United States Effluent Guidelines Division EPA-440/1-84/019-b
Environmental Protection WH-552 July 1984
Agency Washington, D.C. 20460 S
Water and Waste Management
EPA 440-1-84-001B1
EPA Development Proposed
Document for
Effluent Limitations
Guidelines and
Standards for the
Nonferrous Metals
Point Source Category
. Phase II
Supplemental Development
Document For:
Bauxite Refining
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DEVELOPMENT DOCUMENT
for
EFFLUENT LIMITATIONS GUIDELINES AND STANDARDS
for the
NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY
PHASE II
Bauxite Refining Supplement
Jack E. Ravan
Assistant Administrator for Water
Edwin L. Johnson
Director
Office of Water Regulations and Standards
V^D ST4t.f
U.S Environmental Protection Agency
i Priori V, Libiary
231» South Dcai born Street
Chicago, Illinois 60604
Jeffery D. Denit, Director
Effluent Guidelines Division
Ernst P. Hall, P.E., Chief
Metals and Machinery Branch
James R. Berlow, P.E.
Technical Project Officer
July 1984
U.S. Environmental Protection Agency
Office of Water
Office of Water Regulations and Standards
Effluent Guidelines Division
Washington, D.C. 20460
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U,S. Environmental Protsctton Agency
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I
BAUXITE REFINING SUJJCATEGORY
TABLE OF CONTENTS
Section Page
I SUMMARY AND CONCLUSIONS 1
II RECOMMENDATIONS 5
III INDUSTRY PROFILE 7
DESCRIPTION OF BAUXITE REFINING PROCESSES. ... 7
RAW MATERIALS 8
BAUXITE GRINDING AND DIGESTION 8
RED MUD REMOVAL AND LIQUOR PURIFICATION 9
PRECIPITATION AND CLASSIFICATION 10
CALCINATION 12
PROCESS WASTEWATER SOURCES 12
OTHER WASTEWATER SOURCES 12
AGE, PRODUCTION, AND PROCESS PROFILE 12
IV SUBCATEGORIZATION 21
FACTORS CONSIDERED IN SUBCATEGORIZATION 21
FACTORS CONSIDERED IN SUBDIVIDING THE BAUXITE
REFINING SUBCATEGORY 22
OTHER FACTORS 22
TYPE OF PLANT 22
RAW MATERIALS 22
PLANT LOCATION 23
V WATER USE AND WASTEWATER CHARACTERISTICS .... 25
WASTEWATER CHARACTERISTICS DATA 26
DATA COLLECTION PORTFOLIOS 26
FIELD SAMPLING DATA 26
WASTEWATER CHARACTERISTICS AND FLOWS BY
SUBDIVISION 27
DIGESTER CONDENSATE 28
BAROMETRIC CONDENSER EFFLUENT 28
CARBONATION PLANT EFFLUENT 28
MUD IMPOUNDMENT EFFLUENT 29
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BAUXITE REFINING SUBCATEGORY
TABLE OF CONTENTS (Continued)
Section
VI
VII
VIII
IX
X
Page
SELECTION OF POLLUTANT PARAMETERS 59
CONVENTIONAL AND NONCONVENTIONAL POLLUTANT
PARAMETERS 59
CONVENTIONAL AND NONCONVENTIONAL POLLUTANT
PARAMETERS SELECTED 59
TOXIC POLLUTANTS 60
TOXIC POLLUTANTS NEVER DETECTED 60
TOXIC POLLUTANTS NEVER FOUND ABOVE THEIR
ANALYTICAL QUANTIFICATION LEVEL 62
TOXIC POLLUTANTS PRESENT BELOW CONCENTRATIONS
ACHIEVABLE BY TREATMENT 63
TOXIC POLLUTANTS DETECTED IN A SMALL NUMBER
OF SOURCES 63
TOXIC POLLUTANTS SELECTED FOR FURTHER
CONSIDERATION FOR LIMITATION 65
CONTROL AND TREATMENT TECHNOLOGIES 71
CURRENT CONTROL AND TREATMENT PRACTICES 71
MUD IMPOUNDMENT EFFLUENT 71
CONTROL AND TREATMENT OPTIONS 72
OPTION E 72
COSTS OF WASTEWATER TREATMENT AND CONTROL. ... 73
TREATMENT OPTIONS COSTED FOR EXISTING SOURCES. . 73
COST METHODOLOGY 73
NONWATER QUALITY ASPECTS 74
ENERGY REQUIREMENTS 74
SOLID WASTE 74
AIR POLLUTION 75
BEST PRACTICABLE TECHNOLOGY CURRENTLY AVAILABLE. 77
BEST AVAILABLE TECHNOLOGY ECONOMICALLY
ACHIEVABLE 79
TECHNICAL APPROACH TO BAT 79
OPTION E 80
INDUSTRY COST AND POLLUTANT REMOVAL ESTIMATES. . 80
POLLUTANT REMOVAL ESTIMATES 80
COMPLIANCE COSTS 80
ll
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BAUXITE REFINING SUBCATEGORY
TABLE OF CONTENTS (Continued)
Section Page
BAT OPTION SELECTION 81
REGULATED POLLUTANT PARAMETERS 81
EFFLUENT LIMITATIONS 82
BAT EFFLUENT LIMITATIONS UNDER CONSIDERATION
FOR THE BAUXITE REFINING SUBCATEGORY 83
XI NEW SOURCE PERFORMANCE STANDARDS 87
TECHNICAL APPROACH TO NSPS 87
OPTION E 87
NSPS OPTION SELECTION 88
REGULATED POLLUTANT PARAMETERS 88
NEW SOURCE PERFORMANCE STANDARDS 88
NSPS UNDER CONSIDERATION FOR THE BAUXITE
REFINING SUBCATEGORY 88
XII PRETREATMENT STANDARDS 89
XIII BEST CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY . 91
111
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Number
BAUXITE REFINING SUBCATEGORY
LIST OF TABLES
Page
III-1 INITIAL OPERATING YEAR (RANGE) SUMMARY OF
PLANTS IN THE BAUXITE REFINING SUBCATEGORY
BY DISCHARGE TYPE 14
II1-2 PRODUCTION RANGES FOR THE BAUXITE REFINING
SUBCATEGORY 15
III-3 SUMMARY OF BAUXITE REFINING SUBCATEGORY
PROCESSES AND ASSOCIATED WASTE STREAMS 16
V-1 WATER USE AND DISCHARGE RATES FOR MUD
IMPOUNDMENT EFFLUENT 30
V-2 BAUXITE REFINING SUBCATEGORY DIGESTER
CONDENSATE SAMPLING DATA 31
V-3 BAUXITE REFINING SUBCATEGORY BAROMETRIC
CONDENSER (HOT WELL) DISCHARGE RAW WASTEWATER
SAMPLING DATA 38
V-4 BAUXITE REFINING SUBCATEGORY CARBONATION
PLANT EFFLUENT RAW WASTEWATER SAMPLING DATA. . . 45
V-5 BAUXITE REFINING SUBCATEGORY MUD LAKE DISCHARGE
RAW WASTEWATER SAMPLING DATA 50
VI-1 FREQUENCY OF OCCURRENCE OF TOXIC POLLUTANTS
BAUXITE REFINING RAW WASTEWATER 67
VIII-1 COST OF COMPLIANCE FOR THE BAUXITE REFINING
SUBCATEGORY DIRECT DISCHARGERS 76
X-1 POLLUTANT REMOVAL ESTIMATES BAUXITE REFINING
SUBCATEGORY 84
X-2 COST OF COMPLIANCE FOR THE BAUXITE REFINING
SUBCATEGORY 85
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BAUXITE REFINING SUBCATEGORY
LIST OF FIGURES
Number Page
1 BAUXITE REFINING PROCESS 17
III-2 GEOGRAPHIC LOCATIONS OF THE BAUXITE REFINING
SUBCATEGORY PLANTS 19
V-1 SAMPLING SITES AT BAUXITE REFINING PLANT A ... 57
V-2 SAMPLING SITES AT BAUXITE REFINING PLANT B . . . 58
X-1 OPTION E TREATMENT SCHEME FOR THE BAUXITE
REFINING SUBCATEGORY 86
vii
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BAUXITE REFINING SUBCATEGORY
SECTION I
SUMMARY AND CONCLUSIONS
Pursuant to Sections 301, 304, 306, 307, and 501 of the Clean
Water Act and the provisions of the Settlement Agreement in
Natural Resources Defense Council v. Train, 8 ERC 2120 (D.D.C.
1976) modified, 12 ERC 1833 (D.D.C. 1979), EPA has collected and
analyzed data for plants in the bauxite refining subcategory. On
April 8, 1974, EPA promulgated effluent limitations based on best
practicable technology currently available (BPT) and best
available technology economically achievable (BAT), standards of
performance for new sources (NSPS) and pretreatment standards for
new sources (PSNS). See 39 FR 12822-12830, April 8, 1974 and 40
CFR Part 421 Subpart A. In each case, the limitations and
standards required no discharge of process wastewater pollutants
with an allowance for discharge of monthly net precipitation
(i.e., the difference in water volume between precipitation and
evaporation in a one month period) that accumulates in the
impoundments used by bauxite refineries to store the undigested
solids produced in the refining process. This document and the
administrative record provide the technical basis for review of
the promulgated effluent limitations and standards.
The bauxite refining subcategory comprises 8 plants. Of the 8
plants, three discharge directly to rivers, lakes, or streams and
five achieve zero discharge of process wastewater.
EPA first studied the bauxite refining subcategory to determine
whether differences in raw materials, final products,
manufacturing processes, equipment, age and size of plants, or
water usage, required the development of separate effluent
limitations and standards for different segments of the
subcategory. This involved a detailed analysis of wastewater
discharge and treated effluent characteristics, including (1) the
sources and volume of water used, the processes used, and the
sources of pollutants and wastewaters in the plant; and (2) the
constituents of wastewaters, including toxic pollutants. As a
result, four subdivisions have been identified for this
subcategory that warrant separate effluent limitations. These
include:
• Digester Condensate
• Barometric Condenser Effluent
• Carbonation Plant Effluent
• Mud Impoundment Effluent
EPA also identified several distinct control and treatment
technologies (both in-plant and end-of-pipe) applicable to the
bauxite refining subcategory. The Agency analyzed both
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historical and newly generated data on the performance of these
technologies, including their nonwater quality environmental
impacts and air quality, solid waste generation, and energy
requirements. EPA also studied flow reduction reported in the
data collection portfolios (dcp) and plant visits.
Engineering costs were prepared for each discharging plant (and
one zero discharger) for the control and treatment option
considered for the subcategory. These costs were then used by
the Agency to estimate the impact of implementing the option in
the subcategory. For this control and treatment option, the
number of potential closures, number of employees affected, and
impact on price were estimated. These results are reported in a
separate document entitled "The Economic Impact Analysis of
Proposed Effluent Limitations Guidelines and Standards for the
Nonferrous Smelting and Refining Industry."
After examining the various treatment technologies being operated
in the subcategory, the Agency has identified BPT to be
equivalent to the existing promulgated BPT effluent limitations
published on April 8, 1974 (40 CFR Part 421 Subpart A). This
requires no discharge of process wastewater pollutants to
navigable waters, while permitting the discharge of net
precipitation from red mud lake impoundments. Minor amendments
to the regulatory language are being proposed to clarify
references to fundamentally different factors (PDF)
considerations under 40 CFR Part 125 and references to
pretreatment standards under 40 CFR Part 128. As a result, the
bauxite refining subcategory will not incur any incremental
capital or annual costs to comply with the BPT limitations.
For BAT, the Agency is considering revising the promulgated BAT
to include treatment of mud impoundment effluent by pH adjustment
and activated carbon adsorption technology for removal of organic
pollutants. This potential revision is based on new data
collected by the Agency since the previous promulgation that
indicated the presence of phenolic compounds at treatable
concentrations in the mud impoundment effluent.
To meet the BAT effluent limitations based on this technology,
the bauxite refining subcategory is estimated to incur a capital
cost of $7.6 million and an annual cost of $2.98 million.
The technical basis of NSPS is equivalent to the existing
promulgated BAT. In selecting NSPS, EPA recognizes that new
plants have the opportunity to implement the best and most
efficient manufacturing processes and treatment technology.
However, no such processes or treatment technology were
considered to meet the NSPS criteria. Therefore, the technology
basis of BAT has been determined as the best demonstrated
technology, the technology basis of NSPS. However, the Agency is
also considering the application of pH adjustment and activated
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carbon adsorption technology to the mud impoundment effluent for
new sources.
The limitations and standards for BPT, BAT, NSPS, and PSNS are
presented in Section II.
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BAUXITE REFINING SUBCATEGORY
SECTION II
RECOMMENDATIONS
1. No change to the existing promulgated BPT is proposed for
the bauxite refining subcategory. The regulation establishes no
discharge of process wastewater pollutants with an allowance for
discharge of net precipitation from the mud impoundment. The
technology basis for BPT is impoundment and recycle for all
process wastewater.
2. EPA is not substantially modifying the existing promulgated
BAT limitations. However, the Agency is considering the
establishment of limitations providing additional control of
toxic organic pollutants in net precipitation discharges from the
mud impoundment based on pH adjustment and activated carbon
adsorption. The following BAT effluent limitations are being
considered:
Pollutant or Maximum for
Pollutant Property Any One Day (mq/1 )
Phenol 0.010
2-chlorophenol 0.010
Total phenols (4-AAP) 0.010
3. Similar to BAT, EPA is not substantially modifying the
existing promulgated NSPS, but is considering the establishment
of performance standards based on control of organic pollutants
in the discharges from the mud impoundment based on pH adjustment
and activated carbon adsorption. The standards under
consideration are:
Mud Impoundment Effluent
Pollutant or Maximum for
Pollutant Property Any One Day (mq/1)
Phenol 0.010
2-chlorophenol 0.030
Total Phenols (4-AAP) 0.010
4. EPA is not proposing PSES limitations for the bauxite
refining subcategory because there are no existing indirect
dischargers.
5. EPA is modifying the existing promulgated PSNS since it is
unlikely that any new bauxite sources could be constructed as
indirect dischargers.
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6. EPA is not proposing best conventional pollutant control
technology (BCT) limitations at this time.
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BAUXITE REFINING SURCATEGORY
SECTION III
INDUSTRY PROFILE
This section of the bauxite refining supplement describes the raw
materials and processes used in refining bauxite to produce
alumina and presents a profile of the alumina plants identified
in this study. For a discussion of the purpose, authority, and
methodology for this study and a general description of the non-
ferrous metals manufacturing category, refer to Section III of
the General Development Document.
EPA promulgated effluent limitations for BPT and BAT, new source
performance standards, and pretreatment standards for new sources
for the bauxite refining subcategory on April 8, 1974 as Subpart
A of 40 CFR Part 421. The pollutants considered in the
development of those regulations included alkalinity, pH, total
dissolved solids, total suspended solids, and sulfate.
The Clean Water Act of 1977 mandates the achievement of effluent
limitations requiring the application of BAT for toxic
pollutants. In keeping with this emphasis on toxic pollutants,
EPA is re-examining the discharge of toxic pollutants from
process wastewater impoundments in the bauxite refining
subcategory.
Most of the alumina produced by bauxite refiners is sold to the
primary aluminum industry. Aluminum metal is widely used for
building and construction materials, transportation equipment,
and containers and packaging products. The remainder of the
alumina is sold to the chemical, abrasive, ceramic, and
refractory industries for the manufacture of products such as
chemical alums, activated alumina, polishes, electrical
insulators, and heat exchange media.
DESCRIPTION OF BAUXITE REFINING PROCESSES
Bauxite is the only ore of aluminum used commercially in the
United States. Aluminum production is unique among metal
manufacturing techniques in that nearly all purification is
accomplished in the bauxite refining process. No significant
removal of impurities occurs during the subsequent reduction to
metal.
In the United States, bauxite is refined using the Bayer process.
The classic Bayer process may be broadly divided into four major
operations:
1. Bauxite grinding and digestion,
2. Red mud removal and liquor purification,
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3. Precipitation and classification, and
4. Calcination.
A variation of the process, known as the combination process,
allows additional alumina recovery from solid residues when high-
silica bauxites are used as the raw material.
Bauxite refining is characteristically conducted in very large
scale installations. The process is conducted in an essentially
closed circuit with extensive reuse and recycle of process water.
Economic considerations make the maximum recovery of heat and
reagents a necessity. Production processes for the bauxite
refining subcategory are presented schematically in Figure III-l
and described in detail below.
RAW MATERIALS
Bauxite consists of hydrated aluminum oxide and various
impurities, including iron oxide, titanium dioxide, silicon
dioxide, and compounds of phosphorus and vanadium. A basic
distinction is made between monohydrate bauxite, which contains
alumina in the form of boehmite or diaspore (A1203) • H20), and
trihydrate bauxite, in the form of gibbsite (A1203«3H20 or
Al(OH)j), because they require different digestion conditions.
Further distinctions of ore type include high or low silica
content, high or low iron content, and fast- or slow-settling red
mud after digestion.
BAUXITE GRINDING AND DIGESTION
Bauxite ore is crushed and wet-ground with a caustic-rich
solution in preparation for the digestion process. The bauxite
must be ground finely enough to ensure effective digestion but
not so finely that the red mud residue presents problems during
settling and filtration. One plant reports the use of scrubbers
for dust control in the bauxite handling operations. Because the
water from these scrubbers is returned to the process to recover
the bauxite value, it is considered to be a process stream rather
than a wastewater stream.
The ground bauxite slurry is fed to digesters where the hydrated
alumina in the bauxite is converted to a soluble salt, sodium
aluminate. The reaction is accomplished using either sodium
hydroxide or a combination of lime and sodium carbonate.
Wastewater from wet air pollution control on lime kilns at two
plants is sent to the digesters. Because the scrubber effluent
is returned to the process and not discharged, it is considered
to be a process stream rather than a wastewater stream.
Digestion conditions (temperature, pressure, and caustic
concentration) depend on the type of bauxite processed.
Monohydrate bauxites require temperatures between 200 and 250°C
at up to 500 psi pressure. Trihydrate bauxites can be digested
8
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under the more moderate conditions of 120 to 170°C and 50 to 70
psi pressure.
The product of the digestion process is a slurry containing
sodium aluminate in aqueous solution and undissolved solids.
This slurry enters a system of expansion vessels or "flash tanks"
for cooling, pressure reduction, and heat recovery. The stream
recovered from the expansion process is returned to the digesters
to provide some of the heat needed to maintain proper digestion
temperatures. Condensate from the* vapor is frequently used for
boiler water. At one plant condensate is used for hydrate
washing. Excess condensate or condensate which is unsuitable for
use in boilers may be disposed of.
RED MUD REMOVAL AND LIQUOR PURIFICATION
The digested bauxite suspension contains solid, insoluble bauxite
particles of various sizes and compositions in a sodium aluminate
solution. Particles above a certain size, e.g., TOO microns, are
called "sand" and may include undigested bauxite, quartz
particules, or common sand. Sand is usually removed from the
suspension before red mud thickening.
The insoluble residue remaining in suspension after desanding is
commonly known as red mud. Red mud contains iron oxides,
titanium dioxide, aluminum present with silica, and other
secondary impurities. A flocculating agent is added to the
process suspension to enhance settling of the fine red mud
particles.
The overflow from the mud settling and thickening steps is
further clarified by filtration. This step removes red mud
particles from the supersaturated aluminate liquor.
The red mud settled from the process liquor is thickened, washed,
and sometimes filtered to recover caustic and alumina values.
The mud is then moved as a waterborne slurry to a waste area
known as a red mud lake or impoundment for disposal.
When high-silica bauxites such as those from Arkansas are used as
the raw material for alumina production, the "combination
process" can be applied to recover alumina and sodium values
which would otherwise be lost in the red mud. As much as one-
third of the total alumina value produced by a plant using
Arkansas bauxite may be trapped in insoluble sodium
aluminosilicates which are removed from the process with the red
mud.
In the combination process, the red mud is treated fir^t by
filtration to reduce the evaporative load and then by sintering
and leaching to recover alumina. After filtering and washing,
the .remaining solid residue or "brown mud" is sent to a mud lake
for disposal. The very pure filtrate, known as white liquor, is
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either combined with the process stream or precipitated and
calcined separately to produce chemical-grade alumina.
Red muds from various bauxites have different characteristics
which produce differing disposal considerations. For example,
the yield of red mud residue from Surinam bauxite is low
(approximately 1/3 ton per ton of alumina product), and the mud
is amenable to filtration and effective washing on a filter.
Thus, the final residue is relatively easy to handle and disposal
area requirements are moderate. On the other hand, red muds from
Arkansas and Jamaican bauxites are produced in much greater
yield, (approximately 2 tons and 1 ton per ton of alumina,
respectively), because of their larger content of contaminants.
The physical characteristics of Jamaican bauxite red mud are such
that filtration is difficult and countercurrent decantation may
be required. It also settles poorly, reaching a solids
concentration of only about 30 percent after normal settling as
compared to more than 50 percent solids for the muds from other
ores. As a result, area requirements for these red mud lakes are
large.
One company which refines Jamaican bauxite has developed a sand
bed filtration technique. In this technique, red mud is pumped
to a drying bed where the solids concentration of the mud is
increased from 15 or 20 percent to more than 50 percent. The
surface of the mud drying bed is kept dry by drawing water off
the top and, at one of the two plants using sand bed filtration,
pumping it to a "clear lake." Underflow is also drawn out through
the sandy bottom of the bed and sent to the clear lake. Clear
lake water is then recycled to the bauxite refining operations
for use as process water, forming a nearly-closed water system.
The second plant that practices sand bed filtration of red mud
wastes does not have a clear lake, practices no recycle of mud
lake water to the process, and discharges neutralized effluent
directly to surface waters.
Of the alumina plants which do not practice sand bed filtration
of red mud, all report the use of red mud lakes. In addition, a
refinery may have a process water lake for recycle of higher
quality water than is found in the mud lake and a storm water
lake to collect large volumes of rainwater runoff from the plant
site. Minor remaining storage capacity in abandoned red mud
lakes may be utilized to dispose of small quantities of aqueous
wastes which are intolerable in the recycle circuit. Examples of
such wastes are spent acids from equipment cleaning and the
effluent from salting-out evaporators.
PRECIPITATION AND CLASSIFICATION
The purified sodium aluminate solution obtained by removing solid
impurities from the digested liquor passes through heat
exchangers and is cooled before being discharged into large
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precipitation vessels. Vapor produced in the flash cooling area
is condensed and reused in other parts of the plant.
During precipitation, aluminum hydroxide crystallizes from the
super-saturated sodium aluminate in the presence of seed
crystals. The precipitation conditions are carefully controlled
so that the solids formed will be amenable to easy separation and
washing. The precipitated hydrate crystals are classified by
size; small crystals are washed and fed to calcining furnaces.
Aluminum trihydrate scale can also be recovered from the
precipitators and processed to make an activated alumina by-
product.
The spent liquor separated from the hydrate crystals during
classification is returned to the grinding and digestion
processes to recover the caustic value of the stream. The spent
caustic is first heated in heat exchangers by the steam recovered
from the flash cooling of the process liquor before
precipitation. The liquor then passes through evaporators which
remove excess water. The caustic is thus reconcentrated before
being mixed with the bauxite ore in the digesters.
The vapor generated in the spent caustic evaporators is condensed
in barometric condensers using once-through cooling water.
Although occasional upsets may cause entrainment of caustic, the
barometric condensate, also referred to as hotwell discharge,
from properly operated evaporators is-generally a high quality
water which is either impounded with the red mud or discharged
directly to surface waters.
Some provision must be made to bleed off a part of the recycled
caustic to prevent the accumulation of soluble salts in the
system. In some plants, one of the evaporators is a "salting-
out" evaporator which concentrates a portion of the recycled
caustic stream. The concentrated stream is then disposed of in
an old mud lake or a landfull.
An alternate method of removing salts is to mix some of the spent
liquor with the slurry from the digesters. The soluble
contaminants are removed by the red mud which is then filtered
out and discarded. This technique of salt removal has been
demonstrated in only one plant and may not be possible with red
mud from all bauxite ore types.
One plant removes soluble salts from the process by carbonating a
small amount of pregnant liquor from the precipitation process
and some of the hydrate seed. An alumina precipitate is settled
from the carbonated mixture and calcined. The recovered sodium
aluminale is then returned to the process at the mixing and
digestion operation. The solution from which the alumina was
precipitated contains neutralized soluble impurities and is
directly discharged without further treatment.
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CALCINATION
The moist filter cake of aluminum oxide from the precipitation
and classification operations is conveyed tcu.calciners where it
is converted to anhydrous alumina, the form most suitable for
later use in electrolytic reduction to aluminum metal. Dust
control for the calciners is provided by electrostatic
precipitators or baghouse filters.
One plant dries part of the hydrate filter cake rather than
exposing it to the more severe conditions of calcination. The
product of this operation is sold as a dried hydrate. Condensate
from the dryers is collected and reused in the precipitation
process.
PROCESS WASTEWATER SOURCES
A variety of processes are involved in bauxite refining. The
significant wastewater sources that are associated with this
subcategory can be subdivided as follows:
1. Digester condensate,
2. Barometric condenser effluent,
3. Carbonation plant effluent, and
4. Mud impoundment effluent.
OTHER WASTEWATER SOURCES
There are other waste streams associated with the bauxite
refining subcategory. These waste streams include, but are not
limited to:
1. Stormwater other than that which falls within the
process water impoundment area, and
2. Maintenance and cleanup water.
These waste streams are not considered as a part of this
rulemaking. EPA believes that the flows and pollutant loadings
associated with these waste streams are insignificant relative to
the waste streams selected, or are best handled by the
appropriate permit authority on a case-by-case basis under
authority of Section 403 of the Clean Water Act.
AGE. PRODUCTION, AND PROCESS PROFILE
Figure III-2 shows the location of the eight alumina plants
operating in the United States. This figure shows that the
plants are located in the southern states and in the U.S. Virgin
Islands.
Table III-l summarizes the relative age and discharge status of
the eight alumina plants. Most of the plants are between 20 and
12
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40 years old. None of the alumina plants are more than 50 years
old.
Table III-2 lists the 1982^ production ranges for the alumina
plants. Four of the eight plants produce 200,000 to 300,000
kkg/yr as aluminum contained. Two plants produce less than
200,000 kkg/yr, and the remaining two produce more than 400,000
kkg/yr as aluminum contained.
Table III-3 lists the major production processes associated with
the refining of bauxite. Also shown is the number of plants
generating wastewater from these processes.
13
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Table III-2
PRODUCTION RANGES FOR THE BAUXITE REFINING SUBCATEGORY
Type of Alumina Production Ranges for 1982 Total
Plant (Thousand kkg/yr as Aluminum Contained) Number
Discharge 0-200200-300300-400400-600 of Plants
Direct 0300 3
Indirect 0000 0
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19
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BAUXITE REFINING SUBCATEGORY
SECTION IV
SUBCATEGORIZATION
As discussed in Section IV of the General Development Document,
the nonferrous metals manufacturing category has been
subcategorized to take into account pertinent industry
characteristics, manufacturing process variations, and a number
of other factors which affect the ability of the facilities to
achieve effluent limitations. This section summarizes the
factors considered during the designation of the bauxite refining
subcategory and its related subdivisions.
FACTORS CONSIDERED IN SUBCATEGORI2ATION
The following factors were evaluated for use in determing
appropriate subcategories for the nonferrous metals category:
1. Metal products, co-products, and by-products;
2. Raw materials;
3. Manufacturing processes;
4. Product form;
5. Plant location;
6. Plant age;
7. Plant size;
8. Ai'r pollution control methods;
9. Meteorological conditions;
10. Treatment costs;
11. Nonwater quality aspects;
12. Number of employees;
13. Total energy requirements; and
14. Unique plant characteristics.
Evaluation of all factors that could warrant subcategorization
resulted in the designation of the bauxite refining subcategory.
Three factors were particularly important in establishing these
classifications: the type of metal produced, the nature of the
raw materials used, and the manufacturing processes involved.
In Section IV of the General Development Document, each of these
factors is described, and the rationale for selecting metal
products, manufacturing processes and raw materials as the
principal factors used for subcategorization is discussed. On
the basis of these factors, the nonferrous metals manufacturing
category (phase II) was divided in 21 subcategories, one of them
being bauxite refining.
Bauxite refining was considered as a single subcategory during
the previous (1974) rulemaking (40 CFR Part 421, Subpart A). The
1974 rulemaking established BPT and BAT effluent limitations and
21
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standards for new sources and sources discharging to POTWs for
the bauxite refining subcategory. The purpose of this present
rulemaking is to propose minor technical modifications to the
effluent limitations and standards and solicit comment on
additional requirements for the net precipitation discharges
allowed by the existing regulation.
FACTORS CONSIDERED IN SUBDIVIDING THE BAUXITE REFINING
SUBCATEGORY
The rationale for considering further subdivision of the bauxite
refining subcategory is based primarily on the production process
used. Within this subcategory, a number of different operations
are performed, which may or may not have a water use or
discharge, and which may require the establishment of separate
effluent limitations and standards. While bauxite refining is
still considered a single subcategory, a more thorough
examination of the production processes has illustrated the need
for limitations and standards based on a specific set of waste
streams. Limitations and standards will be based on specific
flow allowances for the following subdivisions:
1. Digester condensate,
2. Barometric condenser effluent,
3. Carbonation plant effluent, and
4. Mud impoundment effluent.
OTHER FACTORS
Factors other than manufacturing processes which were considered
in this evaluation either support the establishment of the four
subdivisions or were determined to be inappropriate bases for
subdivision. Air pollution control methods, treatment costs, and
total energy requirements are functions of the selected
subcategorization factors, namely metal product, raw materials,
and production processes. For reasons discussed in Section IV of
the General Development Document, factors such as plant age,
plant size, and number of employees were also evaluated and
determined to be inappropriate bases for subdivision of this
nonferrous metals subcategory.
TYPE OF PLANT
There is fundamentally only one process for refining bauxite: the
Bayer process. The combination process, a variation of the Bayer
process, further treats the red mud waste from the Bayer process
to recover additional aluminum and alkali values. The
differences in the manufacturing processes and wastes produced at
Bayer-process plants and combination process plants are not
significant enough to warrant further subdivision based on plant
type.
RAW MATERIALS
22
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The major process waste associated with the refining of bauxite
is the red mud residue. While the monohydrate content of
different ores requires different digestion conditions at
different plants, the quality of the red mud waste is not
significantly affected. Similarly, the differences in quality
between the red mud from the Bayer process and the brown mud
waste generated when residues from high-silica bauxites are
treated by the combination process do not warrant further
subdivision.
There are differences in the amount of mud generated per ton of
alumina produced which depend on the source of the bauxite*. Only
one-third ton of mud is produced per ton of alumina when Surinam
bauxite is processed; two or more tons of mud are produced per
ton of bauxite when Arkansas bauxite is refined. Nevertheless,
these differences affect the size, not the nature of the disposal
problem. Therefore, the specific type of bauxite raw material
refined is not chosen as a basis for further subdivision.
PLANT LOCATION
The relationship between annual rainfall and annual evaporation
is significant at bauxite refining plants because the process
facilities and red mud lakes typically cover large land areas.
In regions where precipitation exceeds evaporation, collected
rainfall runoff can accumulate and present disposal problems.
However, if provisions are made to segregate process wastewaters
and runoff from plant sites, the runoff can be discharged to its
normal water course. By allowing the discharge of net rainfall
from the impoundment areas, accumulation of water and disruption
of the plant's water balance can be avoided. Therefore, further
subdivision based on plant location is not necessary.
23
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BAUXITE REFINING SUBCATEGORY
SECTION V
WATER USE AND WASTEWATER CHARACTERISTICS
This section describes the characteristics of wastewater
associated with the bauxite refining subcategory. Data used to
quantify wastewater flow and pollutant concentrations are
presented, summarized, and discussed. The contribution of
specific production processes to the overall wastewater discharge
from bauxite refining plants is identified whenever possible.
Section V of the General Development Document contains a detailed
description of the data sources and methods of analysis used to
characterize wastewater from the nonferrous metals category. To
summarize this information briefly, two principal data sources
were used: data collection portfolios (dcp) and field sampling
results. Data collection portfolios, completed for each of the
bauxite refining plants, contain information regarding wastewater
flows and production levels.
In order to quantify the pollutant discharge from bauxite
refining plants, a field sampling program was conducted.
Wastewater samples were analyzed for 124 of the 126 toxic
pollutants and other pollutants deemed appropriate. (Because the
analytical standard for TCDD was judged to be too hazardous to be
made generally available, samples were never analyzed for this
pollutant. Also, samples were never analyzed for asbestos.
There is no reason to expect that TCDD or asbestos would be
present in bauxite refining wastewater.) Two plants were
selected for sampling in the bauxite refining subcategory. A
complete list of the pollutants considered and a summary of the
techniques used in sampling and laboratory analyses are included
in Section V of the General Development Document. In general,
the samples were analyzed for three classes of pollutant: toxic
organic pollutants, toxic metal pollutants, and criteria
pollutants (which includes both conventional and nonconventional
pollutants).
As described in Section IV of this supplement, the bauxite
refining subcategory has been further divided into , four
subdivisions. Differences in the characteristics of the
wastewater streams corresponding to each subdivision are to be
expected and are addressed separately in the discussions that
follow. These wastewater sources are:
1. Digester condensate,
2. Barometric condenser effluent,
3. Carbonation plant effluent, and
4. Mud impoundment effluent.
25
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WASTEWATER CHARACTERISTICS DATA
Data used to characterize the various wastewaters associated with
bauxite refining come from two sources: data collection
portfolios (dcp) and analytical data from field sampling trips.
DATA COLLECTION PORTFOLIOS
In the data collection portfolios, plants were asked to indicate
which of the toxic pollutants were known or were believed to be
present in their effluent. Two plants indicated that toxic
organics were known to be present. Three plants stated that
toxic metals were known or believed to be present in their
effluent. The responses from the three plants which provided
information are summarized below.
Pollutant
23.
44.
48.
65.
68.
70.
86.
114.
115.
117.
118.
119.
120.
121 .
122.
123.
124.
125.
126.
127.
128.
chloroform
methylene chloride
dichlorobromomethane
phenol
di-n-butyl phthalate
diethyl phthalate
toluene
antimony
arsenic
beryllium
cadmium
chromium (Total)
copper
cyanide (Total)
lead
mercury
nickel
selenium
silver
thallium
zinc
Known Present
1
1
1
2
1
1
1
2
2
. 1
1
2
2
1
2
2
1
2
2
1
2
Believed Present
0
0
0
2
0
0
0
2
3
1
2
3
3
0
3
3
2
3
3
2
3
FIELD SAMPLING DATA
In order to quantify the concentrations of pollutants present in
wastewater from bauxite refining plants, wastewater samples were
collected at two of the eight plants. Diagrams indicating the
sampling sites and contributing production processes are shown in
Figures V-l and V-2 at the end of this section.
The sampling data for the bauxite refining subcategory are
presented in tables at the end of this section. The stream codes
listed may be used to identify the location of each of the
samples on the process flow diagrams in Figures V-l and V-2.
26
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Where no data are listed for a specific day of sampling, the
wastewater samples for the stream were not collected.
Several points regarding these tables should be noted. First,
the data tables include some samples measured at concentrations
considered not quantifiable. The base-neutral extractable, acid
extractable, and volatile organics are generally considered not
quantifiable at concentrations equal to or less than 0.010 mg/1.
Below this concentration, organic analytical results are not
quantitatively accurate; however, the analyses are useful to
indicate the presence of a particular pollutant. The pesticide
fraction is considered not quantifiable at concentrations equal
to or less than 0.005 mg/1. Nonquantifiable results are
designated in the tables with an asterisk (double asterisk for
pesticides).
Second, the detection limits shown on the data tables are not the
same in all cases as the published detection limits for these
pollutants by the same analytical methods. The detection limits
used were reported with the analytical data and hence are the
appropriate limits to apply to the data. Detection limit
variation can occur as a result of a number of laboratory-
specific, equipment-specific, and daily operator-specific
factors. These factors can include day-to-day differences in
machine calibration, variation in stock solutions, and variation
in operators.
Third, the statistical analysis of data includes some samples
measured at concentrations considered not quantifiable. Toxic
organics data reported as an asterisk or with a "less than" sign
are considered as detected but below quantifiable concentrations,
and a value of zero is used for averaging. A value of zero is
also used for averaging if a pollutant is reported as not
detected. Finally, toxic metal values reported as less than a
certain value were considered as below quantification and a value
of zero is used in the calculation of the average.
Finally, appropriate source water concentrations are presented
with the sampling data. The method by which each sample was
collected is indicated by number as follows:
1. One-time grab
2. Manual composite during intermittent process operation
3. 8-hour manual composite
4. 8-hour automatic composite
5. 24-hour manual composite
6. 24-hour automatic composite
WASTEWATER CHARACTERISTICS AND FLOWS BY SUBDIVISION
Bauxite refining involves four principal sources of wastewater,
each of which has potentially different characteristics. The
27
-------
wastewater characteristics corresponding to each subdivision will
be described separately in the discussions that follow.
EPA promulgated limitations for the bauxite refining subcategory
on April 8, 1974 as Subpart A of 40 CFR Part 421. The
established limitations allow no discharge of process wastewater
pollutants to navigable waters. A discharge is allowed from the
overflow of a process wastewater impoundment in a volume equal to
the difference between the precipitation that falls within the
impoundment and the evaporation from that impoundment (this is
termed net precipitation). EPA is not proposing any
modifications to the no discharge limitation for process
wastewater pollutants. For this reason, water use and discharge
flow will be addressed only with regard to the mud impoundment
effluent in the discussions that follow.
DIGESTER CONDENSATE
Bauxite ore is digested with caustic to produce a slurry of
sodium aluminate in aqueous solution with undissolved solids.
This slurry enters a system of expansion vessels or "flash tanks"
for cooling, pressure reduction, and heat recovery. Vapor
released in the flash tanks is condensed as a high quality water
suitable for reuse as boiler water or product wash water. The
digester condensate is characterized by treatable concentrations
of phenols, low concentrations of suspended solids, and high pH.
Sampling data for the digester condensate are presented in Table
V-2.
BAROMETRIC CONDENSER EFFLUENT
The spent liquor separated from the hydrate crystals during
classification is returned to the grinding and digestion
processes to recover the caustic value of the stream. The liquor
passes through evaporators which remove excess water and re-
concentrate the caustic stream for reuse.
The vapor generated in the spent caustic evaporators is condensed
in barometric condensers. Although occasional upsets may cause
entrainment of caustic, the condensate, also referred to as
hotwell discharge, is a good quality, somewhat alkaline water.
This stream is characterized by treatable concentrations of
phenols and suspended solids. Sampling data for barometric
condenser effuent are presented in Table V-3.
CARBONATION PLANT EFFLUENT
Some provision must be made to remove soluble salts from the
recycled caustic to prevent the accumulation of impurities in the
process. One plant removes and carbonates a small portion of the
process liquor and the hydrate seed. The resulting alumina
precipitate is returned to the digesters. The overflow from the
carbonation process contains the soluble impurities in a
28
-------
neutralized solution which is characterized by treatable
concentrations of phenols and suspended solids. Sampling data
for carbonation plant effluent are presented in Table V-4.
MUD IMPOUNDMENT EFFLUENT
Red mud is the major waste stream from the bauxite refinery. It
contains all of the impurities from the bauxite, such as iron
oxide, silicon dioxide, and titanium dioxide, as well as by-
products formed during the process, such as sodium aluminum
silicates and calcium silicates. Red mud is discharged to ponds,
along with other process streams, where insoluble solids,
including the oxides of metallic elements, settle out of
suspension. The clarified liquid, characterized by treatable
concentrations of phenols and high pH, can be recycled and
discharged directly from the mud lake or decanted to a "clear
lake" before recycle or discharge.
The water use and discharge rates of this wastewater are listed
in Table V-l in liters per year of mud impoundment effluent.
Sampling data for the effluent from mud impoundments at two
plants are presented in Table V-5. At plant A, the impoundment
effluent is discharged directly from the mud lake without recycle
to the process. At plant B, overflow and underflow from the red
mud drying beds are sent to a clear lake from which water is
recycled or discharged.
29
-------
Table V-1
WATER USE AND DISCHARGE RATES FOR
MUD IMPOUNDMENT EFFLUENT
(liters/yr)
Plant Code Discharge Flow
1171 1 .45 x 109
1141 5.95 x 109
1076 2.983 x 1 08
1136 0
1073 0
1135 0
1032 0
1015 0
NR = Present, but data not reported in dcp
30
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BAUXITE REFINING SUBCATEGORY
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
Section V of this supplement presented data from bauxite refining
plant sampling visits and subsequent chemical analyses. This
section examines that data and discusses the selection or
exclusion of pollutants for potential limitation. The legal
basis for the exclusion of toxic pollutants under Paragraph 8(a)
of the Settlement Agreement is presented in Section VI of the
General Development Document.
Each pollutant selected for potential limitation is discussed in
Section VI of the General Development Document. That discussion
provides information concerning the origin of the pollutant
(i.e., whether it is a naturally occurring substance, processed
metal, or a manufactured compound); general physical properties
and the form of the pollutant; toxic effects of the pollutant in
humans and other animals; and behavior of the pollutant in POTW
at the concentrations expected in industrial discharges.
This section discusses the selection of conventional and
nonconventional pollutants for consideration for regulation. The
discussion that follows also describes the analysis that was
performed to select or exclude toxic pollutants for further
consideration for limitations and standards. Pollutants will be
selected for further consideration if they are present in
concentrations treatable by the technologies considered in this
analysis. The treatable concentrations used for the toxic metals
were the long-term performance values achievable by lime
precipitation, sedimentation, and filtration. The treatable
concentrations for the toxic organics were the long-term
performance values achievable by activated carbon adsorption (see
Section VII of the General Development Document - Combined Metals
Data Base).
CONVENTIONAL AND NONCONVENTIONAL POLLUTANT PARAMETERS
This study considered samples from the bauxite refining
subcategory for three conventional pollutant parameters (oil and
grease, total suspended solids, and pH) and two nonconventional
pollutant parameters (chemical oxygen demand and total
phenolics). Because existing BPT regulations (40 CFR Part 421,
Subpart A) specify zero discharge of process wastewater
pollutants, only sampling data from allowable mud impoundment
effluents were considered in the selection of conventional and
nonconventional pollutant parameters for regulation.
CONVENTIONAL AND NONCONVENTIONAL POLLUTANT PARAMETERS SELECTED
59
-------
The conventional and nonconventional pollutants or pollutant
parameters selected for consideration for limitation in this
subcategory are:
PH
phenolics
The pH values observed in five samples ranged from 11.5 to 11.76.
Effective and consistent removal of toxic organics by activated
carbon or chemical oxidation requires careful control of pH.
Therefore, pH is selected for consideration for limitation in
this subcategory.
Phenolics concentrations in six samples ranged from 0.116 to 1.23
mg/1. The observed concentrations are above those considered
treatable by identified treatment technology. Sampling data from
process wastewater streams, presented in Section V, indicate the
presence of phenolic compounds throughout the bauxite refining
process. Therefore, phenolics are considered for limitation in
this subcategory.
The major source of oil and grease in the bauxite refining
subcategory is from the lubrication of process machinery.
Because oil and grease in process wastewater is not present in
significant concentrations, oil and grease is not selected for
limitation.
Total suspended solids (TSS) concentrations in six samples range
from 2 to 18 mg/1. Although treatable, these concentrations are
not considered to be significant and are not expected to
interfere with end-of-pipe treatment technologies such as
activated carbon adsorption or chemical oxidation. Therefore,
total suspended solids are not selected for limitation in the
bauxite refining subcategory.
TOXIC POLLUTANTS
The frequency of occurrence of the toxic pollutants in the
wastewater samples taken is presented in Table VI-1. These data
provide the basis for the categorization of specific pollutants,
as discussed below. Table VI-1 is based on the raw wastewater
data from mud impoundment effluents at plant A and plant B (see
Section V). All other wastewaters have existing zero discharge
regulations and were therefore not considered here. Treatment
plant and source water samples were not considered in this
frequency count.
TOXIC POLLUTANTS NEVER DETECTED
The toxic pollutants listed below were either not analyzed or not
detected in any wastewater samples from this subcategory;
therefore, they are not selected for consideration in
establishing regulations:
60
-------
2. acrolein*
3. acrylonitrile*
4. benzene*
5. benzidene*
7. chlorobenzene*
8. 1,2,4-trichlorobenzene*
9. hexachlorobenzene*
10. 1,2-dichloroethane*
11. 1,1,1-trichloroethane*
12. hexachloroethane*
13. 1,1-dichloroethane*
14. 1,1,2-trichloroethane*
15. 1,1,2,2-tetrachloroethane*
16. chloroethane*
17. bis (chloromethyl) ether (deleted)*
18. bis (2-chloroethyl) ether*
19. 2-chloroethyl vinyl ether (mixed)*
20. 2-chloronaphthalene*
22. parachlorometa cresol
25. 1,2-dichlorobenzene*
26. 1,3-dichlorobenzene*
27. 1,4-dichlorobenzene*
28. 3,3'-dichlorobenzidine*
29. 1,1-dichloroethylene*
30. 1,2-trans-dichloroethylene*
32. 1,2-dichloropropane*
33. 1,2-dichloropropylene (1,3-dichloropfopene)*
35. 2,4-dinitrotoluene*
36. 2,6-dinitrotoluene*
37. 1,2-diphenylhydrazine*
38. ethylbenzene*
40. 4-chlorophenyl phenyl ether*
41. 4-bromophenyl phenyl ether*
42. bis(2-chloroisopropyl) ether*
43. bis(2-choroethoxy) methane*
45. methyl chloride (chlorotnethane) *
46. methyl bromide (bromomethane)*
47. bromoform (tribromomethane)*
49. trichlorofluoromethane (deleted)*
50. dichlorodifluoromethane (deleted)*
51. chlorodibromomethane*
52. hexachlorobutadiene*
53. hexachlorocyclopentadiene*
54. isophorone*
56. nitrobenzene*
59. 2,4-dinitrophenol
61. N-nitrosodimethylamine*
62. N-nitrosodiphenylamine*
63. N-nitrosodi-n-propylamine*
69. di-n-octyl phthalate*
72. benzo (a)anthracene (1,2-benzanthracene)*
73. benzo (a)pyrene (3,4-benzopyrene)*
74. 3,4-benzofluoranthene*
61
-------
75. benzo(k)fluoranthane (11,12-benzofluoranthene)*
76. chrysene*
78. anthracene*
79. benzo(ghi)perylene (1,11-benzoperylene)*
81. phenanthrene*
82. dibenzo (a,h)anthracene (1,2,5,6-dibenzanthracene)*
83. indeno (1,2,3-cd)pyrene (w,e,-o-phenylenepyrene)*
87. trichloroethylene*
88. vinyl chloride (chloroethylene)*
89. aldrin*
90. dieldrin*
94. 4,4'-DDD(p,p'TDE)*
105. g-BHC-Delta*
113. toxaphene*
116. asbestos
117. beryllium*
118. cadmium*
119. chromium (Total)*
120. copper*
122. lead*
123. mercury*
124. nickel*
128. zinc*
129. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
*We did not analyze for these pollutants in samples of raw
wastewater from this subcategory. These pollutants are not
believed to be present based on the Agency's best engineering
judgement which includes consideration of raw materials and
process operations.
TOXIC POLLUTANTS NEVER FOUND ABOVE THEIR ANALYTICAL
QUANTIFICATION LEVEL
The toxic pollutants listed below were never found above their
analytical quantification concentration in any wastewater samples
from this subcategory; therefore, they are not selected for
consideration in establishing regulations.
1. acenaphthene
6. carbon tetrachloride (tetrachloromethane)
34. - 2,4-dimethylphenol
39. fluoranthene
48. dichlorobromomethane
64. pentachlorophenol
67. butyl benzyl phthalate
80. fluorene
84. pyrene
86. toluene
91. chlordane (technical mixture and metabolites)
62
-------
92. 4,4'-DDT
93. 4/4'-DDE(p,p'DDX)
95. a-endosulfan-Alpha
96. b-endosulfan-Beta
97. endosulfan sulfate
98. endrin
99. endrin aldehyde
100. heptachlor
101. heptachlor epoxide
102. alpha-BHC
103. beta-BHC
104. r-BHC (lindane)-Gamma
106. PCB-1242 (Arochlor 1242)
107. PCB-1254 (Arochlor 1254)
108. PCB-1221 (Arochlor 1221)
109. PCB-1232 (Arochlor 1232)
110. PCB-1248 (Arochlor 1248)
111. PCB-1260 (Arochlor 1260)
112. PCB-1016 (Arochlor 1016)
114. antimony
121. cyanide (Total)
125. selenium
126. silver
TOXIC POLLUTANTS PRESENT BELOW CONCENTRATIONS ACHIEVABLE BY
TREATMENT
The pollutants listed below are not selected for consideration in
establishing limitations because they were not found in any
wastewater samples from this subcategory above concentrations
considered achievable by existing or available treatment
technologies.
115. arsenic
127. thallium
Arsenic was detected above its analytical quantification limit in
five of five samples from two plants. These samples were below
the 0.34 mg/1 concentration considered achievable by treatment.
Therefore, arsenic is not selected for limitation.
Thallium was detected above its analytical quantification limit
in one of five samples from two plants. This sample was below
the 0.34 mg/1 concentration considered achievable by identified
treatment technology. Therefore, thallium is not selected for
limitation.
TOXIC POLLUTANTS DETECTED IN A SMALL NUMBER OF SOURCES
The following pollutants were not selected for limitation because
they were detected in only a small number of sources:
23. chloroform
63
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44. methylene chloride
55. naphthalene
60. 4,6-dinitro-o-cresol
66. bis(2-ethylhexyl) phthalate
68. di-n-butyl phthalate
70. diethyl phthalate
71. dimethyl phthalate
77. acenaphthylene
85. tetrachloroethylene
Although these pollutants were not selected for consideration in
establishing nationwide limitations, it may be appropriate, on a
case-by-case basis, for the local permitter to specify effluent
• limitations.
Chloroform was detected above its treatable limit in three of six
samples from two plants at concentrations of 0.015, 0.026, and
0.063 mg/1. This pollutant is not attributable to any source
within the refinery. It also appears in the source water and it
is commonly used in the analytical laboratories as a solvent.
For these reasons chloroform is not considered for limitation.
Methylene chloride was found above its treatable concentration in
three of four samples from two plants at concentrations of 0.020,
0.051, and 0.170 mg/1. This pollutant is not attributable to
specific materials or processes associated with bauxite refining.
It is, however, a common solvent used in analytical laboratories.
Since the possibility of sample contamination is likely,
methylene chloride is not selected for limitation.
Naphthalene was detected above its treatable concentration in one
of two samples from one plant, at a concentration of 0.02 mg/1.
This pollutant is not attributable to bauxite refining operations
or raw materials; it is also present only slightly above the
treatability concentration. For these reasons, naphthalene is
not considered for limitation.
4,6-Dinitro-o-cresol was found above its treatability
concentration in one sample from one plant, at a concentration of
0.011 mg/1. Because this pollutant is not attributable to any
specific materials or processes in the bauxite refining
operation, and it is present only slightly above the treatability
concentration of 0.01 mg/1, this pollutant is not selected for
limitation.
Bis(2-ethylhexyl) phthalate was found above its treatable
concentration of 0.01 mg/1 in five of six samples from two
plants. This compound is a plasticizer commonly used in
laboratory and field sampling equipment and is not used as a raw
material or formed as a by-product in this subcategory.
Therefore, bis(2-ethylhexyl) phthalate is not selected for
limitation.
64
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Di-n-butyl phthalate was found above its treatable concentration
of 0.01 mg/1 in one of six samples from two plants. This
compound is a plasticizer commonly used in laboratory and field
sampling equipment and is not used as a raw material or formed as
a by-product in this subcategory. Therefore, di-n-butyl
phthalate is not selected for limitation.
Diethyl phthalate was found above its treatable concentration of
0.01 mg/1 in one of two samples from one plant. This compound is
a plasticizer commonly used in laboratory and field sampling
equipment and is not used as a raw material or formed as a by-
product in this subcategory. Therefore, diethyl phthalate is not
selected for limitation.
Dimethyl phthalate was found above its treatable concentration in
one of two samples from two plants at a concentration of 1.5
mg/1. This pollutant is not attributable to specific materials
or processes associated with bauxite refining. The high
concentration is probably due to contamination from laboratory
equipment. Therefore, dimethyl phthalate is not selected for
limitation.
Acenaphthylene was found above its analytical quantification
limit in two of three samples from two plants at concentrations
of 0.018 and 0.086 mg/1. This pollutant has been shown to be
present in the wastewater from briquette quenching operations in
the primary aluminum subcategory. The two sampled plants are
integrated facilities which manufacture a number of aluminum-
based products. Therefore, because it is likely to be generated
by processes outside the bauxite refining subcategory and because
it is not specifically attributable to the bauxite refining
process, acenaphthylene is not selected for limitation.
Tetrachloroethylene was found above its treatability limit in one
sample from one plant, at a concentration of 0.012 mg/1. This
pollutant is not attributable to any process or material in the
refining process; it is present only slightly above its
treatability concentration of 0.01 mg/1 and it is frequently used
in the laboratory, where contamination could occur. For these
reasons, tetrachloroethylene is not selected for limitation.
TOXIC POLLUTANTS SELECTED FOR FURTHER CONSIDERATION FOR
LIMITATION
The toxic pollutants listed below are selected for further
consideration in establishing limitations for this subcategory.
The selected pollutants are discussed individually following the
list.
21. 2, 4,6-trichlorophenol
24. 2-chlorophenol
31. 2,4-dichlorophenol
57. 2-nitrophenol
65
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58. 4-nitrophenol
65. phenol
2,4,6-Trichlorophenol was found above its analytical
quantification limit in three of four samples from two plants
with concentrations ranging from 0.048 to 0.072 mg/1. All three
of those samples were above the 0.01 mg/1 concentration
considered achievable by identified treatment technology.
Therefore, 2,4,6-trichlorophenol is selected for further
consideration for limitation.
2-Chlorophenol was found above its analytical quantification
limit in two of two samples from one plant with concentrations of
0.065 and 0.720 mg/1. Both of those samples were above the 0.01
mg/1 treatability concentration. Threfore, 2-chlorophenol is
selected for further consideration for limitation.
2,4-Dichlorophenol was found above its analytical quantification
limit in four of five samples from two plants with concentrations
ranging from 0.047 to 0.060 mg/1. All four of those samples were
above the 0.01 mg/1 treatability concentration. Therefore, 2,4-
dichlorophenol is selected for further consideration for
limitation.
2-Nitrophenol was found above its analytical quantification limit
in one of three samples from two plants at a concentration of
0.067 mg/1. That sample was above the 0.01 mg/1 treatability
concentration. Therefore, 2-nitrophenol is selected for further
consideration for limitation.
4-Nitrophenol was found above its analytical quantification limit
in three of four samples from two plants with concentrations
ranging from 0.017 to 0.310 mg/1. Those three samples were above
the 0.01 mg/1 treatability concentration. Therefore, 4-
nitrophenol is selected for further consideration for limitation.
Phenol was found above its analytical quantification limit in six
of six samples from two plants with concentrations ranging from
0.034 to 0.750 mg/1. All six of those samples were above the
0.01 mg/1 treatability concentration. Also, phenolics have been
identified as constituents of bauxite ore. Therefore, phenol is
selected for further consideration for limitation.
66
-------
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70
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BAUXITE REFINING SUBCATEGORY
SECTION VII
CONTROL AND TREATMENT TECHNOLOGIES
The preceding sections of this supplement discussed the sources,
flows, and characteristics of the wastewaters generated in the
bauxite refining subcategory. This section summarizes the
description of these wastewaters and indicates the level of
treatment which is currently practiced for each waste stream.
CURRENT CONTROL AND TREATMENT PRACTICES
Control and treatment technologies are discussed in general in
Section VII of the General Development Document. The basic
principles of these technologies and the applicability to
wastewater similar to that found in this subcategory are
presented there. This section presents a summary of the control
and treatment technologies that are currently applied to each of
the sources generating wastewater in this subcategory. As
discussed in Section V, wastewater associated with the bauxite
refining subcategory is characterized by the presence of
treatable concentrations of phenolic compounds and high pH. This
analysis is supported by the raw (untreated) wastewater data
presented for specific sources in Section V. According to
promulgated BPT limitations (40 CFR Part 421, Subpart A), the
only allowable discharge of wastewater pollutants for the bauxite
refining subcategory is from the mud impoundment. The other
three subdivisions (digester condensate, barometric condenser
effluent, and carbonation plant effluent) are all restricted to
zero discharge of wastewater pollutants under the promulgated BPT
regulation. Three plants in this subcategory currently discharge
treated water from the mud impoundment area. One option has been
selected for consideration for BPT, BAT, NSPS, and pretreatment
based on this waste stream.
MUD IMPOUNDMENT EFFLUENT
Red mud is the major waste stream from bauxite refining
operations. It contains the impurities from the bauxite ore as
well as by-products formed during the refining process. Red mud
is deposited in large ponds where insoluble solids, including the
oxides of metallic elements, settle out of suspension. Rainfall
from the plant site is often routed to the mud impoundment.
Water from the impoundment can be recycled to the plant directly
from the mud lake or it can be decanted to a separate clear lake
before recycle.
Three plants currently discharge water from the mud impoundment.
At one plant, water is discharged after pH adjustment without
recycle to the process. At another plant, a portion of the water
7i
-------
which is recycled to the plant from a clear lake is discharged
without treatment. The third plant discharges excess stormwater
from closed mud lakes after pH adjustment. The remaining five
plants in this subcategory currently achieve zero discharge by
permanent lagoon impoundment and partial recycle. However, one
of these plants is considering a process technology change which
would result in a mud impoundment discharge.
CONTROL AND TREATMENT OPTIONS
The Agency examined one control and treatment alternative that is
applicable to the bauxite refining subcategory. The option
selected for evaluation represents an end-of-pipe treatment
technology.
OPTION E
Option E for the bauxite refining subcategory consists of all
control requirements of the existing BPT (no discharge of process
wastewater pollutants, and discharge of net precipitation from
process wastewater impoundments) plus pH adjustment and activated
carbon adsorption treatment of the mud impoundment effluent.
Activated carbon adsorption is used to remove organic compounds,
including phenolics, from the effluent wastewater. Adjustment of
pH is required to ensure consistent removal performance by
adsorption and to meet discharge quality standards.
»
The Agency also considered the use of pH adjustment and chemical
oxidation to remove phenolic compounds from the effluent
wastewater. Adjustment of pH is required to ensure consistent
removal performance by chemical oxidation and to meet discharge
quality standards. Hydrogen peroxide is suggested for the
oxidation of phenols, but other chemicals, such as chlorine
dioxide and ozone, may perform satisfactorily.
72
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BAUXITE REFINING SUBCATEGORY
SECTION VIII
COSTS OF WASTEWATER TREATMENT AND CONTROL
This section describes the method used to develop the costs
associated with the control and treatment technologies of Option
E discussed in Section VII for wastewaters from bauxite refining
plants. Plant-by-plant compliance costs for this option were
developed. Compliance costs for chemical oxidation were also
estimated. The energy requirements of the considered option as
well as solid waste and air pollution aspects are also discussed.
Section VIII of the General Development Document provides
background on the capital and annual costs for the technology
discussed herein.
TREATMENT OPTIONS COSTED FOR EXISTING SOURCES
As discussed in Section VII, one treatment option has been
considered for existing bauxite refining plants. This option is
summarized below and is schematically presented in Figure X-l.
OPTION E
Option E consists of the BPT requirements with additional control
of the mud impoundment discharges by pH adjustment and activated
carbon adsorption. The Agency also prepared capital and annual
costs for pH adjustment and chemical oxidation of the mud
impoundment effluent at one median plant. The calculated costs
were much higher in relation to the costs for activated carbon at
the same plant, therefore, no further consideration was given to
this technology.
COST METHODOLOGY
t
A detailed discussion of the methodology used to develop the
compliance costs is presented in Section VIII of the General
Development Document. Plant-by-plant compliance costs have been
estimated for the nonferrous metals manufacturing category and
are documented in detail in the administrative record supporting
this regulation. The costs for the option in this subcategory
are presented in Table VII1-1.
Each of the general assumptions used to develop compliance costs
is presented in Section VIII of the General Development Document.
Each subcategory also contains a unique set of waste streams
requiring certain subcategory-specific assumptions to develop
compliance costs. The major assumptions specific to the bauxite
refining subcategory are discussed briefly below.
73
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(1) The Option E treatment system consists of pH adjustment
followed by carbon adsorption.
The flows were determined from information provided in the
dcp for red mud impoundment discharge flow only. The
influent concentrations for phenol and 2-chlorophenol were
determined from averages of field sampling data from two
plants. These data are found in Table V-5.
(2) Costs for pH adjustment were based on reduction of pH
from 11.5 to 9 using sulfuric acid.
(3) The carbon exhaustion rate was determined from
adsorption isotherms for phenol and 2-chlorophenol,
influent concentrations from the sampling data, and an
effluent concentration in both cases of 0.010 mg/1.
Using this procedure and an excess of 50% to account
for other adsorbable organics, a carbon exhaustion rate
of 2.321 lbs/1000 gallons was determined.
(4) Plants 1076 and 1141 have pH adjustment equipment in
place; capital cost estimates are included for all
other equipment at the three discharging plants and the
one existing zero discharger who is considering a
discharge.
NONWATER QUALITY ASPECTS
A general discussion of the nonwater quality aspects of the
control and treatment options considered for the nonferrous
metals category is contained in Section VIII of the General
Development Document. Nonwater quality impacts specific to the
bauxite refining subcategory, including energy requirements,
solid waste and air pollution are discussed below.
ENERGY REQUIREMENTS
The methodology used for determining the energy requirements for
the various options is discussed in Section VIII of the General
Development Document. Energy requirements for Option E are
estimated at 11,500,000 kWh/yr. This represents less than 3
percent of the total energy usage of the four plants. It is
therefore concluded that the energy requirements of the treatment
option considered will not have a significant impact on total
plant energy consumption.
SOLID WASTE
No significant amounts of solid wastes are generated by the
technologies considered for this regulation in the bauxite
refining subcategory. Activated carbon is thermally regenerated
either on-site or off-site, and in neither case are appreciable
quantities of solid waste generated.
74
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AIR POLLUTION
There is no reason to believe that any substantial air pollution
problems will result from implementation of activated carbon
treatment and pH adjustment. Thermal regeneration of spent
carbon may release trace quantities of pollutants, but these
should be readily oxidized at the temperatures under which the
carbon is regenerated.
75
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Table VIII-1
COST OF COMPLIANCE FOR THE BAUXITE REFINING SUBCATEGORY
DIRECT DISCHARGERS*
(March, 1982 Dollars)
Total Required Total
Option Capital Cost Annual Cost
E 7,600,000 2,980,000
*Includes one plant currently practicing zero discharge of
process wastewater.
76
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BAUXITE REFINING SUBCATEGORY
SECTION IX
BEST PRACTICABLE TECHNOLOGY CURRENTLY AVAILABLE
EPA promulgated BPT limitations for the bauxite refining
subcategory on April 8, 1974 as Subpart A of 40 CFR Part 421.
EPA is proposing only minor technical modifications to these
limitations.
The following limitations establish the quantity or quality of
pollutants or pollutant properties which may be discharged by a
point source after application of the best practicable control
technology currently available: There shall be no dischage of
process wastewater pollutants to navigable waters.
During any calendar month, there may be discharged from the
overflow of a process wastewater impoundment either a volume of
wastewater equal to the difference between the precipitation for
that month that falls within the impoundment and the evaporation
within the impoundment for that month, or, if greater, a volume
of process wastewater equal to the difference between the mean
precipitation for that month that falls within the impoundment
and the mean evaporation for that month as established by the
National Climatic Center, National Oceanic and Atmospheric
Administration, for the area in which such impoundment is located
(or as otherwise determined if no monthly data have been
established by the National Climatic Center).
EPA does not believe that the data gathered since the original
promulgation warrant any adjustment in the BPT requirements.
Minor amendments to the regulatory language are being proposed to
clarify references to fundamentally different factors (PDF)
considerations under 40 CFR Part 125 and references to
pretreatment standards under 40 CFR Part 128. As a result, the
bauxite refining subcategory will not incur any incremental
capital or annual costs to comply with the BPT limitations.
77
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BAUXITE REFINING SUBCATEGORY
SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
The effluent limitations which must be achieved by July 1, 1984
are based on the best control and treatment technology used by a
specific point source within the industrial category or
subcategory, or by another industry where it is readily
transferable. Emphasis is placed on additional treatment
techniques applied at the end of the treatment systems currently
used, as well as reduction of the amount of water used and
discharged, process control, and treatment technology
optimization.
The factors considered in assessing best available technology
economically achievable (BAT) inqlude the age of equipment and
facilities involved, the process used, process changes, nonwater
quality environmental impacts (including energy requirements),
and the costs of application of such technology (Section
304(b)(2)(B) of the Clean Water Act). At a minimum, BAT
represents the best available technology economically achievable
at plants of various ages, sizes, processes, or other
characteristics. Where the Agency has found the existing
performance to be uniformly inadequate, BAT may be transferred
from a different subcategory or category. BAT may include
feasible process changes or internal controls, even when not in
common industry practice.
The required assessment of BAT considers costs, but does not
require a balancing of costs against effluent reduction benefits
(see Weyerhaeuser v. Costle, 11 ERC 2149 (D.C.Cir. 1978)).
However, in assessing the proposed BAT, the Agency has given
substantial weight to the economic achievability of the
technology.
TECHNICAL APPROACH TO BAT
In pursuing this second round of effluent limitations, the Agency
reviewed a wide range of technology options and evaluated the
available possibilities to ensure that the most effective and
beneficial technologies were used as the basis of BAT. To
accomplish this, the Agency elected to examine one technology
option which could be applied to the bauxite refining subcategory
as an alternative for the basis of BAT effluent limitations. The
treatment technologies considered for BAT are summarized below:
Option E (Figure X-l):
• Zero discharge of process wastewater pollutants
• Discharge of net precipitation from process wastewater
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impoundments
pH adjustment
Activated carbon adsorption
OPTION E
Option E consists of the existing BPT requirements (no discharge
of process wastewater pollutants, discharge of net precipitation
from a process wastewater impoundment), with pH adjustment and
activated carbon adsorption treatment of the net precipitation
discharge. Activated carbon technology is used to remove toxic
organic compounds, including phenolics, from the effluent
wastewater. Adjustment of pH is required to ensure consistent
removal performance by adsorption and to meet discharge quality
standards.
INDUSTRY COST AND POLLUTANT REMOVAL ESTIMATES
As one means of evaluating the technology option, EPA developed
estimates of the pollutant removal estimates and the associated
compliance costs. The methodologies are described below.
POLLUTANT REMOVAL ESTIMATES
A complete description of the methodology used to calculate the
estimated pollutant removal, or benefit, achieved by the
application of the treatment option is presented in Section X of
the General Development Document. In short, sampling data
collected during the field sampling program were used to
characterize the pollutant concentrations in the waste stream
considered for regulation. This information was used with the
wastewater discharge rates measured during sampling or derived
from each dcp to estimate the mass of toxic pollutants generated
by each plant in the bauxite refining subcategory.
The mass of pollutant discharged was estimated by multiplying the
achievable concentration values attainable by the option (mg/1)
by the estimated volume of wastewater discharged by each plant in
the subcategory. The mass of pollutant removed, referred to as
the benefit, is simply the difference between the estimated mass
of pollutant generated by each plant and the mass of pollutant
discharged after application of the treatment option. The total
subcategory removal was. then estimated by summing the individual
plant removal estimates for each pollutant. The pollutant
removal estimates for the bauxite refining subcategory are
presented in Table X-1.
COMPLIANCE COSTS
EPA calculated compliance costs for the bauxite refining
subcategory by developing a wastewater treatment system design
and cost estimation model that estimates capital and annual costs
for the treatment option being considered. This model was
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applied to each plant's flow and pollutant characteristics, and
the calculated capital and annual costs were summed to arrive at
total subcategory costs. These costs, which are presented in
Table X-2, were used in EPA's economic impact analysis.
BAT OPTION SELECTION
EPA promulgated BAT limitations for the bauxite refining
subcategory on April 8, 1974 as Subpart A of 40 CFR Part 421.
These limitations allow no discharge of process wastewater
pollutants to navigable waters. A discharge is allowed from the
overflow of a process wastewater impoundment in a volume equal to
the net precipitation that falls within the impoundment. EPA is
not proposing any modification to these limitations at this time.
However, the Agency is considering the establishment of effluent
limitations based on pH adjustment and activated carbon
adsorption treatment of toxic organic pollutants in the mud
impoundment overflow. This revision is in keeping with the
emphasis of the Clean Water Act of 1977 on toxic pollutants.
Implementation of this organics control option would remove
annually an estimated 4,835 kg of toxic pollutants from the raw
discharge. Estimated capital cost for achieving this option
would be $7.60 million, with estimated annualized costs of $2.98
million.
Activated carbon is being considered because of its ability to
remove toxic organics to very low concentrations. Although no
plants in the nonferrous metals manufacturing category have
installed this technology for organics removal, it is
demonstrated in the iron and steel manufacturing category. EPA
believes that the influent characteristics are similar with
respect to organics for both categories, and that, if proper
design procedures are used, similar removals will be achieved.
Activated carbon will remove adsorbable organics to essentially
nondetectable levels if sufficient carbon and contact time are
provided. These design parameters have been carefully and
conservatively selected by EPA for this subcategory. Therefore,
based on these considerations and the performance data from iron
and steel manufacturing a level of 0.010 mg/1 for phenol, 2-
chlorophenol, and total phenols (4-AAP) can be achieved. The
Agency solicits comments on the costs and performance of
activated carbon, and the applicability of these effluent
limitations to the bauxite refining subcategory.
REGULATED POLLUTANT PARAMETERS
In implementing the terms of the Consent Agreement in NRDC v.
Train, Op. Cit., and 33 U.S.C. 1314(b)(2)(A and B) (1976), the
Agency placed particular emphasis on the toxic pollutants. The
raw wastewater concentrations from individual operations and the
subcategory as a whole were examined to select certain pollutants
and pollutant parameters for limitation. This examination and
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evaluation, presented in Section VI, concluded that six
pollutants and pollutant parameters are present in bauxite
refining wastewaters at concentrations that can be reduced by
identified treatment technologies.
The high cost associated with analysis for toxic organic
pollutants has prompted EPA to consider an alternative method for
regulating and monitoring toxic pollutant discharges from the
nonferrous metals manufacturing category. Rather than developing
specific effluent limitations and standards for each of the toxic
organics found in treatable concentrations in the raw wastewater
from a given subcategory, the Agency is considering effluent
limitations only for those pollutants generated in the greatest
quantities as shown by the pollutant removal estimate analysis.
On this basis, the pollutants being considered for specific
limitation are listed below:
24. 2-chlorophenol
65. phenol
By establishing limitations and standards for certain toxic
organic pollutants, dischargers would attain the same degree of
control over toxic organic pollutants as they would have been
required to achieve had all the toxic organic pollutants been
directly limited. This approach is technically justified because
the design of activated carbon columns must consider the presence
of other organic compounds which will be removed from the
wastewater. Even though the removal of different phenolic
compounds will occur at different rates, treatment of the above
listed organics to the concentration values attainable by the
option will be accompanied by a reduction in concentration of the
unregulated organics. One nonconventional pollutant parameter,
total phenolic (4-AAP), is being considered for limitation to
ensure adequate removal of phenolics other than 2-chlorophenol
and phenol. No toxic metal pollutants are selected for specific
limitation in this subcategory.
The following toxic pollutants are not being considered for
specific limitation on the basis that they would be effectively
controlled by the limitations being considered for 2-
chlorophenol, phenol, and total phenolics (4-AAP):
21. 2,4,6-trichlorophenol
31. 2,4-dichlorophenol
57. 2-nitrophenol
58. 4-nitrophenol
The conventional pollutant parameter pH may be limited by the
best conventional technology (BCT) effluent limitations.
EFFLUENT LIMITATIONS
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The concentrations achievable by application of pH adjustment and
activated carbon are discussed in Section VII of the General
Development Document. The effluent limitations for mud
impoundment effluent under consideration for BAT are shown below.
BAT EFFLUENT LIMITATIONS UNDER CONSIDERATION FOR THE BAUXITE
REFINING SUBCATEGORY
Mud Impoundment Effluent
Pollutant or Maximum for
Pollutant Property Any One Day (mq/1)
Phenol . 0.010
2-Chlorophenol 0.010
Total Phenols (4-AAP) 0.010
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Table X-2
COST OF COMPLIANCE FOR THE BAUXITE REFINING SUBCATEGORY
Direct Dischargers*
Capital Cost Annual Cost
Option (1982 Dollars) (1982 Dollars)
E 7,600,000 2,980,000
*Includes one plant currently practicing zero discharge of
process wastewater.
85
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BAUXITE REFINING SUBCATEGORY
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
The basis for new source performance standards {NSPS) under
Section 306 of the Act is the best available demonstrated
technology (BDT). New plants have the opportunity to design the
best and most efficient production processes and wastewater
treatment technologies without facing the added costs and
restrictions encountered in retrofitting an existing plant.
Therefore, Congress directed EPA to consider the best
demonstrated process changes, in-plant controls, and end-of-pipe
treatment technologies which reduce pollution to the maximum
extent feasible.
This section describes the technologies for treatment of
wastewater from new sources and presents the performance
standards being considered for NSPS in the bauxite refining
subcategory, based on the selected treatment technology.
TECHNICAL APPROACH TO NSPS
EPA promulgated new source performance standards for the bauxite
refining subcategory on April 8 1974. The technology basis for
this promulgation was identical to BAT. EPA is proposing only
minor technical amendments to the promulgated regulation. It is
also considering the limitations described in the previous
section for BAT, i.e., pH adjustment and activated carbon
adsorption of mud impoundment overflow. This result is a
consequence of careful review by the Agency of a wide range of
technology options for new source treatment systems which is
discussed in Section XI of the General Development Document.
This review of the bauxite refining subcategory found no new,
economically feasible, demonstrated technologies which could be
considered an improvement over those chosen for consideration for
BAT. Additionally, there was nothing found to indicate that the
wastewater flows and characteristics of new plants would not be
similar to those from existing plants, since the processes used
by new sources are not expected to differ from those used at
existing sources.
The treatment technology considered . for the NSPS option is
identical to the treatment technology considered for the BAT
option. This option is:
OPTION E
• Zero discharge of process wastewater pollutant
• Discharge of net precipitation from process
wastewater impoundments
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• pH adjustment
• Activated carbon adsorption
NSPS OPTION SELECTION
As discussed earlier, with the exception of minor technical
amendments, the Agency is not modifying the existing promulgated
regulation for the bauxite refining subcategory. The Agency is
considering and solicits comments on performance standards based
on Option E technology.
REGULATED POLLUTANT PARAMETERS
The Agency has no reason to believe that the pollutants that will
be found in treatable concentrations in processes within new
sources will be any different than with existing sources.
Accordingly, pollutants and pollutant parameters being considered
for limitation under NSPS, in accordance with the rationale of
Sections VI and X, are identical to those being considered for
BAT. The conventional pollutant parameter pH is also being
considered for limitation. For NSPS, the Agency is considering
pH limitations for mud impoundment effluent within the range of
7.5 to 10.0 at all times, and solicits comments on this
limitation.
NEW SOURCE PERFORMANCE STANDARDS
The modified performance standards being considered based on pH
adjustment and activated carbon adsorption technology are listed
below.
NSPS UNDER CONSIDERATION FOR THE BAUXITE REFINING SUBCATEGORY
Mud Impoundment Effluent
Pollutant or Maximum for
Pollutant Property Any One Day (mg/1)
Phenol 0.010
2-Chlorophenol 0.010
Total Phenols (4-AAP) 0.010
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BAUXITE REFINING SUBCATEGORY
SECTION XII
PRETREATMENT STANDARDS
EPA is not proposing pretreatment standards for existing sources
at this time because there are currently no indirect discharging
facilities in this subcategory.
EPA promulgated PSNS for the bauxite refining subcategory on
April 8, 1974 as Subpart A of 40 CFR Part 421. The following
limitations establish the quantity or quality of pollutants or
pollutant properties which may be discharged by a new indirect
discharger: There shall be no discharge of process wastewater
pollutants to navigable waters.
During any calendar month, there may be discharged from the
overflow of a process wastewater impoundment either a volume of
wastewater equal to the difference between the precipitation for
that month that falls within the impoundment and the evaporation
within the impoundment for that month, or, if greater, a volume
of process wastewater equal to the difference between the mean
precipitation for that month that falls within the impoundment
and the mean evaporation for that month as established by the
National Climatic Center, National Oceanic and. Atmospheric
Administration, for the area in which such impoundment is located
(or as otherwise determined if no monthly data have been
established by the National Climatic Center).
EPA is not proposing any modifications to PSNS since it is
unlikely that any new bauxite sources will be constructed as
indirect dischargers.
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BAUXITE REFINING SUBCATEGORY
SECTION XIII
BEST CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY
EPA is not proposing best conventional pollutant control
technology (BCT) limitations for the bauxite refining subcategory
at this time.
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