EPA 530/M-9 7-001
CHARACTERIZATION OF MINERAL PROCESSING WASTES AND
MATERIALS
ENVIRONMENTAL PROTECTION AGENCY
1997
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1. Introduction
In its January 25, 1996 Supplemental Proposed Rule, the Agency assumed that land-
based storage units historically have been a significant part of the production process of the
mining and mineral processing industries, primarily because of the large volumes of materials
managed by the industry. EPA believed that the quantities of secondary materials were too
large to be managed in anything other than land-based units.
Based on new data and further analysis, however, EPA has found that generation rates
of wastes from the mineral processing industry are similar to other industrial wastes currently
regulated under RCRA. Further, many of the newly identified wastes have concentrations of
hazardous constituents that are similar to wastes currently regulated under the RCRA Subtitle
C program. The Agency is presenting information indicating that land-based storage units are
not necessarily an integral to the mineral processing industry. The Agency's information
indicates that tanks, containers, and buildings, which provide greater environmental
protection, can be used to store mineral processing secondary materials prior to recycling.
In the Supplemental Proposed Rule, the Agency also raised the issue of whether to
allow mineral processing secondary materials to be recycled in units generating Bevill-exempt
wastes. The Agency has found many cases in which environmental damages were caused by
these Bevill-exempt wastes, including several cases in which non-Bevill feedstocks were
being added to units generating the exempt waste. (See Damage Cases and Environmental
Releases, EPA, 1997). Because of these cases, the Agency is concerned about the
contribution of contaminants from non-Bevill feedstocks. Therefore, the Agency has
compared desirable and undesirable contaminants in virgin Bevill unit feedstocks with
secondary materials that might be used as alternative feedstocks to these units, and found that
these secondary materials often have higher contaminant concentrations than the virgin
feedstock.
2. Comparison of Waste Stream and Toxicity Data
This section first presents current waste stream data and then compares these data with
the data used in the RLA accompanying the January 1996 Supplemental Proposed Rule.
Finally, this section compares mineral processing waste streams with currently listed RCRA
Subtitle C wastes in terms of generation volumes and toxicity..
January 1996 Data vs Data Provided in Public Comments
The Agency received many comments on its January 1996 proposed mineral
processing rule that addressed the amounts and types of secondary materials generated.
Based on a review of those comments, the Agency found that a number of waste streams
either are no longer generated or are generated in different quantities than previously
2
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believed. In addition, one commenter suggested new waste streams should be added to the
analysis.
Exhibit 1 lists all of the waste streams that: 1) have dropped out of the analysis; 2)
have been added to the analysis; or 3) have been assigned a new average facility generation
rate based on the review of new data. As seen in the exhibit, 32 waste streams have dropped
out of the analysis because in most cases the Agency determined that these wastes are either
non-hazardous or not stored in land-based units. Two waste streams, elemental phosphorous
andersen filter media and furnace building washdown were added to the analysis because the
Agency received comments suggesting they were hazardous. Two more waste streams,
elemental phosphorous AFM rinsate and furnace scrubber blowdown were assigned new
generation rates. Please note that average facility generation rates, rather than total sector
generation rates, were used because the Bevill exclusion defines high volume streams based
on average facility generation rates.
Exhibits 2 and 3 graphically present the old and new average facility generation rates
for mineral processing secondary materials for those cases in which the current generation
rates differ from those rates used in the December 1995 RIA supporting the January 1996
Supplemental Proposed Rule. In most cases, changes in generation rates resulted from the
removal of waste streams from the analysis (hence the large numbers of "Os" in the exhibits).
Exhibit 2 shows that facility generation rates for phosphorous andersen media filter and zinc
WWTP solids (both solid wastes) rose because of their recent inclusion in the analysis.
Exhibit 3 demonstrates that the facility generation rates for three liquid wastes, phosphorous
furnace building washdown and furnace scrubber blowdown and AFM rinsate rose between
December 1995. In two of the cases, wastes were added for the January 1997 analysis, while
in the third case, commenters reported a change in generation rate.
In the January 1996 Supplemental Proposed Rule, 148 mineral processing secondary
materials were identified that could be affected by the Phase IV LDRs. However, due to new
information contained in public comment on the proposed rule, as well as other additional
information, the Agency now believes 118 mineral processing secondary materials will be
affected by the Phase IV LDRs. Of these streams, 61 are solid and 57 are liquid.
Current Volumes
Exhibit 4 presents average and maximum facility generation rates for all solid waste
streams in the current data set in ascending order, while Exhibit 5 presents this information for
liquid waste streams.1 These figures were obtained from the mineral processing cost RIA cost
model. Only three waste streams are generated in volumes above the high volume criterion
(45,000 mt/yr for solid materials or 1,000,000 mt/yr for liquid materials) used in the 1990
Report
1 Please note that these generation rates have not been corrected to account for
uncertainty in hazard characteristics, as was done in the cost model for the RIA.
3
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Exhibit 1
Waste Streams Status Changes Since December 1995
Sector
Waste Stream
Waste Type
Action
Reason
Beryllium
Bertrandite thickener slurry
Liquid
Dropped Out of Analysis
Public comment indicate previous
agency decision on beneficiation
processing line
Beryllium
Beryl thickener slurry
Liquid
Dropped Out of Analysis
Public comment indicate previous
agency decision on beneficiation
processing line
Beryllium
Spent barren filtrate streams
Liquid
Dropped Out of Analysis
Public comment indicate previous
agency decision on beneficiation
processing line
Beryllium
Spent raffinate
Liquid
Dropped Out of Analysis
Public comment indicate previous
agency decision on beneficiation
processing line
Boron
Waste liquor
Liquid
Dropped Out of Analysis
Determined to be not-hazardous
Copper
APC dust/sludge
Solid
Dropped Out of Analysis
Not land stored
Copper
Process wastewaters
Liquid
Dropped Out of Analysis
Not land stored
Copper
Scrubber blowdown
Liquid
Dropped Out of Analysis
Believed to be same as acid plant
blowdown, removed to prevent
double counting
Copper
Spent bleed electrolyte
Liquid
Dropped Out of Analysis
Not land stored
Copper
Surface impoundment waste
liquids
Liquid
Dropped Out of Analysis
Double counted (same as process
wastewaters)
Copper
Tankhouse slimes
Solid
Dropped Out of Analysis
Not land stored
Copper
Waste contact cooling water
Liquid
Dropped Out of Analysis
Not land stored
Elemental Phosphorous
AFM rinsate
Liquid
Changed Generation Rate
Commenter provided data
Elemental Phosphorous
Andersen Filter Media
Solid
Added to Analysis
Commenter indicated this material is
hazardous
Elemental Phosphorous
Dust
Solid
Dropped Out of Analysis
Commenter provided data
Elemental Phosphorous
Furnace Building Washdown
Liquid
Added to Analysis
Commenter provided data
4
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Elemental Phosphorous
Furnace offgas solids
Solid
Dropped Out of Analysis
Not toxic
Elemental Phosphorous
Furnace scrubber blowdown
Liquid
Changed Generation Rate
Commenter provided data
Exhibit 1 (Continued)
Waste Streams Status Changes Since December 1995
Sector
Waste Stream
Waste Type
Action
Reason
Gold and Silver
Refining wastes
Solid
Dropped Out of Analysis
Generated at secondary smelter only
Gold and Silver
Slag
Solid
Dropped Out of Analysis
Not land stored
Gold and Silver
Spent Furnace Dust
Solid
Dropped Out of Analysis
Not land stored
Gold and Silver
Wastewater
Liquid
Dropped Out of Analysis
Generated at secondary smelter only
Gold and Silver
Wastewater treatment sludge
Solid
Dropped Out of Analysis
Generated at secondary smelter only
Lead
Acid plant blowdown
Liquid
Dropped Out of Analysis
Fully recycled, not land stored
Lead
Baghouse dust
Solid
Dropped Out of Analysis
Fully recycled, not land stored
Lead
Process wastewater
Liquid
Dropped Out of Analysis
Fully recycled, not land stored
Lead
Surface impoundment waste
liquids
Liquid
Dropped Out of Analysis
No longer generated
Molybdenum
Molybdic oxide refining wastes
Solid
Dropped Out of Analysis
No longer generated
Rare Earths
Spent lead filter cake
Solid
Dropped Out of Analysis
Fully recycled, not land stored
Rare Earths
Waste solvent
Liquid
Dropped Out of Analysis
Fully recycled, not land stored
Rare Earths
Waste zinc contaminated with
mercury
Solid
Dropped Out of Analysis
No longer generated
Titanium and Titanium
Dioxide
Scrap detergent wash water
Liquid
Dropped Out of Analysis
Not hazardous
Titanium and Titanium
Dioxide
Waste acids (Chloride process)
Liquid
Dropped Out of Analysis
Fully recycled/Treated, not land
stored
Titanium and Titanium
Dioxide
Waste ferric chloride
Liquid
Dropped Out of Analysis
Same as Wastes acids (chloride
process)
Zinc
Spent surface impoundment
solids
Solid
Dropped Out of Analysis
No longer generated
Zinc
Zinc-lean slag
Solid
Dropped Out of Analysis
This is a special waste
Zinc
WWTP solids
Solid
Added to Analysis
New information on
management practices
5
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Exhibit 2
Average Facility Generation Rates
December 1995 vs. January 1997
(Solid Wastes - Expected Value Case)
1200
1000
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600
-------
Exhibit 2 (Continued)
Average Facility Generation Rates
December 1995 vs. January 1997
(Solid Wastes - Expected Value Case)
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Exhibit 3
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Average Facility Generation Rates
December 1995 vs. January 1997
(Liquid Wastes - Expected Value Case)
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300000
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Exhibit 3 (Continued)
Average Facility Generation Rates
December 1995 vs. January 1997
(Liquid Wastes - Expected Value Case)
1000000
1000000
900000
800000
700000
600000
500000
400000
300000
200000
100000
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10
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Exhibit 4
Average Facility Waste Generation Rates (mt/yr)
Solid Wastes
Commodity
Waste Stream
Expected
Maximum
Mercury
Dust
1
1
Germanium
Leach residues
2
3
Mercury
Furnace residue
6
11
Platinum
Slag
8
150
Bismuth
Electrolytic slimes
10
200
Calcium
Dust with quicklime
20
40
Zinc
Spent cloths, bags, and filters
25
50
Germanium
Chlorinator wet air pollution contro 1
sludge
27
100
Germanium
Hydrolysis filtrate
27
100
Germanium
Waste still liquor
27
100
Antimony
Stripped anolyte solids
48
95
Lead
Solid residues
65
130
Uranium
Uranium chips from ingot production
75
200
Selenium
Spent filter cake
85
1,700
Selenium
Slag
85
1,700
Selenium
Tellurium slime wastes
85
1,700
Selenium
Waste solids
85
1,700
Zinc
WWTP Solids
125
250
Phosphorous
Andersen Filter Media
230
230
Uranium
Slag
250
1,000
Copper
WWTP sludge
300
600
Lead
Spent furnace brick
330
330
Rare Earths
Electrolytic cell caustic wet APC sludge
350
7,000
Magnesium
Cast house dust
380
7,600
Cadmium
Copper and lead sulfate filter cakes
475
9,500
Cadmium
Copper removal filter cake
475
9,500
Cadmium
Iron containing impurities
475
9,500
Cadmium
Lead sulfate waste
475
9,500
Cadmium
Post-leach filter cake
475
9,500
Cadmium
Zinc precipitates
475
9,500
Bismuth
Slag
500
10,000
Tantalum
Digester sludge
500
500
Tellurium
Slag
500
4,500
Tellurium
Solid waste residues
500
4,500
Zinc
Discarded refractory brick
500
1,000
Aluminum
Cast house dust
830
oo
o
Lead
Baghouse incinerator ash
1,000
10,000
Tantalum
Spent raffinate solids
1,000
1,000
Rare Earths
Solvent extraction crud
1,150
4,500
Aluminum
Electrolysis waste
1,250
2,500
11
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Exhibit 4
Average Facility Waste Generation Rates (mt/yr)
Solid Wastes
Commodity
Waste Stream
Expected
Maximum
Bismuth
Alloy residues
1,500
6,000
Bismuth
Lead and zinc chlorides
1,500
6,000
Bismuth
Metal chloride residues
1,500
3,000
Antimony
Slag and furnace residue
1,750
3,500
Lead
Slurried APC Dust
2,300
2,300
Lead
Acid plant sludge
2,350
4,700
Titanium
Spent surface impoundments solids
2,550
5,100
Zinc
Spent goethite and leach cake residues
5,000
5,000
Zinc
Spent synthetic gypsum
5,300
5,300
Zinc
Waste ferrosilicon
8,500
17,000
Titanium
Smut from Mg recovery
11,000
23,000
Beryllium
Filtration discard
11,500
45,000
Molybdenum
Flue dust/gases
11,500
45,000
Pyrobitumens
Still bottoms
11,500
45,000
Magnesium
Smut
13,000
13,000
Synthetic Rutile
APC dust/sludges
15,000
30,000
Lead
Stockpiled miscellaneous plant waste
22,000
45,000
Rhenium
Spent rhenium raffinate
22,000
44,000
Synthetic Rutile
Spent iron oxide slurry
22,500
45,000
Titanium
WWTP sludge/solids
60,000
60,000
Lead
WWTP sludges/solids
95,000
95,000
12
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Exhibit 5
Average Facility Waste Generation Rates (mt/yr)
Liquid Wastes
Commodity
Waste Stream
Expected
Maximum
Coal Gas
Multiple effects evaporator concentrate
-
65,000
Tungsten
Spent acid and rinse water
-
3,500
Zirconium
Spent acid leachate from Zr alloy prod.
-
430,000
Zirconium
Spent acid leachate from Zr metal prod.
-
800,000
Rhenium
Spent barren scrubber liquor
25
100
Bismuth
Waste acids
50
200
Uranium
Waste nitric acid from U02 production
75
200
Zinc
TCA tower blowdown
125
250
Titanium
Spent surface impoundment liquids
245
960
Molybdenum
Liquid residues
250
500
Germanium
Waste acid wash and rinse water
275
1,000
Germanium
Spent acid/leachate
275
1,000
Uranium
Vaporizer condensate
275
1,000
Uranium
Superheater condensate
275
1,000
Scandium
Spent acids
280
1,000
Scandium
Spent solvents from solvent extraction
280
1,000
Platinum
Spent acids
285
1,000
Platinum
Spent solvents
285
1,000
Tungsten
Process wastewater
370
1,500
Titanium
Pickle liquor and wash water
450
1,100
Cadmium
Caustic washwater
475
9,500
Cadmium
Spent leach solution
475
9,500
Cadmium
Spent purification solution
475
9,500
Cadmium
Scrubber wastewater
475
9,500
Cadmium
Spent electrolyte
475
9,500
Tellurium
Waste electrolyte
500
10,000
Phosphorous
AFM rinsate
2,000
2,000
Antimony
Autoclave filtrate
2,250
9,000
Fluorspar
Off-spec fluosilicic acid
2,500
15,000
Pyrobitumens
Waste catalysts
2,500
10,000
Titanium
Scrap milling scrubber water
2,500
6,000
Bismuth
Spent caustic soda
3,050
12,000
Bismuth
Spent electrolyte
3,050
12,000
Bismuth
Spent soda solution
3,050
12,000
Bismuth
Waste acid solutions
3,050
12,000
Mercury
Quench water
5,500
60,000
Rare Earths
Process wastewater
7,000
7,000
Tellurium
Wastewater
10,000
20,000
Zirconium
Leaching rinse water from Zr alloy prod.
10,500
26,000
Rare Earths
Spent ammonium nitrate processing solution
14,000
14,000
Synthetic Rutile
Spent acid solution
15,000
30,000
13
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Exhibit 5
Average Facility Waste Generation Rates (mt/yr)
Liquid Wastes
Commodity
Waste Stream
Expected
Maximum
Titanium
Waste acids (Sulfate process)
20,000
39,000
Beryllium
Chip treatment wastewater
25,000
1,000,000
Selenium
Plant process wastewater
33,000
33,000
Tantalum
Process wastewater
75,000
75,000
Zinc
Acid plant blowdown
130,000
130,000
Phosphorous
Furnace scrubber blowdown
210,000
210,000
Titanium
Leach liquor and sponge wash water
240,000
290,000
Rare Earths
Wastewater from caustic wet APC
250,000
1,000,000
Zirconium
Leaching rinse water from Zr metal prod.
250,000
1,000,000
Phosphorous
Furnace Building Washdown
350,000
350,000
Zinc
Wastewater treatment plant liquid effluent
435,000
870,000
Rare Earths
Spent scrubber liquor
500,000
1,000,000
Copper
Acid plant blowdown
530,000
530,000
Zinc
Spent surface impoundment liquids
630,000
630,000
Lead
WWTP liquid effluent
880,000
880,000
Zinc
Process wastewater
1,700,000
1,700,000
14
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to Congress on Special Wastes from Mineral Processing in the expected volume case. These
streams, which are described in more detail below, are:
C Wastewater treatment plant sludges and solids from the titanium sector,
C Wastewater treatment plant sludges and solids from the lead sector, and
C Process wastewater from the zinc sector.
Exhibit 6 is a histogram of average facility solid waste generation rates for all streams
presently in the analysis. As can be seen in this exhibit, 48 of the 61 wastes streams have
average facility generation rates at or below 5000 mt/yr. Exhibit 7 provides a more detailed
look at the distribution of these 48 lower volume waste streams. Of these 48 "low volume"
waste streams, 35 are generated at rates at or below 500 mt/yr. Exhibit 8 presents a histogram
of average facility liquid waste generation rates. As can be seen in this exhibit, 31 of the 51
waste streams, are generated at average rates of less than 5,000 mt/yr. Exhibit 9 presents a
more detailed look at these wastes. Of these 35 "low volume" waste streams, 22 are
generated at rates at or below 500 mt/yr. In summary, the Agency found that of the 118 waste
streams, 115 (97 percent) were generated in quantities lower than the respective high volume
Bevill cutoffs for solids and liquids. Even more demonstrative is that 79 (48 solid wastes and
31 liquid wastes) of these 118 wastes steams (67 percent) are generated in quantities less than
5000 tons per year.
High Volume Streams
The three wastes streams that exceed the high volume thresholds are described below, 2
because they may require special consideration in determining appropriate storage practices.
These streams exceed the thresholds in all three cases, because they are generated by
commingling numerous other waste streams, either directly in the case of process wastewater
from the zinc sector or as a result of treatment operations (i.e., the two WWTP sludge
streams).
Titanium - Wastewater Treatment Plant Sludge/Solids
Wastewater treatment plant (WWTP) sludge/solids, a post-mineral processing waste, consists
of sludges and solids resulting from the treatment of the wastewater treatment plant liquid effluent.
Sludge/solids are disposed in on- or off-site landfills. Approximately 420,000 metric tons are generated
annually by the entire sector. Titanium waste may exhibit the characteristics of toxicity (chromium).
Lead - WWTP Sludges/Solids
Wastewater treatment sludges and solids consist of solid materials that settle following lime
neutralization of influent wastewaters. The sludges and solids typically are recycled to the sinter feed
preparation operation. For example, at the Doe Run Herculaneum facility, a thickener serves as the
final collection point for solids in the WWTP. Thickener solids are dewatered using a filter press and
2 US EPA, "Identification and Descriptions of Mineral Processing Sectors and Waste
Streams," December 1995, pp. 401, 711, and 792.
15
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then shipped by rail car to the sinter plant. Approximately 380,000 metric tons of WWTP sludges and
solids
16
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Exhibit 6
50
45
40
35
30
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20
15
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~48T
Histogram
Distribution of Average Facility Generation Rates
(All Solid Wastes - Expected Value Case)
lip
w
¦-
M
0
0
0
0
< = 5,000 < = 10,000 < = 15,000 < = 20,000 < = 25,000 < = 40,000 < = 45,000 < = 50,000 >50,000
Range (Generation Rate in mt/yr)
17
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Exhibit 7
35
Histogram
Distribution of Average Facility Generation Rates
(Low Volume Solid Wastes Only - Expected Value Case)
< = 500 < = 1000 < = 1500 < = 2000 < = 2500 < = 3500
Range (Generation Rate in mt/yr)
< = 4000
< = 4500
< = 5000
-------
Exhibit 8
Histogram
Distribution of Average Facility Generation Rates
(All Liquid Wastes - Expected Value Case)
31
-t-
< = 5,000 < = 10,000 < = 15,000 < = 20,000 < = 25,000 < = 40,000 < = 45,000 < = 50,000
Range (Generation Rate in mt/yr)
19
> 50,000
-------
Exhibit 9
20
-------
are generated annually by the entire sector. The waste generation rate per facility is greater than 45,000
metric tons/yr due to commingling of numerous waste streams. The Newly identified mineral
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processing Waste Characterization Data Set contains data indicating that this waste stream may exhibit
a hazardous characteristic. The lead waste stream may exhibit the characteristic of toxicity (cadmium
and lead). The waste stream is fully recycled and is classified as a sludge.
In April 1991, SAIC conducted a study that contains data on samples of clarifier underflow and
filter press solids collected from the wastewater treatment system (WWTP-1) at Doe Run's
Herculaneum, Missouri facility. The clarifier underflow sample, which is derived from plant
washdown and acid plant blowdown, exhibited the toxicity characteristic for cadmium (8.51 mg/L).
21
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The filter press solids, which are derived from thickened clarifier underflow and sinter plant blowdown,
exhibited the toxicity characteristic for lead (185 mg/L) and cadmium (98.8 mg/L). The Doe Run
samples were not analyzed for any organic compounds. (SAIC, 1991b, pp. 13, 15)
Zinc - Process Wastewater
Process wastewater is generated at all four of the operating zinc processing plants.
Approximately 6.6 million metric tons of process wastewater are generated annually at the four U.S.
primary zinc facilities. (EPA, August 1992) (The excessive generation rate for this wastewater [i.e.,
greater than one million metric tons/yr] is due to commingling of numerous wastestreams.) Zinc
process wastewater may be recycled and may exhibit the characteristic of toxicity for arsenic,
cadmium, chromium, lead, selenium, and silver. It may also exhibit the corrosivity characteristic. The
waste is classified as a spent material. At ZCA's electrolytic refinery in Bartlesville, Oklahoma process
wastewaters consist of small streams from the roasting, purification, electrowinning, and zinc
secondaries processes. Process wastewater and plant runoff collect in two large, clay-lined surface
impoundments and are pumped to the wastewater treatment plant for neutralization. At ZCA's Monaca,
Pennsylvania smelter, wastewaters include plant runoff as well as process wastewater from the blue
powder impoundments and the zinc sulfate circuit. These wastewaters collect in a lined equalization
basin and are treated in a two-stage neutralization process.
Comparison with Similar Listed Wastes
This section compares the volumes, toxicities, and management of mineral processing
secondary materials with several similar industrial wastes currently regulated under RCRA.
The purpose of this comparison is to demonstrate the similarity between mineral processing
secondary materials and RCRA Subtitle C hazardous waste.
Generation Rates
Many mineral processing waste streams are generated in quantities similar to other
industrial wastes that are managed in tanks, containers, and buildings. To compare generation
rates, EPA identified 8 listed waste streams that are similar to mineral processing wastes, or
are generated by industries similar to the primary mineral processing industry. Generation
rates for each of these waste streams were obtained from the Biennial Reporting System
(BRS). An average generation rate for each of the listed wastes was then calculated by
dividing total waste generated by the number of facilities that reported the waste stream in
BRS. These average rates are presented in Exhibit 10. 3 Exhibit 11 compares the generation
rates of the solid listed wastes in Exhibit 10 (F006, F019, K.060, K061, K069, K088, and
K141) with all of the solid newly identified mineral processing wastes. Exhibit 12 provides
3 BRS data include information on wastes managed at commercial treatment, storage,
and disposal facilities (TSDFs), as well as generators. Prior to calculating average facility
generation rates, ICF deleted from the BRS data any entries for known commercial TSDFs
(e.g., Chemical Waste Management, USCPI, Clean Harbors, etc.)
22
-------
more detail on the lower volume (i.e., less than 5,000 mt/yr) mineral processing wastes.
Exhibit 13 compares the generation rates of the liquid listed wastes in Exhibit 10 (K062) with
all of the liquid newly identified mineral processing wastes.
It is evident from Exhibits 11 through 13 that the 14 listed waste streams often are
generated at higher rates than wastes generated in the mineral processing industry. For
example, K069 (Emission control dust/sludge from secondary lead smelting) has the smallest
average generation rate (710 mt/yr) of the solid listed wastes outlined in Exhibit 10.
However, this generation rate is still larger than average generation rates for 35 of the 61
newly identified solid waste streams in the analysis. Twenty-one of the newly identified solid
wastes are generated in quantities similar to the average generation rates of the solid listed
wastes in Exhibit 10, while only five waste streams are generated in larger quantities. Only
two of those five waste streams (lead WWTP sludges/solids and titanium WWTP
sludges/solids) are generated in sufficient quantities to be above the high-volume threshold
for Bevill status. (45,000 mt/yr for solid wastes). K062 (spent pickle liquor generated by steel
finishing operations), has the smallest average generation rate (31,335 mt/yr) of the liquid
listed wastes in Exhibit 10. This generation rate is greater than 39 of the 53 newly identified
liquid waste streams in the analysis. One of the 53 liquid wastes is generated in quantities
similar to the average generation rates of the liquid wastes in Exhibit 10, and thirteen liquid
wastes are generated in larger quantities than the liquid listed wastes. Only one newly
identified liquid waste stream, zinc process wastewater, is generated in sufficient quantity to
be above the high volume threshold of the analysis (1,000,000 mt/yr for liquid wastes).
Toxicities
Many of the newly identified mineral processing waste streams pose threats similar to
those posed by RCRA listed wastes. Of the current 118 newly identified waste streams in the
analysis, 23 are known to be hazardous, and the rest are suspected to be hazardous. Exhibit
14 summarizes the TC metal and corrosivity characteristic data for these 23 waste streams.
This exhibit lists each known hazardous waste stream, the metals for which it fails TC levels,
and the pH level if the waste is corrosive.
Using the RCRA Subtitle C "Identification and Listing of Hazardous Waste"
Background Document (hereafter referred to as the listing background document) as a source,
EPA identified leachate or total constituent concentration data for seven listed wastes. The
listing background document, however, provided concentration data for only three of the
eight TC metals: chromium, cadmium, and lead. In addition, some of the leachate results
presented in the listing background document were obtained using water extraction tests
rather than the EP test. Although water extraction tests and the EP test will not likely produce
the same leachate concentration due to the difference in leaching agents (distilled water vs.
acetic acid), water extraction data can be compared to EP data because:
"wastes may leach harmful concentrations of lead, cadmium, and hexavalent
chromium even under relatively mild environmental conditions. If these wastes
are exposed to more acidic disposal environments, for example disposal
environments subject to acid rainfall, these metals would most likely be
23
-------
solubilized to a considerable extent, since lead, and cadmium (including their
oxides), as well as most chromium compounds, are more soluble in acid than in
distilled water."4
Exhibit 15 presents a summary of the toxicity characteristic data for the seven listed
wastes identified from the listing background document.
In order to easily compare the listed waste leachate concentrations with the leachate
concentrations of the newly identified mineral processing wastes, a combined mean and
maximum range of chromium, cadmium, and lead concentrations for the seven listed wastes
were calculated using the data in Exhibit 15. The mean leachate concentrations for
chromium, cadmium, and lead range from 6.03 mg/1 to 273.23 mg/1, <0.01 mg/1 to 117.5
mg/1, and 1.47 mg/1 to 259.83 mg/1, respectively. Likewise, the maximum leachate
concentrations for chromium, cadmium, and lead range from 12 mg/1 to 4250 mg/1, <0.01
mg/1 to 268 mg/1, and 2.10 mg/1 to 1550 mg/1, respectively. Exhibit 16 presents a.
comparison of the ranges in constituent concentrations exhibited by the listed wastes and the
newly identified mineral processing wastes. As can be seen in Exhibit 16, 15 of the 23
mineral processing wastes exhibit leachate concentrations of chromium, cadmium, and lead
at levels that are equal to or greater than those levels exhibited by the seven listed wastes
summarized in Exhibit 15. These fifteen mineral processing wastes, arranged in
alphabetical order, are as follows:
C Aluminum Cast House Dust;
C Copper Acid Plant Blowdown;
C Elemental Phosphorous AFM Rinsate;
C Elemental Phosphorous Furnace Scrubber Blowdown;
C Lead Baghouse Incinerator Ash;
C Lead Slurried APC Dust;
C Lead Spent Furnace Brick;
C Lead Stockpile Miscellaneous Plant Waste;
C Rare Earths Process Wastewater;
C Selenium Plant Process Wastewater;
C Titanium and Titanium Dioxide Waste Acids (Sulfate Process);
C Zinc Acid Plant Blowdown;
C Zinc Process Wastewater;
C Zinc Spent Goethite and Leach Cake Residues; and
C Zinc Spent Synthetic Gypsum.
A comparison of the remaining eight newly identified mineral processing waste
streams could not be made because the listing background document did not provide data
4 U.S. Environmental Protection Agency, Office of Solid Waste. Background
Document, Resource Conservation and Recovery Act, Subtitle C - Identification and Listing of
Hazardous Waste, Washington D.C., 1980.
24
-------
for arsenic, barium, mercury, selenium, silver, or pH. However, it is important to note that
at least one sample from each of these waste streams exhibits the RCRA characteristics of a
hazardous waste (i.e., exceeds the TC or the characteristic for corrosivity).
Conclusions
Based on the comments received and further evaluation of new data, the Agency has
found the volumes of hazardous secondary materials from mineral processing to be much
lower than earlier believed. Additional Agency analyses also suggest that mineral processing
wastes contain concentrations of contaminants similar to those found in RCRA listed wastes.
Because the newly identified mineral processing wastes exhibit characteristics that are similar
to other RCRA listed metal-bearing waste streams, the Agency believes that the newly
identified mineral processing wastes should be subject to the same storage requirements (and
prohibitions) faced by all other RCRA hazardous wastes (listed and characteristic). These
requirements are described briefly below.
As stipulated in 40 CFR §262.34(a), generators of RCRA hazardous wastes (listed and
characteristic) may accumulate hazardous waste on-site for 90 days or less without a permit or
without having interim status, provided that the waste is placed:
(I) In containers and the generator complies with subpart I of 40 CFR part 265;
and/or
(ii) In tanks and the generator complies with subpart J of 40 CFR part 265, except
§265.197© and §265.200; and/or
(iii) On drip pads and the generator complies with subpart W of part 265 and
maintains the following records at the facility...
(iv) The waste is placed in containment buildings and the generator complies with
subpart DD of 40 CFR part 265...
RCRA hazardous wastes (listed and characteristic) that are stored in excess of 90 days
(unless an extension is granted) must be stored in Part B permitted storage units that meet
minimum technical construction requirements. Furthermore, as stipulated in 40 CFR §268.50,
the land-based storage of wastes that exhibit concentrations of hazardous constituents in excess
of the treatment standards set under the Land Disposal Restrictions program, is prohibited
25
-------
Exhibit 10. Average Facility Generation of Listed Wastes
Waste
Number
Waste Description
Average
Generation (Metric
Tons/Year)
F006
Wastewater treatment sludges from electroplating operations
3,528
F019
Wastewater treatment sludges from the aluminum coating
3,207
K060
Ammonia still lime sludge from coking operations
17,978
K061
Emission control dust/sludg e from the primary production of steel in electric
furnaces
13,975
K062
Spent pickle liquor generated by steel finishing operations
31,335
K069
Emission control dust/sludge from secondary lead smelting
710
K088
Spent potliners from primary aluminum reduction
4,613
K141
Process residues from the recovery of coal tar, including, but not limited to,
collecting sump residues from the production of coke from coal or th e
recovery of coke by-products produced form coal. This listing does no t
include K087 (decanter tank
4,221
26
-------
Exhibit 11
50
45
40
35
30
>»
o
c
©
S 25
57
20
15
10
5
0
-46-
Histogram
Distribution of Average Facility Generation Rates
(All Solid Wastes - Expected Value Case)
K061
K060
0
0
+
-t-
< = 5,000
t
F006, F019, K069, K088, K141
<= 10,000 < = 15,000 < = 20,000 < = 25,000 < = 40,000
Range (Generation Rate in mt/yr)
1
< = 45,000 < = 50,000
> 50,000
27
-------
Exhibit 12
35
Histogram
Distribution of Average Facility Generation Rates
(Low Volume Solid Wastes Only - Expected Value Case)
KO 69
F019
F006 K141
< = 500 < = 1000 < = 1500 < = 2000 < = 2500 < = 3500 < = 4000 < = 4500 < = 5000
Range (Generation Rate in mt/yr)
-------
Exhibit 13
Histogram
Distribution of Average Facility Generation Rates
(All Liquid Wastes - Expected Value Case)
31
13
4-
K062
1 1
0
-+-
5,000 <= 10,000 <=15,000 < = 20,000 < = 25,000 < = 40,000 < = 45,000 < = 50,000 > 50,000
Range (Generation Rate in mt/yr)
29
-------
EXHIBIT 14. SUMMARY OF EP ANALYSIS RESULTS FOR MINERAL PROCESSING WASTE
Sector/Waste Stream
Constituent
TC Limits
(mg/l)
Min
Mean
Max
Number
of
Sample
s
Numbe
r of
detect
s
Number
above
TC
Aluminum Cast House Dust
Cadmium
1
3.5
3.5
3.5
1
1
1
Mercury
0.2
0.84
0.84
0.84
1
1
1
Coal Gas MEE Concentrate
Arsenic
5
3
16
29
2
1
Selenium
1
15
30
44
2
2
Copper Acid Plant Blowdown
Arsenic
5
0.04
884.35
12800
15
12
10
Cadmium
1
0.05
4.28
24.5
15
14
9
Chromium
5
0
0.41
5
15
11
1
Lead
5
0.04
2.83
6.74
15
13
3
Mercury
0.2
0.0001
0.042
0.31
15
8
2
Selenium
1
0.01
1.21
7.63
15
11
3
Silver
5
0.01
0.41
5
15
6
1
pH
212
0.99
2.21
5
17
17
10
Elemental Phosphorous AFM Rinsate
Cadmium
1
4.12
4.12
4.12
1
1
1
Selenium
1
1.03
1.03
1.03
1
1
1
Elemental Phosphorous Furnace Scrubbe r
Blowdown
Cadmium
1
0.005
0.4
2.07
7
4
2
Lead Baghouse Incinerator Ash
Cadmium
1
5.76
5.76
5.76
1
1
Lead
5
19.2
19.2
19.2
1
1
Lead Slurried APC Dust
Cadmium
1
22
22
22
1
1
30
-------
EXHIBIT 14. SUMMARY OF EP ANALYSIS RESULTS FOR MINERAL PROCESSING WASTE
Sector/Waste Stream
Constituent
TC Limits
(mg/l)
Min
Mean
Max
Number
of
Sample
s
Numbe
rof
detect
s
Number
above
TC
Lead
5
959
959
959
1
1
Lead Spent Furnace Brick
Lead
5
63.3
647
1230
2
2
Lead Stockpile Miscellaneous Plant Waste
Cadmium
1
29.4
29.4
29.4
1
1
Lead
5
1380
1380
1380
1
1
Lead WWTP Liquid Effluent
PH
212
7
9.08
13
4
4
1
Lead WWTP Sludges/Solids
PH
212
7.5
9.06
13
5
5
1
Magnesium & Magnesia Smut
Barium
100
14.9
81.95
149
2
2
1
Rare Earths Spent Ammonium Nitrate Processin g
Solution
PH
212
0.1
7.07
9.59
9
9
1
Rare Earths Process Wastewater
Lead
5
0.63
5.31
10
2
2
1
Selenium Plant Process Wastewater
Lead
5
12
12
12
1
1
1
PH
212
0.8
1.35
1.9
2
2
2
Tantalum Process Wastewater
PH
212
3
8.4
12
5
5
2
Titanium and Ti tanlum Dioxide Waste Acids (Sulfate
Process)
Arsenic
5
0.01
1.33
5
5
1
1
Chromium
5
0.08
31.12
83
5
4
3
Selenium
1
0.1
1.21
5
5
0
1
31
-------
EXHIBIT 14. SUMMARY OF EP ANALYSIS RESULTS FOR MINERAL PROCESSING WASTE
Sector/Waste Stream
Constituent
TC Limits
(mg/l)
Min
Mean
Max
Number
of
Sample
s
Numbe
rof
detect
s
Number
above
TC
Silver
5
0.005
1.12
5
5
0
1
pH
212
0
0.33
1
3
3
3
Titanium and Titanium Dioxide Leach Liquor &
Sponge Wash Water
pH
212
0
0.5
1
2
2
2
Zinc Acid Plant Blowdown
Arsenic
5
1.1
2.12
5
4
3
1
Cadmium
1
0.83
8.58
19
4
4
2
Chromium
5
0.03
1.81
5
4
2
1
Selenium
1
0.055
1.69
5
4
2
2
Silver
5
1.53
0.015
5
4
1
1
PH
212
0.5
1.67
3.4
8
8
8
Zinc Process Wastewater
Arsenic
5
0.02
1.59
10
10
2
1
Cadmium
1
0.023
123
589
10
10
6
Chromium
5
0.005
1.13
10
10
1
1
Lead
5
0.025
1.27
5
10
6
1
Selenium
1
0.0025
1.13
10
10
0
1
Silver
5
0.0015
1.13
10
10
0
1
PH
212
1
5.64
10.5
24
24
4
Zinc Spent Goethite & Leach Cake Residues
Arsenic
5
0.014
2.51
5
2
1
1
Cadmium
1
6.68
7.82
8.96
2
2
2
Chromium
5
0.001
2.5
5
2
0
1
Selenium
1
0.001
2.5
•5
2
0
1
Silver
5
0.015
2.51
5
2
0
1
Zinc Spent Surface Impoundment Liquids
pH
212
2
6.02
10
23
23
3
32
-------
EXHIBIT 14. SUMMARY OF EP ANALYSIS RESULTS FOR MINERAL PROCESSING W,
Sector/Waste Stream
Constituent
TC Limits
(mg/l)
Min
Mean
Max
I
Zinc Spent Synthetic Gypsum
Cadmium
1
0.52
5.81
11.1
2
Note: Gray shading indicates detection limit may have been equal to or higher than TC limit.
Exhibit 15
Listed Waste Leachate Concentration Data
(Source: EPA Listing Background Document)
Listed Waste
Constituent
TC Limits
(mg/l)
Mln
Mean
Max
F0061
Chromium
5
<0.01
45.42
400
Cadmium
1
<0.01
67.07
268
Lead
5
-
-
-
K0611
Chromium
5
<0.1
273.23
1248
Cadmium
1
0.05
4.74
13.4
Lead
5
<0.2
6.32
36.7
K0622
Chromium
5
2
1314
4250
Cadmium
1
-
-
-
Lead
5
-
259.83
1550
K0643
Chromium
5
-
-
-
Cadmium
1
8.4
8.4
8.4
Lead
5
7.8
7.8
7.8
K0652
Chromium
5
-
-
-
Cadmium
1
11
11
11
Lead
5
4.5
4.5
4.5
K066
Chromium
5
-
-
-
Cadmium
1
<0.01
<0.01
<0.01
Lead
5
1.0
1.47
2.10
K069
Chromium
5
0.05
6.03
12
Cadmium
1
5
117.5
230
Lead
5
2.5
13.25
24
1 Incorporates both EP and water test data.
2 This listed waste is a liquid; therefore, total concentration data is presented.
3 Based on one data point.
33
-------
Sector/Waste Stream MtWirvC
Wast^!^tream
sup
^Sfestituent
Ex[
TC Limits
ect(&Wtet
Min
M$ffi
Mean
Max
Number
of
Sample
s
Numbe
r of
detect
s
Number
above
TC
m
-------
EXHIBIT 16.
COMPARISON OF LISTED WASTE AND
MINERAL PROCESSING WASTE CONCENTRATION DATA (mg/l)
Sector/Waste Stream
Constituent
TC Limits
Min
Mean
Max
Range of Listed Waste
Concentrations
Mean Max
Aluminum Cast House Dust
Cadmium
1
3.5
3.5
3.5
<0.01 -117.5
<0.01 - 268
Mercury
0.2
0.84
0.84
0.84
Coal Gas MEE Concentrate
Arsenic
5
3
16
29
Selenium
1
15
30
44
Copper Acid Plant Blowdown
Arsenic
5
0.04
884.3
5
12800
Cadmium
1
0.05
4.28
24.5
<0.01 -117.5
<0.01 - 268
Chromium
5
0
0.41
5
6.03 - 273.23
12-4250
Lead
5
0.04
2.83
6.74
1.47-259.83
2.10-1550
Mercury
0.2
0.0001
0.042
0.31
Selenium
1
0.01
1.21
7.63
Silver
5
0.01
0.41
5
PH
212
0.99
2.21
5
Elemental Phosphorous AFM Rinsate
Cadmium
1
4.12
4.12
4.12
<0.01 -117.5
<0.01 - 268
Selenium
1
1.03
1.03
1.03
Elemental Phosphorous Furnace Scrubbe r
Blowdown
Cadmium
1
0.005
0.4
2.07
<0.01 -117.5
<0.01 - 268
34
-------
EXHIBIT 16.
COMPARISON OF LISTED WASTE AND
MINERAL PROCESSING WASTE CONCENTRATION DATA (mg/l)
Sector/Waste Stream
Constituent
TC Limits
Min
Mean
Max
Range of Listed Waste
Concentrations
Mean Max
Lead Baghouse Incinerator Ash
Cadmium
1
5.76
5.76
5.76
<0.01 -117.5
<0.01 - 268
Lead
5
19.2
19.2
19.2
1.47-259.83
2.10-1550
Lead Slurried APC Dust
Cadmium
1
22
22
22
<0.01 -117.5
<0.01 - 268
Lead
5
959
959
959
1.47 - 259.83
2.10-1550
Lead Spent Furnace Brick
Lead
5
63.3
647
1230
1.47-259.83
2.10-1550
Lead Stockpile Miscellaneous Plant Waste
Cadmium
1
29.4
29.4
29.4
<0.01 - 117.5
<0.01 - 268
Lead
5
1380
1380
1380
1.47-259.83
2.10-1550
Lead WWTP Liquid Effluent
pH
212
7
9.08
13
Lead WWTP Sludges/Solids
PH
212
7.5
9.06
13
Magnesium & Magnesia Smut
Barium
100
14.9
81.95
149
Rare Earths Spent Ammonium Nitrate Processin g
Solution
PH
212
0.1
7.07
9.59
Rare Earths Process Wastewater
Lead
5
0.63
5.31
10
1.47-259.83
2.10-1550
Selenium Plant Process Wastewater
Lead
5
12
12
12
1.47-259.83
2.10-1550
PH
212
0.8
1.35
1.9
35
-------
EXHIBIT 16.
COMPARISON OF LISTED WASTE AND
MINERAL PROCESSING WASTE CONCENTRATION DATA (mg/l)
Sector/Waste Stream
Constituent
TC Limits
Min
Mean
Max
Range of Listed Waste
Concentrations
Mean Max
Tantalum Process Wastewater
PH
212
3
8.4
12
Titanium and Ti tanium Dioxide Waste Acids (Sulfate
Process)
Arsenic
5
0.01
1.33
5
Chromium
5
0.08
31.12
83
6.03-273.23
12-4250
Selenium
1
0.1
1.21
5
Silver
5
0.005
1.12
5
PH
212
0
0.33
1
Titanium and Titanium Dioxide Leach Liquor &
Sponge Wash Water
pH
212
0
0.5
1
Zinc Acid Plant Blowdown
Arsenic
5
1.1
2.12
5
Cadmium
1
0.83
8.58
19
<0.01 -117.5
<0.01 - 268
Chromium
5
0.03
1.81
5
6.03-273.23
12-4250
Selenium
1
0.055
1.69
5
Silver
5
1.53
0.015
5
PH
212
0.5
1.67
3.4
Zinc Process Wastewater
Arsenic
5
0.02
1.59
10
Cadmium
1
0.023
123
589
<0.01 -117.5
<0.01 - 268
Chromium
5
0.005
1.13
10
6.03-273.23
12-4250
Lead
5
0.025
1.27
5
1.47-259.83
2.10-1550
Selenium
1
0.0025
1.13
10
Silver
5
0.0015
1.13
10
PH
212
1
5.64
10.5
36
-------
EXHIBIT 16.
COMPARISON OF LISTED WASTE AND
MINERAL PROCESSING WASTE CONCENTRATION DATA (mg/l)
Sector/Waste Stream
Constituent
TC Limits
Min
Mean
Max
Range of Listed Waste
Concentrations
Mean Max
Zinc Spent Goethite & Leach Cake Residues
Arsenic
5
0.014
2.51
5
Cadmium
1
6.68
7.82
8.96
<0.01 - 117.5
<0.01 - 268
Chromium
5
0.001
2.5
5
6.03 - 273.23
12-4250
Selenium
1
0.001
2.5
5
Silver
5
0.015
2.51
5
Zinc Spent Surface Impoundment Liquids
pH
212
2
6.02
10
Zinc Spent Synthetic Gypsum
Cadmium
1
0.52
5.81
11.1
<0.01 -117.5
<0.01 - 268
37
-------
unless the wastes are stored in tanks, containers, or containment buildings on-site solely for the
purpose of the accumulation of such quantities of hazardous waste as necessary to facilitate
proper recovery, treatment, or disposal and the generator complies with the requirement in
§262.34 and parts 264 and 265.
3. Comparison with Bevill feedstock
In the Supplemental Proposed Rule, the Agency raised the issue of whether to allow
mineral processing secondary materials to be recycled in units generating Bevill-exempt
wastes. The Agency has conducted further research on this issue, and found many cases in
which environmental damages were caused by these Bevill-exempt wastes, including
several cases in which non-Bevill feedstocks were being added to the unit generating the
exempt waste (See Damage Cases and Environmental Releases, EPA, 1997). To assist in
determining whether to allow alternative (non-virgin) feedstocks to be added to these
"Bevill" units, the Agency has compared desirable and undesirable constituents of virgin
Bevill unit feedstocks with those of secondary materials that might be used as alternative
feedstocks to these units.
This section begins with a brief description of the minerals purification process.
Typical concentrations of desired and undesirable constituents are then discussed. Next, an
example from the copper sector is used to show how data from mineral processing
operations could be compared with the virgin feedstocks. Finally, we present conclusions
regarding the comparison.
General Review of the Minerals Purification Process
Several stages are involved in the production of valuable products from ore. First,
overburden (the consolidated or unconsolidated material that overlies a deposit of useful ore)
must be remove to expose the ore. The ores are then extracted (mined) by a variety of surface
and underground procedures. Surface mining methods include open-pit mining, open-cut
mining, open-cast mining, dredging, and strip mining. Underground mining creates adits
(horizontal passages) or shafts by room-and-pillar, block caving, timbered stope, open stope,
and other methods. Waste rock, the portion of the ore body that is barren or submarginal rock
or ore that has been mined but is not of sufficient value to warrant treatment, must be
separated from the ore containing value. The ore containing the value must then be
beneficiated (concentrated or dressed).5 As defined in 40 CFR 261.4(b)(7), beneficiation
operations include: crushing; grinding; washing; dissolution; crystallization; filtration; sorting;
sizing; drying; sintering; pelletizing; briquetting; calcining (to remove water and/or carbon
5 U.S. EPA, 1985, Report to Congress: Wastes from the Extraction and Beneficiation of Metallic Ores, Phosphate Rock,
Asbestos, Overburden from Uranium Mining, and Oil Shale, pp. 2-10-2-12.
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dioxide); roasting, autoclaving and/or chlorination in preparation for leaching6; gravity
concentration; magnetic separation; electrostatic separation; flotation; ion exchange; solvent
extraction; electrowinning; precipitation; amalgamation; and heap, dump, vat, tank, and in situ
leaching. Beneficiation typically yields an intermediate product that often is further purified in
mineral processing operations (such as smelting or refining) to produce pure metal and metal
products.
Concentrations of Desired Constituents
Ores typically contain fairly low concentrations of the metal(s) of interest. Exhibit 17
presents estimates of indicates typical metal concentrations in ores. As ores move through
extraction, beneficiation, and processing operations, the percentage of the metals of interest
increases. For example, in pyrometallurgical processing of copper ores (sulfide ores), the ore
(which has an initial concentration of less than one percent) is sent to milling and flotation.
The concentrate from flotation has a copper concentration of 20 to 30 percent. The
concentrate is then sent to smelting, which raises the copper concentration to 50 to 75 percent.
The product of smelting (matte) is sent to the converter, which produces blister copper and
further purifies the copper concentrations to 98 to 99 percent. The blister copper is sent to fire
refining and then electrorefining to produce copper that is 99.99 percent pure.
Exhibit 17. Estimated Percentage Metal in Ore
Mining Industry
Segment
Typical Percentage of Metal in
Ore
Copper
0.6000
Gold
0.0004
Iron
33.0000
Lead
5.0000
Molybdenum
0.2000
Silver
0.0300
Tungsten
0.5000
Zinc
3.7000
Source: Report to Congress: Wastes from the Extraction and Beneficiation of Metallic
Ores, Phosphate Rock, Asbestos, Overburden from Uranium Mining, and Oil Shale,
December 1985, p. 2-11.
Concentrations of Impurities
6 Except where the roasting (and/or autoclaving and/or chlorination)/leaching sequence produces a final or intermediate
product that does not undergo further beneficiation or processing.
39
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Tracking impurities as the ore moves through the production process is more difficult,
because impurities are removed in almost every step of the purification process. Some of
the impurities are removed early in the beneficiation operations, while others that are
physically or chemically similar to or bound with the metal of interest may be carried along
the production process for most of the processing steps.
The copper sector again provides an example of how the concentrations of impurities
increase or decrease as the ore is purified. Because concentration levels of impurities in the
intermediate products were not available, EPA evaluated constituent concentrations in
wastes generated at various points along the production process. These concentrations are
summarized in Exhibits 18 and 19. There are a number of limitations associated with these
data, which were obtained from several facilities over a number of years. These factors add
potential for error because concentrations of impurities vary greatly within and between ore
deposits, each facility is likely to mine a different ore deposit and use a different production
process. In addition, increasing environmental regulation in the last ten years and changing
economic markets have also caused facilities to make changes in their production processes
and ore selection.
Moreover, comparing the constituent concentrations of beneficiation wastes with
mineral processing wastes may not adequately address EPA's underlying question about the
appropriateness of using alternative feedstocks in Bevill units. EPA has examined the
constituent concentrations of both beneficiation wastes and processing wastes in
determining whether any of these wastes should retain their "Bevill" exempt status in two
Reports to Congress. The comparison between extraction and beneficiation waste
concentrations and mineral processing waste concentrations can yield only an insight into
when in the process impurities are removed. For a complete understanding of how
impurities are generated in the production process, waste volume should be considered in
addition to concentration levels.
Several noteworthy trends can be discerned in Table 18, which a compares
concentrations in solid waste from beneficiation and mineral processing operations. The
first trend is that concentrations of both the desired product and impurities are higher in the
mineral processing wastes than in the beneficiation wastes. The next trend is that among the
mineral processing wastes, constituent concentrations vary significantly from one waste to
another. For example, the waste with the highest copper concentration (converter flue dust)
has the lowest arsenic concentration. Table 19 displays contaminant concentrations for
liquid wastes from beneficiation and mineral processing operations. As was seen in the data
for solid waste, the mineral processing wastes have higher concentrations of almost all
constituents than the beneficiation waste. The only exceptions are for chromium in WWTP
liquid effluent and molybdenum in both WWTP liquid effluent and scrubber blowdown.
The variability in constituent concentrations seen in the solid wastes is also seen in the
liquid wastes. The highest levels of the 10 constituents are almost evenly divided between
spent bleed electrolyte and acid plant blowdown. However, scrubber blowdown, which has
the lowest concentration of copper has the highest concentration of mercury.
40
-------
Findings
Concentrations of metallic impurities are often higher in waste steams generated by
mineral processing operations, than in waste streams generated by beneficiation operations.
This trend is shown in Exhibits 18 and 19. Using these data as a basis, it likely that the
impurities in the secondary materials are also higher than in the corresponding virgin Bevill
unit feedstocks. Therefore, reintroduction of mineral processing secondary materials as
alternative feedstocks may increase contaminant concentrations in the wastes generated by
the Bevill units. However, these results need to be understood in light of the following
caveats:
C Beneficiation and mineral processing steps often remove particular
constituents preferentially; concentrations of specific constituents may
therefore decline in wastes generated in later production stages;
C Although concentrations may increase during the production process, waste
volumes tend to decrease, such that the total mass of the hazardous
constituent may be less than that of wastes generated earlier in the production
process; and
C Sector-specific and site-specific variability is significant.
Thus, while the Agency generally expects contaminants to become more concentrated in
mineral processing wastes generated in later productions stages, there may be cases where
contaminant levels are reduced or stay the same.
41
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Exhibit 18. Comparison of Constituents in Solid Wastes in the Copper Sector
Beneflciation Wastes
Mineral Processing Wastes
Surface
Mine
Waste"
Tailings
Pond
Settled
Solids"
Leaching
Material"
Furnace
Flue
Dust"
Converte
r Flue
Dustb
Acid Plant
Blowdown
Solids'
WWTP
Solids'1
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
Arsenic
20.4
7.08
63.1
13,000
100
1,600
Barium
572
408
453
Cadmium
<10
10.2
<69.4
Chromium
27.8
49.9
125
400
Lead
159
120
157
316,000
Mercury
0.14
0.16
0.17
Selenium
7.51
4.86
5.9
100
Copper
1,150
1,190
1,470
220,000
800,000
62,000
225,000
Molybdenum
209
157
210
Zinc
123
137
207
4,800
Sources:
a - Pedco, Evaluation of Management Practices for Mine Solid Waste Storage,
Disposal, and Treatment, 1984, pp. 4-36 - 4-37.
b - Greenwald, Norman, Letter to Matthew Straus, US EPA, June 4, 1992.
c- Rissman Report, 1992.
d - US EPA, "Identification and Descriptions of Mineral Processing Sectors and
Waste Streams," December 1995, p. 280.
42
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Exhibit 19. Constituents in Liquid Wastes in the Copper Sector
Beneficiation
Wastes"
Mineral Processing Wastes b
Tailings Pond
Liquids
Spent Bleed
Electrolyte
Acid Plant
Blowdown
Process
Wastewater
Scrubber
Blowdown
WWTP
Liquid
Effluent
(mg/l)
(mg/l)
(mg/l)
(mg/l)
(mg/l)
(mg/l)
Arsenic
0.0869
2,219
856
14.9
13.98
Barium
0.343
7.19
1.38
0.73
Cadmium
0.045
0.52
62.93
1.26
3.75
0.151
Chromium
0.056
12.59
3.62
1.86
0.28
0.023
Lead
0.14
19.68
1,061
36.39
11.60
3.53
Mercury
<0.0002
0.005
0.32
0.001
0.49
Selenium
0.184
4.25
78.97
0.55
7.20
Copper
0.13
26,787
3,152
227
4.90
130
Molybdenum
1.53
62.58
70.68
14.77
0.90
0.11
Zinc
0.0472
25.84
1,737
8.72
6.24
0.6
Source:
a - Pedco, Evaluation of Management Practices for Mine Solid Waste Storage,
Disposal, and Treatment, 1984, pp. 4-36 - 4-37.
b - US EPA, "Identification and Descriptions of Mineral Processing Sectors and
Waste Streams," December 1995, pp. 273-279.
43
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4. Conclusions
Based on information received from commenters and further research and analysis
conducted by the Agency, EPA has determined that certain assumptions it made in
proposing the Supplemental LDR Rule in January 1996 may not have been valid,
particularly assumptions concerning the volumes of wastes managed by the mineral
processing industry and the need to manage these wastes in land-based units. Specifically,
the Agency has determined that:
C Generation rates for mineral processing wastes do not differ from rates for
other listed hazardous wastes of similar type. In fact, in some cases, mineral
processing waste generation rates were lower than for listed wastes.
Generation rates for mineral processing wastes exceeded the Bevill high
volume threshold in only three of 118 cases.
C Contaminant concentrations found in mineral processing wastes are similar to
concentrations found in listed wastes currently regulated under RCRA
Subtitle C. In addition, the Agency has evidence that damages have resulted
from the storage and disposal of these wastes.
C As ore is processed, minerals of interest become more concentrated. At the
same time, contaminants in the waste streams generated during processing
steps also may become more concentrated.
As a consequence, the Agency no longer believes that land-based storage of
secondary materials is essential to the mineral processing industry. Generated volumes of
waste appear sufficiently small to allow them to be managed in a manner similar to RCRA
Subtitle C hazardous wastes — in tanks, containers, and buildings. Further, because the
Agency has determined that contaminant concentrations in mineral processing wastes may
be similar to concentrations found in RCRA hazardous wastes, the Agency believes that
land-based storage of such materials may pose a significant threat to human health and the
environment. The Agency therefore now believes that tanks, containers, and buildings
should be used to store mineral processing secondary materials prior to recycling. Finally,
due to the likelihood that mineral processing wastes may contain greater concentrations of
contaminants than virgin feedstock, the Agency also believes that it would be inappropriate
to allow these materials to be reintroduced into a Bevill unit while allowing the resulting
waste to retain its Bevill-exempt status.
44
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