&EFA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-80-074
April 1980
Research and Development
Sources and
Treatment of
Wastewater in the
Nonferrous Metals
Industry
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1 Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-80-074
April 1980
SOURCES AND TREATMENT
OF WASTEWATER IN THE
NONFERROUS METALS INDUSTRY
by
Richard T. Coleman, J. David Colley,
Robert F. Klausmeier, Nancy P. Meserole,
Wayne C. Micheletti, and Klaus Schwitzgebel
Radian Corporation
Austin, Texas 78766
Project Officer:
Alfred B. Craig, Jr.
Metals and Inorganic Chemicals Branch
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
ii
-------
FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Ci) assists in developing and demonstrating new and improved
methodologies that will meet these needs both efficiently and economically.
This report presents the findings of an investigation of the sources and
treatment of industrial wastewater which contains metals. The study was per-
formed to assess the existing data base on metal containing wastewaters,
investigate the state of development of the various treatment technologies
being used, and determine whether this information could be applied to the
water treatment problems in the nonferrous metals industry. The results are
being used within the Agency's Office of Research and Development as part of
a larger effort to define the potential environmental impact of emissions
from this industry and the need for improved controls. The findings will
also be useful to other Agency components and the industry in dealing with
environmental control problems. The Metals and Inorganic Chemicals Branch
of the Industrial Pollution Control Division should be contacted for any
additional information desired concerning this program.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
iii
-------
ABSTRACT
In this report, the available literature data were compiled on both the
sources of and treatment technologies for industrial acidic wastewater con-
taining dissolved heavy metals. The intent was to assess the applicability
of existing wastewater treatment technology to the effluents generated by the
primary and secondary copper, lead, and zinc industries.
A list of industries and processes they employ which discharge acidic
wastewater containing metals was compiled by reviewing available literature.
A list of available treatment technologies was compiled both from the litera-
ture and from industrial vendors and users. In addition, the wastewater
sources and treatment technologies in the nonferrous metals industry were
investigated.
Each treatment technology of interest was evaluated based on:
control effectiveness for heavy metals in water,
energy requirements,
• economics, and
secondary process emissions.
As a result of these evaluations, two wastewater treatment processes, hydrox-
ide precipitation and evaporation were found to be widely used commercially
and applicable to the treatment of effluents in the nonferrous metals indus-
try. The applicability of evaporation is limited to arid regions.
Two other processes, sulfide precipitation and ferrite coprecipitation,
have been successfully used in limited applications in Sweden and Japan to
treat metal containing wastewater. These processes appear td be particularly
applicable to the primary nonferrous metals industry because the solid waste
that is generated can be recycled to a smelting furnace.
The sodium borohydride reduction process may be useful for small waste-
water streams containing either valuable or hard to remove metals, e.g.,
mercury and selenium. However, this process is not likely to be used on
large volume, low metal concentration wastewaters.
Starch complexing has been applied in pilot studies as a polishing
process. Good removal efficiencies are reported. However, the solid
waste that is generated when absorbed compounds are released upon
iv
-------
decomposition of the starch results in a concentrated stream which must be
treated by other means. Additional testing is required to determine if this
process is applicable to commercial-scale wastewater treatment problems.
-------
TABLE OF CONTENTS
Foreword ill
Abstract iv
Figures ix
Tables x
1. Introduction 1
2. Project Overview 2
3. Results 3
Sources of Industrial Acidic Wastewater 3
Wastewater Treatment Technology 4
Sources of Acidic Wastewater in the Nonferrous Metals
Industry 13
4. Conclusions and Recommendations 15
5. Industrial Sources of Acidic Wastewater Containing Metal 18
6. Treatment Methods for Wastewater Containing Metals 21
Introduction 21
Hydroxide Precipitation 22
Sulfide Precipitation 31
Ion Exchange 40
Reverse Osmosis 49
Evaporation Ponds 55
Other Treatment Technologies 60
7. Sources of Effluents Containing Metal in the Nonferrous Metals
Industry 70
Introduction 70
Primary Copper Industry 71
Primary Lead Industry 96
Primary Zinc Industry 107
Secondary Copper Industry 115
Secondary Lead/Antimony Industry "..... 129
Secondary Zinc Industry 135
vn
-------
CONTENTS (Continued)
Page
References 90
Appendix A - Summary of Pollutants in Industrial Wastewater Sources 146
viii
-------
FIGURES
/•
Number Page
1 Typical continuous flow hydroxide precipitation
treatment system 24
2 Theoretical solubilities of metal hydroxides as a
function of pH 25
3 Typical batch process chemical precipitation treatment
facility 27
4 Lime precipitation installed capital costs 29
5 Lime precipitation operating and maintenance costs 30
6 Typical continuous flow sulfide precipitation treatment
system 33
7 Theoretical solubilities of metal sulfides as a function
of pH 34
8 Distribution of hydrogen sulfide species as a function
of pH 39
9 Operating cycle for mixed-bed ion exchange system..., 44
10 Typical reverse osmosis plant arrangement 51
11 Cut away drawing of hollow fiber RO system 53
12 Capital costs for evaporation ponds 58
13 Evaporation pond operating costs 59
14 Typical flow diagram of Browder DC/DA process for a
metallurgical plant 81
-------
TABLES
Number Page
1 Sources of Wastewater Containing Heavy Metals 5
2 Treatment Methods for Metal Containing Wastewaters 6
3 Performance of Treatment Technologies 8
4 Wastewater Sources in the Nonferrous Metals Industry 14
5 Comparison of Treatment Process Discharge Concentrations
with Water Quality Standards (mg/£) 16
6 Industries and Associated Heavy Metals 19
7 Hydroxide Precipitation Metal Removal Effectiveness 28
8 Sulfide Precipitation Metal Removal Effectiveness 36
9 Typical Reactions for Ion Exchange Resins 41
10 Ion Exchange Metal Control Effectiveness 45
11 Selectivity Order for Various Ions with Various Exchangers 46
12 Economics of Ion Exchange Water Treatment (1977) 48
13 Typical Rej ections by Reverse Osmosis Systems 54
14 Cost of Water Treatment by Reverse Osmosis 56
15 Performance Data from a Ferrite Coprecipitation Test
Facility 64
16 Performance of Ferrite Coprecipitation in Osaka Unit 65
17 Typical Performance Data Using Starch Xanthate 66
18 Heavy Metal Removal Efficiencies Using Starch Xanthate
as Determined by USDA 66
19 Summary of Pollutants in Industrial Wastewater Sources -
Primary Copper • ^
-------
TABLES (Continued)
Number Page
20 Raw Waste Load in Water Pumped from Selected Copper Mines 78
21 Raw Waste Characterization: Acid Plant Slowdown 83
22 Acid Plant Blowdown Control and Treatment Practice 84
23 Analysis of Arsenic Plant Washdown Water 86
24 Water Requirements for Copper Refineries 88
25 Waste Effluents from Anode Cooling Water 88
26 Contact Cooling Water Control and Treatment Practices 89
27 General Range Analysis of Electrolyte, Refined Copper,
and Anode Slime 90
28 Waste Effluents from NiSOi, Barometric Condenser 92
29 Analysis of Water Used to Cool Refinery Shapes 94
30 Summary of Pollutants in Industrial Wastewater Sources -
Primary Lead 98
31 Analysis of a Missouri Mine Water 100
32 Lead Mill Wastewater Analysis 1Q2
33 Wastewater Treatment at Primary Lead Acid Plants 103
34 Scrubber Wastewater Treatment at Primary Lead Plants 103
35 Waste Effluents from Slag Granulation 1°5
36 Primary Lead Slag Granulation Wastewater Treatment 106
37 Summary of Pollutants in Industrial Wastewater Sources -
Primary Zinc 109
38 Range of Compositions of Zinc Concentrates Ill
39 Ranges of Constituents of Wastewaters and Raw Waste Loads
for Five Selected Mills 112
40 Nominal Chemical Specifications for Brass and Bronze Ingot
Institute Standard Alloys 116
xi
-------
TABLES (Continued)
Number
Page
41 Summary of Wastewater Handling Practice and Disposition
Used by Secondary Copper Industry 118
42 Summary of Pollutants in Industrial Wastewater Sources -
Secondary Copper 119
43 Character of Wastewater from Slag Quenching and Granulation
or Slag Milling after Settling 121
44 Character of Wastewater from Molten Metal Cooling and
Quenching 126
45
Character of Wastewater from Electrolyting Refining 128
46 Summary of Pollutants in Industrial Wastewater Sources -
Secondary Lead 132
47 Summary of Pollutants in Industrial Wastewater Sources -
Secondary Zinc 138
j
A-l Summary of Pollutants in Industrial Wastewater Sources 147
-------
SECTION 1
INTRODUCTION
Industrial effluent waters containing dissolved heavy metals represent
an environmental problem associated with the activities of many industries.
Important sources of such discharges range from metal treatment operations
associated with the automotive industry to smelting and refining of basic
materials such as copper, lead, and zinc. Different control techniques have
been used or studied, both in the United States and abroad, for the many
types of discharges which are involved. Unfortunately there has to date
been no coordinated attempt to determine how applicable technology being
studied or used abroad may be to wastewater problems in the United States.
It is known however, that present control practices are especially limited
for streams containing a number of specific metals such as mercury, selenium,
and hexavalent chromium (Cr+6).
The Industrial Environmental Research Laboratory (IERL) in Cincinnati
is responsible for developing control technology for a number of industries
producing wastewater containing dissolved heavy metals. One of the sources
of such discharges within their areas of responsibility is the primary non-
ferrous metal industries. Discharges from these industries present some of
the most difficult treatment problems. It is the purpose of this study to:
• identify significant sources of industrial wastewaters
containing metal,
• assess the technologies being employed for treating wastewaters
containing metal, and
• evaluate industry's control of the nonferrous metals discharges.
-------
SECTION 2
PROJECT OVERVIEW
A literature search was performed with special attention to reports
from past industry studies by EPA dealing with acidic wastewater sources.
Acidic wastewaters are of particular interest because of the relatively
high solubility of most metals in acidic solutions as compared to basic
solutions. A list of industries and the processes they employ which dis-
charge waters contaminated by dissolved heavy metals was then developed and
characterized as completely as possible from available literature.
In a second step, centers of experience and expertise in dealing with
treatment of metal containing wastewaters were identified and a list of
technologies being employed by different industries was developed. Infor-
mation from the literature was supplemented with background data from
selected vendors and users of wastewater treatment technology. A list of
technologies was developed to show their stage of development and their
industrial applications.
Concurrent with the discharge assessment and control technology inves-
tigation, a study was carried out to define discharges of interest from the
nonferrous metal industries. The data accumulated were used to identify
specific control methods worthy of further evaluation for treatment of dis-
charges from the production of nonferrous metals.
After treatment methods were identified, a process description was
developed and the methods of interest were evaluated from the standpoint of:
• their removal effectiveness for metals in water, individually
or collectively, where a number of heavy metals are present,
• the cost which might be associated with their application
to discharges from the nonferrous metal industries,
• their energy requirements, and
secondary discharges which they might produce.
After completion of the treatment technology assessment, problems that
limit their applicability to the nonferrous metals industry were identified
and approaches to developing solutions for these problems were recommended.
-------
SECTION 3
RESULTS
In this section, the data on the sources and treatment of acidic
wastewater are summarized. These data were gathered from both industry
contacts and the open literature. Information about the following areas
is presented:
• Sources of acidic wastewater containing metals,
• Available wastewater treatment methods
control effectiveness
energy requirements
economics
secondary process emissions, and
• Wastewater sources in the nonferrous metals industry.
SOURCES OF INDUSTRIAL ACIDIC WASTEWATER
The broad survey of available literature on sources and treatment of
acidic wastewater was done to insure that a complete list of available
treatment technologies was developed. The results of this survey indicate
that the major sources of industrial acidic wastewater (pH <7.0) containing
metals are:
inorganic chemicals industry,
organic chemicals industry,
tire manufacturing,
paint and ink production,
electronics industry,
iron and steel industry,
metal fabrication and finishing,
textile manufacturing,
mining industries,
photographic industry, and
steam generation.
The elements most frequently found in discharge streams are:
aluminum
silver
arsenic
chromium
copper
iron
mercury
lead
nickel
selenium
tin
cadmium
manganese
zinc
-------
Concentration ranges reported are shown in Table 1. Each of these sources
is described in more detail in Section 5 and the report Appendix.
Hydroxide precipitation was found to be the most commonly used waste-
water treatment technology in use. However, the data available in the open
literature did not provide a comprehensive picture of the character of indus-
trial wastewater. Rather, as indicated in Table 1 and the report Appendix,
the data are sparse, especially with respect to removal efficiencies for
different treatment technologies. As a result, there was little information
which was suitable for comparison with the data available on nonferrous metal
industry wastewaters and their treatment.
WASTEWATER TREATMENT TECHNOLOGY
A summary of available treatment methods is presented in Table 2. The
important result shown in this table is that only two processes, hydroxide
precipitation and evaporation ponds, are both commercially available and
potentially applicable to the nonferrous metals industry. The applicability
of evaporation, of course, is limited to arid regions.
Two other processes, sulfide precipitation and ferrite coprecipitation,
have been successfully used in limited applications to treat wastewater con-
taining metals. These processes appear to be particularly applicable to the
primary nonferrous metals industry because the solid waste generated can be
recycled to a smelting furnace. The sulfide process has been used to treat
smelter wastewaters at the Boliden Metall copper smelter in Sweden and the
Furukawa Co. Ltd.'s copper smelter in Japan.
The sodium borohydride reduction process may be useful for small waste-
water streams containing either valuable or hard to remove metals, e.g.,
mercury and selenium. Howaver, this process is not likely to be used on
large volume, low metal concentration wastewaters.
Starch complexing has been applied in pilot studies as a polishing
process. Good removal efficiencies are reported. However, disposal of
the solid waste that is generated when the absorbed compounds are released
upon decomposition of the starch results in a concentrated stream which must
be treated by other means. Additional testing is required to determine the
applicability of this process to commercial-scale wastewater treatment
problems.
Both the reverse osmosis and ion exchange processes produce secondary
effluents requiring further treatment. In addition, the pretreatment which
would be required for smelter wastewaters would reduce their potential cost
effectiveness. Activated carbon is primarily useful for removing organics
from wastewater. It is unlikely that this process would be designed specif-
ically to remove metals from a wastewater stream.
The following discussion presents the data collected concerning control
effectiveness, energy requirements, economics, and secondary effluents on the
nine treatment processes mentioned above. A summary of this data is shown in
Table 3.
-------
TABLE 1. SOURCES OF WASTEWATER CONTAINING HEAVY METALS
Industry
Inorganic
Chemicals
Organic
Chemicals
Tire
Manufacturing
Paint & Ink
Electronics
Iron & Steel
Metal Fabri-
cation &
Finishing
Explosives
Industry
Textiles
Mining
Industries
Photographic
Industry
Steam
Generation
Process/Unit Operation
Chloralkali
Pigment
Acids
Basic Chemicals
Fertilizers
Petrochemicals , Polymers ,
Basic Chemicals
Cooling Tower Blowdown
Miscellaneous Process Operations
Batteries
TV Tube Manufacturing
Pickling, Plating, Galvanizing
Spent Acid Pickling Solution
Plating Drag Out
Plating Bath Drums
Others
Lead Azide & Styphnate
Dyes, Rayon, Mills,
Vulcanized Fiber
Copper
Lead & Zinc
Iron: Mine Discharge
Iron: Raw Mill Wastewater
Silver
Bauxite
Ferroalloy Ores
Coal: Mine Wastewater
Coal: Acid Mine Drainage
Fixer, Developer, Wash Water
Air Preheater Wash
Boiler Fireside Wash
Acid Cleaning
Cooling Tower Slowdown
Nature of Discharge rag/H
Al Ag As Cd Cr Cu Fe Hs Mn Pb III Se
18
.5-95 0-12
200-500 P
0.1-0.5 0.1-1 40-250 0.2-0.7
P P P
P P P .04-4.6 .1-288 .4-500 P 66-145
.1
29 P .08 .04-. 4 3-139 P .4-5
P .4-66
400
P .6-85 P 4-800 P P .5-1.4
80,000
50-250 7-240 1-100 0-900 0-60 0-2 0-900
13,000- 2,000- 10,000- 140
45,000 23,000 270,000
14-22 4-880 60 3
0-200
P P P
.1-900 .1-3 .1-3
0-1,000 .1 .02-57 .1-5
.002-2 .001-18 .001-. 1
.2-10 .01-20 .1-5
.3-2 .4-6
6-9
.2-. 7 20-50 1,300- .2-56 2-10
1,500
.01-270 - 40-330 - .01-127 - .01-6
.1-83 22 .02-1 .2-128 20-800 4-14 0-3 0.5-3
450- P p
.4-40 380-
6,000
0-5 0-300
400- 4,000-
1,000 10,000
0-1,300
Sn Zn ..
19.5
P 0.1-3
.1
3-77
61 2-880
0-220
5,000-
34,000
20-
1,000
.1-3
.03-38
.0001-8
.01-10
.4-25
25-77
. 01-13
7-294
0-30
p - present, concentrations not reported.
-------
TABLE 2. TREATMENT METHODS FOR METAL CONTAINING WASTEWATERS
Treatment Method
Status of Development
Comment on Application/Applicability
1. Hydroxide
Precipitation
Commercially available.
2. Sulfide
Precipitation
3. Ion Exchange
Presently installed at
Boliden's copper smelter in
Sweden to control smelter
effluent. Start-up sched-
uled for mid-1978. Also in
operation at Furukawa's
Ashio smelter in Japan.
Commercially available.
4. Evaporation
Ponds
5. Reverse Osmosis
Commercially available.
Commercially available.
Applied as either a batch or continuous pro-
cess for wastewater treatment. Widely appli-
cable. Limitation posed by metal complexing,
does not remove alkaline and alkaline earth
metals and certain anions. Hexavalent chrom-
ium must be reduced before treatment.
Process has the advantage of controlling
heavy metals in acidic solutions. The sul-
fide sludge can be recycled to smelting
furnaces.
Process can be used to control cations and
anions. Process is not suitable as an end-
of-pipe treatment. Additional treatment of
secondary waste stream is required. It is
suitable for concentrating wastes of high
volume and low pollutant concentration and
as a polishing process.
Application is limited to arid regions. End
products are easily resolubilized. Large
land requirements are necessary.
Pretreatment of wastewater is necessary to
avoid membrane damage. Membrane scaling is a
problem if insoluble compounds are present.
Suitable for concentrating dilute waste
streams. A concentrated reject stream is pro-
duced and requires further treatment. Process
is not suitable as an end-of-pipe treatment.
(Continued)
-------
TABLE 2 (continued).
Treatment Method
Status of Development
Comment on Application/Applicability
6. Activated Carbon Commercially available.
7. Ferrite
Coprecipitation
8. Starch
Complexing
9. Sodium Boro-
hydride Reduction
Limited commercial use in
Japan treating scrubber
blowdown from a municipal
incinerator. Also used
by Nippon Electric Co.
Applied in pilot studies as
polishing process.
Limited commercial use.
Primarily suitable for removal of organics.
Secondary removal of inorganics has been ob-
served. It is unlikely that this process
would be applied for treatment of inorganics
alone. Disposal of exhausted carbon can re-
sult in the gradual release of the adsorbed
compounds.
Very good removal efficiency is achieved.
This process appears to be an applicable
treatment technology. However, it has only
been applied on a commercial scale in Japan.
The solid waste generated may be either re-
cycled to smelting furnaces or landfilled.
Good removal efficiency is obtained. Metal
compounds are released when starch decomposes.
Starch manufacture requires carbon disulfide
which is dangerous. Process is still in de-
velopmental stage but warrants further study.
Process application is limited to reducing
semi-noble and noble metals to the elemental
state. Instability of sodium borohydrate in
acidic solutions necessitates operation at pH
8.5 to 9.0. Process may be useful for small
waste streams containing either valuable or
difficult to remove metals, e.g., mercury.
Not likely to be widely used because of high
cost relative to hydroxide precipitation.
-------
TABLE 3. PERFORMANCE OF TREATMENT TECHNOLOGIES
00
Treatment Method
'
1. Hydroxide
Precipitation
2. Sulfide
Precipitation
3. Ion Exchange
A. Evaporation
Ponds
Cost
Capital Cost:*
$0.343/liter/day
($1.3/gallon/day)
Operating and Maintenance
Cost:
$700. /day for 3.785 x 108
liters/day (1 million gallons/
day) capacity and 1 gram per
liter J ime dosage rate
See Figures 4 and 5.
Not given 'in literature.
Should be similar to hydroxide
precipitation.
Depends on capacity and solids
concentration. See Table 12
for details.
Installed capital costs:
$0.063 to $0. 719/liter/day
($0.24 to $2.72/gallon/day).
Operating costs: $0.00018 to
$0.00067/liter ($0.00067 to
$0.00253/gal).
Depends on location and land
cost. Capital cost: $1.49/
liter/day ($5.6/gailon/day)
assuming 76.2 cm (30 inches)
evaporation a year and $1,0,00
per 4046 mz (acre).
Control
Element
Arsenic
Cadmium
Chromium(III)
Copper
Lead
Manganese
Nickel
Zinc
Arsenic
Cadmium
Copper
Mercury
Nickel
Zinc
Cadmium
Chromiura(VI)
Copper
Lead
Manganese
Mercury
Nickel
Zinc
Complete control
Seepage of salts
possible if liner
Effectiveness
Inlet
•mg/t
.2-. 5
1300
204-385
.5-25
5
16.1
.8-132
.4-1.0
50-115
.3-50
.13-. 29
42
.1
8-10. 7
1.02
Outlet
ing/1
.83
.0007
.06
.2-2.3
.01-. 03
.5
.15
.02-. 23
.05-24.4
.008
.5
.01-. 12
.09-. 51
1.16
.001
0-.9
.03
.055-144.8 .0015-. 53
50
1.4-2.8
150-900
6
if liner is used
into groundwater
breaks .
.046
.005
.01
.4
is
Energy Requirement
Energy users are: lime
feeders, wastewater pumps,
clarifier agitator drive,
sludge rake drive, and vacuum
filter.
Energy consumption Is 8 kWh
per 3,785 liters (1,000
gallons) treated and 1 mg/fc
lime dosage. 14 kWh per
3,785 liters (1,000 gallons)
treated and 1,500 mg/Jt lime
dosage.
Unknown.
Energy requirement should be
similar to those given for
hydroxide precipitation.
Pumps are only energy
consumers .
1.1 kWh for 3,785 liters
(1,000 gallons) treated.
Only energy consumers are
pumps. 0.5 kVfh per 3,785
liters (1,000 gallons) of
wastewater is reported.
Residues Produced
Solid metal hydroxides.
Compounds will redissolve
in acidic environment.
Metal sulfides are pro-
duced as end products.
Most sulfides are insol-
uble in acidic solutions.
They can be recycled to
sulfide processing
smelters. Solubilizatlon
is possible upon oxidation
to sulfates.
Regenerant waste stream
will contain high metals
concentration. Low volume
of the waste stream may
make further treatment
more economical.
Process produces salts
which redissolve upon
contact with water.
(Continued)
* 1 gallon - 3.785 liters
-------
TABLE 3 (continued)
vo
Treatment Method
S. Reverse Osmosis
6. Activated Carbon
7. Ferrite
Coprecipitation
8. Starch
Complexing
Coat
Depends on feed characteristics,
pretreatment, and desired con-
version. Installed capital
costs: $0.193 to $0.528/liter/
day ($0.73 to $2.00/gal/day)
capacity. Operating costs:
$0.00017 to $0.00058/llter
($0.00066 to $0.00218/gal).
Data needed.
Not available. Should be simi-
lar to hydroxide precipitation.
Not available.
Calcium
Magnesium
Aluminum
Sulfate
Manganese
Control Effectlvenes
Inlet Cone.
mg/S.
260
170
77
12
1340
43
s
Product
mg/1
.4
.3
t$
.2
.9
.5
Data needed.
Mercury
Cadmium
Copper
Zinc
Chromium
Nickel
Manganese
Iron
Bismuth
Lead
PH
Copper
Nickel
Cadmium
Lead
Influent
mg/!t
7.4
240
10
18
10
1,000
12
600
240
475
31.8
29.4
56.2
104
Chromium(III) 26
9. Sodium
Borohydrlde
Capital Cost: $0.18/liter/
day ($0.67/gallon/day).
Operating Cost: $0.002 to
$0.007 liter ($0.007 to $0.026/
gallon) .
Basis: 57,000 liters/day
(15,000 gallons/day) plant.
(PA- 322)
Silver
Zinc
Iron
Manganese
Mercury
Removes 0.
(1.0 to 4.
54
33
27.9
27.5
100
Effluent
rng/t.
.001
.008
.010
.016
.010
.2
.007
.060
.100
.010
.007
.019
.009
.025
.003
.245
.046
Not
detectable
1.630
.003
.45 to 1.81 kg IDS** /day
Energy Requirement
Pumps are major consumers.
8-10 kWh per 3,785 liters
(1,000 gallons) of water
for a 3,785,000 liter per
day (100,000 GPDt) unit.
Data needed.
Not available. Should be
similar to hydroxide
precipitation.
Not available. Should be
higher than those for hy-
droxide precipitation due
to the high volume of the
precipitate.
Not available.
Residues Produced
Process produces a con-
centrated aqueous efflu-
ent stream containing
practically all incoming
contaminants .
Solid ferrite with heavy
metals coprecipitated.
Concentrated acidic
wastewater stream, If
starch is regenerated.
Exhausted starch, which
decomposes if not prop-
erly stored.
Elemental metals.
, 0 Ibs/day). Reported
effluent concentration is:
Mercury
.010
t GPD - gallons per day.
** 1 gallon - 3.785 liters.
-------
Hydroxide Precipitation
Hydroxide precipitation is widely used to treat acidic wastewater
containing metals. It is sometimes applied as a batch process for waste-
water quantities up to 1.89 x 105 fc/day (50,000 gal/day). Continuous
operation may be used at any discharge rate.
Discharge concentrations for As, Cd, Cr, Cu, Pb, Mn, Ni, and Zn are
cited in this literature (see Table 3). The effluent concentrations reported
are below one ppm. Limitations in the removal efficiency are experienced if
complexing agents are present in the wastewater which cause the metal ions to
remain soluble at high pH values. Chromates (Cr+6) also remain in solution
at high pH values and must be reduced to Cr+3 in order for the hydroxide to
form and precipitate.
Energy consumption depends on the lime dosage rate and therefore the
metal concentrations in the wastewater. Lime addition rates of 100 and
1,500 mg/& require 8 and 14 kWh of power respectively.
The cost of the process depends on the size of the treatment facility.
Capital costs are $1.3 million for a facility treating 3.8 x 10 ft/day (1.0 x
10 gal/day). Operation costs are a strong function of the lime dosage rate
required.
Metal hydroxides precipitated by this process are normally disposed of
as a solid waste. However, they will redissolve if brought in contact with
acidic water and therefore present a secondary waste problem.
Sulfide Precipitation
Sodium sulfide (NaaS) is being used at Boliden Metall's primary copper
smelter in Sweden to remove metals from a 200 m3/hr (1.3 Mgal/day) waste-
water stream. Arsenic, cadmium, lead, zinc, copper, cobalt, antimony, and
selenium are present in the wastewater. As yet, however, no removal effi-
ciencies or effluent concentrations have been reported.
Sodium hydrosulfide (NaHS) is being used at Furukawa Co., Ltd.'s Ashio
copper smelter in Japan to treat sulfuric acid plant blowdown. Removal
efficiencies of greater than 99 percent have been reported for arsenic,
copper, cadmium, lead with effluent concentrations of 0.03, 0.03, 0.3,
and 0.5 ppm respectively.
Energy requirements and economic data have not been published for the
different sulfide processes. Both energy requirements and capital and oper-
ating costs should be similar to those for lime precipitation. Two factors
make this process economically feasible. First, the ability to operate at
low pH values (pH 4 to 5) lowers the neutralization cost. Second, the ability
to recycle the precipitate to the smelting furnaces allows the metal and sul-
fur values to be recovered and eliminates the cost of solid waste disposal.
10
-------
The sulfide sludge generated by this process can present a costly
disposal problem if it cannot be sold or recycled.to a smelter. Oxidation
of the sludge would produce soluble sulfates which will dissolve in water.
Ion Exchange
Ion exchange equipment is commercially available. It is especially
suited to polish streams of high volume and low pollutant concentrations.
The costs of the process depend on capacity and solids concentration. For
a 3.8 x 105 £/day (100,000 gal/day) plant treating water containing 500 ppm
solids, the installed capital cost is $174,000. The yearly operating costs
are $73,000. Effluent concentrations below one ppm could be expected. The
estimated power requirement is 1.1 kWh per 3,785 liters (1,000 gallons
treated.
The ion exchange operation creates a low volume, high concentration
aqueous effluent stream which needs additional treatment.
Evaporation Ponds
The application of evaporation ponds is limited to arid regions. Costs
depend on land availability and evaporation rate. A cost figure of $1.2
million to treat a stream of 570 £/min (150 gpm) is cited, assuming an evap-
oration rate of 76.2 cm/year (30 inches/year) and $1,000 per acre. The only
power consumption is for the pumping requirements which amount to 0.5 kWh/
3,785 liters (0.5 kWh/1,000 gal). The process produces salts which will
redissolve upon contact with water.
Reverse Osmosis
Reverse osmosis (RO) is a commercially available process which produces
a clean product stream suitable for reuse or discharge and a contaminated
reject "stream requiring further treatment before discharge. Therefore, RO
cannot be considered an end-of-pipe treatment.
The removal efficiency and costs associated with RO systems depend on
feed characteristics, pretreatment, and desired conversion. Data show that
Al, Cu, Fe, and Mh are rejected at rates greater than 90 percent. Installed
capital costs for RO systems range from $0.19 to $0.53 per liter per day
($0.73 to $2.00 per gallon per day) of treatment capacity. Reported opera-
ting costs range from $0.17 to $0.58 per thousand liters ($0.66 to $2.18 per
thousand gallons) treated. Of this operating cost, the energy requirement
is minimal. For a 380,000 H/day (100,000 gpd) RO unit, the estimated energy
requirement is 8 to 10 kWh per 3,785 liters (1,000 gallons) of water treated.
Activated Carbon
Beds of activated carbon are normally used to adsorb organic compounds
from water effluents. However, secondary removal of metals has been observed.
11
-------
Energy is required for the absorption step for pumping to overcome the
pressure loss through the carbon beds. The estimated power requirement for
pumping is 0.32 kWh per 3,785 £ (1,000 gallons). This number is only approxi-
mate since the actual amount will vary with each system design and total
dynamic head requirements. The electrical power required is estimated to
be 5.8 kWh per 37.3 kg (100 pounds) of carbon regenerated. Cost data is not
available for an application designed to remove metals from an acidic waste
stream.
The exhausted carbon bed is the only secondary waste. Disposal in a
landfill presents a potential problem because the adsorbed compounds can be
gradually released.
Ferrite Coprecipitation
Ferrite coprecipitation is an effluent control approach which was
developed and is industrially applied in Japan. The metals concentrations
achieved in treated effluent water are in the 1 to 200 ppb range (see Table
3). The precipitated hydroxides are reportedly embedded in ferrites which
are only slightly soluble. The ferrites are magnetic and can be removed
either by filtration or magnetic separation.
Process cost and energy requirements are not available.
Starch Complexing
Starch complexing was applied in pilot studies as a polishing process.
Good removal efficiencies were reported (see Table 3). However, disposal of
the spent starch that is generated after absorbed compounds are released
results in a concentrated stream which must be treated by other means. In
addition, poisonous carbon disulfide is used in the starch generation process.
Cost data and power requirements for the process are not available.
Sodium Borohydride
Sodium borohydride exhibits a strong reduction potential. It is used
commercially for electrolytic nickel plating. It is capable of reducing
noble and semi-noble metals to the elemental state at a solution pH of 8.0
to 9.0. The reported effluent concentration achieved for mercury removal
is 0.01 mg/JL
Capital costs are reported as $667 per 3,785 liters (1,000 gal). Oper-
ating costs are between 1.8 and 7.1 cents per 1,000 liters (6.7 to 26.7)
cents per 1,000 gal). Power requirements are not reported.
Elemental metals are the solid residues generated by this process. They
can be either sold or recycled to recover the metal values. The boron remains
soluble as a borate and exits with the discharge stream. Boron effluent con-
centrations have not been reported.
12
-------
SOURCES OF ACIDIC WASTEWATER IN THE NONFERROUS METALS INDUSTRY
The sources of wastewater in the primary and secondary copper, lead,
and zinc industries are listed in Table 4. In the primary industry, waste-
water emanates from:
• mining,
• c oncent rat ing,
• smelting,
• refining, and
• air pollution control.
The elements and concentrations shown in Table 4 are similar to wastewater
discharged by other industrial sources (see Appendix).
Data for the secondary industries are rather scarce. Metal concentra-
tions were found only for the grinding and gravity separation process and
the ingot cooling and quenching operations. No data were found for secondary
lead and zinc industry effluents.
13
-------
TABLE 4. WASTEWATER SOURCES IN THE NONFERROUS METALS INDUSTRY
Industry
Primary
Copper
Primary
Lead
rrimary
Zinc
Secondary
Copper
Secondary
Lead
Secondary
Zinc
Procaaa/Unlc Operation
Al
Mining (400-3800 m'/day)
Ore flotation 100-500
m'/ton of concentrate
Slag Flotation
Sulfurlc Acid Bloudown
.1-10 i 10' I/day
DMA unit - Preacrubber
Arsenic Plant Waahdoira Water
Anode Cooling Water .1
(Concentration change)
Electrolytic Refining
Spent Hi SO* Electrolyte
Mine Drainage
Concentrating
Contact Acid Plant
Slag Fuming
Mining
Concentrating
Horizontal Retorting
Vertical Retorting
Electric Retorting
Other Sources
Grinding & Gravity
Separation
Insulation Burning Unit
Stean Distillation Dnlt
Hydrothermal Hydrogen
Reduction
Ingot Cooling & Quenching
Electric Crucible Smelting
Metal Cooling Water
Fire Refining
Metal Cooling Water
Electrolytic Refining
Spent Electrolyte Slimes
Battery Breaking
Leaching
Other Operations
Sodium Carbonate Leaching
Other Operatlona
Nature of Discharge tea/It)
As As Cd Cr Cu Fe Hg ttn Pb HI Se Sn
<.01 <.02 .9-1 <.l <.0001 1-2 <.5 <.05 .1
•"-.1 .07 .02-. 05 high .1-2 .05-5 .01-3 .05-3 .003-. 02
.05-6 .001-. 04 .05-.! .03-340 .04-7 .001-. 2 .005-. 5
.004-. 1 .0002-. 03 .0001-188 .001-. 11 .005-. 3 0-.003 0-.03
Similar to Sulfurlc Acid Blovdown
310 1 88 9 8 .75 .04
.01 8.5
500- 50,000 2,000-
12,000 20,000
<.002-.06 <.01-.2 .004-700 <.02-2.5 <. 02-57 .02-. 07
.005-.01 .002-.02 .01-. 4 .03-.5 <-001 .03-.2 .1-2
Similar to effluent In primary copper Industry.
.2 .02
No data.
- .005-. 01 <.02-.7 <.02-.4 .05-. 5 .0001-. 1 <.02-.08 <.!-!. 9
No data.
Ho data.
No data.
Ho data.
<.02-.001 .07-1.7 .12 .07-1250 .007-164 .0003-. 002 .05-43 .2-917 .03-18
Ho data.
No data.
Ho data.
*
<.02 <.05 .02-. 07 .6-3.4 .6-1.8 .133 .5-4.3 .1
No data.
No data.
No data.
No data.
No data.
No data.
No data.
No data.
2o
.1-3
.05-850
.02-36
.002-. 4
37
.25
.008-. 04
.1-.5
.4
.1-.5
.2-983
.3-18
-------
SECTION 4
CONCLUSIONS AND RECOMMENDATIONS
From the results presented in Section 3 and in the report Appendix, it
is clear that the metal concentrations found in nonferrous metal industry
wastewaters are similar to those found in other industries. From this, it
might be concluded that the common treatment technologies, hydroxide pre-
cipitation and evaporation, might be applicable to the nonferrous metals
industry effluents. However, the results also show that the waste streams
in the metals industry are poorly characterized.
Source characterization, therefore, is recommended before a final
judgement can be made concerning the most applicable wastewater treatment
technology. This is especially true in the case of new treatment tech-
nologies where the precipitation kinetics, solution equilibria, and particle
settling properties may not be well understood for solutions containing many
metal ions.
Based on the data presented in Table 5, it appears that with the hydrox-
ide precipitation, sulfide precipitation, and ferrite coprecipitation pro-
cesses the existing EPA drinking water and irrigation standards can be met.
The results presented also indicate that two processes, sulfide precipitation
and ferrite coprecipitation, seem particularly applicable to the nonferrous
metals effluents. Recycling the solid wastes generated by these processes
to the smelting furnaces results in enhanced metals recovery while elimina-
ting the solid waste disposal problem. However, the real effectiveness,
energy requirements, and economic data related to both the sulfide and ferrite
processes are not well documented. Field test programs to develop these data
are necessary before a final judgement concerning the applicability of these
two recommended processes can be made.
The results are not conclusive with respect to either the starch com-
plexing or sodium borohydride processes. Starch complexing has not been
applied on a commercial scale. Commercial use of sodium borohydride has
been limited. This process may be of interest in other small scale applica-
tions where precious or hard to remove metals must be recovered in elemental
form. At this time, these processes are not applicable to the major waste-
water treatment problems in the nonferrous metals industry. However, addi-
tional testing of these processes is recommended, especially in applications
specific to the smelting industry.
Field test programs could be completed in two ways. For the sulfide,
ferrite, or borohydride processes, where commercial-scale plants are already
built a test could be developed to measure the removal effectiveness of the
15
-------
TABLE 5. COMPARISON OF TREATMENT PROCESS DISCHARGE CONCENTRATIONS WITH
WATER QUALITY STANDARDS (mg/£)
As Ba
EPA Primary* & Secondary**
Drinking Water Standards .05 1
Irrigation
Standards (NA-199) z
Hydroxide Precipitation .03
Sulfide Precipitation .05
Ion Exchange
Reverse Osmosis
Activated Carbon
Ferrite Coprecipitation
Starch Complexing
Sodium Borohydride
B Cd Cl Cr Cu F Fe Pb Mn Mo Se~
.01 250 .05 1 - .3 .05 .05 - .01
.75 .01 - .1 .2 2 5 5 .2 .01 .02
.0007 .06 .2 .01 .5
.008 .5
.001 .03 .002 .05
.4 .1
No data available.
.008 .01 .01 .06 .01 .007
.009 .003 .007 0 .03 1.6
t No data available.
Ag Zn 80s" S0»" IDS
.05 5 10 250 1000
5000
.02
1.2
.4
.9
.02
.2 .05
* Federal Register, December 24, 1975.
**Federal Register, March 31, 1977.
t May exceed standard for boron discharge.
-------
specific plant design. For more general studies of either the sulfide,
ferrite, starch complexing, or sodium borohydride processes, small skid-
mounted units would be ideal for testing at different sites. These small
units could examine different dosage rates, pH operating ranges, residence
times, and could alter the feed conditions without interfering with plant
operations. In addition, by treating a small slip stream the cost of both
the test equipment, instrumentation, and raw materials would be minimized.
This type of equipment would also be useful for examining synthesized
waste-streams, especially in conjunction with laboratory investigations.
After studying the chemical equilibria and precipitation kinetics of a par-
ticular treatment process in the laboratory, the skid-mounted unit could be
used to simulate actual field conditions. These types of tests would provide
data on the effectiveness of each wastewater treatment process before commer-
cial-sized plants are built.
The results of this study also indicate that ion exchange, reverse
osmosis, and activated carbon are not applicable as end-of-pipe treatment
processes for the nonferrous metals industry unless the small concentrated
waste stream could be either recycled to the smelter or treated. Extensive
pretreatment of smelter wastewaters would be required with these processes
which would reduce any cost effectiveness gained by concentrating the waste-
water streams using either process. It is doubtful that activated carbon
would be used in any applications where metals removal was the major problem.
17
-------
SECTION 5
INDUSTRIAL SOURCES OF ACIDIC WASTEWATER
CONTAINING METAL
The important results of the investigation into the sources of
industrial wastewater were that:
no previously unknown wastewater treatment technology
was being used by the industries studied, and
• the available literature data on the quantity, metal
contaminant concentration, and treatment technology
effectiveness were very sparse.
Matrix Table 6 is a brief summary of the data avilable from work performed
by IERL and other investigators showing the metals found in various indus-
trial wastewater. It should be noted that some of the metals listed in this
table are present in trace quantities (<100 ppm) and are not specifically
treated for removal.
The report Appendix contains a more specific list of the sources of
acidic wastewater and the reported concentration for each metal. Table 6
quantifies the metal contamination in each industry based on data found by
a literature search. It is not a comprehensive list of wastewater sources.
Rather, it lists some of the significant sources, the published metal con-
centrations in the untreated wastewaters, and the literature references. It
was the intent of this investigation to identify and characterize some of the
common industrial sources of acidic wastewater from the standpoint of quan-
tity, metal concentrations, and treatability. It was then hoped that by com-
paring these sources with those in the nonferrous metals industry it would be
possible to determine which wastewater treatment technologies could be trans-
ferred between industries.
However, it was clear from the small amount of information available
that acidic wastewater characteristics are variable and differ from source
to source. For example, it is not reasonable to expect that spills from the
manufacture of fertilizers could be treated in the same fashion as acid mine
drainage though similarities do exist. Cooling tower blowdown is a good
example of a wastewater stream common to many industries.
18
-------
TABLE 6. INDUSTRIES AND ASSOCIATED HEAVY METALS
INDUSTRY
Cement
Electronics
Explosives
Glass and Ceramics
Inorganic Chemicals
Leather Tanning/Finishing
Metal Finishing
Mining
Organic Chemicals
Paint Formulating, Ink
Formulating
Petroleum Refining
Photographic
Plywood, Hardboard, Wood
Preserving
Pulp and Paper Mills
Steam Generation
Steel and Iron
(including ferro-alloy)
Textile
Tires
Al
X
X
X
X
X
X
X
Al
Ag
X
X
Ag
As
X
X
X
X
X
X
X
X
As
Cd
X
X
X
X
X
X
X
X
Cd
Cr
X
X
X
X
X
X
X
X
X
X
X
X
X
Cr
Cu
X
X
X
X
X
X
X
X
X
X
X
Cu
Fe
X
X
X
X
X
X
X
X
Fe
Hg
X
X
X
X
X
X
X
X
X
Hg
Mn
X
X
X
X
Mn
Pb
X
X
X
X
X
X
X
X
X
X
X
X
Pb
Hi
X
X
X
X
X
X
Si
Se
Se
Sn
X
X
X
X
Sn
Zn
X
X
X
X
X
X
X
X
X
X
X
X
X
Zn
VO
X - Identified In process wastewater streams from this industry.
-------
The most common wastewater treatment technologies used by the industries
listed in Table 6 are hydroxide precipitation and evaporation. Specific
applications use ion exchange, activated carbon, and reverse osmosis to
purify some water streams for use as either process or boiler feed water.
The sodium borohydride reduction process has been used to remove precious
and hard to remove metals from small industrial wastewater streams. The
sulfide precipitation and ferrite coprecipitation processes have been used
in limited applications in Europe and Japan but little data is available on
the effectiveness, costs, and energy requirements for these commercial-scale
applications. These and several other processes are described in more detail
in the following section.
20
-------
SECTION 6
TREATMENT METHODS FOR WASTEWATER CONTAINING METALS
INTRODUCTION
In this section treatment technologies for removing metals from
wastewaters are evaluated. The treatments which are assessed include:
• hydroxide precipitation,
• sulfide precipitation,
• ion exchange,
• reverse osmosis, and
• evaporation ponds.
These technologies were chosen based on their ability to adequately remove
metals present in industrial wastewaters. The assessment of treatment tech-
niques includes:
• a brief process description including the basic treatment
steps and the chemistry or mechanism by which metals are
removed,
• control effectiveness which documents reported removal
levels for certain metals,
• energy requirements which give estimates of the energy consumed
during operation of a treatment system,
• economics which present estimates of the capital and operating
costs, and
• secondary process emissions which qualitatively describe the
air, liquid, or solid emissions which are generated during
the operation of each treatment system.
Following this assessment, a description of other treatment technologies for
metals control in industrial effluents is given. The technologies discussed
include:
activated carbon,
• ferrite coprecipitation,
• starch complexing, and
• sodium borohydride reduction.
21
-------
The evaluation of these treatment technologies is limited to a brief
description of the processing scheme, removal mechanism or chemistry,
metals removal effectiveness, and potential secondary pollutants. These
processes, generally, are not as well developed in the field of wastewater
treatment for metals removal. Consequently, sufficient information was not
available to evaluate their applicability to metals removal from industrial
effluents.
HYDROXIDE PRECIPITATION
Hydroxide precipitation for heavy metals removal from streams is both
an effective and economical treatment technology. The treatment converts
soluble metals into hydroxide compounds. The metals can then be separated
from the liquid through sedimentation and/or filtration. The most commonly
used precipitating agents are lime [CaO or Ca(OH)2] and caustic (NaOH).
Hydroxide precipitation has been applied in treating industrial waste-
waters. The following is a list of some of the industries which use this
technology:
• nonferrous metal processing,
• ore mining and dressing,
• utility power generation,
• metals plating, and
• battery manufacturing.
Process Description
Hydroxide precipitation removes metal contaminants from wastewater by
forming metal hydroxide compounds and precipitating them from solution. To
be successful, the precipitation step depends primarily upon two factors:
1) sufficient available hydroxide to drive the precipitation
reaction to completion, and
2) removal of the resulting solids from the treated water.
To accomplish this, a continuous wastewater treatment process utilizing
hydroxide precipitation consists of four basic steps:
1) pH adjustment - where the hydroxide feed is mixed with the
wastewater and the pH is adjusted,
2) flocculation - where the reactions forming the metal hydroxides
are given time to reach a point where sufficient metals removal
is accomplished and floe growth occurs,
3) clarification - where the water is passed through a quiescent
zone allowing the floe to settle, and
22
-------
4) filtration and pH adjustment - where the overflow from
clarification is filtered to remove remaining solids and
pH is adjusted to meet discharge regulations.
An example of a flow diagram for a continuous flow hydroxide precipitation
system is shown in Figure 1.
In the first step the hydroxide precipitating agent is thoroughly mixed
with the wastewater stream. The sources of hydroxide used in industrial
applications of this technology are quicklime (CaO) , hydrated lime [Ca(OH)2]
or caustic soda (NaOH) . The reactions which begin in the flash-mix tank and
which result in formation of the insoluble metal hydroxides are given below:
for quicklime -
CaO + H20 t Ca(OH)2
M4"*" -I- Ca(OH)2 t M(OH)24- + C
or hydrated lime -
M"*"4" + Ca(OH)2 £ M(OH)24- + Ca"4
for caustic soda -
M** + 2NaOH * M(OH)24- + 2Na
I [
where M is the metal cation removed.
(6-1)
(6-2)
(6-3)
(6-4)
Dosages of the precipitating agent fed into the flash-mix tank are
determined by the characteristics of the specific wastewater being treated.
Those parameters affecting dosage rates include inlet water pH, temperature,
hardness, metals concentration, and the desired system operating pH. The
effect of pH on metal hydroxide solubilities is shown in Figure 2. Predic-
tion of the proper dosages from an analysis of the wastewater is difficult
and could lead to inefficient operation of the system. A method of deter-
mining dosages is to perform laboratory jar tests. These tests also can
determine important design and operating information for the system such as:
optimum operating pH,
most effective alkali feed and coagulant aid,
flash mix and flocculation time, and
settling time.
The resulting data provide the necessary basis for determining the economics
of the process for treating a given wastewater.
From the mixing step, the waters pass to the second step which is
flocculation. Finely divided precipitates or microflocs which were formed
in the mix tank are conditioned in the flocculation zone. Here gentle agi-
tation and circulation are used to agglomerate the microfloc to clumps of
23
-------
ALKALI FEED
RAW WASTEWATER
N>
PH ADJUSTMENT
SLUDGE TO
DISPOSAL ^
FILTRATE
FLOCCULATION
FILTRATION
TREATED WATER
TO PH ADJUSTMENT
CLARIFICATION
SLUDGE DEWATERING
EQUIPMENT
Figure 1. Typical continuous flow hydroxide precipitation treatment system.
-------
100—
0.0001
Figure 2. Theoretical solubilities of metal
hydroxides as a function of pH.
25
-------
settleable size. Coagulant aids added in the mix tank can hasten coagulation
or growth of the microfloc. Time is also provided in the zone for the reac-
tion between the precipitating agent and the dissolved metals to reach
equilibrium.
After coagulation and flocculation the water is sent to clarification
where it is passed through a quiescent zone where the floe is allowed time
to settle out of the water. Settled floe accumulates on the bottom of the
clarifier as a sludge. The sludge is usually mechanically raked into a sump
from which it is drawn off as a slurry for dewatering and disposal.
The treated water which is collected as overflow from clarification is
sent to filtration to further separate solids. These filters are generally
designed for gravity flow and consist of a sand bed or multimedia granular
bed. Following filtration the water may need to be treated for pH adjustment
to satisfy discharge regulations which usually require a pH of 6 to 9.
An alternative processing scheme to the continuous flow treatment
described above is batch treatment. Batch systems are generally preferred
when wastewater flows are small, periodic, or when wastewater characteristics
are highly variable. These systems can be economically designed for flows up
to 50,000 gal/day but systems with capacities up to 100,000 gal/day are fea-
sible (LA-A-347). A typical batch chemical precipitation facility is shown
in Figure 3.
The design of a batch treatment process usually consists of two tanks,
each with the capacity to treat the total wastewater volume expected during
an operating period. This redundancy provides sufficient backup capability
to insure consistent and adequate treatment.
During a process operating period, a tank is filled with the wastewater,
agitated to a homogenous mixture, and a sample is taken to determine the
quality. The wastewater parameters mentioned earlier determine the chemical
dosage requirements. The tank contents, including the precipitating agent,
are mixed and agitated for a sufficient period, usually approximately 30
minutes, to insure complete precipitation. After the reaction has reached
equilibrium, the tank contents are allowed to settle for 2 to 4 hours and
a second sample is taken to insure that sufficient treatment has been accom-
plished (LA-A-261).
Once the desired quality is attained, the clear liquid is decanted and
discharged or treated further. Settled sludge is retained in the bottom of
the reactor and serves as seed for the next batch. Excess sludge must be
withdrawn periodically (LA-A-261).
Control Effectiveness
Hydroxide precipitation is capable of removing certain metals found in
acid wastewaters. Among the metal ions removed are arsenic, cadmium, copper,
trivalent chromium, iron, manganese, nickel, lead, and zinc. Table 7 pre-
sents reported residual concentrations to which hydroxide precipitation can
26
-------
Raw
Waste
Water
Chemical
Feed
Chemical
Feed
Treated
Effluent
1
Reaction
Tank
II
Treated
Effluent
1
Reaction
Tank
#2
Sludge
Figure 3. Typical batch process chemical precipitation
treatment facility.
27
-------
remove these metals. This information is based upon application of hydroxide
precipitation to various industry wastewaters. It is important to note in
Table 7 that in some cases, e.g., lead, cadmium, and zinc, the residual con-
centrations reported are lower than the theoretical solubilities of the pure
element in water (see Figure 2). Several phenomena influence the effective-
ness of precipitation, e.g., ionic strength, coprecipitation, and adsorption.
These phenomena will ultimately determine the residual concentrations in
specific applications, especially in solutions containing several metal ions.
TABLE 7. HYDROXIDE PRECIPITATION METAL REMOVAL EFFECTIVENESS
Metal
Arsenic
Cadmium
Chromium, trivalent
Copper
Iron
Lead
Manganese
Nickel
Zinc
Inlet Concentration
(mg/A)
0.2 - 0.5
ND
1300
204 - 385
10
0.5 - 25
ND
5
16.1
Residual Concentration
0.03
0.0007
0.06
0.2 - 2.3
0.1
0.1 - 0.03
0.5
0.15
0.02 - 0.23
Source: PA-322
Energy Requirements
Energy usage for a hydroxide precipitation facility which treats acid
wastewaters will vary according to site specific design parameters. Esti-
mates for the energy required to operate an example precipitation system are
presented here, though, to indicate the relative magnitude of its energy
usage compared to other wastewater treatment technologies. The estimates
are for a 500,000 gal/day system using lime as the hydroxide precipitating
agent. Primary energy users are the lime feeders, wastewater pumps, clarifier
agitator drive, sludge rake drive, and vacuum filter. For a 100 mg/£. lime
dosage the system consumes about 8 kWh of electricity per 1,000 gallons of
wastewater treated. For a dosage of 1,500 mg/£, the energy requirements
increase to 14 kWh per 1,000 gallons (CO-R-685).
Economics
The costs associated with wastewater treatment by lime precipitation
are discussed below. Figures 4 and 5 present curves for lime precipitation
capital costs and operation and maintenance costs (1977 dollars). The equip-
ment on which the cost curves are based include a lime feeder, flash mix tank
28
-------
Equipment List:
Lime Feeder
Flash Mix Tank
Clarifier/Flocculator
Sludge Thickener
Vacuum Belt Filter
Multi-media Filter
09
E
o
Q
09
O
09
O
O
Q.
O
10—
o.v
O 1
I
10
100
SYSTEM CAPACITY (MILLION GALS/DAY)
Figure 4. Lime precipitation installed capital costs.
29
-------
10
o.o«
o i
too
SYSTEM CAPACITY (MILLION GALS/DAY)
LIME DOSAGE (/LITER)'
I 100 mg
II 1000mfl
III 5000 mg
Figure 5. Lime precipitation operating and maintenance costs.
30
-------
clarifier/flocculator with sludge recycle, sludge thickener, vacuum belt
filter for sludge dewatering, and a filter for final effluent polishing.
This equipment selection represents the most capital intensive treatment
system. If effluent standards could be met and if land were available,
settling ponds and lagoons could be utilized. Capital costs and operating
and maintenance costs might be substantially decreased with such an arrange-
ment since it involves less equipment. However, for the application of
precipitation for metals removal, the low concentrations may require the
more expensive arrangement to obtain adequate overall removals. The costs
presented in Figures 4 and 5 do not include the costs of disposing of the
dewatered sludge.
The effect of different lime requirements on the operating and mainte-
nance costs due to varying inlet stream hardness, operating pH, and metals
concentration is shown in Figure 5. Curve I represents a lime dosage of
100 mg/£. Curve II is for a dosage of 1,000 mg/£ and Curve III for a dosage
of 5,000 mg/£ (CO-R-685).
Secondary Process Emissions
The precipitated solids formed in the clarifier represent a secondary
waste when separated from the wastewater. The sludge is usually processed
by dewatering in a thickener and vacuum filter or filter press to reduce its
volume prior to disposal. However, if land is available, it may be sent
directly from the thickener to ponds for disposal. Care must be exercised
to prevent the metals from being leached or discharged from disposal sites
or ponds. Lagoon or pit bottoms can be lined with natural clays or artifi-
cial liners to prevent excessive amounts of leachate from reaching the ground-
water. Underdrains may also be considered for collection and transportation
of leachate from disposal sites. Also, chemical additives can be used to
help control the mechanism by which metal sludges are leached from a landfill.
SULFIDE PRECIPITATION
Sulfide precipitation of the metallic ions present in acidic wastewaters
is a viable treatment technology. Inherent environmental problems associated
with it have resulted in very few industrial installations, however. As with
hydroxide precipitation, sulfide precipitation relies upon converting soluble
metals into a slightly soluble compound, in this case metal sulfides. The
precipitated compounds can then be separated from the liquid through sedimen-
tation and filtration. The sulfide reagents commonly used are: sodium
sulfide (NaaS), sodium hydrosulfide (NaHS), calcium sulfide (CaS), and
barium sulfide (BaS).
Industrial applications of sulfide precipitation have been limited, as
mentioned, due to environmental problems. The following is a list of those
industries to which this technology has been applied for wastewater treatment;
• Ore mining and dressing,
Nonferrous metal processing,
• Chlor-alkali production, and
• Phosphoric acid production.
31
-------
Process Description
The treatment of acidic wastewaters for metals removal by sulfide
precipitation is similar to hydroxide precipitation in that a slightly
soluble metal compound is formed which can be easily separated from solution.
To be successful, sulfide precipitation depends primarily upon two factors:
1) sufficient available sulfide to drive the precipitation
reaction to completion, and
2) removal of the resulting solids from the treated water.
To accomplish this, a continuous flow sulfide precipitation facility
consists of four basic steps:
1) pH adjustment and flash mixing - where the stream pH is
raised by alkali addition and the sulfide precipitating
agent is mixed with the wastewater,
2) flocculation - where the reactions forming the metal sulfides
are given time to reach a point where sufficient metals removal
is accomplished and floe growth occurs,
3) clarification - where the treated wastewaters are passed
through a quiescent zone allowing the precipitate or floe
to settle out, and
4) final effluent filtration and pH adjustment - where the
treated overflow from clarification is filtered to remove
any unsettled solids and the stream pH is adjusted to meet
discharge regulations.
An example of a flow diagram for a continuous flow sulfide precipitation
system is shown in Figure 6.
In the first step the pH of the acidic wastewater is adjusted to an
optimum operating pH by the addition of an alkali. The optimum pH is deter-
mined by laboratory jar tests and/or pilot tests on the wastewater being
tested. Figure 7 shows the effect that solution pH has on metal sulfide
solubilities. The most commonly used alkalis are lime or caustic.
Following adjustment of the pH of the stream, the sulfide reagent is
added in a flash mix reaction tank. The most commonly used reagents are the
soluble sulfides including sodium sulfide, sodium bisulfide, calcium sulfide,
and barium sulfide. The reactions occurring between these reagents and the
dissolved metal cations forming the metal sulfide precipitates are:
for sodium sulfide -
Na2S £ Na+ + S= (6-5)
M4"4" + S= t MS* (6-6)
32
-------
RAW WASTEWATER
ALKALI FEED
SLUDGE TO
DISPOSAlT
FILTRATE
7
SLUDGE DEWATERING
EQUIPMENT
TERTIARY
FILTRATION
TREATED WATER
TO PH ADJUSTMENT
CLARIFICATION
Figure 6. Typical continuous flow sulfide precipitation treatment system.
-------
10' -\
10
o J
10 '1
io '-1
10~5-J
O
CO
10 °H
io-9H
-10-J
10
10 'H
10
,-13
CoS
PbS
Ag2S
I I I I I I I I I I I
2 34 56 7 8 9 10 11 12 13
pH
Figure 7. Theoretical solubilities of metal
sulfides as a function of pH.
Source: PE-317
34
-------
for calcium sulfide -
CaS + Ca*4" + S= (6-7)
M*"1" + S= * MS4- (6-8)
for sodium bisulfide -
NaHS 2 Na+ + HS~ (6-9)
HS~ ^ H + S (6-10)
M"*" + S= £ MS4- (6-11)
1
for barium sulfide -
BaS * Ba** + S= (6-12)
M4* + S= £ MS* (6-13)
-i-_i_
where M is the dissolved metal cation. As with hydroxide precipitation,
dosage rates for the sulfide reagent depend upon characteristics of the
specific wastewater being treated.
Excess sulfide must be avoided since there is potential for formation of
hydrogen sulfide gas. Therefore, it is very important that sulfide dosages
be properly controlled in order to effectively remove metals without gener-
ating HaS. Two process control techniques have been used to minimize excess
sulfide doses and therefore minimize HaS formation. The first was used at
two pilot plants treating acid mine drainage (LA-326) . When the reactions
between the sulfide reagent and the dissolved metals are completed, a sharp
rise in pH will be observed. This method uses a pH monitor as a feedback
control to regulate the sulfide dosage rate.
The second method was used in two applications, one at a copper smelter
in Japan to treat sulfuric acid plant blowdown (MU-153) , the other at a pilot
plant treating photographic developer effluent (LA-337). This method uses an
oxidation/reduction potentiometer to monitor the electric potential of the
reaction solution. When the precipitation reactions are complete, there is
a sharp negative change in the solution potential.
The remaining treatment steps for sulfide precipitation are f locculation,
clarification, and final effluent filtration and pH adjustment. These are
performed in a similar manner as described earlier for hydroxide precipita-
tion.
An alternative processing scheme to the continuous flow system is batch
treatment. The general batch treatment system described under hydroxide pre-
cipitation could be used also for sulfide precipitation. Figure 3 shows the
flow scheme for a batch treatment facility.
35
-------
Control Effectiveness
Sulfide precipitation is effective at removing most metals found in
acid wastewaters. Among the metal ions reported to be removed are arsenic,
cadmium, cobalt, copper, iron, mercury, nickel, and zinc. The chlor-alkali
industry uses sulfide to remove mercury from their effluents. Sulfide pre-
cipitation is also being applied in the primary copper industry. Table 8
lists reported influent and effluent metal concentrations for sulfide systems
treating various wastewater streams. It should be noted that this informa-
tion is based upon application of sulfide precipitation to various industrial
wastewaters. Wastewater characteristics may vary significantly from site to
site even within a given industry. These characteristics as well as the
design and operation of the precipitation facility will ultimately determine
the effectiveness of sulfide precipitation upon metals removal. For this
reason, the residual concentrations reported in Table 8 should not be taken
as an accurate measure of sulfide's performance in specific applications.
Instead these numbers should be interpreted as an indication of the range
of removal effectiveness for sulfide precipitation.
TABLE 8. SULFIDE PRECIPITATION METAL REMOVAL EFFECTIVENESS
Metal
Arsenic
Cadmium
Copper
Mercury
Zinc
Inlet Concentration
(mg/A)
0.8-132.0
0.44-1.0
50-115
0.3-50.0
42
Residual Concentration
(mg/£)
0.05-26.4
0.008
0.5
0.01-0.12
1.16
Source: PA-322
Furukawa Co. Ltd. uses sodium hydrosulfide (NaHS) to treat sulfuric acid
plant blowdown at their Ashio copper smelter in Japan (MU-153). This is the
only nonferrous smelter which has reported removal efficiencies to date.
The data reported are as follows (MU-153):
Concentration (ppm)
Metal Influent Effluent
As
Cu
Pb
Cd
8,530
120
30
60
0.03
0.05
0.5
0.3
36
-------
These data are from a batch process. Reaction times are between 2 and 3
hours. A sharp negative change on an oxidation/ reduction potentiometer
indicates the reaction end point.
It should also be noted, that HaS is used in the production of primary
cobalt. In this industry, the sulfide is used to selectively precipitate
iron, copper, zinc and then cobalt and nickel at increasing pH values.
Sulfide is used in this process because of its ability to effectively
remove the cobalt and other impurities from the leaching liquor.
Energy Requirements
Because of the limited application of sulfide precipitation, information
in the literature on the energy usage for a full-scale system was not avail-
able. However, since much of the basic processing scheme for sulfide pre-
cipitation is the same as that for hydroxide precipitation the primary energy
users will probably be similar. The one main exception to this is the energy
usage of the sludge dewatering equipment. Sulfide precipitation will prob-
ably result in less sludge being generated per volume of wastewater treated.
This is because a sulfide system can operate at a lower pH than a hydroxide
system and still effectively remove dissolved metals (see Figures 2 and 7) .
Therefore, less alkali is needed to adjust the pH of the waste stream and
less sludge is formed in the flocculator. The size and energy requirement
for the sludge handling equipment, therefore, will be lower than for hydrox-
ide precipitation. The energy requirements of 8 kWh to 14 kWh for the hydrox-
ide precipitation system described in the previous section should be repre-
sentative of the high end of the range of energy requirements for sulfide
precip itat ion .
Economics
As with the energy requirements, estimates for the costs associated with
sulfide precipitation were not found in the literature. However, the costs
associated with sulfide precipitation may be approximated by those given
earlier for hydroxide precipitation. There are several differences in the
two systems that should be noted which will affect the capital and operating
and maintenance costs for sulfide precipitation, though. Those differences
which will probably increase capital costs include:
a separate reaction tank and associated equipment
for sulfide addition,
• hoods on the reaction tank and flocculator/clarifier
for HaS control, and
• special instrumentation to control excess sulfide
addition.
There is one difference which will probably lower capital costs:
• smaller sludge handling equipment due to the lower
operating pH of the system.
37
-------
Smaller sludge volumes will result because of the lower operating pH. At
lower solution pH values, calcium carbonate will not precipitate as in the
hydroxide precipitation system.
With respect to operating cost, the primary difference which will
probably increase the sulfide precipitation costs is the expense of the
sulfide reagent. Sodium sulfide, for example, costs roughly $275 per ton
versus lime costs of $25 per ton and sodium hydroxide costs of $150 per ton.
Those differences which will probably lower the costs are:
• less sludge volume to dewater, and
less lime or sodium hydroxide needed since the operating
pH is lower.
Secondary Process Emissions
The two major environmental problems associated with the sulfide precipi-
tation process are the potential generation of hydrogen sulfide (HaS) gas and
the production of a metal sulfide sludge. Hydrogen sulfide formation results
from the addition of excess sulfide which reacts with water as shown:
2H20 + S= £ 20H~ + H2S+ (6-14)
HaS formation can be minimized either through operating the system at a pH
above 8.0 or by one of the two methods mentioned earlier, i.e., carefully
monitoring the solution pH during sulfide addition or monitoring the elec-
trical potential of the reaction solution. As can be seen in Figure 8, at
a solution pH above 8.0, hydrogen sulfide will disassociate into HS and H .
Operating at a pH of 8.0 is not desirable for smelters first, because of the
additional cost of hydroxide for neutralization and second, because most
metals will precipitate as hydroxides. It is preferable to recycle metals
in the sludge in the form of sulfides rather than hydroxides. Sulfides are
the normal feed to a smelting furnace. Metal hydroxides require more energy
to smelt and are likely to be lost in the smelting furnace slags. Therefore,
it is believed that the optimum pH for a sulfide system may be as low as 4
to 5. As a result, the other control measures were developed to minimize
HaS liberation. As an additional control, ventilation is normally provided
on all of the reaction equipment.
Metal sulfide sludge disposal is the other major environmental problem
associated with sulfide precipitation processes. There are several disposal
alternatives which have been investigated. These include:
maintaining the sludge in an oxygen free environment (SC-A-503).
chemical treatment or fixation (EN-394), and
recycling the sludge to a smelter for metals recovery
(MU-153, CO-A-683).
38
-------
HS"
1.0
0.8 _
c
.3
4J
CO
•H
Q
rH
o
-------
If metal sulfide sludges are placed in a typical landfill, exposure to
air can oxidize the sulfide portion and eventually create an acid environment.
As the pH decreases the heavy metals portion can dissolve and be leached from
the site back into the environment via surface runoff or percolation through
the soil mantle with subsequent groundwater contamination.
Probably the most practical and least expensive disposal technique for
the nonferrous metals smelting industry is recycle of the sludge for recovery
of the metals. A smelting plant in Sweden has installed a sodium sulfide
wastewater treatment facility which will recycle recovered sludge back to
its copper roasters for disposal.
ION EXCHANGE
Ion exchange is a process in which mobile ions of one phase are
exchanged for ions of the same charge in another phase. Although the
most common ion exchange systems consist primarily of a solid phase with
a surrounding liquid phase, some specialized applications employ two immis-
cible liquid phases.
Although the process was first discovered in 1848, the first successful
application occurred almost sixty years later for the purpose of water soft-
ening. While this is still the most common application, the recent demand
for ultrapure water by electric power utilities and transistor and micro-
circuit industries has resulted in many improvements in ion exchange systems.
Currently ion exchange technology is being used in the following industries:
metals plating,
Pharmaceuticals processing,
heavy metals (cobalt, nickel, copper, molybdenum, and vanadium)
recovery and purification, and
• boiler feedwater pretreatment in many industries.
Process Description
The basic mechanism of ion exchange involves the reversible interchange
of similarly charged ions in separate phases, usually a solid resin immersed
in a liquid medium. Ion exchange resins are the heart of the ion exchange
process. These resins may be either strongly acidic, weakly acidic, strongly
basic, or weakly basic, depending on groups attached at the surface. A
strongly acidic resin will contain functional groups derived from a strong
acid such as HaSOi,, whereas, a weakly acidic resin will be derived from a
weak acid such HaCOs. Basic resins that contain functional groups derived
from weak base amines (R-NHa, R-R'NH, and R-R'aN) are termed weakly basic,
while those resulting from quaternary ammonium compounds (R-R'aN OH~) are
considered strongly basic. Table 9 presents representative ion exchange
reactions and appropriate regenerants for the four different exchange resins
(WE-324).
40
-------
TABLE 9. TYPICAL REACTIONS FOR ION EXCHANGE RESINS
Strongly Acidic Cation Exchangers.
a. Hydrogen form, regenerate with HC1 or HaSO^.
2(R - S03H) + Ca2+ £ (R-S03)2Ca + 2H+ (6-15)
b. Sodium form, regenerate with Nad.
2(R - S03Na) + Ca2+ J (R-S03)2Ca + 2Na+ (6-16)
Weakly Acidic Cation Exchanger.
a. Hydrogen form, regenerate with HC1 or
2(R - COOH) + Ca2+ J (R - COO)2Ca + 2H+ (6-17)
b. Sodiunt form, regenerate with NaOH.
2(R - COONa) + Ca2+ J (R - COO)2Ca + 2Na+ (6-18)
Strongly Basic Anion Exchanger.
a. Hydroxide form, regenerate with NaOH.
2(R - R'3NOH) + S042~ ? (R - R'sN^SOij + 20H~ (6-19)
b. Chloride form, regenerate with NaCl or HC1.
2(R - R'3NC1) + S0it2~ £ (R - R'3N)2S04 + 2C1~ (6-20)
Weakly Basic Anion Exchanger.
a. Free base or hydroxide form, regenerate with NaOH,
NHitOH, or Na2C03.
2(R - NH3OH) + S0»,2~ J (R - NH3)2SOi, + 20H~ (6-21)
b. Chloride form, regenerate with HC1.
2(R - NH3C1) + SO*2' t (R - NH3)2SOi» + 2C1~ (6-22)
Source: WE-324
-------
For water and wastewater treatment there are two principal methods for
applying ion exchange, batch and fixed bed. In batch operation a predeter-
mined quantity of ion exchange resin is added to a specified volume of water
and mixed until the exchange reaction attains equilibrium. Normally batch
operation is considered inefficient because only a fractional amount of the
total resin capacity is used. However, batch operation has been effective
in circumstances where the selectivity of the resin for the ion being removed
is very high or when the ion being released by the resin is concurrently
removed from the solution being treated. For instance, if the released ion
is precipitated from solution, batch operation may be more effective than
fixed bed operation.
Fixed bed or column operation is preferred for most applications. Each
column is equipped with top and bottom liquid distributors or collectors.
Usually a porous bed of gravel or anthracite or a screen is placed in the
bottom of the column to support the exchange resin which is loaded approxi-
mately halfway to the top. Generally fixed bed operation follows a four
step cycle:
service,
• backwash,
• regeneration, and
rinse.
During the service step the solution being treated is introduced at the
top of the column and allowed to trickle down through the resin bed to be
removed by a collector system at the bottom. As the solution is fed into
the column, a rather narrow exchange zone will be established where the con-
taminant ions are being exchanged with the counter ions of the resin. With
continued operation the exchange zone will slowly travel downward through the
bed leaving exhausted resin behind. When the exchange zone eventually reaches
the bottom of the bed, breakthrough of the contaminant ions will occur and the
exhausted bed will require regeneration. The amount of operational time
before bed regeneration depends on the feedrate and composition of the solu-
tion and the size of the column. For manual operation, columns are normally
sized to provide a service period of 24 hours in order to reduce labor costs.
If the column is on automatic control then the service period may be short-
ened to four to eight hours in order to reduce equipment size and cost.
Following exhaustion, the resin bed is backwashed to remove fine sus-
pended particles that may have filtered out on the resin. Treated water is
introduced through a distributor in the bottom at a high enough flow rate to
expand the bed about 75 to 100 percent of its original volume. Although fine
particles are carried out through the top collector, the ion exchange resin
is not lost. Backflushing will usually last 15 to 30 minutes, after which
the resin .bed settles to a uniform packing. Any flow channels that may have
been formed during the service step are effectively removed by backflushing.
Regeneration is the third step in the cycle and may be accomplished by
the introduction of a suitable acid, alkali, or neutral salt. Although regen-
eration may'use either•downflow or upflow operation, the latter is usually
42
-------
preferred. With downflow regeneration the very bottom of the bed is not
fully regenerated and subsequent service operation will cause contaminant
leakage. If upflow regeneration is used, the partly regenerated resin is
at the top of the bed and subsequent service operation will only displace
the contaminant deeper•into the bed rather than out with the product. In
addition, upflow regeneration is immediately effective since the contaminants
released from the lower bed portion are flushed through the complete exhausted
upper bed volume where the possibility of removal is negligible. Therefore,
a reduction in the regenerant, rinse, and backwash consumption is achieved,
which results in a decrease in the amount of regenerant waste. This final
point, in reference to regenerant waste, is very important. All ion exchange
systems will generate a waste stream which requires proper disposal. If the
amount of this waste stream can be reduced, disposal will be simpler and more
economic. In some cases, if the contaminant concentration is high enough,
recycling of the regenerant waste or further processing for contaminant
recovery may be economically attractive.
In the rinse step, treated water is very slowly passed through the bed
to displace the remaining regenerant solution. This is followed by a second,
faster rinse to flush residual regenerant and displaced ions to waste. The
rinse water can be collected and used for regeneration in the next operating
cycle. When a predetermined volume or conductivity is reached, the cycle is
ready to be repeated beginning with the service step.
Some ion exchange systems designed for the production of deionized water
incorporate both acidic (cationic) and basic (anionic) resins in a single
column. This mixed-bed treatment has resulted in deionized water of a better
quality than in a two column system. The operating cycle is basically the
same. A downflow service operation is continued until bed exhaustion. Then
an upflow backwash step is used to separate the lighter anion resin particles
from the heavier cation resin particles. For regeneration, an acid is fed up
through the cation resin and an alkali is fed down through the anion resin.
The waste regenerant is drawn off at a zone where the two resins meet. The
resin bed is then completely rinsed and compressed air is used to fluidize
the system and remix the resins. The operating cycle is again ready to be
repeated. The entire cycle is shown in Figure 9.
Control Effectiveness
Ion exchange has an excellent record of performance in wastewater
treatment. Several metals, including copper, lead, nickel, and zinc, have
been removed to levels lower than 0.4 mg/&. Table 10 presents the influent
and effluent concentrations of several heavy metals in water streams treated
by ion exchange processes. This information is not directly based upon the
application of ion exchange to primary nonferrous industry wastewaters.
43
-------
INFLUENT
HCO
3
EFFLUENT
(A)
SERVICE
CYCLE
WASTE
v\\\\\V
TREATED
WATER
(B)
BACKWASH
ALKALI
TREATED WATER
ACID WASTE TREATED WASTE
WATER
(C) (D)
REGENERATION RINSE
AIR
AIR
(E)
REMIXING
Figure 9. Operating cycle for mixed-bed ion exchange system.
-------
TABLE 10. ION EXCHANGE METAL CONTROL EFFECTIVENESS
Inlet Concentration Effluent Concentration
Metal
Cadmium
Chromium , hexavalent
Copper
Lead
Manganese
Mercury
Nickel
Zinc
1 Pilot plant test data.
Source: PA-120
(»g/A)
0.1
8-10.7
1.02
0. 055-144. 81
501
1.4-2.8
150-900
6
(mg/Jl)
0.001
0.0-0.9
0.03
0. 0015-0. 531
0.0461
0.005
0.01
0.4
The control effectiveness of a particular ion exchange resin for a
specific contaminant is determined by the ion selectivity of that resin.
The ion selectivity, in turn, is determined by a number of factors including
solution concentration of the ion, valence of the ion, temperature, pressure,
ion pair formation, structure of the exchange resin, and precipitate
formation. All of these factors are well discussed in literature (SA-136
and WE-324).. Table 11 summarizes the order of selectivity for various ions
with various exchangers (CE-034).
45
-------
TABLE 11. SELECTIVITY ORDER FOR VARIOUS IONS WITH VARIOUS EXCHANGERS
I. Strong Acid Cation Exchanger (8% Cros si inking).
Ba44" > Pb44" > Kg"*"*" > Cu+ > Sr44" > Ca""" > Ni44" > Cd"*4" > Cu44" > Co** > Zn"*4" * Cs+ > Rb+ > Fe"1
> Kg"*"* « K+ > Mn44" > m*+ > Na+ > H+ > Li+
II. Weak Acid Cation Exchanger (Carboxylic) .
H4" > Cu44" > Co"14" > Ni"14" > Ca** > Mg44" > Na+
III. Strong Base An ion Exchanger.
Type I: Benzene sulfonate > salicylate > citrate > I~ > Phenate > HSO^ > Clo" > NO^ > Br~
CN~ > HSOl > BrOl > NOa > Cl~ > HCO^ > I0l > Formate > Acetate > Propionate > F~ > OH"
Type II: Nearly the same except iodide is less that phenate and hydroxide is after bicarbonate.
IV. Weak Base An ion Exchanger.
OH~ > SO^ > CrO^ > AsO" > PO^ > MoO^ > Cl~
V. Chelate Resin (Dowex A-l) .
Pd"14" > Cu"* > Fe44" > Ni44" > Pb44" > Mn44" > Ca44" > Mg44" > Na+
Source: CE-034
-------
Energy Requirements
The only energy required for ion exchange treatment is for pumping.
The average energy requirement is approximately 1.1 kWh per 1000 gallons
of water treated (MA-693). This estimate is independent of the concentra-
tion of total dissolved solids in the feed water.
Economics
Ion exchange is very unique in that the costs of this treatment per unit
volume of water decrease with a decrease in the concentration of the metal
ion. This makes ion exchange a very attractive means for treating wastewater
streams with metals concentrations less than 200 mg/£. Some recently devel-
oped resins, which have improved selectivities for particular metal ions,
may increase the concentration level at which ion exchange systems are
economically attractive. In cases where a reduction in dissolved solids
is of primary importance, ion exchange is considered economically practical
if the solids concentration is less than 1,000 mg/Jl. For solids concentra-
tions greater than 1,000 mg/£, processes such as reverse osmosis and elec-
trodialysis are usually more economical than ion exchange (WE-324).
The capital and operating costs for an ion exchange system can vary
depending on the volume and composition of the stream being treated. The
principal operating cost is regeneration and is highly dependent on the ion
exchange resins employed, the raw water quality, and the operating arrange-
ment. Strongly basic resins will involve higher operating costs than weakly
basic resins because of the regenerant required. Strongly basic resins are
regenerated by solutions of sodium hydroxide, which may cost from 8 to 16
cents per pound (VE-074). Regeneration of strongly basic resins is also
less efficient than for weakly basic resins. Estimated operating costs for
weakly basic resins is on the order of fifteen cents per thousand gallons
per gram per gallon removed (WE-324). In almost every instance, ion exchange
systems are tailored to the specific installation and its wastewater, so that
general economic data is incomplete. Table 12 presents the economics of sev-
eral ion exchange systems based on system capacity and dissolved solids con-
centration.
Secondary Process Emissions
The treatment of any waste stream by ion exchange results in resin
regeneration wastes. These wastes contain the pollutants removed from the
effluent stream that is treated. The pollutants are concentrated in the
acidic or basic regeneration solution. The two solutions are usually com-
bined for neutralization. Further treatment of these wastes is required
prior to their discharge.
47
-------
TABLE 12. ECONOMICS OF ION EXCHANGE WATER TREATEMENT (1977)
00
System Capacity
(103 gal/day)
Dissolved Solids Concen-
tration (ppm)
Installed Capital Cost
(103$)
Operating Costs ($/1000 gal)
Capital Service
Chemical (Regeneration
and Waste, including
Water)
Resin Replacement
Power Ǥ $0.035/kWh)
Labor (@ $10/hr)
Maintenance and Repairs
Total Operating Cost
($/1000 gal)
Yearly Operating Cost
(103 $).*
25
100
68
0.92
0.24
0.05
0.04
0.15
0.10
1.50
13
25
200
70
0.94
0.48
0.05
0.04
0.15
0.10
1.76
15
25
500
73
0.99
1.20
0.05
0.04
0.15
0.10
2.53
22
100
100
145
0.51
0.24
0.06
0.04
0.10
0.08
1.03
36
100
200
170
0.54
0.49
0.06
0.04
0.10
0.08
1.31
46
100
500
174
0.58
1.22
0.06
0.04
0.10
0.08
2.08
73
500
100
275
0.18
0.28
0.07
0.04
0.05
0.05
0.67
117
500
200
275
0.18
0.56
0.07
0.04
0.05
0.05
0.95
166
500
500
275
0.18
1.40
0.07
0.04
0.05
0.05
1.79
313
7,200
20
1,700
0.10
250
* Assumed operating schedule 85% service - 350 days/yr.
Sources: DI-150, MA-693
-------
In addition, a resin bed will eventually require complete replacement
when it can no longer be sufficiently regenerated. The spent resin becomes
a solid waste and is usually disposed of by landfilling.
REVERSE OSMOSIS
Reverse osmosis (RO) is a process designed to purify contaminated streams
by forcing water through a semipermeable membrane. The membrane will readily
allow the passage of water under pressure, but prevents the transport of con-
taminants. The result of wastewater treatment by reverse osmosis is a pure
water product stream and a highly concentrated reject stream.
Undoubtedly the most widespread use of reverse osmosis systems has been
the desalinization of water. Since the early 1970's, however, reverse osmosis
has been commercially used to treat wastewater streams from a number of indus-
tries including:
• electroplating,
printed circuit board manufacturing,
acid battery manufacturing,
metal finishing (such as nickel plating), and
• ore mining.
In some cases, treatment by reverse osmosis resulted in a high volume product
stream of environmentally acceptable quality and a low volume, highly concen-
trated reject stream which required additional treatment before final dispos-
al. In other cases, reverse osmosis was able to provide process makeup water
from the product stream and valuable mineral recovery from the reject stream.
Therefore, for a stream containing heavy metals, reverse osmosis can be used
to concentrate the metals in a lower volume stream for additional treatment
and final disposal or for metals recovery. For smelter wastewaters, however,
filtering would be required as a pretreatment step in order to prevent clog-
ging of the filter membrane.
Process Description
Osmosis is the flow of water from a dilute solution through a semi-
permeable membrane to a more concentrated solution. The driving force is
referred to as osmotic pressure. When a pressure greater than the osmotic
pressure is applied to the concentrated solution, the process can be reversed.
Water will pass from the concentrated solution through the membrane, leaving
dissolved species in the concentrated solution. Once the osmotic pressure is
exceeded, the rate of flow through the membrane is roughly proportional to the
applied pressure (WI-316).
Reverse osmosis should not be confused with ultrafiltration. Since
reverse osmosis uses a "tighter" membrane and operates at considerably higher
pressures (400-1,000 psi) than ultrafiltration, it is capable of rejecting
dissolved electrolytes and organics of much lower molecular weight.
49
-------
A schematic flow diagram of a typical reverse osmosis plant is presented
in Figure 10. The system consists basically of high pressure process pumps
that supply feed to a number of reverse osmosis modules connected either in
series or parallel. If the reverse osmosis modules are arranged in series,
the feed, in effect, will undergo treatment a number of times and a higher
quality product can be achieved. In some cases, the reject stream may be
recycled to the feed stream or fed directly to another RO module to reduce
the volume or increase the concentration for further treatment. Such
recycling or series treatment of the reject stream may be limited by the
ability of the membrane to withstand concentrated contaminants. If the pro-
duct quality is not critical, then the modules can be arranged in parallel to
provide high system capacity.
The plant must also have some feed pretreatment equipment, usually some
form of pH adjustment and filtration, to prevent membrane damage. Most
commercially available membranes can withstand feed streams with a pH between
2.5 and 11, although the most commonly recommended pH is moderately low (4 to
7). In addition, the feed should have a low solids loading to prevent the
membrane from becoming plugged.
While reverse osmosis systems are designed for specific applications,
operating conditions can vary considerably depending on the feed stream to be
processed, the quality of product desired, and the type of membrane material
employed. Typical operating pressures may range from 200 to 1000 psi, while
temperatures may vary from 55 to 95°F. Within this range a reverse osmosis
unit can generally be operated to produce anywhere from 50 to 90 percent of
the total feed volume as product.
A variety of semipermeable membranes have been used in reverse osmosis
units. In the past the most popular membrane material has been cellulose
acetate (GI-019). The membrane was designed to be approximately 100 microns
thick. Of this thickness less than 1 percent was composed of the dense skin
which exhibits the semipermeability required for reverse osmosis membranes.
The remaining portion of the cellulose consisted of a porous substrate that
provided the membrane with structural strength (LY-006).
Recently, however, aromatic polyamide membranes have received more
attention due to their ability to treat a wider range of contaminated feeds.
For example, one manufacturer produces a polyamide membrane which can be
operated at temperatures up to 95°F (@ 800 psi), pressures up to 1000 psi
(@ 77°F), and over a pH range of 4 to 11 (TE-361, RA-579). Two other very
promising membrane materials are a nonpolysaccharide polymer (RO-389) and a
polybenzimidazolone (NE-314). The nonpolysaccharide membrane has been
experimentally used in treating metal finishing wastewaters with a pH range
of 0.5 to 12.9 and has shown no significant signs of deterioration (RO-389).
The polybenzimidazolone membrane was primarily developed for use in water
desalting and has been experimentally shown to handle a pH range of 1 to 12,
resist oxidation by chromic acid, and withstand temperatures up to 140°F
(NE-314).
50
-------
Ijl
REJECT BRINE PUMP
DISCHARGE
PH
ADJUSTMENT
INTAKE
FILTRATION
x"
CHEMICAL
ADDITION
-.1.
> «J
FEEDWATER
PUMP
HIGH
PRESSURE
PROCESS
PUMP
PRODUCT PUMP
t
RO MODULES
PRODUCT STREAM
PRODUCT WATER
STORAGE TANK
Figure 10. Typical reverse osmosis plant arrangement.
Source: HI-041
-------
In addition to the variety of available membrane materials, there are
also several possible membrane configurations. For reverse osmosis systems,
the term configuration refers to the membrane supporting mechanism. Early
reverse osmosis systems relied on relatively simple configurations, such as
plate and frame or tubular membranes. Newer systems are employing either
spiral wound or hollow fiber membranes, primarily because of the increased
membrane surface area and good structural strength. Figure 11 shows the
hollow fiber configuration.
Control Effectiveness
The control effectiveness for reverse osmosis units can vary consider-
ably depending on the feed characteristics, pretreatment, and desired con-
version. The conversion for a particular RO system is the percent of feed
recovered as product. For example, if a reverse osmosis unit was producing
7 gpm of pure water from a 10 gpm feed stream, the conversion would be 70
percent.
The control effectiveness is often reported as the percent rejection for
a particular contaminant, where the rejection is defined as the ratio of the
difference between the feed and product concentrations to the feed concentra-
tion (feed concentration-product concentration/feed concentration). A
rejection of 100 percent would signify complete contaminant removal.
At 70 percent conversion single stage reverse osmosis units have
typically demonstrated 90 to 98 percent rejection for dissolved solids.
Multiple stage RO units can be used to achieve even higher conversion and
better product quality. Reverse osmosis can also remove more than 95 percent
of most organics and all colloidal particles down to 0.05 microns (DI-149).
Table 13 presents typical rejections and concentrations of feed and product
streams for RO treatment of streams containing some metals. The data reveal
that heavy metal ions are removed at least 99 percent. Other tests indicate
that copper is also rejected at the same level (WI-316). The effectiveness
of zinc removal by RO is not nearly as conclusive. One source considers RO
an attractive system for zinc removal (SK-049), while another regards RO as
unsatisfactory (PA-120).
Energy Requirements
The major power consumer in a reverse osmosis unit is the pumps. For
100,000 gpd units and larger, the energy requirements are between 8 and 10
kWh/1000 gallons of water processed for one stage. If multiple stage reverse
osmosis processes are used, the energy requirements will increase almost
directly with the number of stages.
Economics
The economics of RO treatment systems are very site-specific and will
depend on feed stream characteristics, required pretreatment, desired product
conversion and quality, and ultimate disposal of the reject stream. Major
factors influencing capital cost are the feedwater rate and the number of
52
-------
REJECT
SNAP RING OUTLET
OPEN ENDS
OF FIBERS
EPOXY
TUBE SHEET
'0* RING SEAL
FEED
END PLATE
POROUS
BACK UP DISC
SNAP RING
FIBER
SHELL
POROUS FEED
DISTRIBUTOR TUOC
END PLATE
PRODUCT
Figure 11. Cut away drawing of hollow fiber RO system.
Source: MA-392
-------
TABLE 13. TYPICAL REJECTIONS BY REVERSE OSMOSIS SYSTEMS1
Ui
Systems
SPIRAL WOUND3
Feed Water
Product
Rejection (%)*
TUBULAR
Feed Water
Product
Rejection (%)"*
HOLLOW FIBER
Feed Water
Product
Rejection (%)"*
pH
3.1
4.4
— — —
3.4
4.2
— — —
3.4
4.3
^^*""
Cond . 2
2070
17
99.2
1050
46
95.6
1020
32
96.9
Acidity
460
38
91.7
250
46
81.6
210
32
84.8
Ca
260
0.4
99.8
125
2.2
98.2
150
1.2
99.2
Mg
170
0.3
99.8
92
1.4
98.5
115
1.4
98.8
Total Fe
77
0.4
99.8
78
0.9
98.8
110
1.2
98.9
Fe II
64
0.3
99.8
61
1.0
98.4
71
0.8
98.9
Al
12
0.2
99.2
12
1.0
91.7
15
0.8
94.7
SO*
1340
0.9
99.9
660
4.4
99.3
940
4.6
99.5
Mn
43
0.5
98.8
14
0.3
97.8
14
0.1
99.1
units are mg/Jl except pH.
2Cond.-Specific conductance (micromhos/cm).
375 percent conversion.
"^Rejection • 100 (Feed concentration - Product concentration)/Feed concentration.
Source : WI-316
-------
stages employed. Operating costs will depend on a number of variables
including labor, power, maintenance, chemical pretreatment, and membrane
replacement costs. Table 14 presents some typical costs of water treatment
by reverse osmosis. Depending on system capacity, capital costs range from
$0.73 to $2.00 per gallon per day of capacity and operating costs may be
$0.66 to $2.18 per gallon treated. These costs were not specifically derived
from acid wastewater treatment data.
Secondary Process Emissions
Reverse osmosis is a unit operation that requires "integration with other
wastewater treatment processes. Not only must all feeds to an RO unit be
pretreated to some extent, but the reject stream, which contains concentrated
contaminants, must also be treated for proper disposal. The major waste
stream from a reverse osmosis unit is the reject brine stream. This stream
carries the majority of the dissolved solids brought into the process by the
feedstream. This reject brine stream can be a large volume waste stream
C\>25 percent of the original stream). Therefore, reverse osmosis cannot be
considered an end-of-pipe treatment. Reverse osmosis is an attractive means
of reducing the volume of a waste stream and concentrating contaminant
species in order to make other controls more effective and less expensive.
It is expected, however, that extensive pretreatment would be required before
smelter wastewaters could be treated by reverse osmosis thus eliminating any
cost effectiveness of this process.
EVAPORATION PONDS
Evaporation ponds use solar energy to evaporate water from plant waste
streams and thus, collect and concentrate dissolved solids and metals. No
water streams are taken from the ponds and therefore "zero-discharge" of
effluents from a plant is accomplished. The precipitated solids may be
allowed to remain on the bottom of the pond or be removed by periodic
dredging.
Evaporation ponds have been used throughout the chemical and electric
utility industry. Their application is limited primarily by land availa-
bility and cost, net annual evaporation rates, and stream flow rate.
Process Description
Evaporation ponds require a very simple arrangement for dealing with
acid wastewaters. The wastewater streams are pumped to the pond site and
discharged into a single pond or a series of ponds. The water evaporates and
dissolved solids in the waste streams as well as other pollutants are col-
lected and contained within the pond. The pond or ponds may be lined to
prevent seepage of the wastewater into underground water supplies.
The area required for a single evaporation pond which evaporates G
gallons per minute is given by the equation:
19 5 G
Area (acres) = —^— (6-23)
55
-------
TABLE 14. COST OF WATER TREATMENT BY REVERSE OSMOSIS
Ul
System Capacity1
Capital Cost (Installed)
Membrane Cost
Operating Costs ($/1000 gal)
Membrane Replacement2
Power (@ $0.02/kWh)
Labor (@ $10/hr)
Maintenance and Repairs
Chemicals and Filters
Wastewater3 Disposal
TOTAL OPERATING COST ($/1000 gal)
10,000 GPD
$20,000
2,200
0.25
0.34
1.28
0.15
0.12
0.04
$2.18
25,000 GPD
$39,900
5,500
0.25
0.27
0.51
0.12
0.10
0.04
$1.29
100,000 GPD
$91,000
22,000
0.25
0.18
0.14
0.10
0.08
0.04
$0.79
500,000 GPD
$365,000
110,000
0.25
0.17
0.07
0.08
0.05
0.04
$0.66
1Assumed Operating Schedule: 85% Service - 350 Days/Year.
2Assumed 125% Membrane Replacement every three years.
3At 80% Fractional Recovery and Water Cost of $53/Acre-Foot.
Source: MA-693
-------
where V is the effective net annual evaporation rate (inches/year). The
effective evaporation rate for a given location is calculated by subtracting
the yearly rainfall from the gross evaporation rate. The resulting number
which is based on pure water is the net evaporation rate. The contaminated
water in an evaporation pond, however, will not evaporate as fast as pure
water. This is due to the reduction in vapor pressure of the pond water
caused by the waters dissolved solids. The actual or effective evaporation
rate is less, therefore, than the net rate. The effective rate is in the
range of 50 to 70 percent of the net rate (FO-130). For geographical areas
with net annual evaporation rates less than 20 inches, evaporation ponds are
not economical because of resulting large land requirements.
Control Effectiveness
An evaporation pond will provide complete control of a waste stream
since no water is discharged from the pond. However, the possibility exists
that pond water may seep into the soil below the pond and reach underground
water supplies. Liners are installed in ponds to help prevent this, but
over a period of time these may occasionally crack or rupture allowing
seepage to occur.
Energy Requirements
The energy requirement for operating evaporation ponds comes solely from
the energy needed to pump the wastewater to the pond. This requirement will
vary significantly depending primarily upon the distance and height change
from the wastewater source in the plant to the pond. As an example, for a
layout where the wastewater is pumped 1000 feet on level ground, the energy
requirement is 0.5 kWh/1000 gallons of wastewater.
Economics
In Figures 12 and 13, capital and operating costs of evaporation ponds
are shown as a function of water rate to the pond with the effective net
evaporation rate as a parameter. The capital cost is based on a $2/cubic
yard figure for land moved to form a 4 foot high dike with a 27 foot base.
It is also assumed that the pond liner costs $0.25/ft2 and land costs $1000/
acre. The cost of excavation ranges from $2 to $6/cubic yard depending upon
the type of land to be excavated. Liner costs range from $0.20 to $0.40/ft2
depending upon the type and thickness of liner used. Land costs can range
anywhere from $200/acre to $10,000/acre or more. The operating costs are for
pumping and dike area maintenance.
As an example of the cost breakdown, consider a 150 gpm ash pond over-
flow rate for a utility located in a region where the effective net evapora-
tion rate is 30 inches/year. From Equation 6-23, the pond area required to
evaporate 150 gpm is 97.5 acres. The installed capital cost of this
evaporation pond (1977 dollars) is:
57
-------
100
at
i 10
SYSTEM CAPACITY (MILLION GALS/DAY)
100
EFFECTIVE NET EVAPORATION RATE (/YEAR).
I 60 INCHES
II 30 INCHES
III 20 INCHES
Figure 12. Capital costs for evaporation ponds.
58
-------
10-
I
0)
8
1-
o
Q
III
0.01-
0.1
1 10
SYSTEM CAPACITY (MILLION GALS/DAY)
100
I 60 INCHES
EFFECTIVE NET EVAPORATION RATE (/YEARJ' II 30 INCHES
III 20 INCHES
Figure 13. Evaporation pond operating costs.
59
-------
Land Cost ($l,000/acre) $ 100,000
Excavation and building dikes $ 45,000
3-inch thick asphalt liner $1,060,000
Pumps and lines (installed) $ 10,000
TOTAL INSTALLED COSTS $1,215,000
The 3-inch thick asphalt liner costs approximately $0.25/ft2 (FO-130). If
the land is not easily excavated, the cost will significantly increase. The
operating costs are estimated to be $0.25/1000 gallons treated assuming that
the solids can be allowed to accumulate on the bottom of the pond.
Secondary Emissions
For ponds designed to contain the precipitated solids, the only poten-
tial secondary emission would be pond seepage. Proper choice and installa-
tion of a liner should help eliminate or significantly reduce this potential.
For ponds which are periodically dredged, the settled and precipitated solids
removed would be a secondary emission requiring proper disposal.
OTHER TREATMENT TECHNOLOGIES
There are treatment technologies available other than the ones described
previously which can also treat acid wastewaters for metal removal. These
include activated carbon, ferrite coprecipitation, starch complexing, and
sodium borohydride reduction. However, because of limited information and
applicability, only a brief discussion of each is presented.
Activated Carbon
Activated carbon adsorption has long been a widely accepted method for
the removal of organic contaminants from water and wastewater. The overall
flexibility of the carbon adsorption process has resulted in its application
in a wide variety of situations from oil refining to municipal wastewater
treatment. Recently the use of carbon adsorption for trace metals removal
has received more attention.
For organics the principal removal mechanism is physical adsorption onto
the activated carbon. For heavy metals, however, adsorption is only one of
several mechanisms which are thought to contribute to the system's removal
abilities. Other possible mechanisms include precipitation, ion exchange,
filtration or entrapment, and either reduction to metal or oxidation to
insoluble forms. In some instances specially modified carbons, which take
advantage of these other mechanisms, have been investigated with some success.
In true physical adsorption, the dissolved adsorbate (organic or metal)
is attracted to the interior surface of the carbon where a dynamic equilib-
rium is established between a concentrated surface layer and the more dilute
solution. Surface adsorption is usually not very uniform. Those surface
sites which have unsatisfied valence bonds or surface charges will be the
most "active" and adsorption at these sites will be the strongest. Although
60
-------
all portions of the surface, amounting to as much as 1200 m2/g (5.86 x 106
ft /lb), are potential adsorption sites, many sites may be excluded if they
lie within pores that are too small to accommodate extremely large adsorbate
molecules (SM-190). Even so, true adsorption will occur most efficiently for
large molecules (until the point that the molecule becomes too large with
respect to pore size) with a minimum of surface charges and low solubility
(SM-190).
Activated carbon can also remove metal contaminants by precipitation.
For example, if a contaminant of very low solubility is present, the addition
of activated carbon may cause the solution to become supersaturated (SM-190).
The carbon provides a site for nucleation and a precipitate forms on the
surface until the supersaturation condition no longer exists. Precipitation
does not preclude additional contaminant removal by adsorption, but precipi-
tation may clog pores and consequently reduce potential adsorption capacity.
Activated carbon possesses little ability to remove metals by ion
exchange. Activated carbon will contain some functional oxygen-containing
groups such as phenols, carboxyls, ethers, peroxides, lactones, and hydroxyls.
The amounts and surface distribution of these groups will depend on the
history of the adsorbent. In addition to the oxygen-containing groups, other
groups containing sulfur and nitrogen may also be present. Typically these
groups are cation acceptors and various metal cations will displace each
other in a fashion consistent with ion exchange resins. For the most part,
these randomly dispersed functional groups are fast acting and capable of
removing the simple metal ions in the 1, 2, or 3+ valence states (SM-190).
Depending on the initial method of preparation, activated carbon will
contain a variety of impurities which cause the carbon surface to act as an
active catalyst for both reduction and oxidation. If the carbon has surface
impurities of elemental iron, ferrous salts, and ferrous sulfides, then metal
ions such as gold, silver, and mercury may be reduced to their elemental
form. Similarly, a ferrous iron will quickly oxidize in the presence of
dissolved oxygen to a ferric ion, which readily precipitates as Fe(OH)s
when the pH is greater than 4 (SM-190).
Typical granular carbon adsorption systems consist of carbon bed contact
equipment, any necessary pretreatment facilities, and carbon regeneration
equipment, if economically practical. Pretreatment equipment is needed if
excessive quantities of suspended solids, oil, or grease are present. If not
removed, these constituents may filter out on the carbon and increase the
pressure drop. Commonly used pretreatments are chemical clarification, oil
flotation, filtration, and removal.
Following pretreatment, the wastewater stream is contacted with the
activated carbon beds. Several different bed configurations are in use, but
the most common arrangements are fixed beds in series or parallel, moving
beds, or expanded upflow beds. For fixed beds in series, the flow is down-
ward through adsorbers connected in series. For fixed beds in parallel,
the flow is also downward through a parallel train of beds. Operation of the
individual trains is staggered, so that exhaustion of the beds occurs sequen-
tially. In moving beds, wastewater flows upward through the bed while
61
-------
portions of exhausted carbon are removed from the bottom of the unit and
fresh carbon is added at the top. This design is very useful for systems
requiring large amounts of carbon and countercurrent efficiency. In upflow
operations, packed beds are expanded approximately 10 percent of their normal
volume by flow (RI-152). This expansion allows the passage of suspended
solids without an excessive pressure drop. The beds may be operated in
parallel or series.
Following exhaustion, granular carbon must either be properly disposed
of or reactivated. Landfilling is a very common disposal practice. The
exhausted carbon is removed from the adsorber, drained of all liquids, and
then dumped into a pit. The major advantage is the absence of reactivation
equipment and the costs associated with such equipment. The major dis-
advantages are the increased operating costs resulting from the continuous
purchase of replacement carbon and the possible environmental hazard of
contaminant leaching following disposal.
Reactivation of spent carbon can be done either on-site or off-site.
On-site reactivation is usually considered economically advantageous if the
regeneration requirements exceed two hundred pounds of carbon per day
(CO-098). For carbon exhausted by adsorption of organics, reactivation can
be accomplished by partial thermal oxidation of the carbon in either
multiple-hearth furnaces or rotary kilns at temperatures of 816 to 982°C
(1500 to 1800°F). Due to attrition, about 5 to 10 percent of the carbon sent
to reactivation is lost. If the spent carbon contains mostly adsorbed metals,
reactivation can also be readily accomplished by acid wash (SM-190). No data
is available to document the possible loss of metals by volatilization during
this step.
Treatment of wastewater streams by activated carbon for metals removal
has received serious consideration only in the last decade. Metals removal
is more likely to occur by any of the .mechanisms previously described other
than true adsorption. For this reason the efficiency of an activated carbon
system designed for metals removal will depend heavily on the overall com-
position of the feed stream and, subsequently, will be very site-specific.
Recent studies have attempted to qualitatively evaluate the potential for
metals removal by activated carbon. The results of these studies indicate
that at least five metals (antimony, arsenic, bismuth, hexavalent chromium,
and tin) show a high removal potential, while another four metals (silver,
mercury, cobalt, and zirconium) display a good removal potential. A few
other metals (lead, nickel, titanium, vanadium, and iron) show some removal
potential. Several other metals (copper, cadmium, zinc, beryllium, barium,
selenium, molybdenum, manganese, and tungsten) possess little or unknown
removal potential (SI-A-192). These qualitative ratings do not necessarily
imply that carbon adsorption cannot be successfully employed under specific
circumstances. For example, a mining company has developed a process for
concentrating and purifying molybdenum based on the adsorption of molybdenum
blue (SM-190).
62
-------
Ferrite Coprecipitation
The removal of heavy metals from acidic wastewaters by ferrite
coprecipitation was developed in Japan (OK-024). The process, which produces
a marketable residual, was originally developed for preparing high quality
magnetic materials for industrial use. However, with increasing concern
about removing heavy metals from wastewater, the ferrite coprecipitation
process is now being considered as a possible heavy metal control technology.
The objective of ferrite coprecipitation is to convert the soluble metal
ions in solution to insoluble magnetic oxides or ferrites which can be
removed either magnetically or through tertiary filtration. This objective
is accomplished basically by the addition of a ferrous salt, neutralization,
and oxidation.
In the process, the heavy metal bearing wastewater is mixed with a
divalent ferrous salt, usually ferrous sulfate (FeSO^*7HaO). This ferrous
salt is widely available and results as a waste product during the production
of steel or titanium dioxide. The divalent iron ion (Fe*"1") will coexist with
the nonferrous metal ion in solution. Alkali is added to neutralize the
acidic solution and a dark green hydroxide is formed as shown by the reaction:
XM++ + Ve+*f3-x) + 6(OH)~ -»• MxFe(3_x)(°H)6 (6-24)
x = 1, 2, 3
Oxidation with air may follow during which redissolution and complex formation
occurs yielding a black ferrite as shown from the reaction:
M Fe,, ,(OH)S + ^0 -> M Fe,, .Oi* + 3H20 (6-25)
X \-J—X/ X \j—X^
Precipitates produced from this process are ferromagnetic and have relatively
large particle sizes. Consequently, they can be removed effectively from
solution either magnetically or through filtration (OK-024).
The relatively stable sludges produced from the process can be safely
disposed of by landfilling or, alternatively, can be reused as a ferrite-
ferromagnetic material. Ferrite precipitates do not have a tendency to
redissolve and, consequently, potential leaching of heavy metals, if placed
in a landfill, is minimized.
Ferrite coprecipitation performance data have been reported from two
installations currently in operation in Japan. One installation is a test
facility which uses a batch process to treat approximatley 1 m3/hr (4.5 gpm)
of wastewater at a laboratory in Kawasaki. Performance data reported for
this test facility are provided in Table 15.
63
-------
TABLE 15. PERFORMANCE DATA FROM A FERRITE COPRECIPITATION
TEST FACILITY (Concentration, mg/Jl)
Metal Influent Effluent
Mercury
Cadmium
Copper
Zinc
Chromium
Nickel
Manganese
Iron
Bismuth
Lead
7.4
240
10
18
10
1,000
12
600
240
475
0.001
0.008
0.010
0.016
>0.010
0.200
0.007
0.06
0.100
0.010
Source: OK-024
It can be observed that greater than 99 percent removal was achieved for all
metal concentrations reported.
Another installation uses the ferrite coprecipitation process to treat
approximately 4.5 m3/hr (20 gpm) of off-gas scrubber liquor from a municipal
refuse incinerator in Osaka. Performance data from these facilities are
reported in Table 16. These data also show that very high removal efficien-
cies are achieved and that very low residual levels for most metals are
attainable (OK-024).
Laboratory research is also being conducted in the United States by
Industrial Filter and a pump manufacturing company. They report that ferrite
coprecipitation is an effective process for the removal of heavy metals but
no performance data have yet been released.
The major problem associated with ferrite coprecipitation reported to
date is that it is more labor intensive than the more commonly used precipi-
tation processes.
64
-------
TABLE 16. PERFORMANCE OF FERRITE COPRECIPITATION
IN OSAKA UNIT (Concentration, mg/fc)
Metal Influent Effluent
Mercury
Arsenic
Trivalent Chromium
Hexavalent Chromium
Lead
Cadmium
Iron
Zinc
Copper
Manganese
6
0.7
25
0.5
480
15
3,500
650
23
60
0.005
<0.01
0.01
not detectable
0.05
<0.01
0.04
0.5
0.08
0.5
Source: OK-024
Starch Complexing
Heavy metals can be removed from contaminated wastewaters by forming
complex ions with insoluble modified starches. Xanthated starch currently
appears to be the most promising for application on a commercial scale but
other modified non-xanthate starches are being tested.
Xanthates can be synthesized by reacting an epichlorohydrin cross linked
starch with carbon disulfide (CSa) in the presence of sodium hydroxide (NaOH).
The insoluble starch xanthate will react with soluble heavy metals in the
presence of cationic polymers to form a complex salt. Heavy metals are re-
moved as the product sludge is separated from solution (WI-316).
Two methods have been prepared for applying this technology on a com-
mercial scale. One method suggests mixing the starch xanthate and polymer
with the contaminated influent in a reaction tank and pumping the solution
to pressure filters where the complexed metals are separated. Sludge con-
taining the complexed metals is removed by filter backwashing. Another method
recommends precoating a tertiary filter with the starch xanthate. As the
wastewater passes through the filter, the soluble heavy metals will form
complex ions and precipitate in the modified filter (ZI-A-034).
Performance data for facilities using starch xanthate is relatively
scarce. However, a pump manufacturing company has conducted laboratory
studies in a pilot plant used to polish treated effluent from a metal fin-
ishing facility. Typical results reported from their investigation for re-
moving copper, lead, and mercury are presented in Table 17.
65
-------
TABLE 17. TYPICAL PERFORMANCE DATA
USING STARCH XANTHATE
Metal
Copper
Lead
Mercury
Concentration.
, mg/£
Influent Effluent
31.7
10.3
100.0
0.020
0.025
0.003
Source: ZI-037
It can be observed that very low effluent concentrations are attainable and
that starch xanthate appears to be especially effective for removing of
mercury.
The U.S. Department of Agriculture has also conducted studies on the use
of starch xanthate at the Agricultural Research Service (FL-S-092). The re-
sults of their studies are shown in Table 18. These results were obtained by
reacting the contaminated wastewater with the approximate stoichiometric
quantities of reagent. These results also indicate that very high removal
efficiencies are attainable.
TABLE 18. HEAVY METAL REMOVAL EFFICIENCIES USING
STARCH XANTHATE AS DETERMINED BY USDA
Concentration, mg/&
Metal
Copper
Nickel
Cadmium
Lead
Trivalent Chromium
Silver
Zinc
Iron
Manganese
Mercury
Influent
31.8
29.4
56.2
103.6
26.0
53.9
32.7
27.9
27.5
100.0
Effluent
0.007
0.019
0.009
0.025
0.003
0.245
0.046
not detectable
1.630
0.004
Source: WI-309
66
-------
Modified nonxanthate starches are also being investigated for possible
use in heavy metal removal. These starches are reported to have approxi-
mately one-half the removal capacity of xanthated starches and cost approxi-
mately one-half as much. Consequently, approximately twice the sludge volume
can be anticipated for equivalent removal efficiencies (ZI-034). This occurs
because the unreacted nonxanthate starch precipitates along with the portion
reacting with the metal ions.
Disposal of process residuals or sludges is a major problem associated
with the starch xanthate process. Laboratory test results indicate that
heavy metal removal capacity is approximately 0.0011 moles per gram of starch
(ZI-034). Consequently, relatively large sludge volumes will be produced for
the quantity of heavy metals removed. Conventional land disposal does not
appear to be an environmentally acceptable alternative because the organic
structure of the starch xanthate-metal sludge can decompose rapidly and
release the metal to the environment. Incineration is being considered for
possible metal recovery but off-gas scrubbing facilities would be necessary
to insure that heavy metals are not emitted to the atmosphere. Additional
costs associated with these stack gas control facilities may be prohibitive.
Also, the heavy metals collected in the scrubber liquor would again have to
be removed before the liquor could be reused or discharged to a receiving
stream.
Several possibilities for recovering heavy metals for their commercial
value have also been investigated. The starch xanthate-metal complex can be
broken with either acid or heat treatment. However, the development of this
technology is still in the initial stages and little information is available
for an adequate assessment. Charging the process residuals to a smelter fur-
nace for enhanced metal recovery has also been considered, but economics will
be difficult to justify because of the relatively large ratio of sludge volume
to metal contents.
The application of the starch xanthate process is most promising if con-
sidered as a polishing technology following a more conventional process
rather than a substitute treatment alternative. Sludge quantities can be
considerably reduced thereby minimizing the ultimate disposal problem. How-
ever, other associated problems must also be considered. Starch xanthates
lose their removal effectiveness when cyanides are present. Consequently,
the process is severely limited if cyanides are not previously removed.
Additionally, insoluble starch xanthates lose their complexing capacity
rather rapidly and on-site manufacturing is recommended. Caution must be
taken when handling the poisonous carbon disulfide used to synthesize the
xanthates at the treatment facility.
Sodium Borohydride
Sodium borohydride (NaBHi*) is a mild but highly effective reducing
agent. In practice this water soluble reagent can be added to contaminated
wastewaters to reduce heavy metal ions to their neutral state for removal
and/or recovery by filtration.
67
-------
Aqueous borohydride reductions of metals in solution generally proceed
by the intermediate formation of a metal hydride or borohydride which is un-
stable in water and decomposes to produce the free metal. The basic treat-
ment processes for sodium borohydride reduction are similar to chemical
precipitation. Treatment includes pH adjustment, sodium borohydrid.e addition
for reduction and precipitation, and clarification and/or filtration for
solids-liquids separation. The treated effluent may require additional
polishing which can be accomplished with a carbonaceous absorbent or suitable
chelate or exchange resin (JU-A-043) . The sludge that is produced consists
mainly of elemental metals and expensive sludge handling facilities and
ultimate disposal problems can possibly be avoided. However, if multimetal
ions are present and recovery is desirable, metals separation will be
necessary.
The reducing strength of sodium borohydride is greatest under strongly
basic conditions but the kinetic rate of reduction is accelerated as the pH
decreases. This phenomenon suggests that an optimum pH for a specific re-
action exists. Basic solutions of sodium borohydride are generally quite
stable and pH conditions below 8.0 are conducive to borohydride decomposition
resulting in excessive consumption of borohydride and liberation of an
explosive hydrogen gas as shown from the reaction:
+ 4H20 £ B(OH)^ + 4Ht (6-26)
At high pH conditions the rate of reduction decreases the process efficiency.
Consequently, a pH range of 8.5 to 9.0 is generally desirable and additional
safety precautions, including adequate ventilation and elimination of poten-
tial ignition sources should be maintained (ZI-A-034, VE-073) .
Sodium borohydride is relatively expensive, costing approximately $15
per pound, and should only be used with highly efficient mass transfer or
mixing facilities to insure optimization of the borohydride-metal reactions.
Applications should be limited to wastewaters containing small or trace
levels of metallic ions. Additionally, sodium borohydride should only be
considered for use in either batch processes or in continuous processes where
a constant influent metal content is maintained (ZI-A-034) .
In batch processes, the calculated quantity of sodium borohydride is
generally added in small portions after neutralization. An excess of boro-
hydride is usually desirable not only to insure rapid and complete reduction
but also to maintain a strong reducing environment preventing re-dissolution
of the metal by dissolved oxygen or complex formation. A reaction time of
at least five minutes is usually necessary (JU-A-043) .
Sodium borohydride is currently being used on a commercial scale to
recover silver from photographic fixing solutions by reducing the silver-
thiosulfate complex to elemental silver. Although the cost of the reagent
is relatively high, process operating costs are somewhat minimized owing to
the stoichiometric ratios of 1 to 8 as shown from the reaction:
8Ag+ + BH^" + 2H20 t 8Ag4- + BOl + 8H+ (6-28)
68
-------
From this reaction it can be calculated that one pound of borohydride ion
will remove 22 pounds of silver (VE-073).
Sodium borohydride is also being used successfully to recover mercury
compounds from wastewaters emanating from chlor/alkali plants. The soluble
inorganic mercury compounds are reduced at a pH of 9.0 and are removed by
filtration. In this application, one pound of sodium borohydride can theo-
retically remove in excess of 21 pounds of mercury based on the following
reaction:
AHg44" + BH^ + 80H~ t 4Hg4- + B(OH)^ + 4H20 (6-28)
Mercury which appears in the organic form must first be released through
oxidation before borohydride treatment will be effective (VE-073).
Sodium borohydride is also effective for the removal and recovery of
dissolved lead compounds, including lead salts from wastewaters generated
from the manufacture of tetra-alkyl lead compounds. In this application,
both inorganic and organic lead is reduced to the elemental form in one step
(VE-073) .
Little performance data for actual sodium borohydride treatment facili-
ties have been reported and dosage rates and anticipated removal efficiencies
are not presented. However, a mercury level as low as 0.01 mg/£ has been
reported for wastewater treatment at chlor-alkali plants. In general,
sodium borohydride is reported to be effective for the removal and/or
recovery of cadmium, mercury, lead, silver, and gold (VE-073). Capital costs
of $667/1,000 gallons per day and operating costs between 6.7 and 26.7 cents
per 1,000 gallons have been reported (PA-322).
69
-------
SECTION 7
SOURCES OF EFFLUENTS CONTAINING METAL IN THE NONFERROUS METALS INDUSTRY
INTRODUCTION
This section identifies the sources of acidic wastewater in the primary
and secondary copper, lead, and zinc segments of the nonferrous metals indus-
try. For the primary industry, wastewater sources can be divided into the
following four categories:
• Mining
• Concentrating
Smelting
• Refining
The mining and concentrating categories account for the largest quantity of
wastewater at any particular smelting facility (69 to 90 percent) but the
concentration of any particular metal ion is relatively low (typically <1
mg/£). Smelter and refinery wastewaters, however, are relatively low volume
and may have metal ion concentrations ranging from <1 to 1000 mg/£.
Smelter/refinery wastewater can be further classified into contact and
non-contact water. Gas scrubbing water and washwater are typical contact
wastewaters. These contain high concentrations of metal ions (1 to 1000 mg/
£). Mold cooling water or water jacket cooling water are typical noncontact
wastewaters and normally contain less than 1 mg/£ of any particular contami-
nant.
For the secondary industry, wastewater sources can be divided into the
following three categories:
• Scrap pretreatment
Smelting
Refining
The wastewaters from these categories are sometimes difficult to identify
separately because of the close proximity of each type of process within a
particular smelter. In addition, washwater and leaks or spills are likely
to contribute a larger percentage of the total effluent than in the primary
70
-------
metals industry. As in the primary smelting/refining category, wastewater
can be classified as either contact or non-contact with the same relative
difference in metal ion concentrations.
In this section, brief industry descriptions are presented for each
primary and secondary industry. The sources of wastewater in each industry
are then identified and the data available on each wastewater are summarized.
No attempt has been made to separate wastewater generated by washdowns or
general housekeeping from the process wastewater reported in the literature.
PRIMARY COPPER INDUSTRY
Industry Description - Primary Copper
Copper is produced primarily from sulfide ores which typically contain
0.6 to 1.5 percent copper. Raw ore is concentrated in a series of crushing,
grinding, classifying, and flotation steps to produce a concentrate which
normally contains 15 to 30 percent copper. This concentrate may be prepared
for smelting by drying or roasting or it may be charged directly to a smelt-
ing furnace.
Mining of low grade porphyry (fine-grained, dark red or purplish igneous
rock) copper is done primarily in large open pit mines. Drilling, blasting,
loading, and hauling operations take place before the ore is transported to
the beneficiation processes. In general, mining operations account for ap-
proximately 25 percent of the cost of copper manufacture.
Ore bodies normally lie under an overburden of country rock. The over-
burden may be dumped as waste, used for road construction, or leached to ex-
tract the very low grade of copper (0.1 to 0.4 percent) it contains. Leaching
involves the slow oxidation of copper sulfide salts in the presence of water
followed by precipitation on iron scrap. The precipitated copper is de-
watered and recovered as a slurry or pulp that is referred to as cement cop-
per. Cement copper ranges from 70 to 90 percent copper and can be used as a
smelter feed. Not all mines leach their waste rock.
The concentration phase of copper production is necessary because of the
low copper content of a typical ore (0.6 to 1.5 percent copper). Production
of 300 tons per day of blister copper from a moderate size smelter involves
concentrating over 4200 tons of ore per day. Crushing, grinding, classify-
ing, and ore flotation steps are used to obtain a concentrate containing 15
to 30 percent copper. Roughly 97 percent of the ore is normally discarded
as waste rock in tailings ponds near the concentrator site. The concentrate
is filtered and thickened before being sent to the smelter.
There are 16 primary copper smelters operating in the United States at
present. Twelve of these smelters are operated by companies which produce
their own smelters which purchase and blend concentrates prior to processing
them at the smelter. There are eleven copper refineries operating in the
United States at present.
71
-------
Wastewater Source Identification - Primary Copper
Mining, concentration, smelting, and refining of copper in the United
States are accomplished in steps which have become standard in the past 50 to
70 years. Table 19 lists each of the processes for which effluent streams
have been identified and summarizes the available data on the characteristics
of these process specific wastewaters. The following discussion describes
the sources of these wastewaters in more detail.
Mining—
Mining methods are determined by the size, depth, and configuration of
the ore body. Both open-pit and underground copper mines are currently
operating in the United States. Wastewater from copper mining comes from
seepage or runoff from the mine or spoil dumps, and from the water sent into
the mine for utility uses. The wastewater from open-pit copper mines ranges
from zero to 0.3 cubic meter of water per metric ton of ore mined. From
underground mines, the amount ranges from 0.008 to 4.0 cubic meter per metric
ton of ore. Chemical characteristics are typical of those from any sulfide
mine, as given in Table 20.
Spoil is waste rock moved during the mining process as overburden, in
the construction of shafts and tunnels, or as low grade inclusions found
within the ore body. It is disposed of near the mine workings. The spoil
generally contains appreciable amounts of sulfide minerals. These spoils
are placed where they are also exposed to rainfall, seepage, and surface run-
off.
In mining the main body of the ore, stockpiles of ores are frequently
placed either near the mine or near the mill, or both, in order to avoid
having to synchronize operations of these two processes. The stockpiles are
also exposed to the weather, and in some cases are purposely hosed down to
minimize blowing dust.
All of the large open-pit mines are in regions of deficient rainfall,
and some are in desert areas. Natural evaporation within the pit greatly
reduces the volume of wastes that must be pumped out, and seepage from spoil
dumps rarely enters a stream. The water that accumulates is in many cases
disposed of merely by pumping it onto a nearby flat area, where it either
seeps into the alkaline soil or evaporates.
Ore Concentrating—
Concentrating consists of crushing and grinding the ore to a fine
powder, and then separating the minerals by froth flotation. In milling, the
ore is sent through crushers and then through fine grinders. Between each
stage, it is classified (screened), and the final milled product is a mix-
ture of particles between 65 and 200 mesh.
Flotation is the step where the copper-containing particles are actually
separated from the gangue or country rock. In this process, the finely
ground ore is introduced into a series of flotation cells which are sparged
72
-------
TABLE 19. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES - PRIMARY COPPER
Source Flow (i/nin)
Primary Copper Industry
Mining
- Mine wastewater
• underground mine 3815 m /day
• open-pit mine 409 m'/day
Concentrating
Ore flotation water 100-500 ra3/
m ton concen-
trate
NOTE: P - present, but levels not quantified.
Stream Composition (ae/ft)
pH
Cu
Se
As
Zn
Sb
Fe
Mn
Cd
Hi
Mo
Hg
Pb
As
Sb
Cd
Cu
Co
Fe
Mn
Hg
Mo
Ni
Pb
Ag
Se
Zn
CN"
Underground
7.37
0.87
<0.077
<0.07
2.8
<0.5
<0.1
2.22
<0.02
. <0.05
<0.5
<0.0001
<0.1
Open-Pit
6.96
1.05
0.096
<0.01
0.1
<0.5
<0.1
0.9
<0.03
<0.05
<0.2
<0.0001
<0.5
M).07
0.2 -1.0
0.02 -0.05
0.08 -very high
0.04 -1.68
0.1 -2.0
0.05 -4.
0.001-0.
8
05
Ref . Comments
PE-274 Major potential source
of water pollution from
this industry. Impact
somewhat lessened by
location of most mines in
arid regions.
x
PE-274 Largest source of waste-
water in the industry.
Used to sluice tailings
to pond. Partial reuse
of pond water.
0.2 -20
0.05 -3
0.01 -3
M).l
0.003-0.
0.05 -8.
0.01 -0.
02
50
1
(Continued)
-------
TABLE 19 (Continued)
Source Flow (I/Bin)
Primary Copper Industry (Cont'd)
Slag Flotation
- Run-off from slag
granulation
Contact Sulfurlc Acid Plant
Off-gas scrubber liquor .147-10.1x
(I.e., acid plant 10* fc/day
blowdown)
NOTE: P- present, but levels not quantified.
Stream Composition (•«/(.)
pH
CN~
Ka
Cd
Cu
Fe
Pb
Hg
Nl
Se
Zn
Plant 103
7.7
0.005
3.7
0.001
0.12
0.04
0.04
0.0001
0.001
0.001
0.44
PH
cir
As
Cd
Cu
Fe
Pb
Hg
Ni
Se
Zn
Plant 110 Plant 120
8.1 6.
0.050
0.048
0.001
0.05
0.03
0.070
0.0001
0.06
0.54
0.023
Range for 3 Plants
fkf/n. ton)
4-7.6
0.030
5.70
0.042
0.604
340
7.4
0.0001
0.16
0.040
36
1.8 -2.5 pH units
0 -0.0024
0.004 -0.129
0.0002-0.0276
0.0001-[188.2]
0.0014-0.1116
0.0051-0.2501
0 -0.0002
0 -0.0030
0 -0.0268
0.0017-0.436
Ref. Comments
PE-274
Quantity and compo-
sition Is highly
variable.
PE-274 Essentially a weak
HzSOu solution that can-
not be marketed. This
stream frequently combim
with other plant efflu-
ents for treatment or
recycle.
(Continued)
-------
Ui
TABLE 19 (Continued)
Source
Flov (f/mln)
Stream Composition (M/l)
Ref.
Comments
Primary Copper Industry (Cont'd)
DMA SOz Sorption
- Off-gas scrubber liquor
- Purge stream from DMA
unit
18 kg/m ton
SOz prod.
Similar to Contact Sulfuric Acid Plant
Typical composition:
4.5 percent TDS
25 mg/i DMA
18 mg/1 suspended solids
pH 5.8
PE-274
PE-274
Arsenic Recovery
- Arsenic plant wash-
down water
Anode Refining and Anode Casting
- Anode cooling water 950,000 i/day
NOTE: P - present, but levels not quantified.
As
Cu
Zn
Pb
Cd
Hg
Se
Hi
Fe
C1T
pH
Cl~
Al
As
Cu
Zn
310.0
88.4
37.0
7.7
1.05
0.0003
0.04
0.75
9.4
0.01
3.8-4.4
Net Change, mg/t*
8.7
0.12
0.01
8.53
0.25
PE-274 Plant Is washed down
on a daily basis .
Water is mixed with
another waste and dis-
charged to a pond.
*Water used for cooling
is generally a recycle
stream from some other
process step.
(Continued)
-------
TABLE 19 (Continued)
Source Flow (l/mln)
Primary Copper Industry (Cont'd)
Electrolytic Refining
- Spent HzSOii electrolyte
Stream
Cu
As
Sb
Bi
Ni
Composition (mg/i)
45,000-50,000
500-12,000
200-700
100-500
2,000-20,000
Ref. Comments
PE-274 Some refineries reclaim
EN-392 the Cu values from this
stream; however, In other
cases this stream consti-
tutes a significant
waste effluent.
Electrolyte Purification
- Electrolyte acid purge
or "black acid"
- Evaporated water from
the electrolyte
Melting and Casting Cathode
Copper
- Cooling water for cast 320,000 ft/day
shapes in one case
As
Sb
Bl
Parameter
PH
As
Cd
Cu
Fe
Pb
Kg
Se
Zn
Plant X
Inlet
water
7.6
0.001
0.001
0.30
0.02
0.007
0.00350
0.001
0.001
Wlrebar
cooling
7-8
0.001
0.001
0.69
0.13
0.007
0.00425
0.001
0.067
Semlcontin-
uous cake
casting
8.0
0.001
0.001
0.18
0.04
0.003
0.0001
0.001
0.001
Plant Y
Inlet
water
7.1-7.6
0.001
0.0008
0.021
1.2
0.078
0.00004
0.040
0.35
Wirebar
cooling
recycle
8.0-8.4
0.001
0.0021
3.5
1.7
0.068
0.00004
0.040
0.88
PE-274
PE-274
Usually mixed with steam
condenaate and direct
cooling water in baro-
metric leg discharge
devices .
NOTE: P - present, but levels not quantified.
(Continued)
-------
TABLE 19 (Continued)
Source
Primary Copper Industry
Flow (t/«in) Stream Composition (•*/«,)
(Cont'd)
Do re Metal Separation
- Electrolyte acids Few gallons
Intermittently
Heap and Vat Leaching
- Spent leaching stream 350,000- Fe very high
1,000,000 t/
m ton Cu produced
Ref. Comments
PE-274 This represents a rela-
tively insignificant
waste stream.
PE-274
Solvent Extraction
- Bleed stream from con-
centrated acid used to
complex Cu from extractant
Electrowinning
- Water from cathode cleaning
Arbiter Precipitation
- Filtrate from precipitation
- Filter backwash
Arbiter Decomposition
- Filtrate
NOTE: P - present, but levels not quantified.
Fe P
As P
Zn P
Ammonium sulfate solution containing
unprecipltated Cu.
Ammonium sulfate solution.
PE-274
PE-274
PE-274
PE-274 Slurry
PE-274 Similar to stream from
Arbiter precipitation but
containing less Cu.
-------
TABLE 20. SAW WASTE LOAD IN WATER PUMPED FROM SELECTED COPPER MINES
CO
Undergr
Concentration Raw want
Parameter (mg/O
ound Mine Open-pit Mine
B load per unit ore mined Concentration Raw wan IP load per unit ore mined
(kg/1000 metric tons) (mg/fc) (kg/1000 metric tons)
Flow 3,815.3 m'/d«y 17.28 m'/lOOO metric tons 409 m'/day 75 m'/lOOO metric tons
pH 7.37a
TDS 29,250.0
TSS 69.0
Oil & Grease <1.0
TOO <4.5
COO 819.0
B 2.19
Cu 0.87
Co <0.04
Se <0.077
Te 0.60
Aa <0.07
Zn 2.8
Sb <0.5
Fe <0.1
Mn 2.22
Cd <0.02
Ni <0.05
Mo <0.5
Sr 119.0
Hg <0.0001
Pb <0.1
7.37" 6.96a 6.96"
5,053.9 1,350.0 101. 0
11.9 2.0 0.2
<0.173 7.0 0.5
<0.778 10.0 0.75
141.5 4.0 0.3
0.378 0.07 0.005
0.150 1.05 0.08
<0.007 <0.06 <0.005
<0.013 0.096 0.007
0.104 <0.2 <0.02
<0.012 <0.01 <0.0008
0.484 0.1 0.008
<0.086 <0.5 <0.04
<0.017 <0.1 <0.008
0.384 0.9 0.07
<0.003 <0.03 <0.002
<0.009 <0.05 <0.004
<0.086 <0.2 <0.02
20.6 0.8 0.06
<0. 00002 <0.0001 <0. 000008
<0.017 <0.5 <0.04
"value in pH units.
-------
with air after flotation agents are introduced. Flotation agents such as
pine oil or long chain alcohols are used to generate froth. Chemicals known
as "collectors" are also added which preferentially adsorb on the ore parti-
cle surfaces. This changes the properties of the ore particles so that they
attract bubbles preferentially over the gangue particles (or vice versa).
The ore concentrates in the interstitial liquid in the froth bubbles while
the gangue sinks and passes out of the cell as tailings.
This process is the largest source of wastewater in the industry. The
ore flotation water is used to sluice the tailings into a pond. Although
part of the water is recycled to the plant, the remainder is discarded. The
volume of wastewater from this process plus the amount lost by evaporation
will equal the water consumption, ranging from 100 to 500 cubic meters per
metric ton of concentrate. A continuous bleed of this milling and flotation
water is necessary. Reported analyses indicate that the water from the con-
centrator may contain up to 3500 mg/£ of dissolved solids, from 0.01 to 0.01
mg/£ of cyanides, and the following ranges of metallic elements (PE-274):
Element Concentration, mg/£
Arsenic 0.07 approximately
Antimony 0.2 to 1.0
Cadmium 0.02 to 0.05
Copper 0.08 to very high
Cobalt 0.04 to 1.68
Iron 0.1 to 2.0
Manganese 0.05 to 4.8
Mercury 0.001 to 0.05
Molybdenum 0.2 to 20
Nickel 0.05 to 3
Lead 0.01 to 3
Selenium 0.003 to 0.02
Silver 0.1 approximately
Strontium 0.03 to 2.5
Zinc 0.05 to 8.50
The water may also contain thiosulfates and thionates, and the materials,
both inorganic and organic, used as flotation additives.
Slag Flotation—
This process is similar to the ore concentration process. The feed
stream, however, is slag produced from either a smelting or converting
furnace rather than raw ore. The operating principle is the same in that
sulfide materials are recovered in the flotation froth and the waste material
sinks and is discarded as tailings.
79
-------
Slag produced in electric, flash, or continuous smelting furnaces or in
copper converters contains too much copper to be discarded. Consequently,
the slag must be treated either in a cleaning furnace or in a flotation mill.
The tapped slag is slow cooled, crushed, and sent to a concentrator.
Flotation produces a high copper content concentrate which is recycled to the
smelting furnace feed preparation area. An iron-rich tailings (0.5 weight
percent Cu) is discharged.
Water used for cooling and flotation is recycled until impurities build
up which reduce the flotation process efficiency. A bleed stream is then
removed and typically discharged to the ore concentration tailings pile. No
data is available on the characteristics of this effluent stream.
Contact Sulfuric Acid Plant—
For the most part, sulfuric acid is currently produced by the Contact
Process. In the Contact Process, sulfur dioxide is reacted with oxygen over
a vanadium pentoxide catalyst to form sulfur trioxide. The sulfur trioxide
then combines with water in an absorber where the product acid is formed.
Older contact acid plants operated at 95 to 97 percent sulfur dioxide conver-
sion efficiencies (WA-219). At these efficiencies, significant quantities of
sulfur dioxide were emitted to the atmosphere. This problem has been over-
come by modifying the Contact Process to create a Double Catalysis/Double
Absorption (DC/DA) Process. According to Browder (BR-283), if a DC/DA Process
is used to produce sulfuric acid, sulfur dioxide to acid conversion efficien-
cies ranging from 99.7 to 99.9 percent can be achieved. Thirteen of the cop-
per smelters in this country operate contact sulfuric acid plants to treat
all or part of the gases from the metallurgical operations.
A typical flow diagram of the Browder DC/DA Process is illustrated in
Figure 14. The feed gas to the process typically consists of 8.4 to 9.0
volume percent SOz and 8.6 to 9.2 volume percent 02 on a dry basis. Some
conditioning of the feed gas is usually performed prior to its entry into the
acid plant. Gas conditioning is normally accomplished in a series of two or
three towers.
A hollow tower with water spray for gas cooling and dust
removal.
• A packed tower with water spray for final temperature, humidity,
and dust control.
• A mist eliminator to precipitate entrained droplets.
The gas conditioning towers (which are not illustrated in Figure 14) act as a
buffer to changing gas stream conditions (water content, dust loading,
temperature, oxygen content). The blowdown from these towers is one potential
source of wastewater from a sulfuric acid plant.
The hollow tower cools the inlet gas to approximately 58°C (137°F) with
a water spray. Some particulate matter is scrubbed by the water spray, but
gas cooling is the major function of the tower.
80
-------
SULFUR
EXPORTED
POWER
00
AIR
EXCHANGER I CONVERTER
NO. 2
1 PRODUCT GAS
PUMP TANK
98% ACID PUMP
PUMP TANK
98Z ACID PUMP
70-1242-1
Figure 14. Typical flow diagram of Browder DC/DA process for a metallurgical plant
Source: PA-205
-------
The packed tower controls gas temperatures to meet the water balance for
the acid plant. Combustion gases containing large amounts of water may re-
quire refrigeration to remove enough water to allow strong acid to be pro-
duced. Typical gas outlet temperature is 40°C (104°F) from this tower at -10
to -14 inches Had pressure.
Humidified gas from the packed tower passes through a mist eliminator to
remove any sulfuric acid mist present in the gas. Acid mist may form from
S03 present in the gas reacting with water sprays upstream of the mist elimi-
nator. Mist eliminators can be lead-piped electrostatic precipitators or
simply a corrosion-resistant packing which removes the mist from the gas
stream. Following the gas-conditioning section, air is added to the gas
stream if insufficient oxygen is present for the catalytic reaction.
These gas conditioning columns create off-grade weak acid that cannot be
sold. The amount is estimated as 4 to 8 liters for each 10 cubic meters of
gas treated. Table 21 provides typical analyses for this acid plant blowdown.
Acid plant blowdown is sometimes mixed with other waters for treatment or re-
cycle. Table 22 lists the practices of the existing smelter acid plants. If
large volumes of strong acid must be neutralized, the only tested, economical
method of disposal is treatment with limestone, followed by more precise pH
adjustment with lime.
After passing through the gas conditioning towers, the feed gas enters a
drying tower. The dry gas then passes through a series of heat exchangers to
bring the gas temperature to 435°C (815°F). This hot gas then passes through
three catalyst beds with intermediate heat exchange.
After the third catalyst bed, the gas is fed to an absorber where the SO3
is absorbed in a circulating acid stream. The vapor is sent to a fourth cata-
lyst bed. The outlet gas from the last bed is routed to a second absorption
tower where the remainder of the SO3 is absorbed by circulating acid. After
the second absorption tower, the gas passes through a demister to remove any
entrained acid mist before being vented through a stack.
Sulfuric acid from the absorption towers flows to an acid pump tank
where it is diluted, if necessary, to maintain the required strength for ab-
sorption. The acid is then pumped through a series of coolers before it is
returned to the absorption towers. A stripping tower is used to remove dis-
solved sulfur dioxide from the acid fed to the final absorption tower. Pro-
duct acid is removed from the second stage absorption system through product
coolers before it is sent to storage.
DMA SO2 Absorption—
The DMA Absorption process scrubs SOa from a gas stream, then releases
the SOa as a concentrated stream. Waste gases are first cleaned of particu-
late matter and dried as described previously in this Section under Contact
Sulfuric Acid Plant. Next, most of the SOa is absorbed by dimethylaniline
(DMA) as the gases pass through a scrubber. The gases are then scrubbed with
sodium carbonate to remove the remaining S02, then with weak sulfuric acid to
reclaim the DMA in the gas stream. These three steps take place in a single
82
-------
TABLE 21. RAW WASTE CHARACTERIZATION: ACID PLANT SLOWDOWN
oo
u>
Parameter
PH
IDS
TSS
SOiT
CN-
As
Cd
Cu
Fe
Pb
Hg
Ni
Se
Te
Zn
Oil & Grease
Flow, 10s
Production
Flow/Prod
Units
PH
kg/metric ton
kg/metric ton
kg/metric ton
g/metric
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
kg/metric ton
Vday
metric ton/day
kg/metric ton
Plant 1
2.0-2.5
[0.99]a
0.0000
0.044
0.0002
0.0001
0.0014
0.0051
0.0000
0.0000
0.0001
0.0000
0.0017
0.0000
0.147
311. (62)
2,400.0
Plant 2
1.8
78.5
0.102
7.69
0.0000
0.129
0.0014
0.0018
0.0015
0.0142
0.0000
0.0000
0.0000
0.0000
0.215
—
4.16
528. (264)
15,800.0
Plant 3
2.0
410.0
3.74
64.0
0.0024
0.004
0.0276
[188.2]
0.1116
0.2501
0.0002
0.0030
0.0268
—
0.436
0.0
10.1
655. (393)
25,700.0
Average
2.0
244.0
1.92
36.0
0.0008
0.059
0.0097
0.0010
0.0382
0.0898
0.0001
0.0010
0.0090
0.0000
0.218
0.0
—
—
14,700.0
Bracketed values not used in averaging computation.
-------
TABLE 22. ACID PLANT SLOWDOWN CONTROL AND TREATMENT PRACTICES
Plant
Discharge
Control and/or treatment practice
4
5
6
7
8
9
10
11
0
0
0
0
0
3.4 Vsec
50-190 £/seca
Slowdown neutralized with ammonia and used
to precondition converter gases prior to hot
ESP. No discharge.
2/3 of blowdown to reverb brick flue spray
chamber for cooling reverb gases, other 1/3
used to precondition converter gases prior to
hot ESP. Any excess is solar evaporated on
slag dump. No discharge.
Blowdown from packed tower used in open tower
blowdown to clarifier. One-half recycled to
packed tower, other half to two-stage ammonia
neutralization facility. Then 2.2 £,/sec to
converter hot ESP for gas preconditioning and
0.6 Vsec to hot ESP for gas preconditioning
(joins 0.6 Vsec DMA purge). No discharge.
Blowdown to tailings pond. Pond water re-
circulated to mill concentrator. No discharge.
Blowdown from new scrubbers and mist precipi-
tators to recycle and tailings thickener
underflow. No discharge.
Blowdown used in mill concentrator circuit.
No discharge.
Blowdown to settling pond and either recycled
or wasted. No discharge.
Blowdown to acid ponds and reused in copper
precipitation leach facility. No discharge.
Blowdown currently used to blend fluid-bed
roaster feed. Anticipate closed circuit,
but will eventually send to proposed treat-
ment facility.
Blowdown to lime pond, then to tailings pond.
Eventual (8 km of ponds) discharge.
Blowdown to go to new treatment facility with
subsequent discharge.
Anticipated, practice under construction.
Source: PE-274
84
-------
scrubbing column. The gases are then released to a stack. The S02 is
desorbed from the DMA. with steam and recovered as dry, 100 percent sulfur
dioxide, which is compressed, cooled, and stored as a liquid while the DMA is
recovered for recycling.
Scrubbing the gas stream in a weak sulfuric acid column produces a liquid
waste blowdown stream similar to that from a sulfuric acid plant. Normally,
however, the same scrubber is used to treat gases that feed both the acid
plant and DMA plant. This stream could be neutralized and recycled as coolant
to a hot ESP unit, thus returning the metals content to metallurgical proces-
sing.
A liquid waste continuously purged from the DMA process consists of
water, sodium sulfite or bisulfite, and sodium sulfate. The quantity is about
18 kilograms per metric ton of S02 produced, when treating gas with 5 percent
SOa content (PE-274). The stream typically contains about 4.5 percent dis-
solved solids, 25 mg/£ DMA, and 18 mg/£ suspended solids, with a pH around
5.8 (PE-274).
This purge stream is the only waste of this character generated by the
primary copper industry. It is a clear stream with a. BOD and a> COD and is
quite concentrated with nonrecoverable minerals. Each of the three operating
DMA plants treat the purge stream differently. One adds it to the concentra-
tor circuit; one mixes it with the acid plant blowdown, which is in turn sent
to a hot ESP unit; the third uses activated carbon to absorb the DMA content,
then uses it as part of a fluid-bed wet feed blending, which returns it di-
rectly to the metallurgical processing.
Arsenic Recovery—
Most of the arsenic present in a copper ore concentrate will be volatized
in either the roasting or smelting processes. Some will escape into the at-
mosphere with the roaster or reverberatory furnace flue gas. Some arsenic
will appear in the dusts collected from the electrostatic precipitators and
other particulate removal equipment. One smelter with a high arsenic concen-
tration in their feed material treats those dusts to extract arsenic for sale.
Since demand for arsenic is small, this smelter satisfied most of the United
States demand. As a result, effluent streams for this process are specific
for only one site.
The collected dusts are charged to a Godfrey roaster and are heated until
the arsenic vaporizes. The vapors are condensed in chambers, and are then
resublimed and condensed to yield an arsenic trioxide product more than 99
percent pure. Arsenic metal is also produced by reacting arsenic trioxide
with carbon in a reducing atmosphere.
The washdown from this arsenic recovery plant is mixed with another
waste stream and is discharged to a pond. Table 23 indicates that up to a
kilogram of arsenic may enter the pond each day from this source.
85
-------
TABLE 23. ANALYSIS OF ARSENIC PLANT WASHDOWN WATER
Parameter
As
Cu
Zn
Pb
Cd
Hg
Se
Te
Ni
Fe
SO.T
CN~
Oil and Grease
pH
Concentrat ion
mg/£
310.0
88.4
37.0
7.7
1.05
0.0003
0.04
0.43
0.75
9.4
340.0
0.01
0.04
3.8 to 4.4
86
-------
Fire Refining and Anode Casting--
Impure or "blister" copper from the converters must be refined to remove
impurities. This is partially accomplished by fire refining, the last major
process that occurs at a copper smelter.
Blister copper is placed in a fire refining furnace, a flux is usually
added, and air is blown through the molten mixture. Most of the remaining
sulfur oxidizes, some impurities vaporize, and other impurities oxidize and
are removed in the slag. The excess oxygen in the mixture is then removed
by either blowing reformed gas into the molten metal or by forcing wooden
poles under the surface of the melt. The copper is then poured into molds
and cooled with water sprays or by immersion in a tank of water. The result-
ing anodes are sent to an electrolytic refinery for further processing.
Water used for direct (contact) cooling of the casting machine and the
copper anodes is usually a recirculated stream or is reclaimed water from
combined sources. Table 24 shows the water consumption for five smelters.
The water used for anode cooling is reported to pick up additional amounts of
arsenic, copper, zinc, and also aluminum and chlorides, probably from mold
dressing compounds. Table 25 lists the difference between inlet and outlet
concentrations reported for one anode cooling operation. Table 26 lists the
controls of contact cooling water being practiced by the domestic smelters
including water used for cooling of both anodes and blister copper direct
from the converter.
Electrolytic Refining—
Electrolytic refining reduces the total impurities in copper to approxi-
mately 0.05 percent. The refining is done by passing a direct current of
electricity through two copper electrodes that are immersed in a bath of
acidic copper sulfate solution. The anode is a casting of impure copper from
the smelter, and the cathode is a "starting sheet" of refined electrolytic
copper. The electric current causes the copper to dissolve from the anode
and deposit at the cathode. Impurities collect either as slimes in the bot-
tom of the cell or as soluble ions in the electrolyte.
Water is used for washing the electrodes as they are removed from the
cells. This is usually steam condensate, since untreated water contains
minerals that affect the quality of the product. This same water is used for
make-up to the electrolyte system to replace that lost in purge and evapora-
tion.
Most refineries reclaim the copper from spent electrolyte, but two do
not, and therefore create a substantial liquid waste directly from the elec-
trolytic cells. Table 27 lists the composition ranges for the electrolyte
solution, the refined copper, and the slime that is recovered from the bottom
of the cells. Leaks, spills, and occasional major discharges frequently are
not included in these tabulations. One refinery that does not reclaim the
spent electrolyte solution treats this stream by placing it in a lined pond
and allowing it to evaporate to dryness. Dry climatic conditions make
this possible. The other refinery mixes it along with other wastes and
87
-------
TABLE 24. WATER REQUIREMENTS FOR COPPER REFINERIES
Plant
A
B
C
D
E
Water intake, liters per metric
ton of metal producted
4,000
9,000
13,000
3,000
6,000
Water consumed
(Intake minus discharge) ,
liters per metric
ton metal producted
4,000
700
1,200
1,900
0
TABLE 25. WASTE EFFLUENTS FROM ANODE COOLING WATER
Parameter
Chloride
Aluminum
Arsenic
Copper
Zinc
Flow, 10 6
i/day
mg/fc kg/c
Net loading
lay kg/metric ton
8.7 7.8 0.029
0.12 0.11 0.0004
0.01 0.01 <0.0001
8.53 8.07 0.030
0.25 0.24 0.0009
0.95
Production,
metric ton/day
265.0
88
-------
TABLE 26. CONTACT COOLING WATER CONTROL AND TREATMENT PRACTICES
Plant
code
9
10
11
12
13
14
15
Discharge
Intermittent
0
0
0
0
0
5670 ra'/day
18 I/sec
1-340 m3/day
(125 Vsec,
45 min/day)
Control and/or treatment practice
Anode casting: water in closed circuit with
cooling tower, cooling tower blowdown joins
blowdown from wire-bar casting cooling tower
blowdown, entire blowdown to side-stream fil-
ter, anticipate total water recycle.
Anode casting: water directly reused in rail!
concentrator circuit. No discharge.
Anode casting: water collected in mill tail-
ings thickener, all flow recycled (with some
evaporation) to mill concentrator. So
discharge.
Blister cake cooling: air cooled with some
water spray; spray water totally recycled from
cooling pond. No discharge.
Fire—refined (cathode) - shape casting; water
mostly recycled, with small intermittent
discharge.
Fire-refined casting: water to thickener,
verflow recycled. No discharge.
Anode casting: water in closed circuit with
cooling tower, blowdown to evaporation pond.
No discharge.
Anode casting: water in closed circuit with
cooling tower, blowdown reused in mill
concentrator. No discharge.
Anode casting: water to tailings thickener,
reused in mill concentrator. No discharge.
Anode casting: water all used in mill con-
centrator circuit. No discharge.
Anode casting: water in closed circuit with
100 percent circulation. No discharge.
Anode casting: water collected in slag set-
tling pond, part is recirculated for slag
granulation 53,000 raVday. Remainder 5700
m3/day discharged to tailings ponds. Eventual
(8 km of ponds) discharge.
Anode.casting: once-through water, part used
for shot copper cooling, remainder discharged.
Shot copper cooling: Intermittent flow, all
discharged. Plan to treat water in proposed
treatment facility with anticipated discharge.
Blister cake cooling: water consumed during
spraying and air cooling. No discharge.
Source: PE-274
89
-------
TABLE 27. GENERAL RANGE ANALYSIS OF ELECTROLYTE, REFINED
COPPER, AND ANODE SLIME
Electrolyte,
Constituent g/&
Sulfuric 170-230
Copper 45-50
Oxygen
Sulfur
Arsenic 0.5-12.0
Antimony 0.2-0.7
Bismuth 0.1-0.5
Lead
Nickel 2.0-20.0
Selenium
Tellurium
Gold
Silver
Platinum
Palladium
Iron
g/metric ton.
tr. = trace
N.A. = Not available
Refined copper, %
99.95
0.03-0.05
0.001-0.002
0.0001-0.001
0.0002-0.001
0.00001-0.00002
0.002-0.0010
0.0001-0.002
0.0003-0.001
0.0001-0.0009
0.68-0.242a
1. 71-17. la
tr.
tr.
tr.
Raw slime, %
(dry basis)
20-40
2-6
0.5-4.0
0.5-5.0
tr.
2.0-15.0
0.1-2.0
1.0-20.0
0.5-8.0
1,714-10,286
34,285-274,283
N.A.
N.A.
0.1-0.2
90
-------
discharges it into a tailings pond, where lime is added to neutralize the
acid. This refinery is also in an arid section of the country. Both re-
fineries report no discharge into public waters.
Electrolyte Purification—
Impurities accumulate in the electrolyte solution in an electrolytic
refinery. If a portion of the electrolyte is not removed from the circulating
stream, these impurities will begin to deposit with the refined copper. In
most cases, the purge stream is processed to recover the metal value.
All but two of the refineries in this country remove the copper from the
purge stream. This is done in special "liberator" electrolytic cells that
use insoluble lead anodes and sheets of copper as cathodes. The copper and
frequently some of the impurities deposit on the cathode. The plates of
copper return to the metallurgical processing either within the refinery or
in the smelter, depending on quality. Some of the remaining impurities col-
lect in the liberator cells as a sludge.
A few refineries recover a portion of the sulfuric acid from the purge
stream by use of dialysis equipment. The dialyzers provide a partial separa-
tion of the acid and produce a stream in which impurities are more concen-
trated. The acid is returned to the electrolyte circulation.
Effluent from the liberator cells or the dialysis equipment may be con-
centrated further by removing water in vacuum evaporators. Concentration of
the acid produces a sludge, which has a high concentration of nickel sulfate
and usually also contains iron and zinc. This sludge can be filtered out,
and then part of the acid can be returned to the electrolyte system, or it
may be discarded or sold.
Various smelters may practice all, part, or none of these treatments.
Three refineries recover nickel. One refinery consumes all spent electrolyte
in an associated chemical operation.
The waste streams for electrolyte treatment contain almost all the ar-
senic, antimony, and bismuth that comes in with the anode copper. Some of
these elements may be returned to the smelter with liberator cathodes. Ap-
proximately a ton of arsenic may enter the electrolytic refinery with as
little as 500 tons of anodes. Some of the arsenic is known to escape from
the second stage of the liberator cells as arsine (AsH3). Unless these ele-
ments are returned to the smelter with the liberator cathodes, antimony, and
bismuth will exit with a purge of electrolyte acid. This waste stream is
called "black acid."
In some refineries evaporated water from the electrolyte constitutes
another waste stream, which usually is mixed with volumes of steam condensate
and direct cooling water in barometric leg discharge devices. Table 28
provides an analysis from such a source.
91
-------
TABLE 28. WASTE EFFLUENTS FROM NiSCK BAROMETRIC CONDENSER
Parameter
pH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Sulfate (as S)
Arsenic
Cadmium
Copper
Iron
Lead
Nickel
Zinc
Flow, 10 6
Intake ,
mg/£
6.5
90.0
750.0
21,080
21,060
18
1,722
<0.010
<0.20
<0.20
<0.50
<0.50
<0.50
<0.20
Discharge, Net change, Net loading,
mg/S- mg/H kg/day
6.6
450.0 neg
24,000 2,920
24,000 2,920
18
1,060 neg
<0.010
<0.20
<0.20
1.30 <1.3 <15.0
<0.50
<0.50
<0.48 <0.48 <5.4
11.4
£/day
Production, 415.0
metric ton/day
92
-------
Melting and Casting Cathode Copper—
Refined electrolytic copper is either sold or melted and recast into
shapes required by fabrication industries. There is usually also a final
adjustment of the oxygen content of the finished product. Equipment used for
these operations ranges from direct-fired reverberatory furnaces to continu-
ous casting machines. Electric arc and induction furnaces may be used to
melt or hold the molten copper.
Both contact and noncontact cooling waters are used to cool the casting
equipment and the cast shapes. One refinery reports a water usage of 320,000
liters per day. Table 29 lists an analysis of water used for cooling the
refined copper shapes at two refineries. Water from this process is often
cooled prior to discharge, but is not usually specially treated.
Dore Metal Separation—
Dore metal, a mixture of silver, gold, and the platinum group metals, is
separated into specification grades of each metal in a series of chemical and
electrochemical laboratory operations. A special small electrolytic cell,
the Moebius cell, is used to separate the silver, which is further processed
to produce bullion bars of 1000 troy ounces each, analyzing 99-97 percent
silver. Mud from the Moebius cell is melted into anodes and processed in
another special electrolytic device, the Wohlwill cell, which produces gold
of marketable quality. The remaining electrolyte is chemically processed to
separate platinum, palladium, and occasionally iridium, rhodium, ruthenium,
and other metals.
Wastes are insignificant in comparison to other processes. No losses of
metallic elements occur in this process. There are minor evolutions of
nitrous oxides, sulfuric acid mists, and other acid fumes, and occasional
liquid discharges of electrolyte acids in quantities of a few gallons at
most.
Heap and Vat Leaching—
Heap and vat leaching are simple forms of hydrometallurgy, in which
valuable metals are dissolved from ores to form water solutions. In heap
leaching, the ores are placed in a dump, or pile, on the ground. In vat
leaching, they are placed in tanks, with or without pretreatment.
Heap leaching is usually applied to low-grade ore and mine overburden
that contains less than 0.4 percent copper. The ore is placed in an area
provided with drainage ditches and basins, and is flooded with sulfuric acid
solution and then allowed to drain. The copper minerals react to form solu-
ble copper sulfate which washes from the heap with the acid solution. From
70 to 82 percent of the copper in these low-grade ores can be recovered. The
liquor that seeps from the heap has a pH of 1.5 to 2.5 and may contain from
1.0 to 18 grams of copper per liter (PE-274).
Vat or percolation leaching is applied to oxidized copper minerals,
which occur as partially weathered deposits in the mine. These minerals
93
-------
TABLE 29. ANALYSIS OF WATER USED TO COOL REFINERY SHAPES
(Concentrations in mgAO
Parameter
pH
TDS
TSS
SO*
As
Cd
Cu
Fe
Pb
Hg
Se
Te
Zn
Oil and
Grease
Plant X
Inlet
water
7.6
1430.0
0.0
240.0
0.001
0.001
0.30
0.02
0.007
0.00350
0.001
0.001
0.0
Wirebar
cooling
7-8
1250.0
12.5
240.0
0.001
0.001
0.69
0.13
0.007
0.00425
0.001
0.067
2.0
Semicontin-
uous cake
casting
8.0
1400.0
0.0
270.0
0.001
0.001
0.18
0.04
0.003
0.0001
0.001
0.001
0.0
Plant Y
Inlet
water
7.1-7.6
0.2 %
0.5
0.001
0.0008
0.021
1.2
0.078
0.00004
0.040
0.35
0.14
Wirebar cooling
recycle
8.0-8.4
0.1
0.4
0.001
0.0021
3.5
1.7
0.068
0.00004
0.040
0.088
0.1
94
-------
cannot easily be reclaimed by conventional flotation processes. They are
selectively mined and are placed in concrete vats where they are subjected
to alternate flooding with sulfuric acid and draining.
The leaching liquor eventually becomes so rich in iron that it must be
discarded. The volume is reported as varying from 350,000 to 1,000,000
liters or spent liquor per metric ton of copper produced but no effluent
analyses have been reported. Most installations mix the discharge of this
process with mining or concentrating wastes.
Solvent Extraction—
Solvent extraction is used to produce a concentrated copper solution
from a solution of copper that contains other dissolved metals. When organic
solvents are mixed with the impure solution, the copper complexes with the
solvents. The solvents containing the copper form a separate phase from the
aqueous phase containing the impurities. The organic layer is removed and
mixed with sulfuric acid. This breaks down the complex and regenerates the
solvent for reuse. The copper is withdrawn as a solution in the acid.
The concentrated acid solution can be directly treated by electrowinning.
It is likely that there will be a bleed of the concentrated acid to prevent
accumulation of these other elements. The loss of solvent is reported as 1
liter per 10,000 liters of raffinate. This loss is probably kerosene, which
has a slight water solubility. The more expensive chelating compounds should
stay largely dissolved in the kerosene layer. The acid blowdown should be of
a quality that could be reused in other processes. The organics lost in this
waste stream should be biodegradable.
Electrowinning—
Electrowinning is similar to the cells of an electrolytic refinery, ex-
cept that an inert anode is used. Relatively pure copper metal is extracted
from a solution containing copper ions. Copper metal deposits at the. cathode,
and the water in the solution is electrolytically decomposed, liberating
oxygen at the cathode, and generating the sulfate ion as sulfuric acid.
The copper produced by electrowinning is comparable to electrolytic
copper, assaying 99.9+ percent, if the copper solution is relatively pure.
If impure solutions are used, the purity is equivalent to that of the anode
copper from a conventional smelter and the product requires electrolytic
refining prior to sale.
No data is available on the characteristics of the small amount of
liquid waste discharged as a result of cathode washing.
95
-------
PRIMARY LEAD INDUSTRY
Industry Description - Primary Lead
The United States primary lead industry consists of six smelters and five
refineries. Four sites have both smelting and refining. Two sites have only
smelting operations and ship their bullion to another site for refining.
Mining, concentrating, smelting, and refining are the four major phases
of lead processing. Lead is mined from lead sulfide ore which typically
contains 3 to 8 percent lead by weight. In certain areas in Missouri, ore
containing up to 70 percent lead is being mined. Ore is processed in a series
of crushing, grinding, classifying, flotation, and float-sink steps to produce
a concentrate containing 55 to 70 percent lead by weight. The pyrometallurgi-
cal steps in lead smelting are preceded by charge preparation and pelletizing
steps which actually lower the lead concentration of the feed concentrate to
30 to 45 percent. Fluxes, coal, limerock, and return slag are added to insure
proper pelletization and good combustion during sintering.
Prior to 1963, lead ore mined in the United States typically contained 3
to 8 percent lead by weight and contained zinc, iron, nickel, and copper
impurities. In 1963, lead ore containing as much as 70 percent lead was dis-
covered in Missouri. In some places the ore is pure galena. This ore con-
tains smaller concentrations of impurities than ore in the older mines.
Lead ore from the older mines requires dressing or milling before smelt-
ing. Standard grinding and flotation techniques concentrate the lead from the
3 to 8 percent level found in typical ores to 45 to 70 percent. Common flota-
tion chemicals are NaaCOs, CaO, CuSOi*, xanthate, pine oil, cresylic acid, and
NaCN. The product lead concentrate is dewatered, thickened, and filtered be-
fore being sent to the smelter. At this point, the concentrate contains 6 to
15 percent zinc, 5 to 15 percent iron, 13 to 18 percent sulfur, and minor
amounts of cadmium, gold, silver, magnesium, manganese, arsenic, and antimony
(MC-004, KI-048).
The lead smelting phase involves concentrate preparation and pelletizing,
sintering, and reduction in a blast furnace. Feed concentrates for smelting
must be carefully blended with high silica lead ores, by-products, return
sinter, and fluxes to insure complete mixing before being stored in bedding
piles. The bedded charge is normally conditioned to adjust moisture content
to 6 to 8 percent. The charge is then pelletized in a gas or oil fired rotary
pelletizer which maintains the exit gas temperature at 600°F (KI-048). The
pellets (1/8 to 3/16 in.) are then stored as sinter machine feed.
Prepared concentrate is sintered to remove volatiles, to oxidize lead
sulfide, and to produce a charge with enough structural strength to be
suitable for direct feed to a blast furnace. In the sintering step, a condi-
tioned, pelletized charge is ignited on a traveling metal grate. Metallic
sulfates and sulfides in the charge are oxidized to metallic oxides, volatiles
are driven off, and a suitable blast furnace charge or "clinker" is produced.
96
-------
The clinker is broken as it comes off the end of the traveling grate. It is
then charged to a blast furnace with coke, fluxes, and recycled drosses
(normally metal oxides) for reduction.
After the sinter and coke are charged to the blast furnace, reaction heat
is provided through coke combustion by blowing air through tuyeres located
near the bottom of the blast furnace shaft.
The blast furnace reduces the lead oxides formed during sintering to
metallic lead and CO. Four molten layers may form in the blast furnace. Lead
will sink to the bottom of the blast furnace shaft. A layer of speiss (anti-
monides and arsenides of iron and other metals with a specific gravity of 6.0)
will float on the lead. Matte (copper and other sulfides with a specific
gravity of 5.2) will form above the speiss, and slag (silicates with a spec-
cific gravity of 6.0) will form the upper layer. Lead bullion is tapped from
the blast furnace and is either sold as antimonial lead or further refined.
Impurities (mainly iron and zinc) accumulate in the slag and are sent to a
slag fuming furnace.
Refining lead bullion may be accomplished pyrometallurgically or electro-
lytically. Refining involves the step-wise removal of impurities including
copper, antimony, gold, silver, zinc, and cadmium. These impurities are nor-
mally sold as secondary products of lead refining. Refined lead is sold as
soft, semisoft, or hard lead depending on the impurities it contains. Soft
lead is 99.9+ percent pure. Semisoft lead contains 0.3 to 0.4 percent anti-
mony, and up to 0.05 percent copper. Hard (antimonial) lead is typically 5 to
12 percent antimony, 0.2 to 0.6 percent arsenic, 0.5 to 1.2 percent tin, 0.5
to 0.15 percent copper, and 0.001 to 0.01 percent nickel (DA-069). Other im-
purity elements are often substituted to maintain equivalent physical proper-
ties.
The first refining step is dressing to remove copper. The copper in the
dross is recovered in a reverberatory furnace and the reverb slag is recycled
to the blast furnace. Decopperized bullion is then treated in a "softening
furnace" which removes antimony, arsenic, and tin, the elements which make
lead hard.
Gold and residual copper are removed by adding zinc dust to the molten
bath to form a zinc-copper-gold crust. Zinc is again added after the gold
crust is skimmed and a silver-zinc crust forms and is skimmed off. Zinc is
removed by reaction with chlorine or by vacuum distillation. Bismuth is re-
moved in a refining kettle by adding calcium and magnesium. Electrolytic re-
fining may follow any of the above refining steps depending on the type of
lead and secondary product desired.
Wastewater Source Identification - Primary Lead
Table 30 lists each of the processes in the primary lead industry for
which effluent streams have been identified. Unlike the copper industry, most
lead mines, concentrators, smelters, and refineries are located in areas where
rainfall exceeds evaporation. Surface evaporation of wastewaters is not
97
-------
TABLE 30. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES - PRIMARY LEAD
VO
00
Source Flow (l/nln)
Primary Lead Industry
Mining
- Mine drainage (seasonal)
Concentrating
- Tailings slurry from 4 n'/m ton ore
flotation or gravity processed
separation
Stream Composition (rag/It) Ref . Comnents
pH
Cu
Pb
Zn
Mg
Ca
Na
K
Hg
Cd
Cr
Mn
Fe
Sulfate
Chloride
Fluoride
Hg
Pb
Zn
Cu
Cd
Cr
Mn
Fe
Range of Five Missouri Mine
Water Samples PE-274 Water from Missouri
, a o . mines is alkaline, while
o'. 00^700.0 drainage is acidic, re-
0.020-0.065 quiring neutralization.
0.008-0.036
12.0 -15.0
27.0 -30.0
32.0 -54.0
3.0 -4.2
Other Constituents FE-274
0.001-0.002
<0. 002-0. 058
<0. 010-0. 17
<0.02 -57.2
<0.02 -2.5
63.5 -750.0
<0.01 -57.0
0.063-1.2
<0.001 FE-274
0.107-1.9
0.12 -0.46
0.014-0.36
0.005-0.011
0.002-0.02
0.03 -0.169
0.03 -0.53
(Continued)
-------
TABLE 30 (Continued)
5ourc«
Flow (t/»in)
Stream Composition (ag/t)
Ret.
Comments
Primary Lead Industry (Cont'd)
SO
Contact Acid Plant
- Off-gas scrubber liquor In one case 273
(i.e., acid plant n*/day is
blowdown) discharged.*
Blast Furnace
- Slag granulation water*
Slag Fuming
- Slag granulation water 6 million I/day
Final Refining and Casting
- Ingot cooling water
See composition reported for contact acid plant in
Primary Copper.
Parameter
PH
Dissolved solids
Sulfate (as S)
Chloride
Calcium
Copper
Iron
Lead
Magnesium
Nickel
Zinc
Total
plant
intake
mg/i
7.6
408.0
145.0
18.0
70.0
0.02
1.70
0.12
0.31
0.03
0.05
Total
plant
discharge
mg/ft
8.3
500.0
215.0
-
-
0.02
_
0.30
-
0.04
0.12
Net
change ,
mg/t
_
92.0
70.0
~
-.
0
-
0.18
_
0.02
0.38
PE-274
PE-274
PE-274
Process water flow: 6 million liters/day (1.55 Billion gal/day).
Production: Metric tons/day (630 short tons/day).
Source: This contract and 1971 RAPP data.
PE-274
Similar to effluent from
acid plant In primary
copper industry.
*0ther plants combine
with other effluents for
treatment or use in slag
granulation.
*Many plants now charge
slag to slag fuming
furnace rather than di-
rectly to slag granulation.
Either recycled to slag
granulation or dis-
charged to tailings pond.
Liming la sometimes
practiced.
-------
possible. Table 30 summarizes the available data on the characteristics of
these process specific wastewaters. The following discussion describes the
sources of these wastewaters in more detail.
Mining—
Most lead ore is obtained from underground mines. The ore is cut from
the deposit, it is taken to the surface by rail, trackless shuttle cars, or
conveyor belts and is then transported to ore concentrating facilities.
Wastewater from lead mining results from seepage of surface water, intercep-
tion of aquifers, runoff rom spoil dumps, and water sent into the mine for
utility purposes. The water is pumped from the mine at a rate necessary to
maintain mining operations. The required pumping rate is subject to seasonal
variation and bears no relation to the ore output. The rate can range from
tens to thousands of cubic meters per day.
The wastewater contains dissolved and suspended solids that reflect the
composition of the ore being mined. Small amounts of oil and hydraulic fluid
resulting from spills or leaks will also be present. A Missouri mine waste-
water analysis is given in Table 31. The chemical characteristics are typical
of those from any sulfide mine.
TABLE 31. ANALYSIS OF A MISSOURI MINE WATER
pH
7.8
7.8
7.8
8.1
8.1
Cu
4
4
0.5
0.7
Pb
65
20
36
31
53
Zn
8
15
19
22
36
Mg
mg/Jl
13
14
15
12
13
Ca
mg/Jl
30
27
29
30
30
Na
mg/Jl
32
42
53
54
K
mg/Jl
4.2
3.8
3.2
3.0
100
-------
Other typical mine wastewater constituents and their concentrations are
given below.
Component Concentration, mg/£
Mercury 0.001 to 0.002
Cadmium <0.002 to 0.058
Chromium <0.010 to 0.17
Manganese <0.02 to 57.2
Iron <0.02 to 2.5
Sulfate 63.5 to 750
Chloride <0.01 to 57
Fluoride 0.063 to 1.2
Wastewater is generally treated by liming and impoundment as practiced
in copper mining. Since water from Missouri mines is basic, liming may not
be required for pH adjustment. Water from western lead mines is acidic and
is treated in a fashion similar to water from copper mines. After treatment,
the wastewater is normally reused in ore milling operations.
Concentrating—
The concentrating process is similar to the process described for copper
ore concentrating. Except for high-grade galena ore produced in southeastern
Missouri, ore concentration is required to produce feed material suitable for
subsequent metal recovery processes. The process consists of milling the ore
by crushing and grinding, followed by separation into two or more fractions.
The fractions rich in desired minerals are called concentrates, and the frac-
tions low in mineral content are called gangue.
Separation is achieved by both gravity and froth flotation methods. The
gravity method achieves separation because of differences in specific gravity
of the lead-rich minerals and the gangue particles. The flotation method
achieves separation by the use of compressed air and chemical additives that
create a froth in which finely divided mineral particles are floated from
the gangue. The flotation method may serve as a supplement to gravity sepa-
ration to improve the concentrate and is similar to copper ore flotation.
Flotation is practiced chiefly by lead mines in the western United States.
Lead producers of the Mississippi Valley and the eastern United States
use gravity separation because there is considerable difference in specific
gravities of the ore minerals and the gangue. Since the milled ore particles
need not be as small as those required for flotation, the milling costs are
lower. Two modes of gravity separation are commonly used, jigging and float-
sink. In jigging, the crushed ore particles are fed to an agitated,
101
-------
water-filled jigging chamber where the heavier ore particles gravitate to
the bottom and the lighter gangue is displaced to the top and removed. The
float-sink mode utilizes a liquid medium, such as an aqueous ferrosilicon
suspension, with a specific gravity between that of the lead mineral and the
gangue. The mineral particles sink, while the gangue floats to the top for
removal by skimming.
The ore concentrates from the flotation cells are dewatered before ship-
ment to smelters. Liquid waste from the concentrating operation is in the
form of a tailings slurry discharged to the tailings pond. Approximately 4
cubic meters (1,060 gallons) of tailings slurry are discharged per metric ton
of ore processed. Table 32 lists concentrations for a few metals in concen-
trator wastewater.
TABLE 32. LEAD MILL WASTEWATER ANALYSIS
Component Concentration,
Mercury
Lead
Zinc
Copper
Cadmium
Chromium
Manganese
Iron
0.001
0.107 to 1.9
0.12 to 0.46
0.014 to 0.36
0.005 to 0.11
0.002 to 0.02
0.03 to 0.169
0.03 to 0.53
Acid Plant—
The sintering machine produces the only lead smelter exit gases treated
by sulfuric acid production. A detailed description of this process is given
in Section 7, under Contact Sulfuric Acid Plant.
Liquid waste effluents are treated by liming and settling in cooling
ponds. Overflows are recycled to slag granulation or discharged. Tables 33
and 34 give the treatments now practiced for control of acid plant blowdown
and scrubber wastewaters, respectively, by the three primary lead smelters
having acid plants.
Slag Fuming Furnace—
A slag fuming furnace is used to recover metal values otherwise lost in
the slag. Slag is fed molten to the fuming furnace and pulverized coal is
added to maintain reaction temperature. A reaction fume is generated that
normally contains zinc, germanium, lead, cadmium, chlorine, and fluorine.
102
-------
TABLE 33. WASTEWATER TREATMENT AT PRIMARY LEAD ACID PLANTS
Plant
Liquid Effluent Treatment
Discharge
Enters water treatment plant,
limed, thickened, and filtered,
and sent to reservoir for
recycle.
Recycled to slag granulation.
Enters liming sump, then
passed to lime,bed, then to
a cooling pond.
273 m3/day
(72,000 GPD)
TABLE 34. SCRUBBER WASTEWATER TREATMENT AT PRIMARY LEAD PLANTS
Plant
Treatment
Discharge
Enters water treatment plant,
limed, thickened, filtered, and
then sent to reservoir for re-
cycling.
Recycled from a cooling tower.
Sent to a lime sump then to a
settling pit. Most is recycled.
Undetermined
103
-------
The fume is condensed and processed to recover the metal values. The lead
fraction is recycled to the sintering process. A leaching step may be neces-
sary to avoid the accumulation of chlorine and fluorine. A matte is some-
times separated from the slag in this operation for recovery of substantial
amounts of copper and- silver from the slag.
When fuming has subsided, the slag is dumped and cooled with water.
The dumped slag and water used for granulation constitute the major waste
stream from this process. The water-soluble portions of the slag are leached
by the cooling water. Table 35 presents analyses of intake and outflow
streams of water used for slag granulation.
Slag is conveyed with the granulating water stream to a dump or tailings
pond for disposal.
Current treatment and disposal practices for slag granulation water are
variable, as summarized in Table 36. Normally, it is desirable to recycle
the water after cooling and clarification. A smaller stream is bled off
to control buildup of water-soluble components. Using neutralization and
clarification to treat this wastewater, the following effluent concentrations
can be achieved.
Component Concentration, mg/Jl
Cadmium 0.5
Lead 0.5
Mercury 0.005
Zinc 5.0
These values are currently being met by five of the six lead smelters. The
estimated cost of treatment is $2.68 per metric ton ($2.43 per U.S. ton) of
lead produced (PE-274).
Final Refining and Casting—
Refined lead bullion from dezincing or debismuthizing is given a final
purification and cast into ingots. The refined lead is fluxed with oxidizing
agents to remove remaining impurities such as lead oxide and magnesium or
calcium residues. After slag removal by skimming, the purified lead, assay-
ing 99.999 percent purity, is reheated and cast into ingots or pigs. Most
casting is performed by fully automated machines.
Water is used to cool the cast lead ingots by direct contact, at rates
ranging from 300 to 1,500 liters per minute. Direct contact cooling water
becomes contaminated with lead and lead oxides. Several methods are used to
treat the contaminated cooling water. The water is either recycled for use
in slag granulation or is sent to a tailings pond for settling of suspended
solids. Lime precipitation may also be used for metals removal.
104
-------
TABLE 35. WASTE EFFLUENTS FROM SLAG GRANULATION
Parameter
pH
Alkalinity
COD
Total solids
Dissolved solids
Suspended solids
Oil and grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Total
Plant
Intake
mg/A
7.6
203
8
-
408
3
-
145
18
-
-
-
-
70
-
0.02
1.70
0.12
.31
-
-
0.03
-
-
-
-
-
0.05
Total
Plant Net
Discharge Change,
ag/£ og/l
8.3
186 -17
8 0
-
500 92
36 33
-
215 70
-
-
-
-
-
-
-
0.02 0
-
0.30 0.18
-
- -
-
0.04 0.02
-
-
_ -
-
-
0.12 0.38
Net Loading
kg/ton
-
-
0
-
0.89
.32
-
0.67
-
-
-
-
-
-
-
0
-
0.0018
-
—
—
0.00018
_
—
~
_
—
0.0037
Process water flow: 6 million liters/day (1.55 million gal/day).
Production: Metric tons/day (630 short tons/day).
Source: PE-274
105
-------
TABLE 36. PRIMARY LEAD SLAG GRANULATION'WASTEWATER TREATMENT
Plant
Treatment
Discharge
Sent to cooling pond.
8,230 m3/day
(2,200,000 gpd)
2 Sent to settling pit then to
a cooling pond.
273 m3/day
(72,000 gpd)
Sent to settling pond and
recycled.
Sent to two settling ponds in
series.
Discharge is present
but no quantities are
available.
Sent to a slag pile.
No apparent discharge to
surface. Leaching is
not mentioned.
No data.
No data
106
-------
PRIMARY ZINC INDUSTRY
Industry Description - Primary Zinc
The major product of the primary zinc industry is metallic zinc; the
industry also produces zinc oxide, sulfuric acid, cadmium, and occasionally
other chemicals such as zinc sulfate. For the purpose of analysis, the zinc
industry is subdivided into segments: pyrometallurgical zinc production,
electrolytic zinc production, zinc oxide production, and cadmium recovery.
Production of other by-product compounds such as germanium, thallium,
gallium, and indium is not considered as part of this industry because this
is not done at primary zinc smelters.
Generally, ore is mined and concentrated at one location and then trans-
ferred to smelters for the production of zinc, zinc oxide, or both. Cadmium
is normally recovered at smelters from collected dusts and slags with suffi-
cient cadmium content. Direct zinc oxide production uses the same ore con-
centrate as metallic zinc production.
Zinc occurs naturally in many igneous rocks. The principal ore is
sphalerite known as "zinc blende" which is a cubic crystal of zinc sulfide
(ZnS). Sphalerite varies in purity (up to 67.1 percent zinc) and is dis-
persed in various concentrations in the ore. Zinc is normally mined in
underground mines although some open pit zinc mines also exist.
Zinc mined in the United States comes primarily from underground mines
in the form of sulfide ores. Ore is crushed and ground in standard jaw,
gyratory, and cone crushers, then separated by flotation. Concentrates
normally contain 50 to 60 percent zinc, approximately 7 percent iron, and
about 30 percent sulfur. Zinc concentrate is then treated either electro-
lytically or pyrometallurgically to recover zinc metal. Both techniques
require roasting of the concentrate prior to treatment. In the roasting
step, any sulfur present as sulfide must be removed. If electrolytic pro-
cessing follows roasting, some sulfur present as ZnSOit is desirable to
compensate for losses in the electrolytic refining cells. Pyrometallurgical
processing requires nearly complete or "dead roasting".
Smelting of zinc concentrates is accomplished by different techniques at
the two United States smelters which use pyrometallurgical reduction pro-
cesses. In the vertical retort process, concentrate is blended with various
smelter recycle streams, pelletized, dried, and then roasted in flash
roasters. The roasted concentrate or "calcine" is again mixed with recycle
streams and pelletized before being sintered for final sulfur removal.
Sinter is mixed with coal, clay, and sulfite liquor and pressed into bri-
quettes. The briquettes are coked to give them the structural strength and
reactivity required for charging to the vertical retort. The volatile matter
in the coal aids in supporting autogenous combustion during the coking
process.
Vertical retorts have rectangular cross sections and are 12 to 18 inches
wide and 6 to 8 feet long. Walls are constructed of silicon carbide to help
107
-------
transfer heat to the charge from fuel which is fired on the outside of the
retort. Inside the retort, ZnO and carbon from the coal or coke react to
form Zn and CO. The zinc vaporizes and passes out of the retort with the CO
to a condenser. The condensed liquid zinc is removed continuously and the
CO is used as fuel to fire the retort.
The electrothermic process also requires drying, roasting, mixing,
pelletizing, and sintering of the concentrate. However, the sinter and coke
are fed directly to the electrothermic furnace where heating is accomplished
with electrodes submerged in the charge. Zinc and CO leave the furnace as
vapor. The zinc is condensed and removed, while the CO is burned in a pre-
heater to heat the furnace charge.
Electrolytic processing of zinc involves the leaching of roasted concen-
trate with spent electrolyte to remove the soluble zinc oxide. The solution
is filtered and processed through electrolytic deposition cells in which zinc
is plated out of solution on aluminum cathodes.
Some nonsulfur bearing ore is processed by at least one zinc smelter.
Since oxide ore is not amenable to flotation, it is reduced, vaporized, and
oxidized in Waelz kilns. The ZnO is then sintered and combined with the
processed sulfide ores for zinc or zinc oxide production. Lead and copper
ores are also major sources of zinc.
Primary zinc requires little refining after reduction. What little re-
fining is done is usually performed by fabricators prior to casting.
Liquid effluents can be classified as non-contact and contact. Non-con-
tact water is used for cooling in heat exchangers. Contact, or process,
wastewater is produced in operations such as scrubbing of roaster gas and
reduction furnace gas, cooling of metal castings, cadmium production, and
auxiliary air pollution controls. The primary pollutants are zinc, cadmium,
lead, and small amounts of arsenic and selenium.
Table 37 lists each of the processes in the primary zinc industry for
which effluent streams have been identified. Table 37 summarizes the avail-
able data on the characteristics of these process specific wastewaters. The
following discussion describes the sources of these wastewaters in more
detail.
Mining—
Most zinc is mined underground using open shrinkage, cut-and-fill, or
square-set stopping methods. A few mines, particularly in early stages of
operation, use open pit methods which are similar to those used in copper
mining.
Mining consists of drilling, blasting, removing the broken rock and
transporting it to a concentrator. Mining operations range from several
hundred to about six thousand metric tons per day capacity.
108
-------
TABLE 37. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER
Source Flow (t/min)
Primary Zinc Industry
Mining
- Mine wastewater Highly variable
Concentrating
- Mill wastewater 1,000-16,000
Tailings (underflow m /day
from flotation cell)
Overflow from con-
centrate thickeners
Filtrate from con-
centrate dewatering
Horizontal Retorting
- Gas washing water
Stream Composition (mg/l)
Pb
Zn
Range for
pH
!Hg
Pb
Zn
Cu
Cd
Cr
Mn
Fe
CIT
ci-
F-
Zn oxides
P
P
Five Mills
7.9 -8.8
<0. 0001-0.1
<0.1 -1.9
0.12 -0.46
<0.02 -0.36
0.005 -0.011
<0.02 -0.67
<0.02 -0.08
0.05 -0.53
<0.01 -0.03
21.0 -395.0
0.13 -0.26
P
SOURCES - PRIMARY ZINC
Ref . Comments
PE-274
PE-274
PE-274
Metal oxides P
Vertical Retorting
— Gas washing water
Electric Retorting
— Gas washing water
HC
Zn oxides
Metal oxides
HC
Zn oxides
Metal oxides
HC
P
P
P
P
P
P
P
PE-274
PE-274
Oxidizing Furnace
Zinc Melting and Casting
- Casting cooling water
Cadmium Purification and Casting
- Sponge wash water
- Casting cooling water
Same as above.
PE-274
PE-274
PE-274
PE-274
NOTE: P = present, but levels not quantified.
-------
Mine wastewater results from infiltration of groundwater, water pumped
into the mine for machines, hydraulic backfill operations, and infiltration
of surface water. Geographical location rather than the quantity of ore
mined normally determines the quantity of mine effluent. The water required
to maintain operations may range from thousands to 160 million liters per
day. This water is normally contaminated with dissolved metals and such
impurities as blasting agents, fuel, oil, and hydraulic fluid.
Low quantities of water are usually needed in the zinc flotation pro-
cess; mine-water effluent is used at many facilities as mill process makeup
water. Mine water generated from natural drainage is reused in zinc mining
and milling operations whenever possible. The mine water may pass through
the process first, or it may be conveyed to a tailings pond from which it is
conveyed for mill flotation with recycled process water. Discharge may
result because of an excess of precipitation, lack of a nearby milling facil-
ity, or inability to reuse all of the mine wastewater at a particular mill.
Acid mine water is normally neutralized by the addition of lime and/or
limestone. Combining mine water with mill tails in the mill tailings pond
can be an effective treatment for acid mine water containing dissolved
metals. The water may be further treated by lime-clarification and aeration.
C one en t ra t ing—
Zinc ore concentrating is similar to the processes described for lead
and copper ore concentrating. This is necessary because mined sphalerite
is seldom pure enough to be reduced directly for zinc smelting. The zinc-
bearing ore is crushed and ground to a product typically 60 percent smaller
than 325 mesh.
After blending, the ore is pumped to flotation cells as an aqueous
slurry, where flotation agents are added. The zinc sulfide and sometimes
lead, copper, and other metal sulfides are recovered in the flotation froth.
Generally, zinc sulfide flotations are run at a basic pH (usually 8.5 to 11),
and the slurry is periodically adjusted with hydrated lime, Ca(OH)2 (PE-274).
The tailings or gangue materials are sent to a tailings pond for treatment.
The metal concentrates are thickened in settling tanks and the slurry
is fed to vacuum drum filters, which reduce the moisture content to approxi-
mately 10 to 20 percent moisture. Zinc concentrate contains about 55 to 60
percent zinc. Rotary dryers may be used to further reduce the moisture
content of the concentrates to 2 to 5 percent moisture. Table 38 presents
a typical zinc concentrate analysis.
Concentrator water requirement ranges from 330 to 1,100 m3/metric ton
of ore processed per day (PE-274). Mine water is usually used for the mills.
Liquid waste streams from zinc mills vary in volume from 1,000 to 16,000 m3/
day or from 330 to 1,100 m3 per metric ton (PE-274). The raw wastewater from
a lead/zinc flotation mill consists of the tailings streams (usually the
underflow of the zinc rougher flotation cell), the overflow from the concen-
trate thickeners, and the filtrate from concentrate dewatering, along with
any housecleaning water.
110
-------
TABLE 38. RANGE OF COMPOSITIONS OF ZINC CONCENTRATES
Constituent Percent
Pb 0.85-2.4
Zn 49.0-53.6
Au not iden.
A6 not iden.
Cu 0.35
As 0..105-0.15
sb not iden.
Fe 5.5-13.0
Insolubles 3.4
CaO not iden.
S 30.7-32.0
Bi not iden.
Cd 0.24
Table 39 gives the raw and treated waste characteristics of five mills.
None of these mills use total recycle. Feed water for the mills is usually
drawn from available mine waters; however, one mill uses water from a nearby
lake. These data illustrate the wide variations caused by ore mineralogy,
grinding practices, and reagents.
Lime precipitation is- often used for the removal of heavy metals from
mill wastewater. Secondary settling ponds, clarifier tanks, or flocculating
agents (such as polyelectrolytes) are used to enhance removal of solids and
sludge before discharge.
Tailings pond water may be decanted and reused as either makeup water
or process water. Some treatment such as secondary settling, phosphate or
lime addition, pH adjustment, flocculation, clarification, or filtration is
usually required before this decanted water can be reused.
Six lead or zinc ore concentrators now use settling or sedimentation
pond system with a primary tailings pond and a secondary settling or
"polishing" pond with pH adjustment for control of the concentrator dis-
charge. Effluent concentrations are limited to the following average values
(in milligrams per liter): copper = 0.05, mercury - 0.001, lead - 0.02, and
zinc - 0.5 (PE-274).
Ill
-------
TABLE 39. RANGES OF CONSTITUENTS OF WASTEWATERS AND RAW WASTE LOADS
FOR FIVE SELECTED MILLS
Parameter
PH
Alkalinity
Hardness
TSS
TDS
COD
TOC
Oil and grease
MBAS surfactants
Phosphorus
Ammonia
Mercury
Lead
Zinc
Copper
Cadmium
Chromium
Manganese
Iron
Cyanide
Sulfate
Chloride
Fluoride
Range of
concentration
in wastewater mg/£
lower limit upper limit
7.9
26
310
<2
670
71.4
11
0
0.18
0.042
<0.05
<0.0001
<0.1
0.12
<0.02
0.005
<0.02
<0.02
0.05
<0.01
295
21
0.13
8.8
609
1,760
108
2,834
1,535
35
8
3.7
0.150
14
0.1
1.9
0.46
0.36
0.011
0.67
0.08
0.53
0.03
1,825
395
0.26
Range of raw waste load
Per unit ore milled,
kg/1000 metric tons
lower limit
410
460
7
940
6
6.35
5
0.236
0.108
0.064
<0.00013
<0.127
0.089
<0.026
0.008
<0.026
<0.026
0.064
<0.013
130
20
0.370
upper limit
1,600
4,700
285
8,500
4,800
130
21
13
0.876
26.4
0.0026
6.9
17.2
0.158
0.018
1.77
0.290
1.16
0.109
4,800
870
0.944
Per unit concentrate produced,
kg/1000 metric tons
lower limit
1,450
2,290
30
4,800
30
30
30
2.05
0.54
0.32
<0. 00168
<0.900
0.62
<0.18
<0.18
<0.18
<0.45
0.012
0.091
1,260
210
203
upper limit
10,200
32,500
2,000
50,900
50,000
580
130
60.7
2.54
185
0.130
32.2
86.0
1.96
8.85
1.36
10.0
0.198
0.509
33,700
4,070
5.45
in pH units.
112
-------
Vertical Retorting—
The vertical retort process is a continuous reduction/volatilization
method for producing high-purity zinc from zinc oxide by reduction with car-
bon at elevated temperatures in vertical silicon-carbide retorts. Vertical
retorts are large, refractory-lined vessels with externally fired gas cham-
bers. The furnaces consist of three major sections: the charge column, the
reflux section, and the combustion-heating chambers. The retort is rectan-
gular in general cross section, about 0.3 meter wide, 1.8 to 2.4 meters long,
and 10.6 meters high, with a capacity of about 7.25 metric tons of zinc per
retort per day. The coal or coke fed to the vertical retort provides the
carbon used for direct reduction of zinc.
The charge to a vertical retort must be a hard sinter or briquette.
The briquettes are coked in an autogeneous coking furnace in an operation
that also drives off volatiles which serve as fuel.
Coked briquettes are fed to the charging extension at the top of each
vertical retort without intermediate cooling. The charge is heated by gas
in chambers surrounding the retort sidewalls. Incoming combustion air is
preheated in recuperators by gases from the combustion chambers. The charge
passes downward through the combustion or heating zone of the vertical
retort. Heat produced in the combustion chamber is transferred through the
refractory walls of the column to the charge. As the charge moves down
through the retort, the zinc oxide reacts with carbon to form zinc vapors
and carbon monoxide. Approximately 95 percent of the zinc vapor leaving the
retort is condensed to liquid zinc. The residue, containing approximately
10 percent zinc, is removed at the bottom through an automatically controlled
roll discharge mechanism into a quenching compartment, and is removed for
further treatment.
A venturi scrubber is used to control particulate emissions from
vertical retorts. The gas scrubbing water contains zinc and metal oxides,
possibly hydrocarbons, various particulates (as suspended solids), and the
corresponding products of hydrolysis. Only one smelter currently uses ver-
tical retorts. This wastewater is unique to that site.
Electrothermic Furnace—
The electrothermic process overcomes the problem of external heating by
using electrodes immersed in the charge for heating. The charge acts as a
resistance to the potential applied across the electrodes. Some air is fed
to the retort to allow formation of CO as in the vertical retort process and
the reactions which occur are the same.
Electrothermic furnaces are vertical refractory cylinders 2.4 meters
long by 11 meters high. Several sets of graphite electrodes protrude into
the8shaft, each top electrode being linked in a single-phase circuit with a
bottom electrode located about 7 meters below and nearly opposite the first
(KI-048).
113
-------
The bottom of the furnace, which is supported by a refractory-faced
water-cooled steel ring, terminates about 12 inches above a refractory
covered rotating discharge table. This rotary table continuously withdraws
some of the spent charge. A charge height detector controls the speed of
the rotating table, usually to about 0.03 RPM (RP-208).
High-velocity impingement type scrubbers are used to clean gases from
the condenser. The gas washing water contains the same impurities as in
vertical retorting and is specific to the one site using electrothermic
furnaces.
Oxidizing Furnace—
In the direct or American process for zinc oxide production, zinc vapor
from sintering is immediately oxidized without being condensed. The grate-
type furnace, rotary or Waelz kiln, and electrothermic furnace are the three
types of furnaces used for this purpose in the United States. The feed is
reduced to form zinc vapor which is then oxidized and collected as dust.
In the grate-type furnaces, the coal-sinter feed (usually as briquettes)
is spread over grates (traveling or stationary), then the sinter is deposited
on top of the fuel layer. Air is forced through the bed to support combus-
tion. The zinc vapors are ducted to a combustion chamber, where oxidation
occurs and the zinc oxide product is formed.
The Waelz kiln is a large diameter, long rotary kiln that can be used
for production of pure zinc oxide. It is more commonly used to process
residues. Zinc-bearing material and solid fuel are continuously fed to the
kiln, which typically rotates 1 to 1.5 rpm. The heat required for reduction
of the contained zinc is supplied by supplemental fuel. The vaporized zinc
is ducted to a combustion chamber, where air is admitted and the vapor burned
to form zinc oxide.
The St. Joe electrothermic furnace may be modified for use as either a
metal or an oxide producer. Instead of a large "vapor ring" or bulge in the
furnace barrel midway between the upper and lower electrodes, the oxide fur-
nace has openings at four levels between the electrodes, through which the
evolved zinc vapor and carbon monoxide exit the charge. Coke and zinc-
bearing sinter are continuously preheated and fed to the furnace. The heat
energy required for smelting is introduced through electrodes immersed in the
charge.
Water effluents from these processes are not well documented.
Melting and Casting—
In this process, the zinc from an electrolytic or pyrolytic plant is
melted and cast into a marketable form. Pyrolytic zinc is usually molten
whereas stripped electrolytic zinc sheets must be melted. Induction or
gas-fired heating is typically used. The molten zinc is cast into slabs on
a casting machine or blocks in stationary molds.
114
-------
Casting cooling water generally contains suspended solids and oil and
grease consisting of metal oxides, mold washes, and lubricants from casting
equipment. °
Cadmium Purification and Casting—
Cadmium sponge is purified by melting it with a caustic flux, with
distilling and perhaps redistilling, or redissolving the sponge with sulfuric
acid and collecting the cadmium by electrolysis.
In pyrometallurgical processing, the dried cadmium sponge is first mixed
with coal or coke and lime. It is then transferred to a conventional
horizontal-type retort, where the cadmium is reduced and collected as molten
metal in a condenser. For ultra-purity, the metal is distilled in graphite
retorts. Thallium is removed by treatment with zinc ammonium chloride or
sodium dichromate. The metal may then be cast into a marketable form or
further purified by redistillation.
Electrolytic processing of cadmium is carried out in banks of cells
similar to zinc cells. The sponge is dissolved in dilute sulfuric acid
(return electrolyte). The anodes are lead. The cathodes of cadmium are 97
percent pure and represent 90 to 95 percent total recovery of cadmium from
ore to metal. Recovery in the electrolytic step is 96 percent from the
cadmium sponge. The stripped cathode metal is washed, dried, and melted
under a flux, such as caustic or rosin, and cast into various shapes.
Water effluent streams from this process are not well characterized.
Quantities should be small and may contain Cd, HC1, Tl, ZnNHsCl, and organics.
SECONDARY COPPER INDUSTRY
Industry Description - Secondary Copper
The secondary copper industry utilizes copper-bearing scrap to produce
metallic copper and copper based alloys. For the purposes of this discus-
sion, brass and bronze will be considered to be products of the secondary
copper industry due to similarities in the operations and an overlap in the
population of companies producing secondary copper, brass, and bronze. The
processes used in this industry include scrap pretreatment, melting, alloy-
ing, refining, and casting.
According to an extensive industry survey published in 1973 (NA-182),
there were 44 companies producing secondary copper, brass, and bronze
products. A more recently study identified forty-five secondary copper,
brass, and bronze smelters. The majority of this industry's production is
concentrated in the northeast quadrant of the country.
The raw materials used by this industry can be classified first as new
scrap (66 percent), i.e., produced in the fabrication of finished products,
or old scrap (34 percent), from obsolete, worn out or salvaged articles
115
-------
(US-357). Old scrap sources include wire, plumbing fixtures, electrical
machinery, automobiles and domestic appliances. Other materials with copper
values include slags, drosses, foundry ashes and sweepings from smelters and
copper processing industries. The sources of recovered copper were 870,464
short tons of new scrap and 441,841 tons of old scrap (SC-303).
A tabulation of the compositions of various standard brasses and
bronzes is given in Table 40. This table gives the composition of both raw
materials and products for secondary brass and bronze processors. Although
specifications for scrap impurities such as wire insulation, oil, grease, and
paint are not given, these materials often contribute Co the potential
effluents associated with processing.
TABLE 40. NOMINAL CHEMICAL SPECIFICATIONS FOR BRASS
AND BRONZE INGOT INSTITUTE STANDARD ALLOYS
Alloy
No.
1A
IB
2A
2B
2C
3A
3B
3C
3D
3E
4A
4B
5A
SB
6A
6B
6C
7A
8A
SB
8C
9A
9B
9C
9D
10A
10B
11A
11B
12A
12B
Classification
Tin bronze
Tin bronze
Leaded tin bronze
Leaded tin bronze
Leaded tin bronze
High-lead tin bronze
High-lead tin bronze
High-lead tin bronze
High-lead tin bronze
High-lead' tin bronze
Leaded red brass
Leaded red brass
Leaded semi-red brass
Leaded semi-red brass
Leaded yellow brass
Leaded yellow brass
Leaded yellow brass
Manganese bronze
Hi-strength mang. bronze
Hi-strength mang. bronze
Hi-strength mang. bronze
Aluminum bronze
Aluminum bronze
Aluminum bronze
Aluminum bronze
Leaded nickel brass
Leaded nickel brass
Leaded nickel bronze
Leaded nickel bronze
Silicon bronze
Silicon brass
Cu.Z
88.0
88.0
88.0
87.0
87.0
80.0
83.0
85.0
78.0
71.0
85.0
83.0
81.0
76.0
72.0
67.0
61.0
59.0
57.5
64.0
64.0
88.0
89.0
85.0
81.0
57.0
60.0
64.0
66.5
88.0
82.0
SN.Z
10.0
8.0
6.0
8.0
10.0
10.0
7.0
5.0
7.0
5.0
5.0
4.0
3.0
2.5
1.0
1.0
1.0
1.0
2.0
3.0
4.0
5.0
Pb.Z
1.5
1.0
1.0
10.0
7.0
9.0
15.0
24.0
5.0
6.0
7.0
6.5
3.0
3.0
1.0
1.0
9.0
5.0
4.0
1.5
Zn.Z
2.0
4.0
4.0
4.0
2.0
3.0
1.0
5.0
7.0
9.0
15.0
24.0
29.0
37.0
37.0
39.0
24.0
24.0
20.0
16.0
8.0
2.0
5.0
14.0
Fe,% A1,Z Ni.Z Si.Z Mn.Z
1.0 0.6 0.5
1.0 1.0 1.5
3.0 5.0 3.5
3.0 5.0 3.5
3.0 9.0
1.0 10.0
4.0 11.0 2.0 0.5
4.0 11.0 4.0 3.0
12.0
16.0
20.0
25.0
1.5 4.0 1.5
4.0
Source: NA-182
In addition to the scrap, other raw materials necessary for secondary
copper processing include fluxes of boron minerals, old glass and salt; minor
alloying components such as phosphorous, tin, and lead (if required); and
leaching or reaction agents such as sulfuric acid and ammonium carbonate.
116
-------
The classification system used to describe the various grades of
recovered copper roughly corresponds to the various stages of the secondary
refining process. In order of increasing copper purity, these grades of
recovered copper are (NA-182):
1) "White metals" (babbit, lead, and solder) from sweating
process. These may be used internally or sold to another
processor.
2) Copper powder
3) Copper shot
4) Fire-refined copper
5) Electrolytic-refined copper
The products of the brass and bronze industry are hardeners and alloy ingots.
There are 31 standard copper-base alloys produced by the members of the Brass
and Bronze Ingot Industries.
Wastewater Source Identification - Secondary Copper
The secondary copper, bronze and brass industry is typical of the
secondary nonferrous metals industry as a whole in that it is fragmented and
difficult to characterize. Qualitatively, the various processes making up
the industry are well known but hard data on process operating parameters
and effluent characteristics are very limited. Consequently, the process
descriptions in this section include many information gaps with respect to
water effluents.
Aqueous waste streams come from three main sources: 1) liquid wastes
from acidic or basic scrap leaching and dissolution processes, 2) waste
cooling water from pouring and casting operations, and 3) liquid wastes and
slimes from electrolytic refining. Much of the wastewater is either recycled
or disposed of rather than being extensively treated. There should not be
a serious problem if the ultimate long-term disposal is nonpolluting. The
results of a survey of industry practices are given in Table 41.
For each process in this industry segment, aqueous effluents have been
identified and characterized where possible. Table 42 lists each of the pro-
cesses for which effluent streams have been identified and summarizes the
available data on the characteristics of these wastewaters. The following
discussion describes the sources of these wastewaters in more detail.
117
-------
TABLE 41. SUMMARY OF WASTEWATER HANDLING PRACTICE AND DISPOSITION
USED BY SECONDARY COPPER INDUSTRY
NUMBER OF PLANTS (PERCENT)
CONTROL PROCESS
No water use
No treatment, discharge to
Stream
Sewer
Treat, discharge to
Stream
Sewer
Recycled, no discharge
Recycled, some discharge to stream
Periodic
Continuous
Recycled, some discharge to sewer
Periodic
Continuous
Brass and
Bronze
1
2
8
1
4
10
3
1
5
2
( 3)
( 6)
(24)
( 3)
(11)
(29)
( 9)
( 3)
(14)
( 6)
Copper
0
1 (14)
0
1 (14)
0
1 (14)
2 (29)
1 (14)
0
1 (14)
Combined
1
3
8
2
4
11
5
2
5
3
( 2)
( 7)
(18)
( 5)
( 9)
(25)
(11)
( 5)
(11)
( 7)
Source: EN-378
118
-------
TABLE 42. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES - SECONDARY COPPER
Source
Flow (It/min)
Stream Composition (mt.lt.)
Ref.
Comments
Secondary Copper Industry^
Grinding and Gravity Separation
- Slowdown from gravity
separation recycle
stream
72,000-
3,000,000
d/day
Insulation Burning
- Scrubber blowdown
Steam Distillation
- Spent ammonium
carbonate leaching
solution
Intermittent
Hydrothermal Hydrogen Reduction
* Spent ammonium Intermittent
'carbonate leaching
solution
Range tor 4 Plants
CN~
-------
TABLE 42 (continued).
ro
o
Source Flow (i/«in)
Secondary Copper Industry (Cont'd)
Blast Furnace/Reverberatory
Smelting/Converter Smelting
- Furnace cooling water
- Ingot cooling and 18,200-605,600
shot quenching water ft/day
Stream Composition (ng/t) Ref. Comments
Range for
ctr
Sb
As
Cd
Cr
Cu
Fe
Pb
Mn
Hg
Nl
Zn
pll
3 Plants EN-378 Refer to Table 46
~ _„ f°r specific analyses.
0.01
<0.02
<0.05
0.02 -0.066
0.560-3.376
0.63 -1.8
0.5 -4.3
0.133
<0.001
0.1
0.30 -17.8
7.87 -8.9
Electric Crucible Smelting
- Metal cooling water
Fire Refining
- Metal cooling water
Electrolytic Refining
- Spent electrolyte
- Slimes
Electrolytic Winning
- Spent electrolyte
- Slimes
Electrolytic Powder Production
- Spent electrolyte
See above.
See above.
EN-378 The replacement rate for
the electrolyte is as
much as 75% a month.
The blowdown Is usually
treated for metal value
recovery before dis-
charge. See Table 47.
Refer to Table 47.
Refer to Table 47.
-------
Grinding and Gravity Separation—
This process accomplishes the same function as Shredding, but uses an
aqueous separation medium and different input materials. The unit operations
involved in this process are grinding, screening, and gravity separation.
Their purpose is the concentration of the metal value in the scrap so that
the subsequent thermal refining steps will not be overburdened with waste
material.
A wide variety of materials with metal values are processed: a) slags
b) drosses, c) skimmings, d) foundry ashes, e) spills, f) sweepings and g) '
baghouse dust. These materials may be supplied by either an outside source
or other processes at the secondary smelter.
The liquid waste stream would contain any soluble constituents of the
gangue material, which encompasses a great variety of possibilities. Even
if the water in the gravity separation step is recycled, there will be a
blowdown/sludge stream which will create disposal problems. Examples of
wastewater compositions are presented in Table 43.
Insulation Burning—
This process is intended to separate insulation and other coatings from
copper wire by burning these materials in furnaces. The wire scrap is
charged in batches to a primary ignition chamber. Combustion is started with
auxiliary fuel and air. Volatile combustion products are then passed to a
secondary combustion chamber or afterburner. Further treatment of combustion
gases in a scrubber or baghouse is desirable if significant quantities of
particulates or hazardous vapors are generated in this process. In most
cases, the insulation burning is self-sustaining, but there can be problems
with wire coated with polyvinyl chloride, fluorocarbon polymers or other
flame resistant plastic formulations. If non-combustible inorganic materials
such as fiberglass or ceramics are present they must be removed separately,
either before or after burning.
The combustible portion of the wire scrap may include a considerable
variety of materials, such as rubber, paper, natural and artificial fibers
and fabrics, asphaltic materials or plastics such as polyethylene and poly-
vinyl chloride. Metallic and/or nonmetallic inorganic fillers may also be
present. Plastics formulated for flame resistance may have bromine, phos-
phorus and antimony compounds up to levels of several percent by weight.
Liquid waste from this process consists of scrubber blowdown liquid.
The nature of this material and hence the water treatment options required
will be determined by the contaminants present in the furnace effluent gas
stream.
Steam Distillation--
Copper is recovered from the leaching liquor of the ammonium carbonate
process by steam distillation and precipitation as copper oxide. Copper as
121
-------
TABLE 43. CHARACTER OF WASTEWATER FROM SLAG QUENCHING AND GRANULATION OR SLAG MILLING AFTER SETTLING
Product
KT/day
(con/day)
I/day
(gal/day)
Constituent
COD
Solids, diss.
Solids, ousp.
TOC
Phosphorus
Cyanide
Antimony
Cadmiua
Lead
Manganeae
p«
Plant
Iniak.
Cone.,
•8/1
170
23.2
1294
64
0.029
0.005
0.142
0.001
2.46
0.111
0.093
0.005
0.297
0.325
0.0004
0.024
1
9 - H.t Lo.dln«*
Ditch*
Cone . . Lot
«I/1 kg/Hi
-Jl"
(50)
3,000.000°
(792.000)
190 1.325
25.3 0.139
1620 21 . 519
336 18.013
0.031 0.0001
0.004 HLC
0.111 HLC
0.001 HLC
2.60 0.001
0.067 HLC
0.071 HLC
0.007 HLC
0.399 0.0005
0.0003 HLC
0.030 HLC
0.622 HLC
1 HLC
8.32
r«
ding
(Ib/ton)
(2.650)
(0.27B)
(41.18)
(36.03)
(0.0002)
(0.001)
(0.001)
Plant 11 - Gross Loading
Intake Discharge
Cone . . Cone . , Loading.
•g/1 mg/1 kg/KT
TlP
(119)
545.400
(144.100)
2965 14.976
—
— 3900 19.695
—
630 3.1 2
HP"
0.11 0.0006
19.78 0.100
0.120 0.001
13.0 0.066
— 0.35 0.002
80.35 0.631
9.8
(lb/con)
(29.95)
(39.39)
(0.0012)
(0.20)
(0.002)
(0.132)
(0.004)
(1.262)
Intake
Cone . ,
•g/i
71.33
18. 333
421.3
387.67
63.3
0.293
0.053
<0.0
<0.02
0.667
0.067
12
1.833
0.467
<0.001
0.133
6.0
11.0
7.4
Dls
Cone. ,
•g/1 kg/Ml
Alloy
9.7
(10.7)
72,670
(19.200)
104.67 0.250
22.67 0.032
6456 45.210
2953.7 19.224
268.67 1.539
0.403 0.001
0.161 0.001
2.667 0.021
<0. 02 NLC
6.0 0.040
1.6B3 0.012
1250 9.275
163.667 1.212
43.33 0.321
0.002 0.001
18.0 0.134
983.33 7.322
23.333 0.092
8.53
chdrHu
Loading
(Ib/ton)
(0.50)
(0.064)
(90.42)
(38.45)
(3.078)
(0.002)
(0.001)
(0.042)
(O.OBO)
(0.012)
(18.55)
(2.424)
(0.642)
(Q.O02)
(0.268)
(14.64)
(0.184)
Plant
Intake
Cone . ,
•8/1
662.400
(175.000)
685
1,754
1.0
0.10
1)
0.05
0.16
0
9.35.
39 - Htft Loadlnt
Ols. l.oi a.
Cone.. Lootlin^
•g/l kg/Kf
Alloy
43.5
(49)
617,000
(163,000)
733 0.681
1,«52 1.J9
1.0 NI.C
0.11 0.00514
14 0.0142
0.05 MLC
0. 17 0.110014
0 N1.C
9.35
(IH/I..II)
(1. )b)
(2.78)
(0.00028)
(0. <>.•»/, )
(O.UOfl.'H)
* Slag granulation.
b Slag Milling.
c Estimated time for granulation 6 hr/day.
HV ™ not found.
e NLC - no leading calculable.
Suurcti EN-462
-------
cupric ion in an ammonium carbonate solution from the leaching process is
the input material for this process. Boiling the solution precipitates the
copper as the oxide. The steam distillation may take place at either atmos-
pheric or higher pressures. This material is dried before it is sent to
other processes such as hydrogen reduction or blast furnace/reverberatory
smelting for copper recovery.
If the liquid waste is recycled to the leaching process, there is little
potential for water pollution from this step. However, it is a potential
wastewater source.
Hydrothermal Hydrogen Reduction—
As an alternative to the steam distillation the copper may be recovered
from the ammonium carbonate leach solution by hydrothermal hydrogen reduc-
tion. Copper-containing ammonium carbonate solution containing 10 to 30 g/
liter of copper is the input material. The heating of the liquor under
hydrogen pressure precipitates the copper as a powder. The copper is fil-
tered, washed, dried and sintered under a hydrogen atmosphere. The powder
is then ground and screened. The spent liquor is recycled to the leaching
process. The hydrogen reduction is carried out at a temperature of 160 to
225°C (325-400°F) and 3.58 megapascals (500 psig). The spent liquor is a
possible liquid pollutant, but may be recycled to the leaching process.
Blast Furnace/Reverberatory Smelting—
This process uses equipment and techniques similar to primary copper
ore smelting to produce black copper containing 70 to 80 percent copper for
further refining. The feed is scrap of lower grade than that input to other
secondary refining processes. The overall chemical process in the blast
furnace is based on the reduction of copper by the coke fuel and the carbon
monoxide formed from it. Impurities such as iron combine to form a slag
which separates from the molten copper. The slag and metal mixture is tapped
to a reverberatory furnace for separation.
The scrap is charged at the top of the blast furnace and proceeds down-
ward, meeting reduced gases from the fuel at the bottom. The oxides of the
base metals either dissolve in the slag, fume off, or are reduced and dis-
solve in the copper. The black copper product may contain zinc, lead, tin,
bismuth, antimony, iron, silver, nickel, or other metals contained in the
scrap. Sulfur in the coke or other feed materials reacts with the copper to
form copper sulfide; this reaction can be largely avoided by using low-sulfur
coke. The molten product may be cast into ingots or transferred in the
molten state to a converter for further purification.
The scrap types normally charged to a blast furnace include high iron
content copper and brasses, motor armatures, foundry sweepings, slags,
drosses, and skimmings. It was then estimated in 1961 that the minimum
profitable copper content was about 30 percent (SP-058). In 1973, it was
reported that feeds containing as little as 10 percent copper can be pro-
cessed economically (BU-184). Lower grade output of previous scrap prepara-
tion processes are used as inputs to the blast furnace.
123
-------
The coke used as a fuel and reducing agent comprises about 10 percent
of the charge. Limestone and millscale (iron oxides) are added to form an
iron silicate slag for fluxing purposes.
The copper is maintained somewhat above its melting point of 1083°C
(1981°F), usually in the range of 1090 to 1150°C (2000 to 2100°F). The slag
leaves the furnace at about 1040°C (1900°F) (DA-069). A typical secondary
blast furnace has a maximum diameter of 1.3 meters (50 inches), tapering to
1 meter (40 inches) at the top, with a water jacketed section 3 meters (10
feet) high. Air flow required is 38 to 46 m3/min/m2 of area at the bottom
(125 to 150 ft3/min/ft2). The nominal capacity of such a unit would be in
the range of 55 to 65 metric tons/day (60 to 70 short tons/day).
The coke charge supplies both process heat and acts as a reducing agent.
Cooling water is also required by the furnace, and in the ingot casting and
shot quenching operations.
The particulate emissions consist of fly ash, soot, and metal and metal
oxide fumes. Total particulate emissions have been estimated to be 25 kg/
metric ton (50 Ibs/short ton) (SH-106). Particulate control equipment
usually includes settling chambers, baghouses, and possibly electrostatic
precipitators and wet scrubbers.
Wastewater will result from furnace cooling, ingot casting, slag
quenching operations, and possibly scrubber blowdown. Discharge rates can
be minimized by recycling this water.
Converter Smelting—
The black copper from blast furnace/reverberatory smelting can be fur-
ther refined to increase the copper content from 70-80 percent to 90-99
percent. Most of the product, called blister copper, is poured and cast or
transferred molten to a fire refining furnace. A lesser amount of direct
product is produced in the form of copper shot by water quenching.
The process steps involved in converter smelting are a) charging with
molten black copper, b) blowing with air to oxidize copper sulfides and other
metals, c) deslagging, d) secondary blowing, and e) final slag skimming.
Most of the reactions are exothermic; thus, no external heat is required. In
fact, if the iron content of the black copper feed is too high, pure copper
scrap may have to be added to the charge to help keep the temperature under
control. A flux containing silica (e.g, sand or glass) is usually added to
react with iron oxides. This forms an iron silicate phase which is removed
as slag.
Black copper of 70 to 80 percent purity, air, and silica flux are the
feed materials. The impurities in the black copper may be iron or copper
sulfides, and various other metals and metal oxides such as tin, lead,
antimony and zinc.
124
-------
Wastewater from ingot cooling and slag quenching is also generated.
Typical effluent water quality data for a metal cooling operation is given in
Electric Crucible Smelting —
Feed containing low copper values can also be refined by using electric
heating and pure oxygen in place of air for oxidation. Feed can be either
pretreated scrap, raw scrap or black copper from blast furnace/reverberatory
smelting. The same sequence of charging, melting, blowing and skimming
which is used in the previous two processes is also used here. An advantage
of electric heating is the fact that it gives better control over the exo-
thermic portions of the process. Liquid wastes will be similar to the
analogous coke- fueled process.
Fire Refining —
In this process, blister copper is further refined to the 99-9 percent
purity level. Clean, high grade copper scrap can also be charged directly
to this process, which is very similar to the refining process used in the
primary copper refining industry. In the fire refining process, copper may
be either partially refined to a grade suitable for electrolytic purification
or further refined to the practical limit in order to achieve a commercially
salable product.
Fire refining can be accomplished in either a reverberatory or a cylin-
drical tilting furnace. The latter type is generally used with molten copper
feed to cast anodes for electrolytic refining. The production of ingot and
bar or the melting of blister copper ingots is usually done in a reverberatory
furnace .
Both oxidation and reduction of impurities are done in this process.
The process steps are a) charging the furnace; b) melting in an oxidizing
atmosphere; c) skimming the slag; d) blowing with air or oxygen until the
melt is about 10 percent Cu20 (1 percent total oxygen); e) adding a reducing
agent and surface cover of charcoal or coke; f) reducing the oxygen content
to 0.03 to 0.05 percent by forcing green maple or birch logs beneath the
surface of the melt, agitating the melt with reducing gases such as hydrogen,
hydrocarbons, and carbon monoxide that are formed during the "poling" process;
g) reskimming the slag, and h) casting the melt into ingots, wire bars, and
other products. Reformed gas is commonly used as a reducing agent instead of
wooden poles.
Fluxes may be added to extract impurities, e.g., sodium carbonate for
arsenic and antimony. A variety of specialized reagents and procedures are
available for copper material of special composition (SP-058).
The usual liquid wastes for cooling and quenching operations are
produced.
125
-------
TABLE 44. CHARACTER OF WASTEWATER FROM MOLTEN METAL COOLING AND QUENCHING
Plant 26 -
Intake
Gross
Cone., Cone.,
•K/1 Bg/1
Product
MT/day
(ton/day)
Flow
I/day
(gal/day)
Constituent
Alkalinity
COD
Solids Total
Solids, Dlss.
Solids, Susp.
TOC
Phosphorus
Cyanide
Antlauny
Arsenic
Boron
CadBltiB
Chroaiiui
Copper
Iron
Lead
Manganese
Mercury
Nickel
Zinc
Oil and grease
PH
Loading
Discharge
Loading
kg/Mr (Ib/ton)
IKF
(30)
755.000 605,600
(199,500) (160,000)
104
160 275.5
0.29
fffl
— NF
NF
NF
0.
0.000003 0.
0 0.
1.
NF
NF
NF
0.
8.
8.
02
560
89
50
30
5
5
2.316
1.687d
0.006
0.0004
0.010°
0.020i>
0.034
—
—
0.007
0.189
(4.632)
(3.374)
(0.012)
(0.0008)
(0.02)
(0.040)
(0.068)
(0.014)
(0.378)
Plant
Intake
Cone . ,
•g/1
29.500
( 7.800)
79
306
301
5
0.01
0.06
<0.01
<0.02
0.002
0.05
0.60
0.21
0.11
0.20
<.001
<0.1
<0.1
—
7.2
38 - Met Loading
Discharge"
Cone. .
•g/1
Load ln:
kg/Ml
t
Ufa/ton)
Alloy
~T7
(10.7)
18.200
( 4.800)
56.67
25.0
207.3
192.63
14.67
9.33
0.183
0.057
0.01
<0.02
0.047
<0.05
1.067
0.633
0.5
0.133
•c.OOl
0.1
0.4
22.33
7.87
NLC
0.047°
MLC
NLC
0.012
0.018°
0.0003
MLC
0.0002
NLC
0.0001
NLC
0.0001
0.0006
0.0006
NLC
NLC
0.0002
0.0007
0.042C
(0.094)
(0.024)
(0.036)
(0.0006)
(0.0004)
(0.0002)
(0.0002)
(0.0012)
(0.0012)
(0.0004)
(0.0004)
(0.084)
Plane 43 - Gross LoadinR
Intake
Cone . , Cone . ,
•g/1 -g/1
Discharge
Loading
kg/KT (Ib/ton)
Alloy
61.9
(68.2)
75.700
(20,000)
448.8
1160
— 1020
140
0.0833
0
0.066
3.376
1.792
4.337
0. 164
17.834
8.9
0.549
1.419
1.247
0.171
0.0001
NLC
0.0001
O.OO4
0.002
0.0053
0.0002
0.022
(1.098)
(2.838)
(2.494)
(0.342)
(0.0002)
(O.OO02)
(0.008)
(0.004)
(0.0106)
(0.0004)
(0.044)
Includes Borne equipment cooliAg In discharge.
NLC - no loading calculable.
Gross loading.
d Net loading.
Casting lime estimated at 4 hours.
f
HF - ac
Source: BN-378
-------
Electrolytic Refining—
Copper anodes of 99.9+ percent purity may be produced as the output of
the fire refining process. Oxygen is the major impurity in the product
usually at the 0.03 to 0.05 percent level. As the anodes dissolve in the
electrolysis process, impurities either dissolve in the electrolyte or fall
to the bottom of the containing cell to be collected as slime. The cathodes
produced are melted and cast in subsequent processes.
The electrolyte accumulates both soluble anode impurities (antimony,
bismuth, lead, nickel, iron and zinc) and copper. A replacement rate of up
to 75 percent a month of the electrolyte is circulated to liberator cells
with insoluble lead anodes and copper starter sheets as cathodes. The copper
produced is recycled to the appropriate process, depending on its purity.
The effluent liquids may be concentrated and processed for further metal
recovery, e.g. , nickel as nickel sulfate. The slime from both the primary
electrolysis and the electrolyte purification step is filtered or centrifuged.
This material may either be processed further for precious metal recovery or
discarded. Much or all of the wastewater may be treated and recirculated.
One available analysis of electrolytic process wastewater is given in Table
45.
Electrolytic Winning—
Copper is recovered as impure cathodes from a copper sulfate solution
which usually comes from the sulfuric acid leaching process. The copper pro-
duced must be further treated electrolytically to attain the purity of regu-
lar electrolytic copper.
In this process, the spent electrolyte is continuously bled from the
system, regenerated, and recycled. The process steps are a) preparing the
electrolyte, b) electrolyzing copper or starter sheet cathodes, c) removing
the cathodes, d) cleaning the cathodes, e) replacing the starter strips, and
f) regenerating the electrolyte (NA-182).
There will be spent electrolyte residues similar to those of electro-
lytic refining. There will also be slimes formed from other metals. The
amount of slimes formed will depend on the type of scrap originally leached
with sulfuric acid (NA-182).
Electrolytic Powder Production—
Pure copper powder is produced by electrolysis from the copper cathodes
by electrolytic refining. The process steps are a) use pure electrolytic
copper as anodes, b) deposit copper powder, c) filter the powder from the
cell electrolyte, d) recycle the electrolyte, e) rinse the powder, f) dry the
powder in a reducing atmosphere of hydrogen and carbon monoxide, and g)
classify, blend and package the powder. Electricity is required as the
driving force for the electrolytic reaction, and heat is required to dry the
powder.
127
-------
TABLE 45. CHARACTER OF WASTEWATER FROM ELECTROLYTIC REFINING
(TREATED BEFORE DISCHARGE3)
Volume: 94,600 £/day (25,000 gal/day)
Operation: Electrolytic refining
K
Production: 179 MT/day (197 short tons/day)"
Constituent
Alkalinity
BOD, 5-day
COD
Solids
Diss. Solids
Susp. Solids
Total Vol. Solids
Nitrate (as N)
Sulfate (as S)
Sulfite (as SO )
Chloride
Aluminum
Antimony
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Silver
Sodium
Zinc
Oil and Grease
PH
Temp (Win), C(F)
Temp (Sum), C(F)
Intake
mg/Jl
22
16
29
30
40
3
-
8.0
4
6.4
7.6
14 (57)
22 (72)
Discharge,
mg/£
27
0
—
1776
1611
12
336
0.22
1047
12
4.1
0
0.0005
0.0
0.0
94
0.00003
0.00006
0.0047
0.0004
0.0014
0.0027
0
0.00037
7.2
0.00001
3.1
0.00065
8.0
27 (80)
29 (85)
Net Cone.
mg/£
5
16
—
1746
1571
9
336
0.22
1047
0.2
-3.9
-.4
0.0005
0
0
94
0.00003
0.00006
0.0047
0.0004
0.0014
0.0027
0.00037
7.2
0.00001
3.1
0.00065
Net
kg/MT
£.0026
NLCC
NLC
0.922
0.830
0.0048
0.178
0.00013
0.555
0.00017
NLC
NLC
2.6x10 7
NLC
NLC
0.0498
2x10 8
3x10 8
2.6x10 6
1.7x10 7
8.7x10 7
1.3x10 2
NLC
1.7x10 7
0.0039
5xlO~9
0.0018
3x10 7
Loading
(Ib/ton)
(0.0052)
(1.844)
(1.661)
(0.0096)
(0.356)
(0.00026)
(1.110)
(0.00035)
(5.2xlO~7)
(0.0996)
(3x10 8)
(6x10 8)
(5.2x10 6)
(3.5x10 7)
(1.7x10 6)
(2.6x10 6)
(3.4xlO~7)
(0.0079)
(1x10 8)
(0.0035)
(6x10 7)
Discharge would be outflow of excess washdown water from treatment plants
in event of breakdown and is not continuous.
Production at time of permit application (1971).
c
NLC = no loadings calculable.
Source: EN-378
128
-------
Atmospheric emissions include gaseous emissions of carbon monoxide
hydrogen, and possibly arsine and unburned fuel, and particulate emissions
consisting of dusts from the drying and powder hauling steps. No quantita-
tive data are available.
Liquid wastes similar to the spent electrolyte solutions generated by
electrolytic refining are produced.
SECONDARY LEAD/ANTIMONY INDUSTRY
Industry Description - Secondary Lead/Antimony
The secondary lead and antimony industries are grouped together for the
purposes of this assessment because a considerable overlap exists between the
population of companies producing secondary lead and antimony products and
those using similar raw materials. The major differences between these
industries are a) some antimony is recovered from antimony-bearing scrap that
does not contain lead and b) the use of shaft and rotary furnace smelting in
recovering antimony.
The lead/antimony segment of the secondary nonferrous metal industry
recovers, processes, remelts, refines, and alloys lead- and antimony-bearing
scrap to produce lead, lead-antimony alloys, and lead oxides. According to
the Commodity Data Summaries 1976, the secondary lead/antimony segment con-
sisted of 130 individual plants (US-357). Sixty-eight of these plants were
identified in a more recent report (CO-R-720). These plants are mainly
located in or near the following cities: New York, Philadelphia, Baltimore,
Cleveland, Chicago, Baton Rouge, Dallas, Los Angeles, and San Francisco.
The total 1975 domestic recovery of secondary lead excluding that re-
covered at primary plants was 520,000 metric tons (563,000 short tons) valued
at 260 million dollars (US-357). Old lead-bearing scrap accounted for 86
percent of the total secondary recovery of lead metal and alloys. Old and
new scrap accounted for approximately 48 percent of the total domestic pro-
duction and 47 percent of the total consumption. Storage batteries accounted
for 57 percent of this scrap (US-357). The consumption of lead metal and
alloys was by 600 firms in virtually all states (US-357). The major end use
of lead was for transportation, 53 percent as batteries and 16 percent as
gasoline additives (US-357). Other major end-uses of lead and alloys
included: a) electrical materials, b) ammunition, c) paints, and d) con-
struction.
The total 1975 production of secondary antimony was 15,100 metric tons
(16 600 short tons) valued at 58.1 million dollars (US-357). Approximately
55 percent of the 1975 domestic consumption of antimony was derived from
scrap. The major uses of antimony were:
129
-------
Storage batteries (44%)
Chemicals (17%)
Fire retardants (15%)
Rubber products (10%)
Ceramic and glass (6%)
The major types of scrap processed by this segment are (NA-182) :
Soft lead
• Hard lead
Cable lead
• Battery-lead plates
• Mixed common babbitts
• Solder and tinny lead
Type metals
Drosses and residues
• Antimony-bearing metal
The scrap breakdown used in producing antimony for 1975 was (US-357):
Battery plates (65%)
Type metal (14%)
Antimony-bearing metal (21%)
The production of old scrap processed by this segment is relatively high in
comparison to scrap sources for other major segments. Battery scrap is the
major old scrap source; all other types of old scrap are from a variety of
domestic sources. The scrap contains elemental lead, compounds of lead, or
lead alloyed with tin, antimony, arsenic, cadmium, copper, indium, silver,
zinc, tellurium, or bismuth. The scrap can also contain organic contaminants
such as insulation, grease, and oil as well as sulfur compounds. Products
from the lead/antimony segment of the secondary nonferrous metal industry are
(NA-182) :
• Soft lead ingots
• Semisoft lead ingots
• Hard lead ingots
• Lead alloy ingots
• Battery lead oxide
Lead pigments (PbaOif and PbO)
Soft lead is a high-purity lead. These are generally products of pot furnace
refining.
Semisoft lead usually is produced in a reverberatory furnace and con-
tains 0.3 to 0.4 percent antimony and up to 0.05 percent copper (DA-069).
Hard lead is normally a blast furnace product. A typical composition in-
cludes 5 to 12 percent antimony, 0.2 to 0.6 percent arsenic, 0.5 to 1.2
percent tin, 0.05 to 0.15 percent copper, and 0.001 to 0.01 percent nickel
(DA-069) .
130
-------
Wastewater Source Identification - Secondary Lead/Antimony
Lead and antimony are recovered from scrap by three major manufacturing
operations: 1) scrap pretreatment, 2) smelting, and 3) refining/casting.
The scrap pretreatment operation involves physical crushing and separating as
well as sweating in a rotary or reverberatory furnace. The smelting opera-
tions for lead take place either in a reverberatory furnace which generally
produces a semisoft lead, or in a blast furnace, which produces a hard lead.
Antimony smelting operations include shaft, rotary, reverberatory, and blast
furnace smelting. The refining/casting operation involves fluxing partially
refined lead in a pot kettle to produce a soft lead which can be cast as a
product or alloyed, or oxidizing lead products to produce battery lead oxides
or lead oxide pigments.
Five of the sixteen processes in the secondary lead/antimony industry
are potential sources of water pollution. These five processes are: a)
battery breaking, b) zinc leaching, c) shaft furnace smelting, d) reverbera-
tory furnace smelting, and e) blast furnace smelting. The water pollution
from the latter two processes is from the effluent of wet scrubbers.
Aqueous effluents from the battery breaking process are significant
because 57 percent of the total secondary lead production comes from old
storage batteries (US-257). Assuming that the old batteries contain only
one percent sulfuric acid by weight and the average lead concentration in
the scrap batteries is 76 percent (CO-371), the total annual sulfuric acid
emissions from this process would be approximately 3900 metric tons (4300
short tons). This effluent is hazardous and needs to be controlled. The
other constituents in these aqueous effluents consist of dissolved lead,
lead compounds, and metal alloys.
The zinc leaching process is another major source of water pollution in
this industry- The constituents in the wastewater consist primarily of the
spent leaching liquor, sulfuric acid, zinc, antimony, lead, copper, metal
sulfides, and metal chlorides. The effluent from this process is usually
neutralized and sent to unlined settling ponds.
The wet scrubber effluent from the reverberatory and blast furnace
smelting processes contains hazardous constituents found in the processes'
air emissions. These aqueous effluents are usually sent to unlined settling
ponds.
Table 46 lists each of the processes for which effluent streams have been
identified and summarizes the available data on the characteristics of these
wastewaters. The following discussion describes the process specific sources
of these wastewaters in more detail.
Battery Breaking—
Fifty-seven percent of secondary lead and 65 percent of secondary
antimony comes from obsolete automobile batteries. This process separates
the lead from nonmetallic portions of the battery by a) draining, b) crushing
131
-------
TABLE 46. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES - SECONDARY LEAD
Source
Flow (E/nin)
Stream-Composition (mg/t)
Ref.
Comment a
Secondary Lead Industry
Battery Breaking
- Battery acid
Zinc Leaching
- Spent leaching solution
Shaft Furnace Smelting
Rotary Furnace Smelting
Reverberatory Furnace Smelting
Blast Furnace Smelting
Reverberatory Smelting
Blast (Cupola) Furnace Smelting
Concentrated H2SO» containing Fb compounds and
other alloying compounds.
Dilute sulfurlc acid containing:
Zn
Sb
Pb
Cu
Chlorides
Sulfides
EN-399 Neutralized and dis-
charged to settling
ponds.
-------
the battery, and c) manually screening to separate the lead protion from
nonmetallic portions (NA-182). The separated scrap normally has the follow-
ing composition (CO-371):
PbSCK, 30-40%
Pb02, 15-20%
PbO, 2-3%
Nonmetallic content, 4-6%
Pure and antimonial lead, balance
The battery scrap fed to the process is composed mainly of the following
constituents:
pure and antimonial lead from plate grids, connections,
bridges, and terminal posts;
copper from terminals;
lead oxides (PbO and Pb02) and lead sulfate (PbS(H)
pastes;
• separators and outercase residues of ebony, glass
fiber, paper, polyvinyl chloride, and polystyrene
(CO-371).
Waste products are primarily solid, with lesser amounts of liquid and
dusts. Solid wastes include the organic materials used in battery case con-
struction contaminated with residual sulfuric acid and lead compounds.
Liquid wastes are composed of sulfuric acid, water and lead and alloying
compounds.
Zinc Leaching—
In this process, zinc is leached from the collected particulate matter
that is emitted from the Reverberatory Smelting Process. The particulate
matter is washed with a stream of dilute sulfuric acid to dissolve the zinc
and the undissolved residue is fed to the blast furnace.
Baghouse residues contain tin, antimony, copper, zinc, lead, sulfides;
and chlorides and dilute sulfuric acid. Typical concentrations of zinc and
lead are 13 to 18 percent by weight, respectively.
The aqueous effluent consists of dilute sulfuric acid containing zinc
compounds and traces of antimony, lead, copper, sulfides, and chlorides.
The spent leaching liquor is neutralized and discharged to settling ponds
(EN-399).
Shaft Furnace Smelting—
A shaft furnace containing layers of coke is used to melt paste constit-
uents resulting from battery breaking or rotary furnace smelting (mostly
133
-------
sulfates and oxides of lead). The salts are thereby reduced to lead metal
of high purity. Lime may be added to counter the dressing effects of sili-
cates present. Lead sulfate, lead oxides, coke (reducing agent), and lime
are inputs for this process.
Potential effluents from this process are water jacket or mold cooling
water or blowdown from wet scrubbers.
Rotary Furnace Smelting—
Scrap metal and a salt mixture consisting of a paste of metal oxides and
sulfates are introduced into a rotary furnace in which the temperature is
controlled to effect melting of the metal, but not of the salt mixture. The
specific gravity difference between lead and the metal salts causes the salts
to float, which makes possible the separation of the alloyed metal containing
4 to 6 percent antimony (CO-371). The salts are removed and further pro-
cessed in a shaft furnace. The rotary furnace is heated to temperatures of
600 to 700°C (CO-371).
Potential effluents from this process are mold cooling water and
blowdown from wet scrubbers.
Blast Furnace Smelting—
Slag from the reverberatory furnaces, babbitt metal, type metal and
battery scrap are charged to a blast furnace to produce a lead-antimony
alloy. A mixture of these metal scraps, slags, and coke is continuously
charged to the furnace where it is heated to form the molten alloy and waste
slag. The oxides of antimony and lead contained in the slag from the reverb-
atory furnace are reduced to the metallic state by the carbon monoxide formed
by combustion of coke in the furnace. This process is very similar to Blast
Furnace Smelting in the Secondary Lead Smelting segment. Waste cooling water
from the furnace water jacket constitutes a liquid waste stream.
Reverberatory Smelting—
This process is used to partially purify and density lead scrap. The
furnace feed can be pretreated, untreated, or mixed scrap. Pretreated lead
scrap, battery plates, oxides, drosses, lead residues, and collected flue
dusts are all inputs for this process. The process steps are: a) contin-
uously charging the furnace with a mixture of lead scrap and collected flue
dusts as the charge melts, b) periodically tapping the antimonial slag that
rises to the surface of the melt, and c) tapping the molten lead which may
be fed to a refining/casting process or cast into ingots as a semisoft or
possibly hard lead product (NA-182, SI-106). The slag is fed to a blast
furnace.
The temperature in the reverberatory furnace is high enough to oxidize
the sulfides present in the lead scrap to sulfur dioxide and trioxide, which
are emitted in the stack gases along with normal combustion products. Par-
ticulate emission concentrations range from 16 to 50 g/m3 (7 to 22 grains/
134
-------
ft ) and includes oxides, sulfides, and sulfates of lead, tin, arsenic,
copper, and antimony (EN-071). The particle size of unagglomerated particu-
late matter ranges from 0.07 to 0.4 microns, with a mean diameter of 0.3
microns (DA-069). Typical constituents of collected particulate matter
include tin, antimony, copper, lead, zinc, sulfides, and chlorides. The
lead content is typically about 17 to 18 percent (EN-399).
Particulate emissions are generally controlled with a gas settling/
cooling chamber and a fabric filter. Control efficiencies in excess of 99
percent can be effected by this system. Wet scrubbers are sometimes employed
to control sulfur oxide emissions (NA-182, EN-071). A potential wastewater
stream is wet scrubber effluent.
Blast (Cupola) Furnace Smelting—
This process utilizes pretreated scrap, antimonial (reverberatory) slag,
and rerun (recycled) slag to produce a hard lead as a final or intermediate
product. The blast or cupola furnace is used to perform this function. The
blast furnace is a refractory-lined cylinder open at the top into which
alternate layers of metal, coke, and flux are charged. The process steps
are: a) adding the charge intermittently as melting proceeds, b) introducing
air through the tuyeres in the bottom to permit combustion of the coke in the
charge (this reaction provides both heat and a reducing atmosphere), c)
removing the molten lead continuosly, d) removing slag intermittently, and
e) casting the molten hard lead into large ingots or transferring to refin-
ing kettles. Approximately 70 percent of the lead charged can be recovered
as product. The remaining 30 percent is rerun slag.
A typical charge to the blast furnace contains: 82.5 percent drosses,
oxides, leaching residue, and reverberatory slag; 5.5 percent coke; 4.5 per-
cent rerun slag; 4.5 percent scrap iron; and 3 percent limestone (DA-069).
The drosses consist of copper, caustic, and dry drosses from kettle furnace
refining/casting processes. The reverberatory slag is composed of lead,
silica, tin, arsenic, copper, and antimony. The rerun slag is a highly
silicated slag tapped from previous blast furnace runs. The iron and lime-
stone form an oxidation-retardant flux that floats to the top of the melt.
Waste streams produced by this process include atmospheric emissions,
solid wastes, and in some cases, wet scrubber effluent. Gaseous emissions
can be controlled by afterburners or wet scrubbers. Baghouses with pre-
coolers have generally been the most acceptable particulate control devices.
The efficiency of particulate removal by baghouses generally exceeds 95
percent. A potential wastewater stream is wet scrubber effluent.
SECONDARY ZINC INDUSTRY
Industry Description - Secondary Zinc
The secondary zinc industry processes zinc-bearing scrap to produce
metallic zinc and zinc-base alloys. The processes used in this segment of
the nonferrous metal industry include mechanical, hydrometallurgical, and
135
-------
pyrometallurgical scrap pretreatment techniques, remelting and distilling,
scrap zinc oxide reduction to metallic zinc, and zinc oxide production
through modification of distillation operations.
The zinc segment of the secondary nonferrous metal industry consists
of only twenty-three firms (CO-R-720). Three primary smelters and six
secondary smelters accounted for the total secondary zinc slab produced,
44,000 metric tons (49,000 short tons), in 1975.
The raw materials used by the secondary zinc industry are zinc- and
copper-based scrap, fluxes, alloying agents, and individual process inputs
such as sodium carbonate, water, and carbon.
Classes of new scrap consumed by smelters and distillers include new
clippings, skimmings and ashes, die-cast skimmings, galvanizers' dross, flue
dust, and chemical residues. Approximately three-fourths of all new scrap
processed is zinc- and copper-base alloys from galvanizing and die-casting
pots (MC-194). Included in the old scrap category are old zinc engravers'
plates, diecastings, and rod and die scrap. The total amount of zinc scrap
consumed by smelters and distillers in 1975 amounted to 263,000 metric tons
(290,000 short tons) (US-357).
The zinc content of scrap may range from 40 to 100 percent. Typical
die-cast scrap composition may include 3 to 5 percent aluminum and 1 to 3
percent copper, although magnesium is now frequently used in place of copper
(MO-170). The main sources of zinc scrap are listed below (CA-305, MC-200):
• brass mills
• galvanizing plants
• chemical plants
• engraving platemakers
fabricators of products from roller zinc
• die casters
• auto wrecking yards
• electric utilities
railroads
aircraft plants
• demolition contractors
• government agencies.
Other input materials to the secondary zinc industry are alloying agents.
The most common ones are aluminum, copper, lead, and magnesium.
Fluxing agents are used to remove impurities present in scrap. Those
most in use include zinc chloride and ammonium chloride although the latter
causes fuming and is not employed except for special cases. Secondary zinc
is recovered as zinc slabs, zinc dust, and zinc oxide. Zinc slabs can either
be the pure metal or zinc alloys.
136
-------
Wastewater Source Identification - Secondary Zinc
Three general classes of operations are carried out in the secondary
zinc industry: scrap pretreatment, melting, and refining.
The purpose of scrap pretreatment is to partially remove both metal and
nonmetal contaminants and to physically prepare the scrap for further pro-
cessing. The pretreatment processes in use are based on mechanical, pyro-
metallurgical, or hydrometallurgical methods. Mechanical processing involves
physical reduction of the scrap and some means of separating the zinc from
contaminating components. Sweating is the term applied to the pyrometallur-
gical process used to separate zinc from higher melting metal and inorganic
impurities. Kettle, rotary, reverberatory, muffle, and electric resistance
furnaces are employed to sweat zinc-bearing scrap. The primary hydrometal-
lurgical pretreatment method is sodium carbonate leaching which is used to
process skimmings and residues.
In the melting operation, scrap is melted and usually fluxed to remove
impurities in crucible, kettle, reverberatory, or electric induction fur-
naces. The product of this step serves as feed to the refining operation.
Secondary refining is based on distillation of metallic zinc and in some
cases subsequent oxidation. This type of refining removes the metallic and
nonmetallic contaminants remaining after pretreatment and melting. Some
secondary plants carry out reduction processes to recover zinc from dross,
air pollution control residuals, or contaminated zinc oxide.
While only one process is directly associated with a wastewater stream
(Sodium Carbonate Leaching), cooling water used in the casting step is
another potential liquid effluent source. Wastewater from the leaching pro-
cess is treated by precipitation. Metal cooling water is either sent to
settling ponds or to the sewer.
Solid wastes from this process include skimmings, drosses and unmelted
residues from the sweating and melting operations; distillation residues
which contain 10 to 50 percent zinc; and baghouse dusts. Depending on their
metal content and the plant's processing scheme, these solids may be re-
cycled. Residues which are not recycled are typically disposed of in open
landfill sites. Runoff and leachate from these disposal areas represent
potential hazards to surface- and ground-water reservoirs because of the
hazardous constituents contained in these solid wastes.
Table 47 lists each of the processes for which effluent streams have
been identified and summarizes the available data on the characteristics of
these wastewaters. The following discussion describes the sources of these
wastewaters in more detail.
137
-------
TABLE 47. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER
SOURCES - SECONDARY ZINC
Stream
Flow Composition
Source (&/min) (mg/&) Ref. Comments
Secondary Zinc Industry
Sodium Carbonate
Leaching
- Spent leaching
solution No data. No data. CO-R-467 Consists pri-
marily of NaCl
and NazCOs.
Kettle (Pot) Melting
Crucible Melting
Reverberatory Melting
Electric Induction
Melting
- Mold cooling
water No data. No data. CO-R-467 Only in cases
where water
cooling is used.
Sodium Carbonate Leaching—
Residues are chemically treated to leach out and convert zinc to the
oxide form. The scrap is first crushed and washed. In this step, the zinc
is leached out of the material. The aqueous stream is treated with sodium
carbonate (NaaCOs), causing zinc to preciptiate as the hydroxide and/or
carbonate. The precipitate is then dried and calcined yielding crude ZnO.
The output from this process is normally sent to a primary smelter for reduc-
tion to elemental zinc. Aqueous effluents from this process contain sodium
chloride, excess sodium carbonate, and various soluble compounds not pre-
cipitated by sodium carbonate.
Kettle (Pot) Melting--
In zinc scrap melting processes, zinc is separated from nonmetallic
residues and metal attachments having higher melting points, usually with
fluxing. The following steps are involved in kettle melting: a) charging
of scrap to the furnace, b) melting the zinc fraction, c) fluxing, d) agi-
tating to effect separation of the dross, e) skimming, and f) pouring into
ladles or molds. The output trom this process can be sent directly to a
distillation furnace or alloying process unit, or cast into blocks before
further processing. In cases where mold cooling water is used, this would
constitute a liquid waste source.
138
-------
Crucible Melting—
Melting can also be carried out in crucible furnaces (DA-069). Refer
to the description of the process steps involved under Kettle (Pot) Melting.
Sweated zinc scrap and flux are input materials for this process. Mold
cooling constitutes a potential source of wastewater from this process as
in the Kettle Melting process.
Reverberatory Melting—
Zinc melting may also be carried out in reverberatory furnaces. The
charge may be either the product of a reverberatory sweating operation or
other pretreated scrap. Refer to Kettle (Pot) Melting for a description of
the process steps involved. Mold cooling water is a potential source of
wastewater from this process.
Electric Induction Melting—
Electric induction furnaces are also used to melt zinc scrap. In this
process a molten heel must be left in the furnace at the start of each
heating cycle. See Kettle (Pot) Melting for a description of the process
steps. The output from this process is sent to a refining process. Mold
cooling water is the only potential source of wastewater from this process.
139
-------
REFERENCES
BR-283 Browder, T.J. The Parsons Double Catalysis/Double Absorption
Sulfuric Acid Process. Sulfur, No. 83:31-33, 1969.
BU-184 Burson, W.R. and F.B. Morgan III. Recovery and Utilization of
Copper Scrap in the Manufacture of High Quality Cathode. In:
Proceedings of the Fourth Mineral Waste Utilization Symposium,
Chicago, Illinois, May 1974. Eugene Aleshin, ed. IITRI, Chicago.
CA-305 Carrillo, Fred V., Mack H. Hibpshman, and Rodney D. Rosenkranz.
Recovery of Secondary Copper and Zinc in the United States.
I.C. 8622. Western Field Operation Center, Mineral Supply,
Bureau of Mines, Spokane, Washington, 1974.
CE-034 Cecil, Lawrence K., ed. Proceedings of the Second National
Conference on Complete Water Resue: Water's Interface with
Energy, Air and Solids, Chicago, 1975. AIChE, New York, 1975.
CO-098 Collins, John Joseph. Adsorption Process for Water and Nitrogen
Oxides. U.S. Patent 3,674,429. 4 July 1972.
CO-371 Costa, P., and A. Mambelli. Production of Battery Grids Based on
, the Reclamation of Antimony Containing Alloys from Used Battery
Scrap. Paper presented at the 37th International Foundry
Congress, Brighton, England, September 1970, pp 3 ff.
CO-R-467 Coltharp, William M., et oil. Multimedia Environmental Assessment
of the Secondary Nonferrous Metal Industry, 2 vols., final draft
report. EPA 68-02-1319, Task No. 49. Radian Corporation, Austin,
Texas. June 1976.
CO-A-683 Coleman, R.T. and D.A. Malish. Trip Report, Site Visits to Paul
Bergs^e and Son A/S, Boliden Aktiebolag, and Outokumpu Oy. EPA
68-02-2608, Tasks 18,-19, and 20. Radian Corporation, Austin,
Texas. November 1977.
CO-R-685 Colley, J.D., et al. Assessment of Technology for Control of
Toxic Effluents from the Electric Utility Industry, revised.
DCN 78-200-187-09-08, EPA Contract No. 68-02-2608. Radian
Corporation, Austin, Texas. December 1977.
140
-------
CO-R-720 Coleman, Richard T., Jr., Robert Vandervort, and David J. Burton
Process and Occupational Safety and Health Review of the Secondary
Nonferrous Metals Industry, preliminary draft report. NIOSH 210-
77-0008. Radian Corporation and db Associates, Inc., Austin,
Texas and.Salt Lake City, Utah. October 1976.
DA-069 Danielson, John A., comp. and ed. Air Pollution Engineering
Manual, 2nd ed., AP-40. U.S. EPA, Research Triangle Park, North
Carolina, 1973.
DI-149 Dillingham, Ted. Private communication. Hydronautics, Goletia,
California. 5 May 1977.
DI-150 Dillard, Frank. Alternatives for Chrome Reduction in Cooling
Tower Slowdown. Paper presented at the ASCE 1977 Spring Conven-
tion, Dallas, Texas. April 1977.
EN-071 Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors, 2nd ed. with supplements, AP-42. Research
Triangle Park, North Carolina. February 1972, April 1973, July
1973, September 1973, July 1974, January 1975, December 1975,
February 1976, April 1977.
EN-378 Environmental Protection Agency. Development Document for Interim
Final Effluent Limitations Guidelines and Proposed New Source Per-
formance Standards for the Secondary Copper Subcategory of the
Copper Segment of the Nonferrous Metals Manufacturing Point Source
Category. EPA 440/l-75-032c, Group I, Phase II. Washington DC,
February 1975.
EN-394 Environmental Protection Agency. Development Document for Interim
Final and Proposed Effluent Limitations Guidelines and New Source
Performance Standards for the Ore Mining and Dressing Industry,
Point Source Category, 2 vols. EPA 440/1-75-061, Group II.
Washington DC, October 1975.
EN-399 Environmental Protection Agency. Secondary Nonferrous Smelting
and Refining, Section IV, in-house report. Unpublished, pp 272ff.
EN-462 Environmental Protection Agency. Supplemental for Pretreatment to
the Development Document for the Secondary Copper Segment of the
Nonferrous Metals Manufacturing Point Source Category, draft
report. EPA 440/l-76-081b. August 1976.
FL-S-092 Fletcher, A.W. Metal Recovery from Effluents—Some Recent
Developments. In: The Treatment of Sewage and Industrial Liquid
Effluents, Symposium, Yorkshire, England, April 1975. Inst.
Chem. Eng. Symp. Ser. No. 41.
FO-130 Ford, Walt. Private communication. Southern California Edison,
Laughlin, Nevada. 26 May 1977.
141
-------
GI-019 Gillam, W.S. and H.E. Podall. Recent Developments on the Reverse
Osmosis Process for Desalination. Desalination 9(2):201-211,
1971.
HI-041 Hittman Associates, Inc. Reverse Osmosis Desalting State-of-the-
Art, 1969. Columbia, Maryland, 1970.
JU-A-043 Jula, Theodore F- Simplifying Heavy Metal Recovery with Sodium
Borohydride. Process Eng., 1972, p. 123.
KI-048 Kirk-Othmer. Encyclopedia of Chemical Technology, 2nd ed., vols.
1-22. Wiley, New York, 1963-1970.
LA-261 Lanouette, Kenneth H., and Edgar G. Paulson. Treatment of Heavy
Metals in Wastewater. Pollut. Eng. 8(10):55-57, 1976.
LA-326 Larsen, H. Peter, James K.P. Shou, and Laurence W. Ross. Chemical
Treatment of Metal-bearing Mine Drainage. J. WPCF 45(8):1682,
1974.
LA-A-337 LaPerle, Robert L. Removal of Metals from Photographic Effluent
by Sodium Sulfide Precipitation. J. Appl. Photogr. Eng. 2(3):
134, 1976.
LA-A-347 Lanouette, Kenneth H. Heavy Metals Removal. Chem. Eng., October
17, 1977, p. 73.
LY-006 Lynch, Maurice A., Jr., and Milton S. Mintz. Membrane and Ion
Exchange Processes—A Review. J. AWWA 64(11):711-725, 1972.
MA-392 Manka, Josepha, et al. Characterization of Organics in Secondary
Effluents. Env- Sci. Tech. 8(12):1017-1020, 1974.
MA-693 Mason, James W. Economics of Boiler Feed Water Treatment, Reverse
Osmosis vs. Ion Exchange. Technical Report No. 1. Triton Water
Systems, Inc., undated.
MC-004 McKee (Arthur G.) and Company. Systems Study for Control of
Emissions Primary Nonferrous Smelting Industry, final report, 3
vols. NAPCA Contract No. PH 86-65-85, PB 184 884. June 1969.
MC-194 McMahon, Albert D., John M. Hague and Herbert R. Babitzke. Zinc.
Preprint, 1973 Minerals Yearbook. U.S. Bureau of Mines.
MC-200 McMahon, A.D., et al. The U.S. Zinc Industry: A Historical
Perspective. I.C. 8629. Bureau of Mines, 1974.
MC-170 Montagna, D. and J.A. Ruppert. Refining Zinc-Base Die-Cast Scrap
Using Low-Cost Fluxes. R.I. 7315. Bureau of Mines, October 1969.
142
-------
MU-153 Murau, Kenzo and Sei Nakao. Recovery of Heavy Metals from the
Waste Water of Sulfuric Acid Process in Ahio Smelter. In:
Joint MMIJ-AIME Meeting on World Mining and Metallurgical Tech-
nology, Denver, Sept. 1976, Proceedings, vol. 2. AIME, New
York, 1976. pp. 808-816.
NA-182 Nack, H. et al. Development of an Approach to Identification of
Emerging Technology and Demonstration Opportunities. EPA 650/2-
74-048. Battelle-Columbus Laboratories, Columbus, Ohio, 1974.
NE-A-314 New Membrane for Reverse Osmosis. Chem. Eng., October 24, 1977,
p. 72.
OK-A-024 Okuda, T., I. Sugano, and T. Tsuji. Removal of Heavy Metals
from Wastewater by Ferrite Co-Precipitation. Filtration Separa-
tion, 12(5):472, 1975.
PA-120 Patterson, James W. and Roger A. Minear. Wastewater Treatment
Technology, 2nd ed. Rept. No. IIEQ 73-1. State of Illinois
Institute for Environmental Quality, 1973.
PA-S-205 Parsons Double Catalysis/Double Absorption Sulphuric Acid Process.
Sulphur, 93:31, 1969.
PA-322 Patterson, James W. Wastewater Treatment Technology. Ann Arbor
Science, Ann Arbor, Michigan, 1977.
PE-274 PEDCo-Environmental Specialists, Inc. Environmental Assessment of
the Domestic Primary Copper, Lead and Zinc Industries, 3 vols.
EPA Contract No. 68-02-1321, Task No. 38. Cincinnati, November
1976.
PE-317 Permutit Co., Inc. Proceedings of Seminar on Metal Wastes Treat-
ment Featuring the Sulfex Process. Paramus, New Jersey, undated.
RA-208 Rausch, Donald 0. and Burt C. Mariacher, eds. AIME World Sympo-
sium on Mining and Metallurgy of Lead and Zinc, 2 vols. Vol. 2,
Carl M. Cotterill and John M. Cigan, eds. American Institute of
Mining, Metallurgical, and Petroleum Engineers, New York, 1970.
RA-R-579 Radian Corporation. Field Testing, Analytical Results and
Analytical Procedures for the Evaluation of Priority Pollutant
Removal from Effluent Streams of Utility Power Plants, draft
report. DCN 78-200-187-22-11, EPA Contract No. 68-02-2608, Task
22. Austin, Texas. February 1978.
143
-------
RO-389 Rozelle, Lee T., C.V. Kopp, Jr., and K.E. Cobian. New Membranes
for Reverse Osmosis Treatment of Metal Finishing Effluents. EPA
660/2-73-033, 12010 DRH. North Star Research Institute, December
1973.
SA-136 Sabadell, J.E., ed. Traces of Heavy Metals in Water Removal
Processes and Monitoring, Princeton Univ., Nov. 1973, Symposium
Proceedings. EPA 902/9-74-001. EPA, Region II, Philadelphia,
Pennsylvania. 1974.
SC-A-303 Schroeder, Harold J. Copper. Preprint, 1973 Minerals Yearbook.
U.S. Bureau of Mines.
SC-A-503 Scott, Murry. (Senior Marketing Specialists, Permutit Co.,
Paramus, New Jersey). Private communication with Rob Klausmeier.
November 1977.
SH-106 Shannon, L.P., P.G. Gorman, and M. Reichel. Particulate Pollutant
System Study. Vol. 2, Fine Particulate Emissions. PB 203 521.
Midwest Research Institute, Kansas City, Missouri, 1971.
SI-106 Sittig, Marshall. Environmental Sources and Emissions Handbook.
Noyes Data, Park Ridge, New Jersey. 1975.
SI-A-192 Sigworth, E.A., and S.B. Smith. Adsorption of Inorganic Com-
pounds by Activated Carbon. J. AWWA, 64(6):386, 1972.
SK-S-049 Skrovronek, Herbert S., and Mary K. Stinson. Advanced Treatment
Approaches Metal Finishing Wastewaters, 2 parts. Plating Surf.
Finish., 64(10):33, 1977. Plating Surf. Finish., 64(11):24, 1977.
SM-S-190 Smith, Stanton B. Trace Metals Removal by Activated Carbon.
Presented at the Conference on Traces of Heavy Metals in Water:
Removal Processes and Monitoring, Princeton University, November
1973.
SP-A-058 Spendlove, Max J. Methods for Producing Secondary Copper. I.C.
8002. Bureau of Mines, 1961.
TE-S-361 Temperature and Pressure Limits Extended for PERSMASEP B-10
Permeators. Dupont Permasep News 1(1):3, 1977.
US-357 U.S. Bureau of Mines. Commodity Data Summaries, 1976, An Up-to-
Date Summary of 95 Mineral Commodities. Washington DC, 1976.
VE-073 Ventron Corporation, Chemicals Division. Inorganic Reductions
with Sodium Borohydride, Principles and Practices. Beverly,
Massachusetts, undated.
VE-A-074 Vermuelen, T. Process Arrangements for Ion Exchange and Adsorp-
tion. CEP, October 1977, p. 57.
144
-------
WA-219 Waitzman, D., J. Nevins, and G. Slappey. Marketing H2SOi, from
S02 Abatement Sources—the TVA Hypothesis. EPA 650/2-73-051.
Office of Agricultural and Chemical Development, TVA, Muscle
Shoals, Alabama. 1973.
WA-A-356 Watkins, James P. Controlling Sulfur Compounds in Wastewater.
Chem. Eng. 84(22):61, 1977.
WE-324 Weber, Walter J., Jr. Physicochemical Processes for Water
Quality Control. Wiley, New York, 1972.
WI-A-309 Wing, Robert E., et at. Heavy Metal Removal with Starch Xan-
thanatecationic Polymer Complex. J. WPCF 46(8):2043, 1974.
WI-A-316 Wilmoth, Roger C. and Ronald D. Hill. Mine Drainage Pollution
Control via Reverse Osmosis. Min. Eng. 35(3):45-47, 1973.
ZI-A-034 Zievers, James F. Emerging Technologies for Waste Water Treat-
ment. Ind. Finish. 15(6):22, 1975.
ZI-037 Zievers, James F. , et al. Practical Use of Starch Insoluble
Xanthates. Industrial Filter & Pump Mfg. Co., September 1977.
145
-------
APPENDIX A
SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES
The following table contains the data concerning industrial wastewater
containing metals which were found during this study. It is not a comprehen-
sive list of all available data. Rather, it is intended to provide a general
reference for the quantity and type of pollutants present in each wastewater
stream.
146
-------
TABLE A-l. SUMMARY OF POLLUTANTS IN INDUSTRIAL WASTEWATER SOURCES
Source
Stream Composition
(mg/A)
Reference
Comments
1. Cement Industry
Cooling Tower Slowdown
Batteries
- dry cell battery manuf.
- plate forming
Electrical Equipment Prod.
Television Tube Manuf.
3. Explosives Industry
Cr-P
EN-148
Process Operations
2. Electronics Industry
Pb-P
Fe-P
Al-P
EN-148
DE-170
DE-170
From oyster shells
Mn-P
Pb particulate, 5-48
Pb dissolved, 0.4-66.5
Hg-P
Pb, 400
PA-322
PA-322
PA-322
PA-322
RO-385
PA-322
This industry is largest
consumer of Pb. Lead
losses range from 4.54-
6810 mg per battery man-
ufactured. Water usage
was 11-77 gal/battery.
Low pH stream (1.3-2.6)
Second largest user of
Hg.
Ammunition Plant Pb, 6.5
Lead Azide and Lead Styphnate Pb, 0-200
Match and Fireworks Prod. Mn-P
PA-322
EN-439
PA-322
(Continued)
-------
TABLE A-l (Continued)
00
Source
Stream Composition
(mg/A)
Reference Comments
4. Glass and Ceramics Industry
Glass Manuf .
5. Inorganic Chemicals Industry
Boric Acid Production
Caustic Evaporation and
Salt Recovery
Chloralkali Industry
- brine sludge
As-P
Mn-P
Cd-P
Cr-P
Zn-P
As, .036 kg/Mg
Pb, 0-.22 kg/Mg
Hg dissolved, .080-2.8
Hg suspended, 14.0"mg/kg
Hg, 150-1500
PA-322
PA- 32 2
PA-322
DE-170
DE-170
VE-065
VE-065 Pb from corrosion of
anode
PA-322 .05-. 25 kg/Mg
PA-322
PE-222 1.4 m tons/day
* brine clarifier
• brine filter
• salt saturator residue
- wastewater from:
• floor washing
• purge streams from cell
end-box wash water recycle
• purge from brine system
• drainage from filtration
area
• tank cleaning
Hg, 0.3-18
PE-222
110-190 A/min
(Continued)
-------
TABLE A-l (Continued)
vO
Source
5. Inorganic Chemicals Industry
Chrome Yellow Production
Chromic Acid Production
Chromic Oxide Production
Cooling Tower Blowdown
Cooling Tower Blowdown
Cooling Tower Blowdown
Fertilizers
- fertilizer mill
- phosphate fertilizer
production
- specialized fertilizer
production
Molybdatechrome Orange Prod.
PCI$ Production
Pesticides
- production of Paris Green
and calcium meta-arsenate
Stream Composition
(mg/£)
(Cont'd)
Cr, 5.7-7 kg/Mg
Pb, 0-2.1 kg/Mg
Cr, 0.5-1.0 kg/Mg
Cr, 3-95 kg/Mg
Cr, 0-1300
Cr, 0-250
Zn, 0-30
Cr, 10-60
Cu-P
Fe-P
Hg, .00026-. 004
As-P
Cd-P
Mn-P
Cr, 0.6 kg/Mg
Pb, 0.7 kg/Mg
As-P
As-P
Hg-P
As (as AsaOa) , 362
Reference Comments
VE-065
VE-065
VE-065
MA- 7 60
EN-145
CH-A-386
PA-322
PA-322
PA-322
EN-145
EN-145
PA-322
VE-065
EN-150
PA-322
PA-322
PA-322
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(mg/A)
Reference Comments
5. Inorganic Chemicals Industry (Cont'd)
Phosphoric Acid Production
Production of Pigments using
Cadmium Sulfide or Cadmium
Selenide
Sodium Bisulfite Production
Sodium Nitrate Production
Sulfuric Acid Production
Titanium Oxide Production
Titanium Tetrachloride
Production
Zinc Oxide Production
As-P
Cd-P
Cd, 2-120 g/day (8 g/day
avg)
Cu, 0.1-0.5
Cr, 0.1-0.5
Pb, 0.15-0.5
Fe, 40-250
Fe, 0.5
Cu, 1.0
Cr, 0.3
Pb, 0.7
As, 200-500
Ti, 17 kg/Mg
Fe-P
Ti, 50 kg/Mg
Cr, 4 kg/Mg
Fe, 2-380 kg/Mg
V, 2-6 kg/Mg
Al, 4-24 kg/Mg
Cu, 62 kg/Mg
As, 0.05 kg/Mg
Zn, 0.07 kg/Mg
Pb, 0.09 kg/Mg
VE-065
PA-322
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
PA-322
VE-065 Lime treatment
PA-322
VE-065 Lime treatment
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
VE-065
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(ng/A)
Reference
Comments
5. Inorganic Chemicals Industry (Cont'd)
Zinc Yellow Production
Cr, 12 kg/Mg
Zn, 19.5 kg/Mg
6. Leather Tanning and Finishing Industry
VE-065
Dye Rinse
Dye Rinse
Process Operations
7. Metal Fabrication and
Appliance Manuf .
Automobile Assembly
Automobile Heating Control
Brass and Copper Wire Mill
Pickling Wastes
Plating Bath Dumps
Cr, 51
Cr, 40
As-P
Fe-P
Cr(VI), 40
Finishing Industry
Fe, .09-60
Cu, 0-11
Fe, 3-4
Mfg. Cd, 14-22
Cu, 4.4-880
Cu, 0.4-22
Ni, 3
Pb, 140
Zn, 5,000-34,000
Cd, 2,000-23,000
Cr(VI), 10,000-50,000
Cr(VI), 200-75,000
Cr(VI), 10,000-270,000
Ag, 13,000-45,000
EN-156
CH-A-386
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
CH-A-386
PA-322
PA-322
PA-322
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(mg/&)
Reference Comments
7. Metal Fabrication and Finishing Industry
Plating Drag Out
8. Mining Industry
Acid Mine Drainage
Acid Mine Drainage
(Abandoned Mines)
Bauxite Ore - Raw Mine Drainage
from Open Pit Mine
Coal - Mine Wastewater
Pb, 0-2
Zn, 0-220
Ni, 0-900
Cu, 0-900
Cr(VI), 1-100
Cd, 7-240
Ag, 50-250
Fe, 0-60
Ni, 0.46-3.4
As, 0-22.3
Cd, .02-1.0
Cu, .2-128.0
Fe, 20-800
Pb, 0-3.0
Mn, 4.5-14.0
Ni, .03-. 5
Al, .1-82.5
Zn, 6.8-294.0
Al, 5.9-8.8
Zn, .36-25.3
Zn, .01-12.7
Ni, .01-5.6
Al, .01-271
Mn, .01-127
Fe, 40-330
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PU-A-020 Untreated
PU-A-020
PU-A-020
PU-A-020
PU=A-020
PU-A-020
PU-A-020
PU-A-020
PU-A-020
EN-394
EN-394
EN-377
EN-377
EN-377
EN-377
PA-322
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(rng/A)
Reference Comments
8. Mining Industry (Cont'd)
Copper Ores - Discharge Mill
Wastewater
Copper Ores - Raw Mill
Wastewater
Copper Ores - Raw Mine Water
i— i
<-" Ferroalloy Ores - Raw Mill
Wastewater
Ferroalloy Ores - Tailings
Discharge
Iron Ores - Mine Discharges
Pb,
Pb,
Cu,
Ni,
Zn,
Cu,
Fe,
Mn,
Zn,
Cd,
Cu,
Mn,
Pb,
Zn,
Mo,
Fe,
Fe,
Mn,
Mo,
Mo,
Pb,
Hg,
Mn,
Zn,
.1-2.0
<.l-2.8
.08-900
.05-2.8
.05-8.5
0.5-92
0.1-2,000
0.9-100
0.1-172
.19-. 74
21-51
50-56
2.1-9.8
25-76.9
5.3-17.5
1305-1500
0.44-24
0.19-50
0.5-2.2
2.0-4.0
0.001-.100
0.002-2.00
0.001-18.0
0.001-8.0
EN-394 15M - 101M m3/d
EN-394 Settled in tailings pond
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
EN-394
RA-S-614
PA-322 Settled in tailings pond
PA- 32 2
PA-322
PA-322
(Continued)
-------
TABLE A-l (Continued)
Ul
Source
Stream Composition
(mg/£)
Reference Comments
8. Mining Industry (Cont'd)
Iron Ore - Raw. Mill Wastewater
Lead /Zinc Ores - Raw Mine Water
Silver Ore - Raw Mine Wastewater
9. Organic Chemicals Industry
Acetaldehyde Production
Butadiene Production
Dimethyl Terephthalate
Production
Ethylene/Propylene via
Pyrolysis
Methyl Methacrylate Production
Petrochemicals
Fe, 0.20-10.0
Pb, 0.10-5.0
Mn, 0.007-20.0
Zn, 0.006-10.0
Pb, 0.1-4.9
Zn, .03-38
Mn, .02-57
Hg, <.0001-.l
Cd, 0-1,000
Fe, .33-2.05
Mn, .43-6.3
Cr, 2.7
Fe, 45.1
Zn, 1.11
Cu, 29.7
Cr, 3.51
Zn, 3.2
Cr, 4.35
Cu, 288
Fe, 500
Hg-P
Al-P
Sn-P
As-P
Cd-P
EN-394
EN-394
EN-394
EN-394
EN-394 Settled in tailings pond
EN-394
EN-394
EN-394
PA-322
EN-394
EN-394
EN-153
EN- 15 3
EN-153
EN-153
EN-153
EN-153
EN-153
EN-153
EN-153
PA-322 Cl is usually associated
DE-170 with Ca or Al
DE-170
DE-170
DE-170
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(mg/Jl)
Reference Comments
9. Organic Chemicals Industry (Cont'd)
Raw Waste Loads for General
Organic Chemical Process
Operations
Terephthalic Acid Production
Tetraethyl Lead Manuf .
(Gasoline Additives)
10. Paint and Ink Industry
Process Operations
11. Petroleum Refining Industry
Cooling Tower Blowdown
Zn, 0.10-3.2
Cu, 0.10-288
Fe, 0.40-500
Cr, 0.04-4.58
Zn, 1.57
Cu, 24.6
Fe, 12.7
Cr, 4.58
Pb, 45
Pb, inorg. 66.1-84.9
Pb, org. 126.7-144.8
Cr, 0.08
Pb, 0.4-5.0
Zn, 2.6-77.4
Cu, 0.04-0.4
Fe, 2.5-139
Al, 29.5
As-P
Mn-P
Cr, 0-6
EN- 15 3
EN-153
EN-153
EN-153
EN-153
EN-153
EN-153
EN-153
PA-322 This represents second
PA-322 largest use of lead
PA-322
EN-409 Pigments and other
EN-409 reactants
EN-409
EN-409
EN-409
EN-409
PA-322
PA-322
EN-407
(Continued)
-------
TABLE A-l (Continued)
Source
11. Petroleum Refining Industry
Process Operations
12. Photographic Industry
Fixer and Developer Concentrate
Effluents
Wash Water Effluents
13. Plywood, Hardwood, and Wood
Preservatives and Fire
Retardants
Stream Composition
(rng/A)
(Cpnt'd)
Al-P
As-P
Cd-P
Co-P
Cu-P
Fe-P
Hg-P
Pb-P
Ni-P
V-P
Zn, .04-1.84
As-P
Cu-P
Fe-P
Ag, 450-2,950
Ag, 1.3-5.6
Hg
Pb
Preserving Industry
As-P
Cr, 0.23-1.5
Cu-P
Zn-P
Reference Comments
EN-407
EN-407
EN-407
EN-407
EN-407
EN-407
EN-407
DE-170
EN-407
EN-407
EN-407
PA-322
PA- 32 2
PA-322
LA-A-337
LA-A-337
DE-170
DE-170
EN-382
PA-322
EN-382 OH precip.
EN-382
(Continued)
-------
TABLE A-l (Continued)
Source
Stream Composition
(mg/A)
Reference Comments
14. Pulp and Paper Industry
Groundwood Pulp Production
Kraft Process Paper Mill
Newsprint Paper Production
Paper Mill Effluent
Paper Mill Settling Pond
15. Steam Generation Industry
Cooling Tower Slowdown
Metal Cleaning
Acid Cleaning
Air Preheater Wash
Boiler-Fireside Wash
Zn-P
Cu-P
Cr-P
Ni-P
Sn-P
Pb-P
Zn-P
Hg dissolved, .002-. 0034
Hg suspended, 5.6 mg/kg
Hg dissolved, .00008
Hg suspended, 10 mg/kg
Cr-P
Zn-P
Cu, 400-1,000
Fe, 4,000-10,000
Cu, 0.35-40
Fe, 376-6,000
Cu, 0-5
Fe, 0-300
PA-322
PA-322
DE-170
DE-170
DE-170
DE-170
PA-322
PA-322
PA-322 Note: Hg formerly used
PA-322 as fungicides, slimi-
cides , biocides
DE-170
DE-170
SA-S-342
SA-S-342
SA-S-342
SA-S-342
SA-S-342
SA-S-342
(Continued)
-------
TABLE A-l (Continued)
00
Source
16. Steel and Iron Industry
Chrome Plating
Cold Finishing
Degassing
Galvanizing
Open Hearth
Pickling
- pickle bath rinse
- pickle bath rinse
- spent acid pickling
solution
Stream Composition
(mg/£)
Fe, 30.6-42.9
Cr, 49-85.4
Fe, 60-150
Zn, 2.01-7.76
Pb, 0.47-1.39
Mn-P
Cu-P
Al-P
Hg-P
Cr, .56-3.3
Zn, .31-1.1
Fe, 4.8-25.5
Zn, 2.06-880
Mn-P
Hg-P
Cu-P
Cu-P
Ni-P
Mn-P
Fe, 60-96,800
Fe, 60-1,300 (210 avg)
Fe, 200-5,000
Fe, 70,000-96,800
Reference Comments
BR-479
BR-479
PA-322
EN-161
EN-161
EN-161
EN-161
EN-161
EN-161
BR-479
BR-479
BR-479
EN-161
EN-161
EN-161
EN-161
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322
PA-322 Most significant in-
dustrial source of
soluble iron waste.
(Continued)
-------
TABLE A-l (Continued)
Ul
Sources
16. Steel and Iron Industry (Cont
Scrap Detinning
Tin Plating
17. Textile Industry
Alkaline Bemberg Rayon Process
Dyes
Rayon Wastes (General
Textile Mills
Vulcanized Fiber
18. Tire Manufacturing Industry
Cooling Tower Slowdown
Stream Composition
(mg/A)
M)
Fe, 3.7-14.2
Sn, 9.7-1,440
Cr, 0-.15
Fe, 18.3
Cr, 12.6
Sn, 61.4
Cu-P
Cr-P
Zn, 20-1,000
Fe-P
Zn, 100-300
Cr, 0.1
Zn, 0.1
Reference Comments
BR-479
BR-479
BR-479
BR-479
BR-479
BR-479
PA-322 Present as cuproammonium
salts.
EN-146
PA-322
PA-322
PA-322
EN-154
EN-154
NOTE: P = present, but levels not quantified.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-80-074
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Sources and Treatment of Wastewater in the Nonferrous
Metals Industry
5. REPORT DATE
April 1980 issuing date
6. PERFORMING ORGANIZATION CODE
USEPA/IERL-Ci/IPCD
7. AUTHOR(S)
Richard T. Coleman, J. David Coiley, Robert F. Klausmeie
Nancy P. Meserole, Wayne C. Micheletti, Klaus Schwitzgeb
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corp.
8500 Shoal Creek Blvd.
Austin, Texas 78758
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
EPA Contract # 68-02-2608
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Task Final 10/77 - 6/79
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report describes the findings of an investigation on the sources and treatment
of industrial wastewater containing metals. The study was performed to assess the
existing database on metal containing wastewaters, investigate the state of development
on the various treatment technologies being used, and determine whether this information
could be applied to water treatment problems in the nonferrous metals industry. The
results are being used within the Agency's Office of Research and Development as part
of a larger effort to define potential environmental impact of emissions and effluents
from this industry and the need for improved controls. The findings will also be
useful to other Agency components and the industry in dealing with environmental contro'
problems. The Metals and Inorganic Chemicals Branch of the Industrial Pollution Contro
Division should be contacted for additional information desired concerning this program
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Wastewater Treatment
leavy Metals
tonferrous Metals
Neutralization/Precipitati
k'astewater Treatment
Heavy Metals
Nonferrous Metals
on
8. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport-f
UNCLASSIFIED
21. NO. OF PAGES
.172
(This page)
22. PRICE
EPA Form 2220-1 (R«v. 4—77) PREVIOUS EDITION is OBSOLETE
160
i U.S. GOVERNMENT POINTING OFFICE: 1980-657-146/5667
-------
|