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University of Minnesota Executive Summary
Minneapolis, Minnesota 55455
1985 Summer Intern Report
HAZARDOUS WASTE REDUCTION AND METAL RECLAMATION
by Prasad M. Kuchibhotla
Project conducted at Sperry Corp., Roseville, MN
Sperry Corporation is a computer manufacturer with facilities
throughout the U.S. The Roseville Building 2 operations are
concentrated on the manufacture of printed circuit boards and the
assembly of computer components. Wastewater from this facility
is treated using hydroside precipitation to remove hazardous
materials as sludge before discharge. The objective of this
intern project was to evaluate alternative methods of wastewater
pretreatment.
The results of an in-plant survey indicated that the plant
generates an-average 60 gallons per minute of wastewater
containing copper, chrome, lead and tin, with copper being the
major constituent. There are also 1700 gallons per week of batch
dumps being tree ted. The existing pretreatment system yields 2-
3 drums of sludge per day. Chelated wastestreams and batch dumps
are handled separately. Complete characterize lion of all waste
and process streams was made.
Based on this work, process modifications and layout changes were
recommended in order to reduce waste generation to segregate
wastestreams for pretreatment. After analysis of the waste-
streams based on these revisions, options for waste reduction
were identified and evaluated. The following technologies were
seen as having possible application at Sperry Corp.:
o Evaporation
o Reverse osmosis
o Electrodialysis
o Ion exchange/electrolytic recovery
Problems and advantages associated with these technologies are
reviewed in the full report.
Sperry Corp. currently spends more than $100,000 per year on
sludge disposal and is striving to eliminate that cost and
liability or reduce it significantly. The use of ion exchange.
followed by electrolytic recovery of the metals was believed at
the time of this report to be the most feasible system for
building.
The Minnesota Technical Assistance Program is funded through a grant provided by the Waste Management Board.
INTERN PROJECT REPORT
HAZARDOUS WASTE REDUCTION
AND METAL RECLAMATION
SPERRY CORPORATION
ROSEVILLE, MINNESOTA
PRASAD M. KUCHIBHOTLA
ACKNOWLEDGMENTS
I am grateful to the Facilities Department of Sperry
Corporation, Roseville, Minnesota, for giving me an opportunity
to work on this project. I express by gratitude to Duane
Dittberner for helping me in this work, Will Paul for his
guidance, and other Sperry personnel for their cooperation.
I express by thanks to Cindy McComas, MnTAP Director, for
organizing the program and MnTAP (the Minnesota Technical
Assistance Program) for financially supporting this project.
I. INTRODUCTION
Sperry Corporation, with its corporate headquarters in Blue
Bell, Pennsylvania, has various facilities throughout the U.S.A.
It is the major manufacturer of large and small scale computers.
The Roseville/St. Paul, Minnesota (at Building 2) operations
primarily concentrate on the manufacture of printed circuit
boards and assembly of computer components. Hazardous wastes are
generated as a result of printed circuit board manufacturing,
component board cleaning and soldering, spray painting of frame
parts and general maintenance.
The wastewater generated by the Multilayer Printed Circuit
Board facility is sent to the wastewater pre-treatment plant,
where it is treated for metals (primarily copper) by a
conventional precipitation method, designed by Lancy
International. The process flow diagram of the operation is
represented in Figure 1.
The Printed Circuit Board facility at Sperry Corporation,
Roseville, manufactures multilayer printed circuit boards for
internal use in the manufacture of their Sperry computers. The
process is mostly automated technology. The equipment involved
includes photo developer, cupric chloride etcher, resist
stripper, alkaline etcher and various rinse and batch tanks. All
these processes produce various quantities of wastewater
containing different organic and inorganic chemicals in addition
to other metals like copper, chromium, tin and lead. Copper is
the major constituent of the waste stream with other metals present
in smaller quantities.
1
The water is separated into rinse streams and batch dumps.
The rinse streams are pumped to equalization tanks, then sent to
the first stage reactor and kept under acidic medium by the
addition of sulfuric acid. Ferrous sulfate is continuously added
to this reactor to break the chelated copper bonds. The second
stage reactor separates the soluble form of copper as insoluble
copper hydroxide by the addition of lime solution (which is kept
under constant circulation). Sodium bisulfite is added to this
tank to reduce the hexavalent chrome to a more insoluble form of
trivalent chrome. These suspended particles are then
agglomerated in the third stage reactor by the addition of
anionic polymer. Consequently, the water upon entering the
clarifier separates out solids which are pumped to a settling
tank and then to a filter press, where the sludge is removed and
collected in barrels. The water separated out from the sludge in
the clarifier flows by gravity to a tank for pH adjustment,
where the copper concentration is also continuously monitored
before release into the sewer.
The batch dumps (acid, alkaline and electroless copper) are
treated separately and the sludge from the treated water is
pumped out to the settling tank, where it is mixed with the
continuous rinse stream sludge from the clarifier.
The wastewater pretreatment process produces about 2-3
barrels of sludge a day. In addition, approximately 60 gallons/
minute of rinse streams and an average of 1700 gallons of batch
dumps a week are treated.
2
II. PROJECT OBJECTIVE
Currently this wastewater, approximately 60 GPM, is treated
for its organics from photo developing, inorganics and metals.
The treatment process is a standard chemical treatment to
precipitate out the metals in the form of sludge. The total cost
of disposal including the drum, transportation, etc., is about
$200 per drum. Assuming that at least ten drums of sludge are
produced each week, the total cost of disposal is about $100,000
annually. This cost is in addition to the chemicals used in the
waste treatment process, operating personal and other utilities
such as water, electricity, etc.
In the coming few years, the number of hazardous waste
disposal sites will be reduced drastically. EPA and other state
environmental control agencies may totally ban the burying of the
hazardous wastes. In view of this most important reason, and the
continually increasing cost of disposal of wastes, the
environmental management personnel at Roseville, Sperry
Corporation decided to seek alternatives for sludge disposal.
Many technologies have been developed in recent years to
effectively recover the metals in wastewater streams. Thus, the
objective of this project was to characterize the waste streams,
and evaluate and install equipment for metals recovery at the
Roseville, Sperry Corporation facility.
III. APPROACH TO THE PROBLEM
The work began with an "in-plant survey". This survey
included the collection of various technical, process and
analytical data on all the waste streams from the Multilayer
Printed Circuit Board Facility.
This survey included collection of information on tank
volumes, chemical compositions of the streams of all the process
tanks, etchers, developer and gold tab lines.
The next part of the work involved the segregation of the
waste-water streams. Based on their acidity, alkalinity,
chelated and non-chelated properties, etc., it was decided that
these streams were to be segregated in order to effectively
implement the metal recovery technology.
The old schematic diagram was modified to reflect the
current process modifications. This process was also redrawn
taking into consideration the developments to be expected in the
next few months at Sperry.
The next step in the process was the selection of suitable
equipment for waste sludge reduction. This involved careful
consideration of all the data in consultation with one of
Sperry's Senior Production Engineers. Various vendors were
contacted for technical information for this purpose. Selecting
the equipment such as ion exchange columns, electrolytic metal
recovery and others that suited Sperry's needs involved
telephoning and visiting various off-site plant facilities to
hear about and see the efficiency of in-place operation.
Sperry's primary goal was to eliminate sludge production
completely. Realistically, however, the attainability of this goal
will likely be restrained by reasonable costs and equipment
efficiency.
IV. RESULTS
The in-plant survey data is contained in the Appendix of
this report. A brief description and analysis of the data is
given below.
Appendix Tables 1 and 2 contain the analytical results for
all the rinse and batch tanks (total number of tanks involved in
the process is 68), which includes pH values and concentration of
coppers chrome, lead, and tin. For rinse tanks and batch tanks,
the flow rates and dump schedule, respectively, are reported.
Table 3 contains the information on the type of process,
chemical composition, temperature of operation, chemical make-up
and destination of the streams. The plating process uses de-
ionized water or city water, depending on the type of process in
the reaction tank.
Table 4 details the characterization of all the streams
based on the metal contents in each tank. They are categorized
as rich or lean and chelated or non-chelated. This is
particularly useful information because it is vary important in
the equipment selection process. Table 5 explains the process type
and the destination of the streams. Some of the streams do not
need any treatment and are therefore directly sewered. They are
5
within discharge limits. Table 6 provides information on sources
of water for the plating line.
Figures 2 and 3 present the percentages of different waste-
water streams based on: acid dump, alkaline dump or electroless
copper.
Figure 3 details the quality and quantity of dumps that
contribute to the wastewater streams each week. This is a
material balance for Sperry's wastewater streams.
Initially, there was a problem of the material balance of
the waste streams coming into the treatment room. After the
installation of flow restrictors on all the rinse tanks, it
became particularly easy to make a material balance. Now, it is
possible to account for all the water flowing into the wastewater
treatment room.
V. EQUIPMENT EVALUATION
Since Sperry had a general concept regarding what equipment
may be required for the recovery process, various vendors that
supply this type of equipment (Lancy International and DMP) were
contacted. Technical information on this equipment was collected
from these vendors and Sperry is currently in the process of
selecting the most appropriate equipment.
6
FIGURE 2.
Percentage of different kinds of dumps in 16 week period.
AD = Acid dump
AKD = Alkaline dump
ECD = Electroless copper dump
Total flow = 28,950 gallons.
FIGURE 3.
Pattern of weekly dump quantities (gal.)
As needed ECD: 570
AD = Acid dump
AKD = Alkaline dump
ECD = Electroless copper dump
VI. THE ADVANTAGES AND DISADVANTAGES OF VARIOUS TECHNOLOGIES
OF METAL RECOVERY
The most commonly-used recovery technologies for
electroplating baths are: drag-out recovery, evaporation/concen-
tration, reverse osmosis, electrodialysis, ion exchange and
electrolysis.
Drag-out recovery is an often overlooked method that can
recover up to 60% of the losses due to drag-out. Evaporative
recovery is the oldest and most energy-intensive. Reverse
osmosis is one of the newer technologies to be applied to
recovery of metals from rinse-water. It is less energy-intensive
than evaporative recovery but it has a number of drawbacks. One
drawback is the limitation of the membranes, which are fragile,
easily fouled and difficult to replace; second is that the
effluent from this process is not very concentrated due to
pressure limitations. The major economic factor is the life of
the membrane, which is short, even under ideal working conditions.
Electrodialysis is more energy efficient than reverse
osmosis but it is also a membrane technology and so has similar
limitations. Both reverse osmosis and electrodialysis require a
high level of skill on the part of the operator and should be
closely monitored.
Ion exchange is the most energy efficient of the recovery
methods. Metals can be selectively recovered as a slab using
an electrolytic metal recovery cell.
A more practical way to achieve a high surface area cathode
where the metal can be taken out as slabs is to use stainless
steel wool or a porous carbon for the cathode. The use of carbon
7
fibers increases the surface area 25,000 times and hence more
metal is removed even-at the low concentrations. This process of
electro-winning and electro-refining can be achieved with a
recovery cell manufactured by Metal Removal Systems (MTS).
After metal removal, the remaining water can be disposed of to
the sewer.
Currently, Sperry is in the process of designing and
evaluating equipment. This is a very important and interesting
part of the project. With the help of retained consultants (who
are concurrently in the process of collecting some kinetic data
from the waste streams) and Sperry's Senior Production Engineer,
Sperry is well on its way to choosing the best design for
its needs.
A preliminary design of the equipment was made based on the
segregation and properties of the streams. The details of the
work are shown in Figure 4. The rinses and dumps are separated
into chelated and non-chelated constituents. The total flow
rates and total concentrations of each metal in the segregated
streams were calculated. Based on the available capacities of
ion-exchange columns and electrolytic cells, the streams were
directed to different equipment. Chrome rinses and dumps are to
be separately treated: the process is not yet finalized. The
nitric strip solution, where there is major copper constituent,
presents an additional unresolved recovery problem. Now, Sperry
is looking at the practical aspects of this preliminary design to
recover most of the metal without drastically affecting the
efficiency of the equipment.
8
VII. INVESTMENT VERSUS LIABILITY TO A LARGE OR SMALL CORPORATION
The technology that will be proposed for the recovery system
involves significant capital investment. The purchase of ion
exchange columns, electrolytic recovery cells, a sludge dryer and
piping layout modification are the primary cost incurring
portions of Sperry's project. An investment of this magnitude
is justifiable based on the following reasoning: The production
of a hazardous waste sludge, while resulting in an acceptable
discharge effluent, represents a tremendous liability to any
company. Currently, most sludges are either landfilled in bulk
or 55-gallon drums; while this may be expensive, it does get rid
of the waste. Unfortunately, it does not eliminate the "cradle
to grave" liability associated with it. All hazardous waste
landfill sites are someday likely to be on an EPA clean-up list
(no site is 100% secure). When this happens it almost always
costs all the contributing generators. To avoid this scenario a
generator's best alternative it to generate as small a volume of
hazardous waste as possible. For large or small companies, metal
recovery can not only achieve this goal but also recycles a
valuable resource and promotes a safer environment. Metals
recovery is not just economical to large companies. A number of
technologies are available to the small generator which can be
scaled down for small volumes to recover metals cost effectively.
This is especially true when one considers the cost of sludge
disposal in the future and the potential future liability.
9
VIII. FINAL COMMENTS
An expansion of about 20 additional tanks to the existing
electroplating line is expected in the near future. The new
Printed Circuit Development (PCD) laboratory is nearly complete
and the operation of their electroplating tanks may begin at any
time. In view of these two recent developments, some additional
wastewater (as rinses and dumps) is expected to be treated for
recovery. An in-plant survey will be done for the above
mentioned new processes. This survey will add to the already
collected information and will be used in the selection and
sizing of recovery equipment.
10
IX. APPENDIX
11
TABLE 1. July 25, 1985
ANALYTICAL RESULTS OF THE ELECTROPLATING SYSTEM
CONTINUOUS RINSE
TankNo. pH Cu, mg/l Cr, mg/l Pb, mg/l Sn, mg/l Flow,GPM
(0.95-1.0) (220-260)
3 2.95 5
1.2 210
(0.1-0.25) (0.10-0.45)
6 5.93 3
<0.l 40.1
9 (8.8-20.5) <0.05-0.05)
4.6-5.94 3
2.2 < 0.1
13 3.62 (0.2-0.3) (<0.05)
0.5 <0.1 3
17 (0.15-0.50)
4.72-5.93 40.1 5
40.2 1.0
20 4.51 3
(0.2 (1.0
(O.3-0.65)
25 (1.0-2.7)
4.91 3
<0.1
(10-45) (0.2-2.2)
33 4.63 3
4.1 10 2
37 (0.2-1.1)
5.07 5
0.1
39 (2.6-6.8)
4.95-5.12 3
8.1
48 (3.8-12.0)
5.06-5.23 3
2.9
52 (<0.05) (0.9-1.6)
5.18 40.1 <1.0 3
<0.2
59 (35-48) (<0.21
5.3-5.39 0.8 3
40.2 < 1.0
63 (2.4-3.8)
5.51-5.58 3
0.1
67 (0.05-O.1)
5.7-5.83 3
<0.1
Alkaline Operates
Etcher 0.9 Total Chloride: 60 PPM 8
5/hrs/day
Resist Operates
Stripper 6.64 0.1 20
15 hrs/day
NOTE: The values in the parantheses are taken on 6/84
Ihe values without parantheses are taken 7/85
TABLE 2. ANALYTICAL RESULTS OF THE ELECTROPLATING
SYSTEM BATCH DUMPS
Tank No. pH Cu, mg/l Cr, mg/l Pb, mg/l Sn, mg/l Dump Schedule; weeks
Operates at 90-170°F.
1 0.03 1,750 928,000 Returned to Vendor.
16 weeks.
2 0.02 1,200 861,000
5 4.00 65 85 2
o
8 9.4 60 < 2 130 F, 2
11 0.96 8,200 < 2 2
12 0.7 50 2
14 0.49 250 < l 8
15 2.05 3.7 4 1 8
16 0.22 125 8,000 8
19 1.7 40 43 3
22 12.61 3,200 (
(
23 4.5 3,200 ( As needed
(
24 2.48 3,200 (
28 0.54 580 2
29 0.28 16,400 (
( 11
30 0.57 18,300 (
(
31 0.3 24,700 (
34 0.1 110,000 1
36 1.78 580 1
38 0.73 7,300 2
40 0.5 90 2
TABLE 2. (continued)
TankNo. pH Cu, mg/l Cr, mg/l Pb, mg/l Sn, mg/l Dump Schedule; week
41 0.84 18,000
42 0.64 17,100
43 0.33 20,600
44 0.35 19,200
11
45 0.4 17,600
46 0.39 21,400
47 0.44 16,200
50 0.38 18,000
51 1.27 4 10,200 15,100 13
54 1.35 2 50 100 1
55 1.1 4 11,400 14,400 13
56 1.0 <2 12,000 14,400 13
57 0.96 25 11,000 14,900 l3
58 11.21 20 2
62 0.29 1,000 1
66 10.05 20 Operates at 200°F.
16
7/31/85
TABLE 3
PLATING LINE PROCESS PARAMETERS
DumP
Tank Volume Chemical Schedule Destiny of
o
TankNo. Process Name Chem. Comp. Temp. F (Gal.) Make-up (Weeks) the Stream
1,2 Org. Etch CrO3 150 170 13 gal. 16 AD
5 Reducer Na2S2O5 RT 160 100 lbs. 2 AD
8 Soak Alk. Clean 150 170 10 gal. 2 AKD
11 Sodium Na 2 S 2 O 8 RT 170 62 lbs 2 AD
Persulfate H2S04 3 gals.
12 Acid H2SO4 RT 160 13 gal. 2 AD
14 Pre-dip HCl RT 160 5 gal. 8 AD
Pre-dip balance
(mixture of
inorg. salts)
l5,16 Activator HCL RT 170 5 gal. 8 AD
Activator 5 gal.
Pre-dip balance
12 Conditioner Acid RT 160 25 gal. 3 AD
22-24 Electroless Copper Mix RT 170 15 gal. As needed ECD
Copper (Copper Salts,
HCHO)
28 Acid H 2 SO 4 RT 160 13 gal. 2 AD
29-31 Copper Plate CuSO4 RT 300 70 gal. 11 AD/CT1
H2SO4 26 gal.
34 Nitric Strip HNO3 RT 160 90 gal. 1 AD
36 Acid Clean Cleaner 150 170 50 gal. 1 AD
(Org. acid,
surfactant
mix)
38 Sodium Na2S2O8 RT 170 225 lbs 2 AD
Persulfate H 2 SO 4 3 gal.
40 Acid H2SO4 RT 160 13 gal. 2 AD
41-47,50 Copperplate CuSO4 RT 300 70 gal. 11 AD/CT1
H2S04 26 gal.
51 Solder HBF4 RT 300 13 AD/CR
+2
Sn + 2
Pb
TABLE 3. (continued)
Dump
Tank Volume Chemical Schedule Destiny of
o
Tank No. Process Name Chem. Comp. Temp. F (Gal.) Make-up (Weeks) the Stream
54 Acid HBF4 RT 160 l3 gal. 1 AD
55-57 Solder HBF4 RT 300 l3 AD/CT2
+
Sn 2
+2
Pb
58 Alk. Clean Alkali 150 170 100 lbs. 2
(NaOH,
Na2CO3)
61 Copper Chloride from CuCl2 RT 170 170 1 AD
etcher
63 Acid HCl RT 160 26 gal. 1 AD
65-66 Oxide treat NaOH 210 170 1.2gal.(50%) 16 AKD
Na3PO4 16 lbs.
NaClO3 50 lbs.
RT = Room Temperature
AD = Acid Dump
AKD = Alkaline Dump
CT1 = Carbon Treatment 1
CR = Carbon Treatment 2
ECD = Electroless Copper Dump
8/l/85
TABLE 4.
CHARACTERIZATION OF THE STREAMS FROM PLATING LINE
COPPER CHROMIUM LEAD TIN- -
Tank No. Chelated Rich* Lean Rich* Lean
- Rich*
- Lean
- Rich* Lean
1 X
2 X
3 X
5 X
6 X
8 X x
9 X
11 X
12 X
13 X X
14 X X
35 X X
16 X X
17 X X X
19 X X X
20 X X
22 X X
23 X X X X
24 X X
25 X
28 x
29 X
30 X
31
36 X
37 X
38 X
39 X
40 X
41 X
42 X
TABLE 4. (continued)
8/l/85
TABLE 5.
WASTEWATER DESTINATION FROM DIFFERENT EQUIPMENT INVOLVED IN THE PLATING PROCESS
PROCESS NAME DESTINY OF THE STREAM
1. Gold Tab Continuous Rinse (max. 10 GPM)
2. CuCl2 Etcher 1. Vendor
2. Tank 25 & final pH adjustment
3. Sewer
3. Deburr Sewer
4. Alkaline Etcher Continuous Rinse (max. 10 GPM)
5. Scrubbers Sewer
6. Developer 1. Sewer
2. Tank 25 & final pH adjustment
8/5/85
TABLE 6.
WATER SOURCES FOR THE PLATING LINE
Total rinse flow of DI Water 6 gpm
Total rinse flow of City Water 48 gpm
