United States Industrial Environmental Research EPA-600/8-78-010
Environmental Protection Laboratory May 1978
Agency Cincinnati OH 45268
Research and Development
&EPA First Annual
Conference on
Advanced Pollution
Control for the
Metal Finishing
Industry
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3 Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the "SPECIAL" REPORTS series This series is
reserved for reports targeted to meet the technical information needs of specific
user groups The series includes problem-oriented reports, research application
reports, and executive summary documents Examples include state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the results of major research and development efforts
This document is available to the public through the National Technical Informa-
tion Service. Springfield. Virginia 22161.
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EPA-600/8-78-010
May 1978
First Annual Conference
On Advanced Pollution Control
For the Metal Finishing Industry
PRESENTED AT:
DUTCH INN, LAKE BUENA VISTA, FL
JANUARY 17 - 19, 1978
Co-sponsored by:
• The American Electroplaters' Society
• The United States Environmental Protection Agency
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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This report has been reviewed by the Industrial
Environmental Research Laboratory, U. S. Environ-
mental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents neces-
sarily reflect the views and policies of the U. S. Environ-
mental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement
or recommendation for use.
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Foreword
When energy and material resources are extracted,
processed, converted, and used, the related pollutional
impacts on our environment and even on our health often
require that new and increasingly more efficient pollution
control methods be used. The Industrial Environmental
Research Laboratory-Cincinnati (lERL-Ci) assists in
developing and demonstrating new and improved
methodologies that will meet these needs both efficiently
and economically.
These proceedings cover the research papers and
discussions of the "First Annual EPA/AES Conference
on Advanced Pollution Control for the Metal Finishing
Industry." The purpose of the conference was to inform
industry on the range and scope of research efforts
underway at lERL-Ci to solve the pressing pollution
problems of the metal finishing industry. It is hoped that
the content of the conference and the subsequent
proceedings will stimulate industry action to reduce
pollution by showing through government-sponsored
research at lERL-Ci that viable control options are
available. Further information on these projects and
other metal finishing pollution research can be obtained
from the Metalsand Inorganic Chemicals Branch, IERL-
Ci.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
iii
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Table of Contents
INTRODUCTION
George S. Thompson, Jr. and J. Howard Schumacher, Jr 1
CONCLUSIONS OF 1ST ANNUAL CONFERENCE 2
SESSION I
KEYNOTE AND REGULATORY
KEYNOTE ADDRESS
Stephan J. Gage and Steven R. Reznek 3
FUTURE WATER POLLUTION CONTROL REGULATIONS
Robert B. Schaeffer 7
FUTURE AIR POLLUTION CONTROL REGULATIONS
Don R. Goodwin 10
THE EPA SOLID WASTE MANAGEMENT PROGRAM
John Dickinson 13
EPA ACTIVITIES UNDER THE TOXIC SUBSTANCES CONTROL ACT
John B. Ritch, Jr 15
SESSION II
AIR POLLUTION CONTROL
OVERVIEW OF THE EPA R&D PROGRAM FOR AIR POLLUTION CONTROL IN THE METAL FINISHING INDUSTRY
Charles Darvin 19
EVALUATION OF LOW SOLVENT EMISSION DECREASING SYSTEMS
Richard Gerstle, Vishnu S. Katari and Robert L. Hearn 22
HEAT RECOVERY FROM ORGANIC VAPOR INCINERATION
Thomas Ponder 26
SESSION III
WATER POLLUTION CONTROL
OVERVIEW OF THE EPA R&D PROGRAM FOR WATER POLLUTION CONTROL IN THE METAL FINISHING INDUSTRY
Mary K. Stinson 34
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THE FEASIBILITY OF GROUP TREATMENT OF MULTI-COMPANY PLATING WASTES
Marsha Gorden 40
ELECTROCHEMICAL REMOVAL OF TRACE METALS FROM METAL PLATING WASTES
WITH SIMULTANEOUS CYANIDE DESTRUCTION
Ian Kennedy and Dr. S. Das Gupta 49
A COMPARISON OF HYDROXIDE AND SULFIDE PRECIPITATION FOR THE REMOVAL
OF HEAVY METALS FROM WASTEWATER
Allen K. Robinson 59
EVALUATION OF ADVANCED REVERSE OSMOSIS MEMBRANES FOR THE TREATMENT
OF ELECTROPLATING WASTES
Dr. Kenneth McNulty, Peter R. Hoover and Robert L. Goldsmith 66
CORROSION-RESISTANT COATINGS WITH LOW WATER POLLUTION POTENTIAL
Christian D. Staebler, Jr., Bonnie F. Simpers and Hugh B. Durham 76
EVAPORATIVE RECOVERY IN ELECTROPLATING
Howard S. Hartley 86
PROCESSES FOR HEAVY METAL REMOVAL FROM PLATING WASTEWATERS
R. E. Wing 92
SESSION IV
SOLID WASTE CONTROL
AN OVERVIEW OF THE SLUDGE DISPOSAL PROBLEM
Paul S. Minor 107
MINIMIZING THE GENERATION OF METAL-CONTAINING WASTE SLUDGES
Fred A. Steward and Leslie E. Lancy 110
RESEARCH ON IMPOUNDMENT MATERIALS
Robert E. Landreth 115
CONTROL OF POLLUTION FROM LEACHATES
P. Chan, J. Liskowitz, A. J. Perna, R. Trattner and M. Sheih 121
THE EFFECTIVENESS OF FIXATION TECHNIQUES IN PREVENTING THE LOSS OF CONTAMINANTS
FROM ELECTROPLATING WASTES
Philip G. Malone, Richard B. Mercer and Douglas W. Thompson 130
vl
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Introduction
The U. S. Environmental Protection Agency's Metals
and Inorganic Chemicals Branch and the American
Electroplaters' Society have jointly designed a three-day,
broad-scoped conference. This conference, entitled "The
First EPA/AES Annual Conference on Advanced
Pollution Control for the Metal Finishing Industry," was
held on January 17-19, 1978, at Lake Buena Vista,
Florida. The conference's primary purpose was to
develop a dialogue between various key members within
EPA and the metal finishing industry. Focus was placed
on the air, water, and solid waste aspects of pollution
control for this industry. The proceedings from this
conference are contained within this EPA publication.
The program of this first annual conference was
broken into three distinct segments: regulatory, R&D,
and an exchanging viewpoint segment. The primary
purpose of the first segment was to provide all conference
participants with a detailed understanding of EPA's
current and future regulatory impacts on the metal
finishing industry. Key EPA officials, representing the
Effluent Guidelines Division (water), the Office of Air
Quality Planning and Standards (air), the Office of Solid
Waste (solid waste), and the Office of Toxic Substances
(toxics), described the various legislation by which EPA
prepares and promulgates regulations. Each speaker, in
turn, provided the audience with the current status of air,
water, solid waste, and toxic pollutant regulations, with
special emphasis on their direct impact on the metal
finishing industry. The second segment was divided into
three areas: research and development addressing air
pollution control, water pollution control, and solid
waste pollution control. Various EPA- and industry-
sponsored programs addressing these three media were
presented to provide the audience with a better
understanding of the significant research and
development activities. The third segment, exchanging
viewpoints, was conducted during an evening session. An
EPA /industrial panel comprised of EPA officials and
industry representatives opened the floor to a free
discussion. The primary purpose of this third segment
was for EPA to develop a clear understanding of the
research needs considered by the industry to be most
important. These research needs became evident during
the open discussion between the audience and the panel.
This conference, having been attended by over 500 men
and women interested in the air, water, and solid waste
problems associated with the metal finishing industry,
was considered by many to be a complete success. The
primary purpose of the conference, to develop an open
dialogue between industry and EPA, was achieved. The
highest priority research needs of the industry were
brought out during the three-day conference and
solutions are jointly being sought by EPA and AES.
The proceedings of this conference have been
published in order that the benefits gained from this first
annual conference can be disseminated among as many
people as possible who are interested in solving the
intricate pollution problems associated with metal
finishing. These proceedings contain the regulatory
presentations made by the representatives of the four
regulatory groups affecting the metal finishing industry,
as well as the research and development presentations by
various parties actively conducting research and
development programs to solve these same multimedia
problems.
The EPA and the AES hope that these proceedings are
distributed as widely across the metal finishing industry
as possible so that many parties involved in metal
finishing can be made aware of the impacts of this
conference.
George S. Thompson, Jr.
Chief
Metals & Inorganic Chemicals Branch, EPA
J. Howard Schumacher, Jr.
Executive Director
American Electroplaters' Society, Inc.
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Conclusions of
1st Annual Conference
A survey of conference attendees showed that the most
outstanding feature of the conference was the face-to-
face interaction between the Industrial and the
Environmental Protection Agency staffs in an
atmosphere of jointly attacking the technical problems
associated with providing full environmental protection
—while maintaining the efficient use of limited technical
and capital resources.
A consensus was reached that there are specific
problems for which additional R&D can help provide
relief:
I. The disposal of residues from wastewater treatment
is a continuously growing problem. There is inadequate
data to determine the field conditions under which the
waste is actually hazardous. Engineering data suitable for
designing safe disposal sites is almost non-existent, much
more scientific and engineering effort should be focused
in this area.
2. The accuracy and precision of the standard method
for determining levels of cyanide amenable to
chlorination are in doubt. This information could be
important in determining if plants are meeting effluent
standards. It was suggested that the AES work with EPA
in quantifying the accuracy of this method in
electroplating wastewater.
3. There is a need for the continual transfer of R&D
results to the industry.
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KEYNOTE ADDRESS
Stephen J. Gage*
Presented by Steven R. Reznek**
I realize that most of you probably think that all of
EPA is dedicated primarily to the regulation of
environmental pollutants. Actually, however, EPA is a
mix of organizations with varied responsibilities. In my
brief time today 1 would like to give you —without using
organization charts, or hopefully, any bureaucratic terms
— an idea of just what the EPA Office of R&D is trying to
accomplish.
I hope to convince you that our efforts can be helpful to
metal finishers as well as to the Nation. 1 would also like
to enlist your help in assuring that our efforts are
practical and useful.
To give you an idea of the overall EPA R&D program,
we currently run a $250 million a year business. Our job
within the Agency is "research, development and
demonstration" — not "regulation or enforcement."
While we are a separate organization within EPA — I
report to the Administrator — the Office of Research and
Development does however, support the basic regulatory
mission of EPA. It does this by developing the scientific
and technical knowledge and tools needed for protecting
the environment in the most effective way, with as small
an impact on the economy of the nation as is possible.
Although it is easy to say that we will develop scientific
and technical information and methodologies, we all
know that in real life we never are fully prepared but
rather are forced to go forward with less than absolute
certainty. There is no doubt that, under the very
necessary pressures to expedite actions to control the
more obvious and severe environmental problems, we
have been forced, in many cases, to devise remedies
without having all the tools needed for the most cost-
effective solution. When this happens, both the regula-
tors and the regulated are put in an awkward position
where the nation's resources are not as wisely managed
as they have been if all the scientific and technical
information were available to the decision makers. In
view of the large investment this country is making to
improve the environment — it is the largest non-military
expenditure in our history — it is important that every
Stephan J. Gage, Acting Assistant Administrator
Office of Research & Development
U. S. Environmental Protection Agency
"Steven R. Reznek, Acting Deputy Assistant Administrator
Office of Energy Minerals and Industry
Office of Research and Development
U. S. Environmental Protection Agency
effort be made to assure that these resources will be well
managed. This is part of our task in ORD.
The R&D activity is divided into several categories
(Slide 1).
Scientific Basis for Assessment and Enforcement
The first item —developing the scientific basis for
environmental criteria — is an essential task if the nation
is to utilize its resources where they are most needed.
The major concern in establishing environmental
criteria is, of course, health effects. Once a pollutant has
been shown to have an adverse health or environmental
effect, we must try to understand how it moves through
and interacts in the physical environment so that it can be
adequately controlled in the most effective manner. The
basic question, "How much of Compound X will cause a
degree of environmental or health harm?" must be
answered.
Approximately half of our R&D budget is devoted to
studies which we hope will lead to safe but not
unnecessarily restrictive pollution control standards that
can be applied at the appropriate point. This is a
tremendously complex task. To derive optimum
standards requires a thorough and sophisticated
understanding of health, ecology and economy — a
challenge which, in most cases, may actually be beyond
our capabilities in the near term.
Therefore, to be safe, broad, general controls are being
applied to the release of pollutants known to be harmful
to health or environment. This has led to the practice of
applying technology-based standards, that is pollution
control regulations that are based on the demonstrated
capability of technology to control pollutants rather than
on a detailed understanding of the harm a particular
pollutant can cause. I know that many industrial
representatives feel that technology-based standards
waste resources since they can result in overdesign in
some instances — just as industrial facilities are
sometimes overdesigned when there is less than a
SLIDE 1
R&D Activities
• The Scientific Basis for Environmental Criteria
• Measurement Methods for Assessment and Enforcement
• Technology Assessment
• Cost-Effective Pollution Control Technology Development
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desirable amount of data available. As we develop a
better base of scientific data on the behavior and effects
of pollutants in the environment, then future control
methods can be applied more selectively, while still
providing adequate protection.
In essence, then, the studies aimed at obtaining a
scientific basis for environmental criteria are an attempt
to develop information that can eliminate overkill in
regulations as well as require tighter regulations to
protect public health where appropriate. These studies
are pointing to more science and less speculation in
environmental decision making.
Measurement Methods for Assessment and Enforcement
Unless you have the methods to measure the presence
of pollutants in the environment, there is very little
possibility that an adequate scientific understanding of
environmental and health impacts will be obtained. In
addition, it is important that in controlling pollutants, we
must know the sensitivity and limits of detection of our
measurement techniques.
As you will be hearing shortly, the recent emphasis on
addressing the presence of the 129 "priority pollutants" in
industrial wastewaters has given very real urgency to this
aspect of our research program. Also, as many of you are
aware, there is a strong need for less expensive analytical
tools that will allow the required information to be
obtained without placing an obvious analytical burden
on those being regulated. All of these requirements are
addressed by the second item of our responsibility list —
the development of measurement methods for
assessment and enforcement.
Once again, this is not a simple task; it forces EPA to
the forefront in chemistry, physics, and statistical
techniques. In the assessment of potential environmental
damage, for example, not only must we detect the
primary pollutant, but we must be prepared to measure
its decomposition products — and all of this usually must
be done in the presence of potential interfering
compounds. Analytical work of this character is not
routine.
Measurement methods used for enforcement, on the
other hand, must often emphasize simplicity and low cost
since such methods are typically performed in thousands
of plants across the country. In addition, such relatively
simple analytical techniques are required to give
meaningful results in different types of wastewaters
containing a variety of possible masking or interfering
compounds. Air emissions, in addition to the analytical
burden, place a very heavy demand on sampling
technology. The accuracy and limits of detection
associated with each method must be fully understood to
avoid false indications of violations and to avoid missing
dangerous amounts of pollutants.
Technology Assessment
One of the most important types of information
needed for both a standard-setting and research and
development program is a thorough knowledge of both
the capabilities and cost of existing technologies when
applied to impending problem areas. Unrealistic views of
technology (either optimistic or pessimistic) either waste
resources or miss opportunities. As the nation begins to
rely on the widespread application of advanced
technologies in the energy area, for example, a realistic
understanding of these capabilities is essential. We are,
therefore, placing great emphasis on technology
assessment, in which the technological capabilities are
evaluated by those thoroughly familiar with their
projected application.
For example, the energy crisis is expected to bring
changes to manufacturing processes, both in the fuels
and, in some cases, the raw materials used. New energy
technologies — some of which have potentially serious
new environmental effects — will likely be introduced in
the coming two decades. We are attempting to evaluate
those problems while the technology is still in the pilot
stage so that the hardware development progresses with
environmental considerations fully in mind.
This type of evaluation leads to what we are calling
"anticipatory research," which simply means that our
goal is to improve our evaluation of R&D needs so that
information is available when needed.
Eventually, we hope to reach the point where "panic"
environmental situations — the so-called "pollutant of
the month syndrome" — are minimized because we will
have an improved knowledge of the capabilities and
effects of the technologies we are using. As much as
possible we want to avoid the cases where contradictory
data leads opposing sides of an issue to cite studies
leading to opposing conclusions. Unfortunately, we will
probably never see these situations completely
eliminated. It is impossible, or at least impractically
expensive, to do the work required to anticipate all
problems in every new technology in the development
stage. We do hope to avoid the situation where
environmental doubts begin to creep into the application
of a technology after hundreds of millions of dollars have
been committed to or spent on development. This is just
good engineering sense. Once again, it requires a high
level of technical competence and close attention to the
detailed practical aspects of technology.
Cost-Effective Pollution Control Technology
Development
Of course, even a complete and authoritative
understanding of the science behind environmental
standards, combined with perfect measurement methods,
is not of much use unless something can be done to
control the pollution. It is pollution control technology
that finally cleans up the environment. In the eyes of the
metal finisher, this is the major direct cost of
environmental protection. I heard this thought put
another way by an industrialist — "It's where EPA's costs
stop and industry's begin." This is not exactly true,
however, since we do have an interest in seeing that
industry does have good, reliable technology that is as
inexpensive as possible. As a matter of fact, about half of
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the entire R&D budget is related to assessing and
developing control technology. EPA realizes that there
are only so many resources available to the nation, and
the less expensive the technology, the more widely it can
be applied.
This conference is specifically designed to keep you
informed of the results of the control technology
development efforts in the metal finishing industry. The
metal finishing industry, by the way, receives a significant
portion of our industrial pollution control budget. As
you will see, we are encouraging the development of
technology that can be broadly applied at a reduced cost,
either in capital or in energy.
I feel that we have become increasingly sophisticated in
our analysis of pollution control technology because of
our recent efforts to address the interrelationships of air,
water, energy, and solid waste of each problem. In this
respect we often use the term "multimedia," a term which
you will hear quite often from EPA people in this
conference. It is a sign that we are becoming much more
sophisticated in our analyses.
We are also becoming more knowledgeable of the
many manufacturing processes, because we recognize
that reduction of pollution within the plant can be more
beneficial than that accomplished by end-of-the-pipe
controls. We also want to make sure that technologies
developed under EPA sponsorship are compatible with
established manufacturing practices. As any of you who
are in R&D, or technology development, know very well,
a new technology which requires major changes in
manufacturing practices is very difficult to sell.
Budget and Resources
With this background, let us take a brief look at how
EPA spends its R&D funds.
This next slide shows how our budget is divided. As
you can see, it is split about half for technology and half
for science. The science portion covers health effects,
ecological effects, transport and fate of pollutants, and
environmental monitoring.
The next slide shows how we have divided our
resources by category of problem. Energy-environment
problems consume a large portion of our effort. Note also
that there is a large interdisciplinary area.
Areas of Mutual Interest
I hope that I have been able to give you at least a rough
idea of what our R&D program is aiming for, and maybe,
at least, have convinced you that we are not in an ivory
tower — our goals are very practical and may be helpful
to you.
Having seen this very quick view of our R&D program,
a natural question might be, "Why should I cooperate
with EPA R&D? It will just mean more regulations." Let
us take these last few minutes and j ust explore the areas of
mutual interest to see if we can answer this question.
I think that both EPA and industry have learned that
standards and technology developed without an
understanding of the practical aspects of the industry
SLIDE 2
Relative Ord Resource Allocation By Disciplines
QUALITY ASSURANCE
& TECHNICAL SUPPORT
6.4°,
SLIDE 3
Relative R&D Resource Allocations
By Category of Emphasis
RADIATION
0.3%
involved will lead to wasted technical and financial
resources.
I think that originally many industry people thought
that if the technological knowledge of the regulatory
agency could be kept weak, it was more likely that weak
standards would be applied. This just has not proven to
be true.
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What can really happen with inadequate technical
knowledge is poor regulations that can have little
beneficial effect on the problem and a repressive effect on
industry. Good standards require a strong technology
base, and this must be obtained by the technical people of
both EPA and industry cooperating in the solution to
environmental problems. That is why the EPA Office of
R&D has assigned a significant portion of its budget for
technology assessment, which must be done in
cooperation with industry. That is why we have allocated
funds to co-sponsor research for technology develop-
ment with the American Electroplaters Society, the
National Association of Metal Finishers and others in
your industry. If we have good technology assessment
data, we can understand your problems and work toward
a solution.
In technology development, I know you are interested
in meeting your environmental requirements at lower
cost, with less energy use. We are interested in having you
do just that, and we will work with you to prove out
improved technology. We are looking for good projects
for mutual cooperation. In this conference I hope all of
you will make a personal effort to meet the EPA R&D
staff for the metal finishing area.
Summarizing, then, I think that any reasonable person
must recognize that there is a certain built-in conflict
between the regulators and the regulatees — yet, on the
other hand, we are all citizens of the same Nation trying
to resolve problems in the most efficient way. It is not to
anyone's benefit to see resources wasted. There is no
group of people better qualified to devise the most
efficient route to pollution control for the metal finishing
industry than those who are in this room. We have
formulated this conference as a first step toward making
you aware of our R&D program and are inviting your
present and future participation in it. We are very
appreciative of the American Electroplaters' Society's
effort in co-sponsoring the conference.
We hope that this is part of an increasingly cooperative
attitude which will lead to more efficient technology and
to better management of the nation's resources.
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Future Water Pollution Control Regulations
Robert B. Schaeffer*
When we talk about the future water pollution control
regulations, I am reminded of former Washington
Redskins Coach, George Allen's famous saying, "the
future is now." I want to talk today about what the
Agency is about to do with regard to proposing
pretreatment standards for the existing sources for the
metal finishing industry.
For those of you who may not have heard the standard
pitch, I would like to bring you up to speed with a bit of
history. As Howard Schumacher was discussing, the
1972 Act, Public Law 92-500, identified the
electroplating industry as one of the categories of
industry for which we were specifically required to
establish regulations. In March 1974 and again in April
1975 we did issue or propose some BPT and BAT
regulations as well as some pretreatment regulations.
BPT is our acronym for Best Practicable Control
Technology, which was to be met for direct discharges
into the Nation's waters by July 1, 1977. BAT, which is
Best Available Technology Economically Achievable, is
to be achieved by July 1, 1983, and the pretreatment
requirements are to be met 3 years from promulgation.
Because of the controversy associated with those first
regulations, the Agency withdrew them—actually
withdrew part and suspended other parts—in December
of 1976. The intent was to redo them, reassess the
information available, and initiate an additional data
collection effort. As a result of that effort, in July of 1977,
the interim final pretreatment standards, covering a
limited number of pollutants, were issued. These
controlled cyanide, hexavalent chromium, and pH.
These pretreatment regulations were in compliance with
the Consent Decree, which perhaps you are aware of, that
was signed in June of 1976.
The Agency signed this Consent Decree with some
environmental groups to settle four different law suits
that were brought against it. In the settlement, the
Agency agreed to establish standards for toxic pollutants
as defined under Section 307a of the Act. Now, these are
different than the other toxics. So that you don't stay as
confused as 1 am, we'll try to clear up the semantic
problem. The Administrator has the authority to
specifically identify pollutants without regard for the
economic feasibility of the regulations. Under Section
•Robert B. Schaeffer, Director
Effluent Guidelines Division
U. S. Environmental Protection Agency, Washington, DC
307a, limitations may be established strictly on toxicity.
Presently there are six of these regulations in existence
which deal primarily with pesticides and PCB's. Another
part of the Consent Agreement required the Agency to
establish water quality criteria for 65 pollutants and
classes of pollutants. The third lawsuit that was settled
was for the Agency to promulgate pretreatment
standards for eight industries—electroplating being one
of those industries. The July 1976 interim final
pretreatment regulations were issued to comply with the
last part of the Consent Decree.
The regulations we'll talk about in a little while are an
extension of that effort. There will be, however, a
continuing review of the discharges of the 65 pollutants
that 1 mentioned from the 21 industrial categories. You're
lucky again in that you're specifically identified as one of
those 21 categories. We will be reviewing the BAT
regulations, new source performance standards, and
pretreatment, which are to be reviewed and promulgated
specifically looking at the 65 pollutants and classes of
pollutants. These regulations will be issued by December
31, 1979.
Howard was talking about numbers: 21 or 65, and 128
and 129. We'll try to clear that up a little bit. The list of 65
pollutants includes a number of compounds, organic
materials, specifically, that are identified as classes of
compounds. In order for us to be very sure of what we're
looking at, we sat down with our scientists, our analytical
chemists, and the environmental groups and selected
representative compounds from the list of 65. In fact, we
expanded the list of 65 to 129. This includes 13 metals,
114 organics, cyanide, and asbestos.
In order to achieve the mission and the terms of the
Consent Decree, we are undertaking four studies. We will
continue to develop, with the assistance of our R&D
program and you folks, technology-based discharge
requirements. That is one of the studies that will be
undertaken. We are just beginning that study. We have
selected a contractor, one you're familiar with, Hamilton
Standard, and they will be continuing to work with us in
this area. The second study, which is very similar to what
we've gone through in the past, will cover the economic
impact and the costs of these technologies. We again will
look to you for help in assessing, (1) the cost and, (2) what
the impact might be.
The two other studies are a little bit different and are
going to help us in making a final judgment. The first is
the development of environmental criteria. Basically, I
guess it's a matter of how bad these pollutants really are,
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not only from a water standpoint but from an overall
health standpoint. That will be the third study. The
fourth I'd like to characterize as an environmental mass
balance. How does the pollutant get into the
environment? Where does it come from? Where is it
manufactured? What products does it use? How does it
get into the water? We will look at these other two studies
and it will help us make a determination as to what level
of technology is necessary to achieve the desired result.
Let me make an analogy. Suppose we were talking
about regulating a pesticide and we had the choice
between a 10-dollar technology and a million-dollar
technology. When we looked at our criteria studies, we
discovered that the pesticide was pretty bad and ought to
be kept out. However, a look at our environmental mass
balance study might reveal that if we imposed the million-
dollar technology, we might only be solving I percent of
the problem, because 99 percent of the problem would
come from agricultural runoff. We hope to be able to
apply both elements in making proper judgments when
we go into our BAT review.
As a result of the proposal that was issued last July, we
received many comments and have obtained additional
data. Therefore, instead of going final, which is a normal
progression in the establishment of regulations, we have
decided to repropose the regulations and to open them up
for an additional 60-day comment period. Hopefully,
today, or within the next few days, the Administrator will
sign this new proposed regulation and shortly thereafter
it will appear in the Federal Register. Today, however, I
will be able to tell you what it said when I left town. Until
it is signed by the Administrator it is subject to change.
The numbers that appear on these slides, which include
limitations for cyanide amenable to chlorination,
hexavalent chromium, lead, and cadmium, will apply to
discharges of less than 10,000gpd. Many comments with
regard to cyanide that we received after the proposal of
the interim final regulations reveal that metals removal
would have been required to achieve these cyanide levels.
In reassessing our data base, we found that interdispersed
in our numbers were some data points that were taken
after clarification. Therefore, we went back and obtained
additional data and reevaluated it.
This slide shows a daily maximum of 2 milligrams per
liter and a 30-day average of 0.8 milligrams per liter for
amenable cyanide. It also shows a hexavalent chromium
daily maximum of 0.25 milligrams per liter, and a 30-day
average of 0.09 milligrams per liter. The lead and
cadmium numbers are ones; frankly, that we are not too
satisfied with. We believe they ought to be more
stringent. We will be looking very carefully at lead and
cadmium in the next go-round. These numbers are based
on the data that was available to us. Lead and cadmium,
we believe, are particularly troublesome in the
environment and we want to move toward maximum
reduction of these materials. The numbers for lead are 0.8
for daily maximum, 0.4 for 30-day average; for cadmium,
1 and 0.5, respectively.
The cutoff point at a flow of I0,000gpd was chosen to
minimize the impact on the industry. In looking at the
various levels with the high impacts that are forecasted,
we chose this level in an attempt to minimize the impact
on the most sensitive portion of the industry. The
regulations are applicable to any firm that has an
electroplating or metal finishing operation—captive
shops, job shops—the same as has been in the past.
The next slide applies to all discharges greater than
10,000gpd, but these numbers apply to all subcategories.
There is a limitation left off for the precious metals;
however. The only precious metal we are presently
proposing to control is silver, and the number for silver
for a daily maximum will be 1 milligram per liter, and the
30-day average will be 0.34. For plants discharging more
than 10,000 gpd, we are adding limitations for total
cyanide, total chrome, copper, nickel, and zinc. Lead and
cadmium remain the same.
Let me try to explain total heavy metals. Many of you
use more than one line, plate more than one metal. Our
model technology, after precipitation, is solids removal.
The metals, after proper application of this model
technology, are contained mostly in the suspended solids
that are discharged. If you are plating only one metal, the
percentage of this metal in the suspended solids is
significant. If you are plating a number of metals, the
percentage of individual metals is reduced in the
suspended solids. When you are talking about
clarification, what you're trying to control is the
suspended solids level. So we have included individual
metals for those who plate only one metal. If you plate
more than one metal, two number will apply. As you see,
because of our data base and the application of our
statistical analysis, some of them may not always add up
to the total metal number, so the more stringent numbers
will apply. Later on this week we can get into much more
detail as to how this was derived and what we think it
might mean to you.
Table 1 is a very quick rundown of what the numbers
are.
Table 1
Metal Limitations in Discharges
From Electroplating Plants
Metal
Amenable Cyanide
Total Cyanide
Hexavalent Chrome
Copper
Nickel
Total Chrome
Zinc
Lead
Cadmium
pH
Silver
Total Metals
Daily
Maximum
0.2
0.64
0.25
4.6
3.6
4.2
3.4
0.8
1.0
30- Day
A verage
0.08
0.24
0.09
2.0
1.8
1.6
1.5
0.4
0.5
No Limitations
1.0
7.5
0.34
3.9
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I do want to show you another option that we want to
propose. We're doing this because of the dealings that
you may have or may want to have with your local
publicly owned treatment works. If a plant does not use
strong chelating agents that inhibit the precipitation and
removal of metals, if the plant uses lime as the
neutralizing agent and removes solids, we have
substituted a total suspended solids limitation for the
common metals and the total metals limitations. The
waste treatment plants are familiar with handling solids,
measuring suspended solids, and understanding it, and
we are proposing this approach in an attempt to reduce
your monitoring costs.
We still are including limitations on lead, cadmium,
cyanide, and hexavalent chromium, because cyanide and
hexavalent chrome need to be handled before good
metals removal can be achieved; and lead and cadmium
again are of primary concern to us. We are limiting p H in
this option from 7.5 to 10.0. In this option, the amenable
cyanide, the total cyanide, hexavalent chromium, the
lead, and the cadmium numbers are the same as stated for
the earlier limitations. The only addition or substitution
is a limitation of a daily maximum of 15 milligrams per
liter of suspended solids and a 30-day average of 10
milligrams per liter of suspended solids, which was
substituted for the copper, total chrome, nickel, and zinc
limitations. You will notice that in this option we are
specifying the technology to be employed and are
presenting it as an option, if it is adopted, so that you can
choose the approach for treatment that you wish to take.
The Agency has been very concerned over the high
economic impact that is predicted in this area and on this
industry. That is part of the reason that we're almost a
year late with these standards and the reason we are
reproposing them. Much work has been done to look for
ways to mitigate this economic impact. The reason being,
in addition to the concern over the impact, that these
particular pollutants are also of great concern. The
regulations that will be adopted will contain considerable
verbage and they will discuss ways that the Agency seeks
to mitigate the high impact.
There have been high-level Agency discussions
between EPA and the Small Business Administration
(SBA) to make their disaster loan program more
accessible. The regulations will identify individuals in
each of our regional offices who have the responsibility as
the SBA coordinator. They will also identify the local
individual in SBA who is responsible for their loan
program in that geographical area.
We hope that we will be able to provide more such
informational dissemination type seminars around the
country to help folks at the local level through the red
tape and paperwork that we're trying to minimize if the
use of an SBA loan is appropriate. There are other means
that we are looking at and that is part of the reason why
we established, back last July, the interim final
regulations for only a few of the pollutants. That is why
we are reproposing again here and that is why there is up
to 3 years for compliance. We are trying to phase this to
minimize the impact.
We have found that this industry does not necessarily
follow the same characteristics as all of the other
industries in that the job shops, because of their size, are
impacted the most, and the indebtedness of a particular
company also can influence the impact. We would
appreciate any thoughts that you have on further things
that we might do to help along these lines.
With all that we've been talking about since 1972, from
the outset there has been a general agreement between
EPA and the industry associations as to what the
applicable technology is. For some 5 years we have been
discussing what that technology will produce in the way
of effluent limitations. The numbers I have given you
today reflect the data that we have available to us. There
will still be some concern, I'm sure, and we will still be
open to discussion on these particular numbers.
That pretty well covers where we are. 1 had thought
and had hoped that I would have regulations in hand,
enough for everybody, when 1 spoke here. 1 do apologize
for the fact that we haven't processed them through the
Agency as yet, but one good reason is the basic concern
for putting out good regulations. 1 hope that our
discussions over the next couple of days prove fruitful;
and if there is anything that I or Dev Barnes, the project
officer, can do to assist or give you information, we'd be
happy to.
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Future Air Pollution Control Regulations
Don R. Goodwin*
I was pleased when I was invited to participate in this
work seminar and to discuss with you EPA's air pollution
control program as it relates to the control of emissions
from the coating of metals products. The core of the
problem, as has been mentioned previously, is photo-
chemical oxidants. The emissions from your industry —
hydrocarbons — generally are not considered pollutants.
It is what they become that brings the regulatory process
to bear, because in the presence of sunlight, volatile
organics react with other pollutants to form photo-
chemical oxidants or smog, as we have come to know it.
This smog is known to cause many adverse health effects.
Among them the aggravation of heart and lung disease,
particularly among the elderly, including aggravation of
asthma, coughs, chest and eye irritation, and headaches.
An analysis of all the medical data in the late 1960'sled
EPA to promulgate an ambient air standard for oxidants
in 1971. This standard is 0.8 parts per million for a
maximum 1 hour concentration, not to be exceeded more
than once per year. With this ambient standard came a
need to curtail the release of hydrocarbons and other
Volatile Organic Compounds (VOC), which are
precursors of photo-chemical oxidants. In comparison to
the current levels of oxidants in the atmosphere of our
major cities, the national ambient standard is extremely
tight.
Despite a major effort over the past few years to reduce
VOC emissions from automobiles and stationary
sources, most metropolitan areas of the country now
experience oxidant levels well in excess of the national
ambient standard. The standard, therefore, has led to a
great deal of controversy in the past few years. There have
been complaints by States and a consequent lack of
action because they believe the standard to be
unattainable with what they feel were reasonable
regulations.
The industrial community has also suggested that the
standard cannot be achieved and therefore must be
relaxed. In addition, they have pointed to problems of
natural backgrounds. In response to these allegations,
EPA has conducted an extensive review of the standard
and intends to announce the results of this review in
March of 1978. The results could be a reaffirmation of the
present standard or proposal of a less restrictive, or even
a more restrictive standard. Preliminary information that
*Don R. Goodwin
Director, Emissions Standards & Engineering Division
Research Triangle Park, U. S. Environmental Protection Agency
Durham, North Carolina
1 have seen does not show a justification for a major
revision of the standard.
Since the original state implementation plans were
submitted by the states, EPA and state agencies have
been collecting ambient air network data. There is no
doubt these regulations did not achieve the national
health standard for some basic reasons. To name just a
few:
• The regulations were not sufficiently restrictive.
• We did not understand the impact of reactivity and
transport.
• Many sources were not identified in the regulations.
What the marketing also shows is that transportation
related emissions have been dropping as automobile
controls have been imposed, but stationary source
emissions have not been reduced appreciably. At present,
approximately half of the air quality control regions in
the nation are exceeding the standard, in some cases by a
factor of two or three. In addition, oxidants or oxidant
precursors are being transported out of urban areas, with
the result that the oxidant standards are being exceeded
in rural areas almost as regularly as in urban areas.
Obviously, the strategies in effect were not sufficient
and EPA, therefore, was required to direct a number of
states to revise their state regulations. This situation was
addressed by the Congress when they modified the Clean
Air Act Amendments in August 1977. Under the revised
Act, states are required to submit new plans for all non-
attainment areas on January of 1979 — most
metropolitan areas are presently classified as non-
attainment for oxidant. The Act further requires that the
revised state regulations be designed to achieve the
ambient health standard by December 31,1982. It further
stipulates that if a state demonstrates that such attainment
is not possible by 1982, despite implementation of all
reasonably available measures, an extension may be
granted, provided that compliance is achieved as
expeditiously as practicable but not later than December
31, 1987.
It is in the area of all reasonably available controls that
I am here today to discuss what the surface coating
industry and other stationary sources will have to
accomplish over the next few years to meet these
anticipated state regulations. If we look at the first
viewgraph we can see that VOC are released from a
variety of stationary sources as well as motor vehicles.
Approximately 17 million metric tons from stationary
sources are principally traceable to the refining of
petroleum, the manufacture of organic chemicals, the
10
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distribution of gasoline, waste combustion, and the
evaporation of solvents. We note too that no single
source category dominates the list; however, approxi-
mately 2.5 million tons or about 15 percent of stationary
source emissions are generated from the application of
industrial and architectural coatings and related
operations.
This next slide gives you an approximate breakdown
of the thousand metric tons annual emissions from
industrial surface coatings, in such industries as large
appliances, magnetic wiring, automobiles, cans, coils,
paper, fabrics, metal furniture, wood furniture, flat
wood, miscellaneous metal products and the
miscellaneous sources. It comes to about 2 million tons
per year. Those are our approximate calculations of the
impact of hydrocarbon emissions from industrial surface
coatings.
The problem is extremely complex, and the technology
to control sources such as your own is also very complex.
EPA recognizes this problem, and in order to assist states
in assessing this difficult area we have been assembling
control technique guideline documents that review
control technology and costs for almost all principal
solvent emitting sources. To date we have released 10
documents covering sources of approximately 4 million
tons per year VOC. The documents released are
concerned with the petroleum industry, gasoline
marketing, solvent degreasing, and surface coating.
Additional documents are planned over the next year and
a half for the remaining significant sources. We hope to
cover most of the solvent coating industry by the end of
1978. Completed documents encompass surface coatings
for automobiles, cans, coils, paper, fabric, magnetic wire,
metal furniture, and large and small appliances.
This next slide is a brief rundown of what has been
completed and what is in preparation for your industry
for this year. The attempt here is to issue documents that
discuss the technology, give some information on the cost
and give the impact pro and con of the different types of
control technology. These will be made available to the
states, and it is their job to use this as a starting point to
develop their regulations. The plan is to issue these
documents to the states, and allow them one year in
which to submit the regulations.
These control technology documents, which have been
reviewed extensively in final draft stage by the industry
and by environmental groups and state agencies, are
concise, no-frills documents that review the processes
that generate VOC as well as principal control
alternatives and related costs and enforcement
procedures. They do not represent regulations in
themselves. But, they do give a perceptive, normal
emission limit for most sources and as 1 said, are
primarily designed to assist an energetic state technical
person in understanding the technology on which to base
his regulations. So far documents for the first five source
categories have been completed and issued to the states,
and regulations will be due under the state plans by
December 31 of this year.
These control technology documents for surface
coating generally express the emission limits in terms of
solvent mass per unit volume oi coating minus water. For
example, the presumptive limit for top coating of
automobiles is, under the new system, 0.34 kilograms per
liter, or if you are old fashioned like 1 am, it is 2.8 pounds
per gallon. The operator can meet this requirement by
employing a powder coating, a high solids coating that
contains no more than 2.8 pounds of solvent per gallon,
or a typical waterborne coating of 26 percent solids. If the
operator preferred, he could employ stack gas treatment
to achieve the equivalent emission level. It is also a fact
that these limits do represent VOC reductions of 65 to 90
percent compared to conventional coatings.
It is EPA's intent to specify these productive loadings
but not to require any specific control technology so that
the operator is free to choose his most cost effective
approach to achieve the recommended level. Most
installations will choose low solvent coatings, but some
operators may choose incinerators or adsorption because
of characteristics of their process. Some, of course, will
employ innovative application techniques on air
circulation possibly combined with stack gas treatment
or coatings of their immediate solvent content. And what
1 have been outlining so far is an assistance program to
state agencies which will, we hope, assist them in
understanding the technology of your industry and give
them some guidance. They have been pressing very hard
for guidance for a long time to develop reasonable state
regulations.
The second thing that happens is that we will take these
same technology documents and increase the content
considerably and turn them into what we call a standard
support document; that is a technical document
supportive of a national new source performance
standard. That is under Section 111 of the Clean Air Act
and is a regulation that applies only to newly constructed
sources. This documentation is much more detailed,
because the regulation must be based, to a large degree,
on technology availability and on the cost. Under the new
amendments, we also must give consideration to the
environmental impact.
Six months ago we would have assumed that low
solvent coatings would have been the choice to achieve
these reduced emission levels. Low solvent coatings save
sources energy and, by some predictions, save money
for the operator. Generally, we are disappointed with the
lack of acceptance of low solvent coatings method. We
hear many reasons why powder or high solids or
waterborne will not work for some specific applications.
For example, powder coatings are not, so the auto
industry reports, feasible for metallic paints. And 50
percent of our cars now have metallic paints. Also,
powder coatings will not produce the necessary thin film
and they are difficult to apply where frequent color
changes are necessary. Waterbornes are alleged to cause
costly paint line renovations, consume added energy, and
are untried in many products. High solid coatings often
cannot be formulated with sufficiently low level solids to
satisfy the anticipated regulatory requirements.
The task we face in advising the states, with your help,
11
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is sorting out the difficult from the impossible. EPA, in
spite of being able to hire some very qualified contractors
and with some very qualified personnel in house, will not
be able to match industry's expertise in paint formulation
application. We are making much progress, however.
One large automobile company recently proposed to
convert their entire industry to the equivalent of
waterborne in 10 years. Now 10 years is a long time, but
the program that they are proposing costs billions of
dollars and that is a giant step.
In summary then, the guideline documents will focus
on positive control of VOC and not substitution of
compounds of lower reactivity as was the case with the
Los Angeles Rule. The use of low solvent coatings is
emphasized, since they can have a marked and quick
effect on the VOC emissions. For example, an operator
using 30 percent by volume solids could reduce the
emissions by 60 percent by using coatings containing 50
percent solids. Even more dramatic reductions will be
realized by the users of highly diluted coatings, such as
lacquers. In this case, the operator now using 10 percent
solid lacquer could achieve an 88 percent reduction in
emissions by switching to the 50 percent solids enamel.
In the other two areas of control, that is incineration
and carbon adsorption, the progress also has been very
slow. Most of the incinerators in development today are
aimed at high efficiencies and most use heat exchangers.
Vendors report extremely high heat recoveries with con-
comitant minimal fuel inputs. In most instances, these
designs come with higher capital costs than conventional
incinerators, but promise substantial reductions in fuel.
Design improvements are even slower with carbon
adsorbers. The principal new innovation is a continuous
unit in which carbon is pneumatically transferred from
the adsorber to a stripping column. A few such units are
now being installed in this country. We anticipate that
adsorption will find increased usage, particularly in those
areas where the recovered solvent can be reused in the
process.
In conclusion, the solvent coating industry can expect
an increase in pressures to reduce the atmospheric
emissions of VOC. It is too early to tell whether industry's
needs will be met by basic processes and coatings changes
or by add-on, end-of-the-line hardware. In either case,
the challenge is presented to the technical community to
develop solutions rapidly in order to strike a balance
between energy, economy, and the environment.
12
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The EPA Solid Waste Management Program
John Dickinson*
I would like to do three things this morning. One, give
you a brief overview of Resource Conservation and
Recovery Act (RCRA); two, go specifically into
hazardous waste, which 1 think you will be most
interested in, and three, try to tell you specifically, how I
think it is going to affect you.
As you might know, on October 21, 1976, the President
signed the Resource Conservation and Recovery Act.
This is really in update of the Solid Waste Act of 1965 and
the Resource Recovery Act of 1970. The major objectives
of this Act are to regulate hazardous waste, to make sure
that non-hazardous waste is disposed of in an
environmentally sound manner, to promote
comprehensive solid waste planning, and to promote
resource conservation and recovery; thus, the name.
I would like to look now at why the Resource
Conservation and Recovery Act was needed. It was
actually needed to complete the conirol loop. Substances
removed trom the air and water in many cases are going
to the land, and there was no control of these hazardous
residues. In addition, there has been considerable
damage caused by this lack of control, so Congress
wanted to close the loop.
I would like to look at the definition of solid waste that
Congress gave us to work with. The term solid waste
means any garbage; refuse; sludge from a waste treatment
plant, water supply treatment plant, or air pollution
control facility; and other discarded material, including
solid, liquid, semi-solid, or contained gaseous material
resulting from industrial, commercial, mining, and
agriculture operations.
I would like to look at the term disposal, which means
discharging, depositing, injecting, dumping, spilling,
leaking, or placing of any solid waste or hazardous waste
into or on any land or water so that this material may
enter the environment. So it is a very comprehensive
definition, a very comprehensive Act.
First, 1 would like to look at non-hazardous waste for a
moment. Assume that your waste is not hazardous. What
happens to it? Well, EPA is maintaining indirect control
through State plans. For hazardous waste, EPA is in
direct control. The key is to work with the State Directors
and develop a State Plan. This is a very weak
enforcement plan for non-hazardous waste. Mainly,
"John Dickinson
Coordinator, Solid Waste Section, Region IV
U. S. Environmental Protection Agency
Atlanta, Georgia
what we do is define what a sanitary landfill is. (These
criteria are out in draft form now, and they are to be
promulgated shortly.) Everything that does not fit the
definition of a sanitary landfill is an open dump, and they
are illegal. The State Plan must show how these open
dumps are going to be closed. The municipalities or
person operating an open dump can obtain a compliance
schedule up to 5 years to either up-grade an open dump or
close it.
One of the first things EPA is required to do is develop
an inventory of all open dumps. With the way solid waste
is defined, you can imagine how difficult this will be,
because this includes industrial impoundments, lagoons,
anywhere you dispose of solid waste.
Our first priority is to develop a municipal open dump
inventory by working with the States. Thus this will not
affect industry right away. Possibly, in the future EPA's
safe drinking water people will do an industrial
impoundment assessment, so we feel that the industrial
part of the inventory will be sometime in the future. So,
if your community were operating an open dump, it
would go on this inventory and be published in the
Federal Register with a compliance schedule.
Now we feel that by closingthese cheap open dumps we
will promote resource conservation recovery. In addition
to closing open dumps, we have resource recovery panels,
which will be used for doing a lot of studies. These studies
will cover plastics, sludge, and such similar things. We are
also going to require the States that receive our money to
buy a maximum amount of recycled material. In short,
we are closing the open dump and we are trying to
improve the market for secondary materials. We also are
going to try to make the information available to the
public, because we feel as though public education is one
of the big things in municipal solid waste and recycling.
Now let's look at hazardous waste. Section 3001 of
Sub-title C answers the question of what is a hazardous
waste. The way EPA will apply this is in utilizing criteria
and lists, such as flammability, corrosiveness,
radioactivity, biochemical activity, and carcinogenicity.
We have a whole list of things that are bad.
There are two bad aspects: one is transporting
hazardous waste to the disposal site; second, after you get
them to the disposal site, what happens to them? You will
be concerned with both of these, since you might be
treating or disposing on site. So the first thing you do is
determine if your waste is hazardous. EPA has agreed to
help your industry on this, and we have said, based on our
knowledge of the criteria, we feel like water treatment
13
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sludge (and this is not in the promulgated Federal
Register, this is just in the draft stage) from the
electroplating industry is hazardous, based on its
toxicity. If you wantto be removed from the list of those
disposing of hazardous waste, you must go through
toxicity tests and show us that your waste is not toxic.
That is the way the regulations are headed right now.
If you have hazardous waste, what do you have to do?
For one thing, if you generate hazardous waste you do
not need a permit. The Congress specifically did not want
generators to need to obtain a permit. But once you
generate hazardous waste, then Congress wants us to
work with you to make sure it is properly handled. So, the
next set of regulations will be Section 3002, which will be
generator standards. This basically says that you have to
fill out a manifest if you want to ship your waste off site.
This manifest is given to the transporter, who takes it to a
facility with a permit to store hazardous waste. A copy of
the manifest is returned to you stating that the waste has
been received. Then you report to EPA each quarter that
there are no disposal problems. But, you must supply a
list of all the loads of waste and where they went. That list
is compared to a list supplied by the disposal man. If you
store for over 90 days, you must obtain a storage permit.
If you dispose on site, you must obtain a disposal permit.
But we are allowing industry 90 days to accumulate an
economic load of waste before a permit is necessary, but
you will still have to fill out the manifest.
The next set of regulations will cover transporters.
Although this is of little interest to you, I will cover it
briefly. It says the transporter must follow DOT
regulations; he must take the manifest, sign that he has
received a load; ship it according to DOT regulations;
and assure that it reaches only a permitted hazardous
waste treatment storage or disposal facility.
Let me return to the criteria for a moment. The main
thing you will be interested in is the toxicological
properties of your waste. Is it toxic?
The next important part is the standards. If you decide
to treat or dispose on site, the next regulations say,
basically, you must protect the air, ground water, and the
surface water. (This is the first draft of Section 3004,
Draft Regulations.) It says that you have to collect all
water from your disposal site, you must obtain a NPDES
permit, and you must insure that no contaminants get to
the ground water. It is written so that there is no
degradation of the ground water, no endangerment, this
is a technical term. I won't get too deeply into that, but
there are specific standards that you must meet if you
want to treat, store, or dispose on site, and these
standards have been issued. You can obtain a copy of
these if you want or you can work through the society.
Section 3005 of the Act describes how to obtain a
permit. Basically it says that you must meet these
standards and it provides all the details on getting that
permit; it is like all your other permits, you have to go
essentially to the same steps to get your permits.
An important part of the Act to metal finishers might
be Section 3006 that deals with State programs. It says—
and it's EPA's intent—to let the States run the hazardous
waste program if they are equivalent to the Federal
program. They can be more stringent, but not less
stringent. The Act lets EPA give a state interim
authorization for up to 2 years in which time they must
bring their program up to Federal standards. So it has
been EPA's conviction that the State can do a better job
of running a hazardous waste program as long as they
meet national standards that apply to everyone. So,
Section 3006 will be encouraging States to run waste
programs.
Finally, you might ask, what is the first thing I've got to
do under this Act? The first step comes under
notification. What E PA will do is mail you a letter saying
we have reason to suspect that you have hazardous waste
and this is to help you notify us. You can fill in the blanks
— a very brief form — and send it back to us. Unless you
notify us, you cannot treat, store, or dispose of hazardous
waste. So it is very important that you notify EPA that
you have hazardous waste that you are generating,
transporting, treating, storing or disposing of. When is
that going to be? Our regulations were due, all of them, in
April 1978. It looks like it's going to be summer or
possibly fall before some of these get out. So late this year
or early next year, you will receive this letter.
We have talked about Sub-title C regulations, and as
we've tried to indicate where it will affect you and how it
will affect you. 1 know you don't want to have a
hazardous waste, but in order to get off EPA's list, you
will actually have to test.
Thank you.
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EPA Activities Under The Toxic Substances Control Act
John B. Ritch, Jr.*
The Toxic Substances Control Act is now a little over a
year old — yet, thus far little direct effect has been felt. In
fact, from my vantage point it appears that many persons
and firms which deal with chemical substances are just
now learning of the Act's existence and the breadth of its
eventual impact. However, on January 1, 1977, when this
Act became effective, a whole new perspective for the
chemical industry was launched.
We live in a world of chemicals — in the clothes we
wear, in the food we eat, in the air we breathe. It is
estimated that there are between two and three million
known chemical compounds with some 30-40,000 in
commercial production. Several thousand new ones are
discovered each year and several hundred of these
channel into commercial use. Obviously this means that
much of our technical skill is devoted to finding and
developing new chemical substances to afford us a higher
standard of living. It has been this way for many years. So
why have we suddenly become concerned about chemical
substances?
In reality, this is not a sudden concern. Just as our
technology has advanced in the plastics field, the
elastomer field, and the plating field, so has our
technology advanced in the pathology field. Over a long
period we have been learning that while there are great
benefits to be derived from the uses of these substances,
some of the substances also pose severe health risks.
Several studies, especially in the last two decades, have
equated chemical substances with both immediate and
long-term health dangers, as well as severe ecological
damages. These equations led to the regulation of
radiation in the 1950's, followed by further
environmental legislation dealing with air and water
pollution, pesticides, and solid waste disposal. All of
these regulatory actions deal in some degree with the
control of certain chemical substances which might
create either human health or ecological problems. Yet,
Congress felt it necessary to enact TSCA. One could say
this closed a loop.
TSCA came about because there are significant
differences between the environmental contaminants
that have been the focus of air and water pollution
control efforts and the ones that have more recently been
in the headlines—PCBs, PBBs, vinly chloride, kepone,
•John B. Ritch Jr., Chief
Industrial Assistance Branch
Office of Toxic Substances
Environmental Protection Agency, Washington, DC
chloroflurocarbons, and others.
Take air pollution control, for example. Through most
of the 40 to 50 years that any real effort has been made to
reduce air pollution, that effort has been focused on
pollutants, such as paniculate matter, carbon monoxide,
sulfur dioxide, and nitrogen oxides. These pollutants are
by-products, entering the environment entirely through
tailpipes and smokestacks.
Now, take one of the substances recently in the
headlines—polychlorinated biphenyls-PCBs. These are
not by-products of combustion or industrial processes.
They are commercial chemicals. They have been
produced, distributed, sold, used, and discarded, not
only as bulk chemicals but principally in many industrial
and consumer products, such as transformers,
capacitators, and condensers. Though steps are taken to
control PCB discharges during manufacturing and
processing, these have not been sufficient to prevent
PCBs from contaminating the environment and
endangering human health. The discarded items alone
have put PCBs in drinking water systems and have
contaminated lakes and streams and the attendant fish.
Congress felt so strongly about protecting us and future
generations of Americans from the hazards of PCBs that
they put a special section in TSCA to ban the future
production and distribution of PCBs. Since there may be
other substances out there with hazards equally as great
as those we have accidently learned about, Congress has
said—thru this Act—let's find out about these chemical
substances before they hit the environment—instead of
after-the-fact.
It is not the intent of TSCA that EPA ban the
production and distribution of all commercial chemicals.
Far from it. The Agency does have the power from the
Act to prohibit the production and use of chemicals, if
found necessary, but it also has many other ways of
attacking toxic substances problems. One of the major
thrusts of TSCA is to create and maintain a knowledge
base, which will enable preventive, rather than reactive,
positions on any chemical substances determined to be
hazardous. To be able to mount an effective attack on
toxic substances problems, the EPA needs to be able to
determine which chemicals pose truly significant
problems, how those chemicals affect human health and
environmental quality, how they reach the environment,
how great a risk they pose, and how to deal with them
without creating even greater threats. What we are now
setting about to do is to learn about the chemicals
through thoughtful study—not as we have —
15
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unfortunately—so many times in the past—through
accidents.
In specific terms, TSCA authorizes the Environmental
Protection Agency to (1) obtain information about
existing and new chemicals and to take appropriate
action against those which represent unreasonable risks;
(2) require that manufacturers and processors of
potentially harmful chemicals conduct tests and submit
to EPA data on the effects and the behavior of these
chemicals; (3) require that EPA be notified in advance of
the manufacture of new chemicals and supplied with
information necessary to evaluate the effects of these new
chemicals on human health and the environment; and (4)
when necessary, take steps to limit the manufacturing,
processing, distribution, use, or disposal of a chemical
substance which may present an unreasonable risk. Now
let's state this another way.
First, we must identify the existing chemical
substances presently being manufactured or imported.
This gives us a baseline for determining new chemicals.
Second, we must identify whether any existing or old
chemicals may present any unreasonable risk, and we
must establish testing requirements to confirm or
disprove our concern.
Third, we must establish ground rules for determining
whether a new chemical substance may pose adverse
effects before it goes into manufacture, and lastly, we
must have a sound program for taking regulatory action
when a substance presents an unreasonable risk. What
the whole Act really says can be put into two major parts:
(I) let's find out what chemicals are already on the
market—and are any of them hazardous? and (2) let's
take a look at new chemicals before they get out in the
marketplace. Let's be sure they do not pose any
unreasonable risk. And, note that I said unreasonable
risk—I did not say NO risk.
Our first step has been to turn to the task of
determining the substances produced or manufactured in
or imported into the United States. The Act mandated
that such an inventory be made. This date has already
passed and we do not have an inventory.
It would seem a fairly simple task to identify and list
chemical substances. The law has provided some
exemptions, such as pesticides, foods, food additives,
drugs, cosmetics, firearms and ammunition, tobacco
products, and nuclear materials. But, how do you treat
mixtures, such as paint? Should we list all the
innumerable polymeric combinations that are developed
for adhesives, rubber, plastics, etc.? How about alloys
and plating? The task is not quite so simple. There must
be acceptable resolutions to these issues.
One of the best ways to seek resolution is to seek the
opinions of both those the law seeks to protect and those
whom the law seeks to regulate. So, one of our first
actions was to consult industry, environmentalists,
laymen, elected officials, and private citizens—in both
public and private meetings—to bring together all their
views. By doing this, we feel we can come up with what we
believe to be effective and fair, reasonable and responsive
rulemaking procedures.
After several weeks of intensive effort on this task, the
Agency issued on March 9 the proposed regulations for
reporting the manufacture and importation of chemical
substances for the inventory. We also, based on our
consultations, defined the types of substances to be
reported and those that were exempt, such as chemicals
for research and mixtures. Primarily, we sought only to
determine the chemical identity of those chemicals
manufactured.
The weight of the certain comments following our
March 9 proposal convinced Administrator Costle that
our proposed regulations should be revised. Thus, the
reporting requirements were reproposed in the Federal
Register on August 2nd. In addition to reporting
chemical identity of substances manufactured or
imported, the proposal required the site of manufacture,
the volume of manufacture, and whether the material
produced was used only at the site. The August 2nd
proposal also offered a definition of "small
manufacturer" who, for the purpose of this particular
reporting, would be exempt from reporting volume of
production. The requirement for reporting of imports
was modified so that only chemical substances imported
in bulk must be reported.
After the August 2 reproposal another period for
comment was allowed, which ended September 16. We
then became engaged in evaluating the comments
received earlier together with the new comments in an
effort to arrive at the final reporting regulations. This
development, of course, upset the schedule set in the Act.
The final reporting regulations, together with the
appropriate reporting forms, were published in the
Federal Register December 23rd, with a reporting period
of 120 days beginning January 1 and ending May I, 1978.
After this four-month reporting period ends May 1,
1978, the Agency will amalgamate the information from
the reports to come up with the inventory. This
inventory, which we expect to be available in the fall of
1978, will contain t he chemical identity of all the chemical
substances reported to EPA as being manufactured or
imported. It will also contain an Appendix of voluntarily
reported trade mark listings. It will not contain the names
of the producers or importers nor will it contain
quantities. That information will remain within EPA,
Here I want to assure you that EPA is well aware of
manufacturers' concerns regarding confidentiality. EPA
has established a task force to develop procedures to
safeguard proprietary information from both inside and
outside sources and will hold a public meeting soon to
receive comments on its proposed procedures.
Although many persons have been concerned about
the inventory, you should know that the inventory has no
special significance as regards the hazard of the chemicals
listed. No characteristics of any chemicals are asked for
and none will be given; no categorization of hazard can in
any way be attached to the list. We are only seeking to
know precisely what substances, as such, are in fact being
made and where, and how much. That's all.
The real significance of the final inventory is that it
becomes the baseline between the old or existing
16
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chemicals and any newly developed chemicals. It means
that any chemical substance not appearing on this
inventory becomes illegal for use 30 days after its
publication. It also means that all substances produced
for commerce after publication of the inventory and not
appearing on that list will be subject to obtaining
premanufacturing approval. Just to make sure we have
everything on the inventory, we are allowing a 210-day
reporting period, a grace period, following the
inventory's publication, for processors and users of
chemical substances, such as yourselves, to verify that the
substances they purchase appear on the inventory. If they
do not, the processor or user, during this 7 month period,
may report them and they will be added. It now appears
that it will take us about 8 months after the-reporting to
compile the inventory—so it now looks like January 1979
before the initial inventory is published.
Let's consider for a moment how inventory reporting
affects you. If your firm manufactures any of the
chemical substances used in the paint or coatings
business, it must consider its responsibility to report. I
say consider, because it may not have to report if the
manufacture of the substances is only a relative small part
of its business. It may report to insure that the substance
is on the inventory. Chemical substances purchased from
other firms are not your responsibility. They should be
reported by the manufacturing firm. Last but not least,
although there may be a chemical reaction after the
application of the paints or coatings, these are considered
end products in articles and do not have to be reported.
The substances included in the products have to be
reported—but, as mentioned, most of these are probably
purchased. Also, paints or coatings themselves as
mixtures do not have to be reported.
When the inventory is published in January 1979, then,
as processors, your firms should review it to see that the
substances used are listed.
Now let's go back. The second phase of our strategy is
to identify those substances which may pose a risk and
develop the requirements for testing them to confirm or
disprove the risk. To start this process, EPA organized
in February an Interagency Testing Committee
composed of scientists from eight government agencies.
This Committee was charged with the responsibility for
developing a prioritized list of substances recommended
for further testing and reasons for inclusion of each
substance or mixture on the list. The law directs that up
to 50 of the listed substances or mixtures can be
designated by the Testing Committee for priority testing.
The Committee is directed by the Act to give priority
attention to known or suspected carcinogens, mutagens,
and teratogens in developing its recommendations which
may be listed as individual substances or classes of
chemicals.
The Committee's first effort was in the successive
screening of about 3,000 chemical substances which had
previously appeared on various hit lists. In July the
Committee published a Preliminary List of 330
substances and categories of substances selected
primarily on the basis of potential for human exposure
and environmental release. The Committee, on October
4th, submitted its first report to the Administrator listing
four individual substances and six categories of
substances for consideration for EPA's priority review,
with recommendations for the kinds of testing
recommended. The entire text of the Committee's initial
report, outlining the process and the basis of its decisions,
was published in the Federal Register on October 12,
1977.
Now that EPA has this report, it is required by the Act
that the Administrator initiate a rulemaking procedure
with respect to each substance or category, or publish in
the Federal Register his reasons for not initiating such a
proceeding. It should be pointed out here that initiation
of a rule on a substance is not a regulatory action. It
does not ban the chemical nor limit its uses.
Rulemaking on a substance requires the
manufacturers and processors of that substance to
conduct such testing as necessary to develop health and
environmental effects data. Testing must be relevant to a
determination that there is or is not an unreasonable risk
of injury to health or the environment by the chemical
substance in its manufacture, distribution in commerce,
processing, use, or disposal. In his decisionmaking, the
Administrator, before requiring testing, must find that
(1) the chemical may present an unreasonable risk; (2)
there are insufficient data for determining or predicting
the effects; and (3) testing is necessary to develop these
data.
In substance, what the Committee has said is, Here are
ten substances that may present an unreasonable risk.
However, at this point, we do not know whether there are
sufficient data to determine the effects. Therefore, the
Administrator should make this determination and. rule
for testing if necessary. The Agency is now holding
meetings with industry, associations, and environmental
group representatives to develop procedures for
requesting any health and safety studies that may exist on
the substances named by the Committee.
Among the requirements that EPA must lay out are the
standards for the development of the test data. This is an
area where several work groups are now busily engaged.
Much work must be done to determine and standardize
the test procedures and regulations. It should also be
pointed out that whenever a rulemaking on a substance is
developed it will also specify the time period for
developing the test information. In determining the
standards and period to be included in a rule, our
considerations must include the relative costs of the tests
and the foreseeable availability of facilities and
personnel to do the required testing. Thus, it may be seen,
that with rulemaking and a long test program, any
regulatory action on even the priority chemicals may be
quite some time away.
The third phase in our program involves consideration
of the risk of new chemicals before marketing. Thirty
days following publication of the Inventory List, all new
chemical substances—meaning those which do not
appear on the Inventory, whether they are new or not -
17
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and "significant" new uses of chemical substances, will be
subject to TSCA's "premanufacturing notification."
This will be a screening through which chemical
substances must pass before their initiation onto the
Inventory List of existing chemical substances which can
be legally marketed in the United States. By the end of
next year, manufacturers of new chemicals will be
required to notify the Administrator 90 days before
manufacturing.
Here again, we're in the process of planning our testing
procedures and regulations. If we are to carry out the
mandate of the Act that our regulations are not to stymie
technological innovation, our task becomes most
difficult for we must try to find the way to obtain
sufficient data to provide confidence that a substance
may be approved for the marketplace while not requiring
so much data that the costs will impede research and
development of new substances. This is a tough
assignment. And we're very much aware of it. Within the
next six months EPA expects to propose rules on how we
intend to handle this difficult issue. We are considering
using hierarchical testing schemes. After first reviewing
the physical and chemical properties of chemicals, under
a suggested hierarchical method, they would be subjected
to biologic activity testing which would involve relatively
quick and inexpensive tests. Testing for prechronic
toxicology would follow for high volume and high risk
subclasses. Long term bioassay tests involving more
expensive studies would follow in accordance with
lengthier detailed test protocols to be approved by EPA.
That brings me to the question of what EPA is
empowered to do under the TSCA when problems are
identified. Probably the best known new authority that
the Agency has under the Act is the power to ban or
restrict the introduction of new chemicals and significant
new uses. There are, or course, many interesting and
important aspects to the premanufacturing review
process. 1 will mention just two. One is the fact that the
Agency is not empowered to register chemicals or license
particular uses. The Act gives EPA a limited time in
which to review information on new chemicals and
significant new uses; if the Agency fails to take action
within that time—action either to require the submittal of
additional information or to propose a restriction—then
the manufacturer or processor can go ahead and
manufacture the new chemical. A second point worth
mentioning is implied in what I have already said. EPA is
not compelled to make an up-or-down decision on each
new chemical or significant new use. As appropriate, the
Agency can impose a variety of limitations tailored to
prevent unreasonable risks and still permit potential
benefits to be realized. For example, limited uses or
special labeling.
EPA's authority to prohibit or restrict also applies to
commercial chemicals already in use. The Agency can
prohibit or restrict the manufacture, processing,
distribution, use, and disposal of commercial chemicals.
Again, the Agency's action can be tailored to deal with
the particular activity that is causing an unreasonable
risk. This authority is already being used, not only with
respect to PCBs, for which the Act prescribed the action
to be taken, but also with respect to chlorofluorcarbons.
One thing I believe all of us can extract from what 1
have related. This is, that the task of properly regulating
and controlling chemicals to prevent hazard is a complex
one. There are major issues to be decided—such as what
is meant by "substantial risk"? How much data must the
Agency require for premanufacturing approval to insure
reasonable acceptance? Will this requirement not only
tax the laboratory capability but stymie technology and
new products?
We must also work to reduce the overlap of regulation
between agencies. The Act has taken this into account
and has directed the Administrator to integrate our
actions with those of other agencies. Primarily, we must
organize to make better use between agencies of the data
that have been and are being submitted. We are working
hard in this area.
Just a few weeks ago, Administrator Costle announced
that EPA, the Food and Drug Administration, the
Occupational Safety and Health Administration, and the
Consumer Product Safety Commission have pledged to
work together to develop compatible testing standards,
common approaches to risk assessment, coordinated
information systems, and, among other things,
coordinated rulemaking and enforcement activities,
research planning, and communication with the public.
This unprecedented enterprise is aimed at better
administration of Federal laws dealing with toxic
substances. Thus, it should build upon and improve
EPA's ability to deal with such problems under the Toxic
Substances Control Act.
There is no doubt that the implementation of TSCA
will sometimes be painful—both for the Environmental
Protection Agency and the chemical industry. Some very
difficult choices will have to be made. Whether our sons
and daughters will have similar hazards to face 20 or 30
years from now depends on how effectively we implement
and administer TSCA now. And that—in turn—depends
upon how well the Environmental Protection Agency,
the chemical industry—and that's many of you here
today—and every other group interested in these
problems work together to responsibly deal with them.
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Overview of the EPA Research & Development Program
For Air Pollution Control in the Metal Finishing Industry
Charles H. Darvin*
INTRODUCTION
The air pollution problems in the metal finishing
industry come from a number of metal finishing indus-
trial processes. No one industry within this category can
be singled out as the only generator of air pollution.
Specific industries, however, which are addressed by
lERL-Cincinnati Research & Development program
include the can and coil coating industry, the automobile
industry, the machinery and appliance manufacturing
industry and the general category of transportation
sources. The major pollutant problem that is typical for
all segments of the metal finishing industry is considered
to be organic emission. Whether the organic material is
found in the metal coating, paint, or used in metal clean-
ing or machining, it is generally emitted to the atmos-
phere. The most common air pollutant is the volatile
organic solvent. Many of these are toxic in nature at
worst, or at the least add to the national ambient air
oxident problem. The scope of the research program in
this area, although limited, is designed specifically to
attack organic emission problems from metal finishing
operations. The goals of this program are first, to develop
or identify new or improved coating systems; or where
necessary to develop or improve emissions control tech-
nology. Primary emphasis in the present program is to
reduce emissions from metal painting and cleaning
operations.
Air Pollution Overview
The metal finishing and fabrication industrial category
is defined to include a variety of metal preparation, fabri-
cation and coating processes. Industries in this category
include, but are not limited to, automobile manufactur-
ing and painting, shipbuilding, transportation equipment
manufacturing, can and coil coating and appliance man-
ufacturing. This naturally also includes metal fabrica-
tion and plating job shops which by the nature of the
processes used produce some air pollution.
The air pollution research effort for FY 77 and FY 78
will result in the expenditure of approximately $300,000.
Although limited, it represents a 350% increase for this
industry over expenditures prior to 1977. This increase
'Charles H. Darvin
U. S. EPA/Metals & Inorganic Chemicals Branch
Cincinnati, OH 45268
has come about through the realization that part of our
national air pollution problems is due to emissions from
various metal finishing and fabrication operations.
In prioritizing the air pollution emissions from the
metal finishing industry for the expenditure of limited
Research & Development air funds, the most pressing
problem has been determined to be the release of vola-
tile organic solvents to the atmosphere. These pol-
lutants are at worst toxic or at the very least contributing
factors to photochemical oxidant levels in the atmos-
phere.
The major sources of volatile organic pollutants from
industry include industries such as can and coil coating,
automobile painting, architectural painting and degreas-
ing processes such as can be found in many job shops.
The total nationwide emissions of organic pollutants
is estimated by EPA to be about 28 million metric tons
(31 million tons) of which 17 million metric tons (19 mil-
lion tons) are emitted from stationary industrial sources.'
Seven and one-half million metric tons are released from
industrial processes classified as metal finishing pro-
cesses.1 These emissions, therefore, are considered to
place a significant burden upon the nation's ambient oxi-
dant level and health related impacts. Thus, recognizing
the problems associated with organic pollutant emis-
sions, IERL and MICE have placed the major emphasis
of their air research and development programming on
the control of organic emission.
In addressing the air pollution problem of the metal
finishing industry and volatile organic emissions, in par-
ticular, a research and development program has been
designed to encompass a variety of pollution control
approaches. The general approach of the program is to
develop viable low-polluting options to present produc-
tion procedures and materials procedures and where pro-
cess or material changes are not feasible to develop cost
effective control technologies. Figure 1 outlines the
general approach of this program.
Coating Technology Development
The basic fact underlying organic emissions to the
atmosphere from painting and cleaning operations in the
metal finishing industry is that eventually all of the sol-
vent in the coating material will evaporate. Thus, a logi-
cal approach to eliminate this aspect of coating applica-
tions is the reduction or elimination of solvent-based
coatings. Unfortunately, there is no universal coating or a
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Metal Finishing and Fabrication Industries
AIR PROGRAM
COATING TECHNOLOGY PROGRAM
CONTROL TECHNOLOGY DEVELOPMENT
General Coating Development
(Ferrous Metals)
Coating Development
(Plating Substitutes)
Coating Development
(Transportation Sources,
Aluminum)
Solvent Incineration
(Automobile Industry)
Degreasing System
Development
Surfactant Scrubbing
(All Painting
Operations)
FIGURE 1
small group of coatings which will serve all product
requirements. Coatings are product specific and are
formulated for specific product and product require-
ments. Thus, there are an infinite number of coating for-
mulations. Added to limitation on coatings is the require-
ment for extensive testing for new coatings before cus-
tomer acceptance.
Recognizing that it is impossible to develop coatings
for each specific requirement, the coating development
program primarily is limited to programs that have
immediate payoff to industry and their use can be used
by more than one source. Highlighted in this coating
development program is the PACE program. This grant
program with the Steel Structures Painting Council
will evaluate new and generic coating developments. It
is designed to screen new coatings and evaluate their
potential to reduce pollution while maintaining or ex-
ceeding present product standards. This program should
have and is having a major impact on identifying new
coating systems that will reduce pollutant discharge to
the atmosphere.
A second and more limited program cosponsored by
lERL-Cincinnati is being carried out with the USAF.
The goal of this program is the development of a high
solids, high quality coating technology for use on
aircraft. Although, presently directed only toward
military aircraft, the developed coating will have poten-
tial applicability to commercial aircraft painting as well
as other transportation services such as railroad cars and
heavy construction machinery. The resulting coating
system will have applicability on both aluminum and
steel substrate.
A third research project which is directed at both air
and water pollution is with the Grumman Aerospace
Company. This program is investigating various low-
polluting coating systems for application as a potential
coating to machined parts as would be produced by small
job shops. Some of the output of this project is presently
being tested and utilized by a number of companies.
Emissions Control Technology Development
Since new coating systems cannot be developed in a
timely fashion for all coating applications, we also have
incorporated into our R&D program as a parallel avenue
activities directed toward control technology research
and development. Projects in this area are designed to
develop and demonstrate potentially viable control tech-
nology concepts that will capture, contain or destroy
organic emissions. Highlight programs in this area
include a major testing and evaluation program of shop
size vapor degreasing systems.
This study will evaluate state of the art technology for
reducing and containing degreasing solvent emissions.
Various degreasing system design features will be
evaluated to determine their efficiency in reducing
solvent emissions while in operation. This project will
serve as a guide to EPA and industry on the types of
development actions needed to reduce organic pollutant
emissions from degreasing operations and simultane-
ously define emissions and operating characteristics of
these systems.
A second major program in this area is directed at
automobile manufacturing. New design concepts in auto
paint baking ovens may permit reduction of emissions
while significantly reducing the oven's energy
consumption. In cooperation with a major automobile
manufacturer, EPA is presently conducting an evalua-
tion of a paint bake oven system designed for this pur-
pose. The results of the evaluation will verify the feasi-
bility of incineration of solvent-laden oven emissions
from large-scale zoned operations. This project can
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STACK
AIR
DESIGNATES SAMPLE LOCATIONS
FIGURE 2
demonstrate a viable control concept that may reduce
energy consumption of the manufacturing process and
simultaneously destroy organic pollutants. Figure II
describes this control design concept.
A third program involves the use of surfactant
scrubbing technology. This concept has been undergoing
laboratory research under EPA cosponsorship for
approximately two years. We are now considering test-
ing a pilot system in the field on a metal painting spray
booth. If successful this technology may point the way to
a low-cost efficient method of controlling extremely low
concentration solvent-laden gas streams as may be found
in paint spray operations.
Obviously, it is not possible to conduct research in all
of the areas that may benefit from such programs.
However, the aim of the present program is to attack the
most urgent problem areas of the metal finishing indus-
try. As new priorities are established and problem areas
identified, IERL will continue to expand the scope of its
efforts in air research and development for this industry.
21
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Evaluation of Low Solvent Emission Degreasing Systems
Richard W. Gerstle, P. E.. Vishnu S. Katari, P. E., & Robert L. Hearn*
INTRODUCTION
The term solvent degreasing refers to industrial clean-
ing processes in which nonaqueous solvents are used to
remove soil from various metals, glass, plastic, and tex-
tile items. The major users of solvent degreasers are the
automotive, electronics, and appliance industries, and
others involved in metalworking. Solvent degreasing
systems are also used in non-metalworking industries
such as printing, chemicals, and plastics. In fact, most
businesses use solvent metal cleaning processes at least
occasionally, if not regularly. More than 1 million
facilities routinely use solvent cleaning operations and
large companies often have over 100 individual cleaning
operations at one plant location.
In degreasing, a solvent in a liquid or vapor state is
used to remove grease, oil, and dirt. There are two kinds
of solvent degreasing: room temperature operations
(cold cleaning) and vapor degreasing. Cold cleaning is the
simplest and least expensive. The solvent is usually near
room temperature; it may be heated if necessary,
although the temperature must be held well below its
boiling point. Then parts are cleaned by spraying, flush-
ing, brushing, and immersion. Cold cleaning is a batch
operation, but continuous operation is also practiced
with conveyorized cold cleaning equipment. In vapor
degreasing the solvent is heated to its boiling point,
creating a zone of solvent vapor that displaces the air
within the equipment to be cleaned. The parts are
lowered into the vapor zone, where solvent vapors
condense on them until the temperature of the parts
approaches the boiling point of the pure solvent.
Vapor degreasing is performed by batch operation in
open tank degreasers and by continuous operation in
convcyorized degreasers. Of the estimated 30,000 vapor
degreasers in use, 85 percent are open-top units, ranging
in size from 1 by 2 feet up to 6 by 110 feet.
An open-top vapor degreaser emits 10 to 20 times as
much solvent as would a typical cold cleaner, but less
than half as much as a conveyorized degreaser.
Halogenated hydrocarbons are commonly used for
vapor degreasing. Typical solvents are 1, I, 1, trichloro-
ethane, trichloroethylene, perchloroethelene, metheylene
chloride, and fluorocarbons. All these solvents are toxic
at sufficient levels. Recent studies conducted for the
Environmental Protection Agency (EPA) show that
•Richard W Gerstle, P. E., Vishnu S. Katari, P. E.
& Robert L. Hearn
PEDCo Environmental, Inc.
reformulated petroleum solvents including perchloro-
ethelene are photochemically reactive. Some of the
halogenated degreasing solvents, such as 1.1.1 trichloro-
ethane, are almost inert in the troposphere, but they may
have an adverse environmental effect on the upper
atmosphere.
During vapor degreasing, the solvent is emitted into
the atmosphere as pure vapor. Because large numbers of
degreasers are in operation nationwide, their solvent
emissions contribute significantly to the total
atmospheric loading of hydrocarbons. Solvent
degreasing operations emit about 940,000 metric tons per
year, a figure that represents about 4 percent of the
annual total national volatile organic emissions from
stationary sources. The proportion of solvent degreasing
emissions is significantly higher in most urban areas
because metalworking industries are concentrated in
those areas.
Losses of solvent from the degreasing device and the
consequent need to replace the solvent significantly affect
the cost of degreaser operations. Control of emissions
from solvent degreasers is sought, therefore, for both
environmental and economic reasons.
Many open-top vapor degreasers, typically small or
medium size batch-loaded degreasers, are operated in
small manufacturing plants and job shops. Generally,
degreasing is only an incidental step in the manufacturing
operation. Such businesses cannot afford to apply
expensive control systems to their degreasing operations.
Nonetheless, minimizing solvent loss is a primary
concern to these businesses because of the cost of replac-
ing evaporated solvents. Since these same relatively small
operations contribute significantly to the total of
atmospheric emissions attributable to solvent degreasers,
there is both public and private interest in developing
emission reduction techniques that can be applied with
minimal economic and environmental impacts.
Emissions from open-top vapor degreasers are due to
diffusion, convection, carry out, leaks, and waste solvent
disposal. Solvent vapors diffuse from the vapor zone at
the air/vapor interface on the top of the vapor zone, and
are carried into the atmosphere. Solvent vapors are lost
through convection of warm solvent-laden air that passes
upward and out of the degreaser. Solvent is lost through
drag out of liquid and vaporous solvent when clean parts
are extracted from the degreaser. Solvent emission will
also result when waste solvent is disposed of in such a way
that the solvent can evaporate into the atmosphere.
The evaporative solvent emissions can be reduced to a
certain extent by any one of the following techniques:
22
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cleaning process changes, solvent degreasing equipment
modifications, and solvent emissions control systems.
Good operating practices are the primary method of
reducing carry out emissions. There are no general
devices to minimize carry out from the open-top vapor
degreasers.
Cleaning changes (such as water based alkaline
washing metal cleaning method) or process changes such
as liquid degreasing or conveyorized degreasing can be
utilized, however, these methods will not substitute for
vapor degreasing in all cases. Most of the items cleaned
by vapor degreasing can not be cleaned by liquid
degreasing. In some limited cases a conveyorized system
can be substituted for two or more open-top degreasers.
This can make the degreasing process less dependent on
the operating personnel who may tend to overlook the
requirements of minimi/ing pollution.
A typical degreaser includes a cover, a freeboard
(minimum height is at least half the width of the
degreaser), and a water condenser. But it has been a
practice in the industry for the height of the freeboard to
be three-quarters of the width of the degreaser when
methelene chloride and trifluoroethelene are used. In
most degreasers the bulk of the vapor is prevented from
escaping the tank by condenser coils attached near the
top of one or more of the walls of the tank. Open-tank
degreasers of all sizes usually have water jackets with
flowing water around the entire tank (above the coils) for
further condensation action. The vapor loss is primarily
dependent on the partial pressure at the condenser
temperature. Even though tank covers are part of the
original degreaser equipment, it is common for open-top
systems not to be covered when idling or shut down.
During this time, the amount of solvent vapor escaping to
the atmosphere is related to its partial pressure. The
convection losses are estimated to be anywhere from 0.05
to 0.1 Ib/ft2/hr for the open-top area. These losses are
about 10 to 20 percent of solvent loss during both idling
and operation of the degreaser. A significant portion of
such emissions can be prevented by using covers.
Previous EPA-sponsored tests that measured the
effectiveness of covers on halogenated solvent consump-
tion rates showed savings may range from 24 to 50 per-
cent. All tests used the same equipment and solvent; the
use of a cover was the only variable. On the basis of these
limited test results, covers appear to be a wise investment
even without considering air pollution control.
In the same test, increases of the freeboard ratio from
0.50 to 0.75 reduced solvent consumption by 27 percent.
When slight drafts occurred, the comparative effective-
ness of the larger freeboard increased in the same tests to
55 percent. These past tests tentatively indicate that
significant increases in solvent efficiencies and significant
reduction in pollution can be achieved by slight system
modification. Increases in the size of degreaser
freeboards can easily be accomplished by plant personnel
or by degreaser equipment manufacturers. Equipment
modifications such as increased freeboard height,
refrigeration chillers and good maintenance and
operating practice such as using covers during idling time
and shutdown periods may achieve significant reduction
of solvent emissions.
Further reduction in solvent loss from degreasers may
also be achieved by refrigeration chillers. This is done by
installing a second set of condensing coils in the
degreaser. The refrigeration chiller which operates below
or above 0° F temperature, creates a cold blanket above
the vapor zone in the degreaser to prevent escape of the
vapors. Vendor test data have been collected for refriger-
ation chillers operated at below freezing temperatures.
The data show an emission reduction of an effective
range of 16 to 60, with an average expectation of 40
percent. Installation and operation of a refrigeration
chiller results in capital costs, and energy and utility
costs. The operation of refrigeration chillers is either
accompanied by a net profit or by a net additional cost,
depending upon the size of the degreaser and its
operation time. Tests showed that for a degreaser of 5 by
5 feet with a refrigeration chiller operating three shifts a
day, the amount saved in solvent costs exceeded the
additional operating costs of the refrigeration chiller. But
for a comparatively smaller degreaser 2 by 6 feet
operating only one shift per day, the amount saved in
solvent costs was lower than the additional operating
costs of the refrigeration chiller.
Equipment modifications or control devices may
involve some additional investments for those who use
degreasers; however, savings in solvent costs offset most
of the annualized equipment cost and may even yield
profit. In the past, a test program was conducted on the
solvent emission reduction capabilities of different equip-
ment modifications. But since this program was
conducted under inconsistent test conditions, there was
no method of correlating the data.
Following these earlier studies of controls for solvent
degreasers, the EPA has undertaken a study to evaluate
the pollution reduction capabilities of existing vapor
degreasers and new developments in vapor degreasing
systems and operations. EPA has contracted with
PEDCo Environmental, Inc., to perform this study by
testing selected degreaser systems with distinct features
and thus generating data needed to evaluate the emission
reduction capabilities of degreasers with various features
and modifications. This program will generate data on
atmospheric emission quantities fora variety of variables
under carefully controlled operating conditions. The
data will be reported in a form usable to federal, state and
local air pollution agencies and industry. Evaluations will
include economical and environmental impact studies.
The Project
The current study (conducted under EPA Contract
No. 68-02-2535: Mr. Charles Darvin, Project Officer)
will evaluate various degreasing systems in terms of their
capabilities for reducing solvent emissions. A series of
tests will be conducted under carefully controlled
operating conditions to quantify atmospheric emissions.
Degreasers for testing will include conventional devices
with modifications as well as devices incorporating recent
23
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developments designed for reducing emissions. The data
generated in the tests will be compiled and assessed in a
report to EPA.
Project Approach
This project encompasses two principal tasks. The first
is to prepare a detailed test plan describing the types of
degreasers to be tested, the test site, test methods and
variables, and the basis for technical and economic
assessment of degreasers. Upon approval of this test plan
by the EPA, PEDCo will perform the second task, which
consists of conducting the tests in accordance with the
plan and preparing a summary report.
Phase 1: Selection of Degreaser Units and Test Site
The total project will be performed in five phases. The
first includes selection of the vapor degreasers for testing
and selection of the test site. We will examine all vapor
degreasers currently manufactured and observe their
operation in order to select representative systems for
testing. The selected systems will be altered in various
ways to incorporate control features, which are basically
(he same for all vapor degreasers. These controls consist
of a cover, a freeboard, and condenser coils, all of which
are used to minimize solvent loss. A cover provides the
easiest and most effective means of reducing the diffusion
and convection of solvent vapors into the atmosphere.
Most degreaser users, however, especially in small shops,
do not use covers because it is inconvenient to do so, or
because the degreaser is used frequently. A freeboard
primarily serves to reduce drafts near the interface
between air and the solvent vapor. The freeboard of a
vapor degreaser is the distance from the top of the vapor
/one to the top of the degreaser tank. OSHA established
the required freeboard height. Condenser coils are
positioned on the walls of the degreaser to condense the
solvent vapors.
Recent developments in degreasing systems are
believed to be capable of drastically reducing or
eliminating solvent emissions. The effectiveness and the
economic impacts of these developments have not yet
been fully evaluated. Therefore, in selecting degreasers
for testing, we will include one of conventional design,
one modified by higher freeboard than is normally used
and/or by lower condenser temperature, and one of new
design for minimizing emissions. Several manufacturers
have been contacted and have agreed to provide units for
testing. When the size and specifications of the degreasers
have been decided upon, manufacturers of the selected
units will be contacted.
During the first phase, PEDCo will select a test site.
The principal factor to be considered in site selection is
the ability of the test team to accurately monitor solvent
emissions and to control the test variables and operating
conditions. Three test site options are available:
1) Equip a mobile testing facility for on-site testing of
degreasers during operation,
2) Use equipment now set up for testing at various
manufacturing facilities, or
3) Borrow degreasing equipment from manufacturers
and ship it to the PEDCo test laboratory.
Logistics, quality control, and other considerations
favor a single, centrally located test site. A mobile test
facility would be expensive to operate and could not
provide adequate control of ambient air unless the
degreaser were installed in the vehicle. Although the use
of a manufacturer's test facilities would provide accurate
measuring devices and controlled surroundings, these
test facilities vary considerably among manufacturers.
Since the machines to be tested are of a size and type
amenable to shipment at relatively low cost, testing of the
several selected degreaser units at one well-equipped test
facility seems most feasible.
Phase 2: Compilation of Process Variables
The second phase of the project involves compiling all
of the process variables that may affect solvent emissions.
Each of the variables must be distinguished from the
process operating conditions that will be held constant.
At the same time, various methods of measuring and
analyzing hydrocarbon emissions, wastewater effluent,
and sludge will be reviewed in order to ensure the use of
the most accurate methods.
Many variables may affect emissions from vapor
degreasers. Generally, these can be categorized as
equipment related, operation related, and ambient
related. Equipment-related variables are the most effec-
tive controls for open-top vapor degreasers. As discussed
earlier, the major controls consist of covers, freeboards,
and condensers, all of which can be modified in various
ways. The other equipment-related variables to be
considered are geometry of parts to be cleaned (specific
surface area and length/diameter ratio, for example).
Operation-related variables that may affect solvent
emissions include type of solvent, solvent temperature,
operating cycle, load, heat balance, and air cross-
currents. Finally, ambient conditions in the degreasing
area may also contribute to the escape of solvent vapors,
e.g., air movement, ventilation, and humidity.
Because it would be impossible to test and determine
the effects of all variables on solvent emissions, these
variables will be classified and statistically analyzed to
determine the most appropriate means of quantifying
their cumulative impacts upon emissions. Factors that
have the most significant effects on emissions will be
given priority. The number of variables to be tested will,
however, be limited because of time constraints. Factors
with only slight effects on emissions will be held constant
to provide standard operating conditions and a
consistent basis for comparing test results. To ensure that
all relevant design factors and variables are included in
the test plan, PEDCo will review all pertinent reports and
documents and will consult with knowledgeable persons
and organizations.
Phase 3, 4 and 5
The third phase of the project is preparation of a report
summarizing the test plan, including full analysis of the
24
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overall test design. This information will be condensed
into an EPA Capsule Report for industry-wide
distribution. Phase 4 will be the testing of selected vapor
degreasing systems in accordance with the approved test
plan. Concurrently, we will perform Phase 5, which
involves reduction and analysis of the data. Emission
data will be related to the operating parameters of the
degreaser systems so that the need for additional data can
be recognized and accommodated while the units are still
undergoing tests. On the basis of test data, the economic
and environmental impacts of each degreaser system will
be evaluated to determine their capabilities for low-
solvent emissions under comparable conditions. A
summary report presenting test conditions, procedures,
results, and conclusions will conclude the project.
Summary
The principal purpose of this study is to evaluate the
capabilities of existing solvent degreaser systems for
reducing solvent emissions and to determine the
environmental and economic impacts of various control
measures.
From an environmental standpoint, an investigation
of this kind will assist both manufacturers and users of
degreaser systems in identifying and minimizing solvent
losses, which constitute a major source of hydrocarbon
emissions. Very little quantitative data are available with
which to evaluate the emission reduction capabilities of
existing degreaser systems. Although vendors of new
solvent degreasing control systems on the market claim
that these systems are highly efficient, little information is
available to support these claims. Where emission data
are available, they are difficult to evaluate because tests
are often based upon different operating conditions,
assumptions, and test procedures.
From an economic standpoint, this study should aid
the users of solvent degreasers in identifying what is
required of them to achieve adequate emission controls.
In particular, this study should define for the small
manufacturer and job shop operator the measures that
are most effective in reducing solvent losses and therefore
reducing operating costs.
REFERENCES
2.
Emission Standards and Engineering Division,
Chemical and Petroleum Branch, U. S. EPA. Control
of volatile organic emissions from organic solvent
metal cleaning operations (draft document). Research
Triangle Park, North Carolina, April 1977.
The Dow Chemical Company. Study to Support New
Source Performance Standards for Solvent Metal
Cleaning Operations. EPA Contract No. 68-02-1329.
U. S. Environmental Protection Agency, April 30,
1976.
3. JACA Corporation. Air Pollution Control of Hydro-
carbon Emissions - Solvent Metal Cleaning
Operations. U. S. Environmental Protection Agency.
25
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Minimizing Energy Use in Solvent Incineration
Thomas C. Ponder, Jr.*
INTRODUCTION
The metal finishing industry uses organic coatings to
protect or decorate bare metal. The coating processes
release volatile organic compounds (VOC) to the
atmosphere in the form of aerosols, or gases. Although
there are several methods of reducing these emissions,
this presentation will deal only with thermal incineration
equipment, which converts the organics (mostly
hydrocarbons) to water vapor and carbon dioxide by
combustion. The devices used are commonly called
"afterburners."
Although afterburners provide one of the most
effective methods of controlling hydrocarbons, they can
consume substantial amounts of fuel, mainly distillate
oils or natural gas (electric heat has also been used). Since
the oil embargo of 1973, the Federal Government has
urged conservation of these resources, placing industry in
a dilemma between protecting the environment and
conserving energy. This has caused increasing interest in
heat recovery from afterburners.
Heat recovery can be applied to almost every
afterburner. Heat recovery is not 100-percent efficient
but in some cases energy contained in the waste stream
(from solvents) is so high, the afteburner with heat
recovery can actually use less fuel than would be required
if no afterburner were used.
In this paper, I will describe the types of heat recovery
systems offered, and name the major manufacturers. The
efficiency of each type of system will be discussed,
together with the relative cost. Limitations and
advantages of each system will also be covered.
Process Description
The use of an afterburner involves two unit operations,
combustion and heat transfer. Combustion is rapid
oxidation; it requires a combination of an oxidizable
material, an oxidant, and sufficient heat to start and
maintain burning. In this case the oxidizable material is
the VOC; and oxygen (from the air) acts as the oxidant.
Operators are compelled by National Fire Protection
Association (NFPA) codes to dilute VOC to 25 percent of
the lower explosive limit for the exhaust stream, so heat
must be supplied to effect combustion of these
compounds. (Higher concentrations are possible if
proper fail safe methods are used.)
Afterburners commonly employ one of two types of
'Thomas C. Ponder, Jr., P. E.
PEDCo Environmental, Inc.
combustion processes, thermal or catalytic. The thermal
process usually requires temperatures in excess of 1200°
F for retention times of 0.5 second. Time and
temperature, however, are dependent on the
concentration of the organic compound. Catalytic
processes, on the other hand, generally require
temperatures of 900° F or less, since the catalyst effects
combustion at lower temperatures.
Products resulting from incomplete combustion are
detectable in the flue gas as: I) carbon monoxide
(instead of carbon dioxide, which is the fully oxidized
form); 2) VOC; and 3) organic paniculate matter.
Heat recovery efficiency of an afterburner cannot be
100 percent. The main energy loss is from the fact that
combustion products leave the system at much higher
than process inlet temperatures, even after heat recovery.
Other energy losses from an afterburner result from
incomplete combustion and heat losses through the
combustion chamber walls. These losses seldom exceed
1.5 percent of the input heat to the afterburner.
Heat Transfer and Recovery
Heat recovery for afterburners is the transfer heat
energy by a device from the higher-temperature exhaust
stream to the lower-temperature inlet stream. The
minimum exhaust temperature is kept above the dew
point of the exhaust gases to avoid condensation of
corrosive products. The dew point of natural gas-fired
exhaust is about 90° F and that of distillate fuel oil-fired
exhaust is about 160° F to prevent the condensation of
corrosive sulfuric acid. In practice, it is not economical to
achieve such temperatures so dew point is rarely a
problem.
HEAT RECOVERY SYSTEMS
Heat recovery devices are classified by their mode of
heat transfer, i.e., direct or indirect. The mixing chamber
is an example of a direct device, in which mixture of high
and low temperature streams produces 100-percent heat
recovery. This system is shown in Figure 1.
Indirect heat recovery systems, classified as either
"recuperative" or "regenerative", do not mix the streams.
Tubular air heaters, economizers, and heat recovery
boilers are all examples of recuperative heat recovery.
Heat recovery in these devices is limited by the thermal
conductivity of the barrier and the heat transfer fluid.
Air-to-air heat exchangers are the most frequently used
type of heat recovery device, primarily because they are
simple and have no moving parts.
Figures 2 and 3 illustrate single-pass recuperative heat
recovery in the cocurrent and countercurrent gas flow
26
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/ MIXING BAFFLES
STREAM "1 S *2
TEMPERATURE OF MIX
Gas Temperature profile.
Fig. 1—Heat recovery with a mixer.
^_ TUBES OR PLATES jfr
TUBES OB PLATES t
Gas flow diagram
HOTTER STREAM
COOLEB STBEAM
1— LENGTH
Gas tempeialure profile.
Fig. 3—Heat recovery with countercurrent flow recuperator.
Gas temperature profile-
. 2—Heat recovery with cocurrent flow recuperator.
SECOND PASS
Gas flow diagram.
i
HOTTER STflEAIH
TEMPEB»TURE OF TUBE
• NUMBER OF TUBES PASSES
Gas temperature profile.
Fig. 4—Heat recovery with cross flow recuperator
mode. Maximum theoretical heat recovery forcocurrent
is 50 percent where the flows and fluids are identical.
Maximum theoretical heat recovery for countercurrent is
100 percent. Maximum heat recovery for countercurrent
depends on many factors but the economic optimum is
usually 50 percent. Cross-flow is between the two. Figure
4 illustrates a two-pass recuperative system in which
economical heat recovery is usually about 70 percent.
Regenerative devices generally achieve greater heat
recovery than recuperative exchangers. They do this at
non-uniform rates through the use of a heat-absorbing
material that stores the heat for reuse. This material is
thermally recycled, i.e., charged with heat and then
discharged. Two or more devices may be combined to
provide a more uniform recovery temperature. The
regenerative material may be either stationary, with the
27
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TYPICAL VALVES CLOSED
PACKED BED OF
REGENERATIVE
MATERIAL
DISCHARGING HEAT
PACKED BED OF
REGENERATIVE
MATERIAL BEING
CHARGED WITH HEAT
Gas flow diagram.
NOTE: TO CYCLE REGENERATOR
CLOSE©®©® VALVES
OPEN ®®0® VALVES
-~ «- TIME LOST
I I ^-REVERSAL
1
HEATING (CHARGING)
COOLING
(OISCHARGINGI
REVERSAL:
LENGTH
With generator length
Gas temperature profiles.
COOLING HEATING —I
TIME
With time
Fig. 5—Heat recovery with cyclic regenerator.
hot and cold gas streams alternated between multiple
chambers packed with the material; or the regenerative
material may rotate, e.g., as a metal or ceramic wheel
between hot and cold streams (Figure 5 and 6). Table I is
a list of the systems offered, their stages of recovery, use
of heat recovery, and the number of vendors offering
each system.
Appendix A lists the major manufacturers of heat
recovery systems and the types of system each offers.
Advantages and Disadvantages
Heat recovery from afterburners has advantages and
disadvantages. In general, they are as follows:
Advantages
I. Reduced energy consumption
2. Reduced overall costs
Disadvantages
1. Clean waste streams required
2. Increased capital costs
3. Control is complicated
4. Space requirements
Although afterburners reduce energy consumption and
costs, relatively clean exhaust streams are needed to
prevent plugging. Highly pigmented paints, for example,
can foul even the simplest recuperative heat exchanger.
Capital costs rise with the addition of heat recovery
equipment. In addition, control of an afterburner
equipped for heat recovery can be more difficult than a
simple afterburner. In many cases, too, the plant has
insufficient space to install the heat recovery equipment.
Table 2 describes the advantages and disadvantages of
various heat recovery methods: gas mixing (recycle),
recuperative, (waste heat boiler), recuperative (air to air),
regenerative (rotary), and regenerative (fixed bed). The
sections that follow discuss the pros and cons of each heat
recovery method.
Gas Mixing (Recycle)
Gas mixing is commonly used in recycling combustion
gases to curing ovens. This process has the highest
efficiency if 100 percent recycle were possible since this
28
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TREAM #1
I
-; -_
•
PACKED BED OF
REGENERATIVE
MATERIAL BEING
' -- CHARGED WITH
HEAT
_ j
SEAL
1 SHAFT
CHAMBER
.
I PACKED BED OF
• REGENERATIVE
/" MATERIAL
| DISCHARGING HEAT
i '
1
1
1 3
1
I
1 1
1
1
h
b
t
rREAM #1
m
BY DRIVEN S
CM
£
m
LU
Gas flow diagram.
1
HOTTER STREAM
COOLER STREAM
1
HEATING ICHABGINGI
COOLING
IDISCHARGING)
With length or rotating speed.
Gas temperature profiles.
r— COOLING HEATING —|
TIME
With time.
Fig. 6—Heat recovery with heat wheel regenerator.
TABLE 1
TYPES OF HEAT RECOVERY SYSTEMS
Type oj re- Heal recovery
covery syxteni component
Typical use for
recovered heal
Gas mixing
Recuperative
Recycle of portion
of combustion
exhaust gases
Gas to gas heat ex-
changer
Recuperative Waste heat boiler or
economizer
Regenerative Metal rotary ex-
changer
Ceramic rotary ex-
changer
Packed bed
Drying oven
Preheat combustion
feed gas
Provide heat lor build-
ing, dry-off oven or
other use
Generate steam and or
superheated steam
Provide hot water
Recirculate heated ther-
mal fluid to various
heat users
Preheat combustion
feed gas
would require no heat exchange surface. This is not
possible, however, due to condensation, sulfur in the fuel,
particulate, and reduced oxygen levels.
Recuperative (Tubular)
The primary advantage of the tubular recuperative
heat exchanger is its low capital cost and simplicity. This
system has several disadvantages, including low
efficiency, leakage from differential thermal expansion,
and bulk and weight. The metal surfaces are easily fouled
by hydrocarbons and require maintenance and frequent
cleaning. The hot tubular surface can polymerize resins,
causing reduced heat transfer and possible combustion
on the heat exchanger surfaces. Condensation corrosion
is also a problem, since the heat exchangers are normally
made of carbon steel.
Recuperative (Waste Heat Boilers)
The primary advantage of waste heat boilers is their
transfer of heat energy into a more easily transported
medium. Their efficiency is usually higher than that of
simple tubular exchangers. Waste heat recovery as steam
requires the VOC producing process and steam using
equipment to operate in synchrony unless provisions are
made for steam production while the VOC producing
process is down. Finally, condensation corrosion is a
problem in waste heat boilers.
29
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Type
Efficiency
percent
TABLE 2. TYPES OF HEAT RECOVERY
Additional
auxiliary
equipment Limitations, problems Commonly used for
Commonly not used for
Tubular exchanger
Gas, gas
Cross-flow
I stage-50% max
2 stage-62% max
Regenerative
(rotary)
exchanger
Up to 85%
I) May be easily fouled;
frequent cleaning and
maintenance.
2) Failures, differential
thermal expansion.
3) Bulky, heavy, added
roof load and/or floor
space.
5) Corrosion if cools be-
low dew point of flue
gas.
1) Easily fouled. Use
only on relatively
clean streams.
2) Burnout if failure on
rotary drive motor.
3) Requires attention to
pressure balance to
control leakage at
seals.
4) Avoid cooling flue gas
to dew point, but other-
wise is relatively in-
sensitive to corrosion.
Resin curing ovens
Paint drying ovens
Chemical plants
Rendering plants'
Odor control, water
treatment units
Power plants
Any fumes containing
oils, dusts, resins
Flue gas recycle
to oven
30%
Safety con-
trols
Steam generators,
boilers, water heaters
to 75%
Extra burn-
ners and con-
trols; safety
controls
Extra duct-
ing, blowers,
controls
1) Process must be Resin, lacquer curing
compatible with flue ovens, (if low solvent
gas (condensation? release)
Sulfur in fuel? CO or
CO;? Reduced oxy- Litho ovens
gen? Unburned fuel?)
2) Usefulness depends on
temperature and heat
requirements of fume
generating process.
I) May tie steam genera- Plant steam supply
Varnish cookers (com-
bustibles ha/ard) ovens
requiring human access.
Smoke ovens (low tem-
perature)
tion to fume process
and vice versa.
2) Match steam heating
load to afterburning
heat release.
CO burner and boiler
(fluid bed catalytic crack-
ing unit in oil refinery.
Uses supplementary
fuel firing)
Process heat-via
circulating heat
transfer salt (Hytec),
oil, air
to 75%
Exchangers,
piping, reser-
voir, pump.
controls
3) Condensation on cold-
water coils.
I) Ties fume generation
to process.
2) Matches process heat
load to afterburner
heat release (but can
use supplementary
firing for added pro-
cess heat).
Plant heating and air
conditioning units
Asphalt blowing, pre-
heating
One manufacturer claims to have used heat exchangers successfully for rendering plants.
30
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Regenerative (Rotary)
The primary advantage of the regenerative exchanger
is its potential for high efficiency. Shortcomings include
easy fouling, high maintenance necessary to prevent
shortcircuiting across heat exchanger seals and burnout
if the rotating motor fails.
Regenerative (Fixed Bed)
The advantages of this system are high efficiency and
insensitivity to precombustion in regenerative packing.
Disadvantages include large space requirements, and a
complicated valving system requiring much mainte-
nance.
HEAT RECOVERY COSTS
This section contains the costs of several actual heat
recovery systems. These examples are not aimed at show-
ing which systems are always the most economic. In
actual practice, each type of heat recovery should be
evaluated for the actual conditions of the source being
controlled. For economic comparison, the process
stream will be shown with a simple afterburner, and with
an afterburner with heat recovery.
Recuperative (Indirect Recycle) Recovery System
This system contains a two-pass recuperative heat
exchanger to preheat the exhaust stream from an alu-
minum coil coating operation. The system also includes a
fourpass recuperative exchanger to provide makeup air
for the coil coating operation. It has an overall heat
recovery from the afterburner of 85.8 percent, with a
reduction in fuel requirements of 75 percent. As shown in
Table 3, the capital cost of the system is $426,000 in
January 1977 dollars and the annual operating cost is
$127,000, which represents a savings of only $10,000, i.e.
a return on incremental cost of only 3.7 percent when
compared with the costs of a simple afterburner system.
Thus, this heat recovery system is probably not economi-
cally justified.
TABLE 3
RECUPERATIVE HEAT RECOVERY SYSTEM
Heat recovery system with
afterburner
Simple afterburner with-
out heat recovery
Savings
Return on incremental
investment, percent
Capital cost /acfm
Sysiem si/e, acfm
Capital cost
$426,000
$155,800
Annual cost
$127,000
$1.17.000
$ 10.000
3.7
$36.50
11.670
TABLE 4
REGENERATIVE (FIXED BED)
RECOVERY SYSTEM WITH RECYCLED HEAT
Heat recovery system with
afterburner
Simple afterburner with-
out heat recovery
Savings
Return on incremental
investment, percent
Capita] cost acfm
System si/e. aclm
Capital COM
$435.000
$154,000
Annual cusl
$104,000
$183.000
$ 79,000
2H.IH
S 21.75
20.000
Regenerative (Fixed Bed) Recovery System with Recycle
This system contains a three bed regenerative heat
exchanger to preheat the exhaust stream from a steel coil
coating operation. Part of the exhaust gases are recycled
to the oven. This system has an overall heat recovery
from the afterburner of 96.2 percent, with a reduction in
fuel requirements of 97.2 percent. As shown in Table 4,
the capital cost of the system is $435,000 in January 1977
dollars, and the annual operating cost is $ 104,000. When
compared with a simple afterburner system, the savings is
$79,000, or a return on incremental cost of 28.18 percent.
This heat recovery system, therefore, can be
economically justified.
Regenerative (Rotary) Recovery System
With Waste Heat Boiler
This system contains two rotary regenerative heat
exchangers, which use high temperature exhaust from
the afterburner to heat makeup air to a metal coating
operation. The system also uses some of the high-temper-
ature exhaust as partial input into a boiler. This system
has an overall heat recovery from the afterburner of 98.5
percent. Since there is more heat from the afterburner
than the coating system can use, afterburner heat sup-
plants part of the plant boiler's fuel requirement. As
shown in Table 5, the capital cost of the system is
$949,000 in January 1977 dollars; the annual operating
cost is $640,000. Because of the complex nature of this
system, data were insufficient to calculate the savings ob-
tained in comparison with the cost of a simple after-
burner.
Recuperative (Direct Recycle) Recovery System
This system contains a single-pass recuperative heat
exchanger to preheat the exhaust stream from a metal
litho operation. This system also includes partial recycle
of the exhaust stream to preheat the curing oven. It has an
overall heat recovery from the afterburner of 89.7
percent, with a reduction in fuel requirements of 77.3 per
31
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TABLE 5
REGENERATIVE (ROTARY)
RECOVERY SYSTEM
WITH WASTE HEAT BOILER
Capital cost
Heat recovery system with
afterburner
Simple afterburner with-
out heat recovery
Savings
Return on incremental
investment, percent
Capital cost acfm
System size, acfm
$949,000
$172,000
Annual cost
$640.000
$168.000
None
None
$ 31.63
30,000
TABLE 6
RECUPERATIVE
(DIRECT RECYCLE)
HEAT RECOVERY SYSTEM
Capital cost
Heat recovery system with
afterburner
Simple afterburner with-
out heat recovery
Savings
Return on incremental
investment, percent
Capital cost acfm
System size, acfm
$233,000
$ 91,200
A nnual cost
$ 64.500
$ 59,000
None
None
$ 3S.X3
6,000
TABLE 7
RECUPERATIVE (WASTE HEAT BOILER)
HEAT RECOVERY SYSTEM
Capital cost
Heat recovery system with
afterburner $567,500
Simple afterburner with-
out heat recovery
Savings
Return on incremental
investment, percent
Capital cost acfm
System si/e. acfm
$127,000
Annual cost
$214,500
$115.000
None
None
$ 54.00
10.500
cent. The capital cost of the system is $233,000 in Janu-
ary 1977 and the annual operating cost is $64,500 (Table
6). The system would not show a savings when compared
with the costs of a simple afterburner.
Recuperative (Waste Heat Boiler) Heat Recovery System
This system contains a single-pass recuperative heat
exchanger to preheat the exhaust stream from an alu-
minum can production line. It also includes a waste heat
boiler to preheat water for can washing. The system has
an overall heat recovery from the afterburner of 68.0 per-
cent, with a reduction in fuel requirements of 52.0 per-
cent (Table 7). The capital cost of the system is $567,500
in January 1977 dollars, and the annual operating cost is
$127,000. It has no cost advantage over a simple after-
burner.
APPENDIX A
List of Companies and Industry Contacts for
Available Heat Recovery Systems or Components
Company and Contact
Surface Combustion Division
Midland-Ross Corporation
2375 Dorr Street
Toledo, Ohio 43691
Phone Number: (419) 536-4611
TWX 810-442-1651
T. V. Bellinger, Sales Manager
Thermal Process Systems
Tom Schultz
Dean Schmidt
C. E, Air Preheater
Combustion Engineering, Inc.
Post Office Box 372
Wellsville, New York 14895
Phone Number: (716) 593-2700
C. E. Pauletta, Manager
Special Applications
Oxy Catalyst, Inc.
Research-Cottrell, Inc.
East Biddle Street
West Chester, PA 19380
Phone Number (215) 692-3500
K. Allen Napier, Sales
Engineer
Air Correction
U. O. P.
Darien, Connecticut 06820
Phone Number: (203) 655-8711
G. L. Brewer, Product Sales
Manager
Steve Olson, Sales Engineer
Engelhard Industries Systems
Department
2655 U. S. Route 22
Union, New Jersey 07083
Phone Number: (201) 589-5000
Martin F. Collins, Manager Air
and Gas Systems
Type Systems
and Components
Recuperative, recycle
Regenerative, recycle,
recuperative
Recuperative, recycle
Recuperative, recycle.
Heat recovery boilers
Recuperative, recycle
(Continued on next page)
32
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APPENDIX A
List of Companies and Industry Contacts for
Available Heat Recovery Systems or Components
Company and Contact
Type Systems
and Components
Matthey-Bishop, Inc.
Malin Road
Malvern, PA 19380
Phone Number (215) 644-3100
J. H. Povey, Marketing Manager
Thomas H. Snape, Product
Specialist
Granco Equipment
1958 Burlingame, S. W.
P. O. Box 1767
Grand Rapids, Michigan 49501
Phone Number: (616) 241-5603
Charles B. Gentry, President
REECO
Regenerative Environmental
Equipmnt Co., Inc.
P. O. Box 600
520 Speedwell Avenue
Morris Plains, NJ 07950
Phone Number: (201) 538-8585
J. Mueller, President
Allied Air Products Co., Inc.
315 E. Franklin
Newberg, Oregon 97132
Phone Number: (503) 538-8341
TELEX 360 423
William F. Zunker, Vice
President
Sales & Marketing
Trane Thermal Company
Brook Road
Conshohocken, PA 19428
Phone Number: (215) 828-5400
John J. Sudnick, Sales Engineer
Process Systems
KENTUBE
4150 South Elwood
Tulsa, Oklahoma 74107
Phone Number: (918) 446-4661
TELEX 4-2353
Jerry Herrington, Administrative
Sales Engineer
Recuperative, recycle
Regenerative, recycle
Regenerative
Recuperative
Incineration with recupera-
ative heat recovery
Recuperative
APPENDIX A
List of Companies and Industry Contacts for
Available Heat Recovery Systems or Components
Company and Contact
Type Systems
and Components
Eclipse Lookout Company
A Division of Eclipse, Inc.
P. O. Box 4756
Chattanooga. TN 37405
Phone Number: (615) 265-3441
TELEX 558-427
Don Fillers, Heat Recovery
Sales Manager
Heat Recovery Corporation
590 Belleville Turnpike
Kearney, NJ 07032
Q-Dot Corporation
151 Regal Row
Suite 220
Dallas, TX 75247
Phone Number: (215) 630-1224
TELEX 730365
Voss Finned Tube Products. Inc.
4832 Ridge Road
Cleveland, OH 44144
Phone Number: (216) 398-8100
TELEX 810-412-8223
Deltak Corporation
13330- 12th Ave, North
Xenium at 12th Avenue
Minneapolis, Minnesota 55440
(Mailing Address)
P. O. Box 9496
Minneapolis, Minnesota 55440
Phone Number. (612)544-3371
TELEX 29-0812
Gary G. Steele, Sales Engineer
Smith Environmental Corp
1903 Doreen Avenue
P. O. Box 3696
South El Monte, CA 91733
Phone Number: (213) 686-2155
(213) 443-0214
(213)443-0214
J. M. Archibald, Vice-Pres.
Incineration with recuper-
ative heat recovery,
boilers
Recuperative
Regenerative for use in
HVAC systems
Recuperative
Recuperative heat
recovery boilers
Incineration with recuper-
ative exchangers
33
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An Overview of the EPA R&D Program
For Water Pollution Control
In the Metal Finishing Industry
Mary K. Stinson*
The net effect of many different Federal and local laws
and regulations in force or to take effect in the future is to
place increasingly strict limits on the levels of various
substances that can be discharged into wastewaters.
Other Federal and local laws and regulations place
increasingly strict limits on the way in which such
products as sludges from wastewater treatment can be
disposed of. The direction in which these Federal and
local laws and regulations are guiding the metal finishers
is toward a system of materials recovery — the only route
left open.
This paper discusses how EPA water recycling and
research projects are accompanying the metal finishing
industry toward that system of materials recovery.
Another point that I would like to make is the importance
to conserve our natural resources.
As an example of laws that have begun to move the
industry in this direction, the Federal Water Pollution
Control Act (Public Law 92-500) does or will require that
the metal finishing industry like all other industries
remove certain levels of certain pollutants from its
wastewaters before they are discharged either to a
municipal system or a receiving water. Some guidelines
for this industry have been established already. Other
guidelines for direct discharge as well as pretreatment are
still being considered.
The EPA is well aware of the complexity and diversity
of this industry and of the technical and economic
problems inherent in applying pollution abatement
technology to its processes.
It has been estimated1 that there are at least 70,000
facilities in the U. S. which are involved either in simple
or complex metal finishing operations. These facilities
employ a total of 600 different processes. The list of
pollutants regulated to date is not very long. As a matter
of fact, due to the complexity of the industry and the
variety of metals and reagents used, all pollutants may
never be regulated. However, it is anticipated that some
additions of other pollutants to this list will be made in
the future as new and different environmental regulations
are enforced.
"Mary K. Stinson, Project Manager
U. S. EPA/Metals & Inorganic Chemicals Branch
Edison, NJ 08817
EPA's R&D Office carries out developmental and/or
demonstration programs which attempt to demonstrate
methods to reduce some of the major problems of this
industry. Our overall goal has always been to assist the
industry in meeting its current as well as future
regulations. Also, we encourage the development and
demonstration of technology that shows promise of a
long-term solution to the problem, provides economic
incentive to the user, conserves our national resources,
and does not cause other environmental problems.
Selection of the individual projects, or technologies for
development is done by EPA's staff familiar with the
industry and very often with assistance of the members of
the industry themselves or represented by AES or MFF.
The intent is to foster accelerated development of sound
ideas, to assume some of the risk inherent in any new
system, and to expose the technical community to the
subject technology. In practice, grants and contracts can
be awarded to universities, research firms, or in the case
of demonstration projects, the actual user of the new
technology. The product is a report fully documenting
the results. Successful full-scale demonstrations are most
rewarding in that the technology is often employed as a
part of wastewater and/or recovery treatment at the
given facility even after the project is completed.
Examples are some completed projects.
As far as technology is concerned, EPA's R&D co-
sponsors projects ranging from chemical destruction to
physical-chemical concentration and recovery. The most
SLIDE 1
U. S. METAL FINISHING INDUSTRY
70,000 facilities
600 processes
High water use
Chemicals and large fraction of metals are
discharged to the environment.
Major wastestreams:
I. accidental spills
2. spent processing solutions
3. rinsewaters
34
-------
extensive list of EPA projects for treatment of metal
finishing wastewaters and their brief review is given in
Dr. Skovronek's and my paper2 published in October's
and November's issues of Plating as Part I and II. These
projects include state of the art surveys, laboratory
investigations, pilot plant testing, and full-scale
demonstration on an operating line.
Questions now arise as to what is the actual impact of
all these technologies, how can they really help the indus-
try as a whole, and where do we go from here with our
research program? Research completed to date as well as
preliminary results from ongoing projects have already
begun to form a picture of the impact these technologies
will have on industry. This work also throws a little light
down the road we all will be traveling in the future.
To date, most of the industry has used what can be
called conventional technology to meet the current
requirements. It is these conventional technologies,
largely precipitation, which have led to the current and
future problems with sludges. It is generally believed that
conventional treatment is adequate and often the most
cost-effective. Yet it is a temporary measure in many
instances and it is a straight forward cost, offering no
economic benefit or incentive.
As for the adequacy of conventional treatment there
are many instances where this treatment is not reliable.
The systems are labor intensive and subject to employee
error. In the case of heavy metal removal by precipi-
tation, careful pH control and other process controls are
needed to avoid solubilization of residuals by ammonia
and chelating agents which would interfere with the
precipitation reaction. These ideal conditions are not
easily maintained and not all interferences are easily
established. Both AES and MFF recognize the need for
SLIDE 2
DEMONSTRATED TECHNOLOGIES
IN OPERATION
Facility
Technology Comment
Beaton &
Corbin
Anaconda
Integrated
Treatment
Cementation
New England
Plating
Sealectro
Corp.
Advance
Plating
Electrolytic
Ozone
Evaporation
Recovery of
copper and re-
duction of hex-
avalent chro-
mium
Oxidation of
cyanide and
reduction of
chromium
Oxidation of
cyanide
Recovery of
chromic acid
studies that would identify and remove interferences that
cause sudden excursions of metals in the treated effluent.
Meanwhile our program has an ongoing study that will
result in a manual presenting all aspects of the techniques
of conducting precipitation of metals from wastewaters
most effectively.
Some local environmental regulations may be stricter
than the Federal ones and the conventional treatment
may not be adequate there. Some sewer ordinances are
very strict. An example is a sewer ordinance of the City of
Taunton, Massachusetts which sets very low levels for
heavy metals and cyanide.3
Municipal sewer ordinances may also prohibit
acceptance of cadmium-bearing wastewaters unless high
removals are achieved at the source. Conventional
treatment generated sludges containing the very heavy
metals we wish to remove from environment such as
Cu, Zn, Ni, Cd, Cr, etc. Cadmium is a particularly
undesirable component of the municipal sludge and may
be a limiting factor in the agricultural disposal of this
sludge. The sludge generation and disposal problem
cannot be discounted or ignored. If dewatering of sludges
is required, the cost of treatment increases. Also, in some
states there may be no nearby landfill area that would
accept this sludge. In the Commonwealth of Massachu-
.>etts, metal finishing sludge cannot be landfilled at all.
Recovery of metals, particularly from mixed metal
sludge, is not economically feasible at this time.
Resource conservation is another aspect that should
concern us all. The metal finishing industry consumes
almost all commercially important metals, but due to the
inefficiency of the processes employed and other reasons
such as changes in the spent processing solutions, large
fractions of the metals end up in wastewaters. According
to a recent article4 in Metal Progress, the U. S. must im-
port a large number of commercially important metals
and ores. More than 90% of palladium and chromium,
and more than 50% of tin, nickel, zinc, antimony, and
tungsten must be met by imports. Recovery of noble
SLIDE 3
EXCERPT FROM A SEWER ORDINANCE
OF THE CITY OF TAUNTON, MA
Maximum Concentration
Allowable in Milligrams
Substance per Liter
Arsenic
Cadmium
Chromium (Total)
Copper
Cyanides
Lead
Mercury
Nickel
Silver
Zinc
0.1
0.2
1.0
2.0
1.0
1.0
0.01
1.0
1.0
3.0
35
-------
metals and of several other high-priced metals already
has been practiced by the industry. Savings are not only
in the recovered metals alone but also in the avoidance of
sludge generation, ease in meeting discharge or
pretreatment regulations and in reduction of the
Country's dependence on imports. Recovery of metals
from wastes also is often less energy intensive than
production of primary metals from ores. Recovery of
cadmium, for example, from wastewaters may present
additional benefit of complying with regulations for toxic
substances.
It is in techniques where both water and reagent
conservation and recovery can be practiced that one can
begin to see a long-term solution and even a payout. We
all know that except for recovery of noble metals such as
gold, any recovery technique is more expensive than no
treatment at all. However the reality of the present is that
"no treatment" is no longer a viable alternative.
Let's now have a look at some of our programs. In
general the majority of our projects have been concerned
with recovery of either a metal or another reagent of
importance and water.
Our involvement in reverse osmosis (R. O.) spans
seven years, and we have participated in nine projects.
Two are surveys, two laboratory investigations, three
field tests, and finally the most recent one is a design,
construction and field testing of a full scale mobile unit.
We can now say that early EPA-AES participation in the
reverse osmosis development program speeded up
adaptation of this technology to a variety of metal
finishing wastewaters by several years. Of course, reverse
osmosis is best utilized to recover and recyle the
SLIDE 4
REVERSE OSMOSIS PROJECTS
Recipient
The State of Min-
nesota Pollution
Control Agency
AES
AES
AES
AES
AES
AES
AES
AES
Kind of Project
Survey
Survey
Laboratory
(NS-100 membrane)
Laboratory
(PBI membrane)
Field Test
(Copper Cyanide)
Field Test
(Watts Nickel)
Field Test
(Zinc Cyanide)
Pilot Plant (New mem-
branes' Evaluation)
Full-scale mobile unit
chemicals from a segregated rinsewater stream and not
merely to concentrate the rinsewater to facilitate
chemical treatment. Advantages of reverse osmosis are
many and will be discussed in another paper at this
session. Drawback to date has been the lack of suitable
membranes, and our program was concerned with
development of those.
Fewer projects have been carried out in electrodialysis
and other membrane technologies, though all membrane
techniques offer similar advantages to R. O. in that they
can close the loop on the waste treatment system.
Electrodialysis achieves higher concentrations than
R.O., and thought is being given to the idea that the two
techniques can be combined in sequence, R. O. first and
electrodialysis to follow.
Two of our electrodialysis projects are particularly
worth mentioning.
Results from the Risdon project, when extrapolated to
a full-scale system, promise a payback in about 18
months or less.
Preliminary results from a New Jersey Institute of
Technology project shows that electrodialysis, coupled
with ion flotation, can provide a closed-loop treatment of
fluoborate rinses, which are known to be difficult to treat
by conventional methods. What's new here in the
technical development is that electrodialysis is used to
concentrate an anion instead of a cation and thus
promises to provide a practical recovery of costly
fluoborate reagent. One result may be more fluoborate
plating to replace cyanide, when reliable and simple
treatment for fluoborate is available.
We have emphasized advanced treatments for
rinsewaters, but we have also looked at some processing
solutions and sludges for recovery of materials. Some
earlier projects combined plant modifications such as
segregation of waste streams and water conservation
prior to treatment. Materials were recovered by a variety
of techniques. Nickel has been the metal most studied by
a variety of recovery techniques.
Particular interest in nickel recovery has been stimu-
lated by high prices of nickel and its compounds. Also,
the developers of technologies, as well as EPA, feel that
demonstration of metal recovery with a high potential of
financial success will encourage use of the technology.
And the technology demonstrated for one metal paves
SLIDE 5
ELECTRODIALYSIS
Recipient
Risdon Man-
ufacturing
New Jersey
Institute of
Technology
Wastewater
Treated
PROJECTS
Comment
Nickel Rinse- Pilot-plant
water on line
Fluoborate
rinsewater
Laboratory and
small pilot-
plant on real
wastewater
36
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SLIDE 6
NICKEL RECOVERY PROJECTS
Recipient
Technology
AES
Risdon
Manufacturing
Seaboard Metal
Finishing
Houdaille
Industries, Inc.
Reverse Osmosis
(Watts Nickel Field
Test)
Electrodialysis
Donnan Dialysis
Ion-exchange
the way to recovery for other metals. Development of a
PA-300 reverse osmosis membrane resistant to both
alkali and acids may provide recovery/treatment of zinc
cyanide rinsewater and maybe for some chromic acid
rinses. Electrodialysis with a suitable membrane may
recover hexavalent chromium. DuPont's Nafion® poly-
mer provided a membrane for nickel by Donnan Dialysis
and may also work for other metals. Work is being
carried out with other polymers to develop new
membranes for Donnan Dialysis for a variety of metals.
Evaporation produces pure water and recovers
chemicals but is considered to be energy-intensive. Use of
evaporation for recovery of water alone and generation
of soluble and useless salts for disposal has been criticized
as both costly and impractical. However, our two
projects, one with a Corning evaporator for recovery of
chromic acid, and the second with an Alcoa evaporator
for recovery of phosphate cleaning solution revealed that
substantial payoff can be achieved. Recovery of chromic
acid decreased purchases of new acid by 80% and
additional savings came from avoiding chemical
treatment for chromium. Alcoa has developed an
evaporator that works on waste heat. If a steady source of
waste heat is available at the plant, this evaporator can be
economically used on a variety of industrial wastes.
Ion exchange is suitable for material recovery and does
not concentrate organic impurities. However, chemicals
are needed for resin regeneration and there is an effluent
SLIDE 7
RECOVERY TECHNIQUES
Evaporation
Ion-Exchange
Cementation
Integrated Treatment
Reverse Osmosis
Other Membrane Techniques
ZDS™ System
(Solvent rinsing system)
Starch Xanthate
stream. Ingenuity in designing ion exchange systems can
make some applications very attractive.
Lancy Laboratories invented an ion exchange process
based on an "acid retardation" principle, and only water
is used for eluting the acid from the resin bed. EPA is
demonstrating this technique to recover phosphoric acid
used in bright finishing of aluminum.
Another attractive ion exchange system, called
Reciprocating Flow Ion Exchange (RFIE), has been
developed by Eco-Tec Limited of Toronto for recovery of
waste metals from plating operations. EPA is currently
demonstrating the Eco-Tec system for recovery of nickel
from four rinse systems at the Huntington Division of
Houdaille, Industries, Inc. Eco-Tec claims that the
economics of their system are favorable, particularly for
nickel. If a system recovers 5 kg/hr of nickel salts,
payback on capital investment may be as short as 8
months.
We recognize that there are numerous cases where
recovery is not at all practical. Therefore we have had
several projects on advanced treatment technologies
which provided considerable improvements over what
was or is available. Let's have a look at the following
projects.
Here I would like first to draw your attention to three
projects. The first is a sulfide precipitation by insoluble
FeS (Sulfex process) that reduces concentrations of
heavy metals in effluent to very low levels, works well for
mixed metal effluent, and produces easily filterable
sludge. There is some concern over safe disposal of
sulfide sludges, however, because they may be reoxidized
and solubilized.
The second project is the use of ozone as an oxidant for
cyanides instead of chlorine or hypochlorite. The main
SLIDE 8
ADVANCED TREATMENT TECHNOLOGIES
Recipient
Technology
Beaton & Corbin
New England Plating
Atomics
International
University of
Waterloo
MFF
Sealectro Corporation
MFF
MFF
University of
Delaware
Integrated Treatment
Electrolytic
Electrolytic
Electrolytic
Sulfide precipitation
Ozone
Activated Carbon and
other techniques
Activated Carbon and
other techniques
Activated Carbon
37
-------
Recipient
SLIDE 9
NEW APPROACHES
Kind of Project
Reed & Barton
Silversmith
Surface Technology,
Inc.
Feasibility Study of
Group Treatment of
Multi-Company Plating
Wastes
New dielectric surface
activation process
advantages are that no hazardous chemicals need to be
handled or stored, no dissolved solids are added to the
effluent, and the overall cost is comparable with that of
chlorination processes.
The third project I would like to mention is the use of
activated carbon for a polishing treatment of chromium-
containing wastewater. In the case of activated carbon
treatment, the pollutants are not recovered, but the
carbon must be regenerated to achieve attractive
economics. This project, still ongoing, will modify and
improve the regeneration of activated carbon.
Centralized waste treatment for metal finishing waste
as a private enterprise or as a regional facility has been
considered for some time as an alternative approach to
individual treatment systems. The users or co-owners, for
example, would be small plants located in urban areas,
where it is difficult to operate any treatment plant at all.
The centralized facility, on the other hand, can be
designed and operated to utilize the economy of scale.
Our program has made an attempt to explore this
approach as a possible alternative route for a small
plater. A project awarded to the Reed & Barton
Silversmith Co. of Taunton, Massachusetts was a
feasibility study of a joint waste treatment plant owned
and operated by several companies that generate
compatible wastes versus individual treatments by each
company. At the end of the study, the companies decided
against participating in the joint treatment program,
particularly against plant co-ownership. However, the
feasibility study is well documented and may convince
another grouping of companies to undertake this route.
We also realize that development of new finishing pro-
cesses which are less polluting than the presently used
ones is another approach to minimize environmental
problems. We are carrying out one such project, under
contract to Surface Technology, Inc. of Princeton, N. J.,
which is a pilot plant development and demonstration
of a new surface activation process needed to prepare a
dielectric surface for subsequent electroless copper plat-
ing or other types of plating. This process, if successful,
will provide an alternative to the commonly used palla-
dium/tin activation process. As I mentioned, palladium
is almost entirely imported from the U. S. S. R. The new
process will use common metals instead of palladium,
require less chemicals, be less polluting, safer to operate
and provide a good product. I mention this project as an
example of resource conservation rather than of materi-
SLIDE 10
MATERIALS RECOVERED IN EPA PROJECTS
Water
Metals: Ni, Cu, Cr, Zn, Cd
Acids: Phosphoric, Chromic
Anion: Fluoborate
Cleaning Agent: Phosphate
als recovery.
I must admit I have selected very few projects to
illustrate today's discussion, and I have highlighted
primarily their advantages. For the detailed information
about these projects and others which are equally worthy,
one should turn to the EPA reports.
However, we all realize that the results obtained in a
specific evaluation of an individual technique at a single
plant are not necessarily applicable to other plants. On
the other hand a failure of technology at a single facility
should not discredit this technology without careful
examination of the causes for failure.
In other words, EPA-sponsored projects are intended
as catalysts from which firms in the industry can develop
customized processes uniquely applicable to their own
situations by carefully comparing the demonstration
work with their own operations, both from a technical
and from an economic point of view.
Let's say a few words about the future of R&D.
In general, our R&D program will maintain and even
increase its efforts toward development and demonstra-
tion of material recovery systems. Needs for research are
many and I will mention only a few.
There are wastewaters for which there are no adequate
treatments such as effluents with highly complexed
cyanide ions, for example. There are not many economic
control options for small platers. Reliability of presently
used treatment systems can be improved if interferences
with chemical reactions are identified and dealt with. In
shaping our research program we have been listening to
the industry, its associations and its suppliers. We are
looking forward to the evening session on the new
technology needs.
We have seen in the above discussion that the Federal
Pollution Control Act (Public Law 92-500) and local
laws and regulations are placing increasingly strict limits
on the levels of various substances that can be discharged.
Other factors ranging from the shortage of landfill
space to the concern over environmentally safe disposal
of wastes limit the options in which waste treatment
sludges or untreated effluents can be disposed of. And
thus we have seen that the industry is moved towards the
only avenue possible, which is materials recovery.
In addition, dwindling natural resources, recent
material shortages, and higher materials costs expected
in the future are further stimuli to material recovery. We
have seen from brief review that the Agency's research
projects are mainly oriented toward furthering materials
recovery by demonstrating feasibility with such substan-
ces as nickel, copper, zinc, chromic acid, phosphoric
acid, fluoborate and water.
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REFERENCES 2. Skovronek, H. S., Stinson, Mary, K. "Advanced
Treatment Approaches for Metal Finishing, 64, Part
1. Water Pollution Abatement Technology: Capabili- I, No. 10, 30, Part II, No. 11, 24(1977).
ties and Cost - Metal Finishing Industry. Report by 3. Henry C. Gill, "Joint Treatment of Multicompany
Lancy Laboratories for National Commission on Plating Wastes", EPA Grant No. S-805181. Report
Water Quality. PB-248-808, National Technical under review.
Information Service, Springfield, Va. 22161 (Oct. 3. Hurlich, H.,"Planet Earth's Metal Resources,"Metal
1975). Progress, October 1977.
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Group Treatment of Multicompany Plating Wastes
The Taunton Silver Project
Ms. Marsha Gorden*
OVERVIEW
Perhaps the best way to review and evaluate a project
of this nature is to consider the steps through which it has
progressed. Thus the total project can be understood in
terms of its key variables, permitting duplication as
desired.
Step One — Identification of Problem
The concept began at an industrial meeting under the
auspices of the regional Section 208 (PL92-500) program
at the local Chamber of Commerce. That discussion
focused on potential aspects of the pretreatment program
that the city soon would be required to implement along
with the upgrading of its municipal sewage treatment
facility. There was a great deal of uncertainty as to what
the specific requirements for the participating industries
would be, but there was a general sense of a need for strict
metallic limits in order to protect the municipal facility
and meet its discharge permit.
Step Two — Consideration of Cost-Effective Solutions
At the conclusion of the meeting, one of the indus-
trialists in particular, who understood the situation,
explained that he and the others would need help. Since
there were a number of companies in the city with similar
product lines and probably similar waste streams, some
means of group treatment seemed an appropriate
approach to the problem. Subsequent discussions with
several of the plant engineers again showed the concern
of meeting pretreatment regulations and an interest in a
group project. From this start, it was necessary to go to
the management levels of the companies next: first, to
explain the nature of the coming regulations and, second,
to describe a potential group solution.
Step Three — Development of Approach
It was deemed interesting to three companies in par-
ticular, which decided to explore the possibility of EPA
R&D funding, as there was no precedent for establish-
ment of such a group pretreatment program. Upon selec-
tion of an engineering consultant and an institutional
subcontractor to accomplish the work, an application
was submitted to EPA.
*Ms. Marsha Gorden
Development Sciences, Inc.
P. O. Box 144, Sagamore, MA 02561
At that time, the three companies signed a "Letter of
Intent" indicating their agreement to the overall project
and to the designation of one company as "company of
record" on the grant application.
The issues of timing and particularly of enforcement
schedules became a concern early in the project. July
1977 deadlines were approaching and one nearby
company decided not to participate during the initial
discussions, believing his permit schedule would not
allow a delay. One of the primary three companies was in
a similar situation, splitting its effluent between an
NPDES permit to the river and the municipal facility.
This company elected to stay in the project, recognizing
however that most of its waste streams were committed to
the scheduled installation and hence not available to
group treatment.
Similarly, one of the interested secondary companies
in a nearby community was also on a permit schedule and
hence not eligible for full consideration. Just before the
actual grant acceptance, the other secondary company in
a neighboring community was placed on a pretreatment
schedule, disallowing its consideration except in a
marginal sense. However, the primary three companies
continued their participation in the feasibility study as
described and divided their costs on a three-way basis.
Step Four — Designation of Common Elements
At the start of the study each of these three plants was
analyzed for common characteristics of all batch
discharges, including sludges, and of rinse watersystems.
A chart was drawn up showing alkali cleaners, acids with
various metals, cyanides, salvable and inert sludges,
hexavalent chromium, and solids. In this way, the three
companies' waste materials were compared to determine
candidates for group treatment. From this list ten batch
wastes suitable for common treatment and disposal were
described.
Acids
1. Those high in silver-strips, etchants
2. Those high in copper sulfuric pickles, bright dips
3. Those high in nickel-strips, dragout recovery
4. Those that are relatively low in metal content
5. Those containing hexavalent chromium
Cyanides
6. Those high in silver—filter wash water, floor spill,
dragout recovery, strike baths, strips
40
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7. Those high in copper—same sources as for silver
8. Those low in metal content
Sludges
9. Those resulting from waste treatment which have
solids content below 10 per cent solids
10. Those that are untreated—solids removed from the
bottom of a process tank, for example
Step Five — Designation of Discharge Points and
Disposal Recovery System
Next, the issue of size and location of the companies
was considered. Which ones were limited by space and
perhaps personnel, and which had access to receiving
waters as well as to the municipal sewer? Was there a
more centralized location at one plant rather than at
another? Discharge to the municipal sewer would limit
the project to companies within the city, whereas
discharge to a river would limit the size to reasonable
transportation distances within the state.
Step Six — Evaluation of Regulatory Procedures
Discharges both to receiving waters and to the
municipal sewer would require permits, monitoring and
reporting. Similarly, discharge to a hazardous waste
landfill would necessitate a permit, monitoring and
reporting. There were interactions to be considered and
discussed with the EPA regional office, the State Water
Pollution Control Agency, and the city department of
sewers. The city's sewer ordinance, with its specific
metallic limits, was approved by the EPA and the state
but still was under review by the local City Council
during the progress of the study. It was made available,
however, to the three companies and their consultants.
The issue of antidegradation on one segment of the river
became a concern. All of these regulations and
requirements were evaluated as part of the study.
Step Seven — Economic Analysis of Alternatives
The cost-estimating procedure began with individual
plant alternatives considering water conservation
techniques and various known technologies to meet the
different discharge requirements of the river and the
municipal sewer. Group alternatives were then developed
on the basis of the individual alternatives in order to
compare costs. Material recovery proved to be one of the
most important elements of the group treatment
program.
Step Eight — Evaluation of Institutional/
Financial Elements
Similarly, institutional arrangements were analyzed:
who would own the treatment plant(s), how it would be
financed, and how it would be operated. The State
Department of Commerce and Development was inter-
ested in pollution control bonding but was unaware of
IRS consideration of material recovery as part of the pro-
ject. Similarly, local banks were interested in various
financial alternatives. There were some new questions to
ask, and there were some new decisions to make, but it
was institutionally feasible.
Step Nine — Consideration of Potential
Project Expansion
The number of companies likely to participate was
evaluated in a preliminary manner. With the assistance of
the local Chamber of Commerce, a brief questionnaire
was distributed to companies having potential waste
streams matching the ten batch categories. Interest was
expressed on the part of several, but without the city's
proclamation of the sewer ordinance with its metallic
limits, companies were hesitant to release specific
information. Many were not even aware of the upcoming
sewer ordinance and their potential pollutants to the
municipal sewer.
Step Ten — Final Analysis of Alternatives and Decisions
At the completion of the study, the three companies
had received much data—technical, regulatory, financial
and institutional. They are presently evaluating all this
information in order to make required decisions. It is
anticipated that the municipal sewer ordinance will be
released shortly with a compliance schedule, thus
providing a citywide focus on this project.
INTRODUCTION
Objective
This project has been designed to test the feasibility of
bringing together and treating common wastewater
streams from three manufacturers of silver and silver-
plated holloware. In particular, the study has been
planned to explore alternative group industrial
wastewater treatment technologies applicable to this
segment of the electroplating industry for three basic
purposes:
• To determine the potential for cost savings with
group treatment,
• To develop the legal and institutional arrangements
necessary for group treatment implementation, and
• To encourage opportunities for material recovery
and industrial water reuse.
A project of this nature can demonstrate the opportun-
ities for aggregating materials within a region to accom-
plish environmental goals at reduced costs.
The issue of economy of scale for this industry made up
of many small companies has never been demonstrated in
a group project of this nature. Accordingly, this study has
been designed to develop the technical/institutional/
financial factors necessary to evaluate group and
individual treatment alternatives. If the problems were
viewed only from the treatment perspective, its utility as
an example would be limited. However, by incorporating
the legal, institutional and reuse components, a more
complete view of the industry problem is presented. By
including these components, the solution is of value to
Taunton as well as to others looking for answers to
similar problems.
It should be recognized, however, that any example is a
unique combination in terms of size, product, associated
waste streams, and nearby disposal opportunities.
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Consequently, this project should be viewed not as
strictly typical of this industry or the region but rather as
an example presenting a group of variables and
circumstances which are useful as a model. In this way,
the report can be read as a demonstration of an evaluative
approach and thus can be more useful to a larger
audience.
Project History
This project was an outgrowth of a Section 208 (PL92-
500) areawide wastewater management plan under
development by the Southeastern Regional Planning and
Economic Development District (SRPEDD) of
Massachusetts. In the course of investigating the impact
of industrial wastewater discharges, it became apparent
that opportunities existed for joint treatment of similar
industrial waste streams in the study area. Analysis of
industrial effluents in the several river basins under
SRPEDD's planning jurisdiction indicated similar waste
streams in proximity to each other, particularly in the
City of Taunton.
This city has a long history of metal crafting beginning
with America's first ironworks in 1656. From that start
the city has favored industry rather than agriculture,
building a tradition of metalworking which, today, takes
the form of silverware, bronze and copperware, stainless
steel, pewterware, and other metallic items. Many of the
present-day companies employ electroplating processes
that, as a group, release a variety of metals to the Taunton
River, either through direct discharge or through the
municipal treatment plant.
The Companies
The three companies participating in this project
represent an extension of Colonial America's early tradi-
tion of metal craft, which included silver-smithing. Reed
& Barton, founded in 1824, is one of the country's oldest
and largest silverware manufacturers, presently pro-
ducing a varied product line of tableware and holloware.
Poole Silver Company, a Division of Towle Manufac-
turing Company of Newburyport, Massachusetts, has
been in Taunton since 1893 and produces silver-plated
and pewter holloware. These two companies are located
on the Mill River, a tributary of the Taunton, as shown in
Figvre 1, "Classification Map of Taunton River Basin."
F. B. Rogers Silver Company, a wholly-owned
subsidiary of National Silver Industries, Inc., is located
directly on the Taunton River where it has a long history
of producing silverplated and pewter holloware. Detailed
descriptions of the plants are available in the complete
report.
The Community
During the period of this project, the City of Taunton.
with its Conservation Commission, has begun a
Riverbank Beautification Program. With the assistance
of the Comprehensive Employment Training Act
(CETA) employees, initial steps to clear sites for walking
and cross-country running have been taken. The
preliminary plans call for additional land acquisition and
future work to provide foot-bridges over the river, a
bicycle path and a boat landing.* Since most of the
Taunton River has already been identified and now is
charted as a Wampanoag Indian Canoe Passage** across
southeastern Massachusetts, there is additional interest
in the river's past uses for transportation and fishing.
The completion of an industrial pretreatment program
such as this report describes along with the upgrading of
the municipal sewage treatment plant will encourage
these additional activities along the river in accordance
with the water quality goals previously established.
* Further information available from the Taunton Conservation
Commission. P. O. Box 247. Taunton. MA 02780.
""Wampanoag Commemorative Canoe Passage." prepared by
Plymouth County Development Council in cooperation with the
Bristol County Development Council.
Figure 1
Classification Map
Of Taunton River Basin
*Source:
The Taunton River Basin, Part A Water Quality Data
Department of Environmental Quality Engineering Common-
wealth of Massachusetts, Division of Water Pollution Control.
Westborough, Massachusetts. December 1975.
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TECHNICAL ASSESSMENT
The technical assessment required to meet the
objectives of the study includes:
• Analysis of the pollution control problems facing
the three firms, including the mutual problems
caused by manufacturing operations, the unique
problems presented by their location, and the
physical statistics relative to each firm;
• The treatability of the process wastewater;
• The various concepts employed in development of a
multicompany treatment facility.
The technical assessment provides the basis for the
various economic considerations presented later in this
report. Detailed information relative to each firm and
potential group treatment is provided in Appendices A
through D of the complete report.*
Pollution Control Problems
All three firms are large producers of silverplated
holloware. As one would suspect, the basic steps required
to produce silverplated holloware from brass sheet stock
result in many common wet process operations that
produce similar wastewater. Obviously their location in
Taunton, Massachusetts, presents each firm with
common problems relative to meeting regulatory
requirements. Many of the pollution control problems
are unique to this location. This is important to
understand when using the information in this report. In
order to consider the concept of multicompany treatment
of plating wastes for other areas, a description of each
participating firm and its particular pollution problem is
provided. These problems are subdivided into discrete
problems, such as wastewater streams that are common
to all three firms as well as unique to each one.
Common Features
Manufacturing Operations—
In the production of holloware, brass sheet stock is
mechanically pressed into shapes which are then soldered
to each other. The various decorative edgings, legs,
handles, etc. are next soldered to items to produce the
final shape of the finished part. Prior to plating, the
assembled parts are polished and buffed to obtain a
highly reflective surface for finishing operations. The
assembled parts are silverplated using cyanide solutions.
In some cases an underplate of copper and/or nickel is
employed. After plating, a final finishing operation is
used to mechanically produce a product that is uniform
in appearance.
Wet Processing—
The most common wet processing of parts is cleaning.
Depending upon the particular production item, a given
piece of metal may be cleaned as many as seven times
*The report will be available from the Industrial Environmental
Research Laboratory, EPA, Cincinnati, Ohio 45268.
from start to finish. Cleaning is employed in stamping
and drawing steps, before and after annealing, before and
after solder assembly, after polishing and buffing, prior
to plating, and in some cases during final finishing. The
alkaline cleaners used in these steps have been selected to
result in minimum attack on the base metal.
Strong acids are employed to remove annealing scales.
However, the majority of acids used are only mildly
corrosive to the base metal in order to maintain the
appropriate surface finish. All firms employ either
fluoboric acid or proprietary mild acid salts for surface
activation prior to plating to minimize attack on the
polished base metal and to satisfy the demands of the tin-
lead alloys used for decorative and assembly objectives.
Cyanide copper plating is used to cover the parts with
an initial plate, enhancing the adhesion of subsequent
electrodeposits. Conventional acid nickel is plated onto
some parts, either as a final finish or as a preplate prior to
silver. Silverplating is done in conventional cyanide
solutions using proprietary brighteners. Attempts to
replace cyanide solutions with plating baths free of
cyanide have not been successful.
As is common to other plating operations, a modest
percentage of wastewater results from chemical stripping
of plating fixtures, or racks, and the stripping of items for
rework and salvage.
Combined Wastewater—
Another common feature for these three firms, which
is not unique for older plants that were built and were
expanded when concern for pollution control was
minimal, is presented by the multiplicity of drain systems
that combined process water with cooling water and
sanitary wastewater. When these plants were built, the
only concern appeared to be to remove all water from the
plant. Wet processing is scattered throughout the plants
and located to optimize material flow and is not located
to centralize the wet processes—or their wastewater.
Water Waste—
Another common feature for these three firms is the
excessive use of water. When the cost of water was the
only concern, and as it was initially a cheap commodity,
production lines and plating practices were established
wherein large quantities of water were employed in
rinsing and cooling water applications. Excluding water
used for sanitary purposes, the three firms used a total of
425,000 gallons per day. With the concern for water
conservation, changes in the past several years have
reduced this water consumption somewhat. Now, with
the objective of minimizing water pollution control costs,
further conservation effort became mandatory. An
estimated reduction of 280,000 gallons per day can be
realized for these three firms as they act upon recommen-
dations.
Silver Reclamation—
As the value of silver has risen over the years, various
efforts have been implemented by the three companies to
minimize their losses to the sewer. The attention directed
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to these silver reclamation efforts naturally depended
upon the quantity being discharged. For many years,
spent process solutions that were high in silver content
were shipped out for reclamation of silver values. In one
case, where efforts to control pollution were initiated in
1972, silver reclamation was extended to include the
sludges resulting from cyanide oxidation. At another
firm, treatment of some rinses with metallic zinc to
displace dissolved silver by cementation allowed for
partial recovery of silver draining to the sewer. All firms
have recently adopted electrolysis as a means of lowering
the silver content in dragout recovery tanks—and thus
reducing the amount of silver entering the rinse waters.
When the pollution problems are resolved, recovery of
additional silver can be realized.
Wastewater Characterization—
The final common feature of the pollution control
problem relates to the process water itself. All firms have
water that can be segregated into:
• Waters resulting from alkaline cleaning which are
mildly alkaline and low in heavy metals;
• Waters that are acidic and/or alkaline in nature
which contain minor amounts of the heavy metals—
copper, zinc, tin, lead and nickel (only two of three
for nickel);
• Waters that are strongly acidic and contain high
concentrations of heavy metals;
• Cyanide-bearing water that invariably contains
copper and silver; and
additionally, in two of the firms there are waters that
essentially contain only suspended solids. Also, waste-
water contamination levels increase significantly when
spent or contaminated process solutions are dumped into
the sewer.
The Three Companies
Company A has been discharging during a single shift
operation in excess of 220,000 GPD of industrial-use
water, through seven sanitary sewer outlets, with all but
one being combined with sanitary wastewater. Water is
used in thirty departments located in twelve buildings. A
significant problem is presented in the isolation and
collection for treatment from these sources. The problem
is compounded by the need to segregate the wastes for
treatability purposes and magnified by the river dividing
the plant in half. The process wastewater contains objec-
tionable amounts of cyanide (including complexes of
copper and silver) and the heavy metals copper, zinc,
silver, nickel and iron. Lesser amounts of chromium, tin
and lead are present, which will become of concern as
water conservation efforts eliminate the dilution effect.
Historically, the wastewater has been acidic. With the
preponderance of alkaline cleaning and a minimum of
acid processing, it would be expected that the waste-
water would be near neutral or slightly alkaline. It is
believed the acidic condition is as much a result of the
quality of the raw water as it is of the metal finishing
and plating processes employed.
Company B has been discharging during a single shift
operation in excess of 33,000 GPD of industrial-use
water combined with additional sanitary wastewater.
The collection, isolation, and segregation problems are
not as complex as at Company A, but it has no land avail-
able for expansion to install treatment facilities and will
have to use a storm sewer if discharging to the river.
Company C has been discharging during a single shift
operation in excess of 130,000 GPD, with 40,000 GPD
entering the Taunton River under an NPDES permit and
the rest via three connections to the sanitary sewer, two
of which are mixed with sanitary wastewater. Unlike the
other two firms, this company has been treating waste-
water discharging to the river and pretreating most of
its wastewater discharging to the sanitary sewer. As with
Company B, this firm has no adjacent land to use for
additional treatment facilities. The untreated process
wastewater contains objectionable amounts of cyanide
(including complexes of copper and silver) and the heavy
metals copper, zinc, silver and nickel. Lesser amounts
of tin and lead are present. The most pressing problem
facing this company is the necessity to upgrade its
existing treatment facilities in facing the more exacting
limits established by new regulations.
Concepts
The concepts considered under this study include each
firm treating its own wastewater; group treatment of
combined wastewater, in total or in part; and extension
of group treatment facilities to include other firms having
similar wastewater. In addition, considerations have
been given for recovery values for salvable metals, tech-
niques for enhancing the values as volume expansion
permits, and new technology having potential merit.
Detailed descriptions of facilities for each plant are
provided in Appendices A, B and C of the complete
report. Those identified as Primary Design consider each
plant being required to treat its own waste separately and
form the basis for comparison of alternatives. In addi-
tion, the impact caused by discharge point (sanitary
sewer vs. stream) is described. The advantages of reusing
treated process water are brought forth. A description of
joint efforts is provided in Appendix D of the complete
report. In considering expansion of group treatment
effort, some alternatives discussed for the companies
include concentration of rinse waters.
Assessment
From an overall viewpoint it appears that the best
interest of the firms and the total environment will be
served by each plant treating its own flowing rinse waters
and by combining the firm's efforts for treatment of the
batch wastes resulting from the dumping of spent process
solutions, from accidental discharges, and waste treat-
ment operation resident for each plant. Additional bene-
fits can be gained by concentration of selected rinses for
subsequent batch treatment. The values for salvable
metals are improved by the group venture's use of more
efficient technology.
The advantages of group treatment that will influence
any decision to proceed include:
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1. Cost reductions will result from bulk purchases of
treatment chemicals that would not otherwise be
available for each firm acting independently.
2. More efficient sludge handling facilities can be
applied for all firms with a reduction in disposal
costs anticipated.
3. Batch treatment equipment will receive greater utili-
zation by expanded capacity, resulting in a lower cost
per unit treated.
4. Technicians will expend a greater portion of their
time on batch wastes and, in doing so, will become
more skilled, thus enhancing environmental quality.
5. The extramural support (analysis, assay, consulta-
tion) for the single facility will be less than were each
treated separately.
6. The net salvage values received from refiners for
silver, after deducting processing costs, will be
higher.
7. Salvage potentials for copper and nickel become
more practical as the amount involved increases by
multiple company effons.
8. More efficient reclamation methods can be justified
by joint action than for each independently. The
potential for separating copper and silver from
mixed cyanides carries with it certain development
expenses that can be amortized over expanded use.
9. Electrolysis of concentrated cyanide solutions as
proposed for the group treatment is approximately
15-20 per cent of the operating cost required by
chlorination. This capital intense process requires a
minimum quantity of batch cyanide wastewater to
justify the greater cost to buy and install than exist-
ing with chlorination techniques.
10. As the problems relating to solid waste disposal
become resolved, costs will escalate. Disposal in bulk
will reduce expenses to all firms.
It can be concluded that both the environment and the
firms involved themselves will benefit from group treat-
ment of batch wastewaters. The information on the
economics to support this conclusion follows in the next
section.
ECONOMIC ASSESSMENT
The assessment of economic considerations included
the capital investment and operating expenses for: each
plant providing its own complete wastewater treatment
facilities with multiple discharge points; various alter-
natives for each company; group treatment of the three
companies' wastewaters; expansion of the group treat-
ment concept to include other firms; and recovery values.
The data summarized in this section are explained in
detail in Appendixes A through D in the complete report.
Two economic factors have not been included in this
assessment. Depreciation of equipment depends upon
judgment factors and upon tax incentives. The other
economic factor applies to the concept of "cost of
money," wherein annual expenses are attributed to hav-
ing one's capital tied up in nonproductive facilities. At the
present time, the "cost of money" is in the 8 to 10 per
cent range. The reader is left to apply these two factors to
annual operating expenses as desired.
Three Separate Facilities
As a basis for comparison of alternatives and poten-
tial joint treatment of wastewater, the following data are
presented for each firm. Included for Companies A and B
are the economic impacts of not being able to use the river
for discharge of part of their treated wastewater; then
total discharge would be required to the sanitary sewer.
The economic advisability of reusing treated wastewater
has also been estimated.
Company A
The Primary Design—using complete treatment of
some rinse waters prior to stream discharge and pretreat-
ment of other rinse waters prior to discharge to the sani-
tary sewer, together with batch treatment—will require a
capital investment of $640,500 and result in an annual
operating expense of $138,595. A modest reduction in
operating expense will result from partial reuse of treated
waters. If stream discharge is prohibited, expenditures
increase by 15.8 per cent for capital and 27.8 per cent for
operations. Under the total discharge to the sanitary
sewer concept, the savings by reuse of treated water are
much greater and show a 13-month return for additional
invested capital required for reuse of the treated water.
The data shown for the design that considers elimina-
tion of batch treatment facilities may be misleading if
used out of context and compared with subsequent
information concerning group treatment. Certain dis-
crete components would be required for rinse water treat-
ment which might be used also for batch treatment. Since
their common use is practical at a common treatment
site, the capitalization and operating expense should
not be duplicated, but rather prorated as to use by each
company. Caution must also be expressed for the some-
what small increase in operating expense when com-
paring this alternative with the Primary Design. The
costs for contract hauling and disposal reflect present
economics. As the regulations governing this cost
become fully developed, it is believed that the disposal
costs will increase drastically as the cost of disposal is
passed back to the generating source. One source ques-
tioned anticipates a 1000 per cent increase over current
rates.
Company B
As with the previous firm, the most attractive alterna-
tive considered a dual discharge (i.e. stream and sanitary
sewer). This Primary Design is expected to require a
capital investment of $141,000 and result in an annual
operating expense of $37,977. If stream discharge is pro-
hibited, expenditures will increase by 13.7 per cent for
capital and 34.0 per cent for operating expense. Again,
reuse of treated water is advisable—although the rate of
return for additional invested capital is lower than for the
previous firm, as the potential for cost reduction is smal-
ler with only a portion of the available water being
reused.
As with the previous company, the concept that elim-
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inates batch treatment contains the same probability for
escalated disposal costs for collected batch wastes. At
Company A some of the equipment used for treating
rinses finds utilization in batch treatment. However,
for this smaller Company B, transfer of batch treatment
operations to another location does not significantly
reduce capital investment (less than 5 per cent reduction).
This company is presented with an option to replace a
segment of its rinse water treatment system with evapora-
tive recovery. There is little difference in capital invest-
ment. Operating expenses increase approximately 10 per
cent—primarily because of higher energy requirements.
Company C
This company has completed its capital investment for
a major portion of the waste treatment facility during the
past three to four years. The capital values shown are
what one would expect to invest at today's market condi-
tions and do not necessarily reflect actual expenditures in
the past. In addition, certain unique conditions that
caused higher than normal expenses have not been in-
cluded so that the overall picture will be more represen-
tative of the average plant yet to face its pollution prob-
lem entirely. (For example, with normal high tide in the
adjacent Taunton River being 12 to 18 inches below the
plating room floor level, high expenses were realized in
installing five-foot deep sumps used to collect waste-
waters.)
The design approach employed for the Primary Design
was similar to that used for the other two firms, except
that it was influenced by earlier design concepts that
resulted in the existing facilities. Since the present river
discharge is being influenced by the existing upgrade
efforts, it was felt that initially little attention should be
directed toward increasing the facilities used for river dis-
charge. As a result, the Primary Design is not considered
to be the most attractive alternative. Alternative 1 shows
a modest (1.7 per cent) increase in capital expenditure
which is returned the first year through reduced operat-
ing expense. By being located adjacent to the Taunton
River, this company does not have to consider final
filtration at the same time as the other two firms.
Under Alternative Design 1 a greater portion of the
wastewater containing heavy metals is diverted to the
river discharge. Capital expenditures are valued at
$299,500 and an annual operating expense of $49,888 is
expected. Using this concept, little economic advan-
tage is realized through reuse of treated process water.
Again, the design that uses contract hauling in place of
batch neutralization is factored for disposal costs that
are not expected to remain at the present price. Much of
the batch treatment equipment required for complete in-
plant treatment is already installed. Consequently, the
opportunity for reducing capital costs is lower for this
firm. The greatest advantage to this company of using
group treatment facilities will come from reduced
operating expenses and improved silver recovery.
Group Treatment
The economic assessment for group treatment efforts
considers that each plant will install its own treatment
facilities for flowing rinses and that batch wastes will be
treated at Company A. It is not practical within the scope
of this study to factor all the possible permutations
presented by the various alternatives. Rather, the most
practical combinations, and those that are most likely to
occur, are used for the economic assessment of group
treatment.
For the purposes of quantifying the various cost
factors, that portion of Company A's facilities used for
batch treatment is identified as though the group treat-
ment facilities were a fourth identity. Those items that arc
used by both rinse water treatment and batch treatment
have been prorated to each system as an aid to quanti-
fying this option.
Capital Expenditures
The capital expenditures listed consider that each firm
will treat its own flowing rinse waters at its respective
plant; that collection facilities will be provided for segre-
gated batch wastewater and residual wastes from their
treatment facilities; that stream discharge will be per-
mitted for each firm; that there will be maximum utiliza-
tion of treated wastewater; and that batch wastes will be
treated at Company A.
With the same four capital factors as used previously,
the capital expenditures for each company to treat its
rinse waters will be:
Company A $484,500
Company B $141,600
Company C $293,300
with the joint batch treatment facilities being located at
Company A
Joint Treatment Facilities $173,900.
The total capital expenditure amounts to $1,093,300 and
should be compared with the capital required for each
company to install its own complete facilities ($1,096
000). Within the accuracy of cost analysis, these two
figures indicate that there is no capital advantage one way
or the other.
Operating Costs
Using the same basis as applied for capital expendi-
tures, the annual operating expenses will be:
Company A $100,900
Company B $ 31,900
Company C $ 44,300
Joint Treatment Facilities $ 41,300
Comparing this with the expenses anticipated at each
plant if totally treating its own waste, a modest saving of
$3,000 per year is expected. This does not include depre-
ciation of equipment and the cost of borrowing, as pre-
viously discussed.
Cost Variations
The various cost reductions listed in the earlier section
which result in group treatment efforts for batch waste
reductions can be quantified.
Sodium hydroxide, in bulk shipments, will cost
approximately 50 per cent of the price in drum lots
46
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Sludge disposal rates will gain by bulk shipments, which
are prices at $0.13 per gallon versus $0.40 per gallon in
drum lots. It is also expected that the volume of sludge
will be reduced by the more sophisticated handling facili-
ties. Sludges with a solids content of 20 to 25 percent will
result, as compared with 5 to 7 per cent. This will result in
approximately one fourth the amount requiring disposal.
Greater utilization of equipment used for batch treat-
ment will reduce cost factors of equipment depreciation
as applied, for each gallon treated will be approximately
50 per cent. Extramural support will be reduced by
approximately $4,000 per year. This primarily related to
insuring quality of sludges. Other cost variations relative
to reclamation are discussed later in this section of the
report. Cost increases will result from transportation and
these costs are budgeted at $3,000 per year.
Expansion
The expansion of group treatment efforts will depend
upon normal market conditions. Major costs are attri-
buted to the treatment of flowing rinse waters, with far
less capital involved in treating batch wastes. Company
B is a good illustration when considering expansion of
group treatment to include other companies. The oppor-
tunity of reducing capital costs will exist; reduced operat-
ing expenses can also result. It is not practical under the
scope of this study to quantify group treatment expan-
sion in more than the broadest sense.
Expansion is possible without any increase in capital
investment. The facilities included in the joint batch
waste treatment operations are not used 100 per cent of
the time. The various subsystems have been sized to
maximize labor use. This results in some of the equip-
ment being underutilized. As the amount of batch waste
to be treated is expanded, only the direct expenses of
labor, energy, chemicals, supplies and sludge disposal
will increase. When the cost factors that consider applied
overhead and depreciation of equipment are prorated
across each individual batch being treated, then the cost
per batch will decrease according to the total volume
under any expansion concept.
The facilities considered to be a minimum for the three
firms as described earlier have built-in expansion factors
of 40 percent for batch acids, 20 percent for batch cya-
nides, and 80 percent for metal reclamation before any
additional capital investment is required—other than
larger storage facilities for raw waste.
Recovery Values
The previous assessment of economic conditions does
not show an overwhelming ad vantage of group treatment
to produce acceptable water and sludge discharges to the
environment. Attention has been focused on pollution
control itself. Cost advantages do exist relative to the
discharge of residual sludges resulting from waste treat-
ment practices. Where recovery of metal values exists, a
decided advantage can result from use of more sophisti-
cated facilities than can be justified for only the large
plants. In the case of the three firms involved in this pro-
ject, the primary consideration for metal recovery is
silver.
If the volume increases, copper and nickel should be
considered.
Silver reclamation for these companies is extensive.
Paniculate matter removed from dust collection systems
is shipped out to our refiners for reclamation. Some
solutions known to be high in silver are returned to
vendors for reclamation. Metal scrap is salvaged for
silver content. Additional salvage values will result from
processing waste treatment residuals.
Two other metals, copper and nickel, have potentials
for salvage should the volume become larger through
expanded use at the treatment facility. At today's prices,
nickel will bring SI.76/kg($0.80/lb) in solution form and
$0.77/kg ($0.35/lb) in sludges. These values will be
reduced by the costs of shipment and should be consi-
dered only when concentrations are high enough and
volumes warrant bulk transportation. Copper in solution
form can bring $0.88/kg ($0.40/lb), subject to the same
conditions.
Assessment Summary
As discussed earlier, when considering waste treatment
costs to resolve environmental pollution problems alone,
significant dollars are involved. For these three com-
panies, there appear to be marginal advantages to group
treatment of process wastes. However, when including
the recovery values for reclaimable metals, the annual
operating expense is reduced from $218,000 to $88,000.
The full cost reduction can be realized by group treat-
ment. It is believed that the added expense to each firm to
implement individually the recovery aspects will con-
sume at least half of these savings.
In the introduction to this section, two economic fac-
tors were excluded—depreciation and "cost of money."
To fully appreciate the advantage of increased utilization
when applied to the batch treatment system, these fac-
tors should be included. Assuming ten-year useful life for
equipment, the depreciation on a straight-line basis for
the group treatment facilities is $17,390 per year. At an 8
per cent "cost of money," an additional $13,912 per year
is processed. If spread evenly, this will amount to approx-
imately $0.16 per gallon of waste processed. All other
operating expenses for the group batch facility have been
listed at $41,300, or $0.21 per gallon processed. The total
is $0.37 per gallon. Obviously, some process solutions
require a higher share of these costs than others, but
averages can show the advantage of greater utilization.
Depreciation and "cost of money" represent 43 per cent
of the treatment expense with maximum utilization by
these three firms. With less use, as caused by each pro-
viding its own batch treatment facilities, this 43 per cent
expense climbs. By a similar consideration, increased
utilization is possible by expanding the joint facility to
include other firms, which will result in a lowering of this
cost per gallon from $0.16 per gallon to less than $0.10
per gallon.
In spite of the variable cost factors evaluated in this
chapter, group treatment does have an advantage when
metal recovery economics are considered and disadvan-
tages related to individual company treatment operation
are fully appreciated.
47
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ACKNOWLEDGMENTS
The financial support of this project by the Office of
Research and Development, Environmental Protection
Agency, is acknowledged with appreciation. In particu-
lar, sincere thanks are given to Mr. George S. Thompson,
Chief, Metals and Inorganic Chemicals Branch, Indus-
trial Environmental Research Laboratory; and Ms.
Mary K. Stinson, Project Engineer, Metals and Inor-
ganic Chemicals Branch. Both have given their valuable
administrative and technical assistance as well as their
moral support and cooperation.
Mr. Hency C. Gill, Vice President of Manufacturing at
Reed & Barton Silversmiths, was the Project Manager
for the three companies. He and his staff are to be
thanked for their time and efforts in management.
Mr. J. H. Shockcor, P. E., of Woodstock, Vermont,
has served as principal investigator in this project, pro-
viding the technical and economic analyses of the indivi-
dual and group treatment alternatives. Ms. Janet M.
Levy of Environmental Engineers Inc. of Concord, New
Hampshire, assisted in the development of cost relative
to the various alterntives.
Development Sciences Inc. (DSI) of Sagamore,
Massachusetts, provided the overall study approach
Additionally, DSI identified the institutional and finan-
cial factors associated with ownership and operation of
the group treatment alternatives and prepared the final
report. Ms. Marsha Gorden of DSI served in a coordi-
nating capacity among the participating groups.
The cooperation of the City of Taunton's Sewer
Department and their consulting engineers, CE Maguire
Inc. of Providence, Rhode Island, in providing appropri-
ate data is greatly appreciated. Special thanks are due the
Taunton Area Chamber of Commerce for their assis-
tance in the preliminary industrial survey.
The three companies provided technical and engi-
neering assistance as required to meet the time schedule
for the project's work elements. With the direction of
Andrew A. Kurowski, General Manager of F. B. Rogers
Company; Kenneth L. Bundy, Plant Engineer of Reed
& Barton Silversmiths; and Richard Kaplan, Vice
President of Poole Silver Company, the following plant
personnel's services are acknowledged: Robert E. Waits
of F. B. Rogers Company; Donald H. MacDonald, Jr. of
Poole Silver Company; and Thomas M. Kluchko
Francis Souza, and Joseph F. Coelho of Reed & Barton
Silversmiths. The cooperation of all is appreciated.
48
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The Electrochemical Removal of Trace Metals
For
Metal Wastes with Simultaneous Cyanide Destruction
By I. F. T. Kennedy & Dr. S. Das Gupta*
INTRODUCTION
The plethora of problems facing the metal finishing
industry in the area of pollution control stem from the
private and public desire to improve our environment. It
is not a question of whether or not there should be con-
trol of industrial pollution, but rather the how, with
what, at what cost and by whom.
The metal finishing industry is subject to at least three
levels of regulations concerning the discharge of liquid
effluents. These are: Federal, under The Pollution Con-
trol Act Amendments; State, as enacted; and Municipal,
where applicable. Further, the industry is or soon will be,
regulated with respect to the disposal of solid wastes.
The Pollution Control Act Amendments (Public Law
92-500) enacted by Congress in 1972, has as its essence
the cleaning up of the lakes, streams, and oceans of the
United States and to achieve essentially a zero discharge
of pollutants into the Nation's waterways by 1985.
The Environmental Protection Agency was charged
with the herculian responsibility of carrying out this
expression of the public's will. The mandate requires the
establishment of wastewater effluent limitations to be
achieved by all industrial operations whose activities
result in the release of toxic substances into surface
water.
The history of the promulgation of limits for the elec-
troplating and metal finishing industry is not at issue
here, but rather the practical problems facing the indus-
try as a result of these limits. The industry must remem-
ber that the EPA has a public responsibility to enact and
enforce in order to fulfill its charge. Industry's problem
has been the practical solution as to how to meet the
limits being legislated.
I am sure that many of the principal waste treatment
technologies currently available to industry will be ex-
haustively reviewed elsewhere at this conference and it is
therefore the intention of this paper to focus initially on
the rationalization of the existing metal finishing plant
and on the improvement of existing plant practices and
thereafter to detail a new electrochemical system cur-
rently being developed as an advanced pollution control
system.
*l. F. T. Kennedy, President & Dr. S. Das Gupta, Vice-President
H.S.A. Reactors Limited
1010-85 Richmond St. W., Toronto, Ontario, Canada M5H 2G1
The Metal Finishing Industry
The scope of the problem of pollution from the metal
finishing industry in the United States is reflected in the
size of the industry and the quality and complexity of the
effluents being discharged.
The electroplating and metal finishing industry in the
United States is large and complex. The strategic impor-
tance of the industry cannot be underestimated; indeed I
doubt there are many industries which, if forced to cease
production, could as effectively cripple the industrial
productivity and capacity of the United States. The
National Association of Metal Finishers estimate that
they are in direct contact with more than 7,000 electro-
plating and metal finishing facilities and that the true
number may be as much as three times that figure.
The geographical distribution of known facilities
closely follows that of heavy industry in the United
States. The heaviest concentrations are in the North
Central Region which account for nearly 40% of known
facilities, followed by the Atlantic Coast States with
35%, the West Coast, and particularly California, with
6%, with the final 20% being distributed throughout the
remainder of the country.
This geographical distribution indicates the close
relationship between the metal finishing shop and the
source of the work piece processed. This leads to intense
price competition between plating shops and, in general,
metal finishing industry profits are measured in cents
or fractions of cents per work piece. It is therefore readily
evident that management in this industry must be in-
tensely cost and price conscious in order to simply stay
in business. Pollution control equipment is generally
viewed as a capitally intensive, non-productive item re-
quiring an excess of floor area in an industry where work
space is at a premium. To date, pollution control equip-
ment has been regarded by management as an unwanted
expense and there has been little or no economic incen-
tive to install such equipment. Further, most metal finish-
ing shops are small to medium in size, non-integrated or
affiliated, owner-operated, without the in-depth know-
ledge of waste treatment technology to facilitate decision
making and lacking in readily available capital neces-
sary for the purchase and installation of such equipment.
These factors have manifested themselves in the resis-
tance of the industry to pollution control measures and
49
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are further reflected by the uncertainties expressed fre-
quently by industry's management, i.e. "whom do I trust
to tell me what to do, where do 1 obtain the capital for this
system, and after all' of this, will the system as installed
meet the E.P.A. limits".
While readily acknowledging that the answers to these
questions are neither simple nor immediately available,
we at H.S.A. believe that the resolution often lies in the
asking of the right questions. Usually management itself
is quite capable of determining which is the best course
of action after it has carefully and systematically re-
viewed the questions.
It is also important to note that more than 52% of all
electroplating and metal finishing establishments are
located in cities have a population greater than 100,000
and more than three-quarters of the plants are located
in cities with a population greater than 20,000. The dis-
tribution cited above would favour such waste disposal
practices as sewering of liquid wastes (with or without
treatment and solids separation) and off-site disposal of
non-sewerable waste, utilizing contractor services. A
sampling of facilities conducted by Battelle Columbus
Laboratories and reported in 1976 indicated that waste
treatment equipment for chemical in-line and end-of-line
waste water control is generally less than five years old,
although some equipment in a few cases had been utilized
for about twenty-five years.
Metal Finishing Industry Effluents
The toxic and metallic contaminants in the waste
effluents from the electroplating and metal finishing
shops simplistically derive from the work pieces being
plated, the chemicals and solutions additives used in the
plating process, and from the deterioration of the plating
plant equipment. The contamination from the work
piece may be of the oils and greases scale or from the dis-
solution of the work piece during the surface preparation.
The contamination from the plating solutions and chemi-
cal additives is self-explanatory and the contamination
from the plating equipment may be dissolution of anodes
of unprotecting plating tanks or of the pipes carrying pro-
cess solutions from one place to another within the plant.
The principal source of metallic and toxic chemical
contaminants in a plating plant are the rinse waters from
each plating step which are dragged out from concen-
trating solutions. Also included are process solutions
such as alkaline cleaners, acid dips and pickles and con-
version coating solutions some of which are dumped by
some plants at regular intervals. The conventional water
pollution control practice in electroplating and metal
finishing facilities involves the precipitation of the
dissolved potentially hazardous toxic materials, thus
generating a sludge destined for land disposal.
Rinse waters commonly contain alkalies, acid with dis-
solved metals, and possibly cyanides. The metal or metals
being plated on to the work pieces appear as dissolved
salts in the rinse waters following metal deposition steps.
Supporting electrolytes and additives introduced to en-
hance electro-deposition of the deposit may also be pre-
sent. Some plating processes incorporate post-plating
steps intended to alter the metal surfaces by conversion
or filming to improve on the corrosion properties of the
metal deposits. Dragouts from these solutions also
contain metals and chemicals. Normally the rinse waters
from a plant are collected into three distinctive streams.
One carrying all cyanide-bearing wastes, another all the
chromium-bearing wastes, and a third containing all
alkalies and acids and metal salt solutions other than
chromium and those metals which are chemically bound
to cyanide. The chemicals are destroyed or reduced by
treatment in a water pollution control system, metals
are precipitated and separated generating sludges, and
the effluent is discharged to a stream or sewer.
Pollution Control Technology
The range of pollution control technology currently
available to industry mirrors the range of effluents des-
cribed above.
The principal technologies currently available are all
physio-chemical methods and include:
a) Conventional chemical-destruct methods including
chlorination and hydroxide precipitation;
b) Ion exchange;
c) Dialysis and electrodialysis;
d) Evaporation;
e) Reverse osmosis;
f) Carbon adsorption and catalytic and chemical oxi-
dation;
g) Miscellaneous methods such as freezing, ion flo-
tation, liquid liquid-extraction, and ultrafiltration-
h) Electrolytic methods.
This list is illustrative of the different directions from
which the pollution problems are being attacked.
This list further illustrates that since management must
live with its decisions, it is essential that management is
instrumental in making these decisions. Only when man-
agement has a thorough understanding of the specific
problem areas within its own plant can an evaluation be
made of the advantages and disadvantages of the alter-
native solutions available in pollution control.
PLANT ASSESSMENT SURVEYS
Survey Purpose and Method
In view of the range of alternatives available to man-
agement in pollution control technology we believe that
the examination and particularly the installation of a pol-
lution control device is a waste of capital and manage-
ment's time if considered in isolation. The entire metal
finishing plant, with all its sequence of unit operations
and its existing plant practice must be considered as a
total before determining the best approach to pollution
control equipment and practice. Our approach has been
to review the plant as it exists today, ask management
its objectives and work with management in achieving
those goals by rationalizing existing facilities and plant
practice and suggesting any necessary changes, additions
or deletions.
50
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The purpose of a plant assessment survey for pollution
control is to: analy/e current plant physical layout,
operating practices and procedures and recommend any
changes in equipment or practice which would result in
lower contamination levels in the final effluent discharge;
examine process water usage and recommend methods of
reduction; evaluate the efficiency and effectiveness of any
existing pollution control equipment or waste treatment
facilities; recommend any changes or additions in instru-
mentation or equipment with respect to existing pollu-
tion control or waste treatment equipment which would
improve the discharge quality.
The plant assessment survey focuses on the collection
of data, including updating of plant layout, piping and
flow diagrams, arrangement and relationship of plating
lines, the initiation of a program of chemical analysis of
all plating baths and rinse tanks, the analysis of the
material and water balances in order to assess the effec-
tiveness of the existing plant practice, to suggest to
management methods to reduce the metallic contami-
nants in their final discharges and to improve the process
water usages. This logical approach utilizes sound scien-
tific and engineering principles and permits management
to study their own plant in depth and in an organized and
rational manner. By way of example, I would like to indi-
cate what has been accomplished in one plant by progres-
sive management.
Assessment Survey Example
Introduction
The metal finishing plant illustrated here is an existing
operation and is typical of the majority of plating opera-
tions utilizing a full service approach with automatic
chrome rack and zinc barrel lines as well as hand lines for
the plating of zinc, copper, nickel, cadmium and lead
and, occasionally, gold. This plant did not happen to
include such plating processes as phosphating, anodiz-
ing, mechanical plating, electroless nickel or dye opera-
tions. However, the assessment survey approach would
be exactly the same for plants with these types of plating
facilities.
Figure 1 (Slide No. 1) indicates the physical equip-
ment and piping details as well as the materials and flow
balance in an existing plant. This diagram, although not
strictly to scale, is proportional. It indicates that the plant
layout fits the work flow extremely well. The most strik-
ing feature is the huge size and the floor space require-
ments of the installed Waste Treatment Facility. This
unit occupies nearly 25% of the floor area of the entire
plant and approximately equals the floor space allocated
to the productive plating lines.
Analysis of Existing Waste Treatment Facility (WTF)
In order to assess the efficiency of the existing alkali-
hypochloride chemical destruction waste treatment faci-
lity, a programme of daily analysis of the final discharge
was carried out over a period of five weeks. The statisti-
cal mean of the concentrations of various constituent
contaminants in this effluent is given in Table I (Slide
No. 2).
From Table I, it can be generally concluded, that the
chemical destruction process applied to the plant dis-
charge was as effective as could be expected in reducing
the metallic and cyanide levels in the final effluent. The
table illustrates that the system is quite effective in per-
centage removal when initial concentrations of contami-
nants are high and considerably less efficient when the
initial concentrations are low. The use of an in/out ratio
removes the impact of dilution but points out that the
higher the dilution (i.e. the more unnecessary process
water utilized), the more dilute the streams entering the
WTF will be, and the lower the percentage removal will
be (i.e. the WTF is less efficient).
All instrumentation was checked for proper location in
the unit and for accuracy and calibration. The physical
retention times in various tanks were checked against
various chemical reaction rates to ensure that there was
ample time for the completion of all chemical reactions
in the destruction process. It was concluded that suffi-
cient time was being allowed for the oxidation of the
cyanides to cyanates and the subsequent hydrolysis reac-
tions.
It was our conclusion that the Waste Treatment
Facility in isolation was as efficient as could be expected
for a chemical destruction facility of this type; that the
instrumentation controlling the destruction process was
adequate and functioning normally; and that there was
sufficient retention time for the appropriate chemical
reactions to go to completion. It is also evident that the
facility principally treats zinc, iron and cyanides.
Analysis of Rinse Tank Discharges
& Plant Operation Practices
The second stage of the Plant Assessment was to evalu-
ate rinse tank discharges and plant operating practices.
Three areas were examined: a) the levels of metallic con-
centrations discharging from individual rinse tanks to the
sump; b) the levels of cyanide and metals discharging
from individual rinse tanks to the cyanide destruction
unit; and c) the plant usage of process water.
From Table II (Slide #3) it is readily evident that zinc
and iron are the principal metallic contaminants, com-
prising 55% and 37% respectively, or 92% combined, of
the total metal loading of 48 gms/ min being treated by
the final waste treatment facility. It should also be noted,
however, that Tank 51 contains no cyanide and is dis-
charged to the sump while Tank 54 contains significant
cyanide levels and is discharged to the cyanide destruc-
Table 1
Typical Final Effluent
Discharge
In-Flo\v
In/ Out Ratio
% Removal
Fe
7.00
105.00
15.00
93.30
Zn
3.50
157.50
45.00
97.80
Cu
nig /I)
1.00
2.40
2.40
58.30
Crr
2.50
11.75
4.70
78.70
Ni
2.50
7.75
3.10
67.10
C/W
8.00
43.20
5.40
81.50
51
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54
57
St
B»-«
61
85*
CAUSTIC CLEANING MTH
ELECTRIC SOAP CLEANING
ELECTRIC COAP CLEANING KCVEIWe POLARITY
RINSE TANK
RINSE TANK II
ACID IATH
ACID RINSE
ACID RINSE II ,
COPPER CYANIDE PLATING MTH
COPPER RINSE 1
COPPER RINSE II
COPPER RINSE III
NICKEL PLATINVMTH" ~~
COMPOSITION
Cd Cr^C^C?^ Cu
1
t- 7 4
-4- I -U -4-
„- 4 .4-4.
- - -+ -t - - *-
< 1 -4
— »- — • -+ -f
— K
m
- - l
H
-4- --
.if-;
•lji-1
V-"
NICKEL RINSE 1 j < l « 1
NTCKEL RINSE II T - * ~" O- 1 *~^
NICKEL RINSE III 4- •• ^ -l- 'Q. j~~_-
CHROMIC ACIO PLATING IATH
CHROMIC ACIO DRAG-OUT
CHROMIUM RINSE 1 ' IWo' 58 !|I22I2
CHROMIUM RINSE II 1 , __
CHROMIUM RINSE III
DRIP • DRY ANO UNLOADING "*" T " "' T
RINSE TANK "*"
CAUSTIC CLEANING MTH ( HOT ) !
D*
-
Mi Pb 2n Of
^4^;
' 1 tc7- 4*"
— , '< ' I
f- -+-- t— —
- - < i no
^^
3I ""-"
l[_- ,
B-7
rf-rrr"
RINSE TANK 1 - O2SI
IDLE NOT IN UW ,
HYDROCHLORIC ACID PICKLING MTH
RINSE TANK
ZINC PLATING MTH
RINSE TANK 1
RINSE TANK II
CADMIUM PLATIN* MTM
CADMIUM DRAG -OUT
RINSE TANK
COPPER PLATING MTH
COPPER RINSE 1
COTPPER RINSE II
NICKEL PLATING IATH
NICKEL RINSC
- >-. .---. .
0-4 25
r-^ i i'«.izi
12107
» * t -' t
11-1
CADMIUM RINSE ^_ ^ ^_
LEAD PLATING iATH '" ->-•>- * -- 4-
LEAD DRAG -OUT "" 'T " ~p "| "" "r~
CAUSTIC CLEANINO MTM ~*~ * ^~
DRP TANK " " I ± I r
ELECTRIC SOAP CLEANING t T " *" ^_ * "
RINSE TANK " " { ]-' , *0-7*S-6
HYDROCHLORIC ACID PICKLING MTH
RINSE TANK
DRIP TANK
ZINC CYANIDE PLATING MTH
RINK TANK 1
RINSE TANK II
IRIOATE DIP
COLO RINSE TANK
HOT RINSE TANK
CAUSTIC CLEANING TANK
RINSE ( ACIO ft CAUSTIC )
f GOLD PLATINC LINE
CHILLER
: : TT .:
1 - 0-2 3W
i::]Us
j -.- , f- T- —
• ~w" {
- 1 + — (--..
90 1
i
• -4-
L'f
O-T|JO
.-, j-
««c ^'pw
t •
-*•--* 4---
* * t ~
- — .363
- . 27W
- 4- 4 - . .
- i 77
-- t t--f
1 _
Z45 126
1 '
PH. WATER OUTFLOW
I NONE
NONE
T NONE '
en 11 0 NONE
en 10- 0 i 9,5 L /min
en IS' NONE
e/> 4- 0 1C L /min
en 60, 24 L /min.
en 12-0 T NONE
en 10-0 2 L /m,n
en 1- 5 P O,5 L /m,n ^
en" 3-3 T " " NONE 1
en 7 0 ' 2 L /m.n
en B 0 j 3 L /m.n
en 6 0 ' 2 L /m.n ~^
en 0 5 NONE "^
en 0 7 NONE
en 15 I,SL /mm.
en 6-0 1~
en 7-S
en 12-5
en 10 -S
en 0-3
"VARIABLE '
in 12 5
en 125
en 12-5
en 12-0
in 115
in 7-S
en 45
NONE
NONE
NONE
I.SL/m.n
NONE
2 L /m.n |
NOT IN USE
NONE
2O L /m*n
NONE
NOT NOW IN USE
NOT NOW IN USE
NONE
NONE
INTERMITENT SLOW
NONE
SHOULD tt «<«L/»r»
NOW *ljSL /•-.» ,
6 L /mm
NONE
f en 7 -3 t NONE
en fl- 2 I 1 ,5 L /m.n
' T-4 1 ""^"NONE"
en 's-5 t " NONE~" '
» t ._. i
en 12 7 i NONE
' NONE
en 72-7 j NONE
en 10- O ', 8 L. /m.n
en OS
• en 1-5
l en 2-3
en 12-5
en 12 0
en II -0
at l-6~ "
tn 5 5
en 60
en 12-5
"VARIABLT
en 03
NONE
NONE ~^
NONE
14 L /mm 1
NONE ^j
NONE
ABOUT E L /m.n
1 L /min
NONE
NONE
TANK«2 — l.SL /mitt
NONE
3L /m.n
S3
-------
tion unit in the final waste treatment facility. It is also
illustrated that the great bulk of the effluent to be treated
by the waste treatment facility (26% of the total water
and 63% of the total solids) comes from Tank 51. Even
with the high flow rate in this rinse tank and the post-
rinse drip, iron and acid drag-out into Tank 53, the zinc
plating bath, were significant. The significance of proper
management of Tank 51 was emphasized to manage-
ment.
The cyanide level in the final discharge exceeds limits
desired and again it was evident from Table II and from
the amount of free iron in the final discharge that the
majority of this cyanide would be in the form of the stable
ferro-cyanide complex. This complex is not amenable to
effective treatment by chemical destruction type pro-
cesses. Therefore, a positive approach to the reduction of
this cyanide level by the reduction of free iron available
for complexing was recommended to management. This
program involved the identification of sources of free
iron within each plating line and recommendations to
reduce or eliminate these contamination sources.
Process Water Usage
The plant assessment also included a calculation of the
process water utilized as compared to management if
there are any unforeseen water losses. The water survey
in this case was within -8% of the metered amount while
not including boiler make-up water and plant domestic
usage.
Recommendations were made to management to cut
water flows in certain rinse tanks, particularly Tanks 51
8 and 28 which accounted for approximately 52% of the
total plant water usage.
Assessment Survey Results
In all, 13 specific recommendations were made to man-
agement. The sequence of implementation was also sug-
gested, and management was requested to report back
to H. S. A. as these recommendations were carried out
To date, a majority of these recommendations have
been acted upon and the results are given in Table III
(Slide 4).
These results indicate a reduction in zinc contamina-
Table II — Ion flow rales to WTF
Source Water Cr* Cr*3 Cu Fe Ni Zn Cn PH
l/min mg/min
Tank 39
43
54
58
33
total to Cn destruct
Tank 5
7
8
10 (partial
only)
11
12
14
15
16
19
23
25
28
40
49
51
57
62
Chiller
Total to sump
Total
Total metals
% of Total metals
1.5
1.5
14.0
1.0
18
9.5
10.0
24.0
0.5
4.0
0.5
2.0
3.0
2.0
1.5
1.5
2.0
20.0
6.0
8.0
44.0
6.0
1.5
3.0
275.0 182.0 66.0 .15 582.0
22.0 700.0 - 8150.00 6580.0
.6 - 1.0 1.0 - 77.0
.6 - 298.0 883.- 66.0 8227.15 7162.-
0.1 - - O.I -
4.0 2.4 - 2.4
2.4 2.4 - 2.4
26.4 21.0 - - 50.0
2.8 - - - 4.0
0.6
0.2 0.2 704.0 - - 7.0
0.3 - 9.3 -
0.2 0.6
88.0 1682.0 31.4 - 28.0
.
0.4 18.2 0.8 5.0
2.0 2080.0 12.0 216.0
13.0 4.2 475.0 0.6 18.0
5.6 28.8 - 26.4
13.2 14256.0 - 15972.-
158.0 - 3.6 58.6 - 1650.0
13.5 - 1.0 453.0 6.7 189.0
- -
149.0 259.5 1682.0 107.2 16922.4 1236.4 18065.50 72.0
11.5
8.2
12.6
6.5
10.0
8.0
8.0
10.0
8.5
1.5
7.5
7.0
1.5
10.5
variable
7.5
10.0
1.5
5.5
variable
1 _
167.0 260.1 1682.0 405.2 17805.4 1302.4 26292.65 '
47,747.8 mg/min or 47.7 gm/min
0.54 3.52 0.85 37.29 2.73 55.07
54
-------
Table III
Changes In Final Effluent Characteristics
Metallic and Cyanide Contamination Levels
ion/mg/L Cu Ni
Before
After*
2.5
2.6
Cd
0.1
0.1
Zn
3.5
2.2
8.0
2.2
Before
After
•based on average of 5 analysis
Plant Water Usage
57,000 gpd - months April, May, June
39,000 gpd - months September, October
tion of 37%, of cyanides by 72% and a reduction in pro-
cess water utilized of 32%.
The results indicate what can be done by management
simply by critically examining their own facilities and
plant practice. It is also evident, however, that the con-
tamination levels achieved, while significantly lower, are
still not low enough to meet legislated or proposed efflu-
ent guideline limits.
The important factor is that management has now re-
viewed the existing conditions and optimized them. It is
now ready to examine various alternatives in pollution
control technology.
One of the areas of control technology previously men-
tioned is that of electrolytic technology and of specific
interest is the field of electrochemical treatment methods.
In conjunction with the above plant assessment,
H. S. A. operated an industrial scale electrochemical
research reactor system in the same plant.
THE H.S.A. REACTOR SYSTEM
Electrochemical Technology
In recent years, there has been increased activity in the
electrochemical reactor field as the significance and po-
tential advantages of electrochemical process are being
more widely realized. Electrochemical treatment of pol-
lution is an attractive idea, by virtue of its unique "clean"
system where oxidation and reduction take place via an
inert electron, without the need of chemical additions.
Electrochemical treatment of effluents has been postu-
lated for some time, however, owing to unsatisfactory
reactor design, it could not be used to handle large vol-
umes efficiently and at a low cost. The recent develop-
ment of a carbon fibre-based reactor by H. S. A. Reactors
Limited1'2 has made it possible to achieve real time
effluent treatment, at low cost.
Some of the possible applications of the electrochemi-
cal effluent treatment include the reduction process, such
as the removal of heavy metals, including copper, nickel,
lead, zinc, cadmium, gold and silver, and the subsequent
recovery of the metals.3"7 Reduction of the hexavalent
chromium from plating liquors is another example.
Further examples in the oxidation process are the
decomposition of cyanides, phenols, acetates and other
organic compounds. A review of electrochemical
treatment of effluents is given by Kuhn and others.*"7
Carbon Fibre Reactor Design
The patented carbon fibre reactor being developed by
H. S. A.1 •2 radically changes the "potential" of the elec-
trochemical systems for effluent treatment. Most electro-
chemical processes are limited by mass transfer rates and
attempts have been made to develop reactors with greater
mass transfer capabilities, for example the fluidized bed,
the packed bed, and other three-dimensional paniculate
reactors.4. 8 The limitations of these are well docu-
mented9. 10, and include non-uniformity of potential dis-
tribution.
The primary design characteristic of the carbon fibre is
the increase of mass transfer rates while simultaneously
having a controllable and uniform electrode potential
over the entire electrode surface. The carbon fibres are
commercially produced by the high temperature pyroly-
sis of precursor materials such as poly-acrylonitrile, and
have very favourable properties as electrode material
because of its hard vitreous surfaces, electrical conduc-
tivity and high hydrogen and oxygen over-voltage char-
acteristics. Additionally, the fibres have high modulus,
low density, good thermal conductivity, very low co-
efficient of thermal expansion, chemical inertness, ther-
mal shock resistance, a high vibration damping factor
and excellent fatigue resistance.
Another important property of carbon fibres is its
enormous surface area. The fibres are typically between 5
to 15 microns'' in diameter, and one gram of fibre has a
surface area of 2.6 * 106 cm.2 This surface area is about
1,000 times larger than the surface area per unit volume
of other types of particulate reactors. As a result of this
increased surface area, the mass transfer rates in this reac-
tor approach those achieved by some heterogeneous
catalytic reactors. The major operational advantages of
the reactor are: 1. It can operate at lower current den-
sities without a corresponding decrease in output. This
results in a sharp decrease in the cost per unit of effluent
treated.; 2. It is possible to operate processes at a high
throughput in a realistic time-scale (in the order of
seconds).; 3. A reduction in the capital cost is achieved
because effluent can usually be treated in a single pass
process through appropriate design considerations.
Electrochemical Effluent Treatment - Pilot Test
Introduction
Research at the laboratory bench scale led to the devel-
opment of a process utilizing the carbon-fibre electro-
chemical reactor, by which cyanides, metal cyanides and
heavy metal could be removed from effluents generated
by the metal finishing industry.
It has been found that the process can electro-oxidize
and destroy cyanides and metal cyanide complexes more
effectively than the alkali-chlorination process and at
only a fraction of the cost. Free cyanides and cyanide
55
-------
complexes of zinc, copper and cadmium could be com-
pletely destroyed, such that after treatment, cyanide
could not be detected in the effluent. The heavy metals,
including metal complexes of various chelating agents,
could be electro-reduced, and the metals recovered in the
cathode.
As a result of the unique electrochemical properties of
the carbon fibres, including large hydrogen and oxygen
over-potentials, controllable and uniform current and
potential distribution, chemical inertness and high mass
transfer, it was possible to effect complete removal of pol-
lutants in residence times in the order of seconds.
During the summer of 1977 an industrial-scale, electro-
chemical research system was constructed by H. S. A. in
Toronto and shipped by truck to a metal finishing plant
for pilot plant testing. The design of the system permitted
it to be commissioned the day of delivery. The system
operated for five weeks on both the final effluent from
the plant and all rinse tank discharges.
Operation on Final Plant Discharge
The objective of the pilot test-work was to operate the
system in real plant conditions, to examine the system's
ability to efficiently and effectively destroy cyanide, the
cyanide-metal complexes (including the stable ferro-
cyanide complex), while simultaneously removing the
contained trace metallics.
The success of the testwork was to reduce the total
metallic concentration in the final effluent to less than
1 mg/ L (ppm) and reduce the total cyanide to an undetec-
table level (analytically given as 0.1 mg/1).
Table IV (Slide 5) illustrates the input/output of the
final plant effluent through the H. S. A. reactor system.
Operation on Rinse Tank Discharge
Since the majority of the environmental objectionable
species in the metal finishing industry wastewaters come
from the discharge of rinse tanks, the reactor system was
applied to the discharges from zinc, copper, cadmium,
chromium, nickel and lead rinse tanks.
Table IV
Final Plant Effluent Characteristics
Before and
Species
Cyanide i
Lead
Zinc
Cadmium
Chromium r
Nickel
Copper
Reactor voltage
After Electrochemical Treatment
Before Electro-
chemical Treat-
ment (mg/L)
(Currently dis-
charged to sewer)
7.5
O.I
2.7
0.3
2.1
2.3
0.4
of 19.4 Volts at 63 Amps
After Electro-
chemical Treat-
ment (mg/L)
< 0.
< 0.
0.3
< 0.
0.
0.
< 0.
Plating Line Counter Current Rinses
Process Water IN
Plating Bath
1
Metals
Recycled
Rinse Tank 1
H.S.A.
Electrochemica
System
Rins? Tank II Rinse Tank III
1
t
Process Water OUT to HTFi
I
•f
Figure 2 - Closed Loop Treatment of rinse tank discharge.
If the rinse tank discharges are treated at their point of
origin, such that there is only a limited rinse tank
discharge, then the size of the general wastewater
treatment system for the final effluent from the plant can
be smaller and less costly. Figure 2 (Slide No. 6)
schematically illustrates such rinse tank process control
The advantages of treating the rinse tank discharge are-
I. the possibility of significantly reducing the discharge
of wastewater; 2. the economic recovery of drag-out
metals which can then be recycled to the plating bath-
3. the installation of recycling units, obviating the
necessity of constructing a large general wastewater
treatment facility.
The H. S. A. electrochemical system was tested for its
applicability in the following rinse tanks in a metal
finishing plant: a) Cadmium Rinse; b) Copper Rinse-
c) Nickel Rinse; d) Chromate Rinse; e)Zinc Rinse; fj
Lead Rinse.
Laboratory bench scale tests were carried out on other
possible rinses such as electroless nickel.
Treatment of Cadmium Rinse Tank Discharge
The input/output results of the cadmium rinse are
given in Table V.
As the rinse tank discharge is recycled, according to
Figure 2, the output from the electrochemical treatment
system does not have to meet the stringent clean up
regulations.
Treatment of Copper Rinse Tank Discharge
The input/output results of treating the copper rinse
discharge are shown in Table VI.
Figure 3 graphically shows the copper removal and
cyanide reduction achieved electrochemically.
Treatment of Nickel Rinse Tank Discharge
The input/ output of the electrochemical system for the
nickel rinse is shown in Table VII. The nickel plating was
carried out on an acid bath.
Treatment of Chromate Rinse Tank Discharge
The input/output of the electrochemical system for the
chromate rinse is shown in Table VIII.
Treatment of Zinc Rinse Tank Effluent
The zinc plating was being carried out in a cyanide bath
56
-------
TABLE V
Cadmium Rinse Tank Effluent (pH = 11.7, a = 7820)
at a Reactor Voltage of 11-12 V at 375-510 A
Before Electrochemical After Electrochemical Percent
Treatment (mg/L) Treatment (mg/L) Removal
Cadmium
Cyanide
158
2180
3.1
72.5
98
97
TABLE VI
Copper Rinse Tank Effluent (pH = I0.6,a = 2700)
at a Reactor Voltage of 12 V at 370 A
Effluent Before Electro- Effluent After Electro-
chemical Treatment (mg/L) chemical Treatment (mg/L)
Copper
Cyanide (total)
121
270
0.70
3.35
TABLE VII
Nickel Rinse Tank Effluent (pH = 7.8, a = 9650)
Before Electrochemical
Treatment (mgjL)
Nickel
132,0
After Electrochemical
Treatment (mgl L)
14.5
TABLE VIII
Chromate Rinse Tank Effluent
Before Electrochemical
Treatment (mg/L)
2,310
After Electrochemical
Treatment (mg/L)
71.5
TABLE IX
Zinc Rinse
Before Electrochemical
Treatment (mg/L)
Zinc
Cyanide
352.0
258.0
After Electrochemical
Treatment (mg/L)
0.7
12.0
TABLE X
Lead Rinse
Before Electrochemical
Treatment (mg/L)
After Electrochemical
Treatment (mg/L)
1,180 26.4
The conductivity of the rinse tank was 2,420 n mho cm"'.
TABLE XI
Electro-oxidation of Cyanide and Metal Cyanides
Before Electrochemical
Treatment (mg/ L)
Zinc
Copper
Cyanide
117
842
1,230
After Electrochemical
Treatment (mg/ L)
0.27
0.50
< 0.10
and Table IX gives the input/output analysis in the
electrochemical system. The conductivity of this rinse
tank varied between 6,200 to 9,500 umho cm-1.
Treatment of Lead Rinse Tank Effluent
The lead plating was being carried out in an acid bath.
Table X shows the input/output of the electrochemical
system for the lead rinse.
The conductivity of the rinse tank was 2,420 umho
cm"'.
Cyanide Destruction
The electrochemical system can effectively destroy
cyanide, metal cyanide complexes, and remove the
metals without involving the problems of sludge
handling, dewatering and disposal. This is illustrated in
Table XI. The electrochemical system is estimated to
operate at approximately one-sixth the cost of an alkali-
chlorination unit.
Figure 3 - Graphical Representation of Copper-Rinse Treatment
by Two Reactors In Series.
57
-------
Conclusions
In general the results of the test programme are
excellent in that the reactor system achieved a significant
reduction of cyanide and metallic contamination in the
final effluent. This reduction is greater than 99% in most
cases. The application of the H. S. A. system to the final
effluent should meet any proposed legislative standards
for the metal finishing industry.
The electrochemical reactors installed were designed
only for the treatment of final effluent. This effluent is
currently discharged directly to the municipal sewers.
This reactor system, although not designed for the
treatment of rinse tank discharges, was nevertheless
successfully utilized in this application. The results
obtained, as given in Table V to XI, indicate the
reduction of the toxic metals to a level where the rinse
tank waters could form a closed loop resulting in a signifi-
cant reduction in process water usage with the objective
of attaining a zero discharge state.
The H. S. A. reactor system effectively operated on
final waste streams and on rinse tank discharges. The
reactor destroyed cyanides, metal cyanide complexes and
removed trace metallics in both discharges. The reactor
system does not produce sludge. The treated stream,
particularly the rinse tank stream, could be recycled as
plant process water resulting in considerable
conservation of plant water usage. The system is expected
to be cost competitive in both capital and operating cost
areas.
Additionally, the results have also indicated that the H.
S. A. reactor system will:
• be of value to all sizes of metal finishing and plating
plants, particularly small plants, in achieving low
limits;
• because the system is physically small in size and
modular in design, accommodate changes in plant
output (discharge) by the addition or removal of reac-
tor units. Thus the plant expansion or increased pro-
ductive capacity can easily be accommodated by
reactor unit additions to the initial installation with a
minimum of disruption to the plant;
• operate on final effluent discharges before or after a
Waste Treatment Facility (WTF) or directly on pollu-
tion source - the rinse tanks; in all applications be it the
rinse tank or final effluent, the reactor system is an on-
line system with the residence time in the reactor in the
order of seconds;
• resolve many of the current problems concerned with
sludge since NO SLUDGE IS PRODUCED but
rather sheets of metal or concentrated metal liquors in
a chemically suitable form for recycling to plating
baths;
• promote the re-use of process rinse waters by the
continuous, on-line removal of contaminants;
• permit the freeing of floor space for added production
facilities because of the small size of the reactor units
compared to bulky and inefficient conventional
WTFs;
• be more than economically competitive on a capital
basis with conventional WTFs and operate at a frac-
tion of the cost. For example, from the results of the
research test plant it is estimated that for a plant with a
final discharge from WTF of 30 gpm that an H. S. A
system for this application would have a capital cost of
approximately 550,000 U. S. and operating cost of
approximately 80« per hour at 2
-------
Sulfide - vs - Hydroxide Precipitation of Heavy Metals
From Industrial Wastewater
A. K. Robinson*
INTRODUCTION
The most widely used method of removing heavy
metals from wastewater today is the hydroxide process.
Lime is used to raise the pH of the water, and the heavy
metals are concentrated into a sludge which is usually
trucked away to landfill. The hydroxide process removes
heavy metals in general down to 1 or 2 mg/1.
With increasing emphasis on protection of our
environment, new methods of removing heavy metals
from water are being sought. One of these is the sulfide
process which offers considerable promise on account of
the far lower solubilities of heavy metal sulfides
compared with the corresponding hydroxides.
This paper reviews the two processes, hydroxide and
sulfide, indicates some of the advantages and
disadvantages of each, and outlines our planned work in
this area.
Wastewaters Treated
The metal finishing and metal producing industries
produce an extremely wide range of wastewaters con-
taining heavy metals from rinse waters containing a few
mg/1, to concentrated dumped process solutions
containing several hundred thousand mg/1. The princi-
pal heavy metals of concern in these wastewaters are
arsenic, cadmium, chromium, copper, lead, manganese,
mercury, nickel, selenium, and zinc.
Concentrated waste process solutions are often treated
in practice along with dilute wastewater streams, by
"bleeding" them over a period of time into the dilute
stream.
THE HYDROXIDE PROCESS
Clarifier Operation
Precipitation of the hydroxide takes place when the
pH of the wastewater is raised from its normally acid
condition to pH 8-11. Except in small operations, the
process is continuous rather than batch, and large
circular tanks known as "clarifiers", are common. Figure
1 shows such a clarifier. Freshly-slaked "hot pebble lime"
(quicklime, CaO) is generally used, on account of its low
*A. K. Robinson
Manufacturing Research and Development
Boeing Commercial Airplane Co., Seattle, WA 98124
cost and ease of handling, to raise the pH, although in
some cases sodium hydroxide may be used. Polyelec-
trolytes are usually added, in amounts from 0.1 to 1.0
mg/1, at the same time as the lime addition. They can
dramatically improve the settling characteristics of the
hydroxide precipitate (References 2, 6).
Fig. 1—Section through water clarffter.
Cr (II)
Cr*
exists in solution
Cr(OH)2
chromous hydroxide
exists only in strong
reducing conditions
chromous salts
eg. CrSO4
Cr (III)
Cr3*
exists in solution
Cr(OH)j • 3HjO
green chromic
hydroxide preci-
pitated in alkaline
solutions
chromic salts
eg. Cr2(SO4)3
Cr (VI)
Cr6*
does not exist in
solution
Cr(OH)6
does not exist
chromatcs
(CrfV
dichromates
(CnO,)2'
Fig. 2—Chromium compounds.
59
-------
Pretreatments Before Clarification
Chrome Reduction
The metal chromium may be present in a wastewater as
trivaient chromium (chromic salts) or as hexavalent
chromium where it forms part of the anion (Figure 2).
If hexavalent chromium is present - and it usually is -
then it must be reduced to the trivaient form before
feeding to the clarifier. Unless this is done, the hexava-
lent chromium will pass through the clarifier unchanged.
Hexavalent chrome reduction is commonly accom-
plished by reducing pH to approximately 2 and adding
ing sulfur dioxide or sodium bisulfite (Reference 2).
Control of the reduction is readily automated, using
ORP (oxidation-reduction-potential) electrodes. Suf-
ficient retention-tank capacity must be provided to allow
time for the reaction to proceed to completion (approx.
45 minutes, depending on pH) (Figure 3).
Cyanide Removal
Where cyanide-containing streams are present, these
are pre-treated separately to destroy cyanide, before en-
tering the main wastewater stream for removal of heavy
metals. Batch operation of an alkaline chlorination
process is often employed (References 2, 6).
Sludge
Sludge from the clarifier will contain up to 3% solids,
depending on the settling time allowed. Furtherdewater-
ing, to reduce the cost of trucking the sludge away, is
accomplished by natural evaporation in a lagoon, or by
centrifuging, or by filtration. The dewatered sludge con-
tains 12 - 18% solids.
Overall Hydroxide Process
Figure 4 is an aerial view of a hydroxide plant treating
1.5 Ml/day (400,000 gal/day) wastewater from an air-
plane factory.
The heavy metal reductions achieved by this plant are
given in Figure 5 (Reference 5). The lime dosage is ap-
proximately 200 mg/1. These overall reductions are
somewhat better than claimed in the literature (Refer-
ence 3).
Figure 6 summarizes the reported levels of heavy
metals in effluents treated by the hydroxide process.
Effect of Complexing and Chelating Agents
No description of the removal of heavy metals from
wastewater would be complete without a reference to
complexing and chelating agents. These materials are
universally added to meta,! finishing solutions for a wide
variety of purposes, including brightening, cleaning, and
solubilizing of metals. These agents are known to inhibit
and even prevent the precipitation of heavy metals. Some
of the commonly used ones are: tartrates, phosphates,
ethylenediaminetetra-acetic acid (EDTA), and am-
monia. Unfortunately, exact knowledge of the effect of
complexing and chelating agents on hydroxide precipi-
tation is not available, largely because of their proprie-
tary nature.
SO, Mll»b Till
Fig. 3—Process lor reduction of hexavalent chromium.
Fig. 4—Aerial view of hydroxide plant treating 1.5 Ml/day
(400,000 gal/day) wastewater from an airplane factory.
INFLUENT
mg/l
Cu
Cd
Ni
Zn
Cr (hexavalent)
Cr (total)
I
0
(i
(i
2
6
- I0
-2
- I
-2
-20
-60
EFFLUENT
Daily Maximum
Allowed by State Permit
mg/l
O.IO
0.03
O.IO
O.IO
0.25
Fig. 5—Influent and effluent heavy metal concentrations for
hydroxide plant of Figure 4.
60
-------
Heavy Metal
Cii
Cd
Ni
7.M
C"r (trivalcnt)
Cr (total)
mg 1 Concentration
o.o -
o.o -
o.oy -
0.02 -
0.06 -
0.06 -
1
2.5
1.0
1.9
5.4
0.75
4.6
1
Fig. 6—Hydroxide process - reported levels of heavy metals after
treatment.
Pig /—Effect of pH on the concentration of heavy metals in the
effluent.
Effect of pH on Precipitation
Reference to Figure 7 shows that the optimum pH
for precipitation is different for different metals. Con-
sequently, any treatment plant receiving a mixed heavy
metal load must adopt a compromise pH value. A pH of
8.5 or 9.0 is often employed. If a higher pH must be used,
eg. pH 11 for cadmium removal, then subsequent acidi-
fication of the effluent will be required if the local dis-
charge permit requires a pH maximum of 9, as many do
(Reference 7).
THE SULFIDE PROCESS
Advantages of the Sulfide Process
Comparative Soluhi/ilics oj Sulfides and Hydroxides
The chief attraction of the sulfide process lies in the
extremely low solubilities of most metal sulfides. Figure
8 lists the calculated solubilities of some heavy metal
sulfides compared with the corresponding solubilities of
their hydroxides. In this list, the solubilities of the sulfides
are calculated at a pH of 8.0, and those of the hydroxides
at the optimum pH within the range 7-11 (References
8, 9, 10 and 16).
METAL
Iron
Nickel
Zinc
Cadmium
Tin
Lead
Copper
Mercury
Silver
Chromium
SOLUBILITY
Hydroxide
(minimum)
Solubility, mg/1
1.8 X 10 '
9.0 X 10 4
6.0 X 10 ;
16 X 10 '
4.1 X 10 "
2.5 X 10 4
pH
10.5
10.5
9.0
11.0
9.3
9.0
2.0 X 10 ' 1 8.5
Sulfide Solu-
bility at pH 8.0
mg/ 1
3.0 x 10 "
1.6 X 10 '
1.4 X 10 '"
7.6 X 10 "
1.0 X 10 "
1.4 X 10 "
3.4 X 10 :4
2.7 x 10 4"
7.9 X 10 '"
Fig. 8—Theoretical solubilities of sulfides and hydroxides.
Fig. 9—Elimination of hexavalent chrome reduction step by
sultide precipitation process.
Removal of Hexavalent Chromium hy Sulfides
A second attraction of the sulfide process is its ability
to remove chromates and dichromates, i. e. - hexavalent
chromium, from wastewater, without preliminary reduc-
tion of the chromium to its trivalent state. As shown in
Figure 9, this eliminates, in a conventional sulfur dioxide
61
-------
reduction plant, two tanks, with their associated pH and
ORP controls, and the sulfuric acid, sulfur dioxide, and
lime needed to lower pH, reduce, and restore pH during
the pretreatment.
Removal of Complexed Heavy Metals
A third advantage of the sulfide process is its increased
ability to precipitate metals complexed with at least some
complexing agents. Figure 10 shows the effluents, in a
laboratory test, from an input containing heavy metals
complexed with tartrates (Reference 1).
Disadvantages of the Sulfide Process
General
Up to this point, the sulfide process has been referred
to as if it were a single, well-defined process. In fact, there
are at least four main varieties of sulfide process, and
although the advantages claimed apply to all four, the
disadvantages listed here do not necessarily apply to all
varieties of the process.
Odor and Toxicity of Hydrogen Sulfide
This gas is released if dilute acids contact sulfides.
According to Reference 3, air containing:
0.075 mg/m3 may darken paints 30 - 50 mg/m3 has a strong odor
0.5 mg/m3 has a distinct odor 1400 mg/m3 is fatal in 30 minutes
Under normal alkaline operating conditions risk
of H2S evolution is minimal. However, adequate safety
precautions would have to be taken in any plant employ-
ing a sulfide process in conjunction with possibly acid
wastes, to ensure that accidental mixing of sulfide and
acid could not occur.
Cost of Precipitant
Figure 11 shows a direct comparison of the cost of
precipitating, using lime for the hydroxide and sodium
sulfide or hydrosulfide for the source of sulfide (Refer-
ence 4). The "Sulfex" process uses ferrous sulfide as the
precipitant, and some additional chemical cost results
from the cost of the iron used in the preparation of this
precipitant.
Use of Sulfide as a "Polishing" Operation
After Lime Precipitation
The higher chemical cost of the sulfide process - at least
14 times that of the lime process, as can be seen in Figure
11 - suggests the possibility of a two-stage operation.
Lime precipitation could be used to remove the greater
part of the heavy metal load, and the sulfide operation
could follow, to remove heavy metals to a level unattain-
able by lime alone.
The additional cost and complication of a sulfide
"polishing" stage would be offset by elimination of the
chrome reduction stage before the lime precipitation.
It should be pointed out that very little is known of
the effectiveness of sulfide precipitation in extremely
Metal
COPPER
CADMIUM
CHROMIUM
(TRIVALENT)
NICKEL
ZINC
Influent
concentration,
mg/1
4
4
4
4
4
Effluent Concentration,
mg/1
Hydroxide
Process
1.5
1.7
2.0
3.0
1.0
Sulfide*
Process
0.01
< 0.01
3.50
<0.40
^0.03
•"Sulfex" Process
Fig. 10—Comparison of sulfide and hydroxide process r««idua|»
for an Influent containing Rochelle salt complexing agent.
Chemical
Lime, CaO
Sodium Sulfide
Flake, 60% Na2S
Sodium Hydro-
sulfide Flake,
71% NaHS
Price per ton
$28.75
$275
$305
Price per 1 00 Ib of
metal precipitated*
$1.27
$28.15
$18.93
'Calculated for copper.
Fig. 11— Raw chemical cost comparison, lime - n - aulfld*.
(October 1977). *'
Type
A
B
C
D
Precipitant
Soluble Sulfide
Soluble Sulfide
"Insoluble" sulfide
"Insoluble" Sulfide
Co-Precipitant
None
Hydroxide
None
Hydroxide
Fig. 12—The four principal types of sulfide precipitation
dilute (below 2 ppm) solutions. If a "sludge blanket"
technique were found to be essential to the success of the
process, then several days1 operation might be necessary
to build-up sufficient sludge for effective blanketing.
Disposal of Sulfide Sludge
Disposal of metallic sulfide sludges may pose a con-
siderable problem, compared with disposal of the cor-
responding hydroxide sludges which have an established
history of disposal as landfill. At least three suspicions
-------
UIME OR
CAUSTIC
SODA
INFLUENT
H
SOLUBLE
SULFIDE
pH ADJUST
PEROXIDE
MIX
EMERGENCY
SULFIDE
NEUTRAL-
IZER
EFFLUENT
SLUDGE
Fig. 13—Outline of soluble sulfide process.
EFFLUENT
SLUDGE
Fig. 14—Outline of Insoluble sulfide process.
will have to be overcome before sulfide sludges could
become accepted as conventional landfill: (a) The sus-
picion that hydrogen sulfide might be released to the
atmosphere, creating at least a nuisance, and possibly a
toxic hazard, (b) Toxic metals might be leached out and
find their way into surface waters, (c) The sulfide might
oxidize to sulfate and release dilute sulfuric acid to sur-
face waters (this is a problem with certain mine tailings).
Description of the Sulfide Processes
Soluble and Insoluble Sulfldes
At the present time, both soluble and insoluble sul-
fides (References 11 and 12) are used, and each may be
reacted in the presence of lime as a co-precipitant, so that
four main processes are employed, as in Figure 12.
Soluble Sulfide Processes
Figure 13 outlines a process using soluble sulfide, such
as sodium sulfide or sodium hydrosulfide. Hydrogen
sulfide is available in liquid form and could also con-
ceivably be used.
A "specific ion" sulfide-sensitive electrode is used in
a manner analogous to a pH probe, to control the addi-
tion of soluble sulfide (Reference 15). Metallic sulfide
precipitates may be partly colloidal and show poor sett-
63
-------
ling characteristics unless special precautions are taken.
Use of a "sludge blanket" technique in which the precipi-
tating solution is allowed to pass through a blanket of
previously-formed sludge solution is a well known
method (Reference 6). The particles in the previously-
formed sludge grow larger in the blanket, and formation
of smaller individual colloid-sized particles is minimized.
Lime is used with or without the sludge blanket to form a
gelatinous hydroxide precipitate to capture colloidal
particles. Polyelectrolyte aids are also used.
Insoluble Sulfide Processes
Figure 14 shows a process using "insoluble" ferrous
sulfide. In fact, "insoluble" is a relative term, and even
ferrous sulfide, with a solubility product as low as 3.7 X
10 ", still provides enough soluble sulfide for sulfide
precipitation to occur. The only requirements are: a. that
the metal to be precipitated must have an even lower solu-
bility than ferrous sulfide (Reference 12), and b. suffi-
cient solid ferrous sulfide to be present to replace the sul-
fide ions withdrawn from solution by the precipitated
metal.
Figure 15 lists sulfides and their solubility products.
Iron sulfide will precipitate all sulfides below it in the
table. As with the soluble sulfide process, lime and a poly-
electrolyte may be used, and a sludge blanket is an effec-
tive way of avoiding the problem of colloid formation.
Position of Sulfide Precipitation Today
In contrast to the hydroxide precipitation method,
there is no extensive history of industrial use at present:
only a small number of plants are in construction or ini-
tial operation.
BOEING WORK ON THE SULFIDE PROCESS
The Manufacturing Research and Development or-
ganization of The Boeing Commercial Airplane Com-
Metal Sulfide
MnS
FeS
ZnS
NiS
SnS
CoS
PbS
CdS
A&S
BbS,
CuS
HgS
Solubility Product
Ksp
I.4X 10""
3.7 X 10'"
1 .2 X 10'23
1.4X 19"24
I.OX 1Q-25
3.0 X 10"26
3.4 X IO'28
3.6 X 10"2'
1.6X 10"49
I.OX 10"97
8.5 X 10-"
2.0 X 10-"
Fig. 15—List of metal sulfide solubility products.
pany has a cost-sharing grant agreement (Reference 13)
with the EPA to build a laboratory-scale plant for treat-
ing industrial wastewaters by the sulfide and hydroxide
processes (Reference 13). Samples of wastewater will
be collected from typical metal finishers across the
United States, and comparisons will be made between the
two processes. Quality of effluent will be measured by
atomic absorption equipment capable of analyzing for
heavy metals in the p.p.b. range. Optimum operating
conditions will be selected for both sulfide and hydrox-
ide processes, in what is planned to be an objective
impartial study. The study will include cost analysis.
SUMMARY AND CONCLUSIONS
More complete removal of heavy metals from waste-
water is claimed for sulfide precipitation than is possible
by the well-established hydroxide process. In general the
hydroxide process reduces metals — unless complexing
agents are present — to the 0.1 to 2 mg/1 level, and it is
claimed that the sulfide process reduces metals
to the 0.05 mg/1 level, or better.
The sulfide process has the additional advantage of not
requiring preliminary reduction of hexavalent chromium
to trivalent chromium. However, the sulfide process does
have the disadvantages of higher cost (unless offset by
elimination of hexavalent chromium reduction), odor
toxicity, greater sophistication, and possibly, sludge
disposal problems.
Additional work is currently in progress that will lead
to more precise definition of the advantages of the sulfide
process.
REFERENCES
1. Treatment of Metal Finishing Wastes by Sulftde
Precipitation, R. M. Schlauch and A. Epstein EPA
Report No. EPA-600/2-77-049.
2. Wastewater Treatment Technology, Patterson and
Minear, Illinois Institute of Technology Report
number IIEQ 71-4.
3. Pollutant Removal Handbook, Sittig, Noyes Data
Corporation, 1973.
4. Chemical Marketing Reporter, issue dated 10/3/77
Schnell Publishing Co. Inc.
5. National Pollutant Discharge Elimination System
Waste Discharge Permit No. WA-000094-9, State of
Washington Dept. of Ecology.
6. Water Pollution Control for Metal Machining,
Fabricating, and Coating Operations, prepared for
the U. S. Environmental Protection Agency Tech-
nology Transfer Program by Centec Consultants,
Inc.
7. Industrial Finishing, "How Discharge Limits in 36
Cities Compare with EPA and NAMF", December
1975, p. 49.
8. Handbook of Chemistry and Physics, 48th Edition
The Chemical Rubber Co., B-284.
9. Handbook of Chemistry, Lange, tOth Edition Mc-
Graw-Hill Book Co.
64
-------
10. Smiths College Chemistry, 7th Edition, Ehret.
Appleton-Century Crafts, Inc., Section 18-7 "Pre-
cipitation With Hydrogen Sulfide."
11. Sulfex (TM) Heavy Metals Waste Treatment Pro-
cess, Technical Bulletin Vol.: XIII, No. 6, Code
4413.2002, dated 10/1976.
12. U. S. Patent 3,740,331, "Method for Precipitation
of Heavy Metal Sulfides", patented June 19, 1973,
Anderson and Weiss, assignors to the Sybron
Corporation.
13. U. S. Environmental Protection Agency Grant
agreement No. S8054-13010, 8/29/77, Sulfide Pre-
cipitation of Heavy Metals".
14. U. S. Patent 3,317,312, "Processes for Removal
and/or Separation of Metals from Solutions",
patented 1969, Kraus and Phillips.
15. Orion Research Instruction Manual for Sulfide Ion
Activity Electrode Model 94-16, Orion Research
Inc., 1970.
16. Process Design Manual for Sulfide Control in Sani-
tary Sewerage Systems, United States Environmen-
tal Protection Agency, Technology Transfer, Octo-
ber 1974.
65
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Evaluation of Advanced Reverse Osmosis Membranes
For the Treatment of Electroplating Wastes
Kenneth J. McNulty, Peter R. Hoover & Robert L. Goldsmith*
ABSTRACT
Because of the limited pH range over which current commercially available reverse osmosis
membranes can be applied, a test program was initiated to define the applicability of new
membrane materials to the treatment of rinsewaters with extreme pH levels and high oxidant
levels (chromic acid). Life tests were conducted with the PA-300, PBIL, NS-100, MS-200,
SPPO, B-9, andCA membranes on rinsewaters from copper cyanide, zinc cyanide, acid copper,
and chromic acid plating baths. The PA -300 membrane exhibited superior performance for the
treatment of copper cyanide, tine cyanide, and chromic acid rinsewaters, and further
development and demonstration of this membrane is recommended. The NS-200 and PBIL
membranes exhibited the best performance for treatment of acid copper rinsewaters. Efforts are
underway to commercialize all three of the selected membranes (PA -300, NS-200, and PBIL).
INTRODUCTION
Since enactment of the Federal Water Quality Control
Act and its amendments, the metal finishing industry has
become increasingly concerned with techniques for
wastewater treatment. A variety of new technologies
have been developed for the treatment of electroplating
wastewaters; however, none of these technologies
appears to offer an optimum solution to all aspects of the
problem. As a result, many platers are waiting for further
development and demonstration of new technologies
before attempting to make a final decision on the
selection of wastewater treatment processes.
Wastewater treatment technologies for the
electroplating industry can be broadly classified as end-
of-pipe destruction processes or in-plant recovery
processes. The end of pipe destruction processes treat a
total shop effluent to remove a mixture of heavy metals.
At present it is neither technically nor economically
feasible to recover and recycle metals from the end-of-
pipe processes (I). On the other hand, in-plant recovery
processes treat rinsewater from a specific plating bath (or
other operation) making it possible to recover and return
the heavy metals to the plating bath.
It seems reasonable to speculate that most, if not all,
plating shops will require an end-of-pipe treatment
process, particularly for diversified job shops where in-
plant recovery of all rinsewaters is neither technically nor
economically feasible. Even for less diversified shops,
end-of-pipe treatment would be required for spills,
contaminated plating baths, spent cleaners, etc. How-
"Kenneth J. McNulty, Peter R. Hoover & Robert L. Goldsmith
Walden Division of Abcor, Inc.
Wilmington, Massachusetts
ever because of the inherent disadvantages ofend-of pipe
treatment — loss of valuable plating chemicals, cost of
sludge disposal, and cost of treatment chemicals — it is
also reasonable to speculate that platers will use in-plant
recovery processes where the economics for recovery are
favorable or where recovery could reduce the load on the
end-of-pipe system to the extent necessary to meet the
discharge regulations for specific contaminants.
Aside from a few applications in which closed-loop
recovery can be achieved by countercurrent rinsing
alone, some technique must be used to separate the
dissolved plating chemicals from the rinsewater. The
leading techniques for making this separation are reverse
osmosis (RO), evaporation, and ion exchange. This
paper addresses the application of reverse osmosis to the
recovery of electroplating rinsewaters with particular
emphasis on the performance characteristics of new
membrane materials used to treat extreme pH
rinsewater.
Principles of Reverse Osmosis
Reverse osmosis is a pressure driven membrane
separation process in which a feed stream under pressure
(400 - 800 psig) is separated into a purified "permeate"
stream and a "concentrate" stream by selective
permeation of water through a semi-permeable
membrane. There are three major types of commercially
available membrane modules: tubular, spiral-wound
and hollow-fiber. These are shown in Figure 1. Each of
these modules has particular advantages and limitations.
Tubular modules are not susceptible to plugging by
suspended solids and can be operated at high pressures
but their space requirement (ft1 per ft- membrane surface)
is relatively high and their cost is approximately five
times as high as the other configurations for an
66
-------
Casing
a. Tubular Membrane
ROLL TO
ASSEMBLE
FEED SIDE
SPACER
FEED FLOW
PERMEATE FLOW
(AFTER PASSAGE
THROUGH MEMBRANE)
PERMEATE OUT
PERMEATE SIDE BACK(NG
MATERIAL WITH MEMBRANE ON\
EACH SIDE AND GLUED AROUND
EDGES AND TO CENTER TUBE \
<
E*?:.v.v.v.v::.v.Mv:v:-:-i
MMWWM*^!
b Spiral-Wound Module
CONCENTRATE
SIMP RING OUTLET
OffM ENDS
Of FtBCRS
FLOW SCREEN
POROUS
BACK UP DISC
V RING SUd.
FEED
SNAP RING
END PLATE
nets
SHELL
•V RING SEAL /
POROUS FEED END PLATE
DISTRIBUTOR TUBE
c. Hollow-Fiber Module
Figure 1. Membrane Module Configurations
67
-------
equivalent rate of permeate production. Therefore
tubular modules are not recommended for plating
applications.
Spiral-wound and hollow-fiber modules are essentially
identical in cost for an equivalent rate of permeate
production. Hollow-fiber modules have a somewhat
lower space requirement per unit of permeate produced;
while the spiral-wound modules are less susceptible to
plugging by suspended solids.
There are a number of membrane materials presently
under development, but only two types are currently in
commercial use. The most widely applied is cellulose
acetate (or cellulose tri-acetate), which was originally
developed for water desalination and has since been
adopted for many industrial waste treatment
applications. It is available in tubular, spiral-wound, and
hollow-fiber configurations and exhibits excellent water
permeation rates and high rejection of ionic species.
Unfortunately, it is limited to a fairly narrow pH range
(2.5 - 7). Operation beyond this range hydrolizes the
membrane and destroys its ability to selectively pass
water.
The other commercially available membrane is
du Font's polyamide membrane which is presently
available only in a hollow-fiber configuration. It also
exhibits high flux and high rejection, but can be applied
over a somewhat broader pH range (4 - 11).
In general tlv cellulose acetate membrane should be
used at low pH, and the polyamide membrane at high
pH. In the region of pH overlap neither membrane has an
overriding advantage over the other.
Membrane performance is characterized in terms of
flux and rejection. The flux is the rate at which purified
water permeates through the membrane per unit area of
membrane surface and is generally given in gallons per
square foot per day (gfd). The rejection of a particular
dissolved species is given by:
% Rejection = CF ' Cp X 100%
\~-F
where: CF = concentration in feed stream
Cp = concentration in permeate stream.
In general both flux and rejection increase with operating
pressure and decrease with increasing feed concentration.
The flux increases with temperature, but rejection is
essentially temperature independent. The flow rate of
feed tangential to the membrane surface is also an
important parameter and must be maintained at a high
enough level to prevent the build-up of rejected salts at
the membrane surface.
The major advantages and limitations of reverse
osmosis are listed in Table 1. The objective of the present
research effort is to identify new membrane materials
that would broaden the allowable pH range (Limitation
#1) and would reduce the required frequency of
membrane replacement (Limitation #4).
TABLE 1
Advantages and Limitations of RO
Advantages
1. Low capital cost. The modular nature of RO units makes
them particularly well-suited for small-scale installations.
2. Low energy cost. Only power for pumping is required;
there is no phase change as in evaporation.
3. Low labor cost. The process is fully automated and simple
to operate requiring little operator attention.
4. Low space requirements. Since RO equipment is compact
and operates continuously, it requires minimal tankage.
Limitations
1. There is a limited pH range (about 2.5 - 11) over which
current commercially available membranes can operate for
extended periods.
2. RO is incapable of concentrating solutions to very high
concentrations. For ambient temperature baths a small
evaporator is generally required to close the loop.
3. Certain species, e.g., small non-ionized molecules, are not
completely rejected by the membrane.
4. Membrane performance generally degrades with time
requiring periodic replacement of the membrane modules.
Application of Commercially Available Membranes
To Rinsewater Recovery
Because of the potential cost advantage of RO relative
to other recovery processes, EPA and AES have
sponsored a number of projects aimed at developing and
demonstrating RO for the treatment of electroplating
rinsewaters. Work performed under AES Project 32
included both in-house and field tests of commercially
available membranes (2, 3). The in-house tests were
conducted with samples of actual plating baths diluted to
various concentrations to simulate actual rinsewater. A
total of nine different plating-bath rinsewaters were
treated with the two-commercially available membranes
(cellulose acetate and polyamide) using full-scale RO
modules.
It was concluded from these tests that RO appeared
promising for the treatment of nickel baths (Watts,
sulfamate, fluoborate) and copper pyrophosphate.
Treatment of relatively low-pH cyanide baths also
appeared feasible using the polyamide membrane.
However, the commerically available membranes did not
appear to have a suitable operating life for the treatment
of highly oxidizing rinsewaters (chromic acid), low pH
(<2) rinsewaters, and high pH (>11) rinsewaters.
Following in-house testing, various field tests were
conducted to demonstrate the performance of RO under
realistic conditions. The polyamide membrane in hollow
fiber configuration was successfully demonstrated for the
treatment of Watts nickel rinsewaters (4). (The cellulose
acetate membrane in spiral-wound configuration has
also been successfully demonstrated on Watts nickel
rinsewater (5) as part of AES Project 31.) It was
concluded that either of the two commercially available
68
-------
membranes can be used to treat nickel rinsewaters and
that the economics for closed-loop nickel recovery can be
quite attractive. This has been proven in industrial
practice: approximately 100 RO systems have been sold
for the treatment of nickel rinsewaters.
In an effort to expand the application of RO to major
plating baths other than nickel, two separate field
demonstrations were conducted on copper cyanide
rinsewaters using the polyamide membrane (6). In
general, it was concluded that the polyamide membrane
can be used for the recovery of relatively low-pH cyanide
rinsewaters provided that the membrane life is adequate.
However, since rapid membrane deteriorating was
observed in one of the two field tests, the treatment of
copper cyanide rinsewaters cannot be considered a
prOyen application.
Based on these results as well as the known pH
tolerance of the commercially available membranes, it is
evident that new membranes must be developed in order
to expand the applicability of RO to major plating baths
other than nickel. In particular, membranes must be
developed with resistance to pH extremes (<2 and >11)
and with resistance to oxidants (chromic acid). To this
end AES Project 39 was undertaken, and results from
this project are presented and discussed below.
Application of New Membranes to Rinsewater Recovery
During the past two years the Walden Division of
Abcor, Inc. has been conducting life tests with various
new membrane materials exposed to rinsewaters with
both high and low pH and with high levels of oxidants
(chromic acid). The objective of this testing program,
which was jointly funded by AES and EPA, was to
identify new membrane materials which would be
applicable to the recovery of a broad range of
electroplating rinsewaters.
Materials and Methods
Table 2 lists the membranes investigated during this
program along with the manufacturer from which the
membrane was obtained and a brief description of the
membrane configuration and materials. Membranes
other than those listed are under development but, for a
variety of reasons, were not submitted by the
manufacturer for testing during this program. In
addition to the new membrane materials, the two
commercially available membrane types, B-9
(polyamide) and CA (cellulose acetate) were tested in
order to provide a reference level to which the new
membranes could be compared. The B-9 membrane (pH
range 4-11) was the reference for alkaline rinsewaters,
and the CA membrane (pH range 2.5 - 7) was the
reference for acid rinsewaters.
Table 3 lists the plating baths used to prepare the
rinsewaters tested in this program. The major
components and nominal composition are also listed for
each plating bath. These baths were selected because of
their extreme pH levels and, in the case of chromic acid,
high oxidation potential. Rinsewaters were prepared
from each bath of Table 3 by dilution to the appropriate
TABLE 2
Membrane Materials and Configurations Tested
Membrane
Material
PA-300
Source
Fluid Systems Div.
of HOP, Inc.
San Diego, CA
PBIL Walden Div., of
Abcor, Inc.
Wilmington, MA
NS-100 Walden Div., of
Abcor, Inc.
Wilmington, MA
NS-200 Fabric Research
Lab.
Dedham, MA
SPPO General Electric
Company
Wilmington, MA
B-9 E. I. duPont
Wilmington, DE
CA Abcor, Inc.
Wilmington, MA
Description
Rat sheet composite
membrane of poly (ether/
amide) on polysulfone
Rat sheet asymetric
membrane of polybenzimi-
dazolone
1/2-inch tubular compo-
site membrane of poly-
ethyleneimine cross-linked
with tolylenediisocyanate
on polysulfone
0.006-inch ID hollow fiber
composite membranes of
polyfurfuryl alcohol on
polysulfone. Modules
supplied
Flat sheet sulfonated
polyp henylene-oxide
Hollow-fine-fiber asyme-
tric membranes of aroma-
tic polyamide. Mini-
permeator supplied
1/2-inch tubular mem-
brane of asymetric cellu-
lose acetate
TABLE 3
Composition of Plating Baths Tested
Plating
Bath
Chromic Acid
Udylite
Acid Copper
Lea-Ronal
Copper Cya-
nide-1
MacDermid
Copper Cya-
nide-2
R. O. Hull
Zinc Cyanide
R. O. Hull *
Component
Chromic Acid
Sulfate
Catalyst (fluoride)
Copper Sulfate
Sulfuric Acid
Brightener (Copper
Gleem PC)
Chloride
Copper as metal
Free Cyanide (as KCN)
Potassium Hydroxide
Rochelle Salt (Rocheltex)
Brightener (CI Bright
Copper)
(Potassium Carbonate)
Copper as metal
Free Cyanide (as NaCN)
Caustic
Rochell Salt (Roplex)
Brightener
Nominal
Composition
34 oz/gal
0.12oz/gal
Unknown
8-12 oz/gal
22-28 fl. oz/gal
0.4-0.6% Vol.
50 ppm
6.3 oz/gal
2.7 oz/gal
2.0 oz/gal
6% by Vol.
0.2% by Vol.
5.0 oz/gal
3.75 oz/gal
1.17 oz/gal
1.17 oz/gal
2-4% by Vol.
none
Zinc as metal 2.5-3 oz/gal
Free Cyanide (as NaCN) 5-7 oz/gal
Caustic 11-13 oz/gal
Brightener (ROHCO 532) 0.3 fl. oz/gal
69
-------
Concentrate Return Line
DV V
T Booster
Pump Filters
ACC - Accumulator
BPR - Back Pressure Regulator
DV - Drain Valve
F - Flow Indicator
HPS - High Pressure Switch
IPS - Low Pressure Switch
P - Pr.essure Indicator
PRV - Pressure Relief Valve
SOV - Solonoid Valve
TI/C - Temperature Indicator/Controller
Figure 2. Simplified Flow Schematic of Test System
concentration. Life tests were conducted at two dilutions
for each bath: 5% of bath strength and 25% of bath
strength. The dilutions were performed on a volumetric
basis, e.g., one gallon of bath plus three gallons of water
for the 25% dilution.
A simplified flow schematic of the test system is shown
in Figure 2. Feed was withdrawn from the feed tank by a
centrifugal booster pump and passed through two
cartridge filters in series. A high-pressure diaphragm
pump was used to pressurize the feed and pass it through
the membrane test cells. The pressures within the cells
were controlled in the range of 400 - 800 psi with back-
pressure regulators. An accumulator was used to dampen
pressure pulsations from the high-pressure pump, a
pressure relief valve and high pressure switch were used
to prevent overpressurization of the membranes, and a
low pressure switch was used to prevent the pumps from
running dry. A cooling coij with automatic temperature
control was used to maintain the feed at a constant
temperature, and the surface of the feed tank was covered
with polyethylene balls to prevent evaporation and CO:
absorption (by alkaline solutions).
The system was operated in a total recycle mode with
both concentrate and permeate returned to the feed tank.
This mode of operation permits continuous long-term
operation with only a reltively small volume of feed. In
general, the membranes were tested at a temperature of
77° F and at the pressures and feed flow rates listed
below.
Membrane
PA-300
PBIL
NS-100
NS-200
SPPO
B-9
CA
Operating
Pressure, psig
800
800
600
800
600
400
600
Feed Circulation
Rate, gpm
0.3
0.3
0.5
0.5
0.05
0.5
Membrane performance was determined by measuring
the flux and rejection for each membrane as a function of
operating time. The flux was determined by measuring
the permeate flow rate (graduate and stopwatch
technique) for each membrane, and the rejection was
determined by obtaining samples of the feed and the
70
-------
permeate from each membrane analyzing for various
bath constituents. Each membrane was operated for 1000
hours on rinsewaters from each of the 4 plating baths —
500 hours at 5% of bath strength and 500 hours at 25% of
bath strength.
Results and Discussion
Results are presented below for all the plating bath
rinsewaters in the orders in which they were
tested: copper cyanide, zinc cyanide, acid copper, and
chromic acid.
Copper Cyanide
I Copper cyanide was the first plating bath to be tested,
anil during the initial tests the PA-300 and PBIL
membranes were not yet available. Therefore the NS-100,
NS-200, SPPO, and B-9 membranes were tested using the
copper cyanide-1 bath listed in Table 3. The PA-300 and
PBIL membranes were tested at a later time using the
copper cyanide-2 bath listed in Table 3. These baths are
reasonably similar in composition which should permit a
direct comparison of the results for all the membranes.
Table 4 gives the results for tests conducted with
rinsewater at 5% of bath strength. The performance
parameters listed for each membrane are conductivity
rejection, copper rejection, free cyanide rejection, and
flux. Rejections are given as a percentage of the feed
TABLE 4
Membrane Performance During Life Test
with Copper
Cyanide Rinsewater at 5% of Bath Strength (pH = 10-13)
Membrane
PA-300
PBIL
NS-100
(Avg of 5)
NS-200
(Avg of 2)
SPPO
B-9
Performance
Parameter
Conductivity Rejection, 9
Copper Rejection, 9
Free Cyanide Rejection, 9i
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, 9i
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, "/,
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, 95
Flux, cc/min
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, 9
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, 9
Flux, cc/min
Level
at 24
Mrs
6 97.5
fe 99.1
98.2
15
85.4
99.3
i 97.2
13
90.0
96.5
, 91.0
7
96.2
99.0
3 96.5
30
96.2
95.0
3 87.0
9
96.5
99.9
3 98.5
1.8
Level
at 250
Mrs
97.8
98.0
96.7
9
90.0
98.5
94.3
8
92.5
96.3
90.0
6
98.3
99.8
97.0
32
82.0
92.0
80.0
5
98.3
99.3
97.2
2.2
Level
at 500
Mrs
97.9
98.9
99.2
9
90.5
98.7
98.8
8
86.0
96.0
93.0
6
88.0
99.7
98.5
33
68.0
94.0
92.0
4
91.0
99.4
98.7
1.7
concentration rejected, and flux, for the most part, is
given in gallons per square foot of membrane surface per
day (gfd). For the hollow fiber modules (NS-200 and B-9)
the productivity is reported in cc/min since the exact
surface area is difficult to determine and the productivity
per unit membrane area is not directly comparable to the
flux for flat sheet membranes because of the much higher
packing density (ft2/ft3) possible with the hollow fiber
configuration.
The flux and rejections for each membrane are shown
at the start of the test, the mid-point, and the end of the
test. (Actual sampling times varied slightly from the 24,
250, and 500-hour times shown in this and subsequent
tables.) Average results are reported for the NS-100
membrane (five tubes tested in series).
The results of Table 4 indicate that all of the
membranes tested exhibited reasonably stable flux and
rejection for the 500-hour life test at 5% of bath strength.
The apparent drop in conductivity rejection for the NS-
100, NS-200, SPPO, and B-9 membranes is believed to be
an artifact resulting from the absorption of atmospheric
CO? which gradually changed the pH of the test solution
and shifted the ionic equilibria in the direction of more
poorly rejected species. The copper and free cyanide
rejections for these same membranes showed no
significant decline during the test. In subsequent tests,
polyethylene spheres were added to the feed tank to cut
down the amount of CO: absorption and the pH was
more carefully controlled. '
In general the PA-300, NS-200, and B-9 membranes
gave the highest rejections of conductivity, copper, and
free cyanide. Relative to these membranes the PBIL
membrane gave equivalent rejections of copper and free
cyanide but somewhat lower conductivity rejections. The
NS-100 and SPPO membranes gave lower rejections
particularly for copper and free cyanide.
The results for the 500 hours life test at 25% of bath
strength are given in Table 5. At this concentration the
PBIL, NS-200, SPPO, and B-9 membranes showed
significant degradation in performance characteristics.
For the PBIL membrane the flux decreased to an
extremely low level upon exposure to the 25%-of-bath
rinsewaters. The rejections are also poor (< 90%)
probably as the result of the very low flux. Two NS-200
modules were tested on the 25% rinsewater. Both
modules seemed to perform reasonably well until after
about 250 hours. After this time one of the modules failed
resulting in gross leakage between the feed and permeate
sides, and the other module exhibited serious
degradation in conductivity, copper, and cyanide
rejection. The SPPO membrane exhibited extremely low
rejections of all species and rejections decreased with time
indicating degradation of the membrane material. For
the B-9 membrane the rejections of copper and cyanide
declined at a moderate rate, but the flux of the membrane
declined rapidly.
Only the PA-300 and NS-100 membranes showed no
serious degradation in performance during the tests with
the 25%-of-bath rinsewaters. Of these two membranes
the PA-300 is clearly superior. The conductivity rejection
71
-------
Membrane
Membrane
PA-300
PBIL
NS-100
(Avg of 5)
NS-200
(Avg of 2)
SPPO
B-9
TABLE 5
Performance During Life Test
Performance
Parameter
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, cc/min
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, gfd
Conductivity Rejection, %
Copper Rejection, %
Free Cyanide Rejection, %
Flux, cc/min
Level
at 24
Hrs
96.3
98.9
98.6
9
60.6
89.3
87.2
0.8
75.0
92.3
92.5
5
75.0
99.4
97.0
25
30
55
67
10
77
99.0
98.3
0.6
with Copper
Level
at 250
Hrs
97.0
99.0
99.0
7
61.3
86.4
89.6
0.7
76.0
90.0
90.8
5
76.5
96.8
95.5
30
23
37
61
8
80
96.7
95.3
0.2
Level
at 500
Hrs
98.0
99.3
98.8
8
56.7
75.4
77.0
0.9
78.5
87.0
90.2
5
30.0
32
27
(Failure)
22
30
35
4
80
94.1
92.0
0.1
TABLE 7
Membrane Performance During Life Test
Cyanide Rinsewater at 25% of Bath
Performance
Membrane Parameter
PA-300 Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, gfd
PBIL Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, gfd
NS-100 Conductivity Rejection, %
(Avg of 6) Zinc Rejection, %
Free Cyanide Rejection, %
Flux, gfd
NS-200 Conductivity Rejection, %
(Avg of 2) Zinc Rejection, %
Free Cyanide Rejection, %
Flux, cc/ min
SPPO Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, gfd
B-9 Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, cc/mn
with
Zinc
Strength (pH > 13)
Level
Level
at 24 at 250
Hrs
87
99.1
97.3
17
35
-
-
1.1
42
87
78
4
33
93.0
80
75
33
50
57
6
30
98.1
90.0
0.12
Hrs
87
-
-
14
41
-
-
1.1
43
91
88
10
20
95.0
88
92
20
46
41
6
5
98.0
95.0
(.9)
Level
at 500
Hrs
87
99.3
97.0
13
52
96
91
0.9
42
82
77
10
31
93.5
82
75
35
56
31
2
53
95.5
91.3
0.10
TABLE 6
Membrane Performance During Life Test with
Cyanide Rinsewater at 5% of Bath Strength (pH =
Membrane
NS-100
(Avg of 5)
NS-200
(Avg of 2)
SPPO
B-9
Performance
Parameter
Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, gfd
Conductivity Rejection, %
Zinc Rejection, %
Free Cyanide Rejection, %
Flux, cc min
Conductivity Rejection, r/c
Zinc Rejection, ';
Free Cyanide Rejection. r-'(
Flux, gfd
Conductivity Rejection. rt
Zinc Rejection. r,'
Free Cyanide Rejection, ri
Flux, cc min
Level
at 24
Hrs
72
-
88
7
67
—
96.8
100
25
-
50
7
73
-
97.2
I.I
Level
at 250
Hrs
75
97.7
92.7
6
60
99.7
95.4
105
30
72
63
6
81
99.9
98.5
1.0
Zinc
12-13)
Level
at 500
Hrs
81
96.8
91.0
6
67
99.2
91.0
97
41
73
53
6
83
99.9
97.7
0.75
was quite good, the copper and free cyanide rejections
were excellent, and the flux was high. Both flux and
rejection were stable throughout the test. On the other
hand the NS-100 rejections were rather poor and the flux
was only moderate. It is concluded that, for the treatment
of copper cyanide rinsewaters, the PA-300 is the best of
the membranes tested.
Zinc Cyanide
Following the tests with copper cyanide rinsewaters at
25% of bath strength, the NS-200 modules were replaced
with two new modules, and a new B-9 mini-permeator
was installed. The NS-100 and SPPO membranes were
not changed prior to the zinc cyanide tests. The PA-300
and PBIL membranes were not obtained in time for the
zinc cyanide tests at 5% of bath strength but were tested at
25% of bath strength.
Table 6 gives the results for the test with the 5%-of-bath
rinse-water. All of the membranes tested appeared to be
reasonably stable at this rinsewater concentration, and
the commercially available B-9 membrane appeared to
have the highest overall rejections. The low rejections for
the SPPO membrane were probably the result of
membrane deterioration during testing with 25%-of-bath
copper cyanide rinsewater.
Results for the life-test with 25%-of-bath zinc cyanide
rinsewater are given in Table 7. Again, all of the
72
-------
membranes tested exhibited reasonably stable
performance. However, except for the PA-300
membrane the flux and/or rejections of the membranes
were too low for cost-effective recovery of zinc cyanide
rinsewaters at this concentration. The low conductivity
rejections (generally < 50% except fot the PA-300
membrane) could be the result of the high concentration
of hydroxide ion (which is difficult to reject) in the zinc
cyanide rinsewaters. The PA-300 membrane, by contrast,
gave excellent zinc and free cyanide rejections and a
conductivity rejection much higher than for any of the
other membranes. In addition the flux for the PA-300
was quite high and appeared to be leveling off at a stable
value of about 12 gfd. Based on these data it is concluded
that, for the treatment of zinc cyanide rinsewaters, the
PA-300 is the best of the membranes tested.
Acid Copper
Following the tests with the zinc cyanide rinsewater at
25% of bath strength, new PA-300 and PBIL membranes
were installed in the system; however, the NS-100 and
NS-200 membranes were not changed since new samples
of these membranes were not available. The SPPO
membrane was replaced prior to the test at 25% of bath
strength, but during initial characterization tests with a
sodium chloride solution, it was discovered that the new
SPPO membrane was giving very poor rejections
(<60%). This membrane was therefore eliminated from
the test program. The B-9 membrane, which served as a
reference membrane for alkaline solutions, was replaced
by a CA reference membrane for tests with acid copper
and chromic acid solutions. However the CA membrane
was not installed in the test system until after the test
with 5%-of-bath acid copper rinsewater.
Results are shown in Table 8 for the life test with acid
TABLE 8
Membrane Performance During Life Test with Acid
Copper Rinsewater at 5% of Bath Strength (pH
Membrane
PA-300
PBIL
NS-100
(Avg of 6)
NS-200
(Avg of 2)
Performance
Parameter
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, cc/min
Level
at 24
Hrs
I 79.7
99.7
92.9
32
'c 99.4
>99.9
99.8
3.6
fc 20.0
94.7
49.8
11
fc 97.2
99.9
98.7
43
Level
at 250
Hrs
89.2
—
—
23
99.1
—
—
7.2
50.0
—
-
16
97.2
—
—
38
= 1.2)
Level
at 500
Hrs
82.6
—
94.8
14
99.5
-
98.0
4.0
24.2
-
57.1
19
96.0
-
98.1
31
TABLE 9
Membrane Performance During Life Test
With Acid Copper Rinsewater at 25% of Bath Strength
(pH = 0.6-0.9)
Membrane
PA-300
PBIL
NS-100
(Avg of 5)
NS-200
(Iof2)
CA
Performance
Parameter
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, cc/min
Conductivity Rejection, 9
Copper Rejection, %
Sulfate Rejection, %
Flux, gfd
Level
at 24
Mrs
, 78.1
99.9
76.5
12
, 99.2
>99.9
99.3
3.9
3 26.7
98.2
1.6
14.4
, 86.5
97.8
86.1
25
, 92.3
99.9
92.0
4.7
Level
at 250
Mrs
82.6
>99.9
92.2
6
98.3
>99.9
98.1
2.5
31.5
98.3
60.4
7.2
84.8
98.5
91.2
17
57.8
97.2
74.9
8.7
Level
at 500
Hrs
90.0
>99.9
83.0
3.6
99.1
>99.9
94.4
2.8
47.2
96.0
50.9
4.7
91.3
99.0
94.9
18.5
39.1
83.3
49.2
9.8
copper rinsewater at 5% of bath strength. The PBIL
membrane exhibited exceptionally high rejections for all
species including conductivity (rejection >99%), and the
rejection appeared to be stable. Although the flux (~ 4
gfd) is rather low, it is believed that membranes with a
higher flux could be prepared by varying the casting
procedure. (This membrane was still in the process of
being optimized when the test sample of membrane was
obtained.) The NS-200 membrane also exhibited quite
good performance characteristics during this test. Both
the flux and rejection for this membrane appear adequate
for successful application to copper sulfate rinsewaters.
The PA-300 membrane gave a lower level of
performance, and the NS-100 performed poorly in this
test. It is possible that the copper ions in the rinsewater
complexed with amine groups on the NS-100 membrane
surface (and to a lesser extent on the PA-300 surface)
resulting in poor rejection performances.
For all membranes the rejections remained stable with
operating time, but significant declines in flux were
observed for the PA-300 and NS-200 membranes.
Results for copper rejection are incomplete because of
immersion deposition of copper on various stainless steel
components within the test system. Copper
concentrations in the feed solution decreased to very low
levels following the first analysis at 24 hours.
Results are shown in Table 9 for the life test with acid
copper rinsewater at 25% of bath strength. Immersion
deposition was not a problem during this test since
73
-------
significant deposition had already occurred in the
previous test, and copper concentrations in the feed were
much higher. Again the PBIL membrane exhibited
extremely high rejection of all species, but the flux was
low. The flux and rejections were reasonably stable for
the duration of the test with the exception of sulfate
rejection. The NS-200 membrane declined in
performance relative to the test at 5% of bath strength,
but is still considered adequate for successful application
of this membrane particularly in view of the fact that this
same membrane had been used during the zinc cyanide
life tests. The rejection of conductivity, copper, and
sulfate increased during the test, and the flux appeared to
stabilize after an initial decline. The PA-300 membrane
exhibited excellent copper rejections, but the sulfate and
conductivity rejections were low. The PA-300 rejections
generally increased with operating time but the flux
decreased substantially during the life test to only one-
third of its initial value. The NS-100 membranes
exhibited very poor but stable rejections and a
substantial decrease in flux over the duration of the test.
The CA membrane was degraded by acid hydrolysis at
the low pH of the rinsewater. This deterioration is
evidenced by a substantial loss in rejection with a
simultaneous increase in flux.
On the basis of the life tests with acid copper
rinsewaters, it is concluded that the NS-200 and PBIL
membranes exhibit the best performance characteristics.
Chromic Acid
Following the tests with acid copper, new PA-300 and
PBIL membranes were installed in the test system, but
the same NS-100 and NS-200 membranes were retained.
Only one NS-100 tube and one NS-200 module were
tested on the 5%-of-bath chromic acid rinsewater. For
the test at 25% of bath strength, the NS-200 was
discontinued because of severe membrane degradation.
Results of the life test at 5% of bath strength are shown
in Table 10. Of the membranes tested only the PA-300
and PBIL gave stable performance. For the NS-100,
NS200, and CA membranes, the rejections decreased,
and the flux levels increased with operating time. This
behavior is indicative of chemical degradation of the
membrane surfaces.
Both the PA-300 and the PBIL membranes gave
exceptionally stable flux and rejection performance
throughout the life test. Of these two membranes, the
PA-300 exhibited better performance for both flux and
rejection.;
The results for the life test with chromic acid at 25% of
bath strength are shown in Table 11. The NS-f 00 and CA
membranes degraded quite rapidly, and the evaluation of
these membranes had to be discontinued shortly after the
life test was initiated. The PBIL was operated for the
entire 600-hour test but the rejections of both
conductivity and hexavalent chrome declined
substantially. On the other hand the PA-300 membrane
exhibited very good conductivity rejection and excellent
chromium rejection during the entire life test. Although
the flux is low it appeared to be reasonably stable. It is
TABLE 10
Membrane Performance During Life Test
With Chromic Acid Rinsewater at 5% of Bath Strength
Membrane
PA-300
PBIL
NS-100
NS-200
CA
(pH = 1.3-1.7)
Performance
Parameter
Conductivity Rejection, %
Chromium (VI) Rejection, %
Flux, gfd
Conductivity Rejection, %
Chromium (VI) Rejection, %
Flux, gfd
Conductivity Rejection, %
Chromium (VI) Rejection, %
Flux, gfd
Conductivity Rejection, %
Chromium (VI) Rejection, %
Flux, cc/min
Conductivity Rejection, %
Chromium (VI) Rejection, %
Flux, gfd
Level
at 24
Mrs
97.9
98.8
8
95.0
96.8
3.8
43.3
51.0
10
28.3
25.8
17
96.2
97.3
11
Level
Level
at 250 at 500
Hrs Hrs
97.8
98.9
10
95.0
96.6
7.2
23.1
4Z9
36
0.0
11.4
140
88.5
91.4
27
97.5
98.6
9
94.1
96.3
8.6
2Z7
67.4
44
0.0
18.0
150
31.8
42.0
60
TABLE 11
Membrane Performance During Life Test
With Chromic Acid Rinsewater at 25% of Bath Strength
(pH = 1.1-1.2)
Performance
Membrane Parameter
PA-300 Conductivity Rejection, %
Chromium (VI) Rejection,
Flux, gfd
PBIL Conductivity Rejection, %
Chromium (VI) Rejection,
Flux, gfd
NS-100 Conductivity Rejection, %
Chromium (VI) Rejection,
Flux, gfd
CA Conductivity Rejection, %
Chromium (VI) Rejection,
Flux, gfd
Level Level Level
at 24 at 300 at 600
Hrs Hrs Hrs
95.9 97.3 97.5
97.9 99.1 98.8
5.4 2.5 3.1
92.2 77.7 73.3
96.1 90.8 83.4
4.0 2.8 5.1
15.7
33.2
42.3 Discontinued)
(Test
75.3
85.7
21.6 Discontinued)
(Test
believed that the PA-300 could be used to economically
recover chromic acid rinsewater in spite of the low flux
because of the relatively high value of the recovered
chemicals.
It is concluded that, of the membranes tested, the
PA300 is the only one that is suitable for the treatment of
chromic acid rinsewater.
Conclusions
The results of the life tests described above indicate
that the PA-300 is the most promising of all the
74
-------
membranes tested for the treatment of rinsewaters with
extreme pH levels or high levels of oxidants (chromic
acid). The PA-300 membrane was clearly superior to the
other membranes for treatment of copper cyanide, zinc
cyanide, and chromic acid rinsewaters. However the
NS200 and PBIL membranes proved to be betterthan the
PA-300 for the treatment of acid copper rinsewaters.
Of these three membranes, the PA-300 is the closest to
commercialization. A full-scale, spiral-wound,
membrane module containing the PA-300 membrane has
been developed and extensively tested by the Fluid
System Division of UOP for brackish- and seawater
desalting. Although the module has not yet been
officially commercialized, modules are being fabricated
and supplied on a special-order basis. The manufacturer
is currently working on an order to supply a large number
of'6-inch diameter PA'300 modules for a Saudi Arabian
desalting plant.
The NS-200 membrane is being actively developed
toward commercialization by the Fabric Research
Laboratory. At present, hollow-fiber modules with an
output of 100-300 gallons per day (approximately one-
tenth the output of a full-scale module) are being
fabricated for testing on seawater desalination and
various wastewater streams. The manufacturer
anticipates commercialization within one year.
The PBIL membrane is being developed by the Walden
Division of Abcor, Inc. under contract to OWR&T.
Membrane casting procedures have been optimized, and
a program has been recently initiated to develop
procedures for fabricating the PBIL membrane in a
spiral-wound configuration.
Future Work
Before the PA-300 or any other membranes can be
offered to the plater as a viable means of achieving
closed-loop recovery of rinsewaters, the membrane must
be demonstrated on actual rinsewater under practical
operating conditions. A new program, jointly funded by
EPA (Grant No. R805300010) and AES (Research
Project No. 45), has been initiated to demonstrate the
performance of new RO membranes for closed-loop
treatment of rinsewaters, this program will include
fabrication of a full-scale mobile RO system with an
evaporator to permit closed-loop treatment of ambient
temperature plating baths. The system will be fitted with
PA-300 spiral-wound modules, and recovery of zinc
cyanide rinsewaters will be demonstrated at New
England Plating Co.
Acknowledgments
The authors gratefully acknowledge the financial
support of EPA (Grant No. R804311010) and AES
(Research Project No. 39) for this program. Technical
support for this program was received from the EPA
Project Officer, Ms. Mary Stinson, and from the AES
Project Committee: Messrs. Jack Hyner, Joseph
Conoby, Charles Levy, Herbert Rondeau, James Morse,
and George Scott.
REFERENCES
1. Skovronek, H. S., and M. K. Stinson, Advanced
Treatment Approaches for Metal Finishing Waste-
waters (Part II). Plating and Surface Finishing, 64
(11): 24-31, 1977.
2. Donnelly, R. G., R. L. Goldsmith, K. J. McNulty, and
M. Tan, Reverse Osmosis Treatment of Electro-
piling Wastes, Plating. 61 (5): 432-422, 1974.
3. Donnelly, R. G., R. L. Goldsmith, K. J. McNulty, D.
C. Grant, and M. Tan, Treatment of Electroplating
Wastes by Reverse Osmosis, E PA-600/2-76-261, U. S.
Environmental Protection Agency. Cincinnati, Ohio,
1976. 96 pp.
4. McNulty, K. J., R. L. Goldsmith, and A. Z. Gollan,
Reverse Osmosis Field Test: Treatment of Watts
Nickel Rinse Waters. EPA-600/2-77-039, U. S. Envi-
ronmental Protection Agency, Cincinnati, Ohio,
1977. 29 pp.
5. Golomb, A., Application of Reverse Osmosis to Elec-
troplating Waste Treatment (Part III. Pilot Plant
Study and Economic Evaluation of .Nickel
Recovery). Plating, 60 (5): 482-486, 1973.
6. McNulty, K. J., R. L. Goldsmith, A. Gollan, S.
hossain, and D. Grant, Reverse Osmosis Field Test:
Treatment of Copper Cyanide Rinse Waters. EPA-
600/2-77-170, U. S. Environmental Protection
Agency, Cincinnati, Ohio, 1977. 89 pp.
75
-------
Corrosion-Resistant Coatings
With Low Water Pollution Potential
Christian J. Staebler Jr., Bonnie F. Simpers* & Hugh B. Durham**
ABSTRACT
Results obtained to date under this program have shown that many of the new, currently
available, less polluting corrosion-protection systems are viable alternatives to currently used
more polluting systems. Selection of a specific system for use in a given application would
depend on the corrosion-protection requirements for the product being manufactured. Many of
the systems selected for final evaluation and characterization in this program can provide
corrosion protection equivalent to or superior to that for currently used systems. These new
corrosion-protection systems also offer additional benefits such as less waste treatment,
increased operational safety, lower energy consumption, longer service life and greater
production output.
ACKNOWLEDGMENTS
The authors would like to thank the following
companies for providing samples of their products, for
coating test panels, and for providing technical assistance
in support of this test program:
• Bee Chemical Co., 2700 E. 170th St., Lansing, 111
60438
• DeSoto, Inc., 1700 S. Mt. Prospect Rd, Des Plaines,
111 60018
• Enthone, Inc., Box 1900, New Haven, Conn 06508
• Glidden-Durkee Div., SCM Corp., Third & Barn
Sts, Reading, Pa 19603
• B. F. Goodrich Chemical Co., 6100 Oak Tree Blvd,
Cleveland, OH 44131
• Harshaw Chemical Co., 1945 E. 97th St, Cleveland,
OH 44106
• Harstan Chemical Co., 1247 38th St, Brooklyn, NY
11218
• Hi-Shear Corp., 2600 Skypark Dr, Torrance, CA
90509
• Lea-Ronal Inc., 272 Buffalo Ave, Freeport, NY
11520
• LNP Corp., 412 King St, Malvern, PA 19355
• MacDermid, Inc., 50 Brookside Rd, Box 671,
Waterbury, CT 06720
• McDonnell Douglas Corp., Box 516, St. Louis, MO
63166
* Christian J. Staebler, Jr. & Bonnie F. Simpers
Grumman Aerospace Corporation
Bethpage, NY 11714
"Hugh B. Durham
Industrial Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
• M&T Chemicals, Inc., Rahway, NJ 07565
• Plastonics Inc., 230 Locust St, Hartford, CT 06114
• Rilsan Corp., 139 Harristown Rd, Glen Rock, NJ
07452
• Rohm and Haas Co., Spring House, PA 19477
• Shell Chemical Co., One Shell Plaza, Houston, TX
77002
• Sterling Lacquer Manufacturing Co., 3150 Brannon
Ave, St. Louis, MO 63139
• 3M Co., 367 Grove St, Saint Paul, MN 55101
• Triodize Co., Inc., 15701 Industry Ln., Huntington
Beach, CA 92649
• Union Carbide Corp., One University Plaza,
Hackensack, NJ 07601
• U.S. Paint, Lacquer, and Chemical Co., 2115
Singleton, St. Louis, MO 63103
INTRODUCTION
Protection of metallic components from corrosive
attack is of major importance in the aerospace and
metalworking industries. This protection is necessary to
maximize the life-cycle of metallic parts. Protective
coatings are the most effective means in terms of weight
and cost for providing protection against galvanic and
atmospheric corrosion. Many coatings that are currently
in use, however, are formulated from toxic chemicals
which, if not properly treated and controlled, can induce
damaging effects in the environment. Mounting concern
over environmental pollution and more stringent EPA
and OSHA regulations have applied pressure on metal-
finishers to consider new less polluting, corrosion-
protection systems in lieu of currently used organic
solvent paint systems and cyanide electroplating systems.
Under U. S. Environmental Protection Agency (EPA)
76
-------
Grant No. R804331, entitled "Evaluation of Reduced-
Pollution, Corrosion-Protection Systems," Grumman is
conducting a program to evaluate low-polluting,
corrosion-protection systems and to demonstrate that
these systems are viable alternatives to currently used,
higher polluting coatings. The following types of systems
have been evaluated as potential alternatives to those
now being used.
• Water-borne paints in place of organic solvent
coatings
• Non-cyanide cadmium plating in place of cyanide
cadmium plating
•, Non-cyanide copper plating in place of cyanide
j j copper plating
• Mechanical plating in place of cyanide cadmium
\\ plating
• Spray-and-bake aluminum coatings in place of
cyanide cadmium plating
• Fluidized bed/powder spray coatings in place of
organic solvent coatings
• Trivalent chromium plating in place of hexavalent
chromium plating
• Ion vapor deposition (1VD) of aluminum in place of
cyanide cadmium plating.
Where possible, several candidate coating systems
were selected for evaluation in each of these areas. Based
on preliminary screening tests, one system of each type
was selected for additional testing. The results of these
tests have shown that many of these coating types can
provide protection equivalent to that of higher polluting
systems in certain applications. In addition to
determining performance criteria, economic and process
requirements have also been considered. The results of
these evaluations are summarized in Table 1.
Alternatives to Organic Solvent Paints
Water-borne paints and powder coatings were
evaluated as potential alternatives to organic solvent
paints. The need for replacement of these coatings, which
have widespread applications, arises from the toxicity of
the solvents used. Additional problems such as
TABLE 1. EVALUATION OF REDUCED-POLLUTION CORROSION-PROTECTION SYSTEMS
REDUCED-
POLLUTION
CORROSION -
PROTECTION
SYSTEM
WATER BORNE
PAINTS
NONCYANIDE
CADMIUM
NON-CYANIDE
COPPER
MECHANICAL
PLATING
SPRAY AND BAKE
ALUMINUM
CURRENTLY
USED SYSTEM
ORGANIC
SOLVENT
PAINTS
CYANIDE
CADMIUM
CYANIDE
COPPER
CYANIDE
CADMIUM
CYANIDE
CADMIUM
TYPICAL APPLICATIONS
AIRCRAFT SKINS, RIBS AND
FITTINGS, SCREW MACHINE
PRODUCTS. HARDWARE.
AIRCRAFT BULKHEADS.
LANDING GEARS AND
WING-FOLD MECHANISMS
AIRCRAFT BULKHEADS,
LANDING GEARS AND
WING-FOLD MECHANISMS
AIRCRAFT LANDING
GEARS, FITTINGS AND
FASTENERS
AIRCRAFT ARRESTING
HOOKS AND WING-FOLD
SELECTED
SYSTEMS
GLIODEN
AQUALURE
634 W 804
STERLING-
LACQUER
AQUATHANE
II
LEA RON AL
KADIZID
ENTHONE
ENTHOBRITE
CU942
3M
TRANSIFLO
TIODIZE
ALUMAZITE
APPLICATION
PROCEDURE
SPRAY-OVEN
CURE
SPRAY-AIR
DRY
ELECTRO-
PLATING
ELECTRO-
PLATING
TUMBLING
WITH CHEMI-
CALS « BRASS
BEADS
SPRAY-OVEN
CURE
PERFORMANCE
RELATIVE TO
CURRENTLY
USED SYSTEM*
VERY GOOD FOR
MODERATE SER-
VICE
CONDITIONS-
EXCELLENT
EXCELLENT
EXCELLENT
VERY GOOD
EQUIPMENT COST RELATIVE TO CURRENTLY USED SYSTEM
FOR NEW
INSTALLATION
SLIGHTLY
HIGHER
(CURING
OVENS
RF.rvni
EQUIVALENT
EQUIVALENT
EQUIVALENT
MEDIUM
LOW-
MEDIUM
FOR CONVERSION
OF OLD
EQUIPMENT
MINIMAL CHANGE
OVER COSTS
(CURING OVENS
REQ'D)
MINIMAL CHANGE-
OVER COSTS
MINIMAL CHANGE-
OVER COSTS
(LINE TANKS)
MINIMAL CHANGE-
OVER COSTS
(LINE TANKS)
NEW EQUIP-
MENT REQUIRED
NEW EQUIPMENT
REQUIRED
POLLUTION
CONTROL & WASTE
TREATMENT
MAJOR PORTION OF
WASTE TREATMENT
& POLLUTION CON
TROL COSTS
ELIMINATED
CYANIDE TREAT-
MENT STEP
ELIMINATED
CYANIDE TREAT-
MENT STEP
ELIMINATED
CYANIDE TREAT-
MENT STEP
ELIMINATED
SOLVENT RECOVERY
SYSTEM REQUIRED;
COATINGS
FLUIDIZED BED/
POWDER SPRAY
COATINGS
TRIVALENT
CHROMIUM
PLATING
IVO ALUMINUM
MECHANISMS
ORGANIC HOOKS, CLAMPS, HOISTING
SOLVENT ASSEMBLIES, BATTERY
PAINTS BOXES AND CABLES.
TORQUE WRENCHES,
METAL TOYS
HEXAVALENT AUTOMOBILE BUMPERS,
CHROMIC ACID APPLiCANCE PARTS.
PLATING DECORATIVE PARTS
CYANIDE
CADMIUM
AIRCRAFT FASTENERS
ANO FITTINGS
NYLON
HARSHAW
TRICHROME
MCDONNELL
AIRCRAFT
IVAOIZE
FLUIDIZEOBED; EXCELLENT
ELECTRO-STATIC
POWDER SPRAY
ELECTRO-
PLATING
ION VAPOR
DEPOSITION
VERY GOOD
EXCELLENT
MEDIUM
EQUIVALENT
HIGH
NEW EQUIPMENT
REQUIRED
MINIMAL CHANGE-
OVER COSTS
(LINE TANKS)
NEW EQUIPMENT
REQUIRED
WASTE TREATMENT
COSTS ELIMINATED
DUST CONTROL
EQUIPMENT RE
QUIRED;WASTE
TREATMENT COSTS
ELIMINATED
CHROME REDUCTION
STEP ELIMINATED
MAJOR PORTION OF
WASTE TREATMENT
& POLLUTION CON-
TROL COSTS
ELIMINATED
•EXCELLENT - EQUIVALENT OR SUPERIOR TO CURRENTLY USED SYSTEM, GOOD FOR HIGH PERFORMANCE APPLICATIONS
VERY GOOD - EXCEEDS SPECIFICATIONS OF CURRENTLY USED SYSTEM. (BASED ON MIL SPECS MIL C-81773 -COATING. POLYURETHANE. ALPHATIC. WEATHER RESISTANT".
Ml LC 14550 "COPPER PLATING (ELECTRODEPOSITEOI. ANQ FEDERAL SPECIFICATIONS O.Q-C-3320 "CHROMIUM PLATING (ELECTRODEPOSITED. QO-P-416 "PLATING, CADMIUM
ELECTRODEPOSITEDI
•MAY REQUIRE FURTHER DEVELOPMENT FOR SEVERE SERVICE APPLICATIONS SUCH AS IN MIL C 81773
77
-------
flammability, rising prices and decreasing availability of
solvents emphasize the need for replacement. Use of
either water as the volatile component or 100% solid resin
systems virtually eliminates these problems.
Seven water-borne paint systems and three powder
coatings were evaluated. The water-borne paints were
divided into two groups: air-drying and oven-curing
(Table 2). These were applied to pretreated (solvent
clean, alkaline clean, deoxidize and alodine) 2024-T3
aluminum panels according to manufacturers
recommendations. Water-borne primers supplied with
the paints were used. Several of the paints were also
tested with an organic solvent epoxy primer. The powder
coatings were applied to aluminum and steel panels by
electrostatic powder spray. One of the powder coatings
was also applied using a fluidized bed.
Results of the screening tests for the water-borne
paints and powder coatings are shown in Tables 3 and 4.
An air-drying system (Aquathane II with organic solvent
epoxy primer) and an oven-curing system (Aqualure 634-
W-804 with Aqualure primer) were selected for further
testing. These systems provided the best adhesion,
flexibility, and impact resistance of the water-borne
paints tested. The organic solvent epoxy primer was used
with Aquathane II to improve adhesion over that offered
by the Aquathane primer. The nylon and epoxy powder
coatings were found to provide excellent performance in
screening tests. The polyester powder coating did not
provide good impact resistance or flexibility.
Final characterization tests (Table 5) show that the
nylon powder coatings provide better hydrolytic fluid
resistance and hydrolytic stability than the other coatings
te:. ed. Of the water-borne paints, the oven-curing system
(Aqualure 634-W-804) showed slightly better hydraulic
stability. Differences in other properties, such as
extended outdoor weathering resistance (under test), that
could influence the coating choice for a specific
application may also be apparent.
The decision to use a specific coating or coating type
must be based on other factors in addition to perfor-
mance for each specific application. For example,
equipment requirements are such that the air-drying
water-borne paints can replace organic solvent paints
directly in existing applications if the performance
requirements can be met. The oven-curing systems will
require the installation of curing ovens, which may be
justified if additional performance can be obtained fro'm
these systems. Both the air-drying and oven-curing
water-borne paints eliminate the need for organic solvent
pollution control equipment. Powder coatings require
installation of new equipment, either fluidized bed or
electrostatic powder spray, which is amenable to
automation. Both types of powder application can
provide high resin utilization. Although dust control
equipment is needed for powder coating systems, organic
solvent pollution control equipment is not required. In
addition, powder coatings eliminate solvent
compatibility problems, and allow resins such as nylon to
be used as protective coatings.
Alternatives to Cyanide Copper Plating
Non-cyanide copper electroplating solutions were
evaluated as potential alternatives to cyanide copper
plating solutions. Cyanide toxicity and waste treatment
requirements present good reasons for its replacement.
Several non-cyanide copper plating systems are currently
available. The following cyanide-free systems were
TABLE 2. WATER-BORNE PAINT SYSTEMS EVALUATED
PAINT SYSTEM
AQUATHANE
WA-1001
AQUATHANE II
AQUALURE 481-
W-02114
AQUALURE 634-
W-804
SAF-T-300-W-39
SAF-T-300-W-44
CARBOSET514H/
EPON 828
FORMULATION
*EPOXY PRIMER
MANUFACTURER
STERLING LACQUER
STERLING LACQUER
GLIDDEN
GLIDDEN
U.S. PAINT, LACQUER,
CHEMICAL
U.S. PAINT, LACQUER,
CHEMICAL
BF GOODRICH RESIN/
SHELL RESIN
TYPE
EPOXY-ACRYLIC
URETHANE
ACRYLIC
POLYESTER
& EPOXY
& URETHANE
EPOXY-ACRYLIC
MIL-P-23377C MAY ALSO BE COMPATIBLE WITH EACH
CURE
AIR DRY
AIR DRY
149°C
(300°F)-15MIN
177°C
(350°F)-15MIN
AIR DRY
AIR DRY
149°C
(300° F)- 15 WIN
OF THESE SYSTEMS
PRIMER*
AQUATHANE WA1017
AQUATHANE WA1017
AQUALURE 631-1-128
(ACRYLIC)
AQUALURE 631-L-128
(ACRYLIC)
SAF-T-300-G-19A
SAF-T-300-G-19A
NONE REQUIRED
78
-------
TABLE 3. RESULTS OF SCREENING TESTS OF WATER-BORNE PAINT SYSTEMS
PRIMER PRIMER TOPCOAT
SURFACE PRIMER WASTE SURFACE GLOSS
SYSTEM* APPEARANCE ADHESION RESISTANCE APPEARANCE (SIT)
CONTROL SATISFACTORY GOOD SLIGHT OIS- VERYSLIGHT 89
EPOXY PRIMER COLORA- MOTTLING
POLYURETHANE TIOH";NO
TOPCOAT OTHER DE-
FECT
AQUATHANE SATISFACTORY GOOD DISCOLORA- GDOO 73
WA 1017 PRIMER TION";NO
WA 1001 TOPCOAT OTHER DE-
FECT
EPOXY PRIMER SATISFACTORY GOOD SLIGHT DIS SLIGHT 54
ADUATHANE II COLORA- MOTTLING
TOPCOAT " TION":NO
OTHER DE
AHUATHANEWA SATISFACTORY GOOO OISCOLORA- VERYSLIGHT 58
1017 PRIMER TION";NO MOTTLING
AQUATHANE II OTHER DE-
TOPCOAT FECT
ADUALURE631- SATISFACTORY GOOD VERYSLIGHT ORANGE PEEL 29
L 128 PRIMER— (ORANGE PEEL FILM SOFTEN- EFFECT-SUB-
481W02114 EFFECT) ING FACE NOT
TOPCOAT'" LEVEL
AOUALURE631 SATISFACTORY GOOD VERYSLIGHT GOOD 88
L 128 PRIMER— (ORANGE PEEL FILM SOFTEN-
634W804 EFFECTI ING
TOPCOAT—
SAFT300G19A SATISFACTORY FAIL PRIMER FAIL FILM MOTTLING 68
PRIMER LIFTED SOFTENED
SAF-T300W-3S FROM
TOPCOAT SUBSTRATE
SAFT30DG19A SATISFACTORY FAIL-PRIMER FAIL-FILM GOOD 55
PRIMER LIFTED SOFTENED
SAFT300W-44 FROM
TOPCOAT SUBSTRATE
CARBOSET514H ORANGE PEEL 100
EPON82SFOR EFFECT;SUR-
MULATIONTOP FACE NOT
COAT— LEVEL
•ALODINE PRETREATMENT
"NOT CAUSE FOR REJECTION
—BAKE CURE SYSTEMS
evaluated and compared to MacDermid's Rocheltex
cyanide copper plating system:
• Cu-Pure - Lea-Ronal, Inc.
• Enthobrite Cu-942 - Enthone, Inc.
• Copper Fluoborate - Harstan, Inc.
• AC94 Bright Acid Copper - M&T Chemicals, Inc.
• Unichrome Pyrophosphate - M&T Chemicals, Inc.
Hull cell tests were used to screen the five non-cyanide
copper plating systems. Bright range and throwing power
were determined. Enthone's Cu-942 showed the greatest
bright range and excellent throwing power. Lea-Ronal's
Cu-Pure and MAT'S AC-94 has a bright range and
throwing power similar to the cyanide-type control;
however, M&Ps AC-94 had relatively high cost and
maintenance requirements. Based on the Hull cell test
results, the two best systems, Lea-Ronal's Cu-Pure and
Enthone's Cu-942, were selected for further testing.
The selected systems were tested at their optimum
current density, as determined by the Hull cell tests, in
2.5 1 (0.66 gal) baths. These tests (Table 6) showed that
Enthone's Cu-942 is superior to the other baths tested,
including the cyanide-type control. Cu-942 gave a
smooth and bright deposit and no edge burning. No
TOPCOAT TOPCOAT TOPCOAT TOPCOAT
TOPCOAT COATIKG TOPCOAT IMPACT NEAT LUBE OIL
ANCHORAGE ANCHORAGE FLEXIBILITY RESISTANCE RESISTANCE RESISTANCE
GOOD GOOD PASS PASS- NO FILM DEFECTS; NO FILM DEFECTS;
>5.4 JOULES VERYSLIGHT. SLIGHT DISCOl
(48 IN.-LB.) DISCOLORATION" ORATION"
GOOD GOOD FAIL FILM FAIL- NO FILM DEFECTS; NO FILM DEFECTS;
CRACKING 2.3JOULES SLIGHT DISCOLOR SLIGHT OISCOL-
(20 IN.-LB.) ATION" ORATION-
GOOD GOOD PASS PASS- NO FILM DEFECTS; NO FILM DEFECTS.
>5.4JOULES DISCOLORATION" DISCOLORATION"
(48 IN.-LB.)
POOR GOOO PASS PASS- NO FILM DEFECTS, NO FILM DEFECTS.
ADHESION- >5.4 JOULES DISCOLORATION" HEAVY DISCOLOR
BLISTERING (48 IN.-LB) ATION"
GOOD GOOD FAIL-FILM FAIL- NO FILM DEFECTS; SLIGHT FILM SOFT
CRACKING 2.3 JOULES V. SLIGHT ENING; SLIGHT
I20IN..LB) DISCOLORATION" DISCOLORATION-
GOOD GOOO PASS PASS- NO FILM EFFECTS; FILM SOFTENING
>5 4 JOULES V. SLIGHT DIS SLIGHT DIS
(48IN.-LB) COLORATION" COLORATION-
FAIL -TOP- GOOD FAIL FILM FAIL- NO FILM DEFECTS. NO FILM DEFECTS
COAT& CRACKING 2.3 JOULES DISCOLORATION" SOME DISCOLOR
PRIMER (20 IN. IB) ATION
LIFTED
FROM
SUBSTRATE
FAIL-TOP- POOR-FILM PASS PASS- NO FILM DEFECTS: FILM SOFTENING;
COAT LIFTED SEPARATED >5.4JOULES SLIGHT DISCOLOR DISCOLORATION"
FROM FROM (48 IN.-LB) ATION"
PRIMER PRIMER
GOOD GOOO PASS FAIL- NO FILM DEFECTS SLIGHT FILM SOFT
2.3 JOULES ENING (TACKY);
(20 IN.-LB) SLIGHT DISCOLOR
ATION"
gassing or foaming of the bath was observed. Neither the
cyanide control nor the other non-cyanide systems
matched this performance. The plating rate of Cu-942
was 1.5 times that of the cyanide control. In addition, Cu-
942 showed better protection than the other systems
against decarburization of steel subjected to heat
treatment (829° C/15250 F for 10 min).
Final characterization testing of Cu-942 (Table 7)
showed that the adhesion and solderability of the deposit
are excellent. No hydrogen embrittlement was evident in
notched tensile tests of the Cu-942 plated specimens. In
order to substitute a non-cyanide copper plating system
for a cyanide copper plating system, plating tanks must
be lined with PVC or similar material to make them acid-
resistant. Other special equipment is not required. Use of
the cyanide waste treatment system is no longer
necessary.
Alternatives to Hexavalent Chromium Plating
Chromium is extremely toxic in its hexavalent form.
Hexavalent chromium in spent electroplating baths must
be reduced to the trivalent form, which is much less toxic,
prior to precipitation as insoluble chromium hydroxide
79
-------
TABLE 4. POWDER COATINGS - SCREENING EVALUATION
SURFACE COATING
RESIN SUBSTRATE APPEARANCE GLOSS ANCHORAGE
EPOXY ALUMINUM GOOD 96 GOOD
(POWDER
SPRAY)
STEEL GOOD 93 GOOD
POLYESTER ALUMINUM GOOD 79 GOOD
(POWDER
SPRAY)
STEEL GOOD 80 GOOD
NYLON ALUMINUM GOOD 68 GOOD
(POWDER
SPRAY)
STEEL GOOD 69 GOOD
NYLON ALUMINUM GOOD 68 GOOD
(FLUIDIZED
BED)
STEEL GOOD 66 GOOD
ANCHORAGE IMPACT LUBE OIL
(WET TAPE) FLEXIBILITY RESISTANCE RESISTANCE
GOOD PASS PASS* SOME DIS-
COLOR-
ATION
GOOD PASS PASS* SOME DIS-
COLOR-
ATION
LIFTED FAIL-FILM FAIL** SLIGHT OIS-
IN SPOTS CRACKING COLOR-
ATION
GOOD FAIL-FILM FAIL** SOME DIS-
CRACKING COLOR-
ATION
GOOD PASS PASS* SLIGHT DIS-
COLOR-
ATION
GOOD PASS PASS* SLIGHT DIS-
COLOR-
ATION
GOOD PASS PASS* SLIGHT DIS-
COLOR-
ATION
GOOD PASS PASS* SLIGHT DIS-
COLOR-
ATION
RESISTANCE
TO HEAT
SOME DIS-
COLOR-
ATION
SOME DIS-
COLOR-
ATION
V. SLIGHT
DISCOLOR-
ATION
V. SLIGHT
DISCOLOR-
ATION
SLIGHT DIS-
COLOR-
ATION
SLIGHT DIS-
COLOR-
ATION %
DISCOLORED
DISCOLORED
*7.2 JOULES (64 IN-LB)
"2.3 JOULES (20 IN-LB)
for waste disposal. Use of a trivalent chromium
electroplating bath could eliminate this costly waste
treatment step. In addition, the toxic spray generated
during bath operation could be eliminated. A trivalent
chromium plating process developed for decorative
chromium plating is available from Harshaw Chemical
Company.
This process, called Trichrome, was evaluated in
comparison with a standard hexavalent chromium
plating process (Table 8). Test panels were plated with
25.4 Aim (1.0 mil) semi-bright nickel, 10.2 y.m (0.4 mil)
bright nickel, and 0.25 /xm (0.01 mil) chrome.
Appearance of the Trichrome was much brighter than the
hexavalent chromium plate. The adhesion of both plates
TABLE 5. FINAL CHARACTERIZATION TESTS: REPLACEMENT COATINGS FOR ORGANIC SOLVENT PAINTS
COATING SURFACE LOSS OF COATING ANCHORAGE
SYSTEM APPEARANCE GLOSS GLOSS ANCHORAGE (WET TAPE!
CONTROL VERY SLIGHT 89 1 UNIT GOOD GOOD
EPOXY PRIMER MOTTLING
POLYURETHANE
TOPCOAT
EPOXY PRIMER SLIGHT 54 7 UNITS GOOD GOOD
AQUATHANE II MOTTLING
TOPCOAT
AOUALURE63I GOOD 88 10 UNITS GOOD GOOD
L 128 PRIMER
AGUALURE634
W804 TOPCOAT
EPOXY POWDER GOOD 94 - GOOD GOOD
SPRAY
NYLON POWDER GOOD 68 - GOOD GOOD
SPRAY
NYLON GOOD 67 - GOOD GOOD
FLUIZIDED
BED
IMPACT LUBE OIL
FLEXIBILITY RESISTANCE RESISTANCE
PASS PASS1 SLIGHT DIS-
COLORATION
PASS PASS* DISCOLORED
PASS PASS* SLIGHT DIS-
COLORATION
PASS PASS* SOME DIS
COLORATION
PASS PASS* SLIGHT DIS-
COLORATION
PASS PASS* SLIGHT DIS-
COLORATION
RESISTANCE
TO HEAT
VERY SLIGHT
DISCOLORATION
DISCOLORED
VERY SLIGHT
DISCOLORATION
SOME DIS-
COLORATION
SLIGHT PIS-
COLORATION
DISCOLORED
RESISTANCE TO FLUIDS
1H HF 5606 SKYDROL 500
NO
EFFECT
NO FILM
DEFECTS;
SLIGHT
DISCO L
ORATION
NO FILM
DEFECTS;
SLIGHT
DISCOL-
ORATION
NO
EFFECT
NO
EFFECT
NO
EFFECT
SLIGHT
BLISTER-
ING
NO FILM
DEFECTS;
SLIGHT
DISCOL-
ORATION
NO FILM
DEFECTS;
SLIGHT
DISCOL-
ORATION
NO
EFFECT
NO
EFFECT
NO
EFFECT
FILM SOFTENED
- LOSS OF
ADHESION
FILM SOFTENED
- LOSS OF
ADHESION
FILM SOFTENED
- LOSS OF
ADHESION
FILM SOFTEN ED
- COMPLETE
LOSS OF
ADHESION
NO
EFFECT
NO
EFFECT
HYDROLYTIC
STABILITY
NO FILM SOFTEN
ING OR LOSS OF
ADHESION;SLIGHT
DISCOLORATION
FILM SOFTENING;
SOME LOSS OF
ADHESION; DIS
COLORATION
FILM SOFTENING;
DISCOLORATION
BLISTERING; LOSS
OF ADHESION;
SOME DISCOLOR
ATION
NO FILM DEFECTS;
SLIGHT DISCOLOR-
ATION
NO FILM DEFECTS;
SLIGHT DISCOLOR-
ATION
•7.2 JOULES (64 IN LBI
80
-------
TABLE 6. NON-CYANIDE COPPER PLATING — SCREENING TESTS
SYSTEM
MACDERMID
ROCHELTEX
(CYANIDE TYPE
CONTROL)
LEARONAL
GU-PURE
i :
ENTHONE
', ; CU 942
HULL CELL TESTS
BRIGHT
RANGE, THROWING
A/M2(A/SF) POWER
11-387 GOOD
(1-36)
11-324 GOOD
(1-30)
11-1290 EXCELLENT
(1-120)
2.5 LITER (0.66 GAL) SOLUTION TESTS
CURRENT
DENSITY.
A/M2(A/SF)*
270
(25)
390
(36)
780
(72)
SURFACE
CONDITION
SMOOTH
SMOOTH
SMOOTH
& BRIGHT
EDGES
SLIGHT
BURNING
SOME
BURNING
NO
BURNING
COMMENTS
EXCESSIVE
GASSING
SOME
FOAMING
NO GASSING
OR
FOAMING
PLATING
RATE.
^M/MIN
(MIL/MIN)
0495
(0.020)
0.406
(0.016)
0.813
(0X32)
HEAT
RMS TREAT
VALUE EVALUATION
55-100 SOME
DECARB
60-125 MINUTE
DECARB
4555 NO
DECARB
•OPTIMUM CURRENT DENSITY AS DETERMINED BY HULL CELL TESTS
TABLE 7. ENTHONE-ENTHOBRITE CU-942 NON-CYANIDE COPPER PLATING
FINAL CHARACTERIZATION TESTS
PROPERTY
THICKNESS
ADHESION
DECARB PROTECTION
SOLDERABILITY
HYDROGEN EMBRITTLEMENT
•COPPER PLATE IMMEDIATELY
PROCEDURE
PERMASCOPE
SHEET BEND
METALLOGRAPHIC EXAMINATION
SOLDER 232°C (450°F) - SHEET BEND
75% U NTS/200 HR
FOLLOWING NICKEL STRIKE
RESULTS
28-33 juM@ 0.813 AiM/MIN
(1.1-1.3 MILS @ 0.032 MILS/MIN)
EXCELLENT*
NO OECARB
EXCELLENT*
PASS
was good. Corrosion resistance was determined by
subjecting panels to 5% salt spray solution until failure.
Although the hexavalent chromium showed more
consistent results, the Trichrome averaged three times
longer exposure until failure. This indicates that the
trivalent process can provide longer corrosion protection
for the substrate. The scatter in the data for the
Trichrome panels indicates that additional work is
needed to provide consistently good results with this
process. However, these results do show that trivalent
chromium is a viable alternative to hexavalent chromium
plating. Sustained-load tests were also performed to
determine the presence of hydrogen embrittlement.
Notched tensile specimens (4340 steel) were heat treated
to 1790-1930 MPa (260-280 ksi), plated and baked for
three hours for embrittlement relief. The Trichrome-
plated specimens exceeded the 200-hour exposure at 75%
of ultimate notched tensile strength with no failure. The
hexavalent chromium specimens, on the other hand, all
failed in less than seven hours.* These failures may also
be due to differences in the nickel baths used.
Conversion of existing hexavalent chromium plating
operations requires that the lead-lined tanks be lined with
rigid plastic sheet. Lead anodes are replaced with carbon
anodes, which do not deteriorate as the lead anodes do.
No other major changes are required. The chromium
reduction step can be eliminated from the waste
treatment process.
*Normally> chrome plating on high-strength steel is baked for 23 hrs to
provide complete hydrogen embrittlement relief.
81
-------
TABLE 8. TRIVALENT CHROMIUM PLATING: PERFORMANCE EVALUATION
PROPERTY
TRICHROME*
HEXAVALENT CHROMIUM*
APPEARANCE
ADHESION (BEND TEST)
CORROSION RESISTANCE
(5% SALT SPRAY)
HYDROGEN EMBRITTLEMENT
SMOOTH AND VERY BRIGHT
GOOD
48 TO 744 HRS»*
288 HRS AVG
PASS ZOO HRS @ 75% UNTS
SMOOTH AND BRIGHT
GOOD
96HRS*»*
FAIL @ 4.9 HRS @ 75% UNTS
•DECORATIVE CHROMIUM - 25.4A/M (1.0 MIL) SEMI-BRIGHT NICKEL
10.2 A
-------
TABLE
CURRENT
DENSITY,
A/M2 (A/SF)
86(8)
194(18)
302 (28)
410(38)
|j 518(48)
j ',
I !
'WHERE
10. KADIZID
TIME.
MIN
15
15
15
15
15
AREA
^c
NON-CYANIDE CADMIUM PLATING/THROWING POWER —
BENT CATHODE TEST
PLATE THICKNESS, MM (MILS)
AREA 1*
1.02(0.04)
3.05(0.12)
7.11 (0.28)
9.14 (0.36)
13.5(0.53)
1
EA2
AREA 3
AREA 2*
1.02(0.04)
3.05 (0.12)
4.32 (0.17)
9.14 (0.36)
12.4(0.49)
AREA 3*
2.03 (0.08)
8.38 (0.33)
12.7(0.50)
14.5 (0.57)
19.1 (0.75)
COMMENTS
EXCELLENT
EXCELLENT
EXCELLENT
PITTING IN AREA 2
PITTING OVER ENTIRE
SURFACE, STREAKING
IN AREA 3
TABLE 11. EVALUATION OF MECHANICALLY PLATED COATINGS
MECHANICALLY PLATED
PROPERTY
CADMIUM
(WITH CHROMATE
CONVERSION
COATING)
TIN CADMIUM
CYANIDE CADMIUM
ELECTROPLATE
(WITH CHROMATE
CONVERSION
COATING)
APPEARANCE SCRATCHED SCRATCHED SMOOTH
ADHESION PASS PASS PASS
CORROSION RESISTANCE, HRS TO
FAILURE IN 5% SALT SPRAY
SUBSTRATE - D6AC 2664+ 516 2118+
4340 1800+ 558 2514
HYDROGEN EMBRITTLEMENT PASS - PASS
200 HRS @ 75% UMTS (260 KSI) (23 HR BAKE)
than that of the other non-cyanide systems, as well as that
of the cyanide system used as a control.
Kadizid was selected for further testing. Throwing
power, as determined by the bent cathode test (Table 10),
is excellent. A smooth bright finish was obtained when
Kadizid was used to plate an etched panel, showing the
good leveling power of Kadizid. The adhesion of the
Kadizid plate is excellent. Corrosion tests were run on
panels plated to 15.2 to 22.9 urn (0.6 to 0.9 mils) with
Kadizid and chromate conversion coated. These panels
passed the standard 168-hr salt spray test. Hydrogen
embrittlement was not evident in 1790-1930 MPa (260-
280 ksi) high-strength steel plated with Kadizid and
baked for 23 hrs at 191° C (375° F) for embrittlement
relief. This strength level was used for test purposes only;
normally, cadmium electrodeposition is restricted to
1655 MPa (240 ksi) or less. These specimens exceeded 200
hrs at 75% ultimate notched tensile strength (UNTS)
without failure.
The advantage of the non-cyanide type electroplating
system is that a direct substitution can be made for
current cyanide-type systems with no loss of quality.
Equipment must be lined with PVC or other acid-
resistant material; no other equipment changes are
required. In addition, waste treatment of cyanides will
not be required.
Mechanically plated cadmium and tin-cadmium were
also evaluated. The 3M Company's Transiflo process was
83
-------
TABLE 12. SPRAY AND BAKE
PROPERTY
ADHESION -BEND TEST
CORROSION -SALT SPRAY
FLUID RESISTANCE (R.T:I
- SKYDROL500
- 5606 HYDRAULIC FLUID
- DIESTEROIL
THICKNESS
HYDROGEN EMBRITTLEMENT
TIODIZE ALUMAZITE Z
EPOXY PRIMER
NO LIFTING OR PEELING
700 HR TO RED RUST*
HEAVY WHITE PPT @ 650 HR***
NO EFFECT @ 4000 HR
NO EFFECT© 4000 HR
5.1-12.7)im
0.2 - 0.5 mils
PASS200HRS@75%UNTS
(3 SPECIMENS)
ALUMINUM COATINGS
HI-SHEAR HI-KOTE 3
NO PRIMER
NO LIFTING OR PEELING
300 HR TO RED RUST"
WHITE PPT @ 96 HR
GOOD ADHESION @ 4000 HR
NO EFFECT® 4000 HR
NO EFFECT @> 4000 HR
1 0.2-1 2.7 »im
0.4 - 0.5 mils
HI-SHEAR HI-KOTE 3
EPOXY PRIMER
NO LIFTING OR PEELING
200 HR TO RED RUST"
•AVERAGE OF 2 PANELS
"AVERAGE OF 4 PANELS
•"LOSS OF ADHESION OCCURRED PRIOR TO 4000 HRS
TABLE 13. CYANIDE CADMIUM REPLACEMENT COATINGS — ADVANTAGES AND DISADVANTAGES
NON-CYANIDE MECHANICAL
CYANIDE CADMIUM CADMIUM PLATING
SPRAY-AND-BAKE
ALUMINUM
IVD ALUMINUM
ADVANTAGES
• READILY • REDUCES WASTE • ELIMINATES •
AVAILABLE TREATMENT REQ'D CYANIDES
. TECHNIQUESWELL- • ELIMINATES • ELIMINATES •
ESTABLISHED CYANIDES HYDROGEN
EMBRITTLEMENT
. PROVEN SYSTEM • CONVERSION •
COSTS LOW
•
•
•
ELIMINATES CYANIDES
ELIMINATES CADMIUM
REDUCESWASTE
TREATMENT REQ'D
ELIMINATES HYDROGEN
EMBRITTLEMENT
USES CONVENTIONAL
SPRAY EQUIPMENT
CAN BE FORMULATED
FOR MAX. PERFORMANCE
. ELIMINATES CYANIDES
. ELIMINATES CADMIUM
• ELIMINATES WASTE
TREATMENT REQ'D
• ELIMINATES HYDROGEN
EMBRITTLEMENT
• USETO 51(TC(9500F) (CD
LIMITED TO 232°C-450°F)
DISADVANTAGES
« USES TOXIC • HIGHER MAKE-UP • REQUIRES NEW •
CHEMICALS COST EQUIPMENT
• REQUIRES COSTLY . PART SIZE
WASTE TREATMENT LIMITED
ORGANIC SOLVENT
COLLECTION SYSTEM
REQ'D
. REQUIRES NEW EQUIP-
MENT
used for application of these coatings. Bend tests showed
that the adhesion of the mechanical plate is satisfactory.
The corrosion resistance of the mechanically plated
cadmium with a chromate conversion coating is
approximately the same as that of the cyanide cadmium
electroplate with chromate conversion coating (Table
11). Tin cadmium was not chromate conversion-coated
and showed a much lower corrosion resistance. All
panels were tested in 5% salt spray to failure in order to
assess their relative corrosion resistance. High-strength
steel [1790 - 1930 MPa (260 - 280 ksi) and 2070 MPa
(300 ksi)] that has been mechanically plated is free from
hydrogen embrittlement.
New equipment must be obtained for mechanical
plating. Presently available mechanical plating
equipment limits the largest part dimension to 20 cm (8
in.) and the part weight to less than 230 g (0.5 Ib).
Two spray-and-bake aluminum coatings, Alumazite Z
(Tiodize Company) and Hi Kote 3 (Hi Shear
Corporation), were evaluated. These coatings are
84
-------
TABLE 14. CYANIDE CADMIUM
REPLACEMENT COATINGS
ADHESION
SrSTEH («E«0 TEST)
CYANIDE CADMIUM GOOD
ELECTROPLATE'
NON-CYANIDE CADMIUM EXCELLENT
ELECTROPLATE'
(KADIZIO)
MECHANICAL CADMIUM GOOD
PLATING'
SPRAY a BAKE ALUMINUM EXCELLENT
(ALUMAZITEZ)
IVD ALUMINUM EXCELLENT
CORROSION RESISTANCE
HRS TO FAILURE"'
4130 4341 D6AC
SJS 2SH 2118+
PASS
IBS"
1800* 2664*
700
1752
HYDROGEN
EMJRlmEMEKT
PASS
PASS
PASS
PASS
-
•CHROMATE CONVERSION COATING APPLIED TO PLATED PANEL
: "NOTTESTEOTO FAILURE
'I — AVERAGE OF4 PANELS
aluminum-filled resins that are sprayed onto the
substrate. Both coatings exhibit excellent adhesion
(Table 12) with or without epoxy primer (conforming to
MIL-P-2337). The corrosion resistance of these coatings
is also good. The Alumazite Z coating requires the use of
an epoxy primer to provide adequate corrosion
protection (over 168 hrs in 5% salt spray). Without the
primer, panels coated with Alumazite Z failed within 96
hrs in 5% salt spray, use of the epoxy primer increased the
corrosion protection of Alumazite Z to over 70Q hrs in
salt spray. The Hi Kote 3 coating will withstand 300 hrs in
salt spray without primer. With epoxy primer, corrosion
protection was slightly decreased (Table 12). Both of
these coatings exhibit excellent resistance to hydraulic
fluid, diester oil, and Skydrol 500 (Table 12). There is no
evidence of hydrogen embrittlement in coated specimens
of high-strength steel [1790-1930 MPa (260-280 ksi)].
Application of these coatings is accomplished with
conventional spray equipment. Because cyanide and
cadmium are not used, waste treatment costs are
minimal. An organic solvent recovery system, however, is
required for pollution control. It is expected that a water-
borne, spray-and-bake aluminum system may be
developed in the near future. These coatings can be used
in a wide variety of applications because they can be
formulated for maximum performance.
Ion vapor deposition (IVD) of aluminum was
evaluated for adhesion and corrosion resistance. The
adhesion of IVD aluminum, as determined by the bend
test, is excellent. IVD aluminum withstood an average of
1700 hours of salt spray to failure. Although special
equipment is required for application of this coating,
waste treatment is not required. Part size, however, is a
limitation; the maximum part size that can be coated at
this time is 2.1 * 3.7 m (7*12 ft), which is sufficient for
most applications. The temperature limitation for IVD
aluminum is 510° C (950° F) compared to 232° C (450°
F) for cadmium.
None of the coating types evaluated can be considered
optimum for replacement of cyanide cadmium plating in
all applications. The advantages and disadvantages of
each coating type are summarized in Table 13. These
must be weighed with the relative performance of the
coatings (Table 14) to determine the best coating for a
specific application in terms of cost, performance and
waste treatment requirements, and environmental
compatibility.
REFERENCES
1. Beringer, D., Comparative Evaluation of Ion Vapor
Deposition of Cadmium - Phase I, GAC, MP-CEPS-
TR-77-02, 1/19/77.
2. Spiess, E., Evaluation of a Non-Cyanide Cadmium
Plating Solution, GAC, MP-CEPS-TR-75-32,
10/1/75.
3. Sturiale, E., Evaluation of Proprietary Non-Cyanide
Copper Plating Solutions, GAC, MP-CEPS-TR-74-
17, 10/7/74.
4. Whitman, W., Ion Vapor Deposition of Aluminum
Process, GAC, MP-CEPS, TRP-76-7, 8/24/74.
5L Whitman, W., Sustained Load Testing of Coupons
Copper Plated in an Acid Solution, GAC, MP-CEPS-
TR-75-16, 6/2/75.
6. Schrantz, J., Trivalent Chrome Plating: It's In
Production!, Industrial Finishing, May 1977.
85
-------
Evaporative Recovery in Electroplating
Howard S. Hartley*
This presentation will review the role of evaporation
in plating waste recovery, the economics of recovery, and
it will examine the types of evaporators available for
recovery systems.
Not too long ago, the cost determination for plating
parts was straight forward and consisted of figuring the
cost of chemicals, utilities and labor. The cost of liquid
wastes was simply the cost for plant water. Today, plating
cost determinations are more complex because the cost of
waste treatment has become a significant part of the plat-
ing cost. To sharpen their competitive situation, platers
must be familiar with the treatment technologies avail-
able for plating wastes.
In most instances, treatment of an industrial waste is
an expense which adds to the usual cost of production.
Sometimes, however, it is possible to recover valuable
products or by-products from individual waste sources
to help defray the total cost of waste treatment. Plating
happens to be one of those industrial operations where
there exists the opportunity for economic waste recovery.
Furthermore, this recovery can be accomplished by in-
process recycle to the front end of the process; a most
desirable form of recovery.
Block diagram, Fig. 1, shows how an evaporative
recovery system can recover plating chemicals, metals,
and water in a closed loop manner. Plating solution
dragged out by the work is removed in a series of counter-
flow rinse tanks. The first rinse tank contains the most
concentrated rinse water and this is sent to a recovery
system which separates it via evaporation into original
components; plating solution and rinse water. The plat-
ing solution is returned to the plating tank and the dis-
tilled water is recycled to the last rinse tank.
Fig. 2 allows a more detailed look at the operation of
an evaporative recovery system. This is a typical single
effect system. Contaminated rinse water from the first
rinse tank overflows to an intermediate tank which is
called a feed tank. From here the rinse water is drawn
into the evaporator which operates under vacuum condi-
tions. In the evaporator the rinse water solution passes
through the tubes of a shell and tube heat exchanger
commonly called a reboiler. Steam is introduced in the
shell side of the reboiler; Because the solution is at a
lower temperature than the steam, the steam condenses
and transfers its heat energy through the wall of the
reboiler tubes to the solution. This action causes theplat-
•Howard S. Hartley
The Pfaudler Co.
Rochester, NY 14603
ing solution to boil. Water is evaporated and passes
through a de-entrainment device to remove entrained
droplets of plating solution. The distilled water vapor
then enters the condenser which is another shell and tube
heat exchanger. Cooling water at a lower temperature
than the water vapor removes heat and causes it to
condense. The distilled water is then returned to the final
rinse tank. The concentrated plating solution remaining
in the evaporator is returned to the plating tank. No
chemicals are added or discharged to the sewer. This con-
cept is called closed-loop recovery because it virtually
closes off any plating solution discharge.
PLATING
TANK
RECOVERED
CHEMICALS
V
r
DISTILLED
WATER
Fig. 1—Closed-loop recovery.
Fig. 2—Single-effect evaporator.
86
-------
; I
HEC
CH
1 DRAGOUT
PLATING
TANK
OVERED
EMICALS
Rl
• CITY WATER
RECOVERY
SYSTEM
R2
ft
TO
•• TREATMENT (
DISTILLED
WATER
Fig. 3—Open-loop rinsing.
The key to evaporative closed-loop recovery is mul-
tiple counterflow rinse tanks, which help concentrate
the chemicals in rinse water and drastically reduce the
required rinse water flow rate. For example, the amount
of rinse water required for 1, 2 or 3 counterflowed rinse
tanks in order to achieve the same concentration level in
the final rinse, 7300 gal/hr of water are needed for one
rinse; with two rinses this drops to 85.5 gal/hr and with
three counterflowed rinses only 19.5 gal/hr of water are
required. The optimum number of counterflowed rinse
tanks is usually 3 to 5, but there are plating lines with
only two rinse tanks and it may be impractical to add
more. In this case, economic recovery can still be
achieved by recovering the plating chemicals from only
the first rinse tank. This is shown by Fig. 3 and is referred
to as open-loop rinsing. Using this approach, sometimes
more than 90% of the dragout can be recovered from the
first rinse tank. The remaining 10% entering the second
rinse tank is sent to chemical treatment or a demineralizer
can be used to recover the water.
Evaporative recovery can be applied to practically all
types of plating solutions. Systems have been furnished
for cyanide baths for zinc, cadmium, copper, silver and
brass; various proprietary chromic acid baths; nickel
baths; fluoborate solutions for tin, lead-tin and lead-tin-
copper; and zinc chloride solutions.
The possible build-up of impurities in the bath caused
by recycling recovered dragout is a legitimate concern.
Proven techniques are available, however, to purge
excess impurities from the various plating baths. For
chrome baths, the chief impurities are tramp metals and
excess trivalent chromium. These are removed by instal-
ling a cation exchanger in the contaminated rinse water
$/Gal.
Solution Value +
Cad. Cyanide
Chromic Acid
Nickel
1.00
2.00
3.50
$/Ga/.
Treatment
3.00
1.00
0.50
$/Gal.
= Total
4.00
3.00
4.00
Rg. 4—Recovery & potential.
stream before it enters the evaporator. For nickel plat-
ing, purification is achieved in the normal circulation of
'solution through an activated carbon filter. In cyanide
baths, carbonates, created by the decomposition of so-
dium cyanide, are the principle impurities, and these
can be removed by either freezing them out or by chemi-
cal precipitation.
Generally, the main reason for choosing an evapora-
tive recovery system is that it provides an economic
solution to a pollution problem. Several years ago recov-
ery systems were sold only on the basis that the value of
recovered plating solution would pay for the system in 3
years or less. Today, the new environmental laws have
added other economic considerations: the cost of chemi-
cal treatment, heavy metal removal and sludge disposal.
Now, some of the least expensive plating solutions, such
as the metal cyanides, offer very attractive economics
because their treatment costs are relatively expensive.
Fig. 4 shows plating solution value in terms of $/gal and
their estimated chemical treatment cost. Notice that the
inexpensive cadmium cyanide solution has the same total
economic justification for recovery as the relatively
expensive nickel solutions. Thus, a cadmium barrel plat-
ing operation which has a dragout rate of 5 gph and oper-
ates 4000 hours/yr has a gross savings potential of
$80,000/year. Of course the operating expenses of the
recovery system must be deducted from the savings and
these depend on the evaporative capacity of the system
and the type of evaporator.
The evaporative capacity of a recovery system is
expressed as gallons/hour, gph, and equals the amount
of rinse water required to satisfy the rinsing requirements
dictated by the number of available counterflowed rinse
tanks, the dragout rate and the concentration of plating
solution. Once the evaporative capacity has been deter-
mined, the selection of the type of evaporative recovery
system can be considered. There are basically three types
of evaporators available for plating waste recovery sys-
tems: single-effect, multiple-effect and vapor recompres-
sion.
The single-effect evaporator has been the most popu-
lar type for recovery systems for two main reasons:
1) its low capital cost and 2) its simple operation. At
least four types of single-effect evaporators have been
used for plating waste recovery systems:
a. atmospheric tower
b. submerged tube
c. rising-film thermosyphon
d. flash evaporator
Neglecting heat losses to the surroundings, all single
effect vacuum evaporators require approximately 1.07
Ibs. of steam to evaporate 1.0 Ib. of water. Therefore,
their operating costs are nearly the same.
The atmospheric tower evaporator requires more
steam because it must heat large quantities of air in
addition to supplying the energy to evaporate the water.
Fig. 5 shows a schematic of an atmospheric tower. The
contaminated rinse water is pumped through a steam
heated heat exchanger at a high flow rate because the
87
-------
t t
~~t
4. 4
CONCENTRATE I
Fig. 5—Atmospheric tower.
Fig. 6—Submerged tube.
©-© •"'.••»».•«.•
© ,„
CPM
CHROME
EVAPORATOR
F
G
Rg. 7—Rising film thermosyphon.
Fig. 8—Chrome closed-loop recovery with heat recovery.
heat required to evaporate the water and heat up the air
must be supplied by this stream in the form of sensible
heat. The heated rinse water stream enters the top of the
tower, trickles over and down the tower's internal pack-
ing and contacts the air flow which is traveling in a
counterflow direction up the column. Water is evapor-
ated by humidification of the air stream. Its main advan-
tages are: it can double as a fume scrubber, and it does
not need cooling water. It has several disadvantages:
1) its application is limited to plating solutions unaffected
by the oxidizing nature of air, 2) it requires 20- 25% more
heat energy than other single effect evaporators; 3) it does
not recover distilled water for rinsing.
The submerged tube evaporator uses a horizontal heat
exchanger for the reboiler as shown by Fig. 6. Here the
solution is on the outside of the tubes and steam is on the
inside. This design offers a compact system, but it may be
more difficult to clean the exterior of tubes versus the
interior if fouling of the tubes occurs.
The rising film thermosyphon evaporator is shown
schematically by Fig. 7. It usually has a vertical shell and
tube heat exchanger called the reboiler with the solution
on the inside of the tubes and the condensing steam on the
outside of the tubes. The unit can operate with natural
circulation or forced circulation supplied by pump.
The flash evaporator is basically a rising film evapor-
ator, but it can operate at a temperature below that of
some plating baths. This permits the evaporator to
recover waste electrolytic heat generated in the plating
bath by recirculating plating solution through the evap-
orator and "flash cooling" it to a lower temperature. The
excess heat is "flashed-off' as water vapor and condensed
as distilled water. Thus, the steam required to achieve the
desired evaporation rate (rinse water flow rate) can be
reduced accordingly. In Fig. 8 for example, approximate-
ly 250,000 Btu/hr of waste electrolytic heat are converted
into 30 gph of distilled water. This saves almost 270
Ibs/hour of steam. Evaporative recovery systems have
been designed to recover as much as 5,000,000 Btu/hr
of waste electrolytic heat from chromic acid plating
baths. In some cases, cooling coils in the plating tank
have been eliminated and the recovery system has been
used to control the bath temperature.
The majority of the single effect evaporator's operat-
88
-------
ing cost is for steam energy. Steam at $3.50/1000 Ibs
translates to $0.30/gallon of distilled water produced.
The quantity of cooling water required to condense the
distilled water varies with the allowable temperature rise
of cooling water. For a 40° F temperature rise, 25 gal-
lons of cooling water are required for each gallon of dis-
tilled water. The cooling water flow is high in comparison
to the distilled water flow because each Ib of condensing
distilled water has a latent heat of vaporization of 1000
Btu while each Ib of cooling water can take away only 40
Btu at a 40° F temperature rise. The existing cooling
water contains practically all of the energy which was
consumed by the recovery system as steam. This warm
cooling water is not contaminated and can be beneficially
used for other rinsing operations. Warm water does a
more effective rinsing job than cold water, especially for
alkaline cleaner rinses. If there is not a need for the total
flow of cooling water, then the use of cooling tower to
recirculate the cooling water should be examined from an
economic viewpoint. Other cooling water consumers
such as bath cooling coils, rectifiers and air compres-
sors could also be included in the cooling tower system.
Recovery systems also require electrical power to
operate pumps and control panels. This power require-
ment is generally small in comparison to the steam
energy. In addition to the steam, cooling water and elec-
trical power, most evaporative recovery systems need a
couple cfm of compressed air to operate pneumatic con-
trols.
The capital cost of a single effect evaporator is depen-
dent upon two main factors: 1) its evaporative capacity
and 2) its application which dictates the materials of con-
struction. A recovery system designed for cyanide-type
plating solutions needs only carbon steel components to
withstand the environment. Chromic acid plating solu-
tions are extremely corrosive and necessitate the use of
expensive materials of construction such as tantalum for
the reboiler heat exchanger. The cost of an evaporative
recovery system having an evaporative capacity of 60 gal-
lons / hr (gph) would be less than a system with an evapor-
ative capacity of 120 or 200 gph. For these reasons it is
difficult to discuss capital costs of single effect evapora-
COM DENS ATE
tors. Instead, the capital costs of all the types of evapora-
tors discussed here will be compared on a relative scale.
These will be reviewed after the other types of evapora-
tors have been discussed.
The rising-film thermosyphon, submerged tube and
flash evaporators can also be designed as multi-effect
evaporators. A typical double-effect evaporator is shown
by Fig. 9. As can be seen, it resembles two single-effect
evaporators connected in series except there is only
one condenser. Steam is introduced at the first effect and
as with the single-effect evaporator, approximately 1 Ib
of water is evaporated per Ib of steam. The 1 Ib of water
evaporated in the first-effect, however, becomes the
steam supply for the second effect. This one Ib evaporates
about 1 Ib of water in the second effect. Thus, in a double-
effect evaporative recovery system, 1 Ib of steam evapor-
ates 2 Ibs of water. So the steam consumption is reduced
by approximately 50% as compared to a single-effect and
the cooling water consumption is also reduced by 50%.
The double-effect system requires more equipment
and thus costs more than the same capacity single-effect
system. A double-effect system is usually justified by
comparing the steam and cooling water savings against
the extra capital cost. Generally, a double-effect evapora-
tive recovery system is used for larger evaporative capaci-
ties because steam savings are insignificant for small
systems.
There are other factors besides energy savings which
should be weighed when considering a double-effect
system. The first effect of the evaporator must operate
at a higher temperature in order for its evaporated water
to be the heat source for the second effect. This higher
temperature may be detrimental to heat-sensitive solu-
tions such as some of the cyanide baths. Another consid-
eration is the skill and experience of operators who will
be running the recovery system. The operation of a
double-effect system is more complex than a single
effect.
Evaporators can be designed with more than two
effects, but generally, for the electroplating industry, the
required evaporative capacity is not large enough to
justify more than two effects.
n
/- y^'""-""'
COKCfeNT«ATE BETUKI
Fig. 9—Double effect evaporator.
Fig. 10—Thermal recompression
89
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So far this paper has reviewed single and multiple
effect evaporators. The last type to be discussed is vapor
recompression. There are two types of vapor recompres-
sion evaporators: thermal and mechanical.
A typical thermal vapor recompression evaporator
is shown in Fig. 10. This one consists of a single effect
evaporator, although it can also be used with multiple
effect evaporators, and a thermocompressor which is a
steam jet. The purpose of the thermocompressor is to
reduce the steam requirement and operating cost of the
evaporator. Part of the water evaporated enters the
thermocompressor which compresses it with motive
steam to a slightly higher temperature and pressure.
Thus, this pan of the evaporated water becomes the
steam to evaporate additional water. The steam economy
of a single-effect evaporator with a thermocompressor is
about equal to a double-effect evaporator. A limita-
tion of this system is the high pressure steam require-
ment, 100 psi or higher, for the thermocompressor. Also,
the water vapor entering the compressor becomes mixed
with the thermocompressor's steam condensate — and
complicates the recycle of distilled water. Because
of this problem and the high pressure steam requirement,
thermal vapor recompression has very limited appeal as a
plating waste recovery system.
Mechanical vapor recompression, commonly referred
to as MVR, does not have these drawbacks. A typical
MVR evaporator is shown by Fig. 11. This evaporator
is generally considered to be the most efficient evaporator
in terms of energy consumed per Ib. of water evaporated.
Notice that this system does not use either steam or cool-
ing water. It requires only electrical power to operate
its motor. In the MVR system, all the water vapor leaving
the evaporator enters a compressor which boosts its pres-
sure slightly and allows it to be used as steam to evapora-
ate additional water. The reboiler does double duty as the
condenser.
Large MVR evaporators can evaporate a Ib of water
and consume only 30-40 Btu of energy. Compare this to
the 1000 Btu of energy required for a single effect evapor-
Steam
Cooling Water
Electricity
Total $/Hr
Single
Effect
6.35
0.70
0.15
7.20
Double
Effect
3.50
0.40
0.15
4.05
MVR
0
0
1.25
1.25
Fig. 12—Typical operating costs, $/hr 200 GPH evaporator.
Evaporative Capacity
Evaporator
Single Effect
Double Effect
MVR
50 GPH
100
N. P.
N. P.
700 GPH
115
145
170
200 GPH
140
180
210
N. P. = Not Practical
Fig. 11—Mecnanical vapor recompression.
Fig. 13—Relative capital costs "evaporative recovery systems.''
ator and it is evident that an MVR system is equivalent to
a 30 effect evaporator from an energy viewpoint. When
the cost differential between steam and electrical energy
is applied, MVR's operating costs are equivalent of up to
15 effects. This translates to a cost of approximately
$0.002/gal. of water evaporated.
MVR is more expensive than single and double effect
evaporators; however, the cost gap narrows if a steam
boiler and cooling tower must be added to serve the
conventional steam heated evaporators.
MVR evaporators have been successfully used for
recovery systems handling cyanide solutions. Their appli-
cation has been limited to alkaline solutions because the
compressors are built of cast iron and steel components.
They have also been used as waste concentrators to re-
duce large volumes of dilute wastes prior to off-site dis-
posal. As the cost of energy increases, demand for more
corrosion-resistant compressors will grow. Either stain-
less steel or plated compressors would open up applica-
tions for many other plating solutions.
Now let's look at the relative capital costs and operat-
ing costs of the single-effect, double effect and MVR
evaporators. Fig. 12 shows some typical hourly operating
costs for steam, cooling water and electricity for a 200
gph evaporator. If the 200 gph evaporative recovery sys-
tems are operated 6000 hours/year, the single effect
system's utilities would cost $42,000; the double effect
system's would cost $23,700; and the MVR's would cost
$7500.
As expected, a double-effect evaporator costs more
than a single-effect and an MVR evaporator costs more
than a double effect. How much more depends on the
materials of construction and the operating conditions.
Fig. 13 provides a relative cost comparison of evapora-
tive recovery systems designed for alkaline plating solu-
90
-------
tions. The cost differential among evaporative recovery
systems designed for acid-type plating solutions would be
greater. Notice that a recovery system with an evapora-
tive capacity of 200 gph costs only 40% more than a 50
gph system. A 200 gph system can be operated at a re-
duced capacity of 50 gph. Consider that a larger recovery
system can be purchased now for a small premium and
have reserve capacity for future business growth and to
handle a larger dragout produced by different future
parts.
In summary, when solving plating waste pollution
problems, recovery and recycle should be considered
when economics are feasible. Important factors to con-
sider are the value of the metals and chemicals in the
dragout, the cost of alternative chemical treatment and
sludge disposal.
Evaporative recovery systems have been used for the
past 25 years for various plating solutions including
cyanides, chrome, nickel, fluoborates and chlorides.
Field data proves that evaporative recovery systems are
practical and savings are real. Optimized systems have
been installed which utilize waste electrolytic heat in lieu
of steam and have purification loops to prevent build-up
of contaminants.
Larger evaporative capacity systems are available
at a small premium, but can be operated at reduced capa-
cities for the present and provide reserve capacity for the
future. For larger recovery systems, double effect and
MVR evaporators should be considered as the basis of
energy savings.
Recovery is a practical conservation approach which
offers the best long-range solution to both pollution
abatement and conservation of scarce materials. Its use
merits consideration by all platers.
91
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Processes for Heavy Metal Removal
From Plating Wastewaters
R. E. Wing*
INTRODUCTION
Effective waste treatment processes are needed to meet
the stringent effluent standards that are to be set for the
electroplating industry. This urgent need has encouraged
researchers to develop new chemical and physical
processes for meeting these standards. It will be costly to
design effective treatment processes for the various rinse
waters of the plating industry. Some rinses will have to be
segregated for special treatments, while others can be
processed by conventional treatment. The use of dragout
tanks, counter flow rinsing, and other water use
reduction methods is a good start; however, the use of
plating baths that contain unknown proprietary
chemicals does add problems to treatment design. The
following discussion may suggest solutions to some of the
treatment problems.
Over the last few years, numerous publications and
patents have appeared describing technology effective for
the treatment of plating rinse waters. Very little of this
technology has gained wide acceptance for various
reasons, including inadequate promotion, limited
adaptability, unfavorable economics, and uncertainty of
the forthcoming effluent standards.
For 6 years at NRRC, we have been developing
starchbased products for heavy metal removal. Starch, a
naturally occurring polymer derived from agricultural
crops, is very abundant, annually renewable, and
relatively inexpensive. Initially, we used a water-soluble
starch xanthate to bind heavy metal cations in solution
and then used a cationic polymer to yield a
polyelectrolyte complex insoluble in water which
contained the heavy metals (1-3). The use of a two-
component system in the process and less than favorable
economics prevented its broad acceptance. Therefore, we
modified the process to eliminate the expensive cationic
polymer by using a crosslinked, water-insoluble starch as
starting material. We prepared several insoluble starch-
based products containing xanthate (4-8), carboxyl (9),
quaternary ammonium (10), and tertiary amine groups
(10). These products have been evaluated as potential
heavy metal scavengers.
•R. E. Wing
Northern Regional Research Center
Agricultural Research Service
U. S. Department of Agriculture, Peoria, IL 61604
Insoluble Starch Xanthate
Water-insoluble starch xanthate (4-8) (1SX) offers
industry a low-cost product that removes and recovers
heavy metal cations from wastewaters (Figure I). The
effectiveness of ISX for removing uncomplexed heavy
metals from water can be seen in Tables I and 2. The data
show that heavy metals are removed from concentrated
solutions and dilute solutions, in most cases to
concentrations below present discharge limits. From
these data, ISX appears to be effective in removing metal
ions at different concentration levels. If initial metal
concentrations in an industrial effluent exceed 100 mg/1,
it probably would not be economical to use ISX, and
removal by chemical precipitation or another process
could be used. In these cases, the ISX could then be used
in a secondary treatment to further lower metal
concentrations below discharge limits. From our studies
on ISX to date, the following statements can be made:
(a) Its average capacity is 1.1 - 1.5 meq of metal ion/g
ISX.
(b) It is effective over pH rangeof3-l I with maximum
effectiveness above pH 7.
(c) Salt concentrations of up to 10% have little
influence on the effectiveness of ISX.
(d) ISX instantaneously removes metal ions from
solution.
(e) Treatment is applicable to batch-type or
continuous flow systems.
(0 ISX-metal sludge settles rapidly and dewaters to 30
Highly Crosslinked Starch + NaOH + CS2
I H20, MgS04
Insoluble Starch Xanthate [Solid]
Heavy Metal Effluent
I Separation (Stir-Filter)
Insoluble Metal Starch Xanthate + Clean Effluent
I
HN03
Insoluble Starch + H2S04 + Metal Ions
Figure 1. Preparation and use of insoluble starch xanthate (ISX).
92
-------
- 90% solids content after filtration or centrifugation.
(g) Metals can be recovered from the ISX-metal
sludge by nitric acid treatment or incineration.
(h) Preliminary cost-to-make estimate for ISX is
SO. 75/kg.
ISX acts as an ion-exchange material removing the
heavy metal ions and replacing them with sodium and
magnesium. The ISX can be added as a slurry for
TABLE 1
REMOVAL OF HEAVY METAL CATIONS
FROM WATER WITH ISX*
Initial cone., ISX Residual Illinois dis-
Metal mg/l g cone., mg/l charge limit,
Ag*
Au'*
Cd2*
Co'*
Cru
Cu:'
Fe:>
Hg2*
Mn2*
Ni2*
Pb!*
ZnJ*
53.94
30.00
56.20
29.48
26.00
31.77
27.92
100.00
27.47
29.35
103.60
3169
0.32
0.50
0.64
0.64
0.64
0.32
0.32
0.64
0.64
0.64
0.64
0.32
0.016
<0.010
0.012
0.090
0.024
0.008
0.015
0.001
0.015
0.160
0.035
0.294
0.005
—
0.050
—
1.0
0.020
1.0
0.0005
1.0
1.0
0.100
1.0
Synthetic solutions (1,000 ml) containing the individual metals at
the indicated concentrations were treated with the indicated
amount of ISX (capacity = 1.56 meq metal ion/g) at pH = 3.7.
Solutions were stirred for 5-60 min at a final pH of 8.9. After
filtration, the residual metals were determined by a Varian
Techtron A A 120. The theoretical weight of ISX for a divalent
metal is 0.64 g. Value listed with less than (<) was below detection
limit.
TABLE 2
REMOVAL OF METALS
FROM DILUTE SOLUTION WITH ISX*
Metal
Initial cone.,
mg/l
Residual cone.,
mg/l
Cd2'
Co-'
Cr*
Cu-'
Fe-*
Hg2'
Mn2'
Ni:*
5.62
195
2.60
3.18
2.79
10.00
175
193
10.36
3.27
0.001
<0.010
0.026
<0.005
0.001
0.0007
0.010
<0.050
<0.031
0.007
A synthetic solution (1,000 ml) containing a mixture of heavy
metals of the indicated concentrations at pH 3.5 was treated
with ISX (capacity = 1.56 meq metal ion/g, 0.32 g) to a final
pH = 8.9. After filtration the residual metals were
determined by a Varian Techtron AA 120. Values with less
than (<) were below detection limits.
continuous flow operations or in the solid form for batch
treatments. Recently, ISX has been shown to be effective
as a precoat to a filter.
ISX Treatment of Copper Etching Rinse Waters
Ammonium persulfate and alkaline [NH-tCl/NRiOH
or (NH4):CO,/NH4OH] etches are very useful in the
printed circuit industry to etch copper from circuit
boards. Several treatments for completely exhausted
alkaline etch baths are known: (a) treatment with
aluminum (11), (b) water dilution for copper carbonate
precipitation (11), (c) caustic-heat treatment (11-13), and
(d) acid sulfide treatment (14). The "Caper" process
(1516) is effective in keeping the etching rate high by
continuously removing the dissolved copper from
ammonium persulfate etching baths. Rinse waters from
these etching operations contain the CufNHs^2* complex
for which most conventional treatments are ineffective.
Some recent reports (17-20) are available which show
that these rinse waters are treatable.
ISX was evaluated (Figure 2) on several synthetic and
industrial rinses and the copper concentration was
100,000
10,000 -
1000 -
0 0.2 0.4 0.6 0.8 1.0 1.2
ISX. g
Figure 2. Copper ammonia complex removal with ISX.
Copper ammonia complex solutions (1.000 ml) were treated with
increasing amounts of ISX (capacity = 1.5 meq metal ion/g). Aliquots
(10 ml) of the supernatant were removed for copper analysis 5 min after
each addition. Theoretical weight required is 1.02 g for the 50 mg/l
copper ammonia solution.
Curve A. Cu(NHi)42' standard solution (50 mg/l as Cu-initial);
theoretical weight ISX required is 1.02 g.
Curve B. Cu(NHi)r' commercial rinse (53.63 mg/l Cu-initial);
theoretical weight ISX required is 1.09 g.
Curve C. Cu(NHi)u:* commerciai rinse (41.77 mg/l Cu-initial);
theoretical weight ISX required is 0.85 g.
Curve D. Cu(NHi)r' commercial rinse (28.35 mg/l Cu-initial);
theoretical weight ISX required is 0.58 g.
93
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lowered from 28-54 mg/l to less than O.I mg/l. ISX
precoated on filters was also successfully evaluated for
these rinses.
ISX Treatment of Other Copper Complexes
Copper in complexed form (EDTA, Quadrol, etc.) is
very useful for electroless plating in alkaline solutions.
Effective treatment of plating rinse waters from these
plating baths has caused considerable problems.
Recently we evaluated ISX for copper removal from
these rinses and Figures 3-4 show the effectiveness of
copper removal. Acidification of the rinse in the range of
pH 3-6 assists in weakening or dissociating the bonds of
the copper complex, allowing more complete removal
(Figure 3). Figure 4 shows the copper removal using
various amounts of ISX. The best results were always
obtained when the rinse was adjusted to pH 3, ISX
added, and pH readjusted to 3 (Quadrol).
Chromium (VI) Removal with ISX
Commercial anion exchange resins containing tertiary
amine and quaternary ammonium groups are very useful
in industrial wastewater treatment to remove heavy metal
anions. Initial cost to install these exchange resin systems
has limited the industrial application of this anti-pollu-
tion technique. The main reason for the high cost is that
these resins are petrochemically based; because of the
lUU.UUU
10,000
"
ci
s
CJ
s 1000
a.
ra
2
" 100
1
Initial Copper = 53.3 mg/l
!si
"e!3*|^-
!\\
i * •
IV
- \l
1 4
i i
1
i
i
i
i
!
Copper EDTA ^^
"*^«— *-~*~7Snsr
•* *"s,
/ Copper 0/
' Tartrate /
• f
t .*
/ /
' / d
\/ '
• /Copper Quadrol
\ /
"^ /
*+. \ •
! / ^a'XCopper Sulfate
• " **'*»A
I/
i'
D
1 1 1
^K
1 1 1 1 1 1 1 1
01 2 3 4 5 6 7 8 9 10 11
pH
Figure 3. Treatment of copper complexes with ISX vs pH.
Solutions (1.000 ml) containing copper (53.3 mg/l) in complexed form
were adjusted to the indicated pH. !SX(I.Og, 1.5meqmetal/ion/g)was
added and the pH was readjusted. After 30 minutes, aliqubts were
removed and filtered for residual copper analysis.
100,000
10,000 -
. 1000 -
0.0 0.5 1.0 1.5 2.0 2.5 3.0
ISX, g
Figure 4. Treatment of copper complexes with ISX.
Solutions (1.000 ml) containing copper (53.3 mg 1) in complexed form
were adjusted to pH 3 for quadrol. pH 4 for tartrate, and pH 5 lor
EDTA. ISX (1.5 rheq metal ion g) was added in the quantities shown.
After 30 minutes, aliquots were removed and filtered for residual
copper analysis.
present petrochemical shortages, these products will
likely increase in cost and may even be limited in supply.
A possible solution to this cost problem might be to use
a naturally occurring, annually renewable, low-cost
polymer such as starch. Previously we have shown that
cationic starches were effective in chromium (VI) and
ferro- and ferri-cyanide removal (8, 10).
The use of chromates and dichromates in plating and
as corrosion control agents in cooling water systems is
quite extensive. Chromium (VI) is very toxic and must be
removed from industrial wastewaters before discharge.
Chromium (VI) level allowed in waste effluents which are
discharged to natural waterways has been established at a
maximum concentration of 0.09 mg/l. Rinse waters of
plating operations may vary in composition, but they
usually contain 20-100 mg/l Cr"+ and have a pH of 2-3.
These rinses are treated for three reasons: (a) pollution
control, (b) water reuse, and (c) Cr6* recovery.
Treatment for Cr6* usually involves chemical reduction
to Cru with sulfur dioxide, sodium bisulfite, sodium
metabisulfite, or ferrous salts at pH 2-3 (21-25). The Cru
is then precipitated at alkaline pH's as the hydroxide with
caustic or lime. Nonreductive treatments of Crh+ include
anion exchange (26-31) and activated carbon (32).
ISX was evaluated in Cr6+ removal with surprising
results. Since ISX and chromium (VI) species are both
negatively charged, it would seem unlikely that any
removal would occur. Figure 5 shows that optimum
removal occurs below pH 3 after subsequent
94
-------
100,000
10,000
CJl
E=
1000
100
I I I I I I I I
2 3 4
5
PH
6789
Figure 5. Effect of pH on chromium (VI) reduction with ISX.
Solutions (1,000 ml) containing chromate (20 mg/l as Cr") were
adjusted to the indicated pH. ISX (1.0 g, 1.5 meq metal ion/g) was
added and the pH was readjusted. After 30 minutes, the pH was raised
with caustic to 8.0 and aliquots were removed and filtered for chromium
analysis.
lUU.UUU
(
- 10,000
5t
u
c;
i 1000
E
.g
£ 100
'<
x
^v
>\ A (5 min. Settling]
\ \
B {16 h Settling)\ \
\ •
\
-
i i i i
) 0.25 0.50 0.75 1.00
ISX Added, g
Figure 6. Effect on chromium (VI) removal of ISX.
Solutions (1,000 ml) containing chromate (20 mg/1 as Cr"') were treated
with the indicated amounts of ISX at pH 2.5. After 30 minutes, the
solutions were adjusted to pH 8.0 with caustic and aliquots were
; removed and filtered for residual chromium analysis.
neutralization to pH 8. The following equation shows
that in acidic media an oxidation-reduction occurs which
allows chromium removal with ISX.
2CrO:j + 16H" +6Starch-O-C-S- 2Cr" + 8H;O+ 3(Starch-O-C-S ):
ISX Starch xanthide
Upon neutralization to pH 8 with caustic, the chromium
(III) is removed as the chromium (III) starch xanthate or
chromic hydroxide. An advantage of this process is that
as the pH is raised above 7 the starch xanthide reconverts
into ISX to aid metal removal. Figure 6 shows the
effectiveness of chromium (VI) removal with increasing
amounts of ISX, whereas Figure 7 shows the rate of the
chromium (VI) to chromium (III) reduction. Similar
results were also obtained for dichromate and selenium
removal with ISX.
ISX Case History Report
A plating company in the Northeast has been using
ISX for 2 years as a filter precoat to treat rinse waters
from three plating lines. Residual metal concentrations
after the rinses are passed through the ISX-filters are
copper (0.06 mg/l), nickel (0.57 mg/l), and tin-lead (0.33
mg/1-0.09 mg/1). The water is recirculated from the three
filters back to the rinse tanks for reuse.
Two other systems have been designed using ISX: (I)
copper-dye removal (4.75 million liters/day wastewater)
and (2) copper-lignin removal (an 80-90° C wastewater of
100 mg copper/I at 1500 liters/minute and at pH 13-14).
ISX is commercially available in solid form by at least
one supplier. Another company is promoting the on-site
preparation of ISX to be used in conjunction with
precoated filters for heavy metal removal. A 2-week
evaluation last summer at a company discharging 0.2
mg Cu/1 at 300 liters/minute showed a lowering to 0.01
mg Cu/1 when ISX was incorporated. Incorporation of
this ISX process at this plant would cost less than S600
for equipment and treatment facility modification. The
weekly chemical cost would be approximately $10.
Figure 8 shows that ISX has limited stability in solution,
so it wouldshave to be prepared every few days and then
diluted daily for use.
95
-------
10,000
1000
= 100
1
A (5 min. Settling)
B [16 h Settlingj\
0 5 10
Time, minutes
Figure 7. Chromium (VI) reduction rate with ISX.
30
Solutions (1,000 ml) containing chromate (20 mg/l as Cr1") and ISX
(1.0 g, 1.5 meq metal ion, g) were stirred at pH = 2.5 for the indicated
time. The solutions were adjusted to pH 8.0 with caustic and aliquots
were removed and filtered for residual chromium analysis.
High pH-Lime Treatment of Electroless Copper Plating
Rinse Waters .
The electroless plating of copper on printed circuit
boards and plastics is usually an autocatalytic
formaldehyde reduction of a complexed alkaline copper
(33-37). Suppliers to the plating industries use
proprietary organic complexing agents for copper. For
concentrated plating baths (37), treatments such as (a)
raising the temperature to 50-65°C, (b) adding excess
formaldehyde (1.5%) (38), (c) adding palladium activator
(1-50 mg/l) (38), and (d) lowering the pH, have all been
used successfully in decomposing the copper complexes.
After plating is completed, it is necessary to rinse the
plated articles. The rinse waters derived therefrom
contain complexed copper which must be removed to
prevent possible undesirable ecological effects as a result
of introducing the copper to receiving waters or
biological sewage treatment systems. These rinses usually
contain 20-100 mg/l of copper as complexed copper
around pH 10.9. Since usual chemical treatment is not
effective on these rinse waters, special treatments are
required and thus involve segregation of these solutions
from the main process waters. Recently we reported a
treatment method for the removal of copper from these
complexed copper rinse solutions (20, 39, 40). Other
reports have also appeared (41-46).
Our treatment involves the addition of a soluble
calcium compound, i.e., calcium hydroxide, lime,
calcium chloride, or calcium sulfate to rinse at a pH of
11.6-12.0 to precipitate copper hydroxide. The structure
012 4 7
Days
Figure 8. ISX storage stability in solution.
ISX samples were prepared and were stored under the following
conditions. Samples were worked-up on the indicated days and the
remaining capacity determined (as % S).
A. Reaction mixture as is.
B. Reaction mixture diluted with water.
C. Reaction mixture diluted with water and magnesium sulfate.
D. Isolated ISX reslurrcd.
of the complexing agents determines the effectiveness of
the treatment. The order of copper removal for several
complexing agents is EDTA > NTA > HEDTA > NDA
> tartrate ~ citrate > gluconate. The replacement of an
acetate by a hydrogen or a hydroxyl diminishes removal
of copper considerably. Tables 3 and 4 show some copper
removal data from synthetic and actual industrial rinse
baths.
Some general observations and comments about this
treatment process are:
(a) Good removal is obtained over a pH range of 11.6-
96
-------
TABLE 3
COPPER REMOVAL
FROM COPPER-EDTA COMPLEX
Initial*
copper
cone..
Weight Poly-
Calcium of salt. Final mer
salt g pH mg/l
Residual^
copper
cone.,
mgjl
50.0
50.0
50.0
50.0
5
' 100
1,9IO§
CaO
CaCfe
CaSO4
Ca(OH)2
Ca(OHh
Ca(OH)2
Ca(OH)2
0.50
0.75
0.92
0.50
0.50
t.OO
1.29
11.6
11.6
11.7
11.7
11.7
11.6
12.0
1.5
1.5
1.5
1.5
1.5
1.5
2.0
0.14
0.20
0.44
0.09
0.10
0.06
3.40
* Solutions (1,000 ml) of the indicated copper cone, were treated
: with the solid calcium compound. After stirring 5 min, the solu-
tions were flocculated with polymer (anionic) and were filtered
after 15 min settling.
+ Determined using a Varian Techtron A A 120 spectrophotometer.
§ Stock solution (250 ml).
TABLE 4
COPPER REMOVAL
FROM OTHER COPPER-COMPLEXES
Initial* Resuluall
copper Calcium copper
cone., hydroxide. Final cone..
Complex* mg/l ,1; pH mg/1
NTA
HEDTA
NBA
Tartrate
Citrate
Ciluconate
A
B
50
50
50
50
50
50
50
50
0.50
0.50
0.50
0.50
0.50
0.50
0.46
0.48
11.7
11.8
11.7
12.3
12.1
11.8
11.7
11.7
0.06
1.73
2.86
13.48
9.01
23.88
0.32
12.03
NTA = Nitrilotriacetic acid; HEDTA =.N- Hydroxyethylethyle-
nediaminetriacetic acid; NDA = Nitrilodiacetic acid; A = Mac-
Dermid sample; B = Shipley sample.
Solutions (1.000 ml) wore treated with solid calcium hydroxide.
Alter stirring 5 min. the solutions were flocculated with polymer
(anionic. 1.5 nig I) and were tillered alter 15 min settling.
Determined using ;i Varian leclilron AA I20spectrophotometcr.
13.5 in the presence of excess calcium ion (greater than
2.5 moles calcium ion/1.0 mole copper).
(b) Treatment is effective over the temperature range
of 20 - 60° C.
(c) Treatment is effective on concentrated baths as
well as rinse solutions; however, it is ineffective on
copper-Quadra! rinses.
(d) Use of an anionic polyelectrolyte (1.5 mg/l)aidsin
copper removal by promoting rapid settling.
(e) Analysis of the sludge shows it to be mainly copper
hydroxide, except in the case of the tartrate rinse
(calcium tartrate has limited solubility).
(f) Copper hydroxide sludge could be reprocessed to
help defray cost of treatment.
(g) Treatment can be conducted batchwise and
probably could be operated continuously.
(h) Chemical cost of treatment for a 50 mg/1 copper-
EDTA rinse with lime and polymer would be about
SO.07 3.785 liters.
The supernatant after treatment would still contain a
calcium complex which should have a much lower
toxicity and could be biodegradable. If desired, the
residual Ca:* in the treated rinse could be removed by
carbonation with carbon dioxide, which would also give
a concomitant lowering of pH and make the-effluent
more acceptable for discharge. Care should be taken in
discharge of the calcium complex effluent, since the
complexing agent will combine with other heavy metal
ions if the pH is lowered when these segregated streams
are treated further (i.e., in a clarifier with other process
waters) or are discharged to streams or sewers. Oxidants,
i.e., o7.one-UV, could be used in decomposing the organic
chelants to prevent recomplexation with other heavy
metals. However, several recent reports (47-50) do show
that copper in a complexed form, i.e., with EDTA, NTA,
or pyrophosphale, is significantly less toxic than the free
copper ion.
Formate, a byproduct of formaldehyde cataly/ed
electroless copper baths, does not interfere with copper
removal in this proposed treatment and would remain
soluble as calcium formate. The addition of small
amounts of ISX (20), sulfide ion (43), dithiocarbamates
(51), or mercaptoben/othia/ole (52) alter the lime
treatment aids in further copper removal.
High pH-Lime Treatment Case History Report
Recently, an electroless copper plating rinse from a
large company containing copper (173 mg/1) and nickel
(51.9 mg/1) as the tartrate complex was evaluated in our
laboratory. After treatment with high pH-lime, the
residual copper was 0.3 mg/1 and the nickel was0.1 mg/1.
These results were unexpected since treatment of
standard copper tartrate complexes only resulted in 60-
80% copper removal.
These results were reported to the company and, after
similar success in their laboratory, the decision was made
to install hardware for our high pH-lime treatment
process (January 1977 start-up). They had evaluated at
considerable expense reverse osmosis (RO),
electrochemical, low pH-lime, sodium borohydride, and
other techniques. They were using sodium borohydride
reduction until the more economical and more effective
high pH-lime treatment was installed. Presently, they use
a premixed lime-calcium chloride slurry to have a higher
calcium ion concentration, and they modify the mixture
daily depending on the copper-nickel concentrations.
Their electroless copper rinse water (40,000 liters/day)
initially contains copper (50-300 mg/1) and nickel (0-150
mg/1); after the high pH-lime-polymer treatment to pH
11.5-12.0, the residual concentrations are 0.04-0.3 mg/1
copper and 0.03-1.0 mg/1 nickel, which satisfies the river
discharge limit of 1.0 mg/1 for each metal. The sludge is
97
-------
hauled away to an approved landfill.
Another company, using EDTA solutions to
periodically backflush RO membranes after copper
tartrate rinse water purification, is using the high pH-
lime treatment for these process waters, and they report
excellent copper removal. Initial copper concentrations
(50-200 mg/l) are adjusted to pH 10-11.5 with caustic,
lime is added to pH 12.3, and after anionic
polyelectrolyte flocculation the residual copper
concentration is <0.1 mg/I.
Ferrous Sulfate Treatment of Electroless Copper
Rinse Waters
Since several electroless copper rinse waters from
commercial baths (Quadrol-type) were untreatable by
the high pH-lime method, we expanded our
investigations to develop an effective treatment process
for all types of electroless copper rinses (53). We found
that if the pH of the rinse was lowered to where the
complex dissociates, ferrous sulfate was added and the
solution was neutralized to a pH greater than 9, effective
copper removal was obtained (Table 5). This treatment is
effective because the ferrous ion reduces Cu:+ to Cu and
when the pH is raised the copper won't recomplex.
Acidification assists in weakening or dissociating the
bonds in the copper complex and this is evidenced
sometimes by a color change in the rinse from pale blue to
colorless. The color change is a useful guide to the
amount of acid that would have to be added only to that
pH. Several rinses have been required for the pH
adjustment and if companies have rinses that turn
colorless, acid treated effectively without prior
acidification.
As the copper concentration of the rinse increases (10
mg/1 to 1,000 mg/1), the Fe>/Cu:+ ratio can be lowered
from 8.0 to 1.0 for effective treatment. This fact is
especially important from an economic point of view.
Since several companies are going more to counter flow
rinsing techniques for water use reduction, the copper
complex concentration will increase in these rinses, so
more effective utilization of ferrous sulfate will be
realized. The use of lime or sodium hydroxide as
neutralization agents (Table 5) were equally effective in
copper and iron removal; however, the use of sodium
hydroxide in our investigations gave lower dissolved
solids and less sludge. A 5-minute ferrous sulfate contact
time was usually sufficient for good copper removal. As
long as the pH was raised above 9.0 (Table 6), the copper
TABLE 5
COPPER REMOVAL FROM COPPER-QUADROL COMPLEX— DETERMINATION
OF AMOUNT OF FERROUS SULFATE REQUIRED AND EFFECT OF BASE*
Copper cone.,
mg/1
50
50
50
50
50
50
50
50
50
50
50
50
10
10
10
10
1000
1000
1000
Adjusted FeSO*-7H2O,
pH
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
9.5*
7.8
7.2
7.2*
2.7
2.7
2.7
' 5.4*
2.7
2.7
2.7
g
0.3
0.4
0.5
0.75
1.0
0.5
0.75
1.0
0.5
0.75
1.00
1.00
0.20
0.30
0.40
0.20
3.0
4.0
5.0
Fe^jCu*
1.2
1.6
2.0
3.0
4.0
2.0
3.0
4.0
2.0
3.0
4.0
4.0
4.0
6.0
8.0
4.0
0.6
0.8
1.0
Residual copper
Base
Ca(OH>2
Ca(OH)2
Ca(OH>2
Ca(OH)2
Ca(OH)2
NaOH
NaOH
NaOH
Ca(OH):
Ca(OH):
Ca(OH)>
Ca(OH):
Ca(OH),
Ca(OH),
Ca(OH)>
Ca(OHh
Ca(OH)2
Ca(OH)-
Ca(OH),
* Copper-Quadrol solutions (1,000 ml) containing the indicated copper concentration at pH 10. 6-1
Ferrous sulfate was added as a solid and after 5 min.
trolyte was added and the solutions were
* Determined using a
J No acid added, pH
§ Solution lowered to
Varian Techtron AA
the pH was raised to
allowed to settle 5 min before
conc.,§ mg/l
33.0
15.5
0.58
0.16
0.01
1.25
0.22
0.05
0.44
0.01
0.0 1
0.09
6.60
1.42
0.07
1.00
421.0
147.0
0.36
1 .9 were acidified with
Residual iron
conc.,§ mg/l
4.74
8.70
9.46
5.68
2.68
8.42
4.54
5.16
6.38
6.70
7.41
3.06
0.49
1.52
1.00
1.48
27.5
85.0
12.5
!NH:SO4topH2.7.
1 1 .2 with the base listed. Nalcolyte 676 (2.5 mg/ 1) anionic polyelec-
filtering.
120 spectrophotometer.
lowering due to ferrous sulfate
pH 2.7 after ferrous
addition.
sulfate addition.
98
-------
removal was excellent; however, to lower the residual
iron to low values the pH had to be raised to 11.7.
The ferrous sulfate treatment was evaluated on
solutions containing different synthetic copper
complexes (Table 7) and several commercial rinses
(Table 8) with excellent copper removal. The use of
anionic polyelectrolytes (1.0-2.5 mg/1) was very effective
TABLE 6
EFFECT OF FINAL pH* ON COPPER REMOVAL
FROM COPPER-QUADROL COMPLEX
Adjusted
PH
Final
pH
Residual
copper conc.A
mg/1
Residual
iron «wr., t
mg/1
'2.7
2.7
•2.7
2.7
6.4}
6.4}
6.4}
6.4}
9.0§
9.0§
9.0§
7.0
9.0
11.0
11.7
7.0
9.0
11.0
11.7
9.0
11.0
11.7
0.24
0.17
0.14
0.05
1.34
0.01
0.01
0.01
0.01
0.01
0.01
25.4
10.5
4.5
0.31
4S.6
13.8
1.4
0.23
14.1
1.9
0.17
Dilute 39.0 ml copper-Quadrol stock solution to 11 (50 mg
Cu/1) and then adjust the solutions to the desired pH with IN
H;SO4. Treat solutions with ferrous sulfate (FeSCX • 7H2O,
1.0 g) for 5 min, add calcium hydroxide to the indicated pH
and add Nalcolyte 676 (2.5 mg/1) for flocculation. After
settling 5 min, an aliquot (10 ml) was filtered through What-
man 54 filter paper for analysis.
Copper and iron concentrations were determined using a
Varian Tcehtron AA 120 spectrophotometer.
Adjusted to pH 7.0 \viih acid, then to pH 6.4 with ferrous
sulfutc.
Adjusted to pH 9.0 \\ith ferrous sulfate.
in the flocculation and settling of the sludge. Even though
we evaluated only batch treatment, the method could be
operated continuously. The chemical cost of treatment
for a 50 mg/1 copper-Quadrol type rinse with sulfuric
acid, ferrous sulfate, lime, and polymer would be about
S0.36/3,785 liters.
Ferrous Sulfate Treatment Case History Report
Two printed circuit shops are presently using this
method for treating electroless copper and alkaline etch
rinses. A large West Coast PC manufacturer batch treats
1,200 liters/day of a MacDermid C rinse and also floor
spills from electroless plating and alkaline etchant baths
with 5-20 g/1 ferrous sulfate to pH 10.8. After polymer
flocculation (3.0 mg/1), the residual copper
concentration averages 0.1 mg/1 while the residual iron
concentration is below 1.0 mg/1. This company is
presently installing a continuous flow ferrous sulfate
treatment for their more dilute electroless copper rinses.
An East Coast PC manufacturer treats six electroless
copper rinses and one alkaline etchant rinse with ferrous
sulfate in a continuous flow system. The 100
liters/minute flow of 20-30 mg copper/1 consistently
averages less than 1 mg copper/1 after treatment.
Both companies report less volume of sludge than the
previous treatments they were using.
Spent Pickle Liquor Treatment of Copper Complexes
Recently (54) we found that spent pickle liquor gave
excellent copper removal when substituted for ferrous
sulfate in the previous treatment. The "pickling" process
is the removal of oxide scale from steel products by
immersion in hot acid solution. Spent liquor from batch
steel processing contains between 0.5 - 2% by weight free
acid and 5.8 - 8% by weight ferrous ion, while from
continuous steel processing between 4-1% by weight free
TABLE 7
COPPER REMOVAL FROM SYNTHETIC COPPER COMPLEXES WITH FERROUS SULFATE TREATMENT*
Initial Residual Residual
copper cone., 2N H:SO4. pH for colorless^ FeSOi-IHiO. Ca(OH)i, copper com:, iron cone..
Complex nig /I ml solution g g "'#// nig II
EDTA
NTA
Tartrate
Gluconate
Citrate
Triethanol
Amine
Quadrol
50
10
50
10
50
10
50
10
50
10
50
10
50
10
3.8
0.8
2.2
0.7
8.0
2.0
2.5
0.7
4.8
1.8
6.0
1.5
5.9
1.3
4.5-4.8
4.5-4.7
4.0
5.5
3.0
* Solutions ( 1 .000 ml) containing the copper complexes at the indicated
amount of ferrous sulfate was added and the solution stirred for 5 min.
were flocculated with Nalcolyte 676 (2.5 mg 1) anionic polymer. Aft
t pH values listed
is where
copper complex dissociates.
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.16
0.94
1.26
0.44
1.54
0.64
0.88
0.53
0.76
0.45
1.04
0.64
0.73
0.51
0.23
0.28
0.29
0.09
0.75
0.35
0.82
0.09
0.01
0.02
0.11
0.53
0.01
0.07
0.12
0.10
0.11
0.1!
0.21
0.29
32.70
6.20
0.28
0.18
24.48
8.33
2.68
1.00
concentrations were acidified with 2N H:SOt to pH 2.7. The indicated
Calcium hydroxide was added to raise the pH to 1 1.7 and the solutions
er settling the solutions were filtered for analysis.
When no value is listed, the
blue complex does not
dissociate aho\
e pH 1.8.
99
-------
TABLE 8
COPPER REMOVAL FROM COMMERCIAL COPPER COMPLEXES WITH FERROUS SULFATE TREATMENT*
Initial pH for Residual Residual Dissolved^.
cupper cone.. 2NH:SOt, colorless* FeSOt-7HiO, CafOHh, copper iron com:, solids.
Bath nig/1 nil solution g g cone., nig/l nig/I nig/l
MacDermid
A 50 — 1.0 1.42 0.02 7.1 —
A 10 — 0.4 0.4fr 0.02 2.3 —
B 50 15.0 2.7-3.0 1.0 1.69 0.17 17.8
B 10 4.7 0.4 0.50 0.08 6.3 —
C 50 19.0 1.0 2.18 0.09 21.0 —
C 10 6.0 0.4 0.60 0.03 5.9 —
Shiplev
A 50 4.0 4.8 1.0 0.56 0.33 0.53 —
A 10 1.6 0.4 0.27 0.21 0.47 —
B 50 4.5 2.8 1.0 0.61 0.27 24.86 —
B 10 1.1 0.4 0.26 0.31 2.78
C 50 8.2 3.9 1.0 0.94 0.20 14.17 —
C 10 1.8 0.4 0.27 0.11 2.72 —
D 50 3.5 3.8 1.0 0.51 0.12 6.94 1,750
D 10 1.7 0.4 0.34 0.20 1.47 720
D 50 — _____ 817
D 50 3.5" 1.0 0.92 0.08 6.85 2,320 -,
D 50 .3.5 1.0 20.5 ml§ 0.16 8.88 2.064
* Solutions { 1 ,000 ml) containing the copper complexes at the indicated concentrations were acidified with 2N HzSCX to pH 2.7. The indicated
amount of ferrous sulfate was added and the solution stirred for 5 min. Calcium hydroxide was added to raise the pH to 1 1.7 and the solutions
were flocculated with Nalcolyte 676 (2.5 mg/1) anionic polymer. After settling the solutions were filtered for analysis.
f pH values listed is where copper complex dissociates. When no value is listed, the blue complex does not dissociate above pH 1.8.
% Filtered samples were evaporated to dryness, oven dried at I25°C, cooled, and weighed.
$ Sodium hydroxide (IN).
TABLE 9
SPENT PICKLE LIQUOR TREATMENT
OF QUADROL-BASED ELECTROLESS
COPPER PLATING RINSE WATERS*
Initial Neutrali- Residual
copper Pickle zation copper
cone., Initial liquor, agent Final cone.,
mg/l pH ml pH mgjl
50 11.2 10.6 NaOH 11.4 0.05
50 11.2 10.6 Ca(OH)2 11.3 0.04
500 11.6 32.0 NaOH 11.4 0.44
500 11.6 32.0 Ca(OH)2 11.2 0.21
1000 12.0 53.0 NaOH 11.4 0.50
1000 12.0 53.0 Ca(OH)2 1 1.4 0.31
* Solutions (1000 ml, 50-1000 Cu/1) were treated with the indicated
amounts of pickle liquor (18.8 g/1 ferrous ion) at pH 2.5 for 15
minutes. The solutions were neutralized with sodium hydroxide
(5.N) and/or lime (solid) to the indicated pH and then flocculated
with anionic polymer (2.5-5.0 mg/1). The samples were filtered
through filter paper for analysis, using atomic absorption spec-
trometry.
TABLE 10
SPENT PICKLE LIQUOR TREATMENT
OF COPPER-AMMONIA
ETCHANT RINSE WATERS*
Initial copper Pickle Residual
cone.. liquor, - copper com:,
•nig /I nil Final pH mg/1
50 2.65 11.7 15.66
50 5.30 11.7 27.21
50 7.45 11.7 0.65
50 10.6 11.7 0.37
50 10.6 9.4 3.88
50 10.6 10.0 0.57
50 10.6 11.0 0.41
50 10.6 11.3 0.15
* Solutions (1000 ml, 50 mg Cu/1) were treated with the indi-
cated amounts of pickle liquor ( 1 8.8 g/ 1 ferrous ion) at pH 9.4
for 15 minutes. The solutions were neutralized with sodium
hydroxide (5.NJ to the indicated pH and the flocculated with
anionic polymer (2.5 mg/ 1). The samples were filtered through
filter paper for analysis, using atomic absorption spectro-
metry.
acid and 5.1 - 5.9% by weight ferrous ion. Since spent
pickle liquor has little commercial value, our process
would give a possible advantageous use for some of the 2-
4 billion liters of spent pickle liquor produced annually.
Tables 9-10 show the effectiveness of spent pickle liquor
on a copper-Quadrol and a copper-ammonia etchant
rinse. Approximately 11 liters of spent pickle liquor
(6.6% by weight ferrous ion) would be required to treat
3,785 liters of a 50 mg/1 copper quadrol or copper-
ammonia rinse.
100
-------
Treatment of Electroless Nickel Rinse Waters
The electroless deposition of nickel is commercially the
most widely used of the electroless processes. Numerous
articles (34, 55-66) are available which describe the
chemistry and operating conditions of this controlled
autocatalytic reduction of nickel. Both acidic (pH 4-6)
and alkaline (pH 8-10) formulations are used containing
nickel salt (NiSO4 or NiCl:), reducing agent (NaH: PO: or
NaBH4), chelating agent (citrate or glycolate) and pH
control agent (H:SO4-NH4C1 or NH4OH-NH4C1).
Because of the large number of electroless nickel plating
formulations described in the literature, only a few
synthetic baths were prepared and evaluated for
treatment. Several commercial baths were also
1 evaluated.
; Very little has been published (67-68) on the treatment
A 0.35
0.49
0.78
1. 25
I.25
1 0.0
II.O
1 2.0
I2.5
1 6 h settling
1 2.5
39.74
3.49
0.50
0.44
O.I3J
O.I2§
TABLE 11
NICKEL REMOVAL FROM SYNTHETIC
ELECTROLESS NICKEL BATHS*
Ca(OH)2
added, g
Final pH
Residual nickel
cone., mg/l
D
0.10
NaOH
0.09
0.16
0.49
1.47
1.47
0.23
0.43
0.78
1.98
1.98
1.98
9.9
9.5
10.0
11.0
12.0
12.5
16 h settling
12.5
10.0
11.0
12.0
12.5
12.5
16 h settling
12.5
0.07
0.24
50.00
50.00
2.69
0.54
0.24J
0.15§
50.00
50.00
50.00
42.00
42.00
0.12*
O.I8§
* Solutions (1,000 ml, 50 mg Ni/1) were treated with the indi-
cated amounts of calcium hydroxide for 15 minutes and then
flocculated with Nalcolyte 676 (5 mg/l). Samples were then
filtered for analysis.
A = NiCl; • 6H;O(50g), NaH.-PO: • H;O(lOg).glycolicacid
(56 ml) in water to total volume of I I. at pH = 4.2; B =
NiCl; • 6H:O (30 g), NaH_>PO: • H;O (10 g), glycolic acid
(56 ml) in water total volume of I I. at pH = 4.2; C = Bath A
composition with no pH (4.2) adjustment; D = NiCl: • 6H;O
(45 g). NaH;PO: • H:O) (16 g). Na, citrate • 2H;O (82 g),
NH^CI (50 g) in water adjusted to pH 8.9 with NH4OH and a
tiXal volume of I I.
:£ Solutions adjusted to pH 12.5 were allowed to settle 16 h and
reanalyzed.
§ Solutions were stirred at pH 12.5 for 2 hand then flocculated
with polymer. Samples were filtered for analysis.
TABLE 12
EVALUATION OF Ca(OH)3 AND NaOH
FOR NICKEL REMOVAL FROM MACDERMID A
ELECTROLESS NICKEL RINSE WATERS*
Initial
nickel
cone.,
mg/l
Ca(OHh
added. Final
g pH
Residual
nickel
com:,
mg.ll
Residual
NaOH nickel
(5N), cone..
ml mg/l
10
10
10
10
50
50
50
50
500
500
500
0.04 10
O.I I II
0.35 12
1.60 12.5
0.17 10
0.59 11
0.85 12
2.49 12.5
1.33 11
2.73 12
4.93 12.5
10.00
10.00
0.25
0.20
25.00
6.87
1.88
0.61
39.20
30.20
27.75
0.6
14
10.4
1.0
3.8
14.2
8.0
20.0
35.0
6.38
1.76
0.18
26.92
4.50
0.23
81.24
4185
21.53
Solutions (1,000 ml) containing the indicated nickel concentra-
tions from a MacDermid A electroless nickel plating bath at pH
8.6 were treated with the indicated amounts of Ca(OHh or
NaOH(5N). After a 30 minute contact time, the solutions were
flocculated with Nalcolyte 676 (2.5 mg/l) and then analyzed for
residual nickel.
of electroless nickel process waters. Our preliminary
evaluations to see what effect caustic and lime treatments
have on rinse waters revealed that electroless nickel rinse
waters could be treated this way. Tables 1 1-13 show that
low residual nickel concentrations can be attained with
either a caustic or lime treatment at high pH and at
various nickel concentrations. Even though the volume
of sludge is greater with the lime treatment, the polymer-
treated floe settles faster and is more easily removed than
when caustic is used. Another apparent advantage of
using lime is the removal of some of the decomposition
product of the reducing agents used in the plating.
Hypophosphite and borohydride decompose according
to the following equations to yield orthophosphite and
metaborate which form only slightly soluble calcium
Ni:* + H:O + H2PO: -
4NP + 80rT + BH4 -
+ 2H* + Ni
6H:O + 4Ni°
salts, allowing them to be precipitated.
We found (69) that in the treatment of some of the
formulations, a longer contact time at high pH gave
lower residual nickel values. Acid baths contain
compositions having less buffering action (NH4'/NIHi).
and considerably less base is needed to adjust the pH.
Also, the acid bath rinse waters for the most part allowed
better nickel removal at a lower pH (I I vs 12.5) and gave
a faster settling sludge. However, preliminary results in
treating rinse waters from an acidic (pH 5.4) Shipley bath
showed the best results at high pH (12.5) with long
contact times (2-16 h).
101
-------
Electroless Nickel Case History Report
A large Midwestern company using an OMI-Udylite A
electroless nickel plating bath containing Ni:+,
hypophosphite, citrate, and ammonia for plating on
plastics has installed the previously described high pH-
lime-caustic treatment. A previous treatment tried by the
company using phosphoric acid and then caustic was
unsuccessful as some of the nickel-ammonia complex
TABLE 13
EVALUATION OF Ca(OH)2 AND NaOH
FOR NICKEL REMOVAL FROM MACDERMID B
ELECTROLESS NICKEL RINSE WATERS*
Initial Residual
nickel Ca(OH)2 nickel
cone., added. Final cone.,
mg/l g pH mg/l
Residual
NaOH nickel
(IN), cone.,
ml
10
10
10
10
50
50
50
50
500
500
500
500
0.01
0.03
0.04
0.18
0.08
0.13
0.16
0.32
0.82
0.97
1.12
1.56
9
10
11
12
9
10
II
12
9
10
11
12
5.68
1.59
0.51
0.49
0.49
0.44
0.05
0.02
2.27
0.69
0.30
0.29
0.4
0.7
15
3.8
2.6
3.9
6.4
24.4
37
45
54
81
4.50
1.10
0.05
0.05
2.53
0.19
0.21
0.12
6.57
2.47
Z80
1.41
Solutions (1,000 ml) containing the indicated nickel concentra-
tions from a MacDermid B electroless nickel bath at pH 4.7 were
treated with the indicated amounts of Ca(OH>2 or NaOH(lN).
After a 30 minute contact time, the solutions were flocculated
with Nalcolyte 676 (2.5 mg/l) and then analyzed for residual
nickel.
was undestroyed. The company treats 30,000 liters/day
(85-140 mg/1 nickel) of a dragout rinse (pH 8.6) with lime
(45.4kg) to pH 9.5-10.0for I hour with agitation. Caustic
(22.7 kg as pellets) is added to adjust the pH to 12.0-12.5.
A 1% solution of a Benchmark Separaid-10 anionic
polymer (12.5 mg/l) is added forflocculation. The sludge
is settled for 2-3 hours and the supernatant (less than 0.5
mg/l residual nickel) is pumped off and discharged. The
sludge is removed weekly from the pit and filter pressed.
This treatment has allowed this company to lower their
nickel discharge to a zero flow stream from 3.2 kg/day to
0.014 kg/day. Eventually, they would like to install
carbon and ion exchange columns for further effluent
treatment and complete water reuse. Even though our
laboratory treatments on OMI-Udylite A (new bath)
rinse waters were only 95-98% effective, the on-site
treatment by this company has always proved to be 96-
99% effective and sometimes 100% effective on spent
rinse waters.
Treatment Process for Copper Pyrophosphate
Electroplating Rinse Waters
Copper plating in alkaline media with the copper
pyrophosphate complex anion has been known for over
125 years; however, it only gained commercial
importance about 35 years ago (70-71). Numerous
articles have appeared disclosing bath formulations,
operating conditions, and applications (72-76); however,
very little information is available on the treatment of
copper pyrophosphate rinse waters (77-79).
After the articles are plated, they go into a dragout or
stagnant rinse t ink and through a series of flowing rinses.
The dragout rinse usually is added back to the plating
bath for makeup water. The flowing rinse water
containing Cu(P2O7)26", PjCV', and HPO4J~ has to be
treated before discharge to meet the ever more stringent
standards.
TABLE 14
Ca(OH)2 TREATMENT OF ACTUAL COPPER PYROPHOSPHATE ELECTROPLATING RINSES*
Initial Initial Initial Residual Residual Residual
Rinse
A
B
C
A
B
C
A
B
A
B
A
Cu cone..
mg/l
67.36
74.50
70.84
50
50
50
10
10
1 00
1 00
50
Initial P-O74~ cone..
pH
8.9
8. 1
7.7
8.6
8.0
7.7
8.4
8. 1
8.7
8. 1
8.6
mg/l
728.7
686.7
893.6
539
460
625
1 08
92
1. 078
920
539
HPO,-'
cone., mg/l
45.0
347.8
668.7
33.4
233
468
6.7
47
67
466
33.4
Ca(OHh,
mg
992
1,387
2,124
734
929
1,487
147
186
1.470
1,860
550 (as
lime)
CM cone..
mg/l
0.02
0.04
2.54
0.02
0.01
0.02
0.01
0.01
0.02
0.02
0.01
P cone., Ca cone.
mg/l
0.2
0.6
3.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
mg/l
30.2
14.3
3.6
27.4
19.7
44.7
—
—
—
—
* Copper pyrophosphate rinse solutions ( 1. 000 ml) containing the indicated concentration were treated with calcium hydroxide
for 5 min.
filtration.
anionie polyeleclrolyte
(Dow A-23. 5 mg
I) was added
and residual
copper, calcium.
and phosphorous
Final
PH
11.4
11.5
1 1.4
11.1
11.2
11.3
10.6
10.8
11.6
11.6
11.1
Alter stirring
were determined alter
102
-------
Rinse
Initial
Cu cone..
mg/l
Initial
pH
/>,0/
cone.,
mg/l
HPOt Residual
com:, Ca(OH)2, CaCli Cu cone..
mg mg mg mg/l
Residual
P cone.,,
mg/l
Residual
Ca cone.. Final
mg/l pH
TABLE 15
Ca(OH)2-CaCI2 TREATMENT OF ACTUAL COPPER PYROPHOSPHATE ELECTROPLATING RINSES*
Initial
Initial
A
B
C
67.36
74.50
70.84
8.9
8.1
7.7
728.7
686.7
893.6
45.0
347.8
668.7
925
872
1,135
97
751
1,444
0.02
0.01
0.01
0.3
0.2
0.2
25.4
10.2
37.2
11.4
11.4
II.I
A
B
C
50
50
50
8.6
8.0
7.7
539
460
625
33.4
233
468
685
584
794
72
503
I.OII
0.02
0.01
0.02
0.2
0.2
0.2
16.1
16.7
31.5
11.2
11.!
II. 1
Copper pyrophosphate rinse solutions (1,000 ml) containing the indicated concentration were treated with calcium hydroxide and calcium
chloride. After stirring for 5 min. anionic polyelectrolytc (Dow A-23. 5 mg I) was added and residual copper, calcium, and phosphorous were
determined alter filtration.
Preliminary experiments showed that good copper
hydroxide removal (50 mg/l copper lowered to 0.44
mg/l) was obtained by adjusting copper pyrophosphate
rinse waters to pH 12.2 with caustic; however, no
pyrophosphate or orthophosphate removal was
observed. Since strict phosphorus discharge standards
have to be met, an alternate treatment was sought. It is
well known that cations such as Ca2+, Mg:+, Zn2+, A1H
and Fe'+ form insoluble precipitates with HPCV and
PiiO?4 when an excess of cation is present (80-88). Since
calcium hydroxide, lime, and calcium chloride are
economical sources of Ca"*, they were chosen for this
study. As the Ca:* is added to the rinse, it complexes with
the HPQi"' and excess P:O?4 and precipitates them as
their insoluble calcium salts. When the excess P:O74" is
removed, the copper probably precipitates as Cu:P:O?.
The copper pyrophosphate baths and rinses evaluated
were from the printed circuit industry which uses these
baths for through-hole-plating of printed circuit boards.
Since occasional analysis (89-90) for copper,
pyrophosphate, orthophosphate, and ammonia is
required for control purposes to keep the bath in good
operating condition, the plater knows the relative
concentrations of pyrophosphate and orthophosphate in
his rinses. Using this analysis information, a treatment
process has been designed to lower copper and
phosphorous concentrations of synthetic and actufH rinse
waters. The treatment process can be modified as the
orthophosphate concentration builds up. New baths will
contain very little orthophosphate, and treatment of
these rinses with calcium hydroxide or lime at pH's above
9 will give excellent copper and phosphorous removal. As
the orthophosphate concentration builds up to greater
than 90 g/ liter, the substitution of some calcium chloride
for lime will be required to get more Ca"* into solution for
excellent precipitation.
Some experimental results for this treatment are
shown in Tables 14 and 15. Some general observations
and comments about this treatment process are:
(a) Good removal is obtained over a pH range of 9.0-
11.5 in the presence of excess calcium ion.
(b) To lower the copper concentration to less than 0.02
mg/l and phosphorous concentration to less than 1 mg/l,
3.0 mmoles Ca * is required for each mmole of P2O?4" and
2.0 mmoles Ca2* is required for each mmole of HP(V~
(c) Rinses containing high orthophosphate concentra-
tions should be treated with higher proportions of
calcium chloride for greater Ca2* solubility.
(d) Use of an anionic polyelectrolyte (3-5 mg/l) aids
sludge settling.
(e) Treatment can be conducted batchwise and
probably could be operated continuously.
(f) Chemical cost treatment using lime and polymer
for a copper pyrophosphate rinse containing Cu~* (54
mg/l), P;O74 (500 mg/l), and HPOf~ (250 mg/l) would
be about $0.16/3,785 liters.
Copper Pyrophosphate Case History Report
A large tool manufacturer in the Southwest uses
copper pyrophosphate baths for carburizing parts. The
rinse waters (40-50 mg/l copper, 40 liters/minute) up
until a few months ago were not segregated and were
treated with other process waters. This company now
segregates the rinse waters for treatment with caustic at
pH 12.2. This practice enables them to meet their copper
discharge limits and, since they discharge to a sewer, their
phosphorus level is below discharge limits. However,
they are having problems filtering the copper hydroxide
floe and will have to meet stricter phosphorous limits;
therefore, they are evaluating the lime treatment.
The mention of firm names or trade products does not
imply that they are endorsed or recommended by the
U. S. Department of Agriculture over other firms or
similar products not mentioned.
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Waters. Met. Finish, (in press).
70. Stareck, J. E. Method of Electrodepositing Copper
and Baths Therfor. U. S. Patent 2,493,092, January
3, 1950.
71. Coyle, T. G. Unichrome Copper. Proc. Am. Electro-
plat. Soc. 29(2): 113-116, 1941.
72. Passal, F. Copper Plating During the Last Fifty
Years. Plating 46(6): 628-628, 1959.
73. Couch, R. W., and J. E. Stareck. Pyrophosphate
Copper. In: Modern Electroplating. F. A.
Lowenheim, Ed., 2nd ed., John Wiley & Sons, New
York, 1963. pp. 200-206.
74. Dini, J. W. Plating Through Holes in Printed Cir-
cuit Boards. Evaluation of Some Copper Baths.
Plating 51(2): 119-124, 1964.
75. Owen, C. J., H. Jackson, and E. R. York. Copper
Pyrophosphate Plating Without Additives. Plating
54(7): 821-825, 1967.
76. Dini, J. W., H. R. Johnson, and J. R. Helms. Effect
105
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of Some Variables on the Throwing Power and
Efficiency of Copper Pyrophosphate Solutions.
Plating 54(12): 1337-1341, 1967.
77. Yamada, H., and H. Kojima. Removal of Copper
from Pyrophosphate Waste Waters. Japanese Patent
00,295, January 5, 1973.
78. Parsons, W. A., and W. Rudolfs. Lime Treatment of
Copper Pyrophosphate Plating Wastes. Sewage
Ind. Wastes Eng. 22(6): 313-315, 1951.
79. Wing, R. E., W. E. Rayford, and W. M. Doane.
Treatment Process for Copper Pyrophosphate Elec-
troplating Rinse Waters. Met. Finish. 75(5): 101-
105, 1977.
80. Ferguson, J. R., D. Jenkins, and J. Eastman.
Calcium Phosphate Precipitation at Slightly Alka-
line pH Values. J. Water Pollut. Contr. Fed. 45(4):
620-631, 1973.
81. Bishop, D. F., and J. B. Stamberg. Removal of
Nitrogen and Phosphorus from Waste Waters. U. S.
Patent 3,617,540, November 2, 1971.
82. Boehler, R. A., and M. R. Purvis, Jr. Removal of
Phosphorus from Sewage Effluent. U. S. Patent
3,617,542, November 2, 1971.
83. Daniels, S. L., and D. G. Parker. Removal of Phos-
phate from Waste Water. U. S. Patent 3,617,569,
November 2, 1971.
84. Van Wazer, J. R., and C. F. Callis. Metal Complex-
ing by Phosphates. Chem. Rev. 58(11): 1011-1046,
1958.
85. Waiters, J. I., and A. Aaron. Spectrophotometric
Investigation of the Complexes Formed Between
Copper and Pyrophosphate Ions in Aqueous
Solution. J. Am. Chem. Soc. 75(3): 611-616, 1953.
86. Hammer, M. J. Phosphorus Removal. In: Water
and Waste Water Technology. John Wiley and Sons,
Inc., New York, 1975. pp. 452-455.
87. Bobtelsky, M., and S. Kertes. The Polyphosphates
of Calcium, Strontium, Barium, and Magnesium:
Their Complex Character, Composition, and Beha-
vior. J. Appl. Chem. 4(8): 419-429, 1954.
88. Rogers, L. B., and C. A. Reynolds. Interaction of
Pyrophosphate Ion with Certain Multivalent
Cations in Aqueous Solution. J. Am. Chem. Soc.
71(6): 2081-2085, 1949.
89. Konishi, S. Analysis of Copper Pyrophosphate
Baths with EDTA. Met. Finish. 58, 62, 1965.
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Company, Nutley, New Jersey. July, 1968.
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An Overview of the Sludge Disposal Problem
Paul Minor*
This discussion covers an overview of the sludge disposal problem as it affects the metal
finishing industry. It reviews briefly the Federal legislation that has had an impact on the
industry and points up the problems and responsibilities facing both the Government and
industry and shows, in particular, that their goals are not in conflict. The discussion covers the
basic problems, minimizing costs by the manufacturer, and minimizing regulatory overkill.
Illustrations cover the effect of solids concentration on shtdge volume, concentrations
achievable with various dewatering methods, basic problems in sludge disposal, and disposal
costs.
INTRODUCTION
The problems that have been encountered with the dis-
posal of industrial sludges do not come as a surprise.
From the time the Federal Water Pollution Control Act
(Public Law 92-500) was passed 6 years ago disposing of
the residues from industrial wastewater treatment
systems has been a constant concern. Since 1972 the
problem has been continually discussed in both indus-
trial and Governmental sectors. In general, the goal of
cleaning the nation's wastewater discharges is being met,
but the problems of disposing of residues from
wastewater treatment systems are just beginning to be
studied in the systematic manner needed to prevent
wastage of large amounts of resources.
From the environmental point of view, there must be
assurances that the residues removed from the
wastewater at great cost and effort are not reintroduced
into the environment in a harmful manner. On the other
hand, the manufacturer, having already paid a significant
sum for a wastewater treatment system, must keep any
additional costs for sludge disposal at the lowest possible
level necessary to protect the environment.
These two views are not necessarily in conflict.
However, sound scientific data needed to reach a
reasoned judgment on just what is required is lacking.
The fate and the effect of many pollutants in industrial
sludges are not sufficiently understood to allow quanti-
tative decisions to be made.
With the passage of Public Law 94-580, the Resource
Recovery and Conservation Act, however, the legislative
noose is tightening. This law is not necessarily bad for
industry. There has been so much confusion relating to
the relative dangers of some industrial sludges that in
some instances we have seen some stringent restrictions
on the disposal of all industrial sludges.
'Paul Minor, President
Centec Consultants, Inc.
11800 Sunrise Valley Drive, Reston, VA 22091
The problem of sludge disposal is especially
troublesome for manufacturers who are discharging to a
municipal wastewater system and who are forced to
pretreat their wastes. Space for onsite disposal is usually
limited and the manufacturing facilities are often too
small to support a sludge concentration system of
sufficient capability to make hauling relatively
economical. However, once again, close control of truly
hazardous sludges may pave the way toward a reasonable
approach for those sludges which are not hazardous or
which can be disposed of in a non-hazardous manner.
During the discussion on Public Law 94-580, you have
seen that industrial sludges were broadly classified as
solid wastes. The section of the law that is most
significant, however, concerns hazardous wastes. By
Spring of 1978, EPA must promulgate hazardous waste
regulations. But EPA must first establish criteria for
defining these wastes, "taking into account toxicity,
persistence, and degradability in nature, potential for
accumulation in tissue, and other related factors, such as
flamrnability and corrosiveness." Therefore, the
definition finally arrived at by EPA as to what materials
constitute hazardous wastes will be critical in determin-
ing disposal methods.
The criteria currently being developed for use in
defining a substance as "hazardous" address such wastes
as:
Flammable
Corrosive
Reactive
Infectious
Radioactive, and
Toxic.
Methods for determining if a material falls under any
of these categories are being developed. From the
preliminary draft, wastes containing lead, zinc, copper or
cyanide would be considered hazardous—thus it appears
that the electroplating waste treatment residues will be
107
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treated as hazardous in the implementation of the law.
The act also provides financial assistance to states for
solid waste management and encourages states to adopt
and enforce regulations that would be equivalent to the
Federal Government's. In fact, great emphasis is placed
on putting control in the hands of the States.
The Basic Problem
As stated earlier, the goals of industry and the
regulators are not necessarily in conflict. If there were a
sound scientific basis for controlling wastewater
treatment sludges from the electroplating industry that
did not result in substantial added costs needed to
provide a safety factor, it is entirely possible that
regulations could be worked out that would meet the
goals of both parties. The smaller this safety factor can be
made the lesser will be the distance between the two
parties. Like any design situation, safety factors,
although necessary, are expensive—the better the science
behind the regulations, the more precise the regulation
should be. It is to everyone's advantage if we carefully
determine just what protection is needed for industrial
sludges.
It appears that while every plant must take on the
responsibility of cost-effective implementation at its site,
the Government, with its research resources, also must
attempt to minimize the "overkill" in its regulations,
while assisting in the development of technology that can
assist the manufacturers in implementation. If this is
done, perhaps we can take a responsible, effective
approach to the problem.
Minimizing Costs by the Manufacturer
In attempting to resolve the residue problem, the
manufacturer faces a three-way trade off between the
investment required for concentrating the sludge on-site,
the higher hauling and final disposal costs if little or no
investment is devoted to concentration, and the use of in-
plant changes and selection of treatment chemicals which
reduce the sludge volume generated. Minimizing the
amount of sludge generated is extremely important for
some situations and is being addressed by a separate
paper in this session.
The trade off between the cost of concentration and the
cost cf hauling and disposal is an almost classic
optimization problem. In many cases, however, there are
other special factors that are specific to an individual site.
Sludge disposal is often strongly affected by local
opportunities, such as the proximity of a chemical
landfill area or the availability of a contract disposal firm
as well as by the economic balancing of sludge
concentrating investment versus hauling costs.
The need for concentration in many cases is illustrated
in Figure I, which shows the effects of sludge
concentration on the volume of sludge. The relative cost
of the sludge concentration equipment, which can be
used to reach these higher percent solids levels, is shown
in Figure 2. If you superimpose these two figures (Figure
3) you can obtain a good feel for the basic problem in
120
100
(U
tr
•O —
3 m
^••a 80 -
i
•S3
01 £
S£ 60
C
40
20 .
I
;
\
10 20 30 40 50
Percent Solids in Sludqe
Fig. 1—Effect of Solids Concentration on Sludge Volume.
Oentrifxjjatinn
Pressure
Filtration
(Plate and Frame Type)
Vacuun Filtration
20 30 40
% Solids Concentration
Fig. 2—Concentrations Achievable with Various Dewatering Methods.
sludge disposal. To obtain low sludge volume you must
remove a portion of the water associated with the sludge.
This water is often expensive to remove. For the small
manufacturer, the relative cost of the sludge concen-
trating equipment can be quite high, even if the optimum
system is chosen.
Minimizing Regulatory Safety Factors
While the manufacturer is trying to minimize the
resources required to accomplish his portion of the task,
it is equally important for the regulatory agency to
shoulder the burden of making the regulations as precise,
specific, and cost-effective as is possible. To do this, they
108
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Effect of Solid Ccnosntration
en Sludge Itolane
Pressure
Filtration
(Plate and
Frarte Type)
Vacuun
Filtration
10 20 30 40 50
Percent Solids Concentration
Fig. 3—Sludge Volume and Cos! of Concentration vs. Percent Solids.
IJ
li
= -
I
_ X
i
Ln) COM HK«Xl*t Am
ava,06ya
•
I I
nt l«g-!' 1 i
Fig. 4—Disposal Costs (Exclusive of Hauling & Pickup) vs. Method of
Disposal for One Application.
need scientific and cost data. Anyone trying to derive
guidelines that are to be applied nationally quickly learns
that no regulation is cost-effective in every situation, but
an effort must be made to minimize wasted resources.
The vast amounts of funds that are to be expanded as a
result of Federal and state regulations gives tremendous
leverage for the expenditure of R&D funds to provide
more precise regulations—regulations that serve the
intended purpose but do not have excessive overkill built
in. We do need research that will pinpoint the real trouble
spots so that proper attention can be focused on the
important areas.
The affect of the type of final disposal on cost is shown
in Slide 4 for one specific case. The investment curve rises
sharply as we approach the complete containment
systems. We certainly want to keep these rising costs in
mind, and to use the most expensive types of disposal
methods only when necessary.
Summary
Summarizing then, the problem of disposing of the
residues of wastewater treatment is now at hand. We need
a systematic scientific approach for determining the
handling of these residues. The regulation should be
specific enough to prevent treating relatively safe sludges
in the same manner as toxic sludges.
The regulations for disposing of sludges in a way that
protects the environment must not be so imprecise as to
cause a needless adverse economic impact on industry.
The technology must be developed in a way that benefits
both causes. The new Resource Recovery and
Conservation law is not excessively restrictive if properly
applied. Much more authority for enforcement is being
encouraged by the States. Strict compliance is required
only for hazardous wastes. The new law might require
more record keeping and more care in selecting a disposal
site or transporter, but most people agree that this is
badly needed.
The control of the residues is important. We have spent
large sums to clean the wastewater and we do not want to
jeopardize this investment. On the other hand, we cannot
afford to be so sloppy in our science and engineering that
we waste resources. The key is to perform the research
and development necessary to have an understanding of
what we are doing. This session presents results on some
of the efforts that are being directed toward obtaining
this understanding.
109
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Minimizing the Generation
Of Metal-Containing Waste Sludges
F. A. Steward & Leslie E. Lancy*
INTRODUCTION
Chemical treatment is the backbone of all available
technology for treatment of metal finishing waste waters.
While there is an array of other techniques available,
each has a specialized and rather limited field of appli-
cation. For the foreseeable future, chemical treatment
is likely to be an essential component in any complete
treatment plant. Unfortunately, much of the chemical
treatment technology depends on removal of noxious
constituents from the waste water by precipitation as
insoluble solid material, commonly referred to as sludge.
Typical reactions are the precipitation of heavy metals,
water hardness, fluorides, phosphates, and sulfates. The
handling and ultimate disposal of these sludges is, and
will continue to be, a steadily increasing cost factor for
the industry. There are a number of reasons for this.
Metal-containing sludges are hazardous when disposed
in conventional sanitary landfills. Regulatory attention
on this solid waste disposal issue will continue to grow
and regulations will tighten. Approved disposal sites,
operating under regulatory permit, are rare at the present
time and likely to be scarce for years to come. The quan-
tities of sludges presently generated will increase drama-
tically due to the requirement for pretreatment of indus-
trial wastes prior to discharge to sanitary sewage systems.
Finally, there is a tendency to meet extremely tight regu-
latory requirements by treating with significant excess
quantities of sludge-producing materials such as iron or
aluminum salts, clay, peat moss, and organic xanthate
compounds.
The economics of metal recovery are steadily improv-
ing as a result of three factors. There is increasing con-
cern over the potential environmental harm which can be
created by disposal of heavy metal-containing sludges,
especially when combined with sanitary solid wastes. The
value of most metals is climbingdue to scarcity of domes-
tic ore reserves, increasing costs of production, etc., and
finally, there is a constant advancement in the technology
of metal recovery. This shifting framework justifies a
continuous reevaluation of the various recovery schemes
available to our industry. This paper is a review of the
most significant sources of metal salt wastage, and thus
*F. A. Steward & Leslie E. Lancy, Ph.D.
Lancy Division of Dart Environment and Services Company
525 West New Castle Street, Zelienople, PA 16063
sludge genefation, as well as an attempt to critically eval-
uate some of the techniques in current practice.
Even after implementation of expected dramatic ad-
vances in recovery technology, there will be a certain level
of residual waste sludge generated by typical metal
finishing operations. We are strongly of the opinion that
recovery from such mixed waste sludges will not be eco-
nomical in the foreseeable future. Therefore, the subject
of ultimate disposal techniques and associated regula-
tions is very important for our industry. As implied by
the title of this paper, methods to reduce the generation of
metallic sludges will be discussed, but not the problem of
dealing with the valueless mixed residues.
Sources Contributing Metal to the Sludge
The most easily recognized source of pollution in a
metal finishing operation is the dragout of various pro-
cessing baths into subsequent rinsing steps. It is com-
monly assumed that this is the main source of metals
which ultimately generate waste sludge. As reported
earlier1, our investigations show that 70 - 80% of the
metal content in the sludge is derived from various
sources other than dragout. Examples are the dumping of
process solutions, purification of various baths, back-
washing of filters, and accidental spills to the floor. The
basis for our conclusion is the routine design calculations
which have been done for many hundreds of waste treat-
ment plants over the twenty-five years of our company's
experience. Calculations are based upon site investiga-
tions, chemical purchasing records, and dumping sched-
ules for the various process baths. As an illustration, we
find that in large nickel plating installations, more
nickel is lost through the sludgery bottom dumps after
chemical purification and from operation of the filters
than through normal dragout. Equally significant is the
zinc or cadmium that is stripped off the danglers or rack
tips in the acid dip in the cleaning cycle, or removed
from the work in dichromating. One outstanding excep-
tion to this rule is decorative chromium plating where the
main metal loss is due to dragout.
The bulk of metal wastage in our industry is a result of
copper and brass bright dipping, pickling and etching
of various metals, dichromating, stripping, deburring,
and tumbling.
We don't mean to imply that metal losses due to drag-
out are insignificant. Indeed, they can amount to 6-7% of
the metal purchased by a plant. However, we feel it is
110
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important to counter a common misconception since an
intelligent plan for minimizing the generation of metal
sludges must be based on proper understanding of the
sources.
Metal Recovery from Dragout
The majority of the effort to date, and thus the avail-
able technology, is focused on metal recovery from drag-
out. An obvious approach for those process baths which
operate in a reasonably balanced or equilibrium condi-
tion, is to return the dragout directly. Since rinsing, by
definition, dilutes the dragout, some means is needed to
reconcentrate it prior to return. Most systems use coun-
tercurrent rinsing, and one or a combination of the unit
operations of evaporation, reverse osmosis, electrodialy-
sis. and ion exchange. There is voluminous literature
available covering all of these approaches and giving de-
tailed process descriptions, case histories, and operating
cost data. It is beyond the scope of this study to consider
the trade-offs among these approaches in view of the wide
array of potential applications. The wealth of available
published information is a more suitable source for any-
one interested in the subject.
In some processing systems, return of dragout can be
impractical. This is obviously the case with those pro-
cessing baths which become steadily depleted in use since
return of the dragout would simply increase the fre-
quency of dumping. However, it is also true when a
balanced process, such as the typical electroplating bath,
might be harmed by return of contaminating materials
such as trace metals, organic compounds, undesirable
salts such as carbonates, etc. In these cases, recovery can
still be practiced by one of two means.
1. An electrolytic cell can recover the metallic content
from the dragout. A number of cells have been proposed
for removal of mg/1 concentrations of metals in normal
rinse water flows2. These have relatively low current effi-
ciency, and result in a powdery metallic deposit which
requires a special handling technique to separate from the
water stream, dry and melt. As an alternate, we use the
integrated metal recovery approach3*4. A recovery-rinse
liquor is circulated through a specially designed electroly-
tic cell and thus maintained at rather low metal concen-
tration. Drag-out to subsequent rinses is negligible as
far as chemical load sludge generation and value. Because
this approach allows a good electrolyte to be maintained,
the deposit is sound metal with higher resale value and
the potential to be used as anode material in plating
operations. The current utilization efficiency is also
much higher, typically above 98%.
2. Segregated precipitation and collection of a specific
metal sludge can allow recovery of its value. Such sludges
are salable as chemical byproducts. Alternatively they
can be dissolved in an electrolyte solution and deposited
as a high-purity cathodic metal to be sold or used as
anodes.
Because of increasing metal cost, the recovery of even
such low-cost metals as zinc is becoming economically
advantageous. Several firms have recently expressed
interest in purchasing waste slurries of zinc sludge, fur-
ther confirming the steady shift in the economic frame-
work.
Metal Recovery from Processing Solutions
As stated earlier, process solutions which must be peri-
odically discarded because of accumulation of dissolved
metal constitute one of the main sources of metal-
containing sludges. Unfortunately, there are so many
processing solutions which are routinely discarded, each
having its own particular chemical make-up, and each
requiring a specific regeneration approach, that it would
be impossible to discuss all of the problems and all of the
potential solutions. What we would like to do is to discuss
those recovery methods which we have had an
opportunity to investigate, and which, in our opinion,
have been successful as an economical regeneration
approach.
It is also important to stress that economics invariably
dictates a certain minimum size for a regeneration sys-
tem. Even the simplest regeneration set-up requires
investment in equipment, engineering involvement,
space, labor, and maintenance. The calculations to esta-
blish the economics of any process can't be judged by the
apparent low-cost chemical additions, electrical or heat
energy, etc., but have to include amortization of total
investment (which is usually the most significant cost
item), the value and cost of the space occupied, as well as
the labor and maintenance costs. Only large-volume
processors who are wasting significant quantities of
metal will find that the installation of these regenera-
tion processes is economically justifiable.
1. Copper and Brass Pickling.
a. Electrolytic Regeneration Systems have been in
use for many years now and are installed at most copper
rod and wire mills5. Copper rod, flat sheet stock, ex-
truded tubing, etc., leave the hot primary forming opera-
tion (unless the extrusion is performed under a protec-
tive atmosphere) with substantial scale on the surface.
The scale contains both cupric and cuprous oxide which
is removed by a hot sulfuric-acid-type pickling solution.
The cuprous oxide is not soluble in sulfuric acid. Much of
it falls off during the pickling process and accumulates as
a sludge in the acid. Significant quantities are also lost in
the subsequent rinsing operation, particularly when
high-pressure sprays are used to dislodge it. The continu-
ously recirculated pickling solution is pumped through
an electrolytic cell where dissolved copper is plated out
at near 100% cathode efficiency, using insoluble lead
anodes. The copper concentration is maintained in the
range of 25 - 45 grams per liter and sincelhe pickling acid
doesn't have to be discarded, as much as 60%of the drag-
out losses can also be recovered through the use of a
simple dragout reclaim rinse.
b. Brass and the various bronze alloys pose a some-
what different problem. It has been assumed that the
alloying elements interfere with deposition of metallic
copper and cannot provide a smooth, heavy deposit
meeting the cathode plate purity requirements. During
the course of an EPA demonstration project6, the oppor-
tunity was given to prove that cathode plate integrity and
111
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purity could be maintained, with a recovery cell operat-
ing at a lower than normal current density, even though
the pickling acid contained significant concentrations
of other metals such as zinc, nickel, and tin. Especially
the zinc concentration will increase to high levels, but an
equilibrium at these levels is eventually reached due to
dragout losses with no deleterious effect on the pickling
efficiency of the acid or on the cathode plate quality,
c. Basket or barrel pickling of brass pieces may
also create a problem with a red coppery immersion
deposit when the content of the acid exceeds 12 - 15 g/1
copper metal. Traditionally, frequent dumping of the
acid bath was considered the only suitable processing
method. However, installation of an electrolytic recovery
cell allows the copper to be maintained below 10-12
g/1 and perpetuates the use of the bath. The use of special
electrolytic recovery cells, designed to operate with high
efficiency at low metal concentrations, makes these types
of recovery systems feasible. Economical justification
can be found for even rather small size installations.
d. When the pickling or etching bath for copper or
copper alloys contains sulfuric acid and hydrogen perox-
ide, crystallization becomes a more cost-effective
approach for regeneration6,7. The main purpose for
developing the peroxide-containing process baths was
the more thorough removal of cuprous oxide from the
copper and copper alloy surfaces. The hydrogen peroxide
content allows dissolution of the otherwise insoluble
cuprous oxide, accelerates the pickling process, and
results in an overall quality improvement for a variety of
products including copper wire and sheet, beryllium cop-
per parts, and electronic printed circuit boards8. The
driving force provided by the peroxide allows the bath to
be operated near the solubility limit of copper. Thus, the
bath can be operated at slightly elevated temperature
and regenerated by a simple cooling of 20-30 degrees to
cause crystallization. The accumulating high-purity
copper crystals can be sold or used for make-up to an
electrolytic copper recovery cell. Direct electrolytic
regeneration of these baths is also possible, but it in-
creases the consumption of hydrogen peroxide and is
thus less attractive.
2. Steel Pickling Solutions
Steel pickling solutions based on sulfuric acid are
amenable to regeneration by crystallization and contin-
uous removal of the accumulating iron content very simi-
lar to the process as described for copper cleaning.
Increased pickling rate and iron solubility is gained by the
operation of the pickling system at 140 - 160° F and at
the same time the continuous removal of the accumulat-
ing iron content is made simple by cooling a relatively
low volume of recirculated acid, dropping the tempera-
ture by 20 - 30 degrees.
This process has been in use for many years, but
mainly by the primary steel manufacturers. The recovery
systems were designed for the batch treatment or con-
tinuous removal of large volumes of acid and iron crys-
tals. With the development of simple, small-scale crystal-
lizers, this process should be attractive for the metal
finishing plants in a more general sense. Sludge handling
and disposal costs have markedly changed prior assump-
tions regarding economy, the accumulating iron crystals
can be sold most often locally, since many municipal
sanitary treatment plants use iron salts for tertiary treat-
ment and sludge conditioning.
3. Electrodialysis Systems for the Regeneration of
Chromic-Acid-Based Processing Solutions
a. Before plastic parts are plated with a metallic
coating, the surface is etched to promote adhesion. The
typical etch solution contains 200-400 g/1 chromic acid
and 20 - 30% sulfuric acid. It is very viscous, creating a
thick dragout film, and resulting in dragout losses six to
ten times greater than for most other metal finishing pro-
cess baths. The dragout losses are not normally recovered
because it is assumed that the breakdown products of the
dissolved organic materials from the plastic will accumu-
late. Most of the processing baths are maintained by
chemical additions to replenish the heavy dragout losses,
thus allowing an equilibrium to be established where
impurity accumulation is balanced by dragout. Electro-
dialysis of recovered dragout reoxidizes the triyalent
chromium to the hexavalent form, greatly reducing the
required chemical additions.
b. Current efficiency and the quality of the electro-
deposit are both impaired in hard chromium plating if
metallic contamination exceedsS-lOg/lofiron or 10- 12
g/1 of copper. The hard chrome baths gain in these
impurities at a rate which depends on the type of parts
handled and the etching process used before plating.
Usually dragout losses are very low, so that bath must
be purposely wasted to maintain the desired equilibrium.
After many years of development work which has been
hampered by the low iron and copper limits which must
be maintained, we feel that electrodialysis has the
potential to eliminate purposeful wastage of the plating
bath9. This is particularly significant since the sludge
generation is disproportionately high forthe low levels of
metallic contamination due to the chromic acid concen-
tration in the plating bath.
4. Zinc Phosphate Solution Maintenance by Gravity
Settling
Phosphating solutions generate an iron phosphate
precipitate during operation. The precipitated iron phos-
phate tends to clump together and accumulate as a heavy
sludge on the bottom of the tank, or as a scale on the
heat exchanger coils. Continuous recirculation of the
solution from the processing tank to a settling tank
avoids the accumulation of sludge or scale by providing
favorable conditions for the iron precipitates to agglo-
merate and settle in the auxiliary vessel. The need for
periodically dumping the processing solution to be able
to clean out the tank or the heat exchangers can be elim-
inated, and the life of the processing solution perpe-
tuated.
5. Electrolytic Maintenance of Chelated Scale and
Smut Removal Baths
In many plants, highly-stressed steel parts are cleaned
112
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after heat treatment with an electrolytic cleaning bath
containing high concentrations of chelating agents,
and sometimes also cyanide. The process deteriorates
rapidly as the iron content increases. Continuous, low-
current-density electrolytic iron removal is feasible,
and can be accomplished without large losses in cyanide
content, thus extending the life of the process bath
several times over normal expectancy10.
6. Recovery of Nitric Acid and Molybdenum in Light
Bulb Manufacturing
In manufacturing incandescent light bulbs, tungsten
filaments are wound around a molybdenum tube man-
drii. After heat treatment of the filament, the molyb-
denum tube is dissolved in nitric/sulfuric acid, leaving
the wound filament behind. Removal of molybdenum
by precipitation cannot be accomplished except with
high ratios of iron addition to form an iron molybdate
coprecipitation product. The recovery of molybdenum
from this sludge is impaired by the reduced value of the
mixed metallic sludge.
Distilling off the nitric acid from the nitric-sulfuric
acid dissolution bath allows recovery of nitric acid at a
sufficient concentration to be used in the make-up of a
new bath. The sulfuric acid remaining after distillation is
highly concentrated and contains a sludgey precipitate of
molybdenum tri-oxide. After solid-liquid separation, the
sulfuric acid can be reused in reconstituting a new bath
by combination with the nitric acid distillate. The pure
molybdenum oxide is sold to a refiner and ultimately
recycled to the manufacturer of the molybdenum tubing.
7. Recovery of Metals from Stripping Solutions
There are many large-scale industrial recovery sys-
tems in operation for the purpose of metal recovery from
waste materials, purification of scrap, etc. A number of
them are mentioned here to indicate the variety of pro-
cessing methods that are available.
a. Tin is stripped from metal can scrap with a caus-
tic soda solution. The tin is recovered by crystallization of
sodium stannate or electrolytically recovered as the
metal.
b. We have developed a stripping process1' for cop-
per wire scrap, removing the tin with a sulfuric acid-
copper sulfate strip solution, and precipitating the tin
oxide in a purity suitable for the metal refinery. The
copper scrap requires only remelting to prepare ingots for
rolling into wire rod.
c. Cyanide-type silver stripping solutions can be
operated with a continuous electrolytic recovery system
that provides a salable silver foil.
d. A cyanide-type nickel strip solution allows the
simultaneous recovery of a low-purity cathode deposit of
nickel, while the cyanide content of the spent strip
solution is economically oxidized.
e. Electrolytic nickel stripping solutions of sulfate
or nitrate basis can be operated at saturation level insofar
as nickel concentration is concerned. The nickel, as it is
solubilized at the anode, becomes insoluble in the
solution and precipitates as nickel oxide. These types of
solution do not require dumping and the nickel oxide can
be removed as a heavy sludge from the stripping system12.
f. Cadmium can be recovered at sufficient purity
from an ammonium nitrate type stripping solution by
cementation on aluminum powder. The recovered
sponge is sold to the refinery.
The examples are enumerated mainly to show the
varied technology that is available and could be poten-
tially considered for the particular process at hand. It is
hoped that the chemical suppliers of the various stripping
process solutions will provide metal recovery recom-
mendations for their particular process. It can be postu-
lated that if such concern and interest is evidenced by the
industry, competition between the suppliers will auto-
matically channel future developments in this direction.
8. Metal Recovery from Sludges
Segregated metal sludges lend themselves to the
installation of simple and economical metal recovery
systems. Experience along these lines has been gained
over many years in working with the integrated treatment
approach which allows segregated collection of the
various metal sludges.
a. Plating solution losses due to filtration and batch
purification operations are significant. The main purpose
of purification and filtration is the removal of organic
contaminants (breakdown products of the various
brighteners, leveling and wetting agents, etc.). An addi-
tional interest may be the removal of accumulating iron
or other metallic impurities, or of suspended dust par-
ticles which are removed in the filtration process. In
nickel plating systems, we have found that the losses due
to purification and filtration may exceed the losses
through dragout. The sludgey remains after batch puri-
fication may amount to a solution layer of 6-8" on the
bottom of the treatment tank. Attempts to reduce the
volume of this layer cause clogging of the filter which is
used to return the solution to the plating tank. Filters
should be drained before blowing down the accumulated
cake, but even under these conditions, significant losses
occur when the filter media is hosed off before a new filter
is built up again. These combined wastes can be neu-
tralized, the metal precipitated as the carbonate or
hydroxide, and the accumulated sludges collected,
washed and reprocessed for recovery. During the wash-
ing stage, the soluble salts and organics are removed.
The sludge contains the precipitated metal and insolu-
bles such as carbon filter aid and metallic fines.
Metal recovery from the sludge can be accomplished
either through dissolution by a recirculated electrolyte,
that is depleted of metal in an electrolytic cell with a
simultaneous decrease in pH (generation of acid). The
dissolution of the metal hydroxide (or carbonate) rees-
tablishes the working pH and the metal content.
A second approach is through dissolution of the
sludge with a heated, dilute acid solution. The free acid
is neutralized by the metal that is going into solution.
The re-dissolution is very rapid if the metal hydroxide
sludge has not been allowed to dry out and therefore
113
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dehydrate13. As an example, with nickel sludge, the free
acid is neutralized to a pH of 3.6-4.0. A dilute acid solu-
tion is made up to provide a saturated nickel sulfate or
nickel chloride solution at room temperature and is recir-
culated through the sludge until the desired final pH has
been reached. Possible iron contamination can be preci-
pitated with hydrogen peroxide additions and filtration
together with the insoluble carbon, filter aid, etc. An
EPA-sponsored demonstration project is in the planning
stages, and it is hoped that both quantitative and
qualitative data, together with accumulated informa-
tion on operating costs, will provide the desired
background as educational input for a process such as
this for the industry at large14.
b. In aluminum anodizing, caustic soda etching, or
aluminum milling processes, significant quantities of
aluminum are dissolved and ultimately discharged as
sludge. If such aluminum-containing baths are kept
segregated from the chromate and smut removal acid
baths (deoxidizers) which are likely in such a plan, the
resultant sludge can be of sufficiently high purity to
generate a salable byproduct. Trace metallic contam-
inants such as iron, zinc, and magnesium are at low
enough concentrations to be acceptable. Assuming that
the sludges have been segregated, and that calcium has
been used for neutralization, the sludge can be dissolved
in a waste sulfuric anodize solution, which has been sup-
plemented by additional sulfuric acid so as to result in an
aluminum sulfate solution which is at or close to satura-
tion at room temperature. This aluminum sulfate con-
centrate is readily salable as a coagulant for sewage treat-
ment or for waste water treatment in pulp and paper or
other industrial operations requiring alum additions.
Summary and Conclusions
There are many techniques available to reduce the
quantity of metal converted to waste sludge. A thorough
trade-off analysis is needed to select the best candidate
for each specific application.
For recovery from rinse waters, return of drag-out,
electrolytic methods or segregated collection of a salable
sludge are demonstrated.
Discarded process baths represent the largest source of
metal sludge generation. Electrolytic deposition, crystal-
lization, precipitation/sedimentation, electrodialysis,
and cementation have all been demonstrated as practical
techniques for regeneration of process baths, allowing
recovery of metal values, reduced treatment chemical
consumption and reduced discharge of soluble salts.
Further progress will be accelerated as the finishing
industry presses its chemical suppliers for process bath
formulations more suited to such regeneration methods.
REFERENCES
1. Lancy, Division of Dart Environment and Services
Company, Survey and Study for the NCWQ, Re-
garding the Technology to Meet Requirements of the
Federal Water Pollution Act for the Metal Finishing
Industry. U. S. Department of Commerce, NTIS
(No. PB 248-808). Springfield, Va. 22151.
2. Anon., Chemical Engineering 29, 30, Dec. 22, 1975.
3. R. Pinner, Metal Finishing Journal, Oct. 1967.
4. H. Silman, Metal Finishing, June, 1971.
5. L. E. Lancy and R. Pinner, Metallurgia, March,
1966.
6. Volco Brass and Copper Co., EPA Res. Report,
Proj. No. 12010 DPF (1971).
7. B. Mottweiler and P. L. Veil, Plating and Surf.
Finishing, 63, 12 (1976).
8. Anon., Chemical Engineering, 66, Jan. 8, 1973.
9. U. S. Pat. 3,481,851.
10. C. D. Simpson and L. E. Lancy, Product Finishing,
Oct., 1967.
11. U.S. Pat. 4,022,638.
12. U. S. Pat. 3,788,958.
13. U. S. Pat. 3,953,306.
14. Huntington Div., Houdaille Industries, Inc. EPA
Demonstration Grant No. 804-434 (1976).
114
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Research on Impoundment Materials
Robert E. Landreth*
INTRODUCTION
Low permeability materials have been utilized to seal
water impoundments and as canal linings for decades.
Their function is to minimize the loss of water by seep-
age. Most of these applications have been very successful
and are still in use today. However, our highly technolo-
gical and urban society has presented us with a new prob-
lem. Vast quantities of industrial and solid wastes are
being disposed of or stored on the land. These disposal
and storage sites, unless properly constructed, have a
potential for pollution of ground and surface waters by
the leachate generated by the wastes. The availability of
naturally occuring acceptable disposal sites is decreasing
because of environmental and economic impact. There-
fore, the use of artificial liners will most likely increase
in order to minimize the environmental stress and to
utilize those sites not acceptable without lining. The use
of artificial liners will necessitate additional site design.
Since liners are part of a leachate collection system provi-
sions must be made to remove the leachate and disposed
of in an acceptable manner, e.g., treatment, recirculation,
discharge to sanitary sewer, etc. The question being asked
now is which type of liner to use and how long it will last.
The Solid and Hazardous Waste Research Division,
Municipal Environmental Research Laboratory, U. S.
Environmental Protection Agency is attempting to
answer these questions via a series of research contracts.
Due to the variety of waste streams and the differences
in liner materials the research approach is to develop
meaningful test data so that the user community can
determine liner compatibility as relates to leachate
attack.
Four research projects have been initiated to develop
a data base from which evaluation criteria or test proto-
col can be established.
State-of-the-Art
A literature search and state-of-the-art survey of those
liner materials being utilized for containment of seven
general types of industrial wastes has been completed (1).
The objective of this study was to assemble data associ-
ated primarily on chemical interactions of waste and
potential liner materials. Physical properties, cost and
•Robert E. Landreth
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, OH 45268
field performance data were also collected for various
membrane types. Potential liner materials considered
were those listed below:
Polymeric membranes
- Polyvinyl chloride (PVC)
- Polyethylene (PE)
- Polypropylene
- Butyl rubber
- Chlorinated polyethylene (CPE)
- Ethylene propylene diene monomer (EPDM)
- Chlorosulfonated polyethylene (Hypalon)
- Neoprene
Admixed Materials
- Asphalt concrete
- Soil cement
- Soil asphalt
- Asphalt emulsion on non-woven fabric (petromat)
Soil Sealants
- Rubber latex
- Bituminous seal coat
Natural Soil Systems
- Soil Bentonite
- Compacted clays
The generic names, applied to the polymeric mem-
branes, may be further subdivided based on formula-
tions. The manufacturers can produce liner materials
better suited for specific applications by adding various
ingredients such as plasticers, resins, fungicides, biocides,
fillers, etc. These added ingredients also influence the cost
and more specifically the physical and chemical pro-
perties of the final product. No attempt was made to
identify specific formulations or to subdivide the broad
general classification. The intent of this project was to
give guidance on which liner materials to consider from a
waste compatibility standpoint and not to specifically
identify liner performance.
The waste streams considered for containment by these
liners were:
Caustic petroleum sludge
Acidic steel-pickling waste
Heavy-metal-bearing electroplating sludge
Toxic pesticide-formulation waste
Oily refinery sludge
Toxic pharmaceutical waste
Wastes from rubber and plastics industries
115
-------
Waste streams were selected based on general industry
studies. The characteristics of these wastes are described
in detail elsewhere (1). In general, these wastes streams
contained wide ranges of biochemical oxygen demand
(BOD5), (TOC), and total suspended solids (TSS). The
data that were available on the waste chemical character-
istics formed the basis for selecting the liner material(s)
most suited to contain the waste for a given situation.
Through the course of the literature review and discus-
sions with manufacturers, fabricators, suppliers, instal-
lers and trade association representatives a matrix of
data was developed on liner-waste compatibility. This
matrix data is presented in Table 1 which is only to be
used as a guide. However, the final liner material selec-
tion is more complicated and requires additional factors
for consideration. For instance the liner material for-
mulations may be changed to upgrade their performance
for a particular waste stream or to change a physical
property such as tensile or color. The sludge/waste iden-
tified in the table may not be chemically similar to the
one in question and additional compatibility test may
have to be performed. The site conditions and many
placement parameters must also be considered before a
best final selection can be made. However, the table is
functional since it will eliminate from consideration
those materials that are not compatible to the waste
stream being considered.
Liners Exposed to Municipal Solid Waste Leachate
Three years ago a project was undertaken to assess
the status of technology regarding liner materials for
sanitary landfills. The objectives of this study were; to
determine the effects of landfill leachate on the physical
properties of a variety of polymeric membranes and
admixed materials; to develop data in predicting the life
of the liner materials exposed to leachate; and to develop
economic data on the liner materials and associated con-
struction costs. The initial project was to have exposure
periods of 12 and 24 months. Those polymeric (flexible)
and admixed liner materials considered are listed below:
Polymeric membranes
- Polyvinyl chloride (PVC)
- Polyethylene (PE)
- Butyl rubber
- Chlorinated polyethylene (CPE)
- Ethylene propylene diene monomer (EPDM)
- Chlorosulfonated polyethylene (Hypalon)
Admixed materials
- Hydraulic asphalt concrete
- Paving asphalt concrete
COMPATIBILITY OF LINER MATERIALS WITH VARIOUS INDUSTRIAL WASTES
Name of liner
Polymeric Membranes
Butyl rubber
Chlorinated poly-
ethylene
Chlorosulfonated
polyethylene
Elastici/ed polyolefin
Etnylene propylene
rubber
Neoprene rubber
Polyethylene
Polypropylene
Polyvinyl chloride
Admix Materials
Asphalt concrete -
hydraulic
Asphalt membrane
Soil asphalt
Soil cement
Compacted clay
Treated bentonite
Short
name
1IR
CPE
CSM
Hypalon
3110
EPDM
CR
PE
PP
PVC
HAC
-
-
-
-
-
Vulcan-
ized
Yes
\o
No
No
Yes
Yes
No
No
No
-
-
-
-
-
-
Caustic
petroleum
sludge
Yes
Yes
Yes
•»
Yes
Yes
Yes
Yes
'.'
Yes
?
?
Yes
No
No
Acidic
steel pick-
ling waste
Yes
?
Yes
•>
Yes
?
?
?
'.'
No
'.'
No
No
No
No
Electro-
plating
sludge
Yes
?
Yes
Yes
Yes
?
Yes
Yes
?
No
'.'
No
?
No
No
Toxic pes-
ticide for-
mulation
waste
•>
?
•9
Yes
?
?
Yes
Yes
Yes
•t
?
?
•>
?
'*
Oil refi-
nery sludge
No
No
No
-..
No
?
Yes
Yes
Yes
No
No
No
Yes
Yes
Yes
Waste
water from
Toxic phar- rubber and
maceuti- plastics
cal waste industry
? '.'
^ •> •>
? Yes
Yes Yes
? Yes
? Yes
Yes Yes
Yes Yes
Yes Yes
'.' '.'
? ?
? \<>
•'. Yes
? Yes
'.' Yes
' Chemical compatibility of lining materials with various industrial wastes. Indicates the potential suitability of a given type of lining material for confining types ol wastes.
Kor a given type of lining material compositions vary considerably as do the composition and concentration of the waste and environmental conditions under which they
would be confined.
"Yes" = Lining material is probably suitable for confining a wide range of wastes of the type indicated, using a wide range of formulations.
"T = Questionable. Suitability depends on the specific waste and the specific liner material. Immersion tests should be run.
"No" = I he lining material would not or i>mhahl\- mil be suitable lor confining the type of waste shown.
Sec attached.
116
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- Soil asphalt
- Soil cement
The test specimen of polymeric materials were com-
mercially available and contained a seam either made by
the supplier or a seam made in accordance with the man-
ufacturer's recommendation. The test specimen of
admixed materials were formed-in-place in accordance
with the recommended procedure. In addition, 42 other
polymeric liner specimens were placed in the exposure
cells. These materials represented duplicate generic types
of liner materials but from different manufacturers, rep-
presenting different formulations and thicknesses.
The liner materials were mounted at the base of simu-
lated landfill cell lysimeters to better duplicate field
conditions and allow for microbial action. Shredded
municipal refuse was placed in the lysimeters and water
was added on a regular basis to generate the leachate. A
measured amount of water was added on a scheduled
basis to maintain the quality of leachate which was
consistant throughout the lysimeter cells and was
"typical" of that found in actual landfills.
Results of the first 12-month's exposure produced only
minor changes on the physical properties of the liner
materials (2). With the exception of polyethylene and
ethylene propylene diene monomer, all liner material
had small losses in tensile strength. The elongation at the
break increased in all cases; the modulus or stiffness
generally decreased except for polyethylene, ethylene
propylene diene monomer and Butyl rubber in which
case it remained essentially unchanged. The heat sealed
seam retained their strength the best while some major
losses were observed in other seaming techniques. In all
cases, the liner material softened. None of the polymeric
materials allowed leachate to pass during the first year
of exposure although leakage was observed through the
soil asphalt concrete liner materials.
One indication of liner material permeability is the
absorption of leachate by the liner material. Absorption
for both water and leachate was determined. The results
indicated that absorption was a function of the dissolved
solids content of the leachate, both inorganic and
organic. A similar swelling was observed for both water
and leachate immersion in those liner materials charac-
terized as having a high hydrocarbon structure. In chlro-
inated materials such as chlorinated polyethylene,
chlorsulfonated polyethylene and neoprene, a substantial
amount of water absorption was observed. Polyvinyl
chloride had a relative low value for water absorption but
a significant value for landfill leachate.
In view of the relatively small changes to the liner
materials after 12-months exposure it was decided to
extend the 24-month exposure period to 42 months. It is
hoped that this will provide sufficient changes to esta-
blish long-term trends to predict the service life of the
materials.
Liners Exposed to Industrial
Hazardous Sludge Leachates
Increased concern over the pollution potential of
industrial wastes has resulted in a project of exposing
liner materials to industrial wastes. This study will also
provide more detail to the liner-waste compatibility
matrix as presented in Table I.
The objectives of this study are: to determine the
effects of selected liner materials by exposing them to a
variety of industrial wastes over an extended period of
time; to estimate the effective life of the liner materials;
to determine the cost effectiveness of liner materials; and
to develop a test protocol for user community accep-
tance. The project was to have 12 and 24-month exposure
periods. Those liner materials considered for this pro-
ject are listed below:
Polymeric Membranes
- Polyvinyl chloride (PVC)
•- Butyl rubber
- Chlorinated polyethylene (CPE)
- Ethylene propylene diene monomer (EPDM)
- Chlorosulfonated polyethylene (Hypalan)
- Neoprene
- Elasticized polyolefin (3110)
- Polyester elastomer (experimental)
Admixed
- Hydraulic asphalt concrete
- Soil cement with and without surface seal
- Asphalt emulsion on nonwoven fabric (petromat)
- Modified bentonite and sand
- Compacted native fine-grade soil
As with the municipal solid waste leachate study, the
polymeric material test specimens were commercially
available samples which contained factory supplied
seams or seams which were made in accordance with
recommended procedures. The admixed material test
specimens were formed in place according to recom-
mended procedures. Larger liner material specimens (4
feet square) were draped in open tanks with sloping sides.
These large specimens are being exposed to attack from
both the weather and selected waste leachates. A very
critical area in a lined waste pond was the waste/air
interface and specifically the folds in the membrane that
could occur at this interface. The test tanks with sloping
side walls were designed specifically to investigate
this problem. A more detailed description of the experi-
mental set-up has been published (3). In addition to the
primary exposure cells, small liner material specimens
(6" x 6*0 were placed on racks located outdoors for expo-
sure to the elements.
Waste samples were obtained from actual industrial
wastes streams. The general classes of waste are:
• Strong acid
• Strong base
• Wastes of saturated and unsaturated oils
• Lead wastes from gasoline tanks
• Oil refinery tank bottom waste (aromatic oil)
• Pesticide waste
117
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DESCRIPTION OF
INDUSTRIAL WASTE STREAMS
Caustic Petroleum Sludge
Form of waste: Aqueous solution, wash water, spent
caustic.
Industrial source: Petroleum refineries, from 5.7 wt.
% caustic solutions.
Process operations: Used in washing, sweetening,
neutralization, hydrofining, hydrocracking, hydro-
saturator, LTG treating, etc.
Composition: Wastes are 6.2 - 7.2% solids, of which
40 - 50% is caustic.
Pollutants: NaOH, salts.
Components aggressive to linings: Water, high pH,
and high ion concentration.
Oil Refinery Sludge
Form of waste: Oily solids consisting of fine particles
generally suspended in aqueous streams.
Industrial source: Petroleum refineries.
Process operations: Sludge from clarified once-
through cooling water, exchange bundle clearing
sludge, slop oil emulsion solids, cooling tower sludge,
APR/Primary clarifier- separator bottom, dissolved
air flotation float, kerosene filter clays, lube oil filter
clays, waste biosludge, coke fines, silt from storm
water run off, leaded tank bottoms, nonleaded pro-
duct tank bottoms, neutralized HF alkylation sludge
(CAF2), crude tank bottoms, spent lime from boiler
feedwater treatment, fluid catalytic cracker catalyst
fines.
Composition: Oil, water, sand and silt plus some
heavy metals, organics, and corrosion-erosion pro-
ducts resulting from factory operations; range of oil
content: less than 1 to 82 wt.%
Pollutants: Heavy metals, phenols, cyanide.
Components aggressive to linings: Water, oils, orga-
nic chemicals, ions.
Acidic Steel Pickling Wastes
Form of waste: Acidic aqueous solutions from pick-
ling lines, pickling line scrubber discharge and pickler
tank overflow.
Industrial source: Steel.
Process operations: Steel milling to remove scale.
Composition: Low pH, 1.6-3.1; total solids, 400,000
parts from the tank overflow.
Pollutants: Low pH and high iron in water soluble
form.
Components aggressive to linings: Water, low pH.
Heavy Metal-Bearing Electroplating Sludge
Form of waste: Primarily aqueous metal salt solu-
tions, but also sludges, filter cokes, and regenerants
from ion exchange.
Industrial source: Plating industry that applied elec-
trical coatings on surfaces by electrodeposition.
Process operations: Electrodeposition.
Composition: Chromium-bearing wastes, which
include chromium, nickel, and copper, and two cya-
nide-bearing wastes, which include cyanide, copper,
zinc and cadmium.
Pollutants: Chromium, nickel, copper, cyanide, zinc,
and cadmium^
Components aggressive to linings: Water, high ion
concentration.
Toxic Pesticide Formulation Waste
Form of waste: Aqueous base containing suspended
and dissolved solids, e.g. clay.
Industrial source: Pesticide manufacture.
Process operations: Wash water from equipment
clean-up, including filling equipment, liquid formu-
lation lines, pumping systems, scales, spills, drum
washing, air pollution control devices.
Composition: Pesticides, inerts, such as clay, and dis-
solved organics.
Pollutants: Pesticides.
Components aggressive to linings: Water and dis-
solved organics.
Toxic Pharmaceutical Waste
Form of waste: Mostly wash water from product
washings, extraction and concentration by-products,
and equipment wash-down.
Industrial source: Pharmaceutical.
Process operations: Chemical synthesis and fermen-
tation processes, formulation processes, and re-
search.
Composition: These wastes are characterized general-
ly by biochemical oxygen demand, chemical oxygen
demand, total suspended solids, and solids.
Pollutants: Many metals, cyanide, and anti-bacterial
constituents.
Waste Water From Rubber and Plastics Industry
(Not Solid Wastes)
Form of waste: Aqueous solutions with some suspen-
ded solids.
Industrial source:
Plastics industry: Producers of epoxies, melamines,
ureas, and phenolics.
118
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Rubber industry: Tire and tube industry and the
synthetic rubber industry.
Process operations:
Plastics industry: Process waste streams.
Rubber industry: Solutions from the manufac-
turing processes; wash down of processing areas;
run-off from raw material storage areas; spills and
leakages of cooling water; steam and processing
solutions, and organic solvents and lubricating oils.
Composition:
Plastics industry: Alkalinity, oils and greases,
numerous organic chemicals in aqeous solutions.
Rubber industry: Waste water containing oils, sus-
pended solids at various pH's and dissolved orga-
nics.
Pollutants:
Plastics industry: Many heavy metals and organic
chemicals.
Rubber industry: Oil, grease, dissolved solids, and
solvents.
Components aggressive to linings: Water, oils, dis-
solved organic solvents and chemicals, and metal ions.
A limited bench-scale study was conducted prior to
loading of the long-term exposure cells. This study was
used to screen out those liner/waste combinations that
would most likely fail during the long-term exposure
periods. The study did produce results that were bene-
ficial. For example, it was found that oily wastes could
not be safely contained with asphalt liners, oil wastes with
aromatic components may present problems for poly-
meric membranes except whose membranes that are
crystalline. It was also found that bentonite liners,
polymer modified bentonite and soils may not be suit-
able for containing strong wastes containing both an
aqueous phase and an oily phase. These waste streams
may present a special problem because of the need of
the liner material to resist simultaneously two fluids
which are inherently different in their chemical reac-
tion with the liner materials. The bench study not only
produced preliminary results of liner/waste compatibi-
lity, but indicated the need for preliminary exposure tests
prior to initiating long-term testing.
The results of the first year's exposure are not available
at the writing of this paper. These results should be avail-
able early in calendar year 1978.
Liner Materials Exposed to Flue Gas Cleaning Sludges
A program was initiated to investigate the chemical
reactivity of various liner materials exposed to wastes
from the power industry. The project objectives were
to determine the compatibility of the wastes with poly-
meric, admixed and sprayed on liner materials; to deter-
mine the effective life of the liner materials; and to obtain
economic data on materials, placement and construction.
The project had exposure periods of 12 and 24-months.
Those materials selected for inclusion in this study are
listed below:
Polymeric Membranes
- Elasticized polyolefin (3110)
- Neoprene coated nylon
Admixed Materials
- Cement Type I
- Hydrated lime
- Cement with lime
- Polymer benonite blend
- Guartec (UF) (organic filter for food preparation)
- Paving asphalt concrete
- TACSS (several different component mixes)
(petroleum type product)
Sprayed-on
- Polyvinyl acetate (2 types)
- Natural rubber latex (2 types)
- Asphalt cement
- Molten sulfur
These materials are commercially available and were
placed in the test cells in accordance with the manufac-
turer's recommended procedures.
The waste streams utilized were the flue gas cleaning
sludges from coal fired power plants using lime and lime-
stone scrubbing systems. To simulate actual field dis-
posal situations, the exposure test cells were pressurized
to 20 psi to represent a static head of 30 feet of waste
sludge. The pressure was applied in increments of 2 psi
per month for a period of 10 months.
The test cell construction data and first 12-month
exposured data are now being assembled. These results
should be available in early 1978.
Survey of In-Place Liner Materials
Field verification studies for determining liner mater-
ial performance requires a substantial input of research
dollars and time in order to obtain a long-term base. The
ideal field verification study should include 20 liner
materials; 20 waste streams; exposure periods up to 5
years; and be located at 4 different geographic loca-
tions. Since this type of study is not feasible, based on a
limited budget and time constraints, an alternative study
has been selected. The approach to this study is to con-
duct a survey to identify disposal sites where liner materi-
als have been installed. The survey would obtain infor-
mation relating to waste type, waste depth, waste age,
type of liner material, owner, installer and other pertinent
data on the disposal site. These data are being evaluated
to determine if samples of liner materials could be ob-
tained intack from sites of varying ages, then a long-term
field exposure data base for liner performance could be
developed in a relatively short period of time with mini-
mal dollars.
The results (5) of the liner material survey were sepa-
rated into municipal solid waste disposal sites and
selected industrial surface impoundments. Sixty-one
municipal solid waste disposal sites were identified. Of
these sites, 34 used clay soil as a liner when it was installed
and compacted at the base or perimeter of the disposal
119
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site. Sixteen sites used polyvinylchloride as a liner mater-
ial and eight sites used asphaltic type material, either
sprayed or rolled, as a liner material. The remaining
three sites used ethylene propylene diene monomer,
chlorinated polyethylene and butyl rubber.
Only a limited number of industrial waste disposal sites
were surveyed. A wide variety of liner materials consist-
ing of chlorosulfonated polyethylene (Hypalon), neo-
prene, chlorinated polyethylene, polyethylene, concrete,
clay and asphalt were being utilized. At most sites, the
waste composition could only be classified in broad
general terms. Chlorosulfonated polyethylene (Hypalon)
was the most commonly used liner material of those
industrial sites surveyed. Hypalon has been used at liquid
and semi-liquid waste disposal sites for the pulp and
paper industry and for organic and inorganic wastes,
PVC resins and latex, coal and other power plant wastes,
alkaline waste, acid-iron sulfate waste, oil and waste
water, battery manufacturing waste and fertilizer waste
water. Polyvinyl chloride (PVC) has been used as a liner
material by the fertilizer industry to contain lime and
fluoride waste and as a general chemical waste pond
lining. Ethylene propylene diene monomer (EPDM) has
been used for acid wastes, organic wastes, mercury cell
production waste and power plant waste.
One disposal site containing fertilizer waste used
hypalon on the sides and PVC on the bottom. This com-
bination offered economy as well as resistance to wea-
thering at the air/liquid interface. It may also present
some problems at the Hypalon/PVC interface as seam-
ing or joining the two materials may present problems.
Future Activities
The need for information and data on the successful
methods for site preparation and actual liner placement is
becoming more apparent. Known failures with pond
linings can be traced to poor liner selection, impro-
per site design, and placement of the liner under adverse
weather conditions. The research results to date strongly
suggest the need for waste-liner compatibility testing
before the final liner selection. However, the fact that
the liner and waste are compatible only solves half the
problem. The design must take site factors into account
before the job can be completed. As a minimum the liner
design should be based on the following information.
• Waste type and characterization to include pH;
temperature (inlet); flow rate; % solids; aeration
requirements; and particle size of solids.
• Job site location including temperature both high
and low; wind velocity; potential for hail (with
size); proximity of groundwater; type of soil at site
(% sand, % clay, % silt); amount of traffic and type;
access to site by animals (with type); vegetation.
• Pond requirements including size (length, width,
depth and ratio); degree of compaction on the in-
situ soils; number of inlets or outlets with size; type
of vegetation; must liner be attached to concrete;
number, size, and type of stanchions. It would be
very desirable to include a sketch of the pond espe-.
cially it it is irregular in shape.
• Time requirements such as bid date including bid
specification, type of installer preferred; time
allotted for installation, labor requirements (union,
non-union, plant including pay rates); proposed
installation date.
• Payment including terms of contract and delivery.
• End user and design and construction engineering
firm (with location and contact numbers).
With the above information a reasonably good selec-
tion of liner materials can be made. A bench-scale test,
using the actual waste with the candidate liner materials
will increase chances for success but may not necessarily
guarantee it. These bench scale tests should include
samples of both factory and field seams. The physical
properties of the candidate liner materials should be
reviewed before and after exposure to determine any
detrimental changes associated with leachate attack.
When all the above information is obtained and more
then one liner material is considered acceptable then the
economics should probably dictate final selection. Too
many times we consider the economics first without
regard to the technical aspects which results in poor per-
formance of liner materials.
Summary
There are liner materials currently available which
can minimize the potential for groundwater pollution
from landfill leachates. As the requirements for con-
tainment of more complex waste streams increase, new
liner materials will need to be developed to meet those
requirements. The long-term effectiveness of liner
materials to contain a variety of waste streams will
depend upon the correct selection of liner materials, the
use of good engineering practice in the design, construc-
tion and placement of the liner materials, and the oper-
ation of the landfill site.
REFERENCES
1. Steward, W. S. "State-of-the-Art Study of Landfill
Impoundment Techniques" EPA Project R 803585,
May 1975 (To be published)
2. Haxo, H. E., and R. M. White, Second Interim
Report, "Evaluation of Liner Materials Exposed to
Leachate", EPA 600/2-76-255, September 1976
3. Haxo, H. E., and R. S. Haxo, R. M. White, First
Interim Report, "Liner Materials Exposed to Hazar-
dous and Toxic Sludges", EPA 600/2-77-081, June
1977
4. Fry, Z. B. and C. R. Styron, First Interim Report,
"Liner Materials Exposed to Flue Gas Cleaning
Sludges", EPA Project IAG-D5-0785, (To be pub-
lished)
5. Ware, S. A. and G. S. Jackson, "Liners for Sanitary
Landfills and Chemical Hazardous Waste Disposal
Sites", EPA Project 68-03-2460-4, November 1977
(To be published)
120
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Control of Pollution from Leachates
P. Chan, J. Liskowitz, A. J. Pema, R. Trattner and M. Sheih*
ABSTRACT
A laboratory evaluation of the natural sorbents, vermiculite, illite, kaolinite, acidic and
basic fly ashes, and zeolite is presented for the removal of cations, onions and organics under
flowing conditions from an acidic petroleum sludge leachate, a neutral calcium fluoride sludge
leachate, and an alkaline metal finishing sludge leachate. Activated alumina and activated
carbon are involved in this study for comparison purposes since these materials are commonly
used for the treatment of industrial waste streams.
The results indicate that rather than a single sorbent, a combination of acidic and basic
sorbents (which induce acidic and alkaline conditions repectively into the leachate) is required
in a layered system for the removal of all the measurable contaminants present in the leachates.
These are illite, vermiculite and zeolite for the acidic leachate, illite, acidic fly ash and zeolite for
the neutral leachate and illite, kaolinite and zeolite for the alkaline leachate based upon a
comparison of their sorbent capacity (total amount of specific cations, onions or organics
removed by a gram of each sorbent). The sorbent capacities exhibited by the natural sorbents
for the removal of the cations, onions and organics in the leachates are comparable to those
exhibited by the refined sorbents.
pH control of the leachates by combined use of the acidic and basic sorbents is essential for
effective treatment. The removal of the onions in the leachates are favored by acidic conditions,
the cations by basic conditions and the organics either by acidic or basic conditions.
The effectiveness of the sorbents in treating a desired volume of leachate is shown to be
dependent upon the leachate velocity through sorbents and sorbent capacity. The leachate
velocity defines the extent of removal of specific contaminant by the sorbent. The sorbent
capacity whose magnitude is influenced by pH and concentrations of contaminants in the
leachate defines the amount of sorbent required.
INTRODUCTION
The purpose of most waste treatment processes is to
convert the pollutants into a gas, such as carbon dioxide,
or into a solid which can be readily removed from the
waste streams. In the latter instance, the end product is a
sludge which must be disposed of in an environmentally
acceptable manner. At the present time, ocean dumping
and landfills are two methods being utilized for the
disposal of this sludge. However, ocean dumping is to be
banned by congressional action in 1981; thus, landfills
will be the remaining receptacle for these sludges.
The disposal of sludges in landfills can lead to heavy
metal, toxic anions and organic contamination of
surface- and groundwaters from leachate which results
from groundwater seepage or rainwater filtration
through these sludges. In general, this contamination can
be minimized by one of the following treatments:
a) Chemical fixation of the sludge (to prevent
contamination of the leachate). This method applies
*P. Chan, J. Liskowitz, A. J. Perna, R. Trattner and M. Sheih
Environmental Instrumentation Systems Laboratory
New Jersey Institute of Technology, Newark. NJ 07102
physico-chemical principles to fix, or stabilize, the
contaminants in the sludge so that they would not leach
to its environment. While the concept of this approach is
most desirable, it is expensive and leads to a significant
increase in the volume of material that must be disposed
of.
b) Selective location of landfill site. In this method the
landfill is located at adequate distances fr.om surface or
groundwater so that the natural clay components in the
soil will attenuate the pollutants in the leachate. The cost
of this method may be the most inexpensive in certain
cases, but adequate sites are becoming scarce.
c) Lining the landfill site. This method consists of
lining the landfill with an impermeable membrane
thereby collecting the leachate resulting from rainwater
filtration through the sludge, then treating it with con-
ventional physical-chemical methods such as activated
carbon and alumina. While this approach is widely used,
it is expensive because the cost of these refined sorbents
require regeneration facilities. This expense can be
overcome if inexpensive sorbents such as clays in
combination with fly ash can be used to treat the leachate.
121
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The latter treatment method, in essence, simulates
what mother nature does but in a controlled manner.
Further, it is appropriate for sandy areas where little
attenuation of the contaminants in the leachate can be
achieved.
This investigation has been concerned with the latter
treatment. It consists of (1) defining the clay-fly ash
combinations which are most effective in removing the
heavy metals, toxic anions, and organics present in
leachates originating from industrial sludges, (2)
examining the effect of such factors as pH of the leachate
and velocity of leachate through the sorbent in removing
the contaminants, and (3) establishing a design approach
for this treatment.
The sludges used in this study were a calcium fluoride
sludge of the type generated by the electronics and
aircraft industries, a metal finishing sludge, and a
petroleum sludge. These sludges were selected because
their annual production is of significant magnitude to
present disposal problems. The leachate from these
sludges exhibited pHs that were neutral, basic and acidic,
respectively. Also, it was anticipated that their leachates
would contain a cross section of heavy metal hydroxides,
anions such as cyanide and fluoride, and organics.
The sorbents selected for this study were acidic and
basic fly ashes, vermiculite, illite, kaolinite, and zeolite
(natural). The refined sorbents, activated alumina and
activated carbon, which are presently used for the
removal of cations, anions and organics in industrial
waste streams were included in this study for comparison
purposes.
EXPERIMENTAL
The preparation of the industrial sludge leachates and
the analytical procedures utilized in this study are
discussed in the final report (I) submitted to EPA
covering the first phase of this study.
Laboratory Lysimeter Studies
Laboratory lysimeter studies were conducted using 500
g of each sorbent material. Since "pure" clay lysimeters
did not exhibit adequate permeability characteristics,
illite, kaolinite, vermiculite and zeolite were prepared as a
mixture consisting of 80 percent inert Ottawa sand and 20
percent clay. This ration was arrived at after a series of
studies established that this would permit adequate flows
of leachate through these sorbents.
Lysimeters used in the laboratory were constructed of
plexiglass tubing (6.2 cm i.d.; 0.6 cm wall thickness; 90 cm
length), supported in a vertical position. The laboratory
arrangement of the lysimeters are shown in Figure 1. A
164 micron pore size corundum disc (6.10 cm diameter;
Fig. 1—Laboratory Arrangement of Lysimeters.
122
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0.6 cm thickness) was placed in each column, directly
over the drain hole in order to prevent clogging of the
outlet and also to support the sorbent material. The
column was packed with the preweighted sorbent,
placing 3 to 4 cm of Ottawa sand below and above the
sorbent to prevent disturbing the geometry of the sorbent
column during addition of leachate or water. The packed
column was then slowly wetted with leachate to allow
total saturation and to force all entrapped air in the soil
voids out of the column packing. After a saturation
period of at least 24 hours, the column was then filled
with leachate to the level of an overflow drain, which had
been tapped into the top side of the column, in order to
maintain a constant head condition. Leachate was fed to
the top of the column through a valved manifold which
distributed the leachate to ten lysimeters, simultaneously,
from a central reservoir. The central reservoir, a 100 liter
polyethylene carboy, delivered the leachate to the
manifold system by means of a gravity syphon feed
arrangement. Any overflow from the constant head
drains was collected and pumped back up to the central
reservoir. All tubing in the system was made of Tygon
tubing (3/8" i.d.). A constant hydraulic head was
maintained in the lysimeters at all times and the volume
of leachate passing through the columns was continu-
ously monitored. Samples of leachate effluent were
analyzed at predetermined intervals for pH and the
concentration of all measurable constituents remaining
in the effluent. This was continued until breakthrough for
all measurable contaminants had occurred or excessively
low permeabilities were encountered. Breakthrough was
defined as that condition when the concentration of the
species of concern in the collected effluent sample
approached or exceeded that in the influent. After
breakthrough was achieved, water was continually
passed through the sorbent bed until the cations, anions
and organics removed by the sorbents were below
measurable levels in the effluent. The sorbent capacity
exhibited by each sorbent represents the total amount of
specific cation, anion or organic retained by the sorbent.
Results and Discussion
Leachate from the calcium fluoride sludge, metal
finishing sludge and petroleum sludge, prepared and
analyzed (see Table 1) according to procedures described
in an earlier report (1) were passed through individual
lysimeters that contained one of the following sorbents;
acidic fly ash, basic fly ash, zeolite, vermiculite, illite,
kaolinite, activated alumina and activated carbon. The
volume of effluent from each of these lysimeters were
monitored and samples of these effluents were
analyzed for pH, calcium, copper, magnesium, zinc,
nickel, cadmium, chromium, lead, fluoride, total cyanide
and organics. This monitoring and analysis was carried
through repeated washings of the sorbents after
breakthrough of the leachate had occurred until no
measurable contaminants appeared in the wash effluent.
TABLE 1
NATURAL SORBENTS AND THEIR SORBENT CAPACITY FOR REMOVAL
OF SPECIFIC
CONTAMINANTS
Acidic Leachate
Ion (Petroleum
Ca Zeolite
Illite
Kaolinite
Cu Zeolite
Acidic F. A.
Kaolinite
Mg Zeolite
Hike
Basic F. A.
Zn Zeolite
Vermiculite
Basic F. A.
Ni
F Illite
Acidic F. A.
Kaolinite
Total Illite
CN" Vermiculite
Acidic F. A.
COD Vermiculite
Illite
Acidic F. A.
Sludge)
(1390)
(721)
00.5)
(5.2)
(2.4)
(0)
(746)
(110)
(1-7)
(10.8)
(4.5)
(1.7)
(9.3)
(8.7)
(3.5)
(12.1)
(7.6)
(2.7)
(6654)
(4807)
(3818)
1. Bracket represents sorbent capacity (ng of contaminant
IN ACIDIC, NEUTRAL AND BASIC
Neutral
(Calcium
Zeolite
Kaolinite
Illite
Zeolite
Kaolinite
Acidic F. A.
Basic F. A.
Zeolite
Illite
Illite
Kaolinite
Acidic F. A.
Acidic F. A.
Illite
Vermiculite
Leachate
Fluoride)
(5054)
(857)
(0)
(8.2)
(6.7)
(2.1)
(155)
(0)
(0)
(175)
(132)
(102)
(690)
(108)
(0)
LE AC HATES
Basic Leachate
(Metal Finishing
Illite
Zeolite
Kaolinite
Zeolite
Kaolinite
Acidic F, A.
Zeolite
Illite
Basic F. A.
Zeolite
Illite
Acidic F. A.
Kaolinite
Illite
Acidic F. A.
Illite
Acidic F. A.
Vermiculite
Sludge)
(1280)
(1240)
(733)
(85)
(24)
(13)
(1328)
(1122)
(176)
(13.5)
(5.1)
(3.8)
(2.6)
(2.2)
(0)
(1744)
(1080)
(244)
removed/g of sorbent used).
123
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Fig. 2—Ly si meter Studies of pH in Calcium Fluoride Sludge.
Fig. 3—Lysimeter Studies of pH in Metal Finishing Sludge
Leachate.
A N>
— Leachate pH ' .
O Activated Alumina0 J ,..
A Activated Carbon * Ka°l»>lte
• Fly Ash (Acidic) ° Vermlculite
• Fly Ash (Basic)
0 2 4 6 t 10 12
Fig. 4—Lysimeter Studies of pH In Petroleum Sludge Leachate.
The results of monitoring the pH of the effluent using
the acidic petroleum sludge leachate, neutral calcium
fluoride sludge leachate and basic metal finishing sludge
leachate show that in general the sorbents initially define
the pH of the leachate. Considerable variations are
observed in the pH of the effluents collected initially (see
Figures 2, 3 and 4). However, as the leachate is passed
through the sorbents in the lysimeters, the pH of the
effluent becomes the same as the influent. For example,
the effluent from the illite lysimeter is initially acidic, but
then attains the pH of the influent leachate(see Figures 2,
3 and 4). Thus, the pH at which the removals of the
cations, anions and organics in the industrial sludge
leachates occur is regulated initially by the sorbents and
finally by the leachate.
The pH of the industrial sludge leachate was found to
influence the different sorbent capacities for the removal
of the cations, anions and organics present in these
leachates. A comparison of the three most promising
sorbent capacities for the removal of a specific
constituent in each of the three leachates (see brackets in
Table 1) shows increases in the removals of calcium,
copper and magnesium ions as the pH of the leachate is
increased from acidic conditions to alkaline conditions.
For example, the zeolite, acidic fly ash and kaolinite
sorbent capacities for copper removal are 5.2, 2.4 and 0
respectively in the presence of acidic leachate, but
become 8.2, 2.1 and 6.7 ^ig/gm, respectively in the
presence of neutral leachate.
The reasons for the zero sorbent capacities exhibited
by the illite and zeolite for the calcium and magnesium in
the neutral leachate (see Table 1) is not understood at this
time.
The influence of pH of the leachate on the different
sorbent capacities for the removal of zinc, nickel, iron,
cadmium, chromium and lead could not be established in
this study. Unfortunately, the measurable concentrations
of zinc and nickel were encountered only in the acidic and
basic leachates, respectively, whereas the concentrations
of iron, cadmium, chromium and lead were all below
measurable levels in the three types of leachates
examined (see Table I).
Griffin etal. (2) has also reported similar results. In this
study removals of copper, cadmium and zinc increased as
the pH of the leachate progressed from acidic to alkaline
conditions using only kaolinite and montomorillite.
Maximum removals were obtained at about a pH of 8.
The concentration of the contminants in the leachate
also influence the sorbent capacity. As the concentration
increases, the sorbent capacity also increases. The large
zeolite, acidic fly ash and kaolinite sorbent capacities for
copper (85, 13 and 24 /ug/ g) obtained in the basic leachate
are due both to the influence of pH and the relatively high
concentration of copper ion found in this leachate. The
copper concentration ranges from 0.43 - 0.53 mg/1 in this
leachate as compared to the acidic and neutral leachates
(see Table 2). This influence of concentration on the
sorbent capacities is also seen for the other cations and
the fluoride anion. The highest concentrations of calcium
and fluoride are both encountered in the neutral
leachates (see Table 2). The zeolite sorbent capacity for
calcium in the neutral leachate is 5054 ugl gm as opposed
to only 1240 jug/gm in the basic leachate even though
alkaline conditions favor the removal of cations.
Similarly, the illite sorbent capacity for the fluoride is 175
/ug/gm in the neutral leachate as opposed to 9.3 (ug/gm
and 2.2 jug/gm '" the acidic and basic leachates
respectively.
The influence of the concentration of a specific
constituent in the leachate on the sorbent capacities is as
expected. If it is assumed that an equilibrium relationship
exists between the bound and unbound ions in the
124
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leachate, the higher the ion concentration is in the
leachate, the greater the driving force is. As a result,
greater amounts of the ion will be removed from the
leachate in the presence of a given amount of sorbent.
The sorbent capacities for the removal of the fluoride
are also dependent on the pH of the leachate. However,
the influence of pH of the leachate on the removal of this
anion is opposite to that encountered with cations. Here,
sorbent capacities increase as the pH of the leachate
decrease from alkaline to acidic conditions. For example,
the sorbent capacities for illite, acidic fly ash and
kaolinitc arc 2.2, 2.6 and 0 /ig/gm, respectively, for the
removal of fluoride in the basic leachate and increases to
9.3, 8.7 and 3.5, respectively in the acidic leachate (set-
Table 1).
Griffin el al. (2) showed this to be the case for the anion
HASO4 . Maximum removal of this anion was achieved
under acidic conditions around a pH of 6.
The removals of organics also appear to be pH
dependent. The sorbent capacities for the removal of
COD in both acidic and basic leachates are significantly
higher than that achieved with the neutral leachate.
However, a trend in the change of sorbent capacity with
pH is difficult to identify since the concentration of
organics in the acidic leachate is significantly higher than
that measured in the basic leachate (see Table 1). Thus,
both the pH and concentration of the organics influence
the removal of the organics from the acidic leachate.
The pH of the leachate in the lysimeter also influences
the leaching of ions from specific sorbents. When the
leachate in the lysimeter is initially acidic, as indicated by
its effluent pH, the concentration of a specific ion in the
effluent was found to exceed the concentration of this ion
in the influent. However, as the pH of the effluent
approaches the value of 6 and above, the leaching of the
specific ion ceases and, in fact, the sorbent actually begins
to remove the specific ion that was leached from this
sorbent under more acidic conditions. For example, the
copper ion was monitored in the effluent from the
lysimeters containing acidic fly ash and illite using the
acidic, neutral and basic leachates. When the pH of the
sorbent approaches 6, as indicated by the pH of its
Volume of [.palliate Treated, Lite
Fig. 5—Effluent Cu Concentration and pH in Lysimeter (Acidic
Petroleum Sludge Leachate).
effluent, the illite and acidic fly ash either ceases to leach
copper or begins to remove the copper (see Figures 5, 6
and 7). The removal of copper is indicated when its
concentration in the effluent falls below the influent
concentration. This same behavior is observed for the
case of the zinc ion (see Figure 8).
Similar results for fly ash have been recently reported
by Theis and Wirth (3). Here, the average release of the
heavy metals, zinc, copper, nickel, chromium, lead and
cadmium carried out under batch conditions was shown
to be minimal at a pH of 6 and above.
Thus, it is obvious from the above results that regula-
tion of the pH of the leachate is essential for optimum
removal of the anions, cations and organics while
minimi/ing the leaching of specifications from the
sorbents. Initial control of the leachate pH in contact
with the sorbents so that it is slightly acidic will favor the
removal of anions and organics while minimizing the
leaching of specific ions. Further adjustment of the pH of
the leachate so that it is slightly alkaline will favor the
removal of the cations.
The velocity oi the leachate through the sorbent bed in
the lysimeters also was found to influence the removal of
TABLE 2
CONCENTRATIONS OF SPECIFIC CATIONS, ANIONS AND ORGANICS
ENCOUNTERED IN THE ACIDIC (PETROLEUM SLUDGE), NEUTRAL
(CALCIUM FLUORIDE SLUDGE) AND BASIC (METAL FINISHING SLUDGE) LEACHATES
Measured' Pollutant
Ca
Cu
Mg
Ni
Zn
F
Total CN
COD
Acidic Leachate (mg/l)
Neutral Leachate (mg/l)
34-50 180-318
.09-.17 .10-.16
27 - 50 4.8 - 21
below measurable levels
.13- .17
0.95-1.2 6.7-11.6
.20- 1.2
251-340 44-49
Basic Leachate (mg/l)
31-38
.45 - .53
24-26
0.15
below measurable levels
1.2- 1.5
below measurable levels
45 - 50
Fe, Cd, Cr and Pb were analyzed for, but found to be below measurable levels.
125
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Fig. 6—Effluent Cu Concentration and pH Profile In Lyslmeter
(Neutral Calcium Fluoride Sludge Leachate).
Effluent QJ
Effluent oK of Illite
Influent Cone.
Effluent Core, of Illitt
12 14
Fig. 7—Effluent Cu Concentration and pH Profile of Illite In
Lysimeter (Alkaline Metal Finishing Sludge Leachate).
vol'jme of Le
Fig. 8—Effluent Zn Concentration and pH Profile in Lysimeter
(Acidic Petroleum Sludge Leachate).
the cations, anions and organics in the leachates. It does
not effect the total amount of contaminant that can be
removed by a sorbent (sorbent capacity) but it does
define the volume of leachate that can be treated with
maximum removal of the contaminant. For example,
neutral calcium fluoride sludge leachate was passed
through four lysimeters that contained different amounts
of illite to give different leachate velocities. The fluoride
FffLuent Volume
Fig. 9—Effect of Leachate Velocity on the Removal of Fluoride In
Calcium Fluoride Sludge Leachate.
concentration in the effluent was monitored until
breakthrough was achieved.
The results are shown in Figure 9 where the fraction of
fluoride remaining is plotted against the volume of
leachate treated per gram of illite used. Here, it is seen
that as the leachate velocity decreases, the volume of
leachate exhibiting 99 percent fluoride removals,
increases. The sorbent capacities however are not
influenced by the leachate velocity through the sorbent
bed. The different velocities were found to have no signi-
ficant effect on the sorbent capacity exhibited by the illite
for fluoride removals (see Table 3).
An examination of the curves in Figure 8 reveals that
the optimum leachate velocity for treating the largest
volume of leachate with maximum fluoride removal
should be less than 0.042 cm/ min. The curve representing
operation at the optimum leachate velocity should allow
the greatest volume of leachate to be treated with an
almost instantaneous decrease in removal efficiency (or
rise in C / Co to breakthrough) if one compares the curves
obtained for each leachate velocity.
The most effective natural sorbents for the removal of
each cation, anion or organics present in measurable
quantities in the acidic, neutral and basic leachate is listed
in Table 4. There is no single sorbent that can remove all
TABLE 3
Sorbent Capacity Exhibited by Illite
For Removal of Fluoride
At Different Leachate Velocities Through Sorbents
Leachate Velocity
Through the Bed (cm/min)
.140
.138
.079
.042
Sorbent Capacity
HK/K
190
186
179
175
126
-------
the measurable constituents present in the three
leachates. The combination of zeolite, illite and
vermiculite are the most effective for treating the acidic
leachate, zeolite, illite, and the acidic and basic fly ashes
are the most effective for treating the neutral leachate,
and zeolite, illite and kaolinite are the most effective for
treating the basic leachate.
The above various combinations which are effective in
treating one leachate can also be used to treat the other
leachates. However, optimum removal of a specific
constituent for a given weight of sorbent would not be
achieved because the magnitude of the sorbent capacities
are influenced by the pH of the leachate. Thus, a sorbent
such as illite which is the most effective for removing the
fluoride ion in the acidic and neutral leachate could also
be used for removing the fluoride in the basic leachate.
However, it would be less effective than kaolinite (see
Table 1).
The removal capacities exhibited by the most effective
natural sorbents for the removal of the cations, anions
and organics are comparable to the more expensive
refined sorbents activated alumina and activated carbon
in all cases with the exception of the removal of the
fluoride ion in the basic leachate (see Table 4). Here, the
sorbent capacity exhibited by the activated alumina is
some four times that exhibited by the kaolinite.
The above results are significant in that they indicate
that the inexpensive natural sorbents can be utilized in
the same manner and are as effective as the more
expensive activated alumina and activated carbon for the
treatment of leachates from industrial sludges. In
addition, regeneration of these sorbents is not required;
thus the capital investments associated with the
regeneration equipment commonly used with activated
alumina and activated carbon can be avoided.
Unfortunately, the natural sorbents that are effective
for the removal of zinc in the basic leachates and nickel in
the acidic and neutral leachates as well as iron, cadmium,
chromium and lead could not be defined. These ions were
found to be below measurable levels in the leachates
obtained from the industrial sludges selected for this
investigation.
Although the above results show that natural clay-fly
ash combinations are feasible for treating acidic, neutral
and basic industrial sludge leachates, only the
combination that would provide optimum removals of
the cations, anions and organics in calcium fluoride
sludge leachate was further investigated. The most
effective sorbents (zeolite, acidic and basic fly ashes and
illite) were combined in different proportions in a layered
TABLE 4
COMPARISON OF CAPACITIES OF THE MOST EFFECTIVE NATURAL SORBENT
WITH ACTIVATED ALUMINA AND ACTIVATED CARBON
FOR REMOVAL OF SPECIFIC CONTAMINANTS IN ACIDIC, NEUTRAL AND BASIC LEACHATES
Ion
Ca
Cu
Mg
Zn
Ni
F
Total
CN
COD
1. Brackets
Acidic Leachate
(Petroleum Sludge)
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Illite
Act. Al.
Act. Carbon
Illite
Act. Al.
Act. Carbon
Vermiculite
Act. Al.
Act. Carbon
represent sorbent capacity
(1390)'
(200)
(128)
(5.2)
(.35)
(0)
(746)
(107)
(8.6)
(10.8)
(.40)
(I.I)
(9.3)
(3.4)
(1.2)
(12.1)
(0)
(2.4)
(6654)
(411)
(1270)
Neutral Leachate
(Calcium Fluoride)
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Basic F. A.
Act. Al.
Act. Carbon
Illite
Act. Al.
Act. Carbon
Acidic F. A.
Act. Al.
Act. Carbon
(pg of contaminant removed/gram of sorbent
(5054)
(6140)
(357)
(8.2)
(2.9)
(2.0)
(155)
(514)
(3.0)
(175)
(348)
(0)
(690)
(0)
(956)
used).
Basic Leachate
(Metal Finishing Sludge)
Illite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Zeolite
Act. Al.
Act. Carbon
Kaolinite
Act. Al.
Act. Carbon
Illite
Act. Al.
Act. Carbon
(1280)
(737)
(212)
(85)
(6.2)
(16.8)
(1328)
(495)
(188)
(13.5)
(2.3)
(4.7)
(2.6)
(11.4)
(0)
(1744)
(0)
(1476)
127
-------
system to define the optimum arrangement for removal
of the measurable cations, anions and organics present in
this leachate.
The two sorbent combinations selected were: (1) illite,
acidic and basic fly ashes and (2) illite, acidic fly ash and
zeolite. These were placed in lysimeters in a layered
system in the weight ratios of 1:1:1 or 2:2:1 with the illite
being the top layer followed by acidic fly ash and either
basic fly ash or zeolite forming the bottom layer. The
basic fly ash or zeolite was placed at the bottom to
remove the cations such as zinc and copper that are
initially leached from the illite and acidic fly ash during
the period when the leachate is acidic (see Figure 5,
Figure 8). Both the basic fly ash and zeolite show zinc and
copper removal during the initial period when these ions
are leaching from the illite and acidic fly ash.
The sorbent capacities exhibited by the different clay-
fly ash combinations reveal the 2:2:1 ratio of the illite,
acidic fly ash and zeolite to be the most effective for
removing all the measurable contaminants in the calcium
fluoride sludge leachate followed by the 2:2:1 ratio of the
illite, acidic and basic fly ashes combinations with the
exception of total cyanide (see Table 5).
A different calcium fluoride sludge leachate was used
in this portion of the investigation because the volume of
leachate required for this study was greater than the
volume of leachate that remained from the earlier studies.
Analysis of this leachate reveal the presence of
measurable concentrations of total cyanide (see Table 6)
and zinc which could not be measured in the earlier
leachate (see Table 2) even though both sludge leachates
were obtained from the same source but at different
times. Discussions with the plant personnel revealed that
zinc and cyanide were used in several of their processes
during the period that this sludge was collected.
Conclusions
The combination of illite, vermiculite and zeolite, the
combination of illite, acidic fly ash and zeolite, and the
combination of illite, kaolinite and zeolite have been
found to be the most effective in a layered system for
removing the cations, anions and organics in acidic
petroleum sludge leachate, neutral calcium fluoride
sludge leachate and basic metal finishing sludge leachate
respectively. The combinations of natural clay and fly ash
are used because no single sorbents can remove all of the
contaminants present in the industrial sludge leachates
examined. Any of the above combinations can be used to
treat other leachates but they would be as effective as the
selected ones because their removals are pH dependent.
Both pH control of the leachate and the order that the
natural clays and fly ashes are used in a layered bed affect
the removal of the cations, anions and organics in the
industrial sludge leachates. Acidic sorbents such as illite,
kaolinite and acidic fly ash which can initially induce
slightly acidic conditions into the leachate are placed at
the top of the layered system followed by those sorbents
which can induce slightly alkaline conditions in the
leachate. This results in the removal of the anions before
the cations. Slightly acidic conditions (greater than pH 6)
TABLE 5
Removal Capacities' of Combined Sorbents
In Lysimeter for Neutral Calcium
Fluoride Sludge Leachate
Measured
Parame-
ters Description hFa+Fb l+Fa+Fh /+FA+Z
1:1:1 2-2:1 2:2:1
Ca
Mg
Zn
F~
CiT
COD
Sorbent Capacity
Sorbent Capacity
Sorbent Capacity
Sorbent Capacity
Sorbent Capacity
Sorbent Capacity
0
849
5.9
110
1.3
199
0
515
6.1
128
3.9
241
406
866
9.5
J48
1.7
218
Remarks: (I) Sorbent I 'apacities arc expressed in got'contaminant
removal per pram ul .sorhenl used. I - Illite. I u = Fly Ash
(Acidic), hb H> Ash (Basic). / =' /eolite.
(2) C'd. C'r. C'u. I-'e. \i. and Phwereanaly/ed and found
to he below measurable levels.
TABLE 6
Analysis of the Neutral Calcium Fluoride Sludge
Leachate Used for Obtaining Sorbent
Combinations to Provide Optimum Treatment
Measured Pollutant1
Ca
Mg
Zn
F
CN
COD (Organics)
Concentration (mg/1)
119
89
0.31
15.5
0.61
36
I. Cr, Cr, Cu, Fe, Ni and Pb were analyzed for, but found to be
below measurable levels.
and slightly alkaline conditions (less than pH 9) favor the
removal of anions and cations, respectively. Organics are
effectively removed under both acidic and basic
conditions.
Alkaline conditions at the base of the bed are desirable.
This favors the removal of both the cations in the leachate
and the heavy metal cations initially leached from specific
sorbents at leachate conditions below pH of 6. Either
zeolite or basic fly ash was found effective in controlling
this initial leaching of heavy metal ions by the acidic
sorbents.
In the design of a sorbent system, the total amount of a
specific cation, anions or COD that is removed by a
sorbent is indicated by the sorbent capacity. This
property is influenced by pH and the concentration of the
contaminant in the leachate. The volume of leachate that
can be treated with maximum removal is regulated by the
velocity of leachate through the sorbent bed. This
leachate velocity can be controlled by sorbent bed height
varying the amount of inert material added to the clays to
128
-------
regulate their permeability, or varying the particle size of
the sorbents in the bed.
The material costs of the illite-acidic fly ash-zeolite
combination, and illite-acidic fly ash-basic fly ash
combination, in the weight ratios of 2:2:1, required for
the treatment of the leachate from calcium fluoride
sludge during a ten-year period of working the landfill
have been estimated. They are $2.20 per ton of sludge and
$0.62 per ton of sludge, respectively, based upon annual
rainfall of 40 inches, assuming that all the rainfall that
falls upon the landfill becomes leachate. The illite-acidic
fly ash-basic fly ash combination is significantly cheaper
than the illite-acidic fly ash-zeolite combination because
the fly ash is a waste product.
REFERENCES
1. Chan, P., Dresnack, R., Liskowitz, J., Perna, A., and
Trattner, R., "Sorbents for Fluoride, Metal Finishing
and Petroleum Sludge Leachate Contaminant
Control", Final Report, EPA Grant R80371701.
2. Griffin, R., Cartwright, K., Shrimp, N., Steele, S.,
Ruch, R., White, W., Hughes, G., "Attenuation ot
of Pollutants in Municipal Landfill Leachate by Clay
Minerals", Environmental Geology Notes, Part 1,
Part 2, Illinois State Geological Survey, Nov., 1976.
3. Theis, T. L. and Wirth, J. L., Environmental Science
and Technology 11, 1096-1100 (1977).
This research was supported in part by EPA Grant No. R803717-
01 Industrial Environmental Research Laboratory, Cincinnati,
Ohio.
129
-------
The Effectiveness of Fixation Techniques
In Preventing the Loss of Contaminants
From Electroplating Wastes
Philip G. Malone, Richard 8. Mercer & Douglas W. Thompson*
ABSTRACT
A sample of untreated sludge from an electroplating operation and four samples of the
same sludge that had been processed in different ways to prevent the loss of toxic metals were
tested to evaluate the effectiveness affixation processes in preventing the escape of metals. Two
types of tests were employed, a shake or elutriate test and a long-term (approximately two-year
duration! column leaching test. In the elutriate test none of the processes using additives only,
effectively immobilized all the toxic metals studied. AII samples of fixed sludge showed elevated
levels of chromium. The encapsulated sample was not tested in the shake or elutriate test.
Column leach testing demonstrated that a plastic encapsulation system offered the best o verall
containment of toxic metals. Some of the leachate sample from the encapsulated sludge did
show slightly elevated cadmium levels; hut, in general toxic metal levels in leachate were very
low. The fraction of the original chromium and copper lost into the leachate was lowest in the
encapsulation system.
INTRODUCTION
Safe disposal of sludges produced from electroplating
and metal finishing operations have in the past presented
problems with regard to contamination of surrounding
soil and groundwater. Cases where metals, especially
cadmium and chromium, have escaped into groundwater
have been well-documented. Both of these metals are
recognised as toxic to humans even in low concentrations
(I). The maximum allowable concentration of chromium
in drinking water is 0.05 ppm; for cadmium the
maximum level is 0.01 ppm.
At Douglas, Michigan, water from wells on the west
side of town, near a disposal area used by a metal plating
concern, began to turn yellow. Levels of chromate had
reached 10.8 ppm when the wells were removed from
service by the Michigan Department of Health (2). In
another case in Nassau County, New York, plating
wastes were releasing both cadmium and chromium to
the groundwater (3, 4, 5). Chromium concentrations in
groundwater samples reached 49 ppm and cadmium
levels reached 10 ppm. Miller, Deluca and Tessier (5)
reported that at one location in New Jersey a domestic
well near a plating waste lagoon yielded water samples
that contained 150 ppm chromium. Less spectacular
problems have been caused by copper, fluoride, nitrate,
and phenol associated with plating and metal finishing
wastes.
'Philip G Malone, Richard B. Mercer & Douglas W. Thompson
Environmental Engineering Division
USAE Waterways Experiment Station, Vicksburg, MS 39180
The present investigation was undertaken to assess the
usefulness of commercially available fixation techniques
to prevent the loss of contaminants, especially toxic
metals, from plating wastes that are to be landfilled. Parts
of this work have been reported in previous publications
(6, 7, X, 9). The waste material treated here is a sludge
produced by a plating plant waste water treatment
system. The physical and chemical properties of the
samples are summari/ed in fable I and bulk analyses for
metals are presented in Table 2. The waste includes
materials derived from plating, phosphati/ing and metal
cleaning processes. The major wastes contributed by the
plating operations are metal hydroxides produced from
the reduction and precipitation of chromate-based
plating solutions and wastes from the destruction of
cyanide-based plating and rinsing solutions (containing
cadmium, copper, and /inc). X-ray diffraction
examination showed that the principal crystalline phases
present were gypsum (CaS()v2LLO), quart/xand traces
of clay. The metal hydroxides present are not crystalli/ed
and do not appear in X-ray diffraction patterns.
Two types of chemical leaching tests were undertaken
on the raw and fixed sludges to estimate the release of
pollutants to contacting water. In one test procedure, the
raw and fixed sludges were shaken with distilled water
and the contacting water was filtered and analyzed. In the
second procedure the raw and fixed sludges were placed
in 150 cm X 10 cm plexiglas leaching columns and water,
saturated with CO:, was permitted to flow around or
through the sludge for more than two years. The leachate
was collected continuously and aliquots were analyzed at
130
-------
progressively lengthening intervals during the test period.
The data obtained from these tests were used to evaluate
the effectiveness of the fixation procedures in slowing the
loss of contaminants into contacting water.
METHODS AND MATERIALS
Preparation of Fixed Material
All of the fixation procedures used in this investigation
are proprietory; therefore, details on the exact
proportions and exact composition of some of the
additives are not available. The general nature of each
fixation process has been made available by the
processors involved (6). Figure 1 shows the raw and
processed sludge samples.
Process A - This process has been patented and uses
flyash and a specifically prepared, lime-based additive to
produce a pozzolan (concrete-like) material. The sludge
remains alkaline during the entire process. The sludge
was dewatered by settling and approximately 50
kilograms of fixed material was prepared and cast into
7.6 cm X 40 cm cylinders using standard concrete-testing
molds. Process A fixed material was cured under
conditions of controlled humidity for 30 days. The
StUDGE HO.I 200
TABLE 1
SUMMARY OF MAJOR PHYSICAL AND CHEMICAL
PROPERTIES OF ELECTROPLATING WASTE
Sludge '
Raw
Process A
Process B
Process C
Process D
Specific
gravity
2.70
2.49
2.7.1
1.77
I.IK
% Solids
23.00
77.10
54.47
69.8.1
100.00
Coeffi-
cient** of
permea-
bility
(cm /sec)
2.2 x 10"
4.0 X 10 '
I.I X 10'
I.I X 104
--
Slurrv*
pH
7.2
7.5
7.8
5.1
—
— = Not available.
* = From
*' = Data
the elutriate test
from (9).
(8).
PROCESS C
PROCESS D
Figure 1. Examples of raw and fixed electroplating wastes.
finished product contained 25% by weight dry sludge
solids.
Process B - This process is patented and uses two
alkaline additives, one a liquid and one a solid to produce
a soil-like material. The fixed material was cast in a 120
cm X 120 cm X 9 cm block, covered with a polyethylene
sheet and allowed to cure for 12 days. The finished
product contained 90% dry sludge solids by weight.
Process C - Process C is an organic resin solidification
system. Formation of the polymerized resin required that
the residue be acidified. The sludge-resin mixture
polymerized rapidly and no particular time period was
allowed for curing. The finished product contained 67%
dry sludge solids by weight.
Process D - This process is an encapsulation method
using an organic resin to cement the waste into a solid
mass. The solid mass is then inclosed in a 60 mm-thick
layer of plastic. Process D requires dry sludge and special
molding equipment. Cylinders prepared for laboratory
testing were 7.6 cm in diameter and I Ocm in height. Each
cylinder contained 250 grams of dried sludge, the dry
sludge accounted for 50% by weight of the fixed sludge
cylinder.
TABLE 2
BULK ANALYSES OF RAW AND FIXED ELECTROPLATING PLANT SLUDGE
Process
Raw
Process A
Proci-ss 1*
Process C
Process D
Wet weight*
<>i material
(X'») d
12.305
7,385
7.264
6.409
1.252
As
24.0
29.0
13.0
2.6
—
Cd
(nigl kg
687
25.1
407
102
-
Cr
)
-------
Note that the fixation process often results in
considerable dilution of the waste (Table 2). Fixation
may result in an increase, not a decrease, in permeability
(Table 1).
Elutriate Test Procedure
A procedure for a rapid, distilled water shaking or
elutriate test was developed to provide a preliminary
assessment of the effectiveness of fixation. Two hundred
milliliter subsamples of raw sludge were mixed with 800
ml at 2500 rpm for 20 minutes and the centrifugate was
filtered through a 0.45-micron membrane filter. The
fixed sludges, with the exception of samples from process
D, were broken into random-sized pieces and 200 grams
of fixed material was shaken with distilled water using a
procedure identical to that used with the raw sludge. No
attempt was made to run an elutriate test on process D
samples because of their thick encapsulation. All
elutriate tests were conducted in triplicate. The filtrate (or
elutriate) from each was preserved by adding nitric acid
to lower the pH to 2.0. The analytical procedures used
and quality control program for analyses are discussed in
detail in a previously published report (6).
Leaching Procedure
Each raw or fixed sludge was divided into subsamples.
Three large subsamples of approximately 12 kilograms
each were placed in the columns for leach testing. Smaller
subsamples were taken for bulk chemical analyses and
moisture determinations.
Three identical leaching columns were prepared for the
raw sludge and each of the fixed sludges. Data on
leachate from only one set of columns are reported here.
This set was selected for analysis with techniques
allowing very low detection limits. Leachate samples
from the other two sets of column were analyzed using
conventional flame AA methods and the data were used
to confirm the analyses from the set used for low level
measurements. The columns were made from 1.5 meter
lengths of 10.16 cm ID plexiglas tubing (Figure 2). The
bottom of each column was closed with a perforated plate
that allowed the leachate to drain into a 1.27 cm deep
collecting well. The leaching fluid was introduced
through a tube entering the leach column 19 cm from the
top of the column. The tops of the columns were covered
with loose-fitting plastic lids to prevent dust from
entering. The flow of leachate water through each
column was regulated with a teflon stopcock. The bottom
7.5 cm of each column was packed with 60 mm diameter
polypropylene pellets to retard the movement of
paniculate material into the collecting well. Leachate
from each column was collected in a 4.5 liter polyethylene
bottle located below the column.
The raw sludge was placed in the columns directly and
back-flooded with distilled water to remove all air
bubbles. The fixed sludge samples that were not cast into
cylinders (i.e., the samples from Processor B) were
broken into conveniently-handled pieces and placed in
the columns. The fixed sludges that had been cast into
Figure 2. Design of leaching column.
TABLE 3
TECHNIQUES USED IN ANALYSES
Chemical Procedures and/or
species instrumentation*
Limits of
detection
(ppm)
As Determined with a Nisseisangyo 0.005
Zeeman Shift Atomic Absorption
Spectrophotometer
Cd Determined with a Perkin-Elmer 0.0003
Heated Graphite Atomizer Atomic
Absorption Unit
Cr Same as above 0.005
Cu Same as above 0.003
Hg Determined with a Nisseisangyo 0.0002
Zeeman Shift Atomic Absorption
Spectrophotometer
Mn Determined with a Perkin-Elmer 0.03
Heated Graphite Atomizer Atomic
Absorption Unit
Ni Same as above 0.05
Pb Same as above 0.002
Zn Same as above 0.05
'Mention of trade names or commercial products does not
constitute endorsement or recommendation of use.
132
-------
TABLE 4
AVERAGE CONCENTRATIONS OF METALS IN ELUTRIATE SAMPLES
FOR RAW AND FIXED ELECTROPLATING SLUDGE
Fixation
process
Raw sludge
Process A
Process B
Process C
* I'ach reported
pH
1.2
7.5
7.X
5.2
analyses
As* Cll
(ppm) (ppm)
<().0()5 0.39
0.080 0.38
O.OOX 0.59
0.060 25.00
Cr
(ppm)
0.69
3.90
59.00
21.00
Cu
(ppm)
16.00
4.70
13.00
1200.0(1
UK
(ppm)
<0.0002
0.0002
< 0.0002
<0.<)002
Mn
(ppm)
4.10
0.99
1.50
1 1.00
A'V
(ppm)
4.10
0.56
0.84
120.00
Pb
(ppm)
0.020
0.250
0.740
<0.002
(ppm)
7.80
6.20
5.00
330.00
is the average of three samples.
cylinders (i.e., material from Processors A, C and D)
were placed in the columns and polypropylene pellets
were packed around the cylinders. The variations in
column loading procedures were made to accommodate
those processors (A, C, and D), who required their
samples be tested as a monolithic mass rather than as
fragmented or ground material. In each case the
processor felt that the material, as packed in the columns,
reflected the way the material would be placed in a
landfill.
The leaching liquid used in this test was deionized,
distilled water saturated with carbon dioxide. The pH of
this solution is approximately 4.5. Where possible, flow
through the columns was maintained in a range
approximating the rate of flow through the covering
material on a landfill; 7 to 70 ml per day for these
columns. This is equivalent to an hydraulic conductivity
of 1 X 1CT5 to 1 X 10~6 cm/sec. In some cases the natural
flow rate was less than this amount and in other cases, the
flow rate varied unpredictably. If the natural flow rate
was lower then desired, the natural rate was allowed to
regulate the flow. If the flow was too rapid the stopcock
was used to control the flow. If the flow rate was variable,
leachate was collected until 4.5 liters had passed through
the column; then, the flow of leachate was shut off.
Samples of leachate from the columns were preserved
by adding nitric acid to lower the pH to 2.0. The
techniques used in analyses are given in Table 3. A
detailed discussion of analytical procedures is presented
in a previously published report (6).
Procedure for Bulk Digests
Samples of raw and fixed sludges were digested in acid
to provide a bulk analysis of the material that was tested.
Two grams (wet weight) of material were weighed out
and transferred to a covered 100-ml teflon beaker.
Fifteen ml of reagent-grade hydrofluoric acid and 10 ml
of reagent-grade concentrated nitric acid were added to
the sample. The material was heated to 175° C and
maintained at this temperature for 2 to 3 hours. After
digestion the beaker lids were removed and the samples
were evaporated to near dryness and the residue was
redissolved in 6N hydrochloric acid. The samples were
transferred quantitatively to a 100-ml volumetric flask
and brought up to volume with distilled-deionized water.
The techniques used for chemical analysis are given in
Table 3. Separate subsamples of fresh material were
weighed out and percent solids determinations were
made to correct the analyses to a mg/kgdry weight basis.
RESULTS AND DISCUSSION
Elutriate Test Results
The results of the elutriate tests performed on the raw
and fixed (A, B, and C) electroplating sludges are given in
Table 4. Each of the tabulated analyses is the average of
three separate elutriate tests. All of the elutriate from the
raw and fixed sludges contained more cadmium,
chromium, copper, and manganese than would be
permitted in a public water supply (Table 5), and in some
cases the elutriate samples also exceeded the
recommended levels for arsenic, lead and zinc. No
standards have been written for nickel in public water
supplies, but the levels observed in the elutriates are
generally higher than would be considered safe (1).
In some cases, the metal concentrations in the
elutriates from the fixed sludges were actually higher
than concentrations observed in elutriate samples
obtained from the raw sludge. This is especially true for
TABLE 5
PERMISSIBLE LIMITS OF SELECTED METALS
IN PUBLIC WATER SUPPLIES*
Metal
Permissible limit
(ppm)
Arsenic
Cadmium
Chromium
Copper
Mercury
Manganese
Nickel
Lead
Zinc
0.05
0.01
0.05
1.0
0.002
0.05
0.50 «
0.05
5.0
* From (1).
**This level causes damage to plants but no standard has been
set for water supplies.
133
-------
process C, the organic polymer system that required
acidification of the sludge. In process C, for all metals
reported here, with the exception of lead, the elutriate
from the fixed sludge showed higher concentrations than
did the elutriate from raw sludge. Process B did not
reduce the loss of arsenic, cadmium, chromium or lead;
although it did reduce the loss of copper, manganese,
nickel and zinc. Process A did not reduce the leaching of
arsenic, chromium or lead but did reduce the loss of
cadmium, copper, manganese, nickel and zinc. Process
D, the plastic encapsulation system, was not evaluated in
the elutriate test, so this system cannot be compared in
the present study. It can be assumed that if the plastic
jacket on the samples remained intact, only the plastic
would come into contact with water and no appreciable
increase in metals in the elutriate would be observed
(other than metals leached from the plastic).
In the three fixation systems examined in the elutriate
or shake test, no fixation process succeeded in reducing
the concentration of chromium in contacting water
below the level observed with raw sludge. Chromium is
the major potential hazard in electroplating sludge.
Control of the leaching of this metal is critical to treating
electroplating wastes.
Column Leaching Test Results
The column leaching test was designed to simulate the
effects of leaching raw or fixed sludge in an unlined
landfill. Two aspects of potential pollution were
examined: a) the concentration of metals to be
TABLE 6
LEACHATE FROM ELECTROPLATING PLANT SLUDGE
COLUMN 005 RA W
Specific
Sequence
1
2
3
4
6
7
X
9
10
II
12
13
14
15
16
Sequence
1
2
3
4
5
6
7
8
9
10
1 1
12
13
14
15
16
— = No anak
Day
1
8
14
21
39
63
91
126
189
245
353
451
569
708
814
Cr (ppm)
0.026
0.015
0.020
0.021
-
0.019
-
--
<0.005
-
--
0.095
0.0 7X
-
0.027
-
sis.
pH
„
8.3 '
8.4
8.2
8.4
8.2
8.2
8.4
—
82
8.0
8.5
—
8.2
7.2
Cu(ppm) Hg (ppm)
2.500
0.760
3.211 <0.0002
3.300 0.0010
..
3.700 0.0022
_.
—
<0.003 <0.0002
..
..
1.0X6 0.0003
2.067 <0.0002
—
0.650 0.0137
-
Conductance
fit MOHS/cm X /»';
18.80
—
18.00
2.20
—
18.20
18.00
—
15.00
21.00
24.00
-
21.00
23.00
Mn (ppm) Ni (ppm)
0.79 0.30
0.56 2.50
0.19 0.30
0.20 0.40
--
0.20 <0.05
--
—
<0.03 0.90
—
0.15
0.24 0.15
0.16 0.07
—
0.06 0.05
-
As (ppm)
..
<0.005
-
<0.005
<0.005
—
„
<0.005
—
<0.005
<0.005
<0.005
..
0.077
—
Ph (ppm)
_
0.077
0.052
0.592
_.
0.975
._
__
<0.002
..
-
—
—
—
<0(K)2
—
CJ (ppm)
0.0400
0.1000
0.1300
0.0894
0.0696
__
„
<0.0003
__
0.0105
0.0997
„
0.0097
-
Zn (ppm)
0.28
<0.05
0.57
0.40
„
"0.15
._
_
—
<0.05
0.14
O.K)
<0.05
-
134
-------
expected in water percolating through landfilled sludge,
and b) the fraction of each toxic metal present in the
electroplating sludge that might be released from the
sludge during approximately two years of leaching. The
elutriate test addressed itself only to the problem of the
maximum concentration to be expected on the initial
contact of sludge with percolating water; the column
leach test furnishes confirming data and allows long-term
effects to be evaluated. Metal analyses for all leachate
samples are presented in Tables 6-10. Variations in the
concentration of the most important potential pollutant,
chromium, are shown graphically in Figures 3-7.
Ideally the metal levels in column leachates should
always be below levels specified for public water supplies
and the leachate samples from fixed sludges should show
fewer instances of high metal concentrations than
leachate samples from raw sludge. The percentage of
leachate samples that exceeded public water supply
standards for each of the major toxic metals is given in
Table 11. In some cases, the raw sludge column yielded
fewer unacceptable leachate samples than did the
columns of fixed material. The best results were obtained
from the sample fixed by total plastic encapsulation. The
worst results were obtained with the fixing process that
required acidification of the waste.
In order to judge the efficiency with which selected
pollutants were contained in the different sludge samples,
the cumulative percent of metal lost was calculated from
the concentration of metal in the leachate and the volume
of leachate obtained during each sampling interval
(Table 12). Table 13 shows the amount of metal lost from
the test columns over the total leaching period. Table 14
LEACHATE
COLUMN 139
Sequence
1
2
3
4
5
6
7
8
9
10
II
12
13
14
15
Day
14
21
28
35
56
77
133
161
196
259
329
392
476
630
784
Sequence Cr (ppm)
1
2
3
4
5
6
7
8
9
10
II
12
13
14
15
-- = No analysis
1.300
1.600
0.800
0.300
<0.005
0.080
0.041
0.060
0.057
0.226
0.241
0.064
0.015
0.044
—
PH
9.3
9.4
8.1
9.0
7.4
7.5
8.3
8.6
8.1
7.8
7.1
8.3
8.1
7.9
7.5
Cu (ppm)
3.600
1.900
1.800
0.956
1.070
0.880
0.451
0.428
0.202
0.210
0.100
0.182
0.209
1.100
—
TABLE 7
FROM ELECTROPLATING PLANT SLUDGE
PROCESS A
Specific
Hg (ppm)
<0.0002
<0.0002
0.0006
<0.0002
0.0006
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
0.0003
<0.0002
<0.0002
--
—
Conductance
(H MOHS/cm X If?)
14.00
0.90
6.00
4.60
3.50
3.10
3.08
2.00
2.95
2.30
2.00
1.90
2.10
1.93
2.10
Mn (ppm)
<0.03
0.90
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
—
Ni (ppm)
<0.05
0.08
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
—
As (ppm)
0.007
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.006
0.006
<0.005
<0.005
<0.005
0.005
—
Ph (ppm)
0.029
0.034
0.004
<0.002
<0.002
0.006
<0.002
0.035
<0.002
—
<0.002
<0.002
<0.002
-
-
Ccl (ppm)
0.0052
0.1045
0.0195
0.090
0.0020
<0.0003
0.0004
<0.0003
<0.0003
<0.0003
0.0012
0.0003
0.0004
-
—
Zn (ppm)
<0.05
..
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
—
--
135
-------
TABLE 8
LEACHATE FROM ELECTROPLATING PLANT SLUDGE
Seance
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Sequence
\
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
Duv
1
14
21
28
42
56
91
126
161
224
273
365
498
611
735
889
Cr (ppm)
23.600
12.300
6.400
4.500
<0.005
2.850
2.000
3.150
0.970
1.060
1.260
0.916
1.060
1.680
1.710
--
PH
11.9
11.6
11.0
11.2
II. 0
12.0
7.5
10.0
8.6
9.6
6.9
10.0
7.6
9.5
7.7
8.3
Cu (ppm)
13.600
4.000
2.400
2.000
2.100
1.500
1.288
2.740
2.560
1.820
1.950
2.432
2.280
1.250
1.460
-
COLUMN 086
HK (ppm)
0.0009
0.0003
<0.0002
0.0030
0.0028
<0.0002
0.0002
<0.0002
<0.0002
<0.0002
<0.0002
<:o.ooo2
<0.0002
<0.0002
-
--
PROCESS B
Specific
Conductant. e
(H MOHS/cm X 10')
20.00
8.80
6.40
4.H8
4.20
3.00
2.90
2.50
2.20
2.20
2.30
2.30
2.30
2.00
1.80
2.00
Mn (ppm)
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
--
Ni (ppm)
0.17
0.16
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
0.56
<0.05
<0.05
<0.05
<0.05
<0.05
--
As (ppm)
<0.005
<0.005
<0.005
<0.005
<0.005
<0.0()5
<0.005
<0.005
<0.005
<0.005
<0.()05
0.01 1
<0.005
<0.005
<0.005
--
Ph (ppm)
0.381
--
0.003
<0.002
--
<0.002
<0.002
-
<0.002
--
<0.002
<0.002
<0.002
0.003
--
--
Ccl (ppm)
0.0050
<0.0003
<0.0003
0.0008
--
--
0.0028
<0.0003
<0.0003
--
0.0003
<0.0003
0.0103
0.0011
0.0170
-
/.n (ppm)
0.07
<0.05
<0.05
-
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<005
0.18
-
— = No analysis.
136
-------
TABLE 9
LEACHATE FROM ELECTROPLATING PLANT SLUDGE
COLUMN 122 PROCESS C
Sequence
I
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
Sequence
1
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
Duv
1
14
21
28
42
56
91
126
147
210
266
364
44!
518
672
826
Cr (ppm)
298.800
130.000
78.000
16.000
20.000
6.000
7.000
3.900
2.100
1.990
1.890
2.120
0.346
0.715
1.460
-
pH
4.2
4.3
4.4
4.5
5.0
4.5
4.8
5.0
5.4
5.0
4.6
--
4.9
3.9
4.5
4.5
Cu (ppm)
700.000
800.000
670.000
30.000
310.000
180.000
239.988
1 14.940
159.992
180.000
150.000
149.992
35.192
42.200
90.100
—
Specific
Conductance
(H M OH SI cm X 10')
15.50
11.10
9.40
4.55
5.70
3.50
4.00
3.30
2.50
2.25
2.70
--
0.90
1.20
1.80
2.30
Hg (ppm) Mn (ppm) Ni (ppm)
0.0030 6.30 123.00
0.0040 2.80 69.50
<0.0002 4.05 69.00
<0.0002 2.40 38.00
!.50 38.00
<0.0002 0.90 11.00
<0.0002 1.60 22.00
<0.0002 0.58 12.10
<0.0002 0.76 12.20
<0.0002 0.80 8.82
<0.0002 0.80 8.27
<0.0002 0.77 7.98
<0.0002 0.99 1.07
<0.0002 0.10 1.36
0.23 2.94
—
Ax (ppm)
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.010
<0.005
<0.005
<0.005
0.026
0.0 10
<0.005
<0.005
<0.005
-
Pb (ppm)
0.697
0.240
0.138
<0.002
--
0.020
0.031
0.037
0.028
-
0.024
0.066
-
0.019
--
—
Ccl (ppm)
21.0000
14.9970
15.9995
8.5000
9.0000
3.1002
5.9985
5.2994
4.3990
3.3990
2.4000
3.1995
0.4015
0.5240
1.1200
-
Zn (ppm)
368.00
200.00
180.00
104.00
--
39.00
73.00
50.75
38.50
39.30
27.60
25.00
4.44
5.00
11.50
—
— = No analysis.
137
-------
TABLE 10
LEACHATE FROM ELECTROPLATING PLANT SLUDGE
COLUMN 102 PROCESS D
Sequence
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Sequence
1
2
3
4
5
6
7
8
9
10
II
12
13
14
15
Day
1
14
21
28
42
56
91
112
147
210
273
364
515
641
760
Cr (ppm)
—
<0.005
<0.005
<0.005
<0.005
--
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
PH
7.2
7.1
7.3
7.0
7.4
7.2
7.1
7.4
7.2
7.1
7.1
6.4
6.9
8.0
7.7
Cu (ppm)
0.035
0.030
0.037
<0.003
<0.003
<0.003
<0.003
<0.003
<0.003
0.007
0.038
0.020
0.023
0.012
0.007
Hg (ppm)
-
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
<0.0004
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
<0.0002
Specific
Conductance
frMOHS/cm X/0'j
2.40
16.00
4.00
5.10
6.30
4.20
1.60
3.30
2.50
3.32
4.20
7.60
4.00
6.80
21.00
Mn (ppm) Ni (ppm)
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
<0.03 <0.05
As (ppm)
<0.005
<0.005
<0.005
<0.005
<0.005
0.008
<0.005
<0.005
<0.005
<0.005
<0.005
0.010
0.008
0.005
0.008
Pb (ppm)
—
0.003
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
--
0.397
-
0.004
0.002
<0.002
Cd (ppm)
^— ^ •___ _ _
0.0200
0.0145
0.0027
2.4000
0.0036
0.0036
0.0017
0.0036
0.0003
0.0007
0.0020
0.0019
0.0150
0.0075
0.0100
Zn (ppm)
— .
<0.05
—
—
„
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
--= No analysis.
138
-------
shows the amount of each constituent lost as a
cumulative fraction of the amount initially available. In
many cases, the fraction of metal lost through leaching
was larger in the processed sludges than in the raw sludge.
Only process D, the encapsulation system, prevented the
escape of copper or chromium. None of the fixing
systems could prevent a relatively large release of
cadmium. The leachate from the encapsulated samples
(Process D) showed surprisingly high levels of cadmium.
The encapsulation process is so effective in preventing the
escape of chromium and copper that it seems unlikely
that the cadmium found in the leachate is escaping from
the encapsulated sludge. Possibly, cadmium is present in
a catalyst or plastici/er used to form the plastic jacket or
may be used in the molds or release compounds used in
the manufacture of the cylinders.
TABLE 11
PERCENTAGE OF LEACHATE SAMPLES
EXCEEDING CONCENTRATIONS
RECOMMENDED FOR PUBLIC WATER SUPPLIES
Raw Process Process Process Process
Constituent sludge A B C D
As
Cd
Cr
Cu
Hg
Mn
Pb
Zn
12
78
22
67
28
90
67
0
0
23
71
36
0
7
0
0
0
17
93
100
14
0
10
0
7
100
100
100
15
100
36
86
0
27
0
0
0
0
9
0
TABLE 13
TOTAL AMOUNT OF SELECTED METALS
LEACHED FROM RAW AND FIXED SLUDGE
Metal
Cd
Cr
Cu
Raw
sludge
(mg)
0. 14
0.23
6.06
Process
A
(mg)
0.4 1
10.25
29.83
Process
B
(mg)
0.56
231.25
I52.7I
Process
C
(mg)
221.59
1938.52
8623.86
Process
D
(mg)
4.28
0.01
0.60
Metal
Cd
Cr
Cu
TABLE 14
CUMULATIVE FRACTION
OF SELECTED METALS LEACHED
FROM RAW AND FIXED SLUDGE
Raw Process Process Process Procexx
sludge A B C /)
7. 20 x | o'
1.42 X 10"
5.K7 X 10 '
2. 83 X 10' .149 X |() '
9.X2 X 10 ' 1.26 X 10 '
5.45 X 10 ' I.2X x ]() '
4.S5 X 10 ' 5.49
3.06 X 10 |.59
2.X2 X 10 ' |J2
X
X
\
10 ;
10
10
The column leaching indicates that the encapsulation
process is the most dependable system for preventing
unacceptable metal levels from occurring in leachate and
for preventing large long-term leaching losses. This test
agrees with similar leaching experiments reported in the
literature (10). Both the elutriate test and the column
leaching tests indicate systems involving additives
without encapsulation are far less effective and in some
cases the processed material may leach metals more
rapidly than raw sludge.
TABLE 12
VOLUMES OF LEACHATE
Process
Column
Sequence
I
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
— = Not reported.
Raw
005
Time
(Days)
1
8
14
21
28
29.
63
91
126
189
245
353
451
569
708
814
Volume
(Liters)
0.14
0.26
0.29
0.22
0.21
0.22
0.16
0.64
0.24
__
2.98
1.69
..
._
1.86
-
COLLECTED FROM ELECTROPLATING PLANT SLUDGE
Process
139
Time
(Days)
14
21
28
35
56
77
133
161
196
259
329
392
476
630
784
—
A
Volume
(Liters)
1.69
1.98
1.69
1.86
1.98
2.05
2.55
4.50
0.83
4.50
3.41
4.50
4.50
4.50
4.50
—
Process
086
Time
(Days)
7
14
21
28
42
56
91
126
161
224
273
365
498
611
735
889
B
Volume
(Liters)
4.50
4.50
2.24
2.05
2.24
2.46
1.69
2.38
1.77
2.03
3.10
4.50
4.50
3.92
4.50
4.50
Process
122
Time
(Days)
7
14
21
28
42
56
91
126
147
210
266
364
441
518
672
826
C
Volume
(Liters)
2.17
2.17
1.96
3.18
2.15
3.06
1.60
1.94
1.76
3.49
3.15
-
4.50
4.50
4.50
4.50
COLUMNS
Process
102
Time
(Days)
7
14
21
28
42
56
91
112
147
210
273
364
515
641
760
-
D
Volume
(Liters)
2.15
2.08
1.86
1.86
1.55
1.86
2.29
1.62
1.53
3.32
2.27
4.50
4.50
4.50
4.50
—
139
-------
203-R
UNTREATED
100 200 300 H00 £00 B00 700 B00
DRY
900
Figure 3. Variation in concentration of chromium in leachate from untreated (raw) sludge with time. Horizontal line at 0.05 ppm indicates
public water supply standard.
200-fl
PROCESS A
1013 200 300 400 £00 E00 700 600 900
DRY
Figure 4. Variation In concentration of chromium in leachate from process A fixed sludge with time. Horizontal line at 0.05 ppm Indicates
water supply standard.
140
-------
10
UJ
re
LJ
_j
5 S
a:
s: H
Q_
3
2B0-B
PROCESS B
(O.OSppm)
200 300
H00
EBB
500 700
800
900
DRY
Figure 5. Variation in concentration ot chromium in leachate from process B fixed sludge with time. Horizontal line at 0.05 ppm indicates
public water supply standard.
5
2B
IB •
IE •
IH •
12 ••
5 10 +
an
z:
a.
a.
200-C
PROCESS C
(O.OSppfn)
200 300 H00 S00 600 700 B00 900
DRY
Figure 6. Variation In concentration of chromium In leachate from process C tixed sludge with time. Horizontal line at 0.05 ppm indicates
public water supply standard.
141
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0.; ••
0.03 -•
0.0B -•
a.0s -•
5 0.0S
a:
iv
s: 0.0H--
a
0.03 -•
0.02 - •
0.01 -•
200-D
PROCESS D
(O.OSppm)
.BDL
BDL BDL
BDL
SDL
BDL
BDL
100
200
H00 £00
DRY
£00
700
B00
900
Figure 7. Variation in concentration of chromium in leachate from process D fixed sludge with time. Horizontal line at 0.05 ppm indicates
public water supply standard.
CONCLUSIONS AND RECOMMENDATIONS
Of the four hazardous sludge fixation systems
examined, the encapsulation system is the most effective
in containing potential pollutants in electroplating
wastes. Systems using an additive only, with no
encapsulation, showed a wide range of efficiencies in
containment; but, none showed the overall effectiveness
of encapsulation.
Significant reductions in fixation efficiency were noted
in additive systems that required the acidification of the
electroplating waste. Fixation processes that resulted in
increased permeability in the fixed sludge (Processes B
and C) produced samples that leached larger amounts of
pollutants than those that decreased permeability
(Processes A and D).
The elutriate or shake test results were confirmed by
the long-duration column leaching test. The shake test is
a useful system for evaluating the performance of
fixation processes.
On the basis of this investigation, the following
recommendations can be made:
a) Additional work should be undertaken on
developing encapsulation systems. Reductions in
cost and an increase in the proportion of waste that
can be encapsulated would make this disposal
system attractive to potential users.
b) The additive-only processes tested should be used
on electroplating wastes only in cases where strict
control and monitoring of the landfill is possible.
c) Field studies of landfill sites where fixed sludges
have been placed would be a useful step in
confirming the safety or lack of safety involved in
fixed sludge disposal.
ACKNOWLEDGMENT
This study was part of a major research program on the
chemical fixation technology, which is now being
conducted by the U. S. Army Engineer, Waterways
Experiment Station and funded by the Environmental
Protection Agency, Municipal Environmental Research
Laboratory, Solid and Hazardous Waste Research
Division, Cincinnati, Ohio under Interagency Agree-
ment. EPA-IAG-D4-0569. Robert E. Landreth is the
EPA Program Manager for this research area.
REFERENCES
1. National Academy of Sciences, National Academy
of Engineering. Water Quality Criteria, 1972. A
Report of the Committee on Water Quality Criteria,
EPA-R-73-033, U. S. Environmental Protection
Agency, Washington D. C., 1973. 594 pp.
2. Deutsch, Morris. Incidents of Chromium
Contamination of Ground Water in Michigan.
Public Health Service Technical Rept. W61-5, U. S.
142
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Public Health Service, Washington D. C., 1961. pp.
98-104.
3. Perlmutter, N. M., M. Leiber, and H. L. Frauenthal.
Movement of Water Borne Cadmium and
Hexavalent Chromium Wastes in South Farming-
dale, Nassau County, Long Island, New York. U. S.
Geological Survey Professional Paper 475-C, Art.
105, 1963.
4. Perlmutter, N. M. and M. Lieber. Dispersal of
Plating Wastes and Sewage Contaminants in
Ground Water and Surface Water, South Farming-
dale-Massapequa Area, Nassau County, New York.
U. S. Geological Survey Water-Supply Paper 1879-
G, 1970. 67 pp.
5. Miller, D. W., F. A. DeLuca, and T. L. Tessier,
Ground Water Contamination in the Northeast
States. EPA-660/2-74-056, U. S. Environmental
Protection Agency, Washington, D. C., 1974. 325
pp.
6. Maloch, J. L., D. E. Averett, and M. J. Bartos, Jr.
Pollutant Potential of Raw and Chemically Fixed
Hazardous Industrial Wastes and Flue Gas Desul-
furization Sludges. Interim Report. EPA-600/2-76-
182, U. S. Environmental Protection Agency,
Cincinnati, Ohio, 1976. 117 pp.
7. Mahloch, J. L. and D. E. Averett. Pollutant Poten-
tial of Raw and Chemically Fixed Hazardous Indus-
trial Wastes and Flue Gas Desulfurization Sludges.
Unpublished Interim Report, January, 1975. 48 pp.
8. Mahloch, J. L. teachability and Physical Proper-
ties of Chemically Stabilized Hazardous Wastes.
Paper presented at Hazardous Waste Research Sym-
posium: Residual Management/Land Disposal,
Tucson, Arizona, February 2-4, 1976.
9. Bartos, M. J. Jr., Palermo, M. R. Physical and Engi-
neering Properties of Hazardous Industrial Wastes
and Sludges. EPA-600/2-77-139, U. S. Environmen-
tal Protection Agency, Cincinnati, Ohio, 1977. 89 pp.
10. Lubowitz, H. R., R. L. Derham, L. E. Ryan and G.
A. Zakrzewski. Development of a Polymeric
Cementing and Encapsulating Process for Manag-
ing Hazardous Wastes. EPA-600/2-77-045, U. S.
Environmental Protection Agency, Cincinnati,
Ohio, 1977. pp. 167.
143
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/8-78-010
2.
4. TITLE AND SUBTITLE
First Annual Conference on Advanc<
Control for the Metal Finishing Industry
7. AUTHOR(S)
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Metals and Inorganic Chemicals Branch
Industrial Environmental Research Laborat<
Cincinnati, OH 45268
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab-C1n1
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, OH 45268
5. REPORT DATE
•d Pollution May 1978 issulng date
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
)ry
NO.
13. TYPE OF REPORT AND PERIOD COVERED
H nw Conference Proceedings Jan '78
' 14. SPONSORING AGENCY CODE
600/1 2
15. SUPPLEMENTARY NOTES
Additional Sponsor: The American Electroplaters' Society (AES)
16. ABSTRACT
Subject report contains technical research papers given at the First Annual
Conference on Advanced Pollution Control for the Metal Finishing Industry.
This conference was held 1n January, 1978 and was co-sponsored by the USEPA
and the American Electroplaters1 Society (AES). Report contains papers on
IERL-C1 research efforts and covers all facets of air, water, and solid waste
pollution control .
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
Industrial Wastes, Waste waters, Metal
Finishing, Metal Coatings, Evaporators,
Air Pollution, Water Pollution.
18. DISTRIBUTION STATEMENT
Release to Public
b. IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Electroplating, Toxic 68A
Metals, Reverse Osmosis, ' 68C
Solid Waste, Water Reuse, 68D
Water recycle,
19. SECURITY CLASS (This Report) 21. NO. OF PAGES
llnrl»«1fioH 15°
20. SECURITY CLASS (This page) 22. PRICE
Unclassified
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
144
»u.s.i!Ottiiii»ioiTi'iiMm«e<]mcE:>9;«_ 757-140/6922
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