United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-88/008 Mar. 1988
&EPA Project Summary
Waste Minimization in the
Printed Circuit Board Industry-
Case Studies
Thomas Nunno, Stephen Palmer, Mark Arienti, and Marc Breton
The full report presents information
on waste minimization practices cur-
rently employed in the printed circuit
board (PCB) and semiconductor manu-
facturing industries. Case studies
conducted at six facilities evaluated the
technical, environmental and cost
impacts associated with the implemen-
tation of technologies for reducing the
volume and toxicity of PCB metals-
containing sludges and solvent wastes.
The analyses of these data are the basis
for demonstrating waste minimization
technologies to reduce hazardous
waste.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory. Cincin-
nati, OH, to announce key findings of
the research project that is fully doc-
umented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The purpose of this project was to
evaluate the effectiveness of various
waste minimization practices or technol-
ogies in the printed circuit board and
semiconductor manufacturing indus-
tries. The most significant waste streams
in these industries are waste halogen-
ated solvents from photoresist stripping
and developing operations (RCRA Waste
Code F001-F003), and metal-bearing
sludges (RCRA Waste Code F006) from
the treatment of metal plating and
etching rinsewaters. This Project Sum-
mary presents the findings of case
studies conducted at five printed circuit
board manufacturing facilities and one
commercial treatment/recovery facility.
Each facility investigated employs some
practice that requires offsite disposal.
Two of the case studies focus on the
recovery of spent halogenated solvents,
and the remaining four discuss the
recovery or reduction of metal plating and
etching process wastes. Table 1 sum-
marizes characteristics of facilities
investigated that range from small job
shops to large integrated facilities.
Metal Plating Bath Waste
Minimization Case Studies
Metal plating wastes generated from
plating bath dumps, rinses, etching
machines and scrubbing operations
generate copper-, nickel-, tin-, and lead-
contaminated wastes. Four of the six
case studies investigated under this
research project focus on the minimiza-
tion of sludges generated primarily by
copper plating and etchant baths and
copper and tin/lead rinsewaters.
The common objectives of each of the
technologies evaluated are: (1) minimi-
zation of metals sludges generated; (2)
compliance with effluent guidelines or
local discharge limitations; and (3)
reduction in operating costs over other
conventional alternatives. The following
discussion briefly summarizes each case
study, the nature of the minimization
technology, the measurements data
collected and the results obtained.
Facility A
Description
Facility A is an offsite Treatment,
Storage, and Disposal (TSDF) facility
which processes concentrated dumps
-------
Table 1. Summary of Facilities Tested Under Waste Minimization Case Study Program
Facility Name
Description
Wastes Treated/Reduced
Technology
Residuals
Facility A Treatment storage disposal
facility handling electro-
plating baths, waste
etchants, spills, etc.
Capacity: I.OOOgph
(24,000 god).
Facility B Contract PC board
manufacturing shop
Employees: 77
Production: 500,000 sf/yr
Sales: $7 Million/yr
Facility C Computer manufacturer.
Employees: 10,000 •
Facility D Electronic equipment mfgr.
PC board manufacturing using
the subtractive technique iri-
the MacDermid process.
Employees: 260
Facility E Computer manufacturer.
PC board manufacturing using
additive techniques.
Employees: 600
Production: 600,000 sf/yr
Facility F PC Board manufacturer
2-sided single layer circuit
boards.
Production: 480.000 sf/yr
-Nickel plating baths
-Copper plating baths
-Cyanide
-Cupric chloride etchant
-Electroless plating rinses
-Electroplating rinses
-Methyl chloroform resist
developer
-Freon resist developer
-1,1,1 -trichloroethane
resist developer
-1,1,1 -trichloroethane
still bottoms
—Acid copper plating bath
-Acid copper plating
rinsewaters
- Tin/lead plating
rinsewaters
-Sodium hydroxide precipitation
-Sodium borohydride reduction
-Alkaline chlorination
-Sodium borohydride reduction
-Memtek ultrafiltration system
—Solvent distillation/
fractionation recovery of
resist developers.
—2-stage solvent distillation
—(1) DuPont RISTON SRS-120
solvent recovery still
—(2) Recyclene Products, Inc.
RX-25 still
—Activated carbon regeneration
of spent plating baths.
-Agmet Equipment Corp.
-Electrolytic recovery units.
Sludge product
Sludge product
Still bottoms
Still bottoms
Spent activated
carbon
Metal foil
from the metal plating and printed circuit
board industries, including alkaline
etchants, acid plating baths, nitric acid
rack strip baths, and electr.oless plating
cyanide baths. The average total metals
concentration in the incoming waste was
reportedly 12 g/L (12,000 ppm). These
waste streams are classified into the
following four categories: (1) acidic
metals solutions; (2) alkaline metals
etchant solutions; (3) cyanides; and (4)
chelated metals solutions. The case
study for this facility focuses on the use
of a sludge minimizing treatment tech-
nology for the metals and cyanides
wastes.
Initially, the facility was designed to
operate using lime and ferrous sulfate
precipitation of metals as the primary
means of waste treatment. When the
high cost of land disposal of the lime
sludges was considered, alternate
means of treating and disposing of the
waste were evaluated.
The unit processes selected to detoxify
the wastes and recover metals at Plant
A currently include sodium hypochlorite
oxidation of cyanides (alkaline chlorina-
tion), sodium hydroxide precipitation, pH
adjustment, sodium borohydride reduc-
tion (with sodium metabisulfite stabili-
zation), sedimentation, plate and frame
filter press (for sludge dewatering), rapid
sand filtration, and ion exchange
columns for effluent polishing.
Results
The primary purpose of the Facility A
case study was to evaluate sodium
borohydride as a viable waste treatment
alternative for reducing RCRA Hazardous
Waste Code F006 spent electroplating
baths. The evaluation criteria were the
ability of sodium borohydride (SBH) to
effectively meet local compliance stand-
ards and produce a high density, low-
volume sludge. The test program evalua-
tion relies mainly on the trace metals
results to evaluate system performance.
The SBH reactor was sampled for trace
metals on the influent, effluent, and
sludge streams. Both filtered and unfil-
tered samples were collected and ana-
lyzed for eight selected metals. The
unfiltered sample showed little or nc
reduction as expected. However, the
filtered sample showed individual metal:
reduction efficiencies which ranged frorr
16.1 to 99.8 percent. The observed range
in efficiency data was attributed tc
variations in concentration and chemica
potential (quantity of free energy
required for an ionic species to obtair
equilibrium) of each of the metallic ion;
contained in the solution. Overall, SBr
was able to reduce 6.91 kg of the initia
influent metals loading of 7.25 kg. These
results represent a greater than 95
percent reduction in total metals for <
complex waste stream. The remainder o
the metals influent loading (0.337 kg
consisted of over 70 percent calcium.
An additional objective of this progran
was to evaluate the ability of Facility /
to consistently meet local pretreatmen
requirements. The resultant data for tw<
separate batch runs showed discharge:
in excess of effluent limits, apparent!'
due to incomplete polishing caused b'
cation exchange column breakthrough
Since the test program was completed
-------
> Facility A has instituted the use of a
quality control holding tank and further
waste processing optimization to remedy
these problems. Follow-up discussions
with the local sewer authority revealed
that Facility A's effluent quality has
improved considerably and is now con-
sistently meeting compliance guidelines.
In addition to assessing wastewater
effluent characteristics, the testing
program was designed to evaluate
uncontrolled process air emissions. The
results were obtained by Draeger tube
analysis of grab and integrated samples
of exhaust gases taken from the process
reactor exchaust ducts. The emission
results showed a frequent presence of
hydrochloric acid and hydrogen gas
accompanied by occasional presence of
ammonia and sulfur dioxide. One of the
hydrogen emissions grab sample results
(6.0 percent) is significant since this
value is greater than the lower flamma-
ble limit for hydrogen (4.0 percent). Grab
sample concentrations for ammonia and
sulfur dioxide also exceeded adopted
short-term exposure limits (STEL) for
these substances.
Analysis of the nickel/cyanide and
SBH sludges shows total metals contents
(dry weight) of approximately 35 and 6
percent, respectively. Neither sludge
result supported Facility A's claim of 60
to 70 percent metals content (dry basis).
While the SBH sludge result was signif-
icantly below performance expectations
(70 percent metals), the exact cause of
these results was not discernable.
Possible explanations include: (1) a
possible process upset; (2) sampling
error; and (3) analytical error. It seems
most probable that a process upset was
responsible for these results, since
blinding of the sludge press occurred on
the SBH press. Based on other SBH
reduction case study results conducted
under this program, it is reasonable to
assume that these results are not
representative, since typical sludge
metals contents should be greater than
70 percent.
EP Toxicity analyses were also con-
ducted for both the nickel/cyanide and
SBH reactor sludges. The results of the
tests clearly show that for Facility A
influent metals concentrations, the SBH
sludge produced is fairly stable in that
its leachate characteristics are below EP
Toxicity limits for all metals. However,
note that the waste is still classified as
F006 hazardous waste.
Another objective of the Facility A case
study was to evaluate the ability of SBH
to economically reduce F006 waste
streams. At the time of testing. Facility
A reduction chemistry was very ineffi-
cient at $19.80/lb of copper reduced.
However, through process optimization,
chemical costs have reportedly
decreased over 63 percent, bringing
process economics within acceptable
limits. The case study follow-up for
Facility A has indicated that the cost of
copper reduction has been lowered to
$7.27/lb of copper.
Facility B
Description
Facility B is a captive printed circuit
board manufacturing facility employing
77 people in Santa Ana, California. Gross
sales are approximately $7 million
annually on production of 500,000 ft2 of
board. Production at Facility B uses a
special hybrid process, employing ele-
ments of both additive and semi-additive
printed circuit production techniques.
Process wastes of interest to this study
include rinsewaters from the electroplat-
ing and etchant baths. The principal
components of the acid copper electro-
plating baths are copper sulfate and
sulfuric acid. Facility B uses a slower
acting etchant (sodium chloride, sodium
chlorate, and muriatic acid) which etches
copper from the board, and yields cupric
chloride in the waste stream.
Facility B uses a rather unique end-
of-pipe treatment system employing SBH
treatment and ultrafiltration (Memtek)
technology for solids separation. In this
process, incoming plating and etching
wastes are adjusted to pH 7-11 by adding
sodium hydroxide or sulfuric acid.
Sodium borohydride is added to obtain
an oxidation reduction potential (ORP) of
approximately -250 mv or less. The
reacted waste then feeds from the
concentration tank to a Memtek ultrafil-
tration unit from which the permeate is
discharged to municipal treatment, and
the concentrate is returned to the
concentration tank. A small plate and
frame sludge filter press dewaters the
sludge which is drawn from the bottom
of the concentration tank.
Points of interest in evaluating the
Facility B waste treatment system for this
case study were: (1) compliance of the
ultrafiltration permeate (wastewater
discharge) with local and Federal dis-
charge standards; (2) the volume and EP
toxicity of the sludge filter cake; and (3)
economic evaluation against comparable
technology (lime and ferrous sulfate
treatment).
Results
The objective of the sampling program
was to evaluate the effectiveness of the
SBH technology in use by Facility B. The
effectiveness was measured in terms of
metal reduction efficiency and minimi-
zation of hazardous waste streams. Data
derived from the metals concentrations
in the influent and effluent streams were
used to determine the effectiveness of
the SBH reduction system in both meet-
ing effluent guidelines and minimizing
releases to the environment.
Analysis of the influent and effluent
streams metals characteristics showed
that copper was reduced most efficiently
(99.82 percent), while nickel reduction
was the least efficient (45.5 percent).
Differences in removal efficiencies were
attributed to variations in concentration
(higher removals for higher concentra-
tions), but the chemical potential may
also have been a factor. Approximately
144.7 Ib of combined metals were
reduced to elemental form by the SBH
reaction system, representing a com-
bined reaction efficiency of 99.8 percent.
Despite deviations from design operating
conditions, the SBH/ultrafiltration sys-
tem performed very well. EP Toxicity
leachate test results for Facility B filter
press sludge clearly show that the SBH
sludge produced is fairly stable. Leachate
characteristics are below EP Toxicity
limits for all metals. However, note that
the waste is still classified as F006
hazardous waste.
In addition, an economic comparison
of the use of SBH versus lime-ferrous
sulfate chemistries was conducted. The
results demonstrate that in this applica-
tion, SBH would be superior to lime-
ferrous sulfate for the following reasons:
(1) sludge disposal costs and volumes
would be reduced by 93.5 percent; (2)
overall operating expenses would be 48
percent lower; and (3) sludge generated
by the SBH reduction process was 78
percent copper and suitable for reclama-
tion (due to the high copper content).
The use of the SBH and ultrafiltration
treatment at Facility B is favored by the
use of the chloride etch process in lieu
of the more commonly preferred ammo-
nium peroxide etch. The ammonium-
based etchants create borohydride
sludge stability problems which require
tighter treatment process control and use
of stabilizers such as sodium metabisul-
fite. Additional factors that favor the
economics of SBH treatment at Facility
B include: (1) the use of cupric chloride
etchant; (2) nigh copper concentrations
-------
and low organic loadings seen at this
facility; and (3) low effluent limitations
required by the sanitation district.
Based on the above results, it appears
that SBH reduction is an effective
technology which can be utilized to
reduce complex metal electroplating
sludges and render them reclaimable,
and possibly less hazardous. Note that
the economics of SBH technology is
highly dependent on site-specific factors
and warrants a detailed study prior to
implementation.
Facility E
Description
Facility E began operations in January
1982 as a manufacturer of customized,
fine-line multilayer printed circuit
boards. Facility E initiated an ambitious
waste minimization program in mid-
1984. Since that time, production has
roughly doubled, but liquid discharge to
the wastewater treatment plant has
remained constant and wastewater
sludge generation has dropped roughly
30 percent. Waste minimization efforts
continue to center around in-process
modifications to use nonhazardous or
reclaimable solutions, to reduce water
consumption and bath dump frequency,
and to optimize wastewater treatment
operations.
At Facility E, boards are pattern plated
with eight acid copper and one aqueous
tin/lead plating baths in a 48-tank
plating line. The line begins with a nitric
acid (HNO3) rack strip tank. After the
racks are stripped, boards are loaded and
then undergo rinsing, cleaning with
phosphate solutions (H3PO<, Electro-
clean PC2000), and more rinsing before
being plated. Acid copper baths contain
CuSO4, organic brighteners, and chlo-
rides with copper concentrations of 24
oz/gal. The general processing proce-
dure is to activate the board surface (HCI),
plate, clean/rinse and replate.
In plating operations, addition agent
and photoresist breakdown products will
incrementally accumulate and contam-
inate an electrolytic (charge carrying)
plating bath. In the absence of a bath
regeneration system, the manufacturer
would typically be forced to either
discharge the spent plating bath to the
wastewater treatment plant or send it
offsite for disposal. In either case, large
quantities of metals containing sludge
(RCRA Waste Code F006) would be
generated and subsequently land dis-
posed. At Facility E, these spent plating
baths are regenerated through activated
carbon filtration (used to remove built-
up organic bath contaminants) and then
returned to the process. Copper and
solder plating baths are treated with
activated carbon once every three
months and every month, respectively.
The frequency of cleaning is determined
by organic contaminant build-up. Elec-
troplating baths never have to be dumped
with this arrangement under normal
processing conditions.
Activated carbon treatment is per-
formed in a batch mode for acid copper,
solder and nickel microplating baths in
three separate systems. The bath recla-
mation system consists of a holding tank,
mixing tank, and MEFIAG paper-assisted
filter. For acid copper treatment, 2,400
gallons of contaminated solution is
pumped into a 3,000-gallon mixing tank.
Hydrogen peroxide is added and the
temperature of the bath is maintained at
120 to 130°F for 1 hour. Powdered
activated carbon (80 Ib) is added and the
contents are mixed for 3 to 4 hours to
oxidize volatile organic species. The
solution is recirculated through a paper-
lined MEFIAG filter several times to
remove the activated carbon. The filter
solids and paper are removed as needed
when a predetermined pressure drop
across the filter is reached. When the
bulk of the activated carbon has been
removed (generally after three passes of
the solution through the filter), the filter
is precoated with 5 gallons of diatoma-
ceous earth. The solution is again
recirculated through the filter until a
particulatetest indicates sufficient solids
removal (no residue detected on visual
examination of laboratory filter paper).
Total spent solids from plating bath
purification is 1-V4 drums every 3 months
which is landfilled.
Results
The purpose of this case study was to
evaluate the extension of electroplating
bath lifetimes (and subsequent waste
reduction) by activated carbon removal
of organic brightener breakdown prod-
ucts. The acid copper baths were selected
for study since recovery of this sojution
results in the most significant.amount
of waste minimization.
Sampling and analysis were conducted
on three process streams associated with
activated carbon bath reclamation. Based
on resultant analytical data the following
conclusions were drawn:
• Forty-seven percent of the organic by-
products and brighteners were
removed from the contaminate)
solution:
• Low molecular weight organics sue)
as carboxylic acid derivatives are no
preferentially adsorbed;
• Reduced sulfur (a brightening an<
leveling agent) is oxidized and vola
tilized during treatment; and
• Inorganic contaminants such as tir
and lead are also removed (37.£
percent and 24.5 percent, respec
lively) as a beneficial by-product of th(
treatment process.
In recovering spent electrolytic platini
baths. Facility E was able to save ove
$50,000 in hazardous waste disposa
and raw material purchase costs. Thesi
savings represent a payback period o
only 3 months for purchasing the acti
vated carbon recovery system. Thi
relatively short payback period, combinei
with the volume of plating solutioi
regenerated, make activated carboi
treatment a cost-effective and environ
mentally safe technology for reducing thi
quantity of hazardous waste that wouli
otherwise be land disposed.
Facility F
Description
Facility F is an independent manufac
turer of printed circuit boards. Thi
normal production volume of the facilit
is 40,000 ftVmonth. The major wasti
streams of interest to this case study an
rinsewaters that follow electroplatini
and etching processes. Prior to imple
mentation of the electrolytic recover
technology being studied, these rinse
waters contained copper and lead a
concentrations of up to 3,000 mg/L
Because of this, the concentration o
these metals in the final effluen
exceeded pretreatment standards (4.!
mg/L for copper and 2.2 mg/L for leaC
for discharge to the city sewer system
To decrease the concentration of metal
in the effluent, the facility convertei
several rinse tanks into static dragou
tanks in order to recover metals fron
rinse baths following copper electroplat
ing, tin/lead electroplating, electroles
copper plating, and a copper microetc!
process. The quantity of metal recovere
from the electroless copper rinse and th
copper microetch was small. Thus, th
reactors were removed from these bath
and installed at the copper and tin/lea
-------
rinse baths where there was more
potential for metal recovery.
The electrolytic reactors used at this
facility are Agmet Equipment Corp.,
Model 5200* reactors. They consist of
a wastewater sump, a pump, and the
anode and cathode, contained within a
rectangular box with dimensions of
approximately 22 in. x 10 in. x 22 in. The
anode was cylindrical and was encircled
by a stainless steel cathode with a
diameter of 8 in. and a height of 6 in.
The anode material used for copper
plating solutions is titanium. For tin/lead
plating solutions, however, a columbium
anode was required because the fluoro-
boric acid in the tin/lead plating solution
was extremely corrosive to titanium. The
columbium anode increases the cost of
these electrolytic units to $4,500, as
opposed to $3,500 for the titanium anode
units.
Results
At the time of testing, four electrolytic
reactors were being used for recovery of
copper, and three were being used for
recovery of tin/lead. To evaluate the
performance of these units, samples of
the plating bath, dragout, and rinse bath
were analyzed. Conclusions that were
drawn based on the resultant data
include:
• Recovery of copper from the acid
copper solution is very effective—
rates of recovery were 4 to 5 grams/
hour/unit, representing a current
efficiency of nearly 90 percent.
• Recovery of tin and lead was not
effective at the itme of testing-
concentrations of these two metals in
the dragout were not significantly less
than in the plating bath. However,
evaluation of the data was difficult
because the analytical results for
some of these samples were incon-
clusive due to matrix interference.
• Use of in-line electrolytic recovery
was not able to reduce metal concen-
trations sufficiently as to enable this
facility to meet pretreatment
standards.
• Electrolytic recovery would signifi-
cantly reduce the amount of sludge
generated if a lime precipitation
system were utilized to remove metals
"Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
from the final plant effluent. For this
facility, a reduction of 32 tons/year
would be realized.
• At a sludge disposal cost of $200/ton,
the annual cost of electrolytic recovery
would exceed the savings. However,
if sludge disposal costs increased to
$300/ton, the savings (at least for
copper recovery) would exceed the
processing costs.
Electrolytic recovery methods remove
metals from an aqueous solution in a
metallic form which allows for the use
of the recovered material as scrap metal.
Conversely, hydroxide precipitation
removes the metal from solution and
generates a sludge with a low metal
concentration. In most cases, the only
method of handling this sludge is land-
filling at a high cost. Therefore, electro-
lytic recovery is useful in minimizing the
quantities of metal-bearing sludge that
must be landfilled. The cost effectiveness
of this type of technology will increase
as sludge disposal costs increase in the
future.
Resist Developing Solvent
Recovery Case Studies
Two case studies evaluated under this
program focused upon the minimization
of developer solvent wastes and sludges
which might require either land disposal
or incineration. In general, the recovery
of resist stripping and developer solvents
is not unique within the PC board
manufacturing industry. However, the
recovery systems evaluated at the two
facilities discussed below represent
state-of-the-art technology applications.
In the case of Facility C, the technology
involves the separation of a two-solvent
system with subsequent recovery and
reuse of each solvent. In the case of
Facility D, the technology evaluated
further recovers the solvent bottoms
product of the initial recovery unit.
Facility C
Description
Facility C manufactures computing
equipment including logic, memory and
semiconductor devices, multilayer
ceramics, circuit packaging, intermediate
processors and printers. One of the major
hazardous waste streams that is gener-
ated is spent halogenated organic sol-
vents (RCRA Code F002). Methylene
chloride is used in resist stripping of
electronic panels. Methyl chloroform
(1,1,1-trichloroethane) used in resist
developing of electric panels and sub-
strate chips. Freon used in surface
cleaning and developing of substrate
chips. Perchloroethylene used in surface
cleaning of electronic panels.
The spent solvents from photoresist
stripping and developing are contami-
nated with photoresist solids at up to 1
percent, and the solvents used for
surface cleaning are contaminated by
dust, dirt or grease. Waste solvents are
recovered at Plant C by distillation or
evaporation and returned to the process
in which they were used. Several types
of equipment are used including box
distillation units to recovery methylene
chloride and perchloroethylene, flash
evaporators to recover methyl chloro-
form, and a distillation column to recover
Freon.
There are two identical flash evapor-
ators at the facility, each with a capacity
to recover 600 gallons of methyl chlo-
roform (MCF) per hour. The flash
chamber operates at a vacuum of 20 in.
Hg, allowing the MCF to vaporize at 100
to 110°F. The units are operated one to
two shifts/day depending on the quantity
of waste solvent being generated.
A packed distillation column is used
to recover pure Freon from a waste
solvent stream containing approximately
90 percent Freon and 10 percent methyl
chloroform. Waste is continuously fed to
a reboiler where it is vaporized and rises
up the packed column. Vaporized Freon
passes through the column, is condensed
and recovered at a rate of 33 gal/hour.
MCF condenses on the packing and falls
back in the reboiler. The distillation
bottoms are removed when the concen-
tration of methyl chloroform reaches 80
percent (approximately 1 to 2 weeks).
There are also two identical box stills
at the facility, each with a capacity to
recover 475 gph of methylene chloride.
These are very simple units consisting
of ah 800-gal still pot with hot water
heating coils. The contaminated meth-
ylene chloride is heated to between
103°F and 108°F, and clean solvent is
condensed overhead.
Results
Sampling and analysis were conducted
on process streams associated with two
of the solvent recovery processes. One
of these processes was the flash evap-
orator used for recovery of methyl
chloroform (1,1,1-trichloroethane), and
the other was the distillation column
-------
used to recover Freon TF from a Freon/
methyl chloroform mixture. The conclu-
sions drawn from the sampling and
testing program were:
• At least 95 percent of the solids are
removed from the solvent waste
influent;
• The recovered product is at least as
clean as the virgin material; and
• The still bottoms from recovery of
contaminated solvent still contain a
high fraction (90 percent) of solvent.
The recovery of spent solvents at the
facility is motivated primarily by eco-
nomic benefit. In recovering spent
solvent, the company saves over $10
million annually, compared to offsite
recovery. The savings per pound of
methyl chloroform, methylene chloride,
and Freon recovered is $0.18, $0.18, and
$0.61, respectively.
The high cost savings are primarily due
to the fact that the solvents recovered
are reused onsite, thus reducing the
quantity (by greater than 95 percent) of
new or virgin solvent that must be
purchased. Offsite recovery could be
conducted, but at much higher cost.
Since the rate of generation of spent
solvent is so high, the initial expense of
purchasing recovery equipment is
quickly returned.
To landfill or dispose of such a large
quantity of spent solvent by any other
method would be economically
unacceptable. Incentives other than
economic reasons for onsite recovery
include:
• Reduction in the risk of a spill of
solvent in transporting the waste to
aTSDF; and
• Reduced liability related to an accident
at the TSDF resulting in the release
of spent solvent.
Facility C is trying to further reduce the
quantity of waste solvent that must be
sent offsite for recovery. They intend to
do this by recovering the still bottoms
generated by distillation of Freon/methyl
chloroform waste. In addition, they
eventually plan to phase out the use of
methyl chloroform and methylene chlo-
ride and replace these materials with
aqueous-based photoresist developers
and strippers.
Facility D
Description
Facility D manufactures mobile com-
munications equipment components in
Florence, SC. The operation consists of
a small metal-forming shop, prepaint and
painting lines, electroplating, printed
circuit board manufacture, and a 30,000
gpd onsite wastewater treatment plant.
Printed circuit boards are produced
using the subtractive technique and
solvent-based photoresists. Methylene
chloride resist stripper and 1,1,1-
trichloroethane (TCE) developer are
continuously recycled in closed-loop
stills. The TCE developer wastes (Waste
Code F002) are recovered in a DuPont
Riston SRS-120 solvent recovery still
(referrred to as the primary still) and
returned to the developer line. Until
recently, all still bottoms from the
primary still were drummed and shipped
offsite for reclamation at.a solvent
recycling facility. Facility D purchased a
Recyclene Industries RX-35 solvent
recovery system (referred to as the
secondary still) in October 1985, to
further remove TCE from still bottoms
onsite.
The Recyclene Industries RX-35
solvent recovery system is a batch
distillation system with a 30-gallon
capacity, silicone oil immersion heated
stainless steel boiler, a non-contact,
water-cooled condenser, and a 10-gallon
temporary storage tank. The boiler is
equipped with a vinyl liner inside a Teflon
bag. The Teflon bag provides temperature
resistance and the vinyl bag collects solid
residue, eliminating boiler clean-out and
minimizing sludge generation after
distillation. Two thermostats control the
temperature of the boiler and the vapor,
automatically shutting down the boiler
when all the solvent has evaporated. The
maximum operating temperature of the
still is 370°F, so recovery of solvents with
higher boiling points would not be
practical. Recovery of a 20- to 25-gallon
batch of still bottoms requires approxi-
mately 90 minutes at Facility D, and four
to six batches are completed each day.
Results
Evaluation of the system consisted of
the analysis of the contaminated feed,
overhead product, and distillation bot-
toms. Based on a mass balance and
analytical data, the following conclusions
were made:
• Purity of recovered solvent was 99.9$
percent;
• Total solvent recovery was 99.7(
percent;
• Still bottoms contained 7.5 weigh
percent 1,1,1-trichloroethane; and
• Reduction in waste generation was
97.5 percent.
An additional objective of the studi
Was to evalute the economics of the
batch solvent recovery unit. Annual cos
savings ($43,000) and waste reductior
(110,602 gal) were calculated for Plan
D, based on the first year of RX-3E
operations. In addition, the investmen
payback period for the RX-35 was
calculated considering credit fo
reclaimed solvent and reductions ir
waste transportation and disposal costs
The estimated payback period was 7.2
months, given the current level of solven
reclamation. Thus, the low capital cos
of the unit and the relatively high cost!
of virgin solvent ($4.50/gal) favor the
second-stage recovery of TCE developei
still bottoms.
There are several potential drawback!
to the implementation of RX-35 batcr
still that should be discussed. The firs
is that since the bottoms product con
tains 7.5 weight percent 1,1,1-TCE, ii
remains classified as RCRA Waste Code
F002 (halogenated organic solvents) anc
is among those solvent wastes beinc.
considered under the land disposal ban
Thus, while this technology significant^
reduces the volume and toxicity of the
solvent still bottoms, it continues tc
generate a hazardous waste. A seconc
potential concern is the accumulation 01
contaminants and/or breakdown pro-
ducts. For example, 6.7 to 11.0 percent
concentrations of carbon tetrachloride
were found in process feed and exi
streams, indicating a build-up of this
contaminant. Another significant con
taminant found was 2-Butanone, which
represents 3.6 percent of the solven
waste feed stream. It could not be
determined whether a build-up of 2
Butanone was occurring or if it is harmfu
to the system. However, its presence anc
effect on the solvent properties of 1,1,1
TCE should be considered.
A final consideration in the implemen-
tation of any solvent recovery still is the
issue of safety. The unit at Plant D was
housed in a separate structure and
provided with adequate ventilation tc
minimize the risk of exposure or explo-
-------
sion. The RX-35, according to the manu-
facturer, is safe for flammable materials,
and is rated for NFPA Class I, Division
I, Group D environment. These safety
considerations should help to minimize
the risk of chronic exposure or danger
from explosion to personnel. Neverthe-
less, explosion risks from solvent recov-
ery operations should be carefully eval-
uated in planning the layout and
installation of the unit.
Conclusions
The findings of the waste minimization
case studies evaluated under this pro-
gram are presented in Table 2, which
includes data collected by the facilities
and verified by sampling and laboratory
results. These results indicate that a good
variety of technologies exist to minimize
metals-containing and solvent wastes
produced by the printed circuit board and
semiconductor industries. The technol-
ogies discussed range from simple
changes in treatment system reagents
with nominal capital costs to large onsite
solvent reclamation facilities with signif-
icantly higher capital costs.
Four of the case studies investigated
under this program focused on technol-
ogies to reduce metal-plating rinsewater
sludges. The use of SBH as a substitute
for lime/ferrous sulfate was found to be
viable in one case and appeared to be
marginally acceptable in another. The
case study on carbon adsorption recovery
of plating bath wastes found that this
technology significantly reduced both
disposal costs and waste volume. The
case study of electrolytic recovery indi-
cated that this technology is highly waste
stream specific. An acid copper electro-
plating rinse is an ideal waste stream for
electrolytic recovery. However, other
metal-bearing rinses, such as those from
solder (tin/lead) plating or etching, are
not appropriate for use of electrolytic
recovery. Electrolytic recovery units are,
however, generally inexpensive to pur-
chase and can be used in many cases
to supplement an end-of-pipe treatment
process.
Two of the case studies presented in
this Summary involve the recovery of
spent halogenated solvents using batch
distillation units. Both case studies
indicate that onsite solvent recovery is
successful from a technical and an
economic standpoint. In both cases, over
95 percent of the waste solvent was
recovered and reused onsite. Solvent
recovery appears to be a technology that
could be applied to a number of printed
circuit board manufacturing facilities.
The results of this project indicate that
waste reduction can be achieved through
the use of appropriate technology, and
it can be achieved with significant
reductions in cost. The case studies also
indicate that the success of waste
reduction is in many cases waste stream
specific. The technologies will not neces-
sarily be successful in all cases. A slight
variation between one waste stream and
another may make waste reduction
either technically or economically
impractical. Therefore, successful waste
reduction is dependent on a thorough
knowledge of waste quantities and
characteristics.
Table 2. Summary of Findings of Waste Reduction Case Studies
Facility Name
Facility A
Facility B
Facility C
Technology
Sodium borohydride reduction
Sodium borohydride reduction
Solvent batch distillation
Waste Reduction
Metals sludge
Metals sludge
Methylene chloride
Methyl chloroform
Freon
Annual Waste
Reduction
Achieved
a
962 tons
6. 152, 000 gal
Capital Costs
{$)
Nominal
Nominal
709.400
Projected
Annual Cost
Savings
(9)
b
/ 15.870
16.000,000
Facility D
Facility E
Facility F
2-Stage solvent distillation
Carbon adsorption
plating bath reclamation
Agmet electrolytic
recovery unit
1.1,1 • Trichloroethane
Resist developer
still bottoms
Plating bath wastes
(metals sludge)
Metals sludge
10.625 gal
10.600 gal
32 tons
26.150
9,200
30.350
43.105
57.267
(10.685)°
'Not quantifiable, but a significant waste reduction was realized.
"Not demonstrated during testing.
c( ) indicates negative value.
-------
T. Nunno. S. Palmer, M. Arienti, and M. Breton are with Alliance Technologies
Corporation, Bedford, MA 01730.
Harry M. Freeman is the EPA Project Officer (see below).
The complete report, entitled "Waste Minimization in the Printed Circuit Board
Industry—Case Study,"(Order No. PB88-161 575/AS; Cost $19.95, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PA
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-88/008
QC01961 HWER GN
LIBRARY REGION V
230 S DEARBORN ST
CMCAGO
60604
------- |