DEVELOPMENT DOCUMENT
FOR
EFFLUENT LIMITATIONS GUIDELINES
\M
STANDARDS OF PERFORMANCE
THE CONCRETE PRODUCTS INDUSTRIES
Contract No: 68-01-2633
Prepared for
Effluent Guidelines Division
Office of Water & Hazardous Materials
U.S. Environmental Protection Agency
Washington, DC 20460
AUGUST 1975
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Notice
The attached document is a DRAFT CONTRACTOR'S REPORT. It
includes technical information and recommendations submitted
by the Contractor to the United States Environmental
Protection Agency (EPA) regarding the subject industries.
It is being distributed for review and comment only. The
report is not an official EPA publication and it has not
been reviewed by the Agency.
The report, including the recommendations, will be under-
goincr extensive review by EPA, Federal and States Agencies,
public interest organizations, and other interested groups
and persons during the coming weeks. The report and in
particular the contractor's recommended effluent limitations
guidelines and standards of performance is subject to change
in any and all respects.
The regulations to be published by EPA under Section 304 (b)
and 306 of the Federal Water Pollution Control Act, as
amended, will be based to a large extent on the report and
the comments received on it. However, pursuant to Sections
304 (b) and 306 of the Act, EPA will also consider
additional pertinent technical and economic information
which is developed in the course of review of this report by
the public and within EPA. EPA is currently performing an
economic impact analysis regarding the subject industries,
which will be taken into account as part of the review of
the report. Upon completion of the review process, and
prior to final promulgation of regulations, an EPA report
will be issued setting forth EPA's conclusions concerning
the subject industries effluent limitation guidelines and
standards of performance applicable to such industries.
Judgments necessary to promulgation of regulations under
Sections 304 (b) and 306 of the Act, of course, remain the
responsibility of EPA. Subject to these limitations, EPA is
making this draft contractor's report available in order to
encourage the widest possible participation of interested
persons in the decision making process at the earliest
possible rime.
The report shall have scanning in any EPA proceeding or
court proceeding only to the extent that it represents the
views of the Contractor who studied the subject industries
and prepared the information and recommendations. It cannot
be cited, referenced, or represented in any respect in any
such proceedings as a statement of EPA's views regarding the
subject industries.
D.S, Environmental Protection Agency
Office of Watei «nd Hazardous Materials
Effluent Guidelines Division
Washington, D.C. 20460
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QRJWFT
DEVELOPMENT DOCUMENT
FOR
EFFLUENT LIMITATIONS GUIDELINES
AND
STANDARDS OF PERFORMANCE
THE CONCRETE PRODUCTS INDUSTRIES
UJ
(3
T
This is a Draft Contractor's
Report prepared for EPA under
Contract Number Number 68-01-2633
Effluent Guidelines Division
Office of Water & Hazardous Materials
U.S. Environmental Protection Agency
AUGUST 1975
DRAFT
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ABSTRACT
This document presents the findings of an extensive study of
the concrete products industries for the purpose of
developing effluent limitations guidelines for existing
point sources and standards of performance and pretreatment
standards for new sources, to implement Sections 301, 304,306
and 307 of the Federal Water Pollution Control Act, as
amended (33 U.S.C. 1551, 1314, and 1316, 86 Stat. 816 et.
seq. the "Act") .
Effluent limitations guidelines contained herein set forth
the degree of effluent reduction attainable through the
application of the best practicable control technology
currently available (BPCTCA) and the degree of effluent
reduction attainable through the application of the best
available technology economically achievable (BATEA) which
must be achieved by existing point sources by July 1, 1977
and July 1, 1983, respectively. The standards of
performance and pretreatment standards for new sources
contained herein set forth the degree of effluent reduction
which is achievable tnrough the application of the best
available demonstrated control technology, processes,
operating methods, or other alternatives.
Based on the application of best practicable technology
currently available, 1 of the 7 production subcategories
under study can be operated with no discharge of process
wastewater pollutants to navigable waters. With the best
available technology economically available, 5 of the 7
production subcategories under study can be operated with no
discharge of process wastewater pollutants to navigable
waters. No discharge of process wastewater pollutants to
navigable waters is achievable as a new source performance
standard for all production subcategories except concrete
products (Not Elsewhere Classified), concrete pipe and
concrete products (Not Elsewhere Classified), precast and
prestressed.
Supporting data and rationale for development of the
proposed effluent limitations guidelines and standards of
performance are contained in this report.
10.1
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CONTENTS
Section
Abstract iii
I ccr-clusiotis 1-1
II RecomKtenfIcre:,Q;-s 11-1
III Industry Characterization III-1
Purpose and Authority III-1
S\x:nn?ar>/ of Methods Used for
^svelapTsent of Effluent
'%i,fixations Guidelines and
Staaaards of Performance III-2
Genercl Description of Industry
by [cV.-oduct III™8
Production iri this Segment 111-23
IV Industry Categorization IV™ 1
Introduction IV-1
Industry Categorisation IV-1
Factors Considered IV-2
V Water D'se and Waste Characterization V-1
Introduction V-1
Specific water Uses V-1
Process w&sta Characterization V-3
Rationale for Maximum Daily
Values V-88
VI Selection of Pollutant Parameters VI-1
Introduction VI-1
Significance and Rationale for
Selection of Pollution Para-
meters VI-1
Significance and Rationale for
Rejection of Pollution Para-
meters VI-4
VII Control ancl Treatment Technology VII-1
Treatment and Control Practices VII-2
Wast©water Treatment for
v
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Specific Concrete Products
Industries VII-5
Summary of Treatment Technology
Applications, Limitations and
Reliability VTI-32
Pretreatment Technology VII-35
Non-Water Quality Environmental
Aspects, Including Energy
Requirements VII-35
VIII Cost Energy and Non-Water Quality
Aspects VIII-1
Basis for Cost Estimates VIII-1
Cost Estimates for Industry
Subcategories VIII-4
Industry Statistics VIII-37
IX Effluent Reduction Attainable Through
the Application of the Best Prac-
ticable control Technology Currently
Available IX-1
General Water Guidelines IX-2
Process Wastewater Guidelines
and Limitations for the
Concrete Products Point
Source Subcategories IX-3
X Effluent Reduction Attainable Through
Application of the Best Available
Technology Economically Achievable X-1
General Water Guidelines X-3
Process Wastewater Guidelines and
Limitations for the Concrete
Products Point Source
Subcategories X-4
XI New Source Performance Standards and
Pretreatment Standards XI-1
Introduction XI-1
General Water Guidelines XI-2
Effluent Reduction Attainable by
the Best Available Demonstrated
Control Technologies, Processes,
Operating Methods, or Other
Alternatives XI-2
VI
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Pretreatment Standards XI-3
XII Acknowledgements XII-1
XIII References XIII-1
XIV Glossary XIV-1
vxx
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CONTENTS
LIST OF FIGURES
Figure
1 Production of Concrete Block and
Brick (Low Pressure Steam
Curing) V-5
2 Production of Concrete Block and
Brick (Autoclave Curing) V-10
3 Production of Culvert, Storm Sewer
and Sanitary Sewer Concrete Pipe V-15
4 Production of Concrete Pressure Pipe V-16
5 Distribution of Wastewater Hydraulic
Loads at Concrete Pipe Plants V-22
6 Production of Precast and Prestressed
Concrete Products V-26
7 Distribution of Wastewater at Precast
and Prestressed Concrete Products
Plants V-32
8 Production of Ready-Mixed Concrete in
Permanent or Portable Plants V-40
9 Distribution of Wastewater Generated
at Permanent Ready.-Mixed Concrete
Plants V~U<*
10 Distribution of Process Wastewater
Generated and Discharged at
Ready-Mixed Concrete Plants V-U7
11 Distribution of Effluents From
Ready-Mixed Concrete Plants
(NPDES Dataf V-tt8
viii
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CONTENTS
12 Distribution of Wastewater Generated
at Portable Ready-Mixed Concrete
Plants V-61
13 Production of Ready-Mixed Concrete
at Mobile Plants V-66
m Distribution of Maximum to Average
Ratios of Suspended Solids in
Effluents from Concrete Products
Industries V-69
15 Belt Oil Skimmer VII-8
16 API-Type Oil Skimmer VII-9
17 Settling Rates For Concrete Fines
in Truck Washout VII-16
18 Series Settling Ponds VII-20
19 Series Concrete Basins With Straw
Filters VII-21
20 Sloped Slab Separation Basin VII-22
21 Filter Pond VII-24
22 Drag Chain Washer VII-26
23 Screw Washer VII-27
2H Double Screw Washer VII-29
25 Mechanical Screen Separator VII-30
26 Screw Washer and Screen for
Aggregate Separation VII-31
27 Amount of Acid Required For
Neutralization of Concrete
Wastewater VII-33
IX
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CONTENTS
28 Distribution of Loads of Ready-
Mixed Concrete Per Day
Per Truck VIII-21
29 Annual Operating Costs For
Wastewater Treatment at
Ready-Mixed Concrete Plants VIII-23
DRAFT
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LIST OF TABLES
Page
List of Concrete Products by SIC Codes 1-2
Recommended BPCTCA and BATEA
Limitations Guidelines For
Pollutants in Process Wastewater
For the Concrete Products
Industries II-2
II-2 Recommended New Source Performance
Standards II-3
III-1 Summary of Data Base III-5
III-2 Location of U.S. Concrete Operators 111-18
III-3 Production of Concrete Products 111-23
IV-1 Industry Categorization IV-2
V-1 Ready-Mixed 3273 - NPDES*
Application Data 1971 V-55, 56
VII-1 Total Wastewater from Concrete Pipe
Plants VII-7
VII-2 Total Wastewater from Prestressed
and Precast Concrete Plants VII-11
VII-3 Summary of Treatment of Central
Mixer and Truck Washout Water
in Ready-Mixed Concrete Plants VII-12
VII-U Summary of Treatment of Truck Wash-
off Water in Ready-Mixed
Concrete Plants VII-13
VII-5 Wastewater Treatment Technology
from Portable Ready-Mixed
Concrete Plants VII-14
K2.
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VII-6 Summary Treatment Technology,
Applications, Limitations,
and Reliability VII-34
VIII-1 Cost Analysis for a
Representative Plant -
Concrete Block and Brick
(High Pressure Autoclave
Curing) VIII-6
VIII-2 Cost Analysis for a
Representative Plant -
Concrete Block and Brick
(Low Pressure Steam Curing) VIII-8
VIII-3 Cost Analysis for a
Representative Plant -
Concrete Pipe (Small
Wastewater Volume) VIII-11
VIII-4 Cost Analysis for a
Representative Plant -
Concrete Pipe (Larger
Wastewater Volume) VIII-13
VIII-5 Cost Analysis for a
Representative Plant -
Precast and Prestressed
Products VIII-15
VIII-6 Cost Analysis for a
Representative Plant -
Permanent Ready-Mixed
Concrete (1) VIII-18
VIII-7 Cost Analysis for a
Representative Plant -
Permanent Ready-Mixed
Concrete (2) VIII-19
VIII-8 Value of Recovered Aggregate
and Disposal Cost of Cement
Sludge VIII-27
xii
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VIII-9 Cost Analysis for a
Representative Plant -
Portable Ready-Mixed Concrete VIII-38
XIV-1 Metric Units Conversion Table XIV-7
xixi
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SECTION I
CONCLUSIONS
For purposes of establishing effluent limitations guidelines
and standards of performance, the commodities in the
concrete products industries manufacturing point source
category were grouped in three categories. For reasons
explained in Section IV of this report, the three
commodities were further subdivided into seven production
subcategories.
Based on the application, of best practicable control
technology currently available, 1 of the 7 production
subcategories under study„ ready-mixed concrete mobile
plants subca-cegory,, can be operated with no discharge of
process wastewater pollutants to navigable waters. With the
best available technology economically achievable^ 5 of the
7 production subcategories can be operated with no discharge
of process wastewater pollutants to navigable waters0 No
discharge of process wastewater pollutants to navigable
waters is achievable as a new source performance standard
for all production subcategories except concrete products
(Not Elsewhere Classified), concrete pipe, and concrete
products (Not Elsewhere Classified), prestressed and precast
products.
This study includes 3 commodities in the concrete products
industries of Standard Industrial Classification (SIC) Codes
3271,3272, and 3273, with significant waste discharge
potential. Table 1-1 lists the commodities studied in this
report by SIC Code,
1-1
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
TABLE 1-1
LIST OF CONCRETE PRODUCTS BY SIC CODES
1. Concrete Block and Brick (3271)
2. Concrete Products, Not Elsewhere Classified (3272)
3. Ready-Mixed concrete (3273)
1-2
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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SECTION II
R E-OMMENDATIONS
The reconunended effluent limitations guidelines based on
best practicable control technology currently available
(BPCTCA), are no discharge of process wastewater pollutants
(defined in Section IX} to navigable waters for the ready-
mixed concrete, mobile plant production subcategory,,
The above effluent limitations guidelines are also
recommended as the best available technology economically
achievable (BATEA) and the new source performance standards
(NSPS) for this production subcategory.
The recommended effluent limitations guidelines based on
best practicable control technology currently available for
the remaining subcategories (not listed above) of the
commodities in the concrete products industries are listed
in Table II-1.
The recommended effluent limitations guidelines based on
best available technology economically achievable are no
discharge of process wastewater pollutants to navigable
waters for the following products (not already listed under
BPCTCA) :
concrete block and brick and ready-mixed concrete^
permanent and portable plants.
The effluent limitations guidelines based on best available
technology economically achievable for the remaining subca-
tegories (not listed above) of these industries are listed
in Table II-1.
The new source performance standards for those subcategories
other than for those for which no discharge of pollutants in
11-1
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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NOTICE: THfc.TE ARE TENTATIVE RECOMMENEATION3 BASED UPON
INFOKMATION TN THIK KKPOi
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process wastewater has been recommended are listed in
Table II-2.
The recommended pretreatment standards for existing sources,
which are users of a publicly-owned treatment works, for
incompatible pollutants as defined in Section XI, are the
same as the standard of performance for best practicable
control technology currently available listed above and in
Table II-1.
The recommended pretreatment standards for new sources,
which will become users of a publicly-owned treatment works,
for incompatible pollutants as defined in Section XI, are
the same as the standard of performance for new sources
listed above and in Table II-2.
TABLE II-2
Recommended New Source Performance Standards
Limitations
Subcategory Monthly Average Daily Maximum
concrete block and brick same as BATEA same as BATEA
concrete products (NEC) ,
concrete pipe same as BATEA same as BATEA
concrete products (NEC) ,
precast and prestressed
products same as BATEA same as BATEA
ready-mixed concrete,
permanent plant same as BATEA same as BATEA
ready-mixed concrete,
portable plant same as BATEA same as BATEA
ready-mixed concrete,
mobile plant same as BATEA same as BATEA
II-3
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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SECTION III
INDUSTRY CHARACTERIZATION
ls.3 PURPOSE AND AUTHORITY
The United States Environmental Protection Agency (EPA) is
charged under the Federal Water Pollution Control Act
Amendments of 1972 with establishing effluent limitations
guidelines which must be achieved by point sources of
discharge into the navigable water of the United States.
Section 301(b) of the Act requires the achievement by not
later than July 1, 1977, of effluent limitations for point
sources, other than publicly owned treatment works, which
are based on the application of the best practicable control
technology currently available as defined by the
Administrator pursuant to Section 304(b) of the Act.
Section 301(b) also requires the achievement by not later
than July 1, 1983, of effluent limitations for point
sources, other than publicly 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) to 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 6f pollutants which reflects 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. Section 304(b) of the Act requires the
Administrator to publish within one year of enactment of the
Act, regulations providing guidelines for effluent
limitations setting forth the degree of effluent reduction
attainable through the application of the best practicable
control technology currently available and the degree of
effluent reduction attainable through the application of the
best control measures and practices achievable including
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treatment techniques, process and procedure innovations,
operation methods and other alternatives. The regulations
proposed herein set forth effluent limitations guidelines
pursuant to Section 304(b) of the Act for the concrete
products point source category. Section 306 of the Act
requires the Administrator, within one year after a category
of sources is included in a list published pursuant to
Section 306 (b) (1) (A) of the Act, to propose regulations
establishing Federal standards of performances for new
sources within such categories. The Administrator published
in the Federal Register of January 16, 1973 (38 F.R. 1624),
a list of 27 source categories. Publication of an amended
list will constitute announcement of the Administrator's
intention of establishing, under Section 306, standards of
performance applicable to new sources within the concrete
products industries. The list will be amended when proposed
regulations for the concrete products industries are
published in the Federal Register.
2.0 SUMMARY OF METHODS USED FOR DEVELOPMENT OF EFFLUENT
LIMITATION GUIDELINES AND STANDARDS OF PERFORMANCE
The effluent limitations guidelines and standards of
performance proposed herein were developed in a series of
systematic tasks. The concrete products industries were
first studied to determine whether separate limitations and
standards are appropriate for different segments within a
point source category. Development of reasonable industry
categories and subcategories, and establishment of effluent
guidelines limitations and treatment standards requires a
sound understanding and knowledge of the concrete products
industries, the processes involved, wastewater generation
and characteristics, and capabilities of existing control
and treatment methods.
The products covered in this report are listed below with
their SIC designations:
a. Concrete Block and Brick (3271)
b. Concrete Products, N.E.C. (3272)
c. Ready-Mixed Concrete (3273)
This report describes the results obtained from application
of the above approach to the concrete products industries.
III-2
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DRMT
The survey and analysis covered a wxde range of processes,
products, and types of wastes.
IJL.I Categorization and Waste Load Characterization
The effluent limitation guidelines and standards of perform-
ance 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 wastewaters in the plant; and (2) the constituents of
all wastewaters including harmful constituents and other
constituents which result in degradation of the receiving
water. The constituents of wastewaters which should be
subject to effluent limitations guidelines and standards of
performance were identified.
2.2 Treatment and Control Technologies
The full range of control and treatment technologies
existing within each subcategory was identified. This
included an identification of each control and treatment
technology, including both in-plant and end-of-process tech-
nologies, which are existent or capanle of being designed
for each subcategory. It also included an identification of
the amount of constituents (including thermal) and the
characteristics of pollutants resulting from the application
of each of the treatment and control technologies. The
problems, limitations and reliability of each treatment and
control technology were also identified. In addition^ the
non-water quality environmental impact, such as the effects
of the application of such technologies upon other pollution
problems, including air, solid waste, noise and radiation
were also identified. The energy requirements of each of
the control and treatment technologies were identified as
well as the cost of the application of such technologies.
III-3
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2^.3 Cost Information
Cost information contained in this report was obtained
directly from industry during plant visits, from engineering
firms and equipment suppliers, and from the literature. The
information obtained from the latter three sources has been
used to develop general capital, operating and overall costs
for each treatment and control method. This generalized
cost data plus the specific information obtained from plant
visits was then used for cost effectiveness estimates in
Section VIII and wherever else costs are mentioned in this
report.
2.J1 Data Base
The data for identification and analyses were derived from a
number of sources. These sources included EPA NPDES permit
information, published literature, qualified technical
consultation, on-site visits and interviews at numerous
manufacturing plants throughout the U.S., interviews and
meeting with various trade associations, and interviews and
meetings with various regional offices of the EPA. The
references used in developing the guidelines for effluent
limitations and standards of performance for new sources
reported herein are included in Section XIII of this report.
Table III-1 summarizes the data base for the various
subcategories studied in this volume:
III-U
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TABLE III-1
Summary of Data Base
Subcategpry
Total Number of
Plants in US
Data
Visited Available Sampled
1560
Census data/Industry data
Concrete block and)
brick, autoclave )
curing )1388
Concrete block and)
brick, low pressure)
steam curing
Concrete Pipe
Precast Concrete
products
Prestressed and
Precast
Prestressed
Concrete products)
) 7
) 436 9
)3595 app.2500 7
) 3
s) 5
7
153
12
12
11
1
3
2
1
3
Ready-Mixed )
Concrete Permanent)
Plants )
Ready-Mixed )
Concrete Portable) 4915
Plants )
Ready-Mixed )
Concrete Mobile )
Plants )
54
8000
Total
9898
12,496
1
94
437
21
1
658
15
0
0
27
Data was obtained from 6.6 per cent of the plants in these
industries. 0.9 per cent of the plants were visited and
approximately 0.3 per cent were sampled to verify data.
2.5 Notable Plant Selection
The following selection criteria were developed and used for
the selection of plants upon which guidelines were based.
III-5
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(a) Discharge effluent quantities
Plants with low effluent quantities or the ultimate of no
discharge of process wastewater pollutants were preferred.
This minimal discharge may be due to reuse of water, raw
material recovery and recycling, or to use of evaporation.
The significant parameter was minimal waste added to
effluent streams per weight of product manufactured. The
amounts of wastes considered here were those discharged.
(b) Effluent contaminant level
Preferred plants were those with lowest effluent contaminant
concentrations and lowest total quantity of waste discharge
per unit of product.
(c) Water management practices
Use of good management practices such as water reuse, plan-
ning and in-plant water segregation, and the proximity of
cooling towers to operating units, where airborne contamina-
tion of water can occur, were considered.
Land utilization
The efficiency of land use was considered.
(e) Air pollution and solid waste control
Plants were evaluated with regard to overall effective air
and solid waste pollution control, in addition to water
pollution control technology. Care was taken to insure that
all plants selected have minimal discharges into the
environment and that these sites are not those which are
exchanging one form of pollution for another of the same or
greater magnitude.
(f) Effluent treatment methods and their effectiveness
Plants selected shall have in use the best currently
available treatment methods, operating controls, and
operational reliability. Treatment methods considered
included basic process modifications which significantly
reduce effluent loads as well as conventional treatment
methods.
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(q) Plant facilities
Plants chosen had all the facilities normally associated
with the production of the specific product (s) in question.
Typical facilities generally were plants which have all
their normal process steps carried out on-site.
(h) Plant management philosophy
Plants were preferred whose management insists upon
effective equipment maintenance and good housekeeping
practices. These qualities are best identified by a high
operational factor and plant cleanliness.
(i) Geographic location
Factors which were considered include plants operating in
close proximity to sensitive vegetation or in densely
populated areas. Other factors such as land availability,
rainfall, and differences in state and local standards were
also considered.
(j) Raw materials
Differences in raw materials purities were given strong con-
sideration in cases where the amounts of wastes are strongly
influenced by the purity of raw materials used. Several
plants using different grades of raw materials were
considered for those products for which raw material purity
is a determining factor in waste control.
(k) Diversity of processes
On the basis that all of the above criteria are met,
consideration was given to installations having a
multiplicity of manufacturing processes. However, for
sampling purposes, the complex facilities chosen were those
for which the wastes could be clearly traced through the
various treatment steps.
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(1) Production
On the basis that other criteria are equal, consideration
was given to the degree of production rate scheduled on
water pollution sensitive equipment.
(m) Product purity
For cases in which purity requirements play a major role in
determining the amounts of wastes to be treated and the
degree of water recycling possible, different product grades
were considered for subcategorization.
liS. GENERAL DESCRIPTION OF INDUSTRY BY PRODUCT
The commodities in these industries include a number of
different products. The extent of processing varies widely
and the complexity is dependent upon the particular product
being manufactured. High water consumption is not
associated with most of these production facilities. Wastes
are generated usually in the form of suspended solids.
3...1 Concrete Block and Brick
This industry is engaged in the manufacture of concrete
building block and brick. The U.S. Bureau of the Census
shows that in 1972 there were 1,388 establishments in this
industry, with 416 establishments having 20 employees or
more.
Concrete block and brick are classified into the following
products: structural block produced with lightweight
aggregate such as cinder, expanded shale, pumice or other;
structural block produced with heavyweight aggregate such as
sand, gravel, crushed stone or other; decorative block -
such as screen block, split block, slump block and shadowal
block; and concrete brick.
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The 1972 production for each product is given below:
Lightweight block 1,814.7 million block equivalents*
Heavyweight block 833.1 million block equivalents*
Decorative block 90.2 million block equivalents*
Concrete brick 420.7 million block equivalents*
Total 3,. 158.7
*Block equivalents are 20 cm x 20 cm x 41 cm (8 in. x 8 in. x 16 in.)
Industry sources indicate that 62 million kkg (69 million
tons) of concrete block and brick were produced in the U.S.
in 1972.
The process for the manufacture of concrete block and brick
consists of mixing, forming and curing. The raw materials
for the block and brick, aggregate and cement, are shipped
to rhe plant by rail or by truck. The aggregates are
normally stored outside and kept moist until they are
transferred to the batch plant by belt conveyor or screw
conveyor into distribution bins. The cement is usually
received in bulk form either by rail or by truck and
transferred to a storage silo by screw conveyor or airveyot.
Typically, the aggregate, cement and water are weighed and
batched into a three cubic meter (four cubic yard) rotary
mixer. The concrete mix used for production of block and
brick contains less water than ready-mixed concrete. The
mixed concrete is then fed into an automatic block molding
machine, where the moist mix is rammed, pressed or vibrated
into the desired shape. The product is then stacked onto
iron framework curing cars and allowed to condition at 50°C
(120°F) for four hours. The quantity of water in the mix is
critical, as too much will cause severe shrinkage, and too
little will reduce block strength and produce friable
corners. Colors may be added to the mix to produce
decorative block. Occasionally the block may be split to
expose a rough decorative surface or may be sawed to a
particular shape.
The production of a structural high-strength block, within a
reasonable time period, necessitates curing the block under
moist-curing conditions. One of two methods is generally
used in the block industry: low pressure steam (75-85% of
total production); and autoclaves or high pressure steam
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(20-25%). In the low pressure steam process, the loaded
curing cars are placed into a chamber or kiln where low
pressure steam less than 9.7 atm (150 psi) is injected from
perforated pipes for approximately 8-10 hours. The length
of curing is dependent on mix conditions, user
specifications, and ambient temperature. Wastewater from
this curing method consists, primarily, of steam condensate
which contains some suspended solids, dissolved solids, and
a high pH (10-11) due to the calcium oxide content of the
cement. The low pressure steam is generated by a boiler
which requires periodic blowdown.
The autoclave curing method produces a higher strength block
in a shorter time period with less shrinkage than the low
pressure steam curing process. The cars containing preset
blocks are loaded into a large horizontal, cylindrically
shaped autoclave where high pressure steam is injected or
convected. After a curing cycle of about 8 hours the steam
is released to the atmosphere and the blocks are removed and
prepared for storage. One special form of steam production
utilizes a hot oil convection method, where water is placed
in a trough in the autoclave, and hot oil heats the water
into steam. After completing this cycle, the autoclave is
cooled, and a portion of the steam condenses back to the
trough as water. Periodically, this water is discharged
because the alkaline water is corrosive to the steel racks.
3^2 Concrete Products, Not Elsewhere Classified (SIC 3272)
This industry comprises establishments primarily engaged in
the manufacture of concrete products, except block and
brick. The industry produces three basic types of products,
concrete pipe, precast concrete products and prestressed
concrete products.
3.2.1 concrete Pipe
According to the 1972 Census of Manufacturers, the following
is a compilation of concrete pipe products and their
production.
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product
Culvert pipe
reinforced
non-reinforced
Storm Sewer Pipe
reinforced
non-rein forced
Sanitary Sewer Pipe
reinforced
non-reinforced
Pressure Pipe
reinforced
presi recs^i
pretension^d
other pressur>- pipe
Irrigation Pipe and Drain
Tile
Other Concrete Pipe
(e.g., manholes and conduits^
2,691,000 kkg (2,966,000 tons)
228,000 kkg (252,000 tons)
3,321,000 kkg (3,662,000 tons)
150,000 kkg (165,300 tons)
1,738,000 kkg (1,915,000 tons)
279,000 kkg (308,000 tony)
396,000 meters (1,300,000 feet)
7',:>1,, G.JO merers (2,300,000 feet)
H8U,,;o<) meters (2,900,000 fe-r)
V.' t r.iiii- 1 d
i+46,v>;0 K.K.f (49^,000 tons)
],Ht>7,300 kkg (2,05b,300 tons)
The basic raw materials of concrete pxr«- manuf aotur -'- are
Portland cement, aggregate, and water. For reinfot c-.-a t-'^l-^f
a steel wire cage is added as reinforcing to prcvi u
increased strength. The proportions of these materials
vary, depending on manufacturing processes and strength
requirements.
Concrete pipe is generdily produced by three methods. The
vertical packerhead {tamp_i_ngj_ method involves the use of a
moist concrete mix which is compacted and vibrated into a
steel form by a machine called a packerhead. This method is
generally used to produce pipe up to 1.5 meters (5 ft) in
diameter. The vertical, cast method Ccin be used to produce
any size of reinforcea p..pe, btr: it io generally limited to
di a:ne-*-ers over 1.5 meters (5 ft) due to the r.i'-fh eoL>t of
labor and time required. A wet concrete mix 13 pioduced in
a central mixer and transported to a vertical steel form
with transport buckets. ''1:.^ concrete is allowed to set,
then the forms are stripped. The spin ca_s_tirig_ production
method is generally used to produce reinforced pipe up
1.2 meters (4 ft) in diameter. A reinforcing cage is
to
fabricated and positioned in a foi
horizontally on
form is rotated
a high speed roller
which
drive
at a high rate, while the
is then placed
mechanism. The
concrete is
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directed evenly by a reciprocating nozzle on the inside of
the form. The spinning action densities the concrete on the
inside of the form and dewaters it. Water flows off the
inside surface of the pipe, and the concrete surface is
finished by a mechanical roller. Reinforced concrete
pressure pipe, produced by spin casting, uses a permanent
form, i.e., remains with the pipe. A sheet steel cylinder
is fabricated, hydraulicly tested, then placed on the spin
cast machine, and concrete is poured inside as with
reinforced pipe.
In all methods, when the concrete pipe has reached a certain
green strength, it is cured by the application of low
pressure steam either in a kiln or in a chamber constructed
around the pipe. For pipe produced by the tamping method,
the forms are generally stripped before steam curing, while
the spin cast and vertical cast pipe forms are generally
left on the pipe during curing. All of the pipe forms are
coated with a form release oil to facilitate the separation
of the pipe and form.
The production of reinforced pipe other than pressure pipe
uses a welded wire cage for the reinforcing member which is
embedded in the circumference of the pipe. The reinforcing
cage is usually fabricated from the wire coils in an
automatic machine which cuts and welds the wire into a
cylinder.
Pressure pipe production may include the following operations:
(1) fabrication of a steel cylinder;
(2) hydraulic testing of the cylinder;
(3) insertion of the cylinder into a vertical casting form
or spin cast machine;
(4) batch mixing cement, aggregate and water;
(5) pouring, or placing and compacting, the concrete within
the pipe form;
(6) stripping the pipe forms;
(7) curing the pipe with low pressure steam;
(8) circur.-ferentially wrapping the cured pipe with high
strength steel wire;
(9) coating the steel wire wrap with concrete grout, and
(10) inspection and storage.
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The production of pressure pipe involves several more manu-
facturing steps than required for other concrete pipe
including prestressing with high strength wire. These
additional operations make the pressure pipe more expensive
to produce with a resultant increase in selling price.
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3.2.2
Precast Concrete Products
Precast concrete products include:
product
Roof and floor units
slabs and tile
joints and beams
Architectural wall panels
Pilings, posts and poles
Cast stone (products for
architectural purposes)
1972 production
370,000 kkg (396,000 tons)
110,000 kkg (120,000 tons)
694,000 kkg (765,000 tons)
83,500 kkg (92,000 tons)
x
Prefabricated building systems 148,000 kkg (163,000 tons)
Other precast construction prod, x
235,000 kkg (260,000 tons)
139,000 kkg (153,600 tons)
1,050,000 kkg (1,158,000 tons)
1,748,000 kkg (1,926,000 tons)
Buri al vaults and boxes
Silo staves
Septic tanks
Dry-mixed concrete materials
(e.g., Sakrete)
Other precast (e.g., laundry x
tubs)
Precast concrete products, n.s.k. x
Estimated Total 4,577,500 kkg (5,047,000 tons)
Estimated Total (less dry mixed 1,829,500 kkg (2,120,000 tons)
concrete)
x - unknown
The raw materials of precast concrete products are cement,
aggregate and water. Reinforced concrete products contain
steel structural members to provide increased strength.
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The production of simple precast concrete products such as
transformer pads, meter boxes, pilings, utility vaults,
steps, cattleguards, and balconies involves mixing the
cement, aggregate and water in a central mixer, pouring the
concrete into forms and allowing it to cure overnight. The
forms are removed the following morning and the cure is
completed under ambient conditions.
Precast architectural wall panels are generally finished to
produce a decorative surface of exposed aggregate. Although
there are several methods of production, the one frequently
used involves spreading a retarder in the bottom of a form,
placing reinforcing steel in the form, and casting the
concrete mix. The concrete is allowed to set, the form is
removed and the surface with the retarder added is either
washed with a weak solution of acid, sandblasted, or washed
with high pressure water. Since the retarder prevents the
setting of the surface cement, washing exposes the coarse
aggregate. The panel then cures completely in a storage
yard.
Dry mixed concrete materials are of packaged sand, gravel
and cement and mortar mixes. The production process
involves drying, proportioning and mixing the raw materials,
and no water is used in the process.
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3._2^_3 Prestressed Concrete Products
Prestressed concrete products are chiefly used as structural
and architectural components and include:
product production
Single tees, double tees, and 14,402,000 kkg (15,875,000 tons)
channels
Piling, bearing piles, and sheet 1,470,000 kkg (1,620,000 tons)
piles
Bridge beams 470,000 kkg (520,000 tons)
Solid and hollow cored slabs 2,238,000 kkg (2,467,000 tons)
and panels
Other prestressed products 739,700 kkg (815,400 tons)
(e.g., arches)
Joist, girders, and beams 43^ 80 0 kkg (48,300 jtons)
(other than bridge beams)
Total 18,500,000 kkg (20,400,000 tons)
The raw materials of prestressed concrete products are
cement, aggregate, water, and steel tendons. Prestressed
concrete product are manufactured by:
(1) inserting the steel tendons in a metal form,
(2) stressing the steel tendons,
(3) batch mixing in a central mixer,
(4) pouring the concrete into the form,
(5) overnight curing of the product using low pressure steam,
(6) removal of the metal form and release of the external stress
on the steel tendons,
(7) for certain prestressed products, end-sawing or finishing, and
(8) product testing and storage.
Prestressed and precast products are produced similarly
except that prestressed products utilize steel cables
(tendons) in tension in place of steel rods for
reinforcement. Prestressing also prevents tension cracks in
a structural member under design loads. This normally
allows the use of a structural member with a smaller cross
sectional area and lighter in weight. Prestressed concrete
products may be either pretensioned or post-tensioned.
Prestressed pretensioned products are made by placing the
steel cables in tension in the form before concrete is
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placed. Once the concrete is set, cured and the forms are
removed, the external tension is released from the steel
cables. The cable remains stressed due to the compression
of the concrete around the cable. This method of
prestressing predominates in the industry,,
Prestressed post-tensioned products are made by placing
cables in the form, casting the concrete, allowing it to set
and cure to a certain strength, then placing the steel
tendons under tension. Cables must be protected with a
steel or plastic tube or mastic coating to prevent bonding
with the concrete prior to tensioning. Cables may or may
not be grouted while under tension and are locked under
tension by appropriate end anchorage or clamps. An
alternate method of post-tensioning involves casting the
concrete member with a tube or slot for future insertion of
the steel tendon.
3_4.3_ Ready-Mixed Concrete
The Ready-Mixed Concrete Industry includes establishments
engaged in manufacturing portland cement concrete produced
and delivered to the purchaser in a plastic and unhardened
state. Ready-mixed concrete represents the largest category
of portland cement concrete used in the United States.
According to U.S. Bureau of Census figures, 159.4 million
cu m (208.5 million cu yd) were produced in 1972. This
total quantity of ready-mixed concrete was produced by 4,915
total establishments, of which 1,328 establishments operated
with 20 employees or more.
In contrast to this figure, the National Ready-Mixed
Concrete Association (NRMCA) has indicated that there are in
excess of 8,000 ready-mixed concrete plants in the U.S. A
state-by-state listing of the number of companies in this
industry in 1971 provided by NRMCA is presented in
Table III-2.
The two processes used for ready-mixed concrete are batching
and central mixing. At a batch plant, the concrete is mixed
in the truck mixer, while at a central mix plant, the
concrete is prepared in a plant mixer then transferred to a
truck mixer or agitator for delivery.
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TABLE III-2
Location of U.S. Concrete Operators*
States No. States
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
D.C.
Delaware
Florida
Georgia
Hawai i
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
* 1971 NRMCA
111
2
70
93
356
91
44
3
14
142
108
4
43
282
171
221
139
128
115
19
40
48
217
163
86
229
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
TOTAL
No.
43
101
27
20
76
58
207
98
43
216
163
95
195
8
69
67
84
290
62
11
78
78
52
150
36
5,266
The batching and mixing equipment used at ready-mixed
concrete plants ranges in size and complexity from small
portable mixers to automated permanent plants with central
mixers capable of producing several hundred cubic meters of
concrete per hour. The three general classifications of
plants are:
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The raw materials for the concrete, coarse and fine
aggregate and cement are usually shipped to the plant via
rail or truck. However, at some 300 ready-mixed
establishments according to Census figures, the coarse or
fine aggregate is mined or quarried at the plant site. The
coarse and fine aggregates are generally stockpiled in the
open, where they are kept saturated with moisture. The
aggregates are transferred to the plant by conveyor, front
end loader or crane, to distribution bins. The portland
cement is usually received in bulk form either by rail or by
truck, transferred to a cement hopper, and then conveyed to
a storage silo or to the central batch bin. The aggregates
and cement are weighed and blended into a-mixer with a
premeasured quantity of water and the concrete is mixed for
specified length of time. At a batch plant, the mixing is
accomplished in the truck mixer, while in a central mix
plant, a central mixer is used which then transfers the
concrete to an agitator truck.
(1) Permanent - This type of plant uses ready-mixed trucks
which deliver various types of concrete to numerous
customers. The concrete may be mixed in central mixers
and hauled in agitator trucks or may be dry batched into
mixer trucks and mixed in the truck on the way to the
job.
(2) Portable - This is the type of plant used on large
highway and airport paving jobs. The concrete may be
produced in a central mixer and hauled in agitator
trucks or it may be dry batched into trucks and hauled
to a portable mixer at the construction site. The
latter is the older method.
(3) Mobile - The mobile concrete plant utilizes trucks
capable of measuring and mixing the aggregate, cement,
and water at the job site. The raw materials are
transported separately on the mobile truck, proportioned
and mixed in the truck-mounted mixer at the job site.
Mobile ready-mixed concrete is primarily used for small
jobs that can be economically serviced without returning
to the base plant after each job.
The permanent ready-mixed concrete plant may operate either
as a dry batch plant or a central mixer plant. In a dry
batch plant, the mix of aggregate and cement are weighed and
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transferred in a dry state to the ready-mixed trucks along
with a proportioned amount of water, then mixed in the
truck. This type of operation is found in approximately
three-fourths of the plants in the permanent segment of the
ready-mixed industry. The other one-fourth of these plants
uses a central mixer with an average capacity of 4 cu m
(5 cu yd) .
A general practice in the construction industry is to order
slightly more concrete than necessary to complete the job to
prevent running short. This practice results in an excess
of concrete in the truck which must be either dumped or
reused. In some cases, the unused concrete is dumped on the
job site, however, in most cases, it returns to the plant in
the ready-mixed truck to be either incorporated in the
following order, used for paving the plant yard, or flushed
out as waste material. The disposal of the unused concrete
depends on the amount left in the truck, the length of time
since batching, the formulation of the following order, and
other factors. The amount of returned waste concrete varies
but averages between 1 to 3 percent of average daily
production. Ready-mixed concrete plants use water primarily
in the batching of concrete, and for washing out the
ready-mixed trucks and central mixer. The washout is an
essential part of the daily operations of all concrete
plants to prevent hardening of the concrete in the equipment
and consequent lost time and maintenance costs.
The concrete produced by ready-mixed plants can be
considered to be made of two major components, aggregates
and paste. The aggregates generally occupy 60 to 80 percent
of the volume of concrete. The most commonly used
aggregates such as sand, gravel, crushed stone, and air
cooled blast furnace slag produce a normal weight concrete
having a density in the range of 2,166 to 2,568 kg/cu m (135
to 160 Ibs/cu ft). Structural lightweight concretes use
aggregates such as expanded shale, clay, slate and slag.
The lightweight concretes have densities ranging from 1,364
to 1,846 kg/cu m (85 to 115 Ibs/cu ft). Other lightweight
materials such as pumice, scoria, perlite, vermiculite, and
diatomite are used to produce insulating concretes weighing
241 to 1,445 kg/cu m (15 to 90 Ibs/cu ft). Heavyweight
concrete is produced primarily for nuclear applications and
uses heavy aggregates such as barite, limonite, magnetite,
ilmenite, and iron or steel particles.
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In normal-weight concrete, the aggregates are generally
classified into two size groups, fine and coarse. Fine
aggregates consist usually of sand with particle sizes
smaller than a number 4 standard sieve or .approximately
0.6 cm (1/4 inch). The coarse aggregates are usually
crushed stone and gravel with particle sizes retained on a
number 4 standard sieve.
The paste component of the concrete is composed of cement,
water, admixtures and sometimes entrained air. The cement
paste ordinarily constitutes 25 to 40 percent of the total
volume of concrete. The absolute volume of cement is .
usually between 7 and 15 percent - 284 to 567 kg/cu m (375
to 750 Ibs/cu yd) and the water from 14 to 2'1 percent - 174
to 265 kg/cu m (230 to 350 Ibs/cu yd). Air content in
air-entrained concrete range up to about 7.5 percent of the
volume of the concrete. A typical formulation for
normal-weight air entrained concrete is shown below:
Fine aggregate
Coarse aggregate
Cement
Water
Air Entrainment Agent
Air
kq/cu m
410
625
174
104
0.26-0.28
Ibs/cu yd
1,180
1,800
(max. 3/4 in.)
500
300
0.75-0.80
6% by volume 6% by volume
In properly made concrete, each particle of aggregate is
completely coated with paste. Also, all of the space
between aggregate particles is completely filled with paste.
The quality of the concrete is greatly dependent upon the
quality of the paste. The quality of paste is dependent
upon the ratio of water to cement used, and the extent of
curing. The cementing properties of the paste are due to
the chemical reactions between cement and water. These
reactions, called hydration, require time and favorable
conditions.
A notable advance in concrete technology in recent years was
the development of air entrainment. The use of entrained
air is recommended in concrete for nearly all purposes, but
the principal reason is to improve resistance to freezing
and thawing exposure. Air entrained concrete is produced by
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using either an air entraining cement or an air entraining
admixture added during the mixing of the concrete. An air
entraining cement contains material interground with
Portland cement during the process of manufacture. One of
these materials has been described as a mixture of
triethanolamine and a calcium salt of modified lignosulfonic
acid. An air entraining admixture, on the other hand, is
added directly to the concrete materials either before or
during mixing. Typical agents consist of the following: a
saponified natural resin or stabilized wood resin derived
from pulp and paper production, such as Vinsol; a
combination of a primary alkylolamide plus alkyl aryl
sulfonate; a saponin or keratin compound; or generically a
triethanolamine salt of a sulfonated hydrocarbon or fatty
acid glyceride. Some more recently developed agents include
vinyl acetate or a styrene copolymer of vinyl acetate. Many
of these agents contain combinations of air entrainment
agents, wetting agents and dispersing agents.
Other admixtures which may be added to the concrete before
or during mixing include water reducing agents, retarders,
accelerators, and others. A water reducing admixture is a
material used for the purpose of reducing the quantity of
mixing water required to produce concrete of a given
consistency. Some water reducing admixtures such as
lignosulfonic acids and their salts, also can be used for
air entrainment. Other water reducers act as set retarders.
A retarding admixture is a material that is used for the
purpose of increasing the setting time of concrete.
Retarders are sometimes used in concrete to (1) offset the
accelerating effect of hot weather on the setting of the
concrete, or (2) delay the initial set of the concrete where
difficult or unusual situations occur or where desired to
produce special effects on concrete products. Because most
retarders also function as water reducers, they are
frequently referred to as water-reducing retarders; such as
the hydroxylated carboxylic acids and their salts.
An accelerating admixture is used to accelerate the setting
and strength development of the concrete. The most commonly
used accelerating admixture is calcium chloride. There are
many commercial admixtures sold which combine various
functions under one trade name.
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l.-_P_ PRODUCTION OF CONCRETE PRODUCTS
The 1972 production and employment figures for the concrete
products industries were derived either from the Bureau of
the Census (US Department of Commerce) publications or from
data developed from othei sources during this study. These
figures are tabulated in Table III-3.
TABLE III-3
SIC Product
3271 Concrete block S
brick, total
Autoclave Curing
Low Pressure Steam
Curing
3272 Concrete Products,
NEC, total
Concrete Pipe
(excluding pressure
pipe)
Precast and Pre~
stressed Concrete
Products
3273 Ready-Mixed
Concrete, total
1972 Production
kkg (tons)
62,000,000
(69,000,000)
14,000,000
(15,500,000)
48,000,000
(53,500,000)
35,100,000
(38,600,000)
10,700,000
(11 ,800,000)
21 ,400,000
(23,500,000)
378,000,000**
(417,000,000)**
Employment
No. of Employees*
15,200
53,500
56,900
*Production workers only
**Assumed 1.8 kkg per cubic meter of concrete
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SECTION IV
INDUSTRY CATEGORIZATION
1.0 INTRODUCTION
In the development of effluent limitations guidelines and
recommended standards of performance for new sources in a
particular industry,, consideration should be given to
whether the industry can be treated as a whole in the
establishment of uniform arid equitable guidelines for the
entire industry or whether there are sufficient differences
within the industry to justify its division into categories.
For the concrete products industries the following factors
were considered as possible justifications for industry
categorization and subccstegorization:
(1) manufacturing processes;
(2) raw materials;
(3) pollutants in effluent wastewaters;
(U) product purity;
(5) water use volume;
(6) plant size;
(7) plant age; and
(8) plant location.,
2.0 INDUSTRY CATEGORIZATION
These industries were categorized on a commodity basis.
F,ach commodity encompasses some or all of the above-
mentioned criteria (processing^ raw materials, etc.).
However, some differences do exist within a given commodity,
e.g. low pressure steam curing and autoclave curing of con-
crete block and brick* Differences such as these were used
as a basis for subcategorization. Table IV-1 lists the
IV- 1
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three categories and seven subcategories discussed in thin
report.
TABLE IV-1
Industry Categorisation
SIC Code
Concrete Block and 3271
Brick
Concrete Products 3272
(NEC)
Category
1
Ready-Mixed
Concrete
3273
Subcategory
1.1 Autoclave Curing
1.2 Low Pressure
Steam Curing
2.1 Concrete Pipe
2.2 Precast and
Prestressed
Products
3.1 Permanent Plants
3.2 Portable Plants
3.3 Mobile Plants
3.0 FACTORS CONSIDERED
3.1 Manufacturing Processes
The processes generally used in the concrete products
industries include mixing aggregates, cement and water and
transporting the mixture to the job site in the case of
ready-mixed concrete or casting and curing the product in
the case of block and brick and concrete products.
Upon examination of the various processes and wastes
generated therefrom, it is evident that the type of
manufacturing process may be used for subcategorization but
not for major segmentation of the industry.
3_^_2 Raw Materials
The raw materials used are principally cement, aggregates
and water which vary only in proportion in a given product.
Raw materials are not a suitable basis for categorization.
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3.3 Pollutants in Effluent
The principal pollutants from these industries are pH, total
suspended solids and oil and grease. There are occasional
limited instances of deleterious materials such as the many
different types of admixtures that may be used in a concrete
mix.
Although suspended solids are ubiquitous, the treatability
of the effluents varies widely, depending heavily, among
other things, upon the other constituents present in the raw
materials. Because of the common occurrence of suspended
solids, distinguished by widely varying degrees of
treatability,- pollutants in the effluent were not judged to
be an adequate basis for categorization.
3..4 Product Purity;
The manufacturing processes covered in this report yield
products which vary in purity, Product purity was not
considered to be a viable criterion for categorization of
the industry.
3.5 Water Use Volume
In these industries^ water use is determined by the needs of
the individual facility and varies greatly depending mainly
on the operational factors. For the manufacturing processes
studied herein, water use varies from minimal to
10,000 liters per metric ton of product.
Water use was not considered to be a workable criterion for
industry categorization,,
3.6 Plant Size
For these industriest information was obtained from more
than 650 different manufacturing sites. Capacity varied
from as little as 1^360 metric tons per year to
540,000 metric tons per year. The amount of wastes are
related to amount of product; therefore subcategorization
based on plant size is not necessary.
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lil Plant Age
The newest plant studied was less than a year old and the
oldest was 50 years old. There is no correlation between
plant age and the ability to treat process wastewater to
acceptable pollutant levels. Therefore, plant age was not
an acceptable criterion for categorization.
3.8 Plant Location
The locations of the more than 650 manufacturing sites
studied are in all states spread from coast to coast and
north to south.
Some plants are located in arid regions of the country,
allowing the use of evaporation ponds and surface disposal
on the plant site. Other plants are located near raw
material, sand and gravel, deposits which are dispersed
throughout the country.
Geographical location was not found to be a criterion for
categorization.
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SECTION V
WATER USE AND WASTE CHARACTERIZATION
l._Q INTRODUCTION
This section discusses the specific water uses in the
concrete products industries and the amounts of process
waste materials contained in these waters. The process
wastes are characterized as raw waste loads from specific
processes in the manufacture of the products involved in
this study and are given in terms of kilograms per metric
ton or kilograms per cubic meter of product. The specific
water uses and amounts are given in terms of liters per
metric ton or liters per cubic meter of product. Where
appropriate, the water uses and raw waste loads are given in
either liters per day (GPD) or concentration, mg/liter. The
treatments used by the facilities studied are specifically
described and the amount and type of waterborne waste
effluent after treatment is characterized.
2.0 SPECIFIC WATER USES
Water is used in the concrete products industries for four
principal purposes falling under two major characterization
headings. The principal water uses are:
(1) Process water - mix water
wash water
miscellaneous water
(2) Auxiliary processes water
Process water is defined as that water which, during the
manufacturing process, comes into direct contact with any
raw material, intermediate product, by-product or product
used in or resulting from the process.
Auxiliary processes water is defined as that used for
processes necessary for the manufacture of a product but not
contacting the process materials. For example, boiler water
and water treatment regeneration are auxiliary processes.
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The quantity of water use at facilities in the concrete
products industries ranges from zero to 2,830,000 liter per
day (0 to 730,000 gallons per day). Plants using large
quantities of water are those producing pipe by the
spincasting method and ready-mixed concrete plants which do
much washing of equipment.
2.1 Non-Contact Cooling Water
The largest use of non-contact cooling water in these
industries is for the cooling of equipment, such as pumps
and air compressors.
2.2 Contact Cooling Water
Relatively small amounts of contact water are used for saw
blade cooling in the concrete products (NEC) category.
2.3 Wash Water
This water comes under the heading of process water because
it comes into contact with either the raw materials or
products. Wash water is used extensively in this industry
and is usually the greatest source of wastewater. In the
ready-mixed concrete industry, water is used for washing
mixer trucks both internally and externally, and for washing
out central mixers. In the manufacture of concrete
products, water is used for washing transport buckets,
central mixers and forms. At some plants water is used for
washing conveyor belts.
2.4 Process Water
Water is used in these industries in mixing concrete and
remains in the products. Other uses include washing the
surface of wall panels with a weak acid solution or water
under high pressure to expose aggregate for decorative
purposes. Production of concrete pressure pipe requires
additional process water for hydrostatic testing of steel
reinforcing cylinders and the prewetting of reinforced
pressure pipe before outside coating of concrete is applied.
Significant quantities of water may be used to control dust
on plant yards, the amount varying seasonally. This water
in many instances evaporates or percolates.
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SECTION V
WATER USE AND WASTE CHARACTERIZATION
!_._() INTRODUCTION
This section discusses the specific water uses in the
concrete products industries and the amounts of process
waste materials contained in these waters. The process
wastes are characterized as raw waste loads from specific
processes in the manufacture of the products involved in
this study and are given in terms of kilograms per metric
ton or kilograms per cubic meter of product. The specific
water uses and amounts are given in terms of liters per
metric ton or liters per cubic meter of product. Where
appropriate, the water uses and raw waste loads are given in
either liters per day (GPD) or concentration, mg/liter. The
treatments used by the facilities studied are specifically
described and the amount and type of waterborne waste
effluent after treatment is characterized.
2.0 SPECIFIC WATER USES
Water is used in the concrete products industries for four
principal purposes falling under two major characterization
headings. The principal water uses are:
(1) Process water - mix water
wash water
miscellaneous water
(2) Auxiliary processes water
Process water is defined as that water which, during the
manufacturing process, comes into direct contact with any
raw material, intermediate product, by-product or product
used in or resulting from the process.
Auxiliary processes water is defined as that used for
processes necessary for the manufacture of a product but not
contacting the process materials. For example, boiler water
and water treatment regeneration are auxiliary processes.
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The quantity of water use at facilities in the concrete
products industries ranges from zero to 2,830,000 liter per
day (0 to 730,000 gallons per day). Plants using large
quantities of water are those producing pipe by the
spincasting method and ready-mixed concrete plants which do
much washing of equipment.
2.1 Non-Contact Cooling Water
The largest use of non-contact cooling water in these
industries is for the cooling of equipment, such as pumps
and air compressors.
2.2 Contact Cooling Water
Relatively small amounts of contact water are used for saw
blade cooling in the concrete products (NEC) category.
2.3 Wash Water
This water comes under the heading of process water because
it comes into contact with either the raw materials or
products. Wash water is used extensively in this industry
and is usually the greatest source of wastewater. In the
ready-mixed concrete industry, water is used for washing
mixer trucks both internally and externally, and for washing
out central mixers. In the manufacture of concrete
products, water is used for washing transport buckets,
central mixers and forms. At some plants water is used for
washing conveyor belts.
2.4 Process Water
Water is used in these industries in mixing concrete and
remains in the products. Other uses include washing the
surface of wall panels with a weak acid solution or water
under high pressure to expose aggregate for decorative
purposes. Production of concrete pressure pipe requires
additional process water for hydrostatic testing of steel
reinforcing cylinders and the prewetting of reinforced
pressure pipe before outside coating of concrete is applied.
Significant quantities of water may be used to control dust
on plant yards, the amount varying seasonally. This water
in many instances evaporates or percolates.
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Miscellaneous ™a_t?y:
Miscellaneous water uses in these industries include
spraying stockpiles to keep aggregates in the saturated,
surface-dry condition. This water is usually low volume and
may be either evaporated or absorbed in the raw material.
Miscellaneous water uses vary widely among the facilities
with general use for floor washing and clean-up and sanitary
uses. There is also miscellaneous process water used for
yard dust control, aggregate moisture control, chute rinse-
off and equipment, clean-up, which in most plants becomes
yard runoff.
2.6 Auxiliary Processes Hater
Auxiliary processes water .Include blowdowns from boilers and
water treatment. The volume of water used for these
purposes in these industries is minimal.
liP. PROCESS WASTE CH^_CTERIZATIQN
3.1 Concrete Block and Brick JSIC 3271)
Concrete block and brick may be lightweight or heavyweight
depending on the type of aggregate used. The methods of
forming block and brick are similar at most plants in the
industry. However? two different curing methods are used.
Concrete block and brick manufacture was subcategorized
based on curing method, i.e., low pressure steam and
autoclave curing. Low pressure steam curing is predominant
in the industry. Live steam at low pressure is injected
into a kiln in which uncured block has been stacked.
Process wastewater generated by this operation consists of
steam condensate, which has a pH greater than 9 and contains
suspended solids. This is caused by direct contact with the
product.
Autoclave curing utilizes high pressure steam at 9.7 atm
(150 psi) and above in autoclaves which have been loaded
with uncured block, Wastewater from this process includes
autoclave blowdown condensate and autoclave purge, both
having pH greater chan 9 and containing suspended solids
from product contact.
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According to Bureau of Census data, there were 1,388
establishments operated by 1,300 companies producing
concrete block and brick. Industry sources indicate that 62
million kkg (69 million tons) of concrete block and brick
were produced in the U.S. in 1972. Approximately 15% of the
plants use autoclave curing, representing 20-25S of the
total production. In this study 13 plants were visited and
3 plants were sampled. On a total production basis, data
were obtained from 2% of the industry which represents 4X of
autoclave and 1% of low pressure steam production. Plant
ages in this study range from 2 to 35 years.
3.1.1 Low Pressure Steam Curing
3.1.1.1 Process Description
The production of concrete block and brick with low pressure
steam curing includes: batch mixing of cement, water and
aggregates; forming the block in a machine which presses,
rams or vibrates the moist mix into blocks; curing of the
block with low pressure steam in a kiln; and visual
inspection, stacking and loading for delivery. Low pressure
steam is produced in a boiler and is injected into the
kilns. Plant 7103 produces part of its block by atmospheric
curing and the remainder by low pressure steam curing. In
the atmospheric curing process, the formed block is stacked
in the plant yard and cured by ambient heat and humidity
plus the internal effects of the heat of hydration. Plant
7104 cures block by stacking them in an enclosure after they
are formed and allowing them to cure with their heat of
hydration and ambient heat and humidity. A flow diagram for
concrete block and brick produced by the low pressure steam
curing process is shown in Figure 1.
Annual production of concrete block and brick by this
process for the 7 plants contacted ranges from 26,600 to
79,800 kkg (29,300 to 88,000 tons).
3.1.1.2 Raw Waste Loads
Wastewater pollutants from low pressure steam curing are
suspended solids, COD, oil and grease and high pH. Plant
supplied data for plant 7109 was 0.0005 kg/kkg
(0.0010 Ib/ton) TSS, 0.0002 kg/kkg (0.0004 Ib/ton) COD, pH
11.1, and 0.0 mg/liter oil and grease. The concentrations
V-4
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V-5
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of these pollutants are'64 mg/liter TSS and 26 ing/liter COD.
All plants but 7104 have steam condensate containing these
pollutants.
Solid wastes are cement dust from batching, waste concrete
from mixer clean outr and scrap block and brick from
forming, stacking and loading operations. In most cases
cement dust is collected in a baghouse and returned to the
cement storage silos. Solid wastes are used as fill in all
plants contacted.
Miscellaneous waterborne wastes come from equipment washoff,
accidental spill washdown and aggregate moisture control.
Pollutants in storm water runoff were not found to be a
problem in this subcategory. Auxiliary process wastewater
includes boiler blowdown water and water treatment
regeneration wastes.
Raw waste loads vary with production. The waste concrete
and scrap block for plants studied are shown below.
Plant waste Concrete and Scrap Block kg/kkg (lb/1, OOP lb)
7102 26
7103 10
7101 4
7106 19
7108 13
7109 2
7110 9
3.1.1.3 Water Use
The principal process water uses are mixing the concrete and
curing the block and brick. Miscellaneous process water
uses include conveyor belt washing at plant 7104, yard dust
control at plant 7109, aggregate moisture control, delivery
truck washoff at plant 7110, boiler blowdown and non-contact
cooling of bearings and compressors. Other water uses
include make-up water for boilers and water treatment
r eg en er at i on.
Total water use varies with production and duration of
curing. Variance for the plants contacted ranges from 24 to
35 liters/kkg (5.7 to 8.1 gallons/ton). Mix water use per
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unit weight of production varies from 24 to 30 liters/kkg
(5.7 to 7.1 gallons/ton) and becomes part of the product.
Process hydraulic loads at selected plants are shown below:
Amounts, liters/kkg (gal/ton) of
t Mix
*
24
24
24
30
26
24
Water
(5.7)
(5.8)
(5.8)
(7.1)
(6.0)
(5.8)
Low Pressure
Steam
Condensate
10.6 (2.5)
0.2 (0.04)
none
*
*
8.9 (2.1)
*
Plant
7102
7103
7104
7106
7108
7109
7110
* unknown
Conveyor
Belt Washoff
none
none
5.2 (1.3)
none
none
none
none
3. 1.1^4 Wastewater Treatment
Wastewater results from steam condensate and miscellaneous
washdowns. Wastewater quantities are small enough at most
plants so that evaporation or percolation on plant property
is feasible. Wastewater quantities vary with production and
duration of curing. For example, steam condensate is
generated only during the 8 to 10 hour curing cycle.
The methods of wastewater treatment encountered are
summarized below:
Plant
7102
7103
7104
7106
7108
7109
7110
None
Settling Pond
or Basin
x
x
Evaporation or
Percolation
on Property
x
x
x
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3.1.1.5 Effluents and Disposal
Waste stream disposal practices found in the industry are as
follows:
Disposal
Plant
7102
7103
7104
7106
7108
7109
7110
7111
7112
Total
Containment
(pond or basin)
Evaporated/
Percolated
on Property
Discharge
x
X
X
X
X
X
Discharges are small enough at most plants so that they are
evaporated or percolated on site. Based upon NPDES
Application data (1971), some characteristics of the
effluent stream from plants that discharge follow:
Plant
Flow, liters/kkg
PH
Parameter Concentration,
TSS
COD
Oil and Grease
Parameter Amounts,
kg/kkcr
TSS
COD
Oil and Grease
64
26
none
0.0005
0.0002
none
10
56
35
0.0014
0.0080
0.005
5
570
unknown
0.0002
0.025
unknown
*Plant 7111 manufactures both concrete block and concrete pipe,
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liJ_i,2 Autoclave Curing
3.1.2. 1 Proce_ss Description
The production of autoclave-cured concrete block and brick
includes: batch mixing of cement, water and aggregates;
forming of the block in a block machine where the moist mix
is rammed, pressed, or vibrated into shape; curing of the
block with high pressure steam in an autoclave; and stacking
and loading for delivery. High pressure steam is generated
by two methods. Plants 7100 and 7101 use a hot oil
convection process in which oil is heated and piped through
a water trough at the bottom of the autoclave, forming steam
inside the autoclave„ Plants 7105 and 7107 produce high
pressure steam in an external boiler and inject it into the
autoclave. This latter method is used in most plants. A
flow diagram for concrete block and brick produced by the
autoclave curing process is shown in Figure 2.
Annual production of concrete block and brick by this
process for the 6 plants studied ranged from 63,500 to
250,000 kkg (70,000 to 275,000 tons).
lil-_2-sJ2 Raw Waste Loads
Waterborne pollutants include suspended solids, COD, oil and
grease, and high pH, resulting from autoclave blowdown
condensate and in the convection process, autoclave purge.
Miscellaneous waterborne wastes include equipment washoff,
aggregate moisture control and accidental spill clean-up.
Pollutants in storm water runoff were not found to be a
problem in this subcategory.
Solid wastes are cement dust from concrete batching,
concrete from mixer clean-out, and scrap from block forming,
stacking and loading. Cement dust is usually collected in a
baghouse and returned to the cement storage silo. Waste
solids are typically landfilled, however, plant 7100 crushes
broken block for re-use as aggregate.
Raw waste loads vary from day to day due to operating
factors such as housekeeping and ambient temperature and
humidity. The amount of autoclave purge is highly variable
which affects the amount of raw wastes contained in this
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purge. The estimated average raw waste loads for some
plants contacted in this study follow.
Source
autoclave
blowdown
condensate
autoclave
purge
Parameter
TSS
PH
COD
Oil and
grease
TSS
Raw Wastes, kg/kkg of product (Ibs/1,000 Ib)
7100
*
*
0,005**
*
*
*
0.007
PH
COD
Oil and
grease
11,3
0,0024
*
11.5
0.004
*
combined
autoclave
and other
wastewater
7105
0.035
11.5
0.018
*
none
N.A.
none
none
7107
0.02
11.3
*
*
none
N.A.
none
none
none
0.012
12.3
(BOD) 0.001
*
none
none
none
TSS none none none
pH NO&C N.A. N.A. N.A.
BOD none none none none
Oil and none none none none
grease
*unknown
**Versar measured data
N.A. not applicable
3.1.2.3 Water Use
The principal process water uses are mixing the concrete and
curing the block and brick. Miscellaneous process water
includes water used for equipment clean-up and housekeeping
within the plant, and aggregate moisture control.
Incidental water use includes boiler blowdown and non-
contact cooling of bearings and compressors.
Water use varies with operating factors, duration of curing,
and the number of autoclave purges in the convected steam
plants. For these reasons, daily water use for the plants
contacted ranges from 71 to 227 liters/kkg (17 to
0.016
11.6
0.011
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54 gal/ton). Mix water use per unit weight of production,
which becomes part of the product, is relatively constant.
Process hydraulic loads at selected plants are shown below:
Quantity in liters/kkg of product (gal/ton)
7100 7101 7105 7107
mix water 22 (5) 22 (5) 13 (3) 17 (U)
autoclave 19 (5) part of 214 (50) 77 (19)
blowdown autoclave
condensate purge
autoclave 30 (7) 90 (22) none none
purge
3.1.2..4 Wastewater Treatment
Wastewater results from autoclave blowdown condensate and a
periodic discharge (purge) of the water used in the
convection process of steam generation at plants 7100 and
7101. Blowdown condensate results when the autoclave is
vented at the end of a curing cycle (8-10 hours). For this
reason, blowdown condensate is only produced approximately
1-2 hours/day at the plants visited. The discharge of
autoclave purge at plant 7100 occurs once a week resulting
in an intermittent wastewater flow. Plant 7101 discharges
autoclave purge after each curing cycle. Plant 7100 settles
out suspended solids from autoclave blowdown condensate and
autoclave purge in an earthen settling pond. Plant 7105
removes suspended solids from autoclave blowdown condensate
in a concrete settling basin. Plant 7107 treats suspended
solids in an evaporation/percolation pond. Plant 7101 is
installing a wastewater treatment system to settle suspended
solids from blowdown condensate and autoclave purge using a
settling basin. The clarified decant may be used for
aggregate stock pile dust control, thereby eliminating
discharge.
No additional wastewater treatment methods were found in the
U.S. plants contacted, however, a Canadian concrete block
plant (plant 7113) visited had an automatically controlled
acid-neutralization system. This installation consisted of
a 500 gallon acid-proof tank, with a pH sensor that actuated
a solenoid valve controlling the addition of hydrochloric
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acid. The pH control was set to maintain a pH level of
9.0-9.5, but effluent analyses were not available.
3. \.2 .5 Ejffiluents and Disposal
Plants 7100 and 7101 currently discharge their treated
effluent to a waterway? plants 7105 and 7113 to a municipal
storm sewer, and plant 7107 to an evaporation/percolation
pond. Constituents of the treated effluents from plants
7100 and 7105 measured by Versar are:
Plant
7100
7105
1/kkg
(gal/tonX
50 (12)
214 (51)*
Constituents mq/liter
Concentration Amount^ kg/kkg
TSS
PH
COD
Oil and grease
TSS
pH
COD
Oil and grease
20
11.3
48
2
54
11.5
unknown
unknown
lb/1000 .Ibs
0.001
0.0024
0.0001
0.01
unknown
unknown
*plant supplied
3 .2 Concrete Products , N.E.C.
All products in the concrete products (NEC) category require
similar raw materials, cement, aggregate and water, and
differ primarily in the specific use for each product. The
size, shape, mix proportions, amount of steel reinforcement,
surface texture and prestressing are determined by the
ultimate use for the product. The three commodity groups
reported by the Census Bureau are concrete pipe, precast
concrete products, and prestressed concrete products.
Precast and prestressed concrete products have similar water
use and production processes. Furthermore, about 50 per
cent of the plants surveyed produce both types of product.
Characteristics common to both types of products are sawing,
transport of concrete from the central mixer to the casting
area in buckets, washout of central mixer and transport
buckets, and surface texturing by chemical or mechanical
means. The main difference between precast and prestressed
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products is that steel tendons are stressed in the
prestressed products to give the structural member a higher
strength. Because of these similarities, precast and
prestressed products are included in one subcategory.
In the production of concrete pipe and precast and
prestressed products, three curing methods are used.
Atmospheric curing uses ambient heat and humidity to cure
the product. Steam curing involves placing the product in
an enclosure into which steam is injected. Water spray
curing involves spraying the uncured product with a mist of
water to assist curing. There is no wastewater from
atmospheric curing. Wastewater from steam curing and spray
curing contains suspended solids, oil and grease and has a
high pH.
According to the Bureau of the Census, 3,199 companies
operated 3,595 plants in the concrete products (NEC)
industry in 1972. In this study, 24 plants were visited,
data were obtained from 175 plants and 9 plants were
sampled. On a plant basis, data were obtained from 5 per
cent of the industry which represents 30 per cent of the
concrete pipe plants and 3 per cent of the precast and
prestressed products plants.
3.2.1 Concrete Pipe
3.2.1.1 Process Description
The production of concrete pipe includes batch mixing,
fabricating, inserting steel reinforcing, pouring concrete
into a pipe form, curing and finishing. Batch mixing
involves blending cement, aggregates and water in a central
mixer. There are three methods for curing pipe - low
pressure steam curing, atmospheric curing or spray curing.
Finishing may include endsawing or application of grout.
Pressure pipe production is similar but may also include
prestressing with steel wire, fabricating and hydrostatic
testing a steel liner, applying a layer of grout, and curing
a second time using low pressure steam. Figure 3 is a
process flow diagram for the production of culvert, storm
sewer, and sanitary sewer pipe. Figure 4 is a process flow
diagram for the production of pressure pipe.
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V-16
DR^T
-------
DRAFT
Annual production of concrete pipe for the 9 plants visited
ranges from 16,000 to 106,000 kkg (18,000 to 117,000 tons).
3.2.1.2 Raw Waste Loads
Waterborne pollutants include suspended solids, oil and
grease, pH and COD. These pollutants result from central
mixer and transport bucket washout, spincast wastewater,
condensate from steam curing, spray curing wastewater, and
form washout. Waterborne waste solids also originate from
the pre-wetting of imbedded pressure pipe. Pollutants in
storm water runoff were not found to be a problem in this
subcategory.
Solid wastes include cement dust from concrete batching,'
solids from mixer clean-out and broken pipe. The cement
dust is usually collected in a baghouse and returned to the
cement storage silo. Waste solids from mixer cleanout,
broken pipe and waste concrete are usually landfilled.
Waste solids from central mixer and transport buckets
average 35 kg/cu m (100 Ibs/cu yd) of central mixer and
transport bucket capacity for each washout. This value was
used for the estimation of total suspended solids in the raw
waste loads given below. In most cases, the plants are
unable to quantify raw waste loads. Efforts to obtain
samples and thereby directly obtain raw waste data were
unsuccessful in most cases because of rapid solidification
of the samples.
Raw waste loads vary from day to day and depend on operating
factors, number of central mixer and bucket washouts,
duration of curing, and the amount of waste concrete.
Estimated average raw waste loads for plants contacted are
listed together with pH values measured by Versar:
V-17
DRAFT
-------
DRAFT
Estimated Waterborne Raw Waste Loads at Concrete Pipe Plants
kq/kkg product (lb/1000 Ib) , as applicable
Source Parameter
central
mixer and
transport
bucket
washout
Spincast
wastewater
Steam
condensate
Pre-wetting
Spray cure
waste
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
TSS
PH
7201
1.5
#
*
#
0.019**
12.0
0.0009
*
0.02**
8.9
0.0005
*
none
N.A.
none
none
N.A.
7205
none
none
N.A.
none
none
0.01
*
*
*
none
N.A.
none
none
N.A.
7224
26
11.4
*
*
*
11.7
*
*
*
11.0
*
*
none
N.A.
none
*
9.0
7229
2
*
#
*
none
N.A.
none
none
*
*
#
*
none
N.A.
none
none
N.A.
*unknown
**Versar data
N.A. not applicable
V-18
DRAFT
-------
Source
Parameter
Central
mixer and
transport
bucket
washout
TSS
pH
Oil and
grease
COD
1.
*
#
#
5
DRAFT
kg/kkg product (lb/1000 Ib), as applicable
7233 7241 7247*** 7248***
Spincast
wastewater
TSS
pH
Oil and
grease
COD
none
N.A.
none
none
Steam
condensate
TSS
PH
Oil and
grease
COD
none
N.A.
none
none
Pre-wetting
Spray cure
waste
TSS
pH
Oil and
grease
COD
TSS
PH
none
N.A.
none
none
none
N.A.
3
*
*
none
N.A.
none
none
*
*
*
none
N.A.
none
none
none
N.A.
67
11.3
*
16
12.2
*
3
0.07
*
*
0.005
none
N.A.
100
*
20
*
*
10
*
*
*
*
*
#
none
N.A.
*unknown
**Versar data
***Pressure Pipe Plants
N.A. not applicable
3.2.1.3 Water Use
Process water is used for mixing concrete, washing out
central mixers, transport buckets and forms for vertical
cast pipe, curing and prewetting imbedded pressure pipe.
Forms are washed off at 50 per cent of the plants studied.
The water used for curing is either in the form of low
pressure steam or a fine mist. Miscellaneous process water
uses include hydrostatic testing of the steel cylinders for
pressure pipe, yard dust control, and miscellaneous
V-19
DRAFT
-------
DRAFT
7201
42
7
(
(1
10)
.7)
1205
56
(13)
none
7224
30
11
(7.
(2.
2)
6)
7229
42 (10)
**
1233
38
5
<»)
(1.2)
equipment washoff. Incidental water uses include boiler
blowdown and non-contact cooling of bearings and
compressors.
Water use is variable anci depends on operating factors,
number of central mixer and transport bucket washouts, and
the duration and type of curing. Because of these
variables, hydraulic loads in liters/kkg of product
(gal/ton) show a wide range. Mix water in liters/kkg of
product, which becomes part of the product, is relatively
constant.
Quantity, liters/kkg of product (gal/ton)
Mix water
and transport
bucket washout
Steam 28 (7) 31 (7.4) 134 (32) ** none
condensate
Spray cure none none 36 (8) none none
water
Form washout
Pre-wetting
Hydrostatic
testing
**Unknown
1.75
(0.42)
none
none
none
none
none
included
in c/m
washout
none
13 (3)
none
none
none
included
in c/m
washout
none
none
V-20
DRAFT
-------
DRAFT
Quantity, liters/kkg of product (gal/ton)
7239
25 (6)
none
1 (0.25)
none
1.3
(0.31)
none
none
7241
74 (18)
0.92
(0.22)
*#
none
0.92
(0.22)
none
none
7247*
42 (10)
334
(80)
113
(27)
none
none
150 (36)
75 (18)
7248*
42 (10)
21
(5)
83.4
(20)
none
none
**
**
Mix water
Central mixer
and transport
bucket washout
Steam condensate
Spray cure water
Form washout
Pre-wetting
Hydrostatic
testing
*Pressure Pipe Plant
* *Unknown
Additional water use data were obtained from 142 plants
through a survey conducted by the American Concrete Pipe
Association. These data, collected by the association, are
summarized below. Figure 5 shows the distribution of
wastewater hydraulic loads from 138 of these plants.
V-21
DRAFT
-------
DRAFT
U.
O
O
I
10,000-
5,OOOJ
2,000
1,000
500h
200
100
50
20
10
TOTAL OF:
FORM WASHOUT
CUR/NG WATER
BO/LER SLOWDOWN
STEAM CONDENSATE AND OTHER
1251020 4060 80 9095 9899
CUMULATIVE PERCENT OF PLANTS
LESS THAN
FIGURE 5
DISTRIBUTION OF WASTEWATER HYDRAULIC LOADS
AT CONCRETE PIPE PLANTS
(DATA FROM 138 PLANTS)
V-22
DRAFT
-------
DRAFT
Maximum Minimum Average
Production of plants, kkg/day 772 1.9 135
Mix water, liters/kkg of product 417 2.1 58
Form washout water, liters/kkg
of product 235 0.2 21
Curing water, liters/kkg of
product 698 0.5 80
Other water, liters/kkg of
product 8,258 0.6 300
Steam condensate, liters/kkg
of product 8,785 0.1 147
Total wastewater generated*,
liters/kkg of product 8,995 0.2 174
*Excludes mix water
3.2.1.4 Wastewater Treatment
Wastewater comes from central mixer and transport bucket
washout, spincasting, low pressure steam condensate, spray
curing, form washoff, prewetting of imbedded pressure pipe
and miscellaneous sources such as hydrostatic testing.
Central mixer and transport bucket washout are approximately
25 per cent of the wastewater volume.
Wastewater volumes from 3 plants sampled range from 28 to
1,000 liters/kkg of product (6.7-240 gal/ton). Typical
wastewater treatment involves only the removal of suspended
solids. All of the plants studied use settling basins or
ponds to remove suspended solids from central mixer and
transport bucket washout and spincast wastewater. Plants
7224 and 7247 treat low pressure steam condensate, while
plants 7201, 7205, 7229, 7233, 7239, 7241, and 7248 do not.
Plant 7224 collects spray curing wastewater, settles out
suspended solids, and reuses the clarified water for spray
curing. Plant 7247, a pressure pipe plant, combines all
wastewater streams, settles out suspended solids, removes
oil and grease by skimming and sorbant booms, and adjusts
the pH of the clarified decant with sulfuric acid.
V-23
DRAFT
-------
DRAF1]
Ef fluents and
Methods of wastewater disposal at plants studied are given
below.
Plant.
7201
7205
7224
7229
7223
7239
7241
7247
7248
Municipal
Storm Sewer
Evapor at ion/'
Percolation
Waterway
x
x
X
X
X
X
Information on discharged wastewater at concrete pipe plants
based upon Versar measurements is given below.
Plants
Flow, liters/kkg
(gal/ton)
pH
1201
28
(6.7)
11.5
Parameter amounts,
kg/kkg (lb/1000 Ib)
TSS 0.002
COD 0.003
Gil and grease 0.01
Parameter concentra-
tions, mg/liter
TSS" ~ 70
COD 115
Oil and grease 376
7224
161
(39)
9.0
0.13
0.08
0.04
837
466
264
7247 7247*
1,000 743
(245) (178)
7.4 7.5
0.006 0.013
0.16 not measurec
0.003 0.004
6 17
161 not measured
2.9 5.5
#These values represent four months effluent sampling data
supplied by the plant.
V-24
DRAFT
-------
DRAFT
Permit application (NPDES) data for additional concrete pipe
plants were reviewed. Usable discharge data were obtained
from five plants. These are summarized:
7249 725Q 7224 7251 7252
Flow, liters/kkg 1,202 235 1,070 278 329
(Ib/ton) (288) (56) (256) (67) (79)
PH 9.5 8.0 11 9.6 8.8
Parameter amounts,
kg/kkg (lb/1000 Ib)
TSS 0,12 0.002 0.35 0.009 0.03
COD 0.12 0»005 0.1 0.004 0.013
Oil and grease 0.03 0.003 not given 0.017 0.004
Parameter concen-
trations, mg/liter
TSS 100 8 327 32 92
COD 103 20 93 15 39
Oil and grease 26 11 not given 64 11
3.2.2 Precast and. Prestressed Concrete Products
3.2.2.1 Process Description
The production of precast concrete products includes:
preparation of a mold or form; fabrication of steel
reinforcement cages; mixing cement, aggregate and water in a
central mixer; placing the concrete mixture into the form;
initial curing either under atmospheric conditions, with low
pressure steam, or with a water spray; removal of the form;
completion of curing, usually at atmospheric conditions;
and, for special products, a finishing step which may
include sawing, washing, etching, or sand blasting.
Prestressed concrete products are manufactured similarly
with the additional step of pretensioning or prestressing
the steel reinforcing rods, prior to pouring the concrete
into the form. Prestressed concrete products are typically
cured with low pressure steam. Product finishing, similar
to precast products, is common practice. A process flow
diagram for precast and prescressed concrete products is
shown in Figure 6.
V-25
DRAFT
-------
DRAFT
kl
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SI
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COLLECTOR f
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£L
V-26
DRAFT
-------
DRAFT
Annual production of precast and prestressed concrete
products for the 15 plants visited varies from 1,800 to
227,000 kkg (2,000 to 250,000 tons).
3.2.2.2 Raw Waste Loads
Waterborne wastes result from central mixer and transport
bucket cleanout, form washoff, low pressure steam and spray
curing, product finishing and miscellaneous equipment
washoff. Pollutants in the wastewater are suspended solids,
high pH, COD, and oil and grease. Concrete batching
produces cement dust, a solid waste which is usually
collected in a baghouse and returned to the cement storage
silo.
The waste concrete left over at the end of a working day
creates a waterborne waste if washed out, or a solid waste,
if scraped out and landfilled. Most plants landfill waste
concrete. Pollutants in storm water runoff were not found
to be a problem in this subcategory.
Raw waste loads vary from day to day and depend on operating
factors, number of "pours", number of central mixer and
transport bucket washouts per day, duration of curing,
number of products finished, and the amount of waste
concrete. Estimated raw waste loads for selected plants are
shown in kg/kkg of product (lb/1000 Ib) together with pH
values measured by Versar:
V-27
DRAFT
-------
DRAFT
Source
Parameter
7200
Plant
7203 " 7204
*unknown
**not applicable
7206
Central
mixer and
transport
bucket
washout
Curing
Product
Finishing
Waste
concrete
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
0.5
*
*
*
none
**
none
none
none
*
*
*
1.7
2.5
#
*
*
none
**
none
none
0.005
11.7
*
*
none
2 3
* *
* #
* *
* A
jfe s&
* *
* *
none none
* *
* A
# A
H 10
V-28
DRAFT
-------
DRAFT
Source
Parameter
7207
Central
mixer and
transport
bucket
washout
Curing
Product
finishing
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
PH
Oil and
grease
COD
16
*
*
*
none
**
none
none
*
*
*
*
7230
8
*
*
1.5
*
Waste
concrete
TSS
7
*
*
*
none
7231
9
*
*
none
**
none
none
none
**
none
none
1
7232
47
11.7
*
*
*
*
none
**
none
none
5
*unknown
**not applicable
V-29
DRAFT
-------
DRAFT
Source
Parameter
7234
Central
mixer and
transport
bucket
washout
Curing
Product
finishing
Waste
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
pH
Oil and
grease
COD
TSS
4
*
*
*
*
*
*
*
none
**
none
none
5
7235
36
*
*
none
**
none
none
13
*
7240
0.011
7244
1
none
**
none
none
*
*
35
0.012
*
*
*
•ft.
*
*
*
*
*
none
#*
none
none
a
#
*
*
8
concrete
* unknown
**not applicable
Waste solids from central mixer and transport bucket washout
average 35 kg/cu m (100 Ib/cu yd) of central mixer and
transport bucket capacity for each washout. This value was
used for the estimation of total suspended solids in the raw
waste loads given above.
In most cases, the plants are unable to quantify raw waste
loads. Efforts to obtain samples and determine meaningful
raw waste data were unsuccessul. It is impracticable to
process raw waste samples from the industry due to rapid
solidification of the samples.
Plants 7200, 7203, 7207, 7231, 7235, and 7244 use
atmospheric curing and have no curing wastes. Plant 7238
uses dry electric heat for curing.
V-30
DRAFT
-------
DRAFT
3.2.2.3 Water Use
Process water is used for mixing concrete; washing central
mixer, transport bucket and forms; curing (low pressure
steam and spray curing); and product finishing.
Miscellaneous process water uses include yard dust control
and equipment washoff. Incidental water uses include boiler
blowdown and non-contact cooling of bearings and
compressors.
Water use varies from day to day and depends on production,
number of central mixer and transport bucket washouts,
duration of curing, and the type of product finishing.
Because of these variables, water use in liters/kkg of
product for the plants studied shows a wide range. The
distribution of hydraulic loads of total water use is shown
in Figure 7.
Process hydraulic loads at selected plants are shown below in
liters per kkg of product (gallons/ton):
Plants
Mix water
Central mixer
and bucket
washout
Curing
Product
finishing
7200
63
(15)
2
(0.42)
none**
7203
63
(15)
8.2
(2)
none**
7204
54
(13)
14
(3.4)
24
(5.8)
7206
54
(13)
10
(2.5)
*
none
15
(3.5)
none
none
V-31
DRAFT
-------
DRAFT
22
O
o
.
P
o
a:
fc
2
LU
Ld
-s.
i
on
LU
i
I.OOOr
500
200
100
50
20
10
I 1
I 2 5 10 20 40 60 80 90 95 98
CUMULATIVE PERCENT OF PUNTS LESS THAN
FIGURE 7
DISTRIBUTION OF WASTEWATER AT PRECAST
AND PRESTRESSED CONCRETE PRODUCTS PLANTS
(DATA FROM 32 PLANTS)
V-32
DRAFT
-------
DRAFT
Mix water
Cental mixer
and bucket
washout
Curing
Product
finishing
Mix water
Central mixer
and bucket
washout
Curing
Product
finishing
Other (truck
washout)
none
Plants
7207
42
(10)
87
(21)
none**
521
(125)
7235
63
(15)
14
(3)
none**
61
(15)
7230
54
(13)
139
(33)
35
(8.3)
75
(18)
Plants
7238
54
(13)
63
(39)
none
*
7231
54
(13)
8.3
(2)
none**
none
7240
54
(13)
25
(6)
none
*
7232
58
(14)
8.7
(2)
*
none
7244
63
(15)
10
(2.5)
none**
17
(4.2)
7234
63
(15)
104
(25)
209
(50)
none
none
5
d)
none
* unknown
**atmospheric curing
3 .2 . 2.4 Wastewater Treatment
Wastewater results from central mixer and transport bucket
washout; form washoff; curing (low pressure steam condensate
and runoff from spray curing) ; product finishing; and mis-
cellaneous contributions such as wastewater from eguipment
clean-up, runoff from solid waste piles, and any spills thay
may occur. Central mixer and transport bucket washout
V-33
DRAFT
-------
DRAFT
constitute approximately 50 per cent of the d^ily wastewater
volume. Mix water is incorporated into the concrete and
does not become a source of wastewater, Forpi washoff may be
used but was not observed„
Total reported daily wastewater volumes from the plants
contacted ranges from 7 to 608 liters/kkg (2 to
145 gallons/ton).
Wastewater treatment is principally the removal of suspended
solids by sedimentation prior to reuse or discharge. Plant
7238 adjusts pH as part of its treatment method.
Approximately 30 per cent of the plants contacted have no
wastewater treatment.
Suspended solids are removed either by settling in ponds or
basins or by mechanical clarification. At most plants the
removed solids are landfilled. Where pH is adjusted, it is
done with sulfuric acid in a holding or mixing tank.
The methods of wastewater treatment at plants studied are
tabulated below.
Settling Pond, Mechanical pH
Plant None Tank or Basin Clarification Adjustment
7200 x
7203 x
720U x
7206 x
7207 x
7230 x part x part
7231 x
7232 x
7234 x
7235 x
7238 xx x
7240 x
7244 x
V-34
DRAFT
-------
DRAFT
3.2.2.5 Effluents and Disposal
Methods of wastewater disposal at plants studied are shown below:
Plant
7200
7203
7204
7206
7207
7230
7231
7232
7234
7235
7238
7240
7244
Municipal
Storm Sewer
Treatment
Municipal Evaporation/
Plant Percolation
x partial
x partial
x
X
X
X
X
X
X
X
X
X
Waterway Other
Yard runoff
sludge
landfilled
Effluent information on discharged wastewater at plants
studied follows. These data are Versar measurements. Plant
7238 verification data was obtained during startup and is
probably atypical. The oil found by Versar measurement in
this plant's effluent is used for mosquito control not from
the manufacture of precast and prestressed cement products.
V-35
DRAFT
-------
DRAFT
Plants
Flow, liter/kkg
kkg (gal/ton)
pH
Parameter amounts
kg/kkg (lb/1000 Ib)
TSS
COD
Oil arid grease
7203
24
(5.8)
11.5
0.002
0.0009
0.00002
7207
87
(21)
11.4
0.02
0.0014
0.0003
7230
139
(33)
10.9
0.07
0.05
0.0002
7232
8.7
(2.1)
11.7
0.003
0.009
7 x 10-7
Parameter Concentration
mg/liter
TSS
COD
Oil and grease
97
57
0.8
230
16
4
488
335
1.4
353
101
0.08
V-36
DRAFT
-------
7238
Flow, liter/Kkg 201
(gal/ton) (48)
pH 9.8
Parameter amounts
kg/kkg (lb/1000 Ib)
TSS 0.002
COD 0.003
DRAFT
Plant
7238*
249
(36)
7.5
7253**
371
(89)
9.1
0.013
Oil and grease 0.013
Parameter concentration
mg/liter
TSS
0.098
0.046
0.015
COD
Oil and grease
12
14
64
88
264
not given 125
not given 4 1
*Plant supplied information
**Permit application(NPDES) data for seven additional con-
crete product plants were reviewed. Useable information was
obtained from plant 7253.
3.3 Ready-Mixed Concrete (SIC 3273)
The three types of ready-mixed concrete plants - permanent,
portable and mobile — differ markedly in their wastewater
problems. Permanent ready-mixed concrete plants often have
extensive wastewater treatment facilities or room for such.
Their plant yards may be paved. Portable ready-mixed plants
are designed to be moved to locations that are near the
sole, short-term user of their product (highway paving,
building construction, dam construction, etc.). Their plant
sites are generally leased, yards are not paved and space
for wastewater treatment is limited. Strict quality control
requirements are placed on concrete used for paving, thus
more waste concrete may be generated. Mix ratios are not
V-37
DRAFT
-------
DRAFT
changed often, therefore, there are fewer truck washout
operations. Mobile concrete plants use trucks capable of
measuring and mixing, aggregate, cement and water at the job
site. Truck washout is not usually done at the plant site.
Mobile plants represent a small part of the total volume and
most of their sales are to private individuals for small
jobs such as sidewalks and patios.
Major sources of wastewater in the ready-mixed concrete
industry are truck washout and washoff and central mixer
washout.
According to the 1972 census, 3,978 companies operate
4,915 plants in the ready-mixed concrete industry. However,
the National Ready-Mixed Concrete Association (NRMCA) puts
the number of plants at approximately 8,000. NRMCA data
indicate there were 5,266 companies in 1971.
In this study, 57 plants were visited, operating and
effluent data were obtained from 380 other plants and 15
plants were sampled. On a total production basis, data were
obtained from 15 percent of the industry.
3.3.1 Permanent Ready-Mixed Concrete Plants
3. 3.1.J Process Description
Ready-mixed concrete is manufactured by one of three
methods: central-mixed concrete made in a stationary mixer
and is delivered either in a truck agitator, a truck mixer
operating at agitating speed, or a special non-agitating
truck; shrink-mixed concrete mixed partially in a stationary
central mixer and completed in a truck mixer; and completely
truck-mixed concrete.
At a permanent ready-mixed concrete plant, the raw materials
— cement, fine and coarse aggregate, mix water and special
admixtures — are weighed or metered into either a central
mixer and discharged into a mixer truck, or dry-batched
directly into a ready-mixed truck, which serves as the
mixer. The plastic, unhardened concrete is then delivered
to the job site to be poured. Afterward, the mixer truck
returns to the batching plant for another load of concrete.
If the mix recipe is different, the truck is washed out
V-38
DRAFT
-------
DRAFT
prior to receiving a fresh load. A process flow diagram is
shown in Figure 8.
Annual production of ready-mixed concrete for the 437 plants
contacted or visited ranges from 1,530 to 230,000 cu m
(2,000 to 300,000 cu yd). Approximately 25 percent of the
plants use central mixers.
3.3.1.2 Raw Waste Loads
The raw wastes for all plants consist of solid wastes from
concrete batching and waterborne solids from clean-up of
mixer trucks and central mixers. Concrete batching wastes
include cement dust and aggregate fines which are usually
collected in a baghouse and recycled to the storage silo.
Waste solids from washout of the central mixer and mixer
trucks average 35 kg/cu m (100 Ibs/cu yd) of central mixer
and mixer truck capacity for each washout. Average mixer
truck volume is 6.9 cu m (9 cu yd); average central mixer
volume is 3.8 cu m (5 cu yd). This waste value was used for
the estimation of total suspended solids in the waterborne
raw waste loads given below. In most cases, the plants are
unable to quantify raw waste loads. Efforts to obtain
samples and thereby directly obtain raw waste data were
unsuccessful because of rapid solidification of the raw
waste samples.
V-39
DRAFT
-------
DRAFT
V-40
DRAFT
-------
DRAFT
Estimated Waterborne Raw Waste Loads of Suspended
Solids at Ready-Mixed Concrete Plants,
kg per cu m of production (Ib/cu yd)
Truck
Plant
7305
7363
7365
7385
7441
7451
7452
7487
7542
7543
7544
7545
7699
7729
7731
7732
7736
7750
7755
7757
Washout
19
12
12
3
12
13
14
26
24
16
20
29
^9
60
29
66
31
21
23
33
(53)
(33)
(33)
(9)
(36)
(38)
(40)
(74)
(70)
(47)
(56)
(84)
(27)
(173)
(80)
(91)
(90)
(60)
(66)
(96)
Truck
Washoff
0.6 (2)
3 (8)
0.36 (1)
1 (4)
0.4 (1)
0.65 (2)
1.7 (5)
0.59 (2)
2 (6)
5 (14)
2 (6)
1.6 (5)
0.46
(1.3)
1 (3)
0.35 (1)
1.3 (4)
0.49
(1.4)
0.65 (2)
0.28
(0.8)
0.61
(1.7)
Central
Mixer
Washout
none
0.29
(0.8)
none
0.58
(1.7)
0.43
(1.3)
none
none
none
none
none
none
0.3 (1)
none
none
none
none
none
none
0.33 (1)
none
Return
Concrete
1.2 (4)
13 (38)
7 (20)
included in
truck washout
included in
truck washout
23 (66)
13 (38)
included in
truck washout
included in
truck washout
13 (38)
included in
truck washout
included in
truck washout
105 (304)
included in
truck washout
included in
truck washout
included in
truck washout
included in
truck washout
14 (40)
included in
truck washout
included in
truck washout
Yard
Runoff
unknown
unknown
unknown
unknown
9.4 (27)
unknown
unknown
unknown
unknown
10.3 (30)
V-41
DRAFT
-------
DRAFT
The general practice in the construction industry is to
order slightly more concrete than estimated to do the job.
In some cases, the excess is dumped on the job site. In
most cases, it is returned to the plant in the mixer truck
either to be incorporated in the following load or
discharged from the truck as waste. The average amount of
returned concrete is 1 to 4 percent of production and may
generate a waterborne waste if discharged to the wastewater
treatment system or a solid waste if landfilled. At some
plants, returned concrete is molded into useful items such
as splash blocks or patio blocks.
Mix water spillage, mixer truck chute rinse-off and rainfall
contribute to yard runoff.
The raw waste loads vary from day to day and depend on
operational factors, such as number of trucks operating,
number of washouts and washoffs per truck, and the amount of
returned concrete. Most of those raw wastes are usually
generated over a short period of time near the end of the
working day. Consequently, large amounts of waste require
treatment or temporary storage during these times.
Raw waste loads are estimated as follows. Suspended solids
from truck washout were calculated by multiplying the number
of trucks times 1.5 washouts per day per truck times 35 kg
of solids washout per cu m of truck capacity times 6.9 cu m
of capacity divided by the plant daily production.
Suspended solids from central mixer washout were calculated
by multiplying the number of central mixers times 1.5
washouts per central mixer per day times 35 kg/cu m times
3.8 cu m central mixer capacity divided by the plant's daily
production. Suspended solids in truck washofjE were
calculated by multiplying 11.4 kg per truck times 1.5
washouts per day times the number of trucks divided by the
plant's daily production.
Concentrations of suspended solids were also calculated from
these values using the reported flow rates, and they ranged
from 32.5 to greater than one thousand grams/liter. Values
of COD in raw wastes were not reported by the plants. It
was found to be impracticable to analyze raw wastes samples
from the industry due to rapid solidification of collected
samples.
V-42
DRAFT
-------
DRAFT
The plant-supplied pH data obtained for raw waste streams
was
plant 7363 truck washout - 12.3
plant 7365 truck washout - 12.5
plant 7385 yard runoff - 11.2
3.3.1.3 Water Use
Process water consists of mix water, central mixer washout,
and mixer truck washout and washoff. There is also
miscellaneous process water used for yard dust control,
aggregate moisture control, chute rinse-off and equipment
clean-up which, in most plants becomes yard runoff.
Auxiliary water includes boiler blowdown and non-contact
cooling of bearings and compressors.
Water use varies from day to day depending on such operating
factors as number of mixer trucks operating, number of truck
and central mixer washout and washoffs, and amounts of other
miscellaneous water uses. Because of these variables,
hydraulic loads at those plants contacted have a wide range
of liters/cu m of product (gallons/cu yd). The distribution
of hydraulic loads found in this study is shown in Figure 9.
The amount of water used for mixing concrete ranges from 75
to 110 liters/cu m of product (26 to 38 gallons/cu yd). The
plant-by-plant breakdown of process hydraulic loads is given
below. One-fourth of the plants contacted reuse mixer truck
washout water for the same purpose. In addition,
seven plants studied reuse clarified mixer truck washout
water for a percentage of mix water make-up. Some plants
with mechanical aggregate separators use additional water
for aggregate separation. This water use is included in the
mixer truck washout in the following table.
V-43
DRAFT
-------
DRAFT
l,000r
z
o
g
o
U.
O
UJ
H
LJ
O
CQ
O
DC
UJ
Hi
500
EOO
100
50-
20
10
I
I
TOTAL OF:
CENTRAL MIXER WASHOUT
TRUCK WASHOUT
TRUCK WASHOFF AND
MISCELLANEOUS WASH
J I
5 K) 20 50 70 80 90 95 99
CUMULATIVE PERCENT OF PLANTS LESS THAN
FIGURE 9
DISTRIBUTION OF WASTEWATER GENERATED
AT PERMANENT READY-MIXED CONCRETE PLANTS
(DATA BASED ON 385 PLANTS 5
V-44
DRAFT
-------
DRAFT
Process Hydraulic Loads for Ready-Mixed
Concrete (Permanent) , liters/cu m (gal/cu yd)
Plant
7305
7363 *
7365
7385
7441
7451
7452
7487 *
7542
7543
7544
7545
7699
7729 *
7731
7732 *
7736 *
7750
7755
7757 *
Mix
Water
81 (28)
81 (28)
81 (28)
87 (30)
87 (30)
102 (35)
102 (35)
75 (26)
99 (34)
99 (34)
99 (34)
99 (34)
110 (38)
81 (28)
81 (28)
81 (28)
84 (29)
81 (28)
87 (30)
87 (30)
Truck
Washout
58 (20)
15 (5)
9 (3)
29 (10)
52 (18)
87 (30)
73 (25)
29 (10)
20 (7)
15 (5)
15 (5)
12 (4)
15 (5)
165 (57)
49 (17)
186 (64)
26 (9)
44 (15)
38 (13)
81 (28)
Truck
Washoff
9 (3)
9 (3)
3 (1)
1 (0.5)
12 (4)
15 (5)
15 (5)
9 (3)
38 (13)
38 (13)
41 (14)
32 (11)
1 (0.3)
20 (7)
6 (2)
23 (8)
9 (3)
12 (4)
3 (1)
6 (2)
Central
Mixer
Washout
none
1 (0.34)
none
1 (0.67)
6 (2)
none
none
none
none
none
none
3 (1)
none
none
none
none
none
none
3 (1)
none
Miscellaneous
9 (3)
unknown
unknown
145 (50)
unknown
unknown
unknown
unknown
unknown
15 (5)
11 (4)
76 (26)
9 (3)
unknown
unknown
unknown
unknown
unknown
unknown
unknown
* These plants reuse clarified mixer truck washout water
for a percentage of mix water make-up.
3 .3.1.4 Wastewater Treatment
Wastewater comes from mixer truck washout and washoff,
central mixer washout, and miscellaneous sources such as
yard dust control, mixer truck chute rinse-off, equipment
clean-up, and runoff from spills and solid waste piles. The
miscellaneous process water becomes yard runoff. Yard
runoff during rainfall is also process wastewater and needs
to be treated. Mixer truck washout and washoff constitute
approximately 80 percent of the wastewater volume. Mix
water is incorporated into the concrete and does not become
a source of wastewater.
V-45
DRAF
-------
DRAFT
The plants contacted reported wastewater volumes ranging
from 11 to 760 liters/cu m (4 to 260 gallons/eu yd) f with
less than 1 percent (U) of the plants having more than
210 liters/cu m (50 gallons/cu yd.) of w-;;stewater. Usually a
small portion of the wastewatar generated is discharged at
these plants as shown in Figxires 10 and 11.
Wastewater treatment generally involves sedimentation to
remove suspended solids. Two percent of the plants adjust
the pH of the wastewater for discharge as part of their
treatment. Six percent of the plants contacted have no
wastewater treatment. The sedimentation techniques usually
used in this industry are:
earthen ponds
concrete tanks or ponds
sloped slab basins
mechanical clarification units
Where pH is adjusted, sulfuric acid is typically the
chemical used. The wastewater treatment methods used at
plants visited is given as follows.
V-46
DRAFT
-------
DRAFT
500r
z
g
o
8
DC
Q.
U.
O
200
O
O
V.
co
oc
LJ
100
50
20
10
_L
5 10 20
CUMULATIVE
40 60 80 90 95
PERCENT OF PLANTS LESS THAN
FIGURE 10
DISTRIBUTION OF PROCESS WASTEWATER GENERATED
AND DISCHARGED AT READY-MIXED CONCRETE PLANTS
(VERSAR MEASUREMENTS OF 5 PLANTS)
V-47
DRAFT
-------
DRAFT
1
§
£
b
(£
UJ
UJ
o
m
3
UJ
5QOr
200-
2 5 10 20 40 60 80 90 95 99
CUMULATIVE PERCENT OF PLANTS LESS THAN
FIGURE \\
DISTRIBUTION OF EFFLUEMTS
FROM READY- MIXED CONCRETE PLANTS
(NPDES DATA FROM 32 PUNTS)
V-48
DRAFT
-------
DRAFT
Wastewater Treatment Practices at Selected
Ready-Mixed Concrete Plants
Plant
7305
7363
7365
7385
7441
7451
7452
7487
7542
7543
7544
7545
7699
7729
7731
7732
7736
7750
7755
7757
Settling
Pond
Sloped
Slab
Treatment Practiced
Mechanical pH
Clarifier Adjust
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Reuse of
Wastewater
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
3.3.1.5 Effluents and Disposal
The clarified wastewater may be reused for truck washout,
added to mix water, or discharged. In most plants the
solids removed from a sloped slab or a mechanical
clarification system are either sold as basefill material,
reused for batching concrete, or landfilled.
Specific information on wastewater disposal methods used at
some plants is presented as follows:
V-49
DRAFT
-------
Total
Containment
Plant
7305
7363
7365
7441
7451
7452
7487
7542
7543
7544
7545
7699
7729
7731
7732
7736
7750
7755
7757
Mixer truck washout
plants reducing the
DRAFT
Evaporation/
Waterway Percolation
x
X
X
X
X
X
X
X
Comments
Except during
heavy rainfall
Yard runoff dis-
charged during
heavy rainfall
Yard runoff dis-
charged during
heavy rainfall
Yard runoff dis-
charged to waterway
Yard runoff dis-
charged to waterway
Yard runoff dis-
charged to waterway
Landfilled
Discharge to
storm sewer
Yard runoff dis-
charged to waterway
Discharges to
municipal sewer
Yard runoff dis-
charged to waterway
and washoff are reused at many of the
requirements for disposal.
x
x
Twelve plants were found in this study which treat yard
runoff. Eight of the twelve plants combine and treat yard
runoff with other process wastewater.
Effluent information measured by Versar is given.
V-50
DRAFT
-------
Plant
7305*
DRAFT
7365
7542
7543**
Flow, liter/cu m
(gal/cu yd) 24 (8)
pH 12.1
Parameter Amounts,
kg/cu m (Ib/cu yd)
TSS 0.008
(0.02)
COD 0.003
(0.009)
Parameter Con-
centration,
ing/liter
TSS 125
COD 48
* Plant supplied data
** Yard runoff data
Plant 7544**
Flow, liter/cu m
(gal/cu yd) 11 (4)
pH 12.5
Parameter Amounts,
kg/cu m (Ib/cu yd)
TSS 0.0004
(0.0012)
COD 0.0008
(0.002)
Parameter Con-
centration,
mg/liter
TSS 38
COD 73
12 (4)
11.8
0.001
(0.003)
0.0008
(0.002)
89
65
7545
95 (33)
6.5
0.0009
(0.0025)
0.0007
(0.002)
9
7
145 (50)
5.7
0.0006
(0.0017)
0.003
(0.010)
4
23
7545**
76 (26)
10.8
0.005
(0.013)
0.006
(0.016)
61
73
15 (5)
10.1
0.00006
(0.00017)
0.0002
(0.0006)
4
15
7731
42 (14)
11.5
0.001
(0.003)
0.003
(0.009)
15
73
** Yard runoff
Additional effluent parameters measured by Versar are presented,
V-51
DRAFT
-------
Plant
mg/liter
7305*
DRAFT
7365
Plant data
7542
Alkalinity
Hardness, total
Total solids
Total volume
solids
Suspended solids
Dissolved solids
Oil
Phosphate, total
Nitrate
Nitrite
TKN
Sulfate
Sulfide
Fluoride
COD
Al
AS
Ba
Cd
Cr
CU
Fe
Pb
Mg
Mn
Hg
Mo
Ni
K
Se
Na
sr
Zn
PCB
405 695
not given 928
1,660 1,294
1,494 362
125 89
1,535 1,205
2 not
measured
not given 0.5
not given 1 . 7
not given 0.03
not given 5.5
not given 281
not given 0
not given 0.8
48 6.5
not given <0. 1
not given <0.01
not given <0.05
0.02 <0.005
<0.05 0.14
0.45 <0.01
not given 0.77
<0.01 0.75
not given 0. 5
<0.05 0.03
0.0015 <0.001
not given <0.05
<0.05 <0.01
not given 50
not given <1 .0
not given 21
not given 1.9
0.1 0.15
not given 0.003
4
128
7,368
6,988
4
7,364
0.32
0.425
0.4
0.006
16.4
215
0
0.9
23
<0.5
<0.003
<0.1
<0.01
<0.05
<0.05
1.9
<0.2
8.4
0.05
<0.001
0.0
<0.05
40
<1.0
30
0.25
0.05
<0.001
56
110
4,038
3,734
4
4,034
0.88
0.425
0.4
0.001
6.7
80
0
0.1
15
<0.5
<0.003
<0.1
<0.01
<0.05
<0.05
0.0
<0.01
3.38
0.0
<0.001
0.0
<0.05
18
<1.0
20
0.21
0.0
<0.001
V-52
DRAFT
-------
DRAFT
Plant
mq/ liter
Alkalinity
Hardness, total
Total solids
Total volume
solids
Suspended solids
Dissolved solids
Oil
Phosphate, total
Nitrate
Nitrite
TKN
Sulfate
Sulfide
Fluoride
COD
Al
As
Ba
Cd
Cr
Cu
Fe
Pb
Mg
Mn
Hg
Mo
Ni
K
Se
Na
Sr
Zn
PCB
7544
yard
runoff
2,460
510
5,066
462
38
5,028
1 .2
0.50
1.0
0.022
10.3
15
0
*
73
5.3
<0.003
2.0
<0.01
<0.05
<0.05
12.5
<0.05
8.5
0.14
<0.001
0.0
<0.05
900
<1.0
200
15.2
0.31
<0.001
7545
dis-
charge
36
460
5,266
4,406
9
5,257
0.32
0.42
24
0.006
9.5
540
0
0.5
7
<0.5
<0.003
<0. 1
<0.01
<0.05
<0.05
1.5
<0.05
7.2
0.06
<0.001
0.0
<0.05
50
<1.0
6.3
0.42
0.45
<0.001
7545
yard
runoff
108
160
5,192
4,444
61
5,131
0.4
0.49
1.65
0.013
8.9
45
0
0.6
73
2.9
<0.003
<0.1
<0.01
<0.05
<0.05
11.5
<0.05
10.5
0.11
<0.001
0.0
<0.05
40
<1.0
5.2
0.4
0.24
<0.001
7731
780
1,110
1,306
290
25
1,281
1.76
0.5
0.08
0.013
3. 99
473
0
0.9
73
<0. 1
<0.02
<0.05
<0.005
0. 13
0.02
0.05
<0.05
0. 10
0.01
<0.001
<0.05
<0.01
30
<1.0
69
1.9
0.06
<0.001
*not measured
V-53
DRAFT
-------
DRAFT
Effluent information from NPDES application data is given in
Table v-1.
Portable Ready ~Mi xe d Concrete
3 . 3 . 2 ._ 1 Procjass Description
Portable ready-mixed concrete plants use the same
manufacturing process as permanent plants with the following
exceptions:
(1) Mixing is done in central mixers predominantly (95 per
cent of those contacted) rather than in truck mixers.
(2) Only 29 percent of the plants contacted wash off mixer
trucks on a daily schedule.
(3) Mixer trucks make more trips in a day due to proximity
of the plant to the job site.
Annual production of ready-mixed concrete for the 21
portable plants contacted ranges from 13,000 to 153,000 cu m
(17,000 to 200,000 cu yd).
Raw Waste Loads
Raw wastes result from concrete batching and mixer washout
and truck washoff. Cement dust from concrete batching is
usually collected in baghouses located on the storage silos.
Collected dust is usually recycled to the storage silos.
Water borne pollutants include suspended solids, pH and COD
from central mixer washout and mixer truck washout and
washoff.
Waste solids from central mixer and mixer truck washout
average 35 kg/cu m (100 Ib/cu yd) of central mixer and mixer
truck volume. Average mixer truck volume is 6.9 cu m (9 cu
yd) and average central mixer capacity is 3.8 cu m (5 cu
yd) . Suspended solids from truck washout, were estimated by
multiplying the number of trucks times the actual number of
washouts per truck per day times 35 kg/cu m times 6.9 cu m
of average truck capacity divided by the plant daily
production. Suspended solids from central mixer washout
were estimated by multiplying the number of mixers times the
actual number of washouts per day times 3.8 cu m of central
mixer capacity divided by the plant daily production.
DRAFT
-------
DRAFT
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V-55
DRA^T
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DRAFT
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V-56
DRAFT
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DRAFT
The concentrations of suspended solids from truck and mixer
washouts were estimated dividing the above values by total
washout water volumes. Suspended solids from truck washoff
were estimated by multiplying the number of trucks times the
actual number of washouts per truck per day times 11.4 kg of
solids per washout divided by the daily production of the
plant. COD and pH were not reported by the plants for raw
wastes and it was found to be impracticable to collect and
analyze raw waste samples from the industry due to rapid
solidification of the samples.
Returned concrete at portable plants usually is due to
quality control rejection at the job site. The waste
concrete is either landfilled or converted to a waterborne
waste if discharged to a treatment system. Most portable
plants do not make by-products from their returned concrete.
Raw wastes from miscellaneous sources come from mix water
spillage, mixer truck chute rinse-off, and rainfall runoff.
Raw waste loads vary from day to day depending on
operational factors such as number of operating mixer
trucks, number of mixer truck washouts and washoffs and the
amount of returned concrete. The estimated raw waste loads
for twenty-one plants are shown.
V-57
DRAFT
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DRAFT
Raw Waste Loads for Portable Ready-Mixed
Concrete Plants, kg per cu m of product
(Ib/cu yd), and Estimated Suspended Solids
in mg/liter
Plant
7362
7601
7602
7603
7604
7609
7627 *
7633
7641
7649
7691
7706*
7707
7753
7758
Truck
Washout
unknown
53 (107)
4320 **
26 (53)
2160 **
45 (90)
2160 **
13 (27)
2160 **
52 (105)
1130 **
4.0 (8.1)
2160 **
9.4 (19)
380 **
67 (135)
810 **
7.5 (15)
620 **
7.0 (12)
4320 **
49 (99)
1170 **
48 (96)
650 **
16 (33)
540 **
unknown
Truck
Washoff
2.0 (3.9)
300 **
none
unknown
unknown
unknown
0.5 (1.0)
unknown
unknown
0.6 (1.3)
150 **
0.1 (0.2)
25 **
unknown
unknown
1.3 (2.7)
320 **
0.4 (0.9)
110 **
unknown
* Average of 4 plants
** mg/liter
Central
Mixer
Washout
none
0.37 (0.75)
300 **
0.73 (1.47)
120 **
1.2 (2.5)
120 **
0.92 (1.85)
600 **
0.69 (1.39)
120 **
0.30 (0.60)
120 **
0.37 (0.75)
300 **
0.62 (1.25)
30 **
0.21 (0.42)
120 **
0.19 (0.38)
600 **
0.34 (0.68)
100 **
2.2 (4.4)
300 **
0.75 (1.50)
150 **
none
Returned
Concrete
none
unknown
unknown
unknown
unknown
unknown
unknown
unknown
unknown
0.83 (1.67)
unknown
unknown
unknown
unknown
V-58
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lili.2^3 Water Use
Process water is primarily used in mixing, central mixer
washout, and mixer truck washout and washoff. Miscellaneous
process water is used for mixer truck chute rinse-off, yard
dust control, and for spraying stockpiles to moisten the
exterior of the pile to keep aggregate above the "saturated,
surface-dry (s.s.d.) condition". Miscellaneous water is
used for boiler feed and non-contact cooling of bearings and
compressors. Water use varies from day to day and depends
on operational factors such as number of mixer trucks
operating, and the number of mixer truck washouts and
washoff s.
Water use at portable plants is similar to that described
for permanent plants. The amount of water used for mixing
varies depending on the fineness of aggregates, desired
slump of the concrete, amount of cement in the mix and
amount of entrained air. Average amounts of mix water used
at the plants range from 72 to 115 liters/cu m (25 to
40 gallons/cu yd) . The process water use at several plants
is shown.
V-59
DRAFT
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DRAFT
Process Water Use for Portable Ready-Mixed
Concrete Plants, liters/cu m (gallons/cu yd)
Plant
7362
7601
7602
7603
7604
7609
7627 '
7633
7641
7649
7691
7706 '
7707
7753
7758
Mix
115 (40)
72 (25)
87 (30)
87 (30)
101 (35)
75 (26)
72 (25)
101 (35)
unknown
87 (30)
72 (25)
87 (30)
72 (25)
78 (27)
unknown
Truck
Washout
none
9 (3)
8.4 (2.9)
14 (5)
4.3 (1.5)
32 (11)
1.3 (0.45)
17 (6)
58 (20)
8.4 (2.9)
1.1 (0.38)
29 (10)
52 (18)
21 (7.3)
none
Truck
Washoff
4.6 (1.6)
none
none
none
none
1.6 (0.56)
none
none
7.2 (2.5)
0.49 (0.17)
none
none
5.2 (1.8)
10 (3.6)
none
Central
Mixer
Washout
none
0.9 (0.3)
4.3 (1.5)
7.2 (2.5)
1.1 (0.37)
4.1 (1.4)
1.7 (0.60)
0.87 (0.30)
14 (5)
1.2 (0.42)
0.23 (0.08)
2,4 (0.82)
5.2 (1.8)
3.5 (1.2)
none
* average of four plants
Recycle of mixer truck washout water for use as washout is a
fairly common practice at portable ready-mixed plants.
Reuse of clarified mixer truck washout water as part of mix
water make-up is not practiced by this industry because of
strict standards for mix water quality adopted by regulatory
agencies.
3.3.2.4 Wastewater Treatment
Wastewater comes from mixer truck washout and washoff,
central mixer washout and miscellaneous sources. The
miscellaneous sources of Wastewater are yard dust control,
mixer truck chute rinse-off, and runoff from spills and
solid waste piles. Mixer truck washout and washoff
constitute approximately 80 percent of the wastewater
volume.
The distribution of amounts of wastewater generated at the
plants studied is shown in Figure 12. Quantities of
wastewater discharged are less than these generated volumes
V-60
DRAFT
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DRAFT
iOOr
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50
20
10
TOTAL OF:
CENTRAL MIXER WASHOUT
TRUCK WASHOUT
TRUCK WASHOFF
\
J_
I
I I I I
I
I
2 5 10 20 40 60 80 90 95
CUMULATIVE PERCENT OF PLANTS LESS THAN
FIGURE 12
DISTRIBUTION OF WASTEWATER GENERATED
AT PORTABLE READY-MIXED PLANTS
(DATA FROM 18 PLANTS)
V-61
DRAFT
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because of recycle of mixer truck washout and washoff for
truck washout is practiced in the industry.
Typical wastewater treatment involves the removal of
suspended solids in a settling pond. There may be no
effluent from the pond because of evaporation and
percolation. None of the plants contacted adjust pH as part
of wastewater treatment. Ten percent of the plants
contacted had no system for recovery of wash water and hence
no treatment of wastewater.
Facilities to remove suspended solids vary in detail from
plant to plant but are of the following:
(1) earthen settling ponds,
(2) earthen settling ponds with filtered overflow,
(3) mechanical clarification systems.
Mechanical clarification systems are designed to settle and
separate suspended solids in a more compact space than
ponds. Plant 7753, which uses a mechanical clarification
system, uses the aggregate removed from the system for fill
material.
The methods of wastewater treatment used at several plants
are:
V-62
DRAFT
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Settling
Plant Pond
7362
7601
7602
7603
7604
7609
7627
(4 plants)
7633
7641
7649
7691
7706
(4 plants)
7707
7753
7758
x
X
X
X
X
X
X
X
X
X
X
DRAFT
Mechanical
Clarification
& Discharge
Reuse of
Wastewater
Other
no treatment,
no discharge
x
x
X
no treatment
filter pond
no treatment,
no discharge
3.3.2.5 Effluents and Disposal
The methods of wastewater disposal practiced at the plants
studied is presented. At some of the plants, recycle mixer
truck washout and washoff reduces the total volume of
disposed wastewater.
V-63
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Plant
7362
Total
Containment
7601
7602 x
7603 x
7604 x
7609
7627 x
(4 plants)
7633 x
7641
7649
7691 x
7706 x
(4 plants)
7707
7753 x
7758
DRAFT
Disposal
to Waterway
x
Other
Disposal
evaporat ion-percolation
on yard
yard dust control
no treatment
storm sewer
water used only to spray
stockpiles at plant site
Data on the quality of the effluents is not available from
portable plants but it would be similar to that of permanent
ready-mixed plants.
3.3.3
Ready-Mixed Concrete (Mobile)
31_. 3.3.1 Process Description
Mobile ready-mixed concrete trucks, "concrete-mobiles", are
miniature batch plants on wheels. Aggregate, cement, water
and admixtures are loaded in separate compartments on the
concrete-mobile at the batch building. The concrete-mobile
then travels to the job site, where the ingredients are
mixed together in the concrete-mobile mixer as they are
dispensed. In this manner, only the amount of concrete
needed for the job is mixed. Normally, no returned or waste
concrete results. Average capacity of a concrete-mobile is
5. 3 cu m (7 cu yd) .
There are approximately 1,800 mobile ready-mixed plants in
the U.S. ranging in annual production from 2,865 to
57,300 cu m (3,750 to 75,000 cu yd). Most firms use the
V-64
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concrete-mobile for small, homeowner type jobs, where rapid
mixing and dispensing of concrete is not critical.
Approximately 30 permanent ready-mixed concrete firms have
added a concrete-mobile to their fleet for these type jobs.
Figure 13 illustrates the production of mobile ready-mixed
concrete.
3.3.3.2 Raw Was_te Loads
Raw wastes result from loading the ingredients into the
concrete-mobile, mixer washout and truck washoff. Cement
dust from loading is usually collected in baghouses located
on the storage silos. Collected dust is usually recycled to
the storage silos.
Waterborne pollutants include suspended solids, pH and COD
resulting from concrete-mobile mixer washout and concrete-
mobile washoff.
Waste solids from mixer washout and concrete-mobile washoff
for the two plants contacted are estimated below.
Raw Waste Loads for Mobile Ready-Mixed Concrete
Plants, kg per cu m of product (Ib/cu yd)
Concrete-mobile Returned
Plant Mixer Washout Washoff Concrete
7759 0.5 (1.4) 0.6 (1.7) 3.5 (10)
7760 0.7 (2.0) 0.7 (2) none
COD and pH were not reported by the plants for raw wastes
and it was found to be impracticable to collect and analyze
raw waste samples from the industry due to rapid
solidification of the samples.
3.3.3.3 Water Use
Process water is primarily used in mixing, concrete-mobile
mixer washout, and concrete-mobile washoff. Miscellaneous
process water is used for yard dust control and for moisture
control of aggregate stockpiles. Incidental water uses
include boiler feed, and non-contact cooling of bearings and
compressors. Water use varies from day to day and depends
V-65
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V-66
DRAFT
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DRAFT
on operational factors such as number of operating concrete-
mobiles, the number of mixer washouts and the number of
washoffs. The amount of water used for mixing varies
depending on the fineness of aggregates, desired slump of
the concrete, amount of cement in the mix and amount of
entrained air. The process water use at two plants is shown
below:
Process Water Use for Mobile Ready-Mixed Concrete
Plants, liters/cu m (gallons/cu yd)
Plant Mix Mixer Washout Concrete-Mobile Washoff
7759 81 (28) 4.4 (1.5) 2 (0.7)
7760 81 (28) 3 (1) 3 (1)
3.3.3.4 Wastewater Treatment
Wastewater comes from mixer washout and concrete-mobile
washoff and miscellaneous sources. The miscellaneous
sources of wastewater are yard dust control and runoff from
spills and solid waste piles. Concrete-mobile mixer washout
and washoff constitute approximately 75 per cent of the
wastewater volume. Concrete in the plastic state is not a
source of wastewater.
Quantity of concrete-mobile wastewater at plant 7759 is
6.38 liter/cu m (2.2 gal/cu yd); at plant 7760 it is
5.8 liter/cu m (2 gal/cu yd). Since wastewater volumes are
small, treatment practices in the industry are not
sophisticated. Plant 7759 contains its wastewater in a
settling/evaporation area. Plant 7760 collects the
wastewater from concrete-mobile mixer washout in a bucket,
carries it to the next job site, and uses the wastewater to
"prime" the mixer. According to the manufacture of the
concrete-mobile, this later technique is commonly practiced
throughout the industry.
3.3.3.5 Effluents and Disposal
Plants 7759 and 7760 discharge their wastewater into an
evaporation/percolation area. It is estimated that all of
the industry discharges wastewater to an
evaporation/percolation area.
V-67
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fbJi RATIONALE FOR EFFLUENT LIMITATIONS GUIDELINES FOR
MAXIMUM DAILY VALUES
The bulk of the data used in the technical development of
the guidelines for the concrete products industries are
average performance values. For all practical purposes the
discharge data may be regarded as equivalent to monthly
average data.
It is recognized, however, that day to day discharges are
subject to a wide variety of factors which result in a
distribution of daily effluent values around a monthly mean.
Some of the reasons for greater daily variations in the
pollutant discharges are batchwise process aspects, intermi-
tent wo.stewater flows, process and treatment systems startup
and shutdown, the normal imprecision of process controls,
rainfall and other weather variations and the range of
differences among operating personnel.
The daily variability data for the most common pollutant
parameter in these industries, suspended solids is shown
graphically in Figure 14, where the maximum to average ratio
of the amount of suspended solids is plotted against the
cumulative per cent of the occurance. Using this
distribution curve, a daily maximum value based upon a ratio
of 6 to 1 would correspond to 85% of the distribution
falling below this for plants in all three subcategories.
Based on conservative practice, this value is recommended.
V-68
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Id
U.
U-
LU
CO
Q
CO
fc
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16
15
14
13
12
II
10
9
8
7
6
5
4
3
— 2
LEGEND:
® READY-MIXED CONCRETE
m CONCRETE BRICK AND
BLOCK AND CONCRETE
PRODUCTS (NEC)
J
20 30 40 50 60 70 80 90 95 98
CUMULATIVE PERCENT OF PLANTS LESS THAN
FIGURE 14
DISTRIBUTION OF MAXIMUM TO AVERAGE RATIOS
OF SUSPENDED SOLIDS IN EFFLUENT
FROM CONCRETE PRODUCTS INDUSTRIES
V-69
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SECTION VI
SELECTION OF POLLUTANT PARAMETERS
Li.®. INTRODUCTION
The wastewater constituents considered to be significant
pollutants for the concrete products industries are based
upon those parameters which have been identified in the
untreated wastes from each subcategory of this study. The
wastewater constituents are further divided into those that
have been selected as pollutants of significance with the
rationale for their selection, and those that are not deemed
significant with the rationale for their rejection.
The basis for selection of the significant pollutant para-
meters was :
(1) toxicity to terrestrial and aquatic organisms;
(2) substances causing dissolved oxygen depletion in
streams;
(3) soluble constituents that result in undesirable tastes
and odors in water supplies;
(4) substances that result in eutrophication and stimulate
undesirable algae growth;
(5) substances that produce unsightly conditions in
receiving water; and
(6) substances that result in sludge deposits in streams.
2..-J3 SIGNIFICANCE AND RATIONALE FOR SELECTION OF POLLUTION
PARAMETERS
.2-s.l Qil and Grease
Oil and grease exhibit an oxygen demand. Oil emulsions may
adhere to the gills of fish or coat and destroy algae or
other plankton. Deposition of oil in the bottom sediments
can serve to inhibit normal benthic growths, thus
interrupting the aquatic food chain. Soluble and emulsified
material ingested by fish may taint the flavor of the fish
flesh. Water soluble components may exert toxic action on
fish. Floating oil may reduce the re-aeration of the water
surface and in conjunction with emulsified oil may interfere
VI-1
DRAFT
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DRAFT
with photosynthesis. Water insoluble components damage the
plumage and coats of water animals and fowl. Oil and grease
in water can result in the formation of objectionable
surface slicks preventing the full aesthetic enjoyment of
the water. Oil spills can damage the surface of boats and
can destroy the aesthetic characteristics of beaches and
shorelines.
Oil and grease may be present in the wastewaters from
concrete block and brick, concrete products (NEC) and ready-
mixed concrete production.
2,2 pH, Acidity and Alkalinity
Acidity and alkalinity are reciprocal terms. Acidity is
produced by substances that yield hydrogen ions upon
hydrolysis and alkalinity is produced by substances that
yield hydroxyl ions. The terms "total acidity" and "total
alkalinity" are often used to express the buffering capacity
of a solution. Acidity in natural waters is caused by
carbon dioxide, mineral acids, weakly dissociated acids, and
the salts of strong acids and weak bases. Alkalinity is
caused by strong bases and the salts of strong alkalies and
weak acids.
The term pH is a logarithmic expression of the concentration
of hydrogen ions. At a pH of 7, the hydrogen and hydroxyl
ion concentrations are essentially equal and the water is
neutral. Lower pH values indicate acidity while higher
values indicate alkalinity. The relationship between pH and
acidity and alkalinity is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing
fixtures and can thus add such constituents to drinking
water as iron, copper, zinc, cadmium and lead. The hydrogen
ion concentration can affect the taste of the water. At a
low pH, water tastes sour. The bactericidal effect of
chlorine is weakened as the pH increases and it is
advantageous to keep the pH close to 7. This is very
significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress
conditions or kill aquatic life outright. Even moderate
changes from "acceptable" criteria limits of pH are
VI-2
DRAFT
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DRAFT
deleterious to some species. The relative toxicity to
aquatic life of many materials is increased by changes in
the pH of the water. Metallocyanide complexes can increase
a thousandfold in toxicity with a drop of 1.5 pH units. The
availability of many nutrient substances varies with the
alkalinity and acidity.
The lachrymal fluid of the human eye has a pH of
approximately 7.0 and a deviation of 0.1 pH unit from the
norm may result in eye irritation for the swimmer.
Appreciable irritation will cause severe pain. High pH was
found in all the concrete products industries.
2.3 Total Suspended Solids
Suspended solids include .both organic and inorganic
materials. The inorganic components include sand, silt, and
clay. The organic fraction includes such materials as
grease, oil, tar, animal and vegetable fats, various fibers,
sawdust, hair and various materials from sewers. These
solids may settle out rapidly and bottom deposits are often
a mixture of both organic and inorganic solids. They
adversely affect fisheries by covering the bottom of the
stream or lake with a blanket of material that destroys the
fish-food bottom fauna or the spawning ground of fish.
Deposits containing organic materials may deplete bottom
oxygen supplies and produce hydrogen sulfide, carbon
dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams
shall not be present in sufficient concentration to be
objectionable or to interfere with normal treatment
processes. Suspended solids in water may interfere with
many industrial processes, and cause foaming in boilers, or
encrustations on equipment exposed to water, especially as
the temperature rises. Suspended solids are undesirable in
water for textile industries; paper and pulp; beverages;
dairy products; laundries; dyeing; photography; cooling
systems, and power plants. Suspended particles also serve
as a transport mechanism for pesticides and other substances
which are readily sorbed into or onto clay particles.
VI-2
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DRAFT
Solids may be suspended in water for a time, and then settle
to the bed of the stream or lake. These settleable solids
discharged with man's wastes may be inert, slowly
biodegradable materials, or rapidly decomposable substances.
While in suspension, they increase the turbidity of the
water, reduce light penetration and impair the
photosynthetic activity of aquatic plants.
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 sludgeworms and
associated organisms. Total suspended solids are the single
most important pollutant parameter found in the concrete
products industries.
3.0 SIGNIFICANCE AND RATIONALE FOR REJECTION OF POLLUTION
PARAMETERS
A number of pollution parameters other than those selected
were considered, but had to be rejected for one or several
of the following reasons:
(1) insufficient data on degradation of water quality;
(2) not usually present in quantities sufficient to cause
water quality degradation;
(3) treatment does not "practicably" reduce the parameter;
and
(4) simultaneous reduction is achieved with another para-
meter which is limited.
3.1 Toxic Materials
Although arsenic, barium, cadmium, chromium, copper,
fluorides, iron, lead, manganese, mercury, molybdenum,
nickel, selenium, strontium, and zinc are harmful
VI-4
DRAFT
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DRAFT
pollutants, they were not found to be present in quantities
sufficient to cause water quality degradation.
3.2 Aluminum +3
Aluminum may be present in significant amounts in the
wastewater from this industry. Soluble aluminum in public
water supplies is not considered a health problem and
therefore was not included in the Public Health Service
Drinking Water Standards.
3 ..3 Calcium ^£
Although calcium does exist in quantities in the wastewater
of a number of these plants, there is no treatment to
practicably reduce it.
3.4 Carbonate ^£
There is insufficient data for dissolved carbonate to
consider it a harmful pollutant.
3.5 Chloride 3
Although chloride does exist in quantity in the wastewater
in these industries, there is no treatment to practicably
reduce it. A total chloride content of less than
250 mg/liter is considered desirable in drinking water
supplies.
3.6 Chemical Oxygen Demand
COD may be present in significant amounts in the wastewater
from this industry, but there is no treatment to practicably
reduce it.
3.7 Dissolved Solids
Dissolved solids may be present in significant amounts in
the wastewater from this industry, but there is no treatment
to practicably reduce them.
VI-5
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DRAFT
3.8 Magnesium +2
There is insufficient data for dissolved magnesium to
consider it a harmful pollutant.
3 .9 Nitrate - and Nitrite -
There is insufficient data for dissolved nitrates and
nitrites to consider them harmful pollutants and there is no
treatment to practicably reduce them.
3.10 Phosphates
Phosphates, reported as total phosphorus (P) , contribute to
eutrophication in receiving bodies of water. However, they
were not found in quantities sufficient to cause water
quality degradation.
3 ._1 1 Potassium ^
Although potassium does exist in quantity in the wastewater
of some of these plants, there is no treatment to
practicably reduce it.
3.12 Sodium +
Although sodium does exist in quantity in the wastewater of
some of these industries, there is no treatment to
practicable reduce it.
3 Sulfate
Although sulfate does exist in quantity in the wastewater of
some of these industries, there is no treatment to
practicably reduce it.
3_.J_4 Temperature
Temperature is a sensitive indicator of unusual thermal
loads where waste heat is involved in the process. Excess
thermal load even with condensate from steam curing has not
been and is not expected to be a significant problem in
these industries.
Vl-6
DRAFT
-------
DRAFT
SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
Wastewater from the concrete industries may contain
suspended solids, COD and small quantities of oil and have
high pH. The general treatment practices are similar for
all categories. Suspended solids are removed in settling
basins, tanks or ponds, pH is adjusted with sulfuric acid,
oil is removed by skimming from pond or tank surfaces, and
COD is not treated. The ready-mixed concrete category
differs from the rest of the industries in that the
untreated wastewater contains a significantly heavier load
of suspended solids, Handling and disposal of the resulting
solid wastes is a more severe problem. Oil and grease are
not usually found in wastewater from ready-mixed or block
and brick plants, but have been found in the pipe and
prestressed and precast concrete product categories.
Many concrete producing facilities are located in urban or
suburban areas, where land may be scarce and expensive.
Fortunately, the suspended solids generated in this industry
settle rapidly so that tanks and small ponds may still be
used even when space is at a premium.
Wastewater discharges from plants of the concrete products
industries are relatively small. The maximum reported
values of wastewater handled in these plants (but not
necessarily discharged) are: ready-mixed concrete plants
568,000 liters/day (150,000 gallons/day); block and brick
plants 60,000 liters/day (15,000 gallons/day); concrete pipe
400,000 liters/day (100,000 gallons/day); and prestressed
and precast products 57,000 liters/day (14,000 gallons/day).
Since some recycle is practiced and the use of evaporation/
percolation ponds is wide-spread, discharge volumes are
often significantly less than total wastewater volumes
reported.
An estimated 40 per cent of the concrete products plants
usually have no discharge because of evaporation/percolation
ponds, recycle, on-site ground seepage, or no generation of
wastewater:
VI1-1
DRAFT
-------
DRAFT
Treatment/Disposal Technology Percent of Total Plants
Recycle ponds, evap/percolating 30
ponds plus ground seepage
Recycle from clarifiers 7
(ready-mixed only)
No wastewater 3
Other plants which normally discharge wastewater dispose of
this wastewater either to surface waters or to sewers. Of
30 plants, 17 discharge to surface water and 13 to storm
s ewer s.
The wastewater is generally discharged with recycle or
treatment by the concrete block and brick and the concrete
products (NEC) categories. On the other hand, ready-mixed
concrete plants usually practice some recycle and re-use.
1.0 TREATMENT AND CONTROL PRACTICES
Treatment and control practices for wastewater of the
concrete products industries are discussed below in three
areas:
- separation and control of wastewater
- treatment technology
- monitoring
1.2 Treatment Technology
Treatments currently used in these industries for wastewater
consist of settling of suspended solids, neutralization of
high pH discharges, and separation of oil and grease. COD
is not treated.
1.2.1
Settling of Suspended Solids
The aggregate components of concrete wastes settle rapidly.
The cement component also settles fairly rapidly in an
undisturbed settling environment. Many treatment systems
are not designed to provide this quiescent settling and
VII-2
DRAFT
-------
DRAFT
cement fines are often carried over in the discharge. A
detailed discussion on cement settling rates is given later
of this section.
1^. 2.2 Handling and Disposal of Settled Solids
The settled solids usually must be removed from the settling
pond or tank. Handling and disposal methods include:
(1) Pumping the cement slurry into tank trucks and hauling
to a landfill;
(2) Removing the settled sludge from tanks or ponds with
front-end loaders, backhoes, or cranes and dumping
nearby to dry prior to a second loading and hauling
operation for disposal of dried solids in a landdump or
landfill;
(3) Filling of pits with the settled solids, followed by pit
abandonment;
(4) Separation of coarse aggregate by means of clarification
equipment with fine aggregate and cement components
landfilled or landdumped;
(5) Separation of fine aggregate and coarse aggregate
components by means of clarification equipment or sloped
slab basin. Aggregate may be used or sold; cement
landfilled or landdumped;
(6) Separation of fine aggregate, coarse aggregate and
cement followed by reuse of all components.
Except the last, all these methods involve major solid waste
disposal on land.
1_V2^3 Neutralization of High pH Discharges
The clarified wastewater contains sufficient lime to raise
the pH to 11 to 12. Acid treatment is required to adjust
the pH to between 6 and 9. This acid treatment is practiced
by only one or two per cent of the plants studied.
VII-3
DRAFT
-------
DRAFT
1.2.u Restrictions on Use of Treated Water and Recovered
Solids
There is potential for reuse of recovered aggregate, cement
and clarified water. Reuse is limited by regulatory
restrictions and quality uncertainties of concrete produced
with reused materials. Most specifications for concrete
call for potable water to be used in the mix. This prevents
the use of clarified recycle water for this portion of the
business. However, several companies were found that use
treated wastewater where possible with no discernible
difference in physical properties of the resultant concrete.
Once the coarse and fine aggregate have been separated, the
cement can be retained in suspension and used in preparation
of new batches. At least one company has successfully
followed this approach.
1.2.5 Oil Removal
Oil wastes are not usually present in the manufacture of
ready-mixed concrete. However, the manufacture of cast
concrete products involves the use of oil as form release
agent. Oil removal from wastewater is not generally
practiced in these industries.
lil^i COD Removal
Wastewater streams were found to contain COD up to
200 mg/liter. The amounts do not appear to correlate
consistently with any process variable. It is likely that
COD arises from the use of air entrainment agents in
concrete production. These agents are generally organic
materials and their amount and composition vary according to
individual plant formulations. Treatment of COD includes
biological digestion, carbon adsorption, and ozonation. If
the COD is present as biodegradable material, then an
activated sludge system will remove it. If the COD is
present as non-biodegradable material then ozonation or
carbon adsorption may be required. Some non-biodegradable
materials respond to ozonation or carbon adsorption while
others do not. COD treatment is not practiced in the
concrete products industries.
VII-4
DRAFT
-------
DRAFT
1.3 Monitoring
Except for a few of the larger plants, monitoring on a
continuous basis was not found. These few plants measure
flow rate and pH. Many other plants now monitor for
suspended solids level and pH on a grab sample basis.
2.0 WASTEWATER TREATMENT FOR SPECIFIC CONCRETE PRODUCTS
INDUSTRIES
Although all concrete industries use the same basic waste-
water treatment technologies, there are significant
differences among the different categories as to amount of
wastewaters treated.
2.1 Concrete Block and Brick
The concrete block and brick category was subcategorized
into autoclave curing and low pressure steam curing plants.
Below are summarized the treatments used by eleven plants of
either type:
Plant Curing Process Treatment Used
7100 high pressure autoclave no treatment
7101 high pressure autoclave no treatment
7102 low pressure steam evaporation/percolation
pond (some discharge
to sewer)
7103 low pressure steam evaporation/percolation
pond (no discharge)
7104 low pressure steam evaporation/percolation
pond (no discharge)
7105 high pressure autoclave settling pond (discharge
to storm sewer)
7106 low pressure steam no treatment
7107 high pressure steam no treatment
7108 low pressure steam no treatment
7109 low pressure steam no treatment
7110 low pressure steam no treatment
Steam condensate discharge from autoclave plants contains
suspended solids, oil and grease, and has high pH.
Adjustment of pH to 6 to 9 requires addition of acid to the
autoclave sumps or to an external tank. Current practice in
VII-5
DRAFT
-------
DRAFT
some plants is to control corrosion (and pH) by addition of
acidic water treatment agents.
Low pressure steam curing processes as practiced by plants
7102, 7103, and 7104 have such small wastewater flow that
they can often dispose of the water in on-site
evaporation/percolation ponds without treatment. When
discharge is necessary, treatment would be similar to that
for the high pressure autoclave system-settling of suspended
solids in a small pit, sump or tank and adjustment of pH to
6 to 9.
2.2 Concrete Products (NEC)
The concrete products (NEC) category was subcategorized into
pipe and prestressed and precast products.
2.2.1 Pipe
The wastewater from concrete pipe manufacture comes
primarily from washoff of forms, central mixer washouts,
steam condensate from curing operations, and yard runoff.
Oil is present in the wastewater due to the use of oil-
containing form release agents. Other pollutants are
suspended solids and high pH.
Table VII-1 summarizes the wastewater volumes and treatment
utilized in several pipe plants. Those plants with
untreated or partially treated wastewater may need to settle
solids in small pits, tanks or ponds, to adjust pH with acid
addition, and to skim off floating oil with belt units or
small API-type separators or to absorb it in straw or other
absorbents.
Figures 15 and 16 illustrate typical belt and API-type oil-
skimming units. For the usual wastewater volumes from pipe
operations, the belt-type skimmer would be more appropriate.
Absorbent materials can also be used conveniently to remove
small amounts of oil.
2.2.2 Prestressed and Precast Concrete Products
Wastewater from prestressed and precast concrete plants is
usually treated in a similar manner to that of the pipe
subcategory. Ponds or basins are the kinds of settling
VTI-6
DRAFT
-------
DRAFT
Table VI1-1. Total Wastewater From Concrete Pipe Plants
Wastewater Origin
Plant
Code
7201
7205
7212
7223
7224
7229
7233
7239
7241
7247
7248
Treatment
settling pond
e/p
none
settling pond
settling pond
e/p
e/p
none
none
settling pond;
oil removal;
pH adjust
settling pond
i i
aS
x !
ie~
•*—
"5 g
•fc -c
C £
0) D
u >
X
X
X
X
X
X
X
X
0
C i~f"
u_ ^
X
X
X
X
Q)
8
c
£. o
co O
X
X
X
X
X
X
X
.4-
V
o
3
CO
•£ ^
0 3
a. o
!2 _C
d t/)
D O
H1 ^
X
X
X
X
X
X
o
a:
i
c c
(U '^
U co
X
i—
d)
6
X
X
Total
Wastewater
Quantity
liters/day
760
8,370
760
3,200
66,600
unknown
320
184
320
302,800
75,700
e/p- evaporation/percolation,
VII-7
DRAFT
-------
DRAFT
OIL
SCRAPERv
BLADE N
(2)
MOTOR
DRIVE CHAIN
OIL COATED
(BOTH SIDES)
FIGURE 15
BELT OIL SKIMMER
VII-8
DRAFT
-------
DRAFT '
V JL JL. - b
DRAFT
-------
DRAFT
facilities used for removing suspended solids in this
subcategory. One plant studied controls pH by addition of
acid, Amounts of wastewater and types of treatment are
summarized in Table VII-2,
2^_3 RQ_ady-Mixed Concrete
The ready-mixed concrete industry uses several settling
techniques for removal of suspended solids. Some plants
also adjust pH with acid addition. The wastewater from
ready-mixed concrete plants contains suspended solids, high
pH, and COD. Tables VII-3, YI1-4, and VII-5 detail the
types of treatment techniques used throughoxit this industry.
Eighty-two per cent of the permanent ready-mixed concrete
plants reporting use treatment ponds for truck and central
mixer washout water. Fifty-eight per cent of the plants
reported using evaporation or percolation ponds, while 11
per cent use settling ponds, 12 per cent use filter pond2,-
and 1 per cent reported using sloped slab basins.
Clarification equipment is used in 12 per cent of the plants
and 6 per cent have no treatment, pH is adjusted in only
1.6 per cent of the plants studied. Sixty-three per cent cf
the plants using evaporation or percolation ponds have no
discharge (excluding rainwater runoff). The remainder of
the plants using evaporation or percolation ponds discharge
truck washoff or other miscellaneous water from the plant.
Industry sources have indicated that the use of mechanical
clarification equipment is less widespread than the 12 per-
cent found in this study, i.e., 3 per cent. The prevalence
of sloped slab basins is greater than the data reported
indicate since typically a plant with sloped slab basins and
settling ponds would report only the latter.
The portable ready-mixed concrete plants studied which have
treatment use some form of settling ponds or mechanical
clarifiers.
VIl-10
DRAFT
-------
DRAFT
Table V[|-2. Total Wastewater From Prestressed and
Precoste Concrete Plants
Wastewater Origin
Plant
Code
7200
7203
7204
7206
7207
7208
7209
7210
7211
7213
7214
7215
7216
7217
7218
7219
7220
7221
Tin
7225
7226
7228
7230
7231
7232
7234
7235
7236
7238
7240
7242
7243
7244
7245
Treatment
settling pond
settling pond
e/p
settling pond
•settling pond
none
none
not given
none
settling pond
none
none
e/p
none
none
settling pond
settling pond
settling pond;
e/p
settling pond
none
settling pond;
e/p
settling pond
settling pond
e/p
e/P
e/P
settling pond;
e/P
e/p
mechanical
clarification;
settling pond;
pH adjustment
none*
settling pond
none
e/p
none
1
s-
> &
; X
5
l|
SJ
U ?
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
^
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Steam
Condensafe
I
X
X
X
X
;
j
)
14-
u-
O
E-S
0^
a- •$•
Transport
Bucket Washout
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Product
Washdown
X
X
X
X
X
X
X
X
1
t-
o
-C
6
X
X
X
X
X
Total
Quantity
liters/day
190
2,080
8,900
3,800
14,600
80
0
1,900
1,200
1,140
5,300
9,500
15,100
400
49,200
11,360
9,460
5,690
3,800
11,400
490
7,600
13,600
80
3,800
17,000
12,100
27,400
56,800
8,000
3,800
1,500
6,100
29,700
e/p - evaporalion/peicolation.
*Evaporates and percolates on-site.
VII-11
DRAFT
-------
DRAFT
TABLE VII-3
Summary of Treatment of Central fclxer iu/d Truck
Washout Water in Ready-Mix Concrete Operation
(information based on 430 Permanent Ready-Mix Con cr ere Plants)
Treatment Mo, oi : Plants*
Ponds 353 82.1%
Settling ponds 48 11.2ft
Evaporation/percola- 248 51.1%
tion ponds
Filter ponds 50 11.6%
Sloped pond separation 5 1,2%
pond(s)**
Unidentified 2 «b^
Clarification Equipment 53 12,3%
Home-made aggregate 8 1.fe%
reclaimer
Screw 9 2.1%
Drag chain washers 31 1.3%
Screen 3 .7%
Unidentified 2 .5£
pH Adjustment 7 7 1.6%
No treatment 29 29 6.1%
No washout at plant site 34 34 7.9%
*Some of the plants have more than one Kind of treatment.
**For the majority of the plants, information was not
complete enough to identify this treatment.
VII-12
DRAJT
-------
DRAFT
TABLE VII-
Summary of Treatments of Truck Washoff Water
in Ready-Mixed Concrete Operation (Information
Based on 430 Permanent Ready-Mixed Concrete Plants)
Treatment No. of Plants Total % of Total
Treated with truck 221 51.5%
washout
Ponds 187 43.5%
Settling ponds 21 4.9%
Evaporating/percola- 135 31.4%
tion ponds
Filter ponds 28 6.5%
Sloped slab separation 3 0.7%
ponds
Clarification Equipment 33 7.7%
Home-made aggregate 5 1.2%
reclaimer
Screw 4 0.9%
Drag chain washers 19 2.1%
Screen 2 0.5%
Rexnord 1 0.2%
Unidentified 2 0.5%
pH Adjustment 1 1 0.2%
Treated Separately From 7 1.7%
Washout Water
Settling 5 1.2%
Unidentified 2 0.5%
No Treatment 188 43.7%
Becomes yard runoff 155 36.0%
Doesn't become yard 30 7.0%
runoff
Unidentified 3 0.7%
No Washoff at Plant Site 35 35 8.1%
VII-13
DRAFT
-------
DRAFT
TABLE VII-5
Wastewater and Treatment Technology For
Portable Ready-Mixed Concrete Plants
Quantity
Central
Washout
none
2,650
760
1,890
1,890
380
1,890
1,890
1,890
760
7,570
1,890
380
760
760
2,270
760
unknown
190
of Wastewater
Mixer Truck
Washout
none
11,350
7,570
3,780
3,780
1,510
15,100
190
9,840
15,100
1,510
13,250
1,890
9,080
11,350
28,390
7,570
2,270
7,570
(liters/day)
Truck
Wash Off
190
unknown
none
unknown
unknown
unknown
unknown
unknown
unknown
unknown
190
760
unknown
1 ,140
1,420
unknown
760
190
unknown
Code Treatment
7362 evap/perc yard
7595 evap/perc pond
7601 filter pond
7602 evap/perc pond
7603 evap/perc pond
7604 evap/perc pond
7609 evap/perc pond
7627 evap/perc pond
7632 no treatment
7633 evap/perc pond
7641 no treatment
7649 filter pond
7691 evap/perc pond
7701 no treatment
7702 no treatment
7706 evap/perc pond
7707 evap/perc pond
7715 no treatment
7751 evap/perc pond
2.3.1 Settling Ponds
Fifty-two per cent of the plants were found to treat truck
washoff water in the same system used for treating truck
washout water. For thirty-six per cent of the plants truck
washoff water becomes untreated yard runoff. Only 2 per
cent of the plants treat truck washoff water separately from
washout water.
The widespread use of evaporation/percolation ponds is an
indication of small wastewater volumes. For the ready-mixed
concrete industry 50 per cent of the plants with 75 cu m/day
(100 cu yd/day) concrete production have less than
6,500 liters/day (1,700 gallons/day) of total wastewater.
VII-14
DRAFT
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DRAFT
It is likely that a disproportionate number of the plants
with evaporation/percolation ponds are also plants with
small production.
Most settling systems, including ponds, sloped slab basins
and mechanical clarification units, discharge during periods
of heavy rainfall, even if at no other time. The amount of
discharged water may be minimized by reducing the drainage
area and by covering the ponds or tanks.
The design of settling ponds in this subcategory depends on
the amount of land available and the pond clean-out
procedure used, as well as the amount of wastewater to be
handled. Many of the ponds are constructed of concrete with
walls at least one foot in thickness.
2.3.2 Settling Rates and Holding Times for Concrete Fines
Figure 17 gives settling information determined on a sample
of truck washout taken from plant 7363. For this particular
sample a level of 50 mg/liter of suspended solids was
obtained after 4 hours settling time and 19 mg/liter after
20 hours settling time.
Washout from concrete trucks and mixers contains coarse
aggregate, sand and cement. When dumped into a pond the
coarse aggregate and sand settle almost immediately. The
cement and a small amount of fines from the sand and coarse
aggregate settle much more slowly as shown in Figure VII-17.
A residence time of 24 hours in a undisturbed pond should be
adequate for settling pond design in this industry
subcategory.
Settling pond area requirements are of the order of 18.3 m
times 18.3 m (60 ft x 60 ft) for a large plant and less for
smaller plants. Constructed ponds, usually made of
concrete, generally are smaller than this. Ponds that take
advantage of local terrain such as old gravel or sand pits,
quarries, low spots, and bulldozed earthen pits may be of
any size.
Many of the concrete plants are located in neighborhoods
where land availability is limited and the price of
additional land is high. However, ninety-four per cent of
the concrete plants supplying data already have treatment
VII-15
DRAFT
-------
DRAFT
u
I
1
u.
8 w
K 1
£ £
<
~i z
Q_ UJ
(t *
s £ S
g fc K
u-<^
Q s e
ui
05
LU
[Z
-------
DRAFT
facilities and space available. Of the remaining six per
cent it is estimated that most have sufficient land
available for treatment facilities if needed. Therefore,
only an estimated one or two per cent of the plants will
have a problem with availability of land for treatment
facilities and these problems can probably be overcome with
proper selection of treatment technology.
2_i.!_^2-il Sediment. Buildup Rates
Most of the solid wastes that require disposal come from:
(1) waste concrete mix - approximately 1 per cent of
production,
(2) truck washout - approximately 59 kilograms per cubic
meter (100 pounds per cubic yard) at 1.5 washouts per
day per truck,
(3) central mixer washout - approximately 227 kilograms
(500 pounds) per washout, usually once per day,
(U) truck washoff - variable but relatively small number
compared 1, 2, and 3.
Whenever possible returned concrete is disposed of by using
it to make precast structures for which forms are kept
assembled, or for paving the yard of the concrete plant. If
land is available it may simply be dumped. If clarification
equipment is available, the waste concrete may be processed
to recover the aggregate portion.
Truck washout, in the absence of clarification equipment,
will most likely be settled in the pond and constitutes the
major solids contribution.
Truck washoff and central mixer washout may or may not drain
to the pond depending on plant layout.
2..3.2_._2 Evaporation/Percolation Ponds
An evaporation/percolation pond may be natural or
constructed but its primary characteristic is that it
disposes of wastewater througn the dual mechanism of
evaporating water into the air and allowing water to seep
VII-17
DRAFT
-------
DRAFT
into the ground. Since most of these ponds are located in
relatively high rainfall areas and the pond surface areas
are usually small most of the water loss is by percolation.
Many, if not most, of these ponds have no discharge.
2.3.2.3 Local Terrain Ponds
Often the plant can take advantage of some available config-
uration on its property for wastewater treatment or storage.
Low spots, valleys, abandoned quarries or gravel pits,
excavations or other depressions may be used. In some
cases, ponds constructed using these areas have such large
volume that they normally have no discharge.
2.3.2 .U Constructed Earthen Ponds
Since the settling ponds only need to be approximately
15 meters by 9 meters (50 feet by 30 feet), excavation of
earthen ponds is fairly common. As these ponds fill, they
may be abandoned or cleaned out.
2.3.2.5 Concrete Basins or Tanks
Since the settling pond size required is relatively small
and concrete is readily available, many of the settling
ponds are constructed of concrete. The concrete basins or
tanks are more expensive to build than local terrain and
other earthen ponds but are easier to clean and maintain,
and have a better appearance.
2.3.2.6 Series Ponds
In most cases at least two settling ponds are used in
series. The first pond is used for removing the readily
settleable materials. Most of the sand and gravel will
settle within the first minute and most of the cement will
usually settle within the next few minutes. The remaining
fines take hours to settle and are sensitive to any
turbulence or disturbance. Therefore, it is common practice
to have at least two ponds in series - the first a roughing
pond to collect most of the suspended solids and the
subsequent pond(s) for attaining low suspended solids levels
and water storage for reuse or discharge. Quite often the
sand and gravel may be removed by sloped pad collection or a
clarification unit prior to the first pond and the bulk of
VIl-18
DRAFT
-------
DRAFT
the cement removed in the first pond. The first pond also
collects the low density floating particles resulting from
air entrainment agents.
Figure 18 shows two earthen ponds in series. The first pond
collects most of the suspended solids while the second pond
is primarily for final settling and storage. Water can be
recycled without treatment or discharged after pH
adjustment.
Figure 19 shows two concrete basins and a holding pond in
series. The first basin collects the coarse aggregate, the
second basin is for removing cement and other fines. The
water passes from the settling basin through straw bale
filters which not only remove some of the residual suspended
solids but also retain the floating particles caused by air
entrainment agents. The holding or pumping pond can be used
for recycle or pH adjustment prior to discharge.
2jJL^l Sloped Slab Separation Basins
Since the coarse aggregate and sand settle so rapidly, there
is no need for a settling pond to remove them. If the
wastewater is dumped on a slab these components readily
separate from the water. if this slab is gently sloped to
provide drainage of the water, the aggregate will collect on
the sloped surface and can be removed with a frontend
loader. Baffles and other flow diversion installations are
often used to improve the solids removal efficiency. Slope
slab separation basins are generally used in series with
settling basins to remove the concrete fines. Figure 20
shows an example of a sloped slab separation basin used in
series with three settling basins.
Sloped slab basin size is largely determined by the number
of truck stations desired. Allowing 4.6 m (15 ft) space for
each truck four truck stations require 18.4 m (60 ft) slab
length. An inclined slope of 6.1 to 12.2 m (20 to 40 ft) in
width should be ample to collect the coarse aggregate.
Therefore the slab area required may be estimated by
multiplying number of truck stations needed times 56 sq m
(600 sq ft) per truck station.
VII-19
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VII-21
DRAFT
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VII-22
DRAFT
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DRAFT
2.3.3.1 Solids Buildup Rate
Approximately 83 per cent of -the solids in concrete is made
up of sand and coarse aggregate. Most of this will be
deposited on the sloped slat along with some cement. The
use of readily cleanable sloped slab removes approximately
75 per cent of the solids prior to the settling ponds.
Also, separation of the aggregate from the cement in this
way reduces the amount of drying for the concrete wastes
which would have to be dredged. This reduces the amount of
sludge to be dried by 75 per cent.
2_JL_i Filter Ponds
Filter ponds are a special kind of settling pond. In our
study 12 per cent of the plants reported using filter ponds
in their treatment systems. The relative popularity of this
treatment technology stems largely from its simplicity and
low cost.
Figure 21 demonstrates the basic principle of a filter pond.
A portion of the pond wall is constructed of some porous
material such as crushed rock or stone (2 to 15 cm diameter)
so that drainage occurs through this material. Most of the
settling occurs in the filter pond prior to wastewater
discharge through the porous wall. These ponds are
reportedly only about 50 per cent efficient as a settling
pond due to the short circuiting of water and escape through
the filter without sufficient settling time.
In some cases the filter pond is backed up with a holding
pond or basin, in other cases it is not and the filtered
water is directly discharged- Aside from its reduced
settling efficiency, the filter pond is much like an earthen
settling pond. One reason for its popularity for treating
concrete wastewater is ability of the filter to retain most
of the floating material on top of the pond.
2.3.5 Mechanical Clarificatiqn Equipment
Mechanical clarification devices used in this industry are
of three general types: drag chain washers, screw washers,
and screens.
VII-23
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VII-24
DRAFT
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2.3.5.1 Drag Chain Washers
Drag chain washers consist of one or two chambered wash
tanks with progressive drag chains to remove settled solids.
Figure 22 illustrates a drag chain unit. Truck washout
water is discharged into uhe wash tank. The fast settling
coarse aggregate and most of the fine aggregate settle to
the bottom of the tank and are conveyed by the drag chain
out of the tank, and dumped in a pile beside the unit. The
slower settling cement fines are removed by a slow moving
drag chain which conveys the fines over the end of the tank.
The clarified wastewater is collected in a sump and can be
reused. If truck washout water is the only wastewater
handled and it is recycled? the system can probably operate
without discharge. If truck washoff, central mixer washout,
yard runoff and other wastewater is included, some discharge
may be necessary. The discharge from this system requires
further suspended solids removal and pH adjustment.
The drag chain unit is compact, requiring a ground area of
only about 6.1 m x 13.3 m (20 ft x 60 ft). The washout from
at least twenty trucks can be handled in an area this size.
Aggregate is dumped onto a pile convenient for resale or
disposal. Cement sludge is also dumped onto a pile
convenient for handling, bur still needs additional drying
before final disposal. The unit is operated by the truck
driver. Automated cycle operation eliminates the need for
any other manpower except for maintenance.
Drag chain units are currently the most widely used of the
mechanical separation devices (31 units out of 53 plants
reporting).
2.3.5.2 Screw Washers
Inclined screws can also be used for removing coarse aggre-
gate and sand from truck washout water. Depending on the
design of the screw, coarse aggregate alone may be removed
or a mixture of coarse aggregate and sand. At least one
commercially available screw washing unit also separates
coarse aggregate and sand into two separate piles by using
an aggregate screw and a sand screw in series. Figure 23
illustrates a screw washer. Truck washout is dumped into
the lower end of the inclined screw and the coarse material
is dumped out at the upper end.
VII-25
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Vn-26
DRAFT
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DRAFT
VII-27
DRAFT
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DRAFT
Figure 24 illustrates a double screw washer for separation
of coarse aggregate and sand.
The screw washers differ from most of treatment systems dis-
cussed so far, in that their primary purpose is recovery of
waste components for reuse in concrete mixes. Single screws
recover coarse aggregate for reuse. Double screw units
recover both coarse aggregate and sand for reuse.
The units are operated by the truck drivers, with no other
operator being required. The single screw units reported
are relatively old installations of a specialized nature.
Essentially they are add-ons to basic slop slab and settling
pond systems. The double screw units are new and sold as
part of a complete wastewater treatment system. This total
system includes not only the double screw washer but also a
fabricated settling tank assembly for fines removal.
2.3.5.3 Screens
Screens are used to separate coarse aggregate and sand from
cement fines and coarse aggregate from fine aggregate.
Preliminary screening on truck washout will separate the
coarse aggregate from the rest of the waste stream. This
stream can then be passed through a sand screw for sand
recovery. A second alternative is to separate coarse
aggregate and sand, once the mixture has been recovered from
the wastewater stream by a drag chain or screw washer unit.
Figures 25 and 26 represent two different utilizations of
screens for separation purposes.
2.3.6 Recycle of Ready-Mixed Concrete Plant Wastewater
Once the suspended solids have been removed from the wash
water by pond or tank settling, this water is suitable for
several purposes. Reuse accomplishes several desirable
objectives, including reduction in fresh water costs,
conservation of water, and reduction or elimination of
wastewater discharge. Selective recycling of wastewater is
widely practiced today in the ready-mixed concrete industry.
The following discussion covers the uses and problems
encountered.
VII-28
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VII-29
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VII-30
DRAFT
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DRAFT
The most common use for recycled water is truck washout (115
plants of 430 plants). This is logical for a number of
reasons:
- Aside from mix water, truck washout consumes the largest
volume of water used.
- Most settling systems are designed for treating and
recovering truck washout water — the recovered water is
usually stored close to the truck washout systems.
- High dissolved solids and pH for the recycled wash water
are not a problem.
Recycled water is also used for washing out central mixers
in many plants, but this is not a major water use. Use of
recycled wash water for truck washoff has been reported for
a number of plants (73 plants of 430 plants). Use of
recycled water is restricted for this purpose because the
dissolved solids leave a film on the truck surface and
because truck washoff is often remote from recycled water
availability.
2.3.7 p_H Control
After treatment for suspended solids and recycle of all
possible wastewater, it is still necessary in many cases to
discharge a portion of the wastewater. This wastewater
usually has a pH of 10 to 12. Where pH is adjusted, the
most common practice is to use sulfuric acid to lower pH to
an acceptable range, such as 6 to 9. The amounts of acid
required for adjusting pH is given in Figure 27. The
control of pH by addition of acids tends to decrease the
suspended solids and increase the dissolved solids in this
wastewater.
3.0 SUMMARY OF TREATMENT TECHNOLOGY, APPLICATIONS,
LIMITATIONS AND RELIABILITY
Table VII-6 summarizes comments on the various treatment
technologies as they are used in the concrete products
industries.
VII-32
DRAFT
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DRAFT
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FIGURE 27
AMOUNT OF ACID REQUIRED FOR
NEUTRALIZATION OF CONCRETE WASTEWATER
(DEVELOPED FROM FIELD AND LAB TESTS)
VII-33
DRAFT
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4.0 PRETREATMENT TECHNOLOGY
Concrete products operations are often located in urban or
suburban locations with access to publicly-owned activated
sludge or trickling filter wastewater treatment plants. In
areas where publicly-owned facilities could be used,
pretreatment would be required to reduce heavy suspended
solids loads, particularly for ready-mixed concrete
wastewater. In some instances pH control and some reduction
in oil and grease level would also be necessary.
5.0 NON-WATER QUALITY ENVIRONMENTAL ASPECTS
5^1 Solid Wastes
The primary non-water quality environmental impact of wastes
from the concrete products industries is solid waste
disposal. Solid waste comes from waste concrete mix, waste
concrete from truck, bucket and mixer washouts, and dusts
and concrete from truck and yard washoffs. Quantities of
these solids wastes have been given earlier in Section V.
Disposal practices for these solid wastes vary, but
essentially they may be listed as:
(1) drying and land dumping of all solid wastes
(2) drying and land filling of all solid wastes
(3) recovery of aggregates for landfill, and drying and
landfilling or landdumping of cement portion
(4) recovery of coarse aggregate for reuse plus drying, and
landfilling or landdumping of cement plus sand portions
(5) separation of coarse and fine aggregate for reuse, and
drying and landdumping or landfilling of cement portion
(6) separation of coarse and fine aggregate for reuse of
cement portion in new mixes.
VII-35
DRAFT
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DRAFT
5.2 Land Use Practic_es
Treatment technology can be varied to suit land
availability. Treatment systems for even the largest
reported ready-mixed plants with the greatest number of
trucks can be placed on less then 930 sq m (10,000 sq ft)
land space if mechanical clarification is used.
Drying, storage and disposal of solid wastes often takes up
more land area than the treatment system. However, the
solid waste disposal technology may be taiiored to land
availability. In situations where solid waste storage space
is limited, cement sludges may fce sent to off-site landfill
without drying and dry wastes such as aggregate can be
reused, sold, or landfilled without storage.
In many cases ready-mixed concrete plant wastewater treat-
ment facilities reflect the neighborhood in which they are
located. Those located in urban or suburban residential
areas are likely to be compact and constructed of painted
concrete with concrete paving and sometimes enclosed in
buildings. Those treatment facilities located in rural or
suburban commercial areas have more space and are more
likely to use earthen ponds and settling basins,
Concrete products industries other than ready-mixed concrete
require very little land for wastewater treatment purposes.
5 ._3 Energy Requirements for Typical Treatment Systems
The treatment technologies used for concrete products
industries wastewater are not energy-intensive. Truck
washout for the ready-mixed concrete industry is dumped
directly into the treatment facilities. Other wastewater
usually flows by gravity either into treatment systems,
discharge ditches or to ground disposal. Some pumping is
involved in transferring wastewater from one tank to another
and in pumping wastewater to and from the treatment system.
In addition to the energy required for wastewater treatment,
gasoline and other fuels will be needed to operate front-end
loader, trucks and other solid waste handling equipment.
VII-36
DRAFT
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DRAFT
Total energy requirement for the concrete industry
wastewater treatment is estimated to be 1.7 x 109 Kcal/yr
(6.7 x 109 Btu/yr) .
VII-37
DRAFT
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Wastewater Volumes - 50 Percentile Level
5 trucks
Truck washout - 5 trucks x 946 liters/day 4,730 liters/day
Truck washoff - 5 trucks x 246 liters/day 1,230 liters/day
Central mixer washout - 1 x 475 liters/day 475 liters/day
Total Daily wastewater 6,435 liters/day
Similar values for 20 and 40 trucks are
25,740 liters/day and 51,400 liters/day, respectively.
Solid Wastes
Solid wastes are calculated for two situations:
(1) Total disposal of all solid wastes
(2) Recovery of all aggregate and disposal of cement fines
Solid Waste-Total Disposal
5 trucks (6.1 cu m capacity)
Truck washout solids -
5 trucks x 59.4 kg/cu m/wash x 6.1 cu m/truck x 1.5 washes
per day = 2,725 kg
Truck washoff solids -
5 x 11.36 = 57 kg
Central mixer washout solids -
3.82 cu m x 59.4 kg/cu m = 227 kkg
1% waste concrete = 1,781 kg
Total 4,790 kg
Similarly, total solid waste values for 20 and 40 trucks
are 18,478 kg and 36,956 kg.
VIII-31
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DRAFT
Solid Wastes - Total Aggregate Recovery - Disposal of Cement Fines
5 trucks (6.1 cubic meter capacity)
Total solids 4,790 kg/day (dry basis)
Total aggregate recovered 4,143 kg/day (dry basis)
Waste cement 647 kg/day (dry basis)
Option A - Earthen Settling Ponds - Direct Dumping
5 trucks
Basis: (1) Wastewater volume 6f440 liters/day
(2) Production rate 75 cu m/day
(3) Solid wastes 4,790 divided by
0.85 (85% solids) =
5,635 kg/day (wet basis)
(4) Waste density 2,400 kg/cu m
Capital Costs
Pond size: 0.03 ha
Pond cost: $190,000/ha
Operating costs
Pond cleaning costs - $1.50/cu m
Maintenance o> 2% of capital
Taxes and insurance 33% of capital
Costs developed similarly for 20 and 40 truck systems.
VIII-32
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Option B - Concrete Settling Pond System - Direct Dumping
5 trucks
Basis: same as Option A
Capital Costs
Pond size: 0.0006 ha
Concrete cost: $18/cu m
Operating Cos ts
Pond cleaning and on-site disposal of solids - $2.00/cu m
Maintenance 5) 2% of capital investment
Taxes and insurance o> 3% of capital investment
Costs developed similarly for 20 and 40 truck systems.
Option C - Sloped Slab Settling System - Recycle System -
Aggregate Sold at No Profit
5 trucks
Basis: (1) Wastewater volume 6,440 liters/day
(2) Production rate 75 cu m/day
(3) Solid wastes:
(a) aggregate 4,143 kg/day (dry basis)
(b) waste cement 1,294 kg/day (wet sludge
(4) Aggregate sold as basis)
landfill no profit
(5) Waste density 1,444 kg/cu m
VIII-33
DRAFT
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DRAFT
Capital Costs
Concrete system cost: $10,000
Pumps and piping: $3,000
Operating Costs
Pond cleaning and on-site cement disposal: $2.00/cu m
Labor: $4,000
Maintenance 3 5% of capital investment
Taxes and insurance 3) 351 of capital investment
Power: $135/kilowatt - yr
20 trucks
Capital Costs
Concrete system cost: $20,000
Pumps and piping: 5,000
Operating Costs
Same basis as for 5 truck plant except labor costs taken
as $8,000/yr.
40 trucks
Capital Costs
Concrete system costs: $30,000
Pumps plus piping: 7,500
Operating Costs
Same basis as for 5 truck plant except labor costs taken
as $16,000/yr.
VIII-34
DRAFT
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Option D - Mechanical Clarification Units - Recycle System
Aggregate sold at no profit.
5 trucks
Basis: (1) Wastewater volume
(2) Production rate
(3) Solid wastes:
(a) aggregate
(b) waste cement
(c) waste density
Capital Costs
Installed mechanical unit cost:
Operating Costs
6,440 liters/day
75 cu m/day
4,143 kg/day (dry basis)
1,294 kg/day (wet basis)
1,444 kg/cu m
$25,000
Labor: $4,000
Maintenance ft 5% of capital investment
Power: $135/kilowatt-yr
Cement waste disposal: $2.00/cu m
Taxes and insurance a 3% of capital investment
VIII-35
DRAFT
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20 trucks
Capital Costs
Installed mechanical unit cost; $50,000
Operating Costs
Same basis as for 5 trucks
40 trucks
Capital Costs
Installed mechanical unit cost: $75,000
Operating Costs
Same basis as for 5 trucks.
Option E - Complete Recovery and Reuse of All Wastewater
and Solid Wastes
This system is used by only one or two companies.
Costs supplied by one company show:
Capital Investment; $70,000
Operating Expenses; $45,700-$83,000
Capital and operating costs are reported to be relatively
independent of plant size; i.e., a 600 cu m/day plant
would have the same costs as a 300 cu m/day plant.
2^.3^2 Portable Ready-Mixed Concrete Plants
Portable ready-mixed concrete plants are moved to the
desired location and set up. During their time of operation
at this site, the portable plant will have wastewater
volumes similar to a permanant plant. There are several
differences from a permanent plant which are significant to
treatment cost:
VIII-36
DRAFT
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(1) Only the simplest of treatment technology will usually
be employed. Earthen settling ponds will predominate.
Concrete selling basins, sloped slab recovery systems
and mechanical clarification units are rarely used.
(2) The temporary ponds are smaller than those for permanent
facilities, since storage space for only several months
of solid waste load is required.
(3) Settling ponds are not usually dredged.
Estimated costs for portable ready-mixed concrete plants are
given in Table VIII-9.
Cost Variance
All capital and operating costs are directly proportional to
plant size for Level B. For Levels C and D, the capital
costs should vary as the 0.6 exponent of plant size. Plant
age has no significance for a portable plant. Plant
location may be significant in that some climates and local
terrains make it possible to use evaporation/percolation
ponds and eliminate much if not all of the wastewater
discharge.
2.3.3 Mobile Ready-Mixed Concrete Plants
The production of ready-mixed concrete by mobile plants
generates no wastewater which requires treatment.
Therefore, there are no treatment costs for this
subcategory.
3.0 INDUSTRY STATISTICS
Below are summarized the estimated 1972 selling prices for
the individual commodities in this report. These values
were taken from Bureau of Census reports, industry sources
and reference 7.
VIII-37
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TABLE VI11-9
COST ANALYSIS FOR REPRESENTATIVE PLANT
(ALL COSTS ARE CUMULATIVE)
SUBCATE60RY Reody-Mixed Concrete (Portable Plonts)
PLANT SIZE 75,000 Cubic Meters
PER YEAR OF Concrete
INVESTED CAPITAL COSTS!
TOTAL
•ANNUAL CAPITAL RECOVERY
OPERATING AND MAINTENANCE'
COSTS:
ANNUAL 0 a M (EXCLUDING
POWER AND ENERGY)
ANNUAL ENERGY AND POWER
TOTAL ANNUAL COSTS
COST/CUBIC METER of Concrete
WASTE LOAD PARAMETERS
(kg/cubic meter of concrete)
Suspended solids
PH
|
I
[
RAY/
WASTE
LOAD
35
10-12
' LEVEL |
A
(MSN)
0
0
0
0
0
0
35
10-12
B
5,000
600
1,400
100
2,100
0.03
0.001
6-9
C
50,000
8,150
9,700
500
18,350
0.24
0.001
6-9
D
100,000
16,300
20,000
10,000
46,300
0.62
0
-
E
LEVEL DESCRIPTION:
A — No Treatment
B — Pond settling of suspended solids plus pH adjustment
C — Mechanical clarification unit plus pH adjustment
D — Mechanical evaporation of non-recycled wastewater (Level C plus evaporation)
VIII-30
. DRAFT
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Product Selling Price
Concrete block and brick $22/kkg ($20/ton)
Concrete Products, NEC $55/kkg ($50/ton)
Pipe $55/kkg ($50/ton)
Precast $110/kkg ($100/ton)
Prestressed $66/kkg ($60/ton)
Ready-mixed $24/cu m ($18/cu yd)
VIII-39
DRAFT
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DRAFT
SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH
THE APPLICATION OF THE BEST
PRACTICABLE CONTROL TECHNOLOGY
CURRENTLY AVAILABLE
1.0 INTRODUCTION
The effluent limitations which must be achieved by July 1,
1977, are based on the degree of effluent reduction
attainable through the application of the best practicable
control technology currently available. For the concrete
products industries, this level of technology was based on
the average of the best existing performance by facilities
of various sizes, ages, and processes within each of the
industry's subcategories. In Section IV, the concrete
products industries was divided into three major categories.
These categories have been further subcategorized.
Best practicable control technology currently available
emphasizes treatment facilities at the end of a manufac-
turing process but also includes the control technology
within the process itself when it is considered to be normal
practice within an industry. Examples of waste management
techniques which were considered normal practice within
these industries are:
(1) manufacturing process controls;
(2) recycle and alternative uses of water; and
(3) recovery of reuse of some wastewater constituents.
Consideration was also given to:
(a) the total cost of application of technology in relation
to the effluent reduction benefits to be achieved from
such application;
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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(b) the size and age of equipment and facilities involved;
(c) the process employed:
(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) .
The following is a discussion of the best practicable
control technology currently available for each of the
subcategories, and the proposed limitations on the
pollutants in their effluents.
2^0 GENERAL WATER GUIDELINES
2.1 Process Water
Process water is defined as any water contacting the raw
materials, processing chemicals, intermediate products, by-
products or products of a process.
2.2 Cooling Water
In the concrete products industries, cooling and process
waters are sometimes mixed prior to treatment and discharge.
In other situations, cooling water is discharged separately.
Based on the application of best practicable technology
currently available, the recommendations for the discharge
of such cooling water are as follows:
An allowed discharge of all non-contact cooling waters
provided that the following conditions are met:
(a) Thermal pollution be in accordance with standards to be
set by EPA policies. Excessive thermal rise in once
through non-contact cooling water in the concrete
products industries has riot been a significant problem.
IX-2
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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(b) All non-contact cooling waters should be monitored to
detect leaks of pollutants from the process. Provisions
should be made for treatment to the standards
established for process wastewater discharges prior to
release in the event of such leaks.
(c) No untreated process waters be added to the cooling
waters prior to discharge.
The above non-contact cooling water recommendations should
be considered as interim, since this type of water plus
blowdowns from water treatment, boilers and cooling towers
will be regulated by EPA as a separate category.
li.0 PROCESS WASTEWATER GUIDELINES AND LIMITATIONS FOR THE
CONCRETE PRODUCTS INDUSTRY POINT SOURCE SUBCATEGQRIES
3.1 Concrete B3.ock and Brick (Autoclave and Low Pressure
Steam Curing) Production Subcategories
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is:
E£fluent Limit at ion
kg/kkg ton (lb/1000 Ib)
Effluent Characteristic Monthly Average Daily Ma. ximum
TSS 0.005 0.030
pH 6-9
The above limitations for suspended solids were based on the
performance currently achieved by four plants studied, 7100,
7109, 7111 and 7112. The above limitations for pH were
based on the performance of one plant studied, 7113.
IX-3
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Identification of BPCTCA
Best practicable control technology currently available for
the production of concrete block and brick by the autoclave
and low pressure steam curing processes is settling of
suspended solids in ponds or clarification equipment and pH
adjustment.
To implement this technology at plants not already using the
recommended control techniques would require installation of
settling ponds or clarification equipment, pH control
equipment and necessary piping and pumps.
Reason for Selection
At least four plants in this category are presently using
the recommended control technology for suspended solids. At
least one plant in this category is presently demonstrating
the recommended technology for pH control.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, these subcategories as a whole would have to invest
up to an estimated maximum of $2,100,000 to achieve
limitations prescribed herein. There is also an anticipated
increase in the operating cost equivalent to less than 0.5
percent of the 1972 selling price of this product.
It is concluded that the benefits of the reduction of the
discharge pollutants by the selected control technology
outweigh the costs. Approximately 90 percent of these
industry subcategories is presently achieving this level of
pollutant discharge with respect to suspended solids. No
U.S. plants were found meeting the pH limitation in this
study.
IX-4
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT ANE ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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and Sz_§. of Eusmert and Facilities
The data obtained for these subcategories represents plants
with ages ranging from 2 to 35 years and productions ranging
from 26,600 to 250,000 kkg per year (29,300 to 275,000 tons
per year) .
The best control technology currently available is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in these production
subcategories involves weighing, batching and mixing of raw
materials, forming^ conditioning, curing, using autoclave or
low pressure steam, and storage of concrete block and brick.
The processes used by the establishments in this category
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best control technologies currently available is
practicable in these production subcategories because the
technology of settling is widely used in these subcategories
and pH adjustment is used by one plant in these
subcategories .
Process Changes
The recommended control technologies would not require major
process changes . These control technologies are presently
being used by plants in these production subcategories.
IA-5
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Non-Water Quality gnv a r o nn» e n t. a 1 Impact
There appear to be no major non-water quality environmental
impact or major energy requirements for the implementation
of the recommended treatment technologies.
JUJUJ. CQTu:rete Products .INECJ^ Concrete Pipe Production
Subcategory
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent redaction attainable through the application of the
best practicable control technology currently available is:
Ef f 1 u erxt Limi. t a t_i on
_____
3Sf_f_luent Characteristic Mon thly__Ay er age Daily
TSS 0,013 0.078
Oil and grease 0,004 0.02U
pH 6-9
The above limitations were based on tne average performance
currently achieved by one plant studied, 7247
Identification of BPCTCR
Best practicable control technology currently available for
the production of concrete pipe is settling of suspended
solids, followed by oil and grease removal, further settling
of suspended solids plus pH adjustment.
To implement this technology at plants not already using the
recommended control techniques would require the
installation of settling ponds or clarification equipment,
oil removal equipment and pH control equipment.
IX-6
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AMD ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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for Selection
One of the largest plants in this subcategory is presently
using the recommended control technologies.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the subcategory as a whole would have to invest up
to an estimated maximum of $4,400,000 to achieve limitations
prescribed herein. There xs also an anticipated increase in
the operating cost equivalent to less than 0.5 percent of
the 1972 selling price of this product.
It is concluded that the benefits of the total reduction of
the discharge pollutants by the selected control technology
outweigh the costs, On a production basis, approximately
14 percent of this industry subcategory is presently
achieving this level of pollutant discharge.
Age and Size of Equipment and Facilities
The data obtained on this subcategory represents plants with
ages ranging from 2 to 40 years and productions ranging from
4,540 to 175,000 kkg per year (5,000 to 193,000 tons per
year) .
The best control technology currently available is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in this production subcategory
involves weighing, batching and mixing of raw material,
casting and curing of concrete pipe. In addition
prestressing, prewetting, coating, curing and testing is
used for concrete pressure pipe.
IX-7
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT ANE ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
The processes used by the establishments in this subcategory
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering ft spec;': i"
From an engineering standpoint j? the implementation of the
recommended best control technologies currently available is
practicable in this production subcategory because the
technology of settling is widely used in these subcateyoiies
and pH control and oil and grease removal are currently ast-i
by at least one plant.
Proce_ss Changes
The recommended control technologies would not require ir.ajoi
process changes. These control technologies are presently
being used by plants in this production subcategory.
Non-JWater &uaJLity. Envi r onment&l Impact
There appear to be no major non-water quality environmental
impact or major energy requirements for the implementation
of the recommended treatment technologies ,
3, 2 . 2 Concrete Products JNECJ^ Pjcestressed and Forecast
Production Subcateqory
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is:
IX-8
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS EASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE EASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Effluent Limitation
kg/kkg (lb/1000 Ib)
Effluent Characteristic Monthly Average Daily Maximum
TSS 0.013 0.078
Oil and Grease 0.0015 0.009
pH 6-9
The above TSS limitations were based on the performance
currently achieved by 3 plants studied, 7203, 7232, and
7238. The oil and grease limitations were based on the
performance currently achieved by 3 plants studied, 7203,
7207, and 7230. One of the plants studied currently
achieves the pH limitations, 7238.
Identification of BPCTCA
Best practicable control technology currently available for
the production of precast and prestressed products is
settling of suspended solids in ponds or clarification
equipment, pH adjustment and oil and grease removal where
required.
To implement this technology at plants not already using the
recommended control techniques would require installation of
settling ponds or mechanical clarification equipment, pH
control equipment and oil removal equipment.
Reason for Selection
The recommended control technologies are currently used in
at least one plant in this subcategory and are also widely
used in other segments of the industry.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the subcategory as a whole would have to invest up
to an estimated maximum of $5,100,000 to achieve limitations
prescribed herein. There is also an anticipated increase in
IX-9
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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the operating cost equivalent to approximately 0.3 per cent
of the 1972 selling price of this product.
It is cor.clvid.ed that the beiioiit.3 of the reduction of the
discharge r.c-llutants by the se-j ••-:- l^d control technology
outweigh -/v: coats. Approximately 50 per cent of this
industry _^i-category is prc-santly achieving this level of
pollutant discharge.
The data ob'.ained on this sitL-c..st;--j^i'y represents plants with
vicjcs ran»~
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DRAFT
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in this production subcategory.
Non-Water Quality Environmental Impact
There appear to be no major non-water quality environmental
impact or major energy requirements for the implementation
of the recommended treatment technologies.
3.3.1 Ready-Mixed Concrete, Permanent and Portable
Production Subcateqories
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is:
Effluent Limitation
kg/cu m (Ibs/cu yd)
Effluent Characteristic Monthly Average Daily Maximum
TSS 0.001 (0.003) 0.006 (0.018)
pH 6-9
The above limitations were based on the performance
currently achieved by two plants studied, 7542 and 7545.
In addition, four other plants studied currently achieve the
TSS limitations, 7365, 7543, 7544 and 7731. Yard runoff is
included in the above limitations.
Identification of BPCTCA
Best practicable control technology currently available for
the production of ready-mixed concrete by permanent or
portable plants is settling of suspended solids in ponds,
sloped slab basins, or mechanical clarifiers, recycle of
IX- 11
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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clarified water for truck washout and pH adjustment prior to
discharge.
To implement this technology at plants not already using the
recommended control techniques would require installation of
settling ponds, sloped slab basins or mechanical
clarification equipment, pumps and piping for recycle of
washout water and pH control equipment.
Reason for Selection
The technologies of settling are currently used by
approximately 94 percent of the plants contacted in these
subcategories. The recycle of washout water is used by
28 percent of the plants contacted and pH adjustment is
currently used by approximately 2 percent of the plants
contacted in these subcategories.
Total Cost Qf Application
Based upon the information contained in Section VIII of this
report, these subcategories as a whole would have to invest
up to an estimated maximum of $19,000,000 to achieve
limitations prescribed herein. There is also an anticipated
increase in the operating cost equivalent to less than 0.2
percent of the 1972 selling price of this product.
It is concluded that the benefits of the reduction of the
discharge pollutants by the selected control technology
outweigh the costs. Approximately 40 percent of this
industry subcategories are presently achieving this level of
pollutant discharge.
Ag^e and Size of_ Equipment and Facilities
The data obtained on these subcategories represents plants
with ages ranging from 1 to 43 years and productions ranging
from 1,530 to 230,000 cubic meters per year (2,000 to
300,000 cubic yards per year).
IX-12
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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The best control technology currently available is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in these production
subcategories involves weighing, batching and mixing of
cement, aggregates and water and delivery of ready-mixed
concrete.
The processes used by the establishments in this subcategory
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering A spec t s
From an engineering standpoint, the implementation of the
recommended best control technologies currently available is
practicable in these production subcategories because the
technologies of settling are used by approximately
94 percent of the plants contacted in these subcategories.
Washout water is currently recycled at 28 percent of the
plants contacted in this subcategory. The technology of pH
adjustment is used by 1.6 percent of the plants contacted in
these subcategories.
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in these production subcategories.
Non-Water Quality Environmental Impact
There appear to be no major non-water quality environmental
impact or major energy requirements for the implementation
of the recommended treatment technologies.
IX-13
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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3.3.2 Ready-Mixed. CQncrete^ Mobile. Plant Production
Subcateggry
Based upon the information contained in Sections III through
VIII, a determination has been made thac the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is
no discharge of pollutants in process wastewater.
The above limitations were based on the performance
currently achieved by all plants studied,,
Identification of BPCTCk
There is no control technology necessary for the production
of ready-mixed concrete by mobile plants because there is
essentially no wastewater generated, Any wastewater is
either evaporated or percolated into the yard on the job--
site.
IX- 1U
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH
THE APPLICATION OF THE BEST AVAILABLE
TECHNOLOGY ECONOMICALLY ACHIEVABLE
1.0 INTRODUCTION
The effluent limitations which must be achieved by July 1,
1983 are based on the degree of effluent reduction attain-
able through the application of the best available tech-
nology economically achievable. For the concrete products
industries, this level of technology was based on the very
best control and treatment technology employed by a specific
point source within each of the industry's subcategories, or
where it is readily transferable from one industry process
to another. In Section IV, the concrete products industries
was divided into three major categories based on
similarities of process. These major categories have been
further subcategorized.
The following factors were taken into consideration in
determining the best available technology economically
achievable:
(a) the age of equipment and facilities involved;
(b) the process employed;
(c) the engineering aspects of the application of various
types of control techniques;
(d) process changes;
(e) cost of achieving the effluent reduction resulting from
application of BATEA; and
(f) non-water quality environmental impact (including energy
requirements).
In contrast to the best practicable technology currently
available, best available technology economically achievable
assesses the availablility of in-process controls as well as
X-1
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT ANE ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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control or additional treatment techniques employed at the
end of a production process. In-process control options
available which were considered in establishing these
control and treatment technologies include the following:
(1) alternative water uses
(2) water conservation
(3) waste stream segregation
(
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2_^0 GENERAL WATER GUIDELINES
2.1 Process Water
Process water is defined as any water contacting the raw
materials, processing chemicals, intermediate products, by-
products or products of a process.
2_-_2 Cooling Water
In the concrete products industries, cooling and process
waters are sometimes mixed prior to treatment and discharge.
In other situations, cooling water is discharged separately.
Based on the application of best available technology econo-
mically achievable, the recommendations for the discharge of
such cooling water are as follows.
An allowed discharge of all non-contact cooling waters
provided that the following conditions are met:
(a) Thermal pollution be in accordance with standards to be
set by EPA policies. Excessive thermal rise in once
through non-contact cooling water in the concrete
products industries has not been a significant problem.
(b) All non-contact cooling waters should be monitored to
detect leaks of pollutants from the process. Provisions
should be made for treatment to the standards
established for the process wastewater discharges prior
to release in the event of such leaks.
(c) No untreated process waters be added to the cooling
waters prior to discharge.
The above non-contact cooling water recommendations should
be considered as interim, since this type of water plus
blowdowns for water treatment, boilers and cooling towers
will be regulated by EPA as a separate category.
X-3
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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2^3 Discharge of Excess Rainfall From Process Wastewater
Systems
For those subcategories which utilize either treatment
systems for water recycle or impoundments to achieve no
discharge of process wastewater pollutants an untreated
discharge is allowed in excess of that recorded by the
National Weather Service for the mean annual maximum 24-hour
rainfall event. In the most extreme case Ref (27), a
12.5 cm (5 inch) rain on a 2 ha. (5 acre) plant, this
amounts to 1900 liters per minute (500 gal/min).
Ij^P. PROCESS WASTEWATER GUIDELINES AND LIMITATIONS FOR THE
CONCRETE PRODUCTS INDUSTRIES POINT SOURCE SUBCATEGORIES
The following industry subcategory was required to achieve
no discharge of process wastewater pollutants to navigable
waters based on best practicable control technology
currently available: ready-mixed concrete (mobile plants).
The same limitations guidelines are recommended based on
best available technology economically achievable.
liJ. Concrete Block and Brick (Autoclave and Low Pressure
Steam Curing) Production Subcategories
Based upon the information contained in Sections III through
IX, a determination has been made that the degree of
effluent reduction attainable through the application of the
best available technology economically achievable is no
discharge of process wastewater pollutants.
The above limitations were based on the performance
currently achieved by seven plants in these subcategories,
7102-OU, 7106-08, and 7110.
Identification of_ BATEA
Best available technology economically achievable for the
production of concrete block and brick by the autoclave and
low pressure steam curing processes is segregation of boiler
X-4
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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blowdown and non-contact cooling water, total containment of
process water, recycle or evaporation on plant site.
To implement this technology at plants not already using the
recommended control techniques would require installation of
process water impoundments where necessary and pumps and
piping for segregation of non-process water. Recycle of
process water is practicable at some plants for aggregate
moisture control or reuse in autoclave systems using the
convection process.
Reason for Selection
At least 60 per cent of the industry is currently achieving
this limitation.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, these subcategories as a whole would have to invest
up to an estimated maximum of $1,700,000 to achieve
limitations prescribed herein. There is also an anticipated
increase in the operating cost equivalent to less than 0.5
per cent of the selling price of this product.
It is concluded that the benefits of the total elimination
of the discharge pollutants by the selected control
technology outweigh the costs. Approximately 65 per cent of
these industry subcategories is presently achieving this
level of pollutant discharge.
Ag_§ and Size of Equipment and Facilities
The data obtained for these subcategories represent plants
with ages ranging from 2 to 35 years and productions ranging
from 26,600 to 250,000 kkg per year (29,300 to 275,000 tons
per year) .
X-b
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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The best available technology economically achievable is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in these production
subcategories involves weighing, batching and mixing raw
materials, forming, conditioning, curing using autoclave or
low pressure steam, and storage of concrete block and brick.
The processes used by the establishments in this category
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best available technologies economically achiev-
able is practicable in these production subcategories
because nine of the fourteen plants studied have already
implemented this technology. Reuse of process water for
aggregate moisture control or as autoclave make-up water in
the autoclave convection process is both technically and
economically achievable.
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in these production subcategories.
Non-Water Duality Environmental Impact
There appear to be no major non-water quality environmental
impacts or major energy requirements for the implementation
of the recommended treatment technologies.
X-6
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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3.2. 1 Concrete .Pr_oducjts {N_ECJ_A Concrete Pipe Production
Subcateggrv
Based upon the information in Sections III through IX, a
determination has been made that the degree of effluent
reduction attainable through the application of the best
available technology economically achievable is:
Effluent Limitation
kq/kkg (lb/1QOO Ib)
Effliientch_aracteristic Monthly Average Daily Maximum
TSS 0.007 0.042
Oil and grease 0.002 0.012
pH 6-9
The above limitations were based on the best performance
currently achieved by one plant in this subcategory, 72U7.
Identification of BATEA
Best available technology economically achievable for the
production of concrete pipe is settling of suspended solids,
followed by oil and grease removal, further settling of
suspended solids plus pH adjustment. In addition, where
possible, recycle of central mixer and transport bucket
washout water for washout, hydrostatic test water for
hydrostatic resting, and prewetting water for prewetting,
can be used.
To implement this technology at plants not already using the
recommended control techniques would reguire installation of
settling pond or clarification equipment, oil removal
equipment and pH control equipment. Additional settling
basins and pumps and piping will be necessary to recycle
water.
X-7
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Reason for Selection
One of the largest plants in this subcategory is presently
using the recommended control technologies of settling, oii
and grease removal and pH adjustment. Recycle of equipment
washout water is currently demonstrated in the ready-mixed
concrete industry and the technology is transferable.
Hydrostatic test water is currently being completely
recycled by one plant in this subcategory.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the subcategory as a whole would have to invest up
to an estimated maximum of $5,500,000 to achieve limitations
prescribed herein. There is also an anticipated increase in
the operating cost equivalent to less than 1.0 per cent of
the selling price of this product.
It is concluded that the benefits cf the reduction of the
discharge pollutants by the selected control technology
outweigh the costs. On a production basis, approximately
13 per cent of this industry subcategory is presently
achieving this level of pollutant discharge.
Age and Size of Equipment and Facilities
The data obtained for this subcategory represent plants with
ages ranging from 2 to 40 years and productions ranging from
4,500 to 175,000 kkg per year (5,000 to 193,000 tons per
year) .
The best available technology economically achievable is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
X-8
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Process Employed
The general process employed in this production subcategory
involves weighing, hatching and mixing of raw materials,
casting and curing of concrete pipe. In addition
prestressing, prewettinq^ coating, curing and testing is
used for concrete pressure pipe.
The processes used by the establishments in this subcategory
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best available technologies economically
achievable is practicable in this production subcategory
because the technology of settling is widely used in this
subcategory and pH control and oil and grease removal and
currently used by at least one plant. Recycle of equipment
washout water is currently demonstrated in the ready-mixed
concrete industry and the technology is transferable.
Hydrostatic test water is currently being completely
recycled by one plant in this subcategory.
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in this production subcategory.
Non-Water Quality Environmental Impact
There appear to be no major non-water quality environmental
impacts or major energy requirements for the implementation
of the recommended treatment technologies.
X-9
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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3.2.2 Concrete Products (N.E.C.I » Precast and Prestressed
Production Subcategory
Based upon the information contained in Sections III through
IX, a determination has been made that the degree of
effluent reduction attainable through the application of the
best available technology economically achievable is:
Effluent Limitation
kg/kkg (lb/1000 Ib)
Effluent Characteristic Monthly Average Daily Maximum
TSS 0.007 0.042
Oil and grease 0.0015 0.009
pH 6-9
The above TSS limitations were based on the performance
currently achieved by two plants in this subcategory, 7203
and 7232. The oil and grease limitations were currently
achieved by four plants studied, 7203, 7207, 7230 and 7232.
One of the plants studied is currently achieving the pH
limitation, 7238.
Ident ification of BATEA
Best available technology economically achievable for the
production of precast and prestressed products is improved
settling of suspended solids in ponds or clarification
equipment, pH adjustment and oil and grease removal where
required.
To implement this technology at plants not already using the
recommended control techniques would require installation of
settling ponds or mechanical clarification equipment, pH
control equipment and oil removal equipment.
X-10
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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Select ion
The recommended control technologies are currently used in
at least one plant in this subcategory and are also widely
used in other segments of the industry.
Total Cost o_f Application
Based upon the information contained in Section VIII of this
report? the subcategcry as a whole would have to invest up
to an estimated maximum of $5^400^000 to achieve limitations
prescribed herein. There is also an anticipated increase in
the operating cost equivalent to approximately 1 per cent of
the selling price of this product.
It is concluded that the benefits of the reduction of the
discharge pollutants by the selected control technology
outweigh the costs. Approximately 50 per cent of this
industry subcategory is presently achieving this level of
pollutant discharge,
Ag_e and Size p_f Equipment and Facilities
The data obtained on this subcategory represent plants with
ages ranging from 3 to 50 years and productions ranging from
1,360 to 227,000 kkg per year (1,500 to 250,000 tons per
year) .
The best available technology economically achievable is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in this production subcategory
involves mixing cement, aggregate and water, placing steel
reinforcing or tendons in a form, pouring concrete into the
form, curing and finishing precast and prestressed products.
Y- 1 •"
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
The processes used by the establishments in this subcategory
are very similar in nature and their raw wastes are also
quite similar. These similarities will enhance the
application of the recommended treatment technologies.
Engineering Aspects
From an engineering standpoint/ the implementation of the
recommended best available technologies economically
achievable is practicable in this production subcategory
because the technology of settling is widely used in this
subcategory. The technologies of oil and grease removal and
pH adjustment are used in this industry and are transferable
to this subcategory.
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in this production subcategory.
Non-Water Quality Environmental Impact
There appear to be no major non-water quality environmental
impacts or major energy requirements for the implementation
of the recommended treatment technologies.
3.3 Ready-Mixed Concrete, Permanent and Portable Production
Subcategories
Based upon the information contained in Sections III through
IX, a determination has been made that the degree of
effluent reduction attainable through the application of the
best available technology economically achievable is no
discharge of process wastewater pollutants.
The above limitations were based on the performance
currently achieved by seven plants in these subcategories,
7363, 7487, 7729, 7732, 7736, 7756 and 7757. These
X-12
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
limitations are achieved, by other means, by about 40 per
cent of the plants in these sutcategories.
Identification of BATSA
Best available technology economically achievable for the
production of rea-dy-mixed concrete by permanent and portable
plants is settling of suspended solids in ponds, basins or
mechanical clarification equipment, recycle of clarified
water for truck washout and partial reuse as mix water, or
total containment.
To implement this technology at plants not already using the
recommended control techniques would require installation of
settling ponds, basins or mechanical clarification equipment
and piping and pumps for recycle.
Reason for
These technologies are currently being used by eight plants
in these subcatego.ri.es and can also be transferred to other
plants in these sutcategories.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the subcategory as a whole would have to invest up
to an estimated maximum of $180,000,000 to achieve
limitations prescribed herein » There is also an anticipated
increase in the operating cost equivalent to approximately
3.5 per cent of the selling price of this product.
It is concluded that rhe benefits of the total elimination
of the discharge pollutants by the selected control
technology outweigh the costs. Approximately 40 per cent of
these industry subcategories is presently achieving this
level of pollutant discharge.
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
Age and Size of Equipment, and Facilities
The data obtained on these subcategories represent plants
with ages ranging from 1 to 43 years and productions ranging
from 1,530 to 230,000 cubic meters per year (2,000 to
300,000 cubic yards per year).
The best available technology economically achievable is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Process Employed
The general process employed in these production
subcategories involves weighing, batching and mixing of
cement, aggregates and water, and delivery of ready-mixed
concrete.
The processes used by the establishments in these
subcategories are very similar in nature and their raw
wastes are also quite similar. These similarities will
enhance the application of the recommended treatment
technologies.
Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best available technologies economically
achievable is practicable in these production subcategories
because the technologies of settling and recycle of
clarified wastewater for truck washout and for partial use
as mix water are currently used in eight plants in these
subcategories and can be transferred to other plants in this
subcategory. Although the reuse of clarified wastewater for
mix water is only allowed in some areas at this time, it is
reasonable to expect that by 1983 this practice will become
predominant in this industry.
X-14
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
Process Changes
The recommended control technologies would not require major
process changes. These control technologies are presently
being used by plants in these production subcategories.
Non-Water Quality Environmental Impact
There appear to be no major non-water quality environmental
impacts or major energy requirements for the implementation
of the recommended treatment technologies.
X-15
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
AND PRETREATMENT STANDARDS
1^0 INTRODUCTION
This level of technology is to be achieved by new sources.
The term "new source" is defined in the Act to mean "any
source, the construction of which is commenced after the
publication of proposed regulations prescribing a standard
of performance." This technology is evaluated by adding to
the consideration underlying the identification of best
available technology economically achievable, a
determination of what high levels of pollution control are
available through the use of improved production processes
or treatment techniques. Thus, in addition to considering
the best in-plant and end-of-process control technology, new
source performance standards are how the level of effluent
may be reduced by changing the production process itself.
Alternative processes, operating methods or other
alternatives were considered. However, the end result of
the analysis identifies effluent standards which reflect
levels of control achievable through the use of improved
production processes (as well as control technology), rather
than prescribing a particular type of process or technology
which must be employed.
The following factors were considered with respect to
production processes which were analyzed in assessing the
best demonstrated control technology currently available for
new sources:
(a) the type of process employed and process changes;
(b) operating methods;
(c) batch as opposed to continuous operations;
(d) use of alternative raw materials and mixes of raw
materials;
XI-1
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
(e) use of dry rather than wet. processes (including
substitution of recoverable solvents from water) ; and
(f) recovery of pollutants as by-products.
In addition to the effluent limitations covering discnargas
directly into waterways, the constituents of the effluent
discharge from a plant within the industrial category which
would interfere with? pass through, or otherwise be
incompatible with a well designed and operated publicly
owned activated sludge or trickling filter wastewater
treatment plant were identified, A determination was made
of whether the introduction of such pollutants into the
treatment plant should be completely prohibited.
2.0 GSNER AL WATER GJJIJDELINSS
The process water, cooling water and boiler blowdown guide-
lines for new sources are identical to those based on best
available technology economically achievable,
EFFLUENT REDUCTION ATTAINABLE BY THE APPLICATION OF THE
BEST AVAILABLE DEMONSTRATED CONTROL TECHNOLOGIES,
PROCESSES, OPERATING METHODS , OR OTHER ALTERNATIVES
Based upon the information contained in Sections III through
X of this report , the following determinations were made as
to the degree of effluent reduction attainable with the
application of new source standards for the various
subcategories of the concrete products industries.
The following industry subcategories were required to
achieve no discharge of process wastewater pollutants to
navigable waters based on best available technology
economically achievable:
concrete block and brick
ready-mixed concrete, permanent
ready-mixed concrete, portable
ready-mixed concrete, mobile
XI-2
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGS BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
The same limitations are recommended as new source per-
formance standards.
The following industry subcategories are required to achieve
specific effluent limitations as given in the following
paragraphs:
3._\ Concrete Products (NEC) , Concrete Pipe
Same as BATEA.
3.2 Concrete Products (NEC), Precast and Prestressed
Products
Same as BATEA.
q.O PRETREATMENT STANDARDS
Recommended pretreatment guidelines for discharge of plant
wastewater into public treatment works conform in general
with EPA Pretreatment Standards for Municipal Sewer Works as
published in the July 19, 1973 Federal Register and
"Title 40 - Protection of the Environment, Chapter 1 -
Environmental Protection Agency, Subchapter D - Water
Programs - Part 128 - Pretreatment Standards" a subsequent
EPA publication. The following definitions conform to these
publications:
§.i. Compatible Pollutant
The term "compatible pollutant" means biochemical oxygen
demand, suspended solids, pH and fecal coliform bacteria,
plus additional pollutants identified in the NPDES permit,
if the publicly-owned treatment works was designed to treat
such pollutants, and, in fact, does remove such pollutants
to a substantial degree. Examples of such additional
pollutants may include:
XI-3
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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chemical oxygen demand;
total organic carbon;
phosphorus and phosphorus compounds;
nitrogen and nitrogen compounds; and
fats, oils, and greases of animal or vegetable
origin, except as defined below in 4.1 Prohibited
Wastes.
kz. Incompatible Pollutant
The term "incompatible pollutant" means any pollutant which
is not a compatible pollutant as defined above.
c. Joint Treatment Works
Publicly-owned treatment works for both non-industrial and
industrial wastewater.
d. Major Contributing Industry
A major contributing industry is an industrial user of the
publicly-owned treatment works that: has a flow of 50,000
gallons or more per average work day; has a flow greater
then five per cent of the flow carried by the municipal
system receiving the waste; has in its waste, a toxic
pollutant in toxic amounts as defined in standards issued
under Section 307(a) of the Act; or is found by the permit
issuance authority, in connection with the issuance of an
NPDES permit to the publicly-owned treatment works receiving
the waste, to have significant impact, either singly or in
combination with other contributing industries, on that
treatment works or upon the quality of effluent from that
treatment works.
e. Pretreatment
Treatment of wastewaters from sources before introduction
into the joint treatment works.
XI-4
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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4.1 Prohibited Wastes
No waste introduced into a publicly-owned treatment works
shall interfere with the operation or performance of the
works. Specifically,, the following wastes shall not be
introduced into the publicly-owned treatment works:
(a) Wastes which create a fire or explosion hazar in the
publicly-owned treatment works;
(b) Wastes which will cause corrosive structural damage to
treatment works, but in no case wastes with a pH lower
than 5.0, unless the works are designed to accommodate
such wastes;
(c) Solid or viscous wastes in amounts which would cause
obstruction to the flow in sewers, or other interference
with the proper operation of the publicly-owned
treatment works, and
(d) Wastes at a flow rate or pollutant discharge rate which
is excessive over relatively short time periods so that
there is a treatment process upset and subsequent loss
of treatment efficiency.
4_.2 Pretreatment f_or Incompatible Pollutants
In addition to the above, the pretreatment standard for
incompatible pollutants introduced into a publicly-owned
treatment works by a major contributing industry shall be
best practicable control technology currently available;
provided that, if the publicly-owned treatment works which
receives the pollutants is committed, in its NPDES permit,
to remove a specifiec percentage of any incompatible pol-
lutant, the pretreatment standard applicable to users of
such treatment works shall be correspondingly reduced for
that pollutant; and provided further that the definition of
best practicable control technology currently available for
industry categories may be segmented for application to
pretreatment if the Administrator determines that the
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
definition for direct discharge to navigable waters is not
appropriate for industrial users of joint treatment works.
U.3 Recommended Pretreatment Guidelines For New Sources
Recommended pretreatment standards for new sources are:
(a) No pretreatment required for removal of compatible
pollutants - biochemical oxygen demand, suspended solids
(unless hazardous), a pH of 6-9, and fecal coliform
bacteria;
(b) Suspended solids containing hazardous pollutants such as
heavy metals, cyanides and chromates should conform to
or be restricted to those quantities recommended earlier
in Section XI Guidelines for Best Available Demonstrated
Control Technologies, Processes, Operating Methods, or
Other Alternatives;
(c) Pollutants such as chemical oxygen demand, total organic
carbon, phosphorus and phosphorus compounds, nitrogen
and nitrogen compounds, and fats, oils, and greases,
need not be removed provided the publicly-owned
treatment works was designed to treat such pollutants
and will accept them. Otherwise levels should be at or
below NSPS Guideline Recommendations;
(d) Innocuous dissolved solids such as sodium chloride,
sodium sulfate, calcium chloride, and calcium sulfate,
should be permitted provided that the industrial plant
is not a "major contributing industry";
(e) Plants covered under the "major contributing industry"
definition should not be permitted to discharge large
quantities of dissolved solids into a public sewer even
though they might be at the NSPS Guideline
Recommendations of this report. Each of these cases
would have to be considered individually by the sewer
authorities, and,
XI-6
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
(f) Discharge of all other incompatible hazardous or toxic
pollutants from the manufacturing plants of this study
to municipal sewers should conform to NSPS guidelines
levels for discharge to surface water.
XI-7
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON
INFORMATION IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED
UPON COMMENTS RECEIVED AND FURTHER INTERNAL REVIEW BY EPA.
DRAFT
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DRAFT
SECTION XII
ACKNOWLEDGEMENTS
The preparation of this report was accomplished through the
efforts of the staff of General Technologies Division,
Versar Inc., Springfield, Virginia, under the overall
direction of Dr. Robert G. Shaver, Vice President. Mr.
Michael W. Slimak and Mr. Robert C. Smith, Jr., shared the
direction of the day-to-day work on the program:
Messrs. Michael W. Kosakowski and Ralph A. Lorenzetti,
Project Officers, Effluent Guidelines Division, through
their assistance, leadership, and advice have made an
invaluable contribution to the preparation of this report.
Messrs. Kosakowski and Lorenzetti provided a careful review
of the draft report and suggested organizational, technical,
and editorial changes. They were also most helpful in
making arrangements for the drafting, presenting, and
distribution of the completed report.
Mr. Allen Cywin, Director, Effluent Guidelines Division, Mr.
Ernst P. Hall, Jr., Assistant Director, Effluent Guidelines
Division, and Mr. Harold B. Coughlin, Branch Chief, Effluent
Guidelines Division, offered many helpful suggestions during
the program.
Acknowledgement and appreciation is also given to the
secretarial staffs of both the Effluent Guidelines Division
and General Technologies Division of Versar Inc., for their
efforts in the typing of drafts, necessary revisions, and
final preparation of the effluent guidelines document.
Appreciation is extended to the following trade associations
and private companies for their assistance and cooperation
in this program:
American Concrete Institute
American Concrete Paving Association
American Concrete Pipe Association
American Concrete Pressure Pipe Association
Cellular Concrete Association
Centre Concrete Company
XII-1
DRAFT
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DRAFT
Conrock Corporation
Crider 6 Shockey, Inc.
Dravo Corporation
Erie-Strayer, Inc.
Gifford-Hill Co., Inc.
H.T. Campbell & Sons Co.
Houston Shell & Concrete
Interpace Corporation
Jadair Corporation
Jetomatic Systems, Inc.
Lone Star Industries, Inc.
Maloney Concrete
Massey Concrete
Material Service Corporation
Mobile Premix Concrete
National Concrete Burial Vault Association
National Concrete Masonry Association
National Precast Concrete Association
National Ready-Mixed Concrete Association
Prestressed Concrete Institute
Portland Cement Association
Reinforce Concrete Research Council
Rex Nord Division of Rex Industries
Smith, Monroe 6 Gray Engineers
Super Concrete Corporation
Texas Aggregates 6 Concrete Association
The Vince Hagan Company
Twin City Concrete
Underwood Builders Supply Company
Virginia Concrete
Appreciation is also extended to the many other companies
who gave us invaluable assistance and cooperation in this
program.
Also, our appreciation is extended to the individuals of the
staff of General Technologies Division of Versar Inc., for
their assistance during this program. Specifically, our
thanks to:
Dr. R. L. Durfee, Senior Chemical Engineer
Dr. C.^ L. Parker, Senior Chemical Engineer
Mr. L. C. McCandless, Senior Chemical Engineer
Mr. M. G. DeFries, Chemical Engineer
Mr. F. B. Shay, Consultant
XII-2
DRAFT
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DRAFT
Mr. R. S. Wetzel, Environmental Engineer
Mrs. D. K. Guinan, Chemist
Dr. M. K. Khattak, Analytical Chemist
Ms. M. Smith, Analytical Chemist
Ms. C. V. Fong, Chemist
Mr. 5. E. Powers, Chemist
Mr. M. C. Calhoun, Field Engineer
Mr. J. R. Freed, Field Engineer
Mr. D. McNeese, Laboratory Technician
Mrs. N. Ekiert, Laboratory Technician
Mrs. N. Talsania, Laboratory Technician
Ms. R. Metzger, Laboratory Technician
XII-3
DRAFT
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DRAFT
SECTION XIII
REFERENCES
1. Akroyd, T.N.W., Concrete Properties £ Manufacture,
Pergamon Press, New York, 1962.
2. Blanks, R.F., & Kennedy, H.L., "The Technology of Cement
and Concrete", Concrete Materials, Volume I, John Wiley
& Sons, New York, 1955.
3. "Census of Manufactures", 1972, Bureau of the Census,
U.S. Department of Commerce, U.S. Government Printing
Office, Washington, D.C., MIC 72(p)-32B-2 through MIC
72(P) -32E-6.
4. Ferguson, P.M., Reinforced Concrete FundamentaIs, 2nd
ed., John Wiley 6 Sons, New York, 1967.
5. Gaynor, R.D., "Disposal of Wash Water and Returned
Concrete", NRMCA Publication, June 8, 1971.
6. "Design & Control of Concrete Mixtures", 11th ed.,
Portland Cement Association Bulletin, July, 1968.
7. Godfrey, Robert Sturgis, Editor in Chief, Building
Construction Cost Data 1975, 33rd annual ed., Robert
Snow Means Company, Inc., Duxbury, Mass.
8. Harger, H.L., "A System for 100% Recycling of Returned
Concrete: Equipment, Procedures 6 Effects on Product
Quality", NRMCA Publication No. 150, March, 1975.
9. "Industrial Waste Study Report: Flat Glass, Cement,
Lime, Gypsum, & Asbestos Industries", Sverdrup & Parcel
& Associates, Inc., St. Louis, Missouri, July, 1971.
10. Kirk & Othmer, Encyclopedia of Chemical Technology, 2nd
ed.. Volume IV, John Wiley & Sons, New York, 1964.
11. Lauwereins, M.A., "Water Pollution-Chicago Style",
Modern Concrete, May, 1971.
XIII-1
DRAFT
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DRAFT
12. Mather, B., "New Concern Over Alkali-Aggregate
Reaction", Presentation to the Joint NSGA-NRMCA
Engineering Session, New Orleans, La., 28 January 1975.
13. Meiniuger, R.C., "Disposal of Truck Mixer wash Water £
Unused Concrete", NRMC& Publication Mo. 16, December,
196U.
14. Monroe, R.G., "Wastewater Treatment Studies in Aggregate
& Concrete Production"* i£P£™E2-73-Q03, February, 1973.
15. Murdock, L. J. , and Siaekledgs ?- 3.F., Concrete fcat e^
& P.ractice, ^tn s<^* » Edward Arnold Publishers Ltd. ,
London, 1968.
16. Neville, A.M., ££2E§£tie^ £f Concx^ete,, John Wiley 6
Sons, New York, 1973.
17. Orchard, D,F. , Concrete Technology , 3rd ad., Volumes I
and II, John Wiley & Sons, New York* 1973.
18. Perry, R.H., Chilton, C.H., Kirkpatrick^ 3.D. , Chemical
Enqi-neering Handbook , 4th ed. , McGraw-Hill, New York,
1969.
19. Richardson, J.G., Precast Concrete Pro.duction, Cement
and Concrete Association^ London, 1973.
20. Simons, E.N., Cement 6 Concrete Engineering , Frederick
Muller, Ltd., London, 1964.
21. "Symposium Effect of Water Reducing Admixtures & Set
Retarding Admixtures on Properties of Concrete", ASTM
Special Technical Publication 226, 1959.
22. Taylor, W.H., Concrete Technology & Practice, 3rd ed. ,
Angus & Robertson Ltd., London, 1969.
23. Troxell, G. E. , Davis, H.E. , Kelly, J.W. , Composition S
Properties of Concrete, 2nd ed., McGraw-Hill, New York?
1968.
24. U.S. Patent No. 3,885,985, "Additive for Improving
Hydraulic Cement Compositions".
XIII-2
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25. Waddell, J.J., Practical Duality Control for Conereto,
McGraw-Hill, New York, 1962.
26. Walker, S., "Ready-Mixed Concrete", NRMCA Publication
No. 120, April, 1966.
27. USGS, Department of the Interior, National Atlas, 1970,
p. 97.
XIII-3
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SECTION XIV
GLOSSARY
1. Absorption: The relationship of the weight of the water
absorbed to the weight of the dry specimen expressed in
percent.
2. Accelerating Agent; Material added to concrete to
accelerate its setting time and strength development.
3- Admixture: Material, other than aggregate, cement, or
water added in small quantities to concrete to produce
some desired change in properties.
**• Aggregate, Coarse; Crushed stone which is retained on a
Number 4 standard sieve.
5. Aggregate, Fine; Sand with a particle size smaller than
a Number 4 standard sieve or approximately 0.6 cm
(1/4 inch) .
6. Aggregate, Lightweight: Aggregates such as expanded
shale, cinder, clay, slate,pumice, scoria, perlite,
vermiculite, and diatomite.
7. Aggregate, Heavyweight: Aggregate such as iron or steel
particles, barite, limonite, magnetite and ilmenite.
8. Aggregate, Normalweight; Aggregates such as sand,
gravel, and crushed stone.
9. Air-entraining Accent: Substance added to concrete
materials before or during mixing to entrain air in the
concrete to improve resistance to freezing and thawing
exposure.
10. Batching: The weighing and proportioning of two or more
raw materials which go into the manufacture of concrete
products.
11. Baghouse: Chamber in which exit gasses are filtered
through membranes (bags) which remove solids.
XIV-1
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12. Block Equivalent; Standard unit of production of
concrete block and brick, 20 x 20 x 41 cm, (8 x 8 x
16 inches).
13. Central Mixer; Rotary mixer used to mix concrete with
an average capacity of about H cubic meters.
11. Central Mixer Plant; Permanent or portable ready-mixed
concrete plant that prepares concrete in a central mixer
then transfers it to a truck mixer or agitator for
delivery.
15. Concrete^ Heavyweight; Concrete made using aggregates
such as barite, limonite, magnetite, ilmenite, and iron
ana steel particles. Produced primarily for nuclear
applications.
"16. Concrete, Insulating Lightweight; Concrete made using
lightweight aggregates such as pumice, scoria, perlite,
vermiculite, and diatomite.
17. Concrete, Lightweight; Concrete made using lightweight
aggregates.
18- Curing, Atmospheric; Method of curing which uses
ambient heat and humidity.
19. Curing, High Pressure or Autoclave; Method of curing
block and brick in which loaded curing cars are placed
into a large horizontal, cylindrically shaped autoclave,
where high pressure steam is injected or convected for
approximately 8 hours.
20. Curing, Hot Oil Convection; Special type of high
pressure steam curing of block and brick where water is
placed in a trough in an autoclave and hot oil heats the
water to produce steam.
21- Curing, LOW Pressure; Method of curing block and brick
in which loaded curing cars are placed in a chamber or
kiln where low pressure steam (less than 9.7 atm) is
injected from perforated pipes for approximately
8-10 hours.
XIV-2
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DRAFT
22. Curing, Spray: Method of curing in which products are
sprayed with a fine mist of water.
23. Dry Batch Plant: Permanent or portable ready-mixed
concrete plant that transfers weighed amounts of dry
aggregate and cement with a specific amount of water
into a mixer truck for subsequent mixing.
24. Dispersing Agent; Material added to concrete to
separate the individual suspended particles.
25. Friable: Term used to describe concrete made with an
insufficient quantity of mix water that crumbles and
breaks apart easily.
26. Form Releasing Agent: Oil sprayed onto forms prior to
pouring or casting of the concrete to facilitate the
separation of the concrete and form.
27. Grout; Mixture of cement and water or cement, sand, and
water.
28. Hydration: Incorporation of molecular water into a
complex molecule with the molecules of another sub-
stance, in this case cement.
29. Hydrostatic Testing: Testing of pipe or other vessel
for strength and leak resistance by pressurization with
a test liquid.
30. Mortar: Mixture of cement, lime, and sand used for
bonding bricks and masonry.
31. Packerhead: A rapidly revolving and rising steel
element which packs the concrete radially outward
against a stationary form. The force with which the
concrete is packed against the outside form compacts the
concrete sufficiently so that the element can be raised
as more concrete is added.
32. Portland Cemgnt: A hydraulic cement resembling portland
stone when hardened; made of pulverized calcined
argillaceous and calcareous material; proper name for
ordinary cement.
XIV-3
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33- Precast Corjcrete Products; Describes the many types and
varieties of concrete units which are cast in molds
either in a factory or on the site, and are not built
into the structure until they have fully hardened. Most
of the larger precast units are made with steel
reinforcing rods.
34. Pressure Pipe: Reinforced and prestressed concrete pipe
that uses a permanent steel cylinder, which remains with
the pipe, as a form.
35. Prestressed; Process of casting concrete with tensioned
steel bars or cables embedded in the concrete.
36. Pretension; Prestressed concrete made by placing steel
cables under tension in the form before the concrete is
poured. Once the concrete has set, cured, and forms
have been removed, the external tension is released from
the steel cables. The cable retains internal stress due
to the compression of the concrete around it.
37. Post-tension; Prestressed concrete made by placing
cables in the form, casting the concrete, allowing it to
set and cure, then placing the cables under tension.
The cables must be protected with a steel or plastic
tube or mastic coating to prevent bonding with the
concrete prior to tensioning. The cables may or may not
be grouted while under tension and are locked under
tension by appropriate end clamps.
38 • Ready-mixed plant. Permanent; Plant with a fixed
location that uses mixer trucks to deliver the concrete.
The concrete may be mixed in central mixers and hauled
in agitator trucks or may be dry batched into mixer
trucks and mixed on the way to the job site.
39. Ready-mixed plant. Portable; Temporary or transient
type of plant used on large highway and airport jobs.
The concrete may be produced by either a central mixer
or a dry batch plant.
40. Ready-mixed plant, mobile; A ready-mixed truck capable
of transporting all raw materials (aggregate, cement,
and water etc.) separately on the truck and pro-
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portioning and mixing them in the truck mounted mixer at
the job site. (Concrete-mobile)
41. Reinforced concrete: Concrete with structural steel
members added to increase strength.
^2. Reinforced BJjaes Concrete pipe with a steel cage added
to provide increased tensile strength.
^3. Retarding Agent: Material added to concrete for the
purpose of prolonging the setting time of the concrete.
44. Shrink-mixed; Concrete mixed partially in a stationary
central mixer and completely mixed in a truck mixer
either on the way or at the job site.
45. Spin Cast Method For Cor.crete Pipe: A reinforcing cage
(steel cylinder in pressure pipe) is fabricated and
positioned in a form which is then placed horizontally
on a high speed roller drive mechanism. The form is
rotated at a high rate^ while the concrete is added
evenly by a reciprocating nozzle on the inside of the
form. The spinning action densities the concrete on the
inside of the form and dewaters it. Water flows off the
inside surface of the pipe and the concrete surface is
finished by a mechanical roller.
46. Tendons: Steel cables used for reinforcement in
prestressed concrete products.
47. Transport Buckets Bucket used to carry concrete from
the central mixer to the casting area in block, pipe,
precast, and prestressed plants.
48. Vertical Cast Method - Reinforced and Pressure Pipe
Production: Wet concrete mix is produced in a central
mixer and transported to a vertical steel form via
transport buckets. The concrete is poured into the form
containing a reinforcing cage or cylinder, then
mechanically vibrated for compaction. Concrete is
allowed to set and forms removed. This method can
produce any size of reinforced pipe, but is generally
limited to diameters over 1.5 meters (5 ft).
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49. Vertical Packerhead Method - Non-reinforced and
Reinforced Pipe Production: Moist concrete is compacted
and vibrated into a steel form by a packerhead.
Generally used to produce pipe up to 1.5 meters (5 ft)
in diameter.
50. Washoff; Wastewater originating from washing off the
exterior of a ready-mixed concrete truck.
51. Washout; Wastewater originating from the washing of the
interior of a ready-mixed concrete truck mixer or
central mixer.
52. Water Reducing Agent; Material added to concrete for
the purpose of reducing the quantity of mixing water
required to produce a concrete of a given consistency.
53. Wetting Agent; Substance that renders a surface non-
repellent to liquids.
51- Yard Runoff: Wastewater originating from aggregate pile
runoff, dust control spraying, truck chute runoff and
spillage that follows the contour of the land and runs
off the plant's property or into the treatment system.
XIV-6
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