Guidelines
for
Hazardous Waste Reduction
Waste
Reduction . _ ,.
Program and Recycling
Metal Finishing
Printed Circuit Board Manufacturing
a program of
The Department of environmental Quality
July 1989
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GUIDELINES FOR WASTE REDUCTION AND RECYCLING
: ' . METAL FINISHING
'.'>. ELECTROPLATING
PRINTED CIRCUIT BOARD MANUFACTURING
Prepared by the
HAZARDOUS WASTE REDUCTION PROGRAM
OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY
First Revision
July 1989
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The
' -RiG'CN DEPARTMENT OF ; ENVIHCNT-fZ.VTAI. ..SCAlL-TTY .
" -. .HAZARDOUS WASTE 'REDUCTION -PROGRAM . " . .
guidelines- were prepared by the Oregon Department--of
-nvi-oSJirital Quality's Hazardous'Waste Reduction Program. T
orogram was established to provide technical assistance to
businesses' and industries 'to reduce the -amount of hazardous
walte ?ha? thev generate, deducing the amount of waste gener-
at,ed helps to control" costs and protect the environment.-
^he DEQ Hazardous Waste Reduction Program works with facilities
of all,sizes to come up with solutions to the problems asso-
elated with the generation, storage, treatment, and disposal of
hazardous waste. The program can-provide technical information
on waste reduction and recycling methods for your business, .n
addition, the program can provide,on-site assistance to iaen
tify and implement waste reduction opportunities in your
operations. ' ' _. '- _._ ... '.-'..,'
The program also maintains a technical library containing
information on waste reduction and recycling for a wide range
of industries. Publications on specific waste reduction
methods for electroplating, metal finishing, and printeoVcir-,
cuit board manufacturing operations, such,as those listed in
the references are available. Additional background infor-
mation and worksheets for conducting- a waste reduction assess-
ment are also available.
To obtain information, assistance, or publications on waste
reduction or recycling, please contact:
DEQ Hazardous wa/ste Reduction Program
811 SW Sixth Avenue
Portland,- Oregon 97204
Phone. (503) 229-5913 or
Toll Free Within Oregon, 1-800-452-4011
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TABLE OF.- CONTENTS
:HAPTER r. INTRODUCTION
CHAPTER 2 .'WASTE REDUCTION AND RECYCLING .METHODS '. ..' ... .' .. 5
1 GENERAL: WASTE REDUCTION METHODS .'',.; . .---. . . . 5,;
" -; WASTE REDUCTION AND RECYCLING APPLICATIONS. . '. -. 9
Improved Operations and . : ,
.''' - ', Housekeeping Practices .- ... .. . . . . . ' 10.
' ' s ' ' ' ' ,' " " ' '
''' .' , Drag-Out. -Reduction ^. . . . . '. . . . . . . 10
" Rihsewater Modifications . .... .... -12
/Material/Chemical Substitutions . . ';_.. . . . 13
Plating Bath Maintenance ... . ;.-. . . .-. 14
Chemical Recovery Processes . . . . .... 15
' Metal'.Recovery Processes .'.,. . . . .-,'. '.. '. 2.0
, Sludge Management .. . . . . .-.,... 21'
. Solvent Management .... ... - 21
CHAPTER 3 WASTE REDUCTION ASSESSMENTS, . . .... ... . 23
; PLANNING AND ORGANIZATION; . ..... . . . . . .23
ASSESSMENT PHASE . . . - 24
FEASIBILITY ANALYSIS .. . . ?. . . -1 . . .' . . . ... . 31.
IMPLEMENTATION OF WASTE'REDUCTION OPTIONS . . , 34
'REFERENCES ... . . . . . '. '.-'. . . . -.. ., - '....' "-. -. 3S
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CHAPTER 1
INTRODUCTION
* * * * *
There are several good waste reduction and recycling opportu-
nities available for metal' finishing, metal' fabricating, elec-
troplating, 'and printed circuit board- manufacturing operations.
This-manual will help you identify methods that can be used in
these operations to reduce the amount of waste generated and at
the same time help you to achieve other important obj ectives
such as increased profits, productivity, efficiency, and ,
product quality. , ' _ .
' > ' _ - : . ' - f . ^ - . . . _., - ..
WHY SHOULD YOU BE INTERESTED IN WASTE REDUCTION?
Many businesses are finding that waste management is becoming
increasingly more burdensome in terms of time, resources, and
costs, of particular concern to these businesses are such
issues as: '..'/ ''". .-'.' - ' "
- strict limits for.discharging process wastewaters to the
-- sewer' ' - . ;.'..'''."' "" - -'.''-
- costs of wastewater treatment to meet those limits
- regulatory requirements for hazardous waste management:
- costs of managing and disposing of hazardous wastes
- liabilities associated with the management of hazardous
waste " .. '_ ' . ', '' .;-,'; .-'"--. . ' "
- land disposal restrictions of certain hazardous wastes
Waste reduction and recycling can help you address these
problems and reduce the burden of waste management on your
HiVe i ness.' Waste reduction is a means of generating less waste
in'your operations thereby reducing your company's efforts and
resource* required for waste management.
WHAT DOES WASTE REDUCTION AND RECYCLING MEAN?
.waste Reduction; Waste .reduction is any activity that reduces
or eliminates the generation of hazardous waste at the source,
usually'within a production process. These source reduction
methods include such activities as good housekeeping practices,
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' J-
raw satenai substitutions, equipment modifications, production
process changes and waste segregation.
was-e Recycling; waste recycling is the recovery or reuse of
what would otherwise be a waste material. Waste recycling
activities include the direct use or reuse of a waste material ,
in"a process or the reclamation or recovery of a valuable
material from a waste. These activities reduce the. amount of a
waste that requires disposal.
This manual addresses both waste reduction and recycling
activities for metal finishing, metal fabricating, electro-
plating, and printed circuit board manufacturing operations.
These methods generally focus on hazardous wastes-that are
a-enerated in these operations, however, these methods can also
be applied to non-hazardous wastes such as wastewaters, air
emissions, and solid wastes.
HOW CAN MY BUSINESS BENEFIT FROM WASTE REDUCTION?
Waste reduction and recycling activities can help you to:
Reduce cost* associated with 'the treatment and disposal
of hazardous wastes.
Reduce raw material/chemical requirements which lowers
operating costs.
Increase production rates and improve product quality.
Reduce your liability and risks associated with the
management of hazardous wastes. .
Improve your company's public image by taking positive
steps toward, the community's waste problems.
create a safer workplace by reducing exposures to
hazardous wastes.
« Reduce the burden of trying to comply with regulatory
requirements associated with hazardous waste generation.
WHAT TYPES OF INDUSTRIES CAN IMPLEMENT WASTE REDUCTION METHODS?
Any business that generates hazardous waste in their opera-
tions, whether it is a small business or a large corporation,
can implement some method of waste reduction. This manual
specifically focuses on waste reduction and recycling methods
for metal finishing, metal fabricating, electroplating, and
printed circuit board manufacturing operations.
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^r.dustrv- Overview . ....-
Industries involved in metal fabrication-, metal ^ finishing,
elec*-opiating, or printed circuit board manufacturing utilize
a wide range of production processes and operations. These
processes' include: ". . , .
surface preparation/cleaning, . ; ' -.
paint stripping' ' --. ' .'',; ' . , . ,
. -' degreasing.' -,... ' '' -'' " . '' -' '
p ickling . :
bright dipping and.chemical polishing . ;
electroplating '>..-. .
electroless plating .
anodizing
coatings (chromating, phosphating, metal coloring,
'passivating) ' , ...
etching and chemical milling
painting .
heat treating -
fabrication , - ",
machining (cutting, grinding, welding, polishing, buffing)
HY Thaaie Industries ' ... .
These operations can generate potentially hazardous wastes
listed below. The classification of .a particular waste »_s
hazardous depends upon its specific characteristics and
components.
.spent acid or alkaline cleaning solutions
spent solvents . . , , . ,_ *.u
' spent process baths: plating, etching, pickling baths
sludges from process baths
process rinsewaters
wastewater treatment sludges
paint residues and sludges
still bottoms from solvent distillation systems
.spent aatal working fluids (coolants, hydraulic fluids,
lubricating oils, cutting oils, and quenching oils) -t
HOW TO USE THIS GUIDANCE MANUAL
Chapter 2 of this guidance manual describes detailed waste
reduction methods that can be used to reduce or eliminate the
generation of wastes from industrial processes. General-wast<
reduction methods, that can be applied to.a wide range of
industrial processes, are described, as well as process-
specific waste reduction methods for electroplating, metal
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finishing, and printed circuit board manufacturing operations.
Chapter 2 also provides a description of the chemical and metal
recovery processes including evaporation, reverse osmosis, ion
exchange, electrodialysis, ultrafiltration, and electrolytic
recovery.
Chapter 3 describes the procedure for conducting waste
reduction assessments. The assessment is a useful tool for
identifying and evaluating waste reduction opportunities within
a facility's operations.
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,, ; - ' .. CHAPTER' 2
WASTE .REDUCTION AND RECYCLING METHODS
"r * *
GENERAL WASTE REDUCTION METHODS ' -....';
Waste reduction and recycling methods are site- and process-
specif ic> although a number of general- approaches, and tech-
niques have been used successfully across the country to
reduce many types of industrial waste. These techniques range
from low or no cost methods to major 'equipment modifications
requiring large capital investments. These techniques can have.
ah application across a range of industries, and manufacturing
processes/and can apply to hazardous as well as r.er.-hasardous
wastes. These general methods include:
Process and Equipment Modifications
Input Material Changes
Improved Operating and Housekeeping Practices
Recycling
Process and Equipment Modifications - ~
Redesigning or replacing equipment in order generate
' ' . less waste.- -; - - : . / '-.-',-
production process to use less raw
materials and/ or generate less waste.
Use of automation which helps to limit inadvertent
releases and off -spec product generation.
Changes in operating conditions, such as flowrates,
temperature r pressures, residence times.
Implementing energy and water conservation programs.
- -''-.*. " ,-..-," l " * '
Input Material Changes
e Material substitution or replacing a. hazardous substance
used in a production process with a non-hazardous or
less hazardous substance. Examples include replacing a
.solvent cleaner with an alkaline cleaner.
-Material nurifieation involves the purification of /input
or feed materials in order to avoid the introduction of
inerts or impurities into the production process, When
impurities are introduced, the production process must
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eventually be purged in. order to prevent undesirable
accumulation of the c6ntaminants, thus generating a
waste. An example of this method is the use of
deionized water for process baths and rinsewater in
plating operations. ' _
Improved Operating and Housekeeping Practices . .
Tmnroved material tracking and inventory practices can
reduce the waste resulting from overstocking and
disposal of materials with an expired shelf-life.
Examples of these methods include:
- purchasing and using raw materials only as needed.
- keeping inventories of hazardous substances for
each storage area in.the plant.
- monitoring the quantities of waste resulting from
expired stock.
- maintaining Material Safety Data Sheets (MSDSs)
for all materials in use.
- labelling all containers to indicate the name and
type of substance, stock number, health hazards,
suggestions for handling, and first aid
information.
e Improved material u«aa«. handling, and Storage can
reduce loss of input materials due to mishandling and
improper storage. These methods include:
- standardization of materials or using the minimum
number of material types in your operations. This
increases the potential for recycling and reduces
the amount of waste requiring disposal.
- improved operation and maintenance of container
and drum storage arsas. . Good operating practices
include: '
* providing adequate aisle spacing to
facilitate container transfer and easy
access for inspections.
* properly labelling containers with material
identification and health and safety
hazards. s ,
* stacking containers according .to
manufacturers' instructions to avoid
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damaging -the containers from improper weight,
distribution. . , . .
* -segregating different hazardous substances.
to prevent'.cross-contamination and-mixing of
: r ,.-.' incompatibie^materials, 'and 'to facilitate . r
' . ' inventory control.- . / . . ., '
, ' ' . ;' * storing containers on-pallets or similar -
1 device to prevent, corrosion of the
containers which-can result when containers
come in contact with-moisture on the.floor.
. *' constructing secondary containment
structures, such as curbs, around storage
* areas. ' . "''' . '.; . -. -," ..
improved scheduling of. batch production runs to reduce
the frequency of equipment and tanJc cleanings can result
in less waste being generated.
Reeordkeiepina and documentation-of operational proce-
dures promotes the consistency of these'operations,
thereby reducing the likelihood of producing unaccept-
able products which must be discarded, and helps tc
identify practices, that need to be improved. An operat-
ing manual will assist the operators in monitoring .
waste generation and identifying unplanned waste
releases, and assist in responding to equipment ,
failures. '. - ''.-" - -.....-_ ' . , ' '
Recordkeeping should include the following items:
-documentation of process procedures, control
parameters, operator responsibility, and hazards
. in a manual.
- waste generation, waste handling and disposal
' .' COStS. .; -. . ' ;- . - . '- '''
- unplanned waste releases such as equipment .
failures or spills and leaks, and costs of
- cleanup. . _ :.';.''...-' ' , ' : , /'v
; - MSDSs... " /'/.- ;, . ' - -. '_ '" - ' - .
Preventive maintenance improves the efficiency and
longevity of equipment, reduces slow-downs or shutdowns
from equipment failures, and reduces the likelihood of
producing rejected, off-specification products. Pre-
ventive maintenance should consist of regular inspec-
tions and cleaning'of equipment including lubrication,
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resting, measuring, and replacement of- worn or broken
parts. _
spill anH leak prevention includes operational
procedures and precautionary modifications to equipment
and containment areas to minimize leaks and spills.
These measures include: , . . .
- installing and periodically testing overflow
alarms on storage, process, and treatment tanks.
- using tanks and containers according to
. manufacturer instructions and only for their
intended purpose.
- maintaining integrity of tanks and containers.
- 'implementing controlled andi supervised loading,
' unloading, and transfer of all hazardous
substances.
- constructing secondary containment: structures
around tanks or storage areas .containing hazardous
substances.
- developing spill prevention plans.
Waste segregation promotes recycling and recovery of
waste streams and improves the treatability of a waste.
Wastd types should be segregated as follows:
- hazardous from non-hazardous wastes (Note: \
mixing a hazardous waste with a non-hazardous
waste generally results in the entire mixture
becoming a hazardous waste, which must be managed
and disposed as such).
- liquids from solids.
- by hazardous constituent, such as chlorinated
solvents from non-chlcrinatsd solvents.
^ ,
- waste streams containing recoverable metals from
waste streams containing chelating agents.
e Employee education and training is an important element.
of any waste reduction and management program. Employ-
ees directly involved with processes and activities that
generate wastes should have an understanding, of why and
. how wastes are generated, how they are managed, and
costs and liabilities incurred by your company in^
generating hazardous wastes.
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r-piove.' training should" consist of: .,. " - ' '
'- health ;and safety 'aspects of ail hazardous
- ^stances being handled.. .
**r oo«ration- of process equipment and waste
- " llcyclinganS treatment . facilities, .. - .
- procedures for handling Bleaks and spills ,; ' . -. ;
'' include programs, to allocate
r u r~ rMrr~-T *o the
l c,
waste ^reatment
', accounts
and reuse_involv«
. B.cl«acicn or^.=overy >* a >slu,bl. material from ..
. hasardous wasta.
^ ffrryr>rTQN ^D FfryfT.T^ ftPFLKftTI^S
. . '-' ' "
e....
applied to metal - f abrica t ^"^ »« operations are sum-
a?d printed circuit b^ »?^^Can5 evaluating waste reduction
mirized below. ^"^WS^SJ emphasis should be placed
options for your oPer^i°^' « cost Material handling and
first on the simple, , low .or n ° «rjr_ativ-s- have been consid-
process changes., After^these |^^V^dif ication and waste
1
«aste t-n and
recycling metthoda includ«= , ,
..laproved operations and Housekeeping Practices
Drag-out Reduction
Metal Recovery Processes
Sludge Management
solvent Management
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J5 AND HOI
The following practices are easy to implement and require
little o? no capital investment:
Repair all leaking tanks, pumps, valves, etc.
" . inspect tank and tank liners on a re^lar basis to
prevent failures that may result in bath dumps.
steam coils and heat exchangers on a regular
Prevent accidental contamination of steam
of condensat
event accenta con
conate and cooling water or leakage of condensate
and cooling water into the platxng bath.
rinse
. «»
baths when not in use.
* Minimise the volume of water us«d during cleanup
operations . '
£3. s^uW ^ r«ov.d from th. bath wh«n not belng
plated.
np^fi-QUT
*«-.- *.« «.v,4» nla*-*«c: solution that adheres .to the
methods include:
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Modifying- properties of, the placing bach :co improve
' d-ainage of the plating' solutions ..-bade'.. into the. piatir.g'
' baths or reduce: the. concentration of dissolved metal's -r.
the drag-out.; .These, methods .include:
- Decreasing .bath viscosity: by reducing the
-chemical concentration of 'the bath or by
increasing the bath temperature. . . . '
- Decreasing bath surface tension: by adding ,non-
11 ."'.ionic wetting, agents or increasing bath
' "temperature. : , . ,
Lowering the withdrawal rate of parts from a bath. This
method can reduce the thickness of a drag-out layer
.because of surface tension effects.,
increasing the drain time over the plating tank.
installing drain boards, drip bars, and drip tanks to
capture the drag-out. The collected drag-out can be
fully or partially returned to the plating- bath to make ,
up for evaporative losses. These devices save
chemicals, reduce rinse requirements, and prevent
unnecessary floor wettings.
Proper racking: Carefully rack and remove parts so as ..
to minimize entrapment of bath materials on surfaces and
in cavities s
- parts should be raekexl with major surfaces. -
'; ' ' ' vertical. . - '. . ' ' . '
- parts should not: be racked directly over one
another.
- . ...-'. . - ... - , ' %
- parts should b« oriented so that the smallest
surface area of the piece leaves the bath surface
" . ' last. ' ' ; "':_ i ; ;" -' :: - ' :' . :
Designing parts to promote drainage, such as with no
cups or shelves. .
.Designing Plating racks with a minimum surface area,
minimum horizontal surfaces, no pockets, and an
effective orientation to promote drainage.
e Using air knives with oil-free compressed air to Knock
off parts and back into , the plating tanks.
Using, fog and-spray rinses, parts can be spray rinsed
with deionized water over the plating tanks. This
method is. used when tank evaporation rates are
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sufficient to accommodate the added volume of spray
water.
In rack plating: Provide drain bars over the plating
tank from which the rack can be hung to drain for a
brief period.
In barrel plating: Rotate 'the barrel over the plating
tank to remove excess plating solution.
i | * '
RINSEWATER MODIFICATIONS ' ,
Methods are available to improve rinse efficiency.and reduce
the amount: of rinsewater generated. These methods include the
use of one or more of the following:
Still rinse or drag-out tank: A still rinse tank can be
used prior to the rinse tanks with flowing water. As
the concentration of the plating solutions in the still
rinse tank builds up over time, the rinsewater can be
returned to the bath to make up for evaporation losses.
e Rinse tank mixing: The even distribution of fresh water
throughout the rinse tank in addition to aeration can
increase the efficiency of water use.
e Water supply control valves: These are inexpensive
devices to regulate the feed rate of water at an optimum
level.
e Spray rinsing: In this method, when the workpiece is
sprayed with water, the process solution films are
washed off the parts through use of'impact and diffusion
forces. This method, which can reduce water usage as
much as 75%, is effective on simple workpieces, such as
sheets, but has limited application for odd-shaped
pieces.
e Fog rinsing: This method uses water and air pressure to
produce a fine mist which reduces the concentration of
the drag-out film. This method is effective on simple
workpieces but has limited application for odd-shaped
pieces.
e Cascade rinsewater recycling: In this method, overflow
from one rinse tank can be used as the water supply for
another compatible rinsing operation.
Countercurrent rinsing with multiple tanks: In this
arrangement, three rinse tanks are operated in series
with the water flowing- from the tank farthest away from
the plating tank toward the tank closest to the plating
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- > '-ar.'k by g-ravity or pumping. The workplace is
tiall-y'* inaersed in each of the .three rinse .ranks,
counter-current to the rinsewater ' f low, from the, least
pure rinse, tank to 'the cleanest rinse tank. .
- ' Counte-rcurrent rinsing can reduce rinse flows by . :
'''-"' over 95% compared to/single overflow 'rinses.
- '''Disadvantages, with this arrangement include
.additional space requirement's,, additional .
production time', requirements,, and 'costs of >
.additional rinse tanks. ' . .
MATERIAL/ CHEMICAL ?TT?STTTOTTONS . ' ... '.'.-
The incentive for substituting process chemicals containing
nonpolluting materials has surfaced in recent years -in response
to the increasing complexity of pollution control regulations.
BY eliminating polluting process materials such . as hexavalent
chromium or cyanide-bearing chemicals, the treatments retired
to detoxify these wastes are also eliminated. This is desir-
able particularly for hexavalent chromium and cyanide wastes
since they require a special treatment step and equipment to
detoxify - : : ' , .
Material and chemical substitutes are now being gradually
introduced into the marketplace by chemical manufacturers and
suppliers. When evaluating and selecting chemical substitutes
for a particular application, a r.'jsber of factors should b=
considered, such as: ^
. ' Are substitutes available and practical?
Will substitutes, solve .one -problem but create another?
"'".'" - \ ''.-.'-'" ; , ...... - / .-_.
! will tighter chemical controls be required of the bath?
Will product- quality and/ or production rate be affected?
Will the change involve any cost increases or decreases?
Some commonly used material and chemical substitutes in
electroplating, metal finishing, and printed circuit board
manufacturing operations are summarized below:
ical Subsfeitutg* for Alkaline Cvanide Plating
'' in. zinc plating, chemical substitutes include:
, - ammonium or potassium chloride baths for
, ' complex ing' zinc.
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- acid .sulfate, chloride, and fiuoroborate baths.
In cadmium plating, chemical substitutes include:
- acid baths consisting of cadmium oxide, sulfuric
acid, distilled water and anionic compounds.
- cadmium chloride.
in copper plating, copper sulfate can be. used as a
chemical substitute.
In tin plating, acid tin chloride can be used as a
chemical substitute. ' .
Chromium Plating Baths
Trivalent chromium solutions can be used in place of
hexavalent chromium solutions in some situations. This
reduces drag-out concentrations of chromium.
Pickling solution and Brian* Dip Alternatives
Sulfuric acid and hydrogen peroxide can b« used , as ,
substitutes for chromic acid.
Cleaners
Trisodiua phosphate sr asscr.ia can b* us«d a
substitutes for cyanide cleaners.
Coer Etehants
Sulfuric peroxide can be used as a "substitute for
persulfate. , .
PLATING BATH MAINTENANCE
Plating solutions contain valuable metals in high concen-
trations as well as chemical salts. and additives, over a
period of time, contaminants can build up in the plating bath
and reduc* th« effectiveness of th« plating operation. For
reasons of economics, th«s«. plating baths ar« rarely ever
changed out or dunp«d. S«v«ral methods are available to
maintain th« quality of the plating bath and include:
Removing impurities from plating baths: ,
- Suspended solids can be removed by filtering.
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- Nickel baths'can be'purified by 'activated- carscr.
. adsorption. '.. ' .
''- Carbonates in cyanide bath's can. be removed by.
chemical, precipitation. ; . . -
using deionized water for makeup and.- as :rinsewater.
CHFMICAI,
'PROCESSES '
Chemical recovery processes' are available to reconcentrate,
plating solutions from, rinsewater for reuse and to. purify spen.
process solutions. These methods are summarized below. When <
Evaluating a recovery process for a .particular plati.ng oper-
ation, general and site-specific factors must be considered
These factors include the metal being plated, drag-out rates,
concentration of metals in the rinsewater, rinsewater fj£w-
rates, space requirements, personnel requirements, energy
requirements, and cost and payback period of the recovery
system. , ' ' - ' . ' :' . . . - '''".'
Evaporation!
Application:
In this process, rinsewater is boiled to
concentrate the' plating solution. Steam from the
process is.condensed and reused for rinsing. The
plating solution is returned to the plating bath.
This process can recover 90 to 99% of the
dragged-out metals.
Drag-out -recovery of 'rinsevatsrs frcr:
- hot chromium baths
- ambient temperature nickel baths ;
- metal cyanide baths
Use in conjunction with countercurrent
' rinsing. .
Simple,.reliable, widely applicable
process.
, Relatively maintenance-free compared with
other recovery processes.
Disadvantages: High energy use.
Requires periodic removal of impurities
from the recovered plating solutions.
Advantages:
Reverse Osmosis:
'in this process, water is separated from
dissolved metal salts by forcing the water
through a - semipermea'ble membrane at high
,15
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Application:
Advantages:
pressures. A concentrated solution con-
taining the. plating metals is produced and
returned to the plating bath. The purified
water is reused for rinsing. This process
can recover up to 99% of the dragged-out
metals. '
Drag-out recovery of rinsewaters from,the
following plating-baths:
' - acidic nickel (Watts nickel lines)
- nickel sulfamate
- copper pyrophosphate
- copper sulfate
- nickel fiuoroborate
- zinc chloride
- zinc, sulf ate
-cyanide baths for copper, zinc, and
cadmium
For use on lines with heated plating
baths where evaporation is high enough to
allow the concentrate to be fed directly
to the plating bath.
Use in eonjunction with still rinse
tanks, countercurrent rinsing, or other
rinsevater conservation techniques.
Produces m^dina to high ccr.scr.trnticr.3 cf
metal salts for reuse in the plating
baths.
Disadvantages:
Performs efficiently on dilute
rinsewaters.
Nonselective in removing dissolved
substances from the solution. Impurities
such.as organic brighteners, wetting
agents, and unwanted metals may be
returned to the plating bath along with
the recovered metal.
To prevent fouling of the membrane,
prefiltering of the rinsewater is
required to remove solid particles,
oxidizing materials, and oil and grease.
* '
Limited application for solutions with
high oxidation potential (chromic acid)
or extreme pH (i.e. high pH cyanide
baths) -due to destruction of membranes.
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-<*«' s-x-.hanae;' The ion exchange process can be used .or,
'."" ".""" -'removing contaminants from process baths or
' recovering.dissolved metals from rinsewaters.
.The process can recovery 90 to 95% of the metals
', in drag-out.
'There are two types of 'ion exchange units,
cation and anion. The selection- of the type of
: .. ion exchange -unit to use for a particular .
application will depend upon the ionic charge of
the contaminant to be removed or.metal to be
; recovered. --.".-, , . .,-.';
>;> 'A cation exchange unit, contains a specific type
of resin to remove positively charged ions .rom.-
solution, such as metal cations. The cations
removed from the solution are typically
replaced by hydrogen ions that are displaced
from the resin> The solution that exits the
cation exchange unit has a limited potential for
reuse as a rinsewater due the presence of the .
hydrogen ions which make the solution acidic,
After a period of time, the capacity of the
resin to Remove additional metal cations becomes
' limited and the resin must be regenerated if it
is to be further utilized. Regeneration of the
cation exchange unit consists of passing a
strong acid, sucn as sulfuric acid, througn
resin bed. The solution exiting the cation
exchange unit from the regeneration process
contains the metal ions, which can be returned
to plating bath.
An anion exchange unit contains a type of resin
to remove negatively-charged ions from solution,
such as chromate and cyanide. Typically with
anion. exchange units, hydroxide ions are ^
displaced from the resin to replace the anions
removed'from the solution. The anion exchange
units are regenerated with a strong base, such
as sodium hydroxide.
Application: Purification of spent process acids.
Recovery of anodizing baths.
Drag-out recovery of rinsewaters from the
. . following plating baths:
17
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Advantages:
Disadvantages;
- Acid copper
' - Acid zinc
- Nickel
- Tin
- Cobalt .
- Chromium
/
Can remove all metal ions from a
relatively dilute solution.
Low capital and operating costs compared
to other recovery processes .
Not capable of producing a highly
concentrated stream for return to the
plating baths.
Does not remove organic additives from a
wastewater.
Prefiltering of the rinsewater may be
required to remove solid particles and
oil which can cause fouling of the rssin.
Not cost effective when drag-out rates
are low. .
Equipment is complex, requiring tight
operation and aaintsr.anc« .
Monitoring of the ion exchange unit is
required to ensure that the resin
capacity is not exceeded..
Resins require periodic regeneration .with
strong acid or caustic.
E Lec,trod i a 1 vs i s t
Application:
In this process water is separated from
dissolved salts using a network of
alternately-spaced anion-permeable and
cation-permeable membranes. An electric
potential is applied across the membranes to
provide the driving force. This process- can
recover 90 to 95% of the metals in drag-out.
Regeneration of chromic acid etchant..
Drag-out recovery of rinsevaters from the
following plating baths:
- nickel
- acid zinc
18
-------
Advantages:
Disadvantages:
- zinc cyanide
- chromium -' .
gol'd . -
-~ silver
Use 'in conjunction with a still rinse-
tank. ' ' '.-.
' , " - . , ' ! - ' '.";'
Achieves higher concentration o,f metals
than reverse osmosis or ion exchange.
Energy efficient.
Can operate .continuously without,
requiring regeneration.
Requires little; space. :
Nonselective in removing dissolved
substances from the solution. Impurities
such as organic brighteriers, wetting
agents , and unwanted metals may be
returned to the plating bath along with
the recovered metal .
Membranes are sensitive to extreme pH,
flow variations, and suspended solids.
Pref iitering o£ tne rinsewater may oe
required to remove solid particles and
oil which can cause fouling of the
- resins. ..'...' ' . - , ,
Requires careful operation and periodic
maintenance to- avoid damage to the
membranes.
t r a f i 11 ration:
Application:
In this process, a solution is filtered
through an extremely fine filter to -remove .
solids, emulsions, and high molecular weight
organics.
Regeneration of alkaline cleaners,
coolants, or process baths requiring
removal of particles and emulsified oils
wastewater treatment process for volume
reduction of spent coolants, cleaners,
and rinsewaters.
-------
Advantages:
Disadvantages:
Efficient for removing suspended solids,
emulsified oils, and other hrgh molecula:
weight organic compounds.
Low capital and operating costs.
Easy to operate and requires little
maintenance. '
Limited application for recovery of
dissolved metals from rinsevaters.
Requires periodic backwashing to remove,
captured solids.
METAL RECOVERY PROCESSES
E1ectrolvtic Recovery:
Advantage:
This process involves the electro-
chemical reduction of metal ions to
their elemental forms as a powder or
foil. A direct current is passed
through a metal-bearing solution by
means of cathode plate and insoluble
anodes. The cathode consists of a
stainless steel or carbon fiber plate
upon which the recovered metal is
deposited. After the coating is
sufficiently thick, the metal is
peeled off and sent to a refiner or
the coated stainless steel cathode is
used as an anode in plating baths,
serving a source of metals.
Application: Oxidation of cyanide.
Reduction of hexavalent chromium in
wastewaters.
Recovery of metals from plating and
etching bath drag-out, such as gold,
silver, copper, cadaium, zinc, tin, and
lead.
Regeneration of ammoniacal and chloride
etch solutions during metal recovery.
Us* in conjunction with m still.rinse
tank.
Not a labor-intensive operation.
Low energy requirements.
20
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- . - . -. _ Lev energy .requirements".
Disadvantages: Limited application for recovery,of ,'
. ' . chromium from solutions.;
. . '. .' . '. Monitoring of the solution concentration \
' ; -is. required. _'.-.''''.
SLUDGE MANAGEMENT , - ". ' ', " '.'.-"
Sludges produced in process baths and as a result of ' wastewater1
treatment processes are typically hazardous wastes that .must be
appropriately managed., Frequent management problems with these
sludges include" the high volumes-generated that must .be handled
cand costs for disposa'1. Some waste, management alternatives 'are
available, to,help alleviate these problems. /
Sludoe Dewaterino: :- -" ..';'' . - ,.'
Several mechanical dewatering devices that reduce sludge
volumes are commercially available. These devices include:
Centrifuges . ,
Filter presses , . - .
« Vacuum filters . . .
Sludge dryers .
treatment Chemical Selection
A wide range of treatment chemicals is available for
precipitating dissolved metals out of a solution. Some .of
these chemicals produce less sludge-when compared to other
chemicals of comparable removal efficiency. Therefore, the
selection of a treatment chemical for a particular application
is important for reasons of efficiency and sludge volume
.production. ' V ..'',." - ' - - .,
Examples of treatment chemicals that produce less sludge-
include: ".'- :..': _ . _ , . '
use of caustic soda (NaOH) instead of lime (Ca(OH) 2-) '
* use cf polymers instead of ferrous sulfate and alum*.
SOLVENT MANAGEMENT
..'..'-' -M ' - ; . --: --.-..
Organic solvents are widely used in metal finishing operations
for cleaning, decreasing, and paint stripping. The management
and disposal of spent organic solvents are becoming increas--
ingly more difficult and expensive. Some waste reduction and
recycling methods for organic solvents are summarized below.
-------
Material Suhstj*--"* i°-Q ' .
Alternatives to using solvents include:
.Alkaline cleaners
High pressure hot water washings
Steam cleaning .
'
* ecovered and reu.sed.
pece.
The particles can be recovered and reu.sed.
Recovery and Reuse . .
Methods for reusing and recovering spent solvents include the
following: '
reuse: This involves using a spent
finishing applications
e "ffn*;t Beveling:. Several waste management services
* are available for recycling »PV°i££SbS
your facility site or at an offsite location.
22
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..TSR' 3 /- \
.WASTE REDUCTION: ASSESSMENTS
A waste reduction' assessment is a step-by-step procedure that
-an be used by a facility ' s, own employees to identify waste
reduction and recycling opportunities. -The assessment can he.p .
Jou.to understand the facility ' s wastes and processes ^dent,
viable options for reducing wastes, and determine which options
art technically and economically feasible to justify implemen-
tation in your operations.
The amount of effort required for a waste reduction assessment
will depend upon the size and type of your business. Small
facilities with only a few processes will obviously require
less time" and resources for the assessment. Large facilities
with mtny processes may require a team of skilled professionals
to conduct a more detailed technical and economic evaluation of
waste reduction options. , .
considerino the wide range of waste reduction and recycling ..
opSortuni?ies available for metal finishing and'.l^rbplating.
opSrltions, it is likely that your business can implement waste
reduction methods and end up saving money as a result.^ The
following steps will provide you with some general guidance in
identifying and implementing waste reduction and recycling
practices in your operations. Mote that all waste streams
should be considered when conducting an assessment, *uou "
hazardous wastes, wastewaters, air emissions, and non-hazardous
solid waste. Additional sources of information on waste
reduction methods and implementation can be found in the
; .references-, i . . ' . ' . . - - '
There are several different, tasks, involved when conducting. a
waste reduction assessment. These tasks include the following:
Planning and Organization
* Assessment Phase -
e Feasibility Analysis
e Implementation and Evaluation
PTAMNTNG
Planning and organizing waste reduction assessment
are esslntiai: steps to ensure a Program's success. ^^
is conducted prior to actual assessment phase. Important
elements, of this tasfc are summarized below..
23
-------
Get a commitment and support from management. It is
a
_ .e to
provide the time, personnel, financing, and. other
resources required for developing a waste reduction
program. . '
important for the management of a company to support
waste reduction program. The management must be abi<
Develop a formal policy statement describing the waste
reduction program objectives.
.Involve employees in all phases of waste reduction
program development.
Organize a waste reduction assessment team.
- Get people who know the facility, processes, and
operating procedures, and are familiar with your
waste management practices, environmental
"regulations, and waste reduction and recycling
techniques.
Get people from affected departments or groups,
such as production, maintenance, environmental,
safety, sales, purchasing, etc. Involve line
operators and production supervisors.
- Appoint, a team leader who has a strong technical
background and good problem-solving and manag
skills.
Set goals to achieve waste reduction.
Recognize potential barriers and problems that may
hinder waste reduction program development.
ASSESSMENT PHASE
This phase involves an evaluation of the facility's operations,
waste streams, and waste management practices and the identifi-
cation and screening of potential waste reduction and recycling
options. Important steps of this phase include the following:
1)
Faeilitv Information
One of the first steps of the assessment is to gather
background information on production processes, operating
procedures, waste streams, and current waste management
activities, collecting data, will create a basis by which the
assessment team can track the flow and characteristics of. the
waste streams over'time. This will be useful in identifying
24
-------
i 1 4 ^B g* """"
collected ..
team is. better
production, rates ; - .
^ process descriptions and efficiencies
. condition of proce,a ea^ip*ent, such as tanXs, pu,Ps,
pipes/'and valves
. sourc,. or pot.nU.1' spur=« of X..X, and
operating procedures
. maintenance:procedures and schedule.,
.operating and;maintenance costs ,
.energy/utility usage and costs
material inventory
-s
or o«,.r
raw material costs
. «t.ri»l transfer and handling procedures
e storage procedure*
' .source, oi leaX, or spi^s in ***** -
. condition of pipe*. P-PS- tanK,', valve,, and
storage/ delivery areas .
25
-------
Data;
. activities, processes, or input materials that generate
waste streams
physical and chemical characteristics of the each waste
stream
. hazardous classification of ^V^^ant^
which wastes are hazardous and which, are not.)
of waste stream 'generation. (i.e. continuous or
nt, such as from9periodic cleaning activities
or bath dumps) ' .
rates 'of generation of each waste stream and any
variability in these rates
Waste
e current disposition of 'each waste stream (i.e. hew is it
handled, treated, and disposed)
. costs of managing waste streams, including treatment and
disposal costs
* operational procedures for waste treatment units
e efficiency of waste treatment units
quantity and characteristics of all treated wastes,
sludges, and residues
waste stream mixing (are hazardous wastes mixed with
non-hazardous wastes or are potentially recyclable
wastes mixed with other wastes? )^
« Reduction; ,
e current waste reduction and recycling methods being
implemented . '
e effectiveness of those methods ,
sgureea gf Baekq-ramid' m formation
26
-------
--ocess flow diagrams .- '
Material and heat balances for production processes and
waste treatment processes ./, - _ ' -_ . -.
operating manuals and process descriptions : ,
equipment specifications and data sheets,
piping and instrument diagrams ..
plot. and elevation plans '.
sewer diagrams ' . ; , , .
equipment layouts 'and work flow diagrams
hazardous waste- manifests .
emission inventories .
annual hazardous waste reports
envlronmentalSaudit and inspection reports-
. reports (
'or
r.l««« inventoriw (SMI* Title III
requirements) .
product composition' and batch she«ts
material application diagrams .
material safety data sh««ts (MSDS)
product and raw ftatarial inventory records
op«rator data logs
production schedules _,.
d«parta«ntal cost accounting reports
company environmental policy statenmnts
organization charts
in some situations it may b* necessary to develop flow diagrams
and mS?.riaror Sass balances of th* major waste generating
operations. Th«s« flow diagrams and mass glances help to
identify waste sources, concentrations, and rates of
.generation. . ..
2)
q
w**n funds time, and- personnel are limited, it may be
and budget permit.
Items that should be considered when prioritizing include:
compliance with current and future regulations .
costs of waste treatment and disposal
', - .' . 27- . . :'". ' '. - -.
-------
potential environmental and. safety liability
quantity of waste
haza-dous properties of the waste (including toxicity,
reactivity, corrosivity, and ignitability)
safety hazards to employees
potential for reduction, recycling, or recovery
potential for removing bottlenecks in production or
waste treatment
potential recovery of valuable by-products
available budget and expertise for the waste reduction
assessment program and projects
3) SJ-te Inspection
The purpose of the site Inspection is to verify background _
information, fill data gaps and resolve questions raised while
collecting and reviewing data, identify additional sources of
wastes? and collect information on actual operating and waste
management practices. The inspection concentrates on under-
standing how and why wastes are generated.
For each of the selected processes or operations *««£ .
evaluated, the inspection should follow the process from the
point where raw materials enter the process to the point where
products and wastes exit.
Some general guidelines for conducting the site inspection .
include the following: '
Prior to the inspection:
- make a list of items that require clarification.
- notify personnel involved within the process or
area to be inspected.
Schedule the inspection t°'coincide^with_ the particular
operation of interest; if the operation is P«"?^f. or
intermittent in nature (e.g. bath dumping, chemical ,
addition, etc.). ' . . ' .
e During the inspection take notes and P^fF*** th?, t
areas of interest. This helps to recall details that
may be forgotten at a later date.
28
-------
Monitor the .operation at different times' during.the.
shift and during thedifferent shifts, especially, if
waste generation is highly dependent on human , :
involvement. :t ' ;;
interview the operators, maintenance personnel, shift ,
supervisors, and foremen in .the area's being inspected.
Assess .the" operators1 and supervisors' ^awareness of the
waste generation aspects of the operation and familiar-
ity with the impacts their operation may,have 'on other
'operations. . ^ .
Observe housekeeping aspects of the operation. Check
for signs of leaks or spills. Assess the overall
cleanliness -of the site. , Note any odors and fumes.
Evaluate the organizational structure and level of
coordination of environmental activities between various
departments. . ... ''," . .
Evaluate administrative, controls, such" as cost
accounting procedures, material purchasing procedures,
and waste collection procedures. , -
4) Generating Waste Reduction Potions
After the data collection and site inspection stages of the
assessment, the next step involves identifying possible waste
reduction and recycling options* This step requires the
expertise of the assessment team members. Much of this
knowledge comes from their education and on-the-job training.
Other sources of waste reduction and recycling information are
listed below: '. . .. :. : , ',' . " . "';. ;
e Trade associations ,
e Plant engineers and operators
e Published literature such.as technical journals, trade
journals, government reports, conference proceedings,
and research reports,
; e DEQ Waste Reduction Program
e Workshops, conferences, and seminars
e Equipment vendors .
consultants and employees from other facilities
29
-------
Waste -eduction and recycling methods for electroplating, metal
finishing, and printed circuit board manufacturing operations
vere discussed in Chapter 2 of this guidance manual.
5) screening apd Selecting Wasta Reduction 'Qp^ons for Further
Evaluation
Since detailed evaluation of technical and economic feasibility
is usually costly, the proposed waste reduction options should
be screened to identify those that deserve further evaluation.
The screening procedure serves to eliminate suggested options
that appear marginal, impractical, or inferior without a
detailed and more costly feasibility study.
When considering options, emphasis should be placed on process "
changes and other source reduction measures, .followed by recy-
cling and reuse. Many source reduction-.options involve no or
low capital costs and can be easily implemented. After these
alternatives have been considered, then the more expensive
equipment modifications and waste recycling options should be
evaluated. ,
The following criteria should be considered when screening and
selecting options:
existing technology (does the necessary technology exist
to develop the option?)
extent of current use in the industry
i, P , , ,
successful performance history
« cost and cost effectiveness
reduction in the waste's quantity and hazardous
characteristics (toxicity, flammability, reactivity,
corrosivity)
*
reduction of treatment and disposal costs
reduction in safety hazard
e reduction in liability and insurance costs
e "reduction of input material costs
effect on product quality
low capital cost
low operation and maintenance costs
30
-------
c short implementation period ' . ' . , v
o ease, of- implementation ' 7, ' . . . '
o other benefits , . . . : .
FEASIBILITY ANALYSTS . / ' . . .: . ; ~- ' ' ,.'.
After/identifying potential ^waste,reduction and recycling-
options-, the next step is to conduct a detailed analysis of
these options. The analysis of these options .includes both a
technical and economic evaluation.. ,
Technical .Evaluation <_ - ,
The technical evaluation determines whether a proposed waste
reduction option will work in a specific application. The
following criteria should b« considered when conducting a
technical evaluation: : -
- -''," ' .
will th« option work in this application?
- How has it worked in similar applications?
Will the option cr«at« less waste or just move the waste
problem from one form to another?
e Is the system safe for workers?
. « Will product quality -fc'e' azintair.sd? ';,',,' "
e Will the option adversely affect productivity?
Is space available?
Are the hew equipment, materials, or procedures.
; compatible with production operating procedures, work
flow, and production rates?
e Is additional labor required?
Are utilities available or must they be installed?
e How long will .production.be stopped in order to install
-.the system? \"- .-..''" ; "-'' "\ ".' . .' ' ' '.' '.''"..
e Is special expertise required to operate or maintain the
new system?
Does the vendor provide acceptable service?
Does the system create other environmental problems?
' -''-...''. .3,1' ''.'. ''.-".
-------
For equipment: related options: ' '
. V'si* facilities that have installed. the equipment,
These visits can be arranged through equipment vendors
and industry contacts. ,,,
Solicit operator's comments and compare to vendor
claims. .,''
conduct bench-scale or pilot demonstrations. Rental
test units for bench-scale' experiments may be available
from equipment vendors for use.
some vendors may install equipment on a trial, basis,
with acceptance and payment after a prescribed time, if
the user is satisfied.
^valuation
The economic evaluation is conducted using standard measures of
Srofitabilitv such as payback period, return on investment,
!nd net oriseAt value. Most companies have their own methods
fSr S^lSHSS pSjSt. for implementation. In conducting an
economic evaluation various costs and savings must be
considered. Some of these factors are described below.
For the purpose of evaluating a project to reduce waste .
quIntitiSs, some types of costs are more significant and easily
quantified. These costs include:
e disposal fees
transportation costs
predisposal treatment costs
raw material costs
operating and maintenance costs
When conducting the economic evaluation of waste reduction
Sese^costs should be considered first .bmu.« th.y
.
ave a greater effect on project «cononiCVnd^h
effort to estimate reliably. Other elements, such
listed below, are usually secondary in their direct impact and
should be included in fine-tuning the analysis.
Costs;
site development
process equipment
materials
connections to utilities and services
new utility and service facilities
other non-process equipment
construction/installation
32
-------
engineering and'consulting services ,
permitting '-.costs- ; . '
- .contractor's fees . -, ,.
training costs - -, v , , . . ; . . ',
" finance charges .-. = . ;. ,. .
Coeratinq Cost? and Savings; ;, / . ' . , ,
-.Reduced! waste management costs .
I.onsite and,offsite treatment, storage, disposal
costs. ' " ..'.. -
-;state generator fees . .
' - transportation costs - - . ,:.
- permitting, monitoring, reporting, and
recordkeeping costs " . '
' Input material cost savings
insurance and liability savings
Chaha«s in cost associatad with product quality (costs
lor Icrap? reworlc, and quality ^control inspections)
* Changes in utility costs
Changes in operating and maintenance costs for labor,
burden, and benefits
Changes in operating and maintenance supplies
changes in overhead costs
; Changes in revenues from increased (or decreased)
production .
increased revenues from the sale of by-products
Final
and th« .& and
.vaiuations. Th. r«port also
affected groups
be arven tne cnanc* wu review and comment ...
report ShSIldcSUain a discussion of the following
£, 9£*Wfe » ^^^^^ - r
waste reduction options evaluated and results of the
evaluation . , ,
, v - "
.recommended options for implementation
' '. ' ' -33 ''' ' -..'".
-------
. w*ethe~ the recommended technology or procedure has beer.
established in the industry, with a mention of success-
ful applications
.how the project will be implemented
required"resources, such as money, expertise, personnel,
Available in-house and those resources that must be
brought in from outside
estimated construction period and production downtime
expected performance of project
. how the performance of_the project can be evaluated
after it is .implemented
reduction in environmental and safety liability
Th. implantation of selected waste
will Generally follow the procedures established by
compandor implanting any new procedure, Pfocess
cations, or equipment change. The assessment report
to g«£ management approval and funding
the selected projects. Steps involved
reduction project include the following:
Io
help
wait.
a waste
preparing a detailed design
preparing a construction bid package
lelSctinl construction staff and purchasing materials
installing new equipment
training personnel ; .
starting operation
monitoring and evaluating performance
.
justify the development of other waste reduction projects
The waste reduction assessment program ******
options that were not pursued earlier
34
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REFERENCES
Inforaation-'contained in -this-guidance document has been
derived from the fpilowing sources:. , . . . ..
Higg'ins, T. E. , CH2MHill, Evaluating Hazardous-. Waste
Minimization Programs for Metal Fin.^hina Processes..-
Presented at the AOI/AEA/DEQ workshop on "Responsible
Hazardous Waste Management", Wilsonville, Oregon, March
24, 1987,.' ;, * -. . ' -: , . .'
Lorton, G. A., and D. A. Hanlon, Jacobs Engineering .Group
inc., waste Minimi 7*r1 on Assessments. prefente^L^Co
California Aerospace Environmental Association Conference,
Long Beach, California, February 17, 1988. -' '; '
New York State Departnent of Environmental Conservation,
m-aff New York State Hazardous Waste Reduction Guidance
Manual. November 1988.
U.S. Environmental Protection Agency, Su.mm.arv
.. ..
gontrol and T-reatmenfe Technology for the Metal Finishing .
Tndv!strv. Tn-.Planr- changes. Industrial Environmental
Research Lab > Cincinnati; Ohio, , EPA/625/8^82-008, January
;1982. ' ..,''-..' '.,.'. :'-.''. '
U.S. Environmental Protection Agency, fleeing
..
Waste Requirements for Metal Finishers. Seminar
PUS Heat ion. Otfice o£ Researcn and Development,
Cincinnati, Ohio, EPA/625/4-87/018 , September 1987
U.S'. Environmental Protection Agency, Wast;e
..
Environmental Qualifcv with Economic Benefit?, Of f ice of
Solid Waste and Emergency Response, Washington, D.C.,
EPA/530-SW-87-026, October 1987.
U.S. Environmental Protection Agency, TftV SPA Manual f 07
v**±* Minim^M^ian opportunity Assessment , tHazardo,us
wHte Enginiering Research Laboratory, Cincinnati, Ohio,
EPA/5QQ/2-SS/02S, April 1988.
For additional references on waste' reduction and recycling
refer to OEQ's Bibliography of Hazardous
Publications. ;
35
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