-------
strictly on the basis of savings in chemicals such factors
as value of the chemicals, their concentration in the
process bath, and the dragout rate are important in
determining whether a savings is possible
Advantages and frj-roitangos. The following are some of the
advantages of using evaporation for handling plating waste
effluents:
(1) Recovers expensive plating chemicals, which
were either lost by discharge to a sewer or
effluent which would have to be treated or
destroyed prior to disposal; chemicals
concentrated to plating strength can be
returned to the plating tank.
(2) Recovers distilled water for reuse in the rinse
operations, thus lowering water and sewer
disposal.
(3) Eliminates or greatly minimizes the amount of
sludge formed during chemical treatment and
eliminates or reduces the amount requiring
disposal by hauling or lagooning.
(<*) The use of vacuum allows evaporation to accur
at relatively low temperatures (e.g., 110°F)
so that destruction of cyanides or other heat-
sensitive materials is lessened.
(5) The technology of evaporators (conventional and
vapor recompression units) is firmly established,
so their capabilities are well known and their
performance should be readily predictable and
adaptable to plating effluent handling.
Some of the limitations or disadvantages of evaporative
recovery systems are given below:
(1) The rinse water saving (e.g., 1100 1/hr (300 gph))
is rather small, and by itself does not signifi-
cantly lighten the rinse water load on the final
chemical treatment plant.
(2) Evaporative units have relatively high capital
and operating costs, especially for the vacuum
units, steam and coolant water are required.
(3) The evaporative units are fairly complex and
require highly trained personnel to operate
122
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and maintain them.
W separate units are required if or handling the
waste effluent from each line, since various
solutions, such as zinc, nickel, copper,
chromium, cannot be mixed for chemical
recovery.
i*>\ As with all closed- loop systems, evaporation
( } in most cases results in a build-up of impurities
which must be taken care of by a bleed stream
or directly in the closed- loop system.
The advantages offered by evaporative recovery o^ten
outweigh ?he disadvantages. Evaporative recov**y *%*
nromisinq and economical method currently available for
KndlinS plying waste effluents and limiting treatment
SlSnt 2i£e Where existing chemical treatment cyanide
destruction; chromate reduction, and chemical precipitation)
-
chemicals plays the significant role in judging the overall
meri« of the evaporative system for a specific operation.
Process Principles_and Equipment. A representative closed
^himicals and water from a
ve o
ola?inq line with a single-effect evaporator is shown in
?iqure 12 A single-effect evaporator concentrates flow from
the rinse wlte? holding tank. The Concentrated rinse
solution is returned to the final rinse tank. With the
closed^loop system, no external rinse water is added except
fo? Sakeup of atmospheric evaporation losses. The system is
designed for recovering 100 percent of the chemicals,
normally lost in dragout! for reuse in the plating process.
Sinqle-, double-, and multiple-effect evaporators, and
vapo^recompression evaporator units are ^^°* *a*}dl *ng
plating effluent. Open-loop and combined evaporation (i.e. ,
evaporation combined with ion exchange, reverse osmosis or
other systems) are also employed for Handling plating
effluent.
A single-effect evaporator is preferred, if relatively
untrained operating personnel are involved, or low initial
SSpiSl outlSy is desired. It's the simplest in design and
?£ererore the easiest to operate. However, it is less
123
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Concentrotc hold tonk
Distillote hold tank
tasssaaK^i
Plating work travel •
Plotingbath. Rinse
inse tanks (
-------
economical than a double-effect. »>r \?a ;.-.-.-* ^compression unit
with regard to utility casts,, « tfou me- effect evaporator
should be considered when lower opsrati.^ cost is desired
with a modest increase in capital
& vapor-' re compress ion evaporator should foa considered if no
steam or cooling water Is avai'lA&ie. Where utilities for a
conventional steam evaporator &rs available* the high
initial cost of the vapor r^c OKI press! on unit is not
economically justified. Its ope/raxing cost is the lowest of
the three systems. I -is despondence on an expensive and
complex mechanical compressor is th<& Kiai/i disadvantage.
Some sources report considerable Rifii.vi^iiance and down time
and have dispensed with use of evaporator units. Other
sources report little or no trouble sand are very satisfied
with the opera.tior?.. It appears; tnai iihe units can perform
very satisfactorily If tha installation is properly
engineered, and if preventive maintenance and trouble-
shooting are carried oat by fcnowic-dg^fcible personnel.
In some instances, evaporation procedures snaet be used in
combination with chemical or other methods in order to
handle small amounts of impurity build-up (e.g.,
brighteners,, carbonates v. ext.r&neaus metal ions, etc. , in
closed loop operation) or for t nsa tsnerst of minor bleed-off
streams (open-loop^ „
Atmospheric evaporation,, whieii a»es air flow through packing
media in an evaporator, can concentrate plating solution
such as chromic acid tsp -co siSQ g/1 {"4 Ib/galJ .
The corning Glass Company Siss jifstro»5i/:.'e<5 a new concept for
evaporative recovery, h glass shell tiad tv.be heat exchanger
is motanted vertically &n>. -;.r»fese processes. Small
-------
amounts of spxlls, leaks, if segregated, are evaporated to
dryness, and the solid waste sent to a metal recovery unit.
Failing film atmospheric evaporators have been installed in
a tew plants.
, - Status. The "rising film" units are
undergoing pilot and plant test.
Reverse Osmosis
AEElisabjLlity.. Reverse Osmosis uses a pressure differential
across a membrane to separate a solution into a concentrate
and a more dilute solution that may approach the purity of
the solvent. It therefore accomplishes the same type of
fnSJftn1?? a84 di?tlllati°n and has been applied in plating
installations in the same manner. Small units under 300 gph
have been installed to recover plating baths chemicals and
make closed- loop operation of a line possible.
There are limitations on the acidity and alkalinity of
solutions suitable for treatment by reverse osmosis that
eliminate some alkaline baths and chromic acid baths from
consideration unless modifications are made to the solutions
prior to treatment. Another use of reverse osmosis is for
end~of-process water recovery following chemical treatment.
A recently designed system for Plant 11-22 offers promise
that large capacity reverse osmosis systems are possible and
therefore not subject to the size constraints of evaporative
systems. If so, they should play a key role in the design
of plants that will have no liquid effluent.
Most of the development work and commercial utilization of
the reverse osmosis process, especially for desalination and
water treatment and recovery, has occurred during the past
10 years. There is a steadily growing number of commercial
installations in plants for concentration and recovery of
plating chemicals along with recovery of water under
essentially closed-loop conditions. Most of the existing
commercial installations are for treatment of nickel plating
solutions, since reverse osmosis is especially suited for
handling nickel solutions and also because of the favorable
economics associated with recovery and reuse of expensive
nickel chemicals. Commercial reverse osmosis units for
handling acid zinc and acid copper processes also have been
installed, however. Laboratory pilot plant and full-scale
in- plant studies directed at handling cyanide and chromium-
type effluents are under way.
Reverse osmosis is especially useful for treating rinse
water containing costly metals and other plating salts or
126
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materials. Generally, the purified water is recycled to the
rinse, and the concentrated salts to the plating bath. In
instances where the concentrated salts cannot be recycled to
the plating tank, considerable savings will be achieved
because of the reduced amount of waste-containing water to
be treated.
Advantages jgnj ]^i!Ei£ja£i£a§. Some advantages of reverse
osmosis for handling process effluents are as follows:
(1) Ability to concentrate dilute solutions
for recovery of salts and chemicals
(2) Ability to recovery purified water for
reuse
(3) Ability to operate under low power require-
ments (no latent heat or vaporization or
fusion is required for effecting separa-
tions; the main energy requirement is for
a high- pressure
(U) Operation at ambient temperatures (e.g.,
about 60 to 90 F)
(5) Relatively small floor space requirement
for compact high-capacity units.
Some limitations or disadvantages of the reverse osmosis
process for treatment of process effluents are listed below:
(1) Limited temperature range for satisfactory
operation,, (For cellulose acetate systems
the preferred limits are 65 to 85 F;
higher temperatures will increase the rate
of membrane hydrolysis, while lower temper-
ature will result in decreased fluxes but
not damage the membrane) .
(2) Inability to handle certain solutions
(strong oxidizing agents, solvents and
other organic compounds can cause dissolu-
tion of the membrane) .
(3) Poor rejection of some compounds (some
compounds euch as berates and organics of
low molecular weight exhibit poor rejection) .
Fouling of membranes by slightly soluble
components in solution.
127
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(5) Fouling of membranes by feeds high in sus-
pended solids (such feeds must be amenable
to solids separation before treatment by
reverse osmosis).
(6) Inability to treat highly concentrated
solutions (some concentrated solutions may
have initial osmotic pressures which are so
high that they either exceed available
operating pressures or are uneconomical to
treat).
Process Principles and Eouip|jfient. Water transport in
reverse osmosis (RO) is opposite to the water transport that
occurs in normal osmosis, where water flows from a less
concentrated solution to a more concentrated solution. In
reverse osmosis, the more concentrated solution is put under
pressure considerably greater than the osmotic pressure to
drive water across the membrane to the dilute stream while
leaving behind most of the dissolved salts. Salts in
plating baths such as nickel sulfate or copper sulfate can
be concentrated to solutions containing up to 15 percent of
the salt, by weight.
Membrane materials for reverse osmosis are fairly limited
and the bulk of the development work has been with specially
prepared cellulose acetate membranes, which can operate in a
pH range of 3 to 8 and are therefore useful for solutions
that are not strongly acid or alkaline, i.e., rinses from
Watts nickel baths. More recently, polyamide membranes have
been developed that will operate up to a pH of 12, and
several of these units are operating in plants for the
treatment of cyanide rinse waters.
Figure 13 is a schematic presentation of the reverse osmosis
process for treating plating-line effluent. The rinse
solution from a countercurrent rinse line is pumped through
a filter, where any suspended solids that could damage or
foul the membrane are removed. The rinse solution is then
raised to the operating pressure by a highpressure pump and
introduced into the reverse osmosis unit. The concentrated
salt stream is returned to the plating tank, while the
dilute permeate stream is returned to the second rinse tank.
Currently, several different configurations of membrane
support systems are in use in commercial reverse osmosis
units. These include plate and frame, tubular, spiral
wound, and hollow fine fiber designs.
128
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to
Rinse
1
Low-pressure
pump
Concentrate
R everse-osmosis
unit
Permeate
Parts
Makeup
water
FIGURE 13 SCHEMATIC DIAGRAM OF THE REVERSEOSMOSIS PROCESS
FOR TREATING PLATING EFFLUENTS
-------
§y§tejj8. Reverse osmosis units are in
._^ __
operation for recovering nickel from rinse waters. The
concentrate is returned to the plating bath.
Demonstration Status. The reverse osmosis units installed
at the Rock Island Arsenal as part of an en d~of- process
water recovery system, remains fco be demonstrated as a part
of a total successful system, A project sponsored by the
American Electroplating Society ha® demonstrated that
cellulose acetate membranes can operate successfully on
nickel and copper sulfate rinse waters and that spiral wound
and hollow fiber polyamide membranes can be used to treat
copper, zinc, and cadmium cyanide baths. A second phase of
this study is a demonstration in a plating shop of a full
scale reverse osmosis system on copper cyanide rinse water.
The freezing process would be capable of
recovering metal and water values from plating rinae water
to permit essentially closed- loop type operation if fully
developed. The feasibility of using freezing for treatment
of plating rinse waters was demonstrated on a laboratory
scale using a mixed synthetic solution containing about 100
mg/1 each of nickel, cadmium,, chromium,, and sine, along with
30,000 mg/1 of sodium chloride. Greater than 99.5 percent
removal of the metallic ions was achieved in the
experiments, with the purified water product containing less
than 0.5 mg/1 each of the individual plating metals. The
separation tests were carried out using the 9500 1/hr (2500-
gpd) pilot plant unit at Avco Systems Division, Wilmington,
Massachusetts .
Process Princip_les_and_^guigment.- The basic freezing pro-
cess for concentration ana recovery of water from plating
effluents is similar to that used for recovery of fresh
water from the sea. A schematic diagram of the treatment of
plating rinses by the freezing process is shown in Figure
1U. The contaminated reuse water is pumped through a heat
exchanger (where it is cooled by melted product water) and
into a freezer. An immiscible refrigerant {e.g., Freon) is
mixed with the reuse water. As the refrigerant evaporates,
a slurry of ice and concentrated solution is formed. The
refrigerant vapor is pumped out of the freeser with a
compressor. The slurry is pumped from the freezer to a
counterwasher , where the concentrated solution adhering to
the ice crystals is washed off.
The counterwasher is a vertical vessel with a screened
outlet located midway between top and bottom. Upon entering
130
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Pump
Cooling
water
To rinse
Uuuc
Heat exchanger
Metter/
condenser
Counter
washer
1 Concentrate
Refrigerant
(Freon)
f\ Compressor
Refrigerant
vapor
Freezer
FIGURE 14 SCHEMATIC DIAGRAM OF FREEZING PROCESS FOR RECOVERY
FIGURE S CHEMICALS FROM PLATING RINSES (37.38)
-------
the bottom, the slurry forms a porous plug. The solution
flows upward through the plug and leaves the counterwasher
through the screen. A small fraction of the purified
product water (less than 5 percent) flows countercurrently
to the ice plug to wash off concentrated solution adhering
to the ice. The ice is pumped to a condenser and melted by
the release of heat from the refrigerant vapor which had
been originally evaporated to produce the ice, and which had
been heated by compression to a saturation temperature
higher then the melting point of the ice«
Because of the pump work, compressor %»ork, and incomplete
heat exchange, a greater amount of refrigerant is vaporized
than can be condensed by the melting ice. Consequently,, a
heat removal system is needed to maintain thermal
equilibrium. This system consists of a compressor which
raises the temperature and pressure of toe excess vapor to a
point where it will condense on contact: with ambient cooling
water.
The freezing process offers several advantages over some
other techniques. Because concentration takes place by
freezing of the water in direct contact with the
refrigerant, there is no heat-transfer surface (as in
evaporation) or membrane (as in reverse osmosis) to be
fouled by the concentrate or other contaminants. Suspended
solids do not affect the freezing process and are removed
only as required by the end use to be made of the recovered
products.
The heat of crystallization is about 1/7 the heat of
vaporization, so that considerably less energy is
transferred for freezing than for a comparable evaporation
operation. Because freezing is a low-temperature process,
there will be less of a corrosion problem than with
evaporation, and less expensive materials of construction
can be employed. The freezing process requires only
electrical power, as opposed to the evaporation process
which also requires steam generating equipment. The cost of
the freezing method may be only 1/3 that for evaporative
recovery.
A method of freeze drying metal finishing solutions has been
demonstrated in the laboratory. Droplets of the solutions
are injected into cold liquid-hexan* where they are
immediately frozen. The droplets were separated out and the
water removed at subfreezing temperature. The method leaves
a dry chemical residue, and the pure vaporized water could
be recycled to process. The economics of the process on a
practical scale are unknown.
132
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Practical Operating Systems . No commercial utilization of
freezing~f or treatment of waste water from metal finishing
is known.
Demonstration Status. No demonstrations are in progress in
metal finishing plants. However, a 9500 liters/day (2500
gpd) unit is in operation to demonstrate desalination of
water.
Electrodialys is
Applicability. Electrodialys is removes both cations and
anions from solution and is most effective with mult i-va lent,
ions. It is capable of reducing the concentration of heavy
metal ions from solutions whether they are complex or not.
Chromate and cyanide ions may also be removed.
Process Principles aM Equipment. The simplest
electrodialysis system consists of an insoluble anode and an
insoluble cathode separated by an anion permeable membrane
near the anode and a cation permeable membrane near the
cathode. An anode chamber, cathode chamber, and middle
chamber are thereby formed. Upon electrolysis anions pass
from the middle chamber to the anode compartment and cations
pass from the middle chamber to the cathode compartment.
The concentration of salt in the central compartment is
thereby decreased. By employing several anion and cation
permeable membranes between the electrodes several chambers
are created. A stream may then be run through several of
these chambers in which the concentration is successively
increased. The net effect is similar to that of a
continuous moving bed ion exchange column with electrical
energy used for regeneration rather than chemicals.
- practical operating systems
have been reported. However, development has resulted in
several demonstrations, discussed below.
Deroonstira.fciQIi--J&a&*§« Several demonstrations have shown
that electrodialysis is a promising method. Further
development and use of the method may be expected. Copper
cyanide rinse water may be concentrated sufficiently to be
returned to the bath by using two units on a double
counterflow rinse system, i.e., between the first and second
rinse tank and between the bath and first rinse tank.
Copper may be recovered and chromic acid regenerated in a
spent etching solution for printed circuits. The Metal
Finishers Foundation has put priority on a future project on
cyanide removal by electrodialysis^
133
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Ion-Flotation Techniques
Ion- Flotation techniques have not been
developed for application to process rinse water effluents.
If successfully developed into a practical method for
effluent treatment, ion flotation offers possibilities of
reducing the amount of water discharged by 60-90 percent for
some operations. These savings are based on results of
small-scale laboratory studies on solutions containing
cyanides or hexavalent chromium.
Process.^ Principles _and .Bgii^gment, Separation of ions from
aqueous solutions by a flotation principle is a concept
first recognized about 25 to 30 years ago. In the ion-
flotation operation a surface active ion with charge
opposite to that of the ion to be concentrated is added to
the solution and bubbles of air or other gas are introduced
into the solution to form a froth of the surface-active
materials. The foam is separated and collapses to form a
scum containing an ion concentrate. Ion flotation combines
the technologies of mineral flotation and ion exchange. A
schematic diagram of an ion-flotation cell is shown in
Figure 15.
Experimental results indicate that 90 percent of the
hexavalent chromium in a 10 to 100 ppm solution can be
removed with primary amine surface-active agents. However,
the amine suffered deterioration when regenerated for reuse,
since the removal efficiency dropped to 60 percent after two
regenerations of the amine.
Grieves,, et al. , have demonstrated the feasibility of using
ion flotation on dichromatc solutions with a cationic
surfactant (ethylhexadecyldimethylaroonium bromide) . A
continuous operation with a retention time of 150 minutes
was devised. The feed stream contained 50 mg/1 of
dichromate. Approximately 10 percent of the feed stream was
foamed off to produce a solution containing 150 mg/1 of
dichromate, while the stripped solution contained 15 mg/1.
Cyanides have been removed from dilute solutions with mixed
results. The extraction efficiency from a cadmium cyanide
solution containing 10 ppm of cyanide was 57 percent, using
primary,; tertiary, and quaternary ammonium compounds as
collectors. Extraction efficiencies for nickel and iron
cyanide solutions were approximately 90 percent, but these
systems are of relatively little interest.
Practical. _ Operating Systems. There are no practical
operating systems.
134
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Air in
(
lMg
Foam concentrate
lake -off
Purified
solution — «
removal
^njcction port .. -
for collector »*•
ogent
-t-^j-V^J-u-t,
-"-**-"-—
»* »
% 1
0 b
V
•i!
6 0
'U,
i
0
«;
/.
* ft
/ Oi
/
40
'r.«t
poit
FIGURE 15 SCHEMATIC DIAGRAM OF ION-FLOTATION CELL
FOR TREATMENT OF PLATING EFFLUENT
135
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Demonstration fftatus. The process has not been demonstrated
in an operating plant.
Electrolytic Stripping
Applicability. Electrolytic stripping is not in general use
for removing heavy metals although some procedures have been
employed for recovering precious metals.
Process Principles and Equipment. In order to strip a solu-
tion by electrodeposition it is necessary that the metallic
ions in a dilute solution reach the cathode surface at a
sufficient rate so that essentially all of the ions can be
deposited in a reasonable time. 3isrfleet and Crowle have
discussed several methods of accomplishing this. One method
called the "integrated" system uses baffles in a tank to
create a very long path through which the water may be
recirculated at a high velocity. The method is suitable
only for metals having a relatively high limiting current
density for dilute solutions, such aa gold, silver, and tin.
The fluidized bed electrode is a bed of metal spheres or
metal-coated glass spheres that is fluidiaed by pumping the
dilute solution through it and causing aa expansion of 5 to
10 percent, With spheres of 100 to 300 ailerons in diameter,
a total geometric area of 75 cm'/cm3 Is obtained. Thus, the
current density is very low aad the flow of electrolyte
through the bed provides the forced convection to support
high currents. Another system employs electrodes made of
expanded metal and the turbulence arowxd this structure
enhances the rate of deposition of metal when solution is
pumped past it. Turbulence and an increase in the rate of
deposition at a plane electrode may also be promoted by
filling the space between electrodes with a woven plastic
screen, glass beads, etc.
In another system the electrode is introduced into a narrow
gap between two porous carbon electrodes. The bulk of the
solution (99%) is forced through the cathode where copper is
deposited out. Predeposited copper on the anodic electrode
is dissolved into the 1 percent of the electrolyte that
permeates through this electrode and a copper concentrate is
produced. The two electrodes are periodically reversed so
that copper deposited from a large volume of solution is
dissolved into a small volume of electrolyte. Copper in
solution has been reduced from 670 mg/1 to 0.55 mg/1 in the
cathode stream and concentrated to 4ft g/1 in the anode
stream. A similar system has been used for depositing
metallic impurities from strong caustic solutions.
136
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Practical Operating Systems, There are many systems in
operation for the recovery of precious metals.
Demonstration Status. The porous electrode system is still
under development at the University of California and has
been scaled up to handle 250 gpd of copper sulfate solution.
Metal Finishers Foundation has established priority for a
future project to remove zinc from effluent by
electrodeposition.
Carbon Adsorption
Applicability. Activated carbon has been used for the
adsorption of various materials from solution, including
metal ions. Experimental data show that up to 98 percent ot
the chromium can be removed from waste water. The treated
water can be recycled to the rinse tanks.
£rocessi Pr|.nct6lg§ and gguipment. The process relies upon
the adsorption of metal ions on specific types of activated
carbon. In the case of Chromium VI, a partial regeneration
of the carbon can be accomplished with caustic solution
followed by an acid wash treatment to remove residual
caustic and condition and carbon bed for subsequent
adsorption cycles. The equipment consists of holding tanks
for the raw waste, pumps and piping to circulate the waste
through adsorption columns similar to those used for ion
exchange.
Practical Operating Systems. Systems based on adsorption
and desorption are still under laboratory development and no
practical operating systems are known.
Demonstration Status. Pilot p?,.ant equipment has been
operated successfully in an electroplating plant treating
chromium rinses at a flow rate of 19 liters/min (5 gpm) at
concentrations from 100 to 820 mg/1 hexavalent chromium.
Adsorption was continued until the effluent reached
concentrations of 10 ppm of Chromium VI.
Water Conservation by Liquid-Liquid Extraction
Applicability. Liquid-liquid extraction has been used on an
experimental basis only for the extraction of hexavalent
chromium from waste waters. The effect is to concentrate
impurities in a smaller volume,, which in turn will have to
be treated by other means or suitably disposed of. The
fully extracted aqueous phase may be recycled to the rinse
tanks, water savings from 50 to 73 percent appear to be
possible.
137
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—Principj.es—and Equipment. The metal-ion pollutant
is reacted with an organic phase in acid solution, which
separates readily from the aqueous phase. Metal is subse-
quently stripped from the organic phase with an alkaline
solution. Hexavalent chromium, for example, has been
extracted from waste water at pH 2 with tertiary and
secondary amines dissolved in kerosene. After the reaction
of the chromium with the amine and phase separation* the
chromium is stripped with alkaline solution from the organic
phase restoring the amine to its original composition. For
liquid-liquid extraction to be feasible the following
conditions would have to be met:
(1) The extraction of chromium should be virtually
complete
(2) Reagent recovery by stripping would be efficient
(3) The stripping operation should produce a
greatly concentrated solution
(4) The treated effluent solution should be
essentially free from organic solvents
(5) capital and operating costs should be
reasonable.
The equipment required consists basically of mechanically
agitated mixing and settling tanks, in which the phases are
intimately dispersed in one vessel by agitation and then
permitted to flow by gravity to a settling vessel for
separation. Holding tanks for extractant and stripper and
circulating pumps for these solutions, as well as the
purified waste water, are necessary. Equipment for liquid-
liquid extraction would also include horizontal and vertical
columns, pulsed columns and centrifuges.
Practical Operating Systems. Liquid-liquid extraction
systems are not known to be operating for treatment of metal
finishing wastes.
Demonstration status. Experimental evidence exists indi-
cating that up to 99 percent of chromium can be successfully
extracted from rinse waters containing 10 to 1000 mg/1 of
Cr*+. With 10 ppm of Cr«+ in the rinse water, the treated
effluent contained as little as 0.1 mg/1 of the ion; with
100 ppm in rinse water concentration was reduced to 0.4
mg/1. Stripping was effective as long as the amines were
not allowed in contact with the chromium for a prolonged
period of time which would allow oxidation by Cr*+ ions.
138
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The effluent, however, contained from 200 to 500 mg/1 of
kerosene, which is undersirabie.
NfPthods of Achieving No Dj,sch.arae of gollutants
Although chemical methods of treating waste waters are
achieving the low effluent discharges recorded in this
report, they are not improvable to the point of achieving
zero discharge of pollutants. Also the problem of
recycling sludges or solid wastes remains. It is easy to
design systems that will in principle close the process loop
and prevent discharge. In practice, however, this can only
be done with considerable forethought and experience, since
closed systems are in general subject to impurity buildup.
Progress in achieving no-discharge systems is likely to take
place in a series of steps in which the amount of discharge
is consistently reduced until it is negligable.
A major problem with a series of metal finishing processes
in a closed cycle is that of dragin. After a closed cycle
has been run long enough any stagnant tank,, i.e.., a plating
solution that is normally not discarded,, will contain the
same concentration of contaminant as the preceding tank in
the cycle, the assumption being that the volume of dragin
and dragout are equal. Therefore* if the final rinse
following nickel plating contains 12 ppm of nickel and
chromium plating follows, the chromium bath will ultimately
contain 12 ppm of nickel. Nickel is frequently removed from
chromium plating baths by ion exchange* but since the ion
exchanger requires periodic regeneration^ the regenerant
must somehow be returned to the system if it is to be
considered a closed one. The nickel in the regenerant might
be recovered and returned to the nickel bath, but the
dissolved solids, i.e., sodium sulfate? and sodium chloride
are really excess products that cannot be completely
returned to the process, while the main process loop may be
closed, the secondary purification loops may be more
difficult to close. With some process baths, it may not be
possible to find a method for purification that is as
adaptable as is ion exchange to the removal of nickel from a
chromium bath. Alternatives then are to (1) develop
processing baths that can tolerate the impurity buildup or
(2) to design rinse systems in which the concentration of
impurity in the final rinse tank is reduced to a tolerable
level.
Some systems, designed to remove a specific impurity, are
found to remove other components as well, which may require
further treatment. An example of such a system is that used
for removing carbonates from cyanide baths. Whether
139
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freezing or precipitation with calcium is used, the
carbonates occlude and adsorb significant quantities of
cyanide that must then be further treated, with the result
that cyanide is not maintained in a closed system.
Therefore, with present technology, it is likely that there
will be some discharge from a process loop in spite of the
best efforts that are made to close it. Some waste water
effluent will be produced and the next consideration is how
well a waste treatment system can be closed.
The effluent will contain heavy metals, cyanide, and
chrornate all of which can be treated to relatively low
levels to give (1) liquid containing small amounts of heavy
metals, cyanide and chromate and larger amounts of soluble
salts such as sulfate and chlorides, and (2) sludge
containing heavy metals, phosphate, carbonates, flocculating
agents, etc. The liquid, if large in volume may be
concentrated further by evaporation, reverse osmosis, ion
exchange, or some other process followed by a further
purification to reduce the heavy metal effluent to a
negligable value. The liquid may alternatively be passed
through a salt loaded ion-exchange column to remove all
traces of heavy metals and yield an effluent containing
essentially soluble salts that may be discharged to the
ocean if not to a stream or sewage facility. Alternatively,
solutions of soluble salts may be evaporated to dryness and
the solid salt contained or fixed in cement, etc.
Sludge, obtained either directly from waste water or from
ion-exchange regenerants, cleaning and pickling baths, etc.,
would need to be reclaimed for metal values or the metal
salts separated out for return to process tanks in order to
provide a closed or recycle system.
Thus, to attain the ideal of providing a system where input
is energy and materials and output is solely a finished
product will require further research and development,
considerable ingenuity, and expert engineering and design.
However, the capability for progressing towards this goal is
available.
140
-------
SECTION VTII
NONWATER QUALITY ASPECTS
Introduction
In this section, costs associated with the degree of
effluent reduction that can be achieved by exemplary
treatment methods are discussed. The nonwater qualzty
aspects concerning disposal of solid waste and the energy
impact of the waste treatment technologies also are
discussed.
Treatment and Control Costs
Chemical Treatment to Achieve Low Levels of Pollutants
BPCTCA LimitatiQns_JTable_ll. Costs associated with control
technology consistent with the exemplary practice of
chemical treatment in 26 plants avera9ed a1;?^™0 ^"
treated with a standard deviation of $1.91/1000 liters
(Table 27) . Operating costs include a cost of capital equal
to 8 percent of the investment and depreciation equal to 10
percent of the investment.
The operating cost of waste treatment as a percent of cost
of metal finishing for 13 companies is 7.4 percent with a
standard deviation of 5.4 percent. The figures were arrived
at from estimates by the plants themselves concerning the
relative cost of waste treatment.
The plot in Figure 16 shows the large variation in
investment costs for individual plants and reflects the
large deviations reported above. Thus, there are no typical
plants. Rather, costs are highly dependent upon local
conditions. Costs were calculated in terms of volume of
waste water treated rather than surface area finished
because costs are believed to be more closely related to the
volume treated. Water use is highly variable and relating
waste treatment costs to area finished would have provided
even more variable results. For a nominal water use of 80
liters/sq m (2 g/sq ft) the cost of $1.06/1000 liters is
equivalent to $0.085/sq m ($.0079/sq ft).
In addition to the cost data collected from plants with
waste treatment facilities, costs were also estimated by
modeling metal finishing facilities together with waste
treatment facilities providing effluent that would meet
141
-------
TABLE 27 COSTS FOR WASTE TREATMENT FACILITIES
Plant
No.
20-24
33-24
33-25
36-12
33-2
33-4
8-5
6-37
19-11
15-3
9-7
4-9
3J-19
8-8
33-22
33-23
20-22
20-20
33-35
20-23
4-8
5-35
9-2
23-7
30-13
?3-30
19-24
6-35
31-16
46-4
33-29
Investment
Processes (1971)
Plating Cortmon Metals
Plating Cocoon Metals
Plating Coanon Metals
Plating Con. , Prec. Ketals
Placing Free. Metal*
Fiatir.g Free. Metals
Plating Prec. Metals
Plating Prec. Metals
Plating Prec. Xetals
Plating Prec. Metals
Electropainting, Anodizing
Electroless Plating
Electroless Plating
Electroless Plating
Electroless Plating
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Ar.ecizing
Chemical Milling
Chemical Milling
Chemical Milling
Chemical : Li 11 ing
Ciienical Milling
Phosp'-iatiny
Etching
Inversion
Printed Circuits
Elect ropolishing
Elect roaachinlng
34,000
172,000
27,932
200,000
25,000
66,000
300,000
400,000
110,000
66,113
100,000
45,325
23,292
217,725
51,679
193,846
167,575
130,902
155,300
125,000
123,414
17,45?
300,000
'',208/100
1^2 /'06
2y',A?>2
9-'t,500
295,615
5b,°s3
1,05 0,0 00
', 1 , 9.1 '->
Operating
Cost/Year
(1971)
14,195
80,430
10,694
72,809
14,968
18,205
115,995
121,905
49,985
25,552
32,249
45,312
9,746
168,312
13,430
51,515
Ay, 658
113,3-0
/ ' '^
2S^2U
41,855
16,675
33,753
685, 847
3'13 .?!•'>
11,'jl?
19,726
1?G,211
ij,7i -1
23V ,611
:4.">6C
Hours
Operated
Per Year
4,800
4,000
7,200
7,520
1,025
1,800
2,400
2,250
2,000
2,000
4,000
4,000
4 , 000
8,400
4,000*
4,000
6,000
6,oeo
7,200
7,200
6,000
4, BOO
2 , 000
6,000
S.OQO
3,'JjO
3,600
2,000
2,250
4,000
4,170
4 , 000
Volume to
Treatment
Plant, 1/hr
26,497
15,897
4,163
6,813
12,615
24,224
34,065
113,562
45,424
57,727
30,851
1,741
3 , 985
104,087
36,794
9,000
13,925
79,485
129,447
3,028
22,712
7,570
7,570
i89,250
159. OCC
6,813
54,509
6,813
11,356
90,849
30,659
22,710
Volume to
Treatment
Plant, 1/yr
1.271 x 108
6.359 x 107
2.997 x 107
•7
5.123 x 107
1.293 x 107
4.366 x 107
8.176 x 107
2.555 x 108
9.08 x 107
1.154 x 108
1.234 x 108
6.964 x 10t>
1.594 x 107
8.743 x 108
1.471 x 108
3.600 x 10'"
Q
1.135 x 10-
4.769 x 108
Q
9.320 x 10a
2.180 x 10'"
1.362 x 108
-7
3.634 x 107
~J
1.514 x 1C'
1.136 x 109
Q
9.540 x 1U8
2.6?!'. x 107
_.^o^ ,-. .,w
1.362 x 107
2.555 x 10 7
3.633 x 10 ^
1.278 x 103
7
9-Ot'4 x 10'
Invest-
ment/
1/hr
$ 1.28
10.82
6.71
29.36
1.98
2.72
8.81
3.52
2.42
1.15
3.24
26.03
5.84
2.09
1.40
21.54
8.85
2.: 8
1.20
41.28
5.43
2.31
3S.63
15.36
3.66
4.^
i. n
43.39
5.19
11.56
L.37
Operating
Cost/
1000 liters
$ 0.30
1.26
0.36
1.42
1.15
0.42
1.42
0.48
0.55
0.22
0.26
6.51
0.61
0.19
0.09
1.43
0.44
0.24
0.09
1.30
0,31
0.46
5.53
0.60
1'. 'ij
0.43
0.30
8.83
O.b2
0.65
0,1.1
Treating
Cost/
Processing
Cost
14
3
0
5
0.65
7
7.5
33
, 7
• A
'•'<
7 .1,
1.0
18
- - "•
•'< •*
hours jer
-------
I07
1 r
10"
o
•o
o
o
cE
0>
«»
v
>
c
10=
10"
i 1 1
I0a
Capacity Liters.hr
FIGURE 16
INVESTMENT COSTS OP WASTE TREATMENT PLANTS
WITH VARYING VOLUME CAPACITY
-------
BPCTCA standards. By modeling plants it was possible to
derive selfconsistent costs for various degrees of treatment
and for various plant sizes. Plants were sized according to
the number of employees, which is desirable if data are to
be used for cost impact studies. Table 28 and 29 summarize
the results of one cost estimate.
The lowest investment cost of $22,980 is for a 5-employee
urban plant that precipitates heavy metals, does not treat
cyanide or hexavalent chromium, and does not clarify. This
plant also has the lowest operating cost of $12,294/yr. The
highest investment cost of $378,455 is for a plant with HI
employees carrying out complete waste water treatment
including clarification and filtering of sludge. This plant
also has the highest operating cost of $157,894/yr. The
operating cost probably could be reduced somewhat by using a
filter press directly on the neutralized waste water.
However, this technology is not as well established as that
using a clarifier.
Costs per area are $1.02/1000 liters for the 5-man plant
neutralizing only and $1.09/1000 liters for the U7~man plant
doing complete waste treatment. These figures compare
favorably with the $1.06/1000 liters average value for the
plants listed in Table 28.
The operating costs as a function of plant size have been
plotted in Figure 17 and show that in the size range studied
costs are roughly linear with the number of employees. The
makeup of the production processes varies somewhat, both
with the extent of treatment and with plant size. Processes
using cyanide or chromate were not included where treatment
for cyanide and/or chromate was omitted. The smaller plants
were assumed to be concerned with electroplating only while
processes such as anodizing and electroless plating were
confined to the largest plant. Even among the smaller
plants there are some variations in plating processes. Some
of the 5-man plants included cadmium plating as a specialty
while the 10-man plant omitted cadmium but concentrated more
on tin plating. The product mixes listed are only one of
many sets that might have been chosen but reflect in general
the amount of finishing that can be accomplished in the
various sized plants with diverse operations. The amount of
waste water to be treated, and the amount of waste produced
are thus typical of the various size plants.
The productivity of a plant, measured in area processed/
hour will vary with the process mix even though the number
of employees is not changed. Thus, in Table 29 the 5-man
plants that require only coprecipitation (A) or cyanide
144
-------
TABLE 28
TtCATMBTT BQUVMENT COSTS. VALUES IN O. S. DOUAM. 1*74
A.
*.
C.
D.
t.
T.
C.
Item
Concrete Holding Pin
Valves. Cootrob. Monitor] * tecotden
Sturert
Pnmpj
Tan to
Clariflen
Lagoons (Soil)
Pointing Fillers
Evaporator
Ion-exchanger
Sulfonatoc
Chlorinaror
Subtotal A
Treatment Building
Land COM. Urban
Rural
LaoJ Cost. Pin & Lagoon). OlbU
•and
Subtotal B
Urban
Rural
Total A&8
Urban
Rural
Equipment InaaUatton
Tout C4D Urban
Rural
C*D. Urn Cluifttt. Urbn
Sludge Filler (Option)
Urban
Rural
Total E4F
Urban
Rural
A
4»
2,600
1.100
3.140
2.945
12.550
100
2.600
—
—
—
—
26.045
1.990
345
SO
40
10
4.215
4.050
so.s*
10.095
5.210
54.51*
M.3D*
•*•*•
3.868
S.»90
19,390
39.195
SEnp
»
420
4. 850
1.10»
4.TW
3.550
12.559
130
2. TOO
--
—
—
1.550
33.629
5.910
365
75
30
10
C,30S
5.995
39.925
19. CIS
C.72S
4«.*S»
4*.M*
M.KO
4.59*
4.CS9
51.24*
50.9SO
BOIpCCS W ElHplOTCd *vB EMpWl'V
c
sso
S.08*
1.100
4.S4S
4.939
14. 900
230
2. "TOO
—
--
1.550
—
11.8*5
8.160
500
100
30
H
•.•98
•,370
4C.S75
4C.15S
7.5*0
54, IS*
M.73*
30. t*»
4.8SO
4. MO
S9.005
St. CIS
D
60S .
7.215
1.100
8,300
5.300
14.900
230
3,300
—
—
3.550
3.550
46.050
9.960
610
125
45
10
a*. CIS
10.095
S4.66S
56. 145
9.310
«.«5
**.*S*
M.91S
4.300
4.330
70.175
89.685
A
950
2.945
1.100
4.940
3,7*0
19,100
100
S.1SO
—
—
—
—
35.065
9.660
595
120
225
45
__
10.480
9.825
45.545
44.898
7.01S
•2.660
51.905
11.460
7,750
7.880
60.310
59.185
»
945
5.080
1.100
6.330
3.700
19.000
130
3.200
—
--
—
3. SSO
43.095
11.160
720
145
185
40
».«8S
11.91$
SS.780
55.040
•.(20
64. HO
83.660
4.538
7.720
7.850
71.100
71.51*
C
1.335
5.310
1.100
6.800
4.605
23.400
230
5.100
--
—
3.550
--
50.430
15.060
925
185
2*5
CO
M.tT*
15.105
•6.700
CS.7*
10.090
76.798
75.815
•4.190
7.745
7. MB
•4.535
«1.7*»
D
1,350
7,445
1.100
1.490
5, MS)
22.490
230
5. WO
—
—
3.550
3.550
51.T3*
16.7M
1.025
3X5
215
55
M.CH
16.970
75.73*
74.C**
11.545
•7.215
M.S3S
M.CT*
7.14»
7.M8
*5.M*
•4.115
A
1.S4S
3.945
1.100
5.650
l.*95
35.400
ICO
5. 600
—
—
—
—
46.295
13,020
795
160
340
45
M.*35
11. 325
«t.32*
M.sn
•.2*0
CS.SM
M.7M
44.1*8
11. 380
11.510
•0.980
•0.290
»
1.S2S
5.310
1.100
1.110
3,440
25.400
160
6.500
--
--
—
3.550
54.095
11.540
1.135
230
310
IS
». 045
W.84S
74". 14*
73.940
10.820
•4.960
•3.760
**.*•*
I1.S40
11.490
98,200
95.250
C
1.725
5.310
1.100
1.880
S.11S
28.000
230
6,500
--
--
3.SSO
—
60,010
19.050
1.110
235
300
60
20.520
19.345
•0.530
19.355
12.005
•3.535
91.360
«4.*3*
11. MO
12.580
104.915
103.940
D
1.740
7.445
1.100
12.340
7.200
28,000
230
6.500
—
—
3.550
3.550
71.665
21.180
1.300
260
310
65
33.791
31.505
•4.455
93.170
14. IK
1*8.7**
KM. SOS
80.180
12.380
. 12.580
121.17*
120. OK
A
2.490
1.185
2.200
9.300
8.355
41,100
410
14.000
146.000
550
--
--
343.200
29.520
1.810
365
475
95
11. MS
39.9*0
MS. 005
373.180
48.640
123. 64S
321,820
31«,S4»
13. MO
13.220
136. SIS
338.040
41CmplorM*
I
2.S3S
10.610
2,200
11.610
13.95S
41.100
410
14,000
146.000
550
--
3. SSO
252. SSO
33.150
2.0 JO
410
520
105
35,100
33.6SS
2M.280
2M.HS
50,520
138,800
MC. 165
tfl.100
12.938
13.220
3S1.130
S49.98*
C
2.890
9.690
2.200
11. U9
12.230
49.630
600
15.600
144.000
--
3.550
--
254.240
44.310
2.720
545
765
155
41.855
45.010
302.095
299.310
SO. SSO
3*2.945
350.160
10. IK
12. SSO
13.050
365.495
36X21*
D
3.9*3
14.485
2.500
12.140
11.130
50.600
110
IS. COO
146.000
—
1,550
3.550
264.130
45.360
2.180
560
805
160
48.9*5
4*. 010
313. r>*
3tt. 31*
52. (5*
IS*. 901
363.040
31*. 30*
11. SM
11. M*
378.4**
31 6. 898
A-Neutrallunon.
• -Cyanide oxidation pan Mntulizatloo,
C-Chramaie reduction pka noilralltatkio.
D- Cyanide oxidation chromate redcctlon.
-------
TABiuE 29
ANNUAL OPDUTING COSTS, WASTt TMATMENT, U. S. DOUARS, 1ft4
Proceo
«.'•. of Pate.
t~flr,t*l mTj
» 75
-5
Kt
10 17i
171
zy»
» 2»
•>»
tv» cu
1VS
ITS
riant Size
Vic. Treatment
t/hr Type
«.v/>
t.'/'/O
S.O'/O
11. COT
n.c/ii
18.4W
21.200
10.440
M.feW
SC.400
51.'/.)
«5 200
A
B
r
D
A
t
C
D
A
B
D
A
1
of
Capital'"
2.843
3.1T2
4 111
5.270
4. 2-.S
5.151
6.144
8.8«1
6 137
7 403
8.104
25.832
21. 104
28.236
23.213
Chemical
Depreciation^' Uw
3.553
4. CCS
S.41«
6,588
5.2SG
6.438
1,619
8.728
6.958
8.496
9 254
10.879
32.3C5
33.880
38.295
36.591
481
3.300
2.741
4.589
1.5)2
8,919
4.655
10.789
1.793
11,831
5,592
15,413
4,990
15,829
10,110
24,132
Electric
Labor"1 Maintenance**' Power'5'
4.000
4,000
4.000
4.000
12.000
12,000
12,000
12.000
24,000
24,000
24,000
24,000
32.000
32.000
32.000
32.000
711
933
1,084
1.318
1.052
1,288
1,536
1.146
1,392
1,100
1.851
2.116
(.500
8.776
7.059
7.J19
1,440
1,440
1,826
1.82C
2.217
2.217
2,409
2.409
3,036
3,036
3,198
3.195
11,603
11,803
11.288
13.899
Water
ft
SewcrW
240
240
306
306
380
380
402
402
506
sog
634
634
1.918
1.918
2,258
2,228
evaporator
Stodge Ion
RennvaK1" Exchanged) Treatment?*)
1.536
864
3,012
2,016
2.208
2.592
8,184
8.184
3.456
3,456
5,184
S.184
10,464 ' 650
10,464 880
8.619
18,60*
"*
-•
--
--
—
—
8.080
(.080
8.080
a.o«o
Credit
Save<10' Balance
:: ::
••
„
.. -.
..
« ~.
11,828 3.148
11.828 3,748
11.82* a. 14*
11.S28 3. 748
Urban
14,004
19.040
22,178
•28. 913
C8.95!!
39. 10$
40,009
46.708
59.8.V
87.113
10.185
121.434
136,716
131.114
151.894
Total*1"
Rural
1-I.OS4
19. ICO
M.655
85, 7W
23.709
38. 915
39.608
48.040
46.458
57. 396
70.468
1-V.41S
135. 311
130.048
156.180
Total' 5I1 (Vf.tK filter PicaK
No. Clitltler
16. 7.V
19.198
:;.93J
C5. 139
35.305
33.010
43.7iil
41.613
51.513
65. i:5
IK. 014
126. SSS
121.284
141.174
rrfcan
U.-'oi
I5.JT6
19.706
.3.sr
36.513
34. J-'S
4J.OS7
43. :s:
*- •*-*
65.601
110. »Ti<
IS:. 436
fciral
U. Iti
\?.:a
19.851
•'• **
:*..«*!
34.3:3
J4.c:4
4:. ??»
5r.lU
5...1-
6S..S4
121. m
141. It)
ID ! ?ercen of H!««ment
«•» It.V.'bf ,
it, I jtnes of u:\tvrxn
ri, :. JS - '/. i-5 !/l>•-/ lalloni of »«ef added wlib treatment diemlcab
Ci r-.l"'i Cvual n UkcnneL! com
»7) D«u fr>n ?fa«dl« for •>>'> jal/Sr e»r»ralar
fl':, !**jl on a dra?-»i! rate •sf 2 ?ai/IT<)0 iq ft plated and a w!ulU» con of 2.80/gallon
(llj DLfcreoce between »rban and rural li the eon of aewage charge only
(U, <.KtJ*4 for tic COM of ilutje .etro.al, UK I* conjunction Mlth C<|UlBffleK Con Oau,
-------
• l£l^i*il*'*l \ '<:-l'\
^ti* M-£-|.*\\' \\
^~i\\\\l\ ill 1
|£ ifSi? |j: '}
-**sill-l 2 £ a S*
•S t a B ! .ff.fr r '53 S &
a :n
•s t>i 5
3. ^ S S * E
H
»»
-5
is
It
'
a
i
1 M1 i !
11 !
! hi n tl
•i!.1
s
!
M
Ih
U
P $
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Coprecipitatlon only
D Oxidation of cyanide +
coprecipitation
Reduction of chromate +
coprecipitation
X Oxidation of cyanide, reduction
of chromate, coprecipitation
10
20 30
No. of Employees
40
50
FIGURE 17 OPERATING COSTS RELATED TO PLANT SIZE AND
EXTENT OF WASTE TREATMENT
148
-------
oxidation plus coprecipitation for treatment of wastes can
process 75 sq m/hr, while 5-man plants that include chromium
plating and chromating (C,D) can process 100 sq m/hr.
It was concluded that costs for a captive or independent
shop would be similar if the waste treatment plant was sized
for the metal finishing operation only. Captive metal
finishing operations may discharge waste waters into large
systems that handle other plant wastes, but it would be
difficult to estimate what volume percent of waste water
typically came from the metal finishing operations and what
portion of total waste treatment costs should be allocated
to them. Flow sheets of the waste treatment plants that
were costed are shown in Figures 18, 19, 20 and 21.
Another plant was modeled to ascertain investment and
operating costs of a medium large plant employing (1)
segregated chemical treatment of waste waters containing
individual metals, and (2) no discharge of pollutants.
Costs for waste treatment employing destruction of cyanide,
reduction of chromate wastewaters and coprecipitation of all
metals were also developed as a basis of comparison. Table
30 summarizes both investment and operating costs of the
waste treatment plants. Investment and operating costs
increase in the order
(1) Combined chemical treatment and
coprecipitation
(2) Segregated chemical treatment and
coprecipitation
(3) Combined chemical treatment plus
end-of-pipe treatment to eliminate
discharge of pollutants.
The operating cost for combined chemical treatment and
coprecipitation is equivalent to $1.41/1000 liters, which is
approximately 30 percent higher than the $1.09/1000 liter
figure for a similar model in the previous discussion.
While the two models are slightly different the difference
is mainly due to the fact that the two cost values were
arrived at by two cost analysts, each of whom assumed what
he considered were the most realistic costs. Such a
discrepancy is not surprising and indicates the necessity
for making analysis self-consistent. Thus, the results in
Table 28 and 29 were made by one analyst and are set of cost
factors and the cases (1) through (3) above by another
analyst with a different set of cost factors. The
149
-------
High-ond low-level control
ff
Acid-alkali
holding and
mixing
Sump
High-and low-level control
Pressure pumpf I ,. -
Stream
FIGURE 18,.TYPICAL PLANT OPERATION
COPRECIPITATION ONLY
CHEMICAL TREATMENT (A);
150
-------
Acid-alkali
holding and
mixing
Cyanide
holding and
mixing
Cyanide
oxidation
Optional
Filter
Stream
FIGURE 19 .TYPICAL PLANT OPERATION - CHEMICAL TREATMEI^ (*}•
CYANIDE OXIDATION AND coPRECIPITATION "
151
-------
HondL
Acid-alkali
holding and
mixing
Plating
Non-CN/Non-Cr
M
J>H
Neutralization
and
precipitation
Hand L
Chromium
holding and
mixing
->QSufnp
D3
HandL
•W
*-o^
HgSO^T
Chromium
reduction
fro1"*' rv
¥^~J \ ^Circ.
$
Flocculant
To stream
FIGURE 20, TYPICAL PLANT OPERATION - CHEMICAL TREATMENT (C);
CHROMIUM REDUCTION AND CO PRECIPITATION
152
-------
Cr- cont'q
rinses
r
CN- cont'q
rinses
H and L
H and L |T
Acid-alkali
holding and
mixing
3
} Sump
i
1
CN-holdmg
and .
mixing
-c
j Sump
Ha
rr
Cr-holding
and
mixing
I Sump
Neutralization
and
precipitation
jin, „„ ^B «M M. A. «•• •— *^
Filter Pump
HandL1
Tl '
I I I
i
Lagoon
H and L
Cr-reduction
Pump
0
M HzS04 Circ.
OH
S02
Pump
Sump
Settling
Pump
Flocculont
Overflow
H and L
Pump
Filter
Filter
o
Backwosh
To stream
FIGURE 21 .TYPICAL PLANT OPERATION - CHEMICAL TREATMENT (D);
CYANIDE OXIDATION, CHROMIUM REDUCTION, AND
COPRECIPITATION
153
-------
difference is actually much smaller than that of actual
costs reported in Table 27.
The use o!: a system to eliminate pollutant discharge
requires approximately twice the investment and operating
cost as a system for combined chemical treatment. The costs
can be reduced in :~ome situations by in-process recovery
systems where the savings in chemicals more than compensate
for the costs of operating the recovery system. Evaporative
recovery systems were not economical to use in the plants
assumed since the value,, bath concentration, and dragout of
chemicals were not sufficient, to make their in-process
recovery worthwhile., ihe costs of installing more counter-
current rinse tanks, evaporative equipment, and steam more
than offset the savings in
In- process reverse osmosis systems may have lower operating
costs than evaporative systems, bat are still in a
demonstration stage for baths other than nickel. Use of
reverse osmosis systems on the nickel lines in the plant
model would not be expected to reduce overall in operating
costs by more than 5 percent „
Figure 22 shows the operations in the plant and a schematic
iiagram of a segregated waste treatment system. Figure 23
shows a coprecinjtation system and Figure 24 the
modifications made at the end of trie coprecipitation system
with a reverse osmosis unit and. salt evaporator to eliminate
the discharge of pollutants.
Preliminary calculations indicated that use of evaporators
in- process and a'-, the end -of -pipe t.c eliminate pollution
would be more expensive than use of reverse osmosis at end-
of-pipe for the particular metal finishing lines considered.
With the installation, of a reverse osmosis system the
neutralizing agent was sodium hydroxide rather than the lime
used with the coprecipitation and segregated precipitation
systems. Lime was used to precipitate phosphate as well as
heavy metalsf but precipitatS.on products with lime are
likely to foul the reverse osmosis membranes. These
membranes remove phosphate directly and lime is not needed.
The cost of a minimum batch treatment system was also
estimated. The layout is shown in the schematic diagram of
Figure 25. The system was sized to handle tl50Q 1/hr of
waste water, which is less than produced by the 5-man plant
discussed above. For calculating operating costs an 8-hour
day and 5- day week were assumed.,
Small Platers
154
-------
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FIGURE 22 PHASE I, IA, AND II MASTER FLOW PATTERN
-------
MrfM
C*nM!K4 Cnmiit Sotimi
C» • Zi » Cd
CSS • TIO » 115 » UW tpb
'> » Chroraacc Stfcaa
. . 14,1 . 7« . 710 - 113 ' 4^ * -~> gpk
TotjJ ;»-,l ,3*
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:f.' - C3. • 345 - SSi cpfc
tUct. Xi 15^ _jfh
XI rur.n.-i Atul .«r« Sm>m«
»*>.-:.»» ipk
FIGURE 23 COMBINED CHEMICAL TREATMENT AND NEUTRALIZATION-PRECIPITATION
-------
HaC«
Cn
C. . Z. . O)
n: ««i . MC « 75 < 710 fph
110 . 110 . Jtt = "60 jpd
Tcul 970 gjh
iiif; tad Zn Phosplutlng Smuu
• 530 . MS - Si g|*
£• nvnprjtinc 130 cpb
W nana; * Caoiblac* Ackl/AH Sliunu
Ccrabuc4 Acrt Alk 7MO gfk
Total 7410 |f*
to Hnd Axaj Dlipnal
FIGURE 24 COMBINED CHEMICAL TREATMENT AND PRECIPITATION FOLLOWED BY END-OF-LINE
REVERSE OSMOSIS TREATMENT FOR ZERO LIQUID EFFLUENT DISCHARGE
-------
L-_^~Ss_| ?unp
' ??h 1
Cvanice , „
TinrgpH—[ Pu:np
00
Neutralization
Sludge
FIGURE 25- BATCH TREATMENT SYSTEM FOR SMALL PLANT
-------
Costs have been estimated for the 1-4 man shop and 5-9 man
shop and may be found with accompanying assumptions in the
following tables:
Sizing Assumptions
. 1-4 employee shop (3 employees)
. 30 sq m plated per hour
. 80 1/sq m per hour
. 1/4 of the flow is cyanide bearing (and can be
segregated)
. The cyanide concentration is 20 ppm
The concentrations in the rest of the flow are equivalent
to 100 ppm of Fs++*
Engineering Assumptions
. Complete manual operation utilizing minimal equipment
. store 1 day of cyanide containing waste and treat overnight
. Equalize flow in a tanJc corresponding to 1/2 of the
daily output. Operate in backmix with adjustment every
two hours.
. All adjustment from carboys or drums.
Of Chemicals Verfication
Cyanide Total waste flow 2100 1/hr
Cyanide flow 600 1/hr
Total cyanide waste 4800 I/day
Total cyanide in waste 98 gm per day
Chlorine requirement approximately 700 gm per
day or 1.5 Ib
Using hypochlorite (1 Ib Cl£ 1 gal hypochlorite)
1.5 gallons per day.
Using caustic 1 lb/1 Ib of chlorine - say,
1. 5 Ibs/day
Neutralization (Assume that the caustic from cyanide treat-
~ ment is used in the first 1/2 day)
Total caustic required - about 2 gm per gm of iron (120/56)
(120/56) 1/2 day flow 9600 1 960 gm of iron
Caustic required - 2800 gm/or 4.5 Ib.
Additional - 4.5 - 1,5 * 3 Ibs.
Rest of day - 4.5 Ibs.
Total per day - 7.5 Ibs
159
-------
O.K. to add by hand (drum of caustic - approximately
400 Ibs)
O.K. to use a small bucket (8 gals, approximately or
80 Ibs)
Residence time - 4 hours (nominal or actual) for equalization
Equipment List
Equalization tank - 2500 gals.
Agitator - 5 HP
Chlorination tanks - 2 x 800 gals.
2 Agitators - 1 HP
1 Transfer pump
High level alarm - 3
Valves - 5
Other piping and supplies
Installation - 25%
$2500
1000
1500
800
150
400
300
—HP.
$6800
1700
$8500
Instrument
pH meter
colorimeter
400
1PJ2
Total $9100
Area required - 400-500 square feet (assumed available)
Assume that there is room for equipment, e.g. a 2500 gal.
tank of normal configuration is 6.5* in diameter and
101 in height (without legs).
Sizing Assumptions
5-9 employee shop (7 employees)
70 sq m plated per hour
80 1/sq m 5600 1/hr of flow
1/4 flow is cyanide bearing (and can be segregated)
Cyanide concentration » 20 ppm
The concentrations in rest of waste flow are equivalent
to 100 ppm FS++ +
Engineering Assumptions
. Cyanide flow - 1400 1/hr - say, 350 gals/hr.
. Assume that a hand operation once a day is used for
cyanide (Automatic continuous unit would cost about
$18,000-22,000).
. Equalize daily flow in a 1/2 day tank.
. Check for hand addition - or cheapest equivalent.
160
-------
Cyanide . Cyanide total - 11,200 I/day 2800
„ . , .„ gals. (3000)
. Total cyanide in wash - 224 am/day
. Chlorine required - 1500 gm/day say 3 5 ibs
. Hypochlorite - 1 gal/lb of chlorine 3.5
gallons (can be added out of a plastic lined
55 gallon drum with a hand pump)
. Caustic - 3>5 lbg>
Out of a 55 gallon drum ( 500 lb) with a
scoop, (a big scoop is about 5 lb)
pJL.AdJust 2 gm per gm of iron
1/2 day flow (total) 22,400 1. (say 6000 gals)
Ir°« 2,240 gm
Caustic 4,500 gm 10 Ibs.
2 to 3 scoops.
Manual addition from a drum appears feasible.
Material handling equipment - 1 chlorine resistant
hand pump - say $200
Eguipment List
1 Equalization tank - carbon steel 6000 gals. $ 4,100
%S« ^reat tankS ~ carbon steel, epoxy lined* 7,200
(3000 gal)
(35°0) <2 * 10°°>
High level alarms ™
valves (5) *JJ
Other piping and supplies 300
installation - 25%
instruments T°tal $22'900
Hand pump
PH meter
Colorimeter 200
$23,700
*Add 20^ for epoxy lining.
If a 2 hour equalization is required
use a 3000 gal tank «• 5 HP agitator (3000 + 1000) 4,000
instead of 4100 + 3500 (7600)
thus, 18300 - 3600 1a 700
3*700
161
-------
18,400
Save ft ,500
19. OO
The total capital investment and operating and maintenance
costs for both size plants are as follows:
No. of Capital Investment ($1000) Annual OSM Costs ($1000)
employees 80 1/sq m 160 1/sq m 80 1/sq m 160 1/sq m
tnln max min max min max min max
1-4 9.1 13.7 13.7 20.5 3.9 6.5 3.9 6.5
5-9 23.7 35.6 35.6 53.3 4.3 7.1 4.3 7.1
New Source Performance Standards (NSPS1 . New sources that
are required to meet the recommended standards of
performance have the opportunity of designing and building
plants that reduce water flow. Such systems as counterflow,
spray, and fog rinses, interlocks to provide water flow only
during processing sequences, drip tanks, etc., can be
provided. The capital investment for installing an extra 31
x 3' tank in each rinsing sequence of a plating line to
reduce further the water use in counterflow rinsing is of
the order of $3,000. The plant modeled in Figure 22 has 27
rinses so adding one more tank for each rinse would increase
capital investment $81,000 for a total of $300,200 for
combined chemical treatment and precipitation in an urban
plant. It is probable that water use can be reduced 100
percent by installing only half this number of tanks at a
cost of $40,000 or an increase in capital investment of 18
percent over a plant meeting BPCTCA standards. Operating
costs would increase $7200/yr minus a credit of $520 for
water and sewer charges or $6680/yr« The increase in
operating cost is 6 percent as compared to those for a plant
meeting BPCTCA standards.
No Discharge of Pollutants
The elimination of liquid discharge from metal finishing
processes has not been demonstrated with present technology.
Anticipating that future development will make this
elimination possible, it is desirable to have a rough
estimate of the cost impact of doing this. Technically,
evaporative recovery, reverse osmosis, and ion exchange can
concentrate wastes after which the concentrate can be
evaporated essentially to dryness. Purified water can be
returned to process. Approximate cost analysis have been
made for a medium large plant 240 sq m (2600 sq ft) per hour
assuming use of 80 liters/sq m of water. The effects of
closing the liquid loop without a purge on the buildup of
impurities are not known and the cost of solving problems
162
-------
connected with impurity buildup will depend greatly upon how
much impurity must be removed, the development of efficient
systems for their removal, and how many of the components
that are recovered can be recycled rather than discarded.
To determine the cost effectiveness of various control and
treatment alternatives much of the data developed for Plant
33-1 in Phase I was used. For those examples involving
evaporative recovery, an additional investment of $150,000
was allowed for a unit to evaporate concentrate to dryness.
Results of the calculations are shown in Table 31. A
finishing cost of $2.70/sq m ($0.25/sq ft} is equivalent to
$644/hr, and all of the projected costs for waste treatment
are less than 10 percent of this figure. Of course, the
$2.70/sq m figure is too high for soine processes, but
provides a basis for at least a rough estimate of the cost
impact of waste treatment.
Nonwater Quality Aspects
Energy Requirements
Introduction. Energy requirements will be discussed for
chemical treatment, evaporative recovery, ion-exchange, and
reverse osmosis.
Chemical Treatment. Energy requirements for chemical
treatment are low,~"the main item being electrical energy for
pumps, mixers, and control instruments. Electrical costs
have been tabulated for several plants in Table 32. Data
for Plants 33-1 through 33-6 were obtained from the Phase I
study. Results indicate that approximately 5 percent of the
waste treatment cost is for electric power.
It is estimated in the Phase I study that electrical energy
for treating 2.271 x 10* liters per hour by a reverse
osmosis unit for a000 hours per year would cost $6,400. The
electrical energy cost is therefore 7.0*5 x 10-«. The
liters per year processed by all plants listed in Table 32
add up to 3.964 x 10« liters and the cost of electricity for
processing this water by reverse osmosis is $279,200. The
total electrical cost for chemical treatment for the plants
listed in Table 32 is $75,330. These figures can be used to
roughly estimate the increases in electrical power
requirements in going to a system with no liquid effluent.
For best practical control technology currently available
the electrical cost would be essentially that of current
estimates or $75,330. For the best available technology
economically achievable the combination of chemical
treatment and reverse osmosis plus evaporation of the
163
-------
TABLE 31 COST EFFECTIVENESS OF
CONTROL ALTERNATIVES
(247 Sq M/Hr)
Type of Control
Plant 33-1
Rinse System -
Chemical treatment
Three countercurrent
Investment
Cost
$264,274
330,000
Operating
Cost/Year
$112,361
121,387
Water
Treated
1/Hr
25,210
9,766
Operating
Cost per
100 Sq M
$17,30
18.68
rinses - chemical
treatment
Single stage evapor- 890,000
ators (21 units)
Dry evaporator
Five single stage 400,000
evaporative units
and one vapor com-
pression unit - dry
evaporator
Chemical treatment 560,000
plus reverse osmosis
Sludge drier and dry
evaporator for
concentrate
327,895
109,913
161,328
50.47
16.92
24.83
16-4
-------
TABLE
32
COST OF POWER RELATIVE TO TOTAL OPERATING
COST FOR CHEMICAL TREATMENT
Plant
No.
33-1
11-8
36-1
20-14
20-17
3-4
33-3
33-6
33-22
20-20
20-22
33-24
36-12
33-2
33-4
8-5
6-35
30-19
Processes
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr , Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Anodizing
Anodizing
Anodizing
Plating Common Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Chemical Milling
Chemical Milling
Electric
Cost/Year
$ 4,100
668
5,220
6,000
8,940
600
240
1,460
1,948
4,763
12,623
1,212
1,894
1,082
120
16,239
3,897
4,330
x = 4,185
o = 4,454
Waste
Treatment
Operating
Cost/Year
$112,361
391,406
221,009
93,240
798,840
4,064
18,019
77,460
51,515
83,481
113,370
80,430
72,809
14,968
18,205
115,995
83,758
168,312
x = 139,957
a = 187,688
Electric
Cost x
100 /Waste
Treatment
Cost
$ 3.65
0.17
2.36
6.44
1.12
14.76
1.33
1.88
3.78
5.71
11.13
1.51
2.60
7.23
0.66
14.00
4.65
2.57
x = 4.75
a = 4.44
165
-------
concentrate (that would require little electrical energy)
the electrical cost would be $75,330 plus $279,200 or
$354,530. The ratio of $354,530/75,330 is 4.70. On this
basis going to a system without discharge of liquid effluent
will increase the use and cost of electrical energy 5-fold.
fiYfl PgEfrU YSJS.SSO.YAEY.' From the Phase I report the cost of
steam for operating a 300 gph single-stage evaporator is
approximately $2100/yr corresponding to approximately
1,900,000 Ib of steam. The single-effect evaporators
require considerable energy. This requirement can be
diminished by use of multiple stage or vapor-compression
evaporators.
Ion Exchange. The few pumps required for ion-exchange
systems should consume very little power.
Reverse osmosis. The energy requirement for reverse osmosis
systems is the electricity for operating the high pressure
across the membrane and for operating low pressure transfer
pumps. The estimate is $6400/yr for a 6000 gph facility
operating 4000 hours/yr.
Impact of Power Requirements for Waste
Treatment. Domestic production of electrical energy in 1971
was 1.717 x 10»« kwh. For the plating industry the
electrical energy requirement is estimated to be 9.75 x 10»
kwh. The metal finishing industry as a whole is estimated
to consume no more than twice this value, which would be
1.950 x 10« kwh. The percentage of annual power that is
used for metal finishing operations should be no more than:
1.950 x 10it/1.717 x 10»2 = 0.114 percent.
Power for pumps, lights, fans, etc. , and waste treatment
should not more than double this figure to 0.228 percent.
Cost of Recovery of Metal Values from Sludge
Tribler et. al. is a report on the feasibility of recovering
metal values from sludge b digesting the sludge with acid to
dissolve it followed by electrolysis and neutralization
procedures to recover metal values. The case considered was
a sludge containing primarily copper, nickel, chromium, and
zinc values. A cost estimate was included for a small plant
that would treat 45 kg of dry sludge during a 12 hour day to
yield 2.27 kg of copper, 0.09 kg of nickel* and 4.54 kg of
chromium. However, the chromium was obtained as an oxide
mixed with some iron. The investment for a small plant was
166
-------
estimated to be $15,130. Operating cost per day was
estimated to be $85.30. This did not include a cost of
capital, which if assumed to be eight percent of the
investment per year, would raise the daily operating cost to
$91.35. The total weight of metal recovered per day is 6.90
kg so that the cost is estimated to be $13.23 kg. The cost
is obviously very high compared to market prices so that the
small operation would be far from economic. Undoubtedly,
the cost of processing would be less with a larger
installation, but if more than one metal finishing
installation were served there would be an additional cost
for transporting sludge to the recovery operation.
167
-------
SECTION IX
BffST PRACTICABLE CONTROL TECHNOLOGY Cl
AVAILABLE. GyIpELlNES* ANQ LIMITA!
Introduction
The effluent limitations which must be achieved by July 1,
1977, are to specify the degree of effluent reduction
attainable through the application of the best practicable
control technology currently available. Best practicable
control technology currently available is generally based
upon the average of the best existing performance by plants
of various sizes, ages, and unit processes within the
industrial category and/ or subcategory.
Consideration must also be given to:
(a) the total cost of application of technology
in relation to the effluent reduction benefits
to be achieved from such application
(b) the size and age of equipment and facilities
involved
(c) the processes employed
(d) the engineering aspects of the application of
various types of control techniques
(e) process changes
(f) nonwater quality environmental impact
(including energy requirements).
The best practicable control technology currently available
emphasizes treatment facilities at the end of a
manufacturing process but includes the control technologies
within the process itself when the latter are considered to
be normal practice within an 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
facilities.
169
-------
industry Category and Subcategory Covered
The effluent limitations recommended herein cover the
following metal finishing processes: anodizing, chemical
milling and etching, immersion plating, chemical conversion
coating. These processes have been divided into three
categories: Subcategory (1) consists of anodizing,
Subcategory (2) consists of coatings, and Subcategory (3)
consists of chemical etching and milling,
I<3ejltification of Best .Practicable, contffsj,
Technology Currently Ava4J.abj1g
Best practicable control technology currently available for
Subcategories (1) , (2) and (3) is the use of chemical
methods of treatment of waste water at the end of the
process combined with the best practical in-process control
technology to conserve rinse water and reduce the amount of
treated waste water discharged.
Chemical treatment methods are exemplified by destruction of
cyanide by oxidation, reduction of hexavalent chromium to
the trivalent form, neutralization and coprecipitation of
heavy metals as hydroxides or hydrated oxides with settling
and clarification to remove suspended solids prior to dis-
charge or prior to dilution with other nonelectroplating
process water before discharge. The above technology has
been widely practiced by many plants for over 25 years.
However the above technology cannot achieve zero discharge
of heavy metals because of finite solubility of the metals.
In addition, it is not practicable to achieve 100 percent
clarification and some small amount of metal is contained in
the suspended solids. By optimum choice of pH and efficient
clarification it is possible to achieve a significant re-
duction in the heavy metal pcllutional load.
Zero discharge of heavy metals in effluent may be achieved
only by eliminating the effluent itself by such techniques
as reverse osmosis and evaporation, which offer the
possibility of p\irifying all waste water to a sufficient
degree to be recycled to process or by evaporating to
dryness so that waste water constituents are disposed of as
solid waste.
No generalization regarding the degree of metal pollution
reduction is possible because of the mij£ of finishing
processes possible in a single plant and the variety of
metals in the raw waste of most plants. Because of this
fact and the high cost of inplant segregation of all waste
170
-------
streams according to metal» coprecipitation of metals is the
general practice. Thera is an optician pH for precipitating
each metal that results in the greatest removal by
clarification. The optimum pH for removing all metals
cannot be utilized for coprecipitaticn so the pH selected
for a mixture of metals is a compromise. However,
coprecipitation can result in lower discharge of metals than
if each is precipitated separately at its optimum pH value
if synergistic effects of the type shown in Table 26 are
operating. For copreeipitatlost to provide lower discharge
than segregated precipitation in-process dilution must be
minimal.
There are several advanced recovery methods available for
closing up the rinse water cycle on individual metal
finishing operations. These methods ^evaporation, ion
exchange, reverse osmosis, conntarcurrent rinsing) have not
yet been applied to rinse watars from pretreatment and
posttreatment operations. The corresponding rinse waters
plus concentrated solution draps and floor spills may
contain one or all of the pertinent metals (copper, nickel,
chromium, and zinc) in significant amounts requiring
chemical treatment. Thus? chemical treatment of at least
the typical acid/ alkali stream from pretreatment and
posttreatment operations represents the best practicable
control technology currently Available to achieve the
effluent limitations recomroeadaat
Having identified the technology for end-of-process
treatment and recognizing the technical and practical
limitations on removal of heavy metals by this technology
(metal solubility and clarification efficiency), further
reduction in the quantity of matal pollutants discharged
must be achieved by reduction in the volume of treated water
discharged. There are many in-process controls designed to
reduce the volume of waste water which is principally that
resulting from rinsing. Some of these controls, designed to
minimize dragout of concentrated solutions or to reclaim as
much dragout as practical can be considered normal practice
within the industry. It can be assumed according to good
practice that reclaim tanks and/or still rinses are being
used and that all evaporation losses are made up with the
reclaimed solution. Dragout reclaimed does not contribute
to the raw waste load normally discharged from remaining
rinses. There is economic incentive to reduce the chemicals
purchased for bath makeup and the added economic incentive
to reduce the cost of treatment chemicals required for end-
of- process treatment. Reduction of dragout leads to
reduction in water requirements for rinsing.
171
-------
Further reduction in rinse water use can be achieved by use
of a stagnant rinse for recovery or by multiple-tank
countercurrent rinsing. Counteracting the cost of
installing multiple rinse tanks are the savings in treatment
chemicals, water costs, and sewer charges. Further, the use
of advanced recovery techniques (evaporation, ion exchange,
and reverse osmosis) which concentrate the rinse water
sufficiently to allow reclaim of the valuable metal
finishing solution can often provide the economic incentive
to use this technology and justify the cost of recovery
equipment plus the cost of installing multitank
countercurrent rinsing. However, it should be recognized
that the major water reduction occurs because of the
installation and use of multitank countercurrent rinsing.
In the past there has been little economic incentive to
reduce water use for rinsing after preparatory and
posttreatment operations. The cost of the chemicals has not
made their recovery from rinse waters worthwhile. High
dragout from preparatory cleaning solutions has not been
considered an unfavorable factor since the dragout of
impurities along with bath chemicals has prolonged the life
of the bath in some cases. The disadvantage of high dragout
is that more water must be used for rinsing to prevent
significant concentrations of impurities, i.e., grease, from
contaminating the processing solutions.
Best practicable control technology currently available also
includes water conservation through rinsing. A water use of
160 1/sq m/operatlon (4 gal/sq m/operation) has been
estimated as that achievable by the industry. This figure
precludes the use of countercurrent or series rinses.
Exclusive use of single stage rinsing will not meet this
water use. It has been calculated that for 186 sg m/hr
(2000 sq ft/hr) proudction the rinse water need for various
rinsing techniques are:
1 - single rinse 1/hr 499,620 (132,000 gal/lir)
2 - tank countercurrent 2800 1/hr (1HO gal/hr)
3 - tank countercurrent 477 1/hr (126 gal/hr)
4 - tank countercurrent 201 1/hr (53 gal/hr)
5 - tank countercurrent 121 1/hr (32 gal/hr)
This corresponds to a water use of:
1 - single rinse 2686 1/sq m (66 gal/sq ft)
2 - tank countercurrent 15 1/sq m (.37 gal/sq ft)
3 - tank countercurrent 2.56 1/sq m (.06 gal/sq ft)
4 - tank countercurrent 1.2 1/sq m (.026 ga/sq ft)
5 - tank countercurrent .65 1/sq m (.016 gal/sq ft)
172
-------
A 3 - stage series rinse consumes approximately the same
quantity of water as a 2 - stage countercurrent*
The 160 l^q m (U gal/sq ft) takes into account the
contributions made by the pretreatmcnt steps of alkaline
cleaning and acid pickling and allows some use of single
rinses.
An alternative mode of operation to the above is to dump
cleaning baths frequently so that dr&gout of impurities is
minimized. Then the amount of rinae water can be reduced
and can be even further reduced by use of multiple
countercurrent rinsing technique®,, The increased cost of
chemicals from more frequent dumping and the cost of
multiple rinse tanks is counteracted by savings in water and
sewer charges. Water use can therefore be greatly minimized
since preparatory solutions, i.e*? alkaline cleaners and
acid dips contain chemicals that can be tolerated in fairly
high concentrations in subsequent processing solutions,
i.e., plating baths. In general, the amount of rinse water
required should be substantially less for rinsing following
alkaline cleaning and pickling than for ringing following
typical metal finishing operations aueh as electroplating.
While sufficient economic incentive may not be present to
achieve reduction in the volume of the rinse water from pre-
and posttreatment operations, there is an opportunity for
significant reduction in pollution. The above factors are
taken into account in recommending the effluent limitations.
Even in plants currently achieving good waste treatment
results, there are further opportunities for reduction in
volume of effluent discharge.
Rationale fqr Selecting ^he Best practicable
Control— Technology Currently Available
General Approach
In determining what constitutes the best practicable control
technology currently available, it was necessary to
establish the waste management techniques that can be
considered normal practice within the metal finishing
industry. Then, waste-management techniques based on
advanced technology currently available for in-process
control and end-of -process treatment were evaluated to
determine what further reduction in pollution might be
achieved considering all the important factors that would
173
-------
influence the determination of best practicable control
technology currently available.
Management Techniques Considered!
Practice jn the Metal Iloighina Industry
For that portion of the metal finishing industry that
discharges to navigable waters, many are currently using
chemical treatment for end-of-process pollution reduction.
Some of these waste- treatment facilities have been in
operation for over 25 years with a continual upgrading of
performance to achieve greater pollution abatement. Because
of the potentially toxic nature of the chemicals used in the
metal finishing industry, there is a relatively high degree
of sophistication in its water pollution abatement
practices. For example, the accidental release of
concentrated solutions without treatment to navigable waters
is believed to be a rare occurrence today. This is because
adequate safety features are incorporated in the design of
end-of-process waste treatment facilities in conjunction
with good housekeeping within the electroplating facility.
This example and other waste management techniques were con-
sidered as examples of normal practice within the metal
finishing industry in determining the best practicable
control technology currently available. Other examples of
normal practice include:
(1) Manufacturing process controls to minimize
dragout from concentrated solutions such as
(a) proper racking of parts for easy
drainage
(b) slow withdrawal of parts from the
solution
(c) adequate drip time or dwell time
over the tank
(d) use of drip collection devices.
(2) Effective use of water to reduce the
volume of effluents such as
(a) use of rinse water for makeup of
evaporation losses from solutions
(b) use of cooling water for noncritical
rinses after cleaning
174
-------
(c) use of treated waste water for
preparing solutions for waste-
treatment chemicals.
(3) Recovery and/or reuse of waste water
constituents such as
(a) use of reclaim tanks after metal
finishing operations to recover
concentrated solutions for return
to the plating tank to make up
evaporation losses
(b) reduction in waste water volume by the
use of at least two series flow rinse
tanks after each finishing operation
with return of as much rinse water as
possible to the finishing tank.
Other waste-management techniques not considered normal
practice, but currently in use in one or more plants, were
evaluated on the basis of reduction in the quantity of
pollutants in the effluent discharged.
Degree of Pollution Reduction
*>v_ pianos
- _
Aaes. and Processes Using
Treatment Technology
Identification of Best Waste Treatment Facilities
The initial effort was directed toward identifying those
companies that had well engineered and operated metal
finishing process and waste treatment methods. Such
companies were identified on the basis of personal
knowledge, and referrals by people well acquainted with the
industry (EPA regional representatives, state pollution
control authorities, trade associations, equipment
suppliers, consultants) . Representatives of approximately
75 companies returned questionnaires mailed to them and
these representatives were further contacted by telephone or
further correspondence in many cases to clarify the
information in the questionnaires and obtain further data.
Furthermore, visits were made to 11 plants for development
of detailed data on several of the processes. Effluent
samples were collected at five plants and analyzed at
Battelle-Columbus Laboratories. The above constitutes the
data based for the Phase II study.
175
-------
Waste Treatment Results
Volume Capacity of Treatment Plant^sfnigigri- Figure 26 shows
the volume capacity of the waste treatment plants for which
data were received, as measured by the amount, of waste water
treated per hour. The rang© of capacities
approximately two orders o£ magnitude.
covers
The plot ie a cumtnulative on® indicating how snany plants
have a water use leas than r.he voitsrwa corresponding to the
cummulative number. Thu«?, r.S plants have a volume of
100,000 liters/hour or less and 4 plants have a greater
volume.
ConsentratJiop ,.o. £.
-------
100,000 —
.c
^
tO
o>
a
to
o
a»
a
10,000 •-
1000
10 ?-0 30
Cumulative Number of Plants
FIGURE 26. DISTRIBUTION OF WASTEVVIER VOLUME TREATED
177
-------
TABLE 3 3 CGSOSatBATIOa OF BH&DBR COBStlTOSHTS
-J
CO
Plant
So. Processes Ag Al
20-24 1'iating Conon Metals
33-24 Plating Casaaoa Metals
33-26 Plating Coanon Hetals
31-1 Plating CosHBoa Metals
3&-12 Platiag Com, .Free. Metala <0,01
33-2 Plating Precious Metals traces
33-4 Plating Precious Metals
8-5 Plating Precious Hetals
6-37 Plating Precious Metals <5
19- LI Platiag Precious Metals (0)
15-3 Plating Precious Metals
9-7 Electropainting, Amodizing 6.5
9-6 Electropainting
33-34 Electropainting
4-5 Electroless Plating
8-8 Electroless Plating
30-19 Electroless Plating
33-22 Anodizing <0.05
33-23 Anodizing 0.91
20-22 Anodizing 1.0
20-20 Anodizing 3.7
33-35 Anodizing l.OS
20-23 Anodizing 8. IS
47-9 Anodizing
6-35 Chemical Milling <1
9-2 Chemical Milling 0.25
23-7 Chemical Milling 0.5E
33-30 Phosphating
19-24 Etching - 0.5
31-16 Printed Circuits
6-36 Immersion Plating
46-4 Electropolishing
E - estimated
S - soluble
Concentration | mg/1
Total ,
Au Cd CH~ CR Cr Cu F~ Fe RL
0.02 0.54 0,17 11 i.S
<0.025 <1 <0.05 <1 <1
0.05 0.3 7
j __ ]_§
<0, 1
traces 0.1
(0)
<1 <5 <5
(0) (0) <0.5S <1§
0.02 0.04 0.08 0.06 0.03 0.03
'!•
7.7
<0.02
<0.03 0.2 <0.05 20 1.0
0,40 0.37 0.24
0.13 0.05
<0.18
oa (o) i.o
-------
TABLE 33 COHCEMTRATION OF EFFLUENT COMSTITOEKTS (Continued}
v»
Plant
Mo,
20-24
33-24
33-26
31-1
36-12
33-2
33-4
8-5
6-37
19-11
15-3
9-7
9-6
33-34
4-5
§-<
30-19
33-22
33-23
20-22
20-20
33-35
2tt~23
4J-f
*-.15
9-2
23-7
33-30
19-24
31-16
6-36
46-4
Concentration, «g/l
Processes Pb
Plating Common Metals 0.6
Plating Common Metals
Plating Coraaon Metals 0.3
Plating Common Metals
Plating Com. ,Prec. Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Electropainting
Electropaiating
Elect repainting
Electroless Plating
Electroless Plating
Electroless Plating 0.5
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Chemical Milling
Chemical Milling
Chemical Mining
Phosphating
Etching
Printed Circuits <0.2
IsMzcioa Platiaf
ElMtropel 1 ••*•«,
Pt
H>4~3 Metal
<,0
traces
(0)
<0.4
8.1
50
13
180
0.3
0.8
0.17
trace
2
0.15
70-85
Susp.
Sn Zn Solids
<2 0.25 4
<1.0 <25
Mil 78
0.2S
0.5S <10
6
6.9
<20
0.5
10
40
130
<0.02 22.7
100
<10
. 25-60
10
5
16
29
<0.1 <5
(0)
0.1 5
2.2 11
0.1
1-34
Dis.
Solids
676
1400
1250
1642
200
640
2760
250
400
204
500
>10
3600
1500
993
708
300
1690
927
506
220
1200
PH
8.5-9.5
7-9
8.0
7.0-8.0
8.0
5-10
7.5-8.5
7.5-8.0
7-10.5
7-8
7.0
6.2
8.4
7
7
6.5-10
6.5-9.0
6.5-9.0
7.5
6.8-9.2
6.5-9.5
8
8.0
8.6
8.0
S.7
2.6-5.*
Other
BF~ - 75
/COD - 34
ICobalt -
COD = 320
(Barium -
ICOD = 624
Ammonia -
Anemia -
Hitrate -
Hltrate -
mg/1
mg/1
<0.03 •»/:
mg/.i
1.0 mg/1
mg/1
6.8 Bf/1
10 mg/1
50 Bg/1
18 mg/1
-------
TABLE 34 WATER USE IN METAL-FINISH ING PROCESSES
Plant
36-12
30-2
33-30
20-3
33-24
33-5
15-3
9-7
33-34
6-36
31-16
30-19
33-27
33-23
33-22
9-2
20-20
33-35
20-22
20-23
41-2
6-35
47-9
4-8
Line
Sn
Cu-Sn
Rack Cd-Zn
Rack Cd
Barrel Cd
Rack alkaline Sn
Rack acid Sn
Rack Ni, CuPbSn, Sn
Rack zincate dip, Cu,
CuPbSn, Sn
Rack Cu-Sn
Basket Sn
Rack Ni, CuPbSn, PbSn
Rack Cd, manual
Barrel Cd, manual
Barrel Sn, manual
Ditto
Electropaint
Immersion
Electroless Cu
Ditto
"
Electroless Sn
Electroless Ni
Ditto
"
Anodizing Al
Ditto
"
Anodizing Mg
Anodizing Al
Ditto
"
"
"
"
"
Chemical Milling
Ditto
-
Production,
sq m/hr
42.8
122.8
171.5
123.4
45.8
46.5
46.5
9.3
9.3
92.90
21.1
25.1
1.86
11.15
18.58
1.39
139.4
529.5
48.8
23.23
25.08
23.23
13.94
1.39
10.03
11.71
297.4
148.7
83.6
4.65
269.5
55.8
3.253
102.2
16.73
9.29
13.94
37. IT
9.29
9.29
Water Use,
1/hr
454
908
5,995
18,160
11,355
9,463
3.936
6,188
12,737
7,040
3,407
2,725
2,161
220
1,553
2,120
8,395
4,315
1,022
12,491
5,678
5,678
76
1,590
1,590
2,271
18.927
27 , 254
44.895
7,382
79,494
2,082
87 , 064
18 , 927
5,678
2,271
1,930
3,785
1,893
1,893
Number of
Operations
1
2
2
1
1
1
1
3
4
2
1
3
1
1
1
1
1
1
1
5
3
3
1
7
5
10
4
3
4
1
3
6
4
4
4
2
1
2
2
2
Liters/
Sq m/
Operation
10.61
7.39
17.49
147.2
247
203.7
84.7
222
343
37.9
161.5
36.2
1,162
19.7
83.6
1,525
60.22
8.15
20.94
107.5
75.5
81.48
5.45
163
31.7
19.4
15.9
61.09
134.3
1,558.9
98.3
6.2
6.7
46.3
84.9
122.2
138.5
50.9
101.9
101.9
180
-------
TABLE 3 4 (Continued)
Plant
30-9
6-36
33-20
23-7
6-37
30-21
31-16
8-5
15-3
33-4
33-2
36-12
30-19
31-16
Line
Chemical Milling
Ditto
„
-
•>
"
Auto rack silver
Ditto
Man rack silver
Ditto
Auto rack silver
Ditto
,i
.,
Man rack silver
ii
Cont strip silver
Auto rack silver
Stripping silver
Man rack gold
Ditto
Auto rack gold
Man rack silver
Man rack gold
Man rack silver
Ditto
Man barrel silver
Auto rack gold
Man rack gold-silver
Man rack silver-rhodium
Cont strip silver
Chemical etching
Ditto
„
„
n
..
Production,
sq m/hr
92.9
9.29
B9.fi
13.4
24.6
27.9
74.33
293
59.5
11.61
35.3
11.61
22.22
4.65
6.50
6.50
4.65
0.84
1.12
1.39
0.74
8.55
0.093
0.093
0.047
1.86
5.57
1.21
2.79
2.79
31.6
92.9
8.36
16.73
18.6
18.6
11.15
Water Use,
1/hr
6,814
2,725
3, 785
3,028
6,613
15, 141
13, 967
20,363
9,084
8,365
8,270
5,602
9,311
8,316
908
908
5,942
(0)
757
8,138
1,817
1,590
3,028
379
460
462
462
4,637
5,678
1,703
454
13,248
2,271
2,725
3,785
6,624
7,570
Liters/
Number of Sq m/
Operations Operation
2
2
2
3
2
2
4
4
3
4
4
4
4
4
3
2
4
1
1
4
3
2
2
1
2
2
2
3
3
3
2
2
2
2
2
2
2
36.7
146.7
31,8
'16.3
134.4
271.3
46.98
17.40
50.92
180.1
58.57
120.6
100.2
447.6
46.54
65.32
319.8
(0)
658
1,460
815
93
16,280
4,080
4,952
124
41.43
1,281
679
204
7.18
71.3
135.7
81.5
101.9
178.3
340.2
181
-------
TABLE 3 4 (Continued)
Plant
4-9
36-16
33-30
20-25
23-8
46-1
33-29
33-29
4-4
Production,
Line sq m/hr
Chemical etching
Ditto
"
"
Chemical Machining
Ditto
Zn phosphating steel
Ditto
Fe phosphating steel
Electropolishing
Electrochemical machining
(Neutral Salt Electrolyte)
Electrochemical machining
(Acid Electrolyte)
Electrochemical machining
(Neutral Salt Electrolyte)
18.6
13.94
13.94
4.65
6.51
3.12
66.91
464.7
153.4
10.59
0.53
0.37
0.19
Water Use, Number of
1/hr Operations
4,088
1,362
1,362
1,362
5,299
1,514
11,356
11,356
946
1,817
7.6
22,700
7.6
2
2
2
2
2
2
2
2
1
2
1
1
1
Liters/
Sq m/
Operation
110.0
48.9
48.9
146.7
407
203.5
84.9
12.2
6.17
185.8
14.3
61,400
•
40.0
182
-------
The flrsst method of expressing water use requires choosing
what operations in the overall process will be included in
calculating water use «nd what operations will not be
included. "This method was followed in the Phase I guide-
lines, where all operations involving electrodeposition and
posttreatment were included but cleaning and pickling were
omitted. The water use has been calculated in terms of
llters/sq in/operation where the square meters refer to the
finished worK and the operations exclude cleaning and
pickling,
This method of expressing water use allows one to consider
its variation in terms of those operations that are
different from process to process* on the other hand, those
operations that, are common to moat processes, i.e., cleaning
and pickling, and involve about, the aame water use
regardless of'the process in which they occur, can be
eliminated from consideration as a cause of variations in
water use. Calculations for Phase II processes have been
made using the above formula, omitting the initial cleaning
and pickling operations^ but counting all subsequent
operations in. a process.
A.S mentioned previously, lss>8 water is required for rinsing
following alkaline cleaning and pickling than for rinsing
following most other operations.
Data provided by the companies on area processed and water
use ia given in Table 3UM From this data, frequency
distributions for water use Cl/sq m operation) for processes
in subeategories (I) , {2} ©nd (3) were derived. These are
given in Figures 7, 3 and «*. ?he median water use for each
subcategory' %*as used as a basis for the guidelines. It was
felt that the plants identified by the contractor were well
designed and well-operated and therefore the median value
was a good approximation of the ''average of the best
"criteria specified for BPCTC& treatment.
Determination of Effluent Limitationa
Effluent limitations were established from three parameters:
(1) constituent concentration in the effluent* (2) water
use, enfi (3) area processed or plated. Sosie dependence
among these parameters is known* i»e., coagulation of
precipitates out. of dilute eolation is wore difficult than
out of more concentrated solutions and area processed in a
giver, line increases with couples shapes that give higher
dragout awd require more watar for rinsing* Th© plant data
obtain.ec show no evident correlation betw®«n the three
183
-------
factors probably because variations in water use and
concentration due to other factors mask out the relationship
between the three factors mentioned. Within the accuracy of
the information available the three factors will be
considered independent, that is, the concentration
achievable in the effluent by exemplary chemical treatment
is not related to the amount of water used for processing.
The best water use is not necessarily found in a plant
operating an exemplary waste treatment facility and vice
versa. However, once exemplary values for both water use
and concentrations have been established the product of the
two represents an overall figure of merit that takes into
account both parameters. Therefore, the guidelines can be
expressed in terms of the product of the two parameters:
(mg/1) x (1/sq m) « mg/sq m. More water may be used if
lower concentrations are achieved and vice versa.
Concentrations of Effluent Constituents and pH. Table 35
lists the concentrationbasisForeachconstituent, The
values given are for the total amount of constituent,
dissolved and suspended. Therefore, both proper
precipitation and efficient clarification and/or filtration
are required to meet the concentrations considered
achievable.
Water Use. The values of water use for each type of process
cover a wide range. Variations in dragout, the
concentration of dragout, and the degree of rinsing required
vary and are in part responsible for the range of values.
However, inefficiencies in reducing dragout to a minimum,
rinsing beyond requirements, and poor design of rinsing
facilities and waste of water are also responsible for
making in making a wide range of water use . It is
necessary, then, to estimate the minimum water use that can
be achieved by essentially all of the lines of a given type
of process.
Subcategory (1)
The process covered in this subcategory is anodizing.
Data on water use for anodizing operations from ten plants
on eleven different lines are given in Table 34.
Supplemental information and configuration data was obtained
from two of these plants by plant visits.
184
-------
TABLE 35. CONCENTRATION VALUUS FOR WASTBWATBR
CONST ITUL7NTS FOR BPCTCA
Present Phase II
Constituent Proposal, mg/1
TSS 20
Cyanide (oxidizable) .05
Cyanide (total) 0.5
Fluoride 20.0
Cd 0.3
Cr+0 0.05
Cr (total) 0.5
Cu 0.5
Fc 1.0
Pb 0.5
Ni 0.5
Sn 1.0
Zn 0.5
Phosphorus I.Q
PH 6-9
185
-------
Plant 33-23 is an aluminum anodissing plant which has a large
automatic rack line for anodizing aluminum alloy parts.
Figure 27 is a schematic of this facility. The waste
treatment plant for treating the spent processing solutions
and the rinse water effluents from this operation is shown
in Figure 28. Data taken during the plant visit for
treated effluent pollutant concentration are shown in Table
36.
Plant 6-35 is a large chemical anodizing and milling
facility. Although the anodizing line was not operating
during the time of the plant visit. Information on the
sequence of operating steps and analyses of the waste
treatment plant effluent was obtained and is given in Figure
29. Addi tonal data on rinse water flows and production
rates were provided by the plant at a later date. The 65th
percentile water use was found to be 90 i/sq m-operation
(2.2 gal/sq f t-operation) .
Subcater 2
Subcategory (2) covers coatings - phosphating, chromating
and immersion plating.
One immersion plating plant was visited in this study.
Plant 6-36 has an immersion tin plating facility consisting
of one barrel plating line. Treatment of the wastes from
this plant is done in an integrated waste treatment plant
which was installed in 1972. The sludge from the treatment
reservoirs is collected in storage tanks and hauled away by
truck to a landfill several times a year.
Three chemical conversion coating plants were covered in
this study. Two were zinc phosphating on steel and the
other was iron phosphating on steel. The data on water use
for these operations is listed in Table 34. The 65th
percentile was found to be 17 1/sq m-operation (.42 gal/sq
ft-operation) . since there was no apparent reason for this
much smaller water compared to other subcategories, the
largest value reported of 80 1/sq m-operation (2 gal/sq ft-
operation) was chosen as the water use factor.
Subcateaorv (3)
Subcategory 3 covers chemical milling and etching.
Data on nine chemical milling lines in six plants are given
in Tables 33 and 34. Supplemental data on two of these
plants was obtained on visits to these plants.
186
-------
Water •*>-
Batch Treat
Then Sent .
To Tank 1
City and
Used Cooling Water •
Workplaces go
into one of the
threo anodizing
tanks; after
anodizing work
goes to Station II,
and then Stations
15 and 16.
22.
PI Water
Rinse
21.
Dl Water
Rinse
-*r
0.
Diehromata
Sea!
1/10 to 1/2 g/l K2Cr207)
19.
Dl Water
Rinse
«q
KBM
8> Nickel
Acetate Soal
(1/2 g/l Nickel Acetate)
17.
Dl Water
Rinse
-------
Anodizing
Waste Effluents
.Waste
Effluent
Collecting and
Mixing Sump
PH-Controlled
Automatic
Lime Addition
Neutralization
Vessel
Clarified Effluent to Stream
oo
CO
Sludge to
Storage and
Then Hauled
Away to Landfffl
FIGURE 28, SCHEMATIC REPRESENTATION OF WASTE TREATMENT SYSTEM
FOR HANDLING ANODIZING EFFLUENTS AT PLANT 33-23
-------
PUMP
rn
VO
CHROMATE
WASTES
li
71
II
HOLDING
TANK 5
EQUALIZAT!
TANK 1
^-
1
1
j
ON
1
1
1
1
..
/
1
1
I
"\- _ L
r. _=r-riJ- I
...J7] i£..
"
i
V^i
REACTION
TANK 2A
FirjiiR
)H
c
- i
1
',
i
i
I
]
O
......
I *
""•*
~" "™ £1
1 |
_ OPB,-Jrli P
1 V V 2
; L' ^
r7
\^
REACTION
TANK 2B
CPU! PM ATtr QCDDI~C
H
C
— =
-l\l-
-^
1
"^
r f\
LEGEND
[¥] SULFONATOR
O PUMP
O ALARM
I VALVE
C pH & ORP RECORDER -CONTROL
CHEM CAL rEED
NON-CHRQMATE CONTROL SIGNAL
WASTES
" ' A
>.,/-.
r"/w<— f—i
:..<. ..; Q. (LACIrlED)
j pH EFFLUENT
"1 • : (Hb) ID HIVtri
>
>J-tJ APH ,O POINT
?<6S1 rnil 1;
* ** ! ivii ii / \
1 ^ ' v
^ SUMP /' X,
<\X^^
^ ci I-J-R/^I |7ATInl\l
TANK 3 CLARIFIER j
TANK 4 y
SLUDGE TO
DRYING LAGCCM
FC* i-u.\JOLING CHEMICAL MILLING A\D OTHER METAL FINISHING
EFFLL'E ' 73 -T p^ , .- g_35
-------
TABLE 36 COMPARISON OF BCL ANALYTICAL RESULTS WITH TYPICAL ANALYTICAL
RESULTS REPORTED BY PLANT 33-23 FOR TREATED EFFLUENT
Constituent
AT
+ 6
Cr
tot
Cr
PC
4
SS
IDS
pli
Total Concentrat1onB mp/1
Typical Plant 33-23
[ffluent Analysis
0.1
0.30
0.32
9.1
23
3600
7.0
Contractor
Sampled Effluent
0.2
0.10
0.28
10.5
22
3500
8.0
190
-------
Plant 30-9 is a large aluminum and titanium chemical milling
installation. Chemical milling of the two metals is carried
out in the same area and some of the tanks are used
interchangably, since some of the operating steps are
similar.
The spent chemcial milling etchants a d other processing
solution frcm this plant are haule.^ away by a licensed
scavenger, and the rinse waters are it to large Bettl'.r-j
ooiids on company property.
Data on ten etching lines is given in Tables 33 and 34.
Plant 31-16 was visited during this study and data t-°cen
during the plant visit is covered under subcategory <*)
processes.
The 65th percentile water use for this eubcategory is 120
1/sq m-operation (3.0 gal/sq ft-operationj.
Thirty Day Average Vs One D*.y Maximum
Five months of daily data were obtained from plant 15-1.
This data appears in Table 35. ' In this time period the 30-
day average value of 80 mg/sq m-operation for Zn was
exceeded on two occasions, December *&, 1974 and December 10,
1974. The thirty day average of 80 mg/sq m-operation for
CNT was never exceeded. The one-day maximum of 160 mg/sq m-«
operation was never exceeded by Zn or CN.
One month's effluent data was chosen at random from plant
12-6. It appears in Table 36. Ni, TSS, Cu, Zn, CNT are not
out of compliance with the thirty day average or one-day
maximum. cr+* is not out of compliance with the 30-day
average but is out on the one-day maximum three times during
the month.
Five months of twice weekly sampling TSS, for plant 33-15 is
shown in Table 39. CrT. Ni, Cu never exceed the 30-day
average or one-day maximum. Cr^« is not in compliance for
30-day average or one-day maximum.
Plants Meeting the Guideline^
The effluent concentrations and water use factors have been
collected for 21 plants in Table 40. Except as indicated on
the table, all values are in tota*. solids. Plants 36-1, 36-
12, 15-3, 15-1, 12-6, 33-15 and 12-8 meet the 1977
standards. Plants 36-1 and 36-12 meet the new source
performance standards. Plants 11-8 and 33-: were out of
compliance on only one or two parameters.
191
-------
TABLE 37
PLANT 1$ - 1
mgAn2-Operation
DATE
PH
CN CH-6
CrT
Cu
6-01-74
6-02-74
6-03-74
6-04-74
6-05-74
6-06-74
6-07-74
6-08-74
6-09-74
6-10-74
6-11-74
6-12-74
6-13-74
6-14-74
6-15-74
6-16-74
6-17-74
6-18-74
6-19-74
6-20-74
6-21-74
6-22-74
6-23-74
6-24-74
6-25-74
6-26-74
6-27-74
6-28-74
6-29-74
6-20-74
HI
9.3
8.6
8.4
8.6
8.1
8.1
8.7
9.5
8.2
9.0
7.9
8.0
8.6
8.9
9.0
8.6
8.1
8.2
8.5
9.1
8.3
9.5
7.9
8.9
8.8
8.9
9.6
9.8
9.5
8.1
Lo
7.5
6.9
6.9
6.3
6.6
6.8
7.8
8.0 •
6.8
7.1
6.6
6.4
7.4
6.4
7.5
7.2
6.9
6.6
7.3
7.3
7.5
8.3
6.6
7.3
7.2
7.6
7.8
8.0
8.3
7.0
5.7
7.4
5.3
6.2
6.6
7.2
10.6
16.6
35.3
22.3
19.2
7.0
6.6
10.1
6.2
7.0
5.7
5.7
6.2
5-7
6.6
8.4
7.4
5.7
6.2
6.2
6.2
5.7
5.7
3^1
•
.52
5.4
.48
2.2
1.8
1.3
4.8
.52
4.2
.62
.60
1.3
.60
.92
.56
1.3
1.0
1.0
2.8
8.3
8.4
40.3
46.2
.52
5.6
2.2
1.7
7.6
78.0
.28
5.2
6.8
4.8
5.6
6.0
6.5
9.6
5.2
6.0
.72
6.0
6.4
6.0
9.2
5.6
6.4
5.2
5.2
5.6
10.4
30.0
15.2
170.
10.4
16.8
5.6
5.6
6.8
130.
22.4
5.2
12.6
19.2
11.2
12.0
19.5
28.8
5.2
12.0
7.2
12.0
19.2
24.0
36.8
16.8
12.8
5.2
10.4
11.2
20.8
12.0
15.0
20.4
10.4
5.6
16.8
11.2
15.6
15.6
11.2
5.2
20.4
48
44.8
48.0
58.5
67.2
31.2
42.0
50.4
^8.0
57.6
60
73.0
39.2
38.0
41.0
36.4
44.8
41.6
42.0
22.8
61.2
52.
50.4
50.4
33.6
52.0
57.2
19.6
•".•II !•!• IJ
15.6
13.6
*^W " "
38.4
56.0
60.0
84.5
96.0
20.8
42.0
21.6
36.0
57.6
66.0
110.4
56,0
25.6
46.8
36.4
67.2
31.2
66.0
30.4
61.2
41.6
56.0
44.8
39.2
31.2
20.8
8.4
TSS
1508
408
696
476
930
813
3984
2392
690
806
360
536
1560
3588
1736
832
416
806
308
3196
810
2546
1156
1378
1316
980
644
Average 8.7 7.2
8.6
8.0
22.4 16.2
46.0
1950
194
1170
192
-------
TABLE 38
PLANT 12-6
mg/m2-0peratlon
DATE J)H Zn CNT
11-13-74 8 1.3 27-7
11-14-74 7 11.9' 14.5
11-18-74 6 15.8 18.5
11-19-74 7 13.2 22.4
11-20-74 7 48.8 14.5
11-25-74 8 15.8 29.0
11-26-74 10 6.6 31.7
Average 7.6 17.4 23-3
12-02-74 8 10.6 30.4
12-03-74 7 14.5 46.2
12-04-74 7 12.1 29.0
12-05-74 6 55.4 17.2
12-06-74 6 17.2 21.1
12-09-74 ' 9 15.8 31.7
12-10-74 9 92.4 23.8
12-11-74 7 29.0 21.1
12-12-74 10 5.3 23.8
12-13-74 8 37.0 37.0
12-16-74 8 ^7.7 22.4
12-18-74 7 9-2 19.8
12-19-74 7 25.1 17.2
Average 7.6 38.4 26.2
1-03-75 6 10.6 23.£
1-06-75 9 11.9 15.8
1-07-75 7 6.6 19.8
1-08-75 7 7-9 13-5
1-09-75 7 33.0 15.3
1-10-75 8 66.0 18.5
1-13-75 8 13.2 29.0
1-14-75 10 11.9 52.8
1-15-75 8 15.8 27.7
1-16-75 7 13.2 111.5
1-17-75 7 48.8 13.2
1-20-75 6 15.8 18.5
1-22-75 8 6.6 15.8
1-23-75 7 *.6 15.8
1-24-75 8 3^.3 22.4
1-27-75 8 9.2 17.2
1-28-75 6 7-9 18.5
1-29-75 7 1.3 14.5
1-30-75 7 26.4 29.0
1-31-75 7 21. j. 26.'
7.4 18.6 20 9
193
-------
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TABLE 4il
.'U-NT l/m2-op (qal/ft2-or>) Cu Ki • r-i-T ^,+6
2 w — '. **
1--36-1
J. '•36-12
33-5
«5-3
2C-i»
33-2 J.
33-2
S15-1
S12-6
J33-15
*11-8
6-37
43-1
S-7
19-24
2U-17
23-7
30-21
12t (3.0)
...'I (4.4)
29 (.733)
i: (.329)
232 (5.8;
184 (4.6)
232 (5.8)
128 (3-21
4440 (111)
132 (3.3)
60 (1.5)
211 (5.3)
50 (2.0)
52 (1.3)
-
- —
-
-
-
-
.12 .60 .045 .03 .53
1-S* -09 .20 .10 .43
•H -08 .06 .36 .34
.7: - - .S.i
.330 5.7
•2« --4 .07 .023 .1;
.17 I.S .54 . -25
<1-0 - <1.0 -
-------
The plated area is the primary unit of production on which
the effluent limitations in Table 1 «re based. Plated area
in defined with reference to Faraday 2 Law of electrolysis
by the following equation:
JBU
100 kt ^uation 2
whcve s = arec., sq m (sq ft)
v. - cathode current efficiency.,, pcrc
I ~ current used, amperes
T = time,? hours
t = average thickness of deposit ff r,ra
k = a constant for each metal pla-ced baaed on the electro-
chemical equivalent for metal deposition, amp-hr/mm-sq m
(amp-hr/mil-sci ft) ,
The numerical product of current ar»d time (IT) is the value
that would be measured by an ampere-hour meter. Values of
the constant k based on equivalent i/«iffiht ssad the valance of
the metal deposited are shown in Table 41.
Average thickness can be approximated by averaging thickness
measurements at several points on a single plated part, to
establish the ratio of average to minimum thickness.
Minimum thickness is customarily monitored to meet the
specifications of purchasers of electroplated parts, based
on service requirements.
This equation was used in this study to determine the plated
areas per unit cime in each plating oparation when the only
available information was the current used and the average
thickness of deposit. This equation was also used as a
check on estimates of surface area plated provided by the
plants contacted.
To calculate the total plated &sr©£ on which the effluent
limitations are based for a specific plsnt? it was necessary
to sum up the area for each electroplating process line
using Equation (2) . For process lines containing two or
more electroplating operations (such &3 in copper-nickel-
chromium decorative plating^ the plated area is calculated
by Equation (2) for each plating oper&ticn in the process.
The results should be the same, since the same parts are
processed through each operation. However, if the
calculated plated area differed r^..' sach plating operation
in a single process line, the average of the calculated
plated areas for the operations was used. Th? sum of the
plated area for each process line le the total ated area
for the plant.
197
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Process Chanqor?
Process changes are not currently available for the metal
finishing industry that would lead -to greater pollution
reduction than can be achieved by the recommended effluent
limitations. Some possible process changes such as use of
noncyanide plating baths may eliminate one pollution
parameter, but do not eiirnineite all and Bi&y causi. ot-iiar
problems. They may be useful i;i some facilities for
reducing the cost of meeting the effluent limitations
recommended in this document.
Nonwater Quality Environmental Impact
As discussed in Section VIII of this report^ the principal
nonwater quality aspect of metal finishing waste treatment
is in the area of solid waste disposal. Disposal of sludges
resulting from metal removal by chemical treatment is a
current problem in many states that have a high
concentration of facilities. The problem might be partially
alleviated by disposal of drier sludge. Such added costs
for removal of water from sludge would be imposed by the
requirements for solid waste disposal and does not directly
result from the requirement for water pollution reduction.
The use of advanced technology to recover metal plating
chemicals from rinse water rather than chemical treatment
which adds to the sludge is being applied in areas where the
sludge-disposal problem is greatest. Further impetus in the
direction of recovery rather than disposal is expected to be
provided by authorities responsible for solid waste
disposal. This will have an overall beneficial effect on
water pollution because of the concurrent requirements for
water conservation for economic application of recovery
techniques.
It is estimated that many of the existing sources dis-
charging to navigable waters are already using chemical
treatment methods with a high percentage removal of metals.
This is particularly true in geographic areas where water
pollution reduction has been emphasized and the sludge-
disposal problem is most evident.
There will be no direct effect on air quality as a result of
the application of recommended technology for water
pollution reduction. Indirect effects related to increased
energy use are estimated to be modest.
Plated Area Unit of Production
198
-------
Sma.ll discrepencies in the above calculation for two or more
plating operations in the same process line might be related
to a difference in the actual current efficiencies from
those in Table 37 which are to be us«d for the calculation.
However, experience with data from several plants indicated
that the more lively cause of the diicrepancy is the
accuracy of the reported values of &va^fe,g plate thickness.
ThM use of ampere-hour on rectifiers - ..ght have value fo:
monitoring or record keeping for scsva plants In lieu of
measu
-------
TABtK 4 1 jLECTOtiCKEMICAI. EQUIVALENTS AHO tiE'-ATES
(All n»ur«> In this t»'»;« «<• b*«« hf M »-,- !>? ll
dijWUil 9.891 ^.ifedl it to. . ,! *
ld./M| tk iietocnt Htf'-» * iff
It. 05 *J
17.4 ft
10,*
24,1 An
14.3
14.S 11
S.93
9.73 C4 «,.«• , ,fr.lC«
Si.8 Cr 21 » 13
23.1
1».0 Co t,®S li»
17.7 Cu 7.30 100
8.W 3.5* 39-108
14.0 Oa
• is. 6 e«
U.6 Au
12.4
t.t ?,£3 100
U.I Xc. S.1J 56 :«»
29.4 IK
12.1
17. » I* 7.38 tvi
*.91 n I.J3 100
16.3 Ha
8.55 K«
4.27
19.0 »1 8.05 180
28.6 N 12.12
- 21.4 ».07
14.2 6.02
27.6 ?S 11. »? *0
13.85 *•*!» *0
.„».» »0
30. g KB li.OS
23.1 ».?•» *0
15,3? *.:.
»a S K.
13.4 1*
6.14 *t *•«*• i"9
12.4 T*
(.19
3.12 n ,
13,63 IB 6.62 «
7.12 3.31 I''*
13.7 lu 3.80 1UO (ACID)
••* i'J
-------
be defined as any step followed by
a rinse in the electroplating process
in which a metal is «electrodeposited
on a basis material. Electroless
plating on non-metallic materials
for the purpose of providing a
conductive surface on tha basis
material and preceding tJ 3 actual
electroplating stepp and the past
treatment steps of chroirating,
phosphating and coloring uhere an
integral part of tr,3 plating line
and stripping whers DQ^chicted in
conjunction with el a .strop I at, ing for
the purpose of stlvagirscf improperly
plated parts na^ "o
-------
in the effluent da*; to
processes before dilution by
from other processes favarag® fv?,, ?C
sequential daysj .
Determination of Finished Area/Hr/Qperation
•*•"'"• ..... "" m*'**"-*™"-™*-*-****"*** immi IB«^»^»»— •» J»«KII'I IM;I i na^n»»K*^«» 1,1 1. ili*limB.HTH^i»-»iift nslr. i ~- ja» JflBm»B«j j»
The area for each line will be determined ttom
on the (1) average amperes used,, (2) th^ sequence of plating
operations, and (3) the average tMcicn^s in mil o'~ ,-*< h
type of plate. If complete datd on thickness is? la.-kii-g,
the following value will be usedi
Copper 0,,3 ,'RlI
Nickel 0.3 mil
Zinc Q»3 mil
Chromium 0.015 ri'i 1
Where chroma ting follows plating, the area will be the same
an that of tho primary plating operation. The equation:
S = El T/ 100 kt
is then used to calculate plated area.'\ir/cper«<-io»« In a
line with several sequential operations, it is likely that
the calculated plated areas i',v e^ch :\I ;-.ting operation will
vary from each other although the act u '. snea plated should
be the same. The difference in calculatec- areas may vary by
a factor of two or three. When applying t.'bs qt^idelines, the
figure used for area plated should be th ,: at3 bhmetic average
of the calculated pi'\' -^ areas.
Where actual amperes **.& not knowny ,.,' ,-, ., c- equal to 2/3
the installed capacity for the line s-* .-'Jd be u&ed, »-'
information on amperes is completely lackincf for a li>e
water use is available,, i.be sq m/hr may be ileteiisstned by
Sq m/hr -- t£..hr.,jised__?u
(?00 1 /?<--. rn) (no. of
Sq ft/ht - S^lifli, .,!«§S3_2D_£iJS
(5 gal/or) (no. of opera "icr'«^
Once the plated area h--^ ' •:•,.•;* measured tiie t^f'.cJ'- lines can be
used to det^ttfurva tr*e total -v. lowable disr.hara-*: of waste
water constituents fzor? i.he plant Every time the surface
is rinsed, following SOTO ^v>aratLot! in the process; line, it
is assumed that more waste water ia produced, and a greater
quantity of -,'aste wait..-: constit.ueuto may be disefa
-------
therefore incorporated into the rinse following the first
plating operation for purposes of calculating the allowable
amount of waste water constituents discharged. The total
allowable discharge in g/day will b«:
(lO*) (sq m plated/hr) (effluent ilmitatior in mg/sq m)
(No. of oper.) (hr/day)
The total allowable discharge in ib/dey It s
(sq ft plated/hr)(effluent limitation
in Ib/million sq ft (No. of oper.J fhr/day)
These relations hold for each effluent limitations guideline
value listed in Table 1. The relations apply to each
process line or part of a process line if the area plated/hr
changes in the line.
The actual discharge from the plant is the product of the
volume of effluent/hr and the concentration of waste water
constituent in the effluent.
Thus,
q/day » (liters/hr) (mg/1) (10-«J Chr/dayJ
Ib/day = (8.33 x 10-*) (gal/hr) (ng/1) (hr/day)
Figure 30 represents such a situation The line processes
15 sq m/hr. The volume of effluent is 3,000 1/hr. The
plant operates 10 hr/day. There are three operations in
this line, chromium electroplating* etching, and anodizing.
The discharger is allowed: (10-*) (sq m/hr) Jeffluent
limitation in mg/sq m-operation)(number of operation)
(hr/day) = kg/day pollutant
The actual discharge is the product of the volume of efflu-
ent/hr and the concentration of waste water constituent.
Kg/day = (liters/hr) (mg/1) (10-»J ^hr/dayj
Thus, in this example the dischargai .s allowed to discharge
the following amount of chromium fox chromium electroplate
(10-*) (15 sq m/hr) (80 mg/sq m-operation) {1 operatl ,n)
(10 hr/day) = 1.2 x 10-* kg/day
203
-------
for anodizing
(10-6) (15) (t»5) (1) (10) = 6.75 x 10-' kg/day
for etching
(10-») (15) (60) (1) (10) = 9.0 x 10-3 kg/day
In total he may discharge the sum of the three:
2.78 x 10~z kg/day of chromium total.
He may discharge one-tenth of that or
2.78 x 10~1 kg/day of Cr+6
If the final effluent concentration is equal to 0.56 rn.g/1
for CrT and 0.06 mg/1 for Cr+6, the actual discharge will be
(3000 l/hr)(.56 mg/1)(10~6)
(10 hr/day) = 1.68 x 10~2) kg/day of CrT
and
(3000 l/hr)(.06 mg/1)(10-6)
(10 hr/day) = 1.8 x 10-1 kg/day of Cr+6
Thus, the plant is meeting the guidelines.
204
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Alkaline
Clean
Rin&e
Acid
Pickling
I
Rinse
f
Chromium.
Plate
Rinse
Etch
Rinse
Anodi ze
Rinse
Dry
205
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BEST AVAILABLE TECHNOLOGY BCCaOMICALLY
ACHIEVABLE.... Q^lpB^Sf *~_AJfo._.LXMI5?ATIOHS
limitations
„ are o specify r,i;e
attainable through
ch ecoomic
j&troductloja
The effluent
1983 „ are to
attainable through the applies .^
technology economic-"" * i r:hlav&lJ
based on the very !.:-ast convr^s"..
employed by a specific point ^ , r.
category and/or suhrav sgcry cr !".
transferable from one lr,5r:<5-ir" •;
specific finding must be r.ad
control measures and prec-dces t%, ^
pollutants, taking into acr.ou:" w,~
tion.
Consideration must also tj-s given to
(a) the age of the
involved
:•*,< achieved July 1,
'f fluent reduction
of -cLe
best available
*is technology can be
d treatment technology
uilthin the industry
:iology that is readily
,; &£3 tc another. A
r.o the availability of
the discharge of
of such elimina-
facilities
(b)
(c)
(d)
(e)
the process
the ens neevring aep«£Ct & cC ria application
of var* ous types of
process changes
.';v.
Oi
cost of achieving -che
resulting from -the t
reduction
(f) non water qua lit./ etWirc.'^
(including enerc,y requi.'.'.e-
The best available tecL^olog:/ ^.,o:.;
assesses the availaoilicy .In .^ll
controls as well as tirae concrol
techniques employed ar the enfi cf e
A further consideration is the dv&iLl.
control technoloqy at tha pilot plar
levels, which have fieKori^trtt*
performances and economic viability ,•-
reasonably justify
lnve&tir.g
Impact
^wlly achievable also
cases of in-process
.r aa
-------
available technology economically achievable is the hiyLast
degree of control technology that has been achieved or has
been demonstrated to be capable of being designed for plant
scale operation up to and including no discharge of
pollutants. Although economic factors are considered, 1.he
co.ts for this level of control are intended to be top-of-
the-lirsc of current technology siibject to limitations
imposed by economic and engineering feasibility. However,
best available technology economically achievable may be
characterized by some technical risk with respect to
performance and with respect to certainty of costs and thus
may necessitate some industrially sponsored work prior to
its application.
Industry category and Subcat^orx Cgve^ejl
The pertinent industry category is the metal finishing
segment of the electroplating industry divided into
Subcategories (1) and (2) as previously discussed in Section
IV,
Identification,of Best Available Economically Achievable
Subcategory (1)
The best available technology economically achievable is the
use of in-process and end-of-process control and treatment
to achieve no discharge of pollutants. By the use of in-
process controls to reduce the volume of waste water, it
becomes economical to use end-of-process treatment designed
to recover water and reuse the water within the plant thus
avoiding any discharge of effluent :-.o navigable w#Aers.
Solid constituents in the wastewa*. Jt, are disposed of to
landfill or otherwise. A line in Plant J.u-21 plating Oliver
has eliminated liquid effluent discharge for several mcmtha,
and continued demonstration of this operation will support
the fact that technology is available to achieve this.
Plant 11-22, a chromium electroplater studied in £hase I, Is
using a system designed to eliminate liquid effluent by
subjecting effluent from the clarjfier of the chemical
treatment plant to reverse osmosis and recycJ ing water to
process. The concentrate from the reverse osmosis unxt i&
evaporated to dryness. It is expected that other methods
will be developed dux ,.ag the next five years to avoid
discharge of effluent to navigable waters and thus achieve
no discharge of pollutants in an economical manner. While
the above examples of zero discharge are being achieved in
conjunction with electroplating operations, the similarity
of operations in processes in Subcategory (I) to those in
the electroplating processes, and the similarity of the
208
-------
was.-e waters, suggests that techniques of obtaining zero
discharge for electroplatiaq processes are equally
applicable to the other processes in Suboategory (1) .
Subcategory (2) and
The best available technology economically achievable is the
use of in-process and end- of -process contr© and treatment
to achieve no discharge of pollutants Processes in
Subc<.teqory (2) are distinguished from fchoae in Subcategory
(1) only by water use. The operations in the two
subcategorlos are very similar, the types of waste waters
obtained are essentially the same, and the types of waste
treatments that are applicable are the same. The evidence
that zero discharge is being and will be attained for
processes in Subcategory (1) is equally applicable to
processes in Sutcategory (2) .
Rationale for Selegt^op of Best Aval lab. 1 8
Technology Economically Achievable
Age of Equipment and Facilities
Replacement of older equipment and facilities will permit
i-he installation of modern multitank countercurrent rinsing
systems after each operation in each process line with
conservation of water use for rinaing. The use of reclaim
and recovery systems after each finishing operation should
be possible. Use of inprocess controls to the maximum
extent will reduc< the volume of effluent -co the point that
recovery and reuse of water is economically feasible.
Process Employed
The application of the technology for end-of -process
recovery and reuse of water to the maximum extent possible
is not dependent on any significant change in the processes
now used. Most water recovery technology can produce a
higher quality of water than normally available from public
or private water supplies. High purity water for the final
rinse after metal finishing operations is desirable to
improve the quality of the product.
Engineering Aspects of the Application of Various Types of
Control ^echniques
Many slants are successfully using evaporative recovery
systems after one or more plating operations with a net
savings compared to chemical treatment. Evaporative systems
are in current use after copper, nickel, chromi* n, zinc,
209
-------
brass, tin, lead, and gold plating operations. Some pie fits
have succeeded in using recovery systems after all plating
operations in their facility. The engineering feasibility
of in-process controls for recovery of chemicals and reusfe
of water are sufficiently well established. Sufficient
operational use has been accumulated to reduce the technical
risk w*th regard to performance arid any uncertainty with
respect to costs.
The technical feasibility of end-of-process water recovery
systems has been established by extensive development of tint
recovery of pure water in many related Industrial processes.
Although some uncertainty may remain concerning the overall
costs when applied to metal finishing wast* waters, such
uncertainty primarily relates to the volume of water that
must be processed for recycling and reuse. Th© fact th&t
the technology as applied to the electroplating industry has
progressed beyond the pilot plant stage and has been
designed and is being built for fullscale operational use
indicates that the technology is available and probably
economical. These systems are equally applicable to
processes other than electroplating due to the similarity in
the waste water produced.
Process Changes
Application of the technology is net dependent on any
process changes. However, process changes and improvements
are anticipated to be a natural conscience of meeting the
effluent limitations in the most economic mannei1*
Nonwater Quality Environmental Impact
Application of technology to achle^ j no diacterg-e of
pollutants to navigable waters by July 1, 1983, will have
little impact on the solid waste disposal problem with
regard to metal removal as sludge beyoad that envisioned to
meet effluent limitations recommended for July 1;, 1977. The
volume of soluble salts will be substantially increased.
In general, it is anticipated that the technology will be
applied in a manner such that no discharge of effluent to
surface waters occurs. Thus, metal oxide sludges would be
disposed of on land with suitable precautions. The soluble
salts which are largely innocuous should be suitable for
disposal in salt water. Because these salts are not large
in amount and can be dewatered to dry solids (by
incineration if necessary) very little additional impact, on
the solid waste disposal problem is anticipated.
210
-------
No impact on air pollution is expected as the result of
achieving no discharge of pollutants to surface water. The
available technology creates no air pollutants.
B *6 fflLdMLABSiSffcffl of
The recommended effluent limitations to I a achieved by July
1, ,983, for existing sources based on -c '•*« application of
Best Available Technology Economically Achievable is no
dis^harq*.' of pollutants to navigable waters for
Subca -egories (1) r (2) and (3).
Achieving the effluent limitations of no discharge of
pollutants by achieving no discharge of effluent to surfaje
waters is the most direct method that eliminates the need
for sampling and analysis. If th@re is other effluent
discharge to surface waters from the plant not associated
with metal finishing, a determination is required that no
waste waters originating from met&I finishing processes are
admixed with this other plant effluent.
211
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SECTION XI
SOURCE PERFORMANCE STANDARDS
Introduction
The standards of performance which nmat be achieved by new
sources are to correspond to the degree of effluent
reduction attainable through the application of higher
levels of pollution control than those identified as best
avc,:.A.able -sctoG.,ogy economically achievable for existing
sources.. .'he added consideration for new sources is the
degree c/; ' •-:fl;eat redaction attainable through the use of
improver production processes and/or treatment techniques.
The term "new sources" Is defined by the Act to mean "any
source, the construction of ^hich is commenced after
publication of proposed regulations prescribing a standard
of performance."
New source performance stane^rda ar« based on the best in-
plant and end—of-process technology identified as best
available technology economically achievable for existing
sources. Additionel considerations applicable to new source
performance standards take into account techniques for
reducing the level of effluent by changing the production
process itself or adopting alternative processes, operating
methods, or other alternatives. The end result will be the
identification of effluent standards which reflect levels of
control achievable through the use of improved production
processes (as w.-ll as control technology), rather than
prescribing a pa~-.icular type of process or technology which
must be employed,, A further determination must be made as
to whether a standard permitting no discharge of pollutants
is practicable.
Consideration must also be given tos
(a) The type of process employed and process
changes
fb) operating methods
(c) batch as opposed to continuous operations
"-•u uge of alternative raw materials and mixes
of raw materials
(e) use of dry rather than wet processes
(including substitution of recoverable
solvents for
213
-------
(f) r covery of pollutants as by-products.
Standards of performance for new sources are based on
applicable technology and related effluent limitations
coveri'.q discharges directly into waterways.
consideration iust also be given to the fact that Standards
of Performer - for Net-- Sources could require compliance
about three ?^ra sooner than the effluent limitations to be
achieved by eAi.itinq sources by July 1, 1977. However, new
sources should achieve the same effluent limitations as
existir-a sources by July 1, 1983 .
Industry Category and Subcategory Covered
The pertinent industry category is the metal finishing
industry divided into Subcategories (1) and (2) , as
previously discussed in Section IV.
Identification Qf control and Treatment
Ifichnology Applisablg to,
.
Standards and Pretreatment 3tan.da.rde of
New Soytrcei-t
Subcategory (1)
The technology previously identified in Section IX under
Subcategory (1) as best practicable control technology
currently available is al 30 applicable to new source
performance standards. IN addition, a new source can
utilize the best practice in multitank rinsing after each
operation in the process as required to meet the effluent
limitations at the time of construction. Thus, with no
practical restrictions on rinse water conservation after
each operation by multitask rinsing, there are fewer
restrictions on the use of advanced techniques for recovery
of bath chemicals and reduction of wastewater from rinsing
after pretreatment and post treatment. Maximum use of
combinations of evaporative, reverse osmosis, and ion
exchange systems for in-process control currently available
should be investigated. A small end~of-pipe chemical
treatment system can be used to treat spills, concentrated
solution dumps,, and any other water flows not economically
amenable to in-process water and chemical recovery.
The net res a of the improvements cited should be a
reduction in Baiter use as compared to that considered
achievable for best practicable control technology currently
available. This reduction should result in a lowe^
214
-------
discharge of waste water constituents. Although methods are
beinq developed that may make possible a further reduction
in the concentration of constituents and a reduction in the
discharge of waste water constituents in chemically treated
effluents, present technology Is capaiale only of achieving
the concentrations listed in Table 39 by exemplary chemical
treatment. It would be anticipated that some plants now
operating, due to having been designed recently to minimize
water use or because of other favorable circumstances such
as adequate space to make modifications«. are attaining a
water use well below 120 1/sq la/operation. Table 37 shows
12 lines involving processes in Subca^agory fl) that achieve
a water use of less than H5 1/sq m/op©ration. These are
found in Plants 33-23, 33-35, 20-22, 20-23. It is estimated
that a new source can achieve a water use of U5 1/sq
m/operation for processes in Subcategory (1) by use of the
technology described above for reducing water use,
Subcategory (2)
The technology previously identified in Section IX as best
practicable control technology currently available for
processes in Subcategory (2) Is also applicable to new
sources. In addition, a new source can «aa best rinsing
practice and advanced techniques for recovery of bath
chemicals and reduction of rinse water a*3 described under
Subcategory (1) above. The similarity of operations in
processes of Subcategory (2) to the operations of processes
in Subcategory (1) , and the similarity in waste water
compositions and treatment methods can be cited to indicate
that the same methods of reducing water use are applicable
to Subcategory (2) as are applicable to Subcategory (1) .
The application of the same techniques to the two
Subcategories should reduce the waiter proportionately so
that if a reduction of 90 1/sq m/optration to U5 1/sq
m/operation can be achieved by a new source with a
Subcategory (1) process, a reduction from 80 1/sq
m/operation for a Subcategory C2J process in a present
source to 40 1/sq m/operation for the aam© process in a new
source should be achievable. Th«r^fosr«s it is estimated
that new sources can achieve a w&fcer use of HO 1/sq
m/operation for Subcategory {2} processes. Two lines in
Table 34 involving Subcategory (2f processes have a water
use of less than MO 1/sq m/operatioru These lines are in
Plants 6-3&, 20-25, 23-8.
Subcategory (3)
The technology previously identified in Section IX as best
practicable control technology currently avaf .able for
215
-------
processes in Subcategory $2) ia also applicable to new
sources. In addition, a new source can use best rinsing
practice and advanced techniques for recoverv of bath
chemicals and reduction of rinse water as described under
Subcategory (1) above. The similarity of operations in
processes of Subcategory (2) to the operations of processes
in Subcategory (1), and the similarity in waste water
compositions ai-d treatment methods can be cited to indicate
that the same methods of reducing water uss are : [-r »,icafole
to Subcategorv (2) as are applicable to St^ntegorv (1).
The application of the same technique-*- to t! a two
Subcategories should reduce the water proportionately so
that if a reduction of 90 1/sq m/operation to 45 1/sq
m/operation can be achieved by a new source with a
Subcategory (1) process, a reduction from 120 1/sq
m/operation for a Subcategory (2) process in a present
source to 60 1/sq m/operation for the same process in a new
source should be achievable. Therefore, it is estimated
that new sources can achieve a water ue@ of 60 1/sq
m/operation for Subcategory (2) procaaees. Two lines in
Table 34 involving Subcategory (2) processes have a water
use of less than 60 1/sq m/operation. These lines are in
Plants 4-8, 30-9, 9-2, 4-9.
Rationale for Selection of Control and
Treatment Technology Applicable to New
Source Performance Standards
The rationale for the selection of the above technology is
applicable to new sources discharging to navigable waters is
as follows:
(1) In contrast to an existing source, a new
source has complete freedom to choose the
most advantageous equipment and facility
design to maximize water conservation by
use of as many multitank rinsing operations
as necessary. This, in turn, allows for
economic use of in-process controls for
chemical and water recovery and reuse.
(2) in contrast to an existing source which may
have 2c present a large capital investment
in was'-e treatment facilities to meet
effluent limitations by July 1, 1977, * new
source has complete freedom in the selection
the design of new waste treatment facilities.
(3) In contrast to an existing source, a new
216
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source has freedom of choice with regard to
geographic location*
Standards of Performance Apg^JLca|?l^ .to
The recommended St s.ndards of Perfosrffl&nc® t- b® achieved by
new sources discharging to navig*bl« .atera waa shown
previously in Tc.ble 2 of Section II,
The quantitative values for the SO-da^ .average standard for
eaeli p^'-weter in mg/sq K -J'.b*-.. 5o 0*3 ft) is based on a
nomin- 1 water use one-half as l&/gc && tlrioae used to develop
1977 guidelines combined with tits concestrrations achievable
by chemir.al tre&w.-inc as previously shown in Table 39 of
Section IX. For examp^, G.5 asg/* for copper,, nickel, total
chromium, zinc, and total cyanide? 0,05 Rig /I for hexavalent
chromium and .,075 mg/l for oscidlsable cyant'ie, 20 mg/1 fjr
suspended solids, when combined with &$i effluent factor of
45 1/sq m are the basis for the 30*»d&y 8V
-------
Guidelines for the Application of
New Source Performance Standards
The recommended guidelines tor the application of standards
of performance for new sources discharging to navigable
waters are the same as those in Section IX relating to
existing sources based on use of the best practicable
control technology currently available and those in Section
X based on use of best available technology economically
achievable.
218
-------
SECTION XII
ACKNOWLEDGEMENTS
The Environmental Protection Agency was aided in the
preparation of this Development Document by Battelle
Columbus Laboratories under the direction of William H.
Safranek, Luther Vaaler, John Gurklis and Carl Layer on
Battelle*s staff made significant eontributions.
Kit R. Krickenberger served as project officer on this
study. Allen Cywin^ Director, Effluent Guidelines Division,
Ernst P. Hall, Deputy Director, Effluent Guidelines Division
and Walter J. Hunt, Chief, Effluent Guidelines Development
Branch, offered guidance and suggestions during this
program.
The members of the working group/steering committee who
coordinated the internal EPA review are:
Walter J. Hunt, Effluent Guidelines Division
Kit R. Krickenberger, Effluent Guidelines Division
Devereaux Barnes, Effluent Guidelines Division
Murray Strier, Office of Permit Programs
John Ciancia, NERC, Cincinnati, (Edison)
Alan Eckert, office of General Counsel
James Kamihachi, Office of Planning and Evaluation
Acknowledgement and appreciation is also given to Nancy
Zrubek, Kaye Starr, and Alice Thompson of the Effluent
Guidelines Division for their effort in the typing of drafts
and necessary revisions, and the final preparation of this
document.
Appreciation is extended to the following organizations
associated with the electroplating industry:
American Electroplaters0 Society, East Orange,
New Jersey
Aqua-Chem, Milwaukee, Wisconsin
Artisan Industries, Inc., Waltham, Massachusetts
E.I. duPont de Nemours and Co.g Wilmington,
Delaware
Heil Process Equipment Corporation, Cleveland,
Ohio
Haviland Products company, Grand Rapids, Michigan
Industrial Filter and Pump Manufacturing Co ,
Cicero, Illinois
219
-------
Institute of Printed Circuits, Chicago, Illinois
Ionic International, Incorporated, Detroit,
Michigan
Lancy Laboratories, Zelienople, Pennsylvania
M & T Chemicals, Incorporated, Matawan, New Jersey
Electroplating Suppliers* Association, Incorporated,
Birmingham, Michigan
National Association of Metal Finishers, Upper
Montclair, New Jersey
Osmonics, Incorporated, Minneapolis, Minnesota
Oxy Electroplating Corporation, Warren, Michigan
The Permutit Company, Paramus, New Jersey
Pfaudler Sybron Corporation, Rochester, New York
220
-------
SECTION XIII
References
(1) Table 3, pg 36, "1967 Census of Manufacturers",
U.S. Bureau of Commerce.
m "Where to Buy Metal Finishing Services", Modern
Metals, 28 (6), p. 71 (July, 1972).
(3) Institute of Printed Circuits* Chicago, Illinois.
(4) jjgfrfl Finishing, p. 42, March 1972.
(5) Sidney B. Levinson, J. Paint Technology, 44 (569) 49.
(6) J. Schrantz, industrial Finishing, 20-29, October, 1972.
(7) Table 3, p. 7-45, "1967 Census of Manufacturers",
U.S. Bureau of commerce.
(8) Modern Electroplating, Edited by P. A. Lowenheim,
2nd Ed., John Wiley ind Sons (1963), Chap. 7,
pp 154-205.
(9) M»+*l FMpfghincr Guidebook and Directory, Metals
Pstics Publications, Inc., 1973.
(10)
and Plastics Publications, Inc
Metals
i i.
and Plastics Publications, Xnc. 1972.
(11) Modern fi jflcfrr opiating— * P 69
(12) Mo^£D_£l££^rQplflUngy P 708.
^^ Q
Ed. , Van Nostrand Rheinhold, 3rd Ed., 1971, p
(1«») schrantz, J. Industrial Finishing, April, 1973,
pp 37-40.
(15) Stiller, Frank P.., Metals Finishing guidebook and
Directory, Metals and Plastics Publications, Inc.,
pp 548-553, 1972.
(16) George, D.J., Walton, C.J., and Zelly, W.G.,
pahr|c3tion and Finishing. Vol 3, Am Soc for Metals,
1967, pp 387-622.
221
-------
(17J Innesf W.P. , Metal Finisaing Gu4debook and Directory,
1972, p 554. ~~~
(^8) Pocock, Walter, E. Metal Finishing Guidebook and
A£
-------
(33) Environmental Sciences. Inc., "Ultimate Disposal
of Liquid Wastes by Chemical Fixation".
(34) Dodge, B.F., and Zabban. W. , "Disposal of *ljtinj
* ' Room wastes. III. cyanide Wastes" Treatment with
Hypochlorites and Removal of Cyanates", Plating
18 (6), 561-586 (June, 1951).
(35) Dodge, B.F., and Zabban, W. , "Disposal of
( } Room wastes. III. Cyanide wastes: Treatment
Hvoochlorites and Removal of Cyanates. Addendum ,
Plating, 39 (4) , 385 (April, 1952) .
(36) Dodge, B.F., and Zabban. W. . "Disposal of Plating
C ' Room wastes. IV. Batch Volatilization of Hydrogen
Cyanide From Aqueous Solutions of Cyanides",
Plating, 12 (10), 1133-1139 (October, 1952).
(37) Dodge, B.F., and Zabban, W. , "Disposal of Plating
( ' Room Wastes. IV. Batch Volatilization of Hydrogen
Cvanide From Aqueous Solutions of Cyanides.
continuation", Plating, 32 (11). 1235-1244 (November,
1952).
(38) "Overflow", Chemical Week, HI (24), 47 (December,
1972),
(391 ovler, R.W. , Disposal of Waste Cyanides by Electro-
( * ?yt!c Oxidation"? Plating, 16 (4), 341-342 (April,
1949) .
(UO) Kurz, H. , and Weber, W. , "Electrolytic Cyanide
Dedication by the CYNOX Process" , Galvanotechnik
and Oberflaechenschutz, 3, 92-97 (1962).
(41) "Electrolysis speeds Up Waste Treatment", Environmental
Science and Technology", 4 (3), 201 (March, 1970).
(42) Thiele, H., "Detoxification of cyanide-Containing
waste Water by Catalytic oxidation and Adsorption
Process", Fortschritte wasserchemie Ihrer
Grenzgebiete, 9, 109-120 (1968): CA, 70, 4054
(1969) .
rim Bucksteeq, W. , "Decomposition of Cyanide Wastes by
( } Se?hods of Catalytic 6xidation Absorption", Proceedings
of the 21st Industrial Waste Conference, P«rdue
University Engineering Extension series, 688-59b
(1966) .
223
-------
(44) "Destroy Free Cyanide in Compact, Continuous Unit",
Calgon Corporation Advertisemente Finisher's
Management, 19 (2), 14 (February,, 1973),
(45) sondak, N. E., and Dodge, 3. F., W1h« QKidation
of Cyanide Bearing Plating Pastes by Ozone.
Part I", Plating, US (2) 173-180 (February,
1961).
(46) Sondak, N.E., and Dodge, B.F., "The Oxidation
of Cyanide Bearing Plating Wastes by Ozone.
Part II", Plating, J8 (3), 280-284 (March,
1961) .
(47) Rice, Rip G., letter from Effluent Discharge
Effects Committae to Mr. Alien Cvwin? Effluent
Guidelines civiaion, July 9, 1973.
(48) "Cyanide Wastes Might Be Destroyed at One-Tenth
the Conventional Cost", Chemical Engineering,
79 (29), 20 (December 25, 1972).
(49) Manufacturers' Literature, DMP Corporation,
Charlotte, North Carolina (1973*.
(50) Ible, N., and Frei, A.M., "Electrolytic Reduction
of Chrome in Waste water", Galvanotechnik and
Oberflaechenschutz, 5 (6), 117-122 (1964).
(51) schulze, G., "Electrochemical Reduction of
Chromic Acid-Containing Wast® Water*1, Galvanotechnik,
58 (7), 475-480 (1967): CA, 6jfr 15876t C1968).
(52) Anderson, J.P., and Weiss, Charles c%, "Methods
for Precipitation of Heavy Metal 3«lfid
------- OCR error (C:\Conversion\JobRoot\000005YR\tiff\2000LWNZ.tif): Saving image to "C:\Conversion\JobRoot\000005YR\tiff\2000LWNZ.T$F.T$F" failed.
-------
(68) Campbell, R.J., and Eimnerman, O.K. r "Freezing and
Recycling of Plating Rinse Water", Industrial water
Engineering, 9 (4), 38-39 (June/July, 1972).
(69) A.J. Avila, H.A., Sauer, T.J. Miller, and R.E.
Jaeger, Plating, 60 239 (1973).
(70) Dvorin, R., "Dialysis for Solution Treatment in
the Metal Finishing Industry", Metal Finishing,
57 (4), 52-54 4 62 (April, 1959).
(71) Ciancia, John, Plating 60, 1037 (1973).
(72) communication with P. Peter Kovatia, Executive
Director, National Association of Metal Finishers.
(73) "An Investigation of Techniques for Removal of
Chromium From Electroplating Wastes", Battelle,
Columbus Laboratories Report on Program No.
12010 EIE to the Environmental Protection Agency
and Metal Finishers1 Foundation (March, 1971) .
(74) Grieves, R., et al., "Dissolved-Air Ion Flotation
of Industrial Wastes. Hexavalent Chromium",
Proc. 23rd Industrial Waste Conference, Purdue,
University, 1968, p 154.
(75) Surfleet, B., and crowle, V.A., "Quantitative
Recovery of Metals from Dilure Solutions",
Transactions of the Institute of Metal Finishing,
50, 227 (1972).
(76) Bennion, Douglas N., and Newman, John, "Electro-
chemical Removal of Copper Ions from Very Dilute
Solutions", Journal of Applied Electrochemistry,
2, 113-122 (1972).
(77) Carlson, G.A., and Estep, E.E., "Porous Cathode
Cell for Metals Removal from Aqueous Solutions",
from Electrochemical Contributions to Environmental
Protection, a symposium volume published by the
Electrochemical Society, Princeton, New Jersey,
p 159.
(78) "Water Quality Criteria 1972," National Academy of
Sciences and National Academy of Engineering for the
Environmental Protection Agency, Washington, D.C.
1972 (U.S. Govt. Printing Office Stock No. 5501-00520)
226
-------
SECTION XIV
GLOSSARY
Acid Dip
An acidic solution for activating the workpiece surface
prior to electroplating in an acidic solution, especially
after the workpiece has been processed in an alkaline
solution.
Alkaline Cleaning
Removal of grease or other foreign material from a surface
by means of alkaline solutions.
Anodizing
The production of a protective oxide film on aluminum or
other light metals by passing a high voltage electric
current through a bath in which the metal is suspended. The
metal serves as the anode. The bath usually contains
sulfuric, chromic, or oxalic acid.
Automatic Plating
(1) full - plating in which the cathodes are automatically
conveyed through successive cleaning and plating tanks. (2)
semi - plating in which the cathodes are conveyed
automatically through only one plating tank.
garrel Plating
Electroplating of workpieces in barrels (bulk).
Basis Metal or Material
That substance of which the workpieces are made and that
receives the electroplate and the treatments in preparation
for plating.
Batch Treatment
227
-------
Treatment of electroplating rinse waters collected in
adjacent tanks. Water is not allowed to leave the tank till
treatment is completed.
Best Available TechnQloqY_gconomicallv Achievable
Level of technology applicable to effluent limitations to be
achieved by July I, 1983, for industrial discharges to
surface waters as defined by Section 301 (b) (2) (A) of the
Act.
Level of technology applicable to effluent limitations to be
achieved by July 1, 1977, for industrial discharges to
surface waters as defined by Section 301 (b) (1) (A) of the
Act.
Bright Qj.g
A solution used to produce a bright surface on a metal.
Captive Operation
Electroplating facility owned and operated by the same
organization that manufacturers the workplaces.
Process utilizing an addition agent that leads to the
formation of a bright plate, or that improves the brightness
of the deposit.
Chemical Etch ^ng
To dissolve a part of the surface of a metal or all of the
metal laminated to a base.
Chemical Metal Coloring
The production of desired colors on metal surfaces by
appropriate chemical or electrochemical action.
228
-------
The improvement in surface smoothness of a metal by simple
immersion in a suitable solution.
Chromati^jng
To treat or impregnate with a chromate or dichromate
especially with potassium dichromate.
Chrome-Pickle Process
Forming a corrosion^resistant oxide film on the surface of
magnesium-base metals by immersion in a bath of an alkali
bichromate.
cosed-Loop Evaporation
A system used for the recovery of chemicals and water from a
plating line. An evaporator concentrates flow from the
rinse water holding tank. The concentrated rinse solution
is returned to the plating bath, and distilled water is
returned to the final rinse tank. The system is designed
for recovering 100 percent of the chemicals, normally lost
in d ragout, for reuse in the plating process.
Continuous Treatment
Chemical waste treatment operating uninterruptedly as
opposed to bath treatment; sometimes referred to as flow
through treatment.
Conversion Coatipq
A coating produced by chemical or electrochemical treatment
of a metallic surface that gives a superficial layer
containing a compound of the metal, for example, chromate
coatings on zinc and cadmium, oxide coatings on steel.
Deoxidizing
The removal of an oxide film from an alloy such as aluminum
oxide.
Descaling
229
-------
The process of removing scale or metallic oxide from
metallic surfaces.
De s mutt ing
The removal of smut, generally by chemical action,
Draqin
The water or solution that adheres to the objects removed
from a bath,
Draqout
The solution that adheres to the objects removed from a
bath, more preciously defined as that solution which is
carried past the edge of the tank,
Abbreviation for ethylfnediamine-tetr$*cetic acid,,
Effluent
The waste water discharged from a point source to navigable
waters.
Electrobrighten^ng
Electrolytic brightening (electropolishing) produces smooth
and bright surfaces by electrochemical action similar to
those that result from chemical brightening.
Electrochemical Mach|,nin^ (ff9M|
A machining process whereby the part to be machined is made
the anode and a shaped cathode is maintained in elope
proximity to the work. Electrolyte is pumped between the
electrodes and a potential applied with the result that
metal is rapidly dissolved from the work in a selective
manner and the shape produced on the work complements that
of the cathode,
230
-------
Electrodialvsis
Membrane dialysis under the influence of direct current
electricity.
Electroless Plating
Deposition of a metallic coating by a controlled chemical
reduction that is catalyzed by the metal or alloy being
deposited.
fflectropainting
A coating process in which the coating is formed on the
workpiece by making it anodic or cathodic in a bath that is
generally an aqueous emulsion of the coating material.
The electrodeposition of an adherent metallic coating upon
the basis metal or material for the purpose of securing a
surface with properties or dimensions different from those
of the basis metal or material.
Electroplating Process
An electroplating process includes a succession of
operations starting with cleaning in alkaline solutions,
acid dipping to neutralize or acidify the wet surface of the
parts, followed by electroplating, rinsing to remove the
processing solution from the workpiece, and drying.
Electrolytic corrosion process that increases the percentage
of specular reflectance from a metallic surface.
Electrostatic Precipitation
Use of an electrostatic field for precipitating or rapidly
removing solid or liquid particles from a gas in which the
particles are carried in suspension.
Heavy Metals
231
-------
Metals which can be precipitated by hydrogen sulfide in acid
solution, e.g., lead, silver, gold, mercury, bismuth,
copper, nickel, iron, chromium, sine, cadmium, and tin.
Hot Dipping
A method of coating one metal with another to provide a
protective film.
Hydrogen, Embr|,ttleme nt
Embrittlement of a metal or alloy caused by absorption of
hydrogen during a pickling, cleaning, or plating process.
Immersion Plate
A metallic deposit produced by a displacement reaction in
which one metal displaces another from solution, for
example:
Fe + Cu++ Cu * Fe++
Independent
Job shop or contract shop in which electroplating is done on
workpieces owned by the customer.
Integrated chemiqal Treatment
A waste treatment method in which a chemical rinse tank is
inserted in the plating line between the process tank and
the water rinse tank. The chemical rinse solution is
continuously circulated through the tank and removes the
dragout while reacting chemicals with it.
Ion-Flotation Technique
Treatment for electroplating rinse waters (containing
chromium and cyanide) in which ions are separated from
solutions by flotation.
Iridite Dip Process
232
-------
Dipping process for zinc or zinc coated objects that
deposits an adherent protective film that is a chrome gel,
chrome oxide or hydrated chrome oxide compound.
Phosphatizing
Process of forming rust- resistant coating on iron or steel
by immersing in a hot solution of acid manganese, iron, or
zinc phosphate.
An acid solution us«d to r«mov« oxides or other compounds
related to the basis metal from its surface of • metal by
chemical or electrochemical action.
Pickling
The removal of oxides or other compounds related to the
basis metal from its surface by immersion in a pickle.
Point Source
A single source of water discharge such as an individual
plant.
precious petals
Gold, Silver, Platinum, etc.
Electroplating of workpieces on racks.
Reverse osmosis
A recovery process in which the more concentrated solution
is put under a pressure greater than the osmotic pressure to
drive water across the membrane to the dilute stream while
leaving behind the dissolved salts.
Rochell salt
233
-------
Sodium potassium tartrate: KNaCUH4O6 . 4H20.
Shot Peening
Dry abrasive cleaning of metal surfaces by impacting the
surfaces with high velocity steel shot.
Sludgy
Residue in the clarifier of a chemical waste treatment
process.
Strike
nnAAi 7 a thin coafcing of metal (usually less than
0.0001 inch in thickness) to be followed by other coatings.
(2) noun - a solution used to deposit a strike. (3) verb
- a plate for a short time, usually at a high initial
current density.
Stripping
Removal of an electrodeposit by a chemical agent or reversed
electrodeposition.
Workpiece
The item to be electroplated.
234
-------
to
en
MULTIPLY (ENGLISH UNITS)
English Unit
Abbreviation
Conversion Table
by
Conversion
TO OBTAIN (METRIC UNITS)
Abbreviation Metric 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
ga 1 Ion/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square inch (gauge)
square feet
square inches
tons (short)
yard
ac
ac ft
BTU
BTU/lb
cfm
cfs
cu ft
cu ft
cu in
op
ft
gal
gpm
hp
in
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
yd
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
3785
1.609
(0.06805 psig+1)*
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/rein
cu m/min
CU Bt
1
CU On
°c
m
1
I/sec
kv
cm
atir.
kg
cu m/day
kra
atm
sq n>
sq cm
kkg
n>
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
kilowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric tons (1000 kilograms)
meters
Actual conversion, not a multiplier
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