EPA R2-73-044
Environmental Protection Technology Series
JVIAY 1973
Chemical Treatment of Plating
Waste for Removal of Heavy Metals
CJ
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-Q1A-
May 1973
CHEMICAL TREATMENT OF PLATING WASTE
FOR REMOVAL OF HEAVY METALS
By
John J. Martin, Jr.
Project 12010 DMF
Project Officer
John Ciancia
Edison Water Research Division
Edison, New Jersey 08817
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20^0
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
Price 75 cents domestic postpaid or 60 cents QPO Bookstore
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EPA Review Notice
This report has been reviewed by the Environmental Protect-
ion Agency and approved for publication. Approval does
not signify that the contents necessarily reflect the views
and policies of the Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
ENVIRONMENTAL PROTECTION AGENCY
ii
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ABSTRACT
Chemical rinsing of electroplated parts and batch chemical
treatment of spent processing solutions have been demonstrated
to be a practical approach for abating pollution at a small
captive metal finishing facility. The treatment system reduced
the amount of chromium, nickel, zinc, copper and other heavy
metals in the waste to a level where substantial quantities of
water could be reused.
The precipitation of toxic metals in the chemical rinsing
system produced an easily settled dense sludge, which was further
compacted in simple outdoor earthen sludge beds for ultimate
disposal as landfill.
This report was submitted in fulfillment of Grant No.
12010 DMF between the Industrial Pollution Control Section,
ORM of the Environmental Protection Agency and the Beaton &
Corbin Manufacturing Company.
Key Words: Chemical rinses, Electroplating Wastes, Chromium
Treatment, Acid Nickel Treatment, Brass Bright Dip
Treatment, Rinse Water Reuse.
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Construction 15
V Operation 23
VI Discussion 25
VII Acknowledgments 33
VIII References 35
IX Appendix 37
v
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FIGURES
No.
1 Site Plan 6
2 Alkali, Cyanide, Floor Spill,
Acid Collection & Neutralize Flow Diagram 8
3 Integrated Nickel Treatment Flow Diagram 9
4 Integrated Chrome I & Chrome II Flow Diagram 11
5 Integrated Copper Treatment Flow Diagram 12
6 Settling Tank & Sludge Beds 14
7 Automatic Nickel Chromium Plating Machine 17
8 Manual Tube Chromium Plating Line 19
9 Manual Bright Dip Line 20
10 Plating & Treatment Areas 21
vi
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TABLES
No.
1 Effluent Analysis 26
2 Chemical Consumption 28
3 Waste Treatment Costs 2g
4 Unit Treatment Costs
vii
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SECTION I
CONCLUSIONS
1. Discharge of spent processing solutions and dragout
on the work and work carriers in electroplating operat-
ions introduces toxic metal ions into the rinse waters
and causes pollution in streams and waterways.
2. Practical and economical treatment methods are nec-
essary so that the small metal finishing facility is
technically and financially capable of installing and
operating an effective waste treatment system.
3. The use of chemical rinsing of dragout contamination from
parts and batch chemical treatment of spent processing
solutions provide a practical treatment approach for
abating pollution at a small electroplating shop.
4. The waste treatment system produces an effluent
containing less than 0.1 Cr (hexa), 0.5 Cu, 1.0 Ni,
0.5 Zn, and 5.0 suspended solids (all expressed in mg/1),
which complies with the requirements of the authorities
for stream discharge.
5. The type of equipment involved takes up relatively little
space, is familiar to electroplating and plant maintenance
departments and does not require special maintenance
skills or procedures.
6. Control of the treatment processes can be readily
assumed by the electroplater and does not call for
special technical skills.
7. The effectiveness of chemical rinsing, which reduces
the amount of rinse water required and permits sub-
stantial quantities to be reused, has resulted in about a
75% reduction in normal rinse water volume from 90 gpm
to 20 gpm.
8. A simple blow-down, or bleed-off, of about 25$ of the
total water used keeps the dissolved salts at levels
low enough to provide adequate rinsing at selected
areas.
9. Chemical rinsing is not related to the volume of rinse
water used and, therefore, wide variations in flow have
no effect on the efficiency of the treatment.
1
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10. Chromium was removed from the effluent as a dense
hydroxide precipitate at a chemical cost of 38.8
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SECTION II
RECOMMENDATIONS
The program was limited to demonstrating that a suitable
waste treatment system could be developed for the small
captive type electroplating department. Such a system should
be within the technical capacity of the plant personnel to
operate and the effluent should be of a character acceptable
to the authorities for stream discharge. The capital and
operating costs should be within the economic capability of
the company.
The technical and economic feasibility of automatic
controls on the treatment wash solutions should be investigated
and weighed against the present manual control.
Sumps for collecting and returning treatment wash
solutions to the reservoir tank should be of larger capacity.
At times all of the available volume of solution in the sump
can be pumped to the reservoir tank before the level in
the reservoir tank has risen above the overflow and returns
the solution to the wash station. It is necessary to have a
head over the overflow to insure good circulation, but if too
much exists, on shut-down the reservoir drains to the wash
station and thence to the sump and overflows the sump. Increas-
ing the size of the sump from 30 gallons to 80, or 100 gallons
would minimize this problem.
A monthly record of process and treatment chemicals
used should be maintained. Such a record would be a further
check on proper treatment..
Water flow rates should be monitored and logged monthly.
Any significant variation would indicate some defect or
malfunction in the system which can then be promptly invest-
igated.
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SECTION III
INTRODUCTION
The Beaton & Corbin Company was organized in 1893 to
manufacture a then patented specialty in the heating field,
namely the split floor and ceiling plates used where pipe
passes through floors and ceilings to cover the gap between
the hole and the pipe and present a pleasing appearance.
Originally cast iron, these parts are now made of fabricated
steel, assembled and electroplated by the company.
New products were inevitably added and for many years the
company has been bending and forming tubular parts for a
line of plumbers' brass goods. The line includes sink traps,
waste bends, funnels, sink tailpieces, sink plugs, slip joint
elbows, shower rods and water closet combinations. The
majority of these items are electroplated.
The electroplating processes require the use of acids
containing heavy metal ions, alkalies and large volumes of
rinse water. Dragout on the work and work carriers into
rinse waters and the periodic discharge of spent processing
solutions are responsible for the pollution problem- at the
plant.
The plant is located in the Quinnipiac River Watershed
area, and the effluent discharges directly to the Quinnipiac
River which is a very small brook at this location.
On October 16, 1967, the Connecticut Water Resources
Commission issued Order Number 479 directing that the
company install adequate facilities to treat all water-borne
industrial wastes so that they would be acceptable for dis-
charge to the nearby receiving water.
Figure 1 shows the site arrangement and finishing depart-
ment. Two areas appeared ideal for treatment equipment and
sludge drying beds, provided the whole facility could be kept
to a reasonable size. The finishing operations generated
about 90 gpm of contaminated rinse water under full operating
conditions, but contained only a small amount of contamination.
If the pollutants could be kept out of the rinse water, the
treatment could be confined to more reasonable volumes.
The company is representative of over three thousand
similar sources of stream pollution in the New England area
alone. If a system of chemical rinsing could be economically
applied to produce a satisfactory effluent for discharge
-------
2" Polyethylene
\100 psi
\ Below Frost
Legend:
Cast iron pipe
Polyethylene pipe
___ Building Outline
Figure 1. SITE PLAN
-------
or reuse, it would be of significant value to many other
firms facing similar orders to install treatment facilities.
A demonstration grant was obtained to install and
demonstrate the use of a chemical rinsing system as an
effective waste treatment method and to provide technical
and economic data on the system.
c
The processing systems at the plant include alkali
cleaners, weak and strong acids, acid nickel plating,
chromium plating and bright dipping of copper alloys. At
very infrequent intervals, a strong cyanide nickel strip
solution is used on a few 10 in. x 10 in. baskets of parts.
This might be four or five days a year with one or two
baskets stripped per day.
All rinse waters and spent processing solutions were
discharged to the floor where one drain line conveyed the
effluent through a settling tank and thence to the stream.
A larger filter was used occasionally to remove impurities
from the nickel plating bath and this was backwashed to
the floor and the cake washed away with the rinse waters.
If suitable chemical rinses could be provided in
the process lines and were effective in eliminating toxic
chromic acid and heavy metals, then the rinse waters should
be suitable for discharge without further treatment. It
would, of course, be necessary to pipe them to the stream
so that floor spills would not contribute contaminants.
Spent process solutions could be collected and treated as
a batch. This was the basic approach for the design of
the treatment facility.
The methods of treatment for each type of pollutant or
category of pollutant are discussed in the following
paragraphs.
In Figure 2, the method for treating spent processing
solutions is shown. Spent alkalies are collected and batch
treated with spent acids.
Spent acids are collected and batch treated with spent
alkalies, or liquid caustic.
Spent cyanides are collected and batch treated with
sodium hydroxide and sodium hypochlorite.
Floor spills are collected arid batch treated as required
for cyanide with sodium hypochlorite and for chromic acid
with sodium bisulfite. The pH can be adjusted with sodium
hydroxide or spent acids, as necessary.
In Figure 3, the treatment to remove nickel is shown.
Dragout from the nickel plating bath enters a chemical rinse
-------
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Pump
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From Nickel,
Chrome I, Chrome II
and Copper Reservoir
Figure 2. Alkali, Cyanide, Floor Spill,
Acid Collect & Neutralize Flow Diagram
-------
Nickel Chloride
Nickel Sulfate
To Settling Tank
Sump Tank
Recirculating Sump Pump
Mixer
Proportio
ing Pump
35 gjals.
Nickel Treatment
Reservoir
6' dia x 10'9"
2,200 gals.
Nickel Stock Tank
Soda Ash
2' dia x 3'
To Sludge Pump
Figure 3... Integrated Nickel Treatment Flow- Diagram
-------
containing soda ash to wash off the plating solution,
neutralize the acid and precipitate the nickel. The chemical
rinse station is connected to a reservoir tank and the treat-
ment solution is recirculated in a closed loop system. The
reservoir serves as a buffering component in the system to
absorb shock loading caused by irregular changes in the
quantity of nickel plating solution dragout. It also
serves as a clarifier where the insoluble nickel hydroxide,
or carbonate, formed during neutralization can settle.
Soda ash is used to maintain a pH of 8.5 - 9-5 in the
treatment solution. At this pH, nickel ions in the plating
solution react with the soda ash to form a nickel carbonate
and nickel hydroxide precipitate, which settles in the
reservoir. The soda ash also neutralizes any free acid that
may be present in the nickel solution dragout.
In Figure 4, the treatment to remove chromium is shown.
Dragout from the chromium plating solution enters a two-
step chemical rinse system. The first chemical rinse
contains sodium bisulfite to wash off the chromic acid and
reduce the hexavalent chromium to the trivalent state.
The rinse is connected to a reservoir, which provides a
buffering action to absorb shock loads of irregular amounts
of chromic acid dragout. The treatment solution is recir-
culated in a closed system between the wash and reservoir
tanks.
The second chemical rinse contains hydrazine and soda
ash to wash off the trivalent chromium and precipitate it
as chromium hydroxide. This rinse solution is also re-
circulated between a wash and a reservoir tank. The
reservoir provides a buffering component in the system to
absorb shock loads of irregular amounts of trivalent chromium
dragout. It also serves as a clarifier where insoluble
chromium hydroxides and carbonates can settle. The hydrazine
insures that any hexavalent chromium that may not have been
treated in the first chemical rinse is reduced to the tri-
valent state and precipitated as chromium hydroxide.
In Figure 5» the treatment to remove the copper and zinc
metal in the bright dip is shown. Copper and zinc ions
build up in this nitric-sulfuric solution and enter the
rinse waters as dragout. The dragout enters a chemical
rinse containing hydrazine, soda ash and caustic to
wash the dragout from the work. The rinse station is
connected to a reservoir through which the treatment solution
is recirculated. The pH is maintained between 9.5 and 10.5
and the hydrazine concentration between 300 and 700 ppm. The
caustic soda and soda ash neutralize the acid dragout and
the hydrazine reduces the copper ions to the cuprous state.
At the pH involved, cuprous hydroxide is precipitated.
The reservoir acts as a buffering component to absorb shock
loads due to irregular amounts of dragout and as a clarifier
10
-------
Chrome
Plate
Dragout
Chrome I
Treatment Wash
Station
Chrome II Treatment Wash Station
Recirculating
Pump
Chrome I Sump
Tank
Chrome I
Reservoir
'6" x 10'9"
1,200 gals.
Chrome I Stock
Tank
2 1/2' dia x 3 1/2'
Sodium Bisulfite
Chrome II
Sump Tank
To Settling Tank
ilafcing Sump Pump
4
Chrome II
Reservoir
dia x 10"9"
2,200 gals
Chrome II Stock Tank
2' dia x 3'
Hydrazine - Soda Ash
To Sludge Pum;
mp
Figure
Integrated Chrome I & Chrome II Flow Diagram
11
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Copper
Alloy
Bright Dip
1 Nitric
3 Sulfuric
Dragout
Copper 1
Freat Wash
Station
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*-*
To Settling Tank
Sump Tank
Recirculating Sump Pump
A
Proportioning
Pump
Mixer
Copper Stock Tank
2' dia x 3'
Hydrazine - Caustic - Soda Ash
V
Copper Treatment
Reservoir
6' dia x 10'9"
2,200 gals.
To Sludge Pump
Figure 5. Integrated Copper Treatment Flow Diagram
12
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where precipitated metal hydroxides can settle.
All rinse waters are piped to an existing settling
tank where any remaining suspended solids settle and the
clarified water is then discharged to the stream as shown in
Figure 6. Since all spent processing solutions and floor
spills are collected, contamination of the rinse waters from
these sources are eliminated. Toxic dragout on the work
and work carriers has been removed by chemical rinsing,
eliminating this source of pollution in the rinse waters.
Thus, only dragout from mild alkali cleaners, mild acid,
and chemical rinses enter the rinse waters. Therefore,
the rinse waters, with simple clarification, should be
suitable for discharge to the receiving water or reuse for
specific rinsing.
The chemical treatments result in the formation of
precipitated metal hydroxides. The entire volume after
batch treatment and periodic blow-down of the reservoirs
is pumped to outdoor sludge beds., as shown in Figure 6,
for compacting and drying. The compacted sludge, consisting
primarily of inert metal hydroxides and oxides, will event-
ually be removed and used as landfill.
If the quantities of metals were large, the chromium
and nickel precipitates could be salvaged by keeping them
separate.
13
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Rinse Water to Plating Room
From Rinse
Tanks in
Plating Roofl
Existing Settling Tank
8500 gals, (outside)
Water Reuse Pump
Grade
£to Brook 20 gpm
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Sludge Beds A
6000
Grade - 1
Sludge Beds B
6000 gals
Grade - 1
Below Frost
From Sludge Pump in Waste
Treatment Room
Figure 6. Settling Tank & Sludge Beds
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SECTION IV
CONSTRUCTION
The finishing department can be considered to consist
of three areas:
1. The Automatic Nickel-Chromium Plating Machine.
2. The Manual Tube Chromium Plating Line.
3. The Manual Bright Dip Line.
The dumpings of spent alkali cleaners (6-8 ounces per
gallon) from these areas varies,, but averages about 900
gallons every three weeks, with a maximum dump of about
300 gallons. A cyanide nickel strip with about 1 pound
per gallon of cyanide is dumped about every three months
and amounts to about 40 .gallons,. Floor spills should be
negligible in the future except for occasional wash down
which should not be more than 300 gallons. Considering
these volumes, a 1000 gallon Alkali-Cyanide Floor Spill
tank was selected.
The dumpings of spent acid amount to approximately 700
gallons about four times per year with a maximum dump of
300 gallons. This volume indicated that a 1000 gallon
acid collecting and neutralizing tank should be adequate.
The sizes selected would allow the operator to batch
treat approximately once per week. Thus, the operator
would not be required to treat every time a spent process-
ing solution was discharged, but rather at his convenience.
It was recognized that the possibility of acid and cyanide
meeting in the Floor Spill tank did exist. However, there
will always be at least 90 gallons of alkali cleaner in
the bottom of the Floor Spill tank, since the side drain
does not permit emptying the tank completely, and this
alkalinity, or that left from a batch treatment, should be
effective in neutralizing any floor spill acid that might
enter the tank. In addition, the use of cyanide is very
infrequent and by treating batches when discarded the
potential hazard is further minimized. Perhaps most
important, however, is the presence of good ventilation
in the plating department and the long experience of
plating personnel in working with dangerous chemicals.
A sludge pump common to both tanks is used to agitate
the solutions when batch treating and to draw in either
liquid caustic or sodium hypochlorite, as required. If
necessary, sulfuric acid could be added to the neutralizing
tank from carboys with a self-priming chemical transfer
pump, rated at 9 gpm.
15
-------
A caustic stock solution tank of 150 gallons capacity
was selected to hold a 30% solution of caustic. A spent
acid solution of 300 gallons could contain 150 pounds of
acid (6-8 ounces per gallons) and would require about 150
pounds of caustic. A 100 gallon solution of 30% caustic
contains 333 pounds of caustic. Thus, a 150 gallon stock
tank is suitable.
A sodium hypochlorite stock tank of 55 gallons was
selected so that 15$ liquid sodium hypochlorite could be
transferred with the chemical transfer pump from 30 gallon
carboys or 55 gallon drums. The sludge pump is then used
to introduce the sodium hypochlorite when cyanide is treated.
After a batch is treated, the sludge pump is used to
discharge the batch to the outdoor sludge beds. The sludge
pump is also used to pump slugs of precipitated and settled
metal hydroxides from the Chemical Rinse Reservoirs to
the collecting tanks for treatment with spent processing
solutions and thence to the sludge beds. The pump selected
has a capacity of 40 gpm at a 70 foot head. Thus, a tank
could be pumped to the sludge beds in about 25 minutes.
The existing drain in the floor was sealed off so
that floor spill could not be discharged to the stream. A
small sump, 12 in. by 12 in, by 18 in. deep, was constructed
next to the former floor drain and a small self-operating
submersible floor pump installed and piped to the Floor
Spill tank. The floor could now be used to collect spent
alkali and cyanide solutions and convey them automatically
to the Floor Spill tank.
To collect spent acid solutions, a portable self-
primimg pump is connected to the nearest of two stainless
steel quick disconnects which are piped to the Acid Collect-
ing tank. The pump is rated at 9 gpm and about 35 minutes
is required to empty the largest acid tank.
Since the floor is now contained, any drippage between
tanks, tank overflows, accidental spill, or backwash of
the nickel solution filter is prevented from going to the
stream and is automatically transferred to the Floor Spill
tank where it can be tested and appropriately treated.
All rinse tanks are permanently piped to the existing
drain from which the effluent flows to the existing retention
tank and thence to the river.
The Automatic Nickel Chromium Plating machine could have
presented the most problems in applying chemical rinses
because the addition of rinse stations could have been
difficult, if not impractical. Figure 7 shows the existing
stations and how they were converted to chemical rinse stationM
no additional stations were required.
16
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Work In-
(Reuse Water)
(Convert To Chrome II
Treatment Station)
(Convert To Chrome I
Treatment Station)
(Convert To Nickel
Treatment Station)
Alkali
Soak
Cleaner
Work Out
t
Hot
Rinse
Rinse
Rinse
Rinse
Drag-
Out
Chrome
Plate
Rinse
Rinse
Nickel
[ Dragout
Rinse
\lkall
Cleaner
Alkali
Cleaner
Rinse
Mild
Acidex
Rinse
Acidex
Rinse
Rinse
(Reuse Water)
(Reuse Water)
(Reuse Water)
(Convert to Copper
Treatment Station)
Figure 7- Automatic Nickel Chromium Plating Machine
17
-------
The Copper, Nickel, Chrome I and Chrome II treatment
washes overflow to their respective sumps, from which
pumps transfer the treatment solutions to reservoir tanks
in the waste treatment area. The returns from the reservoirs
to the treatment stations are all by gravity.
The Manual Tube Chromium Plating Line is shown in
Figure 8. One new tank for the Chrome I Chemical Rinse
was added and one existing rinse converted to a Chrome II
Chemical Rinse. These overflow to the same sumps used for
the automatic machine and return to the respective reservoirs
Returns from the reservoirs to the treatment stations are
all by gravity.
The Manual Bright Dip Line is shown in Figure 9. The
existing rinse around the acid crocks was converted to a
Copper Treatment Station. The treatment station overflows
to a sump and a sump pump returns the solution to the res-
ervoir in the treatment area. The same sump and pump serve
the copper treatment stations.in the Automatic Machine.
The returns are all by gravity. The alkali chrome strip and
the following stagnant rinse are drained to the floor
where the floor spill sump pump automatically transfers
them to the Floor Spill tank where they can be batch treated.
The relationship between the finishing area and the
waste treatment area is shown in Figure 10. The area between
the boiler room and the finishing room was enclosed and,
with some careful consideration to tank dimensions, provided
sufficient space for the treatment equipment. The proximity
is most advantageous since the operation of the treatment
can be readily assumed by the finishing personnel.
The reservoirs were sized to give adequate head for
gravity return, fit the available floor space and take
advantage of the economy of using standard stock molds.
A minimum of one hour retention in the reservoir was main-
tained to insure good settling and a turnover of twice
per hour in a wash station was considered adequate. Approx-
imately 1 gallon per hour of dragout-was anticipated and
this turnover would insure adequate treatment chemicals in
chemical pre-rinsing. Actually, there was more concern
for keeping the metallic compounds in suspension in the
treatment station than in an adequate chemical supply.
Settling was not a factor in the Chrome I system and the
reservoir was made only half the size of those that were to
function as clarifiers.
The stock solution tanks were sized with the following
considerations:
Chrome I Treatment - About 40 pounds of bisulfite per
week would be required to treat a dragout of 40 gallons per
week of chromium plating solution. A standard 100 gallon
molded polyethylene container was selected.
18
-------
Rinse
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-------
Chrome II Treatment - Sodium hydrosulfite was used
originally and, since this compound breaks down with exposure
to air, the stock solution was to be made daily. Consequently,
a standard 55 gallon molded polyethylene container was selected,
Sodium hydrosulfite was subsequently replaced with hydrazine
since the latter is more stable.
Copper Treatment - Same reasoning as for Chrome II;
sodium hydrosulfite was also replaced with hydrazine in
this case.
Nickel Treatment - It was felt that mixing a small
amount of soda ash could more easily be done in a small
container and settling problems would be avoided. A stand-
ard 55 gallon polyethylene container was selected.
Standard proportioning pumps rated 0-8 gph were selected
to feed the stock solutions to the treatment reservoirs.
22
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SECTION V
OPERATION
The' hydraulics of the installation are very simple.
The sump pumps are started and the treatment solutions are
pumped from the sumps to the reservoirs and then return by
gravity to the treatment stations. With two stations and
one sump, valves regulate the distribution to the treatment
stations. Valves on the pump discharge regulate the flow
rate.
Sumps having a capacity of 30 gallons were selected
and are satisfactory, but a larger sump would allow more
leeway in valve adjustment and accommodate surges on shut-
down.
With all pumps running, the proportioning pumps are
started with an arbitrary flow setting. Simple tests are
provided to determine the chemical levels in the treatment
solutions. Since the control limits are quite large, trial
and error adjustments of the chemical feeds quickly result
in settings which vary little from day to day. The varying
level of chemical concentration does not result in poor treat-
ment since an excess is all that is required for effective
treatment.
The test procedures for the treatment solutions are as
follows:
Chrome I Treatment
pH 2.5 - 4.5 narrow range pH paper, daily.
Sulfite 1000-2500 ppm Spot test, daily, WCR-SOST,
appended.
Solution color: Bluish-green, no pink to brown,
Chrome II Treatment Hydrazine used in place of
sodium hydrosulfite.
pH 7-0-8.5 narrow range pH paper, daily.
Hydrazine 50-200 ppm Spot test, every 4 hours,
WNH-ST, appended.
Solution color: Bluish-white, no yellow.
WCR-NH2 weekly.
23
-------
Copper Treatment
pH 9.5-10.5
Hydrazine 300-700 ppm
Nickel Treatment
pH 8.5-9.5
Hydrazine used in place of
sodium hydrosulfite.
Narrow range pH paper every
4 hours.
Spot test every 4 hours,
WNH-ST, appended, WCR-NH2
appended, weekly.
Narrow range pH paper, daily,
24
-------
SECTION VI
DISCUSSION
A summary of the effluent analysis is presented in
Table 1. Since the dragout from the chemical treatment
wash station into the rinse water would always be of an
alkaline nature, no control was used to adjust the pH of
the effluent. Thus, other than some minimal clarification
in the existing retention tank, the running rinse water does
not receive any treatment.
The effectiveness of the chemical treatment system is
rather dramatically demonstrated by comparing the contamina-
tion before and after the treatment was instituted as shown
in Table 1. In all_areas the values obtained are well
within the limits acceptable to the State for discharge
to this stream.
It was anticipated that the effluent, after treatment
was instituted, should be of value for further reuse. Since
there would be a build-up of dissolved salts if all the
water were reused, it was planned to use this water only
where a slight amount of salt would have no deleterious
effect on the process. The critical areas would'continue
to be supplied with fresh water to replace the bleed from
the system and keep the dissolved salts at a low level.
Thus, after alkali cleaners and acid dips, reuse water is
used. It is not used in the rinse before nickel plating,
chromium plating, as a final hot water rinse, or as make-up
to processing solution.
At present, the discharge from the settling tank to
the stream is running about 20 gpm. Five stations are on
reuse water and three are on city potable water. About
three quarters of the process water is reused in the process.
Without this type of treatment, 90 gpm of rinse water would
be used and discharged.
In Table 2, the actual process chemical and treatment
chemical usage is presented. The caustic requirement was
significantly lower than might be expected because of the
neutralizing effect of the alkali cleaners.
To reduce and precipitate slightly less than 2200 Ibs
of purchased chromic acid required
2388 Ibs of sodium bisulfite @ $26?.60
550 Ibs of hydrazine § 523.00
1000 Ibs of soda ash @ 60.00
or a total of $850.60
25
-------
Table 1
cr\
Effluent Analysis
Chromium
PH
Before Treatment
6/30/65
9-10 3-0
10-11 AM 3.1
11-12 2.7
3/18/65
9-10 AM 2.2
10-11 2.3
11-12 2.3
12-1 2.3
8/24/66 2.8
State Limit
6.5-8.5
After Treatment
10/16/70
Composite 7-0
12/3/70
Composite 7.15
12/16/70
Composite 7.18
Hexa.
10
12
14
8
9
9
10
20.5
1.0
(*ND -
ND
ND
ND 0.
Total
-
-
12
14
12
14
24
-
Not
ND
ND
025
Copper
Sol. Total
6
8
8
15
13
11
11
15-5
1.0
Detectable)
0.09
0.20 0.30
0.25 0.45
(mg/1)
Nickel
Sol. Total
5.0
5.0
3.0
7-0
6.5
5.5
5.5
14.2
1.0
0.95
0.20 0.40
0.60 - 0.60
Zinc
Sol. Total
5.0
2.0
3.0
3.3
3.3
2.6
3-3
- -
1.0
0.29
0.34 0.39
0.44 0.50
S.S.
270
280
304
404
380
400
368
836
30
ND
1.70
2.3
CN Cl
0.9
1.0
0.9
1.0
0.6
0.5
0.5
6.8
0.1 100
ND 31-3
19.0
ND 23-1
S04 NO-3
-
- -
200 100
950 1.76
130 0.20
160 0.20
-------
which is at the rate of 38.8
-------
Table 2
Chromic Acid'
Acid Salts
Sulfuric
Nitric
Muriatic
Alkali Cleaners
Sodium Cyanide
Chemical Consumption 1970
Process', Ibs
2200
3075
4265
960
1800
9375
30
Sodium Bisulfite
Soda Ash
Hydrazine, 5^.4$
Sodium Hypochlorite,
Wetting Agent
Caustic
Treatment,
2388
1200
1320.
75 gal|.
5 gal
2200
28
-------
Table 3
Waste Treatment Costs
Ibs./yr
Chemical
Sodium Bisulfite
Sodium Bisulfite
Soda Ash
Soda Ash
50% Liquid Caustic
Hydrazine, 54.4$
Sodium Hypochlorite,
15%
Wetting Agent
Total Chemical Costs
Labor 480 hrs § $ 5.00
Power 6000 KWH g .02/KWH (approx)
Total Operating Costs per year
Price/lb.
288
2100
700
500
155 gals.
1320
75 gals.
5 gals.
$ 0..20
.10
.05
.07
.46/gal.
95
.68/gal.
4.60/gal.'
$ 57-60
210.00
35.00
35.00
71.30
1252.00
51.00
23.00
$1734.90
2400.00
120.00
4254.90
Building, Sludge Beds, Fencing, Heating, Exhaust, existing
equipment changes, treatment equipment, plumbing, electrical
and technical services $ 47,337-00
With 10 year depreciation $ 4733-00 per year
Carrying charges 6% 2840.00
Amortization $ 7573-00. per year
Total Operating and Amortization Costs $11828.00 per year
29
-------
Table 4 shows the relationship of treatment costs
to product area and dollar value. The area of the product
is significant, as well as its shape, since both determine
the amount of dragout that must be subsequently treated.
30
-------
Table 4
Unit Waste Treatment Costs
Water volume 11,450,000 gals./yr
Total Waste Treatment Cost $11,828.00 per year
Area of Processed Product 660,000 sq ft/yr
Treatment cost per sq ft 1.79
-------
SECTION VII
ACKNOWLEDGMENTS
The cooperation of the Connecticut Water Resources
Commission in reviewing the plans, specifications and
anticipated effluent quality is appreciated.
The construction and operation of the system was
conducted under the direction of A. Ralston, C. Button and
M. Adam of the Beaton and Corbin Company, which included
coping with interruptions in production operations as the
system was installed and the new procedures incorporated.
The accumulation of the data for this report was also
accomplished by this group.
The support of the project by the Office of Research
and Monitoring of the Environmental Protection Agency is
gratefully appreciated and the cooperation of Mr. William
Lacy, Mr. Edward Dulaney, and Mr. John Ciancia, has been
most helpful.
33
-------
SECTION VIII
REFERENCES
1. Ceresa M., Lancy L., Metal Finishing, April, May,
June (1968).
2. Pinner R., Electroplating and Metal Finishing,
20, July, August, September (1967).
3. Lancy L., Plating, 5^,157 (1967).
4. Lancy L., Metal Progress, April (1967).
35
-------
SECTION IX
APPENDIX
Test Procedures: Page
WCR-SOST 38
WNH-ST 39
WCR-NHo 40
37
-------
TEST PROCEDURE: WCR-SOST
TEST: APPROXIMATION OP EXCESS SULPITE
RADICAL IN CHROMIC ACID TREATMENT
SOLUTION I
1. Take a 100 ml sample of the solution and place in a
250 ml Erlenmeyer flask and heat to l40-l60°F.
2. Place one" drop of 2 N H2SOjj and one drop of Diphenyl-
carbazide Indicator in each of several cavities of
a spot plate.
3. Using a stirring rod, place a drop of the solution on
the spot plate so that it comes in contact with the
indicator. The indicator will turn pink If CrO^ is
present, but remains green or the color of the treatment
solution if excess SO^ is still present.
4. From a burette, run in 5 ml of standard chromic acid
solution (10 g/1). Again test a drop of the spot plate
and repeat this process until the indicator turns
pink to violet.
5. Calculations:
Each 5 ml of chromic acid solution used indicates an
excess of .8 g/1 S0= content expressed as NaHSO .
Maintain the S0= concentration in the treatment solution
so that at least 5 ml chromic acid is needed to yield the
pink color. If more than 30 ml chromic acid is used, the
excess S0= is high and the sodium bisulfite additions should
be reduced^ This would be equivalent to an S0= concentration
of between 0.8-5 g/1 for best performance. 3
38
-------
TEST PROCEDURE: WNH-ST
TEST: Hydrazine Spot Test for Excess Hydrazine
SPECIFICATIONS:
Type Quantitative Approximation
Limit of Identification 50 ppm NpH^
Color Pale Yellow
REAGENTS:
1. p-Dimethylaminobenzaldehyde - Dissolve 1 gram of
p-Dimethylaminobenzaldehyde in methyl alcohol and
dilute with methyl alcohol to 100 ml. This indicator
is stable for several weeks if stored in a dark
glass stoppered bottle.
2. Hydrochloric Acid Solution 10% by volume - to 50
ml of distilled water, add 10 ml of concentrated
hydrochloric acid and dilute to 100 ml with distilled
water.
PROCEDURE:
1. Place two droppers full (approximately 2 ml) of
treatment solution to be analyzed in a 100 ml
graduate and dilute to 100 ml with distilled water
and shake to mix.
2. Place one drop of diluted treatment solution in
one cavity of a spot plate. In another cavity,
place one drop of distilled water for a blank.
3- To each spot add 2 drops of hydrochloric acid
solution and mix.
4. Add 2 drops of p-Dimethylaminobenzaldehyde indicator
and mix. Wait one minute for color development.
The sample spot will turn very pale yellow if 50
ppm hydrazine is present. The yellow color will
increase in intensity as the hydrazine concentration
increases. At 700 ppm hydrazine, the spot will
be very deep yellow. The blank should always
remain colorless.
39
-------
TEST PROCEDURE: WCR-NH
Test: Hydrazine Titration - 2
Specifications:
Type Quantitative
Color at End Point red to yellow or light orange
Reagents:
1. Amaranth Indicator Solution, 0.2%. Dissolve
200 mg in water and dilute to 100 ml.
2. Hydrochloric acid, cone.
3. Potassium iodate solution (0.025M). Dissolve
5.
Procedure:
5.350 g KIO in water and dilute to one liter.
1. Pipet a 5 ml sample of previously filtered
treatment solution into a 250 ml Erlenmeyer flask.
2. Add 5 ml of cone, hydrochloric acid and mix.
3- Add 6 drops of Amaranth indicator solution.-
4. Titrate, while shaking or stirring vigorously,
with potassium iodate solution. The sample
color will change from red to yellow or light
orange.
Calculations:
mg/liter (ppm) N^ = ml KIO^ used x 800
ml sample used
-------
n
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
/. Report No.
2.
3. Accession No.
W
4. Title
Chemical Treatment of Plating Waste For Removal of Heavy
Metals
7. Author(s)
John J. Martin, Jr.
9. Organization
The Beaton & Corbin Manufacturing Company
North Main Street
Southington, Connecticut
5. Report Date
6.
8. Performing Organization
Report No.
10. Project No.
12010 DMF
//. Contract /Grant No.
WPRD 2^-01-68
13. Type of Report and
Period Covered
Bavlromaentai Protection A«*iKT
12. S pon tor inf Organization
15. Supplementary Notes
Bivironmental Protection Agency report;
number EPA-R2-73-OW, May 1973
16. Abstract
Chemical rinsing of electroplated parts and batch chemical treatment of spent
processing solutions have been demonstrated to be a practical approach for
abating pollution at a small captive metal finishing facility. The treatment
system reduced the amount of chromium, nickel, zinc copper and other heavy
metals in the waste to a level where substantial quantities of water could be
reused. The precipitation of toxic metals in the chemical rinsing system
produced an easily settled dense sludge, which was further compacted in simple
outdoor earthen sludge beds for ultimate'disposal as landfill.
17a. Descriptors
*Waste Water Treatment, Water Reuse, Reclaimed Water
17b. Identifiers
*Plating Waste Treatment, Chemical Rinsing, Chromium Treatment, Cyanide Treatment,
Acid Bright Dip Treatment
17c. COWRR Field & Group
18. Availability
Abstractor John Jo
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