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
MARCH 1974
\ U.S. ENVIRONMENTAL PROTECTION AGENCY
? Washington, D.C. 20460
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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
Russell E. Train
Administrator
Roger Strelow
Acting Assistant Administrator for Air and Water Programs
Allen Cywin
Director, Effluent Guidelines Division
George S. Thompson, Jr.
Project Officer
March, 1974
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D. C. 20460
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ABSTRACT
This document presents the findings of an extensive study by the
Environmental Protection Agency of the secondary aluminum
smelting industry for the purpose of developing effluent
limitations guidelines and standards of performance to implement
Sections 304, 306, and 307 of the Federal Water Pollution Control
Act, as amended.
Effluent limitations guidelines contained herein set forth the
degree of effluent reduction attainable through the application
of the best practicable control technology currently available
and the degree of effluent reduction attainable through the
application of the best available technology economically
achievable which must be achieved by existing point sources by
July 1, 1977 and July 1, 1983, respectively. The standards of
performance for new sources contained herein set forth the degree
of effluent reduction attainable through the application of the
best available demonstrated control technology, processes,
operating methods, or other alternatives.
The development of data and recommendations in this document
relate to waste waters generated in metal cooling, fume scrubbing
and wet residue processing. The best practicable control
technology currently available, the best available technology
economically achievable, and the best available demonstrated
control technology for each of these waste water streams are
presented in Section II of this report. The effluent limitations
and standards of performance corresponding to these technologies
also are presented.
Supporting data and rationale for development of the effluent
limitations guidelines and standards of performance also are
contained in this report.
111
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CONTENTS
Section
I CONCLUSIONS
II
III
IV
V
VI
VII
RECOMMENDATIONS
Best Practicable Control Technology Currently
Available
Best Available Technology Economically
Achievable
Best Available Demonstrated Control Technology
INTRODUCTION
Purpose and Authority
Methods Used for Development of Effluent
Limitations Guidelines and Standards of
Performance
General Description of the Secondary
Aluminum Industry
INDUSTRY CATEGORIZATION
Introduction
Objectives of Categorization
Definition of the Industry
Process Description
Industry Categorization
WASTE CHARACTERIZATION
Introduction
Specific Water Uses ,
SELECTION OF POLLUTANT PARAMETERS
Introduction
Rationale for the Selection of Pollutant
Parameters
Rationale for Rejection of Other Waste Water
Constituents as Pollutant Parameters
CONTROL AND TREATMENT TECHNOLOGY
Introduction
Waste Water from Metal Cooling
Waste Water from Fume Scrubbing
Waste Water from Residue Milling
Page
1
3
3
5
5
9
9
12
17
17
17
17
17
28
39
39
39
57
57
57
64
67
67
67
71
84
v
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CONTENTS (continued)
Section
VIII
IX
X
XI
XII
XIII
XIV
COSTS, ENERGY AND NONWATER QUALITY ASPECTS
Introduction
Basis for Cost Estimation
Waste Water from Metal Cooling
Waste Water from Fume Scrubbing
Waste Water from Residue Milling
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE—EFFLUENTS LIMITATIONS GUIDELINES
Introduction
Industry Categorization and Waste Water Streams
Waste Water from Metal Cooling
Waste Water from Fume Scrubbing
Waste Water from Residue Milling
BEST AVAILABLE TECHNOLOGY ECONOMICALLY
ACHIEVABLE—EFFLUENTS LIMITATIONS GUIDELINES
Introduction
Waste Water from Metal Cooling
Waste Water from Fume Scrubbing
Waste Water from Residue Milling
NEW SOURCE PERFORMANCE STANDARDS
Introduction
Waste Water from Metal Cooling
Waste Water from Fume Scrubbing
Waste Water from Residue Milling
ACKNOWLEDGMENTS
REFERENCES
GLOSSARY
Page
89
89
89
90
94
96
101
101
101
102
104
108
111
111
112
112
115
117
117
117
118
119
123
125
127
VI
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FIGURES
Number Title page
1 Location of Secondary Aluminum Smelters 15
2 The Total Secondary Aluminum Process 18
3 Recirculated Cooling Water System 69
4 Schematic Diagram of Elements of the Derham
Process 72
5 Chloride Fume Scrubber Waste Water Treatment
(Neutralization-Settling) 81
6 Chloride Fume Scrubber Treatment (Partial Recycle
and Evaporation Pond Discharge) 82
7 Aluminum Fluoride Fume Scrubber System with
Continuous Recycle 83
8 Residue Milling and Alkaline Chloride Fume
Scrubber Waste Water Treatment System 86
9 Capital Cost for Control and Treatment of Metal
Cooling Water 93
Vll
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TABLES
Number
10
11
12
13
14
15
16
17
18
19
Title
Effluent limitations for Treated Fume scrubber
Waste Water Generated During Chlorine
Demagging to be Achieved by July 1, 1977 4
Effluent Limitations for Treated Waste
Water from Residue Milling to be Achieved
by July 1, 1977 6
Summary of Features of Plants Visited 11
Production of Aluminum Alloys by Secondary Smelters
(1970 6 1971) 14
A.S.R.I. Aluminum Scrap Classifications 20
Consumption of New and Old Scrap in the United
States in 1970 and 1971 by Secondary Smelters
22
Secondary Aluminum Smelters A. Those Claiming No
Process Water Use 29
Secondary Aluminum Smelters B. Smelters Using Water
for Ingot Ceding Only 30
Secondary Aluminum Smelters C. Water Used for
Scrubbing and/or Cooling 33
Secondary Aluminum Smelters D. Water Used for
Dross Processing, scrubbing and/or Cooling 35
Cooling Water Disposal Practices 41
Cooling Water Usage by Secondary Smelters 41
Character of Cooling Waste Water (Plant C-7) 42
Character of cooling Waste Water (Plant D-6) 43
Character of Cooling Waste Water (Plant B-11) 44
Fume Scrubbing Waste Water - Generation and
Disposal Practices 46
Quantities of Waste Water Generated in the Wet
Scrubbing of Chlorination Fumes 47
Character of Waste Water from Chlorination Fume
scrubbing (Ko Treatment) 43
Residue Waste Water Generation and Disposal
Practices 51
viii
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Number TABLES (continued)
20 Quantities of Waste Water Generated in the Wet
Milling of Residues per Ton of Aluminum Recovered
21 character of Settled Waste Water from Residue
processing
22 pollutants Subject to Effluent Limitations
23 Magnesium Removal Practice (Demagging) Used by
Secondary Aluminum Industry
24 Treatment of Effluents froir Fume Scrubbing
(Discharged as Noted)
25 Treatment of Effluents from Fume Scrubbing
(No Discharge)
26 Effect of Neutralization and Settling on
Scrubbing Waste Water Loading
27 Cost Benefit of Control and Treatment for
Waste Water from Metal Cooling
28 Cost Benefit of Control and Treatment for
Waste Water from Fume Scrubbing
29 Cost Benefit of Control and Treatment for
Waste Water from Residue Milling
30 conversion Factors
53
54
58
76
77
78
80
92
97
99
131
IX
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SECTION I
CONCLUSIONS
For the purpose cf establishing effluent limitations guidelines
and standards of performance, the aluminum segment of the
nonferrous metals manufacturing point source category was divided
into three subcategories: the bauxite refining subcategory, the
primary aluminum smelting subcategory, and the secondary aluminum
smelting subcategory. This report deals with the secondary
aluminum smelting subcategory.
Secondary aluminum smelting is a single subcategory for the
purpose of establishing effluent limitations guidelines and
standards of performance. The consideration of other factors
such as age and size of the plant, processes employed,
geographical location, wastes generated, and waste water
treatment and control techniques employed support this
conclusion. The similarities of the wastes produced by secondary
aluminum smelting operations and the control and treatment
techniques available to reduce the discharge of pollutants
further substantiate the treatment of secondary aluminum smelting
as a single subcategory. However, guidelines for the application
of the effluent limitations and standards of performance to
specific facilities do take into account the size of the
secondary aluminum smelting facility and the mix of different
recovery processes possible in a single plant.
Approximately 10 percent of the secondary aluminum smelting
industry is currently discharging directly to navigable waters.
The majority of the industry discharges effluents into municipal
treatment works, usually with some treatment. It is concluded
that the industry can achieve requirements set forth herein for
metal cooling, fume scrubbing, and wet residue milling effluents
by July 1, 1977, by the best practicable control technology
currently available. Those plants not presently achieving the
July 1, 1977, limitations for all three operations would require
an estimated capital investment of $20 per annual metric ton and
an increased operating cost of about $9.4 per annual metric ton
of aluminum produced. It is estimated that to decrease the
discharge of pollutants for all three operations to the July 1,
1983, level would require a capital investment of $140 per annual
metric ton with an estimated operating cost of $3.7 per annual
metric ton of aluminum produced.
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SECTION II
RECOMMENDATIONS
In the secondary aluminum industry, waste water 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. Waste waters containing very
large levels of suspended and dissolved solids are produced
during the wet milling of residues containing aluminum.
Best Practicable Control Technology
Currently Available
Metal Cooling Waste water
The best practicable control technology currently available for
metal cooling waste water is air cooling or continuous recycling
of cooling water with periodic removal, dewatering, and disposal
of sludge. The effluent limitation for metal cooling waste
water, to be achieved by existing sources by July 1, 1977 through
the application of the best practicable control technology
currently available, is no discharge of process waste water
pollutants to navigable waters.
Fume Scrubbing Waste Water
The best practicable control technology currently
applicable to effluents from chloride fume scrubbing
removal processes using chlorine) is pH adjustment and
The best practicable control technology currently
applicable to effluents from fluoride fume scrubbing
removal processes using aluminum fluoride) is pH a
settling, and total recycle of water.
available
(magnesium
settling.
available
(magnesium
djustment,
The effluent limitations for chloride fume scrubbing waste water,
to be achieved by existing sources by July 1, 1977, through the
application of the best practicable control technology currently
available are given in Table 1. The effluent limitation for
fluoride fume scrubbing waste water, to be achieved by existing
sources by July 1, 1977, by the application of the best
practicable control technology currently available is no
discharge of process waste water pollutants to navigable waters.
Residue Milling_Waste .Water
The best practicable control technology currently available for
residue milling waste water is pH adjustment with settling and
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TABLE 2. EFFLUENT LIMITATIONS FOR TREATED WASTE
WATER FROM RESIDUE MILLING TO BE ACHIEVED
BY JULY 1, 1977, BASED ON THE BEST PRACTICABLE
CONTROL TECHNOLOGY CURRENTLY AVAILABLE
Effluent Limitations
Effluent
Characteristic
TSS
Fluoride
Ammonia(as N)
Aluminum
Copper
COD
pH
TSS
Fluoride
Ammonia(as N)
Aluminum
Copper
COD
pH
Average of daily values for 30 con-
secutive days shall not exceed
Metric units (kilograms per 1,000 kg
of product)
1.5
.4
.01
1.0
.003
1.0
Within the range of 7.5 to 9.Q
English units (pounds per 1,000 Ib
of product)
1.5
.4
.01
1.0
.003
1.0
Within the range of 7.5 to 9.0
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the judicious application of water recycle to minimize the volume
of waste water discharged.
The effluent limitations for residue milling waste water to be
achieved by existing sources by July 1, 1977 through application
of the best practicable control technology currently available
are given in Table 2.
Best Available Technology Economically Achievable
The best available technology economically achievable for the
secondary aluminum smelting subcategory is equivalent to the
following:
(a) Metal Cooling Waste Water
(1) The use of air cooling.
(2) The use of water cooling, so that
all water is evaporated.
(3) The total reuse and recycle of cooling water by
use cf settling and sludge dewatering.
(b) Fume Scrubber Waste Water
(1) The use of aluminum fluoride for magnesium removal.
(2) The use of one of the alternative processes such
as the Alcoa process, the Derham process or
the Tesiscrb process.<*>
(c) Residue Milling Waste Water
(1) Dry trilling.
(2) A water recycle, evaporation, and salt reclamation
process.
The effluent limitations for the secondary aluminum smelting
subcategory, to be achieved by existing sources by July 1, 1983,
by the application of the best available technology economically
achievable is no discharge of process waste water pollutants to
navigable waters.
Best Available Demonstrated Control Technology
The best available demonstrated control technology, processes,
operating methods cr ether alternatives is equivalent to the
following technologies:
(a) Metal Cooling Waste Water
(1) The use of air cooling.
(2) The use of water cooling, so that all water
is evaporated.
(3) The total reuse and recycle of cooling water
by use of settling and sludge dewatering.
(b) Fume scrutber Waste Water
(1) The use of chlorine for magnesium
removal with wet scrubbing.
(2) The use of aluminum fluoride for
magnesium removal.
(1) Mention of trade names or specific products does not constitute an
endorsement by the Environmental Production Agency
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TABLE 1. EFFLUENT LIMITATIONS FOR TREATED FUME
SCRUBBER WASTE WATER GENERATED DURING CHLORINE DEMAGGING
TO BE ACHIEVED BY JULY 1, 1977, BASED ON THE BEST
PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
Effluent Limitations
Effluent
Characteristic
TSS
COD
PH
TSS
COD
pH
Average of daily values for 30 con-
secutive days shall not exceed
Metric units (kilograms per 1,000 kg
magnesium removed)
175
6.5
Within the range of 7.5 to 9.Q
English units (pounds per 1,000 Ib
magnesium removed)
175
6.5
Within the range of 7.5 to 9.0
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(c) Residue Milling Waste Water
(1) Dry rrilling.
(2) A water recycle, evaporation, and salt reclamation
process.
The standard of performance for new sources in the secondary
aluminum smelting sutcategory is no discharge of process waste
water pollutants to navigable waters. An exception to the
standards of performance is provided for new sources using
chlorine in the magnesium removal process to allow the discharge
of process waste water pollutants from the magnesium removal
process only. The standards of performance for such sources
should be identical to the effluent limitations presented in
Table 1.
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SECTION III
INTRODUCTION
£U£E°.se and Authority
Section 301 (b) of the Act requires the achievement by not later
than July 1, 1977, of effluent limitations for point sources,
other than publicly cwned treatment works, which are based on the
application of the test practicable control technology currently
available as defined by the Administrator pursuant to Section
30U(b) of the Act.
Section 301 (b) alsc requires the acievement by not later than
July 1, 1983, of effluent limitations for point sources, other
than publicly owned treatment works, which are based on the
application of the best available technology economically
achievable which will result in reasonable further progress
toward the goal of eliminating the discharge of all pollutants,
as determined in accordance with regulations issued by the
Administrator pursuant to Section 304 (b) to the Act.
Section 306 of the Act requires the achievement by new sources of
a Federal standard of performance providing for the control of
the discharge of pollutants which reflects the greatest degree of
effluent reduction which the Administrator determines to be
achievable through the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives, including, where practicable, a standard
permitting no discharge of pollutants.
Section 304(b) of the Act requires the Administrator to publish
within one year of enactment of the Act, regulations providing
guidelines for effluent limitations setting forth the degree of
effluent reduction attainable through the application of the best
practicable control technology currently available and the degree
of effluent reduction attainable through the application of the
best control measures and practices achievable, including
treatment techniques, process and procedure innovations,
operation methods and other alternatives. The regulations
contained herein set forth effluent limitations guidelines
pursuant to Section 304 (b) of the Act for the secondary aluminum
smelting subcategcry of the nonferrcus metals category.
Methods Used for Development of Effluent Limitations
Guidelines and Standards of Performance
The effluent limitations guidelines and standards of performance
contained herein were developed in the following manner. The
secondary aluminuir industry, a segment of the aluminum subcate-
gory of the nonferrous metals industry, was first categorized for
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the purpose of determining whether separate limitations and
standards would be appropriate for the different subsegments.
Such categorization was based on water usage, raw materials pro-
cessed, products produced, manufacturing, plant age and size, and
other factors.
General information was obtained on the industry and detailed
information on 69 plants (81 percent) of an estimated 85 domestic
secondary aluminum srrelting plants, The sources and types of
information consisted of the following:
0 Applications to the Corp of Engineers for permits to
discharge under the Refuse Act Permit Program (RAPP) were
obtained for four plants. These provided data on
characteristics of intake and effluent waters, water usage,
raw materials and daily production.
0 Information for the selection of plants for on-site visits
was made through a telephone survey of 69 plants. Data were
obtained on the raw materials used, products produced, type
of furnaces, pretreatment of scrap, methods used for
magnesium removal, degassing methods, air pollution control
methods, solid waste management practice, waste water
management methods and disposition, and availability of cost
data for treatment operations.
0 An on-site inspection of nine plants, selected from the group
above, provided detailed material and water flow information.
Data on waste water treatment equipment and operational
costs, as well as information on process alternatives, were
obtained. Analytical data for various waste streams within
the plant were also compiled whenever available. Table 3
summarizes the features of these plants.
The raw waste water characteristics were identified. This
included: 1) the source of the waste water, 2) the volume of the
waste water, 3) the points of discharge, and 4) the waste water
constituents. The constituents of the waste water, which should
be subject to effluent limitations, were identified. Control and
treatment technologies existing for each type of waste water
produced were identified. This included both inplant and end-of-
process technologies. Also, the effluent levels resulting from
the application of each treatment and control technology were
identified. Limitations, reliability, and problems of such
technology were also identified.
The effects of the application of such technologies upon other
pollution problems, including air, solid waste and noise, were
also identified in crder to establish nonwater environmental
impacts. The energy requirements, as well as the costs of the
application of such technologies, were identified.
This information, as outlined above, was evaluated to determine
what levels of technology constituted the best practicable
10
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TABLE 3. SUMMARY OF FEATURES OF PLANTS VISITED
Features
Operations
Smelters
Refine
A1F
Plants
Residue Mills
Dry
Wet
Air Pollution Controls
Demagging Fumes
Wet scrubber control
Dry control
Milling Dust
Dry
Plant Capacities, thousand metric tons melted aluminum ger month
0.50 or less 1
0.50-1.00 3
1.00-2.00 2
over 2.00 3
Raw Materials
Scrap (solids) only
Residues (dross, slag, etc.) only
Both scrap and residues
Plant Locations
Midwest
East
South
11
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control technology currently available, the best available
technology economically achievable, and the best available
demonstrated contrcl technology, processes, and operating methods
or other alternatives. In identifying such technologies, 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, the nonwater quality environmental impact and other
factors were identified.
Data for identification and analyses were derived from several
sources, including EPA research information, information from
state water pollution control agencies, trade organizations, and
the trade literature. Supplemental data were obtained by making
telephone surveys and site visits to interview personnel and
obtain and analyze samples of water streams at exemplary
secondary aluminum srrelters.
General Description of the Secondary Aluminum Industry
The secondary aluminum subcategory is defined for the purposes of
this document as that segment of the aluminum industry which
recovers, processes, and remelts various grade of aluminum
bearing scrap to produce metallic aluminum or an aluminum alloy
as a product. Although primary aluminum producers recover
captive scrap generated from their own operations, they are not
included in this sutcategory. The secondary smelters buy scrap
in various forms on the open market as their raw material.
Companies that cast cr alloy remelt billets, ingots, or pigs, and
whose raw materials, processes, and products differ from those of
secondary aluminum smelters are not included in this subcategory
of the nonferrous metals manufacturing category of sources.
The scrap raw material used by secondary smelters can be divided
into two categories, solids and residues. The solids are
principally metal and include borings and turnings, new clippings
and forgings, old castings and sheet, and aluminum containing
iron. Residues include (1) dross and skimmings from melting
operations at foundries, fabricators and from the primary alumi-
num industry and (2) slag formed during secondary smelting
operations. It is the task of the secondary aluminum industry
smelters to reprocess the scrap, so that it can be used for
consumer goods. In sc doing, they are recycling a moderately
priced metal, which otherwise would become a solid waste. Such
recycling conserves both natural resources and energy since only
5 percent of the energy needed to produce virgin aluminum is
required tc produce an equal amount of secondary aluminum.
The scrap must undergo a presmelting process before it is con-
verted to the various aluminum alloys. This is done primarily
through selective scrap mixing and blending during melting.
12
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Further refining is attained by chemical treatment and/or
addition of alloying metals.
The types and amounts of products of the secondary aluminum
industry as reported by the Bureau of Mines are listed in Table
4.
i
About 90 percent of metal supplied by the secondary aluminum
producers goes to foundries. Of this amount, 60 percent is con-
sumed in die castings and 25 percent as permanent mold and sand
castings, and in alloy additions to zinc die castings. Most
alloys sold by secondary smelters to the casting industry fall
into the following categories:
(1) Aluminum-copper alloys.
(2) Aluminum-copper-silicon alloys.
(3) Aluminum-silicon alloys.
(4) Aluminum-magnesium alloys.
(5) Aluminum-magnesium-silicon alloys.
These are sold primarily as 15-pound and 30-pound ingots. Larger
quantities are sold in 1000-pound sows or as hot molten alloy.
Although not considered alloy production, some scrap (10 percent)
is melted to produce deoxidizer for use in steel mills either in
the form of shot cr notched bar. Secondary aluminum smelters
have been in operation since 1904, with major growth and
expansion periods in the 1920's and late 1940's and 1950's.
Their numbers have decreased over the last decade due to
industrial consolidation and technical obsolescence.
Most of the 85 plants currently producing secondary aluminum
metal are located near heavily industrialized areas, which give
them proximity to a supply of scrap and to their customers (see
Figure 1). 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. Most of these plants are located in the
Midwest, in or near the Chicago and Cleveland metropolitan areas
and in the Los Angeles area. The east coast has plants located
near the New York City - Philadelphia area. There are none in
the Rocky Mountain states.
These plants produced about 14 percent of the nation's aluminum
in 1970. Annual capacity is considerably above the level shown
for 1970 operations since, unlike primary plants, secondary
smelters do not operate around the clock and, thus, can step up
production by operating extra shifts. On a company basis, the
two largest secondary aluminum smelting companies supply 30
percent of the secondary aluminum produced and the next four
largest companies supply another 30 percent, for a total of 60
percent production by the six largest companies.
Since most secondary smelters offer essentially the same product
line, there is no competitive advantage to be realized from
product offering. In addition, since the products are produced
according to rigid trade specifications, product differentiation
13
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TABLE 4. PRODUCTION OF ALUMINUM ALLOYS BY SECONDARY SMELTERS
(1970 and 1971)
1970
Production,
metric tons
Pure aluminum (Al minimum 97.0 percent)
Aluminum- s i 1 icon :
95/5 Al-Si, 356, etc.. (maximum Cu 0.6 percent)
13 percent Si, 360, etc. (maximum Cu 0.6 percent)
Aluminum-silicon (Cu 0.6 to 2 percent)
No. 12 and variations
Aluminum- copper (maximum Si, 1.5 percent)
No. 319 and variations
Nos. 122, 138
AXS-679 and variations
Aluminum-silicon-copper-nickel
Deoxidizing and other destructive uses:
Grades 1 and 2
Grades 3 and 4
Aluminum-base hardeners
Aluminum-raagne s ium
A luminum- z inc
Miscellaneous
Total
64,295
15,338
42-031
5,342
7,722
741
45,068
918
280,206
15,888
15,658
9,377
4,323
710
4,685
21,871
534,169
Production,
short tons
70,873
16,907
46,331
5,889
8,512
817
49,679
1,012
308,875
17,508
17,260
10,336
4,765
783
5,164
24,109
588,820
1971
Production,
metric tons
77,351
16,543
39,882
4,82u
6,032
425
42,580
1,215
292,210
15,187
14,307
7,542
3,885
799
3,750
23,689
550,169
Production,
short tons •
85,265
18,236
43,962
5,313
6,649
469
46,882
1,339
322,106
16,741
15,771
8,314
4,282
881
4,134
26,113
606,457
Source: U.S. Bureau of Mines
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Figure
,
1.
of se
alumina shelters,
-------
can KCOmmit*ents
can become an
in
hardship in tf^ *«*«ct
* in ^mes of se-
scrap.
ve.
the
Long-
Price
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SECTION IV
INDUSTRY CATEGORIZATION
Introduction
This section describes the scope of the secondary aluminum
smelting industry. Included are technical discussions of the raw
materials used, methods of production, and products produced.
Rationales for possible subcategorization of the industry for the
establishment of separate effluent limitations guidelines are
also discussed.
Objective of Categorization
The objective of industry categorization is to identify and
examine the factors in an industry which might serve as bases for
the further subdivision of the industry for the purpose of
establishing effluent limitations and standards of performance.
Definition of the Industry
The secondary aluminum industry is herein defined as that portion
of SIC 3341 (Secondary Nonferrous Metals) which recovers,
processes, and rerneIts 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.
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) Presirelting preparation.
(3) Charging, smelting, and refining.
<4) Pouring of the product line.
The last three operations vary somewhat throughout the industry,
with • resultant variations in water usage and waste water
generation. Figure 2 gives a generalized flowsheet of secondary
aluminum industry operations. The flowsheet includes initial
collection of aluminum bearing scrap, presmelting scrap
17
-------
TABLE 5. A.S.R.I.ALUMINUM SCRAP CLASSIFICATIONS
CLASSIFICATIONS:
to
o
1. NEW PURE ALUMINUM CLIPPINGS: Shall consist or
new, clean, unalloyed sheet clippings and/or aluminum
sheet cuttings, free trom oil. grease, foil and any other
foreign substance and from punching; less than one-half
inch in size.
2. NEW PURE ALUMINUM WIRE AND CABLE: Shall
consist of new. c'eart, unalloyed aluminum wire or cable
free from hair wire, wire screen, copper, iron, insulation
and any other foreign substance.
3. OLD PURE ALUMINUM WIRE AND CABLE: Shall
consist of old, unalloyed aluminum wire or cable contain-
ing not over 1 per cent free oxide or dirt and free from
hair Mire, wire screen, copper, iron, insulation and any
Other foreign substance.
4. SEGREGATED NEW ALUMINUM ALLOY CLIP-
PINGS: Shall consist of new, clean.unegated aluminum
clippings of one specified aluminum alloy only, freo
from hair wire, wire screen, foil, can stock, stainless
steel, iron. dirt, oil, grease and any other foreign
substance, and from punching! less than one-half inch
in size.
5. MIXED NEW ALUMINUM ALLOY CLIPPINGS: Shell
consist of new, clean, uncoated aluminum clippings of
two or more alloys, none of which shall be allays
containing zinc in excess of .25% I such as 7.000 series],
tin in excess of .30%. and/or magnesium in excess of
2.80%, To be free from hair wire, wire screen. _f oil, tan
stock, stainless steel, iron, dirt, oil, grease and/or any
other foreign substance. Shall not contain punch ings
less than one-half inch in me.
& MIXED LOW COPPER ALUMINUM ALLOY CLIP-
PINGS: Shall consist of new, clean, u negated aluminum
clippings of two or more alloys, none of which shall
exceed a maximum of .40% copper. .25% zinc, .30% tin,
and 2.8O% magnesium; and shall be free from tin-
containing alloys, hair wire, wire screen, stainless steel,
iron, dirt, oil, grease and/or any other foreign substance,
and shall be free from punching! less than one-half inch
in size.
7. SEGREGATED OLD ALUMINUM ALLOY SHEET:
Shall consist of clean, uncoated. old aluminum sheet of
one specified alloy only, free from wrecked airplane
sheet, hair wire, wire screen, foil, stainless steel, iron,
,dlrt, oil. grease and any other foreign substance.
8. MIXED OLD ALLOY SHEET: Shall consist of clean,
uncoated, old alloy sheet aluminum of two or more
alloys not to contain wrecked airplane inset and to ba
free from hair wire, wire screen, oil cans. foil, food or
beverage containers, stainless steel, iron, dirt, oil, grease
and all other foreign substances.
9. SCRAP SHEET AND SHEET UTENSIL ALUMINUM:
Shall consist of clean, uncoaled manufactured theet
aluminum, free from stainless steel, iron, dirt, or any
other foreign substances and to be free from hub caps,
radiator shells, airplane sheet, foil, food or beverage
containers, pie plates, oil cans, bottle caps, and lawn
furniture*
10. SEGREGATED NEW ALUMINUM CASTINGS. FORC-
INGS, AND EXTRUSIONS: Shall consist of new. dean,
uncoated aluminum castings, forging: and extrvsionjof
one specified alloy only and to be free from sowings,,
stain less steel, zinc, iron, dirt, oil, grease and any other
foreign substance*
11. MIXED NEW ALUMINUM FORCINGS AND EXTRU-
SIONS: Shall consist of clean, new, jncoated aluminum
forging* and extrusion! of two or more alloy*, none of
which shall be alloys containing zinc in excess of .25%
(such as 7.000 series!, tin .30% and/or magnesium in
excess of 2.80%. Shall also be free from saw ings, stainless
geel, zinc, iron. din. oil. grease and any other foreign
substance.
12. MIXED NEW ALUMINUM CASTINGS: Shall consist of
dean. new. uncoated alun
i castings of two or more
alloys, none of which shall exceed 3% zinc, .50% tin.
and/or magnesium in excess of 2.80%. Shall be free of
sawings. stainless steel, iron, dirt, oil, grease, and any
other foreign substances.
13. ALUMINUM AUTO CASTINGS: Shall consist of all
clean automobile aluminum castings of sufficient size to
be readily identified and to be free from iron, dirt, brass,
babbitt bushings, brass bushings and any other foreign
materials. Oil and grease not to exceed 2%.
14. ALUMINUM AIRPLANE CASTINGS: Shalt consist of
clean aluminum castings from airplanes and to be fret
from iron, dirt, brass, babbitt bushings, brass bushings
and any other foreign materials. Oil and grease not to
exceed 2%.
15. MIXED ALUMINUM CASTINGS: Shall consist of all
clean aluminum castings which may or may not contain
auto and airplane castings, but no ingots, and to be fra»
from iron, dirt, brass, bobbin and any other foreign
materials. Oil and grease not to exceed 2K.
IB. ALUMINUM PISTONS:
(a) CLEAN ALUMINUM PISTONS; Shall consist of
clean aluminum pistons to be free from struts,
bushings, shafts, iron rings and any other foreign
materials. Oil and grease not to exceed 2V
Ib) ALUMINUM PISTONS WITH STRUTS: Shall consist
of clean whole aluminum pistons with struts to be
free from bushings, shafts, iron rings and any other
foreign materials. Oil and grease not to exceed 2%.
Wbyspecial
arrangement* with purchase!.
28. COATED ALUMINUM (PAINTED OR PLASTIC
COATED. ETCJ: Should be sold by special arrange-
ment! with purchaser. Siding, awnings, and Venetian
blinds should each be packaged separately.
29. CONTAINERS OF ALL TYPES (OIL. FOOD. BEVER^
AGE. AEROSOL): Should be SOW by special arrange-
ments with the puichaaer, and should each be packaged
30. JTEMS NOT COVERED SPECIFICALLY BY ABOVE
CLASSIFICATIONS: Any new item which might appear
and which g not covered specifically by atxm» dassifi-
eations shouM be discussed and sold by special
arrangements wilh the purchaser.
-------
airplanes. Miscellaneous high iron scrap requires special
handling in sweating furnaces. Table 6 gives the consumption of
scrap by type of secondary smelter for the years 1970 and 1971.
The dealer sorts the collected aluminum scrap into groups of
similar composition and physical shape. Sheet, extruded
material, and castings are often baled into 3 x 6 ft bundles.
Some dealers briquette borings and turnings for shipment. High
iron scrap may be treated by the dealer to concentrate the
aluminum, or may te shipped directly to the smelter. The high
iron scrap is heated to above 760°C (1400°F) in a sloping hearth
or grate furnace, which is direct^fired by natural gas (a
"sweating furnace"). The aluminum melts, flows away from the
residual iron, and is cast into pigs (sweated pigs) or sows. In
many cases the various types of scrap are shipped loosely in
large bins.
Many secondary aluirinum smelters have accounts with scrap pro-
ducers and receive segregated shipments directly without dealer
handling. This does not mean that they take over the function of
a dealer, since their sources of scrap define the chemical
composition of the scrap they receive.
The collection, sorting, and transporting of aluminum scrap are
elements of the secondary aluminum industry relatively
unimportant to this study, because such functions are not part of
the secondary smelter operation and water was not used in these
operations. Conceivably a dealer operating a sweat furnace to
recover high iron aluminum may use a wet scrubber to reduce
fumes, although no such case is Known, Such operations typically
employ an afterburner to reduce air pollution.
Presmeltinq^Preparation
The presmelting preparation of scrap varies in accordance with
the type of scrap being handled. Some smelters do considerable
preparation to upgrade and segregate scrap. Those with more
limited facilities bypass some of the preparation steps and rely
upon the furnace tc burn up combustible contaminants. Here,
contaminating metallics taken up into the melt can be diluted
with relatively pure scrap, while free iron can be raked from the
furnace bottom. New clippings and forgings are largely
uncontaminated and require little presmelter treatment other than
sorting, either iranually or mechanically to remove obvious
non-aluminum material. This scrap is stored in tote boxes and
charged directly intc the furnace forewell.
Borings and turnings are often heavily contaminated with cutting
oils. In spite of this fact, some plants charge this material
directly into the forewell. Most, however, pretreat this
material. Typically, this material is received in long,
intertwined pieces and must be crushed in hammer mills or ring
crushers. The crushed material is then fed into gas or oil-fired
rotary dryers to remove cutting oils, grease, and moisture.
21
-------
TABLE 6. CONSUMPTION OF NEW AND OLD SCRAP IN THE
UNITED STATES IN 1970 AND 197l(a) BY
SECONDARY SMELTERS
1970
Consumption
metric tons short tons
New scrap:
Solids
Segregated low copper (Cu max. 0.4%)
Segregated high copper
Mixed low copper
High zinc (7,000 series type)
Mixed clips
J^ Borings and turnings
Foil, dross, skimmings, and other
Old Scrap (solids)
Sweated pig (purchased for own use)
98,769
98,769
12,154
58,904
8,278
46,276
145,150
100,886
113,985
42,976
(108,874)
(108,874)
(13,397)
(64,930)
(9,125)
(51,010)
(160,000)
-------
After drying, the material is screened for removal of fines, with
the oversize passing through a magnetic separator to remove tramp
iron. The undersize material would contribute excessive oxides
if charged into the furnace and is often sold as pyrotechnics.
Of the 69 secondary smelters surveyed in the study, ^3 process
residues (dross, slags, skimmings, etc.). In addition to 10 to
30 percent metallic aluminum, these residues contain oxides,
carbides, 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, in attrition or ball
mills, screened to remove the fines, and passed through a
magnetic separator tc remove any ircn. Large amounts of dust are
created in this circuit and provide a source of air pollution.
Normally, the dust emissions are controlled by passage through
baghouses. Wet dust collection is done at two of the plants
surveyed processing dross. The dry residue waste, after aluminum
removal, is piled en the plant site in the open. Markets for the
high alumina material exist and are being developed.
Six of the 23 plants processing residues use wet techniques.
Generally, the raw material is first fed into a long rotating
drum. Water is passed through the drum 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 screening
undersize are all sources of water pollution.
In some plants, sheets and castings may be charged directly into
the reverberatory forewell, as received. In most cases, this
category of scrap goes to crushers, which reduce it to small
dimensions. The crushed material is passed along vibrating
screens and magnetic separators to remove pulverized nonmetallics
and free iron, respectively.
Aluminum scrap containing considerable amounts of iron generally
is pretreated to eliminate the iron. This may consist of
crushing followed by magnetic separation or, more commonly,
removal in a sweating furnace. The operation of the sweating
furnace has been previously described. Fumes from the furnace
generally are passed through an afterburner before being emitted
to the atmosphere.
In summary, of the various presmelter treatments employed, only
the wet processing of drosses and slags appears to provide a
source of water pollutants.
Smelting
Generally, the smelting of aluminum scrap with reverberatory
furnaces consists cf seven operations or tasks. These are
23
-------
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. There is some variability in the
secondary aluminum industry as to precise techniques used in each
step. These variations and their contribution to waste and
environmental effects are discussed.
Charging. Scrap may be charged continuously into the furnace,
with simultaneous pouring, or may be loaded in batches. De-
oxidant producers, net particularly concerned about the exact
composition of the irelt, often use continuous loading. Specifi-
cation alley producers, however, need to maintain a critical
compositional range through selective melt additions and, thus,
are confined to batch loadings, often residual melt ("heel") is
left in the reverberatory to facilite melting of the new charge.
This results in a shortened heating cycle.
Forklifts or front-end loaders are used to charge the furnace
through the forewell with the various types of scrap. Depending
on the capacity of the furnace (9100 to 82,000 kg), it takes 4 to
75 hours to fully charge a furnace, with the average being 24
hours. Each complete smelting cycle is called a heat. The time
required for each heat is dependent on the materials charged,
size and design of furnace, heat input, fluxing procedures, and
alloying practices.
The addition of scrap into the fcrewell is accompanied by varying
amounts of fuming and smoke generation, depending on the
cleanliness of the scrap as it contacts the molten metal. The
forewell area is scrretimes hooded and vented into an afterburner
for fume and smoke cleanup. The absence of moisture during
charging is necessary for safety reasons. No water is used
during this operation.
Fluxing. The addition of a covering flux to the molten aluminum
melt forms a barrier for gas absorption and oxidation of the
metal. The flux also reacts with ncnmetallics, 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 seme combination containing one or more of the
following: sodium chloride, potassium chloride, calcium
chloride, calcium fluoride, aluminum fluoride, and cryolite. A
common flux mixture is 47.5 percent NaCl, 47.5 percent KC1, and 5
percent cryolite. At the melting point of aluminum, the fluxes
usually range from a tacky semisolid to a liquid depending on the
composition of the mixture and the technique used to remove it
from the melt.
The amount of flux used depends primarily on the material
charged. Scrap containing a relatively large surface area, such
as borings and turnings, creates large amounts of oxides and
24
-------
requires proportionally larger amounts of flux. The flux
generally is added along with the aluminum scrap in amounts from
less than 10 percent to 33 percent by weight of the material
charged.
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. These
additions are usually scrap, which is high in the concentration
of the desired element or, as in the case of silicon, in the pure
state. These are added to the forewell and stirred into the melt
with an inert gas (N2). The addition of the alloying agents and
the stirring produces no solid waste and only minor amounts of
fumes and dust, that are removed from the working area by the
hoods over the forewell.
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.
Mixing is performed nearly continuously in the reverberatory
furnace. Mixing often does double duty and serves as a degassing
operation. In such cases a mixture of nitrogen and chlorine (90
percent-10 percent) is often used. The mixing operation employs
no water and produces no solid wastes. Only when the mixture of
nitrogen and chlorine is used are fumes generated.
Magnesium Removal (pemagqinq)* 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 cr 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
aluminum chloride or aluminum fluoride present in excess
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 mere aluminum dilution or more of the metal.
Chlorination, the methcd preferred by the industry for demagging,
is performed at temperatures between 760 and 816°C (1400 and
1500°F). As a rule of thumb, the reaction requires 3.5 kg of
25
-------
chlorine per kg of magnesium removed. Elemental chlorine gas is
fed under pressure through tubes cr lances to the bottom of the
melt. As it bubbles through the melt it reacts with magnesium
and aluminum to form chlorides, which float to the melt surface
where they combine with the fluxing agents and are skimmed off.
Because magnesiuir 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 aluirinum chloride by magnesium becomes less
likely, and the production of aluminum chloride, a volatile
compound, becomes significant. The aluminum chloride escapes and
considerable 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
4.3 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 treated) and solid waste problem
exist.
Some operators in the secondary industry are little concerned
with the magnesium content of their product, as the deoxidant
manufacturers, and they make no attempt at removing it. They,
thus, do not contend with the magnitude of fumes that the de-
maggers 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 in the forewell, usually with a perforated ladle or similar
device, that permits molten metal to drain back into the
forewell. This is done 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. If stored
in the open, it is a source of ground and runoff water
contamination, because of contained soluble salts (NaCl, KC1,
MgCl2). During dress 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 cr water vapor in the air, release
hydrocarbons and ammonia to the atmosphere. The ammonia also may
become a component of water pollution.
26
-------
Pouring _ and _ Cooling. After the furnace has been completely
charged, the specification composition reached by blending and
demagging, and the melt degassed and skimmed, the molten metal is
cooled to around 732°C (1350°F) fcr pouring. Pouring practices
employed and the related water usage ty any given smelter will,
of course , be dep endent on the company f 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 aluminuir industry is specification alloy ingots to be
used by foundries for casting. Most smelters concentrate on a
few of the basic alleys. Normally automatic casting methods are
used to fill the ingct 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 hct 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, fclcwn with a water mist-air mixture, thus
generating no waste water. Eleven of 69 plants canvassed are
currently air cooling their ingots. The water used for cooling
may be sent to a cooling tower and recirculated, or it may be
used only cnce and discharged. 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 U54 kg (1COO pound) billet logs. The long cylindrical
billet molds are 7 tc 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.
Water lines inside the molds cool the billets. The billet logs
are then removed and cut into shorter two foot sections. The
cooling water is generally cooled and reused, as is the case for
ingot cooling.
. Metal . In some cases, hct metal is tapped from the
reverberatory furnace into preheated portable crucibles. The
crucibles are sealed, placed on a flat bed truck and transported
directly to the customers for use. Presently, crucibles with up
to 6,810 kg (15,OOC It) capacity are used.
Notched Bar. Notched bar is used as a deoxidant by the iron and
steel industry and is normally cast in various 0.9 to 2.3 kg (2
to 5 Ib) shapes.. Four grades are produced, each grade having a
different aluminum content. Notched bar molds are cooled, either
27
-------
with water sprays, internal water lines, or with air. The
used may or may not te cooled and recirculated.
water
Shot. Shot is also used as a decxidant and comes in various
compositional grades. Shot 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, bcrcn, 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.
Industry Categorization
A survey was made of the secondary aluminum industry, which
covered such factors for subcategorization as raw materials used,
product line, processes employed, water usage, plant age, and
plant capacity. Sixty-nine plants, cut of an estimated total of
85, were surveyed. Nine plants were visited by interviewing
teams. The results of the survey indicate that the secondary
industry should be considered as a single category. Rationale
for this judgment is given below.
Results of Industry Inventory
A portion of the information obtained in the industry survey of
69 plants is tabulated in Tables 7 through 10. Respectively,
these tables contain data on plants generating no waste water
(seven each), plants generating only cooling waste water (28
each), plants generating waste water from fume scrubbing and/or
cooling operations (26 each), and plants generating waste water
from the wet processing of residues and/or fume scrubbing and
cooling (eight each). Categorization of smelters on the basis of
waste water generation is not possible, because a given smelting
plant may have any combination of the three waste streams. A
28
-------
H
o
§
at
- £
OH-
M g.
t-> (0
O«
I-' *J (
fcru-
.(
M O 3 O
o-t w
-~.ff.MW
V M r
-------
TABLE 8. SECONDARY AUMINUH SHELTERS B. SHELTERS USING WATER FOR INGOT COOLING ONLY
Plant Raw
Company Age.Trs Employees Materials
... - - • Solids, new
1 0.15-0.20x
106/mo
_ - ~ " Irony Scrap
_ - - •- Solids
O.exlO^b/Bto
=_A - Solids
B~* 7xl06lb/«.
B-S - - Solids
Dross,
12x10 lb/mo
U> B-6 - Solids
0 3.3xlOtllb/m»
g_7 - - Solids
7xl06lb/«o
B-8 - - Solids
Own Slag
2.9xl06lb/mo
B-9 - - Solids ...
B-IB - - solids.
2.3x10 lb/mo
B-ll 45 - Solids
Dross
Slag
20x10 lb/mo
B-12
40 95 Solids
Cu
' Zn
Products
Deox
Shot
Bar
Deox
Shot
Spec Alloy
Ingot
Billet Alloy
6.0 x 106lb/mo
Spec Alloy
Ingot
10x10 lb/mo
Spec Alloy
Ingot
3.0xHTlb/mo
Deox
Shot
Bar ,
6x10 lb/no
Spec Alloy
Ingot ,
2.5x10 lb/mo
Spec Alloy
Ingot
Die Cast
Alloy
Billets
Deox
Shot
Bar
1.5=2.0
xlO°lb/mo
Ingot
Process Water
Usage
u
t? -g H „ . Waitewater
Procea. Air « S S j» s 9 « Treatment ™.^.ffa
or Deoiag Pollution g g*J £gtj SB ""* B
Type Control £ Sa «<">» »S Current Future to
None Dly * "«lrc- Z«°
& Cool
»™* None •*" Recirc. Ground/6 mo.
Hone ,„,...
1000 gal
A1F Bon* * *tone Sanitary Sewer
g^^ Hone -h - Recirc. Sanitary Sewer
106gal
Alp Dry + Hone Recirc. Sanitary Sewer
3 City Approved
C1./A1F Dry -1- Recirc. Zero
2 3 Cooling
Hone Hone +• Recirc. Flood Sewers/
Colling 6 mo.
Cl Hone + Recirc. Own Het Hell
2 (Bag Bouse) Cooling
Soon
+ None Sanitary Sewer
None? None + Hone Fond
Hone Dry + None Recirc. River
80 F Winter
110 F Sua*er
A1F- None + ? - ?
-------
K- i e-
>- «• er o »
"I1" fj?*
rl B 3-1 s
OWMO
'ms-ffi
*• ri O O
M rf X
ff
o
w
OHM
• a v
M* »
uiort
« it .
M >
Oh-
OH«
'Dti
09« A
WOo
O M.
««.
i-- a
M ta
S ^
* A
fflK
.OOIO
• tt A
«P H o
H M
-------
TABLE 8. (Continued)
Company Plant Saw
.N ARC. Yrs. Ebolovees Material*
B_23 - ~ Solids
Dross
Own Slag
1.0xl06Ib/mo
B-24 - - Solids ,
4-4.5x10 Ib/mo
B-25 16 37 Solids ,
0. 65x10? lb/BO
tu 0.25x10 Ib/mo
IO remelted
B-27 20 4 Solids
0.4xl06lb/»o
B-28 97 50-75 Solids,
2.0x10 lb/M>
B-29 . , SolldB ,
0.75xl00lb/w>
Process Water
Usage
So
.0
Process Air .w 3 « "g • • "
or Deraag Pollution g °.£ Hun ** *•
Products Type Control * °* •*"** °
Spec Alloy V11^ Dry +
Ingot J *
IxlO lb/BO
"6000" spec Bone Hone +
i Alloy Ingot
5.5-6xl06lb/sto
Die Cast Alloy Hone Hone +
0.25xl06lb/Bo
Die Cast Ingot +
0.4xl06lb/no
Spec Alloy A1F, Dry +
Ingot
1.3xl06lb/BO
Deox
Shot
Bar ,
0.8x10 /»
Deox Hone Hone +
Shot
Bar
Hastewater
Treatment H«i.rnr
Current Future to
Hone - Sanitary Sewer
Bee Ire. - 7
Cooling
Recirc. Zero
Cooling
Hone Soil Surface
Recirc. Sanitary Sewer
Cooling
Sludge/
6 no
Recirc. Z«ro
Cooling
0.6-0.7x10
-------
££
t
• o
II
M
»*
8
» -•
M o n
o in
M t +
o1 n
• ft •
?l
1
M U
• O
Ul **
V p.
OS
M
•^,
5
A W
M Q
£ "
O
5
g
O
M
I
£°s
«Efr
c e>
M
•-.
g
on
• «i
K a.
S3
CMT.
•1
£
1"
z
1
M 1 T
M 1 C*
Ul
H in U " »
i_ • o * o o
81- Q. MO. O.
• u a « »
• Ul C*
M
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jr if
s
*•* g w w w
KI n M n (6
O a Ob (d
M MO O
tf fr* &*« X
O O B 3 7
o o
rj n p
M H M
1 1 1
v n M M H tn
t- 6 10 1 O
o a. M rv MB<
O>B tt <* ui a
f- B
k-> O M
— O>
8 o- e
' ? ?
V tn t- u H OT
C-TI K CO • -O
HO g 5 M «
O Wfl C-
I— H* W O K«
" ° g4"4 er«S
• 9 n 6 a
n o • n
O ft O
o o n
y M H-
! 1
?ln ui » In
o • ft o
• £ M E &
MB O C B
W B
w
•
in u M
•o . -D
it ui n
n M n
H f-
O MO
•5 ~ Ji "-
1- Q. M Q.
O C O Ul
B
» in MWBrt « -d ovi-oo • it a to j- j
fc K'S'S'5 S " fr & |p
I* * q |ll IV JJ P
S " .q o-
+ + +
O « o. 3?
*i ^ n it
ft Vt B n
eft f **
E C i
* ft & n
rt n » +
10 *" Ho
SB: o**& u!E»^
a M o n u g a
It H It H OQfl H
q 3 $ 3 o™ o
() ft W <
t* e1 PS
£•
"^
* o B* o 5 ?
t- h- ^ H ffl f
^j" 4 " °
« Q Dl o ft
3 3 B.
iv i» n
11 •
13
Cooling
Water
Air
Scrubber
Water
Dross
Processing
£
04
J g
a rt
(/I 9 rr
n n ft
&
cr
n
Discharge
to
h
cS
t K
«
-------
TABLE 9. (Continued)
Comp&tiy
C-16
C-17
018
C-W
C-20
W c'n
022
C-23
024
025
026
Plant Raw
AC*, yr» ba?loye*s Materials
— — Solids
2.7x10* lb/a«.
— — Solid*
>0.5xlO° IB/BO.
~ — Solids
8x10* lb/M.
— — Solld»
3.5x10* lb/BO.
DroH*
Own slag
— — Solids
4-5xl06 Ib/no.
Dross and own
slag. 2.5x10°
Ib/ao. as metal
— — Solids
2.(xl06 Ib/sn.
Dross and own
slog, 1.4 Ib/BO.
metal
— — Solids
4.3x106 Ib/ao,
— — Solids
3.0x10* lb/M>.
Druda • and own
sl-ig, 0.3x106
Ib/oo. wtal
— — Solids
2.2x10° Ib/MO.
•etal
IS 100 Solid*
l.SxlO6 Ib/s0.
IS 250-285 Solids
11-12x10* Ib/so.
Droa* and oun
•lag. 7x10*
Ib/ao.
DsBag
Products Type
Spec alloy Ingot Cl,
2.5xl06 lb/«o.
Spec Alloy tngot Clj
(high HK)
/«o.
Spec 4llo)T tngot Cl,
Hoi tea
Deox *bot
8. 6x10* lb/».
Process Water
Us ace
c
^
Air Pollution "32 n 1 £ 55 Wastevater
-. o • - ^ . S E Treatnenc Discharci-
Control o * 3 « a Q ». Cooling
Het * + None
Dry planned
Hat * * Recycled
Cooled
Cent.
Het * * Vaporltcd
Wet * * Recir.
Cooled
Wet + + Kooe
5000 gph
12 hr/day
Het + + Hone
5000 gph
Wet * + Hone
5000 gph
Wet + + Hone
5000 gph
Wet T ^ Kone
5000 gph
«« + + Non*
Dry
Wet + + None
pH control «nd Sanitary sever
settling O.SslO* jil/aj.
pH control Creek
Recycle cont.
Settling
Dlscharge/aa.
2000 gal
pK control Sanitary seuer
Alkaline
pH control Discharged to
Alkaline gcuimd
s°o* Sanitary sever
6600 gph
None Sanitary sever
3300 gph '
Son« Icperacablc lajooo
1000 gph
No" Sanitary aewer
3000 gph
N°n* Sanltaiy sever
3300 gph
pH control and River
settling
pH control Evaporation pood
Settling
Partially retire.
-------
TABLE 10. SECONnWIY AUWIHUM SHELTERS D. WATER USED FOR DROSS PROCESSING, SCRUBBING ARD/OR COOLING
Plant Raw
Conpany Age, yr* Employees Material*
D-l — — Droaa
Own slag
D-2
Drosa
Slags
3.0-4,5 x 10°
Ib/mo.
D-3 — — Droas
1-2 x 106 lb/
mo.
D-4 21 25-30 Droas
Own slag
3.75 x 10* lb/
OJ mo.
<_H
D~5 — -- Solids
Dross
Own slags
2 x 106 Ib/mo.
D-6 - ~ .Dross
Slags
8 x 106 Ib/mo.
Solids
2-2.5 x 106
Ib/mo.
D"8 — — Droas (10Z)
Slag
Solids •
3.75 x 10°
Ib/mo.
D-9
30 250 Dross
2.5 x 106 lb/
mo. Al
Solids
3.5-4.0 * 106
Ib/mo,
Dentag Air Pollution
Products Tyoe Control
Alloy ingot None Dry and wet
AljOj hot
topping
Alloy sows None Wet and dry
1.2 x 106 lb/
mo.
Alloy sows Rone Wet
0.75 x 106 Dry planned
Ib/mo.
Alloy pig None Rone
0.5 x 106 lb/ Dry being
mo. in* tailed
A 1203 hot
topping
Related products
Spec alloy Cl- Wet
ingot
1.75 x 106 lb/
mo.
Spec alloy Ingot Cl- Dry
RSI e
3.5 x 106 lb/
no.
Spec alloy ingot Cl, Wet
3 x 106 Ib/mo.
0
Spec alloy ingot Cl- Het
901
Molten 10%
5.7 x JO6 lb/
mo.
Process Water Wasteuater
llsaes Treatment
us a ta v
a -o c jj
3 JS « • -H £1 B •
,-1 3 • U •-< 3 « O
8MU O O O W OO
•rfO Mb O O W *<
O ^ Cl) HOI U M QO.
None None + -- — Recirc. dis-
charge/6
months
Bag house
Planned
None + •+• Venturi with
Wet milling recirc. & sludge
removal/8 ht
lime pB control
Solids
removal
Rone Bone + — ~ Settling
Wet milling Floe.
agent ph
control
ponds
Hone Hone + — — Settling
Wet milling Floe.
agent
ponds
sludge
recirc.
•*• + -t- Rone pB control
80 gpm 60 gpm Settling
2 hr/ 6 hr/d.y "*
day v
+ 4- + Bone Hone Ponds
Product pH control
washing
+ + + None pH control Settling
settling ponds
ponds
+ •*• +' Bone pB control Settling
Alkaline ponds
Settling
poniJs
Discharged
to
Evaporation pond
Sludge to pood
1000 g/8 hrs
Dissolved salts
Pond
River
River
Cooling to river
Scrub to sewer
Dr^ss wash to
pond
Cooling to sewer
Scrubber and
wash to ponds
Ponds
Sanitary sewer
-------
more useful approach for the purpose of developing effluent
limitations guidelines is to deal with the waste water streams
themselves. Three distinct streams may be characterized: (1)
cooling waste water, (2) fume-scrubbing waste water, and (3) wet-
residue milling waste water. Each stream has an associated unit
waste loading of pollutants per pound of product produced or
scrap processed. Each may also be associated with an appropriate
effluent limitations guideline. For example, the guidelines
would require a sirelter generating only cooling waste water to
maintain waste loadings under the established level for that
category. A smelter generating cooling, scrubber, and residue
milling waste waters would be required not to exceed its waste
loadings for each respective category of waste water under each
of the established levels.
Factors Considered for Categorization
Consideration was given to a number cf other factors for possible
use in subcategorizaticn of the secondary aluminum industry.
Factors taken into account include raw material processed,
product line produced, processes employed, plant age, plant size,
and air pollution control techniques. Upon application, each of
these factors leads to unmanageable ambiguities in
subcategorization, as described in the following paragraphs.
Raw Materials. The principle groupings of raw materials for the
secondary aluminurr 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, to the first approximation, 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.
Out of 69 smelters interviewed by telephone or plant visit, 46
use only sclid scrap, 19 use bcth solid scrap and residues, and
four use only residues. Although the wet processing of residues
can lead to water effluents different from those of a nonresidue
smelter, subcategorization based on residues is complicated by
those smelters handling bcth residues and solid scrap and that
some smelters, using both forms of raw material, dry process the
residue and have nc water effluent from it,
Products. The main product line of secondary smelters is
specification alleys (ingots or sows) and/or deoxidant (notched
bar, shapes, or shct). 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
36
-------
industry, as are charging and smelting procedures,
the establishment cf a single category.
and support
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 waste water treatment and effluent limitations may
be that the use of chlcrine or A1F3 will generate unique waste
water effluents when the smelter fumes are wet scrubbed. of the
69 smelters interviewed, 46 refine their melts. Of these, 28 use
only C12, 14 use only A1F3, and four use both AlF3 and C12. The
presence, absence, or method of waste water treatment at these
smelters is independent of the demagging process used. Thus, the
response required for the achievement of performance implied by
any effluent limitations guideline would be likewise independent
of current process operation.
The waste products formed during magnesium removal with chlorine
differ from those formed when aluminum trifluoride is used.
Volatile anhydrous metal chlorides are formed when chlorine is
used for demagging at 760°C (1400°F). When aluminum trifluoride
is used, metal fluorides are formed, which have relatively low
volatilities at 760°C. The anhydrous metal chlorides are very
soluble in water; whereas, metal fluorides are sparingly soluble
in water. This difference could be related to categorization.
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 irelt. Low solubility of the scrubbed salts
(after pH adjustment) sets the waste water generated from
fluoride scrubbing apart from waste water generated from chloride
fume scrubbing.
The last process step in secondary aluminum recovery, casting, is
common to the industry, and supports the establishment of a
single category for the industry.
Most (19 of 23) residue processing operations are associated with
solids processing operations, wherein practices of water
interchange and irixed waste treatment have been identified.
Similarly, the wet and dry variations of residue processing are
variously associated with cr 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 untreatajble, except by
37
-------
total evaporation ct 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
waste water character or treatment. Many of the older plants
have updated treatment facilities, while others 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 waste water character or treatment.
38
-------
SECTION V
WASTE CHARACTERIZATION
Introduction
Specific processes in the secondary aluminum industry generate
characteristic waste water streams. In this section of the
document, each waste water stream is discussed as to source,
quantities, and characteristics, in terms of the process opera-
tion from which it arises.
Specif ic Water Uses
The secondary aluminum industry generates
following processes:
waste waters in the
(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.Coolincr
sources. Molten metal in the furnace is generally either cast
into ingot or sow molds or is quenched into shot. In cases where
cooling waste water 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 production 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. From the water bath, they
are conveyed to a dry screening operation.
in a survey conducted on 69 seccndary smelters, 57 were found to
be using water for ceding purposes. It was learned from the
survey that the cooling water used has five possible
dispositions. The water may be (1) completely vaporized, (2)
discharged to municipal sewage or navigable waters after one
passage through the ceding circuit, (3) recycled for some period
and discharged (6-month intervals), (4) continuously recycled
39
-------
with no discharge, and (5) discharged to holding ponds after one
passage through the ceding circuit. The disposition of the
cooling waters by the 57 smelters is as given in Table 11.
Quantities. Data en the quantity of water used for metal cooling
in the secondary industry is very sparse and of questionable
quality. Only a small number of plants had even approximate
water quantity figures. Data gathered was converted to liters
used per metric tens cf metal coded and is given in Table 12.
As is evident, the values vary widely. It is not certain whether
these great differences are real or whether they are due to
grossly inaccurate estimates of water flow. Each of the plants
listed in Table 12 is discharging the cooling waste water after
one passage through the circuit. Plants recycling their cooling
water had very limited information on the amount of water used
per ton of product cccled.
Characteristies. cf the 69 secondary smelters surveyed, one
plant, B-ll, had analytical data on cooling, waste water (for a
Corps of Engineers1 permit). To better characterize the nature
of cooling waste water, sampling teams were sent to plants C-7
and D-6 for water sarrples. Samples obtained were analyzed for
appropriate constituents and related to pollutant loadings per
metric ton of alley cooled. Data on plants C-7, D-6, and B-ll
are given in Tables 13, 1U, and 15. The tables show that
pollutant levels in the cooling waste waters, with the exception
of oil and grease, are relatively low.
A great deal of variability in waste loading is noted in some of
the parameters. Fcr instance, total dissolved solid loadings
range between 0 and 1.34 kg per metric ton of alloy cooled.
Recirculation of ceding 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 (Nad) 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.
Waste Mater From Fume Scrubbing Sources
Aluminum scrap normally charged into the furnace contains a
higher percentage cf 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 by either passing chlorine through the
melt (chlorination), with the formation of magnesium chloride
(MgCl.2) f or by mixing aluminum fluoride (A1F3) 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
40
-------
TABLE 11. COOLING WATER DISPOSAL PRACTICES
Disposition of Cooling Water
Number
Completely vaporized
Discharged directly after use
Discharged after some recirculation
Recycled continuously
Discharged to holding pond
Total
3
26
7
15
6
57
TABLE 12. COOLING WATER USAGE BY SECONDARY SMELTERS
Plant
Water Use liters/metric ton
of metal cooled (gallons/short ton)
Ingot Cooling Shot Quenching
C-7
C-26
C-20
D-6
B-ll
680 (160)
250 (60)
2,300 (550)
570 (140)
11,500 (2,760)
60,000 (14,400)
41
-------
TABLE 13. CHARACTER OF COOLING WASTE
(Plant C-7)
WATER
to
Parameter
Alkalinity
COD
Total solids
Total dissolved
solids
Total suspended
solids
Sulfate
Chloride
Cyanide
Fluoride
Aluminum
Calcium
Copper
Magnesium
Nickel
Sodium
Zinc
Cadmium
Lead
Manganese
Chlorine residue
Oils and grease
Phenols (ppb)
PH
(a) (cone., me/1)
Intake Water
Cone.
(mg/1)
8
4
86
73
6
6
6
<0.02
1.04
0.01
2.38
0.037
1.95
<0.02
3.19
0.031
<0.009
<0.026
<0.010
<0.02
6.3
30
6.7
(water
/_\
Effluent
Loading Vd/
gram/niton
5.
2.
58.
49.
4.
4.
4.
<0.
0.
43
71
4
5
07
07
07
013
706
0.007
1.
0.
1.
<0.
2.
0.
<0.
<0.
<0.
<0.
4.
0.
used
62
025
32
014
16
021
006
018
006
014
28
020
, I/day)
6
6
1000
234
78
102
10
16
0.05
0.84
0.01
2.60
0.037
1.07
0.043
2.81
0.231
0.009
0.026
0.042
0.02
255.6
35
3.4
v 111 r»»**v
Concentrations in
Samples.
(ma/1)
15
16
365
188
118
64
15
12
<0.02
1.36
0.08
3.10
0.037
1.07
<0.02
2.91
0.038
<0.009
0.052
0.042
0.02
64.3
3
7
16
_._
2252
3222
548
2620
21
401
<0.02
0.16
32.0
1.07
0.325
1.37
<0.02
5.06
1.555
0.027
1.147
0.229
<0.02
5180
260
6.1
** J -i nr*
-------
TABLE 14. CHARACTER OF COOLING WASTE
(Plant D-6)
WATER
, , Effluent Concentrations in Samples,
Intake Water (a) (ms/1)
Parameter Cone, (mg/1) 1
Alkalinity
COD
Total solids
Total dissolved solids
Total suspended solids
Sulfate
Chloride
Cyanide
Fluoride
Aluminum
Calcium
Copper
Magnesium
Nickel
Sodium
Zinc
Cadmium
Lead
Manganese
Oils and grease
Phenols
PH
(a) Average of 4 samples.
(b) ND = Not detected.
(c) TConc . effluent-cone .
. Amount of metal
(d) Water flow 30g pm for
292
3.8
203
184
19
12
8.2
ND(b>
2.5
2.7
14.0
ND
1.26
0.08
5.55
0.002
ND
0.10
0.01
4.5
ND
5.4
intake
cooled
260 min
271
228
711
661
50
20
223
.004
2.4
0.3
6.0
ND
2.83
ND
450
0.011
ND
ND
0.30
2
_„
134
788
665
123
25
160
003
2.3
6.3
6.2 .
ND
2.68
ND
375
0.005
ND
0.10
0.23
57.5 60.5
ND
7.5
(mg/l)l x (water
, mtons/day
ND
7.3
used
3
278
456
1663
1412
.251
28
622
ND
2.0
2.2
41.5
0,026
7,50
0.47
1450
0.017
ND
0.10
0.70
36.4
ND
4.9
I/day)
4
355
160
654
567
78
23
108
ND
2.0
0.3
5.1
ND
2.68
0.15
325
0.012
ND
ND
0.15
24.5
ND
5.3
-
x 10"3
5
131
365
2422
2146
276
28
582
ND
2.6
0.5
41.7
ND
6.00
ND
1700
0.022
ND
ND
0.30
891
ND
6.0
gram /rug
6
149
122
639
475
164
19
165
ND
2.6
0.3
9.6
ND
2.63
0.15
100
0.013
0.01
0.10
0.12
484
ND
7.6
Avg.
237
244
1146
989
157
24
310
.004
2.3
1.7
18.4
0.026
4.05
0.26
733
0.013
0.01
0.10
0.30
259
ND
6.4
- loading (gram/
Net Loadings in Waste
Water (c) (gram/niton)
Avg.
___
138
545
465
80
7
174
.002
0.33
0.015
1.61
0.10
420
0.006
0.006
0.17
147
---
™— —
m ton)
Min.
___
68
252
168
18
4
58
0.79
0.04
54
0.002
0.06
12
---
— — —
Max.
36
261
1282
1134
60
9
355
.002
.06
2.1
16.0
3.60
0.22
979
0.012
0.40
512
_ _ —
average time/day
(e) 51 mtons/day(56 tons/day)
-------
TABLE 15. CHARACTER OF COOLING WASTE WATER
(Plant B-ll(a))
Intake Water
Municipal
ma/1
Alkalinity 95
COD NA(cJ
Total solids 192
Total dissolved solids 190
Total suspended solids 2
Ammonia 0,01
Nitrate 0.06
Chloride 25
Fluoride 1.01
Aluminum, fig
Oil and grease, Ib/day —
pH 4.5-6.5
Temperature, F NA
Temperature, C
Discharge Net loading in Waste-
mg/l(a) water gram/mton(b)
Avg . Average
95
15
198
180
18
1.1
0.07
29
0.9
0,7
5 (?)
(7.5 rag/1)
4.5-6.5
97-112
36-44
172
69
...
182
12.5
0.11
46
...
0.008
86
...
-_.
— .
Volume: 80,000 gal/day = 302,800 I/day.
Product: 25-33 tons/day = 23-30 mton/day
(a) Corp of Engineers data.
(b) [ Cone e f fluent- conc int ake ( mg /1) ] x lit.er s_/day
Avg. amount of metal cooled, mtons/day
(c) NA = Not applicable.
x 10"3 gram/mg = loading, gram/mton
44
-------
scrubbing gains resulting pollutants and is the source of a waste
water stream.
Waste water from A1F3 demagging gas scrubbers can normally be
recirculated because of the relative insolubility of fluorides
(which can be settled out). Waste water 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 socn build up to make water unusable. Thus,
the discharge of this effluent is the source of waste water from
fume scrubbing. Table 16 gives data en present smelter practices
in regard to scrubbing waste water. Of 69 plants surveyed, 46
are demagging their melts. No demagging waste water discharges
are reported from these plants using A1F3. All plants using
chlorine are discharging demagging scrubber waste water, whether
to navigable waters, public sewage, or holding ponds.
Quantities. Very few shelters in the secondary industry have
reliable water-use data for their fume scrubbing systems. In one
plant, D-6, water usage measured by the project sampling team was
one-third the usage estimated by company personnel. In general,
data given out by the plants should be used with caution.
Data on the quantities of water used in scrubbing, which were
most consistent in terms of their content, are given in Table 17.
Water usage is given in liters per kilogram of magnesium removed
during the demagging operation. Basing the water use on
magnesium removal provides a common unit for all smelters. The
values in Table 17 are fairly consistent, with the average water
use being 150 liters per kilogram of magnesium removed.
Characteristics. The character of the raw waste water generated
during the scrubbing cf chlorinaticn fumes is given in Table 18.
No similarly detailed -data on this waste water was available in
the secondary aluminum industry. The data on plants C-7 and D-6
were obtained by sending project water sampling teams to the
plant sites for representative samples. The waste water samples
were then analyzed fcr appropriate constituents.
At plant C-7, fumes were scrubbed in a tower, followed by
neutralization and settling of the raw waste water in separate
unit operations. This arrangement permitted sampling the acidic
effluent from the scrubber before it was treated and is one
example of raw fume scrubber waste water collected by a tower.
At plant D-6, the fumes were trapped under a proprietary bell-
shaped device in contact with the molten metal and were scrubbed
with water. This arrangement also permitted sampling of raw
untreated waste water from a different method of fume scrubbing.
Simultaneous scrubbing and pH adjustment is considered a
treatment and the treated waste water is characterized in Section
VII.
Table 18 gives both effluent concentrations (milligrams per
liter) and loadings (grams of pollutants per kilogram of
magnesium removed). For almost every parameter listed, the
45
-------
TABLE 16. FUME SCRUBBING WASTE WATER -
GENERATION AND DISPOSAL PRACTICES
Practice
Number of Plants
* Use A1F» for demagging 14
No air pollution control 5
Dry air pollution control 7
Wet air pollution control . 2
- Water recycled continuously 2
• Use Cl for demagging 28
No air pollution control 3
Dry air pollution control 1
Wet air pollution control 24
Wastewater discharged:
- with no recycling 12
- with some recycling 6
- no discharge-continuously recycled 0
- to evaporation pond 7
- with neutralization 17
- with solids removal 12
• Use both A1F, and Cl. for demagging 4
*5 fc
No air pollution control 1
Dry air pollution control 1
Wet air pollution control 2
Wastewater discharged:
- with no recycling 1
- to evaporation pond 1
- with neutralization 2
- with settling 2
Total Number of Plants Demagging 46
46
-------
TABLE 17. QUANTITIES OF WASTE WATER GENERATED IN THE
WET SCRUBBING OF CHLORINATION FUMES
Company (code)
C-7
D-6
D-8
C-26
Wastewater Generated
I/kg of Mg
95.2
182
190
133d
Removed (Gal/lb)
(11)
(22)
(23)
) (16)
(1) Estimated from data provided by plant on water usage
and rate of Mg removal.
47
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TABLE 18. CHARACTER OF WASTE WATER FROM
FUME SCRUBBING '(No Treatment)
CHLORINATION
C-7
(a)
D-6
(b)
Parameter
COD
Total solids
Total dissolved
solids
Total suspended
solids
Sulfate
Chloride
Cyanide
Fluoride
Aluminum
Calcium
Copper
Magnesium
Nickel
Sodium
Potassium
Zinc
Cadmium
Lead
Manganese
Chlorine residue
Oils and grease
Phenols (ppfa)
pH
(a) Average of
(b) Average of
Cone. ,
123
2910
1885
225
11
4420
<0.02
0.24
472
0.12
0.25
41.2
0.050
3.11
—
0.952
0.066
0.061
0.449
0.257
13.9
20.7
2.1
three composite
five composite
Loading, ,
grams /KgME
12.1
301
194
22.3
0.51
446
-0.08(d>
50.9
-0.215
0.02
3.86
0.003
-0.007
--
0.091
0.006
0.004
0.049
0.027
0.590
-0.002
samples.
samples.
(c) Loading calculated as: [cone, effluent
v Cone,,
536
10,500
480
481
8,671
0.7
6.12
990
1.31
55.8
0.74
770
206
3.58
0.30
0.24
2.34
6.24
1.0
(mg/4) - cone.
Loading, , v
gratns/KeMjr
95.8
1856
83.0
84.4
1560
-0.324
0.615
176
0.236
9.81
0.106
32.7
37.1
0.64
0.054
0.025
0.349
0.403
intake (mg/J&) ] x
quantity of water uaed (£)
quantity of Mg removed (Kg)
(d) Negative numbers indicate that the process apparently reduced the
concentration of this parameter, and are derived from the reports
of analytical results as shown above.
(e) Analytical methods from Standard Methods for the Examination of Water
and Wastewater, 13th Edition (1971),
48
-------
Loadings vary widely. Raw waste waters (averages of composites)
gathered during chlorine demagging have a low pH due to the
hydrolysis of anyhdrous aluminum chloride and magnesium chloride
that make up the fume. The hydrolysis forms hydrochloric acid,
which accounts for part of the high chloride levels present
without the associated total dissolved solids. The data at plant
C-7 suggests that the chloride in excess of that accountable from
aluminum and magnesium had tc c,ome from excess chlorine used
during demagging. A similar imbalance in operation is suggested
by the data on raw waste water for Plant D-6. Unreacted chlorine
was measured as residual chlorine in the raw waste water from
plant C-7, The effect of pH adjustment and settling on the raw
waste water from plant C-7 is described in Section VII.
When chlorine is used for demagging, most of the product is
magnesium chloride during the initial phase of the operation, and
only a little aluminum chloride is formed. At the temperature of
the molten alloy, 760-780°C (mOO-1450°F) , some of the magnesium
chloride is included in the off gases (which may include
unreacted chlorine). As the magnesium level is decreased, the
chlorine flow is decreased, but more aluminum chloride is formed.
When chlorination is done within the furnace, the fumes are
usually wet scrubbed through a series of towers. When done in
the forewell, the fumes are caught in a bell, contacting the
molten metal, and scrubbed with a specially designed aspirator
mechanism. The scrubbing is done with and without neutralization
of the scrubbing liquid.
When aluminum fluoride is used for magnesium removal, both
magnesium fluoride and residual aluminum fluoride remain at the
surface of the melt. Both materials are solid at 780°C (1450°F)
and exert vapor pressures of less than 1 torr. They do react
with water vapor to yield hydrofluoric acid. The recovery of the
fumes during demagging is done with fume hoods over the forewell,
and the gases are scrubbed with recycled water through venturi-
type scrubbers.
Chloride fume scrubber water (when not scrubbed with caustic
solution) has a pH of 1.5 and contains hydrolyzed metal chlorides
of aluminum, magnesium, and other volatile metal halides such as
zinc, manganese, cadrrium, nickel, copper, and lead. In alkaline
scrubber waters, scdium, 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.(See
Section VII.)
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.
49
-------
Fume scrubber water generation is intermittent and coincides with
the 1.5-4 hour magnesium removal cycle for each heat (every 24
hours). The water flow rate during the scrubbing ranges between
3,800-12,500 liters (1000-3300 gallons) per hour producing about
the same amount of discharge. Of the 27 companies practicing wet
scrubbing for air pollution control, scrubbing water is
discharged directly (eight each), discharged with recycle (three
each), discharged after recycling (two each), recycled
continuously (two each) (only those using aluminum fluoride for
magnesium removal), discharged tc pends (five each), and recycled
and discharged tc ponds (two each). Twenty of the 27 companies
neutralized the scrutber water and 15 make an effort to remove
solids as sludge ty settling or by filtration.
Haste Water From Residue Processing
Sources. Residues used by the secondary aluminum industry are
generally composed of 10 to 30 percent aluminum, with attached
aluminum cxide fluxing salts (mostly NaCl and KCl), dirt, and
various other chlorides, fluorides, and oxides. Separation of
the metal from the ncnmetals is done by milling and screening and
is performed wet cr 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 soluble salts from the flux cover residues,
such as a sodium chlcride and potassium chloride. Drosses also
contain aluminum nitride, which hydrolyzes in water to yield
ammonia. When slags are milled, the waste water from dust
control contains mere 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 waste water stream that is similar to the
scrubber waters in make up, but 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 waste water
discharges.
Of the 23 plants recovering aluminum values from residues, eight
use wet techniques, which lead to the generation of highly saline
waste waters. Table 19 lists the general character of these
eight coded plants. Waste water is generated by wet dust removal
systems (dust generated by dry milling of residue), the washing
of residue fractions (sized), and by wet milling the residue to
liberate metallic aluminum. In every case, the waste water is
passed into a settling pond before discharge.
Quantities. Water use for the wet milling of residues has been
based on the tonnage of aluminum recovery rather than the tonnage
50
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TABLE 19. RESIDUE WASTE WATER GENERATION AND DISPOSAL PRACTICES
Plant Codes
Practice
D-l D-2 D-3 D-4 D-5 D-6 D-7 D-i
Wastewater generated by:
Wet dust removal system
Washing of residue fractions
Wet milling of residues
Disposal of wastewater:
Discharge with some recycling
Discharge to settling pond
Chemically treat wastewater to aid settling
Discharge to navigable waters via settling pond
No direct discharge streams from settling ponds
X X
X X
X X
X X
X
X
51
-------
of residues processed. This is because the former quantity is
generally known more accurately by the smelters than the latter.
Table 20 gives available data on the quantity of waste water
generated in the wet milling of residues in liters per metric ton
of aluminum recovered. Values for plants D-3 and D-8 are fairly
close, while the value for plant D-4 is roughly an order of
magnitude higher.
Characteristics. The character of waste water generated during
wet milling of residues or residue fractions is given in Table
21. Two plants, D-4 and D-3, had some analytical data on their
waste water from Corps of Engineers1 permits. To provide better
characterization of the waste water, sampling teams were sent to
plants D-6, D-8f and D-4 to gather water samples for analysis.
As noted in Table 21, waste water loadings are exceedingly
variable. For exairple, chloride loadings are 0.32, 3264, and 150
kg/kkg (0.64, 6500, and 300 Ib/ton) for plants D-3, D-4, and D-8,
respectively. This variability is attributed to variation in the
salt content in the residues being processed at the time samples
were taken. If the dissolved salt (chloride) content is low,
drosses frcm 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-4). Some residue millers operate on a
toll, based on the arrount of molten aluminum recovered, and
process both types cf residues. Therefore, there are highs and
lews in the dissolved salt content of the waste water depending
on the batch of residues being milled. Nontoll 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 waste water as it comes frcm 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 waste water is
about 30 percent by weight. This would be a highly variable
value and dependent 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 plant1s
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 fuire scrubber water and 25 percent fresh water.
The concentrations reported in Table 18 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-ad justed fuire scrubber water. The effectiveness is
52
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TABLE 20. QUANTITIES OF WASTE WATER GENERATED IN THE WET MILLING
OF RESIDUES PER TON OF ALUMINUM RECOVERED
Company (code)
Wastewater Generation
-C/mton of Al recovered
(Gal/ton)
D-3
D-4
D-8
16,690
218,000
28,838
(1)
(1) From Corp of Engineers' data.
53
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TABLE 21. CHARACTER OF SETTLED WASTE WATER FROM RESIDUE PROCESSING
Plants
Parameter
Alkalinity
COD
Total solids
Total dissolved
solids
Total suspended
solids
Sulfate
Chloride
Cyanide
Fluoride
Ammonia
Aluminum
Calcium
Copper
Magnesium
Nickel
Sodium
Potassium
Zinc
Cadmium
Lead
Manganese
Chlorine residue
Oils and grease
Phenols (ppb)
pH
Nitrates
D_3
Loading
(KK/mton Al)
6.47
0.97
13.51
0.121
0.319
0.129
0.33
0.002
<0.001
0
0.053
8.68
0.032
D-6
Cone.
314
2,045
12,920
4,961
1,100
6,492
0.04
2.9
0.75
0.3
58. 8
0.174
32.5
1.2
2,560
1,087
0.015
0.05
0.20
0.16
55.4
--
8.3
D-4
Cone.
(ms/,0
586
24,264
. 15
47
15,465
8.7
350
16.4
23
0.070
6
0.240
11,600
6,470
0.10
0.002
0.020
0.045
--
0
«
9.09
(c)
Loading, v
102
5,144
1.5
1.5
3,264
1.81
73
3.5
-7.4
0.008
3.9
0.009
2,528
1,407
0
0
0.004
0.002
—
0
-„
D-i
Cone.
500
29
17,800
17,400
159
151
8,903
0.05
16.5
0.30
28
48
0.137
76
0.20
3,103
4,802
0,198
0.005
0.028
0.060
--
0.5
0.03
9.2
e(d)
Loading, v
(Ka/mtonr '
-7.5
0.17
326
324
-5.6
1.8
150
0
0.38
-0.03
-1.49
0.17
0.003
1.39
0
46.2
102
-9.1
-0.001
-0,001
0
--
0
0
(a) Calculated from U. S. Corps, of Engineers, concentration data not given.
(b) From residue milling solid waste washing, tonnage values of residue waste processed not
available - loading cannot be calculated. Water flow la 151 Apm.
(c) Data from 7 month and 9 month average and verification data from state: metals verified
composite of 18 samples collected over a period of 6 days*
(d) Represents composite o£ 9 samples collected over 3 days, tailing waste stream Is blended
with scrubber waste stream.
(e) Loading calculated as: [cone, effluent (mg/jfc) - cone, intake (mgAO] x
quantity of_wg_tg_r qs.ed CO
quantity of Al recovered from residue (mton)
(f) Negative values indicate that the process reduced the concentration of this parameter,
and are derived from reported analytical values.
54
-------
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 waste water 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 waste water are less than those attainable
by the use of lime precipitation.
55
-------
-------
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
Introduction
The waste water constituents, which have been determined to be
present in the process waste waters of the secondary aluminum
smelting industry in sufficient quantities to warrant their
control and teatment, are listed in Tatle 22.
This section provides the rationale for the selection, as well as
the rejection, of, pollutant characteristics for this subcategory.
Rationale for Selection of
Pollutant Parameters
Cooling Waste Water
The analyses of cooling waste water streams for three plants are
given in Table 13, 1U, and 15. Examination of the values for the
various parameters shows dissolved solids, lead, manganese, and
oil and grease to be significantly added to this stream.
Fume Scrubbing Haste Water
p^~^™~ " '' ' " , - - - — *•*
Analyses of two typical waste water streams from fume scrubbing
during chlorinaticn are given in Table 18. Examination of the
concentration values shows total suspended solids and chemical
oxygen demand to te significantly added to this stream. The
average pH is noted to be between 1 and 2 and is, thus, a
significant pollutant characteristic.
Residue Millingn_V3aste Water
Analyses of four residue milling waste water streams are given in
Table 21. Three cf these provide concentration levels. The
fourth provides only loading values. From the concentration
levels, it is established that total suspended solids, fluoride,
ammonia, aluminum, ccpper, and chemical oxygen demand are
significantly added to this stream and are considered as
significant pollutants. Total suspended solids, although
typically low, can be at high levels, as is the case for plant C-
6. Ammonia levels and pH are identifiable as contributions from
the process, and are subject to control by currently practicable
control and treatment measures.
57
-------
TABLE 22. POLLUTANTS SUBJECT TO EFFLUENT LIMITATIONS
Treated Wastewater Stream
Pollutant Under
Effluent Limitation
Wet Milling of Residues
Fume Scrubbing
pH
Total Suspended Solids
Fluoride
Ammonia
Aluminum
Copper
COD
Total Suspended Solids
COD
58
-------
Acidity and alkalinity are reciprocal terms. Acidity is produced
by substances that yield hydrogen ions upon hydrolysis and
alkalinity is produced by substances that yield hydroxyl ions.
The terms "total acidity" and "total alkalinity" are often used
to express the buffering capacity of a solution. Acidity in
natural waters is caused by carbon dioxide mineral acids, weakly
dissociated acids,' and the salts of strong acids and weak bases.
Alkalinity is caused by strong bases and the salts of strong
alkalies and weak acids.
The term pH is a logarithmic expressicn of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pK and acidity or
alkalinity is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing fixtures
and can thus add such constituents to drinking water as iron,
copper, zinc, cadmium and lead. The hydrogen ion concentration
can affect the "taste" of the water. At a low pH water tastes
"sour". The bactericidal effect of chlorine is weakened as the
pH increases, and it is advantageous to keep the pH close to 7.
This is very significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Dead fish, associated algal blooms,
and foul stenches are aesthetic liabilities of any waterway.
Even moderate changes frcm "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic
life of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousand-fold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is
more lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Total Suspended Solids
Suspended solids include both organic and inorganic materials.
The inorganic compcnents include sand, silt, and clay. The
organic fraction includes such materials as grease, oil, tar,
animal and vegetable fats, various fibers, sawdust, hair, and
various materials from sewers. ihese solids may settle out
rapidly and bottom deposits are cften a mixture of both organic
and inorganic sclids. They adversely affect fisheries by
covering the bottom cf the stream cr lake with a blanket of
material that destroys the fish-food bottom fauna or the spawning
ground of fish. Eeposits containing organic materials may
59
-------
deplete bottom oxygen supplies and produce hydrogen
carbon dioxide methane, and other noxious gases.
sulfide
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams shall
not be present in sufficient concentration to be objectionable or
to interfere with normal treatment processes. Suspended solids
in water may interfere with many industrial processes, and cause
foaming in boilers, cr encrustations on equipment exposed to
water, especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography;
cooling systems, and power plants. Suspended particles also
serve as a transport mechanism for pesticides and other
substances which are readily sorbed into or onto clay particles.
Solids may be suspended in water fcr a time, and then settle to
the bed of the stream or lake. These settleable solids
discharged with man's wastes may be inert, slowly biodegradable
materials, or rapidly decomposable substances. While in
suspension, they increase the turbidity of the water, reduce
light penetration and impair the photosynthetic activity of
aquatic plants.
Solids in suspension are aesthetically displeasing. When they
settle tc form sludge deposits on the stream or lake bed, they
are often much more damaging to the life in water, and they
retain the capacity tc displease the senses. Solids, when
transformed to sludge deposits, may do a variety of damaging
things, including blanketing the stream or lake bed and thereby
destroying the living spaces for those benthic organisms that
would otherwise occupy the habitat. When of an organic and
therefore decomposable nature, solids use a portion or all of the
dissolved oxygen available in the area. Organic materials also
serve as a seemingly inexhaustible food source for sludgeworms
and associated organisms.
Turbidity is principally a measure of the light absorbing
properties of suspended solids. It is frequently used as a
substitute method of quickly estimating the total suspended
solids when the concentration is relatively low.
Dissolved Solids
In natural waters the dissolved solids consist mainly of
carbonates, chlorides, sulfates, phosphates, and possibly
nitrates of calcium, magnesium, sodium, and potassium, with
traces of iron, manganese and other substances.
Many communities in the United States and in other countries use
water supplies containing 2000 to 4000 mg/1 of dissolved salts,
when no better water is available. Such waters are not
palatable, may not quench thirst, and may have a laxative action
on new users. Waters containing more than 4000 mg/i of total
salts are generally considered unfit for human use, although in
60
-------
hot climates such higher salt concentrations can be tolerated
whereas they could not be in temperate climates. Waters
containing 5000 mg/1 or more are reported to be bitter and act as
bladder and intestinal irritants. It is generally agreed that
the salt concentration cf good, palatable water should not exceed
500 mg/1.
Limiting concentrations of dissolved solids for fresh-water fish
may range from 5,000 to 10,000 mg/1, according to species and
prior acclimatization. Some fish are adapted to living in more
saline waters, and a few species of fresh-water forms have been
found in natural waters with a salt concentration of 15,000 to
20,000 mg/1. Fish can slowly become acclimatized to higher
salinities, but fish in waters of low salinity cannot, survive
sudden exposure to high salinities, such as those resulting from
discharges of oil-well brines. Dissolved solids may influence
the toxicity of heavy metals and organic compounds to fish and
other aquatic life, primarily because of the antagonistic effect
of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or
no value for irrigation.
Dissolved solids in industrial waters can cause foaming in
boilers and cause interference with clealiness, color, or taste
of many finished products. High contents of dissolved solids
also tend to accelerate corrosion.
Specific conductance is a measure of the capacity of water to
convey an electric current. This property is related to the
total concentration cf ionized substances in water and water
temperature. This property is frequently used as a substitute
method of quickly estimating the dissolved solids concentration.
Fluorides
As the most reactive non-metal, fluorine is never found free in
nature but as a constituent of fluorite or fluorspar, calcium
fluoride in sedimentary rocks and also of cryolite, sodium
aluminum fluoride in igneous rocks. Owing to their origin only
in certain types of rocks and only in a few regions, fluorides in
high concentrations are not a common constituent of natural
surface waters, but they may occur in detrimental concentrations
in ground waters.
Fluorides are used as insecticides, for disinfecting brewery
apparatus, as a flux in the manufacture of steel, for preserving
wood and mucilages, for the manufacture ,of glass and enamels, in
chemical industries, fcr water treatment, and for other uses.
Fluorides in sufficient quantity are toxic to humans, with doses
of 250 to 450 mg giving severe symptoms or causing death.
61
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There are numerous articles describing the effects of fluoride-
bearing waters or dental enamel of children; these studies lead
to the generalization that water containing less than 0,9 to 1*0
mg/1 of fluoride will seldom cause mottled enamel in children,
and for adults, concentrations less than 3 or 4 mg/1 are not
likely to cause endemic cumulative fluorosis and skeletal
effects. Abundant literature is also available describing the
advantages of maintaining 0.8 to 1,5 mg/1 of fluoride ion in
drinking water tc aid in the reduction of dental decay,
especially among children.
chronic fluoride pcisoning of livestock has been observed in
areas where water contained 10 to 15 mg/1 fluoride.
Concentrations of 30 - 50 mg/1 of fluoride in the total ration of
dairy cows is considered the upper safe limit. Fluoride from
waters apparently dees not accumulate in soft tissue to a
significant degree and it is transferred to a very small extent
into the milk and to a somewhat greater degree into eggs. Data
for fresh water indicate that fluorides are toxic to fish at
concentrations higher than 1.5 mg/1.
Ammonia
Ammonia is a common product of the decomposition of organic
matter. Dead and decaying animals and plants along with human
and animal body wastes account for much of the ammonia entering
the aquatic ecosystem. Ammonia exists in its non-ionized form
only at higher pH levels and is the most toxic in this state.
The lower the pH, the more ionized ammonia is formed and its
toxicity decreases. Ammonia, in the presence of dissolved
oxygen, is converted to nitrate (N03) by nitrifying bacteria.
Nitrite (NO2), which is an intermediate product between ammonia
and nitrate, sometimes occurs in quantity when depressed oxygen
conditions permit. Ammonia can exist in several other chemical
combinations including ammonium chloride and other salts.
Nitrates are considered to be among the poisonous ingredients of
mineralized waters, with potassium nitrate being more poisonous
than sodium nitrate. Excess nitrates cause irritation of the
mucous linings of the gastrointestinal tract and the bladder; the
symptoms are diarrhea and diuresis, and drinking one liter of
water containing 500 mg/1 of nitrate can cause such symptoms.
Infant methemoglobinemia, a disease characterized by certain
specific blcod changes and cyanosis, may be caused by high
nitrate concentrations in the water used for preparing feeding
formulae. While it is still impossible to state precise
concentration limits, it has been widely recommended that water
containing more than 10 mg/1 of nitrate nitrogen (NO3-N) should
not be used for infants. Nitrates are also ""harmful in
fermentation processes and can cause disagreeable tastes in beer.
In most natural water the pH range is such that ammonium ions
(NH4+) predominate. In alkaline waters, however, high
concentrations of un-ionized ammonia in undissociated ammonium
hydroxide increase the toxicity of ammonia solutions. In streams
62
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polluted with sewage, up to one half of the nitrogen in the
sewage may be in the form of free ammonia, and sewage may carry
up to 35 mg/1 cf total nitrogen. It has been shown that at a
level of 1.0 mg/1 un-ionized ammonia, the ability of hemoglobin
to combine with oxygen is in-paired and fish may suffocate.
Evidence indicates that ammonia exerts a considerable toxic
effect on all aquatic life within a range of less than 1.0 mg/1
to 25 mg/lr depending on the pH and dissolved oxygen level
present.
Ammonia can add tc the problem cf eutrophication by supplying
nitrogen through its breakdown products. Some lakes in warmer
climates, and others that are aging quickly are sometimes limited
by the nitrogen available. Any increase will speed up the plant
growth and decay process.
Copper
Copper salts occur in natural surface waters only in trace
amounts, up to abcut 0.05 mg/1, so that their presence generally
is the result cf pollution. This is attributable to the
corrosive action of the water en copper and brass tubing, to
industrial effluents, and frequently to the use of copper
compcunds for the control of undesirable plankton organisms.
Copper is not considered to be a cumulative systemic poison for
humans, but it can cause symptoms of gastroenteritis, with nausea
and intestinal irritations, at relatively low dosages. The
limiting factor in domestic water supplies is taste. Threshold
concentrations for taste have been generally reported in the
range of 1.0-2.0 irg/1 of copper, while as much as 5-7.5 mg/1
makes the water completely unpalatable.
The toxicity of copper to aquatic organisms varies significantly,
not only with the species, but also with the physical and
chemical characteristics of the water, including temperature,
hardness, turbidity, and carbon dioxide content. In hard water,
the toxicity cf copper salts is reduced by the precipitation of
copper carbonate or ether insoluble compounds. The sulfates of
copper and zinc, and cf copper and cadmium are synergistic in
their toxic effect on fish.
Copper concentrations less than 1 mg/1 have been reported to be
toxic, particularly in soft water, to many kinds of fish,
crustaceans, mollusks, insects, phytoplankton and zooplankton.
concentrations of ccpper, for example, are detrimental to some
oysters above .1 pcm. Oysters cultured in sea water containing
0.13-0.5 ppm of copper deposited the metal in their bodies and
became unfit as a focd substance.
Oil and Grease
Oil and grease exhibit an oxygen demand. Oil emulsions may
adhere to the gills of fish or coat and destroy algae or other
plankton. Deposition cf oil in the bottom sediments can serve to
63
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exhibit normal benthic growths, thus interrupting the aquatic
food chain. Soluble and emulsified material ingested by fish may
taint the flavor of the fish flesh. Water soluble components may
exert toxic acticn on fish. Floating oil may reduce the re-
aeration of the water surface and in conjunction with emulsified
oil may interfere with photosynthesis, water insoluble
components damage the plumage and coats of water animals and
fowls. Oil and grease in a water can result in the formation of
objectionable surface slicks preventing the full aesthetic
enjoyment of the water.
Oil spills can damage the surface of boats and can destroy the
aesthetic characteristics of beaches and shorelines.
Chemical Oxygen Demand
The chemical oxygen demand is a measure of the quantity of the
oxidizable materials present in water and vaires with water
composition, temperature, and other functions. Dissolved oxygen
(DO) is a water quality constituent that, in appropriate
concentrations, is essential not only to keep organisms living
but also to sustain species reproduction, vigor, and the
development of populations. Organisms undergo stress at reduced
DO concentrations that make them less competitive and able to
sustain their species within the aquatic environment. For
example, reduced DO concentrations have been shown to interfere
with fish population through delayed hatching of eggs, reduced
size and vigor of embryos, production of deformities in young,
interference with focd digestion, acceleration of blood clotting,
decreased tolerance to certain toxicants, reduced food efficiency
and growth rate, and reduced maximum sustained swimming speed.
Fish food organisms are likewise affected adversely in conditions
with suppressed DO. Since all aerobic aquatic organisms need a
certain amount of oxygen, the consequences of total lack of
dissolved oxygen due to a high COD can kill all inhabitants of
the affected area.
If a high COD is present, the quality of the water is usually
visually degraded by the presence cf decomposing materials and
algae blooms due to the uptake of degraded materials that form
the foodstuffs of the algal populations.
Rationale for Rejection of Other waste Water
Constituents as Pollutant Parameters
Waste water from the three unit operations, metal cooling,
demagging fume scrubbing and residue irilling, were characterized
in a limited way pricr to the sampling and analysis, as conducted
in this study. The choice of possible pollutant parameters for
which analyses were to be made was based on information supplied
to the Corp of Engineers for permits to discharge under the
Refuse Act Permit Program and on an understanding of the
chemistry associated with each operation waste stream. Some of
these parameters were rejected as significant pollutants. The
64
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reasons for rejection were that either the process did not
contribute to the presence of suck constituents or that the
concentrations of certain constituents, namely oil and grease for
all process waste water sources except cooling/ were considered
to be too small in magnitude to fce significantly reduced by
current technology.
65
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
Introduction
The control and treatment technology for reducing the discharge
of pollutants in waste water from metal cooling, fume scrubbing,
and residue milling is discussed in this section. The discussion
includes control ard treatment alternatives for each type of
waste water stream and identifies process modifications to reduce
or eliminate the discharge of water.
Waste Water From Metal Cooling
The major pollutant in the waste water generated during the
cooling of ingot molds, containing molten alloy, are oil and
grease and suspended and dissolved solids. The oil and 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 frcm 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.
Typically, cooling waste water is discharged by the secondary
aluminum smelters without prior treatment. Many of the smelters
control the discharge of cooling waste water through continuous
recirculation or by adjusting water flow, so that total
consumption (evaporation) takes place. Others have avoided water
usage completely through the use of air cooling.
Control .Alternatives
The amount of waste water generated from metal cooling can be
reduced by recirculation and cooling. A waste water 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.
67
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of 58 secondary smelters canvassed which generate
cooling waste waters, 15 are recirculating the water
continuously, with no discharge whatever. Seven others are
recycling the ceding 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. A flow diagram for a recirculating system is given in
Figure 3.
Discussions with smelter personnel have indicated that it is
possible tc 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.
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 cf 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. Because of this, it is difficult to obtain accurate
Estimates have run from $2000 to $5000 for the spray
pumps, and associated plumbing to
of about
cost data.
cooling, water storage pit,
provide enough capacity for a smelter with an output
0.454'million kg (1 million Ib) of alloy per month.
Maintenance on the recirculation system is largely due to sludge
buildup. This involves approximately four man-days every six
months. Very seldcm 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 these higher concentrations of oil and
grease, removal by skimming is facilitated. Use of more
expensive greases that irelt at higher temperatures and are less
prcne 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 waste water 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 Icnger conveyors to assure that the ingots
have cooled sufficiently to be handled.
68
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COOLING- TOWER
«*-
WATSH STORAGE
SHOT
and
Ingot Cooling
MOLTEN
MSTAL
Figure 3. Recirculated cooling water system.
-------
Ai£ Cooling. Of the 69 secondary smelters canvassed, 13 are air
cooling their ingots and sows. Air ceding 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 en the air-cooled system because of the
longer conveyor, the added heat load on the lubricants, and the
additional blcwer motors. In some cases a water mist is added to
the air tc improve the cooling rate. The water is completely
evaporated.
Treatment Alternatives
The waste water from cooling operations requires treatment to
remove the oil and grease and suspended solids before discharge.
This holds for once-through water and for recirculated water. As
in most treatment processes, it is less difficult to treat waste
water with high concentrations of pollutants than those with low
concentrations. Therefore, treatment of recirculated water would
be preferable.
Oil and Grease, specialized skimiting 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.
Solids Separation. Eoth dissolved and suspended solids are added
to the cooling waste water. Removal of suspended solids requires
settling, which is very slow at lew concentrations, but can be
made more rapid at high concentrations. The components of the
suspended solids are primarily aluminum hydroxide or hydrated
oxide which are kncwn to be excellent coagulants, Recirculation
of cooling water will build the suspended solids level to
concentrations great enough to effect rapid settling between
cooling operation cycles. Sludge is removed periodically,
usually every 6 months. However, others have claimed no need to
remove sludge since buildup was not detected. The supernatant
water is of sufficiently good quality that it can be pumped into
a holding tank during sludge removal from the settling tank or
pit and then reused. The latter procedure appears to be more in
line with a process that evaporates water and which is constantly
replenished. For example, a settling tank or pit with about
37,850 liters (10,000 gallon) capacity and a holding tank of
comparable size would be required to supply water for a 15 metric
ton per day (17 ton) ingot casting operation. Billet "direct
chill" cooling and shot cooling require, typically, about a 3.785
million liter (1.0 million gallon) capacity system.
Sludge from the settling tank, which amounts to about 757 to
7,570 liters (200 to 2000 gallons) every 6 months, is disposed of
in sanitary sewers, stcrm sewers, lagoons, ponds or simply dumped
onto slag, destined fcr land disposal or reprocessing. Since the
sludge is primarily hydrated alumina, the nonwater environmental
impact is considered to be negligible. Disposal in land fills,
after dewatering by filtration, would be the ultimate means of
70
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sludge disposal. The filtrate would be recycled or discharged to
thfc sanitary sewers.
Waste Water Fro ir Fume, Scrubbing
The fumes formed during chemical magnesium removal must be
controlled to reduce air emissions to acceptable levels. Wet
scrubbing techniques have been employed for this purpose and take
numerous forms, some of which are considered to be proprietary.
The discharge from these wet fume scrubbing .devices contains most
of the volatile metal salts entrained in the gas flow, when
chlorine is used for magnesium removal, aluminum chloride and
magnesium chloride are the principal constituents, while
chlorides cf the other alloying elements are also found due to
entrainment. When aluminum fluoride is used for magnesium
removal, the principal volatile products may be silicon
tetrafluoride and hydrogen fluoride which is formed from the
high-temperature hydrolysis of the slightly volatile fluoride
salts reacting with moisture in the air. In both cases, the air
pollutants are transferred into water pollutants. In the case of
chloride fume scrubbing, the salts are mostly soluble in water.
In the case of fluoride fume scrubbing, the salts are only
slightly soluble, but the hydrolysis product, hydrogen fluoride
is very soluble.
Control Alternatives
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.
£2Ui£2i" Three processes exist for reduction and/or removal
of umes 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 Derham Process. < D The Derham process includes equipment
and techniques for magnesium removal, with chlorine, from secon-
dary 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 iragnesium removal, in a liquid flux cover,
with the flux being subsequently used in the melting operations.
The elements Oof the Derham process are indicated in Figure 4.
The principal components consist of a separate bath of the metal
to be treated with its special flux cover, and means to circulate
the molten metal to and from that separate bath.
TTJ Mention of trade names or specific products does not constitute an
endorsement by the .Environmental Production Agency
71
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SCRAP CHARGE.
MOLTEN
METAL
CIRCULATION
FLUX CONTAINING
REVERBERATORY
MELTING
FURNACE
DERHAM
PROCESS
UNIT
NEW FLUX
(NaGl, KC1)
Slag (Metal Recovery
or Discard)
-^ PRODUCT ALLOYS
—*
COMBUSTION
GASES
-»•
CHLORINATION
GASEOUS
EFFLUENTS
GASEOUS CHLORINE
-#* TO STACK
OR SCRUBBER
Figure 4. Schematic diagram of elements of the Derham Process.
72
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The treatment bath may be integral with the smelting furnace or
separate, depending en whether the particular installation is a
new facility or the equipment is being installed on existing
equipment. The molten metal circulation from the main furnace
hearth to the Derham unit is accomplished by pumping (usually
with an air driven siphon) rather than by less direct methods/
such as mechanical stirring or nitrogen gas sparging or
agitation. The molten metal brought to the treatment unit is
treated in the usual manner with gaseous chlorine to achieve
magnesium removal, resulting in the generation of molten
magnesium chloride as the reaction product. By maintaining a
relatively thick cover of molten salt on the fcath in the
treatment unit, the emissions of aluminum chloride to the
atmosphere, usually produced by demagging, are nearly completely
arrested. As the flux cover becomes saturated with respect to
magnesium chloride, it is removed and may be used as a flux in
the main melting furrace.
Any gaseous effluents from the treatment unit are blended with
the combustion gas effluent and released to the stack. Emission
ccntrcl requirements vary, and may be satisfied by blending the
gases. In situations requiring particulate control with
baghouses, the chloride emissions, although hygroscopic, are
usually dilute enough not to interfere with baghouse operation.
Associated engineering features, reported for this process,
include the significant reduction of fuel requirements and
melting time resulting from metal circulation. Heat transfer
rates from the center hearth to the charging well are increased,
so that temperature gradients are decreased. The usual gradient
was quoted as being 200°F between charging well (1300°F) and melt
(1500-1600°F) . With metal circulation, this is reduced to 150°F.
The increase in melt rate was quoted as at least 20 percent.
The efficiency of chlorination is reported to be nearly
stoichiometric down tc 0.1 percent magnesium in the melt. This
is better than ordinary chlcrinaticn rates, which are 50-60
percent efficient at the lower range of magnesium content. No
adverse effects on product quality are reported. One user,
employing the process for degassing only (rather than demagging) ,
reports improved metal quality in the application of the process
in an extrusion plant.
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.
Alcoa Process. <*> 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
73
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for captive scrap processing, The unit is installed between the
holding furnace and a casting machine and removes magnesium
continuously as the metal flews through.
The operation uses no flux salts and attains the high chlorine
efficiencies by means cf 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 frcm 0.5 tc 0.1 percent.
Coated Baghouse JTel^erJ. 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 flew. When blinding occurs, the pressure drop
rises rapidly, and gas flow diminishes.
The Teller modification of baghouse operation has been described
in varying detail, since the inventor considers most information
proprietary (Teller, 1972). Only one system has been installed
at a secondary aluminum smelter. 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 vibration. 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 denragging. A prototype has been installed in such a
facility, where its performance is being evaluated. The
evaluation program should also establish its effectiveness for
the collection of emissions from operations using chlorine for
demagging.
The proprietary system, in the case of fluoride emissions from
glass furnaces, is based on simultaneous filtration and
chromatographic absorption an<3 baghouse recovery. The
chromatographic solid is injected into the gas duct and is then
separated from the gas in a baghouse. The solid serves as an
absorbent for acid gases and as a baghouse precoat to prevent
blinding. The reactive carrier coats the bags and acts as a
filtration precoat. It breaches, rather than blocks, the
interstices and acts as the actual filter, using the bag surface
only as a support. This is the principle of the precoat action.
The chromatographic iraterial consists of a monomolecular layer of
reagent on a reactive carrier. In one application, the carrier
cost was estimated to be $30 per metric ton. In the absorption
of hydrogen fluoride it can provide one transfer unit in 0.0254
cm (0.01 inch) depth of the chromatographic material. With a
duct line injection rate of 0.454 to 0.908 kg per 280 cu m (1 to
2 Ib per 10,000 cu ft) of gas, 80-90 percent removal of hydrogen
74
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fluoride occurred in the duct and
collector.
99 percent in the baghouse
The recovered solids, consisting of the original chromatcgraphic
material, neutralized gaseous fluorides, and the particulates
from the operation can either be recycled (if the discharge is
compatible with feed material being charged to the operation) or
it can be removed to a landfill.
In order to apply the Teller process to specific secondary
aluminum operations, the nature and the variability of the
emission with the types of scrap, and/or the ratio of scrap types
being charged, as well as the rate of magnesium removal, must be
established. To be comprehensive, such a study would require
considerable expenditure.
Treatment Alternatives
Of the 69 facilities canvassed, 46 use demagging to prepare
alloys (see Table 23). of these, 29 employ some form of wet
scrubbing to control air emissions. Three use aluminum fluoride
and 26 use chlorine for demagging. A number of the smaller
volume operations have delayed installing wet air pollution
control devices until water standards are more clearly defined.
In one case, a wet scrubber system has been employed for smoke
abatement, since restrictions on fuel consumption have ruled out
the use of afterburners. No demagging was done at this plant.
Removal of fumes formed during demagging from the air by wet
scrubbing techniques transfers the pollutants to water. Disposal
and treatment prior tc disposal cr reuse are dictated by the
method used for magnesium removal from the molten metal. When
chlorine is used, the anhydrous salts hydrolyze during scrubbing
to form acidic solutions of chloride salts, which even after
neutralization preclude reuse of the water continuously without
buildup of high levels of salt concentration. When aluminum
fluoride is used, scrubbing of the fumes with water produces
fluorides in solution. Subsequent treatment can assure the
formation cf slightly soluble salts, that do not increase their
concentration in water, making continuous recycle of water
possible after settling.
Discharge practices and treatment practices, used on both types
of waste water, are given in Tables 24 and 25 and are described
in the following sections.
Chloride Fume scrubber Haste Water. The water from fume scrubbing
operations7 using chlcrine for demagging, are highly acidic, due
to the hydrolysis of aluminum chloride and magnesium chloride.
Four plants are discharging directly into sanitary sewers without
treatment. Three discharge into sewers after neutralization, and
four after neutralization and solids removal by settling. Such
an effluent provides a source of partially soluble aluminum and
75
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TABLE 23. MAGNESIUM REMOVAL PRACTICE (DEMAGGING)
USED BY SECONDARY ALUMINUM INDUSTRY
Chemical
Used
Number of Smelter
Plants Using
Magnesium Removal
Number of Smelter
Plants Using Wet
Scrubbing to
Control Emission
During Demagging
Aluminum
Trifluoride
14
Chlorine
32
46
(a)
26
29
(b)
(a) Of this total, 4 use both methods for magnesium removal,
(b) Of this total, 2 use both methods for magnesium removal,
76
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TABLE 24. TREATMENT OF EFFLUENTS FROM FUME
SCRUBBING (DISCHARGED AS NOTED)
Number of Smelters Using Given Practice
Neutralize
Solids Removal
Treatment
Neutralize
Cl,
A1F,
Solids No
Removal Treatment
Effluent Control
Discharge Directly
No Recycle
With Recycle
After Recycle
Total
Discharge to:
Stream
Sanitary Sewer
Total
77
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TABLE 25. TREATMENT OF EFFLUENTS FROM FUME
SCRUBBING (NO DISCHARGE)
Number o£ Smelters Using Given Practice
Treatment
Neutralize
Neutralize
Solids Removal
Cln
Solids
Removal
No
Treatment
Affluent Control
Recycled Continuously
Discharge into Fond
Recycle and Discharge
to Pond
Total
-
1
1
-
2
1
2
1
—
78
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magnesium salts, which
precipitation treatment.
are suitable for coagulation and
Neutralization to a pH of 6.0-7.0 will precipitate most of the
aluminum and magnesium as hydroxide. Coprecipitation of heavy
metal hydroxides also occurs. The effectiveness of neutrali-
zation is diminished if too much alkali is added, since
dissolution of aluminum hydroxide occurs at about pH 9. The data
presented in Table 26 indicate that this is true. When
neutralization follows the scrubbing, as is shown in the flow
diagram of the treatment of chloride scrubber water in Figure 5,
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 dissolution of the aluminum hydroxide. 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.
The effluents from chloride scrubbers are also discharged into
streams. Four smelters neutralize and remove solids by settling
before discharging intc navigable waters. Two discharge with
recycling, and two discharge directly after neutralization and
settling to remove solids.
Effluents are also discharged to ponds with impermeable to
semipermeable surfaces, both with and without neutralization.
solids are removed periodically after evaporation of the water.
one practice is tc recycle the neutralized water through the
scrubber until it is too difficult tc 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 of 625 liters (165
gallons). The flow diagram cf a facility employing an
evaporation pond in this manner is shown in Figure 6.
Aluminum Fluoride^Fume Scrubber,Hater. Three of the 1U smelters,
using aluminum fluoride for magnesium removal, use wet scrubbing
for air emission control. Two of the three recycle the water
continuously and neutralize the solution with sodium hydroxide.
The other plant alsc neutralizes the waste water, but since both
chlorine and aluminum fluoride are used at this plant, the
effluent is discharged to a lagoon.
The continuous recycle system shown in Figure 7 scrubs the
emissions with a venturi-type scrubber, followed by a packed
tower and demisting chamber. The waste water is collected in a
settling tank, where it is treated with 5 percent caustic to
neutralize hydrogen fluoride formed from hydrolysis. The sodium
79
-------
TABLE 26. EFFECT OF NEUTRALIZATION AND SETTLING ON SCRUBBING WASTE WATER LOADING
Parameter
Alkalinity
COD
Total Solids
Total Dis. Solids
Total Sus. Solids
Sulfate
Chloride
Cyanide
Fluoride
Aluminum
Calcium
Copper
Magnesium
Nickel
Sodium
Zinc
Cadmium
Lead
Manganese
Chlorine Residue
Oil & Grease
Phenols (ppb)
PH
Waste
Plant C-7 (Case I)
Before Treatment After Treatment
20.1
684
453
45.1
1.03
775
0
-.108
124
-.260
.024
6.03
.008
.002
.140
.009
.009
.132
.078
-.242
-.003
1.7
1.8
6.09
999
710
284
.115
443
0
.053
66.7
-.260
.010
2.01
.008
261
.058
.005
.009
.011
0
.426
-,002
9.2
Loadings, aram of pollutant/kg
Net Effect
-14.0
315
257
239
-.92
-332
0
.161
-57.3
0
-.014
-4.02
0
261
-.082
-.004
0
-.121
-.078
.668
.001
Plant
Before Treatment
2.58
77.4
42.0
16.9
.402
200
0
-.064
13.5
-.182
.017
2.86
.002
0
.053
.004
0
.011
0
1.85
-.001
1.7
of Me removed
C-7 (Case II)
After Treatment
5.47
6.84
450
382
66
.402
234
.047
-.053
15.1
-.182
.007
1.30
.005
143
.036
.002
.006
.006
4.2
3.5
-.002
9
Net Effect
4.26
372
340
49.1
0
34
.047
.011
1.6
0
-.01
-1.56
.003
143
-.017
-.002
.006
-.005
4.2
1.65
-.001
Plant D-6
No Treatment
95.8
1856
83
89.4
1560
—
-0.324
0.615
176
0.236
9.81
0.106
32.7
37.1
0.64
0.054
0.025
0.349
—
0.403
1.0
Plant D-8
Alkali Treatment
No Settling
2754
1.52
4864
3772
1193
41
851 c
0 a
-9.3
184
-0.21
0.01
6.02
0
1919
1.35
0.1!
-o.ofl
0,01
_ —
0
0.02
9.5
-------
32 gpm
SCRUBBER
SYSTEM
KaOH
aoln
REACTION TAHK
1 Floe. Agent
i
MIXING TANK
SETTLING TANK
•Sludge to dump
CENTRIFUGE
FILTER
Figure 5. Chloride fume scrubber waste water treatment (neutralization-settling)
81
-------
Fresh Water
SCRUBBER
Caustic
RECYCLING
TANK
10,000 gal
sediment
Process Wastewater
overflow 40;gpm.
drain once a week
rec
Remove 3, 55 gallon
drums of sludge each
week fipprox, *JQ - 50%
solids after draining
150 epm
EVAPORATION
POND
Figure 6. Chloride fume scrubber treatment (partial recycle and evaporation pond discharge)
82
-------
CO
CO
/
/
/
/
\
/
/
/
/
/
/
/
/
^X" "N. \ PRESATUHATION ,,4W»
1 VTlMvs I \ VENTUHI PACKE
\ . (AcjTnnA^aMftn ' 'LWI1M
of « .. ^* »
^it ,,i _.*,*> NaOH
partlculaleu) no*«i
^n
Continuously (Rake)
Boxed to land Fill SETTLIHG
(Hot Character! seed) ••«
-^Fyg^/
/ / / / XX/vCZ/y./
Stack Gaa
D DEMISTING
CAUSTIC
yf> HttUii
TASK
•* — Hake TO E^O
Figure 7. Aluminum fluoride fume scrubber system with continuous recycle.
-------
fluoride formed reacts with particulate aluminum fluoride carried
with the emission, tc form insoluble cryolite. The magnesium
fluoride which may also be carried with the air stream, cryolite,
and other insolutles are separated in settling tanks, and the
alkaline supernatant is recycled to the scrubber system. The
plant personnel claim that there is no water discharged except
for that removed with the sludge, which is discarded in
landfills. The installation was designed for operation on one
furnace, but plans are to use the system for the three remaining
furnaces. Special retractable panels are being installed to
improve air flows ever the forewell for emission control. Until
these improvements are made, the system remains idle.
waste Water Fr9miaResidue Milling
Water is used by six of the 23 smelters that process residues to
recover metallic aluirinum values. Depending on the nature of the
residue being milled, the amounts of dissolved solids and insolu-
ble solids in the raw waste water vary. When the residues are
slags from secondary smelters, the waste water is very high in
dissolved salts. When the residues are drosses or skimmings from
primary or foundry sources, the amount of dissolved salts in the
waste water is greatly reduced; however, the insoluble solids
fraction in the dross approaches 70 percent by volume. At most
residue milling facilities, both types of residues are handled,
and both types of raw waste water are generated from the same
milling operation. Waste water is also produced from the wet
control of dust generated by a dry milling operation producing a
low salt, high aluirinum product of the solid waste from the dry
milling of residues.
Current Practice
Waste water 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 by
those discharging the waste water into lagoons. Four smelters,
with waste water from residue milling, use such lagoons.
In one plant, all milling residues less than 60 mesh are dis-
charged for treatment in settling pcnds. The first stage, of a
four stage pond system, is treated with a polyelectrolyte to
improve settling. A fourth settling pond, with skimmers, dis-
charges 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 sales or through an industrial disposal contractor.
Residues stored outside are subject to leaching by the rain, and
84
-------
the runoff is
fourth pond.
directed into the plant drainage ditch and the
In another operation shown in Figure 8 (Plant D-8), the discharge
from the milling operation, which contains the insoluble
materials after metallic aluminum was removed, is used to accel-
erate settling of alkaline scrubber solutions from chloride fume
scrubbing waste water discharged into the same ponds. Because of
the mixing occurring in the waste water circuit, the benefits of
this treatment on scrubber waste water loading could not be
determined.
Control Alternatives
The alternative to wet residue milling and the resulting waste
water treatment is dry milling of the residues. Seventeen of the
23 residue processors practice dry milling to eliminate waste
water. 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 en the plant site on the surface of the ground.
Attempts are made to ccntrol the runcff 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, Alternatives
Wet milling of priirary aluminum residues and secondary aluminum
slags by a countercurrent process is claimed by certain segments
of the industry as the only way tc reduce or possibly eliminate
salt impregnation of ground and runcff 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 waste water, 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
85
-------
BAT WATEH 50
HEOIBCULATED
150
volume varies with type
-**-120 gpm
DBQSS. HILL
alkaliae overtreated
20 gpm
DW4 7UHE
SGRUBBEfi
fpumped & Metered
SODA ASH
SLUHHT
Figure 8. Residue milling and alkaline chloride fume scrubber waste water treatment system.
86
-------
for the operation, since they are reusable as fluxing salts in
the secondary aluminum industry. Such a system has not been put
into practice in the United States, although groundwork for
research in the area appears to be developing.
87
-------
-------
SECTION VIII
COSTS, ENERGY AND NONWATER QUALITY ASPECTS
Introduction
This section deals with the costs associated with the various
treatment strategies, available to the secondary aluminum
industry, to reduce the pollutant load in the water effluents.
In addition, other nonwater quality aspects are discussed, since
the entire secondary industry is engaged in recycling scrap
aluminum, it represents significant savings in natural resources,
both in terms of aluirinum ore (bauxite) . and in the reduced
pollution and energy consumption represented by a ton of
secondary aluminum vs a ton of primary aluminum. These aspects
of the industry, therefore, alleviate the nonwater quality
environmental impacts identified for each method of control of
waste water cited in this section.
Because of the nature of the secondary industry, the cost data
obtained are lacking in some details. Often the equipment and
operating costs have been combined with other portions of the
process. Where data were lacking, engineering estimates were
made. All costs are expressed in terms of metric tons. Costs
per ton are ten percent higher.
Easis for Cost Estimation
Capital Investment
Where possible, data en equipment costs and total capital were
obtained from the secondary aluminum processors. These capital
investments were changed to 1971 dollars by the use of the
Marshal and Steven's Index (quarterly values of this index appear
in the publication Chemical Engineering, McGraw Hill). In
addition, where cost data were not available,' equipment costs
were estimated from published data (Peters and Timmerhaus, 1968).
The total capital investment was then calculated as this cost
plus:
Installation
Piping
Engineering
Electrical Services
Contractor's Fee
Contingency
50?6 of equipment.
31X of equipment.
3256 cf equipment.
15% of equipment.
556 cf equipment.
of equipment.
89
-------
Opera-ting Costs
The extent of operating cost data available from the secondary
processors was usually limited to raw materials and maintenance
costs. In order to put all operating costs on a common basis, the
following procedure was used to calculate annual operating cost
items:
Raw material cost - as reported.
Maintenance - as reported or estimated as 5% of total
plant cost.
Depreciation - 10% of the total capital.
Interest - 896 cf total capital.
Tax and Insurance - 1% of the plant cost.
Haste Water From Metal Cooling
Control Costs
There are esentially two means for effecting waste water control:
(1) recycle the cooling water, using a cooling tower to remove
the heat in the water, and (2) perform the ingot cooling in air,
avoiding the use of water altogether.
In a recycle systerr, there will be a build up of dissolved
solids, and some suspended solids, oil and grease, and sludge.
Because of this, a blowdown is carried out about twice a year,
typically amounting to 1,000 gal. In present practice, this
blowdown is discharged. However, total evaporation is
technically feasible for this blcwdcwn.
conversion of a once-through ingot cooling line to a
recirculation system is relatively inexpensive. A capital cost
of about $0.43/annual ton of aluminum with an operating cost of
$0.15/ton, would be required. Elements in this cost calculation
include pumps, settling and slime-settling basin, and the cooling
tower. The operating cost does net include savings, resulting
from the lowered freshwater use. In crder to perform a total
evaporation of the blowdown from the cooling tower, a capital
cost of $Q.30/annual ten, and operating cost of $0.05/ton, would
be added to the costs for the recirculation system.
Addition of an air cooling process necessitates longer conveyor
lines and the installation of blowers. The cost of the air
cooled ingot line relative to the base cost of a once-through
cooling system, hcwever, is dependent en whether the plant is to
be newly constructed or is existing. In the first case, the
smelter is faced with only the difference in initial costs
between water cooling equipment and air cooling equipment
($3.I/annual ton). However, the smelter with an existing water-
90
-------
cooled line is essentially faced with an investment for the total
air-cooled line ($9.2/tcn).
Operating costs for the two cases are air cooling, $2.25/ton, and
water cooling, $1.09/ton. Again, re credit has been claimed for
the water savings. Another consideration is the fact that an
air-cooled ingot line would result in an additional energy
consumption of about 11 kwhr/tcn.
_ Costs
Water from ingot cooling lines contains large amounts of oil and
grease and dissolved solids. The suspended solids content is
about 250 to 500 mg/1, approximately half the concentration of
the oil and grease and dissolved solids. Treatment of this
stream could be done by a separator, which would remove about 7596
of the oil and grease (Patterson and Minear, 1971) and probably
about 50% of the sclids. The equipment consists essentially of a
lagcon with a skimming device. This treatment has capital costs
of about $0.08/annual ton and $0.07/ton operating costs.
Cost Benefit
A summary of the ccst benefit relationship of control and
treatment systems fcr waste water from metal cooling is shown in
Table 27. The data (capital cost) are plotted as Figure 9.
Several points can fce noted from the data presented in Table 27.
No discharge of process waste water pollutants can be achieved by
two means, recycle of the cooling water and evaporation of the
blowdown from the ceding tower in an evaporator, or the use of
air to cool the ingots. Of the two, the recycle scheme is the
most economical, requiring a capital outlay of less than
Si/annual ton. The cne advantage of air cooling is that there is
no water use; whereas, water cooling does result in a water
consumption of about 55 gal/ton (cooling ingot from 1,500° to
100°F). However, the saving in the cost of water does not
justify the use of air coding tc reach no discharge from an
economic standpoint. In addition, the energy requirements of an
air-cooled line are higher, and the air cooling cannot be used
for shot cooling.
In conclusion, it is possible to perform the cooling step and to
achieve no discharge cf process waste water pollutants, either by
recirculation or ty air cooling. Costs involved would add about
$0.15 to $1.0/ton to the cost of the aluminum produced.
91
-------
TABLE 27. COST BENEFIT OF CONTROL AND, TREATMENT
FOR WASTE WATER!FROM METAL COOLING
Discharge
Oil and Dissolved Suspended
grease Solids Solids
kg/ton kg/ton kg/ton
Costs
Capital;
$/annual ton
Operating;
$/ton
Once-through cooling 1.2 0.12 0.63
Recycle cooling water 0,5 0.12 0.13
Recycle cooling water 00 0
with evaporation
Oil Separation 0.4 0.12 0.33
Air Cooling (total) 00 0
Air Cooling (A water) 00 0
0
0.4
0.7
0.1
9.2
3.0
0
0.1
0.2
0.1
2.3
1.1
92
-------
tJ
I 2
3
0
•AIR COOLflMG
RECYCLE
WITH EVAPORATION
O
/RECYCLE
IL SEPARATION
NO
CONTROLx
0
Total Waste Water Constituents, kg/ton
Figure 9. Capital cost for control and treatment of metal cooling :water
-------
Waste Water From Fume^Scrubbinq* >• >
Control^CQSts
The three processes in present use for the control of water
effluent are the Derham Process, the Alcoa Process, and the use
of A1F3 as a demagcing agent.
The equipment cost of the Derham Process was obtained from the
licensing company (Andrews, 1973) as between $5,000 and $10,000
for a production rate of 5,000 kkg (5,5UO tons) of aluminum/year.
The addition of other capital items, installation, piping, etc.,
adds an average ccst of $7,500, and results in a total capital
requirement of $3.^/annual ton. The capital equipment includes
the molten aluminum pumps, an additional holding furnace, and
other items, necessary for conversion of a standard demagging
operation to the Derham Process.
The licensing company claims that several cost savings to the
secondary sirelter would result when the Derham Process is used.
The major savings claimed are:
(1) The reported chlorine usage is 3 kg/kg of magnesium removed,
in lieu of the value of 3.5 kg/kg found in conventional
demagging operations.
(2) An increase in irelt rate of 20*.
The operating cost of $2.5/tcn, calculated for the Derham
Process, includes the savings expected as a result of the two
claims above. However, because cf the present uncertainty as to
whether the Derham process may meet all air pollution control
standards, the costs for this alternative have also been
calculated for two possible cases of scrubber use. If the Derham
process were applied in a small treatment unit (the recommended
method), a relatively small volume of gases would need, to be
scrubbed. This case was calculated en the basis of a caustic
scrubber treating 500 actual cubic feet per minute of gases at
150°C (300°F), and gave additional increments of costs amounting
to $0.55/annual .metric ton capital cost and $0.13/metric ton
operating cost, if the backup scrubber for the Derham process
treated all the gases (i.e., combustion gases and demagging fume
combined), the cost cf the larger scrubber would be higher. This
case is calculated en the assumption that there are some
operational factors, such as lack of space or very stringent air
pollution control conditions, that would lead to the use of the
scrubber on the ccmtined gases. The conditions assumed for this
case were a caustic scrubber, with capacity to treat 11,000
actual cubic feet per minute at 650°C (1200°F), giving a capital
cost of $2.23/annual metric, ton and an operating cost of
$0.5U/metric ten (i.e., over and above the costs of the Derham
process itself).
TTTMention of trade names or specific products does not constitute an
endorsement by the Environmental Production Agency
94
-------
The equipment cost of the Alcoa process was obtained from the
licensee (Demmler, 1972). The equipment cost includes the basic
reactor, the salt tapping vessel, and the metal tapping vessel.
The calculated capital investment, for a 17,000 ton capacity
installation, was $5.9/annual ton.
The operating costs were calculated based on information provided
by the licensee. These represent a difference between the cost
of the Alcoa process and those of the usual fume scrubber
operation. The total operating cost was calculated to be
$2.9/ton. The Alcca process is an entirely dry process. No
water is used for funre control.
The third method of water control is by the use of a wet
scrubbing system in conjunction with A1F3 as the demagging agent.
The major advantage of this scrubbing system over a conventional
chloride fume scrubber is the ability to recirculate the water
used for scrubbing. The fluoride is precipitated with caustic in
the recycle loop. As the process is relatively new, there is not
enough operating experience to determine whether a small bleed
stream would be required. For the purposes of this report, it
was assumed that total recycle is being accomplished.
The capital cost cf equipment was obtained from the equipment
supplier (Waki, 1973) and includes the cost of the scrubber,
packed tower, neutralization facilities, thickening tanks, and
associated pumps. The total capital required is about $14/annual
ton of aluminum. An operating cost of $5.4/ton has been
calculated for the A1F3 process. This cost includes the
additional expense of using AlFjJ, rather than chlorine, as the
demagging agent.
Costs associated with another control technique for fume control
(the "Tesisorb" process) have been calculated, based on data from
a fluoride control installation in a glass plant (Teller, 1972).
These costs were $27.7/annual metric ton capital and $7.3/metric
ton operating. Because of the proprietary nature of the process,
the elements involved in this cost estimate have not been given.
The technical feasibility of this process applied to fume control
in a demagging operation has not teen sufficiently established,
although it does have the advantage of resulting in no discharge
of process waste water pollutants from demagging fume control
operations.
Treatment Costs
The method of treatment of scrubber water, in use at the present
time, is neutralization and settling, costs for this operation
are estimated at $2.8/annual metric ton capital and $1.50/ton
operating. The equipment cost includes the neutralization
facility, settling pcnd, and associated pumps, piping, controls,
etc. The costs of caustic and polyelectrolyte accounts for about
95
-------
1/3 of the total operating cost to neutralize and settle scrubber
water.
Cost Benefit
A summary of the effluent loadings and costs for the treatment
and ccntrol models is given in Table 28. The Derham Process
gives the best cost benefit, of the ether two dry processes, the
Alcoa process is ' cnly slightly more expensive; however, the
installation of the Tesisorb system would result in higher costs.
Hater frQm__Residue_iMillinq
Control Costs
At the present time, the only technically feasible means of
removing the soluble constituents from this waste is evaporation.
The alternative control measure is tc perform the residue milling
on a dry basis.
The costs for evaporation are dependent on the amount of soluble
salts in the residue being milled. The capital cost to evaporate
the water from a low salt content residue (dross) is $16/annual
metric ton, with operating costs of $24/ton. The major equipment
included in the capital cost of evaporation is an evaporator and
crystallizer. The heat, required for the evaporation, amounts to
about 70 percent cf the total operating cost in this cost,
assuming a value of $0.50/million Etu. For a residue with high
salt content (slag), operating costs would be very high (greater
than $300/ton), due to the large amount of heat necessary for
evaporation. For economic feasibility, in the case of water
discharged from slag wet milling, some means must be used to
increase the salt concentration in the water and lower the water
use before evaporation can be considered.
Treatment Costs
Settling treatment in practice has been found to be 99.9+ percent
effective in removing the suspended solids. Dissolved solids,
however, are not removed at all. Ccsts reported from one plant
were $ 8.7/annual ton capital, and $3.3/ton operating.
Corresponding costs, reported from a second plant, were
$15.3/annual ton and $10.9/ton. The reason for the substantial
difference in costs between the two plants is related to the
amount of water use. In the first plant, the residue is
primarily dross, with a low salt content, and consequently, a
water use of only 29,000 liters/ton (7,000 gal/ton). However, in
the second, the water used for the wet milling operation is
217,000 liters/ton (52,000 gal/ton). This difference is due to
96
-------
TABLE 28. COST BENEFIT OF CONTROL AND TREATMENT
FOR WASTE WATER FROM FUME , SCRUBBING
Process
Once -Through
Scrubbing
Neutralize
and Settle
A1F» Process
Derham
Process
Derham
Process
with small
scrubber**
Derham
Process
with large
scrubber**
Alcoa
Process
Tesisorb
(Teller)
Waste Loads,
R rams /kg MB Removed
Suspended Dissolved
Solids Solids Al Mg pH
175 800 50 5 1.5
^50 500 40 1.0 9.1
0 000-
0 000-
- - - -
_
0 000-
0 000-
Costs
Capital
.$ /Annual ton*
0
2.8
14.0
3.4
3.9
5.6
5.9
27.7
Operating
$/ton*
0
1.5
5.4
2.6
2.7
3.1
2,9
7.3
* Ton = metric ton = 2200 Ib.
** Insufficient data available to characterize effluents.
97
-------
the higher
the plants.
salt content of the residue (slag) milled at one of
Cost Benefit
The data on cost benefits are presented in Table 29. Control
costs to reach no discharge of process waste water pollutants are
very high. The only economically feasible method of attaining no
discharge of process waste water pollutants is for new sources to
install a dry milling operation, in lieu of wet milling. At this
point, however, evaporation cannot be ruled out completely,
because of the potential to reduce costs by countercurrent
milling and selective crystallization of saleable salts. On the
other hand, the cost to remove the suspended solids is moderate,
and represents less than half the economic burden of evaporation.
98
-------
TABLE 29. COST BENEFIT OF CONTROL AND TREATMENT
FOR WASTE WATER FROM RESIDUE:MILLING
Process
Waste LoadSj kg/ton
Sus pended Dis soIved
Solids Solids
Costs
Capital
$/annual ton*
Operating,
$/ton*
No Treatment
Settle
720
1.0
Settle and Evaporate,
Low Flow 0
Dry Milling
0
present
present
0
0
35
35
0
0
8.7-15.3
16
130
0
3.3-10.9
24
* Metric ton of aluminum produced.
99
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE — EFFLUENT LIMITATIONS GUIDELINES
Introduction
The effluent limitations, which must be achieved by July 1, 1977,
are to specify the degree of effluent reduction attainable
through the application of the best practicable control
technology currently available. Such control technology is based
on the average cf the best existing performance by plants of
various sizes, ages, and unit processes within the industrial
category. Because of the absence of data on the characterization
of waste water by this industry, the treatment technology and the
corresponding effluent limitations are based on a sampling survey
of waste waters from exemplary plant operations in this
subcategory. Consideration must also be given to:
(a) The total ccst of application of technology in
relation to the effluent reduction benefits to
be achieved from such application.
(b) The size and age of equipment and facilities
involved.
(c) The processes employed.
(d) The engineering aspects of the application of
various types of control techniques.
(e) Process changes.
(f) Nonwater quality environmental impact (including
energy requirements).
The best practicable control technology currently available em-
phasizes treatment facilities at the end of a manufacturing
process. It also emphasizes the control technologies within the
process itself, when they are considered to be noriral practice
within the industry. Other technology currently available was
considered for its degree of economic and engineering
reliability.
Industry Categorization and Kaste tfater Streams
The secondary aluminum smelting subcategory is defined as that
segment of the aluirinum industry which recovers, processes, 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 fcrirs en the open rrarKet as their raw material.
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A more useful approach for the purpose of developing effluent
limitations guidelines is to deal with the waste water streams
themselves. The principal streams are (1) waste water from metal
cooling, (2) waste water from fume scrubbing, and (3) waste water
from residue milling. Each stream has an associated loading of
pollutants per pound of product or scrap processed. For example,
the guidelines require a smelter generating only ccoling waste
water to meet the effluent limitations established for that waste
stream. A smelter generating cooling, scrubber, and residue
milling waste waters would be required to meet the effluent
limitations established for each respective waste water stream.
Bater Froin Metal Cooling
Effluent Limitations Bagg£_Qn the Application of
Best: practicable CcQtKgl Tecfrn9loqy Currently Available
The effluent limitations, baaed on the application of the best
practicable control technology currently available, is no
discharge of process waste water pollutants into navigable
waters.
The achievement cf this limitation by use of the control and
treatment technologies identified in this document leads to the
complete recycle, reuse, or consumption of all water within the
process, with an associated result of no discharge of process
waste water pollutants.
Identif j,cafrion_Q£_qe8t .Practicable Control
The best practicable control techr.clogy currently available for
metal cooling in the secondary aluminum industry is the elimi-
natipn of water discharge through the use of the following
approaches:
(1) Air cooling of ingots.
(2) Total consumption of cooling water for ingot cooling.
(3) Recycle or reuse of cooling water for deoxidizer-
shot cooling or ingot cooling.
With reuse or recycle of water, the need for sludge removal and
oil removal will be dictated by plant operational procedures
(i.e., the care used in controlling contaminants caused by poor
housekeeping)• Dissolved salt contamination may be reduced with
improved housekeeping and improved manufacturing procedures.
Such precautions wculd provide for an extended period of water
reuse, which approaches that cf no discharge of process waste
water pollutants.
The implemention cf the air cooling method or the total
evaporation cooling method (the air cooling method with water
mist added to assist the air cooling) requires:
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(a) The addition of ingot molds to the lengthened
conveyor line.
(b) The installation of blowers.
(c) In the case of total evaporation cooling, the
addition of special nozzles, flow meters, and
controls to existing water lines.
To implement a recycle system for ingot cooling requires:
(a) The additior of a cooling tower, holding tanks,
and pumps tc the existing water cooling facility.
(b) Provisions fcr oil and grease removal.
(c) Provisions for sludge removal, dewatering, and
disposal.
Rationale for Selecting the Best Practicable
Control Technology^Currentlv Available
Thirty-one of the 58 plants canvassed (cr 54 percent) are cooling
ingots by one of the methods given above. Existing cooling
lines, used for once-through water cooling, could be converted to
one of three alternative methods to eliminate the discharge of
water. Shot cooling will continue to require direct water
cooling and only the last option above, (c) , is available to
these plants.
Age and size of Equipment and Facilities. As set forth in this
report, general improvements in production concepts have
encouraged modernization of plant facilities throughout the
industry. This, coupled with similarities of waste water
characteristics from metal cooling for plants of varying size,
substantiate the identification cf total recycle of cooling
and/or consumptive coding as practicable.
in __ Relation __ to Pollutant __ Reduction.
Based on the information contained in Section VIII of this
report, a capital ccst of about $0.43/annual metric ten of
aluminum alloy wculd be required to convert an existing once-
through cooling systems to a recirculation system* An operating
cost of $0.15 per ton would be required, but does not include
savings resulting frcm the lowered fresh water use. Conversion
to an air-cooled ingct line from a water-cooled line is estimated
to require an investment of $9,2 per ton. Operating costs would
be $1.09 per ton, with no credit being claimed for water savings.
Engineering Aspects cf Control Technique Application ,
This level of technology is practicable, because over 54 percent
of the plants in the industry are now achieving effluent
reductions by these methods. The concepts are proven, available
for implementation, and may be readily adopted by adaptation or
modification of existing production units.
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Process Changes. This technology is an integral part of the
whole cost saving and waste management program now being
implemented within the industry. While the application of such
technology requires process changes, each has been practiced by
existing plants in the industry.
Nonwater Quality Environmental Impact. There are four possible
associated impacts 4upon major'™ nonwater elements of the
environment;
(1) An incremental addition to the thermal load of the plant
by thermal radiation from air cooling of ingots.
(2) Added electrical energy requirements of about 11 kwhr
per ton would be needed for air cooling operations.
(3) Negligible impact on air quality is anticipated from
water evaporation either from consumptive water-mist
cooling or from sludge drying.
(U) Solid waste disposal of dried sludge would be a minor
impact, because of very small amounts accumulated, and
its nontoxic character (A1203) . Oil and grease,
collected during recycled water""ccoling operations, may
be disposed of through responsible waste oil disposal
contractors.
Waste Water From Fume Scrubbing
Effluent Limitations Based on the Ap^3.ication gfrthe
Best Practica£le Ccntrol Technology Currently Available
The effluent limitations, based on the application of the best
practicable control technology currently available, are given in
Table 1 for waste water generated during magnesium removal with
chlorine. The effluent limitation based on the application of
the best practicable control technology currently available is no
discharge cf process waste water pollutants for waste water
generated during magnesium removal with aluminum fluoride.
Rationale .£or_ Effluent Limitations Eased on the Application
of the Best Practicable Control Technology Currently Available
The values given in Table 1 were derived as follows:
(1) The 30-day average value for total suspended solids is
the average of the values given in Table 26 (namely 284
gm/kg and 66 gm/kg) for Cases I and II of Plant c-7.
These two values are considered the most representative
available. Both of these "after treatment" values are
higher than the suspended sclids values in the untreated
waste. The increase in values during treatment is due
to the fine particles of reaction products formed during
neutralization, adding to the quantity of suspended
solids.
(2) The 30-day average value for chemical Oxygen demand is
the average of the two values (6,1 and 6,8 grams/kg for
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the same effluents (Plant C-7, Cases I and II,- Table
26) .
(3) The 30-day average ranges of pH given in the limitations
are those estimated to provide the optimum conditions
for acceptable pH and ccprecipitation of both heavy
metals, such as copper, and amphoteric elements, such as
zinc and aluminum.
Identification of the Best Practicable Control
Technology Currently Available ~"
— '-11 Y J 1- _ - ^T I • — i" j. J i — -wi — i f mm
The best practicable control technology currently available for
control of the discharge of pollutants contained in fume scrubber
waste water is as fcllcws;
(1) When chlcrination is used for magnesium removal,
adjustment of the scrubber effluent pH to between 7.5
and 8.5, followed by settling for solids removal. Prior
adjustment of the pH of the scrubber liquor, so that the
resultant effluent from the scrubber is at a pH of 7.5
to 8.5, followed by settling for solids removal is
equally practicable.
(2) When aluminum fluoride is used for magnesium removal,
adjustment of the scrubber effluent pH to between 7.5
and 8,5, followed by settling for solids removal. (In
practice this treatment is an integral part of the
control technology discussed in Section x.) After
neutralization and settling, the supernatant is recycled
continuously. Solid fluorides are removed continuously.
The fume scrubber water from the chlorine magnesium removal
process, upon pH adjustment, cannot be recycled continuously, due
to excessive buildup cf sodium chloride. Partial recycle of the
clarified treated effluent will reduce water consumption.
The use of neutralization and settling treatment, to remove
pollutants from chloride scrubber waste water, requires reaction
tanks for pH adjustment, mixing tanks for polyelectrolyte
addition (if settling is not rapid), a settling tank for solids
removal, and associated pumps, controls, and plumbing.
The implementation of continuous recycle of fluoride scrubber
waste water will require the additions of liquid storage and
pumping capabilities. A chain conveyor for continuous solids
removal would also be required.
Rationale for Selecting the Best Practicable
Control Technoloqy_Currentlv Available
Of the 29 plants using wet scrubbing to control air emissions, 20
(or 69 percent) are fracticing some fcrm cf pH adjustment. Of
these 20, 15 (or 51 percent) are removing solids by settling.
105
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The adjustment of pH to 7.5 to 8.5 and settling are effective in
removing aluminum and magnesium ions as hydroxides from chloride
fume scrubber waste water. Some removal of heavy metals as
hydroxides also occurs with the removal of the aluminum and
magnesium hydroxides. At a pH of 9.0 or greater, aluminum
hydroxide and other amphoteric metal pollutants are dissolved.
Therefore, to maximize the overall metal removal, the pH
generally should net exceed 8.5. (see discussion, Section VI and
Table 26) .
An adjustment of pH tc 7.5 to 8.5 is effective in reducing the
solubility of fluorides by neutralizing the hydrogen fluoride in
the effluent. Acid fluoride salts are more soluble than the
neutral fluoride salts of the ccmmcn pollutants in fluoride fume
scrubber waste water. The limited solubility of the neutral
fluoride salts in water provides a supernatant solution suitable
for recycle in scrubber operation.
Aqe_and Size.of Equipment and.Facilities. Those segments of the
industry that are refining aluminum alloys must remove magnesium
to attain the specifications cf their customers. Therefore,
regardless of the size or age of the facility, chemical removal
of magnesium is practiced. Control of air emissions from
demagging operations with wet scrubbers also is practiced by a
majority of the secondary aluminum smelters. Control of the pH
and solids content of the effluent from the scrubber is also
practiced. In such cases, investments would have to be made for
sludge disposal. In a large tonnage secondary smelter, scrubber
equipment is used continuously and requires larger treatment
facilities than a smaller tonnage plant, A small plant may
require treatment capacity for operations lasting only four hours
per day. The capital investment for treatment equipment per
annual ton would te greater for the smaller plant. However, the
similarities in the fume scrubber waste water generated in each
type of magnesium removal process (chlorine or aluminum
fluoride), regardless of the size or age of the facility,
substantiate the level of pollutants that can be removed by pH
adjustment and settling.
Those plants using aluminum fluoride for magnesium removal can,
by using the same technology, eliminate the discharge of
pollutants by adapting the system to completely recycle the
supernatant after settling.
Total. Cost_ of Applicatjgn in_RelaticnmtoJ?ollutign_Reduction.
Based cn~the information contained in section VIII of the report,
a capital cost of about $2.75 per annual metric ton of aluminum
alloy produced would be required to install a pH adjustment-
settling treatment capability to control pollutant levels from
•the chloride scrubber systems. An operating cost of $1.5 per
metric ton is estimated for such an installation. Lesser capital
expenditure would te required by those already neutralizing the
scrubber effluent. ,
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For those plants using aluminum fluoride for magnesium removal,
treatment of the scrubber waste water requires, in addition to
neutralization and settling, a means to recirculate .the scrubber
water continuously and to continuously remove solids. This would
require an estimated capital investment of $9.9 per annual metric
ton and an operating ccst of $2.US/metric ton.
Engineering Aspects of Control Technique .Applications^ This
technology is practiced by over 51 percent of the plants in the
industry to reduce the discharge of pollutants from fume
scrubbing operations. The concepts are proven and are available
for implementation. They can be adopted to fume scrubbing
effluent streams by those presently not using them as an end-of-
pipe treatment facility.
Process Changes. The technology of pH adjustment and settling to
remove solids is an integral part of the whole waste management
program already implemented by part of the industry. All plants
in the industry use the same or similar demagging processes,
which produce similar discharges. There is no evidence that
operation of any current manufacturing process will affect the
capability of a plant to implement these end-of-pipe waste
treatment technologies.
Nonwater Quality Environmental Impjactj, There is only one
essential iirpact upcn major nonwater elements of the environment.
This is the potential effect on soil systems due to the reliance
upcn the land for ultimate disposition of final solid waste from
the treatment. The solid wastes are primarily inorganic and
nonleachable. The solid waste from fluoride recovery potentially
can affect ground waters adversely and should be disposed of in
an acceptable landfill to prevent the contamination of surface or
subsurface waters.
Selection of Production Units. Effluent limitations specify the
quantity of pollutants which may be discharged from a point
source after the application of the best practicable control
technology currently available. This quantity must be related to
a unit of production, so that the effluent limitations can be
broadly applied to various plants in the same subcategory.
The amount of pollutant generated during the chemical removal of
magnesium from a given heat is dependent upon the amount of
magnesium originally present in the charged scrap and the final
magnesium content desired in the metal produced. Judicious
selection of scrap entering the melt will reduce this difference,
the length of time required for chemical treatment, and the
amount of chemical required for reducing the magnesium content to
the desired level. These variables in turn establish the amount
of material entering the scrubber water. There are variabilities
in the amount of magnesium removed for a unit weight of chemical
agent. Frequently, these are dependent on the furnace operators1
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•techniques and/or plant practices and, therefore, are not suited
for a production unit. An invariant production unit suitable for
the determination of pollutant loadings is the amount of
magnesium removed relative to the amount of metal produced. This
can be determined frcm the percent magnesium contained in the
charge before magnesium removal and the resultant magnesium
content.
The application of this guideline requires the reporting of the
number of pounds cf magnesium removed based on the magnesium
content of the melt before magnesium removal, the magnesium
content of the product metal, and the net weight of the metal
treated for magnesiurr removal. These data are currently a part
of company records. Also required are the flow rate of the
discharge water strearr from the scrubber system, and the analyses
of the pollutants in that stream.
Waste_Water from Residue Milling
Effluent Limitations Based on the Application of the
Best Practicable Ccntrol Technology Currently Available
The effluent limitations based on the application of the best
practicable control technology currently available is that given
in Table 2 in Section II.
Rationale for Effluent Limitations Based on the Application
of the Best Practicable Control Technology Currently Available
The values given in Table 2 were derived as follows:
(1) The 30-day average value for total suspended solids is
that reported for Plant D-4 in Table 21. This value is
used since it was based on verified, seven to nine month
averages of sampling, and is otherwise considered a
valid value on the basis of plant operations and raw
material variation.
(2) The value for fluoride is derived from data for Plant D-
8 in Table 21 and is based en 9 composite samples over a
three day period.
(3) The value fcr ammonia was derived by using the actual
concentration of ammonia in the effluent from a plant
using exeirplary milling practice (0.3 mg/1. Plant D-8,
Table 21), and calculating the loading on the associated
flow (200 gpm, or 1,090,080 liters/day) and production
(37.8 metric tons per day). This use of concentration
reflects the chemistry cf the reaction during alkaline
wet milling. The calculated net loading of ammonia for
Plant D-8 in Table 18 is a negative value, that is, the
discharge water from the alkaline wet milling operation
contained less ammonia than the intake water.
(U) The limitation value for aluminum was derived in the
same manner as the ammonia value (i.e., using the
concentration of 28 mg/1 for Plant D-8 in Table 21).
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The same flow and production as in (3) were used, giving
a value of 1.0 kg/metric ton of metal recovered.
(5) The values of ammonia, aluminum, copper, and pH are
interrelated. The pH specified is to he achieved with
reagents ether than ammonia. However, • if an ammonia
loading were not specified, the specified pH value could
be present due to a high ammonia content. Further,
ammonia and copper interact to form chemical complexes,
whose presence would not necessarily be reflected in the
measurement of pH. Aluminum is specified to prevent
under or ever alkalizaticn.
(6) The value of chemical oxygen demand specified is that
listed for Plant D-3 in Table 21 (0.97 rounded to 1
kg/metric ton). The source of COD in the effluent has
not been fully documented.
Identification of the Best^Practicable
Control Technology Currently,jyailable
The best practicable control technology currently available for
control of the discharge of pollutants contained in waste water
from residue milling is the following:
A settling treatment of three to four stages, with
partial recycle cf the sludge and the clear super-
natant from the fourth stage to the mill. Adjust-
ment of the intake water pH is necessary to reduce
ammonia levels in the waste water during milling.
When milling is dore without pH adjustment of the intake water,
ammonia remains in solution as a pollutant. To aid the settling
of the milling wastes, a polyelectrolyte is frequently added to
reduce the level cf suspended solids. Recirculaticn of the
sludge in the last settling pcnd to the mill will reduce the
overall sludge content of the final pond.
Rationale for Selecting the Best Practicable
Control Technology Currently Available
Only six of the 23 plants (or 26 percent) processing residues use
water for milling. Cf these, cnly three are discharging to
navigable waters after treatment in such ponds. The remaining
three use total impoundment,
Settling is capable of reducing settleable and suspended solids
to very low levels. However, dissolved salts are not removed.
Evaporation and crystallization, although a viable alternative
for salt removal, is not currently practiced in the United
States. The principal reason is that the cost of salt recovery
(for flux cover use) exceeds the price of the salt, even if more
concentrated salt solutions were attainable through process
changes. The alternative to discharge is total impoundment.
109
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Age and Size of Equipment and Plant. Regardless of the size and
age of the facility, "the waste water generated from residue
milling is similar. All plants are practicing the same type of
waste management. Loadings dc vary with techniques employed and
the amount of mclten metal recovered from the operation.
Modernization of this segment of the secondary aluminum industry
has already reduced the number of smelters processing residues
for metal value recovery tc 23 plants. Since 17 of the 23 plants
process the residues dry, this trend is expected to continue.
The life cf the equipment in the wet mill is two to three times
longer than equipment in dry mills, because of the lower energy
requirements needed for comminution.
Io£al_£ost_in_ReJ.aticn tg ggljLytign Deduct ioru Based on the
information contained" in Section Vlll'of this document, a capital
cost of about $8.7 to $15.3 per annual metric ton of alloy
recovered as molten metal and an operating cost of $3.3 to $10.9
per annual metric tor tc treat residue waste water by settling is
estimated. Variations in the cost are dependent upon (1) the
amount of water us€d for milling and (2) the solids content of
the residue.
Engineering Aspects cf_cqntrpl Technique Application^ This level
of technology Is practiced by tHree cf six plants', which process
residues by wet methods. The concepts are proven and are
reliable for implementation.
process Changes. Only minor process changes are foreseen. The
practice of partial recirculaticn of the treated effluent is
currently used by twc plants in the industry.
Nonwater Quality Environmental ^Impaet. ' There is no added impact
upon major nonwater elements cf the environment by the adaptation
of settling for removal of suspended solids. An impact on soil
systems currently exists, due to the reliance upon land for the
ultimate disposition cf the final solid waste from a wet residue
milling operation.
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SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY
ACHIEVABLE— EFFLUENT LIMITATIONS GUIDELINES
Introduction
The effluent limitations which must he achieved by July 1, 1983,
are to specify the degree of effluent reduction attainable
through the application of the best available technology
economically achievable. This technology can be based on the
very best control and treatment technology employed by a specific
point source within the industry category or subcategory, or
technology that is readily transferable from one industry process
to another. A specific finding must be made as to the
availability of control measures and practices to eliminate the
discharge of pollutants, taking intc account the cost of such
elimination.
Consideration must also be given to:
(a) The age of the equipment and facilities involved.
(b) The process eirplcyed.
(c) The engineering aspects of the application
of various types of control technologies.
(d) Process changes.
(e) Cost of achieving the effluent reduction
resulting froir the technology.
(f) Nonwater quality environmental impact (including energy
requirements).
The best available technology economically achievable also
assesses the availability in all cases of inprocess controls, as
well as the control or additional treatment techniques employed
at the end of a production process.
A further consideration is the availability of processes and
control technology at the pilot plant, semi-works, or other
levels, which have demonstrated bcth technological performances
and economic viability at a level sufficient to reasonably
justify investing in such facilities. Best available technology
economically achievable is the highest degree of control
technology that has teen achieved or has been demonstrated to be
capable of being designed for plant scale operation, up to and
including no discharge of pollutants. Although economic factors
are considered, the costs for this level of control are intended
to be top-of-the-line cf current technology subject to
limitations imposed by economic and engineering feasibility.
However, best availatle technology economically achievable may be
characterized by seme technical risk with respect to performance
and with respect tc certainty of costs and, thus, may necessitate
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some industrially sponsored development work prior to its
application.
Waste Water from Metal Cooling
The effluent limitations attainable by the application of the
best available technology economically achievable for cooling
waste waters is no discharge of process waste water pollutants to
navigable waters, as developed in Section IX, The best available
technology economically achievable is identical to the best
practicable control technology currently available.
Haste Water from Fume Scrubbing/1>
Identification of Best Available Technology
Economically Achievable ~
The best available technology economically achievable is the use
of inprocess and end-cf-process controls and treatment to achieve
no discharge of process waste water pollutants into navigable
waters* This can be achieved by using one, of the following
approaches:
(1) The use of currently available processes for fumeless
chlorine magnesium removal
(2) Using a combination cf A1F£ for demagging and continuous
recycling of scrubbing water from emission and effluent
control systems
(3) Using a combination of A1FJ3 for demagging and a coated
baghouse system for air pollution control.
Fumej.ess Chlorine Dejagging Processes, The process developed by
Derham and the process developed by Alcoa are techniques for
removing magnesium frcm molten aluminum scrap with a . minimum of
fume generation, through the efficient use of chlorine. No water
is used for fume control, but a back-up scrubber may be required
with the Derham system. <
In the Derham Process a thick cover ;of fluxing salt over the
molten metal almost completely arrests fume emissions and the
subsequent need for wet scrubbing for their control. Details of
this process are given in section VII.
The Alcoa process operates on a similar principle, using
efficient chlorinaticn of magnesium to minimize emissions. The
unit .is inserted between the casting line and the furnace and
demagging with chlorine takes place as the metal is being cast.
(1) Mention of trade names or specific products does not constitute an
endorsement by the Environmental Production Agency
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A1F3 Magnesium Bemgval_with Continuous Recirculation of Scrubber
water. The uie of A1F3 for removing magnesium" from molten
aluminum scrap is advantageous in that it permits fume scrubbing
waste water to be continuously recycled. The fluoride salts are
relatively insoluble and can be'settled out. The same approach
for wet scrubbing fumes frcm chlorine demagging for emission
control is not possible, because of the dissolved solids buildup.
A1F3 Magnesium_Removal_ Fume control With tlie Coated Baghpuse
(Teller) Process. In this process fumes from A1F3"magnesium
removal are controlled by passing them through chemically treated
filters (bags), which remove the pollutants from the exhaust.
The system eliminates the use of water for fume control.
Rationale for Selecting. Best Available Technology
Economically Achievable ~
Time Available for.Achieving Effluent Limitations^ The effluent
limitation of no discharge of process waste water pollutants from
fume scrubbing is required before July 1, 1983. This allows
sufficient time for the planning, purchasing, installation, and
trial operation cf eguipment needed for the three control
alternatives identified.
Cost of Achieving the Effluent Limitations. The estimated cost of
achieving the "effluent limitations from fume emission control
will depend on which cf the three techniques, given above, is
used. The use of the Derham Process for magnesium removal
involves an estimated capital expenditure of $3.4 per annual
metric ton of capacity and an estimated operating cost of $2.5
per metric ton. The Alcoa Process has been estimated to require
a capital cost of $5.9/annual metric ton and an operating cost of
$2.9/metric ton (with no credit being taken for selling the
magnesium chloride). The use of A1F3 for magnesium removal,
combined with continuous recirculation of scrubber water for
emission control involves an estimated capital expenditure of
$14.0 per annual metric ton and $5.4 per metric ton operating
cost. Use of chemically treated baghouse systems (Teller System)
for removal of air eirission during magnesium removal with A1F_3
was similarly estimated to require a capital expenditure of about
$27.7 per annual metric ton of capacity and an operating cost of
$7.3 per metric ton.
Engineering ^Aspects of^ Control Technique Application^ The
engineering practicability of the Derham Process is demonstrated
by its pre'sent use in the industry. Currently, the process is
under license or is operating at four plants within the U. S. and
in four plants outside the U. S. In a telephone canvass of the
secondary industry, several plants indicated that they were
considering using this process. Both the Derham and Alcoa
processes will require extensive research and development efforts
tc meet their limited capacity (Alcoa) and to reduce their
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reliance on
standards.
secondary scrubbers (Derham) to meet air quality
The use of A1F3 for demagging with continuous recirculaticn of
scrubber water is considered achievable because two large plants
in the secondary industry are using this technique for emissions
and effluent control.
The use of chemically treated fcaghouses (Teller System) for dry
air pollution control during A1F3 demagging is yet unproven from
an air quality standpoint. One major plant in the secondary
industry has installed the system and is presently evaluating its
effectiveness.
Process Changes. The application of the Derham Process or the
Alcoa Process for magnesium removal would require those plants
using A1F.3 to change to chlorine and adopt the appropriate pro-
cedures and safety measures for its application. No major
process changes are anticipated for those already using chlorine.
The use of A1F3 with continuous recycling of scrubber water would
require those plants presently using chlorine to change to A1F3
for demagging. This would not involve a major process change, as
the application cf A1F3 for demagging is simpler than
chlorination demagging, but twice as expensive for the removal of
the same amount of magnesium. Those plants with low energy, wet
scrubbing systems used for chlcrine demagging, would need to
convert to higher energy systems for effective scrubbing of the
fumes generated with the use of AlF^J. Although not a principal
process change, the change to A1F3 demagging would require
extensive modification of present air""pclluticn control equipment
now used for collecting fumes from chlorine demagging in some of
the larger plants.
The chemically treated baghouse system (Teller System) for dry
air pollution control would require those plants using chlorine
for demagging to charge to A1F.3. Those already using AlF^ would
have no process change,
Nonwater Quality Environmental Impact. The use of the Derham
Process results in no known nonwater quality environmental
problems. The residues resulting frcm its application may be too
high in soluble salts for economic processing by residue milling
techniques for metal recovery .and could present a solid waste
disposal problem. Insufficient information exists on the process
to assess this impact.
Application of A1F3 with continuous scrubber water recirculation
could result in a solid waste disposal problem. Fluoride salts
precipitated and settled from the scrubbing water are slightly
soluble and could possibly be leached in a landfill disposal
site.
114
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Application of chemically treated baghouse systems for dry air
pollution control also results in a solid waste as the bag
coating and the collected dust and fumes may contain fluoride
salts that are slightly soluble and leachable to ground water.
Disposal of solid wastes in an acceptable landfill is required to
prevent contamination of surface or subsurface waters.
Waste Hater from Residue Milling
Identification of Best Available Technology
Economically Achievatle
The best availatle technology economically achievable for waste
water from residue milling is the replacement of present wet-
milling operations by totally dry milling methods. In dry
milling, the residue is crushed and the contained salts,
fracturing into small particles, are screened out as undersized
waste material. The dry operation is extremely dusty and
requires extensive air pollution controls.
Recovery of dissolved salts contained in waste streams from wet
milling by evaporation and crystallization is a potential
approach to the ccntrol or elimination of the discharge of
pollutants. The salts can be reused for flux and the condensed
water can be recycled back to the milling process. Salt recovery
has not been demonstrated in the United States, but is used in
Europe.
Rationale for Selecting the Best Available .Technology
Economically Achievatle
Time.Available.for.Achieving Effluent Limitations^ The effluent
limitation of no discharge of process waste water pollutants to
be achieved July 1, 1983, allows time for the retirement of
existing wet milling operations by those plants using this
practice.
Cost_of Achieving the Effluent Limitations, The cost of achieving
no discharge of process waste water pollutants from the milling
of residues is estimated to be abcut $130.00 per annual ton of
aluminum production capacity. This is the cost of building a new
plant, for the changeover from wet to dry milling involves a
complete process change. Data are not available for operating
costs, but estimates frcm the secondary industry indicate such
costs to be higher than for wet processing.
The cost of recovery of salts from waste water from residue
milling is dependent on the type of residue being processed. The
estimated capital cost to evaporate the water from low salt
content residues is $16/annual metric ton of aluminum, while
operating costs are $24/metric ten. When high salt content
115
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residues are processed, the estimated capital costs are
$200/annual metric ten and the operating costs are $124/metric
ton.
Engineering Aspects cf Cgntrcl Application. Dry processing of
residues^for aluminum recovery is practical from an engineering
standpoint since 15 of the 23 plants processing residues use a
totally dry mill operation and generate no associated waste water
stream. Thus, the technology is.well proven by actual practice,
Process Changes. Plants presently wet milling residues will need
to completely alter their presmelter processing facilities to
adopt dry milling practices. Crushing, screening, conveying, and
dust collection equipment will be required for the conversion.
Nonwater Quality Environmental.Impact. Both dry milling and wet
milling of residues generates large quantities of solid wastes,
ranging from 2. 3 to 9 tons per ton of aluminum recovered,
depending on the grade of the residue. Generally this solid
waste from dry milling contains the highly soluble chloride salts
that were washed cut during wet milling. Solids should be
disposed of in an acceptable landfill to prevent contamination of
surface or subsurface waters.
Dry milling also generates large quantities of airborne dust.
Appropriate dry collection systems are normally able to control
the atmospheric emissions of the dust,
Recovery of salts by evaporation from wet milling waste water is
estimated to require additional consumption of thermal energy of
8.6 million kg cal/tcn for the low salt residue waste water and
176 million kg cal/metric ton for the high salt residue waste
water (on the basis cf metric tens of aluminum recovered).
116
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SECTION XI
NEK SOURCE PERFORMANCE STANDARDS
Introduction
The standards of performance, which must be achieved by new
sources, are to specify the degree of effluent reduction attain-
able through the application of the best available demonstrated
control technology, processes, operating methods, or other
alternatives. The added consideration for new sources is the
degree of effluent reduction attainable through the use of
improved production processes and/cr treatment techniques. The
term "new source" is defined by the Act to mean "any source, the
construction of which is commenced after publication of proposed
regulations prescribing a standard cf performance."
New source performance standards are based on the best inplant
and end-of-process technology identified with additional
consideration given to techniques for reducing the discharge of
pollutants by changing the production process itself or adopting
alternative processes, operating methods, or other alternatives.
The standards of performance reflect levels of control achievable
through the use of improved production processes (as well as
control technology), rather than through a particular type of
process or technology, which must be employed. A further
determination must be made as to whether a standard permitting no
discharge of process waste water pollutants is practicable.
Consideration must also be given tc:
(a) The type of process employed and process changes.
(b) Operating methods.
(c) Batch as opposed to continuous operations.
(d) Use of alternative raw materials and mixes of raw materials.
(e) use of dry rather than wet processes (including substitution
of recoverable solvents for water).
(f) Recovery of pollutants as byproducts
Waste Water from -Metal Cooling
Standards of Performance based on the Application of
the Best Available Demonstrated Ccntrcl Technology
The standards of performance to be achieved by new sources is no
discharge of process waste water pollutants into navigable waters
as developed in Section IX of this document.
Identification of the Best Available Demonstrated Control
TechnoloqyT Processes, Operating Methods, or Other Alternatives
117
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The best available demonstrated control technology for metal
cooling waste water is identical to the best practicable control
technology currently available described in Section IX. The
control and treatment technologies identified in Section IX are:
(1) Air coding of ingcts
(2) Total consumption of cooling water for ingot cooling
(3) Recycle or reuse of cooling water for deoxidizer shot
cooling or ingot cooling.
Rationale for the Selection of the Best Available Demonstrated
Control Technology
Thirty-one of the existing plants, or 5U percent of the plants
canvassed during development of these guidelines, were using the
technology identified above and described in section VII of this
document. Thus, the technology is judged to be both available
and demonstrated.
A new source has the freedom to design a technology, initially,
to achieve the standard of performance without any change in
existing equipment. The current practice of these control
technologies by a large fraction cf the industry demonstrates
that there are no significant technical or economic barriers to
the selection and implementation of such technology.
The cost of application of the technologies, identified in
section VIII, is estimated to be the same or less for new sources
than for existing plants.
Waste Mater from Fume_scrubbing*l>
standards of Performance, teased en the Acclication of
the Best Avaj.].able Demonstrated control Technology
The standards of performance to be achieved by new sources
discharging to navigable waters are:
1) Identical to the effluent limitations presentedsin Table
lf Section II, for those plants using chlorine for
magnesium removal
2) No discharge cf process waste water pollutants for those
plants using aluminum fluoride for magnesium removal.
Identification of th€ Best Aya^able Demonstrated Control
Technology^ Processes. Operating Methods, or Othey Alternative^
The technology previously identified in Section X as the best
available technology economically achievable for control of fumes
from chlorine deiragging does not meet the criterion of
"demonstrated". This technology may not be capable of handling
the anticipated capacities of new plants and still permit the
control of air contaminants by dry methods. Therefore, the
technology previously identified in Section IX as best
practicable control technology currently available is considered
THMention of trade names or specific products does not constitute an
endorsement by the Environmental Production Agency
118
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identical to the best available demonstrated control technology
for waste waters froir magnesium removal processes.
Rationale for Selection of__th§_ _Jest_ Available Demonstrated
Control Technology ~ *"
The rationale for concluding that the best available demonstrated
ccntrcl technology is identical to the best practicable control
technology currently available for waste waters from magnesium
removal processes using chlorine is as follows:
(1) Although the technology described in Section X indicates
that the Eerham and Alcoa processes are able to control
fume emissions from chlorine demagging without the use
of water, there are some technical limitations to their
adoption by new sources. The Alcoa prototypes have been
limited to inhouse use for primary aluminum processing
and have not been used by the secondary aluminum
industry in the United States. In addition, the design
may require modification tc meet the casting poundage
rates presently used by most of the industry. In
effect, the system may not be applicable to new sources
without further development work.
(2) The Derham process is used by two secondary aluminum
smelters in the United States to control fumes generated
during the process of magnesium removal with chlorine.
One of these plants was not studied and the other was
found to be not fully operational. Therefore, it was
concluded that insufficient data are available to prove
that the system is effective under typical operating
conditions. A supplemental wet scrubber may be required
with the Eerham process to meet air emmissions
standards. This is the case for at least one plant in
the subcategory. The Derham process is considered
insufficiently demonstrated to be applied to new sources
without further technical evaluation.
Haste Hater from Residue Milling
Standards of Performance Based on the Application of the Best
Available Demonstrated Control Technology
The standard
discharge of
waters.
of performance to be achieved by new sources is no
process waste water pollutants into navigable
Identification of the Best Available Demonstrated Control
Technology.* Processes, operating_Methods, _or Other Alternatives "*"
The best available demonstrated control technology, processes,
operating methods, cr other alternatives for residue milling
waste water are:
(1) Dry milling, currently in practice in existing plants in
the U.S.
119
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(2) The evaporation of waste waters from wet milling of
residues with the associated reclamation and reuse of
fluxing materials. This technology is not currently
demonstrated in any existing plant in the U.S., but is
demonstrated in Europe.
The details and costs of these technologies are presented in
Sections VII and VIII of this document.
Rationale for Selection of the Best Available Demonstrated
Ccntrol_Technoiogv ~ ~"
The rationale for the selection of the
demonstrated contrcl technology is as follows:
best available
(1) A new source has the freedom to choose the most
advantageous residue processing techniques for maximum
recovery of metal and byproducts with the minimum use or
discharge of water.
(2) In contrast to an existing source which may have a large
capital investment in waste treatment facilities to meet
effluent limitations by July lf 1977, a new source has
complete freedom in the selection and design of new
waste treatment facilities.
(3) In contrast to an existing source, a new source has
freedom of choice with regard to geographic location in
seeking any economic advantage relative to power cost or
land cost.
Since the technology for achieving no discharge of residue
milling waste water has been demonstrated for a facility
currently being constructed, it is considered the best available
demonstrated contrcl technology for new sources. The possibility
of a slightly higher cost in relation to several orders of
magnitude reduction in pollution and the possible elimination of
monitoring expense for no discharge of effluent warrants the
selection of this technology as the best available demonstrated
control technology for the secondary aluminum smelting
sutcategory.
CostiofiAchieving No Discharge_Qf_process Waste Water Pollutants.
The cost of achieving no discharge of process waste water
pollutants from the milling of residues is estimated to be about
$130.00 per annual ten of aluminum production capacity. This is
essentially the cost of building a new plant. Data are not
available for operating costs, but estimates from the secondary
industry indicate such costs to be higher than for wet
processing.
The cost of recovery of salts from waste water from residue
milling is dependent of the type of residue being processed. The
estimated capital cost to evaporate the water from low salt
content residues is $16/annual ton of aluminum, while operating
costs are $24/ton. When high salt-content residues are
120
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processed, the estimated capital costs are
the operating costs are $124/annual ten.
$200/annual ton and
Engineering Aspects of Control Application. Dry processing of
residues for aluirinum recovery is practical from an engineering
standpoint, since 15 of the 23 plants processing residue use a
totally dry mill operation and generate no associated waste water
stream. Thus, the technology is well proven by actual practice.
121
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SECTION XII
ACKNOWLEDGEMENTS
The Environmental Protection Agency would like to thank the staff
of the Battelle Memorial Institute (Columbus) under the direction
of Mr. John B. Hallowell for their aid in the preparation of this
document.
The Project Officer, George S. Thompson, Jr., would like to thank
his associates in the Effluent Guidelines Division, namely Mr.
Allen Cywin, Mr. Ernst P. Hall, and Mr. Walter J. Hunt for their
valuable suggestions and assistance.
Mr. Harry Thron, Effluent Guidelines Division, was responsible
for the proposed regulation and development document (October
1973) for this industry.
The members of the working group/steering
coordinated the internal EPA review are:
committee who
Mr. Walter J. Hunt, Chairman, Effluent Guidelines Division
Mr. Marshall Dick, Office of Research and Development
Mr. John Ciancia, National Environmental Research Center,
Edison
Mr. Lew Felleisen, Region III
Mr. Swep Davis, Office of Planning and Evaluation
Mr. Taylor Miller, Office of General Counsel
Appreciation is also extended to the following trade associations
and corporations fcr assistance and ccoperation provided in this
program:
The Aluminum Recycling Associaticn
Apex Smelting Ccrrpany
Diversified Materials, Inc.
Newark Processing Company
Rochester Smelting and Refining Company
U. S. Reduction Company
Vulcan Materials Company
Wabash Smelting and Refining Company
Finally, many thanks are given tc the hardworking secretarial
staff of the Effluent Guidelines Division. In particular,
recognition is given to Ms. Linda Rose, Ms, Kaye Starr, and Ms.
Nancy Zrubek.
123
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SECTION XIII
REFERENCES
(1) Aluminum Association, "Alumirum Scrap Consumption and
Recovery", Aluminum Statistical Review, New York (July,
1969) .
(2) Andrews, C., Vice President, Alurtinum Processes, Inc.,
(3) Danielson, J. A., "Air Pollution Engineering Manual",
U.S. Dept. of Health, Education, and Welfare, Cincinnati,
Ohio (1967).
(U) Demmler, J. A.r Staff Member, Technical Marketing Division,
Aluminum Corporation of America, private communication,
June 22, 1973.
(5) Francis, F. J., "Secondary Aluminum smelter Air Pollution
Control Using a Chromatographic Coated Baghouse—A
Technically New and Economic Solution", Proceedings, 65th
Annual Meeting cf the Air Pollution Control Association
(June 22, 1972) .
(6) Ginsburg, T. H., "Scrap Utilization by Secondary Aluminum
Smelters", Proceedings of the Third Mineral Waste Utiliza-
tion Symposium, Chicago, Illinois (March 16, 1972).
(7) Patterson, J. W., and Minear, R. A., Kaste Water Treatment
Technology, Report # IIEQ71-U, from Illinois Institute of
Technology tc State of Illinois, Institute for Environmental
Quality, August, 1971.
(8) Peters, M. S., and Timmerhaus, K. D., Plant Design and
Economics for Chemical Engingers, 2nd Ed., McGraw Hill
Book~Co., New Ycrk, 1968.
(9) Shirley, W. C., "Secondary Aluminum Industry Emission
Control", Kept, prepared for the Aluminum Smelting Research
Institute (1971).
(10) Siebert, D. L., "Impact of Technology on the Commercial
Secondary Aluirirum Industry", U.S. Bureau of Mines Informa*-
tion Circular 8445 (1971).
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(11) Spendlove, M. J., "A Profile of the Nonferrous Secondary
Metals Industry", Proceedings cf the Second Mineral
Waste Utilization Symposium, M. A. Schwartz, Chm. (March
19r 1970).
(12) Staff, Bureau cf Mines, "Mineral Facts and Problems*-
Aluminum", U. S. Bureau of Mines Bulletin 650 (1970).
(13) Staff, "Metal Statistics—Aluminum Profile", American
Metals Market (1972),
(14) Staff, "Aluminum—Profile of an Industry-Part II", Metals
Week, (August 12, 1968).
(15) Staff, "Process Effluent Water Data Development",
Aluminum Recycling Industry Survey (November 28, 1972).
(16) Stamper, J. K., "Aluminum", U. s. Bureau of Mines Mineral
Yearbook (1971).
(17) Teller, A. J., "Air Pollution Control"< Chemical Engin-
eering-*-Deskbock Issue (May 8, 1972) .
(18) Teller, A, J., "control of Emissions from Glass Manu-
facture", Cerairic Bulletin, Vcl. 51, No. 8 (1972).
(19) Wahi, B., Environmental Research Corp., St. Paul, Minn.,
private communication, June 19, 1973.
(20) Weston, Roy F., Inc., Draft, "Fretreatment Guidelines for
Discharge of Industrial Wastes to Municipal Treatment
Works", Contract No, 68-01-03U6, for the Environmental
Protection Agency (November 17, 1972),
126
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SECTION XIV
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 cf such components.
Borings and Turnings
Scrap aluminum froir. machining cf castings, rods, bars, and
forgings.
Captive Scrap (Runarcund Scrap)
Aluminum scrap metal retained by fabricator and remelted.
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.
Demagqing
Removal of magnesium from aluminum alloys by chemical reaction.
Dross
Residues generated during the processing of molten aluminum or
aluminum alloys fcj oxidation in air.
127
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Effluent
The waste water discharged from a point source to navigable
waters.
Effluent Limitation
A maximum amount p€r 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_CQvering_Flux)T
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.
A fully charged reverberatory furnace containing
of desired compositicr.
aluminum alloy
Heel
That part of the mclten aluminum alloy remaining in the furnace
to facilitate melting of scrap being charged for the preparation
of the following heat.
incompatible, pollutarts
Those pollutants which would cause harm to, adversely affect the
performance ofr or be inadequately treated in publicly owned
sewage treatment works.
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.
128
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Irony _, Aluminum
High iron content aluminum alloy recovered from old scrap
containing iron. Prepared in sweating furnace operating at
temperatures sufficiently high tc melt only the aluminum.
New Clippings and Forgings
Scrap from industrial manufacturing plants such as aircraft and
metal fabricators.
Ingots of aluminum alloy weighing 15 to 50 pounds.
Point Source
A single source of water discharge, such as an individual plant.
Pretreatment
Treatment performed en waste waters from any source prior to
introduction for joint treatment in publicly owned sewage
treatment works.
Residues
Include dross, skimirings and slag recovered from alloy and
aluminum melting operations of both the primary and secondary
smelters and frcm foundries.
Reverberatory Furnace {Beverb)
A furnace used for tte production cf aluminum alloy from aluminum
scrap.
Skimmincfs
Wastes from melting operations removed from the surface of the
molten metal. Consists primarily of oxidized metal, but may
contain fluxing salts.
129
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Fluxing salts removed from the surface cf 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.
Standard of_Perfor IT a jj c e
A maximum weight discharged per unit of production for each
constituent that is subject to limitations and applicable to new
sources as opposed tc existing sources, which are subject to
effluent limitations.
Sweated ,Pigs
Ingots prepared frcm high iron aluminum alloy.
Virgin_Aluminum
Aluminum recovered frcm bauxite.
130
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TABLE 30. CONVERSION FACTORS
Multiply (English Units)
English Unit
acres
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
tons (short)
yard
Abbreviation
ac
ac ft
BTU
BTU/lb
cfm
cfs
cu ft
cu ft
cu in
ft
gal
gpm
hp
in
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
yd
by
Conversion
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609 ,
(0.06805 psig +1) ^a)
0.0929
6.452
0.907
0.9144
Abbreviation
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
To Obtain (Metric Units)
Metric Unit
hectares
cubic meters
kilogram-calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
11ters
liters/second
kilowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric tons (1000 kilograms)
meters
(a) Actual conversion, not a multiplier.
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