EPA-440/l-74-028-a
Development Document for Effluent Limitations Guidelines
and New Source Performance Standards for the
GRAIN PROCESSING
Segment of the
Grain Mills
Point Source Category
MARCH 1974
^
f fr^S^ S U-S- ENVIRONMENTAL PROTECTION AGENCY
\ VM/^ " WasMngton, D.C. 20460
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DEVELOPMENT DOCUMENT
i for
EFFLUENT ^LIMITATIONS GUIDELINES
' • and
NEW SOURCE PERFORMANCE STANDARDS
I
i for the
t __._ ' ' •
i . . •
GRAIN PROCESSING SEGMENT OF THE
GRAIN MILLS POINT SOURCE CATEGORY
Russell Train
Administrator
iRoger Strelow
Acting Assistant Administrator for Air and Water Programs
Allen Cywin
Director, Effluent Guidelines Division
i • . • •
Robert J. Carton
Project Officer
March 197a
Effluent: Guidelines Division ,
Office of |Air and Water Programs
U. S. Environmental Protection Agency
Washington, D. C. 20460
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ABSTRACT
This document presents the findings of an extensive study of the
grain milling industry by, the Environmental Protection Agency for
the purpose of developing effluent limitations guidelines.
Federal standards of performance, and pretreatment standards for
the industry, to. implement Sections 304, 306, and 307 of the
"Act."
Effluent limitations guidelines contained in this document set
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 available technology economically
achievable which must be achieved by 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 the application
of the best available demonstrated control technology, processes,
operating methods, or other alternatives.
'!
Separate effluent limitations guidelines are described for the
following subcategoriesi of the grain milling point source
category; corn wet milling, corn dry milling, normal wheat flour
milling, bulgur wheat flour milling, normal rice milling, and
parboiled rice processing. Treatment technologies- are
recommended for the four subcategories with 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 $2,544,000. An additional $288,000 will be
necessary to install the. solids removal techniques to meet the
1983 standards. The . economic impact of the 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, i
ill
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TABLE OF CONTENTS
SECTION • I
I conclusions t 1
II Recommendations \ 3
III Introduction I 5
Purpose and Authority 5
Summary of Methods 6
Source of Data 7
General Description of Industry 13
Production Processes 22
Waste Water Considerations 34
I
IV Industry Categorization . 37
i • • •
Factors considered 37
I -
V * Water Use and Waste water Characterization 41
Introduction ' 41
Corn Wet Milling 42
Corn Dry Milling 61
Wheat Milling 63
Rice Milling 64
!
VI Selection of Pollutant Parameters 67
1 V
Major Control Parameters 67
Additional Parameters 70
; I
VII Control and Treatment Technology 77
Introduction 77
Corn Wet Milling 77
Corn Dry Milling 88
Wheat Milling 89
Rice Milling - 90
VIII Cost, Energy, and Non-Water Qaulity Aspects 91
' \ ' ' • ' .
. Representative Plants 91
Terminology, 91
Cost Information 92
Non-Water Quality Aspects 104
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r
Section
IX
x
XI
XII
XIII
XIV
Effluent Reduction Attainable Through the Ap-
plication of the Best Practicable control
Technology Currently Available - Effluent
Limitations Guidelines
Introduction ',_,•,_' u 4-v,«
: Effluent Reduction Attainable Through the
Application of Best Practicable Control
Technology Currently Available
Identification of Best Practicable control
Technology Currently Available
Rationale for the Selection of Best
Practicable Control Technology Currently
' Restraints on the Use of Effluent Limitations
Guidelines
>, '
Effluent Reduction Attainable Through the Ap-
plication of the Best Available Technology
Economically Achievable - Effluent Limita-
tions Guidelines
: Introduction ' .
Effluent Reduction Attainable Through the
Application of the Best Available Tech-
nology Economically Achievable
Identification of Best Available Technology
Economically Achievable
Rationale for the Selection of the Best
Available Technology Economically
Achievable
New source performance Standards
Introduction
New Source Performance Standards
Rationale for the selection of New Source
Performance Standards
f I ^ •'.,.'•-":. ',,
Acknowledgments
References j
Glossary (
i . •' .
Conversion Table
107
107
107
108
110
116
119
119
119
120
121
125
125
125
126
129
131
135
137
vi
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; FIGURES
NUMBER i •• . ! Page
1 The corn Wet Milling Process , 23
i - ' - •
2 The Corn Dry Milling Process 26
3 The Wheat Milling Process 28
U The Bulgur Process 30
5 The Rice Milling Process 32
6 The Parboiled Rice Process 33
7 Basic Milling Operations in a Typical
Corn wet Mill I 43
8 Finished Starch'i Production in a Typical
Corn Wet Mill? 44
9 Syrup Production in a Typical
Corn, Wet Mill. 45
10 Effect of Wet Corn Milling Plant Age on
Average BOD5 Discharged . 54
11 Quantity of Waste Water Discharged by
Corn Wet Milling Plants 56
12 Average BOD5 Discharged as a Function of
Corn wet Mill Capacity 57
13 Average Suspended Solids Discharged as a
Function of Corn Wet Mill Capacity 58
14 Average BOD5 Discharged as a Function of
Waste Water Volume 59
15 Average Suspended Solids as a Function of
Waste Water Volume 60
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! TABLES
NUMBER , ,j ...."'."'. Page
1 Uses of Corn Grown in the United States 13
. 2. - Composition by Dry-Weight of'.Yellow" bent Corn. , '14
.. 3 Corn Wet Milling, Companies and Plants, .''" , . ... ;1;5
A , 4, • Bulgur Mills,:,- Locations and 'Estimated capacities, , 19
5 Parboiled Rice Milling Companies 21
6 First and Second Effect Steepwater Condensate
Waste Water Characteristics . ... . 47
7 Finished Starch Production, Waste Water.
Characteristic's '•"'.-. : , . ./" . 48
8 Individual Process Waste-Loads/ Corn .Wet: Milling 49
9 Corn Syrup Cooling, Waste Water Characteristics 50
10 Total Plant Raw :Waste Water Characteristics,
Corn Wet Milling .51
. 11 Waste Water Characteristics Per Unit of Raw
Material, Corn Wet Milling v 53
I
12 Waste Water Characteristics, corn Dry Milling 62
13 Waste Water Characteristics, Bulgur Production 63
1H Waste Water Characteristics, Parboiled Rice
Milling Processing 64
15 Water Effluent Treatment Costs, corn Wet Milling 94
16 Water Effluent Treatment Costs, Dry Corn Milling 98
17 Water Effluent Treatment Costs, Wheat (Bulgar) Milling 100
18 Water Effluent" Treatment Costs, Rice Milling 102
19 Effluent Deduction Attainable Through the Appli-
cation of Best Practicable Control Technology
Currently Available 108
20 Effluent Reduction Attainable Through the
Application of Best Available Technology
Economically Achievable 120
21 New Source Performance Standards 126
V111
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I . SECTION I
j CONCLUSIONS
The segment of -the grain milling industry that is covered in this
document (Phase I) has been classified into six subcategories.
This categorization is based on the type of 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 basis for additional
subcategorization. ;
i '
The subcategories of the grain milling industry are as follows:
1. Corn wet milling
2. Corn dry milling
3, Normal wheat flour milling
4. Bulgur wheat flour milling
5. Normal rice milling
6. Parboiled rice' processing
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SECTION II
; RECOMMENDATIONS
i
The recommended effluent limitations for the waste water
parameters of significance are summarized below for the
subcategories of the grain 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:
BOD Suspended Solids pH
kg/kkg Ibs/MSBu kcr/kkg Ibg/MSBu
Corn wet milling 0.893 50.0 0.893
Corn dry milling 0.071 4.0 0.062
Normal wheat flour j
milling . ;
Bulgur wheat flour '.
milling 0.0T083
Normal rice milling
Parboiled rice
milling 0.140 0.014 0.080
50.0
3.5
no discharge of .process wastes
0.5 0.0083 0.5
no discharge of process wastes
6-9
6-9
6-9
0.008 6-9
Using the best available control technology economically
achievable'the effluent limitations are:
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Bulgur wheat flour
milling
Normal rice milling
Parboiled rice
milling
0
0
BOD
357
0357
0.0050
0.070
Ibs/MSBu
20.0
2.0
Suspended^ Solids
Ibs/MSBu
10.0
1.0
0.179
0.0179
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.
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~™ v ; SECTION III
I INTRODUCTION
. -i • •.
^ • f
PURPOSE AND AUTHORITY | ,
Section 301 (b) of the Act requires the achievement by not later
than July I, 1977, of effluent limitations for point sources,
other than publicly owned; treatment works, which are based on the
application of the best practicable control technology currently
available as defined bjy the Administrator pursuant to Section
304 (b) of the Act, S.ectioh 301 (b), also, requires the
achievement by not later than July 1, 1983, of effluent
limitations for point sources, other than publicly owned
! 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 the discharge of all pollutants, as determined in
accordance with regulations issued by the Administrator pursuant
to Section 304(b) 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 refleqts the greatest degree of effluent
reduction which the Administrator determines to be achievable
through the application of the best available demonstrated
control technology, processes, operating methods, or other
alternatives, including, where practicable, a standard permitting
no discharge of pollutants. . v"
Section 304
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category, which was includedd within the list published January
SUMMARY OF METHODS USED FOR DEVELOPMENT OF THE EFFLUENT
LIMITATIONS GUIDELINES AND STANDARDS OF PERFORMANCE
The effluent limitations guidelines and standards of performance
proposed 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 subcategorization 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 a/11 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. >
. " » .1 . . _. '
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 inplant 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 the chemical, physical, and
biological characteristics of pollutants, of the effluent level
resulting from the application of each of' the treatment and
control technologies. The problems, limitations and reliability
of each treatment and i 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 techriologies 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.
c /~ ,
. • ••: ! . '
The information, as outlined above, was then evaluated in order-
to determine what levels , of technology constituted the "besi
practicable control ,technology currently available," "best
available technology economically achievable" and the "best
available demonstrated jcontrol 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
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employed, the engineering
•types of control techniques
environmental impact (including
factors.
aspects of the application of various
process changes, nonwater quality
energy requirements,) and other
SOURCES OF DATA
The data for identification and analyses were derived from 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 other grain millers, information contained in
Corps of Engineers discharge permit applications, and on-site
visits, interviews, and sampling programs at selected grain
milling facilities throughout the United States. A more detailed
explanation of the data sources is given below. All 'references
used in developing the guide lines for effluent limitations and
standards of performance for new sources reported herein are
included in Section xiir'of this document.
_ i
During this study the trade associations connected with the grain
milling subcategories 'covered by this study were contacted.
These associations are listed below:
Mi 1 ling subcategory
Wet Corn
Dry Corn
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 on the following pages.
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 fand 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. I
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EPA EFFLUENT LIMITATIONS GUIDELINE STUDY
OF THE GRAIN MILLING INDUSTRY
' :. , by •_ . '
Sverdrup| & Parcel and Associates, Inc.
Information Retrieval Guide
; February, 1973
I ; GENERAL |
A. Company name
i . -- _ ' v . -"''-..' . • ,
B. Corporate address
* • •- --1."' - • • •. •• • -
C. Corporate Contact
D. Address of plant reporting
; " ff " .
E. Plant contact
II ;MANUFACTURING PROCESS CHARACTERIZATION (Separate sheet for
each process, i:e., corn wet milling, wheat milling, etc.)
A. Manufacturing process pertinent to this study
.B. Other processes at this plant
C. Products :
D. Plant capacity
1. Annual raw material processed
2. Average daily raw material processed
• f • • : • •. r -,
E. Operating schedule (hours/day and days/year)
i '
F. Number of employees
.6. Age of plant
III WATER REQUIREMENTS
A. Volume and Sources
8
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IV
B. Uses (including volumes)
1. Process j
2. Grain washing
3. Cooling
4. Boilers ;
5. Plant cleanup
6. Sanitary ,
7. Other
C. Ava-iTable information on raw water quality
D. Water treatment provided * '
1. Volume treated
2. Describe treatment system and operation
3. Type and quantity of chemicals used
E. Available information on treated water quality
PROCESS WASTEWATER
A. Volumes and spurces
B. Does the source, volume, or character of the wastewater
vary depending on the type or quality of product?
C. How do wastewater characteristics change during start-up
and shutdown as compared to normal operation?
D. Available data on characteristics of untreated waste-
Waters from individual sources and combined plant
effluent. (Not just single average numbers, but actual
data on weekly or monthly summaries).
1. pH
2. BOD I :; "
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3. COD
4. Suspended solids
5. Dissolved solids
. 6. Total solids
7. Temperature
8. Alkalinity and acidity
H| '
9. Phosphjorus
i- • ! '•••..'•
K I 10. Chlorides
:'" - • '
}; . 11. Sul fates
{;- 12. Oil and grease
1} 13. Other '(all available information should be collected)
ji , , " i
I: E. Wastewater treatment
b •"
f. • 1. Identify wastewater sources and volumes going'to
4 treatment facility
;. 2. Reason! for treatment
j 3. Describe treatment system and operation
!' ' ' ' ' ' '
[•• 4. Type and quantity of chemicals used, if any
\ ' • • •
:'! 5. Available data on treated wastewater quality
! . (Same items as in Section III. D. above)
6. Describe any .operating difficulties encountered
;., ' i '
I 7. Results of any laboratory or pilot plant studies =•,
f f : •-
i, • 8."Known toxic materials in wastewater
I' '• F. Wastewater recycle
!' 1. Is any1 wastewater recycled presently?
ii • - i
j, 2. Can wastewater be recycled? What are the restraints
I on recycling?
10
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VI
6. In-pi ant methods of water conservation and/or waste
reduction '
H. Identify any air pollution, noise, or solid wastes
F
resulting from treatment or other control methods.
How rare solid wastes disposed of?
!
I. Cost information related to water pollution control
1. Treatment plant and/or equipment and year of
1 ! •
expenditure ',
2. Operation (personnel, maintenance, etc,)
3. Power costs
1 \.
4. Estimated treatment plant and equipment life
i
J. Water pollution control methods being considered for
future application <
i ,
COOLING WATER j
' !' ' ' "vl
A. Process steps requiring cooling water
B. Heat rejection requirements (Btu/hour)
C. Type of cooling system, i.e., once-through or recireflating
D. Cooling tower \ •
1. Recirculating flow rate
2. BTowdown rate •
3. Type and quantity of chemicals used
'! • '
4. Slowdown water quality"
E. Once-through water q'uality
1. Flow rate <
2. Type and quantity of chemicals used
3. Discharge water temperature
BOILER • "
1 ' '
A. Capacity !
B. Slowdown flow rate a'nd characteristics
11
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Retrieval Forms
_. Re-burned
16
9
W
6
29
28
5
Industry
Corn wet Milling
Corn Dry Miliing
Wheat Milling
Bulgur Millinq
Rice Milling;
* Ordinary Process
|f Parboiled Process
RAPP^applications to the corps of Engineers for discharges
togetner with computerized RAPP datar supplied, by EPA, were also
of thaS ? S0urce of data. These data included - the identification
£ tne plant, the number of waste discharge points, the volumes
discharge, and the character and quantity of waste. The
numoer of sources included in the RAPP applications was seven in
•I f0rn Wet milling industry, two in the normal wheat milling
industry, and one in the parboiled rice industry.
Retrieval Forms
Returned with
uuUsable_Data
15
4
20
2
9 .
8
2
no visi"ts 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,
!.£ Diluent treatment. A total of eleven plants were visited in
the following subcategories:
Industry
Corn Wet Milling
Corn Dry Milling
Normal Wheat Flour
Bulgur Wheat Flour
Parboiled Rice
Total Plants Visited
5
1
1
1
3
™ -^ £i/i1?n to tne above, several plants in each category were
h° ^a?tect by telephone for information on the industry and waste
nandiing. Detailed data were obtained during these conversations
consisting of raw material description, flow rates, waste
quantities, and waste treatment.
Samplin9 of each industry subcategory was provided at a
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 !
Corn wet Milling !
Corn Dry Milling ;
Bulgur Mining i
Parboiled Rice Milling
Total Plants Sampled
U
1
1
2
12
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GENERAL DESCRIPTION OF THE INDUSTRY
The cultivation, harvesting, and milling of grains dates back to
the beginning of 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 1600fs. 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.
I' . •
The cereal grains, so-rcalled because they can be used as food,
include barley, corn, grain sorghum, millet, oats, rice, rye, and
wheat. This report, however, only covers the milling of the
three principal grains, namely, corn, wheat, and rice.
With an annual agricultural yield of about ItO million metric
tons (5.5 billion bushels), the United States is easily the
largest corn producer inrthe 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^gjE_total_ corn^production
Feed
Export
Wet milling
Dry milling
Alcohol
Seed
Breakfast food
77.3
14.0
5.7
2.2
0.8
0.3
0.2
Corn is milled by dither 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 milling are starch, oil, syrup*
and dextrose. • !
. 13
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it.- ._
Corn_wet Milling-
industry is an American development and
Commercial extraction of starch from corn in
' e When the greatest source of starch was from wheat
P°tat°es Starch from the corn wet milling process Sow
accounts for 95 percent of the American starch output.
The first corn wet mills were segregated to produce either
"
. y.
M« mill developed to produce both starch and syrup.
Many of the present mxlling companies had their beginning at
consolidated. * " ™S± °f the existin* -Ailing plantswere
Today, twelve companies operate 17 plants in seven states with a
total corn grind of over seven million metric tons per year (275
million bushels per year) . A list of the companies and plants is
J-?' ' thS?e S1^8' ei^t were put into operation
. utlll2:Ln9 newly developed equipment and methods of
K o^Provtde ! better products, higher yields, and less
™ °ider ?lan^s meanwhile, have incorporated new process
procedures and replaced nearly all equipment with more efficient
S2£er*;*Pr0Tl'da-2g Jcleaner operating conditions and increased
yields with reduced odors, wastes, and water usage. The raw
material -for corn wet milling is the whole kernel! Most of the
£ rA^rina?ily hy^ridi yell°W dent corn' comes from the midwest
dentCcSn *™^' The composition > of yellow
Table 2
Composition by Dry Weight of Yellow Dent Corn
Carbohydrates
Protein
Oil
Fiber
Ash .<
Percent
80
10
4.5
3.5
2.0
bulhSl 1?? a Si . ^ Ure 2f corn fn the United states is the
SXfiV (l g) .Plant Slze is measured by the number of
bushels of corn processed per day. Wet milling plants receive
? H ?°^n /^neiS at 1° to 25 Percent moisture; The standard
bushel is defined, for purposes of this report, as 25.4 kg (56
Prcent moisture. The 17 corn wet mills in
about 38° tO 305° ^/day (15,000
14
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Table 3
Corn Wet Milling Companies and Plants
American Maize-Products Company
250 Park Avenue
New York, New York 10017 j
Plant: Hammond, Indiana H6326
Anheuser-Busch, Inc.
P.O. Box 1810 Bechtold Station
St. Louis, Missouri 63118 !
Plant: Lafayette, Indiana 47902
.Cargill, Inc. i
Cargill Building i
Minneapolis, Minnesota 55402
Plants: Dayton, Ohio 454:14
Cedar Rapids^ IpWa 52401
Clinton Corn Processing Company
Division of Standard Brands, Inc.
Clinton, Iowa 52732 .1
Plant: Clinton, Iowa 527;32
Corn Sweeteners, Inc. j
P.O. Box 1445
Cedar Rapids, Iowa 52406
Plant: Cedar Rapids, Iowa i52406
CPC International Inc.
International Plaza .'
Englewood Cliffs, New Jersey 07632
Plants: Argo, Illinois 60501
Pekin, Illinois 61555
North Kansas City, iMissouri
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 461206
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
15
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operations, namely
manufacturing as shown
The corn wet milling can be considered as three basic process
/N v>« ^^ —\ -4— J 4-v*«' i-* «_. _. •« ._. T _ _ __. .2 T ^ " • . __ j _ . _ i .•* .. _ "
millingv starch production and syrup
in the accompanying schematic diagram
%
The initial wet milling sequence separates the basic components
of the corn kernel into starch, germ, gluten, and hull. The
individual process «operations include steeping, 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 to corn syrup or
dextrose. In processing the starch slurry from the wet milling
operations, the fractions are proportioned between the starch
finishing and corn sweeteners departments. The supply of starch
distributed to each will depend on daily and seasonal
fluctuations controlled by the 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 to 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. ,
CORN-
STEEPING
k
CORN OIL
EXPELLING
AND REFINING
A
Wl
SE
STEEPWATER !
"!' •
k
GERM
ET MILLING
ID STARCH
EPARATION
HULLS
GLUTEN
r
FEED
DRYING
\ CORN OIL
' ' --WATER.
4r
STARCH
STA
MODI
.ANIMAL f
•f FEED
RCH
ING,
FY1NG
— >M,
SYRUP
HYDROLYSIS
AND REFINING
REGULAR AND
MODIFIED STARCHES
CORN SYRUP
' & DEXTROSE
CORN WET MILLING
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 j 1/4 to 1/3 of the 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.
16
-------
corn Dry Millinq-
com dry milling differs in almost all respects from wst millino
except in the raw material used. The grinding or dry milling If
com predates wet milling by hundreds of years. Today, a little
over two percent of the total com production is processed by the
Q3ry inx J.J.C2TS • !
There are, ^approximately, 126 corn dry mills throuahout the
country, although most are located in the midwestern Co?n Belt
ranging in size from very small millstone operations to large
modern mills with capacities up to. about 1500 to 1775 kka/dav
(60,000 to 70,000 SBu/day.) The larger plants process abSut to
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 Ld product only
ground whole corn meal. These small mills use little. If
water and will not be discussed further in this report!
mil1? emPioy a number of production steps designed to
^the various fractions of the corn, namely the endosperm?
bran, and germ. The primary production sequence is shown on the
SmnP^yiog "gfam- Th^ 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?
Cla!Sify±ng' and; aspirating operations. 9 Tn In
a *^*?' °^rn*. 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-
CLEANING
k
7
k.
"•— ' 7
DRYING,
MILLING,
SIFTING
BRAN
CORN MEAL,
GRITS, FLOUR
CORN DRY MILLING
17
-------
IflL
I
if;'
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 pro-
duction. In this country, about HO percent of the wheat is
milled into flour and the remainder is used for breakfast foods,
macaroni products, :animal feed, alcohol production, and other
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, to-
gether with various additives. These products are formulated^ to
customer specifications to meet the required qualities for f^nal
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.
: '-f '• ' WATER
WHEAT
A STORAGE
fl CLEANING
k
f
TEMPERING
v| MILLING & I k.
PI SIFTING I "
FLOUR
GERM
BRAN
MILLFEED
WHEAT MILLING
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 U.
18
-------
Table 4
Bulgur Mills - Locations and Estimated Capacities
company and_plant location
Archer Daniels Midland Co.
Shawnee Mission, Kansas 66207
Plant: Abilene, Kansas
Burros Mills Division j .
Cargillr Inc. ,
Dallas, Texas 75221 !
Plant: Dallas, Texas
California Milling Corporation
Los Angeles^ California 90Q58
Plant: .Los Angeles, California
Fisher Mills, Inc.
Seattle, Washington 98134
Plant: Seattle, Washington
Lauhoff Grain Company
Danville, Illinois 61832
Plant: Crete, Nebraska
Estimated capacity
.kkg/day ewt/day
227
145
204
408
272
5000
3200
4500
9000
6000
WHEAT
STORAGE
CLEANING
_^
r
WATER
SOAKING «•
COOKING
k
f
fe
r
MILLING &
SIFTING
I GERM
I BRAN
MILLFEED
BULGUR
BULGUR PRODUCTION
Ri'ce ' -" 'v j • • •
The unique nutritional and chemical qualities of rice makes it
one of the world's most important food products. In the United
States, it is used in numerous products and in many forms
including (in descending^ order) :
19
-------
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. Al-
.though 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 pro-
duction 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 mills.
Milling of rice differs from other 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
packaged. Rice hulls, bran, polish, and small pieces of the
grain may be sold separately or combined into so-called millfeed
for animals. The average yields for ordinary rice milling are:
I • . = ..---'.- >- • . . _ . •• , -.
] ; Percent
Whole grain white rice 54
Broken grain rice 16
Hulls and wasipe 20
Bran 8
Rice polish •-•••• 2
VITAMIN
- i . MINERALS
'*,
RICE ' M CLEANING I—-^ MILLING I ^
J__J:
SEPARATION]—Z-^ WHOLE XJRA.N RICE
BROKEN GRAIN RICE
JBRAN
GERM
RICE POLISH
MILLFEED
ORDINARY RICE MILLING
20
-------
parboiling rice has been practiced in foreign countries for years
and differs significantly from ordinary rice milling. The manu-
facturing process was introduced in the United States in 1940.
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.
The manufacturing process, shown below, begins with careful
cleaning of the rice. The rice is then parboiled by soaking in
water and cooking to gelatinize the starch. Procedures for
soaking and cooking are carefully controlled to produce suitable
product properties 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.
Table 5
i
ParboiledJRice Milling Companies
Blue Ribbon Rice Mills, Inc.
Box 2587 ;
Hustpn, Texas 77001 !
- . . "i
Comet Rice Mills, Inc. ;
Box 1681
Houston, Texas 77001 j
i
PSS Rice Mills, Inc. j
Box 55040 j
Houston, Texas 77055 I
Rice Growers Association of
California 111 Sutter Street
San Francisco, California 94104
Plant: Sacramento, California
Riceland Foods
Box 927
Stuttgart, Arkansas 72160
Uncle Ben's, Inc.
Box 1752
Houston, Texas 77001
WATER
RICE-
CLEANING
ffc
,-• *
PARBOILING
r
WASTEWATER . HI
MILLING
W
f
II 1 e',
SEPARATION
BRAN
. GERM
I RICE POLISH
WHOLE
GRAIN RICE
BROKEN
GRAIN RICE
MILLFEED
PARBOILED RICE MILLING
21
-------
3:0
used in milling the various grains differ
cases as summarized earlier in this
<3 discussion provides a more detailed
3-ndustry subcategory of the processes used
in Figure 1, begins with the delivery to
oorn, normally NO. 3 grade or better. The
aremove foreign materials,, stored, and dry
prior to entering the main production
in the process, conditions the grain for
recovery of corn constituents. This
Kernel for milling, helps break down the
particles, and removes certain soluble
^ of a ^series of tanks / usually
and might be termed a batch-continuous
•Holds about 51 to 152 kkg (2000 to 6000
submerged in continuously re circulating
s c) . sulfur dioxide in the form of
to the incoming water to. aid in the
* = %%*% ^1S ^dlscharged for further
s added to that steep tank. Incoming
;ping system is derived from recycled
,-fcaons .at the mill, and is first introduced
oldest corn (in terms of steep time) and
of steeps to the newest batch of corn.
from 28 toH8 hours.
'.n®west corn steep is discharged'to
light steepwater containing about six
4ry weight of the grain. On a dry weight
-the steepwater contain 35 to 45 percent
for addition to feeds. such recovery
-fczrating the steepwater to 30 to 55 percent
-fc j evaporators. The resulting steepinq
pwater, is usually added to the fibrous
I sold as animal feed. some steepwater
22L
-------
PRODUCTION PROCESSES ,
The production methods used in milling the various grains differ
significantly in most; cases as summarized earlier in this
section. iThe following discussion provides a more detailed
description for each industry subeategory of the processes used
in milling.
Corn Wet Milling ' ' .. .
Storage arid Cleaning'" V
"""•!. ' - ' *
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 Iremove foreign materials, stored, and dry
cleaned a second time prior . to entering the main production
sequence. !
' ' " '
Steeping- ' •
Steeping, the first "step in 'the process, conditions the grain for
subsequent milling ani 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 tanksv usually
referred to as, steeps, arid might be termed a batch-continuous
operation. Each steep 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 tne oldest corn (in terms of steep time) and
passes through the series of steeps to the newest batch of corn.
Total steeping time ranges from 28 to U8 hours.
'*"!*! ' "
Steepwater Evaporation^. - . .. ,
f '.'.') • . ••-.-' '.:• .-'-•• - - - 1 . •
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 H5 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
' ' '
22.
-------
!EL
SHELLED CORN
STORAGE AND
CLEAING
STEEPWATER
STEEPTANKS
FEED DRIERS
FEJEDS
STARCH
WASHING FILTERS
.• -_Ji --
j:^__J~ STARCH T
r ^JHOOjFYINGJ
1
STARCH DRI£RS
i
CORN SYRUP
tORN SYRUP
DRY STARCHES
I/HI jiARincj
D E X T R I,N
ROASTESS"
D E X T R 1 N S
STEEPWATER
EVAPORATORS ;
,. / V ^
fATER
RATES
•^
4 HUH
1 "T"™
A GLUTEN
U tlj t KWIIM A 1 UK)
1
GERM SEPARATORS
1
GRINDING MILLS
|
WASHING "SCREENS
1
CENTRIFUGAL
SI PAR AT OR S
GERM
CRUDE
.OIL
OIL EXTRACTORS
FILTERS
•
CENTRIFUGAL
SEPARATORS
' • •'• '
DEODORIZERS
FILTERS
B
REFINED OIL
CORN OIL
MEAL
SYRUP & SUGAR
coNvt RroRS
REFINING
±
DRUM or SPRAYS
DRJERS |
CORN SYRUP SOLIDS I
SUGAR
CR YSTAtllZERS
CENTRIFUGALS
J_
DEXTROSE
' ' :• FIGURE; 1 . . .
THE CORN WET MILLING PROCESS
-------
be sold for use
as
nutrient in fermentation
may, also,
processes. i
Milling- I
The steeped corn then Passes through^ aeger-ninatin, Bills o«hich
starched T-L.5L s r^-o e^alTSe
the
.
Subsequently washed, dewatered, dried, the oil
spent germ then sold as corn oil meal.
The product s
*t this point, the
°a
a
to remo.e
con
any residual gluten and solubles
I
Starch Production- j
Tne pure starch slurry B
basic finishing operations,
starches, and com syrup
ordinary , pearl starch,
vacuum filters or base
In the production of
slurry is dewStered using
Sl discharged starch cake
percent and is further
may be used to make dextrin
Modified! starches
fpr^various
sturry witA selected ! chemicals ^^^^^roduce oxidized,
produce acid-modified, sodium J^P0^?^ ^rc£es. The treated
£S ethylene oxide to! produce ^^^1^^ distribution.
starch is then washed, dried, ana P*J£ *n a more water soluble
Since most chemical ."fcrear?)®^-t5bina of modified starches, may
product, waste waters from ^^f^0* ^addition, because of
contain a large concentration of BOD5. in aa organic
the presence of r^ldujierf ^Sn canno? be reused and must be
a+erials these waste waters ort:en octim<-"- ~*~
discharged to the sewer.
! 24
-------
Sugar-
m 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
cooled for storage and shipping.
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 "jthe contents are further cooled and^the
dextrose crystallizes. After about 60 percent of the dextrose
solids 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.
Corn Dry^Millincf i
1 ,- •
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 1phe 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 from the plant.
I
Tempering, the first process operation, raises the moisture
content of the corn to the 21 to 25 percent level necessary for
milling. The corn passes through a degerminator that releases
the hull and germ frpm the endosperm and the product stream is
dried and cooled in preparation for fractionation. :
Fractionation comprises ja 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 jgerm 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
25
-------
CORN
MILLFEED
. "
RECEIVING
STORAGE &
DRY CLEANING
. 1
WASHING & w
DE WATER ING f
\ ^r
SOLIDS
RECOVERY
WASTEWAtER
' i
.' '".':',. .;hi
••" ' 1 ' " '
1
I
soLibs ;
tp FEED
jets ;: .
GERM
TCM DCD 1 Mr*
1 cIVIr'crilNvi
1
DEGERMING
1
DRYING &
COOLING
1 ,
MILLING & 1
SIFTING.
1 1
1
_JoiL EXPELLING
^j & EXTRACTING
REDUCTION
MILLING
1 CORN GRITS
"' & MEAL
CORN OIL
CORN FLOUR
FIGURE 2
THE DRY CORN MILLING PROCESS
26
-------
separated germ goes to, oil expelling operations, where
approximately 10.7 to 14.3 kg/kkg (0.6 to 0.8 Ibs/SBu) of oil are
recovered from the corn, j
i.
A few of the larger mills further process the grits, meal, and
flour through expanders and/or extruders to produce food, foundry
and feed products. Such processing is not an integral part of
the basic milling sequenc'e and -is not practiced by most small'and
medium sized mills. Only, the basic milling sequence is discussed
in this document. !
i • • ..
Wheat Milling I , :
Wheat milling has been subdivided into two segments, normal flour
milling and bulgur production. The production methods differ
considerably and are discussed separately in the following
paragraphs. j .•.!-.....••
i '• •
Normal FlourMilling-
The wheat :milling process, presented in Figure 3, starts with
dry, matured, graded, sound, and ' partly cleaned wheat seed.
Grain, as needed, is move'.d from storage to the cleaning house for
final cleaning prior to milling. It is here that other seeds,
grains, and 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 ibrihg the moisture content up to desired
levelJs, usually 15 to 20 i percent. The amount and method of
moisture addition^ soaking time, temperature, and conditioning
time will vary for different grades of grains and individual mill
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 br^an, \ endosperm, germ, and bran with. adhering
endosperm are scalped over sifters. The scalped fractions o;f
endosperm go int6-purifiers for separation and grading.
i
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: latterj is sent back to reduction rolls for
further processing. At tlhe end of the milling operation, the
discharged flour is treated with a bleaching agent to mature the
27
-------
WATER
i
j
WHEAT
: 4r
* ^:
WHEAT j
WASHING
WASTEWATER |
i
! I •
1- '
1 ' •
: >' '• : ''I -
•i . i
• i
' . ' ' i
MILLFEED ^•••^
: , ' ' j ...
: i
|
• . ', _ 'i - '
{
ADDITIVE
.i i'
RECEIVING
STORAGE &
DRY CLEANING
L
•BBaOBBBI^HB
pi^2L.
BRAN&
SHORTS
GERM
s
WATER
_ r- STEAM
" TEMPERING
1
BREAKER
„ I
| SIFTER
1
PURIFIEF
I
1
REDUCING
ROLL
I
SIFTER
, 1
~^ 1
BLEACHING &
ENRICHING
FLOUR
FIGURE 3
THE WHEAT MILLING PROCESS
-------
flour and neutralize the color. Depending upon its end use, the
flour may be blended pr 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.
Bulgur Milling- . . . j
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 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 alpng 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 close 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 j in normal flour production, follow the
drying operations. The "dried wheat is conveyed to a polisher
(pearler or huller) followed by a series of grinders and sifters>
which separate th4 fines and bran from the granular finished
product. The combined by-products, approximately 1.0 percent of
the raw materials, arei disposed of as animal feed while the
bulgur is packed in 100 lfc> bags for shipment.
Rice Milling ' !
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),
29
-------
WHEAT
WATER
WASTE WATER/
WATER
STEAM
STEAM
RECEIVING
$TORAGE &
DRY CLEANING
3^J
BRAN
MILLFEED
WASHING
I
SOAKING
PRESSURE
COOKING
DRYING
COOLING
POLISHER
GRINDING
SIFTING
ENRICHING
& BLENDING
BULGUR WHEAT
FIGURE 4
THE BULGUR PROCESS
MEAL & FLOUR
30
-------
and short grain (such |as Pearl). Each variety is graded
according to U.S. Depaartment 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.
r- < • ' \
Nn-rmal Rice Milling- , j ....
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 Boiler 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 peajrlers. 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 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 and1 also cools the rice to reduce stress
cracks. Additional processing in a brush machine removes the
remaining loose bran. . •
Rotating horizontal drum trumbies are used to polish the rice.
The rice is coated in! the . trumbies 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 Crumbles. Finally, the whole and broken
rice kernels are separated to meet product standards.
Parboiled Rice- |
Tir--" -1-- "--L 1L | , -,. , ,
Parboiled rice production begins with basic rice cleaning in
shakers and aspirators. .Precision graders are added in p.arboiled
rice cleaning to -remove the immature small grains and the rice
that has been dehulled in handling.
The parboiling process, a's 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 aitf in the hulls and the voids to allow
water to penetrate into the kernel faster. Hot water (70 to 95
31
-------
ROUGH RICE
HULLS
BRAN &
RECEIVING
STORAGE &
DRY CLEANING
SHELLER
SEPARATOR
RICE POLISH
BRAN
PEARLER
H
BROWN RICE
RICE POLISH
TO MILLFEED
BRUSH
VITAMINS &
TO MILLFEED MINERALS
ADDITION
SCREENINGS
TRUMBLE
1
SECOND HEADS
SCREEN &
SEPARATOR
RICE FLOUR
MILLING
WHITE RICE
RICE FLOUR
FIGURE 5
THE RICE MILLING PROCESS
32
-------
HOT WATER
STEAM
ROUGH RICE
RECEIVING
STORAGE
DRY CLEANING
J.
STEEP
TANKS
I
COOKER
DRYER
COOLER
> WASTE WATER
HULLS
BRAN &
RICE POLISH
TO MILLFEED
SMELLER
WHITENER
PEARLER
BRUSH
TRUMBLE
SCREEN &
SEPARATOR
4-
PARBOILED RICE
FIGURE 6
THE PARBOILED RICE PROCESS
33
-------
Se rl el?*1*15 beCaUSe °f ! thS C0l°r Pick-»P- which woSd
process is essentially th| same as for normal riS! '
> L ! .
WASTE WATER CONSIDERATIONS IN INDUSTRY
aa
existing mimicipal treatment facilities: waters to
There are two potential sources of waste waters from corn drv
Sii8' rm!ly, °0rn Washin9 and car washing. corS waSSq hll
been a standard operation at many, but not all, mills 2£SS • cJ?
washing is practiced infrequently and only at some mlSs
S?*S?te8 ° W?Ste Watersi are relatively smLl, cSmpaSd to
wet mills, ranging up to perhaps 900 cu m/day (240,000 gpd)
'
waste
-
Ordinary wheat milling usually generates no process waste waters
SSn^ atlon' Thfse waste waters contain moderately high levels of
BOD5 and suspended solids. All of the five bulgur mills in %hi
country are believed to discharge these wIsLSto municipal
systems for treatment. Normal rice milling does no? usl any
34
-------
rvrocess waters, hence ho process waste waters. Parboiled rice
/Ws aenerate some waste waters from the parboiling or steeping
Sneration, up to about ;760 cu m/day (200,000 gpd) . These waste
Caters 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.
35
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! 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 subca-tegories are as follows:
1. Corn wet milling :
2. Corn dry milling -
3. Normal wheat flour milling
4. Bulgur wheat flour milling
5. Normal rice milling
6. Parboiled rice milling
FACTORS CONSIDERED ' E| ' .
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.
Raw Materials
Clearly, one basis for sejgmenting 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 wajste water characteristics. Accordingly,
•raw materials were selected as one basis for subcategorization.
37
-------
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'. arid syrup. Wheat milling produces flour for
baking and other purposes and the specialty product, bulgur.
Finally, rice milling 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.
Production Processes
; While similar 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 milling. These highly sophistiLcated.
„ physical, chemical, and biological processes are completely
different from most Iprocess operations in dry corn, wheat, and
•; . rice mills. . ! :
|! - _ | ..=_.-,'---- - , .=--,..-
Dry corn and ordinary i wheat milling employ somewhat, similar
processes. Both require cleaning, tempering, milling, and
mechanical separation of the products although slightly 'different
equipment is used. Bulgur wheat milling differs considerably
i 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 other 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,
|B>- ' i ' • • • ' . -
jj:i;'-.; - Size and Acre of Production 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 ia 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
i; characteristics and size or age of plants.
rl- • . •! • ss
If:
-------
wag-he Water Characteristics
The waste water characteristics from the several types of grain
mills do differ to some degree. Wet corn mill^s 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.
Corn dry mills discharge much smaller waste water quantities with
high BODJ5 and suspended solids levels. Parboiled rice mills
generate amounts of waste water €hat are comparable to corn dry
mills and with a high dissolved BOD5 content. Suspended solids
levels, however, are quite low in rice milling wastes. Finally,
bulgur milling generates small quantities of moderately strong
wastes. j
In summary, while the waste water characteristics do differ,
sometimes significantly, these differences are adequately
reflected by the other factors mentioned above.
Tfeatability of Wastes
• l^»i II ^ I. llll»ll I Ml !• ll • •! il. V !.••! I , [ _ ' . .
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 subcategorizatiori.
39
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SECTION V
WATER USE AND WASTE WATER CHARACTERIZATION
INTRODUCTION
Process water use and waste water discharges vary markedly in 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. By 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 whe^t 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 arid hence, generate modest quantities of
process waste waters. \
This section presents a detailed discussion of water use, indivi-
dual 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 is 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 cpoling
water and boiler blowdown and water treatment plant wastes has
been excluded from the following discussion. These auxiliary
activities are common to many industries and the individual
practices at any giveji plant usually do not reflect conditions
that are unique to the grain milling industry. The types of
treatment employedf for cooling water systems, boiler fee.d 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.
41
-------
CORN WET MILLING
i ' ' ' • "
Water Use |
I
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,I and discharged waste waters are shown on
the attached diagrams. Recycled process waste waters are
identified by the symbol "PW" 'to distinguish them from 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 countercurrent to the product flow direction back
through the mill house to the steepwater evaporators. More
specifically, the process waste waters from 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.
i • • ..•
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, iori exchange, dextrose production, and syrup
shipping, as indicated iin 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, arid corn steeping.
Total water use in this isubcategory varies from less than 3785 cu
m/day up to 190,000 cu in/day (1.0 mgd to 50 mgd) depending, ^in
large measure, oh the itypes of cooling systems employe'd. Those
plants using once-through cooling water have much higher water
demands than those using recirculated systems, whether they be
surface or,barometric cqndensers. 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
be contrasted with the
cooling water almost
grind (300 gal/MSBu). This number should
several plants that use recirculated
exclusively, where the total water use
42
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values 4?:e about 0.007,5 cu m/kkg (50 gal/MSBu) . Information is
hot available on the water use by individual production processes
since tlf^se 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.
Waste Water Characteristics of Individual Production Processes
As indicated in the preceding discussion op water use, many
process waste waters that were discharged to sewers years ago,
are notf ; 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.
Steepwater Evaporation:- ,
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 baro-
metric condensers. Vapors from each of the first two effects
passes.through the subsequent'effect before being discharged to
the sewer. For those systems using surface condensers', the con-
densate from the thir£ 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 secpnd effeqt 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* £OD£ levels ranged from 10 to 75
mg/1 with typical values reported by industry in the range of 25
mg/1. ,
46
-------
; Table 6
First and Second Effect Steepwater Condensate
Waste Water characteristics
BOD5
COD
Suspended1 Solids
Dissolved Solids
Phosphorus, as P '
Total Nitrogen asi N
PH i
Range,
723
1095
10
110
0.
2.
3.
mg/1
5
4
0
-
934
1410
28
292
0.
2.
3.
7
6
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 cpoling water and only discharge the
blowdown from the cooling tower to the sewers. Measurements of
the blowdown 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 (Table 7) indicate that steepwater evaporation systems
.usingoncethrough cooling water generate about 4.5 to 13.4 cu
m/kkg, (30 to 90 gal/SBJu) of process wastes. Recirculating
cooling water systems, 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/kkg (0.05 to 0.16 Ibs/SBu) and a COD range 1.1 to 3.2 kg/kkg
(0.06 to 0.18 Ibs/SBu) . -'..-... .
Modified Starch Productiorv .
! " '
In many, if not most, corn wet mills the waste from the
production of modified starches represents the largest single
source of contaminants 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.
47
-------
Table 7
Finished Starch Production
Waste Water Characteristics
BOD5
COD"
Suspended solids
Dissolved solids
Phosphorus a? P
Total nitrogen as N
pH ;
3549 •
8250 •
918 •
9233 •
25 -
32 -
4.2-
3590
8686
2040
16211
63
41
5.7
These_ very high-strength wastes are highly variable in both com-
position, flow and biodegfadability. Information from earlier
studies on the waste characteristics relative to raw material
input is summarized i*i 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 ibeen established between the types and
amounts of starches being produced and the waste loads from this
operation. •
Syrup Refinery- 1
> - , . - • - [-;••.„. ,^,,'.o, ^ •;••.,>..;* •.!.;-?,:- .. .„:.•.-, : - . -.-*..••
In most mills, wasiie 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 includes activated carbon and ion exchange
treatment. Typically, the so-called sweetening- off procedures
require flushing 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. The 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 1900 mg/1, and in dissolved solids, 2100 to
9400 mg/1. The pH levels of the waste water were quite low,
averaging about 1.8 and the suspended solids averaged 25 mg/11.
Other sources of waste! waters in the syrup refinery include:
syrup (flash) cooling, evaporation, dextrose production, and
shipping^ Samples of wastes from the syrup cooling process at
one plant gave the results shown in Table 9.
48
-------
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syrup solids
-------
• : Table 9
; Corn Syrup Cooling
Wast!e Water Characteristics
• !-'..' .'•'•-•• .'••-••-•'
Concentration
BOD5 i 73
COD ; 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
r^circulation 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. j
Total Waste Characteri stic s
Most of the data accumulated from various sources during this
study relate to the to^tal raw waste characteristics from corn wet
mills. Summary data from 12 of the 17 mills are presented in
Table 10. Waste waters from this grain milling subcategory can
generally be characterized as high-volume, high-strength
discharges. The BOD varies widely, from 255 to 4450 mg/1, with a
corresponding range in COD. Those plants with very low BOD5
values typically have barometric condensing systems using once-
through cooling waiter. At the other extreme, the very
concentrated wastes are from plants using recirculated cooling
water (either surface or barometric condensers). i
'; , .-'','•' ' -ij: ,/;•.::''' '.:..:.."•': r"-'- ;. :;c ::'*•. - '•:';' •-, .:I -.:. . '1 ' •
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
50
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deficient in nitrogen for biological waste treatment. Dissolved
solids levels from certain process operations, as discussed
previously, generally do not constitute 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).
££e. plant numbers in the two tables do not correspond to one
another. . .; — —~
BQD5 in terms of raw material input ranges from 2.1 to 12.5
kg/kkg (119 to 699 llbs/MSBu), and averages 7.4 kg/kkq (415
Ibs/MSBu)1 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/MSBu). These data emphasize
again the wide varicition 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 from 3.1 to 41.7 cu m/kkg (21"to 280 gal/
SBu) 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 employ recirculating cooling water systems.
Factors Affecting Wastescharacteristies
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 some of these factors with raw waste
loads, as discussed in the following paragraphs.
Age of Plant- : .
In some industries, thte 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 BOD5 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, 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 production techniques.
Size of Plant- ;
Several comparisons were made between the size of plant,
expressed in normal grind of raw material, and total plant waste
I
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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 I as a result of vastly different process
and cooling water use practices.
The information on BOD5, 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 pischarge-
;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. ; •
; -*s
Product Mix-*. \ ;
Because certain products, namely. - modified starches, result in
.higher waste .loadings jthan other products^ there was reason to
fbelieve that a relationship might be apparent between product mix
and total waste load. For example, it might be 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 tha|t product mix is a direct measure of the
relative/waste load of different plants.
-The product fmix at the! reporting mills varied from 100 percent
starch to 100 ipercent syrup and sugar, ... At most of the plants,
the product mix varied between about 30 and 70 percent starch.
Even near the two extremes't i.e., zero and 100 percent starch,
there was no discernible relationship between product split and
waste loads. Furthermore, the more limited information on the
quantities of modified starches produced indicated no correlation
with waste loads at different plants.
'•:> ........ I • '
i
Plant Operating. 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
55
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this is not universally the case. Clearly, careful monitoring
arid 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, no 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, indefed, influence the character of the total
waste discharges.
1 i •
CORN DRY MILLING ! . '
I ' -
Water Use >'• '.
'i
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 Characteristics
i, ~~ .•''•
*
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 mil'l
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.
I
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
61
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Concentrations. The raw waste water BOD5 values average 1.14
Jcg/kkg (64 Ibs/MSBu) , and the suspended solids average 1.62
(91 Ibs/MSBu). |
gactors Affecting Waste Water Characteristics
Insufficient data were available to establish any relationships
between waste water characteristics and such factors as plant
age, size, and operating prpcedures. 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 milling of wheat into flour uses water only in
tempering and cooling and np 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.
Water Use
i
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 be added at as many as .four
locations, all, essentially, relating to the same soaking
operation. Water usage ifor 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.
Waste 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 igpd). 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
BOD5
COD
Concentration mq/1
238 - 521
800
63
-------
-Suspended solids 294 -
Phosphorus as P 5.6
Total nigrogen as N 3.6
:pH ; . 5.8
Factors Affecting 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.
RICE MILLING '.
, j - - -'-•-,--•---.- , , - - - -- ---,--
The ordinary milling of rice to produce either brown or white
rice utilizes no process waters and, hence, generates no waste
waters. Water is u;sed in the production of parboiled rice and
the remainder of this discussion will focus on this production
method.
Water Use ': '
In the parboiled rice; process, water is added in the steeping or
cooking operation, as shown in the product flow diagram. Figure
6. Water use in the industry varies from about 1.4 to 2.1 cu
m/kkg (17 to 25 gal/cwt). Additional water is used in boilers
for steam production for the parboiling process. At least one
plant uses wet scrubbers for dust control, thereby, generating an
additional source of waste water,
" I V ' . "•. "„ •']'.• • ..:.. . ."'• ,; - • •' ,.,-. '•' .. - ,'/ I ...'' ". "- .' . -
Raw Waste Water
Limited data are available on raw waste water characteristics
from rice parboiling. The information that is available is sum-
marized in Table 14. The raw waste loads presented in the table
correspond to 1.8 kg/kkg (0.18 Ibs/cwt) of BOD5 and 0.07 kg/kkg
(0.007 Ibs/cwt) of suspended solids. In general, the waste may
be characterized as having a high soluble BODS content and a low
suspended solids level. ~~
Table 14
; Waste Water Characteristics
Parboiled Rice Milling
: , Concentration mq/1
BOD5 1280 - 1305
COD 2810 - 3271
Suspended solids 33 - 77
Dissolved solids 1687
t _ . /-. ... :; , ,..:(-; : . • . -.; - . .- •-, , .:. .:*..- • , . •„.,•... .-:.
, '\ . . , -•• 64
-------
Phosphorus as P
Total nitrogen as N
98
7.0
Water-Characteristics
on the very limited amount of data available, it appears
the was?? characteristics from parboiled rice plants are
Site simillr! While there are some differences in flow volumes,
total waste loads per unit of production are similar.
65
-------
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: BOD5 (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 eqftal
importance. As described below, 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. ;
. i • /
MAJOR CONTROL PARAMETERS ;
The following selected parameters are the most important
characteristics in grain milling 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. BOD5 (5-day), suspended
solids, and pH are, therefore, the parameters selected for
effluent limitations guidelines and standards of performance for
new sources. ; . ,
Biochemical Oxygen Demand CBOD51
Biochemical oxygen demand |(BOD) is a measure of the oxygen
consuming capabilities of organic matter. The BOD does not in
itself cause .direct harm to a water system, but it does exert • an
indirect effect by depressing the oxygen content of the water.
Sewage and other organic effluents during their processes of
decomposition exert a BOD, which can' have a catastrophic effect
on the ecosystem by depleting the oxygen supply, conditions are
reached frequently where all of the oxygen is used and the
continuing decay process causes the production
-------
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i;
.
swimming speed.
aquatic , organisms j need a
consequences of total! lack of
can kill all °
maximum
o slikewis?
flnGe a11 Aerobic
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due to a high BOD
e blooms due
the foodstuffs of
routinely measue BOD
levels in aU Pf the
several hundred to several thoua
wastes to surface waters
damage to aquatic life,
Susti^nded
y
°OmpOS:Ln9 materials and
materials ^ form
measure
can
Apical BOD5
™x? Ulter,hl^h' ranging from
resul? I ~ Dlschar?e of such
result in oxygen depletion and
IS
fraction includes such mat eW2S
animal and vegetable fats, vJriouJ
various materials from, sewlrs .
rapidly and bottom deposits ar^
and inorganic solids!^ Tfaly
c,
S
-terials.
' and Clay' The
^rea!e' oil, tar,
sawdus^ hair, and
may settle out
y advl- mi?JUre of both organic
covering the bottom of tS JtrS L ?fJeCt. f isheries by
material that destroys the f ilh-foSI hn<-? ^ke Wlth a bla"ket of
ground of fish. Deposits con? at n?n m faU^a °r the sP*wning
deplete bottom oxygen JupplJes g Or*anic materials
carbon dioxide, metnlne, S^othJr
n
foaming in boilers, or eus
water, especially as the tempJratuJe
undesirable in water for teSSe
beverages;, .dairy
Processes, and cause
^ulPment exposed to
Suspended solids are
" Paper and
to
•68
-------
light penetration and impair the photosynthetic activity of
aquatic plants, ' 4t *
Solids in suspension are aesthetically displeasing. when they
settle to form sludge deposits on the stream or lake bed, they
are often much more damaging to the life in water, and they
retain the capacity to displease the senses. Solids, when
transformed to sludge deposits, may do a variety of damaging
things, including blanketing the stream or lake bed and thereby
destroying the living spaces for those benthic organisms that
would otherwise occupy the habitat. When of an organic and
therefore decomposable nature, solids use a portion or all of the
dissolved oxygen available in the area. Organic materials also
serve as^ a seemingly inexhaustible food source for sludqeworms
and associated organisms.
Turbidity is principally; a measure of the light absorbing
properties of suspended .solids. It is frequently used as I
SSr? ^ method of quickly estimating the total suspended
solids When the concentration is relatively low.
^n- S?1ids^ l€ivels of t*16 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
ot the organic load in the wastewater.
ES, Acidity and Alkalinity ,
Acidity and alkalinity are reciprocal terms. Acidity is produced
L f^an
-------
can affect the "taste" of the water A+ a i ™, '-a *.
waterway.
—-••——— of pH are
thousand-fold in toxicity
al^n T 44*** *-«..£? . .
with the
Ammonia is
ADDITIONAL PARAMETERS
Chemical Oxygen^Demand ifCOD)
. 70
-------
Tnorganic Dissolved Solids
In natural waters the dissolved solids consist mainly of
ff carbonates, chlorides, sulfates, phosphates, and possibly
nitrates of calcium, magnesium^ sodium, and potassium, with
traces of-"iron* manganese land other substances. :
Many communities in the United States and in other countries use
water supplies containing 2000 to 4000 mg/1 of. dissolved salts,
when no better water is available. Such waters are not
palatable, ;may riot quench thirst, and may have a laxative action
" on hew" users. Waters containing more than 4000 mg/1 of total
salts are'" generally "considered unfit for human use> although -in
hot ' climates ': such higher salt concentrations can be tolerated
whereas "they'could" not'--be in temperate climates. • Waters
containing"5000 mg/1 or more are reported to be bitter and act, as
bladder ; ^and^ intestinal 'irritants. It is-generally agreed, that
the salt -concentration of 'good, palatable water should not exceed
500 mg/1. ' .
Limiting concentrations of dissolved solids for fresh-water fish
may range' from 5,000 to 10,000 mg/1, according to•-species and
prior acclimatization. Some fish are adapted to living in more
saline waters, and a few species of fresh-water forms'have-been
found in natural waters with a salt concentration of 15,000 to
20^000: mcf/l. Fish "can;' slowly; become acclimatized to higher:
salinities, but fish" in waters of low salinity, cannot survive
sudden exposure to high salinities, . such as those resulting from•--
discharges1"of oil-well brines; Dissolved solids :•'may influence
the toxicity •of heavy metals and organic compounds to fj-sh and
other aquatic-life"; primarily because of the antagonistic ' effect
of hardness on metals. ' " '•-•' .••
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water, has 'little; 'Or-
no value for irrigation. ,
Dissolved solids in industrial waters can cause foaming in
boilers and* cause.interference with cieaness, color,.or taste of
many finished products. High contents of.'dissolved .solids also
tend to accelerate corrosion. - .-•••:••- •" ;: . •-
Specific conductance is a measure of the capacity- of water1 to
convey an ''electric current. This property is-related to .the:
total concentration Of ionized substances in .water and. water.
temperature.; ^ This prO"perty is freqtteritly used as a -substitute
method of quicfely estimating' the dissolved solids concentration.u
^ "•-, • -. ,--• ~ .--••- , ---, „. - '-,-,', f • • • v, •• '. • -" - " -.
There are a number of sources'of inorganic dissolved" solids"; in
the various sutocateg'ories of the grain milling industry. Thes^e
include wastes from -water 'treatmentv cooling'.- wat-er'-./fblowd'own,
deionizer regeneration and various processes in;- the. plant. The"
increase1 of- dissolved solids in the waste'- water-s' were;.; not 'found
to large. Moreover, the sources of inorganics mentioned above
are in many cases common to other industries. Since these
71
-------
sin
ml
, - . J .. . . _ _ ... , , ,i _ . , - ,, , ^
Temperature
™
temperatures are too high. Thus a ^^SS r,™? f • 1:L bec
72
-------
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides,, detergents, and fertilizers more
rapidly deplete oxygen in,water at higher temperatures, and the
respective toxicities are likewise increased.
When water temperatures increase, the predominant algal species
may change from diatoms ;to green algae, and finally at high
temperatures to blue-green algae, because of species temperature
preferential, Blue-green algae can cause serious odor problems.
The number and distribution of benthic organisms decreases as
water temperatures increase! above 90°F, which is close to the
tolerance limit for the population. This could seriously affect
certain fish that depend on benthinc organisms as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water. .
Rising temperatures stimulate the decomposition of sludge^
formation of sludge gas, .multiplication of saprophytic bacteria
and fungi (particularly in ;the presence of organic wastes), and
the consumption of oxygen by putrefactive processes, thus,
affecting the esthetic value of a water course.
In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters." Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this!limited tolerance is greater in estuarine than in
open water marine species, temperature changes are more important
to those fishes in estuaries and bays than to those in open
marine areas, because of the nursery and replenishment functions
of the estuary that can be adversely affected by extreme
temperature changes.
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 corn 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 tp treatment or in the treatment process
itself. Non-contact cooling- water is a separate industrial
category 'for which EPA ;will address and issue guidelines at a
later date. Therefore, temperature was not selected as a control
parameter for the purposes of this report.
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Pt~
Phosphorus
which often interfere with water uses and are nuisances
s
there is evidence to substantiate that it is frequently the kev
J^aJni a?-,a11 °f the elenients required by fresh w2ter plants and
JL?I? ; ly P^Sent in the least amount relative to need
~« ? ' *? ^ncrease in Phosphorus allows use of other; al?S3i
S fpr Plant ^owths- Phosphorus is usuSl?
this reasons, as a "limiting factor. «
When a plant population is stimulated in production and
nuisance status,^ a large number of associated liabi?ie
JY ^Parent. ; Dense populations of pond wSlI
dangerous. Boating and water skiing and sometime
y isr&ssss °f0thLs
beauty, reduce or restrict resort trade, lower
capable of being concentrated and will accate in
an
levels of some
I
— &
may be present in the
0 to 65.mg/l. .This information is 'based on 'm
and is- not .sufficient to determine effluent limitations
Ammonia '„
.
only at higher PH levels and is the most toxic in this state
The lower the pH, the more ionized ammonia is formed Lid i?s
toxicity decreases. Ammonia, in the presence of
oxygen, is converted to nitrate (NO3) by P nitrifying
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Nitrite (NO2) , which is an intermediate product between ammonia
and nitrate, sometimes occurs in quantity when depressed oxygen
conditions permit. Ammonia can exist in several other chemical
combinations including ammonium chloride and other salts.
Nitrates are considered to be among the poisonous ingredients of
mineralized waters, with potassium nitrate being more poisonous
than sodium nitrate. Excess nitrates cause . irritation of the
mucous linings of the gastrointestinal tract and the bladder; the
symptoms are diarrhea and diuresis, and drinking one liter of
water containing 500' mg/1 of nitrate^can cause -such, symptoms.
Infant methemoglobinemia, a disease characterized by certain
specific blood changes and cyanosis, may be caused by high
nitrate concentrations in the water used for preparing feeding
formulae. While it is • still impossible to state precise
concentration ;iimitsr it has. been widely recommended that water
containing more than 10 mg/1 of nitrate nitrogen (NO3-N) should
not be used .for infants. Nitrates are also harmful in
fermentation processes and pan cause disagreeable tastes in beer.
In most natural water the pB range is such that ammonium ions
(NH4+) predominate. In \ alkaline waters, however, high
concentrations of un-ionized ammonia in undissociated ammonium
hydroxide increase the toxicity of ammonia solutions. In streams
polluted witlv'sewage, up to one half of the nitrogen in .the
sewage may be in the form of free ammonia, and sewage may carry
up to 35 mg/1 of total nitrogen. It has been shown that at a
level of 1.0 mg/1 un-ionized ammonia, the ability of hemoglobin
to combine with oxygen is: impaired and fish may suffocate.
Evidence indicates that Ammonia exerts a considerable toxic
effect on all aquatic life within a range of less than. 1.0 mg/1
to 25 mg/1, depending on the pH and dissolved oxygen level
present.
Ammonia can add to the problem of eutrophication by supplying
nitrogen through its breakdown products. some lakes in warmer
climates, and others that are aging quickly are sometimes limited
by the nitrogen available. Any increase will speed up the plant
growth and decay process.
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 be necessary to achieve good biological
treatment. However, no information is available to determine
this requirement, nor., to determine effluent limitations.
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i 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-of-process treatment. The
emphasis on waste water control in this segment of .the industry
is, of course1, a reflection of^ the large quantities of waste
waters discharged in contrast to the much smaller amounts
generated by other types of grain milling. In many instances,
the treatment technologies developed for corn wet milling can be
transferred to the other industry subcategories.
CORN WET MILLING . .
Waste Water Characteristics
As developed in detail in Section V, the waste waters from corn
wet mills contain large: amounts of BOD5 and suspended solids.
Depending on the type of :cooling water system employed, t&e
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 BOD5 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 Control 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.
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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 utilize recycled water
wherever possible and generally incorporate up-to-date process
technology. , ^ . °
°f in;Plant :; control practiced by individual mills
reflects many factors;* not the Jieast of which are the physical
constraints of the. existing facility,. The physical space
availably 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 t6 implement in older
plants have been incorporated ' into the construction of new mills
•In the following paragraphs, a number of in-plant modifications
involving water conservation arid/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
must be evaluated for each individual plant.
Cooling Systems- ,
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 i cooling water .area at a later date.- This report concerns
itself with organic contamination of both contact cooling water
(barometric condenser) water and condensates from 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 condfensate is discharged as a concentrated
waste stream, suitable for treatment. Many plants use barometric
condensers; on the evaporators and the resultant condensate 'ia co-
min.gled with the cooling waters, resulting in large volume's of
dilute waste. Because of the. large volume and low concentration,
the removal of entrained BOD5 and suspended solids is both expen-
sive and difficult if 'once-through cooling waters are used.
There >are two possible .remedies to this problem and both are
being implemented lay 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 sur-
face 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 their1 barometric condensers to surface linits.
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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 tower effect some
reduction in the total BOD5 load from the evaporators.
Operational Control of^Evaporators-
The control exercised in the operation of steepwater and syrup
evaporatprs 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 or syrup through-
put 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. Iiack of careful control by the operators is
a second evaporator operational problem. Both situations lead to
the frequent boiling over of the liquor and resultant heavy waste
discharges. Improved operator control and expanded evaporator
capacity can greatly reduce1 these problems.
Improved Evaporator Demi stefs-
The amount of organic carry-over from evaporators can also be
reduced by installing modern entrainment separators or demisting
devices. .Many plants have already incorporated better entrain-
ment 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 plknts 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 milling 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 some mills condensate
! '
,79
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In* ?XrU£ evaP°ratio* 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
Improved Solids Recovery^
~* filters' and centrifugal separating equipment can be
used to recover solids from waste streams directly at their
source. For example, centrifugal devices can be used on starch
rfii^™% S^!a^^t0 rf?over solids 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-uo
and shut-down activities and return these solids to by-product
recovery.
Mob wate*s ,?r°m Jhe 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
•
. ,
Containment of overflows land spills-
In a typical com wet mill, overflows and spills from various
pieces of equipment occur 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 cannot 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 moire 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 re-
ducing total plant waste discharges. Simultaneously, they have *
the added benefit of improving general plant housekeeping. t
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Monitoring of Process Wast.es-
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 reduction has been
increased product recovery, which at least partially offsets the
cost of the monitoring.
General Plant Operation and Housekeeging-
As in many industries, gieneral operational and housekeeping
procedures have a marked effect on the amount of wastes
discharged. Those plants practicing close operational control
and good housekeeping tend to generate far less wastes than
plants at the opposite extreme. Once again, the impetus., for
improving operational and housekeeping procedures must come from
top management if it is to be effective.
Effects and Costs of In-Plant Con-fcrgl-
Because 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 modifica-
tions. 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 dis-
charge 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 diges-
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: :t
M™ P^treatment plant is under construction at a fourth
More limited pretreatment, consisting of settling and some
tion, is provided at 'another plant. Pilot plant StudSS wer
conducted on the joint treatment of municipal and corn wS mill!
ing wastes using the pure oxygen system and ^full-Sale
treatment facility plant is now under construction. The
treatment systems that are in use and the results of two
plant studies are described below.
Complete Treatment- ;
Three corn milling plants have waste treatment facilities
discharge treated effluent directly to the receiving
Each of these plants is of the activated sludge type!
they vary somewhat in the^.r detailed process operations.
nnn ^reat"ment 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 cooling water used at the plant? 2nd which
S^ ™lat±Vfly ,10W Concentrations of BO^T and suspended
solids. The waste water influent to the treatment plant contains
over 3,000 mg/1 of COD and 700 mg/1 of suspended spliS?
. ' „!„ 1 ,....;. . -• . .„,. i1 , ' . - " !(»': •! i : 'i'- '.;'., i1'- >''•.•:' - *' "' - '• ' •''* i '< !"','!, ...... i," ' :>ia'. :' ' " '-' '" -•'
The tre^tment^ sequence itself consists of complete-mix
jJU^;^Jecon5ary Clarification, aeration in two lagSns
iS Jbt! ' an? clorin^ion- No primary clarification 'is provided
in this system. The activated sludge basin provides up to 48
? tentlonf,and the two lagoons following the secondary
prov?-de »P to 16 d^ys additional retention. The first
nnn — 1S --Y aerated' while the last portion of the
second basin is quiescent to provide additional settling.
follows^ characteris-tfcs from this treatment facility are as
Average Range
ma/1 mg/l
BOD5
COD
Suspended Solids,
35
266
169
6-95
102-525
, 8-372
of
f high susPended solids content in the effluent
S°m^ algae growth in ^e lagoons. Thf iatSr4
wastes, however, tends to generate solids
problems in treatment systems. At thi time of the
program at; Plant A, the treatment facility was in an
lt°n eviden^ed bY heavily bulking sludje in thS
H r; ' DUring this Period of ^me' effluent BOD?
from the treatment plant averaged 444 mg/1 with a suspended
solids content of 2:13 mg/1. such upsets are common to all
treatment plants in the corn wet milling industry, and various
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reasons for them have been hypothesized including shock loads of
sugars, specialty starches^ and acids or alkalis.
In terms of 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
another 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 l.Olmgd) containing 1,400 mg/1 of BOD,
'2,10-0 mg/1 of COD, and 350 mg/1 of suspended solids. Once-
through cooling water containing some barometric condensate is
discharged to the receiving wate'r without treatment.
The aerated equalization; basin provides 24-hour retention to
equalize waste load and pH fluctuations. In the summer, the
discharge in the equalization basin may be passed over a cooling
tower in order to reduce the temperature prior to the activated
sludge process. Plant B was designed on the basis of a fop.d-to-
microorganism ratio of 1.1 to 1.75 in terms of CODtMLSS '(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
biological solid.
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 d£te has been well above these effluent levels, in spite of
many modifications to operating procedures. Evaluations by
Environmental Protection Agency personnel indicate that the plant
was overloaded initially with a food-to-microorganism ratio of
0.8 in terms of BOD:MLSS. Effluent BOD5 and suspended solids
were usually several hundred mg/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 0.4. Effluent1
characteristics for €he last six months of 1972 were as follows:
i Average Range
mcr/1 _ma/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
! 83
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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
over 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 solids.
Because 'of its newness, only limited data are available on
effluent characteristics. Effluent BOD5. levels of 200 to HOC
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 to control
sludge bulking.
Pretreatment Plants- "| -
Of the four known pretreatment plants in the industry, three pro-
vide 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 mcjd.) .
About seven months of sampling of treatment plant characteristics
indicated; the following influent and effluent results:
Average Average
Influent Effluent
BOD5
COD
Suspended solids
84
III:
2,330
4,560
895
1,080
2,870
2,215
-------
Data taken during the sampling program for this study indicated
somewhat lower results on both influent and effluent. These
lower effluent values were ppssibly 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 equaliEation 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 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 watier and other wastes from the mill do
not go through this treatment plant. Effluent levels are
reported to be: generally iri the range of 500 mg/1 of BOD.
Results of' the sampling program were somewhat lower, as given
below:
Average Range
__ mcr/1
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 .
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Pilot Plant studies-
At least three new treatment or pretreatment plants are presently
under construction. Data on pilot plant studies for two of these
are available and discussed below, together with the design para-
meters for the third plant.
Plant G—Rather extensive pilot plant studies were run, using
one- and ; three-stage pure oxygen and air activated sludge
systems, on combined wastes from a medium 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 pilot 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 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 bio-
logical 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 ipromote the fungal growth, the system was
operated at a pH of 3.5 to 6.0. Influent BOD5 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. e- -
The results of the pilot plant studies have prompted the company
to construct a 3.0 mgd pretreatment plant, based on fungal diges-
tion. The system will consist of 24-hr equalization, pH
adjustment, fungal 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
more conventional biological treatment systems. There may be
86
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some advantage in terms of solids handling, inasmuch as the
fungal mass apparently can be removed more readily from the final
effluent. Plant I—Presently 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
BObiMLSS 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 BODJ5 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.
Sludge 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 corri 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.
1 i '•''•'.
Limited information is available on the handling of waste treat-
ment plant sludges in this industry, but it is know that several
plants return these solids!to the process stream, presumably for
animal feed. several .methods for accomplishing this can be
suggested including centrifugation, vacuum filtration, and direct
addition to evaporat9rs. ' ;;
It is imperative that sanitary wastes be segregated from process
wastes and' discharged separately to the municipal system, if
biological solids recovery!from the, process waste treatment plant
is to be practiced. Moreover, sterilization by heat or
chlorination may be required 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 house for use in
animal feeds.
87
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CORN 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 mg/1
of suspended solids. Flows from these mills are much smaller
o u thf indwstry is thought to be very limited, as most
SSJ ^S;har?e to Nunicipal systems. One known pretreatmlnt
plant is discussed in; this section.
lnz£lant_cpntrols
i ' . i ' \\ ''"•"..'•' ',- '- -; '-, • ••"•" •"-•%'•• "_ •
Waste waters can arise from only three sources in corn dry mills
namely, j:ar washing, com washing and air scrubbers. Car washing
and at only some mills and wiH not be
" • — - ,m, — Jt —•••••*•- • !*.*..•. ^ m^ V4JIJ.*_4 T» J_ .1.JL I
.. ,, further. ., Dry car cleaning techniques are now
SlSi^ ! .using vacuum systems to replace wet methods. AS
mentioned infection III, water is used in air scrubbers on
~"~="" extruders,.. Water from this source is excluded from
the document as it is not part of
Corn washing is performed by many, but not all, of the corn
™1?"^ S°m® S11S^ 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?
h»4- JSo 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 vet
been demonstrated. ( y
Waste Water Treatment
°nf Plan\ is nown to provide treatment for their process
waste waters. The treatment sequence consists of settling to re-
r i c°Y?r th^.hefYv solids for animal feed, followed by a plastic
•' SS?- trJCflng' fii^r -»a- Discharge to the municipal SyS?5m?
! Sampling data secured at this treatment plant are summarized
• I ' .'•']. .-••''..•• • •'--••-
i Average Average
! i Influent Effluent
; j mcr/1 __JS2/1
!"; BOD5 , . 2,748 608
t| COD .,. J . 4,901 2,983
,i| Suspended Solids ; 3,485 1,313
i -' . • ' ' •• '" . .' -••! "' 88
-------
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 less 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 Disposal
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 incor-
porated into animal feed.;
i
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 not be sgiven 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
quantities 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
municipal 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 characteristics range from about 250 to
500 mg/1 of BOD5 and 300 to UOO mg/1 of , suspended solids.
Effluent levels roughly equivalent to those achieved in well-
operated secondary minicipal sewage treatment plants should be
attainable.
89
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RICE MILLING
•.'(••
r±Ce millin^ involves no process waters and, hence
generates :no process waste waters, six mills parboil rice
waJLsPr°C;hS d06S reSUlt ±n m°*est amoul*s of Process
waters . These waste i waters are high in dissolved BOD
approximately 1,300 mg/1, but low in Suspended solIdsTaO: to 80
The waste water comes from the steeping process, and in-nlarn-
controls cannot be effected that will influent apprlciSlf ?h1
C5ara?ter -°f the wa=te waters. At least five" of7 the
- vriCe ^Plants Discharged their wastes to municipal
systems and no known treatment is practiced by any mill. once
again, however, the general nature of the wJste water in dicatSs
that it can be treated ; by biological processes in a similaJ
S^SrSlV0^ m±lli?gH?r 5UlgUr Product^n, inasmuch aS the 5^5
JL H ^ a soluble form- The rather constant character of
the waste stream should make it more amenable to stable treatment
* n than C03bl Wet '"iUing waste waters?
00 CTer ^feS' i'e<" fr°m 265 t0 76° CU "/«
?ke the wastes m«ch more manageable. it is
K - Jhe bi9logical solids from any tleatment procesl
could be included with the bran and hulls as animal feed? pr°°eSS
90
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SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
The following '• presents detailed cost estimates toy: the various
treatment ,alternatives and the rationale used in developing this
information. !
Data have been developed for investment, capital, operating and
maintenance, depreciation, land energy costs using various sources
including information from .'individual grain mills, Sverdrup &
Parcel files, and literatxire 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 ito 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.
'.fit'' '- . • ''"'• ..I''''
REPRESENTATIVE PLANTS |
Because of 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
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 15 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
91
-------
I 'I
53*
the con*ro1- facilities are estimated on the basis of
Capital costs
e o are calculated, in all cases, as 8 percent of
of ind^X™ i I S^ C°S*S- Consultations with representatives
Sat w??h and *he facial community lead to the conclusion
that, with the limited data available, this estimate is
reasonable for this industry. estimate is
Depreciation
Straight-line depreciation for 20 years, or 5 percent of the
total investment cost, is used in all cases. .
Operation and Maintenance Costs
mainj?nanfe cost? include labor, materials, solid
™ oo ' effluent monitoring, added administrative
expense, taxes, and insurance, when the control technology
JS^?S T r^reCyCi:Lng' a °redit of $0-30 Per i'000 gallons iJ
applied to reduce the, operation and maintenance costs! Manpower
requirements are based upon information supplied bv the
representative plants as far as possible. A total salary cost of
SL S^ man:hour is used in all cases. The costs of .chemicals
used for maintenance and operation.
Energy and Power Costs
Power costs are estimated on the basis of $0.025 per kilowatt-
COST INFORMATION
??h i"vesjment 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
:92
-------
Corn Wet Milling
As a basis for developing control and treatment cost information,
a medium-sized corn wet mill, with a daily grind of 1524 kkg
(60,000 SBu) was synthesized. This hypothetical plant practices
good in-plant control and uses recirculated cooling water. The
waste water char act eristic;s 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)
BODS 7.14 kg/kkg (400 Ibs/MSBu) 960 mg/1
Suspended solids 3.57 (200 Ibs/MSBu) 480 mg/1
A number of alternative treatment systems are proposed to handle
the waste waters from this hypothetical mill. The investment and
annual cost information for each alternative, and the resultant
effluent qualities are presented in Table 15. The specific
treatment technologies are described in the following paragraphs.
Alternative A — Activated Sludge
This alternative provides for grit removal, pH adjustment,
nutrient addition, complete-mix activated sludge, secondary
sedimentation, and centrifugation for solids dewatering". The
treatment system does not include equalization or primary
sedimentation. Effluent BOD5_ 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 kg/kkg (63 to 104 Ibs/MSBu).
Costs. Investment costs of approximately $2,388,000.
i
Reduction Benefits. BODJ5 and suspended solids
reductions of about 80 and 58 percent respectively.
Alternative_ 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 pro-
posed in this alternative* Another similar facility provides
pretreatment for a third mill.
Costs. Incremental costs are approximately $156,000
over Alternatives for a total cost of $2,544,000.
93
-------
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Reduction Benefits^ BOD5 and suspended solids will be
reduced by about 90 and 80 percent respectively.
i
Alternative C — Equalization, Activated Sludge, and Stabilization
Lagoon :
For Alternative C, a stabilization basin following secondary
sedimentation is added to -the preceding treatment system. This
stabilization. lagoon will provide 10-day detention for
stabilizing the remaining BOD5 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 BPD5 and suspended solids are expected from Alternative
C. The resultant effluent, waste load will be 0.223 to 0.447
kg/kkg (12.5 tp 25.0' Ibs/MSBu) for both BOD5 and suspended
solids.
Costs. Incremental costs of approximately $288,000
over Alternative -B for a total cost of $2,832,000.
Reduction Benefits'. BODJ5 and suspended solids reductions
of about 95 and 90 ;percent respectively.
Alternative 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
tp effluent loads of 0.15 to 0.22 kg/kkg (8.3 to 12.5 Ibs/MSBu)
of BOD5 and 0.07 to 0.15 kg/kkg (4.2 to 8.3 Ibs/MSBu) 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. . "',
95
-------
T -m~ ss -s
-fu( Ibs/MSBu) for both constituents. NO treatment
in the entire industry provides this level of treS?men??
°f approximately $1,244,000
C Or D f- - total -st of
oaou9n S°DS an\susP^ded solids reduction
or^afcout 99.5 and 99.0 percent respectively. The
effluent should be suitable for at least partial
M£ernatiye_F — Equalization, Activated Sludge, Deep Bed Filtra-
tion, Activated carbon Filtration, and Reverse
Osmosis
^•«tSSST?fSTt^;«ss?Stgf92J;SS!:C00
™=?ti°n^enef^S* BOD5 and suspended solids reductions
equal to those in Alternative E, i.e., 99.5 and 99 o
The ef f luent should be
Alternative..6 — Recirculating Cooling Water System
recirculating cooling water systems. CompSraSJ siJSI
using once-through cooling waters will be confronted with
additional cost of installing cooling towers to reduce to
waste water flows. -'A separate cost has been developed for such
of about
Cost. Incremental costs of adding a coolina tower are
approximately $288,000. ^-M.Any -cower are
96
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Corn Dry Milling
3(
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. The investment and annual cost information for each
alternative, and the resultant effluent qualities are presented
in Table 16. This synthesized plant generates a waste water that
reflects actual industry practice as follows:
Flow 492. cum/day (130,000 gpd)
BQD5 1.13 kg/kkg (63 Ibs/MSBu) 1750.mg/1
Suspended Solids 1.61 (90 Ibs/MSBu) 2500 mg/1
Alternatiye_A — Primary Sedimentation
This alternative consists only of primary sedimentation and
reduces the BQD5 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 solids. 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.
Alternative 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) for both pollutant parameters.
Costs. Incremental costs of approximately $271,000 over
Alternative A for;a total cost of $291,000.
Reduction Benefits BOD5 and suspended solids reductions
of about 94.3 and 96.0 percent respectively.
Alternative C — 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 t!o 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. BOD5 and suspended solids reductions
of about 97.4 and 98.2 percent respectively.
97
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Alternative D — Primary Sedimentation, Activated Sludge, and
Deep Bed Filtration
Deep bed filtration following the activated sludge system
comprises this alternative. The concentration of BOD5 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 BOD5 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. BOD5 and suspended solids reductions
of about 98.6 and 99.4 percent respectively. -
Alternative E — Primary Sedimentation, Activated Sludge, Deep Bed
Filtration, and Activated Carbon Filtration
The final alternative presented herein adds acitvated carbon fil-
tration to the activated sludge - deep bed filtration system of
the previous alternative.; Treated effluent quality is expected
to be 5 mg/1 of both BOD5 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. BODJ5 and suspended solids reductions
of about 99.7 and 99.8 percent respectively
Wheat Milling (Bulgur) :
Inasmuch as ordinary wheat milling usually generates no process
waste waters, this discussion will be limited to bulgur
production. The investment and annual cost information for each
alternative, and the resultant effluent qualities are presented
in . Table 17. The synthesized bulgur mill is of medium size, 203
kkg/day (8000 Sbu/day) and discharges waste waters with the
following characteristics:
Flow
BOD5
Suspended .Solids
56-. 7 cu m/day
0.104 kg/kkg
0.093 kg/kkg
<15,OPO gpd)
(6.25 Ibs/MSBu)
(5.62 Ibs/MSBu)
400 mg/1
360 mg/1
Alternative A — Activated Sludge
The first alternative provides an activated sludge (extended
aeration) system with nutrient addition and secoqdary
sedimentation. No primary sedimentation is provided because of
the low flows. Moreover, it is anticipated that factory built or
99
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TABLE 17
TYPICAL' PLANT
RATER EFFLUENT. TREATMENT COSTS
• • WHEAT (JiULGAR) MILLING
Treatment or Control Technologies Identified
under Item III of the Scope of Work:
Investment
Annual Costs:* .
Capital Costs ;
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
Total Annual Cost*"
Costs in thousands of dollars
'Effluent Quality-
Effluent Constituents
•Parameters ; . (Units)
BOD ' ;
Suspended Solids
' kg/Kkg
BOD
•Suspended Solids
A
$24.2 ; .
2.0
i-2
6.7
2.5
11.4
1
$93.
7.4
4.7
12.7
'3
27.8 .
fi
$380
30.4
19
20.5
4.5
. 74.4
mg/l
Raw
Waste
Load
0.104
0.093
400
360
Resulting Effluent
Levels
0.0078
0.0078
30
30
0. 0027-0. 0052
0.0013-0.0027
10-20
5-10
0.0013
0.0013
5
5
TOO
-------
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 BOD5 and
suspended solids corresponding to 0.0078 kg/kkg (O.U7 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 of 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.
Alternative 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.BODS and
suspended solids or an effluent waste load of 0.0013 kg/kkg (0.08
Ibs/MSBu).
Costs. Incremental costs of approximately $287,000 over
Alternative B for' a total cost of $380,000.
Reduction Benefit. BOD5 and suspended solids reductions
of about 98.8 and 98.6 respectively.
Rice Milling (Parboiled^Ricel.
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) . The
investment and annual cost information for each alternative, and
the resultant effluent qualities are presented in Table 18. Raw
waste water characteristics are:
Flow 492 cu m/day (130,000 gpd)
BOD5 " 1.88 kg/kkg (0.188 Ibs/cwt) 1380 mg/1
Suspended Solids 0.075 kg/kkg (0.0075 Ibs/cwt) 55 mg/1
101
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102
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Alternative_A — 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
millfeed (animal feed). Treated waste water concentrations of
100 mq/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. BOD5 reductions of about 92.8 percent.
Alternative,! — 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 BOD5
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/qwt) . ,
'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.
AlternatiYg_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.•£or a total cost of $347,000.
Reduction Benefi€. BOD5 and suspended solids reductions
' of about 98.2 and 86,4,percent respectively.
Alternative,!) —'• 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 isiexpected to be 5 mg/1 of both BOD5
and suspended solids or an effluent waste load of 0.007 kg/kkg
(0.0007 Ibs/cwt) .
103
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T
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 TECHNOLOGIES
Air Pollution Control
With the proper operation of the types of biological treatment
systems presented earlier in this section, no significant air
pollution iproblems 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 odor 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
K . o? .grain milling waste waters will give rise to
substantial quantities of solid wastes, particularly biological
solids from activated, sludge or comparable systems. Several
avenues are available for the disposal of these solids including
^?hSi°? and^and^' .incin^tion, and other conventional
methods fo handling biological solids. Alternately, the solids
Can* x, 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
Section1?!! S°lldS recoverv and sludge disposal is contained in
Energy Reguir ements
The treatment technologies presently in use or proposed in this
document do not require any processes with unusually high enercrv
requirements. Power will be required for aeration, pumping?
centrifugation, and other unit operations. These requirements'
generally are a direct function of " the volume to be • treated
Thus, the greatest requirements will be in the corn wet milling
subcategory and the least in bulgur waste water treatment.
For the hypothetical treatment systems described previously in
Men3, S1fnA°n' ^he P°wer 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
. . 104
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105
!J
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' SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations that must be achieved July lr 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-house 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
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 and product mix;
d. the engineering aspects of the application of various
types of control 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 reliability 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 engineering and economic
practicability of the technology at the time of commencement of
construction or installation of the control facilities. :
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST
PRACTICABLE CONTROL 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 19. These values represent the maximum
107
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below.
of
o
av«rage 30-day values listed
Industry Category
and - - -•
Table 19
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Bulgur wheat flour
milling
Normal rice milling
Parboiled rice milling
BOD5
kg/kkg Ibs/MSBu
Suspended Solids
kg/kkg Ibs/MSBu
0.893
0.071
50.0
4.0
0.893
0.062
50.0
3.5
(pH 6-9 all subcategories)
No discharge of process waste waters
0.0038 0.5 0.0083 0 5
No discharge of process waste waters
0.0.14 0.080 0.008
*Maximum average of daily values for
any period of 30 consecutive
CONTROL TECHNOLOGY CURRENTLY
implement the specified^SSLt fJSjSj?1^1 means available to
for each subcategory. e±fluent limitations are presented below
CQrn_Wet Milling
SS
plant modifications and biological wi!L ll\ln°lude both in~
follows: f uioiogicai waste water treatment as
1- ?Sa?ment.and COllectin9 the major waste streams for
2. Eliminating
cially from
_,v,_ , ~— f^v^i.^4. emu syrup evaporators Thi«5
. ^r^bs4»^-sjsssttsgss.?si-
'108'
-------
I- 1
3.
5.
6.
7.
condensers with surface condensers.
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.
Diking of all process areas subject to frequent spills in
order to retain lost product for possible reuse or by-
product recovery.
Installing and maintaining modern entrainment separators
in steepwater and syrup evaporators.
Monitoring the major waste streams to identify arid control
sources of heavy product losses.
Providing extensive waste treatment for the resulting
process waste waters consisting of: flow and quality
equalization* neutralization, biological treatment, and
solids, separation. The biological treatment methods
available include Activated sludge, pure oxygen acti-
vated sludge, bio-discs, and possible combinations of
other biological systems.
Corn Prv 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. Biological treatments using activated sludge or a com-
parable system. .
4. Final separation of solids by sedimentation prior to
• discharge. .
• f '• . ' *
Wheat Milling <
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.
109
-------
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. Biological treatment using activated sludge or a
comparable system.
3. Final separation of solids by sedimentation prior to
discharge.
- Rice 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
to discharge,
RATIONALE' FOR THE SELECTION OF BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
Corn Wet Milling
Cost of Application-
Data developed on the cost 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 Production Facilities- : ;
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.
no
-------
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 loads. 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 place some restraints on the
ability of a particular plant to implement some 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 order to reflect the effect
of plant size. The control technologies discussed in Section
VII, however, are applicable to all mills regardless of size.
Production Processes-
The basic processes employed in corn wet mills are essentially
uniform throughout this segment of the industry. From corn un-
loading through basic starch separation, the production methods
are quite standard although slightly different types of equipment
may be used at the various.mills.
Product 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 charac-
teristics 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 lability of the mill to implement the best practical
control technology currently available.
Engineering Aspects of Application-
! m
-------
5S
" ,Mthou* treatment p uses do
met the and operated system should be able ' to
meet the effluent limitations developed in this document it
least one mill presently meets these effluent limitations n,i™
an overall industry basis, these effluent
will result in a BOD5 reduction^ of aiprSlSaJelv SB
to 90 percent and 85 percent reduction of suspended SSliS? Y
The concentrations of contaminants in the waste waters
plants usmg once-through barometric cooling waSJ aS fn
an?e'/-e- approximatSly 250 to nfo mg/1 o
g/1 °f susPen<3ed solids, as shown in Table
s Jss^.s^yiSS
™ m^icipal plants should be ahvble
proper treatment of these wastes, in establishing the effluent
reduction attainable, as presented in Table 19, therefore Sn
"lor" ^3°^1 °f -^ susPend^ soliJs'anfloSf'wS
r Thf Lv^ Plf^f.^xng once-through contaminated cooling
water. The levels established in Table 19 are
of 20 tS^B
rcirutdo-
recxrculated coolxng
process water sources and use
systems. The effluent waste
112
-------
concentrations, therefore, ,are much hicrher than fnr- +h^,~ i ^
be on +S £ aSf d °n the Present total waste water flow will
Process
xmpact For example, , the power requirements for
€S P^acticable control technology currently
6 «*» estimated to be
Corn Dry Millirig
Cost of Application-
113
-------
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 Production Methods-
The^pnly source of process waste waters in corn dry mills is the
washing operation (water from air scrubbers on extruders and
expanders are not covered by these guidelines). 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.
Engineering Aspects of Applicatign-
Few, if any, corn dry mills provide extensive waste water treat-
ment with discharge direqtly 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 demon-
strated 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 19. 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
BOD5 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 BOD5 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.
Non-Water Quality EnviT-onmg»Ti-t-ai Tmr^t-
ntal impac
guired f 02
compared to the total
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 tota]
114
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energy requirements for a corn dry mill and, therefore, the
impact of the control facilities is considered insignificant.
Wheat Milling
' * ' - - "- ' ' ' l
The only process waste water in wheat milling arises from the
tempering operations used in bulgur flour production. No cor-
relation 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 mate-
rial 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 to 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 19.
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.
Non-water quality environmental impact will be restricted to a
small increase in power consumption for the treatment plant.
These power needs are minimal and not of major significance.
Rice Milling , •
Waste waters from the production of parboiled rice represent the
only source of process waste waters in rice milling. The charac-
teristics 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 goal. 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
115
-------
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 BOD5 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 19 will achieve about 90
to 95 percent BO D5 reductions and result in a treated waste water
containing about 100 mg/1 of BOD5 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,
'* ' I ,-''•• •', '-...-.'-•, - *-• * i,j- ..'.,„."
RESTRAINTS ON THE USE OF EFFLUENT LIMITATIONS GUIDELINES
j The effluent limitation guidelines presented above can generally
;f ! be aPPlie
-------
onsy
occur that result in higher BOD5 and suspendedoliS discEargel
the1" t^Jf11'. While the in'Plant edifications and controls^
S^H J?eatinent sequence defined as best practicable control
technology currently available will minimize these upsets?
sr
day
for both BOD5 and suspended solids.
117
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION '.
i : '.
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 applicationJ
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
costs 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 REDUCTION 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
119
-------
reductions attainable through the application of the best
available technology economically achievable are those presented
in Table 20. 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 20 .
' , 'i ..-•"••-: . ' . : .••,;.'. . • ....
Effluent Reduction Attainable Through the Application of
Best Available Technology Economically Achievable*
Industry
subcateqory
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Bulgur wheat flour
milling
Normal rice milling
Parboiled rice milling
BOD5
kg/kkg Ibs/MSBu
Suspended Solids
kg/kkg Ibs/MSBu
0.357
0.0357
20
2.0
0.179
0.0179
10
1.0
No discharge of process waste waters
0.0050 0.3 0.0033 . 0.2
No discharge of process waste waters
0.070 0.007 0.030 0.003
(pH 6-9 all subcategories)
*Maximum average of daily values for any period of 30 consecutive
days
IDENTIFICATION OF
ACHIEVABLE
BEST AVAILABLE TECHNOLOGY ECONOMICALLY
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 bio-
logical 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. : ' :-
f . _,_.•*
'/ ~ • / "
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.
120
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Ifft-'-
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.
RATIONALE FOR THE SELECTION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE
Corn Wet Milling
Cost of Application-
As presented in Section VIII, the investment cost for providing
the best 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 on operating,
maintenance, power, and other costs is contained in Section VIII.
Acre, SizeT and Type of ^Production 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.
Engineering Aspects of Applicatign-
The control technologies ispecified herein have not been fully
demonstrated in any segment;of the grain milling industry. The
basic 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 BOD5 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.
121
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•• •.»; •"
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. ,:;.., :,
recognized /.that - the soluble BOD5 level in some of the:
-*..£-• generate concentrated .waste streams may; not permit
attainment of BOD5 levels represented by the values in 'Table 20 ^
using only end-of-process treatment, it is expected that the in-
plant control measures that have been recommended 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. • • : ' ; .-' • ' '-•• -}' -~; '••- ; '<•-..- '••'•• • ..•:< o •-;;-,...'...- :,...-.
In summary, the combined effect of the application of the best
available technology economically achievable:'and'application:,.oft
ax± practicable in-plant control measures, should permit the corn
wet mills to meet the effluent levels presented in: Table 20. -
Process ChanqfeS-
LC process changes will be necessary to implement tliege
w"^?i -technologies. In fact, many of the in-plant
modifications _have already been made by some corn wet^'mills. ^ ' '
Non-Water puality_
^^of«S±6aH?n ?f 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
oof i 1S 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. fj-^^
Corn Dry Milling ! •
The cost of applying,, the best available technology economically
achievable, 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
122
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system are small compared to the overall production demands.
Other environmental considerations will not be affected by the
application of; this control technology.
Wheat Milling
The best available technology economically achievable can be ap-
plied 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 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.
Rice Milling (Parboiled
Application of the specified best available control technology
economically 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.
123
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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 of 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 "no 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 21.
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. '
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.
125
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Table 21
New Source Performance Standards*
Industry
subcategory
BOD5
kg/kkg Ibs/MSBu
Suspended Solids
kg/kkg Ibs/MSBu
Corn wet milling
Corn dry milling
Normal wheat flour
milling
Bulgur wheat flour
milling ;
Normal rice milling
0-357 20 0.179 10
0.0357 2.0 0.0179 1.0
No discharge of process waste waters
0.0:050 0.3 0.0033 0.2
No .discharge of process waste waters
0.030 0.003
0.007
<
Parboiled rice milling 0.070
(pH 6-9 all subcategories)
^Maximum average of daily values for any period of 30 consecutive
RATIONALE FOR THE SELECTION OF NEW SOURCE PERFORMANCE STANDARDS
The specific , control technologies to meet the new
performance standards are not presented in this . document, it has
d?™/ ka?lccPr!:*iSe' however, that all of the ih-plant controls
discussed xn Sectxon VII would be incorporated in a new mill, m
addxtxon, the end-of-process treatment system is to be equivalent
aoh^ MSUgge»ted f?r.the best control "technology economically
achxevable. Recognxzing 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 ^n-plant
controls and the new treatment technology will meet the new
source performance standards. Factors considered in developing
these standards are summarized in the following paragraphs.
Production
The basic production process used in corn wet milling cannot be
sxgnxficantly altered. The industry has historically ^Sn very
aggressxve xn developing and utilizing new production technology.
Whxle new plants will undoubtedly incorporate some new or
^r°T ed.tv?es of equipment, the basic process, will remain
largely xn xts present" form .for the foreseeable future.
' " '*„••-- ' "
Operating Methods
Plants offer the possibility of instituting better operating
o e1Ss;?n/?;P^tCOntr0lS- .Without the Physical constraint!
Sf ™ 5 "g ?aciflties' essentially all of the in-plant controls
dxscussed xn Sectxon VII can be implemented. Instrumentation is
126
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also available to improve plant operation and reduce accidental
waste discharges. Greatly reduced waste loads should be attain-
able by these and other in^plant improvements.
'.-,,-• »
Engineering Aspects of Applicatign-
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 BOD5 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
source performance standards, as given in Table 21. 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 Operations-';
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
subcategoryv but no additional .improvements that would have a
major impact on the waste water discharges have been developed.
By-Product Recovery- '.'•-•
By-product recovery has long been practiced in corn wet mills.
Application of the best in-plant controls will undoubtedly in-
crease by-product recovery, but will probably offer no new
recovery avenues. ,
Corn Dry Milling ' "' '
The new source standards for corn dry mills are based ori 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 other 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.
127
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. i -i ,„: . ,,..,-
Barring a total changeover to dry cleaning methods, little can h^
.accomplished in reducing total plant waste loads? in-Sant
controls and operating,methods may reduce total flows, but will
not appreciably affect;the total quantities of contaminants.
The effluent levels to be achieved under the new s
performance standards for bulgur production also rSflec?
SS1^0? of ^ beSt availabl* end-of-process technology as
described in Section x. The basic production process requires
S0akin? (or cooking) and this single Source of process
°annKt b€ ^limina*ed. Operating methods, in-plln?
.by-Product recovery will not influence procelS
n except perhaps in terms of quantity of waste water?
Some by-product ^recovery, i.e., the use of biological treatSnt
of
Rice Milling (Parboiled Rice)^
wate:Fs ^n Parboiled rice production originate from
a ho-erati0nT ™S Un±t °Perati°n is integral lo S5
faJ1?..ParJolling. process and cannot be eliminated or changed
significantly. Likewise, in- plant controls and operating methods
can reduce the total waste water flow in some instance's/bSt no?
the total amount of pollutants. The new source standards of
performance, therefore, provide for the application of the best
SSX 5 technology economically achiS?able aS described In
!;^XOn^X- Eecovery of biological solids from the treatment
system for use in animal feed is envisioned. ™«rrc
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SECTION XII
ACKNOWLEDGMENTS
The Environmental Protection Agency wishes to acknowledge the
contributions to this project by Sverdrup & 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 David
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. Brown, Mr. R. C. Brandquist, Mr. F. W. Velguth, and
Mr. G. R. D. Williams of CPC International Inc;
Mr. Donald Thimsen of General Mills;
Mr. E. M. Eubanks, Mr. R. Roll, 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. Homan 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. f ;
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 Hansborougn, Patricia Dugan, Max Cochrane, Linda
Huff, Arlein Wicks, Reinhold Thieme, Taylor Miller, Kenneth
Dostel and Gilbert Jackson* '
129
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SECTION XIII
REFERENCES
1. Bensing, H. O. and Brown, D. R., "Process Design for Treatment
of Corn Wet Milling Wastes," Proceedings Third National^
Symposium of Food Processing^Wastes, New Orleans, Louisiana,
March 28-30, 1972.
2. Bensing, H. O., Brown, D. R., and Watson, s. A., "Waste Utili-
zation and Pollution Control in Wet Milling," American
Association of Cereal Chemists, Dallas, Texas, October
13, 1971.
3. "CRA 1973 Corn Annual," Corn Refiners
I
Washington, D. C., 1973.
4. Church, B. D., Erickson, E. E., and Widmer, C. M., "Fungal
Digestion of Food Processing Wastes," Food Technology,
36, February, 1973. '
5. Church, B. D., Erickson, E. E., and Widmer, C. M., "Fungal
Digestion of Food Processing Wastes at a Pilot Level,"
Seventy-second National Meeting, American Institute of
Chemical Engineers, St. Louis, Missouri, May 21-24, 1972.
6. Consolidated Feed Trade Manual and Grain,Milling_Catalog,
National Provisioned, Inc., Chicago, Illinois, 196U.
7. Crop Productionf 1972 Annual Summary, Crop Reporting Board,
Statistical Reporting Service, U.S. Department of
Agriculture, Washington, D. C., January 15, 1973.
8. current Industrial Reports, Flour Milling Products, Bureau
of the Census, U.S. Department of Commerce, February,
1973.
9- Flour Milling Products - Current Industrial Reports, U.S.
Department of commerce. Bureau of the Census, Industry
Division, Washington, p. C., February, 1973,
10. Gehrig, Eugene J., "Mounting Tide of 'Bulgur' Pacific wheat
Specialty Rolls Out from Seattle Mill," American Miller
and Processor,' December, 1962.
11. Inglett, G. E., corni Culture^ Proces s ing, Products, AVI
Publishing Company, Inc., Westport, Connecticut, 1970.
12. Matz, Samuel A., Cereal Technology, AVI Publishing Company,
Inc., Westport, Connecticut, 1970.
13. "New Wheat Processing Plant in Hutchinson Set for Export
Trade," American Miller and Processor, January, 1963.
-------
!*• 1967-Census of Manufacturers, Grain Mill_PrgdmrhRr U.S.
Department of commerce. Bureau of the Census, Auqust,
1970.
* -
15. Parolak, G. M., "Field Evaluation of Aerated Lagoon Pre-
Treatmeht of Corn Processing Wastes," M.S. Thesis,
Purdue University, December, 1972.
16. Patent. #2,884,327, Method of Processing wheat. D. H. Robbins.
Fisher Flouring Mills. v
17. Polikoff, A. and comey, D. D., "American Maize-Products
Company - Preliminary Report", Businessmenforthe
Public Interest. Chicago, Illinois, May, 1972T~
18. Progress Report Summary^ Air Products and chemicals Pilot
Plant Studies^ 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, lowa^" Stanley Consultants, 1968.
20. Seyfried, c. F., "Purification of Starch Industry Waste Water,"
. Proceedings_Qf_the 23rd Industrial Waste conference,
Purdue University, Lafayette, Indiana, May 7-9, 1968.
i
21. Smith Robert, Cost_c-f Conventional and Advanced Treatment of
Waste Waters, Federal water Pollution Control Administration,
U.S. Department of the Interior, 1968. i
22. Smith, Robert and McMichael, Walter F., Cost_and_Performance
Estimates for Tertiary. Waste Water Treat^n^jPr^r-^ggogT"
Federal Water Pollution Control Administration, U.S~
Department of the Interior, 1969.
23. "United States Statistical Summaries," The Northwestern
Miller, Volume 278, No. 9, Minneapolis, Minnesota,
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," Environmental Protection Agency,
Cincinnati, Ohio^, May, 1972. '
25. Willenbrink, R. V., "Wast^ Control and Treatment by a Corn and
Soybean Processor," Proceedin2s_of_the_22nd_Industrial
Waste Conference. Purdue UniversityT 517, 1967.
26. Witte, George c.. Jr., "Rice Milling in the United states,"
Bulletin - Association of Operative Millers, 3147-3159
February^ 1970. '
27. World Rice Crop Continues Decllrvgr U.S. Department of Agri-
132! ' :
-------
culture,Foreign Agriculture Circular FRI-73, Washington,
D. C., February, 1973. •
133
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SECTION XIV
GLOSSARY
1. Aspirators ,
Milling machine equipment that separates loosened hulls from
the grain.
2. Bran, Rice
The pericarp or outer cuticle layers and germ of the rice
grain. .
3. Bran.i Wheat
The several-layered covering beneath the wheat husk that
protects the kernel.
4. Brown 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. Bulgur
Wheat which has been parboiled, dried and partially debranned
for later use in either cracked or whole grain form. (Wheat
Flour Institute, 1965.)
6. Corn Starch
Substance obtained from corn endosperm and remaining after
the.removal of the gluten.
7. Corn_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.
9. Endosperm
The starchy part of the grain kernel.
10. Germ
The young embryo common to grain kernels (e.g., corn, wheat).
135
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High protein substance found in the endosperm of corn and
tj&ea-t grain.
12. Hulls
The outer covering of the corn and rice kernel. The rice
hull is normally called the lemma.
13. Middlings
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.
15, Parboiled Rice
Rice which has been treated prior to milling by a technical
process that gelantinizes the starches in the grain. (Rice
Millers Association, 1967).
16« Pearlers (Whitener, Huller) ,
Rice milling machine equipment employed to remove the coarse
outer layer of bran from the germ. .
17. Rice Polish
\ f ,
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.
136
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I
I*
METRIC UNITS
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)
ENGLISH UNIT ABBREVIATION
acre • ac
acre - feet ac ft
British Thermal BTU
Unit
British Thermal BTU'/lb
Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic laches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds .
million gallons/day
mile.
pound/square inch
(gauge)
square feet '
square inches \
tons (short)
yard yd
'by
CONVERSION
0.405
1233.5
0.252
0.555 '
TO OBTAIN (METRIC UNITS)
ABBREVIATION METRIC UNIT
ha
cu m
kg cal
kg cal'/kg
cfm
cfs
cu ft
cu ft
cu in
•«F
ft
gal
gpm
hP_
in"
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
0.028
1.7
0.028
28.32
16.39
0.555 (°F-32)*
... 0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609 .
(0.06805 psig +1)*
0.0929
6.452
0.907
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
atm
sq m
sq cm
kkg
0.9144
hectares
cubic meters
kilogram-calories
kilogram calories7
kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
kilowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres
(absolute)
square meters
square centimeters
metric tons
(1000 kilograms)
meters :--
*Actual conversion,1 not a multiplier
pounds/hundred weight cwt
standard bushel, corn
(56 Ibs) SBu
standard bushel, wheat
(60 Ibs) SBu
10.0
25.4
27.2
kilograms/metric ton
kilograms
kilograms
*U.S. GOVERNMENT PRINTING OFFICE: 1974 546-319/390 1-3
137
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