweeteninq-off procedures require flushinq the spent carbon or
ion exchange resin with water prior to regeneration. The first flush of
such water is usually sent to the syrup evaporator for reclamation. Thit-
final rinse water is very dilute in syrup content and is discharged from
the plant. Sampling data indicate that waste waters from the ion
exchange regeneration are high in organic content, with BOD5 levels of
500 to 900 irg/1, and in dissolved solids, 2100 to 9400 mg/1. The cH
levels of the waste water were quite low, averaging about 1.8 and the
suspended solids averaged 25 mg/1.
Other sources of waste waters in the syrup refinery include: syrup
(flash) coding, evaporation, dextrose production, and shipping.
Samples of wastes from the syrup cooling process at one plant gave vhe
results shown in Table 9.
Table 9
Corn Syrup Cooling
Waste Water Characteristics
Concentration
ECC5 73
CCD~ 177
Suspended solids 44
Dissolved solids 291
Phosphorus as P 0.2
Total nitrogen as N 0.4
pH 6.7
The concentration of wastes from syrup evaporation again depends on the
type of condensers used, i.e., surface and barometric with recirculation
versus barometric with once-through cooling water. Other data on the
waste waters from the various activities in a syrup refinery are
included in Table 7.
Other_Processes-
Waste water streams of less importance include discharges from feed
dewatering, oil extraction and refining, and general plant cleanup.
Sampling data taken at one plant indicate that the waste waters from the
feed house contained about 140 mg/1 of COD, 40 mg/1 of suspended solids,
and negligible amounts of phosphorus and nitrogen, and had a pH of 5.9.
Other data are also presented in Table 7.
Total_Waste_Characteristics
Most of the data accumulated from various sources during this study
relate to the total raw waste characteristics from corn wet mills.
Summary data from 12 of the 17 mills are presented in Table 10. Waste
waters frcm this grain milling subcategory can generally be
characterized as high-volume, high-strength discharges. The BOD varies
43
-------
w
o
•H
0)
-P
gfl
•H
bO
O H
H -P -H
to ;>,
(U Is
H 0) -P
£ -P JJ
03 W 13:
Bl a
*H
!* o
o5 O
ft
H
nd bO
a) a
Tl
a *
-
1
O
o
H
CM
O
o
LfN
ON
H
H
•
VD
o
o
CM
O
t—
o
oo
CM
H
CM
CO
LfN
H
"bO
a
§
PQ
0)
bO
a
a
w
(L>
bO
03
?H
0)
5
O
o
o
oo
1
o
o
-=f
0
0
-=i-
H
o
CM
OO
^J-
1 1
^t
VD
-=t
LfN J-
CM H
VO VD
H
O
O
CO
tr-
1
O
LTN
VO
O
CO
OO
CM
1
O
LfN
J-
OO
I
O
•
u-\
o
vo
OO
ON
I
CM
O
CM
H
CO
ON
*
t-
CM
OO
LfN
OO
00
1
LTN
CM
CM
OO
CO
CM
1
CO
ON
t-
VO
CM
LfN
i
00
o
00
_*
-*
_4-
vo
o
o
o
•%
CO
H
1
oo
J-
LTN
ON
co
o
o
o
«t
0
^t
1
tr-
-J"
oo
o
vo
LTN
-*
o
o
o
9t
LTN
CM
CO
oo
CM
0
oo
oo
CM
t—
O
o
_*
ON
1
o
H
j-
OO
Lf\
J-
CM
1
O
O
0
*l
H
1
O
OO
t-
0
LfN
-4-
J-
OO
1
O
o
t—
o
o
oo
•*
o
H
0
LT\
t^
o
o
LfN
oo
o
t—
oo
CM
VD
J-
CM
H
0
LfN
VO
H
ON
vo
H
CM
OO
CO
ON
LfN
CM
1
(
CO
rH
VO
1
VD
.4-
H
OO
ON
ON
o
H
|
H
00
1
00
t—
^t
1
LfN
CM
CM
H
H
-3"
-4-
t—
t-
1
ON
H
CM
VO
CO
!
(
CM
ON
LfN
T
L^
VO
-4-
OO
LfN
CM
CM
H
44
-------
widely, from 255 to 4450 mq/1, with a corresponding range in COD. Tho?f-
plants with very low BOD5_ values typically have barometric condensing
systems using once-through cooling water. At the other extrema, *-.h«
very concentrated wastes are from plants using recirculated coolinq
water (either surface or barometric condensers).
Suspended solids levels in the total waste streams show similar
variations ranging from 81 to 2458 mg/1. Once again, the plants with
low suspended solids concentrations are those using barometric
condensers with once-through cooling water.
Other waste parameters indicate that the pH of the total waste ranges
from about 6.0 to 8.0. These average pH values, however, are somewhat
misleading inasmuch as wide pH fluctuations are common to many plants,
Typically, the waste may be somewhat deficient in nitrogen for
biological waste treatment. Dissolved solids levels from certain
process operations, as discussed previously, generally do not constitut"
a problem when combined in the total waste stream. In those plants that
have minimized water use, dissolved solids build-up may be a future
concern.
The information contained in the preceding table is presented in Table
11 in terms of raw material input, i.e., kg/kkg (Ibs/MSBu) . The plant:
UUfflb^ES in the two tables do not correspond to one another^
EOD5_ in terms of raw material input ranges from 2.1 to 12.5 kg/kkg (119
to 699 Ibs/MSBu), and averages 7.4 kg/kkg (415 Ibs/MSBu). Similarly,
the suspended solids in the total plant waste waters range from 0.5 to
9.8 kg/kkg (29 to 548 Ibs/MSBu) and average 3.8 kg/kkg (211 Ibs/MSEu).
These data emphasize again the wide variation in waste characteristics
from the corn wet milling industry. Possible correlations between plant
size, age, or other factors will be discussed in the next section. The
waste water flows vary frcm 3.1 to 41.7 cu m/kkg (21 to 280 gal/ SPu)
with an average of 18.3 cu m/kkg (123 gal/SBu). Those plants with lower
waste flows per unit of production are those that emplcy recirculating
cooling water systems.
Factor s_AfJecting_ Wast e_Characteristj.c_s
As noted previously, waste waters from corn wet milling plants vary
greatly in quantity and character. This variability is a function of
many different factors and attempts have been made in this study to
correlate seme of these factors with raw waste loads, as discussed in
the following paragraphs.
_of_Plant-
In some industries, the character of waste generated is directly related
to the age of the plants. Such is not the case in corn wet milling, as
evidenced in Figure 10, which relates plant, age to the BODJ5 in the total
plant effluent. The data have been gathered into three groupings with a
dark circle representing the mean, and the boundaries of the rectangles
representing the range of average values in each grouping. Clearly,
45
-------
to
^)
•rt
H
O
CO
•d
f\]
UJ
<&
P
CO
p!
CO
5
CO
s
CO
,0
H
bO
•s
,y
bO
44
ON 0
H LA
CM -3-
ON O
00 CO
ON OO CO
LA CM -J-
H CM H
CO O VO
CM -^ CM
ON o t-
CM t— CM
H
LA OO OO
0 H CM
VO CM CO
CM VO VO
CM CVI
O t— CM
-* -=t H
CO H
J- H
LA CM
CO CO
ON oo
o
o
&3
1fts
CO
0) O -p
H -H 0)
P -P IS
CD
EH -H
in
0)
-P
CO
CM
H
oo
CM
CM
O
CM
ON
O
o
ON
oo
LA
ON
H
3
CO
t—
oo
co
vo
OO -d-
LA ON
H 00
H
VO
O
CM
VO
CM
CO
CO
b
cd
a
^
0
fi
s
o
n
O
ffl
A
CO
s
CO
ft
H
j-
ON
oo
bC
3
M
ta
X
o
t—
oo
ON
vo
-*
CM
H
ON ON vo
ON ON J-
_* VO CM
ON LA -rt
CO* CM *
ON
3
H
CM
ITN
CM
CM
O
-*
ON
ON
CM
oo
LTN
0
ON
LfN
LTN
O
H
0 0
00 LA
CM OO
rH 00
j- vo
ON
OO
VO
J-
i
LTN
H
-=f
_*
t-
-
vo"
H
CO
CO
H
0
co
CM
O
CO
CM
t—
H
J-
OO
VO
CM
t—
vo
LA
CM
H
CM
H
t-
CM
CO
O
_=)-
H
t—
VO
O
H
OO
OO
ON
_=)-
t— IfN
CO LA
H
oo
CM
VO
ON
•
tr-
CM
CM
CO
00
•
CO
0)
bfl
H
M
CM
oo
VO
CO
ON
?l
46
-------
a
•o
c
a
m
10
n
"5
o>
O)
c
a
C
m
c
CO
8
0
1
o
0
o
1
o
0
00
M
C
(0
a.
o
o
1 1
0 0
<5 iO
1
0
o
•*•**•
1
o
o
CO
1
o
o
CN
8 °
- 2
O
co
O
CN
O
O>
O
00
O
•O
O
CO
o
CS
to
ID
C
n
o
a>
O)
ra
o
UJ
O
a:
Q
o
GO
UJ
2
tt
UJ
o
Ul
O Z
O
QC
O
o
H
UJ
u.
O
O
UJ
UJ
(nqoOOl/ sqi)
I
O
I
O
puBLuap ueBAxo
47
-------
there is no discernible relationship between the total waste load and
the age of the plants. In fact, at least one of the new plants
generates more wastes per unit of raw material input than several of the
older plants. It should be noted that the age of plant in this industry
does not accurately reflect the degree of modernization in terms of
types of equipment. Because of competition and market demands, most
corn wet mills are reasonably modern and very similar in basic produc-
tion techniques.
Size_of_Plant-
Several comparisons were made between the size of plant, expressed in
normal grind of raw material, and total plant waste loads as shown in
Figures 11, 12 and 13. The total daily volume of waste water discharged
was found to show a general relationship with the plant capacity, Figure
11, as might be expected. At the same time, the data reflect a wide
range in waste water discharges as a result of vastly different process
and cooling water use practices.
The information on BOD^ and suspended solids has been grouped into three
plant size ranges, which might be termed small, medium, and large. As
shown in Figures 12 and 13, no discernible relationship can be found
between plant capacity and either of these two pollutant parameters.
Water_Use_and_Waste_Water_Discharge-
It has been speculated that there might be a relationship between the
total waste load and the volume of water used or discharged.
Figures 14 and 15 were developed to evaluate this hypothesis and clearly
indicate that no such correlation exists. Once again, the data have
been grouped in a convenient manner for presentation.
PgQ<3uct_Mix-
Because certain products, namely modified starches, result in higher
waste loadings than other products, there was reason to believe that a
relationship might be apparent between product mix and total waste load.
For example, it might fce reasoned that a plant producing only corn syrup
would have a lower raw waste load per unit of raw material input than
one producing a product mix with a high percentage of modified starches.
The available data from 12 plants regarding both product mix and raw
waste characteristics showed absolutely no correlation between these two
variables. It is known that changes in product mix at a given plant
will alter the total plant raw waste load, but the data refute any claim
that product mix is a direct measure of the relative waste load of
different plants.
The product mix at the reporting mills varied from 100 percent starch to
100 percent syrup and sugar. At most of the plants, the product mix
varied between about 30 and 70 percent starch. Even near the two
extremes, i.e., zero and 100 percent starch, there was no discernible
relationship between product split and waste loads. Furthermore, the
48
-------
o
o
o
o
§
CN
T3
C
O)
>- "5
ra c
•D C
II
Q.
O
z
_J
_J
s
H
UJ
z
oc
o
o
DO
Q
UJ
u. u
O
cc
UJ
UJ
I
u.
o
Z
1
0
1
00
1
-t
CN
JS^BAA jo aiun|OA
49
-------
of average plant da
value
,
t
a
(0
"5.
a
"a.
O
O
o
i
O
o
o
CO
o
CN
-S
0
oo
0
CN
- o
o
o
o
O
O
O
>
H
O
O
o
o
co
o
o
o
CN
S
H
UJ
oc
O
O
, "J5
nj C
-D C
I1 o
-o * c*
Q
UJ
u
oc
<
T
O
o
o
oa
UJ
oc
ID
88°
( nqoOOU sqi)
>o
uo) oujauj/saiEJ6o|i>(
pueuiap ua6Axo
50
-------
a
T»
c
ID
O)
IB
$ «
5 =
«- IB
O >
01 c
01 a
6 i
(0
*tf
JD
"a.
en
n
a.
>o
-8
0
10
o
-t
o
CO
O
CN
O
_O
O
co
o
o
o
oo
O
o
m
o
cr>
o
CM
0
_o
o
cs
o
_o
o
o
o
o
•a
c
O)
o
c
8
O
o
O
o
O
o
O
o
O
o
O
o
O
o
O
o
O
o
sqi)
u-)
1
O
>O
H
O
U
-I
I
H-
UJ
z
-------
n •
s «-
1 £"fc
* / \
! 1 / \
i i / \
? s / \
a E / \
/ \
/ \
" / \
CM
im
n :•:•: :•:•:•:•:
C t-X-X-X-X-X-X-X-X-X-X-X-X-X-X-X-X-.-X-X-X-X-XvX-Xl
(B y'-x xo > x->xyx:x-x::-:^-::x:x-x-:-x'x-v'x-:-x-:-:-x
iii i i i i r i
ooooooooooo
oooooooooo
CN
• co
o
" CO
00
- CN
-8
•t
" CN
CN
• cs
o
~ cs
-2
- CM
_ o
- 00
a
5
c
o
'S
O)
~ ^ c
g
O
-CN
O
-o
o
"CO
-8
1 ! 1
20 40
ters/day
water discharged
" H-
E 0
o 2
O
£E
LU
i
UJ
-------
range of average plant data [: ';••;]
0
o
0
c
(0
A
i / \
/ \
/ \
y) -. . • • • • •. . .•- .- •-•.•.- •.-.
C - - •,-,.. •;:*•:•••:•:.::::•:
a ; ; ;: .. ; • •' :• ...; • .x: ..'.: ':•••
„ • •./•• v:\ •:';:.-.:•.•: x •::;:;
»•• • • • '.'-;.• .• .• •.-. -.•
O. :' . ':•'." •'. -';::- :''::™x '':'':^'.-:-'^
^ . -. •' . :• ': .; • • ••:••;: .:•:••••.:.•.: '.'•••: ••^<.'Q
" T " 1 '
0 40
jay
er discharged
^ « CO
0) $
OJ i^
E 0
IE
o 2
S 9
0 ° >
UJ
cc
Ui
Ul
O
£ ^
^ o
UJ Z
oc ^
=) n.
S3 <
"• co
(A
O
_l
O
CD
D
UJ
Q
Z
IU
Q.
(O
UJ
C3
<
cc
UJ
spjios papuadsns
53
-------
more limited information on the quantities of modified starches produced
indicated nc correlation with waste loads at different plants.
Pl<*nt_QEerating_Procedures-
There appears to be a definite relationship between general plant
operating procedures and the amounts of wastes discharged. Those plants
known to have good housekeeping operations and close operational control
do tend to have lower waste loads, although this is not universally the
case. Clearly, careful monitoring and control of process operations
will reduce spills and, hence, the total amounts of waste discharged.
The effect of good housekeeping and operational controls is difficult to
quantify, although some industry sources indicate that waste reductions
of 20 to 30 percent, or more, can be achieved through these measures.
Summary.-
In summary, nc quantitative relationships could be established between
the total plant raw waste loads and such factors as plant size, age,
product mix, water use, and operational procedures. At the same time,
it is important to recognize that many of these considerations will,
indeed, influence the character of the total waste discharges.
CORN DRY MILLING
Water_Use
Water use in corn dry milling is generally limited to corn washing,
tempering, and cooling, as shown on the product flow diagram presented
earlier, Figure 2. Not all mills use water to clean the corn, probably
because the resultant waste waters constitute a pollution problem. It
is believed that most of the larger mills, however, do wash the corn
although data on the number of such installations is not available.
Water use for this purpose ranges from about 0.45 to 1.2 cu m/kkg (3 to
8 gal/SBu).
After washing, water is added to the corn to raise the moisture content
to about 21 to 25 percent in order to make it more suitable for
subsequent milling. Only enough water is added in this operation to
reach the desired moisture content and no waste water is generated.
Waste^Water^Characteristies
Other than infrequent car washing, the only process waste water in corn
dry milling is that originating from the washing of corn. Data on raw
waste characteristics from three plants are presented in Table 12. In
one instance, the plant also processes soybeans and the waste waters are
combined. This same mill generates some waste water from air pollution
control equipment (wet scrubbers) on corn and soybean processing
systems. These wastes are excluded from the data in Table 12 inasmuch
as they originate from secondary processing of milled corn rather than
the basic milling sequence covered in this document.
54
-------
a
0)
bO
O
H
03
-p
O
EH
hO
CM
oo
H
to
f_l
O PM H
ft CQ M|
tQ oj
O
A
PH
O
•
on
CO
tJ tn
S -d H
-------
Average waste water discharges from the three mills range from about
0.48 to 0.9 cu m/kkg (3200 to 6000 gal/MSBu). The waste waters are
characterized by high BOD5 and suspended solids concentrations. The raw
waste water BOD5 values average 1.14 kg/kkg (64 Ibs/MSBu), and the
suspended solids average 1.62 kg/kkg (91 Ibs/MSBu).
Factors_Affeeting_Waste_Water_Characteristics
Insufficient data were available to establish any relationships between
waste water characteristics and such factors as plant age, size, and
operating procedures. Clearly the size of plant and the type and
cleanliness of the corn will influence both the flow and waste
characteristics, but in ways that cannot be defined at this time.
WHEAT MILLING
The normal trilling of wheat into flour uses water only in tempering and
cooling and no process waste waters are discharged. A few normal flour
mills do wash the wheat, but the vast majority use dry cleaning
techniques. Accordingly, the remainder of this discussion will
concentrate on bulgur production.
Vjater_Use
As indicated in the product flow diagram, Figure 4, water is added to
the wheat in the soaking operation. Depending on the specific process
employed, water may te added at as many as four locations, all
essentially relating to the same soaking operation. Water usage for
typical bulgur plants ranges from about 115 to 245 cu m/day (30,000 to
65,000 gpd), Most of this water is used to raise the moisture content
of the wheat from 12 percent, as received, to about 42 percent.
W§§te_Water_Characteristics
The only source of process waste water, in the production of bulgur, is
from steaming and cooking. As the grain is transferred from bin to bin,
water is added on the conveyors and waste water is discharged. The
total quantities of waste water from a given bulgur plant are quite
small, ranging from 38 to 115 cu m/day (10,000 to 30,000 gpd). Raw
waste data from two plants are presented in Table 13. The BOD5 values
cited in the accompanying table correspond to an average of about 0.11
kg/kkg (5.9 Ibs/MSBu) of BOD5 and 0.10 kg/kkg (5.5 Ibs/ MSBu) of
suspended solids.
Table 13
Waste Water Characteristics
Bulgur Production
Concentration mg/1
BOD5 238 - 521
COD 800
56
-------
Suspended solids
Phosphorus as P
Tctal nigrogen as N
pH
294 - 414
5.6
3.6
5.8
?^£t2E§_Mj:e_cting_Waste_Water_Char act eristics
Factors influencing waste water characteristics undoubtedly include the
particular production methods used, type of wheat, and operational
procedures. Unfortunately, insufficient data are available to evaluate-
quantitatively the influence of these factors.
PICE MILLING
The ordinary milling of rice to produce either brown or whit^ ricc-
utilizes nc process waters and, hence, generates no waste waters. Viator
is used in the production of parboiled rice and the remainder of this
discussion will focus on this production method.
Vjater_0se
In the parboiled rice process, water is added in thc steeping or cookina
operation, as shown in the product flow diagram. Figure 6. Water use ir:
the industry varies from about 1.4 to 2.1 cu m/kkg (17 to 25 gal/cw1-) .
Additional water is ue^ed in boilers for steam production for -t-h^-
parboiling process. At least one plant uses wet scrubbers for dus*-
control thereby generating an additional source of waste water.
Paw_Vaste_Water_Characteri. sties
Limited data are available on raw wast<= water characteristics from ric-
parboil inq. The information that is available is summarized in Tafcl'
14. Th- raw waste loads presented in the table correspond to 1.8 kg/kk<,
(0.18 Ibs/cwt) of EOD^ and 0.07 kg/kkg (0.007 Ibs/cwt) of su
solids. In general, the waste may be characterized as having a
soluble BODj) content and a low suspended solids level.
Table 14
Waste Water Characteristics
Parboiled Rice Milling
Concentration mg/1
BOD5
COD
Suspended solids
Dissolved solids
Phosphorus as P
Total nitrogen as N
1280 -
2810 -
33 •*
1687
98
7.0
1305
3271
77
57
-------
Factors Affecting Waste Water Characteristics
Based on the very limited amount of data available, it appears that the
waste characteristics from parboiled rice plants are quite similar.
While there are some differences in flow volumes, the total waste loads
per unit cf production are similar.
58
-------
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
The waste water parameters which can be used in characterizing the
process waste waters from the grain milling industry are as follows:
EOD5 (5-day), suspended solids, pH, COD, dissolved solids, nitrogen,
phosphorous, and temperature. These parameters are common to the entire
industry but are not always of equal importance. As described b°low,
the selection of the waste water control parameters was determined by
the significance of the parameters and the availability of data
throughout each industry subcategory.
MAJOR CONTROL PARAMETERS
The following selected parameters are the most important characteristics
in grain irilling wastes. Data collected during the preparation of this
document was limited in most cases to these parameters. Nevertheless,
the use of these parameters adequately describes the waste water
characteristics from virtually all plants in the industry. POD5 (5-
day) , suspended solids, and pH are, therefore, the parameters selected
for effluent limitations guidelines and standards of performance for new
sources.
(.BOD_5]_
BOD5_ is an important and widely accepted measure of the biodegradability
of organic matter in waste waters. Most plants routinely measure EOD5_
in their waste waters. Typical BOD5_ levels in all of the subcategories
are quite high, ranging frcm several hundred to several thousand mg/1.
Discharge of such wastes to surface waters can result in oxygen
depletion and damage to aquatic life.
The suspended solids levels of the raw waste waters, in most segments of
this industry, are quite high, ranging from about 500 to 3500 mg/1.
Parboiled rice mills and specific plants in other subcategories, may
have substantially lower suspended solids levels. The very high
suspended solids level common to the industry, however, may constitute a
serious pollution problem if discharged to surface waters. Moreover,
the solids are generally finely divided grain particles and represent a
sizable fraction of the organic load in the wastewater.
EH
The pH levels in the wastes from the various subcategories covered in
this document vary appreciably. Generally, the waste waters tend to be
neutral or slightly acidic. Under certain conditions, in some wet corn
irills, the combined waste stream may be very acid or quite alkaline at
59
-------
different times. pH is an essential control parameter for treatment of
the waste and regulation of the discharges.
ADDITIONAL PARAMETERS
Chemical. _Oxygen_Demand (COD)_
COD is a chemical measure of the organic content and, hence, oxygen
demand, of the waste water constituents. As with most food wastes, the
COD is considerably higher than the BOD, usually by a factor of 1.5 to
2.0 Several companies in the grain milling industry rely on COD as a
much more rapid measure of the organic content than BOD, and use it as a
rapid monitoring technique for the waste. In most instances, the ratio
of COD to EOD5 in the raw waste can be established fcr a given plant and
COD can serve as an excellent control parameter. However, the COD data
collected during the preparation of this report was sparse. No
definitive relationship between COD and BODjS (5-day) can be established
at the present time. The fact that the chemical nature of the organics
may differ from plant to plant may preclude the use of a uniform COD
standard for each subcategory. Therefore, it was concluded tha4-
effluent limitations guidelines and standards of performance could not
be determined for COD.
Inorganic_Dissolved Solids
There are a number of sources of inorganic dissolved solids in the
various subcategories of the grain milling industry. These include
wastes from water treatment, cooling water blowdown, deionizer
regeneration and various processes in the plant. The increase of
dissolved solids in the waste waters were not found to large. Moreover,
the sources of inorganics mentioned above are in many cases common to
other industries. Since these problems are difficult to handle
practically and economically, EPA will consider effluent guidelines for
these sources at a later data, and they are not discussed in this
report.
Many operations in grain milling inherently elevate the temperatures of
the resultant process waste streams. This is especially true where
steeping, soaking, or cooking processes are used, such as in wet corn
milling, bulgur production, and parboiled rice manufacture. Direct
contact barometric cooling water is a major source of heated waste water
in some ccrn wet mills. Temperatures from selected waste streams and in
some instances from combined total plant wastes, sometimes approach 38
degrees C (100 degrees F). Elimination of once through barometric
condenser water by the use of cooling towers will significantly reduce
this problem. The blowdown from the cooling tower will be discharged to
the treatment plant where it will either be cooled prior to treatment or
in the treatment process itself. Non-contact cooling water is a
separate industrial category for which EPA will address and issue
60
-------
guidelines at a later date. Therefore, temperature was not selected as
a control parameter for the purposes of this report.
Phosphorus levels in corn wet milling waste waters generally appear ro
be quite lew. The data on other subcategories indicate that levels of
some significance may be present in the wastes. In particular, corn dry
milling and parboiled rice production appear to generate high
conceritraticns of phosphorus ranging from about 30 to 65 mg/1. This
information is based on limited data, and is not sufficient to determine
effluent limitations.
Nitrogen
Nitrogen levels of the wastes have been measured throughout the industry
and generally tend to be below 20 mg/1, usually below 10 mg/1. These
levels may te necessary to achieve good biological treatment. However,
no information is available to determine this requirement, nor to
determine effluent limitations.
61
-------
SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
INTRODUCTION
Except in the corn wet milling industry, little attention has been
focused on either in-plant control or treatment of the wastewaters.
Many of the mills discharge to municipal systems while the waste waters
from other plants flow into large rivers where the impact has not been
of great concern until recently. Only in corn wet milling has
considerable attention been focused on both in-plant control and end-ot->-
process treatment. The emphasis on waste water control in tnis segment
of the industry is, of course, a reflection of the large quantities of
waste waters discharged in contrast to the much smaller amounts
generated by ether types of grain milling. In many instances, the
treatment technologies developed for corn wet milling can be transferred
to the ether industry subcategories.
COFN WET MILLING
Wagte_Wat€r_Charact.erist ics
As developed in detail in section V, the waste waters from corn wet
mills contain large amounts of BOD^ and suspended solids. Depending on
the type of cooling water system employed, the concentrations of these
constituents range from moderate to high. Most plants have isolated
their major waste streams into a concentrated stream for treatment.
Once-through cooling water systems are being replaced with recirculating
systems, in several instances.
In concentrating the waste streams, the mills have reduced the volume of
water to be treated and, hence, the cost of treatment, but have
increased the operational difficulty of achieving low effluent
concentrations. In essence, it is much more difficult to reduce a raw
waste BOD5 of 1,000 mg/1 to an effluent of 30 mg/1 than it is to reduce
an influent BOC5 of 250 mg/1 to the same 30 mg/1.
In evaluating waste water control in the corn wet milling industry, it
is essential to evaluate both in-plant control measures and effluent
treatment systems. Good in-plant controls can greatly reduce the total
raw waste load and improve treatment plant efficiency.
In-Plant_ Centrcl_Measures
All corn wet mills presently incorporate many water recycling and reuse
techniques. In the early days of corn wet mills, little if any water
conservation or by-product recovery was practiced. Through research,
new markets were found for materials that were once wasted, such as
steepwater. Efforts to improve product recovery and simultaneously to
reduce waste discharges, have led to innovative process operations which
63
-------
utilize recycled water wherever possible and generally incorporate up-
to-date process technology.
The degree of in-plant control practiced by individual mills reflects
many factors, not the least of which are the physical constraints of the
existing facility. The physical space available in the plant may
prevent the installation of certain types of in-plant controls, such as
holding tanks for overflows. While physical constraints are not
necessarily a reflection of plant age, many process controls difficult
to implement in older plants have been incorporated into the con-
struction of new mills. In the following paragraphs, a number of in-
plant modifications involving water conservation and/or waste reduction
are suggested. Many of these have been incorporated in one or more
plants in the industry, but the ability to implement any of them rrust be
evaluated fcr each individual plant.
Cooling_Sy,stenis-
The cooling systems used in this industry can be characterized as non-
contact cooling surface condensers and contact cooling (barometric
condensers). They can be further subdivided into once-through and
recirculating systems. Since non-contact cooling water, both once
through and recirculated are common to many other industries, EPA will
issue guidelines on the non-contact cooling water area at a later date.
This report concerns itself with organic contamination of both contact
cooling water (barometric condenser) water and condensates frotr, surface
condensers.
One of the major waste loads from any corn mill is the condensate from
steepwater and syrup evaporators. Where surface condensers are
employed, the condensate is discharged as a concentrated waste stream,
suitable for treatment. Many plants use barometric condensers on the
evaporators and the resultant condensate is ccmingled with the cooling
waters, resulting in large volumes of dilute waste. Because of the
large voluire and low concentration, the removal of entrained BOD5 and
suspended solids is both expensive and difficult if once-through cooling
waters are used.
There are two possible remedies to this problem and both are being
implemented by various companies in the industry. One approach is to
convert all barometric condensers to surface condensers, but this
solution is not always practical. Physical restraints in some plants
prevent the installation of large surface condensers. Moreover, such
condensers are expensive and generally require more maintenance than
barometric condensers. In spite of these difficulties, several plants
have converted many of their barometric condensers to surface units.
An alternate approach, also being employed by several companies, is to
recirculate the barometric cooling water over cooling towers. In this
manner, the waste volume is reduced to the blowdown from the cooling
system and is much more concentrated than in the once-through system.
Moreover, physical and biological processes active in the cooling tcwer
effect some reduction in the total BOD5 load from the evaporators.
64
-------
Cger at i.onal_Contr ol_o^_ Evaporator s-
The control exercised in the operation of steepwater a no syrup
evaporators can have a significant effect on the total organic carryover
in the condensate. From a waste reduction standpoint, two problems are
prevalent in evaporator operation. The emphasis in operation is on
obtaining maximum steepwater cr syrup throughput in the evaporators and
not on minimizing organic carry-over. Accordingly, a number of plants
operated their evaporators at very heavy loading rates, rates which are
not commensurate with good waste control. Lack of careful control by
the operators is a second evaporator operational problem. Poth
situations lead to the frequent boiling over of the ligucr and resultant
heavy waste discharges. Improved operator control and expanded eva-
porator capacity can greatly reduce these problems.
Ihe arrount cf organic carry-over from evaporators can also be reduced by
installing modern entrainment separators or demisting devices. Many-
plants have already incorporated better entrainment separators and
research continues on ways to reduce organic carry-over even further.
It is also important that this type of equipment be well maintained.
Reuse_of_Process_Waste_Waters-
Although major recycling and reuse of process waste waters is practiced
at all corn wet mills, additional recycling is possible at most plants
and will have a significant effect on total waste effluent. At the same
time it must be recognized that the extent of reuse is subject to
restraints imposed by the Food and Drug Administration regarding good
manufacturing practices for food processing. Typically, fresh water
enters the irilling operation in the starch washing, and waste waters
from ordinary and lightly modified starches is reused in numerous
processes in the starch, feed, and mill houses. In these three areas of
the plant, waste waters are primarily generated only from the washing of
modified starches and from steepwater evaporation.
Water reuse practices in the refinery area vary considerably from mill
to mill. In many plants, waste waters are sewered from syrup cooling,
enzyme production, carbon treatment, ion exchange regeneration, syrup
evaporation, dextrose production, and syrup shipping. At least some of
these wastes are lightly contaminated and suitable for reuse. For
example, at seme mills condensate and syrup evaporation is used as input
water for activated carbon and ion exchange washing and regeneration.
Such practice not only greatly reduces total water use in the refinery,
but also decreases the total waste load from these operations. In
essence, product recovery is increased by this type of water reuse.
Improved Solids _gecpyery-
Screens, filters, and centrifugal separating equipment can be used to
recover sclids from waste streams directly at their source. For
example, centrifugal devices can be used on starch filtrate streams to
65
-------
recover sclids passing through holes that develop in the filter media.
Such solids can then be returned directly as product. In some mills,
filters or screens are used in the gluten processing area to recover
solids during start-up and shut-down activities and return these sclids
to by-product recovery.
Waste waters from the finished starch department, exclusive of highly
modified starch wastes, can be directed to a clarifier or thickener to
accomplish additional solids recovery. Rather substanital quantities of
solids can be recovered by this method and returned either to process or
sold directly as mill starch. Several mills have used settling tanks
for this purpose for many years.
Containment of Qerf lows
In a typical corn wet mill, overflows and spills from various pieces of
equipment cccur quite frequently. When sewered directly, these spills
constitute a large waste source. Although good operation can minimize
the frequency and amount of such process upsets, they cannc> be
eliminated and in-plant provisions should be made to contain these waste
water.
Specifically, those areas prone to upsets should be diked and sumps or
monitoring tanks installed in the area to retain the overflows. The
floor spillage can then be discharged gradually to these sewer, thus
reducing shock loads on the waste treatment system.
In new plants, the specific equipment overflows can be piped directly to
monitoring tanks and floor spillage largely eliminated. This same
practice can be instituted in existing plants, but to a more limited
degree. Once the overflows have been contained, their contents can be
analyzed and decisions made as to whether the material can be recycled
back into the process, discharged to by-product recovery, or if
absolutely necessary, discharged to the sewer. Such monitoring controls
are used by a few plants in the industry and have proved very effective
in reducing total plant waste discharges. Simultaneously, they have the
added benefit of improving general plant housekeeping.
Wa s te s -
Perhaps the most effective means of reducing overall plant waste loads
is to institute a careful monitoring program of all major process waste
streams. Such a program involves frequent sampling of the waste streams
and analysis for both product losses and waste load. Initially, the
program will identify the major sources of wastes and permit production
personnel to correct any process deficiencies thereby reducing, and
perhaps eliminating, many waste sources.
The effectiveness of such a monitoring program is limited by the
importance attached to it by company management. Where management has
recognized the need for reducing waste discharges and has supported the
monitoring effort, very substantial reductions in the quantities of
pollutants discharged have been realized. commensurate with this waste
66
-------
reduction has been increased product recovery, which a+ least partially
offsets the ccst of the monitoring.
General_Pl.ant_Orjeratj.on_and_]lous_ekeejDing-
As in many industries, general operational and housekeeping procedures
have a marked effect on the amount of wastes discharged. Those planrs
practicing clcse operational control and good housekeeping tend to
generate far less wastes than plants at the opposite extreme. Cnce
again, the impetus for improving operational and housekeeping procedures
must come from top management if it is to be effective.
Eecause of the unique nature of each plant in this subcategory, it is
impossible to estimate the overall effect on total waste discharge
achieved by instituting the above in-plant modifications. In general
terms, it is likely that total waste loads can be reduced by 25 percent
or more by these activities in plants where they are not practiced at
this time.
It is equally difficult to quantify the costs associated with effecting
these in-plant controls, inasmuch as the needs and the equipment costs
will vary for each plant. These costs will have to be evaluated on an
individual plant basis, taking into account various alternatives, plant
layout, physical restraints, and other factors.
Treatment Processes
Of the seventeen plants in the industry, at least seven provide some
type of treatment or pretreatment of the plant effluent. There are
three activated sludge systems in operation that discharge directly to
surface waters and one additional system that is under construction.
Three activated sludge pretreatment plants discharge to municipal
systems and a unique fungal digestion pretreatment plant is under
construction at a fourth plant. More limited pretreatment, consisting
of settling and some aeration, is provided at another plant. Pilot
plant studies were conducted on the joint treatment of municipal and
corn wet milling wastes using the pure oxygen system and a full-scale
treatment facility plant is now under construction. The various
treatment systems that are in use and the results of two pilot plant
studies are described below.
Ccm£l.ete_Treatment-
Three corn milling plants have waste treatment facilities that discharge
treated effluent directly to the receiving waters. Each of these plants
is of the activated sludge type, although they vary somewhat in their
detailed process operations.
Plant A — Vvaste treatment Plant A handles about 2,460 cu m/day (650,000
gpd) of concentrated wastes from a medium-sized corn wet mill. The
treatment plant does not receive the large quantities of once-through
67
-------
cooling water used at the plant, and which contain relatively low
concentrations of BODjjj and suspended solids. The waste water influent
to the treatment plant contains over 3,000 mg/1 of COD and 700 mg/1 ot
suspended solids.
The treatment sequence itself consists of complete-rrdx activated sludae,
secondary clarification, aeration in two lagoons operated in series, and
clorination. No primary clarification is provided in this system. The
activated sludge basin provides up to 48 hours detention, and the -trwo
lagoons following the secondary clarifier provide up to 16 days
additional retention. The first of the lagoons is fully aerated, while
the last portion of the second basin is quiescent to provide additional
settling.
Effluent characteristics from this treatment facility are as follows:
Average Range
BOD5 35 6-95
COD 266 102-525
Suspended Solids 169 8-372
The relatively high suspended solids content in the effluent, prohably
reflects some algae growth in the lagoons. The nature of corn milling
wastes, however, tends to generate solids handling problems in treatment
systems. At the time of the sampling program at Plant A, the treatment
facility was in an upset condition as evidenced by heavily bulking
sludge in the secondary clarifier. During this period of time, effluent
BOD5 from the treatment plant averaged 444 mg/1 with a suspended solids
content of 213 mg/1. Such upsets are common to all treatment plants in
the corn wet milling industry, and various reasons for them have been
hypothesized including shock loads of sugars, specialty starches, and
acids or alkalis.
In terms cf BOD5_ removal, Plant A represents the best treatment in the
industry. Suspended solids removal, however, is below expectations.
Plant B — The second plant to be discussed handles the waste from ancther
medium-sized corn wet mill. The facility consists of an aerated
equalization basin, two parallel complete-mix activated sludge basins,
secondary clarification, and dissolved air flotation. This plant has
been the recipient of an Environmental Protection Agency demonstration
grant and has been in operation for about two years.
The plant receives a concentrated waste stream of about 3,030 to 3,785
cu m/day (0.8 to 1.0 mgd) containing 1,400 mg/1 of BOD, 2,100 mg/1 of
COD, and 350 mg/1 of suspended solids. Once-through cooling water
containing seme barometric condensate is discharged to the receiving
water without treatment.
The aerated equalization basin provides 24-hour retention to equalize
waste load and pH fluctuations. In the summer, the discharge in the
68
-------
equalization basin may be passed over a cooling tower in order to reduc«
the temperature prior to the activated sludge process. Plant R was
designed en the basis of a food-to-microorganism ratio of 1.1 to 1.7r in
terms of COD:MLSS (mixed liquor suspended solids) , and provides about
16-hour detention. The dissolved air flotation following secondary
clarification was intended to polish the final effluent by removing any
floating fciclcgical sclid.
The design effluent from the plant is a BOD5 of less than 40 mg/1 and a
suspended solids content of less than 45 mg/1. Performance to date has
been well above these effluent levels, in spite of many modifications to
operating procedures. Evaluations by Environmental Protection Aacncy
personnel indicate that the plant was overloaded initially with a food-
to-microorganism ratio of 0.8 in terms of BOD:MLSS. Effluent POD5 and
suspended solids were usually several hundred mo/1 during the early
periods of operation. Efforts by plant personnel have reduced the raw
waste loading to the plant and the food-to-microorganism ratio
(BOD:MLSS) has now dropped to about O.U. Effluent characteristics for
the last six months of 1972 were as follows:
Average Range
_ rncj/l_
BOD5 79 5-994
Suspended Solids 142 4-1260
Sampling data taken during this study over a four-day period indicated
an effluent BOD5 of 10 mg/1 or less and a suspended solids content of
about 50 mg/1. The performance of Plant B, particularly during the
first three days of the sampling, was exceptionally good and believed to
be the best operation yet achieved by this facility. Towards the end of
the sample period, however, sludge bulking occurred and the final day's
suspended solids analysis was just over 100 mg/1. Plant performance
during the week of the sampling program was a graphic illustration of
the effect that upsets in this industry can have on treatment
efficiency. The equalization basin certainly dampens the effect of
shock loads, but upsets still occur frequently.
The performance of Plant B in recent months is a vast improvement ever
early operations. As the waste load to the plant has been reduced by
in-plant modifications, the average effluent quality has improved.
Based on the information available about this plant, it appears that
future activated sludge systems should be designed with a maximum
BOD:MLSS ratio of 0 . 4 and possibly lower.
Plant c-~ the third treatment facility, Plant C, is a new, complete mix
activated sludge plant handling about 760 to 1,600 cu m/day (200,000 to
425,000 gpd) of concentrated wet milling wastes from a small mill. The
system consists of primary sedimentation, complete-mix activated sludge,
and clarification. A cooling tower is provided to reduce the
temperature of the wastes during summer months. Influent waste
concentrations are about 1,600 mg/1 of BOD and 600 mg/1 of suspended
69
-------
solids. Because of its newness, only limited data are available on
effluent characteristics. Effluent BOD5 levels of 200 to 400 mg/1 and
suspended solids of 150 to 300 mg/1 have been reported. The common
problem of solids separation has already appeared at this facility and
efforts are apparently underway tc control sludge bulking.
I! £§ t £§ a £m e D t _ P la n t s_ -
Of the four kncwn pretreatment plants in the industry, three provide
some form of activated sludge treatment prior to discharge to a
municipal system. The fourth plant, which will not be discussed in
detail, provides some settling and limited aeration.
Plant D--Pretreatment Plant D serves a small mill and consists of two
large aerated lagoons that can be operated either in parallel or in
series. They provide about 5 days detention for the influent flow which
averages about 3,785 cu m/day (1.0 mgd) . About seven months of sampling
of treatment plant characteristics indicated the following influent and
effluent results:
Average Average
Influent Effluent
BOD5 2,330 1,080
COD 4,560 2,870
Suspended Solids 895 2,215
Data taken during the sampling program for this study indicated somewhat
lower results en both influent and effluent. These lower effluent
values were possibly the result of the recent reactivation of one of the
lagoons which had been drained for repairs. In any event, the
pretreatment plant provides adequate treatment under the contractual
terms with the local municipality. It should be noted that effluent
solids from the treatment plant exceed the influent values reflecting
the production of biological solids in the system.
Plant E — The second pretreatment plant provides complete-mix activated
sludge treatment for a design flow of below 3,785 cu m/day (1.0 mgd)
from a small mill. The system consists of two aerated equalization
basins with nutrient addition and pH control, followed by a complete-mix
activated sludge process, and secondary clarification. This plant is
relatively new and has been subject to frequent upsets. Effluent COD
and suspended solids are reported to be about 1,000 mg/1 and 260 mg/1
respectively. In general, the effluent levels are sufficient to meet
the pretreatment limitations proposed by the local municipality.
Treatment plant efficiency is expected to improve markedly as the
production plant operations and, hence, raw waste characteristics
stabilize.
Plant F--This pretreatment plant receives the concentrated waste flow
from a large corn wet mill. The influent waste flow is about 3,210 cu
70
-------
m/day (0.85 mgd) with a BOD5 level of about 2,600 mg/1. The facility
consists of four aeration basins and secondary clarification prior to
discharge to the local municipal system. Certain cooling water and
other wastes from the mill do not go through this treatment plant,
Effluent levels are reported to be generally in the range of 500 mg/1 of
BOD. Results of the sampling program were somewhat lower, as given
below:
Average Pange
BOD5 280 68-415
COD 1317 488-2206
Suspended Solids 889 288-1395
Sludge bulking has been a frequent problem at this plant over the years
that it has been in operation. The facility itself consists of various
aeration basins, some operated in series and others in parallel. Many
of the basins have been converted from other prior uses and it is
difficult, if not impossible, to extrapolate treatment practices at this
plant to the design of new facilities.
Pilot Plant Studies-
At least three new treatment or pretreatment plants are presently under
construction. Data on pilct plant studies for two of these are
available and discussed below, together with the design parameters for
the third plant,
Plant G--Pather extensive pilot plant studies were run, using one- and
three-stage pure oxygen and air activated sludge systems, on combined
wastes from a mediuir sized corn wet milling plant and the local
municipality. The reported pilot plant data on both plants were
somewhat sporadic, particularly in terms of suspended solids removal.
Generally, the data demonstrated the applicability of both pure oxygen
and air activated sludge systems for the treatment of the combined
wastes. The process design consultants have concluded that the pure
oxygen system offered certain advantages, particularly in terms of
solids handling. Effluent BOD5> values for the first three months of the
oxygen pilct plant usually ranged from 200 to 400 mg/1, but dropped well
below 100 mg/1 for the last two months of operation. Results with the
air system appear to be roughly comparable to those achieved with
oxygen.
A full-scale pure oxygen system has been designed and is now under
construction to handle the combined municipal and industrial wastes.
Design criteria for the plant are for a BOD:MLSS ratio of 0.5 to 0.7
with a MLSS concentration of 3,000 to 4,000 mg/1. There are indications
that pure oxygen may offer some advantages in reducing sludge bulking,
but the available information throughout the country in related
71
-------
industries does not yet substantiate this hypothesis. Treatment Plant G
will certainly provide an adequate test for this theory.
Plant H--This pretreatment plant will receive wastes from a medium sized
corn mill. The system is quite unique in that it depends on fungal
disgestion as opposed to more conventional biological treatment methods.
Pilot plant studies were conducted in a 50,000 gal aerated tank with a
detention time of 16 to 24 hours. In order to promote the fungal
growth, the system was operated at a pH of 3.5 to 6.0. Influent EOD5
concentrations ranged from 700 to 4,800 mg/1, with effluent values
normally ranging between 100 to 500 mg/1. The mixed liquor suspended
solids, in this case the fungal mass, ranged from 500 to 1,800 mg/1.
The results of the pilot plant studies have prompted the company to
construct a 3.0 mgd pretreatment plant, based on fungal digestion. Th^
system will consist of 24-hr equalization, pH adjustment, funqal
digestion, and final clarification using settling and filtration.
The pilot plant results, while quite interesting, do. not appear to
indicate any substantial improvement in effluent quality over mor°
conventional biological treatment systems. There may be some advantage
in terms of solids handling, inasmuch as the fungal mass apparently can
be removed more readily from the final effluent. Plant l--Pres<" nt ly
under construction, this treatment plant is designed to handle about
11,355 cu m/day (3.0 mgd) of wastes from a large corn mill. In-plant
control measures are being taken to isolate the major waste sources into
a concentrated waste stream, which is expected to have a BOD5 content of
1,600 mg/1.
The treatment system will consist of grit and oil removal, nutrient
addition and pH control, equalization, cooling over a cooling tower when
necessary, a roughing plastic-media trickling filter, activated sludge,
secondary clarification, chlorination, and mixed-media filtration.The
plant will be the most elaborate treatment facility in the industry and
incorporates a great many flexible concepts. The aeration basins are
designed on a BOD:MLSS ratio of 0.3 with a total detention time of 18
hours. The roughing filters are designed to remove about 60 percent of
the influent EOD5 ahead of the aeration system. The design effluent
levels are 5 mg/1 of suspended solids and 20 mg/1 of BOD. It should be
emphasized that these design levels are far below those which have been
achieved by any other plant in the corn wet milling or related
industries and cannot yet be considered as demonstrated technology.
gludge Handling
The disposal of suspended and biological solids from the treatment of
corn wet milling waste waters constitutes a major problem, as it does
for any waste treatment plant handling high-strength organic materials.
Experience with waste activated sludge has indicated several methods of
disposal which can be applied to corn wet milling. These include
dewatering with disposal on land, incineration, or by-product recovery.
In this instance, the highly nutritious biological solids potentially
provide a material that can be recycled into animal feeds.
72
-------
Limited information is available on the handling of waste treatmen*-
plant sludges in this industry, but it is know that several riant?
return these solids to the process stream, presumably far animal f-~d.
Several tnethcds for accomplishing this can be suggested including
centrifugation, vacuum filtration, and direct addition to evaporators.
It is imperative that sanitary wastes be segregated from process waster
and discharged separately to the municipal system, if biological sclids
recovery from the process waste treatment plant is to be practiced.
Moreover, sterilization by heat or chlorination may be recmired in some
instances. In summary, if the sanitary wastes are separated from
process wastes, as they are at most plants, solids from the treatment
system can be dewatered and/or recycled directly into the feed housc for
use in aninral feeds.
COPN DRY MILLING
Waste waters from dry corn mills, as detailed in Section V, average
about 1,500 to 2,000 mg/1 of BOD5 and 1,500 to 3,500 mq/1 of suspended
solids. Flows from these mills are much smaller than from corn wet
mills, averaging some 0.00045 to 0.0013 cu m/kkg (3 to 8 gal/MSBu) .
Treatment in the industry is thought to be very limited, as most mill?
discharge to municipal systems. One known pretreatment plant is
discussed in this section.
In^Plant^Controls
Waste waters can arise from only two sources in corn dry mills, namely
car washing and corn washing. The former is practiced infrequently and
at only some mills and will not be considered further. Dry car cleaning
techniques are now available using vacuum systems to replace wet
methods.
Corn washing is performed by many, but not all, of the corn mills. Some
mills, because of the condition of the corn as received or other
factors, feel that wet washing is not necessary. At the mills where wet
washing is practiced, little can be done in terms of in-plant control to
improve the system. It is possible that some mills use more water than
is required, but the total amounts of contaminants should remain
constant. These contaminants reflect the nature of the corn as it is
received and little can be done to reduce the total amounts. It is
possible that partially clarified waste waters could be recycled into
the corn washing operation, but this has not yet been demonstrated.
Waste_Wat.er_Treatment
Only one plant is known to provide treatment for their process waste
waters. The treatment sequence consists of settling to recover the
heavy solids for animal feed, followed by a plastic media trickling
73
-------
filter and discharge to the municipal system. Sampling data secured at
this treatment plant are summarized below:
Average Average
Influent Effluent
mcj/1 5D2/1
BODS 2,me 608
COD" 4,901 2,983
Suspended Solids 3,485 1,313
Tests run on settled samples from this treatment plant indicated
additional removals of about 50 percent of the BOD5_ and 70 percent of
the suspended solids could be achieved by secondary clarification.
The results from this pretreatment plant clearly demonstrate that wastes
from corn dry mills are amenable to conventional biological treatment.
It is anticipated that treatment of these wastes will be somewhat l«ss
difficult than those from wet corn mills, inasmuch as lower volumes and
perhaps less exotic constituents are involved. Specifically, it is
anticipated that sludge bulking will be less of a problem with this type
of waste water than with the very high carbohydrate waste waters from
corn wet mills.
Sludge_Dis£gsal
The prevalent practice in the corn dry milling industry is to recover
the heavier solids from the wash water for use in animal feed. If
biological treatment of the waste waters is provided, it would appear
that waste biological solids could also be incorporated into aninral
feed,
WHEAT MILLING
Ordinary wheat milling generates little in the way of process waste
waters except from car washing and wheat washing. Both of these
activities are not practiced at most mills and consideration will net be
given to these waste waters in this section. Wet car and wheat washing
systems presently in use can be replaced by dry cleaning systems.
The several plants that produce bulgur do generate limited guantities of
waste water. In view of the rather small quantities of waste water,
ranging from 38 to 114 cu m/day (10,000 to 30,000 gpd) , it is not
anticipated that the raw waste characteristics can be greatly influenced
by in-plant controls. Observations at one bulgur mill, however„
indicated that the quantities of waste water might be reduced by more
careful operational control.
All of the bulgur producers presently discharge their wastes to
minicipal systems and no treatment of such wastes is practiced in this
country. The waste strength, however, indicates that it should be
amenable to conventional biological treatment processes. The raw waste
74
-------
characteristics range from about 250 to 500 mg/1 of BOD5> and 30C tc 400
mq/1 of: suspended solids. Effluent levels roughly equivalent to th^cc.
achieved in well-operated secondary minicipal sewaqe treatment plant;-
should he attainable.
RICE MILLING
Ordinary rice milling involves no process waters and, hence, g°ncratcs
nc process waste waters. Six mills parboil rice, and this process dees
result in rnodest amounts of process waste waters. These waste waters
are high in dissolved BOD, approximately 1,300 ing/1, but low ir.
suspended solids, 30 to BO mg/1.
Tho waste water comes from the steeping process, and in-plant control?
cannot be effected that will influence appreciably thD quantity or
character of the waste waters. At least five of the six parboiled rice
plants discharged their wastes to municipal systems and no known
treatment is practiced by any mill. Once again, however, the general
nature of the waste water indicates that it can be treated by biological
processes in a similar manner to corn milling or bulgur production,
inasmuch as the BOD^ is largely in a soluble form. The rather constar.-'-
character of the waste stream should make it more amenable to stable
treatment plant operation than corn wet milling waste waters. Moreover,
the waste water volumes, i.e., from 265 to 760 cu m/day (70,000 to
200,000 gpd) make the wastes much more manageable. It is possible that
the biological solids frcm any treatment process could be included with
the bran and hulls as animal feed.
75
-------
SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
The following presents detailed cost estimates for the various treatment
alternatives and the rationale used in developing this information.
Data have been developed for investment, capital, operating and
maintenance, depreciation, and energy costs usina various sources
including information from individual grain mills, Sverdrup ? Parcel
files, and literature references 21 and 22. Generally, the cost data
from industry relate to specific items of equipment and are of limited
utility. Moreover, most of the treatment systems presently in use in
the grain milling industry were built over a period of years and the
cost data that is available is difficult to extrapolate and to relate to
the proposed treatment alternatives. As a result, the cost estimates
are based principally on data developed by the contractor and the
references cited previously.
REPRESENTATIVE PLANTS
Because cf the variations in plant opeation, waste water
characteristics, and treatment systems, it was impractical to select one
existing plant as typical of each of the grain milling subcategories.
Therefore, hypothetical plants were developed (or synthesized) for
purposes of developing cost data. Each of the synthesized plants was in
the medium to moderately large production size range for the subcategory
under consideration. Flow and waste water characteristics were selected
to reflect average values for existing plants in the industry as
reported in Section V.
TERMINOLOGY
Investment costs are defined as the capital expenditures required to
bring the treatment or control technology into operation. Included, as
appropriate, are the costs of excavation, concrete, mechanical and
electrical equipment installed, and piping. An amount equal to from 1?
to 25 percent of the total of the above is added to cover engineering
design services, construction supervision, and related costs. The lower
figure is used for larger facilities. Because most of the control
technologies involved external, end-of-plant systems, no cost is
included for lost time due to installation. It is believed that the
interruptions required for installation of control technologies can be
coordinated with normal plant operating schedules. As noted above, the
control facilities are estimated on the basis of minimal space
requirements. Therefore, no additional land, and hence no cost, would
be involved for this item.
77
-------
Costs
The capital costs are calculated, in all cases, as 8 percent of the
total investment costs. Consultations with representatives of industry
and the financial community lead to the conclusion that, with the
limited data available, this estimate is reasonable for this industry.
Straight-line depreciation for 20 years, or 5 percent of the total
investment cost, is used in all cases.
Maintenance Costs
Operation and maintenance costs include labor, materials, solid waste
disposal, effluent monitoring, added administrative expense, taxes, and
insurance. When the control technology involved water recycling, a
credit of $0.30 per 1,000 gallons is applied to reduce the operation and
maintenance costs. Manpower requirements are based upon information
supplied by the representative plants as far as possible. A total
salary cost of $10 per man-hour is used in all cases. The costs of
chemicals used for maintenance and operation.
Power Costs
Power costs are estimated on the basis of $0.025 per kilowatt-hour.
COST INFORMATION
The investment and annual costs, as defined above, associated with the
alternative waste treatment control technologies are presented in this
section. In addition, a description of each of the control technologies
is provided, together with the effluent quality expected from the
application of these technologies. All costs are reported in terms of
August, 1971 dollars.
Corn Wet Milling
As a basis for developing control and treatment cost information, a
medium-sized corn wet mill, with a daily grind of 152-4 kkg (60,000 SBu)
was synthesized. This hypothetical plant practices good in-plant
control and uses recirculated cooling water. The waste water
characteristics from the mill reflect actual industry practice based on
average data received from existing mills. These waste water
characteristics are as follows:
Flow 11,355 cu m/day (3.0 mgd)
BOD5 7.14 kg/kkg (400 Ibs/MSBu) or 960 mg/1
Suspended Solids 3.57 (200 Ibs/MSBu) or 480 mg/1
A number of alternative treatment systems are proposed to handle the
waste waters from this hypothetical mill. The investment and annual
78
-------
cost information for each alternative, and the resultant efflu^n*
qualities are presented in Table A-l. The specific treatment
technologies are described in the following paragraphs.
Alternative_A — Activated Sludge
This alternative provides for grit removal, pH adjustment, nutrien^
addition, complete-mix activated sludge, secondary sedimentation, and
centrifugation for solids dewatering. The treatment system does not
include equalization or primary sedimentation. Effluent EOD5 and
suspended solids concentrations are expected to be 150 to 250 mg/1 for
both parameters. In terms of raw material input, the effluent values
correspond to 1.12 to 1.86 kq/kkg (63 to 104 Ibs/ MSBu).
Ccsts. Investment costs of approximately $2,388,000.
Reduction Benefits. BOD5_ and suspended solids reductions of
about 80 and 58 percent respectively.
Alt§EE<|tiye_B — Equalization and Activated Sludge
Alternative B includes 12 to 18 hours of aerated equalization ahead of
the complete-mix activated sludge process and associated chemical feed,
sedimentation, and sludge dewatering facilities proposed in Alternative
A. Average effluent levels are estimated to be about 75 to 125 mg/1 of
both BOD5 and suspended solids. These concentrations correspond to 0.55
to 0.91 kg/kkg (31 to 52 Ibs/ MSBu) for both parameters.
Two mills now provide the general type of treatment system proposed in
this alternative. Another similar facility provides pretreatment for a
third mill.
Costs. Incremental costs are approximately $156,000
over Alternative A for a total cost of $2,544,000.
Reduction Benefits. BOD5 and suspended solids will be
reduced by about 90 and 80 percent respectively.
Ai£§££3iive_C — Equalization, Activated Sludge, and Stabilization
Lagoon
For Alternative C, a stabilization basin following secondary sedi-
mentation is added to the preceding treatment system. This
stabilization lagoon will provide 10-day detention for stabilizing the
remaining EOD5 and reducing suspended solids. One mill presently
provides a version of this treatment sequence, but without equalization.
Effluent concentrations of 30 to 60 mg/1 of BOD5 and suspended solids
are expected from Alternative C. The resultant effluent waste load will
be 0.223 to 0.447 kg/kkg (12.5 to 25.0 Ibs/MSBu) for both BOD5 and
suspended solids.
79
-------
Cos-ts. Incremental costs of approximately $288,000
over Alternative B for a total cost of $2,832,000.
Reduction Benefits. BOD5 and suspended solids reductions
of about 95 and 90 percent respectively.
Alternatj.ye_D — Equalization, Activated Sludge, and Deep Bed
Filtration
In this proposed system, deep bed filtration is added to the activated
sludge system presented as Alternative B. The stabilization basin of
Alternative C has been deleted. A treatment system similar to
Alternative D is now under construction. BOD5_ and suspended solids
concentrations of 20 to 30 mg/1 and 10 to 20 mg/1 respectively are
expected in the effluent from this alternative. These concentrations
correspond tc effluent loads of 0.15 to 0.22 kg/kkg (8.3 to 12.5
Ibs/MSBu) of EODJ and 0.07 to 0.15 kg/kkg (4,2 to 8.3 Ibs/MSEu) of
suspended solids.
Costs. Incremental costs of approximately $288,000 over
Alternative B for a total cost of $2,832,000, the same
cost as Alternative C.
Reduction Benefits. BOD5 and suspended solids reductions of
about 97.4 and 96.9 percent respectively.
Alt§.rnatiye_E — Equalization, Activated Sludge, Deep Bed Filtra-
tion and Activated Carbon Filtration
Activated carbon filtration is added to the activated sludge with the
deep bed filtration system proposed as Alternative D. The effluent
concentrations are estimated to be 5 mg/1 for both BOD and suspended
solids. This level corresponds to a waste load of 0.037 kg/kkg (2.1
Ibs/MSBu) for both constituents. No treatment facility in the entire
industry provides this level of treatment.
Costs. Incremental costs of approximately $1,244,000
over either Alternative C or D for a total cost of
$4,076,000.
Reduction Benefits. BOD5 and suspended solids reduction
of about 99.5 and 99.0 percent respectively. The
effluent should be suitable for at least partial
recycle.
Alternative^?1 — Equalization, Activated Sludge, Deep Bed Filtra-
~ tion, Activated carbon Filtration, and Reverse
Osmosis
This alternative includes reverse osmosis to reduce the total dissolved
solids. Effluent levels will be comparable to those given in
Alternative E, but with a maximum dissolved solids content of 500 mg/1.
80
-------
Costs. Incremental costs of approximately $1,884,000
over Alternative E for a total cost of $5,960,000.
Reduction Benefits. BOD.5 and suspended solids reductions
equal to those in Alternative E, i.e., 99.5 and 99.0
percent respectively. The effluent should be suitable
fcr complete recycle.
— Recirculatinq Cooling Water System
The synthesized corn wet mill described previously is assumed to have
good in-plant water conservation practices including recirculatinq
cooling water systems. comparably sized mills using once- through
cooling waters will be confronted with the additional cost of installinot
cooling towers to reduce total waste water flows. A separate cost hots
been developed for such plants based on a recirculai-ing cooling water
demand of about 34,000 cu m/day (9.0 mgd or 6250 gpm) .
Ccst. Incremental costs of adding a cooling tower are
approximately $288,000.
Cgrn_Dry
A hypothetical corn dry mill of moderate to large size, i.e. 762 kkg/day
(30,000 SBu/day) , was selected as a basis for developing costs data.
This synthesized plant generates a waste water that reflects actual
industry practice as follows:
Flow 492 cu m/day (130,000 gpd)
BOD5 1.13 kg/kkg (63 Ibs/MSBu) or 1750 mg/1)
Suspended solids 1.61 kg/kkg (90 Ibs/MSBu) or 2500 mg/1)
A "" Primary Sedimentation
This alternative consists only of primary sedimentation and reduces the
BOD5 and suspended solids to about 1,000 mg/1 and 500 mg/1 respectively.
These concentrations correspond to effluent waste loads of 0.65 kg/kkg
(36 Ibs/MSBu) of BOD5 and 0.32 kg/kkg (18 Ibs/ MSBu) of suspended
sclids. Presumably some corn dry mills have clarifiers similar to that
provided for Alternative A.
Cost. Investment costs of approximately $20,000.
Reduction Benefits. BOD5_ and suspended solids reductions
of about 43 and 80 percent respectively.
B — Primary Sedimentation and Activated Sludge
Alternative B includes primary sedimentation, nutrient addition,
complete-mix activated sludge, secondary sedimentation, and sludge
dewatering. Expected effluent levels are 100 mg/1 of BOD5 and suspended
solids corresponding to a treated waste load of 0.065 kg/kkg (3,6
Ibs/MSBu) fcr both pollutant parameters.
81
-------
Costs. Incremental costs of approximately $271,000 over
Alternative A for a total cost of $291,000,
Reduction Benefit. BOD5 and suspended solids reductions of
about 94.3 and 96.0 percent respectively.
—• Primary Sedimentation, Activated Sludge, and
Stabilization Lagoon
This alternative adds a 10-day stabilization lagoon in series with the
activated sludge system as given in Alternative B. Effluent quality is
expected to be 30 to 60 mg/1 of BOD5 and suspended solids or an effluent
waste load of 0.019 to 0.039 kg/kkg (1.1 to 2.2 Ibs/ MSBu) for both
constituents.
Costs. Incremental costs of approximately $25,000 over
Alternative B for a total cost of $316,000.
Reduction Benefit. EOD5 and suspended solids reductions
of about 97.4 and 98.2 percent respectively.
^iij§££^iiYS_2 "*~ Primary Sedimentation, Activated Sludge, and
Deep Bed Filtration
Deep bed filtration following the activated sludge system comprises this
alternative. The concentration of BODjj and suspended solids in the
treated effluent is expected to be 20 to 30 mg/1 and 10 to 20 mg/1
respectively. These effluent concentrations are equivalent to waste
loads of 0.013 to 0.019 kg/kkg (0.7 to 1.1 Ibs/MSBu) of EOD5 and 0.006
to 0.013 kg/kkg (0.36 to 0.7 Ibs/MSBu) of suspended solids.
Costs. Incremental costs of approximately $32,000 over
Alternative B for a total cost of $323,000.
Reduction Benefit. BOD^ and suspended solids reductions
cf about 98.6 and 99.4 percent respectively.
A.itSJU^iy.fL.I; — Primary Sedimentation, Activated Sludge, Deep Bed
Filtration, and Activated Carbon Filtration
The final alternative presented herein adds acitvated carbon filtration
to the activated sludge - deep bed filtration system of the previous
alternative. Treated effluent quality is expected to be 5 mg/1 of both
EOD.5 and suspended solids for an equivalent waste load of 0.003 kg/kkg
(0.18 Ibs/MSBu).
Costs. Incremental costs of $174,000 over Alternative
D for a total cost of $497,000.
Reduction Benefit. BOD^ and suspended solids reductions
of about 99.7 and 99.8 percent respectively
82
-------
Vvhea^_Milling (Bulgur)
Inasmuch as ordinary wheat milling usually generates no process v;aste
waters, this discussion will be limited to bulgur production. Thr
synthesized bulgur mill is of medium size, 203 kkg/day (8000 Sbu/day)
and discharges waste waters with the following characteristics:
Flow 56.7 cu m/day (15,000 gpd)
BOD5 0.104 kg/kkg (6.25 Ibs/MSBu) or 400 in/1
Suspended Solids 0.093 kg/kkg (5.62 Ibs/MSBu) or 360 mg/1
Alternatiye_A — Activated Sludge
The first alternative provides an activated sludge (extended aeration)
system with nutrient addition and secondary sedimentation. No primary
sedimentation is provided because of the low flows. Moreover, it is
anticipated that factory built or so-called package treatment systems
can be used. Sludge will be hauled away several times a year for land
disposal. The treated effluent quality is expected to be 30 mg/1 of
both BODJ and suspended solids corresponding to 0.0078 kg/kkg (0.47
Ibs/MSBu) .
Costs. Investment costs of approximately $24,000.
Reduction Benefit. BOD5 and suspended solids reductions
of about 92.5 and 91.7 respectively.
Alternative_B — Activated Sludge and Deep Bed Filtration
This alternative adds deep bed filtration to activated sludge system.
The filtered effluent is expected to contain 10 to 20 mg/1 of BOD5 and 5
to 10 mg/1 cf suspended solids. The corresponding effluent waste loads
are 0.0027 to 0.0052 kg/kkg (0.16 to 0.31 Ibs/MSBu) of BOD5 and 0.0013
to 0.0027 kg/kkg (0.08 to 0.16 Ibs/MSBu) of suspended solids.
Costs. Incremental costs of approximately $69,000 over
Alternative A for a total cost of $93,000.
Reduction Benefit. BOD5 and suspended solids reductions
of about 96.2 and 97.8 percent respectively.
Alternatiye_C — Activated Sludge, Deep Bed Filtration, and Activated
Carbon Filtration
This final alternative incorporates activated carbon filtration as a
final polishing step after Alternative B. The treatment effluent
quality is expected to be 5 mg/1 of both BOD^ and suspended solids cr an
effluent waste load of 0.0013 kg/kkg (0.08 Ibs/MSBu).
Costs. Incremental costs of approximately $287,000 over
Alternative E for a total cost of $380,000.
Reduction Benefit. BODj> and suspended solids reductions
cf about 98.8 and 98.6 respectively.
83
-------
R.ice_Millinc[
This discussion will be limited to parboiled rice milling since ordinary
rice milling generates no process waste waters. The hypothetical rice
mill selected for developing cost data is a moderately large plant
processing 363 kg/day (8000 cwt/day) . Raw waste water characteristics
are:
Flow
BOB5
Suspended Solids
492 cu m/day
1.88 kg/kkg
0.075 kg/kkg
(130,000 gpd)
(0.188 Ibs/cwt) or 1380 mg/1
(0.0075 Ibs/cwt) or 55 mg/1
— Activated Sludge
The first treatment alternative provides nutrient addition, complete mix
activated sludge and secondary sedimentation. Waste activated sludge is
dewatered by a centrifuge and mixed with the millteed (animal feed) .
Treated waste water concentrations of 100 mg/1 of BOD and 60 to 80 mg/1
of suspended solids are expected. These effluent levels correspond to
waste loads of 0.14 kg/kkg (0.014 Ibs/cwt) of BOD5 and 0.08 to 0.11
kg/kkg (0.008 to 0.011 Ibs/cwt) of suspended solids.
Costs. Investment costs of approximately $313,000.
Reduction Benefit. BODJ5 reductions of about 92.8 percent.
£i£ernatiye_B — Activated Sludge and Stabilization Lagoon
This alternative merely adds a 10-day stabilization lagoon to the
activated sludge system of Alternative A to effect greater BODj> and
suspended solids removals. The effluent quality from Alternative B is
expected to be 30 to 60 mg/1 of BOD5 and suspended solids or an
equivalent waste load of 0.041 to 0.081 kg/kkg (0.004 to 0.008 Ibs/cwt).
Costs. Incremental costs of approximately $35,000 over
Alternative A for a total cost of $348,000.
Reduction Benefit. BOD5_ reduction of about 96.7 percent.
Alternative_C — Activated Sludge and Deep Bed Filtration
Alternative C consists of the activated sludge system proposed in
Alternative A followed by deep bed filtration. The concentrations of
BOD5 and suspended solids in the effluent are expected to be 20 to 30
mg/1 and 5 to 10 mg/1 respectively. These concentrations correspond to
effluent waste loads of 0.027 to 0.041 kg/kkg (0.0027 to 0.0041 Ibs/cwt)
of BOD5_ and 0.007 to 0.014 kg/kkg (0.0007 to 0.0014 Ibs/cwt) of
suspended solids.
Costs. Incremental costs of approximately $34,000 over
Alternative A for a total cost of $347,000.
84
-------
Reduction Benefit. BOD5 and suspended solids reductions
of about 98.2 and 86.U percent respectively.
Alternative_D — Activated Sludge, Deep Bed Filtration, and Acti-
vated Carbon Filtration
In this last alternative, activated carbon is added to the activated
sludge and deep bed filtration treatment system. Treated effluent
quality is expected to be 5 mg/1 of both BOD5 and suspended solids cr an
effluent waste load of 0.007 kg/kkg (0.0007 Ibs/cwt).
Costs. Incremental costs of approximately $181,000 over
Alternative C for a total cost of $528,000.
Reduction Benefit. BOD5_ and suspended solids reductions
of about 99.6 and 90.9 percent respectively.
NON-WATER QUALITY ASPECTS OF TREATMENT AND CONTROL TFCHNOLOGIES
Air_Pcllution_Contrgl
With the proper operation of the types of biological treatment systems
presented earlier in this section, no significant air pollution problems
should develop. Since the waste waters from the grain milling industry
have a high organic content, however, there is always the potential for
odors. At least one present treatment plant has experienced rather
severe odcr problems from a sludge lagoon. Care should be taken in the
selection, design, and operation of biological treatment systems to
prevent anaerobic conditions and thereby eliminate possible odor
problems.
Solid^Waste^Disposal
The treatment of grain milling waste waters will give rise to sub-
stantial quantities of solid wastes, particularly biological solids from
activated sludge or comparable systems. Several avenues are available
for the disposal of these solids including digestion and landfill,
incineration, and other conventional methods fo handling biological
solids. Alternately, the solids can be dewatered and added to the
animal feed already being produced at these mills. This practice has
found some acceptance in the grain milling industry, particulary in the
corn wet milling segment, and is strongly recommended. Additional
discussion of solids recovery and sludge disposal is contained in
Section VII.
l£s rgy._R eg u ir emen t s
The treatment technologies presently in use or proposed in this document
do not require any processes with unusually high energy requirements.
Power will be required for aeration, pumping, centrifugation, and ether
unit operations. These requirements, generally are a direct function of
the volume to be treated. Thus, the greatest requirements will be in
85
-------
the corn wet milling subcategory and the least in bulgur waste water
treatment.
For the hypothetical treatment systems described previously in this
section, the power requirements are in the range of 375 to 450 kw (500
to 600 hp). This level of demand is small relative to the requirements
for the entire mill. Similar projections in the other grain milling
subcategories lead to the conclusions that the energy needs for
achieving good waste water treatment constitute only a small portion of
the energy demands of the industry. These added demands can readily be
accomodated.
86
-------
SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE EEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations that must be achieved July I, 1977 are to
specify the degree of effluent reduction attainable through the
application of the best practicable control technology currently
available. The best practicable control technology currently available
is generally based upon the averages of the best existing performance by
plants of various sizes, ages, and unit processes within the industrial
category or subcategory. This average is not based on a broad range of
plants within the grain milling industry, but on performance levels
achieved by a combination of plants showing exemplary in^hcuse
performance and those with exemplary end-of-pipe control technology.
Consideration must also be given to:
a. The total cost of application of technology in relation
tc the effluent reduction benefits to be achieved from
such application;
b. the size and age of equipment and facilities involved;
c. the processes employed and product mix;
d. the engineering aspects of the application of various types
of ccntrol techniques;
e. process changes; and
f. non-water quality environmental impact (including energy
requirements).
Also, best practicable control technology currently available emphasizes
treatment facilities at the end of a manufacturing process, but includes
the control technologies within the process itself when the latter are
considered to be normal practice within an industry. A further
consideration is the degree of economic and engineering reliatility
which must be established for the technology to be "currently
available." As a result of demonstration projects, pilot plants, and
general use, there must exist a high degree of confidence in the engi-*
neering and economic practicability of the technology at the time of
commencement cf construction or installation of the control facilities.
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE EEST
PRACTICABLE CCNTROL TECHNOLOGY CURRENTLY AVAILABLE
Based on the information presented in Sections III through VIII of this
report, it has been determined that the effluent reductions attainable
through the application of the best practicable control technology
currently available are those presented in Table 15. These values
represent the maximum average allowable loading for any 30 consecutive
calendar days. Excursions above these levels should be permitted with a
87
-------
maximum daily average of 3.0 times the average 30-day values listed
below.
Table 15
Effluent Reduction Attainable Through the Application of
Best Practicable Control Technology Currently Available*
Industry Category
and Subcategory
i I
Corn wet rrilling
Corn dry irilling
Normal wheat flour
milling
Eulgur wheat flour
milling
Normal rice milling
Parboiled rice milling
BOD5
kc[/kkg Ib
Suspended Solids
0.893
0.071
50.0
4.0
0.625
0.062
35.0
3.5
6-9
6-9
No discharge of process waste waters
0.0038 0.5 0.0083 0.5 6-9
No discharge of process waste waters
0.140 0.014 0.080 0.008 6-9
^Maximum average of daily values for any period of 30 consecutive days
IDENTIFICATION
AVAILABLE
OF
BEST
PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
The best practicable control technology currently available for the
grain milling industry generally consists of a high level of waste
treatment coupled, in some instances, with certain in-plant modi-
fications. The specific technological means available to implement the
specified effluent limitations are presented below for each subcategory.
Corn Wet_Milling
The corn wet milling segment of the grain milling industry must under-
take major pollution abatement activities in order to meet the effluent
limitations. These activities will include both in-plant modifications
and biological waste water treatment as follows:
1. Isolating and collecting the major waste streams for
treatment.
2. Eliminating once-through barometric cooling waters, espe-
cially from the steepwater and syrup evaporators. This
change can be accomplished by recirculating these cooling
waters over cooling towers or replacing the barometric
condensers with surface condensers.
3. Isolating once-through noncontact (uncontaminated) cooling
waters for discharge directly to the receiving waters or
provision of recirculating cooling tower systems with the
blowdown directed to the treatment plant.
88
-------
U. Diking of all process areas subject to frequent spills in
order to retain lost product for possible reuse or by-
product recovery.
5. Installing and maintaining modern entrainment separators
in steepwater and syrup evaporators.
6. Monitoring the major waste streams to identify and control
sources of heavy product losses.
7. Providing extensive waste treatment for the resulting
process waste waters consisting of: flow and quality
equalization, neutralization, biological treatment, and
solids separation. The biolcgical treatment methods
available include activated sludge, pure oxygen acti-
vated sludge, bio-discs, and possible combinations of
ether biological systems.
Corn_Dry_Milling
Waste waters from corn dry mills are generated almost exclusively in
corn washing. Little can be done to reduce the waste load from the
plant and treatment of the entire waste stream will be necessary as
follows:
1. Collection of waste waters from car washing operations,
where practiced.
2. Primary solids separation by sedimentation.
3. Biolcgical treatment using activated sludge or a com-
parable system.
4. Final separation of solids by sedimentation prior to
discharge.
The effluent limitation for the milling of ordinary wheat flour permits
no discharge of process wastes. Inasmuch as most ordinary wheat mills
do not use process waters, this effluent limitation can be met with no
plant changes. For the few mills that wash the wheat, dry cleaning
systems are available to eliminate this waste source.
Bulgur wheat milling generates a relatively small quantity of process
waste water that will require treatment to meet the effluent standards.
Such treatment will include:
1. Primary solids separation by sedimentation.
2. Biolcgical treatment using activated sludge or a comparable
system.
89
-------
3, Final separation of solids by sedimentation prior to discharge.
Pice._Milling
Normal rice milling involves no process waters and, hence, the effluent
limitation of no discharge of process wastes is already being met. The
few mills producing parboiled rice generate a relatively small amount of
high strength process waste water. The best practicable control
technology currently available for the parboiled rice subcategory is as
follows:
1. Biological treatment using activated sludge or
comparable systems.
2. Final separation of solids by sedimentation prior
tc discharge.
RATIONALE FOR THE SELECTION OF BEST PRACTICABLE CONTROL TECHNGIOGY
CURRENTLY AVAILABLE
Ccrn_Wet_Milling
Cost_gf_Ap_Elication-
Data developed on the ccst of applying various treatment technologies
are presented in Section VIII. For a 1524 kkg (60,000 SBu) corn wet-
mill, the investment cost for implementing the best practicable control
technology currently available is about $2,544,000, exclusive of the
costs for in-plant control. Additional information on operating and
maintenance costs is contained in section VIII.
Age_and_Size_of_Productign_Faci].ities^
The mills in this subcategory range in age from two to over 60 years.
The chronological age of the original buildings, however, does not
accurately reflect the degree of modernization of the production
facilities. In order to meet changing market demands and strong
competition, most mills have actively developed new production
techniques. As a result, it is difficult to differentiate between the
basic production operations at the various plants based on age, except
perhaps for the newest two or three mills.
Similarly, waste water characteristics from the corn wet mills cannot be
classified according to plant age. While several of the newer mills
generate low raw waste loads in terms of BOD5 and suspended solids, at
least one of the newer mills yields raw waste loads near the high end of
the spectrum. Conversely, several older mills have low raw waste leads.
The comparison of age versus raw waste load presented in Section V
clearly demonstrates the absence of any correlation based on plant age.
Accordingly, the age of the mill is not a direct factor in determining
the best practicable control technology currently available. Indirectly,
the age of the plant as it may be reflected in equipment layout may
90
-------
place some restraints on the ability of a particular plant to implement
seme recommended in-plant changes.
The size of the mill has a direct influence on the total amounts of
contaminants discharged. In general, the larger the plant the greater
the waste load. The effluent limitations presented herein have been
developed in terms of unit of raw material input, i.e., kg/kkg or
Ibs/MSBu, in crder to reflect the effect of plant size. The control
technologies discussed in Section VII, however, are applicable to all
mills regardless of size.
The basic processes employed in corn wet mills are essentially uniform
throughout this segment of the industry. From corn unloading through
basic starch separation, the production methods are quite standard
although slightly different types of equipment may be used at the
various mills.
!£2<3uct_Mix-
The product mix at a given plant varies significantly on a monthly,
weekly, and even daily basis. As a result, the raw waste
characteristics at the plant may vary widely. Certain highly modified
starches, for example, will result in higher waste loads per unit of raw
material. In spite of the recognized influence of product mix on the
raw waste characteristics of a given plant, no relationship between the
raw waste characteristics from all the mills and their product mix can
be distinguished based on available data, as previously discussed in
Section V.
Thus, while consideration was given to the variability of the raw waste
characteristics in developing the specified effluent limitations, this
variability could not be quantitatively defined in terms of product mix.
Moreover, there is no evidence to suggest that waste waters from any
specific process so affect the character of the total plant waste stream
as to substantially reduce the ability of the mill to implement the best
practical control technology currently available.
The engineering feasibility of achieving the effluent limitations using
the technology discussed has been examined. Each of the in-plant and
treatment control technologies presented are being used by one or more
corn wet mills, although not necessarily in combination. Furthermore,
each of these control steps effectively reduces the waste volume or the
total waste load, or improves the quality of the treated effluent.
Several of the control measures result in the isolation and resultant
concentration of the process wastes into a smaller volume suitable for
more economical treatment. Such practices have been in effect in a
number of mills for several years. Once-through barometric cooling
waters are of particular importance in this regard because they
91
-------
represent a high volume waste with low concentrations of pollutant
constituents.
In-plant housekeeping and good operation can have a major impact on the
raw waste leads from a mill. Diking of spill areas, monitoring, and
careful operation have been reported to reduce raw waste loads by 25 to
50 percent in some plants.
Treatment of corn wet milling wastes with activated sludge and ether
biological systems has been demonstrated at seven mills as detailed in
Section VII. Although treatment plant upsets do occur, a properly
designed and operated system should be able to meet the effluent
limitations developed in this document. At least one mill presently
meets these effluent limitations using an activated sludge system
followed by aerated lagoons. While this system includes one additional
treatment step, the plant does not presently recirculate all barometric
cooling water, a suggested control procedure.
The combination of in-plant controls and proper waste treatment
constitutes a practicable means for achieving the specific effluent
limitations. On an overall industry basis, these effluent limitations
will result in a BODJ5 reduction of approximately 85 to 90 percent and 85
percent reduction of suspended solids.
The concentrations of contaminants in the waste waters from plants using
once-through barometric cooling water are in the moderate strength
range, i.e., approximately 250 to 450 mg/1 of BOD5 and 100 to UOO mg/1
of suspended solids, as shown in Table 10. These wastes are generally
slightly stronger than normal domestic sewage, but the secondary
effluent limitations that have been established for municipal plants
should be achievable by the proper treatment of these wastes. In
establishing the effluent reduction attainable, as presented in Table
15, therefore, an effluent level of 30 mg/1 of both suspended solids and
EOD5 was selected for the plants using once-through contaminated cooling
water. The levels established in Table 15 are equivalent to estimated
effluent concentrations of 20 to 30 mg/1 for such plants.
Many plants isolate the major process water sources and use recirculated
cooling water systems. The effluent waste concentrations, therefore,
are much higher than for those plant using once-through contaminated
cooling waters. Raw wastes from these plants contain from 600 to U500
mg/1 of EOD5 and 300 to 2500 mg/1 of suspended solids. The best
practicable control technology currently available will effect
approximately an 85 to 90 percent reduction in BOD.5 and suspended solids
for these concentrated wastes. Effluent concentrations of 100 mg/1 of
BOD^ and 75 mg/1 of suspended solids are selected as general goals to be
achieved by the effluent limitation guidelines. The 30 mg/1 goal that
was applied to dilute corn wet milling wastes cannot be achieved by the
proposed technologies for these highly concentrated waste streams. The
effluent limitation guidelines proposed in Table 15 will result in
estimated effluent concentrations of 50 to 200 mg/1 of BODJ5 and 35 to
140 mg/1 of suspended solids. The higher values of these ranges are
92
-------
generally for new plants that practice maximum water recycling and
produce highly concentrated waste steams of 3000 mg/1 or higher.
Eased on present waste water volumes in the industry, therefore, the
average treated effluent resulting from these effluent limitations will
contain about 50 mg/1 of BOD. For those plants presently using once-
through barometric cooling water, the effluent quality based on the
present total waste water flow will be on the order of 20 to 30 mg/1 of
BOD. For those mills that utilize recirculating cooling water systems
and have concentrated raw waste streams, the effluent limitations vvill
require an effluent quality of approximately 100 mg/1 of BOD5 and 75
mg/1 of suspended solids.
The application of this control technology may require modifications to
certain process equipment, but the basic process will remain unchanged.
Some of the in-plant control measures have already been implemented at
some mills.
~Lr\ terms of the non-water quality environmental impact, the only item of
possible concern is the increased energy consumption to operate the
treatment plant. Relative to the production plant energy needs, this
added load is small and not of significant impact. For example, the
power requirements for the application of the best practicable control
technology currently available to a medium sized corn wet mill are
estimated to be U50 kilowatts (600 hp) . This demand represents a small
percentage of the mill's total power usage.
Corn prY_Milling
Cos t _o f _ A_g£l i cat ion -
The investment costs for implementing various control technologies were
presented in Section VII. These costs were estimated for a moderately
large corn dry mill to be $291,000.
Plant _Age ^ Size_and Product ion Methods^
The only source of process waste waters in corn dry mills is the washing
operation. Some mills do not wash the incoming corn, apparently
reflecting a cleaner raw material or, possibly, less stringent quality
control practices. Based on the limited data available, no correlation
can be established between the raw waste characteristics and such
factors as plant age, size, or production methods. Equally important,
these factors do not affect the ability to apply the control
technologies presented earlier in the section.
_gf _Ap_p_licati.on-
93
-------
Few, if any, corn dry mills provide extensive waste water treatment with
discharge directly to the receiving waters. The best practicable
control technology currently available does not represent practice
achieved by any corn dry mill. Rather, this technology reflects the
transfer of treatment practice demonstrated on other high strength food
processing wastes. Data from one pretreatment plant clearly show that
this type of waste water is amenable to biological treatment and
suspended solids removal. Accordingly, the treatment technology
recommended is considered to be quite practicable. The raw waste
characteristics for corn dry mills indicated a BOD5_ of 600 to 2700 mg/1
and a suspended solids level of 1000 to 3500 mg/1, as shown in Table 12.
The best practicable control technology currently available will provide
approximately 90 percent reduction of the strength of these wastes. An
effluent concentration of about 100 mg/1 for both BOD5_ and suspended
solids was considered a practical goal and was used in developing the
data given in Table 15. Estimated average effluent levels achievable,
using the proposed effluent limitation guidelines, are about 105 mg/1 of
BOD5 and 90 mg/1 of suspended solids. Based on limited data for
existing plants, the BOD^ is expected to be between 80 and 150 mg/1, and
suspended solids, between 70 and 115 mg/1. The treatment achieved
represents 90 to 95 percent removal of both BOD5_ and suspended solids,
Activated sludge or comparable biological treatment will achieve about
90 to 95 percent BODjS and suspended solids reductions. The final
effluent concentrations to be realized by applying the specified control
technologies will be about 100 mg/1 of BOD5 and suspended solids.
The non-water quality environmental impact is restricted to the
increased power consumption required for the treatment facility. This
power consumption is quite small compared to the total energy
requirements for a corn dry mill and, therefore, the impact of the
control facilities is considered insignificant.
Wheat Milling
The only process waste water in wheat milling arises from the tempering
operations used in bulgur flour production. No correlation can be
established between the raw waste characteristics or ability to apply
the specified control technologies and such factors as plant age or
size, production methods, and raw material quality. No bulgur mill is
known to provide waste water treatment at this time. The treatment
technology defined previously, however, represents practice in related
areas of food processing. Waste water from bulgur production should be
amenable tc solids separation and biological treatment. The waste
strength is somewhat higher than normal sanitary sewage, but well below
the high levels common in the other milling categories. As a result,
treatment to effluent levels of about 30 mg/1 of BOD5_ and suspended
solids is practicable and will be achieved by the effluent limitations
presented in Table 15. Approximately 90 percent BOD5 and suspended
solids reductions will result. The investment costs to provide the best
practicable control for a medium sized bulgur plant were estimated in
Section VIII to be $24,000.
94
-------
Non-water quality environmental impact will be restricted to a sirall
increase in power consumption for the treatment plant. These power
needs are irinimal and not of major significance.
Rice_M i JL1 i ng
Waste waters from the production of parboiled rice represent the only
source of process waste waters in rice milling. The characteristics of
this high-strength soluble BOD5 waste cannot be related to plant age or
size, production methods, or """raw material quality. Likewise, the
applicability of the specified control technologies is not dependent on
any of these factors.
At present, no rice mill in the country provides waste water treatment.
The best practicable control technology currently available, therefore,
represents the transfer of treatment practice from other food processing
industries. Pilot plant studies have demonstrated that the waste is
amenable to biological waste treatment. Raw wastes from parboiled rice
milling contain a high level of BOD, approximately 1,300 mg/1, as shown
in Table 14, but a low level of suspended solids. Treatment of these
wastes, using the best practicable control technology currently
available, will achieve about a 90 to 95 percent reduction of BOD. Once
again, an effluent BOD5 concentration of 100 mg/1 was selected as a
practical gcal. The suspended solids level that has been specified,
represents about 80 mg/1, almost all of which represent biological
solids produced in the activated sludge system. Thus, the effluent
suspended solids show no appreciable decrease, although their character
has changed through the biological treatment sequence. In essence, the
effluent suspended solids level is dictated by the type of treatment
technology applied as opposed to the influent suspended solids levels.
Estimated effluent BODE> levels for two plants are 80 to 130 mg/1 with
suspended solids levels of 50 to 75 mg/1. The effluent limitations
given in Table 15 will achieve about 90 to 95 percent BOD5_ reductions
and result in a treated waste water containing about 100 mg/1 of EODj>
and 80 mg/1 of suspended solids. As presented in Section VIII, the
investment cost to provide this level of control for a moderately large
plant will be about $313,000.
Non-water quality environmental impact will be restricted to a small
increase in power consumption to operate the treatment plant.
RESTRAINTS ON THE USE OF EFFLUENT LIMITATIONS GUIDELINES
The effluent limitation guidelines presented above can generally be
applied to all plants in each grain milling category. Special
circumstances in individual plants, however, may warrant careful
evaluation, especially in corn wet milling.
Corn wet mills are, by their very nature, sophisticated chemical plants
producing a variety of products. Raw waste characteristics are
dependent en many factors, not the least of which is product mix. It
must be emphasized that, even with the implementation of the in-plant
95
-------
controls detailed earlier in this section, some plants will not be able
to reduce their raw waste loads per unit of raw material input to the
same low levels achieved by other mills.
Isolating all major process waste streams in some of the older plants
may be very difficult and expensive. A similar situation may exist in
the case of sanitary sewers. The discharge of sanitary wastes to the
treatment plant will not adversely affect the treatment process, but it
will eliminate the possibility of using waste solids from the treatment
plant in feed preparations. Alternative solids disposal methods will
have to be selected in such cases.
Conversion of barometric condensers to surface condensers is suggested
as one means of concentrating waste streams, but such conversion is not
without seine problems. Specifically, surface condensers are more
expensive than barometric units and they require considerably more
maintenance. In some plants, existing equipment layouts prohibit.
conversion to surface condensers. Some mills have found that
recirculation of barometric cooling waters over cooling towers can be
readily accomplished and provide results that are comparable in terms of
pollutant constituent levels in the waste stream.
Finally, it must be recognized that the treatment of high strength
carbohydrate wastes is difficult. Upset conditions may occur that
result in higher BODJ5 and suspended solids discharges than normal.
While the in-plant modifications and controls and the treatment sequence
defined as best practicable control technology currently available will
minimize these upsets, they may still occur. However, the limitation
described above make adequate allowances for this possibility. The
maximum daily average is three times the maximum allowable 30-day
limitation for both BODJ5 and suspended solids. However, the limitations
described above make adequate allowances for this possibility. The
maximum daily average is three times the maximum allowable 30 day
limitations for both BOD5 and suspended solids.
-------
SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations that must be achieved July 1, 1983 are to
specify the degree of effluent reduction attainable through the
application of the best available technology economically achievable.
This control technology is not based upon an average of the best
performance within an industrial category, but is determined by
identifying the very best control and treatment technology employed by a
specific plant within the industrial category or subcategory, or readily
transferable from one industry process to another.
Consideration must also be given to:
a. The total cost of application of this control technology
in relation to the effluent reduction benefits to be
achieved from such application;
b. the size and age of equipment and facilities involved;
c. the processes employed;
d. the engineering aspects of the application of this control
technology;
e. process changes; and
f. non-water quality environmental impact (including energy
requirements).
Best available technology economically achievable also considers the
availability of in-process controls as well as end-of-process control
and additional treatment techniques. This control technology is the
highest degree that has been achieved or has been demonstrated to be
capable of being designed for plant scale operation up to and including
"no discharge" of pollutants.
Although economic factors are considered in this development, the ccsts
for this level of control are intended to be the top-of-the- line of
current technology subject to limitations imposed by economic and
engineering feasibility. However, this control technology may be
characterized by some technical risk with respect to performance and
with respect to certainty of costs. Therefore, this control technology
may necessitate some industrially sponsored development work prior to
its application.
EFFLUENT PEDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST
AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
Based on the information contained in Sections III through VIII of this
document, it has been determined that the effluent reductions attainable
through the application of the best available technology economically
97
-------
achievable are those presented in Table 16. These values represent the
maximum average allowable loading for any 30 consecutive calendar days.
Excursions above these levels should be permitted with a maximum daily
average of 3.0 times the average 30-day values listed below.
Table 16
Effluent Reduction Attainable Through the Application of
Best Available Technology Economically Achievable
Industry
BOD5
Suspended Solids
pH
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Eulgur wheat flour
milling
Normal rice milling
Parboiled rice milling
0.357
0.0357
20
2.0
0.179
0.0179
10
1.0
6-9
6-9
No discharge of process waste waters
0.0050 0.3 0.0033 0.2 6-9
No discharge of process waste waters
0.070 0.007 0.030 0.003 6-9
*Maximum average of daily values for any period of 30 consecutive days
IDENTIFICATION OF BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
For all of the segments of the grain milling industry, the best
available technology economically achievable comprises improved solids
separation following activated sludge or comparable biological
treatment. Improved solids separation can be represented best by deep
bed filtration although alternative systems may be available. It is
anticipated that the technology of removing biological solids by
filtration will improve rapidly with the increased use of such treatment
processes in many industries and municipalities.
In the corn wet milling subcategory, a combination of end-of-process
treatment, as described above, and in-plant controls will be necessary
to meet these effluent limitations. All of the in-plant controls
presented in section IX will have to be implemented, and additional
controls instituted as follows:
1. Isolate and treat all process waste waters. No process
wastes should be discharged without treatment.
2. Institute maximum water reuse at all plants over and
above the current levels of practice.
3. Provide improved solids recovery at individual waste
sources.
98
-------
RATIONALE FOE THE SELECTION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE
Corn_Wet_Milling
Cost_gf_A2Elicatign-
As presented in Section VIII, the investment cost for providing the test
available technology economically achievable for a treatment plant
serving a hypothetical medium-sized corn wet mill is $2,832,000. This
cost is exclusive of any expenditures for in-plant controls. Detailed
information en operating, maintenance, power, and other costs is
contained in Section VIII.
AgeJL_Sizex_and_Ty-p_e_of_Productign^Facilities-
As discussed in Section IX, differences in age or size of production
facilities in the wet corn milling subcategory will not significantly
affect the application of the best available technology economically
achievable. Likewise, the production methods employed by the different
mills are similar and will not influence the applicability of this same
technology.
Engineerin3_AS£ects_of_A2£lication-
The control technologies specified herein have not been fully demon-
strated in any segment of the grain milling industry. The tasic
treatment processes, however, namely activated sludge and deep bed
filtration, have been used in industrial and municipal applications in
recent years to provide a high quality effluent. One corn wet milling
company is currently installing such a system. This treatment plant
should demonstrate the applicability of this level of technology to
grain milling wastes.
In developing the effluent limitation guidelines attainable using the
best available technology economically achievable, it was concluded that
end-of-process treatment could effect an additional EOD5_ and suspended
solids removal of 50 to 70 percent, compared to the levels achieved by
the best practicable control technology currently available. Deep bed
filtration will remove most of the remaining suspended solids following
secondary clarification. In so doing, experience has shown that over 50
percent of the remaining BOD is normally associated with these suspended
solids and is therefore removed.
For the dilute waste waters from plants using once-through contact
cooling water, effluent concentrations of 10 mg/1 of BOD5_ and suspended
solids should be achieved. For those plants using recirculated cooling
water, effluent concentrations of from 30 to 50 mg/1 can be accomplished
by application of this level of treatment.
It is recognized that the soluble BOD5 level in seme of the plants that
generate concentrated waste streams may not permit attainment of BOD5
99
-------
levels represented by the values in Table 16, using only end-of-prccess
treatment. It is expected that the in-plant control measures that have
been recorrmended will reduce the net raw waste loads sufficiently to
permit attaining the effluent limitations as proposed. Each of the in-
plant control measures is practiced by one or more plants, although not
necessarily at the same plant. Thus, the in-plant control technology is
available, although its application may be restricted in certain mills.
In summary, the combined effect of the application of the best available
technology economically achievable and application of all practicable
in-plant control measures should permit the corn wet mills to meet the
effluent levels presented in Table 16.
Process^Changes-
No basic process changes will be necessary to implement these control
technologies. In fact, many of the in-plant modifications have already
teen made by some corn wet mills.
Non-Wat er_2u§ lit y__Environment al_ As p_ects-
The application of the best available technology economically achievable
will not create any new sources of air or land pollution, or require
significantly more energy than the best practicable control technology
currently available. Power needs for this level of treatment technology
were estimated to be about 225 kw (625 hp) for the model plant developed
in Section VIII. This demand is small when compared to the total
production plant power requirements.
Corn_Dry^Milling
The cost cf applying the best available technology economically achiev-
able, defined above to a moderately large mill, has been estimated in
Section VIII to be $323,000. Data on operating, maintenance, and power
costs are presented in Section VIII.
The application of this control technology is not dependent upon the
size or age of mill. As discussed under corn wet mills, the treatment
technology has not been demonstrated in the grain milling industry, but
is transferable from other waste treatment applications. Power
requirements for the prescribed treatment system are small compared to
the overall production demands. Other environmental considerations will
not be affected by the application of this control technology.
Vyheat,, Milling (Bulgur^
The best available technology economically achievable can be applied to
a medium-sized bulgur mill for an investment cost of about $93,000.
Other cost information is contained in Section VIII.
Plant size and age and other production factors will not influence the
applicability of the suggested control technology. Experience in other
100
-------
waste treatment applications amply demonstrate the technical feasibility
of the control system. Energy, air pollution, noise, and other
environmental considerations have been evaluated and will not be
significantly affected by the application of this technology.
Fice_Milling (Parboiled_Rice^
Application of the specified best available control technology eco-
nomically achievable to a medium-sized parboiled rice plant is estimated
to cost $347,000. Section VIII contains additional information on
operating, maintenance, and energy costs.
Once again, the prescribed control technology has been demonstrated in
related waste treatment applications. Energy needs are small compared
to the production power demands. Other environmental factors such as
noise and air pollution will be little affected by the application of
this control technology.
101
-------
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
INTRODUCTION
Standards of performance are presented in this section for new sources.
The term "new source" is defined to mean "any source, the construction
of which is commenced after the publication of the proposed regulations
prescribing a standard of performance." These standards of performance
are to reflect higher levels of pollution control that may be available
through the application of improved production processes and/or
treatment techniques.
Consideration should be given to the following factors:
a. The type of process employed and process changes;
b. operating methods and in-plant controls;
c. batch as opposed to continuous operations;
d. use of alternative raw materials;
e. use cf dry rather than wet processes; and
f. recovery of pollutant as by-products.
The new source performance standards represent the best in-plant and
end-of-process control technology coupled with the use of new and/or
improved production processes. In the development of these performance
standards, consideration must be given to the practicability of a
standard permitting "nc discharge" of pollutants.
NEW SOURCE PERFORMANCE STANDARDS
The performance standards for new sources in the grain milling industry
are identical to the effluent limitations prescribed as attainable
through the application of the best available technology economically
achievable as presented in Section X. These new source performance
standards are given in Table 17.
These values represent the rraximum average allowable loading for any 30
consecutive calendar days. Excursions above these levels should be
permitted with a maximum daily average of 3.0 times the average 30-day
values listed below.
At the present time, a "no discharge" standard is not deemed
practicable. It is anticipated that continued advancement in end-of-
process treatment methods and in-plant control measures will result in
future revisions in the new source performance standards.
103
-------
Industry
Table 17
New Source Performance Standards*
BOD^ Suspended Solids pH
Corn wet irilling
0.357
20
0.179
10
6-9
0.0357 2.0 0.0179 1.0 6-9
No discharge of process waste waters
Corn dry irilling
Normal wheat flour
milling
Eulgur wheat flour
milling 0.0050 0.3 0.0033 0.2 6-9
Normal rice milling No discharge of process waste waters
Parboiled rice milling 0.070 0.007 0.030 0.003 6-9
*Maximum average of daily values for any period of 30 consecutive days
RATIONALE FOR THE SELECTION OF NEW SOURCE PERFORMANCE STANDARDS
C g r n_Wet_Mi11i ng
The specific control technologies to meet the new source performance
standards are not presented in this document. It has been a basic
premise, however, that all of the in-plant controls discussed in Section
VII would be incorporated in a new mill. In addition, the end-of-
process treatment system is to be equivalent to that suggested for the
best control technology economically achievable. Recognizing that this
level of waste water treatment has not been demonstrated in the grain
milling industry, it is nonetheless felt that the combined effect of
complete in-plant controls and the new treatment technology will meet
the new scurce performance standards. Factors considered in developing
these standards are summarized in the following paragraphs.
££°3uctign_Prccess-
The basic production process used in corn wet milling cannot be
significantly altered. The industry has historically been very
aggressive in developing and utilizing new production technology. While
new plants will undoubtedly incorporate some new or improved types of
equipment, the basic process will remain largely in its present form for
the foreseeable future.
Ogerating_Methgds^and_ln-Plant_Cgntrols-
New plants offer the possibility of instituting better operating methods
and in-plant controls. Without the physical constraints of existing
facilities, essentially all of the in-plant controls discussed in
Section VII can be implemented. Instrumentation is also available to
improve plant operation and reduce accidental waste discharges. Greatly
reduced waste loads should be attainable by these and other in-plant
improvements.
104
-------
The control technology recommended to achieve new source performance
standards is equivalent to that represented by the best available
technology economically achievalble, namely an activated sludge system
followed by deep bed filtration. Inasmuch as this type of treatment has
not been specifically applied to corn wet milling wastes, initial
operating experience with such systems may not fully meet the expected
50 to 75 percent BODj> and suspended solids removals form the secondary
clarifier effluent. The application of complete in-plant controls and
the use of good operating methods in new plants should significantly
reduce the raw waste loads from these facilities. Accordingly, the
effluent reductions specified by the proposed new source performance
standards should be achievable for all new plants. As experience is
gained with the end-of-process treatment, particularly the removal of
suspended materials by filtration, it may be possible to reduce the new
scurce performance standards, as given in Table 17. At the present
time, however, these standards represent the best engineering judgment
of those levels that would be achievable for new sources.
Changes^ in^Unit Qperations-
As stated above, the basic corn wet milling process is likely to remain
unchanged for the immediate future. Minor modifications in unit
operations are continually being made in this industry subcategory, but
no additional improvements that would have a major impact on the waste
water discharges have been developed.
Ev-Prpduct_gecoyerY-
Ey-product recovery has long been practiced in corn wet mills.
Application of the best in-plant controls will undoubtedly increase by-
product recovery, but will probably offer no new recovery avenues.
Corn Dry Milling
The new scurce standards for corn dry mills are based on the application
of the best available technology economically achievable as represented
by a high level of end" of -process treatment. Corn washing, the one
source of process waste waters, is considered to be essential by many
mills. Although some mills only dry clean the corn, many ether
companies believe that washing is necessary to control microbiological
contamination and product quality. Depending on raw material quality
and technical food product considerations, it is expected that most new
mills will require corn washing.
Barring a total changeover to dry cleaning methods, little can be
accomplished in reducing total plant waste loads. In-plant controls and
operating methods may reduce total flows, but will not appreciably
affect the total quantities of contaminants.
105
-------
Mi 1 1 i ng__(Bu Igur )
The effluent levels to be achieved under the new source performance
standards for bulgur production also reflect the application of the best
available end-of-process technology as described in Section X. The
basic production process requires water for soaking (or cooking) and
this single source of process waste water cannot be eliminated.
Operating methods, in-plant controls, and by-product recovery will not
influence process waste loads except perhaps in terms of quantity of
waste water. Some by-product recovery, i.e., the use of biological
treatment solids in animal feeds, may result from the application of the
prescribed treatment technology.
Process waste waters in parboiled rice production originate from the
steeping operation. This unit operation is integral to the basic
parboiling process and cannot be eliminated or changed significantly.
Likewise, in-plant controls and operating methods can reduce the total
waste water flow in some instances, but not the total amount of pollu-
tants. The new source standards of performance, therefore, provide for
the application of the best available technology economically achievablp
as described in Section X. Recovery of biological sclids from the
treatment system for use in animal feed is envisioned.
106
-------
SECTION XII
ACKNOWLEDGMENTS
The Environmental Protection Agency whishes to acknowledge the
contributions to this project by Sverdrup G Parcel and Associates, Inc.,
St. Louis, Missouri. The work at Sverdrup & Parcel was performed under
the direction of Dr. H.G. Schwartz, Jr., Project Manager , and assisted
by Jesse Nachowiak and Bavid Schenck.
Appreciation is extended to the many people in the grain milling
industry who cooperated in providing information for this study.
Special mention is given to company representatives who were
particularly helpful in this effort:
Mr. William Graham of the American Maize-Products Company;
Mr. Arthur DeGrand of the Anheuser-Busch, Inc. Company;
Mr. W. B. Holmes of Burrus Mills Division, Cargill, Inc.;
Mr. Leonard Lewis and Mr. Howard Anderson of the Clinton Corn
Processing Company;
Mr. E. J. Samuelson and Mr. William Von Minden of Comet Rice
Company;
Mr. D. R. Erown, Mr. R. C. Brandquist, Mr. F. W. Velguth, and
Mr. G. R. C. Williams of CPC International Inc;
Mr. Donald Thimsen of General Mills;
Mr. E. M. Eubanks, Mr. R. Koll, and Mr. G. C. Holltorf of the
Grain Processing Corporation;
Mr. H. Kurrelmeier of Illinois Cereal Mills, Inc.;
Mr. D. Smith of Lauhoff Grain Company;
Mr. V. Gray of P£S Rice Mills, Inc.;
Mr. Tom Mole of Quaker Oats Company;
Mr. William Hagenbach, Mr. Robert Popma, Mr. Joe Wasilewski, and
Mr. John F. Hcman of the A. E. Staley Manufacturing Company;
and Mr. W. J. Staton and Mr. W. H. Ferguson of Uncle Ben's Rice Company.
Acknowledgement is also given to the following trade associations who
were helpful in soliciting the cooperation of their member companies:
American Corn Millers Federation, Corn Refiners Assoc., Inc.; Millers
National Federation; National Soft Wheat Millers Assoc.; Protein Cereal
Products Institute; and the Rice Millers Assoc.
Appreciation is expressed to those in the Environmental Protection
Agency who assisted in the performance of this project: John Riley,
George Webster, Pearl Smith, Acquanetta McNeal, Frances Hansborough,
Patricia Dugan, Max Cochrane, Linda Huff, Arlein Wicks, Reinhold Thieme,
Taylor Miller, Kenneth Dostel and Gilbert Jackson.
107
-------
SECTION XIII
REFERENCES
1. Sensing, H. O. and Brown, D. R., "Process Design for Treatment.
of Corn Wet Milling Wastes," P£Oceedings_Third_Nat ional
SYm£Osium_of_Food_Prccessin2_Wastes, New Orleans, Louisiana,
March 28-30, 1972.
2. Sensing, H. O. , Brown, D. R. , and Watson, S. A., "Waste Utili-
zation and Pollution Control in Wet Milling," American
^SSOciati.on_of_Cereal_Chernists, Dallas, Texas, October
13, 1971.
3. "CRA 1973 Corn Annual," Corn_Ref iners_Assgciationx_Inc^x
Washington, D. C.f 1973.
H. Church, B. D. , Erickson, E. E. , and Widmer, C. M. , "Fungal
Digestion of Food Processing Wastes," Food_TechnologYr
36, February, 1973.
5. Church, B. D. , Erickson, E. E. , and Widmer, C. M., "Fungal
Digestion cf Food Processing Wastes at a Pilot Level,"
Seventy^ second National Meeting, American_institute_of
Chemicjal^Engineers^ St. Louis, Missouri, May 21-24, 1972.
6 • Q2D§2li^ted_Fe ed_Tra de_Manua l_and_Gr a in_Mi ]. 1 i ng__Ca t al og ,
National Provisioner, Inc., Chicago, Illinois, 1964.
7- Crog_ProductignA_]:972_Annual_SurnmarY» Crop Reporting Board,
Statistical Reporting Service, U.S. Department of
Agriculture, Washington, D. C. , January 15, 1973.
8- Current_Industr i al_Repor t s , Flour Milling Products, Bureau
of the Census, U.S. Department of commerce, February,
1973.
9 . Fl our _M i 1 ling_Pr o due t s_- _Cur r ent_Indus tr i a l_Regort s , U.S.
Department of Commerce, Bureau of the Census, Industry
Division, Washington, D. C. , February, 1973.
10. Gehrig, Eugene J. , "Mounting Tide of 'Bulgur1 Pacific Wheat
Specialty Rolls Out from Seattle Mill," Anieri.can_Mil_ler
December, 1962.
11. Inglett, G. E. , Corn_^ __ CultureJL_Processi.ngx_Products, AVI
Publishing Company, Inc., Westport, Connecticut, 1970.
12, Matz, Samuel A., Cereal_Technolggy, AVI Publishing Company,
Inc., Westport, Connecticut, 1970.
13. "New Wheat Processing Plant in Hutchinson Set for Export
109
-------
Trade," Amer_ican_Mi^ ler _and_Proc e s sor , January, 1963.
C ensus_of _Manuf actur er sx_Gr ain_Mi ll_Pr oduc t s , U.S.
Department of Commerce, Bureau of the Census, August,
1970.
15. Parolak, G. M. , "Field Evaluation of Aerated Lagoon Pre-
Treatment of Corn Processing Wastes," Mi_Si_Thes i s ,
Purdue University, December, 1972.
16. Patent_J2x8^Ux327A_Method_of_Processin3_Wheat, D. H. Robbiris,
Fisher Flouring MillsT"
17. Polikoff, A. and Comey, D. D. , "American Maize-Products
Company - Preliminary Report", Businessmen_f or _ the
iHt§£§Si » Chicago, Illinois, May, 1972.
18 . PAiPOductsandChemica]. sPilot
liant_Studiesx Stanley Consultants, June 19, 1972.
19. "Report on Industrial Water and Waste Program, Phase I -
Water and Waste Inventory for Grain Processing Corpora-
tion, Muscatine, Iowa," Stanley Consultants, 1968.
20. Seyfried, C. F. , "Purification of Starch Industry Waste Water,"
Proceedings of the__ 2 3rd_IndustrialWaste_Cgnference,
Purdue University, Lafayette, Indiana, May 7-9, 1968.
21. Smith Robert, Cost_of_Conventional_and_Advanced_Treatment_of
Wa^st §_Wat er s , Federal Water Pollution Control Administration,
U.S. Department of the Interior, 1968.
22. Smith, Robert and McMichael, Walter F. , Cgst_and_Performance
Federal Water Pollution Control Administration, U.s
Department of the Interior, 1969.
23. "United States Statistical Summaries," The^Northwestern
MjJ.ler, Volume 278, No. 9, Minneapolis, MinnesotaV
September, 1971.
24. West, A. W., "Report on April 19, 1972 Investigation of the
Wet Corn Milling Waste Treatment Plant, CPC International,
Inc., Pekin, Illinois," Enyirpnmental Protect ion_ Agency,
Cincinnati, Ohio, May, 1972.
25. Willenbrink, R. V., "Waste Control and Treatment by a Corn and
Soybean Processor," Proceedings_of_the_222d_Industrial
^§_§t e_Conf er ence , Purdue University, 517, 1967.
26. Witte, George C. , Jr., "Rice Milling in the United States,"
Bulletin - AssQgiat ion of Operative Millers , 3147-3159,
February, 1970.
110
-------
27. World_Rice_Cro2_Continues_Decline, U.S. Department of Agri-
culture,Foreign Agriculture""circular FRI-73, Washington,
B. C., February, 1973. •
111
-------
SECTION XIV
GLOSSARY
1 • £ sgi. rator s
Milling machine equipment that separates loosened hulls froir
the grain.
The pericarp or outer cuticle layers and germ of the rice
grain.
3 « Eran^_Wheat
The several-layered covering beneath the wheat husk that
protects the kernel.
U . Erown_Rice
Rice from which the hull only has been removed, still retain-
ing the bran layers and most of the germ. (Rice Millers
Association, 1967.)
5 . Eulgur
Wheat which has been parboiled, dried and partially debranned
for later use in either cracked or whole grain form. (Wheat
Flour Institute, 1965.)
6 • Coyn Starch
Substance obtained from corn endosperm and remaining after
the removal of the gluten.
7 . Ccrn Syrup
Produced by partial hydrolysis of the corn starch slurry
through the aid of cooking, acidification and/or enzymes.
8 • Dextrose
Corn sweetener created by completely hydrolyzing the corn starch
slurry through the aid of cooking, acidifying and enzyme action.
The starchy part of the grain kernel.
10. Germ
The young embryo common to grain kernels (e.g., corn, wheat).
113
-------
11. Gluten
High protein substance found in the endosperm of corn and
wheat grain.
12. Hulls
The outer covering of the corn and rice kernel. The rice
hull is normally called the lemma.
13 . Midd lings
Fractured wheat kernels resulting from the milling operations.
14. Modified_Starch
A form of corn starch whose characteristics are developed by
chemically treating raw starch slurry under controlled conditions,
1 5 . Farboiled_Rice
Fice which has been treated prior to milling by a technical
process that gelantinizes the starches in the grain. , (Rice
Millers Association, 1967) .
16. Fear_l§r;§ (Whitener, Huller)
Pice milling machine equipment employed to remove the coarse
outer layer of bran from the germ.
1 7 .
The aleurone or inner cuticle layers of the rice kernel, con-
taining only such amounts of the outer layers and of the
starchy kernel as are unavoidable in the milling operation.
18. Steepwater
The water in which wet-miller corn is soaked before preparation.
114
-------
CONVERSION TABLE
Multiply (English Units) by_
ENGLISH UNIT CONVERSION
cubic feet 0.028
degree Fahrenheit 0.555(5
feet 0.30U8
gallon 3.785
gallon 0.003785
gallon/minute 0.0631
horsepower 0.7^57
million gallons/day 3,785
pounds 0.^5^
pounds/hundred weight (cwt) 10.0
standard bushel, corn 25-^
(56 Ibs) (SBu)
standard bushel, wheat 27.2
(60 Ibs) (SBu)
To Obtain (Metric Units)
METRIC UNIT
cubic meters
degree Centigrade
meters
liters
cubic meter
liters/second
kilowatts
cubic meters/day
kilograms
kilograms/metric ton
kilograms
kilograms
115
-------
>:-.-.t'-»?tii.n Agency
-
- -ive
cia 60606.
------- |