>EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/625/7-90/006
July 1990
Technology Transfer
Guides to Pollution
Prevention
The Fabricated Metal
Products Industry
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EPA/625/7-90/006
July 1990
GUIDES TO POLLUTION PREVENTION:
THE FABRICATED METAL PRODUCTS INDUSTRY
RISK REDUCTION ENGINEERING LABORATORY
CENTER FOR ENVIRONMENTAL RESEARCH INFORMATION
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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NOTICE
This guide has been subjected to U.S. Environmental Protection Agency's
peer and administrative review, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use. This document is
intended as advisory guidance only to the fabricated metal products industry in
developing approaches for pollution prevention. Compliance with environmental
and occupational safety and health laws is the responsibility of each individual
business and is not the focus of this document.
Worksheets are provided for conducting waste minimization assessments of
metal fabrication facilities. Users are encouraged to duplicate portions of this
publication as needed to implement a waste minimization program.
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FOREWORD
This guide provides an overivew of the metal fabrication processes and
operations that generate waste and presents options for minimizing waste
generation through source reduction and recycling. Such processes are an integral
part of aerospace, electronic, defense, automotive, furniture, domestic appliance,
and many other industries. Fabricated metal processes generate various hazardous
waste streams, including oily wastes from machining operations, heavy metal-
bearing streams from surface treatment and plating operations, and additional
wastes related to paint application.
Reducing the generation of these wastes at the source or recycling the wastes
on- or off-site will benefit the metal fabricating industry by reducing raw material
needs, reducing disposal costs, and lowering the liabilities associated with hazardous
waste disposal.
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ACKNOWLEDGMENTS
This guide is based in part on waste minimization assessments conducted by
Jacobs Engineering Group, Inc. Pasadena, California for the California Department
of Health Services (DHS). Contributors to these assessments include: David Leu,
Benjamin Fries, Kim Wilhelm, and Jan Radimsky of the Alternative Technology
Section of DHS. Much of the information in this guide that provides a national
perspective on the issues of waste generation and minimization for metal fabricators
was provided originally to the U.S. Environmental Protection Agency by Versar,
Inc. and Jacobs Engineering Group, Inc. in "Waste Minimization - Issues and
Options, Volume II," ReportNo. PB87-114369 (1986). Jacobs Engineering Group
Inc. edited and developed this version of the waste minimization assessment guide,
under subcontract to Radian Corporation (USEPA Contract 68-02-4286). Jacobs
personnel contributing to this guide include: Carl Fromm, project manager;
Michael Meltzer, principal author; Michael Callahan, contributing author; and
Sally Lawrence, technical and production editor.
Lisa M. Brown of the. U.S. Environmental Protection Agency, Office of
Research and Development, Risk Reduction Engineering Laboratory, was the
project officer responsible for the preparation and review of this guide. Other
contributors and reviewers include: Dr. Marvin Heischman, chemical engineering
professor, University of Louisville, Kentucky; Larry Foss, Foss Plating Co., Santa
Fe Springs, California; Rick Slaney, Ronlo Engineering Ltd., Camarillo, California;
and Dennis Bronk , plant manager, Hansen's Laboratory Furniture Industries, Inc.,
Newbury Park, California.
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CONTENTS
Section Page
Notice . ii
Foreword iii
Acknowledgments iv
1. Introduction
Overview of Waste Minimization
Assessment 1
2. Fabricated Metal Industry Profile 5
3. Waste Minimization Options for
Fabricated Metal Products Facilities 13
4. Guidelines for Using the
Waste Minimization AssessmentWorksheets 35
References 63
APPENDIX A
I. Fabricated Metal Product Facility Assessments:
Case Studies of Plants 65
APPENDIXB
II. Where To Get Help: Further Information on
Pollution Prevention 72
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SECTION 1
INTRODUCTION
This guide was prepared to provide plant operators
ar environmental engineers of commercial fabricated metal
Facilities with guidelines and options to minimize both
hazardous and non-hazardous wastes. Others who may
find this document useful are regulatory agency
representatives and consultants.
The worksheets and the list of waste minimization
optionsweredevelopedthroughassessmentsofLosAngeles
area firms commissioned by the California Department of
Health Services (DHS 1989). The firms' operations,
manufacturing processes, and waste generation and
management practices were surveyed, and their existing
and potential waste minimization options were
characterized. Economic analyses were performed on
selected options.
Four types of processes used in metal fabrication are
examinedin this guide: machining operations, parts cleaning
and stripping, metal surface treatment and plating, and
paintappUcation.Theseprocessesuseavarietyof hazardous
materials, including metal-working fluids, solvents, alkaline
and acid cleaning solutions, treatment andplating solutions
that contain hazardous metals such as chromium and
cadmium, as well as cyanide and other chemicals, and
paints containing solvents and heavy metals. Many of
those hazardous substances are being phased out in some
applications, in favor of more benign compounds.
Waste minimization is a policy specifically mandated
by the U.S. Congress in the 1984 Hazardous and Solid
Wastes Amendments to the Resource Conservation and
Recovery Act (RCRA). As the federal agency responsible
forwritingregulationsunderRCRA,theU.SEnvkonmental
Protection Agency (EPA) has an interest in ensuring that
new methods and approaches are developed for minimizing
hazardous waste and that such information is made available
to the industries concerned. This guide is one of the
approaches EPA is using to provide industry-specific
information about hazardous waste minimization.
EPA has also developed a general manual for waste
minimization in industry. The Waste Minimization Oppor-
tunity Assessment Manual (USEPA 1988) tells how to
conduct a waste minimization assessment and develop
options for reducing hazardous waste generation at a
facility. It explains the management strategies needed to
incorporate waste minimization into company policies and
structure, how to establish a company-wide waste minimi-
zation program, conduct assessments, implement options,
and make the program an on-going one. The elements of
waste minimization assessment are explained in the Over-
view, next section.
In the following sections of this manual you will find:
An overview of the fabricated metal industry
and the processes used in it (Section Two);
Waste minimization options for the industry
(Section Three);
Waste Minimization Assessment Guidelines
and Worksheets (Section Four)
An Appendix, containing:
Case studies of waste generation and
waste minimization practices of three
facilities;
Where to get help: Sources of useful
technical and regulatory information
Overview of Waste Minhnizaition
Assessment
In the working definition used by EPA, waste
minimization consists of source reduction and recycling.
Of the two approaches, source reduction is usually
considered preferable to recycling from an environmental
perspective. Treatment of hazardous waste is considered
an approach to waste minimization by some states but not
by others, and thus is not addressed in this guide.
A Waste Minimization Opportunity Assessment
(WMOA), sometimes called a waste minimization audit, is
a systematic procedure for identifying ways to reduce or
eliminate waste. The steps involved in conducting a waste
minimization assessment are outlined in Figure 1 and
presented in more detail in the nextparagraphs. Briefly, the
assessmentconsists of acarefulreview of aplant'soperations
and waste streams and the selection of specific areas to
assess. After aparticularwastestream or area is established
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Figure 1. The Waste Minimization Assessment Procedure
The Recognized Need to Minimize Waste
PLANNING AND ORGANIZATION
' Get management commitment
' Set overall assessment program goals
1 Organize assessment program task force
Assessment Organization &
Commitment to Proceed
ASSESSMENT PHASE
Collect process and facility data '
Prioritize and select assessment targets
Select people for assessment teams
1 Review data and inspect site
' Generate options
Screen and select options for further study
Select New Assessment
Targets and Reevaluate
Previous Options
Assessment Report of
Selected Options
FEASIBILITY ANALYSIS PHASE
Technical evaluation
Economic evaluation
Select options for Implementation
Final Report, Including
Recommended Options
IMPLEMENTATION
Justify projects and obtain funding
Installation (equipment)
Implementation (procedure)
Evaluate performance
Repeat the Process
Successfully Implemented
Waste Minimization Projects
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as the WMOA focus, a number of options with thepotential
to minimize waste are developed and screened. The
technical and economic feasibility of the selected options
are then evaluated. Finally, the most promising options are
selected for implementation.
To determine whether a WMOA would be useful in
your circumstances, you should first read this section
describing the aims and essentials of the WMOA process.
For more detailed information on conducting a WMOA,
consult The Waste Minimization Opportunity Assessment
Manual.
The four phases of a waste minimization opportunity
assessment are:
Planning and organization
Assessment phase
Feasibility analysis phase
Implementation
PLANNING AND ORGANIZATION
Essential elements of planning and organization for a
waste minimization program are: getting management
commitment for the program; setting waste minimization
goals; and organizing an assessment program task force.
ASSESSMENT PHASE
The assessment phase involves a number of steps:
Collect process and facility data
Prioritize and select assessment targets
Select assessment team
Review data and inspect site
. Generate options
Screen and select options for feasibility study
Collect process and facility data. The waste streams
at a facility should be identified and characterized.
Information about waste streams may be available on
hazardous waste manifests, National Pollutant Discharge
Elimination System (NPDES) reports, routine sampling
programs and other sources.
Developing a basic understanding of the processes
that generate waste at a facility is essential to the WMOA
process. Flow diagrams should be prepared to identify the
quantity, types and rates of waste generating processes.
Also, preparing material balances for various processes
can be useful in tracking various process components and
identifying losses or emissions that may have been
unaccounted for previously.
Prioritize and select assessment targets. Ideally, all
waste streams in a facility should be evaluated for potential
waste minimization opportunities. Withlimitedresources,
however, a plant manager may need to concentrate waste
minimization efforts inaspecific area. Suchconsiderations
as quantity of waste, hazardous properties of the waste,
regulations, safety of employees, economics, and other
characteristics need to be evaluated in selecting a target
stream.
Select assessment team. The team should include
people with direct responsibility and knowledge of the
particular waste stream or area of the plant.
Review data and inspect site. The assessment team
evaluates process data in advance of the inspection. The
inspection should follow the target process from the point
where raw materials enter the facility to the points where
products and wastes leave. The team should identify the
suspected sources of waste. This may include theproduction
process; maintenance operations; and storage areas for raw
materials, finished product, and work in progress. The
inspection may result in the formation of preliminary
conclusions about waste minimization opportunities. Full
confirmation of these conclusions may require additional
data collection, analysis, and/or site visits.
Generate options. The objective of this step is to
generate a comprehensive set of waste minimization options
for further consideration. Since technical and economic
concerns will be considered in the Liter feasibility step, no
options are ruled out at this time. Information from the site
inspection, as well as trade associations, government
agencies, technical and trade reports, equipment vendors,
consultants, and plant engineers and operators may serve
as sources of ideas for waste minimization options.
Both source reduction and recycling options should be
considered. Sourcereductionmaybe accomplished through:
Good operating practices
Technology changes
Input material changes
Product changes
Recycling includes:
Use and reuse of waste
Reclamation
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Screen and select options for further study. This
screening process is intended to select the most promising
options for full technical and economic feasibility study.
Through either an informal review or a quantitative deci-
sion-making process, options that appear marginal, im-
practical or inferior are eliminated from consideration.
FEASIBILITY ANALYSIS
An option must be shown to be technically and
economicallyfeasibleinorderto merit serious consideration
foradoptionatafacility. Atechnicalevaluation determines
whether a proposed option will work in a specific
application. Both process and equipment changes need to
be assessed for their overall effects on waste quantity and
productquality. Also.anynewproducts developed through
process and/or raw material changes need to be tested for
market acceptance.
An economic evaluation is carried out using standard
measures of profitability, such as paybackperiod, return on
investment, and net present value. As in any project, the
cost elements of a waste minimization project can be
broken down into capital costs and economic costs. Savings
and changes in revenue also need to be considered.
IMPLEMENTATION
An option that passes both technical and economic
feasibility reviews should then be implemented at a facility.
It is then up to the WMOA team, with management
support, to continue the process of tracking wastes and
identifying opportunities for waste minimization,
throughoutafacilityandby way of periodic reassessments.
Either such ongoing reassessments or an initial investigation
of waste minimization opportunities can be conducted
using this manual.
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SECTION 2
FABRICATED METAL INDUSTRY PROFILE
Industry Description
Fabricated metal products are classified under Standard
Industrial Classification (SIC) 34, and include industries
engaged in processes that machine, treat, coat, plate, paint
and cleanmetal parts. There are two major segments of the
industry: job shops that process materials owned by other
parties on a contractual basis, and captive shops-that are
owned and part of larger manufacturing facilities. Metal
fabrication processes are integral parts of aerospace,
electronic, defense, automotive, furniture, domestic
appliance, and many other industries. Fabricated metal
processes generate various hazardous waste streams,
including oily wastes from machining operations, heavy
metal-bearing streams from surface treatment and plating
operations, and solvents, alkaline and acid solutions from
metal cleaning and stripping operations, and additional
wastes related to paint application. Each of the major waste
generating processes is profiled below.
Machining Operations
Machining operations involve various metal cutting
: processes that include:
turning
drilling
. milling, ,
' reaming
threading
broaching
grinding
polishing
planing
cutting and shaping
Machining processes use cutting tools of some sort
that travel along the surface of the workpiece, shearing
away the metal ahead of it. Most of the power consumed
in cutting is transformed into heat, the major portion of
"Whiehiscarriedaway by themetalchips, while theremainder
is divided between the tool and workpiece. Interface
temperatures of up to 200°F have been, measured (Baumeis-
ter!967).
Turning processes and some drilling are done on
lathes, which hold and rapidly spin the workpiece against
the edge of the cutting tool. Drilling machines are intended
not only for making holes, but for reaming (enlarging or
finishing) existing holes. This process is also carried out by
reaming machines using multiple cutting edge tools. Mill-
ing machines also use multiple edge cutters, in contrast
with the single point tools of a lathe. While drilling cuts a
circular hole, milling can cut unusual or irregular shapes
into the workpiece.
Broaching is aprocess whereby internal surfaces such
as holes of circular, square or irregular shapes, or external
surfaces like key ways are finished. A many-toothedcutting
tool called a broach is used in this process. The broach's
teeth are graded in size in such a way that each one cuts a
small chip from the workpiece as the tool is pushed or
pulled either past the workpiece siarface, or through a
leader hole (Baumeister 1967). Broaching of round holes
often gives greater accuracy andbetter finish than reaming.
MET ALWORKING FLUIDS
Metalworking fluids are those liquids (or sometimes
gases) that are applied to the workpiece and cutting tool in
order to facilitate the cutting operation. A metalworking
fluid is used:
1) to keep tool temperature down,
preventing premature wear and damage;
2) to keep workpiece temperature down,
preventingitfrombeingmachinedtoawarped
shape or within inaccurate dimensions;
3) to provide a good finish on the workpiece;
4) to wash away chips; and
5) to inhibit corrosion or surface oxidation of
the workpiece.
Also, and very important, metalworking fluids are
frequently used to lubricate the tool-workpiece interface,
in addition to simply cooling it.
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Metalworking fluids can be air-blasted, sprayed or
drawn through suction onto the tool-workpiece interface.
Types of fluids include water (either plain or containing an
alkali); emulsions of a soluble oil or paste; and "straight"
oils (those that are not water-based) such as mineral,
sulphurized, or chlorinated oil.
Air drafts are often used with grinding, polishing and
boring operations to remove dust and chips, and to cool to
a certain extent. Aqueous solutions containing
approximately one percent by weight of an alkali such as
borax, sodium carbonate or trisodium phosphate exhibit
high cooling properties and also provide corrosion
prevention for some materials. These solutions are
inexpensive and sometimes are used for grinding, drilling,
sawing,andh"ghtmillingandtumingoperations(Baumeister
1967).
Emulsions consist of a suspension of oil or paste in
water, typically at the ratio of one part oil to lOto 100 parts
water, depending on the application. Rich mixtures of oil
to water are used for broaching, threading and gear cutting,
while a 1:20 ratio suffices for most lathe work, drilling and
screw machine work.
Oil areusedformetalcutting where lubrication rather
than cooling is essential for tool life and/or work quality.
WASTE STREAMS
The major wastes from machining operations are
spoiled or contaminated metalworking fluids which are
treated as hazardous wastes because of their oil content, as
well as other chemical additives that some contain such as
chlorine, sulfur and phosphorus compounds, phenols,
creosols and alkalies. While fresh metalworking fluids
contain varying degrees of oil depending on their function,
"tramp" hydraulic and lubricating oils also find their way
into the fluids during the course of operations. Spent
metalworking fluids are at present either disposed of or
recycled on- or off-site. Recycling typically consists of
separating the oils through such methods as centrifuging
and refining them or using them as fuel.
Solvent wastes resulting from cleaning of parts and
equipment also comprise a sizable waste stream. This
stream is examined in the "Metal Parts Cleaning and
Stripping" section.
Many fabricated metal industries generate cuttings
andotherscrapmetal. Scrapthatisdestinedforreclamation
is not regulated as hazardous waste. If metal chips from
machining operations are mixed with hazardous
metalworking fluid wastes, however, the waste stream is
treated as hazardous.
While metalworking fluid purchases typically account
for less than 0.5 percent of the cost of operating a machine
tool (Schaffer 1978), the problems that contaminated and
degradedfluids can causecanbeexpensiveand troublesome.
Proper coolant and cutting oil maintenance is necessary to
prevent excessive machine tool downtime, corrosion, and
rancidity problems.
Metalworking fluid rancidity, perhaps the most
common problem, can affect productivity and operator
morale. Rancidity odors are produced in contaminated
fluids due to bacterial action. The odors are especially
strong when machines are started up after periods of
downtime. The odors are frequently unpleasant enough
that the fluid must be changed.
Insufficient maintenance of cutting fluids, especially
water-based fluids, can result in workpiece and machine
tool corrosion. Many cutting fluids are relied upon to
protect in-process parts from corrosion, but they will not
offer thisprotection if they havedeteriorateddueto rancidity,
or if they are not maintained at the recommended
concentrations. Cutting fluids also must not be allowed to
penetrate into gear boxes or into lubricating oil reservoirs,
or internal damage to machines can result.
Contamination of water miscible metalworking fluids
by "tramp" lubricating and hydraulic oils constitutes one of
the major causes of fluid deterioration. The tramp oils
interfere with the cooling effect of the fluids, promote
bacterial growth, and contribute to oil mist and smoke in
the shop environment. Tramp oils impair the filterability
of metalworking fluids through both disposable and
permanent media filters, and thus inhibit recycling. Tramp
oils also contribute to unwanted residues on cutting tools
and machine parts (Sluhan, W. A.)
The most serious problem caused by tramp oils is the
promotion of bacterial growth, primarily Pseudomonas
oleovorans, in the metalworking fluid. Such bacteria
degrade lubricants, emulsifiers and corrosion inhibitors in
the metalworking fluids, and liberate gases, acids and salts
as byproducts of their growth (Sluhan, W.A.). Bacterial
growth also interferes with the cooling effect of
metalworking fluids.
The tramp oils that most contribute to bacteria growth
are hydraulic oils (used in hydraulic assist systems), due to
their high water miscibility compared to lubricating oils,
and to the phosphorus antiwear compounds they contain,
which catalyze microbe growth. Lubricating and machine
ramp oils create less problems, because their lower
miscibility causes them to float to the surface of the
coolant.
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Metal Parts Cleaning And Stripping
Cleaning and stripping operations are integral to
numerous processes in industries involved with the
manufacture of metal parts and equipment. Virtually all
fabricated metal objects require some form of cleaning.
Machined parts are cleaned with solvents; paint, oxidation
and old plating is stripped from workpieces using caustics
and abrasives; and workpieces in plating lines are cleaned
several times using water, acids, caustics and detergents.
Implementation of proper, environmentally sound cleaning
and stripping techniques will markedly reduce toxicities
and volumes of wastewater, as well as reducing process
chemical requirements.
PROCESS DESCRIPTION
Five types of metal cleaning media are utilized by
industry: 1) solvents (both halogenated and
nonhalogenated); 2) alkaline cleaners; 3) acid cleaners; 4)
nonchemical, abrasive materials; and 5) water. Alkaline
andacid cleaners are usually referred to as aqueous cleaners.
Mixtures of solvents and alkalines are frequently used.
Mixtures where water-immiscible solvent is emulsified in
water (often containing otheradditives) aretermedemulsion
cleaners.
Although metal parts cleaning is frequently thought of
as a simple operation requiring little more than washing a
part in solvent, many metal parts require sophisticated and
rather complex sequences of cleaning steps. The design of
a cleaning operation is generally dependent upon three
interrelated factors:
The nature of the contamination. It is important
to know the composition as well as the history
of contaminants on the metal's surface, in order
to design the proper cleaning system and
sequence of baths or other operations. Alkaline
cleaners are often used to remove heavy soils
and some solid oils, while caustics are good
paint stripping agents. Acid cleaners and
abrasives are employed to remove oxidation
scale and rust. When parts have, been
contaminated with several materials,
sequencing of cleaning operations can be
important. For instance, a layer of oily
contamination might be removed by an alkaline
cleaner before abrasives are used to remove a
rust layer.
The metal substrate. The contaminant must be
removed to the required degree without
adversely affecting the metal substrate.
Reactivity of different metals with alkaline and
acids varies, and thus cleaners that are
appropriateforonemetalmaynotbeforanother.
The degree of cleanliness required. The cleaning
that a metal surface requires varies depending
upon the particular surface treatment, plating
or coating operations it will be subjected to.
For instance, parts going to a cyanide-zinc
plating bath do not usually need to first receive
a high level of cleaning since cyanide-based
plating solutions exhibit strong cleaning actions
of their own. For a nickel plate to adhere to a
metal surface, on the other hand, the surface
must be extremely clean. Thus, thorough and
rigorous cleaning operations are needed prior
to the nickel plating.
It is frequently the case that no one cleaning operation
can be specified as best based simply on reviewing the
above factors. Several cleaning methods often appear
appropriate, and only through experiment can the best one
be selected.
Cleaners, exceptfor abrasives, are normally contained
in large open tanks, with the parts to be cleaned mounted
on racks or in perforated horizontal barrels. The decision
to use racks or barrels depends on the size and shape of the
part as well as the type of coating it requires.
SOLVENT CLEANING
Solvents are the most widely used class of cleaners.
They are employed for removing oil-based contaminants,
in either cold cleaning, diphase cleaning, or vapor phase
cleaning operations.
Cold cleaning generally employs unheated or slightly
heated nonhalogenated solvents, and is the most common
type of cleaning. The four categories of cold cleaning are:
1) wipe cleaning; 2) soak cleaning; 3) ultrasonic cleaning;
and 4) steam gun stripping. Wipe cleaning consists.of
soaking a rag in solvent and wiping the metal part clean.
Soak cleaning involves the immersion of the parts in a
solvent tank. Ultrasonic cleaning is identical to soak
cleaning, except that an ultrasonic unit is added to the tank,
which provides a vigorous cleaning action throughout the
tank. The main application of steam gun stripping is for
paint removal from metal objects. A stripper made up of
nonhalogenated solvents is fed into a steam line, through
an adjustable valve, mixed with the steam and ejected at
high speed from a nozzle.
Diphase cleaning systems are so named because they
use both water and solvent phases for cleaning. Parts to be
cleaned first pass through a water bath, then a solvent
spray. Vapor phase cleaning, also cal led vapor degreasing,
consists of a tank of halogenated solvent heated to its
boiling point. Parts to be cleaned are placed in the vapor
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zone above the liquid solvent. The vapor that condenses on
thecoolerpartdissolves oil-based contamination andrinses
the part clean. Since the potential exists for considerably
greater air emissions from vapor phase cleaning than from
cold cleaning tanks, specialrecovery equipmentis installed,
consistingofcoolingjackets and/or finnedcoil condensers.
By cooling the air above the vapor, a dense cool air blanket
is formed which helps suppress vapor from escaping. The
second unit, a finned coil condenser, is installed inside the
tank and condenses any vapor that reaches it.
AQUEOUS (ALKALINE AND ACID) CLEANING
AND STRIPPING
The cleaning action of aqueous cleaners relies mainly
on displacement of soils rather than on their dissolution, as
is the case with organic solvent Since both alkaline and
acidaqueous cleaners andstrippers use thesameequipment,
they are discussed together. Alkaline cleaning solutions
contain builders (sodium salts of phosphates, carbonates,
silicates, and hydroxides) and surfactants (detergents and
soaps). Other additives may include anti-oxidants and
stabilizers as well as small amount of solvents. Alkaline
cleaners and strippers are employed to remove soil from
metal parts, as well as old plating and paint Acidic
cleaning solutions may contain mineral acids (nitric, sulf uric
and hydrochloric), organic acids (sulfamic, acetic, oxalic
or cresylic), detergents, chelating agents and occasionally
small amount of solvents. Acid cleaners remove rust,
scale, and "smut", which is formed from electrocleaning.
Very strong alkaline cleaners containing cyanide and
cleaning agents have recently been formulated to'replace
acid cleaners. No matter what type of aqueous cleaner is
used, soak tanks similar to those used for solvents are the,
most common cleaning method employed. Someaqueous
cleaners, however, are used in electrochemical cleaning, in
which the workpiece is connected to a source of current In
direct current electrochemical cleaning, the workpiece is
attached to the cathode, causing hydrogen gas to be formed
at the part's surface that provides a scrubbing action. Smut
formation (theplating of metal contaminants in the solution
onto the workpiece) does sometimes occur, however, as
well as hydrogen embrittlement of the metal. These
disadvantages are avoided in reverse current cleaning, or
electropolishing, in which the workpiece is attached to the
anode. Metal substrate is dissolved electrolytically,
liberating the surface contaminant
ABRASIVE CLEANING AND STRIPPING
Abrasive cleaners are designed for removing rust,
oxides and burrs, old plating and paint, and to create a
smooth surface. Typical abrasives are aluminum oxide or
silicon carbide mixed with an oil or water based binder.
The abrasive-binder mixture is applied to a buffing wheel
made from an absorbent material such as cloth. The metal
part is held against the spinning wheel. Vibratory finishing
is another method of abrasive cleaning in which a load of
metal parts is immersed in a vibrating tank containing
abrasive material and water. Similar cleaning methods
employ tumbling barrels and centrifugal barrel finishing.
WATER CLEANING
Water cleaning is an integral part of every parts
cleaningprocess. Mostofthecleaningoperationsmentioned
above require that a water wash be performed before and
after each operation. The washing is generally done either
in a soak tank, or using a spray unit. Because rinse water
generally comprises the largest waste stream in metal
fabrication processes, measures for reducing the amount of
water required (such as extending water bath life by
preventing its contamination by other cleaning media) are
very important in reducing the overall volume of wastes.
WASTE STREAMS
The primary wastes associated with metal parts
cleaning are listed in Table 1, along with their sources. The
composition of the waste depends on the cleaning media
used, type of substrate, and the type of soil removed (oils,
greases, waxes, metallic particles, oxides, etc.). If a facility
has a wastewater treatment system, primary rinse water,
alkaline and acid cleaning solutions can be mixed together
(one acts to neutralize the other) and then treated.
Secondary rinse water (if secondary rinse is employed)
is usually used to replace discarded primary rinse water
and/or used as a makeup for cleaning solutions. .For
facilities using small amounts of cleaner, the tendency is to
drum the material for disposal. Solvent waste can be sent
to an off-site recycler or recycled on-site using distillatipn
equipment.
i . - . i -.,''..
Metal Surface Treatment And Plating
Operations ;
Metal surface treatment and plating are practiced by
most industries engaged in forming and finishing metal
products, andinvolve the alteration of the metal workpiece's
surface properties, in order to increase corrosion or abrasion
resistance, alter appearance, or in some other way enhance
the utility of the product. Plating and surface treatment
operations are typically batch operations, in which metal
objects are dipped into and then removed from baths
containing various reagents for achieving the required
surface condition. The processes involve moving the
object to be coated (the workpiece) through a series of
baths designed to produce the desired end product.
Workpieces can be carried on racks or in barrels. Large
workpieces are mounted on racks that carry the parts from
bath to bath. A set of small parts can be contained in barrels
that rotate in the plating bath.
8
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Table 1. Metal Parts Cleaning Wastes
No.
1.
2.
3.
4.
5.
Waste
Description
Abrasive
Solvents
Alkalines
Acids
Rinse
water
Process
Orgin
Removal of rust,
scale polishing
of metal
Removal of oil-
based soils
Removal of
organic soils,
descaling
Removal of
scale, smut
Removal of
previous
cleaning
material
Composition
Aluminum oxide, silica
metal, water, grease
Halogenated and non-
halogenated solvents,
oil-based contaminants
Alkaline salts,
additives, organic
soils, water
Acids, additives,
dissolved metal salt, water
Water with traces of
cleaners and additives
PROCESS DESCRIPTION
Platingoperationscanbecategorizedaselectroplating
and electrolessplatingprocesses. Surface treatmentincludes
chemical and electrochemical conversion, case hardening,
metallic coating, and chemical coating. Most metal surface
treatment and plating processes have three basic steps:
surface cleaning or preparation (which was examined in
the previous action); the actual modification of the surface,
involving some change in its properties (e.g. casehardening,
or the application of a metal layer); and rinsing or other
workpiece finishing operations. .
Chemical and Electrochemical Conversion
Chemical and electrochemical conversion treatments
are designed to deposit a coating on a metal surface that
performsa corrosion protectionand/ordecorativefunctioh,
andinsomeinstancesisapreparationforpainting. Processes
include phosphating, chromating, anodizing, passivation,
and metal coloring. . Phosphating treatments provide a
coating of insoluble metal phosphate crystals that adhere
strongly to the base metal. The coatings provide some
corrosion resistance, but their main function, due to their
absorptivity, is as abase for theadhesion of paints, lacquers,
and oils to the metal surface. Chromate coatings are
applied to minimize rust formation and to guarantee paint
adhesion. Chromating baths' ingredients include hexavalent
chromium, oneor two mineral acids (e.g. sulfuric or nitric),
and often several organic or inorganic activating
compounds.
Anodizing employs electrochemical means to develop
a surface oxide film on the workpiece, enhancing its
corrosion resistance. Passivation is a process by which
protective films are formed through immersion in an acid
solution. In stainless steel passivation, embedded ion
particles are dissolved and a thin ocide coat is formed by
immersion in nitric acid, sometimes containing sodium
dichromate.
Case Hardening
Case hardening produces a hard surface (the case)
over a metal core that remains relatively soft. The case is
wear-resistant and durable, while the core is left strong and
ductile. Case hardening methodologies include carburizing,
carbonitriding,nitriding,microcasing,andhardeningusing
localized heating and quenching operations.
Carburizing, the most widely used case hardening
operation, involves diffusion of carbon into a steel surface
at temperatures of 845° to 955°C, producing a hard case in
the high carbon areas. Nitriding processes diffuse nascent
nitrogen into a steel surface to produce case-hardening.
Nitriding is accomplished using either a nitrogenous gas,
(usually ammonia), or a liquid salt bath, typically consisting
of 60 to 70 percent sodium salts, miainly sodium cyanide,
and 30 to 40 percent potassium salts, mainly potassium
cyanide. Carbonitriding and cyaniding involves the
diffusion of both carbon and nitrogen simultaneously into
a steel surface.
Applied energy methods are those that generate a case
through localized heat and quenching, rather than through
use of chemicals. Very rapid heat application results in
surface hardening with little heat conducted inward. Since
no carbon or nitrogen is diffused into the workpiece, it is
the existing carbon content of the ferrous metal that
-------
determineshardnessresponse. Heatingcanbeaccomplished
through electromagnetic induction, hightemperatureflames
or high velocity combustion product gases.
Metallic Coatings
Metallic coatings provide a layer that changes the
surface properties of the workpiece to those of the metal
beingapplied. The workpiecebecomesacomposite material
with properties generally not achievable by either material
singly. The coating's function is usually as a durable,
corrosionresistantprotective layer, while the core material
provides the load-bearing function. Metallic coatings as
defined here refer to diffusion coatings (in which the base
metal is brought into contact with the coating metal at
elevated temperatures allowing lattice interdiffusion of the
two materials); spraying techniques; cladding (application
usingmechanical techniques); vapor depositionand vacuum
coating.
Hot dipping is a diffusion process that involves partial
or complete immersion of the workpiece in a molten metal
bath. Common coating materials include aluminum, coated
lead, tin, zinc, and combinations of the above. The coating
metal in a cementation diffusion process is applied in
powdered form at a high temperature (800 to 1100° C), in
a mixture with inert particles such as alumina or sand, and
a halide activator. The main applications of sprayed
diffusion coatings are for workpieces difficult to coat by
other means due to their size and shape, or that are
damageable by the high temperature heating required of
other methods. Vapor deposition and vacuum coating
produce high quality, pure metallic layers, and can
sometimes be used in place of plating processes. A layer
of metal cladding can be bonded to the workpiece using
high pressure welding or casting techniques. Cladding can
offer an alternative to plating in some situations.
Electroplating
Electroplatingisachievedbypassinganelectriccurrent
through a solution containing dissolved metal ions as well
as the metal object to be plated. The metal object acts as a
cathode in an electrochemical cell, attracting metal ions
from the solution. Ferrous and nonferrous metal objects
are typically electroplated with aluminum, brass, bronze,
cadmium, chromium, copper, iron, lead, nickel, tin, and
zinc, as well as precious metals such as gold, platinum, and
silver. Common electroplating bath solutions are listed in
Table 2.
The sequence of unit operations in an electroplating
operation is very similar when either racks or barrels are
used to carry parts. A typical sequence involves various
types of cleaning steps, stripping of old plating or paint, the
actual electroplating steps, and rinsing steps between and
after each of the above operations.
Table 2. Common Electroplating Bath
Compositions
Electroplating Bath Name Composition
Brass and Bronze
Copper cyanide
Zinc cyanide
Sodium cyanide
Sodium carbonate
Ammonia
Rochelle salt
Cadmium cyanide
Cadmium oxide
Sodium cyanide
Sodium hydroxide
Cadmium fluoroborate
Fluoroboric acid
Boric acid
Ammonium fluoroborate
Licorice
Copper cyanide
Sodium cyanide
Sodium carbonate
Sodium hydroxide
Rochelle salt
Copper fluoroborate
Fluoroboric acid
Copper sulfate
Sulfuric acid
Copper pyrophosphate
Potassium hydroxide
Ammonia
Copper cyanide
Potassium cyanide
Potassium fluoride
Chromic acid
Sulfuric acid
Chromic acid
Sulfate
Fluoride
Electroless plating uses similar steps, but involves the
deposition of metal on a metallic or non-metallic surface
without the use of external electrical energy.
WASTE STREAMS
Common plating and surface treatment process wastes
are listed in Table 3. Two of the waste streams, spent
alkaline cleaning solutions and spent acid cleaning
solutions, are generated by periodic replacement of
contaminated solutions. Rinse waters are generated from
overflow "of rinse tanks and contamination by drag-out
from cleaning baths. Waste removed from plating tanks by
the continuous filtering of the baths results infilter sludges.
Cadmium Cyanide
Cadmium Fluoroborate
Copper Cyanide
Copper Fluoroborate
Acid Copper Sulfate
Copper Pyrophosphate
Fluoride-Modified
Copper Cyanide
Chromium
Chromium with
Fluoride Catalyst
10
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Table3. Process Wastes
Waste
Description
Spent process
solutions
Filter sludges
Quench oils
and quench oil tank
cleanup wastes
Spent salt bath
Wastewater treatment
sludge
Vent scrubber wastes
Ion exchange resin
reagents
Process
Origin
Plating and chemical
conversion
Plating and chemical
conversion
Case hardening
Carburizing, nitrid-
ing, cyaniding
Wastewater treatment
Vent scrubbing
Demineralization of
process water
Composition
See Table 2.2
Silica, silicides,
carbides, ash, plating
bath consituents
Oils, metal fines,
combustion products
Sodium cyanide and
cyanate. Potassium
cyanide and cyanate.
Metal hydroxides,
sulfides, carbonates
Similar to process
solution composition
Brine, HCI, NaOH
Wastes produced at aparticular facility will be similar
to those listed, but their precise composition will depend on
the specific process. Some or all of the waste types listed
may be combined into a single stream before treatment and
disposal. It is common to combine concentrated cyanide
wastes from plating and cleaning solutions, for instance,
with filter sludges. These are generally kept separate,
however, from acidic wastes and from the dilute cyanide
solutions.
On a volume basis, contaminatedrinsewater accounts
for the majority of plating process waste. As shown in the
previous sections, plating processes can involve many
rinsing steps. Rinsewater is used to wash off the drag-out
from a workpiece after it is removed from a bath. Drag-out
refers to the excess solution that adheres to the workpiece
surface and gets carried out of the solution bath upon
withdrawal of the workpiece from the bath. In general, the
use of small part barrels in the plating process (barrel
plating) produces more drag-out than rack plating. This is
because a barrel carries in it more plating solution upon
withdrawal from the bath than a rack does, and because
drainage of the drag-out back into the bath is more difficult
with barrels. If the drag-out from one bath is carried into
the next bath in the sequence due to incomplete rinsing, it
is referred to as "drag-in," and is considered a contaminant
in the latter bath.
Spentcleaningandplatingsolutionsareanother source
of plating wastes. Several types of cleaning solutions are
used to prepareametal surface forelecfroplating. Stripping
wastes are a special type of cleaning waste. They result
from the stripping off of the old plated deposit prior to the
deposition of anew metal plate. Cleaning solutions may be
acidic or basic, and may contain organics. Heavy metals
are usually not present, although some cleaning solutions
contain cyanide. Spent plating solutions contain high
concentrations of metals. These solutions are not regularly
discarded like cleaning solutions, but may require purging
if impurities build up.
Wastes produced from spills and leaks are usually
present to some extent in an electroplating process. Water
is used to wash away floor spills, and the resulting
wastewater contains all of the contaminants present in the
original solutions. Wastewater is also produced from the
wet scrubbing of ventilation exhaust air.
Wastewater produced in an electroplating process
may contain a variety of heavy metals and cyanide. The
metals are typically removed by adding lime or other
precipitating agents, and precipitated under alkaline pH.
The resulting metal hydroxide precipitate forms a.dilute
sludge, which is thickened and then disposed of by
landfilling.
Paint Application
The application of paint is practiced within most
fabricated metal industries. Surface coatings are used
wherever it is desired to provide decoration, protection,
and/or safety marking to a product or item. Most paint
coatings for fabricated metal products are solvent based
11
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although many shops are replacing these with water based
materials.
PROCESS DESCRIPTION
Before a product coating can be applied to a surface,
the surface mustbe free from contamination. As described
above, many different types of abrasives, alkalines, acids,
and solvents, as well as water, are used by industry to clean
metal surfaces. Once a part is cleaned, surface treatment
such as phosphate coating can be applied if desired. The
purpose of surface treatment is to condition or prepare the
surface so that the paint forms a better bond with the metal
surface.
After the item has been cleaned and treated, paint can
be applied. Depending on the size, shape, complexity, and
quantity ofitemstobepainted,differentapph'cationmethods
can be employed. When itis desired topaintalarge number
of very small items, the most commonly used methods are
tumbling, barreling, or centrifuging. For all three methods,
the parts are placed inside a barrel, solvent-based paint is
poured onto the items, and the barrel is then rotated. After
a short time and at the correct point of tackiness, the parts
are transferred to an oven in a wire basket. While paint
consumption using these methods is very small, the
empirical nature of the operation requires that the operator
be highly experienced to achieve reliable results.
For cylindrical items; a commonly used method is
dipping. Here the paint is held in a large tank and the object
to be painted is slowly lowered into the tank and then
withdrawn. Many complex items can be dip painted
provided that the drainage points (the places where the
excess paint drips off), can be located where they are not
noticeable.
Flow coating is often employed for items that would
be difficult to dip because of their size or shape, or as a
means of avoiding the installation and operation of large
dip tanks. A flow coating system operates by using high
pressure sprays to flood the item with solvent-based paint.
After spraying, the item is allowed to drain and the excess
paint is recirculated. Since a considerable amount of
bubbling occurs due to spraying, the item is then passed
through a solvent chamber where the solvent vapors allow
the paint to reflow. Following this operation, the item is
then oven-dried. The main disadvantage of flow coating is
high solvent loss, which can be three times as large as for
dipping and twice as great as for spraying.
For relatively flat items of large area, roller coating
and curtain coating machines are used. Roller coating is
used extensively by the canning industry for painting flat
metal sheets that are then fabricated into cans. Itis also used
for spreading or applying glue to wood in the manufacturing
ofplywood. Arollercoatingmachineoperatesbymetering'
paint or coating material onto a roller and then transporting '
the item past the roller by means of a conveyor belt. A
curtain coating machine consists of a pressurized container
along the bottom of which is an adjustable slit that allows ;
the coating to flow and form a vertical curtain. A Conveyor .
belt is placed on each side of the curtain so that work items
are passed through the curtain and coated without the
conveyor belts being coated. «
While all of the above-mentioned methods have found
widespread acceptance by industry, the most widely used
method for applying paint is still the spray gun. A spray
gun operates by using compressed air, to atomize the paint
and produce a fan or circular cone spray pattern. Many
installations are automated so that a fixed gun is turned on
when an object passes in front of it. In its simplest use, the
gun is hand-held and the object remains stationary. Some
of the variations on spray gun painting are airless spray
guns and electrostatic spray guns. Airless spray guns force
the paint out at high pressure so that air is not require for
atomization. By eliminating the use of compressed air,
operating costs are lower, spray mists are not produced,
and expensive exhaust systems are not required.
Electrostatic spray units are designed so that the atomized
paint leaving the gun has a positive charge. This positive
charge causes the paint to be attracted to the object which
is connected to ground. Since more of the paint reaches its
target(therebyreducingoverspray),less waste is generated.
Following the application of paint, the item is passed
through a drying or curing oven. The curing methods
employed, infrared or ultraviolet, will depend on the type
of paints being used. Once dried, the items are sent to ;
inspection and final packaging or assembly. If a part fails
inspection because of a bad finish, it is usually reworked by
stripping off the paint and returning it to the cleaning
operation.
WASTE STREAMS
The primary wastes associated with product coating
applications consist of empty paint containers, spent
cleaning solutions, paint overspray (including paint
collectedby air pollution control equipment), spent stripping
solutions, and equipment cleaning wastes. Waste
minimization methods for stripping and cleaning are
examined under the "Parts Cleaning" heading in Section
Three; source reduction and recycling methods for the
other waste streams are examined under "Paint Wastes" in
Section Three.
12
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SECTIONS
WASTE MINIMIZATION OPTIONS
FOR FABRICATED METAL PRODUCT FACILITIES
Introduction
The list of individual primary fabricated metal industry
waste streams and their sources along with a list of source
reduction and recycling methods is presented in Table 4.
Recommended waste reduction methods and identified
procedures are discussed in the following sections. These
methods came from industry contacts and published
accounts in the open literature.
In addition to the waste reduction measures that are
classified as process changes or material/product
substitutions, a variety of waste reducing measures labeled
as "good operating practices" has also been included. Good
operatingpracticesaredefinedasprocedures or institutional
policies that result in a reduction of waste. The following
describes the scope of good operating practices:
Waste stream segregation
Personnel practices
Management initiatives
Employee training
Procedural measures
Documentation
Material handling and storage
Material tracking and inventory control
Scheduling
Loss prevention practices
Spill prevention
Preventive maintenance
Emergency preparedness
Good operating practices apply to all waste streams.
Material Handling And Storage
Improper storage and handling can result in spoilage
and obsolescence of raw materials, resulting in the
generation of hazardous and other waste streams. Efficient
operating practices can reduce or eliminate waste resulting
from obsolescence andimproper storage. Source reduction
methods for reducing waste include:
Material Preinspection
Materials should be inspected before being accepted
and unacceptable or damaged materials returned to the
manufacturer or supplier. This avoids both disposal of a
nearly full container of unusable material and printing an
unacceptable product
Proper Storage of Materials
Many chemicals are sensitive to temperature and
humidity. Much waste can result from improper storage.
Chemical containers list the recommended storage
conditions. Meeting the recommended conditions will
increase their shelf life.
Restrict Traffic through Storage Area
To prevent raw material contamination, the storage
area should be kept clean. Also, the storage area should not
1 be open to through traffic. Through traffic will increase
dust and dirt in the storage area, increasing possible
contamination. In addition, spills in; the storage area will
be easier to contain if traffic is restricted.
Inventory Control
Inventories should be kept using the "first-in, first-
out" practice. This will reduce the possibility of expired
shelf life. Thispractice may notworkfor specialty materials
that are seldom used. Computerized inventory systems can
track the amounts and ages of the raw materials.
Purchase Quantities According to Needs
Raw material order quantities should be matched to
usage. This avoids having a large, partly used container of
ink going bad in storage because it wasn't properly sealed.
Large shops should order materials in large containers,
which maybe returnable, thereby eliminating or reducing
the need to clean them. It takes less lime to scrape out the
large single container than several small ones. Ordering
materials in returnable tote bins may maximize these
advantages.
13
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Table 4. Waste Minimization Methods for Fabricated Metal Industry Processes
Process
Material Handling
and Storage
Waste Stream
Machining Wastes ttfetalworking
Fluid
Parts Cleaning Solvents
Aqueous Cleaners
Abrasives
Rinsewater
Surface Treatment Process Solutions
and Plating
Rinsewater
Source Reduction Options
Material Preinspection
Proper Storage of Materials
Restrict Traffic through
Storage Area
Inventory Control
Purchase Quantities
According to Needs
Use of High Quality
Metalworking Fluid
Demineralized Water Use
Concentration Control
Sump and Machine Cleaning
Gasket, Wiper and Seal
Maintenance
Cleaning of Metalworking Fluid
Assigning Fluid Control
.Responsibility
Tank Lid Installation
Increase in Freeboard Space
Installation of Freeboard Chillers
Cross-Contamination Avoidance
Appropriate Makeup Solutions
Solvent Standardization
Consolidating Operations
Media Substitution
Sludge Removal
Use of Dry Cleaning and
Stripping Methods
Media Substitution
Use of Greaseless or Water-Based
Binders
Use of Liquid Sprays
Water Level Control
Synthetic Abrasives
Rack and Barrel System Design
Rinse System Design
Spray and Fog Rinses
Chemical Rinsing
Deionized Water
Increasing Solution Life
Material Substitution
Process Substitution
Chemical Coating
Mechanical Cladding
and Coating
Recycling Options
Test Expired Material
Usefulness
Filtration of Metalworking
Fluids
Skimming
Coalescing
Hydrocycloning
Centrifuging
Pasteurization
Downgrading
Gravity Separation
Filtration
Batch Distillation
Fractional Distillation
Use as Fuel
On- and off-site Recycling
Oil Separation
Pickling Bath Recycling
Reduction in Drag-Out of
Process Chemicals:
Speed of Withdrawal
Surface Treatment
Plating Bath Concentrations
Use of Cleaning Baths as pH
Adjusters ,
Metal Recovery
Evaporation
Reverse Osmosis
Ion Exchange
Electrolytic Recovery
Electrodialysis
Rinsewater Reuse
14
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Table 4. Waste Minimization Methods for Fabricated Metal Industry Processes (cont'd)
Process
Waste Stream
Surface Treatment
and Plating
(cont'd)
Treatment Wastes
Case Hardening
Wastes
Paint Application Empty Containers
Paint Application
Waste
Sojurce Reduction Options
Surfactant Use
Solution Temperature
Workpiece Positioning
Drag-Out Recovery
System Design Considerations:
Rinsetank Design
Multiple Rinsing Tanks
Reactive Rinsing
Fog Nozzles and Sprays
Automatic Flow Controls
Rinse Bath Agitation
Precipitating Agents and Other
Treatment Chemicals
Trivalent Chromium Use
Waste Segregation
Sludge Dewatering
Selection of Clean Processes
Waste Segregation
Bulk Purchasing
Minimizing Residuals
Overspray Reduction:
Equipment Modifications
Operator Training
Material Substitution Replacing
Solvent-Based Coatings with:
Water-Based Coatings
Radiation-Curable Coatings
Powder Coatings
Recycling Options
Reusing Solvent Paint Mixtures
Recovery through Distillation
Recovery through Filtration
15
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Test Expired Material for Usefulness
Materials having expired shelf-life should not
automatically be thrown out Instead, this material should
be tested for effectiveness. The material may be usable,
ratherthanbecomingawaste. Arecyclingoutletshouldbe
found for left over raw material that is no longer wanted.
Machining Wastes
SOURCE REDUCTION METHODOLOGIES
Aprimary problem in metalworkingfluidmanagement
iscontamination with tramp oil and theproblemsthatresult
from this. While the best solution for tramp oil problems
is to prevent the oils from entering the metalworking fluid,
some contamination will occur as the machines and their
oil seals and wipers wear. This can be reduced through
preventive maintenance such as periodic seal and wiper
replacement. Optional metalworking fluid performance
starts withapreventivemaintenanceprogram that includes:
use of high quality, stable cutting and grinding
fluids;
useofdemineralizedwaterformixingpurposes;
fluid concentration control;
control of fluid chemistry (pH, dissolved
oxygen, etc.);
fluid contamination prevention;
periodic sump and machine cleaning;
periodic gasket, wiper and seal inspections and
replacements to minimize tramp oil
contamination;
regularcleaningofmetalworkingfluidthrough
filtering orcentrifugation, in order to minimize
microbe growth by controlling tramp oil
buildup; and
assignmentofresponsibilityforfluidcontrolto
one person.
Fluid cleaning can be accomplished through filtration
and clarification, using bag, cartridge or disc filters, chip
wringers and centrifuges. Periodic addition of specialized
biocides into the metal working fluid can also extend its
life, by combating microbe growth (Zabik 1987; Porter
1988).
An irritating problem in many shops is the
contamination of fluids with trash such as cigarette butts,
food or food wrappers that find their way into sumps.
B etterhousekeepingprocedures, including operator traning
and coverage of sumps with screens or solid covers, can
help reduce this ongoing problem.
Because water constitutes 90 to 99 percent of water
soluble cutting and grinding fluids, high mineral content
water can adversely affect fluid performance by
deteriorating emulsions, causing corrosion and enhancing
microbial growth. Purification of water through
deionization or reverse osmosis before it is mixed with the
fluid can help reduce these problems.
It is important to carefully select the metalworking
fluid most suitable for the particular application, in order to
maximize performance and long fluid life. Fluid selection
should be done from an overall, plant-wide perspective, in
order to find the best products as well as to minimize the
number of differentfluids in use. With thebroadapplications
of some high quality fluids, it is sometimes possible to
employ only one type in an entire plant, although different
applications in the plant may require different proportions
of water and concentrate.
A periodic schedule of metalworking fluid testing can
alert plant staff to deteriorating fluid qualities in time to
prevent failure of the fluid. Tests might include analyses
for pH, specific component concentration including
additives,particulatematter,trampoil,rustinhibitor,biocide
concentrate, and dissolved oxygen. Low pH values indicate
low product concentrations, and thus related problems
such as increases in metal fines or other suspended solids,
and heightened vulnerability to microbe growth and tramp
oil contamination (Porter 1988).
In order to make informed choices of fluids, it is
important to know not only about the fluids' cutting and
grinding abilities, but also about factors such as their
resistance to bacterial attack, the residues they leave on
machine tools and workpieces, the corrosion protection
they offer, the health dangers they present, such as skin or
respiratory irritation, and the environmentally hazardous
chemicals they contain. Chemically active lubricants are
often used, for instance, that contain chlorine, sulfur or
phosphorus (Centrico 1986). Fluids can also contain
phenols, creosols and harsh alkalies. Tramp oils often
carry other, hazardous contaminants into metalworking
fluid, and can lead to breakdown of the fluid and formation
of hydrogen sulfide.
Use of synthetic metalworking fluids can sometimes
result in dramatically increased fluid life. Synthetic fluids
are made up of chemicals such as nitrites, nitrates,
phosphates and borates. Synthetic fluids contain only zero
to onepercentsolubleoils in thefluidconcentrate, compared
to 30to90percentsolubleoilinnon-synthetic metalworking
fluid concentrates. While the lubricity of synthetic fluids
is lower than many non-synthetic fluids, an advantage of
synthetic fluids is that tramp oils are not able to contaminate
them as easily as non-synthetic fluids, for they are not able
toreadilyenterthefluidemulsion, which leads to breakdown
16
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of the fluid's qualities (EERC1988). Many synthetic fluids
offer greater thermal stability at high temperatures, resisting
oxidation better than non-synthetic fluids.
Gases can sometimes be used in place of coolants,
because they offer cooling of workpieces and tools with no
workpiece contamination. Air is the most frequently used
gas, and is employed both in dry cutting or with other
fluids. Nitrogen and carbon dioxide are occasionally used
as well, but their cost is high and therefore their applications
are limited (Porter 1988).
RECYCLING METALWORKING FLUIDS
Byrecycling deteriorated orcontaminatedfluids, costly
hauling and disposal can be reduced. Also, recycling will
minimize the need for purchase of high priced fluid
concentrates. While many shops engage off-site recycling
companies to handle their spent fluids, it is very feasible for
larger shops to recycle in-house. The processes recyclers
employ separate oily wastes from water. The water is
released to the sewer while the oil is refined or used as fuel.
In-house recycling typically has a different focus than off-
site: to extend the usable li fe of metal working fluids, rather
than to separate and refine the oils it contains. Continuous
in-house filtration of fluids in machine sumps reduces the
requirements for new fluids, avoids recycler's charges, and
saves money by reducing machine downtime for cleaning
and coolant recharge.
Methodologies for recycling metalworking fluids
include filtration, ultrafiltration for water removal,
skimming, flotation, coalescing, hydrocycloning,
centrifuging, pasteurization and downgrading. In gravity
pressure and vacuum filtration technologies, the waste
coolant is passed through a disposable filter to remove
solid particles. Diatomaceous earth filters are also used at
times, but their adsorptive properties are so high that they
can actually remove additives from a metalworking fluid.
In skimming separations, the metal working fluid is allowed
to sit motionless until immiscible tramp oil floats to the
surface, where it is manually removed or skimmed
automatically using oil-attracting belts, floating ropes or
wheels. If the oil contaminants are fairly miscible, as is the
case with hydraulic oils, or if the coolants in the fluid have
emulsified the oils, they will not rise to the surface on their
own, and other separation techniques must be used.
Separation of oil contaminants can sometimes be enhanced
through dissolved air flotation. In this method, the
metalworking fluid waste stream is put under high pressure
and air is injected. When the pressure is released, the air
comes out of the solution, attaches to the oil and grit in the
fluid, and floats it to the surface, where it can be skimmed
off.
In coalescing techniques, the fluid is brought into
contact with an oleophilic ("oil loving") medium formed
into a high surface area shape such as corrugated plates or
vertical tubes. Oil droplets impinge on the media and cling
to it, eventually coalescing to form large droplets that float
to the surface of the fluid and are skimmed off by adjustable
weirs. Coalescers are not effective for removing water-
miscible hydraulic oils or emulsified lubricating oils, for
these do not readily separate from the metalworking fluid.
A hydrocyclone uses centrifugal force to separate
solid contaminants from the fluid. Waste fluid is pumped
underpressure into the top of a cone-shaped compartment
in which a vortexis setup. As the spinning fluidaccelerates
down the cone, solids are forced to the outer wall. The
solids move downward and are discharged, while the clean
fluid is forced by back pressure to move upward through
thecenterofthecone. Hydrocyclones can remove particles
down to aboutS microns; they cannot, however, efficiently
remove small quantities of tramp oil. The advantage of this
type of system is that it is mechanically very simple and
relatively easy to operate,
Centrifuging involves mechanical rotation of the
metalworking fluid, providing several thousand G's of
separating force. Centrif ugation is able to remove hydraulic
oils and other emulsified tramp oils as well as "free" oils.
Low RPM centrifuges are also used as "chip wringers" to
separate reusable oil clinging to metal chips.
One recycling method gaining popularity is a
combination of pasteurization and low speed centrifuging.
While this method is promising for certain applications,
pasteurization is a tremendously energy intensive process,
and is only marginally successful in controlling microbe
growth. Pseudomonas aeruginosa and Pseudomonas
oleovorans are two coolant-attacking bacteria that are
notoriously hard to kill. Pasteurization can also cause de-
emulsification of oils, and if the metalworking fluid has
degraded to the point where it has a gray color and emits a
hydrogen sulfide odor, pasteurization and centrifugation
can only remove the odor and color, but often cannot
restore the fluid's lubricity and corrosion inhibition.
Used high performance hydraulic fluids that no longer
fulfill exacting specifications can often be downgraded
and employed as cutting oils. For instance, certain mil spec
hydraulic oils cannot be employed in their original
application oncetheirviscosity has droppedduetopolymer
17
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shearing, butif theoils have been kept clean, additives can
bemixed into them to make excellent metalworking fluids.
Parts Cleaning
SOURCE REDUCTION METHODOLOGIES
Solvents
Themost common pieceofequipmentusedfor solvent
cleaning is the soak tank, followed by the vapor degreaser.
The main methods for reducing waste from both types of
equipment are the same. The two most important source
reduction goals are to minimize evaporation vapor loss and
to maintain solvent quality. By reducing evaporation loss,
the composition of the solvent will be maintained as close
as possible to its original composition. By maintaining
solvent quality, the need for replacement is reduced.
Halogenated solvents contain chemical stabilizers that
helppreventacidformationandremoveacid contaminants
from the bulk of solution. As a solvent is used, its ability
to neutralize or prevent acid formation lessens. 'Unless
measures are taken to maintain quality and prevent a
solvent from "going acid," the entire quantity of solvent
will have to be replaced more often. Measures that are
considered helpful in maintaining quality and minimizing
vapor loss include:
Installation of tank lids
Increase in freeboard space
Installation of freeboard chillers
Avoidance of cross-contamination
Sludge removal
Use of appropriate makeup solutions
Solvent standardization
Consolidating operations
Besides maintaining quality and minimizing loss,
substitutions of hazardous solvents with other media is
often a very effective means of source reduction. Media
substitution is discussed attheendof this Source Reduction
section.
Installation of lids on tanks. Lids should be placed on
all tanks when they are not in use. By installing a cover
duringperiodsof non-use, vapor degreaser solventloss can
bereducedby24 to SOpercent. Additional reductions have
been achieved by installing covers designed to allow the
bath to be used even while the cleaning operation is in
progress. Known as "silhouette entries," the openings in
the covers have shapes that match the shapes of the parts
being degreased and therefore minimize the area for vapor
loss. Covers shouldbe designed to slideclosed horizontally
across the open surface. This disturbs the vapor zone less
than covers that are hinged.
Increase infreeboard space. Freeboard is the distance
between the top of the vapor zone and the top of the tank.
EPA regulations recommend a vapor degreaser freeboard
of 75 percent of the tanks width. For shops where air
turbulence is present, increasing the freeboard to 100
percent can provide an additional reduction. Increasing the
freeboard on other tanks containing volatile solvents as
well as on degreasers is effective in reducing solvent usage
and solvent waste stream volumes.
Installationoffreeboardchillersinaddition to cooling
jackets. In this approach, a second set of refrigerated coils
is installed above the vapor degreaser's condenser coils.
These coils chill the air above the vapor zone and create a
secondary barrier to vapor loss. Therefore, special water
collection equipment is also frequently required, due to
water contamination of the solvent from frost build-up on
the coils.
Avoidance of cross-contamination of solvent is an
issue to be addressed, especially when the types of solvents
being used have similar sounding names. As little as one-
tenth of one percent 1,1,1-trichloroethane mixed into a
tank of trichloroethylene can cause an acid condition and
render the bath unusable for many applications (Smith
1981).
Water contamination as well as solvent cross-
contamination can lead to acid formation. In addition,
water contamination increases diffusion of solvents
increasing evaporative loss. To avoid water contamination,
the water separator should be cleaned and checked
frequently for proper drainage. Next, the temperature of
the water exiting the condenser coils should be maintained
at 90 to 100°F. Finally, parts should be checked to see that
they do not enter the degreaser while wet. This may call for
using oil-based abrasives and cutting oils in production
steps prior to cleaning.
Sludge that collects in the bottom of the tank should
always be removed promptly. Contaminants such as paint
absorb solvent, dissolve into solution, and reduce cleaning
efficiency. Zinc and aluminum fines, which are particularly
reactive in chlorinated solvents, can lead to acid formation,
if allowed to collect. Organic soil contamination should
not be allowed to exceed 10 percent for cold cleaning
operations and 25 percent for vapor degreasers. When
these levels are exceeded, acid formation can occur.
Using appropriate makeup solutions for the solvent
bath. As solvents are used, their ability to neutralize acid
lessens. Often, when an acid acceptance test indicates that
a solvent is close to going acid, fresh solvent is added to
18
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boost the level of stabilizers in the tank This, however, is
a poor practice, since the level of stabilizers in the tank can
never be made equal to the level of stabilizers in fresh
solvent. The proper technique is to analyze the solvent and
add specific components rather than fresh solvent. Usually,
the expense of analysis will be offset by the savings in
solvent for tanks of 500 gallons or more (Durney 1984).
This method should also be useful for facilities that recycle
their solvent, since distillation removes most stabilizers
from the solvent.
Solvent standardization. For facilities using a large
number of cold cleaning tanks, standardizing the solvent
used would help by increasing the potential for recycling
and minimizing the chances of cross-contamination from
other solvents. Standardizing in this context implies using
a minimum number (preferably one) of types of solvents in
all operations in the plant.
Consolidating operations. Once solvent
standardization has been implemented, the next step is to
consider consolidating cold cleaning operations into a
centralized vapor degreasing operation. Whilecoldcleaning
solvents must usually be discarded when the level of
contamination exceeds 10 percent, vapor degreasers can
operate up to a level of 25 to 30 percent contamination. In
addition, vapor degreasers provide much better cleaning,
and the parts leave the unit dry.
Other waste reduction techniques based on better
operating practices include locating cold cleaning tanks
away from heat sources, controlling the amount of heat
supplied to vapor degreasers, avoiding spraying parts
above the vapor zone or cooling jacket, and avoiding
solvent vapor drag-out.
Solvent vapor drag-out from a tank occurs when a
workpiece is inserted or withdrawn from the tank too
quickly. The speed of withdrawal of the work should not
exceed 11 feet per minute. In addition, the geometry of the
workpiece can affect drag-out. If the space between the
wall of the tank and the workpiece is too narrow, then a
piston effect will force solvent vapor out of the tank. As a
general measure, the cross-sectional area of the work load
should not exceed 50 percent of the tank's open area.
Aqueous Cleaners
Aqueous cleaners include, as mentioned above, alkaline
andacidcleaningsolutions. Alkaline cleaners areemployed
to remove organic contaminants from metal surfaces and
can replace solvent cleaners in many applications. Acid
cleaners are used to remove oxidation, scale, and rust from
metal surfaces. Aqueous cleaners are most commonly
applied in heated soak tanks, often with spray units installed
if alkaline solutions are being employed. Source reduction
methods for reducing aqueous cleaning wastes include:
Frequent removal of sludge. Separator units designed
to remove sludge and paniculate matter continuously from
alkaline or acid baths can reduce waste stream volumes and
save on disposal costs. One typical unit for alkaline baths
consisting of a pump, hydrocyclone and sludge retention
tank has reduced replacement chemical costs in a steel
cabinet manufacturing shop by 20 percent, and the time
interval between dumping and total cleanout of the system
has been lengthened from four to thirteen weeks (Report to
Congress 1986).
Use of dry cleaning and stripping methods. Cleaning
and stripping of parts can often be accomplished by
employing sand or bead blasting techniques. In one
decorative plating shop, hazardous sludge production was
reduced 75 percent by replacing alkaline stripping of old
paint and plating layers with sand blasting. The dry wastes
produced were minimal, and were much less expensive to
dispose of than the sludge (Jacobs 1986).
Abrasives
Abrasive powders are usually mixed with an oil-based
or water-based binder and are then applied to a polishing or
buffing wheel. Waste from this operation consists of worn
out cloth wheels saturated with abrasive, metal particles,
binder, and various oxides. Wastes from vibratory or mass
finishing operations consist of abrasive, metal particles,
water, and oxides dispersed in a slurry. Alkaline or acid
cleaners are sometimes added to the slurry so that additional
cleaning action is provided. Usually slurries are discarded
when the abrasive has undergonea given amount of attrition
or breakdown. The following source reduction methods
are applicable for abrasive cleaners:
Use of greaselessorwater-basedbindersforpolishing
or buffing. When oil-based binders are used, the factional
heat generated during buffing can cause the binders to
burn. This in turn leads to theneedfor additional workpiece
cleaning such as alkaline soaking. When properly used,
greaseless compounds leave the buffing wheel clean and
dry (Durney 1984). Also, greaseless compositions adhere
well to the surface of the wheel, extending wheel life.
Use of liquid spray compositions. Most abrasive
compositions are formulated for use in bar form (the bar is
held against the wheel to apply abrasive). With a liquid
spray system, a spray gun applies the compound to the
wheel automatically. Since the optimum quantity of
compound can be maintained on the wheel more easily
withaspraysystem.wheelwearduetocompounddeficieney
andcompound waste due to over-application are minimized.
Also, since spray compounds are usually water-based,
there should be no need for subsequent cleaning due to
burned binder material deposits on the workpiece.
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Careful control of water level in mass finishing
equipment. If insufficient water is used in mass finishing
operations, work items leaving the equipment will be dirty
and the attrition rate of the abrasive and its replacement
frequency will increase (Durney 1984). Water levels must
thus be carefully metered in these operations.
Synthetic abrasives. Abrasive cleaning and deburring
of workpieces is sometimes accomplished by putting both
workpieces and abrasive grit into a tumbling barrel and
rotating until the parts are finished. Beach sand and river
rocks are often used as abrasives. These will grind down,
however, into a large volume of fine silt mixed with metal
fines that must be treated as a hazardous waste. This
problem can be reduced by using aluminum oxide grit in
plaeeofbeachsand,andceramicabrasivedeburringmaterial
in place of river rock.
Rinsewater
Water is used to remove or dilute cleaning solutions
that are dragged out with cleaned parts. If these cleaning
solutions arenot removed, they can affect thequality of the
work and contaminate subsequent cleaning and processing
operations. Sincerinsingisessentiallyaprocess of dilution,
the general trend in the past was to use large volumes of
water. Today, however, efficient rinsing is required to
achieve the proper level of dragout dilution and also
conserve water. By conserving water, capital and operating
costs for waste treatment units are minimized. Source
reduction methods for reducing cleaning solution drag-out
and the amount of water required include:
Proper design and operation of rack system
Proper design and operation of barrel system
Proper design and operation of rinse system
Installation of spray rinses
Installation of fog nozzles
Chemical rinsing
Deionized water use
Proper Design and Operation of Rack System
Through proper design and operation of arack system,
solution drag-out can be significantly reduced. Parts
should be racked so that the surface is nearly vertical and
the longest dimension is horizontal. Also, the lower edge
should be tilted from the horizontal (this allows run-off to
occur at a corner rather than the entire edge). Withdrawal
from the cleaning solution should be made slowly and the
part allowed to drain over the tank for a minute or two.
Additional drainage time can be provided by installing
sloped drain boards at the end of the tank.
For items with cup-shaped recesses, drainage can be a
difficult problem. If the part cannot be positioned to allow
for drainage, special measures must be taken. Some of
these measures include drilling or repositioning drain
holes in the part, tilting the rack as it is removed from the
bath, and/or installing air jets to blow off cleaner solution
from the part.
Rack maintenance is also important. If rack insulation
is cracked, solution can be carried out in the gaps and
fissures. In addition, exposure of the rack metal during
electroplating operations can lead to contaminated Bath
solutions. Uninsulated racks used for cleaning should be
strippedregularly since thorough surface will hold solution
by capillary action.
Proper Design and Operation of Barrel System
While barrels are normally fully immersed during
electroplating operations, maximum rinsing efficiency
occurs when the barrel is only immersed partially. The
proper depth and rate of rotation depends on many factors
but normally occurs when the barrel is immersed to about
38 percent of its diameter. In most plants, rinse tanks for <
barrel operations are designed and operated the same way
as electroplating baths (i.e., the barrel is fully immersed).
After immersing the barrel, it is raised over the tank while
rotating and is allowed to drain. At a minimum, two
counterflow cold rinses and a final hot rinse should always
be used.
Proper Design and Operation of Rinse System
Since the process of rinsing is one of dilution, good
practice should assure that the rinse tank is well mixed at
all times. Tanks can be mixed by agitating the Water with
oil-free air, introducing fresh water at the bottom of the
tank, and by other mechanical means. The water in the tank
should exhibit arolling turbulence without undue splashing.
For cleaners that are not very easy to rinse off, heated rinse
tanks are often employed.
Once agitation and complete mixing in the tank have
been assured, the next concern is the number of rinses.
Pinkerton and Graham (1984) presented evidence that use
of a second rinse can cut water requirements by over 90 -
percent. For facilities with limited floor space, single rinse
tanks can often be converted to multiple rinses by welding
one or more dams across the tank. Most modern facilities
are designed with multiple rinse tanks after each cleaning
operation.
If the spentrinsewater is used as makeup for evaporation
from the process bath, hazardous chemicals are prevented
from entering the waste streams, reducing the risk to the
environment that they pose. If evaporation from the
process bath is not great enough for the bath to accommodate
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the quantity of spent rinsewater produced, an evaporator
can be added to the process bath. Alternatively, some
shops raise the temperatures of their process baths at night,
adding the spent rinsewater as makeup the next morning.
Installation of water sprays on rinse tanks. For
installations with single rinse tanks and limited space,
rinsing efficiency can easily be increased by installing a
spray system. By spraying work items with fresh water as
they are raised above the rinse, the equivalent of an extra
one-half counterflow bath is obtained. Sprays should be
properly designed to provide uniform coverage on the part
and not produce undue splashing. Spray rinsing is also
beneficial on multitank counterflow systems where each
spray unit is fed water from the succeeding rinse tank.
Installation of fog nozzle on heated aqueous cleaner
tanks. A fog nozzle is a special high pressure water spray
unit that produces a finely atomized mist of water or fog.
Since the water is so finely dispersed, only a small amount
of water is used compared to a normal spray unit. Therefore,
fog nozzles can be used over heated cleaner tanks for
rinsing work items without introducing a surplus of water.
Two main benefits of using fog nozzles are that: 1) they
help cool the part so that the cleaning solution has less
chance of drying on the part; and 2) they reduce drag-out
by diluting the solution retained on the part.
Chemical rinsing. In some facilities, rinse water from
an alkaline cleaning operation is reused to rinse parts from
an acidcleaning operation. The basic premise is to combine
rinsing and waste treatment in one operation. While this
procedure reduces theambuntofwasterinse water generated
and the degree of wastewater treatment required, the
potential for contaminating the parts with metal hydroxide
precipitates is increased. Therefore, this method should be
limited to those parts not requiring rigorous cleaning.
Use of deionized water for rinsing. Use of regular tap
water is a major source of impurities in any closed loop
system. By employing deionized water, many rinses can
bereclaimed using asimple evaporation system. In addition,
use of deionized water can extend plating bath life by
reducing impurity drag-in as well as the number of rejects
produced. Many packaged systems commercially available
can supply deionized water of adequate quality because
most electroplaters do not require extremely high purity
water. ;
Media Substitution
Replacement ofsolventswithless toxic solvents. Since
the choice of which cleaning medium to use is seldom clear
cut, many opportunities exist for substituting one cleaning
medium with another. Toxic solvents can often be replaced
with safer alternatives. For instance, perchloroethylene
(PCE) and trichloroethylene (TCE) are currently being
replaced by 1,1,1,-trichloroethane in many applications.
Benzene and other toxic aromatics are often replaced by
aliphatic solvents such as Stoddard naphthas.
Other substitutes may include dibasic acid esters,
terpenes, amines, or alcohols. Prerequisites include low
flammability, low vapor pressure, low toxicity, high
solvency and low cost.
Terpenes, essential oils isolated from plants through
genfleheatingor steam distillation,areespeciallypromising
as potential substitutes for many solvents as well as aqueous
cleaners. Terpenes are less toxic and more biodegradable
than most solvents. Limonene cleaners, commercially
important terpenes made from oils of lemon or orange, are
listedasGRAS (Generally Recognised As Safe) substances
in the Code of Federal Regulation (Hayes 1987). Limonenes
have tested favorably against solvents, solvent emulsions,
and alkaline cleaners for removal of heavy greases,
carbonized oils and oily deposits.
Reported disadvantages of terpenes include difficulty
in separating oily wastes from them in order to recycle the
cleaning solution. Ultrafiltration is being tested as one
means to recover the cleaning solution. In addition, because
of their low volatility, terpenes are not usable in vapor
degreasing operations.
Surfactants added to terpenes forms emulsifiable
cleaning compounds that are water rinseable. Products on
the market include BIOACT (manufactured by Petrotem
Inc.), a substitute for chlorinated solvents and
chlorofluorocarbons (BIOACT's; atmospheric ozone
depletion factor is zero since it contains no chlorine or
bromine) and Citrikleen, a limonene manufactured by
Penetone (Tenafly, New Jersey) that can be sprayed, foamed
or brushed on workpieces, or used in immersion baths.
Replacementof'solvents with aqueouscleaners. There
is currently a major effort to switch from cold tanks using
non-halogenated solvents and vapor degreasers using
halogenated solvents to cold tank alkaline and emulsion
cleaners. This changeover is largely driven by regulatory
pressure to reduce air emissions from degreasing operations.
Numerous examples exist of successful substitution
of aqueous cleaners for solvents. In one case, an electronic
manufacturing facility thatoriginally cleaned printed circuit
boards with solvents found that by switching from a
solvent-based cleaning system to an aqueous-based system,
the same operating conditions and workloads could be
maintained. The aqueous-based system cleaned 6 times
more effectively. This resulted in a lower product reject
rate, and eliminated a hazardous waste (USEPA 1983a).
The Torrington Company in Walhalla, S.C. also reduced
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the hazard posed by its waste streams by replacing 1,1,1-
TCA used to clean metal bearings with a considerably less
expensive alkaline degreaser that employed a two-stage
washer and hot air drier (Kohl, Moses and Triplet! 1984).
Emulsion cleaners combine solvent cleaning with
aqueous cleaning so that water-immiscible solvent is
dispersed in the aqueous phase with the aid of emulsifiers,
surfactants and coupling agents. The large surface area of
the dispersed solvent phase can sometimes attain results
achievable with pure solvent. Solvent vapor pressure and
evaporation losses are suppressed in emulsion cleaners.
Disadvantages include residual oil film on the part (which
necessitates an additional cleaning step in applications
where a high degree of cleanliness is required), relatively
low saturation capacity, and difficulties in recycling by
separation of oil and reconstituting the cleaner.
Replacement of solvents with mechanical and thermal
alternatives. Solvents are of ten used to dry parts following
a waterrinse operation. As an alternative, air blast systems
utilizing a high velocity air jet can blow water droplets and
other contaminants from glass, metal, or wood parts. Dry
stripping and cleaning using a plastic or sand blast media
to clean and strip parts can reduce disposal costs and water
usage and has been shown to significantly reduce labor
costs. The blasting media can also be recycled. Hill Air
Force Base in Ogden, Utah, has successfully employed
plastic beads propelled by high pressure air jets to remove
paintfromaircraftexteriors. Besides eliminating generation
of hazardous waste, the use of bead blasting improved
personnel working conditions, was easier to perform than
sol vent paint stripping, costless and usedless raw material.
Other abrasive blasting materials, such as sand and CO2
pellets, are also used for paint stripping.
Replacement of aqueous cleaners and strippers with
abrasive media. Use of abrasives can eliminate the need
for aqueous cleaners in some situations. In one example,
a manufacturer that cleaned nickel and titanium wire in an
alkaline chemical bath installed a mechanical abrasive
system. In another situation, a decorative electroplating
shop reduced its hazardous sludge buildup 75 percent by
using sandblasting rather than alkaline strippers to remove
paint and old plating from workpieces about to be replated.
RECYCLING METHODOLOGIES
Solvents
In vapor degreasing.coldsolventcleaningand aqueous
cleaning, the soil removed accumulates in the equipment.
Eventually thesolventbecomes too contaminatedfor further
use and must be reclaimed or disposed of via incineration.
To simplify waste solvent handling and to make
recycling feasible, the following procedures should be
followed:
Keep solvents segregated. In the recycling
process, it is much easier to separate a solvent
from its impurities than to separate two solvents.
Specific recommendations are to always
segregate:
- chlorinated from nonchlorinated solvent
wastes;
- aliphatic from aromatic solvent wastes;
- Freon from methylene chloride; and
- water waste from flammables.
Keep waste solvents as free from water solids
and garbage as possible. Label the container
clearly, keep the container closed and, if
possible, sheltered from rain. Drums should be
covered to prevent contamination with water.
Solids concentration should be kept at a
minimum to allow for efficient solvent
reclamation.
Keep a chemical identification label on each
waste container. Record the exact composition
and method by which the solvent waste was
generated.
EPA estimates that up to 50 percent of all solvent
wastes are currently being segregated and managed for
energy recovery, reclamation or recycling.
Solvent can be recycled on-site, or transported to off-
site, commercial recycling facilities. On-site recycling of
solvent is recommended to reduce transportation liabilities
and is found to be economical when at least 8 gallons of
solventwaste is generatedperday (Schwartz 1986). Where
recycling of solvent waste is viable, the choice between on-
site versus off-site recycling must be made. Major factors
that may influence a decision are shown in Table 5.
On-site Solvent Recycling
Some of the most commonly used on-site recycling
techniques are:
Gravity separation. Simple settling of solids and
water is often sufficient for reuse of solvent. For example,
paint thinners may be reused many times if solids are
allowed to settle.
Filtration. Filters can be used to remove solids from
many solvents thus extending solvent life. To minimize
waste, reusable filters (e.g. metal mesh or filter bags) as
opposed to disposable cartridges should be used when
possible.
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Table 5. Evaluation of On-Site Recycling
Advantages
less waste leaving the
facility;
owner control of reclaimed
solvent's purity;
reduced reporting (mani-
festing); and
reduction in reporting
(manifesting); and
lower liability
possible lower unit cost of
reclaimed solvent.
Disadvantages
capital outlay for
recycling equipment;
liabilities for worker
health, fires, explosions,
leaks, spills, and other
risks as a result of
proper equipment operation;
possible need for operator
training; and
additional operating costs.
Reported Difficulties
loss of solvent during
distillation process;
low solvent recovery
efficiency;
installation problems; and
maintenance problems.
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Batch distillation. A batch still vaporizes the used
solvent and condenses the pure vapors in a separate vessel.
Solids or high boiling residues (>400°F) remain in the still
as residue. Solvent stills range in size from 5 gallon to 500
gallon-capacity.
For recycling a waste solvent from a vapor degreaser,
thedegreasercanbeusedasabatchstill. This is often done
by employing proper boil-down procedures. Detailed
discussion of these procedures is available from major
solvent suppliers.
In many applications, it is necessary to keep the water
contentof the recovered solvent to less than lOOppm. This
can often be accomplished by distilling off the solvent-
water azeotrope, decanting water, and then drying the
remaining solvent with amolecular sieve, ion exchange, or
other desiccant. The water removed in this operation must
then be either treated or drummed for disposal.
Fractional distillation. Fractional distillation is carried
out in a refluxed column equipped with either trays or
packing. Heat is supplied by a reboiler located at the
bottom of thecolumnwhileheatisremovedatthe top of the
column by a condenser. Fractional distillation allows for
separation of multicomponent mixtures or mixtures of
solvents andcontaminants with very similar boilingpoints.
Fuel use. Boilers can beadapted to burn waste solvent
for the recovery of heating value. Generally, boiler fuels
require a minimum flash point of 135°F. Thus only high
flash point solvents (140°F minimum) are suitable. Federal
regulations pertaining to the use of solvent as fuel may be
found in the Code of Federal Regulations (CFR) 40,
section 266.
Off-Site Solvent Recycling
If recycling of waste solvent on site is impractical,
several off-site recycling schemes are available. All of the
items listed in Table 5 should be investigated before
deciding on an off-site recycling scheme.
Some viable off-site recycling arrangements include
the following:
TollrecyclersoffeiSQrvices to generators by supplying
solvent wash equipment, solvent and waste recycling
services. The solvent wash equipment is maintained by
these companies and the solvent is replaced periodically.
The used solvent is recycled at an off-site facility. Costs for
these services range from 50-90 percent of new solvent
cost.
Safety Kleen Inc. (headquartered in Illinois) provides
a batch-tolling service for degreasing solvents, and leases
the process equipment and solvents as one system. Safety
Kleen's mobile units provide fully-contained degreasing
systems to automobile repair shops. Safety Kleen
periodically replaces the spent solvent with fresh solvent.
The spent solvent is then recycled at a central facility. This
arrangement is popular with small quantity generators.
Another advantage of the toll system is thateach generator's
solvents can be recycled separately. This separation reduces
the chances of the recycled solvent being contaminated
with substances foreign to the processes of the generator.
Cement kilns are successfully being used to recover
the heating value and chlorine content of organic wastes
that contain halogenated solvents (up to 4 percent chlorine
by weight). If more chlorine is present, then fuel blending
is employed.
Waste exchanges are not as much a technology as an
information service. The principle behindawaste exchange
is in matching a generator of waste with a facility that can
use the waste as raw material. Wastes currently recycled
through waste exchange include acids, alkalis, other
inorganic chemicals organics and solvents, and metals and
metal sludges. Of these wastes, solvents and metal wastes
are most frequently listed by waste exchanges because of
their high recovery value.
Aqueous Cleaner Recycling
Oil separation. Aqueous cleaners contaminated with
oily wastes can be recycled using oil separation techniques.
Oil separators are designed for gravity separation of free
floating oils, as well as some settleable solids, from water.
Pickling bath recycling. Pickling bath acids become
increasingly diluted over time by the formation of ferrous
salts. Closed-loop recycling is necessary when the acids
become ineffective. Recycling of sulfuric acid baths
involves crystallizing the ferrous salts into ferrous sulphate
hydratesJ'The crystals are drained, washed and partially
dried, and can be sold as a chemical product used in
manufacturing inks, dyes, pigments and fertilizers, and as
a flocculating agent in waste treatment plants. Recovered
acid can be reused in the pickling tanks after fresh
concentrated acid is added to bring it up to the desired
strength (Krofchak and Stone 1975). Hydrochloric acid
pickle liquors can be completely recycled, without
generating any solid, liquid or gaseous waste streams.
Unlike other mineral acids, hydrochloric acid can be
removed from spent pickle liquors through vaporization,
without decomposition into other compounds.
Surface Treatment And Plating Wastes
SOURCE REDUCTION METHODOLOGIES
Process Solutions
Process solutions for surface treating and plating
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contain high concentrations of heavy metals, cyanides, and
other toxic constituents. Process baths are not discarded
frequently, but rather are used for long periods of time.
(The chemicals they contain, however, are lost, sometimes
at high rates, through drag-out on workpieces, spills and
leaks). Nevertheless, the baths do require periodic
replacement due to impurity build-up or the loss of solution
constituents by drag-out. A contaminated or exhausted
plating solution is highly concentrated with toxic
compounds and requires extensive treatment. The source
control methods available for reduction of spent plating
and other process waste include increasing solution life
and material substitution.
Increasing solution life. The lifetime of a plating
solution is limited by the accumulation of impurities and/
or by depletion of constituents due to drag-out. The
impurities come from five sources: racks, anodes, drag-in,
water make-up, and air. Corrosion and salt buildup deposits
on the rack elements will contaminate plating solutions
upon dipping and falling into the solution. Proper design
and maintenance (mainly cleaning) will minimize this
form of contamination.
The use of purer metal for anodes also extends the
plating solution life, because during plating, metal from the
anode is dissolved in the plating solution, and impurities
contained in the original anode matrix can eventually
accumulate to prohibitive levels.
Efficient rinsing of the workpiece between different
plating baths reduces the carryover of plating solution into
the next bath. Using demineralized or distilled water as
makeup to compensate for evaporation is preferred over
tapwater, since tapwater may have a high mineral or solids
content, which can lead to impurity buildup. Another
method that has been successfully used to increase the
longevity of plating solutions is periodic filtering to keep
levels of impurities low. In many shops, continuous or
daily circulation of plating baths through carbon or small-
hole (typically 10 micron) filters have dramatically
lengthened bath life by reducing sludge buildup, which
eventually would impair plating quality (Normandy 1988;
Foss 1988).
Material substitution. Cyanide plating solutions can
be replaced withless toxic cyanide-free solutions. Cyanide-
zinc solutions, for instance, can be replaced with non-
cyanide, non-chelated alkaline zinc solutions eliminating
the problem of handling cyanide-containing wastes.
Replacing cyanide solutions with non-cyanide solutions,
however, often requires upgrading of the degreasing/
cleaning techniques used, because the non-cyanide
replacements may require a much more thoroughly cleaned
surface to ensure high quality plating. The primary barrier
to non-cyanide bath use is that military contracts often
specify the use of cyanide solutions, thereby preventing
electroplaters from using non-cyanide replacements.
Replacement of cadmium-based plating solutions is
feasible in many applications. Cadmium is used in a wide
variety of products for its excellent protective properties.
Cadmium-plated products are highly resistant to corrosion
in land and marine environments. For this reason, the U.S.
military specifies cadmium plating for a large variety of
naval and aerospace equipment. It is possible in some
instances however to replace cadmium plating with other
materials such as zinc, titanium dioxide (using vapor
deposition), aluminum (using ion vapor deposition or
ivodizing),andaluminum using spray-and-bakeapplication.
None of these coatings have exactly the same properties as
cadmium, but nonetheless may prove to be satisfactory
substitutes. Aluminum ion vapor deposition is a very
attractive process, but is considerably more expensive than
electroplating. Excellent adhesion and corrosion resistance
andlittleorno hydrogen embrittlement is exhibited by both
spray-and-bake aluminum coats and the Ivodized coat.
Replacement of hexavalent chromium with trivalent
chromium offers important environmental advantages.
Trivalent chromium is considerably less toxic than
hexavalent. Trivalent systems use far lower concentrations
of chromium metal andalsoproducefew toxicair emissions,
while hexavalent systems involve a reaction that produces
hydrogen bubbles which entrain chromium compounds
and carry them out of the baths. Trivalent chromium is
readily precipitated from wastewater, while hexavalent
chromium solutions must go through an additional step in
a treatment system in which the chromium is reduced to its
trivalent form before precipitation. It has been shown that
trivalent chromium systems can successfully replace
hexavalent ones for decorative chrome applications.
Trivalent chromium systems are not suitable for hard
chrome applications.
Because there can be a substantial amount of highly
toxic waste generatedduringachrornium plating operation,
the elimination of any unnecessary use of chromium would
be beneficial from the environmental standpoint. For
example, some automobile bumpers are currently being
painted rather than plated during finishing operations.
Process substitution. Certain processes can offer an
alternative to electro- and electroless plating. Hot dipping
of tin and other metals, for instance, in which the workpiece
is immersed in a molten metal bath, could provide a way of
reducing toxic effluent levels. A disadvantage of hot
dipping is that it is energy intensive, for the metal in the
bath must be maintained in a molten state.
Chemical coatings. Chemical vapor deposition (CVD)
is the gas-phase analog of electroless plating (Kirk-Othmer
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1981), in that it is catalytic and involves a chemical
reduction of a species to a metallic material which forms
the coating. CVD coatings are extremely pure, and thus
suitable for many electronic applications. The reactions
require temperatures up to 1500°C, although work is in
progress to design low temperature processes that can be
used on workpieces unable to withstand high temperature.
In vacuum coatings, the metal coating is vaporized in
a vacuum which is low enough to ensure that most of the
evaporated atoms migrate to the workpiece with few
collisions with background gas molecules. The atoms
impinging on the workpiece condense to a solid phase.
Thermal sources used to vaporize the coating include
resistance heating, induction heating, electron-beam
heating, and laser irradiation.
Mechanical cladding and coating. Metals can be
bonded to the workpiece using mechanical techniques in
which the coating material is forced under high pressure
into contact with the workpiece. The pressure at the
interface between the two metals must be high enough to
disrupt and disperse boundary oxide films and initiate
thermal interdiffusion and mechanical attachment. Roll
bonding is a type of cladding in which one strip of metal is
pressed onto another with the aid of bonding rollers. Metal
claddings can also be melted into place using welding or
casting techniques. Cladding generally produces thick
coatings compared to other methods.
Metal powder can also be coated on to the workpiece.
The 3M Company has developed a cold welding technique
in which the workpiece, the metal powder, water, glass
shotandadditives are tumbled together inabarrel. Coatings
are limited to ductile metals such as Cd, An, Sn, Pb, In, Ag,
Cu, brass, and tin/lead solder; the method is generally
suitable only for small parts, and it doesn't produce a fine
surfaced, cosmetic coating. Costs are comparable to those
for electroplating with afterbake (Kirk-Othmer 1981).
Waste Rinsewater
Waste rinsewaters account for the largest fraction of
waste volume produced in surface treatment and plating
processes. Anymethodofreducingtheamountofrinsewater
used will significantly reduce the total waste volume from
aprocess.Largeamountsofrinsewaterareusedtorinseoff
drag-outon a metal surface after the metal is removed from
a plating of cleaning bath. Rinse waters usually contain
dilute solutions of bath salts, such as cyanides and heavy
metals. There are several methods available to reduce the
amount and/or toxicity of waste rinsewater produced. The
methods can be grouped into two techniques: drag-out
minimization and rinsewater minimization. Drag-out
minimization results in a decrease of the heavy metal
contentoftherinsewaterandof the ultimate waste (treatment
sludge). Decreasing rinsewater consumption without
reduction in drag-out may thus result in a smaller, but more
toxic, volume of treatment sludge.
Drag-out minimization. By minimizing the amount of
drag-out carried from a plating or cleaning bath to arinsing
bath, a smaller amount of water is needed to rinse off the
workpiece. Also, less of the plating solution constituents
leave the process, which ultimately produces savings in
raw materials and treatment/disposal costs.
It must be stressed that drag-out minimization is not
effective unless accompanied by a means of purging the
bath of impurities that build up and that otherwise have no
outlet. Impurities such as dirt, grease, and carryover from
previous process baths that were purged from the plating
bath by being dragged out on workpieces now must be
removedby means such as periodic or continuous filtration,
which is discussed earlier in this section. Otherwise, sludge
will build up, plating quality will be impaired, and the bath
will have to be disposed of sooner, raising the environment
of risk and defeating the purpose of reducing the drag-out.
The amount of drag-out from a bath depends on the
following factors:
Speed of workpiece withdrawal and drainage
time. The rate at which the workpiece is
withdrawn, the time allowed for drainage over
the mother tank, as well as the orientation with
which the work is withdrawn from the bath,
affect the amount of drag-out produced.
Surface tension of the plating solution. A
plating solution with a high surface tension
tends to be retained in the crevices and surface
imperfections of the workpiece when it is
removed from the plating bath, thus increasing
drag out.
Viscosity of the plating solution. Highly viscous
solutions result in larger amounts of drag-out.
Physical shape and surface area of the
workpiece. The shape of the workpiece affects
the amount of plating solution that gets dragged
out of the bath. With all other parameters
remaining the same, a larger workpiece surface
area results in more drag-out. It is noted that
barrel plating operations produce more drag-
out than rack plating.
include:
Drag-out minimization techniques typically
Reducing the speed of withdrawal of workpiece from
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solution and allowing ample drainage time. The faster the
workpiece is removed from the bath, the higher the drag-
out will be. The workpiece should be removed as slowly
and as smoothly as possible. Ample time should be
allowedfor draining thesolutionback to the tank, especially
for higher viscosity solutions. Usually, 30 seconds allows
most of the drag-out to drain back to the tank. However, in
applications where quick drying is a problem, or where
production schedules do not allow a long drainage time, a
10 second draining still permits good drag-out recovery.
Lowering the concentration of plating bath
constituents. A decrease in the concentration of metal salts
and other components of the plating solution directly
reduced the amount of hazardous substances dragged out
of the bath. It also leads to lower solution viscosity, which
results in less drag-out volume. Many concentration
reductions have been successfully implemented. Notably,
it has been found that acceptable chromium plate can be
obtained from baths containing only 25-50 g/1 CrO3 com-
pared to traditional concentrations of 250 g/1 CrO3 (Report
to Congress 1986).
Use of surfactants. Wetting agents have been used to
lower the surface tension of plating solutions and reduce
drag-out. A solution with a high surface tension is retained
in the crevices and surface imperfections of the workpiece
upon removal from the plating bath. Only nonionic wetting
agents, which will not be degraded by electrolysis in the
plating bath, should be employed. The use of surfactants
is sometimes limited due to their adverse effect on the
quality of the plate produced.
Increasing plating solution temperature. The increased
temperature lowers both the viscosity and the surface
tension of the solution, thus reducing drag-out. Theresulting
higher evaporation rate may also inhibit the carbon dioxide
absorption rate, slowing down carbonate formation in
cyanide solutions. Unfortunately, this benefit may be lost
due to the formation of carbonate by the breakdown of
cyanide at elevated temperatures. Additional disadvantages
of this option include higher energy costs, higher chance
for contamination due to increased make-up requirement,
and increased need for air pollution control due to the
higher evaporation rate.
Proper positioning of the workpiece on the plating
rack. When a workpiece is lifted out of a plating solution
on a rack, some of the excess solution on its surface (drag-
out) will drop back into the bath. Proper positioning of the
workpiece on a rack facilitates drainage of the drag-out
back into the bath. The position of any object which will
minimize the carry-over of drag-out is best determined
experimentally, although the following guidelines were
found to be effective (Durney 1984):
Orient the surface as close to vertical as possible.
Rack with the longer dimension of the workpiece
horizontal.
Rack with the lower edge lilted slightly from the
horizontal so that the runoff is from a corner rather than an
entire edge.
Improveddrag-outrecovery. A drainboard positioned
between a plating bath and rinse bath can capture the
solution dripping from a workpiece and route it back to the
plating bath. The drain board can be made of either plastic
or metal. For acidic solutions, drain boards can be made of
vinyl chloride, polypropylene, polyethylene, or Teflon-
lined steel. Another option is to incorporate a drip tank
between the plating bath and the rinsing bath. The drip tank
is an empty tank for collecting the dripping solution, which
can be returned to the plating bath.
A third alternative is the use of a still rinse tank with
contents periodically transferred back into the plating.
Installing a still (or dead) rinsing tank immediately after a
plating bath allows for metal recovery and lowered
rinsewater requirements. In such a system, the workpiece
is immersed in the still rinse tank following the plating
operation. Since the still rinse has no inflow or outflow of
water, the concentrations of the plating bath constituents
build up in it. When the concentrations become sufficiently
high, the contents of the still bath is not discarded but is
used to replenish the plating bath.
Rinsewater can also be reduced through system
redesign. The aim of rinsewater minimization is to use the
smallest volume of water necessary to adequately clean the
workpieces. Whilereducingrinsewaterrequirementsdoes
not directly reduce the quantity of hazardous materials in
the plating line effluent, it does reduce the load on the
treatment plant (which can result in more hazardous
substance removal or neutralization from the waste stream)
as well as saving money through reduced water
requirements. Several system design methods exist for
lowering rinsewater requirements, including:
Rinse tank design. The most Important factor in the
design of rinse tanks is ensuring complete mixing of
rinsewater, thus eliminating short circuiting of feed water
and utilizing the entire tank volume (Pollution Prevention
Tips. 1985 (a)). In a rinse tank in which the water
distribution line is located on the bottom at the far end of
the tank from where the work is introduced, incoming
water creates a rolling action that mixes the tank contents,
and helps to scour workpieces clean. A flow control valve
can also be installed in the distribution line to restrict
freshwater feed to an optimum level. A conductivity
control system can be used as an alternative to a flow
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control valve, which measures the level of dissolved solids
in the rinse tank, and opens the freshwater feed valve at a
predeterminedmaximum solids level. Airagitationremoves
plating solution clinging to the workpiece surface, and also
mixes the tank contents. Installing the air distribution line
diagonally across the bottom of the tank helps even
distribution of the air.
Multiple rinsing tanks. The use of multiple rinsing
tanks is one of the most common rinsewater reduction
techniques, and can dramatically reduce rinsewater
requirements. In a typical counterflow three-tank rinsing
system, the workpiece initially enters the first rinse tank,
which has the most contaminated rinsewater. It is then
moved to the second tank, and then to the last, where it
contacts fresh rinsewater. Fresh rinsewater enters only the
last (third) rinsing tank. The water from the third tank
flows into the second tank and then into the first tank, from
whichitcanberoutedeitherintotheplatingtankasamake-
up, or to the treatment system.
It is preferrable to route the rinse system effluent back
into the plating bath, in order to prevent release of the
chemicals they contain to the environment One chrome
plater (Foss 1988) whose shop was examinedfor this study
accomplished this by lowering the flow through his
counterflow system to 0.5 gal/min or less, and installing an
evaporator on the plating tank capable of vaporizing up to
350 gal/day.
A second wastewater reduction method with a high
implementation potential is the reuse of rinsewater.
Electroplating operations use rinsewater at several stages
in theprocess, and itis oftenpossible to use the same stream
at more than one stage. The main problem with this
techniqueisthatthequalityoftheproductmustbemonitored
carefully. A rinse stream can be used a second time only
if the contaminants from thefirstrinsedo not interfere with
the quality of the second rinse.
Reactive Rinsing. This technique takes advantage of
the chemical makeup of the rinsewater to not only reduce
water usage, but to increase rinsing efficiency as well
(Pollution Prevention Tips 1985 (c)). For example, a
typical nickel plating line might consist of the following
sequential processes:
Alkaline Cleaning
Rinse
Acid dip
Rinse
Nickel Plating
Rinse
Water from the nickel rinse tank can be fed back into
the acid dip rinse tank allowing nickel plating solution
dragged out of the process bath to be dragged back into it.
This will not harm the rinse, and will allow the water feed
to the acidrinse tanks to be turned off. Thus, both water and
process chemicals are conserved, and the quantity of toxic
process chemicals in the effluent is reduced.
The acid rinse can be further recycled to the alkaline
cleaner rinse tank. This conserves water by allowing the
fresh water feed to the alkaline rinse to be turned off, and
also improves rinsing efficiency by helping to neutralize
the dragged in alkaline solution. This will prolong the life
of the acid bath because the rinsewater dragged into it will
already be partially neutralized. Thus the acid bath will not
have to be dumped as often.
Rememberthatwheneveran open-loop system process
line is replaced by or modified into a closed-loop
arrangement, attention mustbe given toperiodicallypurging
the impurities that will build up.
Fog nozzles and sprays. Spraying water directly onto
a workpiece can rinse contaminants from it using
considerably less water than immersing the part in a bath.
A major limitation of spraying is that it is not effective on
many oddly-shaped objects, since the spray cannot make
direct contact with the entire surface of the object. But for
simple workpieces such as sheets, it is highly effective. A
variation on the spray nozzle is the fog nozzle. A fog nozzle
uses water and air pressure to produce a fine mist. Less
water is used than with a conventional spray nozzle.
Automatic flow controls. The lowest possible
rinsewater flow rate which can ef ficiently rinse a workpiece
can be determined for all systems. This flow then can be
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automatically controlled to avoid variations associated
with water line pressure changes and manual control by
operators.
Rinse, bath agitation. Agitating a rinsing bath
mechanically or with air increases the rinsing efficiency
and cuts down on water demand.
Treatment Wastes
Toxic metal sludges result from conventional treatment
processes used to remove metals from aqueous wastes.
Metals are usuallyprecipitated as hydroxides or carbonates,
resulting in sludges which require further treatment and
disposal. Lime is commonly used as the precipitating
agent The volume and toxicity of the sludge produced can
be lowered by reducing the metal content in the plating and
rinse waters, or by using different precipitating agents.
Methods available to accomplish this include:
Use of different precipitating agents and other
treatment chemicals. Normally, hexavalent chromium in
waste rinsewater or plating solutions is treated by being
reduced to trivalent chromium with a reducing agent,
followed by precipitation with lime. Sodium hydroxide
has been examined as a substitute for lime (Report to
Congress 1986). Sodium hydroxide precipitation agents
produced 12 percent less dry solids than lime precipitation.
Chemical treatment to destroy cyanides and remove
metal contaminants is the most common typeof wastewater
treatment for plating and surface treating lines. Treatment
processes create hazardous waste sludges. The sludge
volume generated is present in part on proper selection of
treatment chemicals. Caustic soda used as a neutralizer
and precipitation agent, for instance, can in some situations
generate up to 90 percent less sludge than using lime.
Polyelectrolyte conditioners employed as flocculating
agents to improve floe formation do not contribute to
sludge formation as do alum (a common coagulant) and
ferric chloride, a flocculant (PRC 1988).
Use of trivalent chromium instead of hexavalent
chromium for plating. One operation reported a 70 percent
reduction in sludge production when trivalent chromium
was used for plating instead of hexavalent chromium,
because it avoided the necessity of precipitating gypsum
associated with excess sulfate ions introduced during the
reduction step. (Report to Congress 1986).
Waste segregation. Segregating wastes and treating
them separately can also reduce sludge volumes generated.
Ferric sulfide, for instance, is useful for breaking down
metal complexes in waste streams containing chelating
agents. But the iron in ferric sulfide precipitates out and
leads to considerable sludge generation. Ferric sulfide use
can be minimized if chelating agent waste streams are kept
separate from others. Batch treating spent process baths
rather than adding them to the wastewater treatment stream
can also reduce waste generation. The spent baths can be
analyzed for contaminant levels, and just the necessary
amount of chemicals added to treat it. (PRC 1988)
By isolating cyanide-containing waste streams from
waste streams containing iron or complexing agents, the
formation of cyanide complexes is: avoided, and treatment
made much easier (Dowd 1985). Segregation of wastewater
streams containing different metals also allows for metals
recovery or reuse. For example, by treating nickel-plating
wastewater separately from other waste streams, a nickel
hydroxide sludge is produced which can be reused to
produce fresh nickel plating solutions. Scrubber waste
from chromium plating baths, if segregated, has been used
as makeup for the bath, resulting in less discarded waste
and increasing the longevity of the plating solution.
More efficient sludge dewatering. The volume of
sludge produced can be greatly reduced through the use of
new dewatering technologies which remove a greater
percentage of water than traditional dewatering techniques
(Report to Congress 1986). These involve efficient filter
presses and thermal and air-drying techniques that can
reduce the sludge to a nearly-dry cake.
Source Reduction for Other Types of Metal Surface
Treatment
Case hardening. Case hardening processes involving
diffusion of carbon or nitrogen into the workpiece requires
source materials from which these elements can be
generated. After the case hardening is completed, these
source materials frequently become hazardous wastes.
Source reduction for case hardening operations frequently
involves choosing cleaner processes. For instance, pack
carburizing uses solid pack materials such as coke or
charcoal as a source of carbon. Spent packing must be
disposed of as hazardous waste. This waste stream can be
eliminated, however, if gas carburizing is employed.. Gas
carburizing burns natural gas inasealed furnace asasource
of carbon and produces no hazardous waste stream.
The salt baths in somenitriding andcyanidingprocesses
also constitute hazardous wastes when spent. Nitriding
and cyaniding baths for example, contain sodium and
potassium cyanide and cyanate. Implementation of gas
nitridingeliminates this waste stream. Gas nitridingemploys
ammonia gas to supply the nitrogen, and produces no
hazardous waste stream.
Another possibility for source reduction in case
hardening operations, especially in those involving ferrous
metals, is to switch to applied energy hardening methods
that generate a case through localized heating and
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quenching, without use of chemicals. It is the existing
carbon content of the metal that facilitates the hardness
response when heated.
RECYCLING METHODOLOGIES
Recyclingandresourcerecovery include technologies
that either directly use waste from one process as raw
material for another process or recover valuable materials
from a waste stream before the waste is disposed of. Some
of the spent chemical process baths and much of the
rinsewater can be reused for other plant processes. Also,
process chemicals can be recovered from rinsewaters and
sold or returned to theprocessbaths. This section describes
some of the recycling and resource recovery technologies
available to the metal finishing industry.
Waste Material Reuse
The more thoroughly a metal finishers understands the
chemistry of their waste streams, the better able they are to
assess then: potential for reuse as raw materials, or in other
applications. Successful recyclingrequiresachangeon the
part of management and plant staff, to view their waste
streams as resources, rather than as something to be thrown
away.
After rinse solutions become too contaminated for
their original purpose, they may be useful for other rinse
processes. For example effluent from a rinse tank that
follows an acid cleaning bath can sometimes be reused as
influentwatertoarinsetankfollowinganalkalinecleaning
bath. This technique must be used with caution, however,
for it can lead to precipitation problems.
The drag-out film on the workpieces coming from the
alkaline bath is alkaline. Recycled water from acid bath
rinses has an acid pH, and thus tends to neutralize the drag-
out film. This reduces its viscosity and accelerates the
rinsing process (PRC 1988; USEPA1982).
Otherrinsewaterreuseopportunitiesarealsoavailable.
Acidcleaningrinsewatereffluentcan be used as rinsewater
for workpieces that have gone through a mild acid etch
process. Effluent from a critical or final rinse operation,
which is usually less contaminated than other rinse waters,
can be used as influent for rinse operations that do not
require high rinse efficiencies. Another option is using the
same rinse tank to rinse parts after both acidic and alkaline
baths.
Spent process baths can also be reused for other
purposes. A common example is to use spent acid or
allcalinecleanersforpHadjustmentduringindustrial waste
treatment. Typically, these cleaners are dumped when
contaminants exceed an acceptable level. However, these
solutions remain acidic or alkaline enough to act as pH
adjusters. Alkaline cleaners, for instance, can be used in
chrome reduction treatment. Since spent cleaners often
contain high concentrations of metals, they should not be
used for final pH adjustments, however.
Metal Recovery and Water Reuse
In the past, metal recovery from metal finishing
wastewater was not considered economical and was rarely
done. Present effluent pretreatment standards, however,
have dramatically increased the cost of treatment. Also,
the cost of handling and disposing of spent process baths
and sludges containing heavy metals has increased
significantly because of the increased regulatory
requirements placed on the handling and disposal of
hazardous wastes. As a result, metal finishers may find it
economical to recover metals and metal salts from spent
process baths and rinsewater and to reuse rinsewater.
The waste reduction and economic savings actually
achieved through metal recovery will depend on the
rndividualmetalfinishingplant. Factors thatwill determine
whether metal recovery is economically justifiable include
the volumeof waste thatcontains metals, the concentrations
of those metals in the waste, and the potential to recirculate
some of the metal salts. Many systems may not be
economically feasible for small surface treatment and
plating operations because the capital costs of installing the
necessary equipment might outweigh the saving from
recovering process chemicals.
Metal recovery can be achieved in two ways: (1)
recovered metal salts can be recirculated back into process
baths, or (2) recovered elemental metal can be sold to a
metals reclaimer or reused in the plating process. Some of
the technologies that are being successfully used to recover
metals and metal salts include:
Evaporation
Reverse osmosis
Ion exchange
Electrolytic recovery
Electrodialysis
While these treatment technologies are typically used
to recovery chemicals from rinsewater effluent, they can
also be employed for spent process baths. The wastewater
that is produced after the metal recovery is often pure
enough to be reused for rinsing.
Recovery systems can be used strictly for rinsewater
recycling and not for chemical recovery. In that case,
rinsewater waste streams need not be segregated since
process chemicals are not being recovered. Rinsewater
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effluent from a variety of plating or cleaning processes can
be commingled and fed to a single, centralized recycling
unit, such as ion exchange. The effluent can then be
returned to the rinse systems and the residual disposed of.
Various methods for recovering process chemicals
and rinsewater from rinsewater effluent are described
below:
Evaporation. Evaporation has been successfully used
to recover a variety of plating bath chemicals. Water is
boiled off from rinsewater to reduce its volume sufficiently
to allow the chemical concentrate to be returned to the
process bath. The water vapor is condensed and can be
reused in the rinse system. There are two basic evaporator
designs that are typically used: atmospheric and vacuum
evaporation (Metals Handbook 1987). Atmospheric
evaporation principles are similar to those of a heated open
tank, with the exception that the heated liquid is sprayed
over plastic packing in order to increase its surface area and
accelerate evaporation. Atmospheric evaporation works
well for chrome plating lines because they can do double
duty as plating bath fume scrubbers. Atmospheric
evaporators have lower capital costs than vacuum
evaporators, butsuffer from the disadvantage that vaporized
water is not recovered. When evaporation is performed
under partial vacuum conditions, temperatures can be low
enough to prevent degradation of platingadditives. Because
evaporation does not remove contaminants from the
concentrate, it is necessary that the system have a method
of controlling buildup of metallic and organic impurities.
Additional recycling techniques such as ion exchange can
be used for this purpose.
There are limitations to use of evaporation, one of the
most serious being that it is a very energy intensive
methodology and is generally only economically feasible
when employed in conjunction with multistage counter-
current rinse systems or other methods that reduce the
quantity of rinsewater required.
A variation on standard evaporation technology that is
much less energy intensive is the mechanical vapor
recompression vaporization process. This uses the same
evaporation separation principle, but an increased vacuum
is employed so that water evaporates at temperatures of
50°F to 70°F.
Reverse osmosis. Reverse osmosis (RO) is a pressure-
driven membrane separation process. The RO process uses
a semipermeable membrane that permits the passage of
purified water while not allowing dissolved salts to pass
through. These salts can be recovered and returned to the
process bath. The permeate rinsewater can then be returned
to the rinse system for reuse. The most common application
of RO technologies in metal finishing operations is the
recovery of drag-out from acid nickel process bath rinses.
RO membranes are not suitable for solutions having high
oxidation potential such as chromic acid. In addition, the
membranes will not completely reject many nonionized
organic compounds, and thus other methods such as
activated carbon treatment must be used in conjunction
with RO.
Ion exchange. Ion exchange (IE) can be used to
recoverdrag-outfromadiluterinsesolution. Thechemical
solution is passed through a series of resin beds that
selectively remove cations and anions. As the rinsewater
is passed through a bed containing the resin, the resin
exchanges ions with the inorganic compounds in the
rinsewater. The metals are then recovered from the resin
by cleaning the resin with an acid and/or alkaline solution.
The treated water is of high purity and can be returned to
the rinse system for reuse. IE units can be used effectively
on dilute waste streams and are less delicate than RO
systems. A common use of ion exchange for process bath
recovery is for the treatment of rinsewater from a chromic
acid process bath.
IE equipment requires careful operating and
maintenance practices. In addition, recovery of chemicals
from the resin columns produces significant volumes of
regenerant and wash solutions, which may add to the
wastewater treatment load.
Electrolytic recovery (Electro-winning).
Electrowinning is the recovery of the metallic content from
solution using the electroplating process. It is employed to
recover a variety of metals, including cadmium, tin, copper,
solder alloy, silver and gold. In a typical electrowinning
process, cathodes made of thin starter sheets of the metal
being recovered, or stainless steel blanks from which the
recovered metal can be stripped, are mounted in an open
tank. As the current passes from the anode to the cathode,
the metal deposits on the cathode. This type of system
generates a solid metallic slab that can be reclaimed or used
as an anode in an electroplating tank.
Several basic principles well known to the
electroplating industry are employed in electrolytic
recovery: expanded cathode surface area, close spacing
between cathode and anode, and recirculation of the rinse
solution. Electroplaters can design their own units by
closely spacing parallel rows of anodes and cathodes in a
plating tank and circulating rinse solutions through the
tank. Air agitation is especially useful in most situations,
increasing plating quality and current efficiency.
Electrowinning can also be used on spent process baths
prior to their treatment in the wastewater treatment system.
Electrodialysis. Electrodialysis employs selective
31
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membranes and an electric potential as a driving force to
separate positive from negative ions in the solution into
two streams. To accomplish this, the rinse solution is
passed through cation and anion-permeable membranes.
Cation exchange membranes allow cations such as copper
or nickel to pass, while anion exchange membranes pass
anionssuchassulfate,chlorideorcyanide. Theconcentrated
solutions can berecycled to theplatingbaths, while the ion-
depleted water can be recycled through the rinse system.
While electrowinning is most efficient for recovering
metals from concentrated solutions such as spent plating
baths, electrodialysis is very effective on dilute solutions
like waste rinse waters.
Paint Wastes
SOURCE REDUCTION METHODOLOGIES
Empty Containers
Facilities that use small quantities of paint and a large
variety of colors often purchase paint in small cans and
containers (less than five gallons) for use in spray gun
equipment. After emptying the can of paint into the spray
gun's holding cup, acoating of paintremains inside the can.
Since these cans are seldom cleaned, the entire can must be
discarded as waste. Also included in this waste stream
should be outdated or leftover paint removed from storage.
Source reduction methods for this waste stream include:
Waste segregation. By preventing the contamination
of non-hazardous materials such as trash with potentially
hazardous materials such as solvent-based paint), the
volume of hazardous waste will be reduced.
Bulkpurchasing. Container waste is generated by the
paint that remains inside a can after the can is emptied and
by the paint thatis placed in storage, not used, andbecomes
outdated. Facilities should strive to consolidate paint use
so that the purchase of paint in bulk is practical. Since one
large bulk container has much less surface area than an
equivalent volume of small cans, the amount of wasted
paint is much less. Large bulk containers can often be
returned to the paint manufacturer for cleaning and reuse
(while cleaning still generates some waste, the paint
manufacturer is in a better position to handle it).
Minimizing residuals. When the purchase of paint in
bulk containers is not practical, then paint should be
purchasedinthesmallestamountrequiredso as to minimize
the amount of residual. Workers should not open a one
gallon can of paint when only a quart or two are required.
While the per unit cost of paint when purchased in various
small quantity containers is greater than the cost of paint
when purchased in larger quantities, the savings in reduced
paint wastage and disposal costs could still be substantial.
Paint Application Waste
The wastes generated during paint application are
primarily due to: 1) paint overspray, and 2) the failure of
all of the paint to reach the target. The following source
reduction measures are noted:
Use of paint application equipmentwith low overspray
characteristics. When comparing different types of paint
application equipment, the transfer efficiency or degree of
paint overspray produced can vary considerably. Brewer
(1980) lists the following efficiency ranges for several
different spray systems:
Spray Method Efficiency
Conventional air-atomized 30-60%
Conventional pressure-atomized 65-70%
Electrostatic air-atomized 65-85%
Electrostatic centrifugally-atomized 85-95%
Other types of equipment that can yield even higher
efficiency values are roller and flow coating machines (90
to 98 percent) and electrocoating systems (90 to 99 percent).
Roller and flow coating machines, however, are limited in
their applicability based on the shape of the parts.
Electrocoating systems require a shift from solvent-based
to waterbased paint.
Operator Training
Since many spray systems are manually operated, the
equipment operator has a major impact on the amount of
waste produced. When air pressures are set too high, the
paint has a tendency to bounce off the surface and increase
overspray. Another reported factor affecting overspray is
the practice of arching the spray gun instead of keeping it
perpendicular to the surface. When the gun is arched 45
degrees away from the surface at the end of each stroke,
overspray can be great and an uneven coat of paint can
result. Manual operations have been eliminated altogether
in many facilities with the use of robots.
Preventive maintenance also plays a critical role in
reducing the amount of overspray, stripping waste, and
equipment cleaning waste produced. Whenever a bad
finish is produced, the paint is normally stripped off and the
entire paint application procedure is begun again. By
maintaining all application equipment in good working
order, the likelihood of producing a bad finish is lessened.
Spray guns should be cleaned after use or whenever there
will be an appreciable interval between use. For hand-held
units, a solvent rinse with occasional blow-back
(accomplished by covering the fluid tip and operating the
trigger; this blows the paint back to its container) is
32
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adequate. Allmovingparts should be lubricated frequently
and properly adjusted. A spray gun should always be able
to provide a smooth change from solid fan to round cone by
adjustment of the controls.
Roller coating and flow coating machines must also be
properly maintained if they are to produce good finishes.
Rollers on roller coating machines should be cleaned
regularly to remove dried paint and inspected for swelling
of the material. If swelling is evident, the rollers should be
replaced immediately. Curtain or flow coating machines
have a curtain head that must be kept clear at all times. If
this aperture becomes blocked, the curtain will break and
give an uneven finish. To clean the machine, solvent
should first be circulated through the machine. After this,
the aperture should be fully opened and cleaned with a soft
rag or brush. Metal instruments should never be used for
cleaning the curtain head.
By fully inspecting parts before they are painted, the
painting of potential rejects can be avoided. Whenever a
part is painted and then rejected, additional stripping,
cleaning, and painting wastes are generated. If potential
rejects are discovered before painting, they can probably
be corrected (cleaned if the problem is contamination) and
then painted with very little increase in waste generation.
Material Substitution
Conventional solvent-based systems for paint
application often pose potential health hazards, due to the
emission of toxic solvents and the disposal of a large
amount of waste paint sludge. To minimize the quantity
and toxicity of waste paint requiring disposal, new coating
types have been developed which eliminate the hazardous
components of the paint and also allow for maximum re-
use of paint overspray, thus increasing the efficiency of the
paint application process. These alternatives include the
use of water based, radiation-curable, or powder coating
techniques.
Water-based coatings. Water-basedcoatingsarepaints
containing a substantial amount of water (often as much as
80 percent) in place of the volatile solvent. The polymers
used include alkyd, polyester, vinyl acetate, acrylic, and
epoxies, and can be dissolved, dispersed or emulsified.
These coating are supplied as baking finishes, as well as
air-drying formulations. One feature which makes water-
based coatings attractive is that no major equipmentchanges
are necessary to apply water-based coatings with solvent-
based coating equipment Another advantage lies in the
ease of recovering paint overspray. Overspray from a
waterbased coating can be collected or captured with water
in the spray booth. The solution can subsequently be
concentrated and reused as paint again. In addition to
substantial reductions in environmental hazards due to
significantly lower air emission levels and smaller amounts
of waste paint sludge generated, water-based coatings can
also provide energy savings by making possible the
recirculation of the hot air used to cure the paint. Water-
based coatings have increasingly been used by indusuy as
an alternative to solvent-based systems. For example,
Emerson Electric Company has reported the use of a water-
based electrostatic paint system in place of a conventional
organic solventpaintsystem (Huisinghetal. 1985),resulting
in a number of favorable changes, including:
Improved quality of application.
Decrease of down time from 3% to 1%.
Reduction in generation of aromatic
waste solvent by 95%.
Reduction of paint sludge by 97%.
Increase in efficiency with up to 95%
recovery and reuse of paint.
Thenew system also reducedhazardous waste disposal
costs and decreased personnel and maintenance costs by
40%.
The appendices to this booklet contain a case study of
another facility thathadfavorableresults from switching to
a water-based painting system.
Radiation-curable coatings. Another alternative to
solvent-based coatings isradiation-curable coatings. These
coatings do not contain or use organic solvents. Reactive
monomers are applied as a liquid to a surface which is then
exposed to high energy radiation such as UV or 1R light.
Radiation-curablecoatingsaccountforasubstantial fraction
of the curable coating market (Campbell and Glenn 1982).
The advantages of using this coating technique include the
reduction in waste from solvent loss and a decrease in
energy and maintenance requirements.
Powder coatings. Powder coatings represent an
attractive third alternative to solvent-based coatings. Use
of powder coatings has been referred to as a "dry painting
process". The process is simple in operation and can be
done manually or by highly automated equipment. With
manual systems, the powder is sprayed on the object and
the overspray is readily retrieved and recycled, something
thatisverydifficulttodowithh'quidpaints. Oversprayand
other unused powder are returned to the feed hopper for
reuse. This ability to recycle the coating material provides
a very high efficiency-use ratio. In a well-designed spray
system, the coating powder remains clean at all times and
the potential for waste generation (contaminated powder)
is nearly zero. Powder coatings can also be effectively
33
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applied in a fluidized bed (Report to Congress 1986).
RECYCLING
Paint application equipment - spray guns, hoses, as
well as brushes and rollers - is often cleaned with solvents.
Cleaning wastes can sometimes be recycled in ways such
as (Lorton 1988):
collectingandreusingthesolvent-paintmixture
in the next compatible batch of paint as part of
the formulation;
distilling the mixture either on- or off-site, in
order to reuse the solvent and possibly the paint
as well;
separatingoutthepaintsludgethroughfiltration,
centrifugation, or decantation, and reusing the
solvent, and
collecting the cleaning wastes and reusing for
cleaning - perhaps in another application - until
the solvent is too contaminated for further use.
34
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SECTION 4
GUIDELINES FOR USING THE WASTE
MINIMIZATION ASSESSMENT WORKSHEETS
Waste minimization assessments were conducted at
several fabricated metal facilities in Los Angeles area. The
assessments were used to develop the waste minimization
questionnaire and worksheets that are provided in the
following section.
A comprehensive waste minimization assessment
includes a planning and organizational step, an assessment
step that includes gathering background data and
information, a feasibility study on specific waste
minimization options, and an implementation phase.
Conducting Your Own Assessment
The worksheets provided in this section are intended
to assist facilities in systematically evaluating waste
generatingprocesses andin identifying waste minimization
opportunities. These worksheets include only the
assessment phase of the procedure described in the-Waste
Minimization Opportunity Assessment Manual. For a full
description of waste minimization assessment procedures,
refer to the EPA Manual.
Table 6. List of Waste Minimization
Assessment Worksheets
1. Plant Description '
2. Process Identification
3. Waste Minimization Program Organization
4. Input Materials Summary
5. Material Storage and Dispensing Practices
6. Process Flow Diagram
7. Process Information
8. Documentation Available
9. Products Summary
10. Waste Stream Identification
11. Individual Waste Stream Generation and
Characterization
Table 6 lists the worksheets that are provided in this 12. Waste Stream Summary
section
13. Waste Minimization Options
35
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Plant.
Oatt.
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet J_ of ±_ Page of
WORKSHEET
PLANT DESCRIPTION
Firm:
Plant:
Department;
Area;
Street Address;
City;
Stata/ZIP Cod*:
Tetiphon*; (
Major Products;
SIC Codes:
EPA Generator Numbers:
Major UnH or.
Product OR
Operations;
Plant/Equipment Age;
1.001 UC-3/m
36
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Plant
Data
Wast* Minimization As**s*m*nt Prepan
Checke
Pmj Ma. Sheet _
5d8y
dBv
1 of t Paae of
WORKSHEET PROCESS IDENTIFICATION
Industrial Process** Employed at Plant
SIC
37
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Plant.
Date.
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet J_ of J_ Page
WORKSHEET
3
WASTE MINIMIZATION
PROGRAM ORGANIZATION
FUNCTION
NAME
LOCATION
TELEPHONE NO.
Program Manager
Plant Program Coordinator
Organization Chart
(sketch)
F*fWUAUMt.001 UC-VW
38
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Plant Wast* Minimization Assessment Prepared By
Date pn?j NO
Checked By _
Sheet 1 of
t Paoe of
WORKSHEET INPUT MATERIALS SUMMARY
Attribute
Material Name/10
Source/Supplier
Hazardous Component
Annual Consumption Rat*
Purchase Price, $ per
Overall Annual Cost
Delivery Mode*
Shipping Container Size l> Type*
Storage Mod*4
Transfer Mode*
Empty Container Disposal/Management
Shelf LJf*
Supplier Would
accept expired material (Y/N)
accept shipping containers (Y/N)
revise expiration date (Y/N)
Acceptable Substitutes), M any
Alternate Suppliers)
Description1
Stream No.
Stream No.
Stream No.,
.
1 stream numbers, If applicable, should correspond to those used on process flow diagrams.
e.g., pipeline, tank car, 100 bW. tank truck, truck, etc.
e.g., 58 gal. drum, 100 to. paper bag, tank, etc.
e.g., outdoor, warehouse, underground, aboveground, etc.
e.g., pump, toffcon, pneumatic transport, conveyor, etc.
e.g., crush and landfill, clean and recycle, return to supplier, etc.
FvWMAUMI.OQt UC-tti
39
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Plant.
Date.
Wast* Minimization Assessment
Proj. No.
Prepared By ._
Checked By
Sheet J_ of J_ Page of
WORKSHEET
MATERIAL STORAGE AND
DISPENSING PRACTICES
Complete a separate sheet for each material Identified In Worksheet 4.
(Material
Stream Number.
a. Describe how this material Is used:
b. Storage container:
D 55 gallon drum D Containers (specify volume)
D Aboveground tank D Underground tank
Art tight-fitting lids provided on drums?
Are bung holes sealed or fitted with tight valves?
c. Storage area:
D Indoors
D Outdoors
D Covered
D Uncovered
D Concrete
D Asphalt
Q DM
D Locked
D Unlocked
d. Delivery system:
D Gravity spigot
D Othar
D Pump
D Funnel
a. How la material usage controlled?
D Stockroom attendant
D Access nmKed to designated personnel
D Sign-out sheet
D fitotertals readily accessible to aH personnel
NTWMAUMI.OH uc-vm
40
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'lam.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet 1_ of J__ Page of
WORKSHEET
6
PROCESS FLOW DIAGRAM
41
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Plant.
Dale.
Wast* Minimization Assessment
Proj. No.
Prepared By _^^
Checked By
Sheet J_ o< _8_ Page of
WORKSHEET
7a
PROCESS INFORMATION
Worksheet 7 contains sections on the following Industrial processes that generate hazardous waste:
Machining Operations
Metal Parts Cleaning & Stripping
Metal Surface Treatment & Plating Operations
Paint Application
Other:
Complete the appropriate sections of this worksheet that correspond to processes practiced In your plant
1. MACHINING OPERATIONS
Complete for each machine!
Description of machine:
Identification number:
Type of metal working fluid used:.
Actual water-to-fluld ratio used:
Slzs of sump:
Frequency of sump cJeanout:
Is manual or hard-piped fluid addition employed?.
How often Is the machine Inspected for:
hydraulic and lubrication oil leakage?
sump and fluid condition?.
fluid leakage or spillage?
What is the reason why the machine's fluid Is dumped?.
What fluid cleaning/filtering devices are used?
Preeeaa Information:
How Is metal working fluid removed from machines?.
Where Is M taken?.
How often are fluid storage areas Insected for spills and leaks..
Quantity of fluid used per week:
peryear:_
Par MUUH 1«7« UC-tti
42
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lant.
Date
Wast* Minimization Assessment
Prbj. No.
Prepared By _^_
Checked By
Sheet 2_ of JL Page of
WORKSHEET
7b
PROCESS INFORMATION
1. MACHINING OPERATIONS (continued)
List types and amounts of fluid* used:
of Fluid
Annual Amount
Cost of waste fluid disposal:
COM of virgin fluid:.
Current waste management techniques:
Waste Minimization Opportunities:.
Potential wast* minimization savings of Input materials and wast* management costs:
Comments:
43
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By -
Sheet 3_ of 8 Page .of
WORKSHEET
7C
PROCESS INFORMATION
METAL PARTS CLEANING AND STRIPPING
Solvent Cleaning Technique*;
Are solvents used for cleaning purposes? _
If so, which of the following are employed?
ID Vapor Degreaser D Rag Wtpedown
I] Spray Chamber D Brush scrubbing
U Covered Solvent Cold Cleaning Tank D Other
H Uncovered Solvent Cold Cleaning Tank
Chemical Technique fin*** numi*, t «a««i
AonuaLUaaae
How are spent solvents managed?
O Stodegradable; dispose of In sewer
D Recycled onstte
D Recycled offstte
D Treated or Incinerated onstte
D Treated or Incinerated offstte
D Ottief
Annual Costs:
For onstte recycling, to residue hazardous?.
How am used rags disposed of?
Annual Costs:
Aqueous Chemical Cteenmo; Technique*:
What cleansers, strippers, surfactants and detergents are used In the plant?
Types of aqueous cleaners used: :
Chemtol Deaerlptlon Aeflva Ingredient
D Alkaline surfactant cleaner
D Alkaline detergent cleaner
D AftaJIne stripper
D Acid cleanser
D Acid stripper
Ftr MM* UM I.OOTe MC-M*
44
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _4_ of _8_ Page of
WORKSHEET
7d
PROCESS INFORMATION
(conono«a)
2. METAL. PARTS CLEANING AND STRIPPING (continued)
Process Techniques:
G Spray chamber
G Alr-spargod bath
G Agitated bath
TvtM> of Aaueoua Cleaner
G Sink
G Mag wiping
G Brush
Technique (indudt ** tnd numb*)
Annual Uaaoe
How ant spent cleaners managed:
G Biodegradable; disposed of In sewer
G Transported offsite
G Treated onstte
Annual Costs:
Abrasive Cleaning and Stripping
Annual Costs: ,
Descrtoe abrasive cleaning and stripping techniques used (e.g., Masting boxes, buffing machines, etc.)
How are wastos from abrasives techniques managed (e.g., dust, worn discs, etc.)
Annual Costs:.
ftfWHAUHt.007* MC-3M
45
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _5_ of J
WORKSHEET
7e
PROCESS INFORMATION
(eononiMd)
2. METAL PARTS CLEANING AND STRIPPING (continued)
Water CtMnlna
Annual Costs:
Size of fltnae Bath
Application1
Continuous
or Still Rinse*
An» spray rlns« tschnlquM used wKhln th« plants?
Tamp.
Annual Usage
Describe spray rinse operations:
Is the spray rinsing done In combination with or Instead of Immersion rinsing?
Am spent stin rinses used as makeups for the process baths?-
Is the counter-current rinsing employed at the plant?
Describe how It Is used (Give the number of tanks In each counter-current series, the flow rates and the
process chemicals rinsed from the workpleces.):
Water use rate for entire plant rinsing operations:
Is defended water or reverse-osmosis filtered water used for rinsing/cleaning? Whera?-
Is air sparging or mechanical agitation used In the rinse baths?
List which technique Is used In which bath:
1' (Le, Wtut proces* volutions are rinsed fn
2 (Give ftew rate for continuous bath*.)
by the bath?)
FtrWMAU»1.00fe MC-Mi
46
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Plant
Date
WORKSHEET
7f
2. METAL PARTS CLEANING A
Is the spent water recycled o
G settled
G filtered
G chemically classified
Is the spent water treated on
Is the recycling or treatment
If yes, how Is It managed?
Waste minimization opportut
Potential waste minimization
Waste Minimization Assessment Prepared By
Checked By
Pmi MO Sheet 6 of 8 Pace of
PROCESS INFORMATION
(cononutd)
NO STRIPPING (continued)
,H^9
residue hazardous *
idles In metal parts cleaning and stripping:
savings of process materials and waste management courts;
C~nn»nt*-
3. METAL SURFACE TREATME
Complete a worksheet for ea
Description of tank's functlo
Identification number:
Size:
Composition of process soK
Temperature'
Work volume (square feet of
Quantity of makeup solution
Quantity of chemicals ad
What chemicals are add*
How much of the makeup vo
Replenishing evaporattw
Is detonized or reverse-osnv
NT AND PLATING OPERATIONS
ch process tank.
n:
itton:
workptece surface per week)*
eKKNQ |Mr W99K.
Irleirl-
>^j«t.
IQY m L
lOlBOTf
MIS I1R4KM WSIsK UMO In tlW ptDCTM &1UW (
47
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Plant
Date
Waste Minimization Assessment Prepared By
Checked By
Proj. No. Sheet 7 of 8 Page of
W°7qEET PROCESS INFORMATION
(contmuM)
3. METAL SURFACE TREATMEN-
Are dragout reduction technique*
Which anas?
r AND PLATING OPERATIONS (continued)
mployad?
What Is the dump schedule for the process tank?
Is the process line manual or a
Is rack or barrel plating employ
What Is the production rat* of 1
Art baths air sparged or mecru
Are personnel trained to thorot
another bath?
utomatlc?
red In the tank?
he tank (In ft2 of workplecc surface area per week)?
intealfv aqltated?
ighty drain workpleces above baths before movlna thtm to
Are they oertodlcaltv retrained?
Are there spaces between process baths and their rinse tanks that allow chemicals to
drip on the floor?
Are process baths filtered to remove partteulates?
4. PAINT APPLICATION
Which palm application techniques are employed at the plant?
VQhme Qf Work Paint ComiMMttlon Waste Generation
Spray coating 1 1
Dip coating LJ
Flow coating LJ
RoKercoatlng EH
Curtain coating LJ
Electro-coating LJ
Brush coating 1 1
Powder coating 1 1
Radiation curable LJ
coating
(ft1 of work surface (l.e., water based or solvent. Bate
coated per week) Ghra solvent type. Are any (GalJMonth)
lead-based paints used?)
F*rWMAUM1.007|
48
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _8_ of J3_ Page of
WORKSHEET
7h
PROCESS INFORMATION
4. PAINT APPLICATION (continued)
Small part paint application:
Tumbling LJ -
Barreling IJ -
Cantrifuglng IJ -
What size paint eontainars are purchasad?
How la leftover paint wa«ta in container* managed?
What measure* are taken to control/manage ovanpray and drippings? -
What temperature* are bake ovena run at?
5. MISCELLANEOUS
Ara any matai oxide waataa generated in welding or aoMering operation* In your plant?
Note: W so, thay must be managed aa hazardous waste.
AJII aiiy hazardous flux** u**d In wekDng or aoldariiig operation*?:
How are tha above wastes managed?
6. OTHEH PROCESSES THAT GENERATE HAZARDOUS WASTE
Annual Amount
Annual Cost of
Management
otentlal Source Reduction and Recycling Opportunities.
F*WMAUM1.007h UC-Mi
49
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Plant Was
Dat9 Prop
te Minimization Assessment prepai
Check
Jo. Sheet
red By
edBv
1 Of 1 Pace erf
WORKSHEET
8
Pme*M Llna:
DOCUMENTATION AVAILABLE
Operation Type: LJ Continuous C
O Batch or Semi-Batch C
Document
Process Flow Diagram
Material/Energy Balance
Dtflgn
Operating
Row/Amount Measurement*
Stream
Analyses/Assays
Stream
Process Description
Operating Manuals
Equipment Us*
Equipment Specifications
Piping & Instrument Diagrams
Plot and Elevation Pton(s)
Work Flow Diagrams
Hazardous Waste Manifests
Emission Inventories
Pretreatment Records
Sewer use Permit
Annual/Biennial Reports
Environmental Audit Reports
Ptrnntt/Permtt Applications
Batch Sheet(s)
Materials Application Diagrams
Product Composition Sheets
Material Safety Data Sheets
inventory Records
Operator Logs
Production Schedules
Discrete
Cther
Status
Complete?
(Y/N)
Current?
(Y/N)
Last
Revision
I
Used In this
Report (Y/N)
Document
Number
-
Location
!.QOi UC-Mi
50
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Plant
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet J_ of _l_ Page of
WORgHEET
PRODUCTS SUMMARY
Attribute
Name/ID
Hazardous Component
Description1
Stream No.
Stream No.
Stream No.
Annual Production Rat*
Annual Revenues, f
Shipping Mode
Shipping Container Size ft Type
Onette Storage Mode
Containers Returnable (Y/N)
Shelf Life
Rework Possible (Y/N)
Customer Would:
relax specification (Y/N)
accept larger containers (Y/N)
stream numbers, If applicable, should correspond to those used on process now diagrams.
51
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet j_ of j2_ Page of
WORKSHEET
10a
WASTE STREAM IDENTIFICATION
1. Check the wastt streams below that are generated In the plant
PROCESS
Machining Operations
Metal Parts Cleaning and Stripping
Surface Treatment and Plating
Palm Application
Other Proce
WASTE STREAM
Coolant/Cutting Fluid
Other:
Solvents
Alkaline Wastes
Acid Wastes
Abrasives
Waste Water
Air Emissions
Other
Spent Bath Solutions
niter Waste
Rinse Water
Spins and Leaks
Solid Waste
Air Emissions
Other.
Leftover Paint In Containers
Overspray
Drippings
Air Emissions
Other:
Leftover Raw Materials
Other Process Wastes
Types of Wast**:
Pollution Control Residues
Watt* Management Residues
Other Wastes:
a
a
a
a
a
a
a
a
a.
a
a
a
a
a
a
a
a
a
a
a
a
a
a
P*WMAUMt«10l MC-Mi
52
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Plant Waste Minimization Assessment Prepaid Ry
Date prrfj Na
Checked By
Sheet 2 of 2 Page of
-, r
WORKSHEET
fQU WASTE STREAM IDENTIFICATION
(cenamMd)
2. Which wast* streams, If any, contain
compounds of:
Cyanide
Chlorine
Bromine
Sulfur
Cadmium
Chromium
Copper
iron
Lead
Nickel
Silver
Tin
Zinc
Other
Hazardous
Components
I
Identify the Compounds:
_
53
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Plant.
Date.
Waste Minimization Assessment
Proj. No.
Prepared By
Checked By _...
Sheet _l__ of _4_ Page of
WORKSHEET
INDIVIDUAL WASTE STREAM
GENERATION AND CHARACTERIZATION
1.
2.
4.
7.
Waste Stream Name/ID:.
Process Unit/Operation.
Stream Number -
Waste Characteristics (attach additional sheets with composition data, as necessary.)
EH gas D liquid D solid D mixed phase
Density, Ib/cufl
Viscosity/Consistency
pH .Flash Point.
High Heating Value, Btu/fc
Waste Leaves Process as:
D air emission D waste water DsoMwasts D hazardous wacte
Waste Generation Is:
EH continuous '
EH periodic.
length of period:
EH sporadic (Irregular occurrence)
EH non-recurrent
What Determines « To Be A Waste?
EH Chemical Analysis
EH Process Type
EH Industry Type
EH EPA Chemicals Ust
What CouM Eliminate This Waste Generation?
EH Improved Operations
EH Material Substitution*
EH Other
Generation Rate
Annual.
toe per year
Maximum
Average _
bstcnee per.
Batch Size.
rang*
AVWMAUMI.OIU uc-
54
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Plant.
Pate
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet 2_ of J_ Page of _
WORKSHEET
INDIVIDUAL WASTE STREAM
GENERATION AND CHARACTERIZATION
(eontirHMd)
6.
Wast* Stream.
Wast* Origins/Sources
PHI out this worksheet to Identify the origin of the wast*. H the waste Is a mixture of wast*
streams, fill out a sheet for each of the Individual waste streams.
is the waste mixed with other wastes? D Yes D No
Is waste segregation possible? D Yes D No
K yes, what can be segregated from ft?
If no, why not?
How Is the waste generated?
O Formation and removal of an undesirable byproduct compound
CD Removal of an unconverted Input material
EH Depletion of a key component (e.g., drag-out)
Q Equipment cleaning waste
D Obsolete Input material
Q Spoiled batch and production run
D Spill or leak cleanup
Q Evaporative loss
IH Breathing or venting losses
D Other:. ;:
55
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Plant.
Data
Wist* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet 3_ of _4_ Page of
V/ORKSHEET
11C
INDIVIDUAL WASTE STREAM
GENERATION AND CHARACTERIZATION
(oonontMd)
7.
Wast* Stream
Management Method
Leaves alt* In
bulk
roll off bins
55 gal drums .
D other (describe)
Disposal Frequency
Applicable Regulations'
Regulatory Classification*
Managed
Recycling
Q onstte Q offsite
Q commercial TSDR
Q own TSDR ;
D other (describe)
CI dtosct u*s/re-use .
l~] combusted for energy content
D redlstlBsd
D othsf(d«scrlbs).
Raetaltned material returned to sits?
n Y*« D NO n
rssidu* yield
byethera
How Is the residue managed?
Note* Ret federal, stats * local regulations, (e.g., RCRA, TSCA, etc.)
Note * Hat pertinent regulatory classification (e.g, RCRA Ustsd K011 wsote, etc.)
TSDR Treatment, Storage, Disposal or Recycling Facility
56
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Plant.
Date
Wasta Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _4_ of _4_. Pag« . of
WORKSHEET
INDIVIDUAL WASTE STREAM
GENERATION AND CHARACTERIZATION
(continued)
Wasta Stream
7. Managemant Method (continued)
Traatmant
biological
1_| oxidation/reduction
CD incineration
CD pH adjustment
CD. precipitation
soHdlflcatlon/stabHlzatlon.
other (describe) .
Which final disposal Is Involved In management of the waste or Ra residue?
C] tantifll !
Qpond. : ,
CD lagoon _
CH daepweil
ocean
CD other (descrfbo).
What > the projected data lor phasing out this disposal practice?
Coats of ; (quaitar and year)
Cost Element:
Unit Price
Reference/Source:
OnsHa Storage * HandOng
Pretraatment
Contatnar
Transportatton Fee
Disposal Fee
Local Taxes
Total Disposal Cost
town*UN tuni« MC-M*
57
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Plant
Oats
WORKSHEET
12
w»
- Proj.
it* Minimization Assessment Prepared By
No
Checked By
Sheet 1 of 1 Paga of
WASTE STREAM SUMMARY
Attributa
Wasta ID/Name:
Sourca/Orlgln
Hazardoua Componant
Annual Ganaratlon Rata funtta )
Ovarali
Componant(s) of Coneam
Coat of Olapoaal
Unit Coat ($ par. )
Ovarali (par yaar)
Mathod of Management1
Prtortty Rating Crftarta*
Regulatory Compltanca
Traatmant/Dlapoaai Coat
Potential Liability
Waata Quantity Generated
Waata Hazard
Safety Hazard
Minimization PotanttaJ
Potential to Remove Bottleneck
PntftnttflJ ft\f-nmAt*+ RaWWATV
wtnw
Sum of Prtortty Rating Score*
Prtortty Rank
Description1
Stream No.
HeninQ \**j n X wff
i4 Ji /
! t
Straam No.
Rating (R) RxW
£ ,
KRxW)
Stream No.
R*tlng(R) RlW
KRiW)
Notea: 1. Stream numbers, It applicable, should correspond to those used on process now diagram*.
2. For example, sanitary landfill, hazardous waste landfill, onstte recycle, tnclnoratlon, combuatton
wtth heat recovery, dJatltlatton, dawaterlng, etc.
3. Rate each stream In each category on a acafa from 0 (none) to 10 (high).
4. A vary Important criteria for your plant would receive a weight of 10; a relatively unimportant
criteria might be ghren a weight of 2 or 3.
HC-Mi
58
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Plant.
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet j_ of j4_ Page of
WORKSHEET
13a
WASTE MINIMIZATION OPTIONS
Source reduction and recycling options for each metal fabrication Industrial proctss are listed below
(and discussed In detail earlier In this report). Select those that appear most promising for your plant,
and enter these on Worksheet 13. Remember that source reduction options frequently offer both
environmental and economic advantages over recycling.
PROCESS
Machining Operations
Motal Parts Cleaning and Stripping
OPTIONS (Chtctt *MM fat tfptv promiting for your pitnt)
Source Reduction:
Preventing Metal Working Fiulld Contamination
Optimal Fluid Selection
Periodic or Continuous Filtration
Demlnerallzed Water Use
Fluid Concentration Control
Material Substitution: Synthetic Fluids
Other
Recycling:
Filtration
Summing
Coalescing
Hydrocyclonlng
Csntrifugatton
Pasteurization
Downgrading and Reusing Fluids
Other _
Source Reduction:
General Operating Procedures
Process Controls
Operator Training
Drainage Techniques
Storage and Distribution Measures
Other.
Solvents
Vapor Degreeser Use
Covered Immersion Tanks
Dramboard installation
other
Material Substitution
G
G
G
G
i |
G
,u
G
G
G
G
G
G
G
G
G
G
C
G
59
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Plant.
Oatt
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _2_ of _4_ Page of
WORKSHEET
13b
WASTE MINIMIZATION OPTIONS
(conamwd)
Mttal Parts Cleaning and Stripping
Source Reduction (continued):
Aqueous Cleaners
Sludge Removal
Tank Lids
Other .
Abrasives
Use of Water-Based Binders
UquM Spray Abrasives
Predeanlng of Workplace
Other _^_
Recycling:
Solvents
Filtration
Distillation
Abrasives
Reusable Blasting Media
Metal Surface Treatment and Plating
Source Reduction:
Dragout, SpM and Leek Reduction
Efficient Drainage
Viscosity and Surface Tension Control
Other .
Bath Solution Waste Reduction
Rinse System Design
3t» Rinse Design
Counter Current Rinsing
Efficient Drainage
Use of No-Rinse Costings
Other : .
Solid Waste Management
n
G
r~i
5
D
n
G
G
G
G
G
G
n
a
G
Q
G
0
G
60
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Plant.
Date
Wast* Minimization
Proj. No.
Prepared By
Checked By
Sheet 3 of 4
3_ of _4_ Page o<
WORKSHEET
13C
WASTE MINIMIZATION OPTIONS
(eontiniMd)
Metal SurtacsTreatment and Plating
Source Reduction (continued):
Product Substitution
Cadmium Plating Alternatives
Chromium Plating Alternatives
Cyanide Bath Alternatives
immtocBsle Rinses
Other
Recycling:
Process Bath Recycling
Rlneewater Recycling
Other ! __
Paint Application
Source Reduction:
Process Modifications
Reducing Empty Container Wastes
Reducing Overspray
Drip Reduction
Bake Oven Temperature Control
Equipment Maintenance
Other '.
Product Substitution Options
Water Based Coatings
Radiations Curable Coating
Powder Coatings
Other
Recycling:
Overspray
Container Waste*
Other __
Otnor Processes
D
D
r
D
C
'n
n
-G
Q
D
a
a
a
a
a
a
a
fm MMUM t.OiJe
61
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Plant.
Date,
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet _4_ of _4_ Page of
WORKSHEET
13d
WASTE MINIMIZATION OPTIONS
Good Operating Practice*
Malarial Handling improvements
Waata Stream Segregation
Los* Prevention Practice*
Preventive and Corrective Maintenance
Personnel Practice* and Training
Management initiative*
Employee Training
Employee incentive*
Procedural Meaaure*
Documentation and Tracking
Storage
Other Good Operating Practice*
L.
r;
C
62
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References
Baumeister, T., ed. 1967. Standard Handbook for
Mechanical Engineers. McGraw-Hill. 1967. pg. 13-
' 71.
Brewer, G. 1980. Calculations of Painting Wasteloads
Associated with MetalFinishing.USEPA, Cincinnati,
Ohio.
Campbell, M., and Glenn, W. 1982. Profit from Pollution
Prevention - a Guide to Industrial Waste Reduction
andRecycling. Pollution Probe Foundation. Toronto,
Ontario.
Centrico Inc. Fall 1986. "How Borg-Warner Automotive
Recycles Coolants". Centrifacts. No. 49.
DHS. 1989. Waste AuditStudy:FabricatedMetalProducts
Industry. Prepared by Jacobs Engineering Group for
Alternative Technology Section, Toxic Substances
Control Division, CaliforniaDept. of Health Services.
Dowd, P. 1985. "Conserving Water and Segregating
Waste Streams." PlatingandSurfaceFinishing. 72(5):
104-8.
Durney, L.J. ed. 1984. Electroplating Engineering
Handbook. 4th Edition. Van Nostrand Reinhold.
New York. 1984.
EERC. 1988. Guide toOilWaste Management Alternatives.
Energy and Environmental Research Corporation,
Robert H. Salveson Associates, and Evergreen Oil,
Inc.
Foss Plating. August 1988. Personal Communication.
Santa Fe Spring, CA.
Hayes, M.F. December 1987. "Chlorinated CFC Solvent
ReplacementintheElectronicsIndustry. TheTerpene
Hydrocarbon Alternative." Proceedings of the 3rd
Annual Hazardous Materials Management Conference
West. Long Beach, CA.
Huisingh, D.,Hilger, H. Thesen, S. andMartin,L. Proven
Profit from Pollution Prevention. Institute for Local
Self-Reliance. Washington, D.C.
Jacobs Engineering Group. December 1986. CaseStudies
of Minimization of Cyanide Waste from Electroplating
Operations. USEPA, ContractNo.68-01-7053,Task
#46.
Kirk-Othmer: Encyclopedia of Chemical Technology.
1981. ThirdEdition. Volume 15. John Wiley & Sons,
New York.
Kohl, J., P. Moses, and B. Triplet!. 1984. Management
RecyclingSolvents:NorthCaroHriaPracticesFacilities,
and Regulations. North Carolina State University,
Raleigh, N.C..
Krofchak, D., and Stone, J.N. 1975. Science and
Engineering for Pollution-Free Systems. Ann Arbor
Science Publishers Inc. Ann Arbor, Michigan.
Lorton, G. April 1988. Journal of Air Polluitn Control
Association. Vol. 38, No. 4.
pg.424.
Metals Handbook. Ninth Edition. Volume 5. Surface
Cleaning, Finishing, and Coating. March 1987.
American Society of Metals Park, Ohio.
Normandy Refinishers. March 1988. Personal
Communication. Pasadena, CA.
Pinkerton, H.L. and Graham, K.A. 1984. "Rinsing."
ElectroplatingEngineeringHandbook.Fourth Edition.
Durney, L.J., editor. Van Nostrand Reinhold Co.,
New York. pg. 691-709.
Pollution Prevention Tips. 1985. (a) "Water Conservation
for Electroplaters: Rinse Tank Design"; (b) "Water
Conservation for Electroplaters: Counter-Current
Rinsing"; (c) "Water Conservation for Electroplaters:
Rinse Water Reuse." Pollution Prevention Pays
Program, North Carolina Department of Natural
Resources and Community Development.
Porter, C.L. December 1988. Minimization of Metal
WorkingFluidWastes. MasterofEngineeringThesis.
University of Louisville, Speed Scientific School,
DepartmentofChemicalEngineering. Thesis Advisor:
Marvin Fleischman, Professor, ChemicalEngineering.
PRC Environmental Management, Inc. May 1988. Waste
Audit Study: Metal Finishing Industry. California
Dept. of Health Services.
Report to Congress. 1986. Waste Minimization Issues and
Options, Volume 2, Appendix B: Process studies.
Prepared by Jacobs Engineering Group for USEPA,
Officeof SolidWaste, Waste TreatmentBranch. EPA/
530-SW-86-042.
Schaffer, G. February 1978. "Recycling Coolant Reduces
Cost." American Machinist.
Schwartz, S.I. October 1986. "Recycling of Hazardous
Waste Solvents: Economic and Policy Aspects."
Solvent Waste Reduction Alternatives Symposia
Conference Proceedings. Los Angeles, CA. Sponsored
by California Department of Health Services.
Sluhan, W.A. The Application of High Speed, Disc Bowl
63
-------
Centrifuges to Water Miscible Cutting and Grinding
Fluids. Master Chemical Corporation, Perrysburg,
Ohio.
Smith, C. November 1981. "Trouble Shooting Vapor
Degreasers." Product Finishing.
USEPA. 1980. Development Document for Effluent
Limitations: Guidelines and Standards for the Metal
Finishinglndustry. EnvironmentalProtection Agency,
Office of Water Regulations and Standards. EPA-
440-1-80-091A.
USEPA. 1982. ControlandTreatmentTechnologyforthe
Metal Finishing Industry: In-Plant Changes.
USEPA. April 1988. Waste Minimization Opportunity
Assessment Manual. U.S. Environmental Protection
Agency, Hazardous Waste Engineering Research
Laboratory, Cincinnati, EPA/625/7-88/003.
Zabik, M.J., Wildman, J.L., Moran, C. May 1987. Unique
Methods for Extending the Life of Synthetic
MetalworkingFluidsinaManufacturingEnvironment
- A Case Study. ASLE Paper No. 87-AM-6B-3,
Anaheim, CA. pg. 1-3. ,
64
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Appendix A
FABRICATED METAL PRODUCT FACILITY ASSESSMENTS:
CASE STUDIES OF PLANTS
In 1988 the California Department of Health Services
commissioned a waste minimization study (DHS 1989)
that included assessments of three fabricatedmetalproducts
facilities. The objectives of the study were to:
Gather site-specific information concerning the
generation, handling, storage, treatment, and
disposal of hazardous waste;
Evaluate existing waste reduction practices;
Develop recommendations for waste
management through source reduction,
treatment, and recycling techniques; and
Assess costs/benefits of existing and
recommended waste reduction techniques.
In addition, the results of the waste assessments were
used to prepare waste minimization assessment worksheets
to be completed by other facilities in a self-audit process.
The first steps in conducting the assessments were the
selection of the plants, and contacting the plants to solicit
voluntary participation in the audit study. Plant selection
emphasized small businesses which generally lack the
financial and/or internal technical resources to perform a
waste reduction audit. One relatively large plant was also
selected for study because it offered the opportunity to
evaluate a wide variety of operations, as well as a number
of in-place waste reduction measures. A total of three
plants was audited.
This Appendix section presents both the results of the
assessments of the plants here identified as A, B and C and
thepotentiallyuseful waste minimization options identified
through the assessments. Also included are the practices
already in use at the plants that have successfully reduced
waste generation from past levels. During each of the plant
audits, the audit team observed operations; inspected waste
management facilities; interviewed the plant manager,
environmental compliance personnel, and operations
supervisors; and collected records pertinent to waste
generation and management.
65
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Plant A Waste Minimization Opportunity
Assessment
Plant A manufactures metal laboratory furniture. It
employs 20 production personnel and 10 administrative
staff. Its operations, which correspond to SIC category
2522, include sheet metal cutting, shearing, notching,
punching, forming, cleaning, welding and painting. These
operations are used in the manufacture of base cabinetry,
wall cases and fume hoods.
The plant was opened in 1972, although much of the
equipment is considerably newer. The plant currently
produces 3500 units of furniture per year, with annual
revenues of $3 million.
PROCESS DESCRIPTION
The plant utilizes 30 to 40 tons per year of
nongalvanized, unfinished cold rolled plate steel in its
processes. The steel plate is first sheared to size, then
punched on a turret punch press, and formed on multiple or
single stage brake presses. The workpieces are then
assembled using spot welding, and finished by grinding
andsandingoperations. Next, the workpieces are immersed
in a series of cleaning tanks that include the following
processes:
High pH sodium hydroxide caustic bath. 1000
Ibs of Amclene 17 sodium hydroxide are used
each year to produce a 50 percent caustic
solution;
Water bath and hose rinse;
Acidphosphatizingbath, employing Americoat
105 iron phosphate;
Water rinse;
Rustinhibitorbath. ApH-adjustedphosphoric
acidsolutionismadeup.usingAmsealNC 155
AandB.
Spentcausticandacidcleaning solutions aredischarged
to the sewer, after pH adjustment if necessary. The pH
must be between 6 and 10 before wastes can go into the
sewer. The acid baths are normally very close to pH 6. The
caustic bath often needs adjustment, for it ranges in pH
from 12 to 14. The sludge buildup at the bottom of the
cleaningtanksmustperiodicallybeshovelledout. Itisthen
dried and disposed of as nonhazardous waste.
INPUT MATERIALS
Input materials purchases for plant processes include
nongalvanized, unfinished cold rolled steel, paint (mostly
water-based acrylic enamel), wash solvent and rags for
equipment and workpiecewipedown, Amclean 17 (pH 14)
caustic bath, Number 105 phosphatizer (containing pH 5
sulfuric acid), and Amseal biogradable final rinse (all from
American Research Products).
WASTE MINIMIZATION
Waste streams generated by the plant include solvent
wastes and paint sludge. Until 1986, the plant generated
twelve 55-gallon drums per year of solvent and paint
waste, which were picked up for offsite recycling at a cost
to the plant of $80 per drum. When the recycler raised its
price to $800 per drum, the plant decided to implement
major waste minimization methods, the most dramatic of
which was a change from solvent based paints to water
based paints with very small amounts of solvent in them.
The acrylic enamel water based paints that have been
adopted are oven baked after application to produce a
durable surface comparable to that of the solvent based
paints formerly used. Dried wastes from the water based
acrylic have been shown to be nonhazardous in fish biopsy
tests. The water based paints have a shelf life considerably
longer than solvent paints, which spoil by the time they are
6 months old. This additional shelf life results in less paint
being thrown away, and thus also is responsible for mini-
mization of wastes. The change in paints has reduced the
plant's total drummed hazardous wastes by 75% - from 12
to three 55-gallon drums per year. Changing paints did
require achange to electrostatic spray equipment, however,
which cost $4500. Operator training time to learn to use the
new equipment was minimal. Solvent is still used in the
spray process to purge paint lines, and it is this operation
that produces much of the three 55-gallon drums per year
of spent solvent and sludge. Wash solvent is also used to
wipe down workpieces. The commercial offsite recycler
takes the drummed wastes, charging $40 to recycle a drum
of liquid solvent, but $12.50 per gallon to handle sludge.
The water based paints are slightly more expensive
than the solvent based ones ($17/gal as compared to $14),
and cover only 100 ft^gal, whereas the solvent-based
paints covered 125 ft2. But the solvent paints had to.be
baked at 380°F for thorough drying and a durable finish,
whereas the water based paints only need a temperature of
280°.
The paints are applied in a spray booth. Overspray is
drawn into a closed loop waterfall; the paint sludge is
separated out and the water is recycled.
Paint sludge is air dried in an open tank and discarded
as nonhazardous waste. Empty paint containers are rinsed
out (into the drain) and are also disposed of as nonhazardous
waste.
Plans for the future include reducing the shop's water
66
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use by replumbing the shop so as to route cooling water
from the spot welder into the rinse tanks. The shop could
also save water, and reduce the wastes being drained into
the sewer, by using its rinse baths as makeup water for the
Opportunity
Assessment
Plant B is a machine shop that performs contract work
for aerospace companies, computer firms and other
businesses. The company was founded in 1969, although
they have been in their present location only 2 years. The
plant employs a total staff of 80 to 90 personnel, with
annual revenues of $6 million.
The shop machines all types of metals, from extremely
tough inconel to mild steel. The shop specializes in high
quality, close tolerance work, has made parts for the space
shuttle, and uses computer controlled, automatic machining
equipment for most of its work.
PROCESS DESCRIPTION
A typical workpiece starts out in the shop as bar stock,
and is then sawed, turned on a lathe, milled and ground to
the proper shape. If plating, anodizing, etc. is required, the
workpiece is sent offsite for these operations. Upon its
return to the plant, it is inspected, deburred and shipped.
Parts are cleaned using 1,1,1 trichloroethane (TCA).
This is the only solvent employed in the shop. It is
furnished, and maintained, by a commercial solvent
recycler. Most of the solvent is used in open immersion
tanks, in which themanufacturedcomputerparts arecleaned.
Computer parts make up about 15% of the shop's volume.
INPUT MATERIALS AND WASTE STREAMS
The plant receives up to 240 gallons of TCA per week,
and produces an average of 800 gallons of solvent waste in
80 days.
The only coolant used by the shop in its machining
equipment is Cincinnati 1011, a water based coolant
containing some oil. Synthetic coolants were tried 5 years
ago, with poor results, including removal of paint from the
machines. The Cincinnati coolant is diluted with water to
ratios of 20: 1 to 40: 1 depending upon the application. Tap
water is used for this dilution. 4000 gallons of diluted
coolant are disposed of every year.
The shop uses 300 to 400 gal/yr of light hydraulic oil
in its machines and a small amount of kerosene (less than
55 gallons every 2 years) as a manual cutting oil for
machining of tooling for the computer-ran machines. The
shop buys mostly aluminum, steel and stainless steel for its
work, and a small amount of carbide for making cutting
tools.
WASTE MINIMIZATION
Plant B is in the process of converting to a deionized
(DI) water system for dilution of the machine coolant. The
minerals in tap water have caused various problems,
including difficulties in mixing, and uneven concentrations
of chemicals to the cutting tools. DI water use is expected
to lengthen tool life as well as to reduce bacteria growth and
lengthen the coolant life.
The plant used to manage its spent machine coolant by
draining its own sumps and storing the waste onsite until it
was hauled off for disposal. Several years ago, accidental
contamination of a truckload of waste coolant with TCA
resulted in disposal costs to the plant of $20,000 instead of
the expected cost of $500.
The danger of contamination is greatly lessened today
by having the haulers pump the waste coolant directly from
the machine sumps, instead of allowing it to sit around in
drums. The plant is considering using an offsite "Trimsol"
coolant management service in the future that includes
periodic inspectionsofcoolantcontarninantconcentrations,
draining of the sumps when necessary and replacement
with recycled coolant. The periodic inspection and testing
will prevent degradation of the coolants to the point where
they cannot be recycled.
Spent solvent (800 gallons every 80 days) is taken by
a commercial offsite recycler who currently pays the plant
$ 1.50 for each gallon of recyclable solvent, but charges for
disposing of all still bottoms generated. The recycled
solvent is sold back to the plant at $4 per gallon.
Themostpromisingareafor future waste minimization
appears to be solvent use reduction. Plant B uses
approximately 10,000 gallons of 1,1,1 trichloroethane per
year, most of which is employed in open immersion
troughs in which workpieces are dipped and hand scrubbed
after buffing operations. The evaporation rate is quite high
from these troughs, andless than 4000 gal/yr of solventare
recoveredfor recycling. Besides putting substantial VOC's
into the air, the open trough system is expensive. Recycled
solvent costs the plant $4/gal, while it receives only about
$1.50foreachgallonitgivestotherecyclers. Thus,current
solvent costs run $40,000/yr minus the $6000 for recyclable
solvent, adding up to $34,000/yr.
There are several possibilities for reducing the plant's
evaporative solvent losses. One method that would incur
moderate rather than high costs would be to install sliding
covers on the two solvent troughs 'that could be operated
automatically with a foot pedal or switch, along with a
strong agitating device to remove the buffing grit - either
a jet manifold or an ultrasonic generator - and a drainage
shelf. The cover would normally be kept closed. When
67
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there was work to be cleaned, the cover would be opened,
the work would be put in the tank, the cover closed again,
and the jets or the ultrasonic generator turned on to agitate
the solvent and provide cleaning action. If the system
operated successfully, little or no hand scrubbing would be
necessary. The operator would be freed to perform other
tasks while the work is being cleaned. When the cleaning
is completed, the operator would open the tanks, remove
the work from the solvent and place it on the drainage shelf
to dry (the shelf would be installed inside the tank). The
operator would then place new work into the solvent and
close the tank, returning later to remove the dry work from
the drainage shelf and the solvent. The only times-that the
sliding cover would be opened, allowing solvent vapors to
escape from the tanks, are when the operator is either
adding workpieces to the tank, transferring them to the
drainage shelf, or removing them. :
While the proposed system appears promising, it must
be mentioned that the plant manager felt that much of the
soil on workpieces could not be removed by high pressure
jets, but required hand scrubbing. The jets might also
increase the solvent evaporation rate, raising rather than
lowering materials costs. The plant has already
experimented with using ultrasonic cleaners for removing
buffing grit. Initial results were not encouraging for
removing very fine grit particles, indicating the need for
more powerful agitation.
Plant C Waste Minimization Opportunity
Assessment
Plant C is a decorative chrome electroplating shop
(SIC 3471) that employs approximately 50 personnel, of
which 45 are production staff and 5 are administrative
staff. The company has been in business since 1948, while
the present plant was opened in 1968. The machines
presently used were installed in 1974.
THE PLATING LINE
An "automatic" plating line is employed in the plant,
inwhichcomputercontrolledcranes advance the workpiece
through the plating lines, immerse them in the baths,
remove them and let them drain. The plating line includes
nickel undercoat baths and a chrome topcoat bath, and
consists of the following steps:
Preprocessing
Soak cleaning. High pH caustics are used to
remove grease and oil from the workpiece.
Running rinse. Tap water is used, at a flow of
3 gal/min.
Pickling. Hydrochloricaciddescalingsolutions
are used.
Running rinse. Same rinse tank as above.
Rustpreventative. This is a proprietary, nitrate
based bath that is considered nonhazardous by
the plant management.
Polishing
Belt sanding and buffing. Dust produced is
nonhazardous and disposed of as municipal
waste.
Cleaning
Vapor degreasing or solvent wipedown. 1,1,1-
trichloroethane is used in the vapor degreaser,
while a proprietary Stoddard-type solvent is
employed for wipedown.
Soak cleaning. Two baths, employing
proprietary cleaners.
Water rinse. Tap water is used. This is the final,
least clean stage of counterflow system A (a
three part system). After use, water is pumped
to treatment system and then disposed of down
drain.
Electrocleaner. Caustic with a reverse electric
current is employed.
Water rinse. Second stage of counterflow
system A.
Sour dip. 10% muriatic acid solution:
Water rinse. Second, least clean stage of
counterflow system B (a two-stage system).
This system uses cooling water from a bank of
rectifiers. At present, spent water ispumped to
treatment system and then disposed of, but in
the future, it will be used as makeup for the
nickel bath.
Nickel Plating
Semi brite nickel. Composition: 30 oz/gal
nickel sulfate, 5 oz/gal nickel chloride, 7 oz/gal
boric acid, plus small quantities of organic
brighteners. Total nickel metal content in the
salts, 8 oz/gal. The nickel baths are maintained
at 140°F to 150°F.
Bright nickel. 35 oz/gal nickel sulfate, 14 oz/
gal nickel chloride, 7 oz boric acid, and
saccharine. Total nickel metal content in the
salts: 10 oz/gal.
Proprietary nickel dip. A proprietary
"microporous" nickel solution that gives
68
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porosity to the plating layer, to inhibitcorrosion.
Uses the same nickel compound and boric acid
concentrations as the bright dip.
Cleaning
Standing nickel dragout. A deionized (DI)
water still rinse that is used as makeup for the
bright nickel dip. 300 to 400 gallons per day of
the rinse is added to the bright nickel bath.
Water rinse. First stage of counterflow system
B. Any nickel remaining on the workpiece is
precipitated in this bath.
Chrome Plating
Chrome bath. 30 oz/gal chromic acid.
5 stage counterflow rinse system C. DI water
at a flow rate of 3 gal/min and a temperature of
105oF is used. Water from the fifth, least clean
stage of the system is employed as makeup
water for the chrome bath. An evaporator is
attached to the chrome bath so that sufficient
water from the plating solution is evaporated to
allow the makeup water to be added. This
closed loop prevents virtually all of the
chromium from reaching the treatment system
and being disposed of either in the effluent to
the sewer, or in the dried sludge.
After the workpieces go through the 5-stage rinse,
they are allowed to dry, are inspected, and if acceptable,
packaged and shipped.
INPUT MATERIALS AND PRODUCTS
Input materials to the plating processes include 3000
Ib/month of soakandelectrocleaners, which contain caustics
thatare neutralized in the plant's treatment system, 500 gal/
mo of muriatic acid, up to 1500 Ib/year nickel chloride and
1000 Ib/year nickel sulfate, 150 gal/mo of 1,1,1-
trichloroethane, 200 gal/yr of Stoddard solvent, 1000 Ib/yr
of chromic acid, and 4 million gal/yr of water.
The plant currently produces about 100,000 ft2/mo of
plated surfaces, and receives just under $2 million per year
in revenue. 1.8 million gal/yr of treated wastewater is
released to the sewer; 2.2 million gal/yr is evaporated.
WASTE STREAMS AND TREATMENT SYSTEM
Waste streams from the plating lines include cleaning
solution wastes, pickling wastes, rinse water, 1,1,1-
trichloroethane (TCA) from the vapor degreaser, and spills
and leaks from the baths. The TCA wastes are sent back to
the supplier (Rho Chem), who recycles them and returns
the reconstituted solvent. The other wastes from the
plating line are sent to the plant's treatment system.
In the treatment system, caustic cleaners are mixed
with acid pickling wastes. Additional caustic is added to
adjust the pH to 9.5, and flocculants are added for settling
of the precipitates and solids. Plant personnel have found
that a pH of 9.5 provides the best settling. The treatment
effluent is released to the sewer, while the sludge is filtered
and dried using heaters.
The effluent typically contains 0.5 to 1 ppm nickel.
Chrome levels are usually much lower, and often non-
detectable, because the chrome line is, a closed loop system.
Chrome that does reach the treatment system is mainly
from spills. Nickel levels areexpected to also drop once the
nickel line is made closed loop.
The sludge is filter pressed and heated to evaporate its
water. The dried filter cake typically contains 500 to 700
ppm chrome, and 70,000 ppm nickel (nickel levels will
drop once a closed loop nickel line is implemented). Most
of the nickel is in the form of nickel hydroxide. The dried
filter cake is shipped to World Resources Corporation in
Arizona for recovery of the metals.
WASTE MINIMIZATION MEASURES
The plant has been quite innovative in instituting a
variety of waste minimization measures throughout its
processes. These measures include:
Increased dwell time for parts being drained
above process baths;
Counterflow rinses;
Closed loop process line;
Deionized water use;
Process tank filtration;
Elimination of cyanide use;
Process water recycling;
Solvent recycling;
Filter cake recycling; and
Process line design.
Increased Dwells
The computerized automatic plating line was
reprogrammed to increase dwell time for better drainage of
workpieces after removal from process baths, and to
decrease dragout. The automatic equipment takes 6 sec-
onds to remove a workpiece from a bath. It used to be
programmed to aUow 3 additional seconds of drainage
after removal of the workpiece; the dwell has now been
increased from 3 to 10 seconds.
,69
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Counterflow Rinses
Several counterflowrinses are used in theprocessline,
in order to reduce rinse water use. A three-stage and a two-
stage counterflow rinse is used in the nickel process, and a
five-stage counterflow is employed in the chrome line.
Closed Loop Process Line
The entire chrome line, consisting of a chrome bath
and a 5-stage counterflow rinse system, is a closed loop
system. Overflow from the last (least clean) stage of the
counterflow rinse is fed back into the chrome bath. This
flow amounts to about 3 gal/min. The chromebath does not
overflow because an evaporator vaporizes water from the
bath at a rate equal to the inflow.
This setup ensures that almost all of the chrome
dragged out of the chrome bath by the workpieces and into
the rinses eventually finds its way back into the chrome
bath, and not down the sewer. Besides being
environmentally beneficial in that it prevents most chrome
wastes from entering the environment, this practice also
offsets theadditional capital and operating (mostly energy)
costs in three different ways: 1) lower sewer surcharges;
2) lower water use charges; and 3) lower treatment
system maintenance expenses, since considerably less
water goes into the treatment system.
The nickel line has a smaller closed loop, although the
plant management plans to modify it into a closed loop
similar to that of the chrome line. At present, the bright
nickel, proprietary nickel and standing nickel dragout
tanks form a closed loop. Workpieces emerging from the
proprietary nickel tank (the last nickel plating bath) are
immersed in the standing dragout tank. When this still rinse
is dirty, it is used as makeup for the bright nickel tank. The
bright nickel tank is kept at a temperature of 140 to 150°F,
andasaresult, 300 to400 gal/day of water evaporates from
it, and is made up from the still rinse.
Deionized Water Use
DI water is used to replenish the standing nickel
dragout bath and the 5 stage chrome line counterflow loop
systems. If DI water was not used, impurities would build
up much faster than they do. At present, the chrome line
closed loop has been in operation for 2 years, and the
chrome bath has not yet needed draining and replenishing.
Process Tank Filtration
The purity and long life of the process baths is due not
only to use of DI water, but also to other factors, one of
which is their continuous filtration. The process baths are
filtered atrates of between 15 and 20,000 gal/hr. The baths
are 3500 gallons in volume.
Elimination of Cyanide Use
The plant used to use cyanide based plating and
stripping solutions, and had to dispose of 1000 gallons of
8 oz/gal cyanide solution every 60 days. Theplantreplaced
these solutions with noncyanide based chemicals. The
nickel process uses nickel sulfate and chloride, and the
cleaning and stripping is done with caustic, muriatic acid
and electrocleaning techniques.
Process Water Recycling
As mentioned above, spent water from some of the
rinse tanks is used as makeup water for plating baths. In
addition to this recycling, the rinsewater itself is recycled
water in some of the systems. Rinse water in counterflow
rinse system A comes from cooling water in the vapor
degreaser and boiler cooling pumps. Water in counterflow
rinse system B is taken from cooling water for a bank of
rectifiers.
Solvent Recycling
Spent 1,1,1-trichloroethane from the vapor degreaser
is recycled offsite by Rho Chem, who supplies the plant
with reconstituted solvent.
Filter Cake Recycling
Dried filter cake from the treatment system filter
presses and drying ovens is sent to the World Resource
Corporation in Arizona for recovery of the nickel and
chrome it contains.
Process Line Design
Theprocess tanks are installed butted up tightly against
each other to minimize spills onto the floor due to dragout.
Separate spill collection systems areincludedforthenickel
line and the chrome line, so that the different chemicals in
any spills maybe segregated from each other if necessary.
Future Waste Minimization Plans
Theplantisconsideringimplementingadditional waste
segregation measures. Some of the process rinse water, for
instance, remains clean enough to be disposed of directly
into the sewer without treatment. It is now treated, but if
this practice were eliminated, it would cut down on sludge
and filter cake production.
Wastewater from bulk pickling processes could also
be disposed of directly into the sewer, with perhaps a pH
adjustment. The only metal in this stream is iron, which is
nonhazardous. If the stream goes to the treatment system,
however (as it does at present), any sludge produced must
be handled as hazardous waste, since it is mixed with
hazardous sludges.
70
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The plant envisions replacing the hexavalent chrome
used for plating with trivalent chrome. There are many
advantages to this. Most importantly from an environmental
point of view, trivalent chrome is far less toxic than
hexavalent. Also, a trivalent system requires only a dilute
concentration of 1.5 oz/gal of chrome, while the hexavalent
system requires 13 oz/gal of the muchmore toxic hexavalent
chrome. Since concentrations are higher in hexavalent
process baths, they tend to be higher in their waste streams
as well. In addition, the higher concentration hexavalent
baths are far more viscous than the trivalent baths, leading
to more dragout from the hexavalent baths. Trivalent
systems have little air emissions, while in hexavalent
systems, hydrogen bubbles are formed that entrain
chromium compounds and lead to air emissions. In a
hexavalent chrome setup, the waste treatment system must
convert to hexavalent chrome to trivalent in order to
precipitate it. This step is avoided in the trivalent setup.
Finally, the plant management believes that the trivalent
system will be far more efficient, produce fewer rejects and
increase production.
71
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APPENDIX B
WHERE TO GET HELP
FURTHER INFORMATION ON POLLUTION PREVENTION
Additional information on source reduction, reuse and
recycling approaches to pollution prevention is available
in EPA reports listed in this section, and through state pro-
grams (listed below) that offer technical and/or financial
assistance in the areas of pollution prevention and treat-
ment.
In addition, waste exchanges have been established in
some areas of the U.S. to put waste generators in contact
with potential users of the waste. Four waste exchanges are
listed below. Finally, EPA's regional offices are listed.
EPA REPORTS ON WASTE
MINIMIZATION
U.S. Environmental Protection Agency. "Waste
Minimization AuditReport: CaseStudies of Corrosive
and Heavy Metal Waste Minimization Audit at a
Specialty Steel Manufacturing Complex." Executive
Summary.*
U.S. Environmental Protection Agency. "Waste
Minimization Audit Report: Case Studies of
Minimization of Solvent Wastefor Parts Cleaningand
from Electronic Capacitor Manufacturing Operation."
Executive Summary.*
U.S. Environmental Protection Agency. "Waste
Minimization Audit Report: Case Studies of
Minimization of Cyanide Wastes from Electroplating
Operations." Executive Summary.*
U.S. Environmental Protection Agency. Report to
Congress: Waste Minimization, Vols. I and II. EPA/
530-SW-86-033 and -034 (Washington, D.C.: U.S.
EPA, 1986).**
U.S. Environmental Protection Agency. Waste
Minimization - Issues and Options, Vols. I-in EPA/
530-SW-86-041 through -043. (Washington,' D.C.:.
U.S. EPA, 1986).**
* Executive Summary available from EPA,
WMDDRD, RREL, 26 West Martin Luther King Drive,
Cincinnati, OH, 45268; full report available from the
National Technical Information Service (NTIS), U.S.
Department of Commerce, Springfield, VA 22161.
**AvailablefromtheNational Technical Information
Service as a five-volume set, NTIS No. PB-87-114-328.
WASTE REDUCTION TECHNICAL/
FINANCIAL ASSISTANCE PROGRAMS
The EPA's Office of Solid Waste and Emergency Re-
sponse has set up a telephone call-in service to answer
questions regarding RCRA and Superfund (CERCLA):
(800) 242-9346 (outside the District of Columbia)
(202)382-3000 (in the District of Columbia)
The following states have programs that offer technical
and/or financial assistance in the areas of waste minimiza-
tion and treatment. ,
Alabama :
Hazardous Material Management and Resources Recov-"
ery Program
University of Alabama
P.O. Box 6373
Tuscaloosa, AL 35487-6373
(205) 348-8401
Alaska
Alaska Health Project
Waste Reduction Assistance Program
431 West Seventh Avenue, Suite 101
Anchorage, AK 99501
(907)276-2864
Arkansas
Arkansas Industrial Development Commission
One State Capitol Mall
Little Rock, AR 72201
(501)371-1370
California
Alternative Technology Section
Toxic Substances Control Division
California State Department of Health Service
714/744 P Street
Sacramento, CA 94234-7320
(916) 324-1807
Connecticut
Connecticut Hazardous Waste Management Service
Suite 360
900 Asylum Avenue
Hartford, CT 06105
(203) 244-2007
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Connecticut Department of Economic Development
210 Washington Street
Hartford, CT 06106
(203)566-7196
Georgia
Hazardous Waste Technical Assistance Program
Georgia Institute of Technology
Georgia Technical Research Institute
Environmental Health and Safety Division
O'Keefe Building, Room 027
Atlanta, GA 30332
(404) 894-3806
Environmental Protection Division
Georgia Department of Natural Resources
Floyd Towers East, Suite 1154
205 Butler Street
Atlanta, GA 30334
(404) 656-2833
Illinois
Hazardous Waste Research and Information Center
Illinois Department of Energy of Energy and Natural
Resources
1808 Woodfield Drive
Savoy, IL 61874
(217) 333-8940
Illinois Waste Elimination Research Center
Pritzker Department of Environmental Engineering
Alumni Building, Room 102
Illinois Institute of Technology
3200 South Federal Street
Chicago, IL 60616
(313)567-3535
Indiana
Environmental Management and Education Program
Young Graduate House, Room 120
Purdue University
West Lafayette, IN 47907
(317) 494-5036
Indiana Department of Environmental Management
Office of Technical Assistance
P.O. Box 6015
105 South Meridian Street
Indianapolis, IN 46206-6015
(317)232-8172
Iowa
Center for Industrial Research and Service
205 Engineering Annex
Iowa State University
Ames, IA 50011
(515) 294-3420
Iowa Department of Natural Resources
Air Quality and Solid Waste Protection Bureau
WaUace State Office Building
900 East Grand Avenue
Des Moines, IA 50319-0034
,(515)281-8690
Kansas
Bureau of Waste Management
Department of Health and Environment
Forbes Field, Building 730
Topeka, KS 66620
(913) 269-1607
Kentucky
Division of Waste Management
Natural Resources and Environmental
Protection Cabinet
ISReillyRoad
Frankfort, KY 40601
(502) 564-6716
Louisiana
Department of Environmental Quality
Office of Solid and Hazardous Waste
P.O. Box 44307
Baton Rouge, LA 70804
(504)342-1354
Maryland
Maryland Hazardous Waste Facilities Siting Board
60 West Street, Suite 200 A
Annapolis, MD 21401
(301)974-3432 .
Maryland Environmental Service
2020 Industrial Drive
Annapolis, MD 21401
(301) 269-3291
(800) 492-9188 (in Maryland)
Massachusetts
Office of Safe Waste Management
Department of Environmental Management
100 Cambridge Street, Room 1094
Boston, MA 02202
(617) 727-3260
Source Reduction Program
Massachusetts Department of Environmental Quality En-
gineering
1 Winter Street
Boston, MA 02108
(617)292-5982
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Michigan
Resource Recovery Section
Department of Natural Resources
P.O. Box 30028
Lansing, MI 48909
(517) 373-0540
Minnesota
Minnesota Pollution Control Agency
Solid and Hazardous Waste Division
520 Lafayette Road
St. Paul, MN 55155
(612) 296-6300
Minnesota Technical Assistance Program
W-140 Boynton Health Service
University of Minnesota
Minneapolis, MN 55455
(612) 625-9677
(800) 247-0015 (in Minnesota)
Minnesota Waste Management Board
123 Thorson Center
7323 Fifty-Eighth Avenue North
Crystal, MN 55428
(612) 536-0816
Missouri
State Environmental Improvement and Energy
Resources Agency
P.O. Box 744
Jefferson City, MO 65102
(314) 751-4919
New Jersey
New Jersey Hazardous Waste Facilities Siting
Commission
Room 614
28 West State Street
Trenton, NJ 08608
(609) 292-1459
(609) 292-1026
Hazardous Waste Advisement Program
Bureau of Regulation and Classification
New Jersey Department of Environmental
Protection
401 East State Street
Trenton, NJ 08625
Risk Reduction Unit
Office of Science and Research
New Jersey Department of Environmental Protection
401 East State Street
Trenton, NJ 08625
New York
New York State Environmental Facilities
Corporation
50 Wolf Road
Albany, NY 12205
(518) 457-3273 ,
North Carolina
Pollution Prevention Pays Program
Department of Natural Resources and
Community Development
P.O. Box 27687
512 North Salisbury Street
Raleigh, NC 27611
(919) 733-7015
Governor's Waste Management Board
325 North Salisbury Street
Raleigh, NC 27611
(919) 733-9020
Technical Assistance Unit
Solid and Hazardous Waste Management Branch
North Carolina Department of Human Resources
P.O. Box 2091 .
306 North Wilmington Street
Releigh.NC 27602
(919) 733-2178
Ohio
Division of Solid and Hazardous Waste Management
Ohio Environmental Protection Agency
P.O. Box 1049
1800 WaterMark Drive
Columbus, OH 43266-1049
(614)481-7200
Ohio Technology Transfer Organization
Suite 200
65 East State Street
Columbus, OH 43266-0330
(614) 466-4286
Oklahoma
Industrial Waste Elimination Program
Oklahoma State Department of Health
P.O. Box 53551
Oklahoma City, OK 73152
(405) 271-7353
Oregon
Oregon Hazardous Waste Reduction Program
Department of Environmental Quality
811 Southwest Sixth Avenue
Portland, OR 97204
(503) 229-5913
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Pennsylvania
Pennsylvania Technical Assistance Program
501 F. Orvis Keller Building
University Park, PA 16802
(814)865-0427
Center of Hazardous Material Research
320 William Pitt Way
Pittsburgh, PA 15238
(412) 826-5320
Bureau of Waste Management
Pennsylvania Department of
Environmental Resources
P.O. Box 2063
Fulton Building
3rd and Locust Streets
Harrisburg,PA17120
(717) 787-6239
Rhode Island
Ocean State Cleanup and Recycling Program
Rhode Island Department of Environmental Management
9 Hayes Street
Providence, RI02908-5003
(401) 277-3434
(800) 253-2674 (in Rhode Island)
Center for Environmental Studies
Brown University
P.O. Box 1943
135 Angell Street
Providence, RI 02912
(401) 863-3449
Tennessee
Center for Industrial Services
102 Alumni Hall
University of Tennessee
Knoxville.TN 37996
(615) 974-2456
Virginia
Office of Policy and Planning
Virginia Department of Waste Management
11th Floor, Monroe Building
101 North 14th Street
Richmond, VA 23219
(804) 225-2667
Washington
Hazardous Waste Section
Mail Stop PV-11
Washington Department of Ecology
Olympia, WA 98504-8711
(206) 459-6322
Wisconsin
Bureau of Solid Waste Management
Wisconsin Department of Natural Resources
P.O. Box 7921
101 South Webster Street
Madison, WI53707
(608)267-3763
Wyoming
Solid Waste Management Program
Wyoming Department of Environmental Quality
Herchler Building, 4th Floor, West Wing
122 West 25th Street
Cheyenne, WY 82002
(307)777-7752
WASTE EXCHANGES
Northeast Industrial Exchange
90 Presidential Plaza, Syracuse, NY 13202
(315)422-6572
Southern Waste Information Exchange
P.O. Box 6487, Tallahassee, FL 32313
(904)644-5516
California Waste Exchange
Department of Health Services
Toxic Substances Control Division
Alternative Technology & Policy Development Section
714 P Street
Sacramento, CA 95814
(916) 324-1807
U.S. EPA REGIONAL OFFICES
Region 1 (VT, NH, ME, MA, CT, RI)
John F. Kennedy Federal Building
Boston, MA 02203
(617) 565-3715
Region 2 (NY, NJ)
26 Federal Plaza
New York, NY 10278
(212) 264-2525
Region 3 (PA, DE, MD, WV, VA)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-9800
Region 4 (KY, TN, NC, SC, GA, FL, AL, MS)
345 Courtland Street, NE
Atlanta, GA 30365
(404)347-4727
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Region 5 (WI, MN, MI, IL, IN, OH)
230 South Dearborn Street
Chicago, EL 60604
(312) 353-2000
Region 6 (MM, OK, AR, LA, TX)
1445 Ross Avenue
Dallas, TX 75202
(214) 655-6444
Region 7 (NE, KS, MO, IA)
756 Minnesota Avenue
Kansas City, KS 66101
(913) 236-2800
Region 8 (MT, ND, SD, WY, UT, CO)
999 18th Street
Denver, CO 80202-2405
(303) 293-1603 -
Region 9 (CA, NV, AZ, HI)
215 Fremont Street
San Francisco, CA 94105
(415) 974-8071
Region 10 (AK, WA, OR, ID)
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-5810
76
* U.S. GOVERIMENT PRIMPING OFFICE: 1994-550-001/00178
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