-------
rainfall, is discharged only after filtration through a
filter bed.
The use of settling ponds is effective in reducing the
suspended solids loadings; heavy metal loadings are
correspondingly reduced (Alternative 1 compared with
Alternative 2). Further reduction in the loading is
realized if part or all of the waste water is recycled
(Alternative 1 versus Alternatives 3 and 4).
There is a noticeable effect of pH of the waste water dis-
charge on metal loadings, especially for copper, lead,
nickel, and zinc, Ar a pH near 7 (Plant 38f Alternative 4) ,
the levels of zinc, nickel, lead, and copper are greater
than those at pH of about 8.2 (Plant 43, Alternative 3),
even though solids removal was greater for Alternative 4.
Therefore, it is necessary to maintain a high pH of the
discharge. Because of the possibility of redissolving the
arnphoteric hydroxides of lead and zinc (Plant 11,
Alternative 2), the pH should not be maintained too high. A
pH between 8 and 9 appears to be suitable for maximum
reduction of heavy metal loadings. No apparent reduction of
the oil and grease loading occurred for Plant 38; however,
this might be explained by the fact that additional oil and
grease was contributed by cooling water that entered the
closed circuit beyond the point where the slag milling water
was sampled.
Total elimination of the waste water discharge is practiced
by Plant 11 (Alternative 5). After most of the solids had
been removed by a spiral classifier, a minus IG-mesh, 50
percent solids slurry discharged from a settling tank is
dewatered on a disk filter. The filtrate and rhe overflow
from the settling tank are recirculated from four holding
tanks back to the milling operation. Sulfuric acid is added
to maintain a pH near 8 for the recirculated water. In the
three months the system has been operational, there have
been no severe problems with its operation.
Waste Water from Furnace Exhaust Scrubbing
The dusts, smoke, and fumes formed in the furnace operations
used by secondary copper or copper alloy smelters must be
removed from the furnace exhaust before being discharged to
the atmosphere. Cupola and blast furnace operations produce
large quantities of particulate matter from dusty charge
materials, such as fine slags and from coke ash. Emissions
are also produced from the combustion of coke and organic
wastes in the charge materials. Metal oxide fumes are
131
-------
produced from zinc, lead, or other volatile metals present
in the charge materials.
Reverberatory and rotary furnaces produce some smoke,
especially if the charge contains organic waste materials or
when green-wood poles are inserted to deoxidize the bath.
Particulate emissions are produced during the charging of
fine slags or fine flux materials. Metal oxide fumes are
also produced from zinc, lead, or other volatile metals
present in the charge materials.
Emissions from converters contain metal oxides of all of the
metals present, including some copper oxide and the oxides
of sulfur, phosphorus, or other nonmetals present in the
original bath of metal. Emissions from furnace operations
are usually directed to individual exhaust cleaning
equipment, although more than one furnace exhaust may be
treated by a single emission control facility.
A considerable amount of zinc oxide and some lead oxide fume
is formed during pouring of brass or bronze alloys that
contain these volatile metals. This fume is generally
collected along with the combustion exhaust gases and
directed to the furnace exhaust cleaning equipment.
In Table 5, the types of air pollution control used by the
industry were summarized. Of the 41 plants responding to
the survey, 52 percent use only dry air pollution control,
20 percent use only wet air pollution control, and 11
percent use both types to control emissions. Another 11
percent presently do nor use emission control devices.
Identification of Control Alternatives
The amount of waste water generated during wet scrubbing of
exhausts from furnace-related operations and the loadings of
pollutants can be reduced by recirculating treated waste
water. Such an approach is currently being used by plants
employing wet scrubber systems. To eliminate the discharge
of waste water from furnace exhaust emission control
devices, dry air pollution control devices such as oaghouses
or electrostatic precipitators are used. Over 5C percent of
the industry employs such dry emission control methods. The
solids collected from exhaust cleaning consist primarily of
metal oxide fumes such as zinc oxide and lead oxide and are
sold or used for their metal content. Therefore, efficient
recovery of particulates in the exhaust gases provides some
return on investment in emission control devices.
132
-------
Dry Air Pollution Control s. The most common dry air
pollution control system is a baghouse. The gases are
cooled either by dilution with air, by water cooling of the
hot gas ducts, or with water sprays inside of the ducts.
The exhaust, before it is filtered, must be cooled to below
the ignition or fusion point of the bags. The ignition
point of the bags varies with the type of fabric used to
make them. Cotton or wool bags have the lowest operating
temperature and glass fiber bags have the highest operating
temperature. Cooling water used on the outside of the ducts
is generally recycled. Water sprayed inside of the ducts
for cooling the exhaust must be completely converted to
steam to prevent blinding of the bags.
Six of the 44 plants surveyed used electrostatic exhaust
cleaning systems to reduce emissions. These are in addition
to either baghouse or wet scrubber control systems. They
claimed no waste water was generated in the operation or for
cleaning of electrostatic precipitator emission control
devices.
Metal oxides, especially zinc oxide, are very small in
particle size (less than 1 micron) and removal from
baghouses can be an extremely dusty operation. The dust
level during gathering and loading for shipment is reduced
by agglomeration with very small amounts of water. For
plants surveyed, the use of dry air pollution control
systems, despite the dust problem, has been a very effective
way to reduce emissions without the need for a waste water
discharge.
The proposed performance standards for emissions from new
secondary copper alloy production plant furnaces have been
recommended<* *> to be as follows.
From reverberatory furnaces:
(1) No more than 5C mg/Nm3 (undiluted)
or 0.022 gr/dscf,
(2) No more than 10 percent opacity.
From electric or blast furnaces:
(1) The opacity of visible emissions
shall be no more than 10 percent.
The background information on which these recommended
standards were based was developed from data taken at plants
using fabric filter baghouses. Some also employed
electrostatic precipitators. Generally, although no
scrubber has yet been used to control emissions to the level
of the proposed standard, such levels are within the
capability of scrubbing technology. This conclusion was
133
-------
based on only one copper alloy producer who used a low
efficiency wet scrubber with a closed-loop water recycle
system. High efficiency venturi-type wet scrubbers,
however, approach these new source air emission performance
standards.
Wet gas scrubbers selected by secondary copper smelters are
of the high-energy venturi type. These scrubbers have a
pressure drop of about 0.123 atm (50 inches of water), and
remove 90 to 99 percent of the entrained solids. Most of
the solids are removed from the water with thickeners and/or
filters, and the water is discharged to storage. The sludge
recovered from brass and bronze operations contains over 50
percent zinc as zinc oxide and is sold to zinc smelters.
The sludge recovered from exhaust scrubbers used by copper
smelters contains about four percent copper and is usually
recharged into the furnaces or stored for possible future
recovery of the values by the same company or by other
smelters. Water discharged to a pond or settling tank from
a thickener will contain appreciable amounts of solids (of
about the same composition on a dry basis as the sludge
removed) and soluble constituents. The soluble
constituents will include most of the soluble salts in the
feed water plus the addition of the soluble constituents in
the exhaust gases. The soluble constituents contributed by
the process when a cover flux is used are mostly oorax and
its metal-borate reaction product or soda ash. Hydrolysis
of such materials increases the pH of the scrubber waste
water.
Organic residues, soldering fluxes, various plastics,
especially polyvinyl chloride, etc., in the scrap material
oxidize in the furnace to produce water soluble constituents
that lower the pH of the scrubber waste water. Therefore,
depending on the specific plant1s method of scrap
preparation and smelting (i.e., if insufficient alkalinity
is not contributed by the flux constituents or by recycled,
mixed process waste water), the exhaust scrubber waste water
may require pH adjustment by the addition of caustic or lime
slurry. Waste waters with pH values between 8 and 1C are
recycled, which assures removal of soluble heavy (trace)
metals during solids removal steps in the treatment of the
recycle water.
The large volumes of water necessary to operate wet
scrubbers make it economically necessary to recirculate the
water. Treatment for solids removal provides a sludge of
primarily metal oxides (zinc oxide and lead oxide) that has
seme market value and is dust free. After most of the
134
-------
solids are removed by a thickener and/or a filter or
centrifuge, some form of settling is always used. - Cooling
towers are used when the volumes of water are large. The
amount of water added to the operation replaces that lost by
evaporation and in the dewatered sludge. All of the six
plants visited that use wet scrubbers recycle the waste
water from the scrubbers after treatment for solids removal.
The discharge from the treatment is either recycled directly
to the scrubber or it becomes part of the mixed process
waste water that is recirculated.
Alternative technologies currently being used for treatment
and control of scrubber waste water by the industry are
illustrated in Figure 9. They range from solids removal and
discharge to closed loop circuits of process or mixed
process waste water. The technologies indicated are
discussed in more detail in the section on treatment
alternatives.
Identification of Treatment Alternatives
The waste water discharged from wet scrubbing devices used
to control emissions contains suspended solids, dissolved
heavy (trace) metals, and some oil and grease from the
exhaust of furnaces used for smelting operations. Before
discharge or reuse of the water, the solids must be removed
and the amount of heavy metals reduced, primarily by pH
adjustment and the removal of suspended solids by settling
and filtration. The pH of the waste water must usually be
adjusted with caustic or lime to counteract the effect of
acid formation by the contaminants charged with the metal
scrap. In some cases where pH adjustment is not used, the
waste water attains a high pH from the alkaline flux carried
from the furnace by the exhaust.
The treatment technologies that are currently being used by
the industry to remove solids and dissolved heavy metals are
illustrated in Figure 9, Only one plant discharges waste
water from exhaust scrubbing after adjusting the pH with
ammonia (Alternative 1) . The remaining plants surveyed
recycle their water after one of the methods illustrated as
Alternatives 2,3,4,5, and 6.
In order to determine the effectiveness of the various
alternative technologies for the reduction of pollutant
parameters, it was necessary to sample plants that employed
Alternative 6 at points in the process, which would yield
information on successive steps in solids removal and a
characterization of raw waste water as it left the scrubber.
Plant 9, an unalloyed copper producer, and Plant 38, a
135
-------
Water Source
UJ
r
~1
Discharge
Recycle Water
or
Discharge
©
Recycle WntkT
or
Discharge
©
Recycle Water
or
Discharge
©
Recyclo Wator
©
Recycle Water
or
Discharge
-------
copper alloy producer, were chosen. The concentrations of
selected pollutants at various sample points in the process
are given in Tables 39 and 40, respectively. From this
information (and waste water flows and the daily production
of molten metal) average loadings for each sampling point
were determined.
In Plant 9, the raw waste water characteristics had to be
taken as the sum of loadings observed in a quench circuit
thickener discharge and a scrubber hydroclone discharge
because both were involved in removing solids from the
emission. The quench circuit operated as a closed circuit
with no discharge of waste water except for that removed
with the sludge. In Plant 38, the raw waste water was
sampled at a thickener discharge just after the scrubber
operation.
Effectiveness of Alternatives 2, 4 , 5, and 6 for the
reduction of suspended solids, copper, lead, zinc, and oil
and grease are indicated in Table 41. A progressively lower
loading in suspended solids is observed as the level of
technology increases in sophistication. There is also a
reduction in copper, lead, and zinc loadings and an
accompanying reduction in loadings for cadmium, lead,
mercury, and nickel. The effectiveness of extended settling
periods in lagoons {Alternative 6) is obscured because of
the mixing of waste water from other processes. For Plant
38 the effectiveness of one or three lagoons is presented
under Alternative 6 as Plant 38-1 and Plant 38-2,
respectively.
It should be pointed out that under Alternative 6, the pH of
the recycled water is about 7 for Plant 38-1, while that of
Plant 9 is about 8. This lower pH might explain the higher
loadings for copper, lead, and zinc for Plant 38-1, even
though the suspended solids removal is less.
Plant 9 discharges part of the mixed process waste water,
while Plant 38 recycles the mixed waste water to a wet
milling operation. Plants 17, 26, and 9, which employ
Alternatives 4, 5, and 6, respectively, do not discharge the
treated scrubber water, but recycle it and use water to
replace that lost by evaporation.
Waste Water from Electrolytic Refining_Operatigns
Electrolytic cells in tank houses electrolytically refine
anode copper into high purity cathode copper. The
electrolyte solution consists of demlneralized makeup water,
copper sulfate, and sulfuric acid. Normally, the
137
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TABLE 39. RESUlffS OF SAMPLING WASTE WATER FPCM
FURNACE EXHAUST SCRUBBIBG, COMPANY 9
00
Wasiewater Discharge
From Hydroclone,
. ma/1
Parameter
Susp. lolldi
Cadmium
Copper
Lead
Mercury
Nickel
Zinc
ml andOrcaw
PH
High
822
2.789
0. 165
0,742
0. 00022
0.028
7.4GO
<1
a. 04
Low
527
0.238
0.048
0.216
10,001
0.016
0.497
<\
• 7.B3
Avg
680
1.514
0.107
0.479
O.Q001I
0.022
3.979
<1
rt. 3-1
Wasiewater Discharge
Prom Thickener
Concent rat ion, ing /I
High
331
2.579
0.055
0.284
0.00108
U. 022
13.428
<1
7.63
LOW
223
1.731
0.023
0. 186
<0, 001
0.019
6.416
<1
7 .if)
Avg
(c)
277
2.158
0. 039
0.235
0. 000 &4
0.021
9.922
-.1
7 *2
Loading.
kfi/kkg
34.85
0.272
0.005
0.030
0.00007
0.003
1.248
0
Wasiewater Discharge
After Hydroclone
Con central Ion, mg/1
HiRh
3179
«. 102
0,067
0.49&
0.00046
0.013
O.U95
4.n
'J. 00
Low
3046
0.048
0.051
0.334
<0. 0001
0.006
0.497
hv W pert-cm less or S. 700. coo 1'day.
(cl Flow e Rim alt d 10 be ilic tamt ai Ilic dijcharRi; (hi -S. 700. dp" 1 day
(d) Flow 175gpni ot 9M.OOU I .day.
(e) Plow nsgpm or 95-1. ooc l/day.
(f) Flow 222. 000 gpd or 840,000 I/day.
-------
TABLE 40. RESULTS CF SAMPLING WASTE WATER FROM FURNACE EXHAUST
SCRUBBING, AND MILLING AND CLASSIFYING SIAGS, COMPANY 38
Wasiewater Ilischarge After Waste water Discharge After Wastewater Discharge After
Thickener and Centrifuge, Thickener, Centrifuge, and Settling. Solids Removed and Two Settlings.
nig/l mg/1 mg/1
Parameter Hifih Low Av^ High I.ow Avg High
(I') (0
Susp. solids -I-16H 100 1RC1 97 -tS 7U 109
Cadmium 4 1 2.3 "2 o. 9 1. 6 o. 1
Coppct fil'C III 210 (i C 3.7 luO
Uad 1,'idO L'd 557 10 1 o 50
Mercury (>. GOG •.<>. U01 i>. o03 <('. 0(Jl <('. uOl <5
7.7 7.9
Wastewatet Recycled After
Complete Treatment,
mg/1
High
65
0. I
30
7
<0.001
0.2
10
20
8.2
Low
2
<0.05
2
3
O.001
<0. 1
3
<5
7.4
Avg
34
0,07
12
5
<0. 001
0.1
6
11
7.7
Wastewater Discharge After
Milling and Classifying Slags,
rng/l
High
7505
3
2400
1500
0.020
30
2000
47
9.2
Low
1057
<0.05
450
350
0.003
9
450
<5
7.4
Avg
3502
2
1250
917
0.012
18
983
22
-•
(a) Production S»,7 KKg day <>f copper alloy.
(h) Wastewater flow 22, 000 I/day.
(c) Wastcwatet flow U. 4uu I/day.
(d) Wastewater flow 67.400 I/day.
(c) Wasiewater flow 72, 700 I/day.
(f) Wastcwater How 72.700 I/day.
-------
17J3LE 41.
OF TREAIMiMT ALTERNATIVES
TOR WASTE'; WATER FROM '.
SCRUBBING
h-1
*.
o
Loading, kg/kkg metal produced tor ID/lOUU lb metal)
PolluLaiiL
P_nrameters
Susp. solids
Cadmium
Copper
Lead
Mercury
Nickel
X i nc
Oil & grease
pll
Table
Referenced
(a) Plant 9
(b) Plant 38
Treatment Alternative
1 245 6
Plant Plant Plant Plant Plant Plant Plant Plant
9(a) 38 (b) 9(a) 38(b) 9 0.548 0.001 0.476 0.001 0.005 0.001 0
0.029(0 3.565 0.009 1.263 0.009 0.007 0.003 0
7xLO-5 IxHr6 6xiO-5 IxlO'7 2xlO~6 1.5xlO~6 2xlO"5 1
0.0028
-------
electrolyte solution is continuously circulated through
thickeners and filters to remove the solids (slimes) and
recycled back through the electrolytic cells. The cells
operate hot so that makeup water is required to replace the
amount evaporated. Most of the makeup water is generally
added during the daily washdown of the tops of the cells.
Waste water from electrolytic refining operations originates
from spills, cell maintenance and repair/ and catastrophic
accidental losses. Depending on the quality of the anodes
and the impurities from the scrap metal that are carried
through the fire refining, soluble metal concentrations
build up in the electrolyte which cannot be removed as
slimes. When this occurs, a bleed stream of the electrolyte
is required. Such waste electrolyte normally is treated to
remove the copper content first by high-voltage deposition
and finally by cementation with iron. At one plant, the
high nickel concentrations permit the byproduct recovery of
NiSOit by means of barometric condensers. The resulting
solution may then be neutralized and filtered before
discharge. some electrolytic refineries have a ready market
for the contaminated electrolyte. Most of the plants sell
their slimes (for the precious metal value they contain) to
primary copper refiners or others equipped for precious
metal recovery. Plant 1 operates an on-site precious metal
recovery facility.
Makeup water, which must be low in total ion content, comes
from boiler condensate or demineralizing systems. The
backwash from ion-exchange resins used to treat boiler water
feed or backwash from demineralizers could in effect be
considered part of the waste water load of electrolytic
refining. However, these are considered to be boiler-
related operations and not process waste water from
secondary copper manufacturing.
Identification of Control Alternatives
Except for Plant 1, unless a refinery has a market for waste
electrolyte, there is no viable control alternative other
than to treat the waste stream for copper recovery and to
neutralize the acid content. At Plant 1, the waste water
generated from the electrolytic refining of anodes contains
a buildup of nickel which allows an economical recovery of
nickel values by the evaporation techniques employed by
several primary copper refineries (i.e., recovery of nickel
sulfate). The amount of arsenic present in secondary
electrolyte solutions is negligible. The value of the
sulfuric acid alone does not warrant evaporation of the
141
-------
spent electrolyte for acid value recovery after
has been removed.
the copper
Copper is reduced in the bleed electrolyte by using
insoluble anodes and depositing the copper on cathodes.
Such recovered copper is recharged into anode furnaces.
Another method is to cement out the copper using scrap iron.
The copper is recharged into the copper smelting circuit,
usually at the converter or anode furnaces. The depleted
electrolyte is then typically treated before discharge or
reuse. Electrowinning and cementation can also be used in
series for copper content recovery.
At Plant 8, the depleted electrolyte is reacted with iron to
reduce the hydrogen ion concentration to give a pH of 7 for
the combined process waste water discharge. The mixed
process waste water is then discharged into a joint primary
sewage treatment plant shared with other industries in the
area. The iron sulfate adds coagulant to the joint
treatment plant. At Plant 12, the electrolyte is treated
only when breakdown occurs. The depleted electrolyte is pH
adjusted with caustic or lime, thickened, and passed through
a sand filter before discharge. The unit is sized to handle
about 95 cu m/day (25,000 gpd) and the tank house
substructure is designed to hold all of the electrolyte in
the cells in case of catastrophic loss of electrolyte and to
prevent any discharge.
The control and treatment technology alternatives currently
used by the industry for waste water from electrolytic cells
are illustrated in Figure 10.
Identification of Treatment Alternatives
The treatment alternatives illustrated in Figure 10 are
currently being used by the industry. Plant 12, which is
the newest of the electrolytic refiners, is capable of
recycling electrolyte for extended periods of time without a
bleed stream. Plants 1,8, and 9 use a bleed stream to
reduce impurities. All remove slimes for eventual recovery
of precious metals.
The effectiveness of Alternative 3 can be only estimated.
The discharge from Plant 8, which is a mixed process waste
water, was \isei as representative of Alternative l. The
discharge of treated waste water from Plant 12, even though
it is not continuous, was chosen as representative of
Alternative 3. The results are given in Table U2. The
apparent effectiveness of the treatment for reducing
loadings is influenced by the small flows involved.
142
-------
Wat«r Sourc«
Treatment For
SpilU-Upsets-Bl««d«
DUcbars*
Figure 10. Current control and treatanent technology alternatives
for waste water frcr. electrolytic refining.
143
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TABLE 42. EFFECTIVENESS OF TREATMENT ALTERNATIVES FOR SflASTE
WATER FROM ELECTROLYTIC REFINING
Loading, kg/kkg
metal produced
Treatment Alternative
Pollutant
Parameters
Suspended solids
Cadmium
Copper
Lead
Mercury
Nickel
Zinc
Oil & grease
PH
Table Referenced
1
Plant 8 (a)
3.334
NR(C)
0.092
0.035
NR
0.061
0.127
NR
7
V-7
2
Plant 12<.b;
0.0048
NLC(d>
3xlO'8
1.7xlO"7
NLC
1.7xlO~7
3xlO"7
NLC
8.0
V-23
(a) Mixed-process-was tewater discharge to joint
treatment plant.
(b) Discharge would be outflow from treatment plant of
excess wash-down water in event of breakdown and is
not continuous .
(c) NR - not recorded in analytical data.
(d) NLC - no loadings calculable.
Note: Jjoadims also eru.ivalent to Ih/lOnnih retal
144
-------
However, even if the flows were an order of magnitude
greater, this treatment technology reduces loadings
significantly. Alternative 4r the byproduct recovery of
NiSO4 by usage of barometric condensers, produces no process
waste water at Plant 1. Well maintained and highly
efficient deintrainment pads are employed in the condensers
to minimize carryover. Except for Plant 1, slimes are sold.
Plant 1 produces a very small volume of process waste water
during precious metal recovery (23 cu m/day (6,000 gpd)).
Currently, part of this flow is impounded in lined ponds and
the remainder is discharged.
Combined Waste Water Streams
Plant 32, which melts number 1 grade copper scrap into wire
bar, recently (1973) made a considerable investment for the
reduction of pollutants from smelting and related
operations. Extensive pipe segregation preceded the
installation of a treatment plant for pH adjustment (lime
treatment) and sludge removal. The number of process waste
water discharge pipes was reduced from 10 to 4. All of the
sanitation waste water is directed to one of these
discharges and eventually will be sent to a municipal
treatment facility. The processes discharging waste water
into the plant treatment facility are laboratory water,
plant wash down, furnace exhaust gas cooling before (dry)
gas cleaning, and a chemical recovery system for precious
metals.
The treatment facility is shown schematically in Figure 11.
The industrial process water enters a polyvinyl chloride
(PVC)-lined, concrete surge tank. This tank evens out the
fluctuating inflow, allowing the level in the tank to rise
or fail while allowing the pumps to discharge a constant
flow to the mixing tanks. Agitation is also provided in
this tank to mix acid and alkaline incoming streams and
obtain some natural neutralization. The three transfer
pumps provide flexibility to handle varying flows while
maintaining sufficient capacity to handle excessive flow
conditions.
The waste water, of about pH 1.5, is pumped to the first
stage of three PVC-lined, concrete mixing tanks. A lime (3
percent calcium hydroxide) slurry or, alternately, caustic
(50 percent NaOH), depending on availability and cost, is
added to the first stage where the pH is brought up to 4.5.
The water then flows into the top of the third stage where
caustic is added to bring the pH up to 8.2. The water is
then "polished" in a rapid mix tank, a treatment consisting
145
-------
FROM
PLANT
GENERAL WASTE
SURGE TANK
(30,000 GAL.)
NEUT. SYSTEM
NO.
EFF. METER
PIT
TO
ROTARY
VACUUM
FILTER
SLUDGE TO
SCAVENGER
pipp viar>tc '-':ttcr
(Plant 32)
-------
of complete mixing and a final caustic addition to raise the
pH to 8.8 (considered to be the optimum precipitation
level). A solution of ferric sulfate is also added as a
coagulant. Facilities are also available for coagulant aid
(a polyelectrolyte solution) addition; however, this is not
presently employed. The rate of addition of lime or caustic
is automatically regulated by continuous pH monitoring with
feedback to proportional controllers on the caustic or lime
feed pumps for the various mixing tanks.
The neutralized water is then pumped to a centerflow
clarifier. The clarified water is collected in a circular,
90-degree V-notch, wired trough, and then flows to a tank
where the effluent is discharged. Concurrent with the
settling and clarification operations is an automatic
semicontinuous sludge dewatering process. Here, three
days/week for eight hours/day, the sludge is drawn off and
filtered on a rotary vacuum filter. The filter operates
with a three inch precoat of diatomaceous earth. The sludge
is "cut" off the filter and falls into a hopper located
above a truck. The collected material, 35 percent solids,
is trucked to an on-site landfill area. The filtrate is
collected and recycled back to the rapid mix tank.
The entire plant is located in an area approximately 60 x
120 feet, with all the equipment except the clarifier
located indoors. An elaborate instrumentation room was
designed into the facility; from the control room all
operations can be monitored and most can be controlled
manually. The effectiveness of the new facility was
determined by comparing the combined discharge from the
plant before the treatment facility was installed (RAPP
data) with the data after the new facility had been in
operation for two months. Weekly analysis reports for a
period of six to eight weeks of operation after shakedown
were used to determine the average loadings. For the
comparison, it should be noted that certain plant operations
had been eliminated from the plant site and that extensive
segregation of drainage pipes also was done. By so doing,
the number of process waste water discharge pipes (to the
treatment plant) was reduced from 7 to 3. The effectiveness
of the treatment plant in reducing loadings is indicated in
Table 43.
In another case, Plant 10 uses continuous recycle of its
mixed process waste water after settling and filtration.
The same system is employed to treat discharge from the
plant when rainwater exceeds that lost by evaporation in
various processes, and for this reason, the system can be
considered an end-of-pipe treatment.
147
-------
r.ABT£ 43. EFFECTIVE JES£ OF n-JD OF ^IPF,
ror- OYCT;JT> 7"rrrci
Plant 32
Loadings, kg/kkg (Ib/ton) metal produced
Pollutant
Parameter
Before Treatment
Installed
(Combination of 1
Discharges)
After Treatment
Installed
(Combination of 3
Discharges)
Susp. solids
Cadmium
Copper
Lead
Mercury
Nickel
Zinc
Oil and grease
pH
0.828 (1.656)
9xlO~6 (1.8xlO~5)
0.034 (0.068)
0.014 (0.028)
6.9xlO"6 (1.4xl(T5)
0.004 (0.008)
0.016 (0.032)
0.051 (0.051)
5.8
0.036 (0.072)
NT* (a)
0.0007 (0.0014)
0.0003 (0.0006)
NR
0.0003 (0.0006)
0.0002 (0.0004)
NR
9.0
Source: RAPP data and v?eekly analysis reports to regional
EPA office.
(a) NR - not reported in analytical data.
148
-------
"Dirty" process water from contact and noncontact cooling
operations and from slag quenching and milling is pumped to
a holding pond for settling, then pumped through three sand-
and-coal filters, and then stored in a concrete reservoir.
Makeup well water is pumped directly into the reservoir.
The filtered water and makeup water are then pumped to the
various water-using process steps. The filters are
automatically backwashed when the flow is restricted (once
every day or two). The backwash solids are sent to a small
holding pit and then pumped back to the settling pond.
(Backwash formerly went to the thickeners in the slag
milling and classification area when it was operating.)
Periodic cleaning of the pond (dredged once or twice a year)
removes these accumulated solids, which are sent to the
depleted slag piles.
Plant 10 normally does not discharge waste water, and for
this reason, no effluent characterization was available from
state or regional environmental agencies.
149
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-------
SECTION VIII
COSTS, ENERGY, AND NONWATER QUALITY ASPECTS
Introduction
This, section deals with the costs associated with the
various treatment strategies available to the secondary
copper industry to reduce the pollutant load in the water
effluents from contact water cooling, slag granulation, slag
milling and classifying, exhaust gas scrubbing, and
electrolytic cell operations. In addition, other nonwater
quality aspects are discussed.
For the purpose of developing cost data on control and
treatment processes, a distinction was considered to exist
between control technology and treatment technology. The
former refers to any practice applied in order to reduce the
volume of waste water discharged, such as waste water
recycle and conversion from wet (water using) to dry
(nonwater using) processes. Treatment technology refers to
any practice applied to a waste water stream to reduce the
concentration of pollutants in the stream before discharge.
This section is presented in the following format:
(1) Economics of present control
practices,
(2) Economics of present treatment
practices,
(3) Cost effectiveness of present
practices,
(4) Economics of additional control
and treatment processes,
<5) Nonwater quality aspects.
Basis for Cost Estimation
Data on capital investment and on operating costs for
present control and treatment practices were obtained from
selected secondary copper companies. These data were modi-
fied as needed in the following way to put all costs on a
common basis:
(1) The capital investment reported was
changed to 1971 dollars by the use of
the chemical Engineering Plant Cost
151
-------
Index (quarterly values of this index
appear in the publication Chemical
Engineering, McGraw Hill).
(2) The operating cost was recalculated
to reflect common capitalized charges.
To do this, the annual operating cost
was calculated as follows:
Operating and maintenance - as
reported by the secondary copper
companies.
Depreciation - 5 percent of the 1971
capital.
Property tax and insurance - C.8
percent of the 1971 capital,
Interest - 8 percent of the 1971
capital.
Other - as reported by secondary
copper companies.
The majority of the data presented in this section was
estimated from equipment specifications only. The present
control practices costs, and other control processes costs,
were estimated by the following procedure. Equipment costs
were estimated from published data in references<*2*. The
total capital investment was then calculated as this cost
plus:
Installation 50 percent of equipment
Piping 31 percent of equipment
Engineering 32 percent of equipment
Electrical
Services 15 percent of equipment
Contractor1s
Fee 5 percent of equipment
Contingency 10 percent of equipment
The operating cost was calculated by estimating labor and
raw material requirements, and then adding the following
items:
Maintenance 5 percent of investment:
Depreciation 5 percent of investment
Tax and
Overhead 0.8 percent of investment
Interest 8 percent of investment
In the following discussion, capital costs are expressed in
$/kkg ($/ton) of annual production capacity of copper metal.
152
-------
and operating costs are expressed in $/kkg ($/ton) of copper
metal produced.
Economics of Present control Practices
The economic data received from surveyed plants, which are
discussed in this section, are summarized in Table 44. The
table and accompanying Figures 12 through 16 present a total
picture of present control and treatment alternatives with
respect to the cost for control and treatment of waste water
in the secondary copper industry. However, cost information
is absent for some categories. The following words have
been used to denote the reasons for the absence of cost
information:
(a) Not used - no wet-type pollution
control device is used,
(b) Untreated - the water is discharged
untreated,
(c) Not done - the operation was not
performed at this plant.
Those plants not included in Table UU are those for which
insufficient information was obtained to perform a cost
estimate.
Spray and Quench Cooling of Molten Metal
Essentially, there are two basic methods to control the
waste water effluent from the contact cooling of molten
metal: (a) eliminate the use of contact water by conversion
to noncontact cooling, and (b) collect the waste water from
contact cooling, remove the undesired contaminants, and
recycle.
Some estimates of the total capital cost of equipment
installation and necessary plant facilities to cool and
recycle noncontact cooling water were obtained during the
survey of secondary copper producers. In this survey,
eleven companies reported capital investments for noncontact
water cooling and recycle system in the range of $0.56 to
$6.23/ annual kkg ($0.51 to $5.65/annual ton).
The conversion to noncontact cooling would necessarily
involve additional capital expenditure for new water cooled
casting molds and new mechanical systems for ancillary
operations. However, the costs for the water treatment
system would be lower than those for installing an entirely
new system since existing equipment could be modified to
provide at least part of the treatment.
153
-------
TABI£ 44. SUMMARY OF OJRRZ2JT WASTE WA2ER CONTROL
TREATMENT COSTS BY OPEPATICN AND BY COMPANY
Spray and Quench
Cooling of Molten Metal
Cost Treatment
Plant
No.
8
9
10
11
12
17
19
26
32
36
38
39
41
43
Capital Operating
$/annual kkg $/kkg
1.18 0.22
3.45 0.65
0.79 0.13
0.78 0.13
0.56 0.10
4,57 0.78
Untreated
0.47 0.09
2.81 0.56
0.69 0.13
0.05 0.01
Capital Operating Alter-
$/annual ton $/ton native <-a'
1.07 0.20 5-RD
3.13 0.59 5-R
0.72 0.12 6-R
Not
0.71 0.12 4-RD
0.51 0.09 2-R
4.14 0.71 2-D
Untreated 1-D
Not
Not
0.43 0.08 3-R
2.55 0.51 5-RD
0.63 0.12 2-D
0.05 0.01 2-D
Fraction
of Flow(")
1.0
0.28
0.20
done
0.50
0.40
0.70
0.50
done
done
0.04
0.60
0.25
1.0
154
-------
TABIE 44. (contijuied)
Slag Granulation
Cost Treatment
Plant
No.
8
9
10
11
12
17
19
26
32
36
38
39
41
43
Capital Operating Capital Operating Alter-, .
$/annual kkg $/kkg ?/annual ton $/ton native^
Not
4.44 0.84 4.03 0.76 4-R
0.39 0.06 0.35 0.05 4-R
Not
0.78 0.13 9.71 0.12 5-R
0.28 0.05 0.25 0.05 2-R
Fraction
of Flow
-------
TABI£ 44. (continued)
Slag Milling
and Classifying
Cost Treatment
Plant Capital Operating Capital Operating Alter- Fraction
No. $/annual kkg $/kkg $/annual ton $/ton native*-3-' of Flow
-------
TABLE 44. (continued)
Melting and Refining
Furnace Exhaust Scrubbing
Cost Treatment
Plant Capital Operating Capital Operating Alter- Fraction
No. $/annual kkg $/kkg $/annual ton $/ton native^3' of Flow^b^
8 0.69 0.13 0.63
9 13.60 2.67 12.34
10
11
12
17 10.49 2.02 9.51
19
26 17.06 9.85 15.47
32 13.96 5.45 12.66
36
38 10.37 9.41
39 10.74 9.74
41
43 -
0.12 6-RD 1
2.42 6-RD 1
Not done
Not done
Not done
1.83 4-R 1
Not done
8.93 5-R 1
4.94 4-D 0
Not done
3.02 4-R 1
2.08 5-R 1
Not done
_ _
.0
.0
.0
.0
.38
.0
.0
_
157
-------
TABLE 44. (continued)
Equipment and/or Molten
Metal Noncontact Cooling
Plant
No.
8
9
10
11
12
17
19
26
32
36
38
39
41
43
Cost
Treatment
Capital Operating Capital Operating Alter-, , Fraction
$/annual kkg $/kkg $/annual ton S/ton native13-' Of Flow(b)
2.03 0.39
4.44 0.84
0.79 0.13
3.21
0.56
1.96
0.55
0.10
0.34
Untreated
6.23 1.19
3.58 0.67
1.07 0.20
1.89
4.03
0.72
0.35
0.76
0.12
2.91 0,50
0.51 0.09
1.78 0.31
Untreated
5.65 1.08
3.25 0.61
0.97 0.18
4-R 1.0
5-R 0.36
5-R 0.20
Not done
4-RD 1.0
0.40
0.30
0.50
1.0
1.0
0.09
2-R
2-0
1-D
4-RD
4-R
5-R
Not done
Not done
158
-------
TftBJJE 44. (continued)
Electrolytic Cell
Operations
Cost Treatment
Plant
No.
8
9
10
11
12
17
19
26
32
36
38
39
41
43
Capital Operating Capital Operating Alter—
$/annual kkg $/kkg $/annual ton $/ton native'3'
1.31 0.32 1.19 0.29 3-D
0.0 0.0 0.0 0.0 2
Not
Not
2.08 0.40 1.89 0.36 3-D
Not
Not
Not
Not"
Not
Not
Not
Not
Not
Fraction
of Flow(b>
1.0
1.0
done
done
1.0
done
done
done
done
done
done
done
done
done
(a) Control and treatment alternatives as illustrated in Figures 12
through!6. Note: -D signifies an alternative which ultimately
discharges, -R signifies an alternative which employs complete
recycle, and -RD signifies an alternative which employs recycle but
has a bleed or blowdown discharge.
(b)
fraction of the total flow to a combined treatment facility,
generated by a specific operation, times the total combined
treatment cost.
159
-------
Water Source
I
i . .1
1
SPRAT SJ'KAY
AND/OR AND/OR
fjL'F.SCH 0,1'KNCH
r.OOf.INC COO .IMC
of or
MOt.TCN MMI.'II.N
MJ.TAL METAL
SfRAY
AND/OR
QULSCH
COOLING
OF
HOI.TEN
METAL
1
PRIMARY
SOL! OS
KIIWVAL
1
!
PRIMARY
soi, ins
REMOVAL
i
i
SPRAY
AND/OR
QUENCH
COOLING
Of
MOLTEN
METAL
\
L
COOLING
TOWER
i
SPRAY
AND/OR
QUENCH
COOL I NG
OF
MlH.TI'N
METAL
1
l»J
~r ~i
+ \ T
s luugo 9 f
blowi oun
f Other
1
CLARiriCATION OtVicr
other
Proce»» — »•
Uitrr
I Water
MIXED
i'HOCIiSS
WATER
RKSKKVOIR
MIXf.U
HATF R
RKSERV01R
MIXED
1'KOCE.SS
WATEI!
EXTENDED
SETTI,iNi.i
AS'D
t
s 1 ml yet
*
SPRAY
AND/OR
QUENCH
com. ING
OF .
HOI.TEN
METAL
MIXED
PROCESS
WATER
SETTLING
AND
COOL I NO
*_ Other Proc«*e
W.ter
J
sludges E*ckf«sh
f-
FILTRATION
Dlich«cg* Recycle Hci:ycle Recycle Recycle Recycle
Wjiifr WaiL'r Water Water Water
Or Or Or Or Or
Dli charge Discharge Discharge Disc large Dlicharg*
©
CD
CD
©
cr.jntro
v;aste vati-'-r1 tnTm rontart c-nolina r^ rolfj£?n mot^I.
-------
Water Source
SLAG
QUENCH
AND
CKANLTLATION
1
VIM charg*
SLAG
QUENCH
AND
GRANULATION
PRIMARY
SOLIDS
REMOVAL
1
Sludge
Recycle Water
Or
DU charge
1
SLAG
QUENCH
AND
GRANULATION
SLAG
QUENCH
AND
GKANULATION
MIXED
PHOCESS
WATER-
RE SRRVOIH
PRIMARY
SO- IDS
Rf.t.'0'JM
•
Proce«» l
Water f
MIXED
PROCESS
^Crther FTOC.M UATER.
"" SOI.
ns
,*J ' , — . REMOVAL
eludga Sludg*""^
Backwash
•« — 1 FILTRATION! '
1
i
l_
— i
•>
•
SLAC
QUEKCH
AND
GRANULATION
PRIMARY
SOLIDS
REMOVAL
T~
Sludge
COOLING
i
Recycle W«t«r Bleed Recycle W»t«r Slowdown R«c
Or
Discharge
Oc Wa
DLscharga 0
CD
DUchirg*
©
rioure 13. Qirr^r t rrsntrol and tr^atmRnh technoloov alternatives
for v-.ste water from slag Benching and granulation.
-------
I ©
-------
Water Source
tT>
U)
gflBGE
•ludgd
Discharge
CD
gasei
•ludg*
Recycle Water
or
Discharge
©
gases
1 ENTRAINMENT 1
| SEPARATOR |
g**ee
1 ENTRAINMENT 1
I SEPARATOR 1
g«i*i
Recycle Water
ot
Discharge
©
Recycle Water
or
Dtacharge
©
Recycle Water
or
Discharge
©
Recycle Water
or
Discharge
©
Figure 15. Current control and treatment technology alternatives
for waste water frotr furnace exhaust scrubbing.
-------
W«t«t
VUcharg*
(D
Tr«
Spille-Up
• Cnent For |->P.e'<5<"*
e-Upseta-Bleed* _* . om-«i"
Figure 16. . Current control and treatment technology alternatives
for waste water from electrolytic refining.
164
-------
Operating costs for treatment of noncontact cooling water
with recycle obtained from the survey ranged from $0.10 to
$1.19/kkg ($0.05 to $1.08/ton). Contact and noncontact
cooling water for both equipment and molten metal cooling
are often treated together. Therefore, capital and operat-
ing costs for the individual operation were calculated as a
fraction (prorated by flow) of the treatment cost of the
combined flows.
Cost information for the control and treatment of contact
cooling water with recycle was also obtained in the survey.
AS noted in Table U4, Plants 9, 10, 12, 17, 38, and 39
employ some form of recycle system resulting in no discharge
or a partial discharge of a bleed stream. Capital costs
ranged from $0.56 to $3.45/annual kkg ($0.51 to $3.13/annual
ton) with an average of $1.33/annual kkg ($1.21/annual ton).
These costs include only the water control circuit; namely,
primary solids removal and cooling in thickeners, ponds,
canals, or cooling towers, and in some cases secondary
solids removal such as additional holding reservoirs or
filters, and associated pumps and piping. Operating costs
ranged from $0.13 to $0.65/kkg ($0.12 to $0.59/ton) with an
average of $0,25/kkg ($0.237 ton). Disposal costs for the
collected charcoal (when used) were included in the
operating costs, since it is considered impractical to
regenerate the charcoal.
Slag Granulation
Two alternatives exist for the control of waste water from
slag granulation and cooling: (a) air cool and mechanically
(dry) crush the slag to a .more easily handled form, and (b)
recover and recycle the slag granulation water.
Slag treatment must necessarily be discussed in terms of
metal-rich slag and depleted slag. The normal practice for
metal-rich slag treatment is the use of metal cooling pots
where the slag is air cooled, followed by mechanical size
reduction, and then by the metals recovery process.
Therefore, discharges, if applicable, of slag granulation
water are normally associated with processing of depleted
slag.
The cost for water treatment with the first alternative (dry
processing) would be nil since no water is involved.
However an "effective" control cost for this dry size
reduction alternative, defined as the difference in the cost
for the entire dry processing system and the cost for the
wet slag granulation system with no water treatment (costs
based on new installation, no retrofit costs were included),
165
-------
can be estimated. The effective cost, by definition, is a
calculated number assigned to a dry process alternative as a
waste water control cost so that it can be directly compared
with the waste water control costs associated with wet
process alternatives. The capital cost for a new dry system
(installed), including cooling potsf crushers, material
handling equipment, and other ancillary equipment, wa s
estimated at $U.69/annual kkg ($4.25/annual ton), and
operating costs were estimated at $0.89/kkg ($C.81/ton).
The capital and operating costs for a new wet slag
granulation facility, including only the quench and
granulation trough, and slag pile were estimated at
$0.59/annual kkg (SO.54/annual ton) and $0.11/kkg (S0.10/
ton), respectively. The effective water control capital and
operating costs for the dry system would be, therefore, the
difference, or approximately SU.lO/annual kkg ($3.72/annual
ton) and $0.77/kkg ($0.7C/ton), respectively. Capital and
operating costs for a slag granulation water control circuit
are given in Table 4U. As can be seen, only five of the 13
companies from which cost data were ootained practice slag
granulation. All five, however, employ some form of
recycle. Capital costs for water treatment range from £0.23
to $4.44/annual kkg (30.25 to $U.03/annual ton). These
costs include primary solids removal in tanks, thickeners,
and ponds, and in one case, additional cooling in coolina
towers, as well as associated pumps and piping. The capital
costs average $1.32/anriual kkg ($1.20/annual ton).
Operating costs range from iO.05 to $C.84/kkg (SO.C5 to
$0.76/ton) with an average of $C.25/kkg (iC.23/ ton). Costs
for disposal of the depleted slag are included in -chose
cases where the slag is landfilled, but not for those
companies that sell or reprocess their slag.
Milling and_Classifying
Essentially, there are two alternatives for the control of
waste water effluents from the metal-rich slag reprocessing
for metal value recovery: (a) remelt the processed slags in
a cupola, recover the metal values, and then cool and crush
the depleted slag (as discussed under tne slag granulation
section) and (b) wet mill and classify the metal-rich slags,
thereby recovering the metal values, remove the depleted
slag and other unacceptable contaminants from the waste
water and recycle the waste water.
The cost for the treatment of the waste water effluent
produced from the first alternative is nil (except for the
slag granulation step discussed in the section on slag
granulation). Therefore, "effective" waste water control
166
-------
costs were calculated for the purpose of comparing the wet
and dry waste water control costs. The effective cost is
defined as the difference between the cost for the entire
dry processing system (with adequate air pollution controls)
and the cost for the wet processing system with no water
pollution controls. The capital cost for a new dry system,
including the cost of screening, pelletizing, and materials
handling equipment, plus a complete installed cupola
facility equipped with air pollution controls and associated
equipment was estimated at $13.24/annual kkg ($12.01/annual
ton); and operating costs were estimated at $2.72/kkg
($2«47/ton). These costs would therefore be the cost of
conversion from the wet to the dry system (excluding
retrofit costs). The capital and operating costs for a new
milling and classifying facility including crushers, ball
mills, jigs, tables, etc., but minus the water control cir-
cuit, were estimated at $9.26/annual kkg ($8.40/annual ton)
and $1.76/kkg ($1.60/ton), respectively. Therefore, the
effective water control capital and operating costs for the
dry treatment system would be the difference, or $3.98/
annual kkg ($3.61/annual ton) and $Q,96/kkg ($0.87/ton),
respectively.
Costs for the water control circuit for slag milling and
classifying facilities were obtained in the survey. Capital
costs ranged from $0.88 to $16.91/annual kkg ($0.80 to
$15.39/ annual ton), with an average cost of $6.UU/annual
kkg (S5.84/ annual ton). These costs include primary and,
in some cases, secondary solids removal in ponds or tanks,
and associated pumps and piping. Operating costs ranged
from $0.32 to $5.14/kkg ($0.29 to $U.66/ton), with an
average of $1.757 kkg ($1.58/ton).
Melting and Refining Furnace Exhaust Scrubbing
There are essentially two alternatives to the control of
waste water effluents from melting and refining furnace
exhaust cleaning; (a) employ dry air pollution controls such
as baghouses or electrostatic precipitators and (b) wet
scrub the gases, collect the waste water, remove the
unacceptable contaminants, and recycle the waste water.
The cost for the treatment of the waste water from the first
alternative is necessarily zero since no water is used. In
a manner similar to that described previously, an effective
cost can be estimated to compare the costs for dry and wet
air pollution controls. Capital and operating costs were
estimated from published data at $3.72 to $4.78/annual kkg
($3.37 to $4.34/annual ton) and $0.44 to $0.72/kkg ($O.UC to
167
-------
$0.65/ton), respectively, for new baghouse facilities, and
$7.78 to $8.78/annual kkg ($7.06 to $7.96/annual ton) and
$0.67 to $0.89/kkg ($0.61 to $0.81/ton), respectively, for
new electrostatic precipitator facilities.
Therefore, for example, the average cost to convert from the
wet to the dry collection system would be the average of the
above costs, or $6.27/annual kkg ($5.69/annual ton) capital
cost, and $C.68/kkg ($0.62/ton) operating cost (based on the
average of the range of baghouse and electrostatic
precipitator costs). The capital costs for a new high
energy venturi scrubber (including installation) without the
water control circuit were estimated at $1.56 to
$2.17/annual kkg ($1.41 to $1.97/annual ton), and the
operating costs at $1.61 to $2.50/kkg ($1.46 to $2.27/ton).
The "effective" waste water control capital and operating
costs for the dry exhaust gas cleaning alternative were
estimated as the difference in control costs for the dry and
wet systems, or $4.40/annual kkg ($3.99/annual ton) and
$1.38/kg (-$1.25/ton) operating costs, respectively. The
effective cost by definition is a calculated number assigned
to a dry process alternative as a waste water control cost
so that it can be directly compared with waste water control
costs associated with wet process alternatives. Ine
negative effective cost means, therefore, that the dry
process (a baghouse or an electrostatic precipitator) would
have a cost advantage over the wet process (a venturi
scrubber) even before the waste water control costs are
added to the wet process control costs.
The costs for the treatment and recycle of the scrubber
effluent alternative were obtained from the industry survey.
Capital costs ranged from $0.69 to $17.06/annual kkg ($0.63
to $15.47 annual ton), with an average cost of $11.80/annual
kkg ($10.70/annual ton) . These costs include primary and,
in many cases, secondary solids removal, sludge dewatering,
and associated pumps and piping. Operating costs ranged
from $0.13 to $9.85/kkg ($0.12 to $8.93/ton), with an
average of $3.31/kkg ($3.00/ton). These costs included the
pH-adjusting medium, namely, lime, caustic, or ammonia.
Electrolytic Cell Operations
There are essentially three basic alternatives for ths
control of waste water effluents from electrolytic cell
operations: (a) sell the spent electrolyte, and (b) treat:
spent electrolyte to recover or remove valuable or
168
-------
undesirable contaminants and reuse the water for process
water requirements, such as for slag granulation, wet
scrubbers, etc., and (c) evaporate the spent electrolyte to
recover nickel values as
As discussed in the section on control and treatment tech-
nology, secondary copper electrolytic cell operations are
basically closed-loop systems. The bleed solution is either
sold or treated to extract the valuable components of the
contaminated electrolyte. The costs for waste water control
and treatment when the contaminated electrolyte is sold are
zero since no water treatment is involved. The costs for
the treatment of the electrolyte were obtained in the
industry survey from two plants. Capital costs ranged from
$1.31 to $2.08/annual kkg ($1.19 to $1. 89/annual ton), with
an average of $l,70/annual kkg ($1. 54/annual ton). These
costs include cementation tanks for copper removal, and in
one plant, pH adjustment tanks and solids removal
facilities. After the more extensive of the two treatment
processes, the water is of sufficient quality for general
purpose uses and could (depending on the operations
performed at the plant) be reused without further treatment.
Operating costs ranged from $0.32 to $0.40/kkg ($0.29 to
$0.36/ton), with an average of $0.36/kkg ($0.33/ton). These
costs included the cost of the iron for the cementation of
copper and the cost of pH-ad justment materials (when used) ,
without credit for recovered copper.
Economics of Present Treatment Practices
In the following paragraphs, only the economics of those
treatment processes applied to waste water on a once-through
basis are discussed. Process water recycle was considered a
control rather than a treatment technology, and was covered
in the previous paragraphs. Only the cooling of molten
metal involves a treatment process without waste water
recycle.
Costs for treatment of spray and quench cooling water were
obtained from two plants (Plants 19 and 41, Table 45) .
These costs include only the water treatment circuit, con-
sisting of primary solids removal and associated pumps and
piping. Because the primary treatment is also employed for
other operations, the costs were apportioned on a flow basis
to obtain the costs of spray and quench cooling water
treatment alone.
Plant 19 reported their water treatment capital and
operating costs at $4.57/annual kkg ($4. 14/annual ton) and
$0.78/kkg <$0.71/ton), respectively; the capital and
169
-------
TABLE 45. COST EFFECTIVENESS FOR CONTROL AND TREATMENT
OF WATER FROM MOLTEN METAL COOLING
Capital Operating
Costs(b), Costs'-5''
Alternative. $/annual kkg $/kkg
Designation '($/ annual ton) ($/ton)
1
2
4
5
5
6
Noncontact
System
0.0
(0.0)
0.05
(0.05)
0.78
(0.71)
2.81
(2.55)
0.56
(0.51)
0.79
(0.72)
6.23
(5.65)
0.0
(0.0)
0.01
(0.01)
0.13
(0.12)
0.56
(0.51)
0.10
(0.09)
0.13
(0.12)
1.19
(1.08)
Loadings, k /kkg (Ib/ton)
Suspended
Solids Copper
1.69
(3=38)
0.171
(0.342)
0.126
(0.252)
0.0056
(0.0112)
0.0
(0.0)
0.0
(0.0)
0.052
(0.1041
0.010
(0,020)
0.004
(0.008)
0.0028
(0.0056)
1.7xlO"5
(3.4 x 10 ~5
0.0
(0.0)
0.0
(0.0)
9.7x10"^
Zinc
0.034
(0.068)
0.0053
(0.0106)
0.0047
(0.00941
4.4x!0"6_6
)(8o8 x 10
0.0
(0.0)
0.0
(O0o;
,NLcCd)
Oil
and
Grease
NR^C)
NR
NR
NR
)
0.0
(0.0)
0.0
(0.0)
NLC
(a) Control- and treatment-alternative designation defined in Figure 12.
(b) Ref: Table 44 and Table 36.
(c) NR = not reported.
(d) NLC = nc loadings calculable.
170
-------
operating costs for Plant 41 were reported at $l.Q2/annual
kkg <$0.93/annual ton) and $0»19/kkg ($Q.17/ton),
respect!vely*
Cost Effectiveness of Present Practices
Contact Cooling of Molten Metal
The cost data for spray and quench cooling of molten metal
presented in Table 45 were plotted against a single waste
water pollutant, suspended solids. As noted in Figure 3 the
reduction in copper and zinc follows the same pattern as the
reduction in suspended solids concentration (i.e., treatment
capable of removing one of these pollutants will also remove
the others). Therefore, only suspended solids loadings were
employed in the cost effectiveness curves in Figures 17
through 21.
In Figure 17, it is clearly shown that the costs of
pollutant removal follow an exponential relationship. The
most costly treatment alternative is noncontact cooling to
achieve no discharge of pollutants. The capital and
operating costs for noncontact cooling were estimated at
$6.23/annual kkg (S5.65/annual ton) and $1.19/kkg ($1.087
ton), respectively*
In comparison with a noncontact cooling alternative, the use
of extended settling in a mixed process water reservoir is
shown to be equally effective in achieving no discharge (as
demonstrated by Plant 9P see Table 44) at comparatively
lower costs (i.e., $2.81/annual kkg ($2.32/ annual ton) and
$0.56/kkg ($0051/ton) for capital and operating costs,
respectively). These costs would be a function of the size
and the construction material of the settling facilities.
Plant 10 (see Table 44) lias been able to employ a smaller
pond by placing sand filters in the recycle circuit for
suspended solids removal. These costs are shown to be
considerably lower, $0.79/annual kkg.($0.17/annual ton) and
$0.13/kkg ($0.11/ton) for capital and operating costs,
respectively.
Simple settling and recycle appear to be even lower in cost
while maintaining the same control effectiveness (no dis-
charge. Plant 17). This option, however, applies only to
those operations not employing a charcoal cover over the
molten metal.
Thermal discharge, which is not plotted on these graphs,
would show a similar cost effectiveness curve when loadings
are calculated in kg-cal/kkg (Btu/ton) discharged to
171
-------
- a
7
6
§ 5
4-1
r,
4-1
0 4
u -••
I— 1
(0
u
-H
a
ca
o 3
2
1
0
7
6 £
i|
5
00
^
- 4
U
cn
O
U
1— 1
ra
•H 3
a
crj
_ u
2
1
J-
0
1
*
1
)
0
(0
t
v-ft/--5* Noncontact Cooling System —
I
,
1
©5
1
I
_l
A
\ ^ Average
^^-_
5 A3 t
O
1 1 | j 1
LEGEND
Numbers: Control and Treatment Alternative
Designation Defined in
Figure 12
O : Capital Cost Data Point
/\ : Operating Cost Data Point
Q4
~~~ " ~A—
i i i i,l II i i 1
.0 0.05 0.10 0.
.0) (0.10) (0,20) (0.
1
—"~
• — -_- „.,
/TVi 3 . 1 ,
1 UJl i . /YA -4
1.2
1.0
M
^ „ ^
0.8 3
„
4J
cn
O
a
•H
CO
$-i
QJ
a
n , o
0.4
n o
u. /
,0.0
.7
-1.0
.. o.e
o
•c/y
**
4J
U
C
4J
CD
M
11
- 0,4 ex
o
- .
-0.2
J3.0
30) (3.4)
SUSPENDED SOLIDS LOADINGS, kg/kkg (lb/ ton)
Figure 17. Cost effectiveness of control and t
of water fror molten rretal conlina.
-------
5
-t
Capital Cost
ho U
1
0
5
4
00
* 3
1 !
Capital Cost
hO
1
0
(0
~4 ''- -Dry System
n
-\
^ — \^ Average
1
.0 0.02 0.04
0) (0.04) (0.08) (
LEGEND
Numbers: Control- and Treatment -Alternative
Designation Defined in
Figure 13
O : Capital Cost Data Point
A : Operating Cost Data Point
A
i
l I \ \ /\
0.06 0.08 0.10 0.12 0.14 ^
0.12) 0.16) (0.20) (0.24) (0.28)
SUSPENDED SOLIDS LOADING, kg/kkg (lb/ ton)
—
~"
1
,, .. I f"\ •„ ,
r 304 3
(6.8) (7,
1.0
0.8
bO
0.6 £
o
4>
Operating Cost,
u.z
1
0.0 -
6
2)
-.1.0
0.8
0.6
0.4
0.2
_ 0.0
Figure 18. Cost effectiveness of control and treatment
water from slag quenching and granulation.
-------
24
22
20
18
16
c
o
Z 14
J" 12
en
o
"10
to
-U
•i 8
ra
U
6
4
2
0
20
18
16
<* ^
^
^
£ 12
~ 4-)
01 i n
o 10
u
r-t
ro o
ij "
•H
a
ra
u 6
4
2
0
(0.
£
3
r;
>
i
r^ 4,
8
0)
^, Dry System
O4
A4
Average
^
,
1
(2
.c
.(
LEGEND
Numbers: Control- and Treatment-Alternative
Designation Defined in
Figure 14
O : Capital Cost Data Point
A : Operating Cost Data Point
i i i 1 f i 1 1 1
2,0 3
)) . (4.0) ^ (6
—
—
—
2
— Q 1 1
^ A.-frf A *rrt
V ' \/
.0 26.0 l 32.
.0) (52.0) (65.
5
~
4
A!
X
4J
to
O
o
oc
c
•H
u -
9 ro
*- ^
Q)
a
o
1
0
6
2)
^
4
o
4J
3 <^
4J
(0
O
O
M
l-> 10
Operatin
0
SUSPENDED SOLIDS LOADINGS, kg/kkg (Ib/ton)
Figure 19. Cost effectiveness of control and treatment of
v/atox from slao millino and classification.
-------
(.n
20
20
-
i
i ic
, A
O
4-)
co" 12
-U
co
O
U
I-H
ra
-1-1 B
>rf o
O.
CO
U
4
1
1U
-
j*?
^ 12
u
y)
o
" 8
ra
•H
ti.
\ 5 ' —
^5,6
O6
\xr— -- Averaefe
Ao5
>A
LEGEND
Numbers :
O
6
\
5 \ - Baghouse
\ -"/
\ /^'/ 4
t 6\ X / r^4
\ ADVr / C J
ra u\ (A A / ~
° CvtxT
4** ^
-------
-1.
-------
navigable waters. Again those alternatives effective in
removing the other waste water pollutants would also reduce
thermal discharges.
The following conclusions can be drawn at this time
regarding the cost effectiveness of control and treatment of
waste water from spray and quench cooling of molten metal:
(1) The most cost effective means of
control for new plants universally
applicable is settling in a relatively
small mixed process water reservoir
combined with filtration and recycle.
(2) The most cost effective treatment
alternative for existing plants
would be (a) settling and
recycle, or (b) settling, filtra-
tion, and recycle, depending on the
particular aspects (e.g., charcoal
cover on ingots) of the casting
operation.
Slag Granulation
Slag granulation waste water control and treatment costs,
together with the waste water pollutant loadings, are given
in Table 46. The capital costs and the operating costs, as
a function of these loadings, are presented in Figure 18.
Again, the cost effectiveness curve shows an exponential
relationship. The most expensive alternative is conversion
to the dry processing system with approximately $4.69/annual
kkg ($4.25/annual ton) and $0.89/kkg ($0.81/ton) capital and
operating costs, respectively. Simple settling for solids
removal and recycle is also shown to be an effective control
alternative, but with much lower costs, namely, $0.28/annual
kkg ($0.25/annual ton) and $0,05/kkg ($0.057 ton) capital
and operating costs, respectively.
The following conclusions can be drawn concerning the cost
effectiveness of various alternatives for control of slag
granulation waste water.
(1) The most cost effective means of
control for new plants is primary
settling and complete recycle for
mixed process water.
(2) The most cost effective means of
control for existing plants is the
same system, namely, combined pri-
mary settling and complete recycle.
177
-------
TABLE 46. COST EFFECTIVENESS FOR CONTROL AND TREATMENT
OF WATER FROM SLAG QUENCH AND GRANULATION
Capital
Costs (b)
Alternative $/annual kkg
De s igna t ion(a)( $ / annua 1 t on)
1
2
4(d)
4
5
Dry-System
Conversion
Dry-System
Effective
Cost
0.0
(0.0)
0.28
(0.25)
0.39
(0.35)
1.87
(1.70)
0.78
(0.71)
4.69
(4.25)
4.10
(3.72)
Operating
Costs (b)
$/kkg
($/ton)
0.0
(0.0)
0.05
(0.05)
0.06
(0.05)
0.37
(0.34)
0.13
(0.12)
0.89
(0.81)
0.77
(0.70)
Loadings , *•
Suspended
Solids Copper
3.51
(7.02)
0.0
(0.0)
= 0.0
(=0.0)
0.0056
(0.0112)
0.126
(0.252)
0.0
(0.0)
0.0
(000)
NLC(C)
0.0
(0.0)
= 0.0
(=0.0)
1.7xlO"55
3.4 x 10"
0.0028
(0.0056)
0.0
(0.0)
0.0
(0.0)
^ kg/kkeflb/torrt
Zinc
NLC
0.0
(0.0)
= 0.0
(=0.0-)
)(1. 4 x 10"
0.0078
(0.0156)
0.0
(0.0)
0.0
(0,0)
Oil
and
Grease
NLC
0.0
(0.0)
= 0.0
(=0.0)
(e)
NR
NR
0.0
(000)
0.0
(0.0)
(a) Control- and treatment-alternative designation defined in Figure 13.
(b) Ref: Table 44 and Table 37.
(c) NLC = no loadings calculable.
(d) Seasonal discharge only, with heavy rainfall.
(e) NR = not reported.
178
-------
mary settling and complete recycle. --
Slag Milling and Classifying
The cost effectiveness data pertinent to. waste waters from
slag milling and classifying;are given in Table 47. These
data are plotted in Figure 19. Again? the exponential
relationship is noted. The m"b:st:costlyr alternative is the
conversion from conventional wet milling and classifying to
pyrometallurgical processing in a .cupola- These conversion
costs are approximately $13.24/annual kkg. ($12aOd/annual
ton) and $2.72/kkg ($2.47/ton). capital and .operating/costs „
respectively. However, these., high capital costs would "be
incurred only when a plant converted from the wet to the dry
system. The effective waste water control capital and
operating costs for the dry system {defined earlier as the
cost of the complete dry system minus the cost of the wet
system without controls) have been estimated at $3.98/annual
kkg ($3.61/annual ton) and $0.'96/kkg {S0.87/ ton) 9
respectively. The least costly alternative is primary
settling, filtration, and recycle; these capital and operat-
ing costs are $0.88/annual kkg ($0.80/annual ton) and $C,96/
kkg ($0.87/ton), respectively. The average capital and
operating costs for the present practices by the industry in
waste water control technology are estimated at $6,44/annual
kkg ($5.84/annual ton) and $1.75/kkg ($1,587 ton)f
respectively.
The following conclusions can be drawn at this time regard-
ing the cost effectiveness of waste water pollutant control
from slag milling and classifying water.
(1) The most cost effective means of
control for new plants is the instal-
lation of.a pyrometallurgical
processing facility (based on industry
average costs).
(2) The most cost effective means of
control for existing wet processing
plants is settling in a. relatively
small reservoir, followed by additional
solids removal by filtration and
complete recycle.
Melting and Refining Furnace Exhaust Scrubbing
Cost effectiveness data for furnace exhaust scrubbing are
presented in Table 48. These data are plotted against the
suspended solids loadings in Figure 20.;.
179
-------
TABLE 47. COST EFFECTIVENESS FOR CONTROL AND TREATMENT
OF WATER FROM SLAG MILLING AND CLASSIFYING
Capital Operating
Costs O^t Costs G>)»
Alternative $/ annual kkg $/kkg
Designation^a{$/annual ton) ($/ton)
1
1
2
3
3(e)
4
4
5
Dry- System
Conversion
Dry-System
Effective
Cost
0.
(0.
0.
(0.
2.
(1.
0.
(0.
16.
(15.
10.
(9.
1.
(1.
0.
(0.
13.
(12.
3.
(3.
0
0)
0
0)
06
87)
05
05)
97
39)
31
35)
97
79)
88
80)
24
01)
98
61)
0.
(0.
0.
(0.
0.
(0.
0.
(0.
5.
(4.
1.
(1.
0.
(0.
0.
(0.
2.
(2.
0.
(0.
0
0)
0
0)
38
34)
01
01)
14
66)
93
75)
32
29)
96
87)
72
47)
96
87)
Loadings , kg/kkg(lb/ton)
Suspended
Solids Copper
25.99
(51.98)
32.6
(65.2)
3.182
(6.364)
1.247
(2.494)
= 0.0
(=0.0)
0.266
(0.532)
= 0.0
(=0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
9
(18
0
(0
0
(0
0
(0
_
.275
Zinc
7
.550) (14
.11
.22)
.10
.20)
.044
.088)
0.0
(=0.0)
0
(0
~
.095
.190)
0.0
0
(0
0
(1
0
(0
^
.322
,644)
,00014
,00028)
.631
.262)
.22
.44)
0.0
(=0.0)
0
(0
=
.047
.094)
0.0
(=000^ (=0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
Oil
and
Grease
0.092
(0.184)
NLC
(c)
NR(d)
NR
= 0
(=0
.0
.0)
0.087
(0.174)
= 0
(=0
0
(0
0
(0
0
(0
.0
.0)
.0
.0)
.0
.0)
.0
.0)
(a) Control- and treatment-alternative designation defined in Figure
(b) Ref: Table 44 and Table 38.
(c) NLC = no loadings calculable.
(d) NR = not reported.
(e) Seasonal discharge only, with heavy rainfall.
180
-------
TABUS 48. COST EFFECTIVENESS FOR CONTROL AND
TREATMENT OF WATER FROM WET SCRUBBING
Capital % Operating
Loadings (b)_, ka/kksClb/ton)
Costs (b) , Costs (b) ,
Alternative, N $/annual kkg $/kkg Suspended
Designation CS /annual ton) ($/ton) Solids Copper
1
1
3(c)
4
4
5
5
5
6
6
6
Dry-System
Conversion
Dry-System
Effective
Cost
0
(0
3
(3
6
(6
6
(6
10
(9
11
(10
17
(15
10
(9.
10
(9
16
(14
17
(15
4
(3
4
(3
.14
.13)
.44
.12)
.77
.14)
-
.93
.29)
.49
.51)
.10
.07)
.06
.47)
,74
74)
.37
.41)
.11
.61)
.46
.84)
,25
.85)
.40
.99)
0
(0
0
(0
1
(1
2
(2
2
01
2
(2
9
(8
2
(2
3
(3
3
(2
4
(4
1
CO
— 1
C-l
.03
.03)
.63
.57)
.35
.22)
-
.22
.01)
.02
.83)
.21
.00)
.85
.93)
.29
.08)
.33
.02)
.15
.86)
.72
.28)
.-8
.53)
.38
.25)
128.5
(257.0)
7.
C150
66
C133
-
4.
(8.
0.
CO.
0.
Cl.
0.
CO.
0.
CO.
0.
C00
0.
Cl.
0.
C00
0.
(0.
0.
fOt
521
042)
.6
.2)
22
44)
0
0)
779
558)
0
0)
0
0)
113
226")
568
136)
050
100)
0
Oi
0
0')
0.
(0.
0.
(1.
0.
(0.
0.
(0.
0.
(0.
0.
(0.
0.
(0.
0.
CO.
0.
C00
0.
(0.
0.
CO,
0.
C00
0.
ro.
006
012)
548
096)
001
002^
-
476
952)
0
0)
001
002)
0
0)
0
0)
005
010)
001
002)
018
036)
0
0)
0
0)
Zinc
1
(2
2
(5
0
(0
1
(3
0
CO
0
CO
0
(0
0
(0
0
(0
0
CO
0
(0
0
(0
0
CO
.024
.048)
.971
.942)
.016
.032)
-
.776
.552)
.0
.0)
.003
.006)
.0
.0)
.0
.0)
.181
0362)
.0142
00284)
.009
.018)
.0
.0)
.0
.0)
Oil
and
Grease
0.0
(0.0)
0.321
(Oe642)
0.053
(0.106)
-
0.133
(00266)
oeo
(000)
0.034
CO. 068)
0.0
(0.0)
0.0
(0.0)
0.007
(0.014)
0.002
CO. 004)
0.016
(00032)
0.0
C000)
0.0
(0.0)
(a) Control- and treatment-alternative designation defined in Figure 15.
(b) Rcf: Table 44 and Table 41.
(c) Alternative not currently explored but amenable to cooling and solids
separation requirements
181
-------
The most costly alternative is wet scrubbing with extensive
water treatment rather than conversion to a dry system for
air pollution control. The dry system baghouse costs were
$4,25/annual kkg ($3.85/annual ton) and $0.587 kkg
($0.53/ton) for capital and operating costs, respectively.
The capital and operating costs for the entire dry air
pollution system were much lower than the wet scrubbing
water treatment circuit alone. Comparison of the installed
cost for a complete dry system with that for a complete wet
system/ excluding the water treatment and recycle circuit,
shows that the effective capital and operating costs for the
dry system were $2.38/annual kkg (32.16/annual ton) and
$l.U8/kkg {S1.34/ton), respectively*
All the control systems employed involve complete or nearly
complete recycle. The no discharge system had similar
control and treatment costs. The most costly recycle option
was primary and secondary settling, sludge dewatering, pH
adjustment, and complete recycle. These capital and operat-
ing costs were $17.06/annual kkg ($15.47/annual ton) and
59.85/kkg <$8.93/ton), respectively. The least costly no
discharge option was primary settling, sludge dewatexing, pH
adjustment, and complete recycle. The capital and operating
costs were $10.49/annual kkg ($9.51/annual ton) and
$2.02/kkg <$l,83/ton), respectively. Therefore, even the
least costly no discharge water treatment alternative is
more costly than dry collection methods.
The following conclusions can be drawn from the data
presented*
(1) The most cost effective means of
control for new plants is the dry
(baghouse) air pollution control
for furnace exhaust fumes,
(2) The most cost effective means of
control for existing wet scrubbing
facilities is primary settling,
sludge dewatering, pH adjustment,
and complete recycle.
Electrolytic Cell_ Operations
Cost data for two electrolytic refining operations are
presented in Table U9, These cost, data are plotted against
the suspended solids loadings in Figure 21. The data show
that current treatment technology is available to limit
significantly the quantity of waste water pollutants
discharged.
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TAKE 49. COST EFFECTIVENESS FOR CONTROL AND TREATMENT
OF WATER FROM ELECTROLYTIC CELL OPERATIONS
Capital Operating Loadings kg/Jckgdb/ton')
Costs(b-> > Costs(b) , Oil
•Alternative $/annual kkg $/kkg Suspended and
Designation^'($/annual ton) ($/ton) Solids Copper Zinc Grease
1
2(d)
3
1.31
(1.19)
-
2.08
(1.89)
0.32
(0.29)
-
0.40
(0.36)
3.38
(6.76)
-
0.0048
(000096)
0.092
(0.184)
-
3xlO'8f
6 x 10~£
0.127
(0.254)
-
. 3xlO~7
*X6 x 10"
NR(C)
-
7NLC(6)
7)
(a) Control- and treatment-alternative designation defined in Figure i6
(b) Ref: Table 44 and Table 42.
(c) NR = not reported ,
(d) Plant sells electrolyte, no costs or loading available.
(e) NLC = no loadings calculable
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Plant 8 (see Table 44) treats a continuous bleed of spent
electrolyte by cementation with scrap iron before discharge
to a municipal-industrial primary treatment plant. Capital
costs for cementation were estimated at approximately
$1.31/annual kkg ($1.19/annual ton) and operating costs ,at
$0.32/kkg ($0.29/ton). At Plant 12, waste electrolyte is
produced only during breakdown. The waste electrolyte is
cemented with iron, pH adjusted, and sand filtered before
discharge to a mixed process water reservoir (a lake which
continuously discharges), and recycled to a central water
treatment plant serving the entire facility. Capital costs
were estimated at $2.OS/annual kkg {$1.89/annual ton), and
operating costs at $0.40/kkg ($0.36/ton). A portion of the
process waste water produced during precious metals recovery
at Plant 1 is currently impounded in lined ponds. The
capital costs of these ponds with areas totalling about
0.405 ha (1 acre) is approximately $40,000.
Because of the limited data available, control and treatment
effectiveness and costs were assumed to follow the usual
relationship. It is expected that for no treatment the
costs will be less and the pollutant loading much higher,
and for additional end-of-pipe treatment, such as total
evaporation or reverse osmosis, the cost would be at least
two to three times greater while improving the waste water
quality only slightly.
The following conclusions can be drawn from the data
presented.
(1) The most cost effective means of
control for new plants is treatment
(cementation, pH adjustment, and
filtration) followed by recycle
to processes with low quality water
requirement.
(2) The most cost effective means of
treatment for existing facilities
is cementation, pH adjustment, and
filtration.
Economics of Additional Control and
Treatment Processes
An indepth cost study of those secondary copper facilities
currently known to be discharging process waste water to
navigable waters has been made. Approximate costs as needed
to achieve compliance to the recommended no discharge of
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process was-te water pollutant guidelines are presented
below.
Plant 1
This plant is a secondary copper facility practicing
electrolytic refining. The process starts at the blasr
furnace where scrap is charged. Fluxes are added and copper
matte and slag are tapped. The slag is granulated at the
furnace site, and the matte, along with blister copper
received from both domestic and foreign sources, is charged
into a reverberatory furnace. The resultant copper is casr
into anodes for subsequent electrolytic refining. The
product cathode copper is melted with high grade scrap and
cast into billets, wire cars, cakes, and tubes. Slimes are
collected from -cue rank house and are blended with purchased
slimes. On-site recovery of precious metals is practiced.
Electrolyte is purged from the tank house circuit, and after
copper removal by means of electrowinning calls, Ni3O4 is
produced as a byproduct. Two barometric condensers with
deintrainment devices are used for this byproduct
operation. Copper powder is also produced on-site by
intentionally operating the electrolytic tanks incorrectly.
Recently, numerous changes to existing plant water circuits
were made. Conversion of furnace fume scrubbers to
baghouses has eliminated this large source of process waste
water. Part of the Bosh water is in complete closed circuit
with two cooling towers, while the remainder is operaced on
a noncontact basis. Spent electrolyte is evaporated for
NiSO4 production and the barometric condensers are operated
with efficient deintrainment: devices. Slag milling is not
performed on-site. A cooling tower will be used on the
current once-through slag granulation process waste water
source; the anticipated blowdown of this 3,000 1/min (800
gpm) source is unknown, but has been conservatively
estimated at 10 percent for the purposes of this analysis.
Three process waste water sources are currently generated
during precious metals recovery from slimes. Part of the
largest source from selenium recovery will be used to cool
the furnace gases prior to particulate removal in the new
baghouses, while the remainder (assumed to be a maximum of
23 cu m/day (6,000 gpd}j will be discharged. The other rwo
sources, much smaller in volume, are currently impounded in
four lined ponds.
Various recycle and reuse approaches for the small remaining
flow (i.e., 10 percent blowdown from slag granulation and
small precious metals recovery flow equal to maximum of 435
cu m/day (80 gpd) plus 23 cu m/day (6,000 gpd) or U58 cu
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in/day (121,000 gpd) ) are available in order to achieve
compliance to the recommended no discharge of process waste
water pollutants to navigable waters guideline. In order to
develop a cost estimate, the costs of artificial evaporation
are used, which should represent the maximum costs that this
facility should have.
Capital Costs
Recycle and reuse
$/Annual kkg ($/Annual ton)
Annual Costs
Recycle and reuse
$/kkg ($/ton)
1971 $
$534,000
2.78 (2.55)
$/year
$270,000
1.40 (1.28)
Plant 7
Plant 7 is a secondary brass and bronze facility. Data
indicate that ingot quenching water is used to indirectly
cool an aluminum furnace door and is then discharged. This
discharge is extremely small and has been estimated at a
maximum of 2,500,000 gal/month, since a large unknown
portion is lost through volitilization. Simple pumping and
repiping of this small volume back to the ingot quenching
pit should provide compliance. Costs are negligible.
Plant 26
This is a secondary brass and bronze facility, which
currently recirculates all of its scrubber water with no
discharge. Some ingot quenching water (maximum of 12 cu
m/day (3,080 gpd)) is commingled with nearly 227 cu m/day
(60,000 gpd) of noncontact cooling water. One method for
complying to the recommended limitation would be to
segregate the contact portion of the discharge, settle out
suspended solids and recycle this flow. Costs for this
alternative are as follows:
1971 $
$4,000
0.58 (0.53)
Capital Costs
Clarifier for contact water
$/Annual kkg ($/Annual ton)
Annual Costs
Negligible
Plant 32
Plant 32 is a secondary copper electrolytic refinery which
186
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operates its wire bar casting cooling line in a noncontact
mode. A treatment facility operating on an electrostatic
precipitator and precious metal scrubber effluents is
currently discharging extremely low concentrations of metals
in about 380 cu m/day (100,000 gpd) of process waste water.
Plant personnel indicate that there would be no technical
difficulties in recirculating this flow. Piping and pumping
costs are considered negligible.
Total Costs
The total estimated costs to Plants 1 and 26, on the basis
of 1971 dollars, are $538,000 capital and $270,000
operating, most of which is attributable to additional
treatment and control technology at Plant 1.
Nonwater Quality Aspects
Energy Requirements
Specific data on energy requirements were not available from
any of the plants surveyed. Electrical energy is consumed
in the waste water treatment for operation of process
equipment, such as pumps/ blowers, centrifuges, and filters.
The vast majority of operations was located outdoors in
unheated and unlighted areas, and little fuel and
electricity consumption was required. Mechanical operations
totaling 50 HP or less are typical; these energy
requirements would amount only to 14.9 kwhr/annual kkg (13.5
kwhr/annual ton) (for 7200 hr/yr, and 18,000 kkg annual
secondary copper production) or $0.15/kkg ($0.14/ton) (at
$0.01/kwhr), which is negligible when compared with the
total energy consumption in the industry.
Thermal energy requirements are nearly nonexistent in all
waste water treatment processes, except for the dry
processing of the metal-rich slag. This alternative
involves remelting the metal-rich slag and low-grade scrap
metal in a blast furnace, cupola, or rotary furnace. The
thermal requirement for fuel for the slag treatment is
estimated at 150,510 kg-cal/kkg (542,670 Btu/ton) (10,000
tons/year of slag processed) or $1.75/kkg ($1.59/ton) (at
$0.01/kwhr).
Solid Waste Production
Only
very few control and treatment technologies
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identified in this document produce solid waste as an
adjunct to their operation. Solid wastes are produced in
pH-adjustment operations employed for the purpose of
neutralization (resulting in precipitation of insoluble
salts) or to increase the insolubility of metal hydroxide^s.
The only instance where pH adjustment is universally
employed is in wet scrubber operations. The lime or caustic
addition in this case is not for the control and -treatment
of waste water effluents, but for the protection of the
scrubber's metal surfaces against corrosion.
One treatment process (Plant 32) involves extensive use of
pH adjustment, settling, and filtration for the treatment of
effluents from copper smelting operations. A sludge pro-
duction of 98 kg/kkg (196 Ib/ton), containing 35 percent by
weight of solids, was reported.
All other solid wastes noted result from the collection of
solids involved in the production process (e.g., charcoal
employed for metal oxidation prevention) or are combined
with production solid wastes (e.g., a small quantity of
neutralization sludge at Plant 11 is discharged with the
depleted slag after the milling and classifying operation).
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES
Introduction
The effluent limitations that must be achieved by July 1,
1977, are to specify the degree of effluent reduction
attainable through the application of the best practicable
control technology currently available. Such control
technology is based on the average of the best performance
by plants of various sizes and ages, as well as the unit
processes within the industrial category. This average is
not based upon a broad range of plants within the secondary
copper industry, but upon the performance levels achieved by
the exemplary plants. Additional consideration was also
given to
(1) The total cost of application of
technology in relation to the effluent
reduction benefits to be achieved
from such application.
(2) The size and age of the equipment and
plant facilities involved.
<3) The process employed.
(4) The engineering aspects of the
application of various types of
control techniques.
(5) Process changes.
(6) Nonwater quality environmental
impact (including energy requirements).
The best practical control technology currently available
emphasizes effluent treatment at the end of a manufacturing
process. It includes the control technology within the
process itself when the latter is considered to be normal
practice within the industry*
A further consideration is the degree of economic and
engineering reliability, which must be established for the
technology to be currently available. As a result of
demonstration projects, pilot plants, and general use, there
must exist a high degree of confidence in the engineering
and economic practicability of the technology at the time of
commencement of construction or installation of the control
or treatment facilities.
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Industry CategQry_and Waste_Water .Streams
The secondary copper industry is herein defined as that
portion of SIC 3341 {Secondary Smelting and Refining of
Nonferrous Metals) which consists of plants primarily
engaged in recovering copper metal and copper alloys from
scrap and from residues from copper and copper alloy melting
operations. The definition includes plants melting and
refining copper alloys from produced secondary brass and/or
secondary bronze scrap sources to produce alloyed copper
ingots, as well as those melting and refining purchased
copper-bearing scrap to recover pure copper (unalloyed
copper) . Not included in this category are plants that were
designed primarily to process virgin copper from ores, or
plants that remelt scrap produced in their own process.
Rather than attempt to recommend effluent limitations
guidelines for subcategories of the industry that are
difficult to specify, a more practical approach for this
purpose is to deal with the various waste water streams
themselves. The streams identified are
(1) Waste water from direct contact cooling
of metal (ingots, anodes, billets, or
shot).
(2) Waste water from slag quenching and
granulation.
(3) Waste water from slag milling and
concentration.
(4) Waste water from wet air pollution
control systems.
(5) Waste water from electrolytic refining.
Each stream has an associated loading of pollutants per unit
of product produced. For example, the recommended
guidelines would require a smelter generating only contact
cooling waste water to meet effluent limitations established
for that waste stream. A smelter generating waste water
from contact molten metal cooling, slag granulation, and wet
air pollution control would be required to meet the effluent
limitations established for each respective waste water
stream.
On the basis of information: contained in sections III
through VIII of this report, a determination has been made
as tc the degree of effluent reduction attainable for each
of the process waste water streams listed through the
application of the best practicable control technology
currently available.
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Waste Water From_.Metal Cooling
Effluent Limitations Based on the Application
of the Best Practicable Control Technology
Currently Available
The recommended effluent limitation based on the application
of the best practicable control technology currently
available is no discharge of process waste water pollutants
to navigable waters.
The achievement of this limitation by use of control and
treatment technologies identified in this document leads to
the complete recycle, reuse, or consumption of all water
within the combined processes of the industry with an
associated result of no discharge of water.
Identification of_Eest Practicable Control
Technology Currently Available
The best practicable control and treatment technology
currently available for waste water from the direcr contact
cooling of metal in the secondary copper industry is the
elimination of water discharge by recycling and reuse of all
waste waters. With reuse or recycle of water, the need for
solids and oil removal will be dictated by plant operational
procedures. Removal of solids such as the charcoal used to
cover copper alloy ingots and the oxide scale and mold wash
from anode casting requires settling and filtration before
the water is reused. The pond used for settling provides
cooling. Alternatively, a cooling tower circuit can provide
settling capacity. For smaller tonnage operations, the
recycling could occur on a periodic basis when the metal
cooling pit required cleaning for the removal of sludge.
This would require a tank to hold the water during cleaning
of the cooling tank pit. To implement a recycle system for
molten metal cooling, the requirements are
(1) The addition to existing facilities
of cooling towers and holding tanks
or a pond, pumps, and filters (with
capability for backwashing).
(2) Provisions for oil removal.
(3) Provisions for sludge removal,
dewatering, and disposal.
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Rationale for Selecting the Best Practicable
Control Technology Currently Available
Of the 44 plants surveyed, 37 (84 percent) cool ingots,"
anodes, billets, or shot with water. Twenty-five percent
recycle process waste water with no discharge, 22 percent
recycle with periodic discharge, and 12 percent recycle with
a continuous discharge. The plants recycling with periodic
or continuous discharge could adapt to a no discharge-type
recycle at minimum cost. Greater expenditure would be
required by the remaining plants (41 percent) which do not
recycle metal cooling waste water.
Age and Size of Equipment and Facilities
As set forth in this report, general improvements in
production concepts have encouraged modernization of plant
facilities throughout the industry. This, coupled with
similarities of the characteristics of waste water from
metal cooling for plants of varying size, substantiates the
identification of total recycle of cooling water as
practicable. Slightly more sludge would be expected from
smooth, copper alloy ingot production that uses a charcoal
cover on ingots than from plants producing other types of
copper alloy or unalloyed copper. Thus, more sludge would
have to be removed from ponds or settling tanks of plants
practicing charcoal covering in production.
Engineering Aspects of Control Technique Application
This level of technology is practicable because 47 percent
of the plants in the industry are now achieving effluent
reductions by these methods. The concepts are proven, are
available for implementation, and may be readily adapted to
existing production units.
Process Change
This technology is a part of the whole cost savings and
waste management programs now being implemented within the
industry. While the application of such technology requires
process changes, it is practiced by existing plants in the
industry.
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Nonwater. Quality Environmental Impact
Solid waste disposal of dewatered sludge, especially from
those plants using charcoal covers, would have only a minor
impact because of its nontoxic character. Sludges recovered
from unalloyed copper production, because of their copper
value, are recycled to the metal recovery process. Oil and
grease in excess of that removed with the sludge would be
collected during recycle water cooling operations and may be
disposed of through waste oil disposal contractors.
Waste Water From Slag Quenching and Granulation
Effluent Limitations Based on the Application of
the Best Practicable Control Technology Currently
Available
The recommended effluent limitation based on the application
of the best practicable control technology currently
available is no discharge of process waste water pollutants
to navigable waters.
The achievement of this limitation by use of the control and
treatment technologies identified in this document leads to
the complete recycle, reuse, or consumption of all water
within the combined processes of the industry with an
associated result of no discharge of water.
Identification of Best Practicable Control
Technology Currently Available
The best practicable control technology currently available
for waste water from slag quenching and granulation in the
secondary copper industry is the elimination of water
discharge by one of the following approaches:
For copper-rich slags
(1) Recycle or reuse of waste water from
slag quenching and granulation after
treating the stream to reduce
suspended solids by settling and
filtration.
(2) Air cooling molten slag cast into
193
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slag pots for subsequent solid metal
recovery by dry processes.
For depleted (waste) slags
(1) Recycle or reuse of waste water from
slag quenching and granulation after
treatment to reduce suspended solids
by settling and filtration.
To implement a recycle system for slag quenching and
granulation of both types of slag, the requirements are
(a) A lagoon or pond to provide
settling and cooling or a cooling
tower with some settling capacity.
(b) A filter system with a capability
for backwash.
Implementation of air cooling of copper-rich slags would
require the use of heavy metal pots with shapes that permit
easy discharge of the solidified slag. Their combined
capacity would have to be designed to meet smelting sched-
ules of various size furnaces and be related to the amount
of slag generated by the smelting technique employed at the
plant.
Rationale for Selecting the Best Practicable
Control Technology Currently Available
Of the 37 copper-alloy producers surveyed, the four {11
percent) that use water to quench copper-rich slags recycle
their waste water after settling and report no discharge of
process waste water pollutants. These plants process
copper-rich slags recovered from their own and other copper
alloy smelter operations. The remaining 33 use slag pots
and air cool their slags either for shipment or for their
own use in subsequent metal recovery operations.
Of the seven unalloyed copper producers, four (57 percent)
quench depleted slag. Three of these four recycle the
quench water after settling. The remaining three use high
grade scrap and produce only small amounts of a copper-rich
slag that is recycled or sold for its copper content. Waste
waters originating from both types of slag granulation are
reusable after settling to remove suspended solids. Buildup
of dissolved salts is not a problem in plants practicing
total recycle.
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Age and Size of Equipment and Facilities
Plants processing copper-rich slag by melting inherently
produce large tonnages of depleted slag, which makes
air-cooling impractical and the resulting mass difficult to
handle. Granulation produces a depleted slag product that
is easily handled and has a limited market. Therefore, slag
granulation by quenching with water in such operations is
necessary. The waste water, regardless of plant size, is
similar in character and makeup.
Engineering Aspects of Control Technique Applications
This technology of recycle and reuse of water is practiced
by six (75 percent) of the eight plants surveyed that quench
depleted slag to reduce the discharge of pollutants from
such streams. The concepts are proven and are available for
implementation.
The process employing air cooling and mechanical size
reduction of copper-rich slag which eliminates water use is
practiced by 84 percent of the industry.
Process Change
Only minor changes in waste water handling would be required
to permit plants using water for slag quenching and granu-
lation to effect solids removal and completely recycle the
waste water with no discharge of process pollutants. Con-
version to a nonwater-using system employing air cooling and
mechanical size reduction of copper-rich slags would require
only minor process changes.
Nonwater Quality Environmental Impact
The copper-rich slags that have been quenched and granulated
with water are processed further to recover solid metal
values and are a commodity, not a solid waste. Elimination
of the use of water by air cooling of copper rich slags can
be an added burden for air pollution control. Similarly,
mechanical size reduction, a very dusty operation, would
require additional air pollution control.
195
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The granulated, depleted slags have been used as ballast and
as a source of roofing granules. Amounts in excess of these
commercial demands are dispersed to landfill. They are
generally inert but may impart alkalinity to the landfill
through very slow hydrolysis and leaching. The sludges
recovered from waste water treatment would be expected to be
of similar composition and be suitable for landfills.
Waste Water From Slag_ Milling and Classification
Effluent Limitations Based on the Application
of the Best Practicable Control Technology
Currently Available
The recommended effluent limitation based on the application
of the best practicable control technology currently
available is no discharge of process waste water pollutants
to navigable waters.
The achievement of this limitation by use of control and
treatment technologies identified in this document leads to
the complete recycle, reuse, or consumption of all water
within combined processes of the industry with an associated
result of no discharge of water.
Identification of the Best Practicable
Control Technology Currently Available
The best practicable control technology currently available
for copper-rich slag milling and classifying is the elimina-
tion of water discharge through the use of the following
approaches.
(1) Recycle and reuse of all waste waters
after treatment to reduce solids
content by pH adjustment to between
8 and 9, if necessary, and settling,
followed by filtration.
(2) Elimination of direct water use by
melt-agglomerating the metal in a blast,
cupola, or rotary furnace.
With the reuse or recycle of all waste waters, solids re-
moval and pH adjustment is necessary. Lagoons or settling
tanks followed by filtration to "polish" the water are used
to remove solids. The pH is maintained near a value of 8
with acid to control the extent of hydrolysis of the basic
metal oxides in the slag.
196
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Recovery of metals from copper-rich slags by melt
agglomeration is done in either a blast, cupola, or rotary
furnace. Such technology requires minor size reduction of
the slags, pelletizing of fines, fuel in the form of coke or
oil, and extensive air pollution control systems on exhausts
from the furnace.
Rationale for Selecting the Best Practicable
Control Technology Currently Available
Six (29 percent) of the 21 plants processing copper-rich
slags use wet milling and classification. Of the six, three
(50 percent) reported no discharge of process water, while
the other three discharged recycled water only periodically.
Fifteen (71 percent) of the 21 plants use a furnace to
recover the metal content from copper-rich slag.
Age and Size of Equipment and Facilities
Regardless of size and age of the facility, the waste water
generated from milling and classifying of copper-rich slag
is similar in character and makeup.
Operation of furnaces for the recovery of metal by melt
agglomeration is most economically done on a continuous
basis. Therefore, such an alternative is better suited for
large tonnage processors of slag. Wet milling is better
suited for processing a plant's own slags with enough
material purchased to keep the operation at full capacity 24
hours a day.
Engineering Aspects of Control
Technique Application
This level of technology is practicable because 50 percent
of the wet milling facilities are now achieving effluent
reductions by these methods. The concepts are proven,
available for implementation, and may be readily adapted to
existing production units.
The level of technology associated with melt agglomeration
is also practicable because 71 percent of the processors of
slags presently using furnaces for metal recovery from slags
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are achieving effluent reductions by this method. With the
use of furnaces, there will be an associated use of water
for noncontact cooling of the equipment and air pollution
control systems (dry). In this area, also, the concepts are
proven and available for implementation.
Process Changes
Only minor process changes would be required to permit the
plants to settle and recycle the waste water without dis-
charge. A partial bleed from the system is realized through
the removal of a sludge made up of residual slag.
Conversion from wet milling for metal recovery to a furnace
process would require extensive process changes. However,
such a transition would not involve technology unfamiliar to
the industry.
Nonwater Quality Environmental Impact
The wet milling of slag generates large amounts of solid
waste. Because of its relatively high copper content of
four to five weight percent, this solid waste is usually
stored at the plant site in heaps or landfills. Slow
hydrolysis of the basic metal oxide content could release
alkalinity to the soil. The additional amounts of solids
recovered in upgrading the waste water for reuse would be
small compared with the amount of residual slag.
Metal recovery from copper-rich slags with a furnace
produces about equal amounts of depleted slag per unit
weight of metal as does wet milling. The amount of
hydrolyzable basic metal oxide content is reduced in the
melting operation. This depleted slag is usually quenched
and granulated with water. The amount not sold is usually
disposed of in a landfill. Except for some potential
hydrolysis that could increase the pH of the surrounding
soil, it is considered suitable material for a landfill.
The use of furnaces will require fuel in the form of coke,
oil, or natural gas, depending on the type of furnace
employed; whereas, wet milling requires electrical energy
for comminution and classifying.
Waste Water From Furnace Exhaust Scrubbers
Effluent Limitations Based on the Application
of the Best Practicable Control Technology
Currently Available
The recommended effluent limitation based on the application
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of the best practicable control technology currently
available is no discharge of process waste water pollutants
to navigable waters.
The achievement of this limitation by use of the control and
treatment technologies identified in this document leads to
the complete recycle, reuse, or consumption of all water
within the combined processes of the industry with an
associated result of no discharge.
Identification of the Best Practicable
Control Technology Currently Available
The best practicable control technology currently available
for waste water from furnace exhaust gas scrubbing is the
elimination of water discharge by one of the following
approaches.
(1) Recycling all of the waste water from
furnace exhaust scrubbing after pH
adjustment to between 8 and 9, and
removal of solids by settling and
filtration or centrifugation.
Cooling towers may or may not be
necessary depending upon the waste
water storage capacity available,
the size of the emission control
system, and the period of time it is
operated each day.
(2) The use of dry air pollution control
equipment (baghouse air filters).
For implementation of a total recycle system for scrubber
waste water, the requirements are that existing plants,
using wet scrubber recycle systems, improve solids removal
operations by pH adjustment to between 8 and 9 and
filtration or centrifugation. Some additional settling
capacity and/or cooling towers would be necessary in some
plants. The discharge from the treatment may be recycled
directly to the scrubber or it can be combined with other
process waste water and reused in other operations.
Rationale for Selecting the Best Practicable
Control Technology Currently Available
Wet air pollution control of furnace exhausts is practiced
by 13 (30 percent) of the 44 plants surveyed. Of the 13
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plants using furnace exhaust scrubbing, eight (62 percent)
recycle all their water. Of the plants surveyed, 77 percent
use either total recycle of the scrubber waste water or bag-
houses to eliminate the discharge of waste water.
Age and Size of Equipment and Facilities
All plants regardless of size or age have installed or have
made plans to install air pollution control equipment to
meet air pollution control standards. As a result, most of
the air pollution equipment is relatively new, regardless of
the size or age of the plants. Of the 13 plants that
operate wet air pollution control equipment, complete
recycling with no discharge is practiced by old, new, small,
and large plants. Among those plants that discharge all or
part of the scrubber waste water, the size or age of
facilities has no bearing on this practice.
Engineering Aspects of Control Technique Application
This level of technology is practicable because 62 percent
of the plants surveyed that use wet scrubber systems are now
achieving effluent reductions by this method. Buildup of
dissolved solids is limited by the constant removal of
dewatered sludge and has not been shown to be a problem for
plants practicing closed-cycle operations. The level of
technology implied by the use of baghouses is practicable
because 64 percent of the plants surveyed are now using them
to achieve effluent reductions. In both cases, the concepts
are proven, are available for implementation, and may be
adapted to existing production units.
Process Changes
Only minor changes would be required in the handling of
waste water from scrubbers to permit recycle of this stream.
No changes would be required in the process itself. The use
of baghouses would not require extensive changes in the
furnace operations, but would require extensive additional
gas cooling capability.
Nonwater Quality Environmental Impact
In both alternatives, the solids recovered from furnace
exhaust gases are either sold or recycled for their metal
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content. Recovery of the solids from baghouses is an
inherently dusty operation and emission control during
recovery is necessary. The energy requirements of both the
recycled wet scrubber system and the baghouse control
alternative are estimated to be equivalent.
Waste Water From Electrolytic Refining Operations
Effluent Limitations Based on the Application
of the Best Practicable Control Technology
Currently Available
The recommended effluent limitation based on the application
of the bast practicable control technology currently
available is no discharge of process waste water pollutants
to navigable waters.
The achievement of this limitation by use of the control and
treatment technologies identified in this document leads to
the complete recycle, reuse, or consumption of all water
within the combined processes of the industry, with an
associated result of no discharge of water.
Identification of Best Practicable Control
Technology Currently Available
The best practicable control technology currently available
for waste water from electrolytic refining is the elimina-
tion of water discharge by treating the bleed or breakdown
stream from electrolytic cell operations so that it is
suitable for reuse in other plant processes or suitable for
sales or production of copper or nickel sulfate. For reuse,
the treatment consists of removal of copper by cementation
with iron metal and/or electrowinning, lime neutralization
to a pH of between 8 and 9, and sand filtering the waste
stream to remove solids before discharge into a combined
process water reservoir serving other plant water needs.
Implementation of such a treatment requires that a treatment
facility have
(1) Storage capacity for waste electro-
lyte equivalent to the total capacity
of the electrolytic cells.
(2) Cementation tanks, lime treatment
201
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facilities, and sand filters with
associated pumps and plumbing sized
to process total electrolyte volume
in 1 to 2 days of operation.
The best practicable control technology currently available
for the relatively small volume of process waste water
generated during precious metals recovery is to reuse this
flow for baghouse hot offgas cooling, or for other plant
uses, after, as needed, neutralization and precipitation.
Rationale for Selecting the Best Practicable
Control Technology Currently Available
Of the four producers of secondary unalloyed copper, one
plant (25 percent) employs such an operation for spent
electrolyte. Of the remaining three, one has a market for
the electrolyte, one treats the electrolyte by cementation
and the resultant iron sulfate solution is discharged into a
joint treatment plant, and one evaporates the solution
during metal sulfate recovery. Only the first case deals
with treatment of the waste water to a level suitable for
reuse in other processes within the plant.
Only one of the four plants is known to recover precious
metals on-site, and the small production of process waste
water can easily be reused elsewhere.
Age and Size of Equipment and Facilities
The characteristics of waste water from electrolytic
refining operations will vary with the nature of the scrap
and slags used to make anodes. If high concentrations of
metals such as nickel develop in the electrolyte during
electrolysis, then recovery of nickel sulfate by evaporation
is warranted. However, where the buildup of valuable metal
sulfates is small or nonexistent, the variation in the
characteristics of the waste water would be independent of
the age and size of the facility. Therefore, waste waters
can be treated, in the manner described, to a level suitable
for reuse in other processes in the plant.
Engineering Aspects of Control
and Treatment Applications
This level of technology is practicable because 25 percent
of the plants that electrolytically refine copper are now
202
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achieving effluent reductions by these methods. The
concepts are proven, are available for implementation, and
may be readily adapted to existing units.
Process Changes
This technology is part of the waste management programs now
being implemented within the industry and requires
essentially no process changes.
Nonwater Quality Environmental Impact
The solid waste, primarily hydrated iron oxide and calcium
sulfate, recovered from the filters, would have only a minor
impact in the landfills used for their disposal.
Combined Process Waste Water
In all of the secondary copper industry plants, water is
consumed through evaporation and sludge removal. Therefore,
with judicious water management, including that collected in
rain water runoff, only makeup water need be added. The
buildup of dissolved salts does not impair the closed-loop
operations since sludge removal provides the means for a
bleed of salts from the system. In effect, the discharge of
water from secondary plants could be reduced to the amount
of rainwater in excess of the amount evaporated during plant
operations. The treatments for individual waste water
process streams described in the preceding sections are also
applied to combined process waste waters. Treatment just
before transfer into storage for recycle with the option to
discharge the treated water during extended periods of heavy
rainfall is being used in one plant (Plant 10). Considering
the levels of pollutants in a waste water discharge after an
end-of-pipe treatment used by Plant 32, this waste water
would appear to be suitable for reuse or recycle water. For
purposes of reducing loadings, part or all of this water
could be recycled to existing plant operations to assure
complete consumption.
Storm Water Runoff
Special provisions to this no discharge of process waste
water pollutants to navigable waters proposed limitation
follow:
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A process waste water impoundment which is designed,
constructed and operated so as to contain the
precipitation from the 10 year, 24 hour rainfall event
as established by the National Climatic Center, National
Oceanic and Atmospheric Administration, for the area in
which such impoundment is located may discharge that
volume of process waste water which is equivalent to the
volume of precipitation that falls within the
impoundment in excess of that attributable to the 10
year, 24 hour rainfall event, when such event occurs.
During any calendar month there may be discharged from a
process waste water impoundment either a volume of
process waste water equal to the difference between the
precipitation for that month that falls within the
impoundment and the evaporation within the impoundment
for that month, or, if greater, a volume of process
waste water equal to the difference between the mean
precipitation for that month that falls within the
impoundment and the mean evaporation for that month as
established by the National Climatic Center, National
Oceanic and Atmospheric Administration, for the area in
which such impoundment is located (or as otherwise
determined if no monthly data have been established by
the National Climatic Center).
Any process waste water discharged pursuant to the above
paragraph shall comply with each of the following
requirements:
Effluent limitations
Effluent Average of daily
characteristic Maximum for values for 30
any 1 day consecutive days
shall not exceed
Metric units (mg/1)
TSS 50 25
Cu 0.5 0.25
Zn 10 5
Oil and Grease 20 10
pH Within the range 7.0 to 10.0
204
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English units (ppm)
TSS
Cu
Zn
Oil and Grease
PH
50
0.5
10
20
Within the range
25
0.
5
10
7.0 to 10
25
.0
Total Costs
On the basis of information contained in Section VIII of
this document, it is concluded that those two plants not
currently achieving the recommended best practicable
limitations would require an estimated total maximum capital
investment of about $538,000 and an increased operating cost
of about $270,000/year to achieve these limitations.
205
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SECTION X
BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE—EFFLUENT
LIMITATIONS GUIDELINES
The best available technology economically achievable is
identical to the best practicable control technology
currently available. The corresponding effluent limitation
is no discharge of process waste water pollutants to navi-
gable waters.
207
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SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
The best available demonstrated control technology,
processes, operating methods, or other alternatives are
identical to the best practicable control technology
currently available. The corresponding standard of per-
formance is no discharge of process waste water pollutants
to navigable waters.
209
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SECTION XII
ACKNOWLEDGMENTS
This development document was prepared by the Environmental
Protection Agency on the basis of a comprehensive study of
this industry performed by Battelle Memorial Institute,
Columbus, Ohio, under contract no. 68-01-1518. Mr. Eugene
Mezey, under the direction of Mr. John B. Hallowell,
prepared the original (contractor's) report.
This study was conducted under the supervision and guidance
of Mr. George S. Thompson, Jr., Project Officer.
Preparation, organizing, editing, and final rewriting of
this report was accomplished by Mr. Thompson.
The following members of the EPA working group/steering
committee provided detailed review, advice, and assistance:
W.J. Hunt, Chairman
G.S. Thompson, Jr.,
Project Officer
S. Davis
D. Fink
J. Ciancia
T. Powers
Effluent Guidelines Division
Effluent Guidelines Division
Office of Planning and Evaluation
Office of Planning and Evaluation
National Environmental Research
Center, Edison
National Field Investigation Center,
Cincinnati
Excellent guidance and assistance were provided to the
Project Officer by his associates in the Effluent Guidelines
Division, particularly Messrs. Allen Cywin, Director,
Effluent Guidelines Division, Ernst P. Hall, Deputy
Director, and Walter J. Hunt, Branch chief.
The cooperation of individual secondary copper companies,
who offered their plants for survey and contributed
pertinent data, is gratefully appreciated. These include:
Cerro corporation
Chemetro
Southwire company
American Smelting and Refining Company
Franklin Smelting and Refining Company
Interstate Smelting and Refining Company
Libberman-Gittlen Metal Company
Nassau Smelting and Refining
North Chicago Refiners and Smelters, Inc.
Reading Metals Company
211
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River Smelting and Refining Company
Roessing Bronze Company
I, Schuman and company
Acknowledgment and appreciation are also given to Ms. Kay
Starr, Ms. Nancy Zrubek, and Ms. Brenda Holmone of the
Effluent Guidelines Division secretarial staff.
212
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SECTION XIII
REFERENCES
(1) Spendlove, Max J- , Retired, Bureau of Mines, Private
Communication-
(2) "Copper Industry in December, 1972", Mineral Industry
Surveys, U. S. Dept. of Interior, Bureau of Mines,
Washington, D. C., (February 28, 1973).
(3) "Copper Industry in July, 1973", Mineral Industry
Surveys, U. S. Dept. of Interior, Bureau of Mines,
Washington, D. C. (September 28, 1973).
(4) Rombert, B., Operations in the Nonferrous Scrap Metal
Industry Today, Fine, P., Rasher, H. W., and Wakesberg,
Si (Eds.) published by the National Association of
Secondary Material Industries (1973).
(5) Spendlove, Max J. , "Methods for Producing Secondary
Copper", U. S. Dept. of Interior, Eureau of Mines
Information Circular 8002 (1961).
(6) Anon,, "AMAX: in Perspective; Carteret-copper,
Specialty Alloys and Precious Metals", Engineering
and Mining Journal (September, 1972).
(7) National Air Pollution Control Administration, "Air
Pollution Aspects of Brass and Bronze Smelting and
Refining Industry", U. S. Dept. of Health, Education,
and Welfare (November, 1969).
(8) Branner, George C., "Secondary Nonferrous Metals
Industry in California", U, S. Dept. of Interior,
Bureau of Mines Information Circular 8143 (1962).
(9) Dorrielson, J. A. (Ed.) Air Pollution Engineering,
2nd Edition, Office of Air and Water Programs,
Environmental Protection Agency (1973).
(10) "A Study to Identify Opportunities for Increased
Solid Waste Utilization", National Association of
Secondary Materials Industries, Inc., Vols. II through
VII (1972), PB-212 730.
(11) Anon., "Technical Report No. 11 - Secondary Brass
or Bronze Ingot Production Plants" in Background
Information for Proposed New Source Performance
213
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Standards, Vol I, U. S. Environmental Protection
Agency/ Office of Air and Water Programs, Office of
Air Quality Planning and Standards, APTD-1352a, Research
Triangle Park, North Carolina (June, 1973).
(12) Peters, M., and Timmerhaus, K., Plant .Design and
Economics for Chemical Engineers, McGraw-Hill, New York
(1968).
214
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SECTION XIV
GLOSSARY
Act
The Federal Water Pollution Control Act Amendments of 1972.
Alloying
The process of altering the ratio of components in base
metal, such as copper, by the addition or removal of such
components. Brass and bronze are alloys of copper.
Anode
A casting of fire-refined copper of a suitable shape that
fits into an electrolytic cell for further refining. The
positive terminal of an electrolytic cell.
Baghouse
An air cleaning system consisting of multiple bag filters.
Best Available Technology Economically Achievable
Level of technology applicable to effluent limitations that
is to be achieved by July 1, 1983, for industrial discharges
to surface waters as defined by Section 301(b)(2)(A) of the
Act.
Best Practicable Control Technology
Currently Available
Level of technology applicable to effluent limitations that
is to be achieved by July lr 1977, for industrial discharges
to surface waters as defined by Section 301(b) (1) (A) of the
Act.
Copper Eillet
A large copper casting suitable for fabrication into piping,
wire, or similar products.
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Blinding of Bags in Baghouses
A restriction of the flow of air through the bag due to any
fine dust, moisture, oilr or other material that fills up in
the pores of the filter bag.
Capital Costs
Financial charges which are computed as cost of capital
times the capital expenditures for pollution control. cost
of capital is based upon the average of the separate costs
of debt and equity.
Casting wheel
A disc-shaped array of molds used to prepare ingots or
anodes from molten metal.
Category and Subcategory
Divisions of a particular industry which possess different
traits that affect waste water treatability and require
different effluent limitations.
Cathode
The negatively charged electrode of an electrolytic refining
cell on which copper is deposited during refining.
Cathode Copper
Finished product from the electrolytic refining of copper.
Cement Copper
Copper that has been precipitated out of a solution by
metallic iron scrap.
Copper-Rich Slag
Slag recovered from melting furnaces with recoverable free
copper or copper-alloy value.
216
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Depleted Slag
A slag recovered from furnaces with very little or no free
metal content.
Demineralized Water
Water treated to remove most of the cations (metal ions) and
anions*
Effluent
The waste water discharged from a point source.
Effluent Limitation
A maximum amount per unit of production (or: other unit) of
each specific constituent of the effluent that is subject to
limitations in the discharge from a point source.
Electrolyte
A solution that is an electric conductor in which electric
current is carried by the movement of ions.
Electrolytic Cell .
Device for the purification of copper. Copper from impure
copper anodes is electrically plated onto pure copper
cathodes through the electrolyte.
Electrostatic Precipitator
An air cleaning system in which dust particles are
electrically charged and then collected on plates of the
opposite electrical charge.
Fire-Refined Copper
Copper metal prepared by a smelting procedure employing
oxidation to remove impurities (converting), followed by
reduction with carbon or green poles (poling).
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Flux
A component added to a slag cover on a bath of molten copper
or copper alloy to alter the slag fluidity.
Ganque
A waste rock or slag material remaining after most of the
metal values have been removed.
Lime, Slaked Lime, Hvdrated Lime
Calcined limestone, CaO, or hydrated lime, ca(OH)2.
Matte
A crude mixture of sulfides of copper and other metals,
which is formed when sulfur-containing copper ores or
residues are melted.
One cubic meter at standard conditions of pressure and
temperature.
Pigging Machine
An endless conveyerized mold system that is used to prepare
ingots (pigs) that weigh about 25 pounds.
Point Source
A single source of water discharged from an individual
plant.
Pollutant Parameter
Constituents of waste water determined to be detrimental and
requiring control.
Rasorite
A flux used in copper refining which is primarily composed
of borax (Na2B407»10 H20).
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Residues
Slags, drosses, or skimmings that are recovered from metal
operations for metal content.
Rough Brass or Bronze Ingots
Commercial 25-pound ingots cast with no protective cover.
These ingots leave a rough surface caused by gas evolution.
Skimmings
Wastes from melting operations that are removed from the
surface molten metal; the wastes consist of metal that is
contained in oxidized metal.
Sla<
A molten mixture of oxides that protects the surface of a
molten bath of copper or copper alloy. After use, the slag
may contain metal , metal oxides , and impurities from the
molten metal.
Smooth Brass and Bronze Ingots
Commercial 25-pound ingots cast with charcoal cover. These
ingots have a smooth surface.
Soda Ash
Sodium carbonate, Na2C03_.
Solids
Copper or copper alloy scrap metal.
Standard of Performance
A maximum weight discharged per unit of production for each
constituent that is subject to limitations. The weight is
applicable to new sources as opposed to existing sources,
which .are subject to effluent limitations.
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Table Classifier
A vibrating, ribbed table designed to separate dense ore or
metals from the lighter constituents. Normally the
classifier is used with a flow of water.
Tank House
A building containing a series of electrolytic cells.
Tuyere
A nozzle through which an air blast is delivered to a cupola
or a blast furnace.
Venturi Air Scrubbers
An air cleaning system consisting of intense water-spray
cleaning of the air at a point where the air goes through a
restriction (venturi) in the duct.
Waste Water Constituents
Materials which are carried by or dissolved in a water
stream for disposal.
220
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MULTIPLY (ENGLISH UNITS)
TABLE 50
METRIC TABLE
CONVERSION TABLE
by
TO OBTAIN (METRIC UNITS)
ENGLISH UNIT
acre
acre - feet
British Thermal
Unit
British Thermal
Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square
inch (gauge)
square feet
square inches
ton (short)
yard
ABBREVIATION
ac
ac ft
•BTU
BTU/lb
cfm
cfs
cu ft
cu ft
cu in
°F
ft
gal
gpn
hp
in
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
yd
CONVERSION ABBREVIATION METRIC UNIT
hectares
cubic meters
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
(0.06805 psig +1)*
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
atm
sq.m
sq cm
kkg
m
* Actual conversion, not a multiplier
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric ton (1000 kilograms)
meter
221
J
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*
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U.S. ENVIRONMENTAL PROTECTION AGENCY (A-107)
WASHINGTON, D.C. 20460
POSTAGE AND FEES PAID
ENVIRONMENTAL PROTECTION AGENCY
EPA-335
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