EPA 440/ 1-76/081-c
Supplemental For
PRETREATMENT
to the
Interim Final Development Document
for the
SECONDARY ALUMINUM
Segment Of The
NONFERROUS METALS
MANUFACTURING
POINT SOURCE CATEGORY
*
U.S. ENVIRONMENTAL PROTECTION AGENCY
DECEMBER 1976
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SUPPLEMENTAL FOR PRETREATMENT
to the
DEVELOPMENT DOCUMENT
for the
SECONDARY ALUMINUM SEGMENT
of the
NONFERROUS METALS MANUFACTURING
POINT SOURCE CATEGORY
Russell E. Train
Administrator
Andrew W. Breidenbach, Ph.D.
Assistant Administrator for
Water and Hazardous Materials
Eckardt C. Beck
Deputy Assistant Administrator for
Water Planning and Standards
Robert B. Schaffer
Director, Effluent Guidelines Division
Patricia E. Williams, P.E.
Project Officer
December 1976
Effluent Guidelines Division
Office of Water and Hazardous Materials
U.S. Environmental Protection Agency
Washington, D.C. 20460
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ABSTRACT
This document presents the findings of a study by the
Environmental Protection Agency of the secondary aluminum
smelting industry for the purpose of developing pretreatment
standards for existing sources to implement section 307 (b)
of the Federal Water Pollution Control Act, as amended.
The development of data and identified technology presented
in this document relate to wastewaters generated in metal
cooling, fume scrubbing and wet residue processing. The
pretreatment levels corresponding to these technologies also
are presented.
Supporting data and rationale for development of
pretreatment levels based on best practicable pretreatment
technology are contained in this report.
111
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CONTENTS
Section Page
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 5
IV INDUSTRY CATEGORIZATION 19
V WASTE CHARACTERIZATION 25
VI SELECTION OF POLLUTANT PARAMETERS 39
VII CONTROL AND TREATMENT TECHNOLOGY 45
VIII COSTS, ENERGY AND NONWATER QUALITY ASPECTS 65
IX BEST PRACTICABLE PRETREATMENT TECHNOLOGY 119
X ACKNOWLEDGMENTS 125
XI REFERENCES 127
XII GLOSSARY 129
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FIGURES
Number
VII- 1
VII-2
VII-3
VII-4
VIII-1
VIII-2
VIII-3
VIII-4
VIII-5
VIII-6
VIII-7
VIII-8
VIII-9
Title
Production Distribution by Size for
Secondary Aluminum Smelters
Ingot Cooling Water Recycle
AlF3_ Demagging Scrubwater Recycle System
Neutralization of Chlorine Demagging
Scrubber Water
Residue Milling Wastewater Partial
Recycle-Plant 17
Pump Costs
Costs of Pipes
Holding and Mixing Tank Costs
Cooling Tower Costs
Ingot Cooling Water Recycle
Ingot Cooling Water - Oil and Grease
Removal and Discharge
Chlorine Demagging Scrubwater Treatment
and Discharge
A1F3_ Demagging Scrubwater Recycle System
Residue Milling Wastewater Partial Recycle
Page
10
47
50
53
60
68
69
70
71
78
87
92
102
112
VI
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TABLES
Number Title Page
III-1 Comparison of Process Frequencies for n
Secondary Aluminum Smelters
III-2 Characteristics of Secondary Aluminum is
Smelters - POTW Dischargers
IV-1 Number of Secondary Aluminum POTW Dis- 22
chargers Using the Various Sizes and
Types of POTW
V-1 Water Used and Discharged at Secondary 26
Aluminum smelters
V-2 Chemical Characteristics of Metal Cooling 28
Water at POTW Dischargers
V-3 Comparison of Chemical Characteristics of 29
Metal Cooling Water for Direct and POTW
Dischargers
V-U Characteristics of Wastewater from Aluminum 30
Shotting
V-5 Chemical Characteristics of C12 Demagging 32
Scrubber Wastewater at Plant #1 and
Plant #12
V-6 Comparison of Chemical Characteristics 33
of C12 Demagging Scrubber Wastewater for
Direct and POTW Dischargers
V-7 Chemical Characteristics of Scrap Crusher 34
Scrubber Water at Plant #12
V-8 Comparison of chemical characteristics of 37
Residue Processing Wastewater for Direct
and POTW Dischargers
VII-1 Chlorine Demagging Scrufcwater Treatment 54
with Soda Ash - Plant #12
VII-2 Chlorine Demagging Scrubwater Treatment 55
with Caustic Soda - Plant #5
VII-3 Effectiveness of pH Adjustment and Settling 56
on Aluminum Removal
VII
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VII-4 Treatment Effectiveness, Lime Treatment 57
and Settling
VIII-1 Model Control Costs, Ingot Cooling and 79
Water Recycle (Large Plant)
VIII-2 Cost Components, Ingot Cooling and Water 80
Recycle (Large Plant)
VIII-3 Model Control Costs, Ingot Cooling and 81
Water Recycle (Small Plant)
VIII-4 cost components. Ingot Cooling and Water 82
Recycle (Small Plant)
VIII-5 Model Control Costs, Settle, Discharge to 83
POTW for Ingot Cooling (Large Plant)
VIII-6 Cost Components, Settle, Discharges to 84
POTW for Ingot Cooling (Large Plant)
VIII-7 Model Control Costs, Settle, Discharge to 85
POTW for Ingot Cooling (Small Plant)
VIII-8 Cost Components, Settle, Discharge to 86
to POTW for Ingot Cooling (Small Plant)
VIII-9 Model Treatment Costs, Ingot Cooling with 88
Oil and Grease Removal, Discharge
(Large Plant)
VIII-10 Cost Components, Ingot Cooling with Oil and 89
Grease Removal, Discharge (Large Plant)
VIII-11 Model Treatment Costs, Ingot Cooling with 90
Oil and Grease Removal, Discharge
(Small Plant)
VIII-12 Cost components. Ingot Cooling with Oil and 91
Grease Removal, Discharge (Small Plant)
VIII-13 Model Treatment Costs, Chlorine Demagging 93
Scrubwater (Large Plant)
VIII-14 Cost Components, Chlorine Demagging 94
Scrubwater Treatment (Large Plant)
VIII-15 Model Treatment Costs, Chlorine Demagging 95
Scrubwater (Small Plant)
Vlll
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VIII-16 Cost Components, Chlorine Demagging 96
Scrubwater Treatment (Small Plant)
VIII-17 Model Control Costs, Derham Demagging 98
Process (Large Plant)
VIII-18 Cost Components, Derham Demagging 99
Process (Large Plant)
VIII-19 Model Control Costs, Derham Demagging 100
Process (Small Plant)
VIII-20 Cost Components, Derham Demagging 101
Process (Small Plant)
VIII-21 Model Control Costs, Aluminum Fluoride 103
Demagging Scrubwater with Water Recycle
(Large Plant)
VIII-22 Cost Components, Aluminum Fluoride Demagging 104
Scrubwater with Water Recycle (Large Plant)
VIII-23 Model Control Costs, Aluminum Fluoride 105
Demagging Scrubwater with Water Recycle
(Small Plant)
VIII-24 Cost Components, Aluminum Fluoride 106
Demagging Scrubwater with Water Recycle
(Small Plant)
VIII-25 Model Treatment Costs, Aluminum Fluoride 108
Demagging Scrubwater with Water Discharge
(Large Plant)
VIII-26 Cost Components, Aluminum Fluoride 109
Demagging Scrubwater Treatment with
Water Discharge (Large Plant)
VIII-27 Model Treatment Costs, Aluminum Fluoride no
Damagging Scrubwater with Water Discharge
(Small Plant)
VIII-28 Cost Components, Aluminum Fluoride Demagging
Scrubwater Treatment with Water Discharge
(Small Plant)
VIII-29 Model Treatment Costs, Residue Milling
Wastewater with Partial Recycle
(Large Plant)
IX
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VIII-30 Cost Components, Residue Willing Wastewater 114
with Partial Recycle (Large Plant)
VIII-31 Model Treatment costs, Residue Milling 115
Wastewater with Ammonia Stripping
(Large Plant)
VIII-32 Cost Components, Residue Milling Waste- lie
water with Ammonia Stripping
(Large Plant)
VIII-33 Cost/Benefit of Pretreatment Technologies 117
VIII-34 Summary of Pretreatment Costs 118
VIII-35 Metric Table 132
x
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SECTION I
CONCLUSIONS
This report deals with that portion of the secondary
aluminum smelting subcategory which introduces pollutants to
publicly owned treatment works (hereafter referred to as
POTW dischargers).
Secondary aluminum smelting may be considered a single
subcategory for the purpose of establishing pretreatment
standards. The consideration of other factors such as age
and size of the plant, processes employed, geographical
location, wastes generated, and wastewater treatment and
control techniques employed support this conclusion. The
similarities of the wastes produced by secondary aluminum
smelting operations and the control and pretreatment
technologies and techniques available to reduce the
discharge of pollutants further substantiate the treatment
of secondary aluminum smelting as a single subcategory.
Eighteen of the 71 secondary aluminum plants in the US are
POTW dischargers. The remaining plants either have no
discharge of process wastewater pollutants or discharge to
navigable waters (referred to hereafter as direct
dischargers).
One of the conclusions of this study was that certain
constituents discharged by this industry would pass through
or would interfere with the operation of publicly owned
treatment works. It was found that this industry can apply
measures to limit the discharge of such pollutants. The
identified levels of control can be achieved by the
application of treatment technologies such as pH control,
ammonia removal and oil and grease removal. Many plants may
find it economically advantageous to achieve this level of
control by incorporating various degrees of recycle and
reuse of water. These technologies are not specifically
required since the conference report to the Water Pollution
Control Act of 1972 (P.L. 92-500) makes it clear that
Congress did not intend to specifically promote the use of
recycle technologies where POTW dischargers are concerned.
The most common process wastewater introduced to POTW from
secondary aluminum smelters is metal cooling water, which is
usually untreated before discharge. This wastewater has low
levels of metals. Apart from oil and grease levels, and
occasionally low pH's (i.e., 4.0-5.0), this wastewater
appears compatible with POTW operation, although this water
is often recycled.
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Untreated fume scrubbing water from either chlorine or
aluminum fluoride demagging operations is characterized by
low pH (i.e., from 1.0-2.0) and must be neutralized before
entering a sewer. The levels of dissolved aluminum will be
controlled by controlling pH. The complete recirculation of
wastewater from chlorine demagging is not possible because
of the accumulation of sodium and potassium chlorides.
However, aluminum fluoride wastewater may be treated and
recycled more economically than if it were treated for
introduction to a POTW. Since zinc and cadmium were
occasionally found in demagging scrubber waste waters,
guidance levels are suggested for these parameters.
Only one plant introduces residue milling water to a POTW
after settling of the coarse solids. Only low
concentrations of metals were found. Although the
concentrations of chloride, sodium and potassium are high,
and these parameters will pass through a POTW essentially
untreated, there is no practicable, economical treatment for
these parameters in this particular waste at this time.
Ammonia was found at one direct discharge plant. It was not
found at the single plant which is a POTW discharger when it
was sampled three years ago. However, since the POTW
discharger may operate so that ammonia would appear in the
wastewater, a limitation has been established for this
parameter.
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SECTION II
RECOMMENDATIONS
In the secondary aluminum industry, wastewater is generated
principally from three operations: cooling of molten
aluminum alloy, wet scrubbing of fumes during chemical
magnesium removal, and the wet milling of aluminum melt
residues such as dross and slag. Ingots and shot are cooled
with water by direct contact with the mold and metal.
Magnesium content in aluminum alloys is adjusted by the
chemical removal of magnesium, using either chlorine or
aluminum fluoride. Wastewaters containing very high levels
of suspended and dissolved solids are produced during the
wet milling of residues containing aluminum.
Pretreatment Standards
Metal Cooling Waste Water
The best practicable pretreatment technology for metal
cooling wastewater is the removal of oil and grease by
skimming. The pretreatment level for this subcategory
limits oil and grease, as shown below.
Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any 1 day values for 30
consecutive days
shall not exceed
Oil and Grease, mq/1 100.0
Fume Scrubbing Waste Water
The best practicable pretreatment technology for effluents
from demagging fume scrubbers is pH adjustment. The
pretreatment control levels for demagging operations are
shown below.
Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any 1 day values for 30
consecutive days
shall not exceed
pH Within the range 5.0 to 10.0
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As guidance for local POTW authorities, zinc limitations of
2.5 mg/1 (30 day average) and 5.0 mg/1 (daily maximum), and
cadmium limitations of 0.2 mg/1 (30 day average) and 0.4
mg/1 (daily maximum) are recommended, should control of
these parameters be necessary.
Residue Milling Waste Water
The best practicable pretreatment technology for residue
milling wastewater is pH adjustment and ammonia removal by
stripping, if necessary. The pretreatment control levels
are shown below.
Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any 1 day values for 30
consecutive days
shall not exceed
Ammonia-N, mg/1 100.0 50.0
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SECTION III
INTRODUCTION
Purpose and Authority
The Environmental Protection Agency (EPA or Agency) is
required to establish pretreatment standards for existing
sources pursuant to sections 307(b) of the Federal Water
Pollution Control Act, as amended (33 U.S.C. 1317(b), 86
Stat. 816 et seq; P.L. 92-500) (the Act). 40 CFR Part 128
establishes general provisions dealing with pretreatment
standards for an existing source introducing pollutants into
a publicly owned treatment works (POTfo) which source would
be an existing source subject to section 301 of the Act if
it were to discharge pollutants directly to navigable waters
of the United States.
(a) Legal Authority
Section 307(b) of the Act requires the Administrator to
promulgate regulations establishing pretreatment standards
for the introduction of pollutants into treatment works
which are publicly owned for those pollutants which are
determined not to be susceptible to treatment by such
treatment works, or which would interfere with the operation
of such treatment works. Pretreatment standards established
under this section shall prevent the introduction of any
pollutant to treatment works which are publicly owned where
the pollutant interferes with, passes through, or is
otherwise incompatible with such works.
(b) Purpose of the Regulations
Subsequent to the promulgation of general pretreatment
standards (40 CFR 128) on November 8, 1973, the Agency has
proposed and promulgated numerous pretreatment standards
relative to specific industry category wastewater discharges
for both existing sources and new sources. The purpose of
this regulation presently being promulgated in interim final
form is to establish specific pretreatment standards for the
nonferrous metals industry. Although pretreatment standards
have previously been proposed for the bauxite, primary
aluminum, primary copper, primary lead and primary zinc
subcategories, they were not included in the present effort
since very few, if any, of the plants in these subcategories
are believed to discharge to POTW. The secondary copper
pretreatment standards and technologies are discussed more
fully in a separate document.
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(c) Statutory Considerations
The Act was designed by Congress to achieve an important
objective -- "restore and maintain the chemical, physical,
and biological integrity of the Nation's waters." Primary
emphasis for attainment of this goal is placed upon
technology based regulations. Industrial point sources
which discharge into navigable waters must achieve
limitations based on Best Practicable Control Technology
Currently Available (BPCTCA) by July 1, 1977 and Best
Available Technology Economically Achievable (BATEA) by July
1, 1983 in accordance with sections 301 (b) and 304 (b). New
sources must comply with New Source Performance Standards
(NSPS) based on Best Available Demonstrated Control
Technology (BADCT) under section 306. Publicly owned
treatment works (POTW) must meet "secondary treatment" by
1977 and best practicable treatment technology by 1983 in
accordance with section 301 (b) and 201 (g) (2) (A) .
Users of a POTW also fall within the statutory scheme as set
out in section 301(b). Such sources must comply with
pretreatment standards promulgated pursuant to section
307 (b) .
Section 307 (b) is the key section of the Act in terms of
pretreatment. It provides that the basic purpose of
pretreatment is "to prevent the discharge of any pollutant
through treatment works...which are publicly owned, which
pollutant interferes with, passes through, or otherwise is
incompatible with such works." The intent is to require
treatment at the point of discharge complementary to the
treatment performed by the POTW. Duplication of treatment
is not the goal; as stated in the Conference Report (H.R.
Rept. No. 92-1465, page 130) "In no event is it intended
that pretreatment facilities be required for compatible
wastes as a substitute for adequate municipal waste
treatment works." On the other hand, pretreatment by the
industrial user of a POTW of pollutants which are not
susceptible to treatment in a POTW is absolutely critical to
attaining the overall objective of the Act, both by
protecting the POTW from process upset or other
interference, and by preventing discharge of pollutants
which would pass through or otherwise be incompatible with
such works. Thus, the mere fact that an industrial source
utilizes a publicly owned treatment works does not relieve
it of substantial obligations under the Act. The purpose of
this regulation is to establish appropriate standards for
the secondary aluminum industry.
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Toxic pollutants are not considered. The relationship of
any toxic pollutant limitations established under section
307(a) to users of a POTW or to the POTW itself will be
established under section 307(a) .
In determining numerical pretreatment standards the initial
step was to classify the pollutants introduced by a source
to a POTW in terms of the statutory criteria of
interference, pass through, or other incompatible effect.
These pollutants will fall, generally, into three classes.
The first class is composed of those pollutants which are
similar, in all material respects, tc the pollutants which
are found in municipal sewage and which the typical POTW is
designed to treat. For such pollutants, no pretreatment
would be required and the numerical standard will be "no
limitation." The second class of pollutants are those which,
in large quantities, would interfere with the operation of a
POTW but which are adequately treated by the POTW when
received in limited quantities. Such pollutants will be
subject to pretreatment standards designed to allow their
release into the POTW in treatable amounts. Finally, the
third class of pollutants are those which are of a nature
that requires the maximum feasible pretreatment in order to
prevent interference with the POTW or pass through of the
pollutant or other incompatibility. Such pollutants will be
subject to pretreatment standards based upon the practical
limits of technology.
(d) Technical Basis for Pretreatment Standards
JPhe Act requires that pretreatment standards for both new
sources and existing sources be promulgated to prevent the
introduction of any pollutant intc a POTW which would
interfere with the operation of such works or pass through
or otherwise be incompatible with such works. Such
standards would allow the maximum utilization of a POTW for
the treatment of industrial pollutants while preventing the
misuse of such works as a pass-through device. The
standards also protect the aquatic environment from
discharges of inadequately treated or otherwise undesirable
materials.
The primary technical strategy for establishing pretreatment
standards consists of the following provisions: (1)
pretreatment standards should allow materials to be
discharged into a POTW when such materials are similar, in
all material respects, to municipal sewage which a "normal
type" biological POTW is designed to treat; (2) pretreatment
standards should prevent the discharge of materials of such
nature and quantity, including slug discharges, that would
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mechanically or hydraulically impede the proper functioning
of a POTW; (3) pretreatment standards should limit the
discharge of materials which, when released in substantial
concentrations or amounts, reduce the biological
effectiveness of the POTW or achievement of the POTW design
performance, but which are treatable when released in small
or manageable amounts; and (4) the pretreatment standards
should require the removal, to the limits dictated by
technology, of other materials which would pass through
untreated or inadequately treated — or otherwise be
incompatible with a biological POTW.
Methods Used for Development of Pretreatment Standards
The best practicable pretreatment technologies herein were
developed in the following manner. That portion of the
secondary aluminum industry which discharges to publicly
owned treatment works (POTW), was considered by identifying
any potential basis for subcategorizing the industry into
groups for the purpose of establishing separate limitations
and standards. The raw waste characteristics of the
wastewaters produced were identified. The constituents of
wastewater which should be subject to pretreatment standards
were then identified. Control and treatment technologies
applicable to each type of waste water produced were
identified, including both in-plant and end-of-process
technologies. The effluent levels resulting from the
application of each treatment and control technology, as
well as the limitations, reliability, and problems derived
from and associated with these technologies, were also
identified.
The effects of the application of technologies upon other
pollution problems including air, solid waste, and noise
were identified, to establish nonwater environmental
impacts. The energy requirements and costs of the
application of the technologies were identified.
This information, as outlined above, was evaluated to
determine a level of technology generally analogous to the
best practicable control technology currently available. In
identifying such technology, the following factors were
considered: the total cost of the application of the
technology in relation to the effluent reduction benefits to
be achieved from such application, the processes employed,
the engineering aspects of the application of control
techniques proposed through process changes, nonwater
quality environmental impact, and other factors.
Information sources utilized in this study included
published literature (references appear in Section XI),
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trade literature, and all of the data collected in the
development of effluent limitations guidelines and standards
for the secondary aluminum smelting industry (Federal
Register, April 8, 1974 and accompanying development
document EPA 440/1-74/019-6, published March, 1974).
Representatives of the secondary aluminum industry were
contacted, of which 18 were subsequently determined to
discharge wastewaters to POTW.
Description of
POTW
Secondary Aluminum Smelters Discharging to
The secondary aluminum industry contains about 71 plants, of
which 18 discharge to publicly owned treatment works, 34 are
at zero discharge of pollutants and 18 discharge to surface
or subsurface waters and the status of two plants is
unknown. Plants at zero discharge of pollutants and plants
which discharge to surface or subsurface waters will be
called 'direct dischargers1 throughout this document, to
distinguish them from the POTW dischargers. There are no
significant differences between direct and POTW dischargers
with respect to locational patterns. Generally, the
geographical distributions are consistent with a
concentration around the Great Lakes, particularly Chicago
and Cleveland. There are only three of each type of
discharger located west of the Rocky Mountains. There is no
real need for them to be near plentiful supplies of
electrical power and water, as in the case of primary
aluminum smelters.
Production data does show some significant differences
between direct and POTW discharges. All of the POTW
discharges are found in the production range of 500 to 4999
tons/month. The direct dischargers, in contrast, are more
uniformly distributed over the total range of production.
The comparisons can be seen in Figure III-l. A comparison
of the processes used is shown in Table III-l.
Definition of the Industry
The secondary aluminum industry is herein defined as that
portion of SIC 3341 (Secondary Nonferrous Metals) which
recovers, processes, and remelts various grades of aluminum
bearing scrap to produce metallic aluminum or an aluminum
alloy as a product. This does not include the casting or
alloying of remelted billets, ingots, or pigs, nor those
operations of the primary aluminum industry, which recycle
certain categories of scrap.
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Figure 111-1. PRODUCTION DISTRIBUTION BY SIZE CLASS*
FOR SECONDARY ALUMINUM SMELTERS**
SIZE CLASS: A
B
C
D
E
PRODUCTION
KKG/month
0-90
91 -453
454 - 906
907 - 4534
4535-9069
short tons/month
0-99
100 - 499
500 - 999
1000 - 4999
5000 - 9999
••THE PERCENTS OF PLANTS FOR WHICH PRODUCTION DATA IS AVAIL-
ABLE FOR EACH OF THE THREE TYPES OF DISCHARGERS ARE AS
FOLLOWS:
DIRECT DISCHARGERS 83%
POTW DISCHARGERS 88%
ZERO DISCHARGERS 62%
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General Process Description
The recovery of aluminum from various forms of aluminum
scrap involves four rather distinct operations. These are:
(1) Collection, sorting, and transporting.
(2) Presmelting preparation.
(3) Charging, smelting, and refining.
Pouring of the product line.
The last three operations vary somewhat throughout the
industry, with resultant variations in water usage and
wastewater generation. The following is a general
description of each operation listed. More detailed
information is contained in the effluent guidelines
development document (Reference 1) .
Collection, Sorting, and Transporting
Nearly 95 percent of the secondary smelting raw material is
supplied from scrap aluminum purchased from scrap dealers
and industrial plants. Nowhere in the classification and
grading of scrap is there a specification of the magnesium
content in the aluminum scrap, only the levels of copper,
silicon, and zinc (and iron) . The reason for this practice
is that magnesium can be removed from the alloy by chemical
action (demagging) , while the others, because of their lower
reactivity, cannot be removed by chemical action.
Adjustment in concentration of elements other than magnesium
is done by dilution or blending with pure aluminum.
New clippings, forgings, and other solids originate from the
aircraft industry, fabricators, industry manufacturing
plants, and government manufacturing plants. Borings and
turnings are derived mainly from the machining of castings,
rods, and forgings by the aircraft and automobile
industries. Residues (dross, skimmings, and slag) originate
from melting operations at primary reduction plants,
secondary smelting operations, casting plants, and other
foundries. Old castings and sheet may come from many
sources, as automobile parts, household items, and
dismantled airplanes. Miscellaneous high iron scrap
requires special handling in sweating furnaces.
Presmelting Preparation
The presmelting preparation of scrap varies in accordance
with the type of scrap being handled. Some smelters do con-
siderable preparation to upgrade and segregate scrap. Those
with more limited facilities bypass some of the preparation
12
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steps and rely upon the furnace to burn up combustible con-
taminants.
Borings and turnings are often heavily contaminated With
cutting oils. Most plants crush this material and it is
then fed into gas or oil-fired rotary dryers to remove
cutting oils, grease, and moisture.
About one-third of all the secondary smelters process
residues (dross, slags, skimmings, etc.). In addition to 10
to 30 percent metallic aluminum, these residues contain
oxides, carbides, nitrides, fluxing salts, and other
contaminants. To recover the metallic aluminum, it is
necessary to liberate it from the contaminants. This can be
done in either wet or dry processes.
In the dry circuit, the material is crushed, screened, and
passed through a magnetic separator to remove any iron.
Large amounts of dust are created. Normally, the dust
emissions are controlled by baghouses. Wet dust collection
is done at two plants.
About one-fourth of the plants processing residues use wet
techniques. Generally, the raw material is first fed into a
drum. Water is used to wash the feed, carry away the
fluxing salts and chemicals, and liberate the aluminum. The
washed material is then screened, dried, and passed through
a magnetic separator. The nonmagnetics are then ready for
the smelter. Fine particulates, dissolved salts, and
undersize screenings are all sources of water pollution.
In summary, of the various presmelter treatments employed,
only the processing of drosses and slags appears to provide
a source of water pollutants.
Smelting
Generally, the smelting of aluminum scrap with reverberatory
furnaces consists of seven operations or tasks* These are
charging scrap into the furnace, addition of fluxing agents,
addition of alloying agents, mixing, removal of magnesium
(demagging), degassing, and skimming. Any given smelter may
not necessarily incorporate all seven steps, as demagging or
addition of alloying agents in the case of deoxidant
producers, and may not follow the above order. Because the
demagging operation may produce wastewater, this operation
will be discussed in greater detail than the others.
Charging. Scrap may be charged continuously into the
furnace, with simultaneous pouring, or may be loaded in
13
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batches. Often residual melt ("heel") is left in the
reverberatory to facilite melting of the new charge. This
results in a shortened heating cycle.
Fluxing. The addition of a covering flux forms a barrier
for gas absorption and oxidation of the metal. The flux
also reacts with nonmetallics, residues from burned coating,
and dirt in the scrap, collects such impurities and allows
physical separation from the molten aluminum. The exact
composition flux cover used varies from smelter to smelter,
but is generally one or more of the following: sodium
chloride, potassium chloride, calcium chloride, calcium
fluoride, aluminum fluoride, and cryolite.
Alloying. Alloying agents, normally added to the aluminum
melt, include copper, silicon, manganese, magnesium, and
zinc. Usually these are added after the furnace has been
charged with aluminum scrap and analyzed for its
composition. The amounts of additions required to bring it
up to specifications are then added.
Mixing. Mixing of the metal to insure uniform composition
and to agitate the solvent fluxes into the melt is generally
accomplished by injecting nitrogen gas. Aside from
homogenizing the melt, the mixing step is beneficial in
bringing to the surface dissolved gases, such as hydrogen,
and intermixed solids. Once on the surface the impurities
combine with the fluxing agent and can be skimmed off.
Magnesium Removal (Demagqing). Scrap aluminum, received by
the secondary smelters, averages about 0.3 to 0.5 percent
magnesium, while the product line of alloys produced
averages about 0.1 percent. Therefore, after the furnace is
fully charged and the melt brought up to the desired
chemical specification, it is usually necessary to remove
the excess magnesium. This is done with chlorine or
chlorinating agents, such as anhydrous aluminum chloride or
chlorinated organics, or with aluminum fluoride. Magnesium
chloride or magnesium fluoride is formed and collected in
the fluxing agents on top of the molten melt. As the mag-
nesium level is depleted, chlorine will consume aluminum and
the excess aluminum chloride or aluirinum fluoride present
volatilizes into the surrounding air and is a source of air
pollution.
Magnesium is the only metal removable from the alloy in this
manner. Other metal alloy levels must be adjusted by the
addition of either more aluminum (dilution) or more of the
metal.
14
-------
Chlorination is performed at temperatures between 1400 and
1500°F. As a rule of thumb, the reaction requires 3.5 kg of
chlorine per kg of magnesium removed. Elemental chlorine
gas is fed under pressure through tubes or lances to the
bottom of the melt. As it bubbles through the melt it
reacts with magnesium and aluminum tc form chlorides, which
float to the melt surface where they combine with the
fluxing agents and are skimmed off. Because magnesium is
above aluminum in the electromotive series, aluminum
chloride will be reduced by any available magnesium in the
melt. At the beginning of the demagging cycle, the
principal reaction product is magnesium chloride. As
magnesium is removed and there is less available for
reaction with chlorine, the reaction of chlorine with
aluminum becomes more significant, the reduction of the
aluminum chloride by magnesium becomes less likely, and the
production of aluminum chloride, a volatile compound,
becomes significant. The aluminum chloride escapes and con-
siderable fuming results from the chlorination, making
ventilation and air pollution equipment necessary. Control
of fumes is frequently done by wet scrubbing and, thus, is a
source of water contamination.
Aluminum fluoride as a demagging agent reacts with the
magnesium to form magnesium fluoride, which in turn combines
with the flux on top of the melt, where it is skimmed off.
In practice, about U.3 kg of aluminum fluoride are required
per kg of magnesium removed. The air contaminants exist as
gaseous fluorides or as fluoride dusts and are a source of
air pollution. The fluorides are controlled by either dry
or wet methods. When done dry, a solid waste problem
exists. When done wet, both a water pollution problem
(which must be ameliorated) and solid waste problem exist.
Some operators in the secondary industry are not limited by
a magnesium content in their product, particularly the
deoxidant manufacturers, and they make no attempt at
removing the magnesium. They, thus, do not contend with the
magnitude of fumes that the demaggers do and as a result, do
not require extensive air pollution control equipment and
related water usage.
Skimming. The contaminated semisolid fluxing agent, known
as slag (sometimes as dross), is removed from the surface of
the melt just before tapping the reverberatory furnace to
pour ingots. The slag is placed in pans to cool or in an
internally water-cooled dross cooler.
Once cooled, the slag is either stored until shipped to a
residue processor, reprocessed by the company, or is dumped.
15
-------
If stored in the open, it is a source of ground and runoff
water contamination, because of contained soluble salts
(NaCl, KCl, MgC12). During dross cooling, thermiting
generates fumes and is a source of air pollution. The
thermiting, as well as reactions in the smelting, produce
nitrides and carbides of aluminum which, upon reacting with
water or water vapor in the air, release hydrocarbons and
ammonia to the atmosphere. The ammonia also may become a
component of water pollution if the residue is milled using
wet methods.
Pouring and Cooling
After the furnace has been completely charged, the
specification composition reached, and the melt degassed and
skimmed, the molten metal is cooled to around 1350°F for
pouring. Pouring practices employed and the related water
usage by any given smelter will, of course, be dependent on
the company's product line. The product lines of the
secondary aluminum smelters have been grouped into six
categories. These are specification alloy ingots, billets,
hot metal, notched bar, shot, and hardeners.
Specification Alloy Ingots. The most important product of
the secondary aluminum industry is specification alloy
ingots to be used by foundries for casting. Most smelters
concentrate on a few of the basic alloys. Normally
automatic casting methods are used to fill the ingot molds.
The molds are, generally, the 15 or 30-pound size.
Cooling often is accomplished with a water spray, that
contacts both the molds and hot metal as they move along a
conveyor track above a casting pit. Cooling also is
performed by a few companies by passing water through
passages in the mold, in which case water does not contact
the hot aluminum metal. In some cases, the molds are cooled
by passing the hot ingots through a cooling tunnel, blown
with a water mist-air mixture. Recirculated water often
builds up sludge in both the cooling tower and cooling pit.
This necessitates sludge removal at regular intervals and is
accompanied by a discharge of system water.
Billets. Secondary aluminum for use in the extrusion
industry is cast into 1000 pound billet logs. The long
cylindrical billet molds are 7 to 10 inches in diameter and
about 10 feet long. The molds are arranged in circular
arrays. A riffle above each array splits the molten metal
into fractions, filling each simultaneously.
16
-------
Water lines inside the molds cool the billets. The cooling
water is generally cooled and reused, as is the case for
ingot cooling.
Hot Metal. In some cases, hot metal is tapped from the
reverberatory furnace into preheated portable crucibles.
The crucibles are sealed and transported directly to the
customers for use. Presently, crucibles with up to 15,000
Ib capacity are used.
Notched Bar. Notched bar is used as a deoxidant by the iron
and steel industry and is normally cast in various 2 to 5 Ib
shapes. Four grades are produced, each grade having a
different aluminum content. Notched bar molds are cooled,
either with water sprays, internal water lines, or with air.
The water used may or may not be cooled and recirculated.
Shot. Shot is also used as a deoxidant and is produced by
pouring the molten metal onto a vibrating feeder, where
perforated openings in the bottom allow the molten metal to
drop through into a water bath below. The droplets solidify
in the water, are dried, sized, and packed for shipment.
The oversize shot is recharged into the furnace. Quenching
water is usually sent to a cooling tower and recirculated.
Sludge build-up occurs and must be removed regularly on an
annual or semi-annual basis.
Hardeners. Hardeners are sometimes produced by specially
equipped secondary smelters. The hardeners are alloys of
high-purity aluminum with titanium, boron, and chromium.
They are produced in small capacity 908 kg (2000 Ib)
induction furnaces, rather than reverberatory furnaces.
In summary, water usage in the pouring phase of secondary
aluminum smelting is for mold cooling or shot quenching. In
some cases, water contacts hot aluminum and, in other cases,
it contacts only the mold cooling lines. Some smelters cool
and recirculate the water, while others use fresh water
continuously. The recirculated water is periodically
discharged, normally at six-month intervals. Table III-2
presents a summary of the operations found at each smelter.
17
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18
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SECTION IV
INDUSTRY CATEGORIZATION
Introduction
Th'e development of pretreatment standards must give
consideration as to whether the industry can be treated as a
whole in the establishment of uniform and equitable
standards or whether there are sufficient differences to
justify its division into subcategories.
Factors Considered
A survey was made of the dischargers to POTW in the
secondary aluminum industry for the purpose of ascertaining
whether this segment required subcategorization on the basis
of raw materials processed, products produced, processes
employed, plant age and size, air pollution control
techniques employed, type and size of POTK, plant location
and wastewater generation. It was found that the mix of raw
materials and processes employed by POTW dischargers is the
same as those employed by direct dischargers. Upon
application, each of these factors leads to unmanageable
ambiguities in subcategorization, as described in the
following paragraphs. For these reasons, it is not
considered necessary to subcategorize on the basis of size,
age, raw materials, products, or processes. However,
separate pretreatment standards are suggested for the
different water-using processes, which are based upon raw
materials, demagging operation and type of metal cooling.
Raw Materials. The principal groupings of raw materials for
the secondary aluminum industry are (1) new clippings and
forgings, (2) old casting and sheet, (3) borings and
turnings, (4) remelted ingot and sweated pig, and (5)
residues. With the possible exception of residues, these
raw materials provide no firm basis for subcategorizing the
secondary industry. The first four groupings are handled by
nearly all smelters at various times (the exception being a
few plants using only residues). The first four groupings
will be referred to collectively as solids and the fifth
grouping as residues.
Although the wet processing of residues can lead to water
effluents different from those of a smelter not processing
residues, subcategorization based on residues is complicated
by those smelters handling both residues and solid scrap and
19
-------
that some smelters, using both forms cf raw material, dry
process the residue and have no water effluent from it.
Products. The main product line of secondary smelters is
specification alloys (ingots or sows) and/or deoxidant
(notched bar, shapes, or shot). These products are common
to the industry and support the identification of a single
category.
Processes. The main processes in secondary aluminum
recovery of scrap consist of (1) scrap preparation, (2)
charging scrap into reverberatory forewell, (3) smelting,
(4) refining, and (5) casting. Scrap preparation procedures
are common to the industry, as are charging and smelting
procedures, and support the establishment of a single
category. The basic operations for secondary aluminum
smelting are common throughout the industry and are not
significantly different between direct and POTW dischargers.
A variation exists in refining, as some smelters use
chlorine as a demagging agent, while others use A1F3.
Deoxidant producers generally have no need to refine or
demag their melt. Significant to wastewater treatment may
be that the use of chlorine or A1F3 will generate unique
wastewater effluents when the smelter fumes are wet
scrubbed. The presence, absence, or method of wastewater
treatment at these smelters is independent of the demagging
process used.
The waste products formed during magnesium removal with
chlorine differ from those formed when aluminum trifluoride
is used. The anhydrous metal chlorides from clorine
demagging are very soluble in water; whereas metal fluorides
from A1F3I demagging are sparingly soluble in water. Both
react with water by hydrolysis to yield acidic wet scrubber
solutions, which are amenable to treatment by pH adjustment
and settling to reduce pollutant concentrations. The
similarity in scrubber water treatment suggests a single
industrial category, regardless of the chemical system used
for magnesium removal. However, the lower volatility of the
fluorides places reduced load on the scrubber system for a
fixed amount of magnesium removed from the melt. Low
solubility of the scrubbed salts (after pH adjustment) sets
the waste water generated from fluoride scrubbing apart from
wastewater generated from chloride fume scrubbing. At the
present time, no plant using aluminum fluoride is
discharging scrubber wastewater to a POTW.
20
-------
The last process step in secondary aluminum recovery,
casting, is common to the industry, and supports the
establishment of a single subcategory for the industry.
Most residue processing operations in the industry are
associated with solids processing operations, wherein
practices of water interchange and mixed waste treatment
have been identified. Similarly, the wet and dry variations
of residue processing are variously associated with or are
independent of solids processing. This complex pattern of
process distribution further supports the above described
approach to deriving regulations. In addition, residues
from secondary smelters (slags) containing high levels of
soluble salts (NaCl and KCl) are processed along with the
residues (dross) containing low levels of salt. Soluble and
insoluble wastes from each material are similar and are
suited to the same type of treatment to reduce suspended
solids. In both cases, the soluble portions are
untreatable, except by total evaporation of the water.
Therefore, establishment of a single industrial category is
still supported.
Plant Age. From interviews with various secondary smelters,
there appears no consistent connection between plant age and
wastewater character or treatment. Many of the older plants
have updated treatment facilities, while ethers have not.
Plant Size. Plant size is directly related to the number of
furnaces employed (usually 2 to 8). The number of furnaces
is, however, unrelated to wastewater character or treatment.
Type and Sijze of POTW. The publicly owned treatment works
receiving process wastewater from secondary aluminum
smelters include both primary (i.e., sedimentation) as well
as secondary treatment works (i.e., activated sludge,
trickling filter). Four of the 15 POTW which receive
secondary aluminum smelter influents are primary plants, and
the remaining 11 are secondary POTW. One of the primary
POTW is planning to add secondary treatment.
Table IV-1 shows the size ranges and types of POTW utilized.
The size of the POTW ranges from 30 to 350 MGD. One primary
POTW will be expanded during the addition of secondary
treatment to enlarge the capacity from 80 to 120 MGD.
The secondary POTW range in size from 0.6 to 900 MGD. Five
of the eleven plants are in the 10-49 MGD range. The five
aluminum smelters constitute 33% of the secondary aluminum
plants discharging to POTW for whom data is available.
Although it would be expected that the type of POTW
21
-------
TABLE IV-1. NUMBER OF SECONDARY ALUMINUM POTW DISCHARGERS*
USING VARIOUS SIZES AND TYPES OF POTW's
Primary POTW
Secondary POTW
SIZE OF POTW's
< 37,850
m3/day
<10mgd
0
2
37,850-189,249
m3/day
10 - 49 mgd
1
3
189,250-378,499
m3/day
50 - 99 mgd
2*«
1
> 378 ,500
m3/day
> 100 mgd
1
5
*Of the 17 secondary aluminum POTW dischargers, data is available for 15 of the POTW recipients.
••One 302,800 m3/day (80 mgd) primary POTW is planning to expand to a 454,200 m3/day (120 mgd)
secondary POTW.
22
-------
receiving the wastes would make a difference as far as the
quantity of metals pollutants removed in the process (i.e.,
physical-chemical plants would remove more metals than
biological plants), there is only one physical-chemical
plant treating wastes from the secondary copper industry.
Moreover, suspended aluminum would probably be removed as
well in a biological as a physical-chemical POTW.
Plant Location Although those secondary aluminum plants
which discharge to POTW are in more urbanized areas than the
direct dischargers, it would appear that, apart from usage
of POTW, this has not significantly affected the wastewater
generation or treatment. No significant differences can be
found as regards the effect of climate.
Wastewater Generation Categorization of smelters on the
basis of wastewater generation is not possible, because a
given smelting plant may have any combination of the three
waste streams. A more useful approach for the purpose of
developing pretreatment standards is to deal with the waste-
water streams themselves. Three distinct streams may be
characterized: (1) cooling wastewater, (2) fume scrubbing
wastewater, and (3) wet residue milling wastewater. Each
stream may be associated with an appropriate pretreatment
standard.
23
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SECTION V
WASTE CHARACTERIZATION
Introduction
Specific processes in the secondary aluminum industry
generate characteristic wastewater streams. In this section
of the document, each wastewater stream is discussed as to
source, quantities, and characteristics, in terms of the
process operation from which it arises.
Specific Water Uses
The secondary aluminum industry generates wastewaters in the
following processes:
(1) Ingot cooling and shot quenching.
(2) Scrubbing of furnace fumes during demagging.
(3) Wet milling of residues or residue fractions.
Waste Water From Metal Cooling
Sources. Molten metal in the furnace is generally either
cast into ingot or sow molds or is quenched into shot. In
cases where cooling wastewater is generated, the ingot molds
are attached to conveyors which carry the molds and their
molten charge of aluminum over a cooling pit. Here water is
sprayed onto the mold to solidify the aluminum and allow its
ejection from the mold. In some cases the molds contain
internal cooling lines through which water is passed. In
these cases the water does not contact the molten metal.
Sows are generally air cooled and have little associated
water use.
The productioh of shot involves water usage for the rapid
quenching of molten metal. Here the molten metal is poured
into a vibrating porous container which allows the metal to
pass through as droplets. The drops of molten metal fall
into a water bath below and are quickly solidified.
Quantities. Data on the quantity cf water used for metal
cooling in the secondary industry was gathered and converted
to gallons used per ton of product and is given in Table V-
1. These values vary widely. It is not certain whether
these great differences are real or whether they are due to
inaccurate estimates of water flow. Each of the direct
25
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TABLE V-1. DISCHARGE LOADINGS FOR THE MAJOR PROCESS WASTEWATER
SOURCES-SECONDARY ALUMINUM [GALLONS/SHORT TON (GPD)]
PLANT
CODE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
WASTEWATER VOLUME [Gallons/Short Ton (GPD)]
METAL COOLING
USED
—
1,234 (72.000)
864 (72,000)
1,234 (72,000)
*
—
—
»
*
360 (24,000)
120 (2,000)
108 (3,600)
2.4 (100)
33.8 (900)
343 (40,000)
*
*
110(7,000)
DISCHARGED
*
1,234 (72,000)
864 (72,000)
1,234 (72,000)
*
—
—
*
*
*
120 (2,000)
108 (3,600)
2.4 (100)
33.8 (900)
343 (40,000)
*
*
110(7,000)
EMISSIONS CONTROL
USED
—
#
—
«
90 (1,500)
*
*
—
—
96 (6,360)
*
216 (7,200)
*
*
300 (35,000)
—
38f (3,600)
*
DISCHARGED
6.4 (30)
*
*
*
90 (1,500)
*
*
*
*
96 (6,360)
*
216 (7,200)
*
»
300 (35,000)
—
38 f (3,600)
*
WET MILLING
USED
*
*
*
*
#
#
*
*
#
*
*
*
*
562.5 (15,000)
#
»
2020t (192,000)
*
DISCHARGED
*
*
*
*
*
*
*
*
*
*
»
*
*
562.5 (15,000)
*
*
1010t (96,000)
*
•NO FLOW RATE NEEDED BECAUSE OF THE FOLLOWING POSSIBILITIES: 1) PROCESS NOT USED;
2) PROCESS DOES NOT REQUIRE WATER; 3) WATER COMPLETELY RECYCLED;
4) WATER COMPLETELY EVAPORATED.
fDATA OBTAINED FROM BATTELLE TRIP REPORT
26
-------
discharger plants shown in Table V-3 is discharging the
cooling wastewater after one passage through the circuit.
Characteristics. Table V-2 shows the chemical
characteristics and loading for ingot cooling water at POTW
dischargers. Table V-3 is a comparison of metal cooling
wastewater quality between direct dischargers and POTW
dischargers. Table V-H shows the chemical characteristics
of wastewater produced by aluminum shotting. Higher
concentrations of oil and grease were found in one of the
direct discharger's wastewater, which probably contribute
largely to the high concentrations of total suspended solids
and COD. The other parameters exhibit a consistency between
the two types of dischargers with respect to concentrations.
Generally, housekeeeping practices and the degree of
recirculation practiced will influence wastewater
characteristics for this type of water use more than any
other factors.
Recirculation of cooling water produces sludge and
accumulates oil and grease contamination. The sources of
sludge include collection of airborne solids from ambient
air during spray cooling of the water, buildup of hydrated
alumina from chemical reaction with the molten aluminum and
debris and dust from the plant floor. Flux salt buildup
(NaCl) occurs in recirculated water used for shot cooling.
Water used once and discharged will contain oil and grease
contaminants. There are operations in which the rate of
water flow for cooling is controlled to assure total
evaporation.
Of the 12 POTW dischargers which use water for metal
cooling, 2555 attain total recycle while 8% practice partial
recycle of this water. Only three of the POTW dischargers
pretreat this type of waste, while the remaining 6 discharge
it untreated.
Waste Water From Fume Scrubbing Sources.
Aluminum scrap normally charged intc the furnace contains a
higher percentage of magnesium than is desired for the alloy
produced. It is, therefore, necessary to remove a portion
of this element from the melt. Magnesium removal, or
"demagging," is normally accomplished ty either passing
chlorine through the melt (chlorinaticn), with the formation
of magnesium chloride (MgCl2), or by mixing aluminum
fluoride (Al^3) with the melt, with the removal of magnesium
as MgF2. Heavy fuming results from the demagging of a melt,
and these fumes are often controlled by passing them through
a wet scrubbing system. Water used in the scrubbing
27
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TABLE V-4. CHARACTERISTICS OF RAW WASTEWATER FROM ALUMINUM
SHOTTING - POTW DISCHARGER PLANT 15A
PARAMETER
pH
TSS
OIL AND GREASE
Cl
f
Na
Al
Cd
Cr
Cu
Ni
Pb
Zn
CONCENTRATION
(mg/l)
7.55*
4
<1
10.8
0.99
12.0
2.1
<0.011
0.083
<0.04
<0.02
<0.03
0.14
LOADING
kg/MT
_
0.04
<0.009
0.097
0.0089
0.11
0.019
< 0.000099
0.00075
< 0.0004
<0.0002
<0.0003
0.0013
Ib/ton
_
0.07
<0.02
0.19
0.018
0.22
0.038
< 0.00020
0.0015
<0.0007
<0.0004
<0.0005
0.0025
A AVERAGE OF 4 SAMPLES
* pH UNITS
30
-------
collects fume pollutants and is the source of a wastewater
stream.
Wastewater from A1F3 demagging gas scrubbers can normally be
recirculated because of the relative insolubility of
fluorides (which can be settled out). Wastewater from the
scrubbing of chlorine demagging fumes, however, can be
recycled only to a very limited degree. This is because the
chloride salts are highly soluble and would soon build up to
make water unusable. Thus, the discharge of this flow is
the source of waste water from fume scrubbing. No demagging
wastewater discharges are reported from those plants using
A1F3. All plants using chlorine are discharging demagging
scrubber wastewater, whether to navigable waters, public
sewage, or holding ponds.
Quantities. Data on the quantities cf water used in
scrubbing are given in Table V-1. Water usage is given in
gallons per ton of aluminum.
Characteristics. The chemical characteristics of the POTW
dischargers visited during the course of this study are
shown in Table V-5. Table V-6 compares the concentrations
in the raw waste of the direct dischargers and the POTW
dischargers. It should be noted that Plant 12 is located at
the same site as a secondary zinc smelter, and that cross-
over contamination may have occurred. However, the data
from other POTW dischargers indicates slightly higher metals
concentrations than were found in waste from direct
dischargers.
An additional process at Plant 12 consists of the crushing
and drying of oily scrap, with a wet scrubber used for air
pollution control. All available sources indicate that this
operation is unique to this plant. This particular
wastewater is discharged to a sanitary sewer or partially
reused for ingot cooling before discharge. Chemical
characteristics of this wastewater are shown in Table V-7.
Raw wastewaters (averages of composites) gathered during
chlorine demagging have a low pH due to the hydrolysis of
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up the fume. The hydrolysis forms hydrochloric acid, which
accounts for part of the high chloride levels present
without the associated total dissolved solids.
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solution) has a pH of 1.5 and contains hydrolyzed metal
chlorides of aluminum, magnesium, and other volatile metal
halides such as zinc, manganese, cadmium, nickel, copper,
31
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33
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TABLE V-7. CHEMICAL CHARACTERISTICS OF SCRAP CRUSHER
SCRUBBER WATER AT PLANT 12* - POTW DISCHARGER
PARAMETER
PH
TSS
Oil and Grease
COD
Cl
F
Na
Al
Cd
Cr
Cu
Ni
Pb
Zn
CONCENTRATION
(mg/t )
6.10 **
1620
34
259
116
<1
13
294
0.03
0.79
21.0
1.05
14.1
138
LOADING
(kg/metric ton)
—
0.53
0.011
0.085
0.038
< 0.0003
0.0043
0.097
0.00001
0.00026
0.0069
0.00035
0.0047
0.046
(Ib/short ton)
—
1.07
0.022
0.17
0.077
< 0.0007
0.0086
0.19
0.00002
0.00052
0.014
0.00069
0.0093
0.091
*Grab sample
**pH units
34
-------
and lead. In alkaline scrubber waters, sodium, potassium,
and calcium are present, with a corresponding reduction in
the amount of dissolved heavy metals, aluminum and
magnesium. The pH range is 9-11. Slightly higher
quantities of zinc, copper and cadmium were found in fume
scrubber wastewater from POTW dischargers than from direct
dischargers, although these parameters were not found at
high concentrations at all plants.
The water from aluminum fluoride fume scrubbing contains HF
which is neutralized with caustic. Any metal fluoride or
partially hydrolized fluoride particulates would be expected
to react in the scrubber system to form insoluble fluorides
after pH adjustment. The supernatant should contain
fluorides of magnesium and aluminum and perhaps cryolite,
all of which are only sparingly soluble. Most of the heavy
metal fluorides associated with the alloying metals may end
up in the fumes and subsequently in the scrubber sludge.
Fume scrubber water generation is intermittent and coincides
with the 1.5-4 hour magnesium removal cycle for each heat
(every 24 hours). Ten of the POTW dischargers use wet air
pollution control methods, while 5 employ dry methods. The
remaining three smelters do not practice demagging and
consequently no air pollution control has been deemed
necessary.
Two of the ten POTW dischargers using wet systems are
achieving total recycle of the scrubber wastewater, while
four plants practice partial recycle. The remainder are
once through systems. The demagging practices at the ten
plants with wet air pollution control systems are as
follows:
Aluminum fluoride - 2 plants
Chlorine - 6 plants
Derham process - 2 plants.
Waste Water From Residue Processing
Sources. Residues used by the secondary aluminum industry
are generally composed of 10 to 30 percent aluminum, with
attached aluminum oxide fluxing salts (mostly NaCl and KCl),
dirt, and various other chlorides, fluorides, and oxides.
Separation of the metal from the nonmetals is done by
milling and screening and is performed wet or dry. When
performed dry, dust collection is necessary to reduce air
emissions. Milling of dross and skimmings will produce a
dust that, when scrubbed wet, will contain insoluble solids
in suspension, such as aluminum oxide, hydrated alumina, and
35
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soluble salts from the flux cover residues, such as sodium
chloride and potassium chloride. Drosses also contain
aluminum nitride, which hydrolyzes in water to yield
ammonia. When slags are milled, the wastewater from dust
control contains more dissolved sodium and potassium
chloride and fluoride salts from the cryolite, than from
drosses or skimmings. Some of the oxides of heavy metals
are solubilized in the slag and leached from the dust.
With wet milling, the dust problem is minimized, but the
operation produces a wastewater stream that is similar to
the scrubber waters in make up, tut more concentrated in
dissolved solids contaminants. The aluminum and alumina
fines are settled rapidly and are used to assist the
settling of more difficult to settle components, obtained as
sludges from related wastewater discharges.
Quantities. Water use for the wet milling of residues is
shown in Table V-1.
Characteristies. Residue processing can be performed with
or without water. Two of the POTW dischargers employ wet
processing, one of which impounds the wastewater while the
other mixes scrubber water with dross processing wastewater
for the purpose of partial recycle.
Table V-8 shows chemical analyses of wastewaters from direct
dischargers and a POTW discharger. Plant D-8 was formerly a
direct discharger, but has since become a POTW discharger.
If the dissolved salt (chloride) content is low, drosses
from primary aluminum melt operations are being processed
(e.g., plant D-3). If they are high, then slags (and
drosses or skimmings) from secondary aluminum melting
operations are being processed (e.g., plant D-U). Some
residue millers operate on a toll, based on the amount of
molten aluminum recovered, and process both types of
residues. Therefore, there are highs and lows in the
dissolved salt content of the waste water depending on the
batch of residues being milled. Nontcll millers process
both types of residues also, low salt residues for their
high aluminum content and home slag for improved aluminum
recovery within the plant. In some cases, such plants will
also accept slag from secondary smelters not equipped to
process their own. The raw wastewater as it comes from the
mill and screening operation contains large amounts of
insoluble solids that settle very quickly. Isolation of the
raw discharge stream, to determine the amount of solids
present, could not be done; but, it was estimated that the
solids content in the wastewater is about 30 percent by
weight. This would be a highly variable value and dependent
36
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TABLE V-8. COMPARISON OF CHEMICAL CHARACTERISTICS
OF RESIDUE PROCESSING WASTEWATER FOR
DIRECT AND POTW DISCHARGERS*
PARAMETER
PH
TDS
TSS
Oil and Grease
COD
a
F
Na
Al
Cd
Cr
Cu
Ni
Pb
Zn
Ammonia
CONCENTRATION (mg/J)
DIRECT DISCHARGER
D-6
8.3t
12920
4961
55.4
2045
6492
2.9
2560
0.3
0.5
-
0.174
1.2
0.20
0.015
0.75
D-4A
9.09t
-
15
0
—
15455
8.7
11600
16.4
0.002
-
0.070
0.240
0.020
0.10
350
D-3 C
8.68
-
7.2
3.1
58
—
7.7
—
0.1
—
-
0.24
-
-
-
19
POTW
DISCHARGER**
D-8 B
9.2t
17400
159
0.5
29
8903
16.5
3103
28
0.005
—
0.137
0.20
0.028
0.193
0.3
*Data taken from Reference 1, p. 54.
**D-8 was a direct discharger at the time the samples were taken; however, the plant is
now a POTW discharger.
t pH units.
A Data from 7 month and 9 month average in addition to verification data from state.
B Represents composite of 9 samples collected over 3 days.
C Calculated from RAPP data.
37
-------
upon the type of residue being processed at the time.
Settling is a very effective way to remove the insoluble
solids. However, there is variation in a plant's ability to
remove suspended solids (compare plants D-4 and D-8).
Milling at plant D-8 is done with a mixed stream, containing
75 percent alkaline fume scrubber water and 25 percent fresh
water. The concentrations reported in Table V-6 have been
adjusted for this variation and are reported only as the new
gain in concentration due to milling. The data suggest that
milling with an alkaline stream reduces the ammonia
concentration appreciably from that resulting from milling
with unaltered intake water (0.30 mg/1 vs 350 mg/1 for D-4)
and suggests an effective way to reduce the level of this
pollutant. The mixed stream is also claimed to be effective
in reducing the suspended solids load in the pH-adjusted
fume scrubber water. The effectiveness is attributed to the
rapid settling of the coarser milling wastes, which carry
down with them the hydrated alumina and magnesium hydroxide
in the treated fume scrubber water, as well as the
associated heavy metals. Fluoride in milling wastewater is
due to the cryolite or aluminum fluoride contained in the
slag (flux cover). The presence of aluminates in the
alkaline milling water acts on fluoride to limit its
concentration. Fluoride content in the slag is also quite
variable and depends on the source of the residue being
milled at the time. The concentrations of fluoride found in
the milling wastewater are less than those attainable by the
use of lime precipitation.
38
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SECTION VI
SELECTION OF POLLUTANT PARAMETERS
Rationale for the Selection of Pollutant Parameters
The wastewater constituents which are present in the process
wastewaters of the secondary aluminum smelting industry in
sufficient quantities to warrant consideration for the
establishment of pretreatment standards are:
PH
Oil and Grease
Ammoni a
pH.
Although not a specific pollutant, pH is related to the
acidity or alkalinity of a wastewater stream. It is not a
linear or direct measure of either, however, it may properly
be used as a surrogate to control both excess acidity and
excess alkalinity in water. The term pH is used to describe
the hydrogen ion - hydroxyl ion balance in water.
Technically, pH is the hydrogen ion concentration or
activity present in a given solution. pH numbers are the
negative logarithm of the hydrogen ion concentration. A pH
of 7 generally indicates neutrality or a balance between
free hydrogen and free hydroxyl ions. Solutions with a pH
above 7 indicate that the solution is alkaline, while a pH
below 7 indicates that the solution is acid.
Knowledge of the pH of water or wastewater is useful in
determining necessary measures for corrosion control,
pollution control, and disinfection. Waters with a pH below
6.0 are corrosive to water works structures, distribution
lines, and household plumbing fixtures and such corrosion
can add constituents to drinking water such as iron,
copper, zinc, cadmium, and lead. Low pH waters not only
tend to dissolve metals from structures and fixtures but
also tend to redissolve or leach metals from sludges and
bottom sediments. The hydrogen ion concentration can affect
the "taste" of the water and at a low pH, water tastes
"sour".
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
deleterious to some species. The relative toxicity* to
39
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aquatic life of many materials is increased by changes in
the water pH. For example, metalocyanide complexes can
increase a thousand-fold in toxicity with a drop of 1.5 pH
units. Similarly, the toxicity of ammonia is a function of
pH. The bactericidal effect of chlorine in most cases is
less as the pH increases, and it is economically
advantageous to keep the pH close to 7.
The raw wastewater from demagging fume scrubbers is very
acidic, with a pH range of from 1.0 tc 2.5. While metal
cooling water is not quite as acidic, the pH range is still
from 4.5 to 6.5. Residue milling wastewaters, in contrast,
are alkaline with pH ranging from 8 to 9.5.
Oil and Grease.
Because of widespread use, oil and grease occur often in
wastewater streams. These oily wastes may be classified as
follows:
1. Light Hydrocarbons - These include light fuels such
as gasoline, kerosene, and jet fuel, and
miscellaneous solvents used for industrial
processing, degreasing, or cleaning purposes. The
presence of these light hydrocarbons may make the
removal of other heavier oily wastes more
difficult.
2. Heavy Hydrocarbons, Fuels, and Tars - These include
the crude oils, diesel oils, #6 fuel oil, residual
oils, slop oils, and in some cases, asphalt and
road tar.
3. Lubricants and Cutting Fluids - These generally
fall into two classes: non-emulsifiable oils such
as lubricating oils and greases and emulsifiable
oils such as water soluble cils, rolling oils,
cutting oils, and drawing compounds. Emulsifiable
oils may contain soap fat or various other
additives.
4. Vegetable and Animal Fats and Oils - These
originate primarily from processing of foods and
natural products.
*The term toxic or toxicity is used herein in the normal
scientific sense of the word and not as a specialized
term referring to section 307 (a) of the Act.
40
-------
These compounds can settle or float and may exist as solids
or liquids depending upon factors such as method of use,
production process, and temperature cf wastewater.
Oils and grease even in small quantities cause troublesome
taste and odor problems. Scum lines from these agents are
produced on water treatment basin walls and other
containers. Fish and water fowl are adversely affected by
oils in their habitat. Oil emulsions may adhere to the
gills of fish causing suffocation, and the flesh of fish is
tainted when microorganisms that were exposed to waste oil
are eaten. Deposition of oil in the bottom sediments of
water can serve to inhibit normal benthic growth. Oil and
grease exhibit an oxygen demand.
Levels of oil and grease which are toxic to aquatic
organisms vary greatly, depending on the type and the
species susceptibility. However, it has been reported that
crude oil in concentrations as low as 0.3 mg/1 is extremely
toxic to fresh-water fish. It has been recommended that
public water supply sources be essentially free from oil and
grease.
Oil and grease in quantities of 100 1/sq km (10 gallons/sq
mile) show up as a sheen on the surface of a body of water.
The presence of oil slicks prevent the full aesthetic
enjoyment of water. The presence of cil in water can also
increase the toxicity of other substances being discharged
into the receiving bodies of water. Municipalities
frequently limit the quantity of oil and grease that can be
discharged to their wastewater treatment systems by
industry.
This parameter was found at high levels in metal cooling
water, well in excess of 100 mg/1. The normally accepted
limit for POTW is 100 mg/1 oil and grease, which is a level
which will not cause interference to the POTW operation.
Ammonia.
Ammonia occurs in surface and ground waters as a result of
the decomposition of nitrogenous organic matter. It is one
of the constituents of the complex nitrogen cycle. It may
also result from the discharge of industrial wastes from
chemical or gas plants, from refrigeration plants, from
scouring and cleaning operations where "ammonia water" is
used from the processing of meat and poultry products, from
rendering operations, from leather tanning plants, and from
the manufacture of certain organic and inorganic chemicals.
Because ammonia may be indicative of pollution and because
41
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it increases the chlorine demand, it is recommended that
ammonia nitrogen in public water supply sources not exceed
0.5 mg/1. The WHO European Drinking Water Standards set a
recommended limit of 0.5 mg/1 as NH4.
Ammonia exists in its non-ionized form only at higher pH
levels and is most toxic in this state. The lower the pH,
the more ionized ammonia is formed, and its toxicity
decreases. The toxicity of a given concentration of
ammonium compounds toward fish has been found to increase by
200 percent or more between pH 7.4 and 8.0. Ammonia, in the
presence of dissolved oxygen, is converted to nitrate (NO3_)
by nitrifying bacteria. Nitrite (NC2), which is an
intermediate product between ammonia and nitrate, sometimes
occurs in quantity when depressed oxygen conditions permit.
Ammonia can exist in several other chemical combinations
including ammonium chloride and other salts.
Nitrates are considered to be among the objectionable
components of mineralized waters. Excess nitrates cause
irritation to the gastrointestinal tract, causing diarrhea
and diuresis. Methemoglobinemia, a condition characterized
by cyanosis and which can result in infant and animal
deaths, can be caused by high nitrate concentrations in
waters used for feeding. Evidence exists that ammonia
exerts a toxic effect on all aquatic life depending upon the
pH, dissolved oxygen level, and the total ammonia
concentration in the water. Ammonia concentrations in the
range of 0.3 to 24.4 mg/1 have been reported to be acutely
toxic in various species of fish. An indicated mode of
toxicity is a decreased ability of the hemoglobin to combine
with oxygen in the presence of ammonia and hence cause
suffocation. Ammonia concentrations as low as 0.3 mg/1 have
been observed to cause a noticeable drop in the oxygen
content of the blood of fish. Algae, which thrive on high
nitrate concentrations, appear to be harmed or inhibited
when the nitrogen is in the form of ammonia. A significant
oxygen demand can result from the microbial oxidation of
ammonia. Approximately 4.5 grams of oxygen are required for
every gram of ammonia that is oxidized. Ammonia can add to
eutrophication problems by supplying nitrogen to aquatic
life. Ammonia can be toxic, exerts an oxygen demand, and
contributes to eutrophication.
Ammonia is present in some residue milling wastewaters.
However, this parameter is generally amenable to biological
treatment, by nitrification-denitrification, if present in
very limited quantities. However, less than 10% of POTW are
equipped for nitrification-denitrification. At higher
concentrations, it may disrupt POTW operations.
42
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Rationale for the Rejection of Pollutant Parameters
The following parameters were determined not to warrant
inclusion as parameters for pretreatment standards:
Chemical Oxygen Demand
Total Suspended Solids
Copper
Cadmium
Zinc
Aluminum
Chemical Oxygen Demand. Although chemical oxygen demand was
found to be present in very significant quantities from
residue milling wastewaters (up to several thousand mg/1),
this parameter is treatable by a POTW. However, the
concentrations found may be excessively high, sufficient to
overload a POTW if the waste were undiluted. It is
expected, therefore, that this waste stream will be diluted
sufficiently prior to inflow at the POTW so that normal
treatment can take place. The available data does not
reveal the source of the high loadings, although it is
postulated that they derive from oil and grease and ammonia,
which are to be controlled.
Total Suspended Solids. Very high levels of TSS were found
in the wastewaters from metal cooling and residue milling.
In particular, the quantities found in residue milling
wastewaters were such that, left untreated, could cause
blockage of sewer lines. Suspended solids, including both
organic and inorganic materials, do not normally pass
through or interfere with the operation of publicly owned
treatment works (POTW).
Copper. Copper, as well as most metals, is generally not
susceptible to treatment by biological treatment processes
at POTW. Research has shown that up to half of the input
metal will pass through the treatment plant, with about 30
to 50 percent of the copper which passes through the plant
appearing in the soluble state. Digestion has been impaired
by copper continuously fed at 10 mg/1, and slug doses of
copper at 50 mg/1 for four hours in an unacclimated system
have resulted in greatly decreased efficiencies of treatment
plants for up to 100 hours. However, the highest
concentration of copper found was less than 5 mg/1, and
other plants showed only trace quantities. Therefore,
copper was not regulated.
Cadmium. Since only one plant exhibited a high level of
cadmium in fume scrubber wastewater, this was not included
43
-------
as a parameter. This may be regulated by individual POTW on
a case-by-case basis, and guidance levels are suggested in
Section IX.
Zinc. Dissolved zinc is generally not susceptible to
treatment by biological treatment processes at POTW. In
slug doses, and particularly in the presence of copper,
dissolved zinc can interfere with cr seriously disrupt the
operation of POTW using biological processes by reducing
overall removal efficiencies, largely as a result of the
toxicity of the metal to biological organisms. However,
zinc solids {in the form of hydroxides or sulfides do not
appear to interfere with biological treatment processes on
the basis of available data. Such solids accumulate in the
sludge, where subsequent effects depend on the sludge
disposal method. By establishing a pH range, the amount of
dissolved zinc will be limited. This parameter may also be
regulated by individual POTW on a case-by-case basis, and
guidance levels are suggested in Section IX for total zinc.
Aluminum. Very high levels (over 16,000 mg/1) of aluminum
were found in demagging fume scrubber wastewater. However,
the dissolved form will be limited by adherence to the pH
limits of 5 to 10, while the suspended form will settle out
in primary settling.
44
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
Introduction
The control and pretreatment technologies available to those
plants in the secondary aluminum industry which discharge to
POTW are in many ways the same as these available to those
which are direct dischargers. The significant difference is
that POTW dischargers may utilize the treatment capabilities
of the POTW for treatment. Consequently process wastewater
discharges from POTW users will generally receive less or no
treatment prior to discharge. pH adjustment, settling and
grease removal are the major pretreatment technologies
employed at present.
The recirculation of water as a control practice appears to
be employed to at least the same degree by POTW and direct
dischargers. Recirculation is widely employed and may
result in minimizing, or in many cases completely avoiding
sewer district user fees which are partially based on the
volume discharged to the POTW. An increasing number of
plants have changed over to systems which allow dry air
pollution controls to be used, thus eliminating or
drastically reducing wet scrubber wastewater.
As used in this report, "control technology" refers to
practices used in order to reduce the volume of wastewater
discharged. "Treatment technologies" refers to practices
which reduce the concentrations of pollutants in the
wastewater streams before discharge. Control and treatment
technologies used by POTW dischargers are discussed for the
following process wastewaters:
Metal cooling wastewater
Fume scrubbing wastewater
Residue milling wastewater
Metal Cooling Wastewater
The most prevalent use of water at POTW dischargers is for
cooling of metal ingot and shot. Twelve of the POTW
dischargers use water for metal cooling.
The major pollutant in the wastewater generated during the
cooling of ingot molds, containing molten alloy, are oil and
grease and suspended and dissolved solids. The oil and
45
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grease, used to lubricate mold conveyor systems, is washed
from equipment as the ingots are sprayed from the underside
with water. The water is collected in a pit, which is
drained to a sump. The dissolved solids and suspended
solids are attributable to poor housekeeping in the area of
the cooling pit. In those operations where cooling water is
spray-cooled before recycling, dust is removed from the air
in the vicinity of the plant. The production of deoxidizer
shot differs from ingot cooling, in that the molten metal
shot contacts the water as it is quenched. During the
quench, some aluminum reacts with the water to eventually
form a sludge.
Compatibility with POTW. Analyses of metal cooling
wastewater presented in Section V show that with the
exception of aluminum, none of the metals had a
concentration greater than 1 mg/1. Aluminum was found to be
only 10 mg/1 or less. The data for direct dischargers
indicates that oil and grease removal and pH adjustment may
sometimes be necessary to satisfy the limitations of the
POTW. Two of the plants presently discharging to POTW
employ grease traps prior to discharge, thus indicating that
appreciable oil and grease are contained in the wastewater.
Control. Eight of the twelve POTW dischargers using water
for metal cooling do not recycle cooling water. Three of
the 12 plants totally recycle metal cooling water and one
practices partial recycle. Cooling towers are employed as
shown in Figure VII-1 to cool water before reuse.
The amount of wastewater generated from metal cooling can be
reduced by recirculation and cooling. A wastewater
discharge could be eliminated by adopting a concept of
either total consumption through regulated flow or air
cooling. However, the latter two alternatives are not
suited to smelters producing deoxidizer shot.
Recirculation. Of 58 secondary smelters canvassed which
generate cooling wastewaters, 15 are recirculating the water
continuously, with no discharge whatever. Seven others are
recycling the cooling water but discharge the holding tanks
periodically, usually at six month intervals. The reason
for the discharge is to permit sludge removal from cooling
towers and pits.
Discussions with smelter personnel have indicated that it is
possible to discharge the cooling water into an auxiliary
holding tank to permit sludge removal from the main system.
The water could then be returned to the system after sludge
removal.
46
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Figure VIM. INGOT COOLING WATER RECYCLE
INGOT QUENCHING
& SHOT QUENCHING
WATER
QUENCHING
PIT
COOLING TOWER
—
I
WATER
STORAGE
TANK CLEANOUT
TO SEWER OR CONTRACT DISPOSAL
SERVICE OR EVAPORATION
RECYCLE TO
QUENCHING
47
-------
Installation of a recirculation system involves the
construction of a cooling tower, possible enlargement of the
cooling pit, an auxiliary holding tank, associated plumbing,
and necessary pumps. The size and cost of these facilities
would depend on the production capacity of the smelter.
Generally, this type of equipment has been engineered,
built, and installed by smelter personnel.
Maintenance on the recirculation system is largely due to
sludge buildup. This involves approximately four man-days
every six months. Very seldom are any maintenance problems
mentioned in connection with the recirculation system
itself. The amount of sludge buildup appears to vary from
plant to plant. Those that do not have a sludge problem
claim to recirculate their cooling water continuously and
must replenish the water that has evaporated. They
attribute the sludge buildup by others to poor housekeeping
more than removal of solids from the air. Similar comments
were made about dissolved salts; however, as their
concentration increases, total evaporation of cooling water
through flash cooling on hot ingots may be a viable disposal
alternative. Oil and grease accumulation would appear to be
unavoidable. However, at higher concentrations of oil and
grease, removal by skimming is facilitated. Use of more
expensive greases that melt at higher temperatures and are
less prone to erosion have been suggested as a means of
controlling this pollution problem.
Total Consumption of Cooling water. Of the 58 smelters using
cooling water, three have reduced the flow rates such that
the water is essentially totally evaporated by the hot
ingots. As such, no wastewater is generated. Specially
designed nozzles exist to give a water-mist spray, that
reduces the steam-to-metal interface. However, these
nozzles are inclined to get plugged with dirt and, thereby
present a maintenance problem. Such approaches require
longer conveyors to assure that the ingots have cooled
sufficiently to be handled.
Air Cooling. Of all the smelters canvassed in the industry,
13 are air cooling their ingots and sows. Air cooling is
accomplished by conveying the hot ingots through an air
tunnel, fitted with entrance and exhaust blowers. The
conveyors need to be approximately twice the length of water
cooling conveyors. Maintenance is higher on the air-cooled
system because of the longer conveyor, the added heat load
on the lubricants, and the additional blower motors. In
some cases a water mist is added to the air to improve the
cooling rate. The water is completely evaporated.
48
-------
Treatment. Of the eleven POTW dischargers which have
discharges, eight discharge without any pretreatment, while
three of the plants remove oil and grease before discharge
to the POTW.
The wastewater from cooling operations requires treatment to
remove the oil and grease and suspended solids before dis-
charge. This holds for once-through water and for re-
circulated water.
Oil and Grease. Specialized skimming devices are available
for the removal of oil and grease pollutants from water.
Grease (and oil) traps can reduce the levels, so that such
specialized equipment is not overloaded.
Fume Scrubbing Wastewater
As discussed previously, the use of chlorine or aluminum
fluoride for removing magnesium produces a fume which when
scrubbed with water results in an acid wastewater. Seven
POTW dischargers use chlorine for demagging, while five use
aluminum fluoride and three use the Cerham process which
eliminates or greatly reduces the need for wet scrubbing.
Three plants do not practice demagging. Cnly seven of these
plants discharge the scrubber water.
Compatibility with POTW. The pH of untreated fume
scrubber wastewater will not meet the minimum pH
requirements. Data indicates that levels of copper, zinc
and cadmium in the fume scrubber wastewater prior to
treatment may occasionally be high. Suspended aluminum
would not be expected to interfere with POTW operation and
would tend to settle out in primary treatment.
Control. Because of the salt build-up in scrubber wastewater
from chlorine demagging, total recycle is not possible. Two
plants recycle most of the scrubber water after pH
adjustment but bleed off small volumes for discharge to the
POTW.
Because there is less soluble salt build-up in scrubber
wastewater from A1F3 demagging, the wastewater may be
recycled after pH adjustment and settling as shown in Figure
VII-2. One plant avoids any discharge to the POTW of this
wastewater by this method. Three plants use dry air
pollution controls in conjunction with A1I^3 demagging. One
plant uses a A1F_3 scrubber wastewater neutralization system
infrequently.
49
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Figure VII-2. ALF3 DEMAGGING SCRUBWATER RECYCLE SYSTEM
DEMAGGING
FUMES
*
WATER
RECYCLE
FUME
SCRUBBING
*
SETTLING
TANK
MAKEUP
^~ WATER
CAUSTIC
TANK
SLUDGE TO LANDFILL
50
-------
The use of the Derham or other demagging systems which avoid
the production of acid fumes and consequent necessity for
wet scrubbing are viable control techniques.
Control of air emissions during magnesium removal can be
done dry as well as wet. Dry emission control techniques
must contend with rather corrosive gases for both types of
magnesium removal. Anhydrous chloride salts hydrolyze to
produce hydrogen chloride gas, which in turn reacts with
water vapor to form hydrochloric acid. Hydrogen fluoride
and hydrofluoric acid are formed only at high temperatures;
however, once formed, they remain in the gases being
scrubbed.
Fume Control. Three processes exist for reduction and/or
removal of fumes without major use of water either in the
process or in fume control. These are the Derham process,
the Alcoa process, and the Teller process. The processes
are more completely described in Reference 1.
The Derham Process.<*> The Derham process includes
equipment and techniques for magnesium removal, with
chlorine, from secondary aluminum melts with a minimum of
fume generation and without major use of water in either the
process or in fume control. The principal concept is the
entrapment of magnesium chloride, the reaction product of
magnesium removal, in a liquid flux cover, with the flux
being subsequently used in the melting operations. The
Derham process is generally satisfactory in terms of meeting
air pollution restrictions. Although a second scrubber may
be desirable under stringent regulations and/or transient
process conditions, the loading should be very low. Water
use would not be completely eliminated, but recycling of
water could be done more easily.
The Alcoa Process.*1? The Aluminum Company of America is
allowing the licensing of a "fumeless" demagging process,
that claims achievement of 100 percent efficiency in
chlorine utilization for magnesium removal. It recovers
molten magnesium chloride as a product. At present, it is
being used in England for captive scrap processing. The
unit is installed between the holding furnace and a casting
machine and removes magnesium continuously as the metal
flows through.
The use of trade names does not constitute
endorsement or recommendation for use.
51
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The operation uses no flux salts and attains the high
chlorine efficiencies by means of extended gas residence
times provided by gas-liquid contactors. For very dirty
scrap, a short period of prechlorination in the furnace is
necessary to improve fluxing. The system has been operated
on a commercial scale at an alloy flow rate of 5900 kg
(13,000 Ib) per hour, with a magnesium removal rate of 27 kg
(52 Ib) per hour. Magnesium content was reduced from 0.5 to
0.1 percent.
Coated Baghouse (Teller) Process.<*> Baghouses have not
been effective in the removal of fumes from demagging
operations. Blinding occurs during collection of submicron
particulates. These particles enter the interstices of the
weave and create a barrier to gas flow. When blinding
occurs, the pressure drop rises rapidly, and gas flow
diminishes.
The Teller modification of baghouse operation has been de-
scribed in varying detail, since the inventor considers most
information proprietary (Teller, 1972). Basically, the
system differs from a normal baghouse in that the bags are
precoated with a solid to absorb effluent gases as well as
particulates, supposedly without blinding. Upon saturation,
the coating is removed along with the collected dust by vi-
bration. A fresh coating is then applied. The collected
particulate and spent coating are to be disposed of in a
landfill. The system is suited for collection of emissions
from operations using aluminum fluoride for demagging.
Treatment. Four of the seven POTW dischargers who use
chlorine demagging employ pH adjustment and/or settling
before discharge. pH adjustment is generally done crudely
by manual methods with unsophisticated pH adjustment and
settling. Figure VII-3 shows this treatment sequence for
Plant 12 and Table VII-1 gives the concentrations of
selected parameters before and after treatment with soda
ash. Table VII-2 shows the concentration of selected
parameters before and after treatment with caustic soda at
Plant 5. It should be noted that Plant 12 is planning to
convert to a dry air pollution control method, thus
eliminating the need for scrubber water treatment. The
before and after treatment chemical analyses indicated some
cadmium and zinc in raw and treated water, and copper and
lead in treated water. Table VII-3 shows the 'effect of pH
on aluminum removal. Table VII-4 shows the concentrations
before and after treatment of similar wastes.
The use of trade names does not constitute
endorsement or recommendation for use.
52
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Figure VI1-3. NEUTRALIZATION OF CHLORINE DEMAGGING SCRUBBER WATER
Ci2
*
DEMAGGING
FURNACE
1
WET
SCRUBBER
(VENTURI)
SODA ASH-
I
ACID
SCRUBWATER
NEUTRALIZATION
TANK
T
SUPERNATANT
TO
SEWER
53
-------
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55
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TABLE VII-3. EFFECTIVENESS OF pH ADJUSTMENT AND
SETTLING ON ALUMINUM REMOVAL*
CONCENTRATION (mg/t)
INFLUENT
PH
2.8
3.0
3.0
2.8
2.8
2.8
2.8
2.9
Al
23.75
13.5
18.6
44
43
14
14
14.8
EFFLUENT
pH
6.8
7.6
6.0
10.5
9.9
7.9
7.5
7.2
Al
0.8
1.5
0.33
12
12
1
1
0.12
'Samples from bauxite processing plants
obtained by Calspan Corporation in
preparation of development document
for Ore Mining and Dressing Effluent
Guidelines
56
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TABLE VII-4. TREATMENT EFFECTIVENESS, LIME TREATMENT AND SETTLING
Parameter
PH
TSS
Oil&
Grease
Al
Pb
Cu
Zn
Cd
Concentration, (mg/i)
Composite
Analysis of
C>2 Demag
Scrubwaterd)
2.42
364
5
355
0.28
1.30
11.5
0.49
Raw Wastewater
from Secondary
Lead Smelters(2)
1.3
134
-
-
76
0.41
0.53
0.83
Raw Emissions
Scrubwater
Secondary
Copper & Free.
Metals Smelter(3)
1.75
25
2.8
-
22.9
38.4
1280
0.040
Treated
Wastewater
from Secondary
Lead Smelter (2)
8.35
24
-
-
0.41
0.03
0.03
0.005
Treated Emissions
Scrubwater from
Secondary Copper
and Precious
Metals Smelter (3)
8.3
1.3
4.1
-
0.060
0.160
2.28
0.015
(1) Average Analysis of raw C\2 Demag scrubwater from 5 plants.
(2) Data on lead plant from Draft Development Document for Miscellaneous Nonferrous Metals
prepared for Effluent Guidelines Division by Calspan Corporation, I976.
(3) Data on Secondary Copper obtained by Hamilton Standard Corp.
57
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Neutralization to a pH of 7.0 will precipitate most of the
aluminum and magnesium as hydroxides, while zinc and other
heavy metals are most effectively removed as hydroxides
around pH 9.0. The effectiveness of neutralization for
aluminum removal is diminished if too much alkali is added,
since some resolubilization of aluminum hydroxide occurs at
about pH 9. When neutralization follows scrubbing, not all
of the aluminum is precipitated when the pH is raised to
9.0-9.2. This could, in part, be due to over-treatment with
alkali, causing solution of the aluminum hydroxide. Table
VII-3 shows the effectiveness of pH adjustment and settling
on aluminum removal at bauxite processing plants. The
scrubbing operation is done directly with an alkaline
solution at plant D-8, and the data suggest that the
aluminum loading is high, due to the high pH. The heavy
metals are decreased; however, due to the high pH, the total
solids and sodium loading is increased. Smelter personnel
using pH control instrumentation for alkali feed claim that
they are unreliable and require frequent maintenance. Under
conditions of failure, over-neutralization occurs. Other
smelter personnel are using pH indicator papers for checking
the pH reached after manual addition of the neutralizing
agent. Discussions indicated that these pH papers tended to
cause the wastewater to be overneutralized, since they did
not change color until around pH 9 or greater. There are,
however, pH papers on the market which can be read at 0.2 pH
increments or less and which might be more suitable for this
purpose.
Effluents are also discharged to ponds with impermeable to
semipermeable bottoms, both with and without neutralization.
Solids are removed periodically after evaporation of the
water. One practice is to recycle the neutralized water
through the scrubber until it is too difficult to pump. The
slurry is then discharged to the pond. Another practice is
to employ a settling tank for neutralization, from which the
supernatant is discharged into the evaporation pond and is
recycled to the scrubber, as needed. The settling tank was
drained weekly into the pond in order to remove the sludge
accumulation.
Aluminum Fluoride Fume Scrubber water. Two of the smelters
use wet scrubbing for emission control. Both neutralize the
solution with sodium hydroxide. One recycles the water
continuously, while the other disposes of this wastewater to
a waste hauler.
58
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Residue Milling Wastewater
Only two of the POTW dischargers utilize residues (including
drosses, slags and skimmmings) as part or all of their raw
materials. One of these plants does not discharge its
residue processing wastewater to the POTW — instead, it is
discharged to holding ponds. Plant 17, however, recycles
approximately two-thirds of the process water and discharges
one-third to a POTW as shown in Figure VII-4.
Wastewater generated during wet milling of residues is
treated in settling ponds, in which the insoluble materials
are removed. No control of the dissolved salts is practiced
by the two plants discharging into streams and the one
discharging into municipal sewers. Some dissolved salt
control by evaporation is claimed fcy those discharging the
wastewater into lagoons.
In one plant, all milling residues less than 60 mesh are
discharged for treatment in settling ponds. The first
stage, of a four stage pond system, is treated with a
polyelectrolyte to improve settling. A fourth settling
pond, with skimmers, discharges the clear overflow into the
midcourse of the receiving stream. The sludge from the
fourth stage is recycled back into the first pond and is
removed with the aid of the material passing through 60
mesh. The insoluble residue is disposed of through sale or
through an industrial disposal contractor. Residues stored
outside are subject to leaching by the rain, and the runoff
is directed into the plant drainage ditch and the fourth
pond.
Compatibility with POTW. The levels of heavy metals
encountered in settled residue milling wastewaters would not
be expected to interfere with normal POTW operation. The
high concentrations of chlorides, potassium and sodium would
probably be highly diluted in passage through the POTW but
would not interfere with plant operation. However, these
parameters would tend to pass through the plant essentially
untreated. The effect that these salts may have on
operation of a biological treatment plant is unknown. They
probably would not influence a primary treatment plant
(i.e., plain sedimentation) or a physical-chemical treatment
plant. Ammonia, however, may be present in fairly high
concentrations, possibly sufficient to disrupt POTW
operations.
Control. Recycle of residue milling wastewater is feasible
for approximately two-thirds of the water used, as shown by
Plant 17. Buildup of high salt concentrations (such as
59
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Figure VII-4. RESIDUE MILLING WASTEWATER PARTIAL RECYCLE - PLANT 17
DREDGING AND
SOLIDS DISPOSAL
100ton/wk
to LANDFILL
MAKEUP
WATER
i
50 gal/min
RESIDUE
MILLING
I
200 gal/min
SETTLING
PIT
(COARSE MAT.)
SETTLING
PIT
(FINE MATERIAL)
t
i
150 gal/min
RECYCLE
i 50 gal/min
(72,000 gal/day, 3 days/wk)
BLEED DISCHARGE TO SEWER
60
-------
sodium, potassium and chloride) makes complete recycle of
this wastewater unfeasible.
The alternative to wet residue milling and the resulting
wastewater treatment is dry milling of the residues.
Seventeen of the 23 residue processors in the industry
practice dry milling to eliminate wastewater. Impact mills,
grinders, and screening operations are used to remove the
metallic aluminum values from the nonmetallic values. The
high levels of dust formed in these operations are vented to
baghouses. The baghouse dust and the nonmetallic fines from
the screening constitute the solid waste from the operation.
These are stored on the plant site on the surface of the
ground. Attempts are made to control the runoff by
containing dissolved salts in drainage ditches.
Contamination of surface and subsurface waters is
unavoidable as the solid waste handling is practiced now.
Markets for the "field leached waste" are developing in the
cement industry, since the waste consists mostly of impure
aluminum oxide. The purity is claimed to be too low for use
as a substitute for bauxite ore.
Those practicing dry dross milling in areas where land for
solid waste disposal of the waste is limited are using the
services of industrial waste disposal contractors.
Treatment. Immediate settling of the coarse solids (up to
30% by weight) present in the residue milling wastewater
occurs in settling pits. This results in an extremely large
quantity of high salt residue (about 100 tons/week) which
must be landfilled. The disposal of the remains of the
residue is a process-related item, rather than one
attributable to pollution control, and is analogous to the
use of scale pits in hot forming operations in the steel
industry, in that scale pits must be used and the scale
periodically disposed of, or otherwise the sewer pipes
leading from the operation may become blocked by the large
quantities of coarse solids. Chlorides, sodium, potassium
and fluorides are present in appreciably high
concentrations. At the present time, there are no
practicable, economical methods for reducing the levels of
sodium, potassium and chloride in this industry. There are
treatment techniques which can be utilized for the removal
of these parameters, such as evaporation, reverse osmosis,
etc., but they are not practicable on a wastewater flow such
as found here. Fluorides can be readily removed to 15 mg/1
or less by lime precipitation, however that level is greater
than the level measured in the settled residue milling
wastewater.
61
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Wet milling of primary aluminum residues and secondary
aluminum slags by a countercurrent process is claimed by
certain segments of the industry as the only way to reduce
or possibly eliminate salt impregnation of ground and runoff
water from the discarded solid waste. By using a
countercurrent milling and washing approach, two advantages
could be realized. The final recovered metal would be
washed with clean water providing a low salt feed to the
reverberatory furnaces. The wastewater, with the insolubles
removed, would be of a concentration suitable for economical
salt recovery by evaporation and crystallization. Heat for
evaporation could be supplied by the waste heat from the
reverberatory furnaces. The process would have to contend
with the ultimate disposal of the dirt, trace metals, and
insolubles recovered from the brine, which should contain
very low levels of soluble salts. Such salt recovery
installations are operating in England and Switzerland, and
the salts recovered assist in paying for the operation,
since they are reusable as fluxing salts in the secondary
aluminum industry.
Ammonia may be present in residue milling wastewaters at
concentrations of several hundred mg/1. Removal may be
accomplished by several methods: air stripping, steam
stripping, chlorination and others. Ammonia can be removed
from wastewaters by either biological (in a nitrification-
denitrification system) or physical/chemical treatment. The
data suggest that milling with an alkaline stream reduces
the ammonia concentration appreciably from that resulting
from milling with unaltered intake water (0.30 mg/1 vs 350
mg/1 for D-4) and suggests an effective way to reduce the
level of this pollutant. However, plant personnel state
that high concentrations of ammonia may occasionally be
found, even when using alkaline milling water. If only
occasionally present in high concentrations, equalization
basins or ponds might be employed to reduce the
concentration. The mixed stream is also claimed to be
effective in reducing the suspended solids load in the pH-
adjusted fume scrubber water. The effectiveness is
attributed to the rapid settling of the coarser milling
wastes, which carry down with them the hydrated alumina and
magnesium hydroxide in the treated fume scrubber water, as
well as the associated heavy metals.
Biological treatment by activated sludge in a nitrification-
denitrification system can reduce ammonia concentrations to
less than 5 mg/1. Ammonia is oxidized to NO3 in aerobic
treatment and the nitrate broken down to nitrogen and oxygen
in anaerobic treatment. A study done on the biological
treatment of ammonia liquors from cokemaking operations,
62
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which are at concentrations of over 1,000 mg/1, indicated
that this system is effective, but the costs may be high
with large volumes of waste to be treated. Probably less
than 25X of American public treatment works use
nitrification, and probably less than 10X employ
denitrification.
Physical/chemical treatment may involve either removal of
ammonia from wastes by stripping or oxidation by breakpoint
chlorination. Breakpoint chlorinaticn requires at least 2.0
moles of chlorine per mole of ammonia. Ammonia is first
converted to chloramines. Then the chlorine will oxidize
the chlorinated compound and the ammonia will be oxidized to
nitrogen and hydrogen. After this point, there will begin
to be a free chlorine residual — hence the name 'breakpoint
chlorination.'
Air stripping, i.e., using air to remove the ammonia, is
employed for municipal wastes. However, this technique may
result in some air quality deterioration. It involves
contacting sufficient air with the ammonia - laden wastes,
possibly in a packed tower.
Steam stripping is commonly used in both the steel and
fertilizer industries for removal of ammonia from wastes.
It has been used for treating wastes of high concentrations
and generally involves liming to cause the fixed ammonia in
the wastes to convert to free ammonia and distillation to
remove the ammonia. Commonly, the ammonia is then converted
to ammonium sulfate by treating with dilute sulfuric acid.
Stripping can recover ammonia in either the aqueous or
anhydrous forms. The large operating costs associated with
the process are offset by the savings realized by sale or
reduced purchases of ammonia. The break-even point as far
as cost of stripping vs. sale of ammonia is at around 1,000
mg/1 ammonia in the influent to the stripper.
Ion exchange is used in the fertilizer industry for removal
of ammonium nitrate from wastewater and regenerating it from
the resins. It may also be applicable here. However, this
is a fairly complicated system requiring two operators per
shift (for a flow of 1000 gpm). Increased labor costs
alone, therefore, may make this option economically
impractical at this time.
63
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SECTION VIII
COSTS, ENERGY AND NONWATER QUALITY ASPECTS
Introduction
In Section VII of this report various control and treatment
technologies for limiting or eliminating discharges of
process wastewaters into POTW have been presented.
Additionally, the compatibility and treatability of these
wastes in POTW have been evaluated. This section presents
the capital and annual costs for applying various
technologies for the control and treatment of the following
process wastes when discharged to POTW.
Ingot cooling water
Chlorine demagging wastewater
Aluminum fluoride demagging wastewater.
Residue milling wastewater.
The capital and operating costs of the Derham process, which
to a great extent eliminates the requirement for wet
scrubbing of demagging fumes are presented.
Separate cost estimates have been given for model plants
which are large and small so that relative cost impacts may
be assessed for small and large plants.
The costs given are for "worst cases", i.e., the maximum
that may be required for any process, including removal of
total metals, if the local POTW should require that level of
pretreatment.
Basis for Cost Estimation
The derivation of the investment and annual costs for
treatment processes employed in this industry is described
in this section. All costs are given in fourth quarter 1975
dollars.
65
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The items used for cost preparation and presentation are as
follows:
Investment
Facilities
Equipment
Installation
Transportation
Contingency
Engineering
Land
Annual Costs
Amortization
Operation and Maintenance
Sludge/Slag Disposal
Energy
Materials
Taxes and Insurance
Costs pertaining to each item are discussed in the following
sections.
INVESTMENT
Facilities. The types of facilities include concrete
settling and holding pits, buildings and special units and
modifications required by the Derham demagging process
considered for this industry.
Holding and settling pits are constructed of 8 in reinforced
base slabs and 16 in walls. A general cost estimating
relationship was developed from Reference 1 resulting in a
base slab cost of $20/m2 and a wall cost of $30Q/m* of
concrete in place. The costs include setup and layout,
excavation, concrete, backfill and cleanup.
For example, the cost of a 6 m3 pit (3 x 2 x 1 m) is
computed as follows:
(3x2x$20) + (2) (3x1x.4x$300) + (2) (2x1x.4x$300) = $1,320.
Building costs are based on average factory costs presented
in Reference 2. A cost of $20/ft2 is used, which includes
site work, masonry, roofing, glass and glazing, plumbing,
heating, ventilating and electrical work. Buildings are
included for treatment processes which employ lime or
caustic soda neutralization. A standard sized structure of
220 ft2 is provided in all cases.
66
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The installation of the Derham process, which essentially
eliminates scrubber wastewater resulting from chlorine
demagging, requires furnace modifications and the
construction of a Derham unit. The furnace modification
cost is $5,000; the Derham unit cost is $15,000. Both costs
are from Reference 3.
Equipment. Certain types of equipment such as pumps,
piping, storage and mixing tanks are widely used in the
treatment processes applicable to the waste streams
generated by the secondary copper and aluminum industries.
Parametric cost curves were developed for such items to
facilitate the cost computations. Individual costs were
obtained for equipment items with only very limited
application.
Pumps. Costs of water and slurry pumps, including motors,
are shown in Figure VIII-1 as a function of capacity
expressed in liters/min. The costs shown are for
representative types of pumps and are based on Reference 4.
It is noted, however, that the types and sizes of pumps
required for a particular activity can vary widely,
depending on the characteristics of the material being
pumped and the height and distance the material must be
transported.
A special circulation pump is used in the Derham process.
Its cost is $3,400 and it is powered by a 4.6 hp motor (Ref.
3).
In the subsequent description of process costs, the number
of pumps assigned is shown as, for example, 3+1 or 4+2. The
first number indicates the number of pumps operating in the
system at a given time. The second number represents spare
or standby pumps assigned to prevent disruption in treatment
system operations.
Piping. Pipe costs as a function of pipe diameter are shown
in Figure VIII-2. The pipes are cast iron, class 150. The
pipe material costs are from Reference 2 and increased by 20
percent to account for ancillary items such as connectors,
T's and valves.
Holding and Mixing Tanks. Tank costs shown in Figure
VIII-3 are from Reference 5. The tanks are of steel
construction. The costs of the agitators used in the mixing
tanks are from Reference 4.
Cooling Towers. The cooling towers costed in Figure VIII-
4 are designed to cool water from 130°F to 90°F at 78° wet
67
-------
100
10 —
8
o
T- -i- »•---T—j—f-T-f-f-
-f r I r-rrt-r
—+-+-4-
}.—j—
---+
1,000
10,000
100,000
CAPACITY I /min
Figure VIIJ-1 PUMP COSTS (1975 $)
68
-------
110
100
90
80
70
uJ 60
50
40
30
20
10
10 20 30
PIPE DIAMETER - cm
40
50
Figure VIII-2 COST OF PIPES (1975 $)
69
-------
100
10
CO
O
U
1.0
0.1
.,___—f.—^,.~—......---f,---f—,-..f..(.„,.„---,.. _
-4
0.1
1.0
10
100
CAPACITY nT
Figure VIII-3 HOLDING AND MIXING TANK COSTS (1975 $)
70
-------
8
o
8,000
7,000
6.000
5.000
4,000
CAPACITY m3/min
Figure VIII-4 COOLING TOWER COSTS (1975 $)
71
-------
bulb. The towers are packaged units. Costs are based on
Reference 6.
Flocculant Feed System. The system consists of a tank, a
feed pump mounted under the tank, interconnecting piping
with relief-return system and stainless steel agitator. The
system design and cost are from Reference 7.
Tank Size Cost
50 gal. $1,600
150 gal. $2,035
500 gal. $3,500
Systems are selected for employment at plant operations
based on treatment flow requirements.
Lime Neutralization System. Lime neutralization systems
using hydrated lime are employed in a number of treatment
processes. The major system components are:
Lime Feeder
Lime Mix Tanks
Flash Mix Tank
Instrumentation, valves. Fittings
The lime feeder includes a mechanical vibrator and conical
bin. Its cost of $1,800 is from Reference 4. The sizes of
the lime neutralization units employed within the secondary
copper and aluminum plants considered fall within a
relatively narrow range. The same feed is used with all
systems.
The lime mix tanks are selected to hold a 1 week supply of
lime slurry stored as a 19 percent solution, 2 Ib/gal. The
flash mix tanks are generally sized for 10 minute retention.
The costs of the lime mix and flash mix tanks are obtained
from Figure VIII-3. Instrumentation is estimated to cost
$5,000. This is a Calspan estimate.
For example, consider a lime neutralization system required
to treat a flow of 760 1/min of wastewater with 0.32 kg of
hydrated lime per 1,000 1. A total of 760 1/min x 1440 min
x 5 days (5,470 m3) of wastewater must be treated each week
using 1750 kg (0.32 kg/m3 x 5,470 m3) of hydrated lime.
Mixed as a 19% slurry, this requires 7,293 1 (5,470 m3 x
0.32 kg/m3 divided by 0.24 kg/1) of lime slurry storage
capacity. The flash mix tank, sized for 10 minute
retention, has a capacity of 7,600 1 (10 min x 760 1/min).
The resultant system cost is as follows:
72
-------
Lime Feeder $ 1,800
Lime Mix Tanks (2) 3.7 m3 ea. 10,200
Flash Mix Tank 8 m3 6,800
Instrumentation 5,000
Total $23,800
Caustic Neutralization System. A packaged treatment tank
and instrumentation system is employed. The unit consists
of an electronically equipped control panel, a reaction
chamber with high speed stirrer and storage tanks for
reagents. System costs based on Reference 8 are as follows:
Capacity Cost
2,500 gal/hr $11,000-13,000
6,250 gal/hr 21,000
12,500 gal/hr 25,000
Systems are selected for employment at plant operations
based on treatment flow requirements.
Solids Separators. Included in this category are separators,
centrifuges and disk filters employed by various plants in
the industries. The types of equipment considered and their
costs are listed below.
Super Separators (Reference 9)
150 - 225 gal/min $3,150
200 - 300 gal/min 4,100
Industrial Separators (Reference 8)
200 - 400 gal/min $3,245
400 - 700 gal/min 3,630
Centrifuges (Reference 10 & 11)
15" x 17" $1,800
20" x 17" 2,200
12" x 30" 40,000
Disk Filter (Reference 12)
5 disks - 4' - 1 hp $17,000
The costs of vacuum pumps used in connection with disk
filters are as follows (Reference 4):
73
-------
208 fta/min 9.5 hp $5,000
310 ft3/min 23 hp 7,400
Classifier (Reference 12)
D = 24" - 14'9", 2 hp $9,000
Oil and Grease Removal. Units with an oil removal capacity
of 64 and 96 gal/hr are applied. The costs of the units are
$1,400 and $1,800, respectively (Reference 13).
Installation. Many factors can impact on the cost of
installing equipment modules. These include wage rates,
whether the job is performed by outside contractors or
regular employees and site dependent conditions, i.e.,
availability of sufficient electrical services.
In this study, installation cost is computed as 90% of the
cost of equipment which is installed. This factor is
derived from a brief analysis of data contained in Reference
14. The equipment cost used is the total equipment cost
less the cost of such items such as spare pumps and slag
bins; i.e., items which do not require installation.
Transportation. This cost is sensitive to the type of
equipment, its weight and volume and the transport distance.
After review of the transportation costs listed for
pertinent equipment items in Reference 4 and assuming
transportation distances of 200-500 miles, 1 percent of the
equipment cost appears to be a reasonable estimate for this
activity. This factor is applied in the study.
Contingency and Fee. This cost is computed as 15% of the
sum of the costs for facilities, equipment, installation and
transportation.
Engineering. This cost is estimated as 30% of equipment
cost. One exception is the Derham process which requires
payment of a license fee. The latter includes provision of
detailed engineering drawings. In this instance, the
license fee is used as the engineering cost.
LAND
The locations of secondary copper and aluminum refineries
range from highly industrial to semi-rural sites. The cost
of land is estimated as $6,000 per acre.
74
-------
ANNUAL COSTS
Amortization . Annual depreciation and capital costs are
computed as follows:
CA = B(r)
where CA = Annual Cost
B = Initial Amount Invested
r = Annual Interest Kate
n = Useful Life in Years
The computed cost is often referred to as the capital
recovery factor. It essentially represents the sum of the
interest cost and depreciation.
An interest rate of 10 percent is used. The expected useful
life of facilities is 20 years. The costs of equipment,
installation, transportation and engineering are amortized
over a 10 year period. No residual or salvage value is
assumed.
Operation and Maintenance. This cost includes facility and
equipment repair and maintenance and operating labor.
Facility repair and maintenance are included as 3 percent of
facility costs; equipment repair and maintenance as 5
percent of the combined equipment and installation costs.
Personnel costs are based on an hourly rate of $12.00. This
includes fringe benefits, overhead and supervision
(Reference 2) . Personnel are assigned for specific
activities as required.
Sludge and Slag Disposal. Disposal costs can vary widely.
Chief cost determinants include the amount and type of
waste, on- site vs. contractor disposal, size of the disposal
operation and transport distances. The following disposal
costs are employed in this study:
Dried Sludge/Slag
Contractor Disposal
$4.55/ton
Liquid Sludge
Contractor Disposal
$0. 19/gal
Dried Sludge/Slag
On- Site Disposal
75
-------
$1.82/ton
Dried Sludge/Slag
On-Site w/Ground Sealing
2.2 7/ton
Energy. Energy costs are based on the cost per horsepower-
year, computed as follows:
CY = 1.1 HP x 0.7475 x Hr x Ckw
E X P
where
CY = Cost
HP = Total Horsepower Rating of Motors
E = Efficiency Factor
P = Power Factor
Hr = Annual Operating Hours
CkW = Cost Per Kilowatt-Hour of Electricity
A 10 percent allowance is included to account for
miscellaneous energy usage. Efficiency and power factors
are each assumed to be 0.9; the cost per kilowatt-hour,
$0.03.
Materials. The material costs shown below are used in this
study:
Sulfuric Acid
$0.054/lb
(Reference 15)
Flocculant
$0.91/lb
(Reference 16)
Hydrated Lime
$70.00/ton
(Reference 15)
Caustic Soda
$380/ton
(Reference 15)
Taxes and Insurance. The combined costs are included as 1
percent of the total investment cost.
The following presentations give the capital and annual
costs for alternative control and treatment processes for
76
-------
the various process wastewater which may be discharged to
POTW from secondary aluminum smelters. Costs of
alternatives are given for both small and large model
plants.
Metal Cooling Water
Metal Cooling. The control and treatment processes shown in
Figure III-5 are considered for the large and small model
plants. The control process consists of cooling, storage
and recycling, the treatment process of settling followed by
discharge to a POTW. The water storage/settling pit is
cleaned out periodically. The wet sludge removed from the
pits amounts to 30,280 1 and 7,570 1 per year, respectively
for the large and small plants, which are disposed by a
contract disposal service. Costs for the model plants are
shown in Tables VIII-1 to VTII-4 and VIII-5 to VIII-8.
Metal Cooling - Oil and Grease Removal. As shown in Pig.
VIII-6 belt-type oil skimmers are assumed used for the
removal of oil and grease from the ingot cooling water.
Facility requirements include a concrete pit for the
temporary retention of the wastewater for oil removal. The
recovered oil and grease are disposed of by an outside
contractor. Costs for 2 model plants are presented in
Tables VTII-9 to VI11-12. Where recycling or settling is
required in addition to oil and grease removal, the costs
shown in Tables VIII-9 and VIII-11 should be combined with
other "ingot cooling" costs as appropriate.
Demagging Fume Scrubber Water
Chlorine Demagqinq Scrubwater (Discharge to Sewer). The
treatment process as shown in Fig. VIII-7 consists of
neutralization using caustic soda, followed by flocculation
and settling. The overflow from the settling tank is
discharged to a sewer. The underflow is put through a
centrifuge. Only a small amount of sludge is generated
which is transported to a landfill by a contractor. Costs
for two model plants are shown in Tables VIII-13 through
VIII-16.
Chlorine Demagging - Perham Process. The Derham process is
a technique for removal of magnesium from aluminum scrap
during smelting and refining. Generally, wet scrubbers are
not required and no process wastewater is generated.
Capital costs incurred with the implementation of the
process include:
77
-------
INGOT QUENCHING
& SHOT QUENCHING
WATER
QUENCHING
PIT
I
COOLING TOWER
WATER
STORAGE
RECYCLE TO
QUENCHING
TANKCLEANOUT
TO SEWER OR CONTRACT DISPOSAL
SERVICE OR EVAPORATION
FIGURE VIII-5: INGOT COOLING WATER RECYCLE
78
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TABLE VIM- 1. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 50.000 MT f55.OOP ST)Plant
PLANT WASTEWATER FLOW: 115.5 1/min. 8 hrs/dav. 250 davs/vr
TREATMENT ALTERNATIVE: Cool, store, recycle
INVESTMENT ($)
FACILITIES $16.400
EQUIPMENT 11.800
INSTALLATION 9.500
TRANSPORTATION 100
CONTINGENCY AND FEE 5.600
ENGINEERING 3,500
TOTAL INVESTMENT $46.700
LAND ($) $ 1.500
ANNUAL COSTS ($)
AMORTIZATION $ 5,040
OPERATION AND MAINTENANCE 4»550
SLUDGE/SLAG DISPOSAL 1,510
ENERGY 67°
MATERIALS
TAXES AND INSURANCE 41°
TOTAL ANNUAL COSTS $15,140
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.44 CO.401
79
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TABLE VIII-2: COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 30,000 MT (33,000 ST)
TREATMENT ALTERNATIVE: Cool, store, recycle
Facilities:
Storage pit (4) 30 m3 5 x 3 x 2 m $16,400
Equipment:
Cooling tower (113.5 1/min) 5 HP 4,000
Pumps
3+1 water pumps (150 1/min) $1,500 - 2 HP ea. 6,000
Piping 75 m of 10 cm pipe at $24/m 1,800
Labor:
1 hr/day; 250 days/yr at $12/hr 3,000
Waste Disposal:
30,280 1/yr at $0.05/1 1,510
Energy:
11 HP, 8 hrs/day, 250 days/yr 670
Land:
0.1 ha at $15,000/ha 1,500
-------
TABLE VIII- 3. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY:
Secondary Aluminum
PROCESS: Ingot Cooling „... .,
"jmal 1
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 15.630 MT f 15.OOP SI") Plant
PLANT WASTEWATER FLOW: 568 1/min. 4 hrs/dav. 25Q davs/vr
TREATMENT ALTERNATIVE: Cool, store, recycle
INVESTMENT ($)
FACILITIES
EQUIPMENT
INSTALLATION
TRANSPORTATION
CONTINGENCY AND FEE
ENGINEERING
TOTAL INVESTMENT
$ 6.800
10.400
8.200
100
5.800
5.100
$52.500
LAND ($)
ANNUAL COSTS ($)
AMORTIZATION
OPERATION AND MAINTENANCE
SLUDGE/SLAG DISPOSAL
ENERGY
MATERIALS
TAXES AND INSURANCE
TOTAL ANNUAL COSTS
$ 4.350
4.150
580
330
320
$ 9,510
COST PER METRIC (SHORT) TON OF PRODUCT ($)
$0.70 (0.65)
81
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TABLE VII1-4: COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 13,650 MT (15.000 ST)
TREATMENT ALTERNATIVE: Cool, store, recycle
Facilities:
Storage pit (4) 7 m3 2.2 x 2.2 x 1.5 m $6,800
Equipment:
Cooling tower (56.8 1/min) 5 HP 4,000
Pumps
3+1 water pumps (100 1/min) $1,300 - 2 HP 5,200
Piping
50 m of 10 cm pipe at $24/m 1,200
Labor:
1 hr/day; 250 days/yr at $12/hr 3,000
Waste Disposal:
7570 1/yr at $0.05/1 380
Energy:
11 HP, 4 hrs/day, 250 days/yr 330
Land: negligible
82
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TABLE VIII- 5, MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
p-—
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 50,000 MT (53,000 ST) plat,t
PLANT WASTEWATER FLOW: 1,135 1/min, 8 hrs/day, 250 days/yr
TREATMENT ALTERNATIVE: Settle, discharge to POTW
INVESTMENT ($)
FACILITIES $8.200
EQUIPMENT 1,200
INSTALLATION 1»100
TRANSPORTATION ""
CONTINGENCY AND FEE lr60Q
ENGINEERING 40°
TOTAL INVESTMENT $12,500
LAND ($)
83
ANNUAL COSTS ($)
AMORTIZATION & 1.400
OPERATION AND MAINTENANCE 2.760
SLUDGE/SLAG DISPOSAL 1,510
ENERGY "
MATERIALS "~
TAXES AND INSURANCE
TOTAL ANNUAL COSTS $ 5,800
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.19 CO.
-------
TABLE VIII- 6. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 50,000 MT (33,000 ST)
TREATMENT ALTERNATIVE: Settle, discharge to POTW
Facilities:
Settling pit (2) 30 m3 5x3x2
Equipment:
Piping 50 m of 10 cm pipe at $24/m
Labor:
4 hrs/week; 50 weeks/yr at $12/hr
Waste Disposal:
30,280 1/yr at $0.05/1
Land:
$8,200
1,200
2,400
1,510
negligible
8.4
-------
TABLE VIM- 7. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
bmall
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 13.630 MY CIS.000 ST) Plant
PLANT WASTEWATER FLOW: 568 1/min. 4 hrs/day. 250 days/yr
TREATMENT ALTERNATIVE: Settle, discharge to POTW
INVESTMENT ($)
FACILITIES J5.400
EQUIPMENT 600
INSTALLATION §00_
TRANSPORTATION "
CONTINGENCY AND FEE ML
ENGINEERING 200
TOTAL INVESTMENT $5,400
LAND ($)
ANNUAL COSTS ($)
AMORTIZATION $ 700
OPERATION AND MAINTENANCE 1-360
SLUDGE/SLAG DISPOSAL
ENERGY
MATERIALS
TAXES AND INSURANCE §P_
TOTAL ANNUAL COSTS $2.490
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.18 CO.161
85
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TABLE VIII- 8. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 13,630 MT (15,000 ST)
TREATMENT ALTERNATIVE: Settle, discharge to POTW
Facilities:
Settling pit (2) 7 m3 2.2 x 2.2 x 1.5 m $3,400
Equipment:
Piping 25 m of 10 cm pipe at $24/m 600
Labor:
2 hrs/week, 50 weeks/yr at $12/hr 1,200
Waste Disposal:
7,570 1/yr at $0.05/1 380
Land: negligible
86
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INGOT COOLING &
SHOT COOLING WATER
QUENCH
PIT 56.78 m3
(15,000 gal)
OIL
SEPARATOR
TANK
CLEANOUT
DISCHARGE TO SEWER
27.25 m3/D (7200 gpd)
TO SEWER OR CONTRACT
DISPOSAL OR EVAPORATION
FIGURE VIII-6: INGOT COOLING WATER - OIL AND GREASE REMOVAL AND DISCHARGE
87
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TABLE VIII- 9. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
Large
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 30.000 MT (33.000 ST1 Plant
PLANT WASTEWATER FLOW: 227 1/min; 8 hrs/day; 350 days/yr
TREATMENT ALTERNATIVE: Oil anc* grease removal, discharge to sewer
INVESTMENT ($)
FACILITIES $5.400
EQUIPMENT 1,800
INSTALLATION 1,600
TRANSPORTATION "
CONTINGENCY AND FEE 1. OOP
ENGINEERING 500
TOTAL INVESTMENT $8,300
LAND ($)
88
ANNUAL COSTS ($)
AMORTIZATION $1,050
OPERATION AND MAINTENANCE 1,470
SLUDGE/SLAG DISPOSAL 76°
ENERGY 30_
MATERIALS
TAXES AND INSURANCE 80
TOTAL ANNUAL COSTS $5,570
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.11 (0.10)
-------
TABLE VIII- 10. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 30.000 MT (55,000 ST)
TREATMENT ALTERNATIVE: Oil and grease removal; discharge to sewer
Facilities:
Concrete pit (2) 7 m3 2.2 x 2.2 x 1.5 m $3,400
Equipment:
Oil skimmer 1/3 HP 1,800
Labor:
2 hrs/week, 50 weeks/yr at $12/hr 1,200
Oil Removal:
15,140 1/yr at $0.05/1 760
Energy:
1/3 HP; 8 hrs/day; 350 days/yr 30
Land: negligible
89
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TABLE VIII- 11. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
Small
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 15.630 MT (15.000 ST1 Plant
PLANT WASTEWATER FLOW: 114 1/min: 4 hrs/dav: 250 days/yr
TREATMENT ALTERNATIVE: Oil and grease removal; discharge to sewer
INVESTMENT ($)
FACILITIES $2.000
EQUIPMENT 1.4QQ
INSTALLATION lf2QQ
TRANSPORTATION --
CONTINGENCY AND FEE ZQ°
ENGINEERING 4QQ
TOTAL INVESTMENT $5.700
LAND ($)
90
ANNUAL COSTS ($)
AMORTIZATION $ 720
OPERATION AND MAINTENANCE 1,390
SLUDGE/SLAG DISPOSAL 58°
ENERGY ±iL
MATERIALS
TAXES AND INSURANCE 60_
TOTAL ANNUAL COSTS $2,560
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.19 CO.17)
-------
TABLE VIII-12. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Ingot Cooling
MODEL PLANT ANNUAL CAPACITY: 13,650 MT (15,000 ST)
TREATMENT ALTERNATIVE: Oil and grease removal; discharge to sewer
Facilities:
Concrete pit (2) 3.5 m3 1.9 x 1.9 x 1 m $2,000
Equipment:
Oil skimmer - 1/3 HP 1,400
Labor:
2 hrs/week, 50 weeks/yr at $12/hr 1,200
Oil Removal:
7570 1/yr at $0.05/1 380
Energy:
1/3 HP, 4 hrs/day, 250 days/year 10
Land: negligible
91
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CHLORINE DEMAGGING
SCRUBWATER
NaOH
TANK
25% NaOH
PH _*^
SENSOR •**
*
REACTION TANK
MIXING TANK
1
FLOCCULANT
FLOCMIX
TANK
SETTLING
TANK
DISCHARGE TO
SEWER
FILTRATE
UNDERFLOW
CENTRIFUGE
T
SLUDGE TO LANDFILL
FIGURE VIII-7: CHLORINE DEMAGGING SCRUBWATER TREATMENT AND DISCHARGE
92
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TABLE VIII- 13. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demagging scrubwater
Large
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 30,000 MT (33,000 ST) Plant
PLANT WASTEWATER FLOW: 132 1/min; 10 hrs/day; 550 days/yr
TREATMENT ALTERNATIVE: Neutralization, flocculation, settle,
sludge dewater, discharge to sewer
INVESTMENT ($)
FACILITIES $ 4»400
EQUIPMENT 34>400
INSTALLATION 29,800
TRANSPORTATION 522
CONTINGENCY AND FEE 10,500
ENGINEERING 10»500
TOTAL INVESTMENT $89,500
LAND ($) $ 3.000
ANNUAL COSTS ($)
AMORTIZATION $12.710
OPERATION AND MAINTENANCE 11.740
SLUDGE/SLAG DISPOSAL 580
ENERGY 1.490
MATERIALS 6.740
TAXES AND INSURANCE 90°
TOTAL ANNUAL COSTS $54,160
COST PER METRIC (SHORT) TON OF PRODUCT ($) $1.14 (1.04)
93
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TABLE VIII-14. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demagging scrubwater
MODEL PLANT ANNUAL CAPACITY: 30,000 MT (55,000 ST)
TREATMENT ALTERNATIVE: Neutralization, flocculate, settle, sludge
dewater, discharge to sewer
Facilities:
Building $4,400
Equipment:
Caustic neutralization system - 1.5 HP 13,000
Flocculant feed system 2,000
Mixing tank 4 m3 2.5 HP 5,300
Settling tank 8 m 3,000
Centrifuge C12-60A) 2,200
Pumps
4+1 water pumps (150 1/min) $1,300 - 2.5 HP ea. 6,500
Pipe 100 m of 10 cm pipe at $24/m 2,400
Labor:
2 hrs/day, 350 days/yr at $12/hr 8,400
Sludge Disposal:
11,590 1/yr at $0.05/1 580
Energy:
14 HP; 10 hrs/day, 350 days/yr 1,490
Material:
Caustic 31 kg/day at $418/MT 4,540
Flocculant 3.15 kg/day at $2.00/kg 2,200
Land:
.2 ha at $15,000/ha 3,000
94
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TABLE VIII-15. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS- Chi01""16 demagging scrubwater
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 13,630 MT (15,000 MT) piant
PLANT WASTEWATER FLOW: 95 1/min; 4 hrs/day; 250 days/yr
TREATMENT ALTERNATIVE: Neutralization, f locculation, settle,
sludge dewater. discharge to sewer
INVESTMENT ($)
FACILITIES $ 4>400
EQUIPMENT 30»200
INSTALLATION 26,100
TRANSPORTATION
CONTINGENCY AND FEE 9 ' 10°
ENGINEERING 9 ' 10°
TOTAL INVESTMENT $79,200
LAND ($) $ 3,000
ANNUAL COSTS ($)
AMORTIZATION $11.220
OPERATION AND MAINTENANCE 5.950
SLUDGE/SLAG DISPOSAL 120
ENERGY 550
MATERIALS 1,440
TAXES AND INSURANCE 790
TOTAL ANNUAL COSTS $19,870
COST PER METRIC (SHORT) TON OF PRODUCT ($) $1.46 (1.35)
95
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TABLE VI11-.16. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demagging scrubwater
MODEL PLANT ANNUAL CAPACITY: 13.650 MT (15.000 ST)
TREATMENT ALTERNATIVE: Neutralization, flocculation, settle, sludge
dewater, discharge to sewer
Facilities:
Building $ 4,000
Equipment:
Caustic neutralization system - 1.5 HP 11,000
Flocculant feed system 1,600
Mixing tank 2.8 m3 2 HP 4,600
Settling tank 5.7 m 2,500
Centrifuge (12-157A) 1,800
Pumps
4+1 water pumps (120 1/min) $1250 - 2 HP ea. 6,300
Piping
100 m of 10 cm pipe at $24/m. 2,400
Labor:
1 hr/day, 250 days/yr at $12/hr 3,000
Sludge Disposal:
2365 1/yr at $0.05/1 120
Energy:
11.5 HP, 4 hrs/day, 250 days/yr 350
Material:
Caustic 9.5 kg/day at $418/MT 990
Flocculant .9 kg/day at $2.00/kg 450
Land:
.2 ha at $15,000/ha 3,000
96
-------
- License Fee
- Furnace Modification
- Derham Unit
- Circulation Pumps
The license fee is a one-time payment and totals $75,000.
It may be paid in cash or in "kind", i.e., metal trading
credits.
The only significant operating and maintenance costs
incurred are in connection with the circulation pumps.
costs for 2 model plants are shewn in Tables VIII-17 to
VIII-20. The large plant operates 4 furnaces and the small
plant 2 furnaces.
Installation of the Derham process can result in savings and
benefits in a number of areas. Chief among these are:
1. Reduction in the amount of chlorine required for
magnesium removal.
2, Higher aluminum recovery because excess chlorine
combines with aluminum to form aluminum chloride.
3. Reduction in the amount of purchased flux. In the
Derham process, the magnesium chloride generated forms
an ingredient of the spent salt which can be used in the
charging well of the furance.
4. Reduced refining time (magnesium removal). The time
saved may be viewed as extra production capacity or
extra operating time to permit better fluxing practices.
The actual benefits obtained will depend in part on
production levels, operating schedules, raw material and
end-product prices. Under favorable conditions, capital
costs can be recovered within 12-24 months with comparable
benefits accruing in subsequent years.
A1F3 Demaqqing Scrubwater (Recycle). As shown in Fig.
VIII-8 the scrubber wastewater is treated with caustic,
allowed to settle and recycled. The relatively small amount
of a sludge removed from the settling tank is transported to
a landfill by a contract disposal company. Costs for 2
model plants are presented in Tables VIII-21 to VIII-24.
A1F3 Scrubwater (Discharge to Sewerj_. The treatment process
is identical to that described earlier for "chlorine
97
-------
TABLE VIII-17. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demagging
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 30,000 MT (53,000 ST)
PLANT WASTEWATER FLOW: 12 hrs/day. 250 days/year
TREATMENT ALTERNATIVE: DERHAM process
INVESTMENT ($)
FACILITIES $ 80.000
EQUIPMENT 20.400
INSTALLATION 12.200
TRANSPORTATION 200
CONTINGENCY AND FEE 16.900
ENGINEERING 75,000^
TOTAL INVESTMENT $ 204,700
LAND ($) -
AMORTIZATION
ANNUAL COSTS ($)
$ 23,480
OPERATION AND MAINTENANCE 48,400
SLUDGE/SLAG DISPOSAL
ENERGY 1,670
MATERIALS
TAXES AND INSURANCE 2,050
TOTAL ANNUAL COSTS $ 75,600
COST PER METRIC (SHORT) TON OF PRODUCT ($) $2.52 (2.29)
98
-------
TABLE VIII-18. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demagging
MODEL PLANT ANNUAL CAPACITY: 50,000 MT (53.000 ST)
TREATMENT ALTERNATIVE: DERHAM process
Facilities
Furnace modification (4) $ 5,000 ea. $ 20,000
Derham units (4) $15,000 ea. 60,000
Equipment:
Circulation pumps
4 + 2 at $3,400 - 4.6 HP ea. 20,400
Engineering
Licensing fee (amortized over 20 years) 75,000
Labor
2 hrs/day, 250 days/year at $12/hr. 6,000
Sludge Disposal
Energy
18.4 HP, 12 hrs/day, 250 days/yr. 1,670
Land negligible
Pump Maintenance
4 furnaces at $10,000/furnace 40,000
99
-------
TABLE VIII-19. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS- Chlorine demagging
— — — - • - Small
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS:15.630 MT flS.OOO SI") Plant
PLANT WASTEW ATE R FLOW: 12 hrs/d.qy, 250 days/year __
TREATMENT ALTERNATIVE: FIFRHAM
INVESTMENT ($)
FACILITIES $ 40.000
EQUIPMENT _ 13,600
INSTALLATION _ 6.100
TRANSPORTATION _ 100
CONTINGENCY AND FEE _ 9.000
ENGINEERING _ 75.000
TOTAL INVESTMENT $ 143,800
LAND ($)
ANNUAL COSTS ($)
AMORTIZATION $ 16.680
OPERATION AND MAINTENANCE 24.200
SLUDGE/SLAG DISPOSAL "
ENERGY 840
MATERIALS "
TAXES AND INSURANCE 1,440
TOTAL ANNUAL COSTS $ 43,160
COST PER METRIC (SHORT) TON OF PRODUCT ($) $3.17 (2.88)
100
-------
TABLE VIII-20. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Chlorine demaggin&
MODEL PLANT ANNUAL CAPACITY: 13.635 MT (15,000 ST)
TREATMENT ALTERNATIVE: DERHAM process
Facilities
Furnace modification (2) $ 5,000 ea. $ 10,000
Derham units (2) $15,000 ea. 30,000
Equipment:
Circulation pumps
2+2 at $3,400 - 4.6 HP ea. 13,600
Engineering
Licensing fee (amortized over 20 years) 75,000
Labor
1 hr/day, 250 days/year at $12/hr. 3,000
Sludge disposal
Energy 9.2 HP, 12 hrs/day, 250 days/yr. 840
Land negligible
Pump Maintenance
2 furnaces at $10,000/furnace 20,000
101
-------
WATER
RECYCLE
DEMAGGING
FUMES
*
FUME
SCRUBBING
I
SETTLING
TANK
MAKEUP
WATER
CAUSTIC
TANK
SLUDGE TO LANDFILL
FIGURE VIII-8: ALFj DEMAGGING SCRUBWATER RECYCLE SYSTEM
102
-------
TABLE VIII-21. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: ALF3 demagging scrubwater
Large
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 30.000 MT C35.000 STl Plant
PLANT WASTEWATER FLOW: 132 1/min, 10 hrs/day. 250 days/year
TREATMENT ALTERNATIVE: Neutralization, settle, recycle
INVESTMENT ($)
FACILITIES $ 4,400
EQUIPMENT 21.700
INSTALLATION 18.400
TRANSPORTATION 200
CONTINGENCY AND FEE 6r700
ENGINEERING 6J500
TOTAL INVESTMENT $57 f 900
LAND ($) 3.000
ANNUAL COSTS ($)
AMORTIZATION $ 8,140
OPERATION AND MAINTENANCE 8.140
SLUDGE/SLAG DISPOSAL 990
ENERGY 490
MATERIALS 3,240
TAXES AND INSURANCE 580
TOTAL ANNUAL COSTS $21.580
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.72 CO.651
103
-------
TABLE VIII- 22. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: ALFj demagging scrubwater
MODEL PLANT ANNUAL CAPACITY: 30,000 MT (33,000 ST)
TREATMENT ALTERNATIVE: Neutralization, settle, recycle
Facilities
Building $ 4,400
Equipment
Caustic neutralization system 1.5 HP 13,000
Settling tank 5.3 m3 2,400
Pumps
2+1 water pumps (150 1/min) $1,300 - 2.5 HP ea. 3,900
Piping
100 m of 10 cm pipe at $24/m 2,400
Labor
2 hrs/day, 250 days/yr at $12/hr. 6,000
Sludge Disposal
19,870 1/yr. at $0.05/1 990
Energy
6.5 HP, 10 hrs/day, 250 days/yr. 490
Material
Caustic 31 kg/day at $418/MT 3,240
Land
.2 ha at $15,000/ha 3,000
104
-------
TABLE VIII- 23. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: ALFs demagging scrubwater
(Small
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 13.650 MT f 15.OOP ST1 Plant)
PLANT WASTEWATER FLOW: 95 1/min. 4 hrs/day. 250 days/yr.
TREATMENT ALTERNATIVE: Caustic neutralization, settle, recycle
INVESTMENT ($)
FACILITIES $ 4.400
EQUIPMENT 19.200
INSTALLATION 16,100
TRANSPORTATION 200
CONTINGENCY AND FEE 5»600
ENGINEERING 5,800
TOTAL INVESTMENT $ 51,500
LAND ($) 5.000
ANNUAL COSTS ($)
AMORTIZATION $ 7.250
OPERATION AND MAINTENANCE 4,900
SLUDGE/SLAG DISPOSAL 280
ENERGY 170
MATERIALS 990
TAXES AND INSURANCE
TOTAL ANNUAL COSTS $ 14,100
COST PER METRIC (SHORT) TON OF PRODUCT ($) $1.03 (0.94)
105
-------
TABLE VIII-24. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: ALF3 demagging scrubwater
MODEL PLANT ANNUAL CAPACITY: 13,630 MT (15,000 ST)
TREATMENT ALTERNATIVE: Neutralization, settle, recycle
Facilities
Building $ 4,400
Equipment
Caustic neutralization system 1.5 HP 11,000
Settling tank 3.8 m3 2,000
Pumps
2+1 water pump (1.20 1/min) $1,250 - 2 HP ea. 3,800
Piping 100m of 10 cm pipe at $24/m 2,400
Labor
1 hr/day, 250 days/yr. at $12/hr. 3,000
Sludge Disposal
5,680 1/yr. at $0.05/1 280
Energy
5.5 HP, 4 hrs/day, 250 days/yr. 170
Material
Caustic 9.5 kg/day at $418/MT 990
Land
.2 ha at $15,000/ha 3,000
106
-------
demagging scrubwater" (Tables VIII-13 to VIII-16). The
costs are repeated in Tables VIII-25 to VHI-28.
Residue Milling.
Residue Milling Wastewater (Settling). Two settling pits
are used in the treatment process as shown in Figure VIII-9.
One is for settling coarse materials, the other for fine
materials. Water is recycled except that there is a bleed
discharge from the second settling pit to a sewer three days
per week. The settling pits are dredged twice per week. A
total of 91 MT of solids are removed each week and
transported to a sealed, on-site dump because of the high
soluble salt content (NaCl, KCl) of the residue. Model
plant costs are shown in Tables VIII-29 and VIII-30.
Residue Milling Wastewater (Ammonia Stripping). A packed
column air stripper was used, since a maximum ammonia
concentration equal to that of Plant D-U was assumed. The
column itself was scaled from an existing ammonia air
stripper operated by Union Carbide Corporation; caustic
dosage rates were approximated at 10 It NaOH/1,000 gal of
wastewater; and a mix time of 10 minutes were assumed.
Model plant costs are shown in Tables VIII-31 and VIII-32.
Cost-Effectiveness
A comparison of the effluents produced to the cost of the
treatment or control techniques is shown in Table VIII-33.
Pretreatment Costs
Table VIII-34 shows an estimate of the cost of pretreatment
at all the POTW dischargers. Note that this table has been
completed on a "worst case" basis-for example, some plants
may be required to remove metals before discharge to a POTW
because of high concentrations in demagging scrubber
wastewater and this cost has been included therefore for all
POTW dischargers with demagging scrubbers.
107
-------
TABLE VIII-25. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: ALFx scrubwater
—.
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS:30,000 MT (53,000 ST) Plant
PLANT WASTEWATER FLOW: 132 1/min, 10 hrs/day. 350 days/yr.
TREATMENT ALTERNATIVE: Neutralization, flocculation, settle,
sludge dewater. discharge to sewer
INVESTMENT ($)
FACILITIES $ 4.400
EQUIPMENT 34,400
INSTALLATION 29.300
TRANSPORTATION 50°
CONTINGENCY AND FEE 10'300
ENGINEERING 10»300
TOTAL INVESTMENT $ 89,500
LAND ($) $ 3,000
ANNUAL COSTS ($)
AMORTIZATION $ 12.710
OPERATION AND MAINTENANCE 11.740
SLUDGE/SLAG DISPOSAL 58°
ENERGY 1.490
MATERIALS 6.740
TAXES AND INSURANCE 900
TOTAL ANNUAL COSTS $ 34,1 fin
COST PER METRIC (SHORT) TON OF PRODUCT ($) $1.14 (1.04)
108
-------
TABLE VIII-26. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: ALF3 scrubwater
MODEL PLANT ANNUAL CAPACITY: 30,000 MT (53,000 ST)
TREATMENT ALTERNATIVE: Neutralization, flocculate, settle
sludge dewater, discharge to sewer
Facilities
Building $ 4,400
Equipment
Caustic neutralization system 1.5 HP 13,000
Flocculant feed system 2,000
Mixing tank 4m3 - 2.5 HP 5,300
Settling tank 8m3 3,000
Centrifuge (12-60A) 2,200
Pumps
4+1 water pumps (150 1/min) $1,300 - 2.5 HP ea. 6,500
Pipe
100 m of 10 cm pipe at $24/m 2,400
Labor
2 hrs/day, 350 days/yr at $12/hr 8,400
Sludge disposal
11,590 1/yr. at $0.05/1 580
Energy
14 HP, 10 hrs/day, 350 days/yr. 1,490
Material
Caustic 31 kg/day at $418/MT 4,540
Flocculant 3.15 kg/day at $2.00/kg 2,200
Land
.2 ha at $15,000/ha 3,000
109
-------
TABLE VIII- 27. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: ALF3 scrubwater
— Small
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS: 13.630 MT f 15.OOP ST") Plant
PLANT WASTEWATER FLOW: 95 1/min, 4 hrs/day, 250 days/yr.
TREATMENT ALTERNATIVE: Neutralization, flocculation, settle,
sludge dewater, discharge to sewer
INVESTMENT ($)
FACILITIES $ 4.400
EQUIPMENT 30»200
INSTALLATION 26'100
TRANSPORTATION 300
ENERGY
CONTINGENCY AND FEE 9.100
ENGINEERING 9.100
TOTAL INVESTMENT $ 79.200
LAND ($) $ 3»°00
ANNUAL COSTS ($)
AMORTIZATION $ 11.220
OPERATION AND MAINTENANCE 5'950
SLUDGE/SLAG DISPOSAL 12°
350
MATERIALS 1>44°
TAXES AND INSURANCE Z?JL
TOTAL ANNUAL COSTS $ 19,870
COST PER METRIC (SHORT) TON OF PRODUCT ($) $1.46 (1.55)
110
-------
TABLE VIII-28. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: ALF3 scrubwater
MODEL PLANT ANNUAL CAPACITY: 13.630 MT (15,000 ST)
TREATMENT ALTERNATIVE: Neutralization, flocculation, settle, sludge
dewater, discharge to sewer
Facilities
Building $ 4,400
Equipment
Caustic neutralization system 1.5 HP 11,000
Flocculant feed system 1,600
Mixing Tank 2.8m3 - 2 HP 4,600
Settling Tank 5.7m3 2,500
Centrifuge (12-157A) 1,800
Pumps
4+1 water pumps (120 1/min) $1250 - 2 HP ea. 6,300
Piping
100 m of cm pipe at $24/m 2,400
Labor
1 hr/day, 250 days/yr. at $12/hr. 3,000
Sludge disposal
2365 1/yr. at $0.05/1 120
Energy
11.5 PH, 4 hrs/day, 250 days/yr. 350
Material
Caustic 9.5 kg/day at $418/MT 990
Flocculant .9 kg/day at $2.00/kg 450
Land
.2 ha at $15,000/ha 3,000
111
-------
Figure VIII-9. RESIDUE MILLING WASTEWATER PARTIAL RECYCLE - PLANT 17
DREDGING AND
SOLIDS DISPOSAL
100 ton/wk
to LANDFILL
MAKEUP
WATER
i
50 gal/min
RESIDUE
MILLING
I
200 gal/min
SETTLING
PIT
(COARSE MAT.)
SETTLING
PIT
(FINE MATERIAL)
150 gal/min
RECYCLE
*50 gal/min
(72,000 gal/day, 3 days/wk)
BLEED DISCHARGE TO SEWER
112
-------
TABLE VIII- 29. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Residue milling wastewater
Large
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TQMS:30,000 MT (35,000 ST) Plant
PLANT WASTEWATER FLOW: 757 1/min. 24 hrs/davt 5 days/week f 5Q weeks/yr.
TREATMENT ALTERNATIVE: Settle, partial discharge/recycle
INVESTMENT ($)
FACILITIES $ 44,100
EQUIPMENT 8,400
INSTALLATION 5,900
TRANSPORTATION 100
CONTINGENCY AND FEE 8»800
ENGINEERING 2»500
TOTAL INVESTMENT $ 69.800
LAND ($) $ 5.000
ANNUAL COSTS ($)
AMORTIZATION $ 7,910
OPERATION AND MAINTENANCE 16'440
SLUDGE/SLAG DISPOSAL ""
ENERGY 5,280
MATERIALS ""
TAXES AND INSURANCE 700
TOTAL ANNUAL COSTS $ 28.330
COST PER METRIC (SHORT) TON OF PRODUCT ($) $0.94 (0.85)
113
-------
TABLE VIII-30. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Residue milling wastewater
MODEL PLANT ANNUAL CAPACITY: 30,000 MT (33,000 ST)
TREATMENT ALTERNATIVE: Settle, partial discharge/recycle
Facilities
Settling pits (2) 536 m^ 18.3 x 12.2 x 2.4m $ 44,100
Equipment
Pumps
3+1 water pumps (900 1/min) $1800 - 10 HP ea. 7,200
Piping
50 m of 10 cm pipe at $24/m l,2iO
Labor
24 hrs/week, 50 weeks/yr at $12/hr. 14,400
Energy
30 HP, 72 hrs/week, 50 weeks/yr. 3,280
Land
.2 ha at $15,000/ha 3,000
114
-------
TABLE VIII- 31. MODEL-PLANT CONTROL COSTS FOR
INDUSTRY: Secondary Aluminum
PROCESS: Residue Milling (Plant 17)
PLANT ANNUAL CAPACITY IN METRIC (SHORT) TONS:_3_L^{]
PLANT WASTEWATER FLOW: 7*17 l/min* ?4 Vvrc/rlay 5
TREATMENT ALTERNATIVE: Ammonia air stripping
n MT (34 2nn ST)
^L(\ rlavc/vT
INVESTMENT ($)
FACILITIES
EQUIPMENT
INSTALLATION
TRANSPORTATION
CONTINGENCY AND FEE
ENGINEERING
TOTAL INVESTMENT
LAND ($)
ANNUAL COSTS ($)
AMORTIZATION
OPERATION AND MAINTENANCE
SLUDGE/SLAG DISPOSAL
ENERGY
MATERIALS
TAXES AND INSURANCE
TOTAL ANNUAL COSTS
COST PER METRIC (SHORT) TON OF PRODUCT ($)
$ 29,600
89,000
78.400
900
29,700
26,700
$254,300
$ 3.000
$ 35,250
21,260
— —
20,420
71,940
2,540
$151,410
$4.81 (4.37)
115
-------
TABLE VIII-32. COST COMPONENTS
INDUSTRY: Secondary Aluminum
PROCESS: Residue Milling
MODEL PLANT ANNUAL CAPACITY: 31,500 MT (34,200 ST)
TREATMENT ALTERNATIVE: Ammonia air stripping
Facilities
Wastewater holding pit 11.7 x 11.7 x 4 $25,200
Building 4,400
Equipment
Packed Tower 75 HP 30,000
Caustic Soda System 13 HP 46,500
Pumps
2+1 water pumps 1 m /min $1,900 - 12 HP ea. 5,700
Piping
200 m of 15 cm pipe at $34/m 6,800
Labor
4 hrs/day, 250 days/yr at $12/hr 12,000
Materials
327 MT NaOH/yr at $220/MT 71,940
Energy
112 HP 20,420
Land
0.2 ha at $15,000/ha 3,000
116
-------
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117
-------
TABLE VIII-34. SECONDARY ALUMINUM INDUSTRY: COSTS FOR PRETREATMENT FOR
DISCHARGE TO POTW AND TREATMENT FOR RECYCLE
(ZERO DISCHARGE) [$1975]
PLANT NO.
1
2
3
4
5
6
7
8
9
10(2)
11
12
13
14
15
16
17
18
TOTALS
PRETREATMENT COSTS
CAPITAL
$ 87,900
8,300
8,300
8,300
5,700
5,700
5,700
87,900
9,100
5,700
87,900
5,700
100,800
92,500
349,800
8,300
$877,600
ANNUAL
$ 22,430
3,370
3,370
3,370
2,560
2,560
2,560
22.430
1,760
2,560
22,430
2,560
37,530
34,160
185,570
3,370
$352,590
$/METRICTON
$1.65
0.11
0.11
0.11
0.19
0.19
0.19
1.65
0.06
0.19
1.65
0.19
1.25
1.14
6.19
0.11
TREATMENT COSTS FOR RECYCLE
CAPITAL
$176,100
48,200
48,200
48,200
143,800
32,300
32,300
32,300
86,600
32,300
176,100
32,300
32,300
252,900
204,700
204,700
48,200
$1,631,500
ANNUAL
$ 52,670 (1)
13,140
13,140
13,140
43,160(1)
9,510
9,510
9,510
23,610
9,510
52,670<1)
9,510
9,510
88,740 (1)
75,600 (1)
75,600 (1)
13,140
$521,670
$/METRIC TON
$3.86 (1)
0.44
0.44
0.44
3.17<1>
0.70
0.70
0.70
1.73
0.70
3.86 (1)
0.70
0.70
2.96<1>
2.52<1>
2.52<1>
0.44
(1) The implementation of the treatment process may result in savings from reduced material input requirements
and/or increased productivity. Potential benefits are not considered in the costs.
(2) Addition of settling tank to existing system.
118
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SECTION IX
BEST PRACTICABLE PRETREATMENT TECHNOLOGY
Introduction
The best practicable pretreatment technologies are based on
the average of the best performance by plants of various
sizes and ages, as well as the unit processes within the
industrial category. Additional consideration was also
given to:
(1) The total cost of application of
technology in relation to the effluent
reduction benefits to be achieved
from such application.
(2) The size and age of the equipment and
plant facilities involved.
(3) The process employed.
(4) The engineering aspects of the
application of various types of
control techniques.
(5) Process changes.
(6) Nonwater quality environmental
impact (including energy requirements) .
The best practicable pretreatment technologies emphasize
effluent treatment at the end of a manufacturing process.
It includes the control technology within the process itself
when the latter is considered to be normal practice within
the industry.
Industry Categorization and Wastewater Streams
The secondary aluminum smelting subcategory is defined as
that segment of the aluminum industry which recovers, pro-
cesses, and remelts various types of aluminum scrap to
produce metallic aluminum alloy as a product. Although
primary aluminum producers recover captive scrap generated
from their own operations, they are not included in this
subcategory. The secondary smelters buy scrap in various
forms on the open market as their raw material. Fabrication
operations are not included.
A useful approach for the purpose of developing effluent
limitations guidelines is to deal with the wastewater
streams themselves. The principal streams are (1)
wastewater from metal cooling, (2) wastewater from fume
119
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scrubbing, and (3) wastewater from residue milling. Each
stream has an associated loading of pollutants. For
example, the indicated pretreatment control levels require a
smelter generating only cooling wastewater to meet the level
established for that waste stream. A smelter generating
cooling, scrubber, and residue milling wastewaters would be
required to meet the pretreatment levels established for
each wastewater stream.
General Factors
Because the information on water flow rates, as discussed
previously, is somewhat erratic, and there is limited
information on the flow rates at POTW dischargers, the
limitations have been established in terms of
concentrations. This is further supported by the relatively
non-toxic nature of the wastes.
The Conference Report accompanying the Water Pollution
Control Act Amendments of 1972 (P.L. 92-500) discourages the
setting of standards which promote recycle and reuse
technologies for industrial facilities discharging to POTW.
A review of water use practices in various plant systems has
shown that recycle technology is widely practiced in the
industry. As an economic matter, as detailed in Section
VIII of this document, indirect dischargers may choose to
completely recycle process wastewaters rather than install
the pretreatment technologies identified.
Pretreatment Control Levels
The pretreatment standard for metal cooling wastewaters is
as follows:
Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any one day values for 30
consecutive days
shall not exceed
Oil and grease, mg/1 100.0
The pretreatment standard for deiragging fume scrubber
wastewaters is as shown below.
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Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any one day values for 30
consecutive days
shall not exceed
pH Within the range 5.0 to 10.0
The pretreatment standard for residue milling wastewaters is
shown below.
Pretreatment Levels
Effluent Maximum for Average of daily
Characteristic any one day values for 30
consecutive days
shall not exceed
Ammonia-Nr mg/1 100.0 50.0
Identification of Best Practicable Pretreatment Technology
Metal Cooling Wastewater The best practicable pretreatment
technology available for the metal cooling wastewaters is
identified as oil and grease removal by skimming.
This is supported by the fact that two of the plants
presently discharging metal cooling wastewaters to public
sewers are presently employing grease traps for oil removal
from this waste, while a third uses settling. As discussed
previously, the other constituents of this waste are not
expected to interfere with POTW operation, or to pass
through untreated, and therefore do not require regulation
as part of a pretreatment standard.
Demagging Fume Scrubber Wastewater The best practicable
pretreatment technology for demagging fume scrubber
wastewaters is identified as pH adjustment.
As discussed previously, the constituent of concern in this
wastewater is aluminum. Alum is used as a flocculating
agent in many POTW, at levels of up to or over 200 mg/1 as
A1S(34»18H2O. Therefore, it is advantageous for the POTW
receiving the waste, as long as aluminum is present in
concentrations no greater than would be present by
deliberate addition and as long as the addition is
relatively constant. Although zinc, copper and cadmium may
121
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be present in the effluent from some plants, these
parameters were not found present at high concentrations at
all plants. Because of local conditions, individual POTW
may limit these parameters on a case-by-case basis. All of
these metals may be satisfactorily removed by using
flocculation and settling after adjusting the pH to around
9.0. As guidance for local POTW authorities, zinc
limitations of 2.5 mg/1 (30 day average) and 5.0 mg/1 (daily
maximum), and cadmium limitations of 0.2 mg/1 (30 day
average) and 0.4 mg/1 (daily maximum) are recommended.
The guidance limitation for cadmium was selected after an
examination of the information presented in the pretreatment
development document for the secondary copper industry
(Reference 17), since none of the plants in the secondary
aluminum industry with significant concentrations have
exemplary treatment. Plant V of the secondary copper
industry shows a reduction in cadmium from an initial
concentration of 2 to 2.3 mg/1 to an effluent level of 0.07
mg/1 after lime and settle treatment. Additionally, recent
sampling data from an electroplating operation with pH
adjustment and settle treatment show that this system can
consistently achieve 0.2 mg/1 cadmium in the effluent. The
zinc guidance limitation was selected in light of the
treatment effectiveness of Plant R in the secondary copper
industry (Reference 17), which showed a reduction of the
zinc concentration from an influent level of 1280 mg/1, to
an effluent level of 2.28 mg/1, after lime and settle
treatment. The influent pH was 1.75, while the effluent was
at pH 8.3.
Residue Milling Wastewater The pretreatment technologies
available for residue milling wastewaters are settling and
ammonia removal by air stripping.
The constituent of concern in this wastewater is ammonia.
Ammonia was not found to be present in high concentrations
at the only plant which discharges this waste to a POTW but
plant personnel indicate it may be occasionally present in
high concentrations and therefore, costs are included for
reduction in loadings of this parameter by air stripping of
ammonia. Settling will reduce the concentrations of coarse
solids sufficiently for acceptability by the POTW sewer
system, and is commonly practiced in the industry. Ammonia-
nitrogen concentrations of less than 50 mg/1 have been
routinely achieved in the fertilizer industry by stripping
(Reference 18).
The pretreatment technologies identified are all end-of-pipe
techniques and are commonly employed in the industry or in
122
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related industries. Therefore, the age of the plant
involved will have little, if any, impact on the
implementation of the recommended technologies. Energy
requirements for the selected technologies are minimal.
Rationale for the Selection o_f_ the Identified Pretreatment
Technology
(1) The selected technologies are capable of achieving
significant reductions in discharge of pollutants.
(2) The technologies are compatible with industry
variations, including age and size of plant,
processes employed, raw material variations, plant
location, and nonwater quality environmental
impact.
(3) The technologies, as end-of-pipe treatments, can be
an add-on to existing plants, and need not affect
existing internal process and equipment
arrangements.
(4) The maximum daily concentrations of pollutants,
with the exception of oil and grease, are set at
twice the demonstrated long-term averages. This
factor of two was selected after an assessment of
the variability of demonstrated technologies which
do not appear to vary much beyond a 2 to 1 factor.
Oil and grease levels are established to prevent
slug discharges.
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SECTION X
ACKNOWLEDGEMENT S
The Environmental Protection Agency would like to
acknowledge the contributions of Calspan corporation under
the direction of P. Michael Terlecky, Jr. for their aid in
the preparation of this document.
The Project Officer, Patricia E. Williams, would like to
thank her associates in the Effluent Guidelines Division,
namely Mr. Ernst P. Hall, Mr. Walter J. Hunt and Mr. John E.
Riley for their valuable suggestions and assistance.
The members of the working group/steering committee who
coordinated the internal EPA review are:
Mr. John E. Riley, Chairman, Effluent Guidelines Division
Ms. Margaret Stasikowski, Office of Research and Development
Mr. Steven Singer, Office of Analysis and Evaluation
Mr. Don Wood, Office of Planning and Evaluation
Mr. Lee DeHihns, Office of General Counsel
Mr. Gary Otakie, Office of Water Programs
Finally, many thanks are given to the exemplary staff of the
Effluent Guidelines Division. In particular, recognition is
given to Ms. Linda Rose, Ms. Kaye Starr and Ms. Nancy
Zrubek.
125
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SECTION XI
REFERENCES
a. Development Document for Effluent Limitations Guidelines
and New Source Performance Standards for the Secondary
Aluminum Smelting Subcategory of the Aluminum Segment of the
Nonferrous Metals Manufacturing Point Source Category, U.S.
Environmental Protection Agency, EPA-440/l-74-019e, March
1974.
2. Building Construction Cost Data 1975, Robert Snow Means
Company, Inc. 33rd Annual Edition.
3. Visit to Aluminum Processes, Inc., Cleveland, Ohio, June
2, 1976.
4. Process Plant Construction Estimating Standards,
Richardson Engineering Services, Inc., Soland Beach,
California, 1975.
5. Cost of Standard-Sized Reaction and Storage Tanks,
Reprint from Chemical Engineering, Revised, November 1975.
6. Correspondence with the Johnson Equipment Co., Inc.,
Rochester, N.Y., Representatives of Marley Corporation, May
1976.
7. Telecom with Calgon Corporation, Water Management
Division, Pittsburgh PA, May 1976.
8. Telecom with Sethco Manufacturing Corporation, Freeport,
N.Y., June 1976.
9. Telecom and correspondence with Laval Separator
Corporation, Fresno, California, May 1976.
10. Telecom and correspondence with A.M. Lavin Machine
Works, Hatboro, Pa., May 1976.
11. Telecom and correspondence with Eird Machine Company,
Inc., So. Walpole, Massachusetts, May 1976.
12. Telecom with Denver Equipment Company, May 1976.
13. Telecom and correspondence with Aerodyne Development
corporation, Cleveland, Ohio, May 1976.
127
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14. Capital and Operating Costs of Pollution Control
Equipment Modules, Vol. 1, User Guide, U.S. Environmental
Protection Agency, EPA-R5-73-023z, July 1973.
15. Telecom with Bison Laboratories, Inc., Buffalo, New
York, May 1976.
16. Telecom with NALCO Chemical Company, Oakbrook, Illinois,
June 1976.
17. "Supplement for Pretreatment to the Development Document
for the Secondary Copper Segment of the Nonferrous Metals
Manufacturing Point Source Category", U.S. Environmental
Protection Agency, December 1976.
18. "Development Document for Effluent Limitations
Guidelines and New Source Performance Standards - Basic
Fertilizer Chemicals Segment of the Fertilizer Manufacturing
Point Source Category", U.S. Environmental Protection
Agency, March 1974.
128
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SECTION XII
GLOSSARY
Act
The Federal Water Pollution Control Act Amendments of 1972.
Alloying
The process altering the ratio of components in a metal by
the addition or removal of such components.
Borings and Turnings
Scrap aluminum from machining of castings, rods, bars, and
forgings.
Captive Scrap (Runaround Scrap)
Aluminum scrap metal retained by fabricator and remelted.
COD
Chemical oxygen demand, a parameter used to assess water
quality.
Compatible Pollutants
Those pollutants which can be adequately treated in publicly
owned sewage treatment works without harm to such works.
Demagging
Removal of magnesium from aluminum alloys by chemical
reaction.
Dross
Residues generated during the processing of molten aluminum
or aluminum alloys by oxidation in air.
Effluent
The wastewater discharged from a point source to navigable
waters.
Effluent Limitation
A maximum amount per unit of production (or other unit) of
each specific constituent of the effluent that is subject to
limitations in the discharge from a point source.
Fluxing Salts (or Covering Flux)
Sodium chloride or a mixture of equal parts of sodium and
potassium chlorides containing varying amounts of cryolite.
Used to remove and gather contaminants at the surface of
molten scrap.
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Heat
A fully charged reverberatory furnace containing aluminum
alloy of desired composition.
Heel
That part of the molten aluminum alloy remaining in the
furnace to facilitate melting of scrap being charged for the
preparation of the following heat.
Incompatible Pollutants
Those pollutants which would cause harm to, adversely affect
the performance of, or be inadequately treated in publicly
owned sewage treatment works.
Ingots
A mass of aluminum or aluminum alloy shaped for convenience
in storage and handling. Sizes according to weight are 15,
30, 50, and 1000 pounds.
Irony Aluminum
High iron content aluminum alloy recovered from old scrap
containing iron. Prepared in sweating furnace operating at
temperatures sufficiently high to melt only the aluminum.
New Clippings and Forgings
Scrap from industrial manufacturing plants such as aircraft
and metal fabricators.
Pigs
Ingots of aluminum alloy weighing 15 tc 50 pounds.
Point Source
A single source of water discharge, such as an individual
plant.
Pretreatment
Treatment performed on wastewaters from any source prior to
introduction for joint treatment in publicly owned sewage
treatment works.
Residues
Include dross, skimmings and slag recovered from alloy and
aluminum melting operations of both the primary and
secondary smelters and from foundries.
Reverberatory Furnace (Reverb)
A furnace used for the production of aluminum alloy from
aluminum scrap.
Skimmings
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Wastes from melting operations removed from the surface of
the molten metal. Consists primarily of oxidized metal, but
may contain fluxing salts.
Slag
Fluxing salts removed from the surface of molten aluminum
after charging and mixing. Contains 5 to 10 percent solid
aluminum alloy.
Solids
Aluminum scrap metal.
Sows
Ingots weighing 500 to 1000 pounds.
Sweated Pigs
Ingots prepared from high iron aluminum alloy.
Virgin Aluminum
Aluminum recovered from bauxite.
131
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TABLE VIII-35
METRIC TABLE
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS) by TO OBTAIN (METRIC UNITS)
ENGLISH UNIT ABBREVIATION CONVERSION ABBREVIATION METRIC UNIT
acre
acre - feet
British Thermal
Unit
British Thermal
Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square
inch (gauge)
square feet
square inches
ton (short)
yard
Actual conversion, not a multiplier
ac
ac ft
BTU
BTU/lb
cfm
cfs
cu ft
cu ft
cu in
°F
ft
gal
gpm
hp
in
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
yd
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
(0.06805 psig +1)*
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
atm
sq m
sq cm
kkg
m
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
1i ters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric ton (1000 kilograms
meter
132
ir U. S. GOVERNMENT PRINTING OFFICE : 1977 O - 228-923
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