United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-81-028
February 1981
Research and Development
&EPA
Third
Conference on
Advanced Pollution
Control for the Metal
Finishing Industry
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EPA-600/2-81-028
February 1981
Third Conference
On Advanced Pollution Control
For the Metal Finishing Industry
PRESENTED AT:
ORLANDO HYATT HOUSE, KISSIMMEE, FL
APRIL 14 - 16, 1980
Co-sponsored by:
• The American Electroplaters' Society
The United States Environmental Protection Agency
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Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Disclaimer
This report has been reviewed by the Industrial
Environmental Research Laboratory, U.S.
Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents
necessarily reflects the views and policies of the U.S.
Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorse-
ment 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 presentations from the
"Third 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 by EPA and others to
solve the pressing pollution problems of the metal
finishing industry. It is hoped that the content of this
proceedings will stimulate action to reduce pollution by
illustrating approaches and techniques high-lighted by
the wealth of excellent papers presented at this
conference. Further information on these projects and
other metal finishing pollution research can be obtained
from the Nonferrous Metals and Minerals Branch,
lERL-Ci.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
ill
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TABLE OF CONTENTS
INTRODUCTION
George S. Thompson, Jr. and J. Howard Schumacher, Jr 1
INTRODUCTION TO CONFERENCE
EPA WELCOME TO THE THIRD CONFERENCE ON ADVANCED POLLUTION CONTROL
FOR THE METAL FINISHING INDUSTRY
William A. Cawley 2
"STATUS OF AES RESEARCH"
J. Hyner 3
STATUS OF EPA RESEARCH
George S. Thompson, Jr 5
SESSION I
WASTEWATER
STATUS OF WASTEWATER REGULATIONS
Robert B. Schaffer 9
POTW REMOVAL CREDITS AND REVISED CATEGORICAL PRETREATMENT STANDARDS
Jon L. Olson and Richard W. Eick 11
SESSION II
WASTEWATER
ELECTROCHEMICAL REACTOR AND ASSOCIATED IN-PLANT CHANGES AT
VARLAND METAL SERVICE, INC.
Edwin Roof 16
THE APPLICATION OF SEPARATION PROCESSES IN THE METAL FINISHING INDUSTRY
Peter Crampton 23
DOES RECOVERY REDUCE TREATMENT NEEDS?
F. A. Steward 30
REGENERATION OF WASTE CHROMIC ACID ETCHING SOLUTIONS IN AN
INDUSTRIAL-SCALE RESEARCH UNIT
L. C. George, D. M. Soboroff and A. A. Cochran 33
LIQUID ION EXCHANGE IN METAL RECOVERY AND RECYCLING
Lawrence V. Gallacher 37
ACHIEVING EFFLUENT CRITERIA—NOT FINAL ANSWER
A. F. Lisanti and R. Helwick 43
SESSION ill '; •;
SOLID WASTE
LUNCHEON PRESENTATION: THE RESOURCE CONSERVATION AND RECOVERY ACT
Rebecca Hanmer 45
RESOURCE CONSERVATION AND RECOVERY ACT
Kurt W. Riegel 48
REPORT ON THE RESULTS OF THE AES/EPA SLUDGE CHARACTERIZATION PROJECT
Kenneth R. Coulter 51
SOLIDS REMOVAL AND CONCENTRATION
Richard W. Grain 56
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MAKING HAZARDOUS WASTES NONHAZARDOUS
Robert B. Pojasek, Ph.D 63
RADIOCHEMICAL STUDIES OF THE LEACHING OF METAL IONS FROM
SLUDGE BEARING CONCRETE
John D. Mahoney, Elaine A. Dwyer, Walter P. Saukin and Robert J. Spinna 65
SESSION IV
SOLID WASTE
STABILIZATION OF HEAVY METAL WASTES BY THE SOLIROC PROCESS
J. M. Rousseaux and A. B. Craig, Jr 70
ROUTES TO METALS RECOVERY FROM METAL FINISHING SLUDGES
Anil Mehta 76
SOLVENT RECOVERY FOR THE SMALLER COMPANY
C. Kenneth Claunch 80
SESSION V
AIR POLLUTION AND ENERGY RECOVERY
VOC INCINERATION AND HEAT RECOVERY - SYSTEMS AND ECONOMICS
Roy M. Radanof 84
ENVIRONMENTAL AND ENERGY BENEFITS ACHIEVABLE BY COMPUTER CONTROL OF
AIR FLOW IN BAKE OVENS
Matt Heuertz 92
EMISSIONS FROM OPEN TOP VAPOR DECREASING SYSTEMS
Charles H. Darvin 98
V.O.C. CONTROL EFFORTS BY A HEAVY DUTY TRUCK MANUFACTURER
Edward W. Kline^., 102
SESSION VI
CENTRALIZED TREATMENT
CENTRALIZED TREATMENT AND DISPOSAL OF SPECIAL WASTES IN THE
FEDERAL REPUBLIC OF GERMANY
N. Roesler 104
EPA'S CENTRALIZED TREATMENT PROGRAM
Alfred B. Craig, Jr., and George C. Cushnie Jr 115
HAZARDOUS WASTE MANAGEMENT FACILITIES: THE SITING PROBLEM AND
POSSIBLE SOLUTIONS
Frank Boni 132
GROUP TREATMENT—OPTIONS AND ECONOMICS
Erich W. Salomon and Edward H. Comfort 135
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INTRODUCTION
"The Third EPA/AES Conference on Advanced
Pollution Control for the Metal Finishing Industry" was
held in Kissimmee, Florida, on April 14- 16, 1980. This
broad scoped colloquium was jointly designed by the
American Electroplaters' Society and the U.S.
Environmental Protection Agency's Nonferrous Metals
and Minerals Branch. The primary objective of this
conference was to continue the dialogue established at
the First EPA/AES Conference (1978) and strengthened
at the Second EPA/AES Conference (1979) between key
members of the EPA and the metal finishing industry.
The proceedings, contained herein, of this Third
Conference reflect the primary points of the gathering:
the status of EPA's wastewater and solid waste
regulations, and both EPA's and industry's research
efforts to effectively address the ramifications of these
regulations. Air pollution and energy recovery, financial
pollution control alternatives, and centralized treatment
of metal finishing residuals were also discussed at the
conference and reports of this work appear in these
proceedings.
The program of the conference was broken into six
segments: wastewater, regulation and research; solid
waste, regulation and research; an exchange of
viewpoints between members of the government and
industry; air pollution and energy recovery, regulation
and research; centralized treatment as an alternative to
on-site treatment of waste water and solid waste residuals;
and concurrent sessions addressing detailed inquires on
the pollution problems and finiancial alternatives
available to the metal finishing industry. Since attendees
of the first and second conferences placed extreme
emphasis on wastewater and solid waste, the first two
segments of the Third Conference were structured to
provide conference attendees with a detailed
understanding of the potential impact of current and
future regulations in these two important environmental
areas, as well as the research being conducted to address
wastewater and solid waste pollution problems. Key
EPA officials, representing EPA's water and solid waste
regulatory offices and research office, described the
procedures by which EPA prepares and promulgates
regulations and conducts research activities having direct
impact on metal finishers. Industrial participants
described, in various papers, examples of current and
potential solutions to wastewater and solid waste
pollution problems.
The third segment, entitled 'Exchanging Viewpoints"
was conducted during an evening session. A panel
comprised of EPA officials and industry representatives
opened the floor to a free discussion in order to permit
EPA and industry to commonly and clearly understand
those research needs considered to be of paramount
importance. This objective was fulfilled as the needs
became evident during frank discussions between the
attendees and the panelists.
The fourth segment of the conference discussed air
pollution regulations and research activities, as well as
the energy recovery potential available to the metal
finishing industry. Besides a discussion of current and
pending air pollution regulations by an EPA official,
various EPA research projects structured to produce
cost-effective technologies and approaches to the
primary metal finishing industry's air pollution problems
were described.
Centralized treatment, the fifth segment, was discussed
during the entire final session of the conference. Papers
on this viable alternative to on-site treatment of
wastewater and solid waste were presented by industrial
representatives from the United States. Centralized
treatment as practiced in West Germany since 1964 was
described by an esteemed colleagues from the Federal
Republic of Germany. EPA's research program on
centralized treatment was also discussed in detail.
A group of concurrent sessions comprised the sixth
segment of the conference. Individual groups of speakers
representing the various sessions of the conference
provided detailed commentary on his or her area of
expertise. Attendees of the conference were permitted to
attend the various detailed concurrent sessions
depending upon their interests. A special room was
established for individual attendees to receive detailed
information on pollution control financial alternatives.
This conference, attended by more than 600 persons
interested in the environmental problems faced by metal
finishers, was considered an extraordinary success. The
principal purpose of the conference, to continue a fruitful
dialogue between industry and EPA, was achieved. The
high-priority research needs of the industry were
identified and solutions to pressing problems are being
sought—some jointly—by EPA and AES.
The proceedings are published here in order that the
important material presented at the Conference can
benefit as many people as possible interested in solving
the intricate problems inherent in metal finishing
processes. These proceedings contain the presentations
made by representatives of various EPA regulatory
groups affecting the metal finishing industry, as well as
presentations by parties actively addressing research and
development in this same industrial area.
The EPA and the AES are pleased to have cooperated
in this mutual endeavor which has improved
communications and which should foster continued
research resulting in sound technical solutions to the
environmental problems of metal finishers.
George S. Thompson, Jr.
Chief
Nonferrous Metals & Minerals Branch, EPA
J. Howard Schumacher, Jr.
Executive Director
American Electroplaters' Society, Inc.
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EPA Welcome to the Third Conference
On Advanced Pollution Control
For the Metal Finishing Industry
William A. Cawley*
I would like to extend to you EPA's "welcome" to this
Third Conference on Advanced Pollution Control for the
Metal Finishing Industry. In addition, I offer a special
thanks to Howard Schumacher and his staff, to Mike
Murphy and to other AES members who have worked
diligently to make the conference possible. We hope our
efforts are successful in providing you with an
understanding and an awareness of EPA's regulatory and
R&D activities impacting the metal finishing industry.
We in EPA view this conference as a timely and cost-
effective tool for us to obtain the metal finishing
industry's evaluations of and recommendations for our
ongoing and planned programs. Consequently, this
conference is a critical activity in EPA's metal finishing
R&D program. This year we again solicit your
participation and comments after each presentation and
particularly at the Tuesday evening discussion session.
Members of my staff who are responsible for the
development and implementation of the metal finishing
R&D program and who are present at our Conference
are George Thompson, Chuck Darvin, Fred Craig, and
Anil Mehta. George and his people will be actively
soliciting your comments and reactions during this
conference's discussion periods and through informal
contacts. We intend to compile this information and
distribute it to you for comment along with the
conference proceedings.
The major goal of the R&D efforts is to develop and
evaluate pollution control methods that are broadly
applicable to the metal finishing industry, that present
cost-effective options for meeting regulations, and that
minimize or eliminate intermedia transfer of the
pollution problem.
At our first EPA/AES conference we attempted to
bring to you the status of EPA's total efforts in air, water,
solid waste, and toxic substances which are likely to
impact your industry. Last year we focused on the
Agency's water and solid waste programs which we feel
will have the greatest impact in the near term. This year,
our primary emphasis is on water and solid waste with
lesser emphasis on air, financial alternatives and
centralized treatment.
I personally would like to encourage you to critically
evaluate the ongoing and planned R&D activities in view
of the major R&D goal I have stated, and to provide your
candid comments on each project and the overall
program direction. Your participation is essential to the
success of the conference and to EPA and the industry's
efforts to control pollution from the metal finishing
industry.
Once again, I am glad you are here and hope that I have
the opportunity to meet many of you during the next
three days.
•William A. Cawley
Deputy Laboratory Director
Industrial Environmental Research Laboratory
Cincinnati, Ohio
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"Status of AES Research'
J. Hyner*
Even before our nation became conscious of the effects
of pollution upon our environment, the AES had
sponsored research projects with the goal of rendering
harmless the effluents and solid waste of the metal
finishing industries.
Of the nine AES research projects currently active, five
are directed towards solving some aspect of pollution. Of
the five pollution oriented projects, two are co-sponsored
by the EPA.
I'll review the reason for choosing each active pollution
project and bring you up to date on the current status of
each.
PROJECT NO. 48
Title: The Effect of Anions on the Precipitation of
Heavy Metal Ions from Electroplating Wastewater
Site: Columbia University; Project Director: Dr. Huk Y.
Cheh; Co-sponsored with the EPA
All who have effluent purification systems operating
have learned that theoretical hydroxide precipitation of
heavy metal ions is not always obtained. You have
learned that even though today you may be meeting your
standard for copper, or zinc, or any other metal,
tomorrow you cannot do better than 5 ppm. We long
suspected that assorted anions often interferred with and
prevented complete precipitation of the heavy metals.
The purpose of Project No. 48 is to determine which
anions commonly used in plating interfere with complete
precipitation, by what mechanism does interference
occur, and most important, how do we control or
neutralize the interferences so that theoretical
precipitation can occur, allowing us to successfully meet
EPA standards. Although authorized a year ago, the
project is just getting started since Dr. Cheh was on
sabbatical leave for a year. Isidore Cross, a past president
of AES is chairman of the project committee. In talking
to him this morning I learned that his committee is
complete and ready to start getting the project underway.
Phase I is expected to be completed some time during the
coming year.
PROJECT NO. 49
Title: The Effect of Electroplating Wastewater Sludge as
an Admixture on the Physical Properties of Concrete
Site: Manhattan College; Project Director: Dr. Robert
Spinna; Not co-sponsored with the EPA
*J. Hyner, Chairman
AES Research Board
Whyco Chromium Company, Inc.
Waterbury Road, Thomaston, CT 06787
Purifying our wastewater is now a common practice in
the plating industry and, within the next few years,
should be universal. The problem of what to do with the
tons of metal salts removed from the contaminated
rinsewaters has become pressing. Most of the metals have
been removed in the form of insoluble hydroxides. What
shall we do with them? The ideal solution, of course,
would be to remove the metals from the sludge and reuse
them. This is technically possible with current
knowledge. However, until much more tonnage
accumulates, it is not really economically feasible. Even
though a few hundred tons of sludge may be a
tremendous amount to a plater, it is very little to a refiner,
so that of necessity very few refiners would be needed in
the United States. The cost of transporting sludge great
distances is tremendous and, at current metal prices,
makes refining uneconomical.
What can we do with our sludge for the next few years -
for the time it takes all shops to get on stream and maybe
enough sludge is generated to make area refineries
economically feasible, if ever?
We have known for several years that the Japanese and
Europeans have encapsulated and immobilized sludge in
concrete. Cement is alkaline, insoluble, and theoretically
could serve to keep the metal hydroxides from dissolving
and leaching back into the environment. Our project was
not set up to repeat the work of the Japanese and
Europeans, whose interest was only in finding a place to
safely dispose of sludge without concern for the strength
and properties of the altered concrete. We are interested
in the concrete as well as in giving the platers a safe
disposal site in almost every city in this country. If
incorporation of some sludge in the concrete does not
alter the properties of the concrete, every batching plant
theoretically becomes a disposal site. The head of our
project, Dr. Spinna, is a professional engineer whose
specialty is concrete and construction. Associated with
him are chemists whose specialties are applied to leaching
and the chemical structure. Tomorrow, Dr. Mahony,
who has been conducting leaching studies using
radioactive tracers will report on his results.
Tests to date on the strength and properties of sludge-
modified-concrete show that the incorporation of sludge
containing 11A - 2% solids into concrete to replace water
does not appreciably alter the physical properties of
cured concrete, and the concrete is so insoluble that
leaching of metals is in the order of parts per billion—
completely safe to the environment.
This project has not been co-sponsored by the EPA.
That agency was a bit skeptical in the early days of the
project. Now that the first two phases of study have been
so successful, we will again submit a proposal for further
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work to the EPA and to the Office of Solid Waste.
Hopefully this time around, the AES, the EPA, and
Portland Cement Association will be able to work
together. We desperately need safe, convenient disposal
sites for our sludges generated by the clean up of other
effluents.
PROJECT NO. 51
Title: Immiscible Rinsing of Plating Solutions
Site: United Technologies Research Center; Project
Director: Dr. Jordan Kellner; Not co-sponsored with the
EPA
The best way to control pollution is to close the loop
and not discharge plating waste, most of which comes
from rinsing after plating. During the last few years
reverse osmosis, electrodialysis, Donnon dialysis, ion
exchange and evaporation have been both researched
and employed to capture and reuse the plating solution
rinsed off the plated parts. Incidently, more of the closed
loop type of methods were researched under EPA grants,
some with AES cooperation. All have been used to some
extent. All the above processes require expensive
equipment and skilled attention, which often makes the
process economically unattractive, even though
technically satisfactory.
If we had a non-aqueous immiscible solvent that would
rinse off the plating solution and then allow the rinsed
solution to either sink or rise, the solution could easily be
returned to the plating tank for reuse without further
treatment. This may be a long shot, but if successful, an
ideal way to save solution and solve a pollution problem.
In research to date, twenty-five different solvents were
mechanically shaken to react the solvent with chromium
plating solution—a solvent would be useless if it rinsed
well but contaminated the chromium bath. Of the
twenty-five initially tested, five were chosen for
continuing tests because of low reactivity with chromium
solution, low cost, toxicity and boiling points. The
chosen solvents also represented different chemical
structures consisting of saturated, long-chain
hydrocarbons, saturated, branch-chain hydrocarbons,
an aromatic ether and an aromatic hydrocarbon. Tests
with the five solvents are now underway, and some results
should be available by July, 1980.
PROJECT NO. 53
Title: Development of a Reactor to Eliminate Cyanide in
Electroplating Effluents
Site: Ontario Research Foundation; Project Director:
Al Cadotte; Not co-sponsored with the EPA
Chlorine oxidants and peroxides are almost
universally used to destroy cyanides. They are very
expensive and sometimes dangerous to handle. A
cheaper, technically sound method to destroy cyanides
used in the metal finishing industry would be universally
welcomed.
It's been known for many years that cyanides can be
destroyed by hydrolysis when heat and pressure are
applied.
Experiments at the Ontario Research Foundation
have indicated that heating a cyanide-containing
solution, for example, a copper cyanide plating bath, in a
sealed container to 210° C, approximately 450° F, for
only a few minutes will effectively destroy the cyanide.
Based on its laboratory work, Ontario Research is
building a flow-thru reactor of standard stainless steel
pipe to determine the feasibility of using this principle in
practice.
I am personally tremendously enthusiastic about this
project. I believe that it will be successful and that within
a relatively short time will be the means of saving metal
finishers thousands of dollars annually and, at the same
time, eliminating cyanide very effectively from our
effluent.
PROJECT NO. 55
Title: Sludge Characterization
Site: Centec Corporation; Project Director: Mr. Paul
Minor; AES/EPA Cooperative Agreement
The EPA required more information about the
leaching characteristics of electroplating sludges, and
with the information gained, it would have the basis for
establishing safe, segregrated disposal sites for solid
waste. It also required a rapid on-site test of sludge so that
a disposal site operator could quickly test a batch of
sludge sent in for disposal and determine whether or not
it could safely be dumped at the disposal site.
Twelve different sludges, from twelve plating plants
covering most of possible types of sludges produced by
the plating industry, have been collected, leached and
analyzed. I believe that when the testing program is
completed, results will show that metal hydroxide
sludges from plants with satisfactorily operating effluent
systems can safely be placed in segregated landfill sites
with no potential harm to the environment. Analysis
showed that the only soluble metal ions were in the
interstitial liquid and that the amount of leached metal
was so minute that leaching of the interstitial water in the
rains would yield concentrations below levels acceptable
for discharge.
Future work will research more of what happens to the
interstitial water and will also investigate models for a
satisfactory disposal site.
The sludge characterization and concrete projects will
be covered in more detail later in the program.
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Status of EPA Research
George S. Thompson, Jr.*
INTRODUCTION
Fourteen months have past since our Second
EPA/AES Conference. During this time period, many
things have happened affecting the metal finishing
industry. Not only has the cost of raw materials and
energy skyrocketed, but environmental regulations have
been - or are shortly to be - established for the air, water,
and solid waste pollution generated by the industry.
Pretreatment regulations for electroplaters were
promulgated in September of 1979. Revised BAT will be
proposed in the near term. Regulations for solid waste
generators should be out before the end of this month.
Regulations specific to solvent degreasers and other
sources of volatile organic compound (VOC) emissions
will shortly be established.
Where does research fit into such a complex and fast
movirtg situation? Our purpose is well established - to
provide, in a timely way, cost-effective technologies and
approaches through research, development, and
demonstration that will meet or surpass the requirements
established by air, water, and solid waste regulations. For
those of you who were not present at the Second
EPA/AES Conference or who have not seen the Second
Conference "Proceedings," I represent the research arm
of EPA - EPA's Office of Research and Development
(ORD). My Branch, the Nonferrous Metals and
Minerals Branch (which during the past 14 months has
received a new name resulting from a reorganization) is
part of one of ORD's field laboratories - the Industrial
Environmental Research Laboratory - located in
Cincinnati, Ohio. Now in our fifth year, we are chartered
to conduct R&D on the air, water, and solid waste
discharges from a number of industries including the
mining and milling of nonfuel minerals; the smelting and
refining of nonferrous metals; the manufacture of glass,
ceramics, cement and lime; and, of course, metal
finishing and fabrication.
Recent Achievements and Research Goals
The last 14 month period has seen an increased
understanding of our metal finishing research goals
related to solid waste and an overall attempt to accelerate
our efforts to establish more timely answers. Before I
describe these goals, allow me to list our achievements
since we last met:
• Publication of three reports for broad dissemination:
-"Environmental Pollution Control Alternatives:
"George S. Thompson Jr., Chief
Nonferrous Metals and Minerals Branch
Industrial Environmental Research Laboratory
U. S. EPA, Cincinnati, Ohio 45268
Economics of Wastewater Treatment Alternatives
for the Electroplating Industry"
- "Summary Report - Control Technology for the
Metal Finishing Industry - Evaporators"
- "Summary Report - Control and Treatment
Technology for the Metal Finishing Industry -
Sulfide Precipitation
• Completion of data package for Mechanical
Products and Electrical/Electronic Products
Industries
• Completion of the EPA/AES Cooperative
Agreement on Metal Finishing Sludge
Characterization
• Completion of EPA-Inhouse Metal Finishing
Sludge Stabilization Study
• Completion of Solvent Degreaser Evaluation
Project
• Completion of Computer Program for Quantifying
Energy Savings From Increased Operating Lower
Explosion Limit (L.E.L.) on Paint Curing Ovens
• Completion of First Two Phases of Centralized
Treatment Program
• Input to EPA's Office of Water Planning and
Standards (OWPS) on Structure and Detail of "8-
City Seminar Series for Electroplaters"
• Publication of R&D Reports
The current goals of our metal finishing research
program and our plans and methods to meet these goals
follows.
Goal I - Complete Investigations on Inplant Changes
Many metal finishers have stated that such in-plant
changes as water conservation steps, reducing chemical
usage, etc. are "old hat" or "common knowledge." This
knowledge is, of course, new to some of you, but
certainly not to all of you. I have quickly become aware of
the significance of in-plant changes and how these
changes have an effect on wastewater and solid waste
pollution generation and the economics of treatment
and/or disposal. Our efforts to identify in-plant changes;
to measure their effectiveness in reducing wastewater
volume, wastewater pollutant loading, chemical usage,
and sludge generation; and to ascertain the associated
costs to implement these in-plant changes continues. Ed
Roof or Varland Metals Services will be describing the
various in-plant changes used at his job shop during this
afternoon's water session. I would also like to make
reference to Clarence Roy's presentation at the Second
EPA/AES Conference (published in "Proceedings")
which discussed in-plant changes and their impact on
sludge generation.
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Whether you already have wastewater control (i.e.,
concentrating techniques) and/or treatment techniques
in-place or are now "shopping around" for solutions,
please go back to your metal finishing processes and
evaluate the impact of utilizing in-plant changes.
Hopefully, we will have a detailed report on in-plant
changes reviewed and published by August, 1980.
Goal II — Provide Wastewater Control and Treatment
Technologies That are Easy to Operate, Non-capital
Intensive, Do Not Produce a Sludge, etc.
This goal is (and may continue to be) one of our most
difficult goals to achieve; many parties in both the public
and private sectors have attempted to achieve this goal
over the past decade with only partial success.
Our approach to achieving this goal changed 14
months ago. Previously, we sought novel ideas and then
funded or co-funded laboratory-scale, bench-scale, pilot-
scale, and full-scale demonstrations. Some of our
previous research efforts were stopped due to some form
of failure or limitation of a technical or economic nature.
Others proved successful. The primary reason for
changing to a different approach was TIME.
Wastewater regulations and guidelines have been
established for portions of the metal finishing industry;
regulations and guidelines for the remainder of the metal
finishing industry will be set in the near future. The
compliance period for some metal finishers (e.g.:
electroplaters discharging to Publicly-Owned
Treatment Work: [POTW's]) has started and this goal
must be achieved soon to have impact.
Our new aproach to achieving this goal is three-fold:
• Clearly identify existing solutions. Identify their
applications, as well as their limitations. Document,
by evaluating full scale applications, their capital
costs and operating and maintenenace costs as well
as operating problems. Broad dissemination is used
to "spread the word" as far as possible so that the
largest number of readers will benefit from our
evaluations. Our "Alternatives Report" and
"Summary Report on Evaporators" (described
under "achievements" above) are examples. We
have a similar summary report on ion exchange
nearly ready for review and publication. We have
also completed several major efforts on soluble and
insoluble sulfide precipitation; a summary report on
this treatment technology has been published and
copies of this full color report are available at the
EPA table. A decision was reached several months
ago to prepare a brief status report on reverse
osmosis, since this control technology does have
some excellent applications. We do not plan to
perform further RD & D on this technology.
• Complete RD & D on promising approaches that
have excellent potential. Several technologies fall into
this category. One is an electrochemical reactor
which we have been demonstrating at Varland Metal
Services. Ed Roof, who is discussing in-plant
changes this afternoon, will also describe the status
of the demonstration on cadmium, zinc cyanide and
chloride, copper cyanide, chromium, and nickel
plating wastewaters. We are also completing a
demonstration of electrodialysis. Last month, we
funded an effort to develop an anionic membrane
for Donnan dialysis; this technology is very
promising and if such a membrane can be
successfully developed, we will enter into a full-scale
demonstration.
• Evaluate "Emerging Technologies" for wastewater
control and/or treatment. At our Second
EPA/AES Conference, I explained portions of what
became our Emerging Technology Program. This
program is currently being implemented. The
purpose of this program is simply stated. We are not
aware of numerous wastewater (this program also
addresses air and solid waste, but current emphasis
is on wastewater) control and treatment
technologies and alternatives. This program should
maximize our awareness. An "Awareness Bulletin
for Metal Finishers" will, on a bimonthly basis,
canvas numerous trade (and related) publications
and provide to the reader a synopsis of findings.
Copies of the first "Awareness Bulletin" are
available at the EPA table for review and comment.
Besides the bimonthly Bulletin, the Emerging
Technology Program is structured in three phases:
(1) Identification of candidate emerging
technologies, usually through received telephone
calls and other forms of correspondence, and
prioritizing of these candidates for "third party
evaluation" based on established prioritizing
criteria; (2) Detailed or "third party" evaluations of
the highest prioritized technologies requiring field
visits and possible sampling; and (3) Dissemination
of results by means of a Summary Report
publication. The technologies we are looking for are
those that are either operational on a very small scale
(one or two plants) or are close to commercialization
and, in both cases, are potential national solutions to
aiding us in reaching our goal.
As I did at the Second EPA/AES Conference, I
solicit any "Emerging Technologies" that you may
be aware of so that we can consider them for our
ongoing program.
Goal III - Provide Guidance to Upgrade Existing End-of-
Pipe Wastewater Treatment Facilities and to Improve
the Design of New Facilities.
Several research activities are either completed or
nearly completed that should allow us to achieve this
goal. One activity has just been initiated that will
hopefully address methods of upgrading existing end-of-
pipe systems for better wastewater pollutant removal and
sludge formation.
For new end-of-pipe neutralization/precipitation
systems, a Manual of Practice has been prepared and has
undergone extensive review. Publication of this manual
is forecasted by July, 1980. Even though it is not a design
manual, it has been prepared to provide guidance to
metal finishers (and other industrial users who employ
conventional neutralization/precipitation technology)
when faced with the need to purchase and/or fabricate
such a system. Sludge is also addressed in this manual.
Our recently published Summary Report on Sulfide
Precipitation describes soluble sulfide polishing
techniques that can be added to existing hydroxide
systems to achieve better effluent quality. Similarly, the
Summary Report on Ion Exchange, which is currently in
first draft form, provides detail on the application of i^n
exchange for polishing conventional end-of-pipe
treatment technology effluents.
-------
A new research activity has just been initiated which
resulted from the recently completed EPA/AES Sludge
Characterization project. Current plans for this new
activity call for field visits back to the electroplating
plants visited during the initial 3-phase project. The end-
of-pipe wastewater treatment systems at each plant will
be scrutinized to determine possible "upgrading" steps,
such as removing certain influents, using different
neutralizing chemicals and/or flocculants, etc. Screening
of possible changes will be conducted in the laboratory
and verification of the most promising will be field
demonstrated. Since the quality and quantity of the
sludge generated by the wastewater treatment system is
directly related to the design and/or operation of this
system (conclusion resulting from EPA/AES Sludge
Characterization study), this new research activity could
provide methods for improving effluent quality, chemical
usage, and sludge quality and quantity. More detail on
this new project is provided under Goal IV.
Goal IV - Provide Solutions to the Metal Finishing
Industry's Sludge Problem.
The approach to achieving Goal IV is quite complex.
The EPA/AES Cooperative Agreement on Metal
Finishing Sludge Characterization has been completed.
Ken Coulter will provide more detail on this project
tomorrow. The AES and EPA have jointly defined a
follow-on laboratory/field project. This project has been
partially funded this year; we hope to complete the
funding of this project next year through another
cooperative agreement with the AES.
We have just initiated a project on documentation of
current practices in "sludge usage/waste exchange." Our
investigation will cover the United States, Japan and
Western Europe. The finding and documenting of several
environmentally safe uses of sludge may lead us to
additional uses and may also prove to be part of our goal.
We are currently establishing an inhouse program to
determine the best metallurgical techniques for cost
effective recovery of metals from single and multiple-
metal sludges. The concept is simple and justified - the
sludges being investigated are hazardous sludges due to
their toxic nature; their toxicity is caused by their metal
content. Therefore, the metal content must be reduced to
a degree that makes the sludge non-toxic. Two product
streams will be produced - recovered metals and
nonhazardous sludge. Anil Mehta of our staff is
responsible for this inhouse effort and will explain his
approach on Tuesday.
Another potential solution which may enable us to
reach our solid waste goal is Centralized Treatment. This
alternative would not only prove to be technically and
economically advantageous for metal finishing
wastewater, but also for sludge. As witnessed from our
investigation of West German Centralized Treatment,
segregated retention areas for metal hydroxide sludge
have been established for waste exchange and metal
recovery. As the volume of "retained" sludge grows,
metals recovery becomes more economically viable and
the Centralized Treatment concept is the best collection
and "retention" alternative available.
One last R & D activity, which is now in its second
year, is a combination of Centralized Treatment and
metals recovery from cadmium-bearing sludge. This is a
cooperative agreement with the International Lead/Zinc
Research Organization. The approach under
investigation is the collection of metal finishers'
cadmium-bearing sludges and transport to a primary zinc
smelter (cadmium is a byproduct of primary zinc
production) and the subsequent recovery of cadmium
values in the zinc production circuit.
Goal V - Provide Centralized Treatment to the Metal
Finishing Industry as a Technically Sound and
Economically Viable Alternative to On-site Wastewater
Treatment and Sludge Disposal.
Our metal finishing Centralized Treatment Program is
now in its 13th month. Fred Craig, of my staff, and I
originally envisioned this program as a four phase effort,
with the third phase calling for demonstration and the
forth phase evaluating and disseminating the results of
the demonstration. Fourteen months ago, Fred Craig
described this four-phase effort and some attendees
commented that our program on Centralized Treatment
was dynamic, but not timely enough for metal finisher's
needs. What we have now, after having completed the
first two phases is sufficiently detailed information on
Centralized Treatment to act as a catalyst for you to
implement the concept. Not enough can be said about
this alternative for metal finishers - the findings of the
first two phases of this program are very enlightening
and, in summary, I believe that the necessary tools are
now available for you to determine if Centralized
Treatment can provide a partial or total solution to your
wastewater and/or sludge problem. Note on your
conference program that the entire Wednesday morning
session is devoted to Centralized Treatment; I urge you to
attend this session - it will prove to be quite enlightening.
Goal VI - Provide Techniques for the Control of Volatile
Organic Compound (VOC) Emissions
The use of solvents in the metal finishing industry,
whether in solvent degreasers or as part of a paint
formulation, leads to the atmospheric discharge of VOC.
Some metal finishing operations are major sources of
VOC.
We currently have a number of research activities,
including some field evaluations and full-scale
demonstrations, focused toward the above goal.
One major activity on solvent degreasers is essentially
completed and Chuck Darvin of my staff will report on
the important findings of this study during the Tuesday
afternoon "Air Pollution and Energy Recovery Session."
Chuck provided interim status of this activity at both the
First and Second EPA/AES Conferences. If you
currently use degreasers, or plan to use them in the future,
I strongly suggest that you listen to Chuck's presentation
- especially since the New Source Performance Standard
for this VOC source will soon be proposed.
We are currently fabricating a scrubber, which uses
surfactants as the scrubbing media. This summer, we will
test it at our inhouse facility followed by field testing at a
Cincinnati firm. If you operate a company in the
Cincinnati area that discharges VOC from metal coating
operations and would like to test the surfactant scrubber
at your plant, please contact us.
We have set up a microprocessor at the EPA
Conference display table. The demonstration from this
microprocessor is part of a joint project with the
Department of Energy. The overall goal of this joint
effort is to monitor and control the lower explosion limit
(LEL) of paint bake oven atmospheres in order to safely
increase the LEL. By increasing the LEL from 5-10% to
25-50%, significant fuel savings will result and VOC
-------
destruction can be economically practiced with primary
and secondary heat recovery. Trie controlling mechanism
will be an inexpensive microprocessor. A presentation on
this joint EPA/DOE project will be made during
Tuesday afternoon's air session. If you are interested in
the economic incentives resulting from increasing your
curing oven's LEL, please visit our display table and
witness the economic calculations. If you have the
necessary data on your curing oven(s), please provide this
data to us and the economic calculations will be made for
you. We are hoping that this display will give you the
incentive to seriously consider the objectives of this
project; we are also currently looking for a
demonstration plant.
Recently, we initiated a "fact finding" study on fugitive
VOC emissions from paint application. If you are aware
of any novel techniques for collecting fugitive VOC
emissions from this source, please contact us.
Several other metal finishing/VOC activities are
nearly complete, such as our environmental/energy
evaluation of a gas recirculation system. Some of these
projects address new coating formulations that are low in
solvent content.
In the near term, we plan to conduct RD & D on "low
temperature incineration." If you have any research ideas
on this subject, please contact us.
Goal VII - Disseminate All Pertinent Findings. Ensure
the Highest of Quality in these Findings
The metal finishing industry has more plants, both
large and small/captive and job, than any other
industrial category. When pertinent findings are made,
they must be broadly disseminated in order to have
visability and, in-turn, impact.
We have thus far published three full color reports for
broad dissemination that address wastewater control and
treatment technology for metal finishers (solid waste is
also covered, but to a lesser extent). Two of these three,
published last June, have already been distributed to over
10,000 individuals and companies both in the U. S. and
abroad. These reports are part of our Summary Report
Series for Metal Finishers. Two more reports will be
published to temporarily complete this Series: one on
"Ion Exchange" and the other on "Emerging
Technologies". We plan to prepare others, especially
when pertinent solid waste/sludge findings are made.
We also publish reports for most of our research
projects. A complete list (as of January 1979) of these
publications is contained in the Second EPA/AES
Conference "Proceedings".
Besides dissemination through written materials, we
feel that workshops, seminars, and conferences are
important tools, especially for 2-way communication.
Our First and Second EPA/AES Conferences have
afforded us the opportunity to not only understand your
problems, but to also gather your research ideas.
The second part of this goal is to achieve high quality
output. Again, this Conference allows us to describe our
current and planned activities and our major areas of
emphasis. As stated in this year's (and last year's) "EPA's
Opening Remarks", EPA's Office of Research and
Development views this Conference as an excellent
source of critique and constructive criticism. The quality
of our products can never exceed the quality of our
program goals and the approaches to achieve these goals.
We attempt to have our "final drafts" reviewed and
commented on by as many interested parties as possible
from both the public and private sectors. If you would
like to provide constructive criticism of any of the
activities described in this presentation, please contact us.
Lastly, I offer our products to the metal finishing
industry's trade magazines for "peer review."
During the past nine months, we have been deeply
involved with other EPA Offices and industrial
representatives in structuring what we term the "Eight
City Seminar Series for Electroplaters". This series,
which should start during the last week in August, is
designed to explain technological wastewater and solid
waste control and treatment alternatives, as well as
discussions on financial alternatives available to
finishers. For more information on this seminar series,
please contact my office or Ms. Francis DeSalle at
(202) 426-7874.
In conclusion, I have attempted, during this
presentation, to describe the goals of EPA's air, water,
and solid waste metal finishing research program. I solicit
any comments you may have on these goals and on our
approaches to achieve them.
-------
Status of Wastewater Regulations
Robert B. Schaffer*
I appreciate the opportunity to spend this time with
you every year. As in our previous two conferences, I
have some new information to provide to you. I consider
these descussions with you to be a very important part of
my job. Although getting the regulations out on time is
important, dealing with the regulated public through
interchanges and discussions is also a very important
aspect of providing good regulations. As with last year
and the year before, I arrrgoing to continue to give you a
preview of what is to come. I will also discuss the final
pretreatment guidelines as they were promulgated last
fall. Also, I will tell you about all the changes we have
subsequently made to the promulgated regulations.
As you may know, the pretreatment regulations, after
they were promulgated, were challenged by the National
Association of Metal Finishers. The main issues brought
forth have been discussed in a continued spirit of
cooperation for accomplishing good regulations. We
believe that the problem areas have been resolved and the
necessity to proceed with litigation has been eliminated.
We are currently in the process of putting together the
results of those negotiations and I am going to discuss,
unofficially at least, the changes to the regulations, which
will be proposed shortly. If they are finalized without
significant change after a proposal and comment period,
our agreement is that the litigation will be dropped.
The most significant changes will be in the revision of
the total cyanide limitation. The total cyanide limitation
will increase from 0.8 to 1.9 milligrams per liter. Second,
we are going to eliminate the 30 day limits. In their place,
we will establish four day limits. This change was made to
eliminate the possibility of extensive and burdensome
monitoring requirements. The new cyanide numbers
were taken from monitoring data and, even though they
differ numerically, still describe the performance of the
technology.
We are also going to remove the requirements for
monitoring that were included in the promulgated
pretreatment regulations, primarily because of the
difficulty in specifying good monitoring requirements for
all unique situations that exist. The requirements
themselves, will not be in the categorical standards but
will be included in the general pretreatment regulations
as a guide to those who will be implementing a
pretreatment program.
Finally, and of significance, the Agency has agreed not
to propose more stringent pretreatment regulations for
several years. The reason, which I'm sure is obvious to
•Robert B. Schaffer, Director
Effluent Guidelines Division
U.S. Environmental Protection Agency
you, is to give a target that is going to stand still for a
while. Because it takes time to get the necessary
equipment purchased, shaken down, and installed and
because you need some flexibility in financing, the
Agency has agreed to let these regulations stand for
several years. Don't ask me what several years means, I
don't have the answer to that question. Generally,
however, a period of five years is not an unreasonable
expectation. The direct dischargers with a permit have
that amount of time. I think that kind of philosophy is
going to follow through in this particular instance;
however, no commitment has been made on either side.
Let me make that clear.
There are, of course, still questions associated with the
electroplating pretreatment regulations and the general
pretreatment regulations that Steve Schatzow mentioned
earlier in his keynote speech. These regulations are in the
process of being modified.
We continue to be concerned over the impact on
municipal sludges, the severity and the magnitude of that
impact, and how to determine whether it is a good idea to
have heavy metals in municipal sludge. Within the
Agency, there have been a few different philosophies and
conflicts which we finally referred to as "big piles" and
"little piles." Some feel that it is very important to have
very tight control over toxic materials and that they
should not be indiscriminately discharged into the
municipal systems to contaminate municipal sludges, a
practice that would prevent their disposal in ways that are
potentially beneficial or more economical. On the other
hand, others believe that these materials are more
manageable if kept in municipal systems and in
municipal sludges, because then you would have a better
handle on where they are. You would know that the
sludge is within a particular jurisdiction and who has the
responsibility for proper disposal of the solids. The issue
is still under discussion, and I expect it will be for a while.
We initiated a study on municipalities which I refer to
as the 22nd industry. BAT is looking at toxics from 21
industries. We decided that there might be another one - a
pretty good size one - that is the municipalities. So we
initiated the study to look at the occurrence and fate of
toxic pollutants in municipal treatment systems. We have
completed about 40 to 50 percent of that study and have
the results back on 30 percent of it. We tried to select
representative cities that have properly operated
treatment systems that are achieving the secondary
treatment requirements for municipal discharges. We
tried to pick plants that had different types of treatment
technologies installed, such as trickling filters, activated
sludge, etc. We also tried to select plants with differing
geographical locations and with different amounts of
industrial inputs.
-------
The results so far have been very interesting. With no
surprise, we find that the heavy metals are consistently
removed in the municipal systems, up to the point where
they are concentration limited (i.e., solubility limited).
But assuming that a significant amount of metals enter
the plant, the level that is discharged is reasonably
independent of the type of industrial or non-industrial
city that is being sampled. The effluent concentration of
heavy metals from municipal treatment systems is pretty
much the same whether it is from a "dirty city" (i.e., one
having a lot of industrial discharge to be treated) or from
a more domestic residential city where the industrial
contributions are relatively low. There is however a
small, but identifiable pass through in the effluent from
cities with a higher influent concentration. We are also
finding that the organic materials that are entering the
POTW's are also removed to a very high degree. Part of
our reason for summarizing some of the initial data is to
see what kind of impact this will have on the credit policy
that is included in the general pretreatment regulations.
To see what kind of consistent removals we might find, it
turns out that, in highly industralized cities, there are
slightly higher removal efficiencies than in nonindustrial
cities. This generalization is very broad. For most of the
heavy metal pollutants that are in the influent that you
would be discharging and that we are concerned over, a
rough average of about 50 percent removal efficiency
through the municipal system has been initially
determined. This percentage varies somewhat; but from
metal to metal, from city to city, it looks like 50 percent.
By pooling all of the data we have, we will have the
necessary confidence for determining- credits. Much of
this information, as well as additional work of
determining the effect of toxic pollutants on the
municipal treatment systems, will be presented at the
Water Pollution Control Federation meeting in Las
Vegas in October. We expect that our POTW study will
be completed and the results will be presented along with
the results of some research work that is to be conducted
on organics and heavy metals.
Looking into the future and ensuring my invitation to
our next EPA/AES conference, I will now explain our
current BAT efforts on the Mechanical Products
Industry. Electroplating is often found to be part of this
industry. The industry covers about 40,000 facilities
ranging from automobile and aircraft manufacturing to
very small manufacturers of mechanical and electro-
mechanical products. We are finding that the greatest
volume of discharge comes from the electroplating
operation at these plants. We still haven't decided exactly
how to go about subcategorizing this very complex
industry. Also, we will have to decide how to handle what
we call combined treatment, that is the mixing of
electroplating wastewater with wastewater from other
sources prior to treatment. This "comingling" of waste-
water, treating each process source separately, has in
most situations a sound engineering basis. But
comingling also causes great consternation amongst
people in the Agency for very good reason. Since most of
the technologies that we are talking about are
concentration limited, mixing wastewaters that contain
heavy metals can lead to a scenario where many more
toxic materials can be discharged. Since the treatment
technology is concentration limited, independent of the
influent concentration, the increased discharge results in
an increase in total pounds that are released to the
environment. This issue is still under active discussion
within the Agency.
The daily maximum numbers that are in the regulation
at present are:
Copper
Chrome
Nickel
Zinc
4.5 mg/1
7 mg/1
4.1 mg/1
4.2 mg/1
Our study is showing - and this DOES include
combined treatment systems - that we are able to achieve
lower metal concentrations with better technologies that
we are evaluating. Such technologies include chemically-
assisted clarification. We are finding that copper can be
reduced from 4.5 to 2.5 mg/1, chrome from 7 to 2.5 mg/1,
nickel from 4.1 to 0.7 mg/1, and zinc from 4.2 to 1.4 mg/1.
These are the kinds of differences we are seeing in our
preliminary evaluation of our data base. When we have
our technical report together, as an informal rule making
process that we go through, we will circulate the
information to you for your review. This step is not a
formal ruling; it will be your opportunity to comment on
the technical aspects and technical merits of our data
base. One thing that is important, though, is that we do
not have a great deal of information. We are looking at
many other industries that have similar types of problems
and are pooling the data. For example, the inorganic
chemicals industry has many heavy metal problems that
are similar; we also have applicable treatment technology
data from that industry.
Also of interest to you, is a "treatability" manual
currently being developed under a joint effort between
my office and EPA's Office of Research and
Development under the direction of Bill Cawley, who
spoke to you earlier. Our data on organic and inorganic
pollutants is being utilized to describe how various
technologies will perform when properly operated. This
manual will be used in the field by regional and state
officials to assist in making determinations where
guidelines may not directly apply to a given problem or to
a given industrial facility. The manual should be
available by mid-year. It will not be published as a formal
regulation; it will be made available for comment and I
urge you to take a look at it.
I have mentioned organics briefly. In our BAT study,
we have found significant amounts of some toxic organic
pollutants being discharged. We feel that the source of
these organics is the dumping of solvents. These solvents
should be placed in a drum for disposal or, when we reach
a point when it is economical, let's go with resource
recovery. We are going to try to discourage solvent
dumping.
Finally, Steve Schatzow mentioned our interest in
incentives, in innovative technologies with the goal of
approaching zero discharge. I heard this morning that the
goal is not impossible. I head this morning that your
association is looking in that direction. We are not in a
position nor do we want to be in a position of saying that
we must reach zero discharge by 1985. But we are
extremely interested in these kinds of pursuits and we
fully encourage them. It is also encouraging to me that we
have the opportunity or the options down the road of
having economical ways to approach the goal of the Act.
I hope that when I see you again next year, you have all
your treatment in, all your pretreatment programs
operable, and that you will be looking forward to the
solid waste regulations.
10
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POTW Removal Credits and
Revised Categorical Pretreatment Standards
Jon L. Olson and Richard W. Eick*
INTRODUCTION
The Sanitary District of Rockford wastewater
treatment plant provides a secondary-type treatment for
an estimated connected population of approximately
200,000 people and wastewaters from some 500
industries belonging to the U.S. Environmental
Protection Agency's 21 subcategories.1 Based upon
District information, it has been determined that 38
industries can be defined as belonging to the
Electroplating Subcategory and presently discharge
approximately 8 MOD to the sanitary sewer
(approximately 20-25% of treatment plant flow).
In the early 1960's the District final effluent, which
received primary and trickling filter-type secondary
treatment, contained a considerable amount of cyanide
(see Figure 1). As a result, there were a few fish kills in the
receiving stream, which required action by the Sanitary
District and, consequently, by Rockford Industry. In
1966, the District approved a 2.0 mg/L cyanide limit on
all industrial discharge to the sanitary sewer. The
addition of a secondary wastewater treatment system by
the District in 1969 improved the amount of cyanide
removed in the treatment process, resulting in lower
effluent cyanide concentration. In 1974, Ordinance 309
went into effect and lowered the cyanide limit to 1.2
mg/L and included for the first time heavy metal
limitations on industrial discharges.
Ordinance 309 industrial discharge limitations for
cyanide and heavy metals were calculated by the
District's staff who took into consideration, for the first
time, the amount of pollutant removed by the wastewater
treatment plant. The District derived the following
pollutant discharge formula, which was incorporated
into Ordinance 309:
Pollutant Discharge Formula
Effluent Standard
100-(%) Removal
X
SDR Flow
Pollutant Flow
_ mg/L Pollutant Discharge
~~ Limit
Where:
EFFLUENT STANDARD is the applicable Federal,
State or Local Effluent standard for any specific
pollutant, in mg/L.
% REMOVAL is the average percent removal of the
specific pollutant effected by passage through the
*Jon L. Olson, District Director
Richard W. Eick, Plant Operations Manager
Sanitary District of Rockford
treatment works during the preceding twelve months
based upon daily analysis.
SDR FLOW is the average flow received at the
treatment works during the preceding twelve months, in
millions of gallons per day.
POLLUTANT FLOW is the total of Hows from all
known sources which contain or may contain the
pollutant for which the calculation is being made, in
millions of gallons per day.
POLLUTANT DISCHARGE LIMIT is the
maximum allowable concentration of the specific
pollutant which may be discharged to a public sewer, in
mg/L.
The industrial pollutant discharge limits, as calculated
by the above formula and incorporated into Ordinance
'General Pretreatment Regulations for Existing & New Sources of Pollution.
Federal Register June 26, 1978, Part IV. Appendix C.
Figure 1—Final Effluent Cyanide Concentration (annual averages).
FINAL EFFLUENT CYANIDE CONCENTRATION
. (ANNUAL AVERAGES)
11
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Table 1
Ordinance 309/341 Pretreatment Standards
Pollutant
Cyanide (by distillation]
Copper
Cadmium
Nickel
Chromium (Total)
Chromium (Hexavalent]
Zinc
Iron
Lead
Ordiance 309 passed in
Ordiance 341 passed in
Pollutant
Ordinance
1.2
17.6
2.0
6.7
21.8
3.6
16.5
56.0
1.5
1974
1976
Discharge Limit mg/L
309 Ordinance 341
0.9
17.6
2.0
6.7
21.8
3.6
16.5
56.0
1.5
309 (present Ordinance 341), is given in Table I. These
limitations have been and are presently being applied to
industries regardless of their subcategory.
The 1979 annual average cyanide and heavy metals
concentrations in the final effluent are given in Table II
along with their respective treatment plant removal
efficiency. This data has been collected since 1973 and
collection will continue in the future, with some changes
to reflect the Proposed Amended General Pretreatment
POTW sampling requirements.2
The USEPA's removal credit formula to revise
categorical standards was given in the General
Pretreatment Regulations of June 28, 1978 Federal
Register as follows:
Revised Categorical _ Categorical Standard
Standard ~ 1 - r
Where "r" is the percent of the pollutant (expressed as a
fraction) that is removed by the POTW.
Although the basic concept of applying the POTW
removal credits to an industrial discharge limit is
common to both the District and the USEPA methods,
the overall formula and application differs considerably.
The major difference, as outlined in Table III, will result
in stricter limits under the USEPA method. This is, of
course, only conjecture at this time and assumes the
approval of the removal credit concept by the USEPA
method. In order for the Sanitary District to receive
conditional revisions of categorical pretreatment
standards, if at all, there is a considerable amount of
work to be completed by Industry, the USEPA, and the
POTW. Once all the data and reports are completed, an
appropriate decision can be made by the USEPA as to
the applicability of removal credits.
Procedure for Revising Categorical Pretreatment
Standards to Reflect POTW Removal
The October 29, 1979 proposed amendments3 to the
General Pretreatment Regulations outline seven
provisions to be included in a POTW application for
revised categorical pretreatment standards.
(Section 403.7 (b)(2)(v)(i-vii). The Sanitary District of
Rockford has indicated to the USEPA, Region V , in a
letter and general method outline dated December 18,
1979, of its intention to so apply. It is important to the
Sanitary District's pretreatment program and to
'Federal Register Volume 44, No. 210. October 29, 1979, Section 403.7(c)(2)(ih)
and (iv).
'Federal Register Volume 44, No. 210 October 29, 1979.
Copper
Month
January
February
March
April
May
June
July
August
September
October
November
December
Average
mg/L
0.27
0.25
0.42
0.33
0.30
0.13
0.14
0.14
0.08
0.09
0.12
0.24
0.21
%
Rem.
80.0
79.2
53.8
54.8
66.3
83.8
84.9
84.9
90.0
89.4
87.9
71.1
77.6
Table II
Final Effluent Quality and Percent Removal
Total
Cadmium Nickel Chromium 6+ Chromium
mg/L
0.07
0.07
0.08
0.07
0.07
0.03
0.02
0.02
0.01
0.02
0.02
0.05
0.04
%
Rem.
63.2
69.6
57.9
58.8
58.0
88.9f
92.0
91.3
94.7
91.7
90.0
73.7
77.5
mg/L
0.21
0.18
0.18
0.15
0.14
0.12
0.12
0.09
0.11
0.14
0.16
0.20
0.15
%
Rem.
34.4
28.0
28.0
16.7
33.3
33.3
42.9
47.1
56.0
56.3
50.0
52.4
33.9
mg/L
0.10
0.08
0.08
0.07
0.04
0.02
0.022
0.021
0.02
0.04
0.04
0.05
0.05
%
Rem.
85.1
88.7
79.5
75.0
89.5
95.0
94.2
95.5
95.0
92.2
91.3
86.1
88.9
mg/L
0.05
0.04
0.04
0.03
0.02
0.02
0.002
0.001
0.00
0.00
0.00
0.01
0.02
%
Rem.
90.9
77.8
63.6
70.0
80.0
93.9
93.3
90.0
100.0
98.3
98.0
85.7
86.8
for 1979
Zinc
mg/L
0.70
0.61
0.85
0.66
0.56
0.29
0.29
0.33
0.21
0.26
0.34
0.45
0.47
%
Rem.
76.2
80. 1
61. 5
55.1
72.8
88.1
88.1
86.0
87.8
86.0
81.7
75.9
77.6
Iron
mg/L
0.68
0.22
0.38
0.36
0.21
0.18
0.18
0.24
0.14
0.20
0.33
0.32
0.29
%
Rem.
93.3
95.0
89.0
87.0
94.2
95.6
95.6
97.9
95.7
93.4
92.4
90.5
93.3
Cyanide
mg/L
0.029
0.021
0.026
0.033
0.040
0.031
0.031
0.051
0.062
0.055
0.061
0.061
0.042
%
Rem.
90.3
93.6
91.0
84.3
86.7
87.6
87.6
83.0
73.0
80.4
80.9
74.6
84.2
12
-------
Ts ble III
Comparison of USEPA and SDR Pretreatment Standards Determination and Application
Item
\. Basis of Pollutant Limit
2. Removal Efficiency, "r"
3. Number Days "r" Determined
4. Pollutant Concentration Consistency
5. Industrial Sampling Point
6. Industrial Flow Diluted at POTW
7. Contaminated POTW Sludge
8. Limitation for 24-hour Composite
9. Limitation for Grab Sample
SDR Method
Treatment Plant NPDES Limitations
Annual Average
365 Days
Same Limit for All Industrial Categories
Limit Applied End of Pipe from Entire Plant
Accounted for in the Pollutant
Discharge Formula
Not Considered, Applying Sludge to Landfill
Limit as Calculated by Formula
5 Times the 24-hour Limit
USEPA Method
National Technology Based Standards
Average of Lowest 50% of Values
48 Days (12 Days per Season)
Pretreatment Limits Vary with Each Category
Limit Applied After Fretreatment for
That Category
Dilution by POTW not considered in Formula
To be Considered, Must Meet 405 Sludge
Regulations
Limit as Calculated by Formula
Same as Composite Sample
Rockford Industry to determine, as quickly as possible,
which pretreatment standards will apply: revised or
existing categorical standards. It is also hoped that an
early application will help to clarify some of the existing
problems and unknowns. The following seven
provisions. A thru G, will be part of the Districts's
application for revised categorical standards.
A.Industrial Reporting Requirements
These reporting requirements apply in the case of
Rockford industry to the Electroplating Subcategory
since they are presently the only group in Rockford with
applicable final pretreatment standards. If these reports
are not submitted by April 6, 1980, the applicable
electroplating industry will not be eligible for the revised
pretreatment standards, should they be granted by the
USEPA. The seven elements of electroplating reporting
requirements are given below:
1. The name and address of the Industrial User.
2. The location of such Industrial User.
This is the address of the Industrial Plant that is
discharging the electroplating wastewater (if different
from plant headquarters).
3. The nature, average rate of production, and
standard industrial classification of the operation(s).
It is assumed that the SIC code and average rate of
production would be useful should the District choose to
utilize mass limitation based upon volume of product.
4. The average and maximum flow of the discharge(s).
The District also requires that the industry submit not
only the total flow of each discharge, but also the volume
of categorical process water, which in the case of the
electroplating industries would be rinse wastewaters
resulting from operations of alkaline cleaning, acid
pickling, stripping, coloring, and waste which comes
about from spills, batch dumps, and scrubber blow-
down.
It is the District's understanding, at this time, that
tumbling operations prior to plating (i.e. deburring) will
not be included in the term electroplating process
wastewater. The wastewater from this operation will be
considered under the group 18, "Machinery and
Mechanical Products Manufacturing."4
5. The nature and concentration of pollutants in the
discharge from each regulated process.
This should include not only the concentration at the
end of the pipe, but also the • concentration of the
electroplating process wastewater (or after pretreatment
of such wastewater, if available).
6. A statement indicating whether Pretreatment
Standards are being met and, if not, whether additional
operation and maintenance (O and M) and /or additional
pretreatment is required.
As written, the electroplating industry must respond as
to whether they are meeting the electroplating
pretreatment standards. However, if the Sanitary
District has received approval from the USEPA to use
the revised standard, then the Industries would respond
to these. Also, these comparisons must be made not at the
end of the pipe, but at the point where all the
electroplating process wastewaters are combined.
7. If additional pretreatment and/or O and M will be
required, the shortest schedule by which the Industrial
User will provide such additional pretreatment.
To answer items 6 and 7 it is important that the
eleetroplater know as soon as possible which
pretreatment standards will have to be complied with: the
existing electroplating pretreatment standards or the
revised standards.
B.The Sanitary District must comply and submit data in
accordance with the requirements of 403.7 (c)(l)-(7).
1. The District must supply a list of pollutants for
which the revised pretreatment standards are requested.
2. Treatment plant influent and final effluent
concentrations for the above pollutants must be
presented on a daily basis using 1979 data. These influent
and final effluent samples were taken on a 24-hour basis
at a frequency of 6 grabs per hours using a refrigerated
FMC composite sampler. However, this past data,
although comprehensive, is not entirely compatible with
those of the proposed General Pretreatment amendments
because of sampling techniques employed.
a. The influent and final effluent composite samples
were not taken proportional to flow. This was changed
this year under completion of an addition to the plant
activated sludge system, and also a new influent
4Federal Register June 26, 1978, Volume 43, No. 123 "General Pretreatmenl
Regulations . . .," Appendix.
Federal Register June 26, 1978, Volume 43, No 123 "General Pretreatmenl
Regulations . . .," Section 403.7 (c)(l-7).
13
-------
sampling room which was part of the new
administration building expansion. Henceforth, the
samples will be taken proportional to flow.
b. The final effluent composite samples must
incorporate the concept of detention time into the
sampling sequence. This has not been done in the past,
i.e. both the influent and final effluent composite
samples were pulled daily at 12:00 midnight. This was
changed on January 1, 1980 when the influent
composite sample was changed at 12:00 midnight,
while the final effluent was pulled at 10:00 a.m., i.e. a 10
hour average POTW retention time was used.
Henceforth, the influent and final effluent composite
samples will be taken as described above.
c. The cyanide analyses were made daily on the
usual 24-hour composite samples rather than on the
grab samples as required by 403.7 (c)(2)(iv). The grab
sample techniques can be utilized in the future for
comparision with the present method of determining
the removal efficiency.
The Sanitary District believes that the data on the
above influent-final effluent samples collected as
described above, will give an accurate and demonstrable
indication of the pollutant removal efficiency,"especially
since 365 individual days' removal efficiencies will be
examined for each pollutant using an IBM 370 computer.
The program will be written to compare consistent
removal determined by ... "the average of the lowest 50
percent of removal measured. . . ."6
It is the District's belief that, because of the prodigious
amount of influent-effluent data, the 1979 data used will
adequately demonstrate the removal efficiencies.
3. The Sanitary District will supply a list of all the
industries that are presently known to be members of the
Electroplating Point Source Category and which of the
pollutants each discharges.
4. The proposed revised Electroplating Pretreatment
Standards that will apply to the above industries will be
submitted. The formula, as given in 403.7 (c)(4)(i) shall be
used to calculate the revised pretreatment standards.
Revised Categorical __
Standard
Categorical Standard
1-r
Where "r" is the percent of the pollutant (expressed as a
fraction) that is removed by the POTW.
5. A table listing the concentrations of the
approximate pollutants as found in the sludge
thickening tank underflow sludge for 1979 will be
submitted. This underflow sludge, which is composed of
50% primary and 50% waste-activated sludge, is sampled
on a composite basis every two weeks and the
appropriate analysis made.
The above sludge is pumped to the vacuum filter
building for conditioning with lime and ferric chloride,
followed by dewatering with Komline Vacuum Filters.
The resulting cake is disposed of in an Illinois EPA
approved landfill. This vacuum filter cake is also sampled
and analyzed every two weeks for these same pollutants.
6. A description of the POTW's current sludge
disposal methods will be supplied to the USEPA. Any
current sludge disposal permits with the IEPA will be
included with the description.
"Federal Register October 29, 1979; Volume 44, No. 210, Section 403.7 (a)(I).
7. The District will certify that, except where noted,
the pollutant removals and the revised standards were
determined as outlined in the USEPA regulations.
C. Industrial Compliance Schedule with the POTW
Electroplating type industries who are not able to meet
the electroplating categorical pretreatment standards (or
revised pretreatment standards, if known and approved
by the USEPA) must enter into a compliance schedule
with the Sanitary District of Rockford. This compliance
schedule should culminate with pretreatment systems
that will insure compliance by October 7, 1982. In this
regard, it is imperative that the electroplating industries
know whether revised pretreatment standards will be
allowed. Industrial failure to submit a compliance
schedule or to meet any of its scheduled events will mean
the industry will not be eligible for revised pretreatment
standards.
Another similar issue is whether the BAT pretreatment
standards, yet to be promulgated, will have stricter
standards for the typical electroplating pollutants.
Industry needs to know and so does the POTW.
D. The Sanitary District Must Apply for the
Pretreatment Program Approved in a Timely Manner
This will be done and, in fact, the majority of the data
regarding Rockford Industries and toxic pollutants,
especially cyanide and heavy metals, has already been
collected. The Sanitary District is waiting for a State
Grant approval so that an inspector can be hired to
concentrate on organic priority pollutants and Rockford
Industry. It is expected that this yet to-be-hired
individual will make inspections of all Rockford industry
with a knowledgeable industrial representative from each
industry.
This information along with the effluent, and sludge
organic priority pollutant analysis (which was already
completed separately by the USEPA and the University
of Washington, Seattle) should give us a good picture in
this area.
The Sanitary District must enter into a compliance
schedule for development of the pretreatment program
which will be made part of a revised Illinois EPA NPDES
Permit. This compliance schedule will serve as a guide
post to gauge the District's progress toward pretreatment
program approval.
E. Termination of Conditional Removal Credits
The conditional revised standard will be terminated by
the control authority if the District does not comply with
the following:
1. Unable to maintain removal efficiencies
2. SDR does not apply for the pretreatment program
in a timely manner.
3. The District does not comply with the sludge use as
defined in Section 405 guidelines or any other guidelines.
Should the District fail to comply with 1,2, or 3 above,
the industries must achieve compliance with the
applicable pretreatment standards before the prescribed
time period for those standards.
F. Company Failure to Comply
If a company fails to comply with its reporting
requirements, or fails to submit or meet the compliance
dates, then the conditional standards for that particular
14
-------
company are terminated. That company must meet the
applicable pretreatment standards in the required time
period.
G. The Sanitary District must submit the name and
address of each Industrial User that has been given
conditionally revised discharge limits each December
31st. Upon revocation, the District must submit, to the
control authority, the industrial information as given in
II, A, 7-7. The Industry limits will than revert to the
categorical pretreatment standards.
CONCLUSION AND DISCUSSION
Under the new pretreatment regulations, the Rockford
industries belonging to Electroplating Subcategory will
be required to meet stricter discharge limits than
presently imposed by District Ordinance. To what extent
will depend upon whether POTW removal credits will be
allowed. It is imperative for Industry and the POTW that
an early decision on this concept be made by the
USEPA.
The issue of contaminated POTW sludge resulting
from cyanide and heavy metal removal is one of the
primary factors influencing this concept. It is hoped that
the 405 sludge regulations will define the sludge disposal
options that are available to the POTW. It would appear,
from many previous comments by the USEPA, that only
agricultural application of municipal sludge will be
considered. What is to happen with the municipalities
that are presently using approved incineration or landfill
disposal techniques? The decisions made by the USEPA
on the desired sludge "quality", once made, must be
applied uniformly and equally throughout the United
States.
Another problem that the USEPA must resolve is the
application of different pretreatment concentration
limits of a similar pollutant from different subcategories
to a single industrial discharge. If this single company has
a common pretreatment system, which pretreatment
standards are applicable?
The POTW will be responsible for submitting its
Pretreatment Program to the control authority for
approval in a timely manner. The Sanitary District of
Rockford is committed to this and expects to receive
approval by the July 1983 deadline. If past experience is
any guide, there are many as yet unknown problems
ahead for the District in the fair, reasonable, and just
application of these regulations to Industry.
The Industries, as required, will have to install
appropriate pretreatment systems to meet the discharge
limitations to the sanitary sewer. Industry should, at this
point, consider two very important factors that will
determine the.ultimate success of their pretreatment
system: (1) if necessary, have an experienced consultant
help with the design engineering. Checking with his past
clients could be informative. (2) Have a qualified
pretreatment system operator to run the operation and
make him responsible for the effluent quality. This
operator must regard the effluent quality as his final
product. After all is said and done, it is the effluent
quality that is of primary concern and the reason for the
Pretreatment Program.
15
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Electrochemical Reactor and Associated
In-Plant Changes at Varland Metal Service, Inc.
Edwin Roof
INTRODUCTION
This report will describe the background and present
status of the Joint Demonstration Project sponsored by
the Metal Finishers Foundation and the Environmental
Protection Agency at Varland Metal Service,
Incorporated, Cincinnati, Ohio.
The purpose of this demonstration project is: to
evaluate the use of a unique electrochemical system
designed to reduce pollutants from an electroplating
plant to meet EPA regulations; to evaluate the capability
of the system to recover the valuable metals in the rinse
water for re-use in the plating processes; and to minimize
the formation of sludge.
Varland Metal Service, Inc. - Background
Varland Metal Service, Inc., is an electroplating job
shop. The Company was founded in 1946 and
incorporated in 1947 by Curtis M. Varland, W. Wilson
Loveless, and Edwin Roof.
The Varland plant is a multi-process plant with the
following processes: (1) automatic barrel cyanide zinc; (2)
hoist barrel zinc, cyanide and chloride, (3) hoist barrel
cyanide copper, bright nickel, tin, cyanide cadmium,
cyanide brass; (4) automatic barrel cyanide copper and
bright nickel; (5) hoist phosphating, barrel and rack; (6)
hoist rack zinc and cadmium, cyanide; (7) automatic rack
cyanide zinc; (8) rotary barrel chromium; (9) basket and
rack chromium; (10) mechanical plating, zinc, cadmium,
and tin; (11) chromating, bright dipping of brass,
passivating of stainless steel and other similar processes.
The Varland plant has approximately 47,000 total
square feet of floor space. Annual sales are in the
$2,500,000 to $3,000,000 range; total employment
numbers 60 to 70.
In 1974, a major step towards furture compliance with
local and federal anti-pollution regulations was the
establishment of a modern laboratory for analysis of
waste streams. Included was an atomic absorption
spectrophotometer for analysis of metal discharges.
Later in 1974, an engineer was employed to set-up a
comprehensive sampling and analytical program to
determine what steps should be taken to meet
regulations.
By the end of 1976, it was clear that much work needed
to be done. City of Cincinnati revised regulations of Sept.
*Edwin Roof, Executive Vice Pres., Chemical Engr.
Varland Metal Service, Inc.
Cincinnati, Ohio
1, 1976 with a compliance deadline of July 1,1979, called
for the following limits:
CN-T
CN-A
Zn
10 mg/L
2mg/L
6 mg/L
Cr-T
Cd
pH
6 mg/L
3 mg/L
6.0 to 10.0
Final EPA pretreatment limits had not yet been
promulgated, but they were expected to be even tighter.
By contrast a typical analysis of the wastewater at that
time was
PPM IN
Usage, gal
216,000
pH
7.0
24 HR COMPOSITE SAMPLE
CN-T
15.8
Cd Cr Cu Ni
1.0 11.8 3.3 6.7
Zn
37.5
It was obvious that some type of waste treatment
should be installed. Accordingly, an intensive real estate
acquisition program was pursued to buy some additional
land adjacent to the plant and a successful campaign was
waged at City Hall, in spite of some neighborhood
resistance, to get the newly acquired land rezoned so that
waste treatment facilities could be installed.
By the end of 1977, an engineering firm was retained,
and preliminary work was begun on design of a
conventional treatment plant to treat 300,000 gallons of
waste per day, to allow for growth. We felt we already
had good water conservation with Dole flow restrictor
valves on all rinses, and with all rinses being counter-
flow. At this point in time, we received the opportunity to
participate in the MFF-HSA research project.
HSA REACTORS LIMITED - BACKGROUND
HSA Reactors Limited of Toronto, Canada is a
company formed to research, manufacture and market
these electrochemical systems. The system is based upon
research undertaken in 1974 by Drs. Das Gupta and Fleet
in the Department of Chemistry at Imperial College,
University of London, England. The system features the
use of an electrochemical cell with graphite electrodes
designed to increase the mass transfer rates and thus
increase the efficiency of the metal removal process.
Early in 1975 this work was brought to the attention of
Ian Kennedy, now the President of HSA Reactors
Limited, by Dr. A. Barringer, of Barringer Research,
Toronto, an alumnus of and visiting professor at
Imperial College. During the latter part of May, with the
help of numerous scientific and engineering consultants,
an extensive test program was designed for the
electrochemical system. This test program was conducted
-------
at Imperial College under the supervision of Mr.
Kennedy in early June, 1975, with completely
satisfactory results. An agreement to finance the ongoing
research, development and commercialization of the
system was rapidly concluded, and the company was
incorporated on July 19, 1975.
The cell was orginally envisioned as having three
possible practical industrial applications, namely
pollution control of metals in solution, hydrometallurgy,
and organic synthesis. At an early date, HSA decided to
focus its efforts on pollution control applications.
BACKGROUND OF THE
JOINT DEMONSTRATION PROJECT
In June, 1976, at the AES Convention in Denver, Ian
Kennedy met Simon Gary, of Scientific Control
Laboratories, Chicago, and they discussed the invention.
Mr. Gary recommended that HSA contact NAMFs
Metal Finishers Foundation, and this was done. As a
result of this contact, Bill Crawford of Chrome-Rite
Company of Chicago and Ed Durkin of Advance Plating
Company, Cleveland, went to Toronto to investigate the
use of these cells in the metal finishing environment. They
were both impressed with the possibilities for the use of
this cell in pollution abatement in the metal finishing
industry and invited Mr. Kennedy to appear in December
of 1976 at a meeting of the trustees of the Metal Finishers
Foundation in Atlanta. Based on a presentation by Mr.
Kennedy and confirmed by the observations of Mr.
Crawford and Mr. Durkin, the trustees of the MFF
appropriated $15,000 towards the cost of a
demonstration project in the Chrome-Rite plant in
Chicago.
In June, 1977, at the Chrome-Rite plant, industrial
scale research reactors were demonstrated by HSA
personnel. All analytical work evaluating results was
done by Scientific Control Laboratories. At the same
time, a full scale plant assessment was done by HSA
personnel, locating and classifying the point sources of
pollutants in the Chrome-Rite plant.
The results of the demonstrations were phenomenal.
This was later documented by Mr. Kennedy in a paper
presented to the first EPA/AES Pollution
Control Conference in Lake Buena Vista, Florida, in
January 1978. The demonstrations confirmed the
feasibility of an eJectrochemical treatment approach. The
system was applied to end of pipe discharges both before
and after a conventional alkali chlorination system as
well as on individual rinse tanks discharges.
In October, 1977, following extensive discussions with
Mr. George Thompson of EPA, HSA Reactors
submitted to the Metal Finishers Foundation a proposal
to participate in a joint demonstration program to
demonstrate the technical and economic capabilities of
their electrochemical reactor in waste treatment. MFF
accepted the proposal and applied to EPA for a grant of
$155,000. to finance a portion of the demonstration
program. The grant was approved by EPA in June, 1978
and Varland Metal Service Incorporated, in Cincinnati
was designated as the metal finishing plant for the
demonstration program.
The Varland plant was one of five plants selected by
MFF. Mr. Kennedy inspected the five plants and with the
approval of EPA and MFF selected the Varland Plant.
The joint demonstration program was to be
implemented in three phases. The initial part of Phase I
involved a Plant Assessment Survey of the- Varland
operations, as shown in Figure 1.
The remainder of Phase I was to include a follow-up to
the recommendations of the survey report and the design,
construction, and installation of a series of reactor units.
Phase II of the program was to be composed of a six-
month operation period for the reactor systems.
Phase HI was to allow for a four-month analysis and
evaluation of the operating data prior to submission of
the final project report.
PLANT ASSESSMENT
1. Analysis of plant layout and operating
practices
2. Examination of process water usage
3. Identification of sources of pollution
4. Recommendations for step-by-step
program of changes
5. Basis of plan for controlling pollution
Figure 1
STRATEGY FOR POLLUTION CONTROL
The Joint Demonstration Program involves a rational
approach to pollution control and to achieving
compliance with effluent regulations. Rather than
planning "end of pipe" treatment for existing plant
operations, the strategy which Varland is following
involves:
I. A thorough Plant Assessment (see Figure 1).
2. Implementation of point source recovery and
treatment wherever possible.
3. Installation of final treatment equipment as
necessary.
The first two steps in this strategy will reduce both the
volume of process water and the pollution loading in this
water which must be treated at "end of pipe." This is
expected to result in lower cost for pollution control as
well as significantly reducing the generation of sludge.
PLANT ASSESSMENT
In August, 1978, the Phase I Plant Assessment Survey
was carried out by HSA at Varland, and a report of this
Assessment was submitted to Varland and the EPA in
October, 1978. The Plant Assessment included: (a)
analysis of plant physical layout, operating practices and
procedures and the recommendations of any changes
which would result in lowering the contaminant levels in
the final plant effluent discharge; (b) examination of
process water usage and recommendation of ways to
reduce the plant usage of process water as well as
identification and segregation of the process waters not
requiring final treatment; (c) sampling to determine the
type, quantity and nature of the pollutants; isolation and
identification of the point sources within the plant of
these pollutants; (d) formulation of a step by step
program to effect in-plant control of pollution, and; (e)
providing a plan for compliance with local and EPA pre-
treatment guidelines.
The Assessment resulted in more than forty
recommendations for improving general operating
17
-------
PLANT ASSESSMENT
RECOMMENDATIONS
• Elimination of pollution sources
• Reductions in process water usage
• Housekeeping and maintenance
• Attitude toward pollution control
Figure 2
practices. (See Figure 2)
Most of the Recommendations made by HSA have
been implemented or are planned to be implemented in
our program to control pollution. In addition, we have
applied the concepts discussed with HSA along with
ideas from our own staff in continuing to look for other
ways to reduce pollution levels.
Many of the changes which have been made are
difficult to evaluate in terms of cost and more difficult to
relate to specific benefits. For example, longer drainage
times on some lines have slowed down production rates.
However, we feel that the longer drainage times have
contributed to reduced dragout and hence have
facilitated the reduced usage of process water and saving
of process chemicals.
Some specific results from the Plant Assessment can be
identified as follows:
1. Process water usage has been reduced approximately
45% for a c,ost saving of $15,000 per year. More
importantly, the basic principles will make possible
further water savings in the future.
2. An annual saving of approximately another $11,000
has been achieved through a decrease in chemical
usage.
VARLAND METAL SERVICE
FINAL EFFLUENT ANALYSIS
Total Cyanide
Free Cyanide
Cadmium
Chrome
Copper
Nickel
Zinc
BEFORE PLANT
ASSESSMENT
(GRAMS)
11,973
9,191
885
9,925
2,195
5,812
27,451
AFTER PLANT
ASSESSMENT
(GRAMS)
10,513
5,356
743
5,751
1,780
4,054
22,064
DIFFERENCE
(GRAMS) (PERCENT)
—1 ,460 —1 2
—3,735 —41
-142 —16
—4,174 —42
-415 —19
-1 ,758 —30
—5,287 —20
Daily Process
Water Usage
(Gallons) 205,000
Figure 3
113,000 —92,000 -45
3. The above reductions in process water usage and
chemical usage will make a very significant
contribution to reducing the pollution loadings in the
final effluent and the costs for pollution abatement.
(See Figure 3)
4. Another result of the implementation of the survey
recommendations is a noticeable change in the
attitude of our employees - a realization that success in
meeting goals of the pollution abatement program is
an absolute necessity in guaranteeing the future of
their jobs.
5. The direct costs incurred to achieve the above savings
consist of: (a) $5,000 capital cost of new conductivity
cells and timer control valves (with an estimated 5 year
life, for simplicity this can be considered as a $1,000
annual cost); (b) $7,500 annually for additional
maintenance for the conductivity cells, additional
cleaning of tanks, etc.
PLANT ASSESSMENT
COSTS/BENEFITS
PER YEAR
15,000
11,060
26,060
1,000
7,500
DIRECT TANGIBLE BENEFITS
Reduced process water usage
Reduced chemical usage
COST TO IMPLEMENT
Conductivity cells
Labour (Maintenance)
Net annual savings
PLUS:
Reduced pollution control costs
Figure 4
See Figure 4 for Cost/Benefit Ratio.
Some other costs required to meet Assessment
Recommendations, but which are not directly connected
with the cost savings are; (through Dec. 31, 1979).
8,500
17,560
1. Lining Tanks, Previously Unlined $8,530
i2. Titanium Anode Baskets to Replace Steel
Baskets.in Cyanide Plating Solutions (This
does not complete the replacement program) $5,833
3. New tanks, to set-up the "well ordered" lines,
to replace some "disorganized lines" $9,970
Total other costs $24,333
Other highly significant information developed in the
Plant Assessment is that the amount of production in a
given process varies widely from week to week, and that,
not surprisingly, the amount of the particular metal
pollutant also varies widely from week to week,
practically in direct proportion to the sales. This
relationship was charted for barrel copper plating, barrel
zinc plating, and barrel cadmium plating over a 5 week
period. The sales variability (and pollution variability),
defined as maximum weekly sales divided by minimum
weekly sales, was approximately 3 to 1 for cadmium, 2 to
1 for zinc, and 6 to 1 for copper. This points out the
fallacy of depending on any 1 day effluent monitoring to
get a true picture of a particular plant's pollution
problem; a longer study is necessary unless it is first
established that the particular plant has very uniform
production.
Also highly significant is the fact that regular "dumps"
of process solutions contribute greatly to the pollution
load. These are not "dumps" of plating solutions or
concentrated process solutions or dips, discarded
18
-------
alkaline cleaner solutions, acid pickling solutions, etc.
These solutions are normally bled into the discharge
slowly so that the normal pH control keeps the effluent
within acceptable limits. The contribution of such
"dumps" for one typical week to the effluent was, in
mg/1:
HSA REACTOR PROCESS FLOW
z«
23
Cu
0.4
Ni
0.3
Cd
0.1
Cr
8.8
HSA has identified the above problem and is
presumably working to develop a solution.
HSA REACTOR
The main thrust of the HSA Reactor program thus far
has been the development of a closed loop reactor
treatment system to work with cyanide plating solutions,
cadmium, copper, and zinc, to destroy the cyanide and
recover the metals from the rinses immediately after the
plating bath.
A cadmium unit has been in operation in the plant for
almost one year, but has been extensively modified or
rebuilt from time to time, a normal procedure for
research and development units. A unit similar in design
principles to what will be offered in the near future as a
commercial unit is presently in operation in the plant,
and that unit will be described here.
SCHEMATIC OF HSA REACTOR SYSTEM
t
Figure 7
reactor handles the cadmium from two sources. Our
production is normally higher in the barrel line and the
dragout tank is smaller (160 gal vs 700 gal), thus this
arrangement sends the highest concentration of metal
into the reactor, allowing it to operate most efficiently.
PROCESS FLOW DIAGRAM FOR CADMIUM REACTOR
SYSTEM INSTALLATION AT VARLAND
BARREL LINE
WORKFLOW
DRAGOUT
ORAGOUT
RINSE WATER
I RINSE EFFLUENT A
HOIST LINE
RINSE EFFLUENT B
PROCESS IN
• Metals
Metal Cyanides
Free Cyanide
OUTPUT
*• Low concentration
of metals, cyanide
High Surface Area
Electrode
Figures
Figure 5 is a schematic representation of the reactor
system. During the plating step, the metal is deposited on
the carbon fibre cathode while cyanide is electro-oxidized
and electrochlorinated at the anode. After the cathode is
sufficiently loaded, the metal is stripped into a separate
solution. The metal is recovered either by electrowinning
from the strip solution or by using a strip solution
compatible with the plating bath and adding the metal
CADMIUM PLATING SEQUENCE
FROM
CLEANING'
TO
POST DP
Figure 6
concentrate directly to the bath. Figure 6 shows,
schematically, the work flow through the cadmium
plating bath and the Reactor Process Solution. Figure 7
shows the solution flow and Figure 8 shows the combined
work flow and process solution flow in our plant.
The solution from the dragout tank on the cadmium
barrel line is pumped through the reactor to the dragout
tank on the cadmium hoist line, then back to the
cadmium barrel line to close the loop. In this way, one
SEWER
Figure 8
The comparatively large volume of hoist rinse solution
acts as a buffer and prevents sudden surges in cyanide or
cadmium concentrations.
The closed loop process solution is maintained at pH
10 with NaOH and sodium chloride is maintained at 100
g/1-
• Sample prior to barrel addition.
• Sample Immediately altor barrel addition
Tlmefmln.)
CADMIUM REMOVAL — BARREL DRAQ-OUT TANK
Figure 9
Figure 9 shows the performance of the unit for
cadmium removal. As each barrel is rinsed,
19
-------
approximately 11/2 liters of solution, 27 grams Cd and
100 grams CN, is dragged into the system. In the test
shown here, the maximum cadmium dragged out from
the HSA process rinse into the running rinse was about
.18 grams of cadmium per barrel, thus effectively
removing 99.4% or more of the cadmium that would
otherwise have gone into the effluent. The reactor plated
out enough cadmium so that a low concentration would
be found in the process tank when the next barrel load
was rinsed. The D. C. power to the reactor was 600 amps
at 4 volts; flow rate was 40 liters per minute.
Removal rates for cadmium depend on the
concentration of the solution entering the reactor. With a
comparatively low production level during this test,
cadmium was removed at an average rate of 0.6 mg per
minute or, at 600 amps, 1 mg per ampere minute. Other
tests, not shown in detail here, indicated cadmium
removal rates of 8 mg per ampere minute with an input to
the reactor of 200 to 250 mg/1 from the process solution.
In this test, cyanide was not completely removed. The
flow rate at 40 liters per minute and the current, 600 amps
at 4 volts, remained unchanged. This concentration in the
drag out tank would correspond to 99% removal of the
cadmium that would otherwise be discharged to the
sewer. If this removal rate is considered in relation to an
average total plant flow of 300 liters per minute, a
production rate of 5 barrels per hour would still leave the
cadmium in the effluent from this source at less than 0.1
ppm; without the reactor, the cadmium would be 10 ppm
from this source.
34mD/A-nHl> j
202 g 1
Time (minutes)
REMOVAL RATE FOR CYANIDE
Figure 10
Figure 10 shows Removal Rate for Free Cyanide under
the same conditions as shown in Figure 9 for cadmium
removal; 600 amps at 4 volts, flow of 40 liters per minute.
Removal rates shown here and confirmed by other work
indicate a removal rate of about 4 mg per ampere minute
with input to the reactor in the 200 to 600 mg/1 range. A
production rate of 1.4 barrels per hour would be at
equilibrium with this removal rate. If this is compared to
an average total flow of 300 liters per minute, free cyanide
in the effluent from this source would be under .03 mg/1.
Without the reactor, free cyanide would be almost 8 mg/1
at 1.4 barrels per hour.
The reactor system used in the above tests had one
reactor module containing six reactor frames. A system
of this size under our operating conditions was able to
treat the dragout from 1.4 barrels per hour. More frames
can be added to the module and additional modules can
be added to the system according to operating conditions
and dragout levels to be treated.
The size system required also depends on whether or
not cyanide removal is to be done entirely by the reactor
system. As previously indicated, one could take
advantage of significantly higher metal removal rates if
some of the cyanide were to be destroyed with chlorine or
sodium hypochlorite.
CADMIUM REACTOR
PERFORMANCE
OCT. 24, 1979
Time (hours)
Figure 11
Figure 11 shows a different test of cadmium reactor
performance - in this graph, the cadmium removal and
the cyanide destruction are shown together. The removal
rates are essentially the same as previously stated.
To summarize, if this reactor unit is operated with one
6 frame reactor module, 600 amps, 4 volts, and a
production rate of 1.4 barrels per hour average, and total
plant effluent is 300 liters per minute, total contribution
to the effluent from this source will be under .015 mg/1
cadmium, under .03 mg/1 free CN. Without the reactor
system in place, the comparable contributions would be
2.8 mg/1 cadmium and 7.8 mg/1 free CN. This constitutes
better than 99 1/2% removal of both cyanide and
cadmium. The same reactor unit could give
approximately the same level of cadmium in the final
effluent at a considerably higher production rate, but
some portion of the cyanide would have to be destroyed
with NaOCl. Also, satisfactory performance could be
achieved at any production rate by increasing the size of
the system.
Please note that the above capacity figures do not
allow for lost reactor time for stripping, down time for
maintenance, etc. However, on the other side of the coin,
removal and destruction capacity can be increased
somewhat, but not proportionately, by increasing the
amperage from 600 to 800.
Please also note that all cyanide analyses are for "free"
cyanide - no distillation step was used as is required in
CN-T analysis for final effluent.
Much of the experimental work done to date deals with
the method of stripping and recovering the cadmium
from the cell. The initial method used a sulfuric acid
solution; this worked quite well. The cadmium could be
recovered from the solution by electrowinning.
By modifying the cell design, it is possible to use a
different stripping scheme. This utilizes a heated cyanide
solution, made up by using some of the plating solution
from the bath and augmenting the cyanide content. The
enriched solution will be returned at intervals to the bath
and fresh plating solution will be made available for
20
-------
CONTRIBUTION
(ppm)
1.2 — 2.0
0.4 — 0.6
0.3 — 0.5
TREATABLE BY
HSA REACTOR
CADMIUM LEVEL IN FINAL EFFLUENT
POINT SOURCE
Hoist/Barrel drag-out
Cleaners/Strips
Dips
HSA predicts:
PROCESS FLOW DIAGRAM FOR ZINC REACTOR
SYSTEM INSTALLATION AT VARLAND
Cadmium in final effluent
Without
HSA Reactor ^-1.9 — 3.1 (ppm)
With
HSA Reactor -^- 0.4 — 0.6 (ppm)
Figure 12
stripping. This method also seems to work well. None of
the enriched solution has yet been added to the
production bath, but Hull Cell tests indicate that such
additions will cause no difficulty.
Figure 12 is an estimate by HSA of what our cadmium
will be in the final effluent based on full time use of the
existing reactor unit in the plant and based on total
cadmium production being approximately where it has
been for the last year. The 0.4 to 0.6 is, of course, well
below EPA's standard of 1.2 for daily maximum and 0.7
for the 4 day average.
BARREL ZINC PLATING SEQUENCE
FROM
CLEANING
D
POST
DIP
Figure 13
COPPER AND ZINC UNITS
The Reactor Unit for Copper (to be used on two
cyanide barrel copper plating operations) was delivered
on April 7,1980, and was installed and operating by April
14, 1980. No test data on its use in our plant is yet
available, but test results from HSA's lab indicate it
should operate well. The unit has 4 reactor cells,
connected in parallel for solution flow and in series
electrically. Stripping of the copper from the cell will be
done with a cyanide solution. The process flow diagram
will be quite similar to that shown for zinc. The zinc unit
is scheduled for delivery and installation April 30, 1980.
Figure 13 shows the work flow through our barrel zinc
automatic plating machine. Figure 14 shows the planned
process solution flow from the various zinc sources to the
reactor.
In both the copper and zinc systems, we will use a surge
tank to supply process solution to the reactor. This tank
has two compartments separated by an overflow dam -
total volume is 550 gallons. The zinc reactor pumps from
the dirty side, zinc wise and cyanide wise, through the
reactor, returning the solution with decreased zinc and
Figure 14
cyanide content to the clean side. At the same time,
"clean" process solution is pumped to the dragout
recovery tanks on the various zinc lines, three.of which
are shown here. The loop is closed by returning "dirty"
process solution back to the "dirty" side of the surge tank.
PROPOSED CLOSED-LOOP TREATMENT
SYSTEM FOR ZINC PLATING LINE
f \
Figure 15
Figure 15 shows how we plan to complete the job on
our zinc plating operations by using a closed loop
treatment system for rinsing after acid pickling before
plating. We plan to settle or filter out the iron in the rinse
while allowing the zinc to remain in solution and be
dragged into the plating bath.
Finally, Figure 16 shows a brief summary of the
desirable features of the HSA Reactor System.
I want to take this opportunity to thank the personnel
at HSA for their help with this paper and for their
continued work in our plant to help us, and hopefully
much of the plating industry with what appears to be a
FEATURES OF HSA
REACTOR SYSTEM
• Electrochemical system
• Metal recovery without
impurities
• Low operating costs
• No sludge produced
• Compact, modular units
Figure 16
21
-------
very valuable tool in pollution control. I particularly
want to thank Ian Kennedy, Sankar Das Gupta, Bernard
Fleet, John Moore, and Graham Dickson.
REFERENCES
1. Ian F. T. Kennedy, Electrochemical Cell for Treating
Plating Wastes, AES/EPA Seminar, Buena Vista,
Florida, January, 1978.
2. I. F. T. Kennedy and S. Das Gupta, Electrochemical
Treatment of Metal Finishing Industry Effluents in
Chicago in June 1977. Metals Finishers Foundation
Report, January, 1978.
3. I. F. T. Kennedy and E. Durkin of MFF, Application
document to EPA for Grant, November 1977.
4. HSA Staff, Regular progress reports on
demonstration project as regularly submitted to EPA,
the Metal Finishers Foundation and to Varland Metal
Service, Inc.
22
-------
The Application of Separation Processes In
The Metal Finishing Industry
Peter Crampton*
ABSTRACT
The high cost of raw materials and pollution control provides the economic incentive to
invest in process units which reclaim raw materials from waste streams. Evaporation, ion
exchange, reverse osmosis, and electrodialysis are separation processes which have found
application for raw material recovery. The range of applications of these processes, as well as the
economic factors which limit their use are explored. Low cost plating drag-out recovery systems
and the economics of wastewater recycle processes are high-lighted. A ko discussed is the
application of metal selective ion exchange resins to "polish" the effluent from a conventional
hydroxide treatment process.
INTRODUCTION
Today, both economic and regulatory pressures are
having significant impact on the cost of doing business in
the metal finishing industry. Raw materials and utility
prices have increased markedly. Environmental controls
on wastewater discharges and solid waste disposal
impose an additional penalty for inefficient use of raw
materials. The economic incentive for making more
efficient use of energy, water, and raw materials is
significantly greater for metal finishing firms than it was
several years ago.
Processes which recycle raw materials from what were
formerly waste streams have found increasing use. The
justification for the recovery processes are derived from
reduced operating costs for end-of-pipe pollution control
and raw material savings. These processes have in
common the ability to separate specific compounds from
a water solution, yielding a concentrate of those
compounds and relatively pure water. The processes
which have enjoyed the broadest commercial success in
this area include evaporation, ion exchange, reverse
osmosis, and electrodialysis.
EVAPORATION
Figure 1 shows an evaporator used to concentrate rinse
water and recycle drag-out back to the plating bath.
Plating chemical recovery is the only commercially
significant application of evaporation in the metal
finishing industry. As shown, the condensed vapor
overhead is of high purity and is reused for rinsing. This
particular system utilizes closed loop recovery. The
closed loop recovery system has the advantage of totally
eliminating a water discharge from the plating process.
Such an approach, however, requires sufficient water to
be evaporated and recycled to satisfy rinsing
requirements. With the high cost associated with energy,
*Peter Crampton
CENTEC Corporation
Fort Lauderdale, FL
high evaporative rates can quickly erode the savings
associated with raw material recovery.
Figure 2 depicts an evaporative recovery system
reclaiming chemical dragout from a chromium plating
operation. This recovery system is an open-loop type.
The rinse rate in the recovery rinse section is set to achieve
the maximum savings in terms of operating costs. The
balance of the rinsing is be accomplished in the free rinse,
which discharges to waste treatment.
PRODUCT FLOW
AND DRAG-OUT
SUMl/F
FIRST Ik SECOND / THIRD
RINSE // RINSE U( RINSE
TANK U\ TANK // TANK
DISTILLATE
CONCENTRATED PLATING
• STEAM OR HOT WATER
• COOLING WATER
Fig. 1—Closed-Loop Evaporative Recovery System.
DRAG-OUT = 1gph / 40 oz/gal
H,CrO.
TO WASTE TREATMENT
DISTILLATE
CONCENTRATE
Fig. 2—Open-Loop Evaporative Recovery of Chromium Plating Drag-Out.
23
-------
Evaporators, which are available in materials of
construction suitable for non-corrosive or highly
corrosive applications, have been demonstrated for
recovery of chemical dragout for virtually every plating
solution in commercial use today. Despite this versatility,
reliable operation and process simplicity, the use of
evaporators for dragout recovery has been limited to
plating operations with high dragout rates, due mainly to
the considerably savings needed to justify the high cost of
installing and operating conventional evaporative
recovery systems.
Figure 3 illustrates this limitation by comparing the
return on investment of an evaporative recovery system
to the quantity of chemical drag-out from a chromium
plating; operation. In this analysis, investment cost for a
o
a:
x
<
LU
U.
40
30
20
10
DRAG-OUT RATE
(Ib H2 CrO,, /hr)
Basis
$30,000 Investment required
for 25 gph evaporator Energy
cost equals $4/10" btu
Operation 4000 hr/year
Tax rate is 48% of profit
Fig. 3—Drag-Out Recovery Investment Justification as a Fuction of Drag-
Out Rate.
capacity units were available. Referring back to the open-
loop recovery system shown in Figure 2, what would be
the optimum recovery rinse rate in terms net operating
savings?
Net operating savings are defined as the value of
recovered chemicals and savings in pollution control
costs minus the utility cost to operate the evaporator. As
shown in Figure 4, based on an energy cost of $4 per
million Btu's savings are maximized at a recovery rinse
rate of six gallons per hour. Or looking at it another way,
savings are maximized when 6 gallons of rinse water are
evaporated and recycled per gallon of dragout. At that
rinse rate, 95 percent of the chemical drag-out is
recovered and the energy cost associated with the
evaporative duty is less than 25 cents pe_r hour.
in
o
2 3
>
1/1
o
z
I >
UJ
o.
o
I
I
0 5 10 15 20 25
RECOVERY RINSE RATE (gph)
Basis
Net savings are defined as savings
in recovered raw materials and pollu-
tion control costs minus utility cost
to operate the evaporator.
Energy cost = $4/10* BTU
Fig. 4—Optimum Recovery Rinse Rate for Open-Loop Recovery System
Shown in Figure 2.
25 gallon per hour evaporator was assumed to total
$30,000 and the unit depreciated over 10 years; energy
cost equal to $4 per million Btu's and typical labor and
maintenance costs were used to determine operating
costs. Savings were based on raw material recovery,
wastewater treatment cost reductions and reductions in
solids waste quantities. These savings totalled $1.80 per
pound of chromic acid (H2CrO4) recovered. Using this
basis, a reasonable return on investment is achieved for
drag-out rates above three pounds of chromic acid per
hour. For plating baths with drag-out rates below two
pounds per hour of chromic acid, installation of this
recovery system is not economically feasible.
It should be pointed out that tax credits associated
with investments in pollution control hardware were not
included in the above analysis. The credits would
improve the economics of investments that would
otherwise be marginal; however, a plating operation with
low drag-out rates would still not be able to justify such a
recovery system.
The range of applications for evaporative recovery
systems could be increased significantly if low cost, low
Considering the low evaporative rate needed to gain
the lion's hare of the dragout losses from this plating step,
it would seem unnecessary to purchase a continuous
automated evaporative recovery system. These systems
typically have minimum size units with capacities of 25
gallons per hour and installed cost in the range of $25,000
to $35,000.
Two low cost evaporative recovery techniques are
available. They are direct drag-out recovery by recycle of
rinse water to the plating bath to make up for surface
evaporation losses and the use of low cost, low capacity
batch evaporators to concentrate rinse water for recycle.
Recycle of rinse water to the plating bath to make up
for surface evaporation losses (Figure 5) is a form of
evaporative recovery that has the advantage of minimal
investment requirements. For high temperature baths
operated in the 150° F temperature range, sufficient
evaporation will occur to reclaim the bulk of the dragout.
Use of air agitation in the plating tank will increase the
surface evaporation rate. Make-up to the bath can be
done manually or automated as shown in Figure 5. In the
Figure, level sensors control make-up to the bath and
24
-------
SURFACE EVAPORATION
WATER SUPPLY
PLATING BATH
— LEVEL CONTROLLER
Fig. 5— Automatic Rinse and Recycle Recovery System.
additions of fresh rinse water.
For baths where the surface evaporation rate is not
sufficient to effectively utilize rinse and recycle recovery,
a simple batch evaporator, or still, can be used to enhance
recovery.
Stills of the sort recommended for this application can
be constructed in the shop or purchased. Figure 6 shows a
home made unit used to augment surface evaporation
from a nickel plating solution. Steam supplied to the coil
heats the solution, which humidifies air bubbled through
the solution. A convenient recovery procedure using a
batch evaporator of this type is presented in Figure 7.
HUMIDIFIED
AIR
SUPPLY '
NTRATE
NG BATH
|
M
.
.11
(c
a
C<
°o°o o°o "o0*0 o
*
D
< STEAM
AIR SPARGER
Fig. 6—Batch Atmospheric Evaporator.
MAKE-UP WATER
•*•
cr
P
PLATING
BATH
-p c
-i^^Jq-
STILL
RINSE A
BATCH
EVAPORATOR
p
STILt
RINSE B
FREE
RINSE
TRANSFER SEQUENCE
1) TRANSFER EVAPORATOR CONCENTRATION TO PLATING BATH
2) TRANSFER STILL RINSE A TO EVAPORATOR
3) TRANSFER STILL RINSE B TO STILL RINSE A
4) ADD FRESH WATER TO STILL RINSE B
Fig. 7—Batch Recovery System Daily Sequence.
For baths with no surface evaporation losses, the
evaporator can be fed a blend of rinse water and plating
solution to provide the volume in the plating bath for
recycle of the concentrate.
Figure 8 is a schematic of an atmospheric concentrator
which sells commercially for approximately $6000. The
unit has an evaporative rate between five to ten gph.
Although this and the unit shown in Figure 6 may not be
HEAT
EXCHANGER-
EXHAUST
A
PACKED COLUMN
SUCTION PUMP
BLOWER
SUMP
Fig. 8—Batch Atmospheric Evaporator.
energy efficient, the fact that they consume only small
amounts of energy makes insignificant the cost penalty
associated with the inefficiency.
In summary, the use of evaporation is still the most
reliable, versatile, and easily understood separation
process for recovery of dragout. Cost effective utilization
of evaporative recovery can be realized in many cases by
direct drag-out recovery to make up for plating bath
surface evaporation or where necessary, augmenting
surface evaporation with low cost, low capacity batch
evaporators.
ION EXCHANGE
Ion exchange is a versatile separation process which
has found application within the metal finishing industry
for:
• Concentration of plating chemical dragout for
recycle to plating bath and rinse water reuse
• End-of-pipe wastewater treatment
• Mixed wastewater deionization and water reuse
• Polishing after conventional wastewater treatment
to reduce the concentration of dissolved metals
• Purification of spent acids
• Water supply deionization
LOADING
DILUTE
SOLUTION
H+FORM
CATION
RESIN
COLUMN
V
DILUTE H2S04
REGENERATION
CONCENTRATED!
CuSoi,
SOLUTION
A
EX-
HAUSTED
CATION
RESIN
COLUMN
10IH2SOtt
SOLUTION
SOLUTION
Fig. 9—Ion Exchange Concentration of Copper Sulfate Solution.
25
-------
Ion exchange is a reversible process where a solution is
passed through a bed of resin particles which exchange
ions attached to the solid resin matrix for similarly
charged ions in the solution. In Figure 9, the exchange is
between copper ions in solution for hydrogen ions
attached to the cation resin. When the resin's exchange
capacity has been exhausted, the bed is regenerated with
a suitable solution, in this case sulfuric acid, which elutes
the collected copper ions and returns the resin bed to its
original form. The copper in the feed solution has not
been changed chemically, but it has been concentrated
into a much smaller volume.
The early ion exchange systems were of the fixed bed
variety. These systems were often made continuous by
duplexing of the columns to allow for sustained
operation during regeneration. The significant cost and
complexity of such fixed-bed systems minimized their
application for recovery of plating chemicals from rinse
solutions.
The development of the Reciprocating Flow Ion
Exchanger enhanced the potential application of ion
T
Cation
Exhaust
(to waste
treatment)
Product
4
Cation
t
Rinse
Water
f 1 '
Anion Cation
•
. -
Purified
water
Exhaust
(to waste
treatment)
Anion Cation
i i
i
_^LjT
NaOH
exchange for plating drag-out recovery by providing a
lower cost, compact, automated ion exchange recovery
system. This unit was especially developed for purifying
the bleed stream of a large volume solution, such as the
overflow from an electroplater's rinse tank. The
operating principal of a reciprocating flow unit for
chromic acid recovery is presented in Figure 10. The unit
operates on the principle that for the short period it goes
off-stream for regeneration, the build-up of
contaminants in the rinse system is negligible. The
advantages of this unit over fixed bed systems for such
applications include:
• Reduced equipment cost (due primarily to the small
resin volume required)
• The unit automatically regenerates itself minimizing
labor requirements
• Compact size
Reciprocating flow units are currently being utilized
for dragout recovery from chromium, copper, and nickel
plating rinses, for purification of spent process acids and
for mixed wastewater deionization.
ON STREAM (LOADING)
Rinse water is pumped from the chromium
plating rinse tanks through the prefilter to
remove any solids, then through the first
cation bed where cationic contaminants
(e.g., Fe+3, Cr+3) are removed by the resin.
The rinse water then passes through the
anion bed where the chromate ions are
removed. The purified rinse is returned to the
rinse system. While the unit is on stream, the
second cation bed is regenerated.
REGENERATION
After a preset period of time, the unit goes
off stream. The first cation bed is regenerated
with sulfuric acid and washed with water.
The anion bed is regenerated with sodium
hydroxide and the effluent is passed through
the second cation bed; the concentrated
chromic acid solution resulting is returned to
the plating tank.
Water
_L
Cation
\
Anion
Exhaust
(to waste
treatment)
Cation
Concentrated f
NaOH I
I | Water
^^^A^^riS^fJ
J
WASHING
The three beds are then washed with water,
as the product from the anion bed contains
the excess caustic used in the regeneration
step, it is mixed with concentrated NaOH
and used in the next regeneration cycle.
The unit then goes back on stream.
Fig. 10—Reciprocating Flow Ion Exchanger Operating Cycle.
26
-------
The use of ion exchange for mixed wastewater
deionization and reuse is an application which could see
considerably more use in the future.
Figure 11 shows a commercially operated wastewater
deionization treatment system which has been operated
since 1975. The system was designed to process lOOgpm
of plating wastewater containing copper, nickel, and
trivalent and hexavalent chromium. The wastewater also
contains trace amounts of cyanide.
TO CLAR1FIER
TYT Y
WATER TO PLATING
© - CONDUCTIVITY PROBE
Fig. 11—Ion Exchange Wastewater Reuse System.
The system features:
• Activated carbon prefilters to trap oil, free chlorine
and suspended solids which might foul the resin bed
• A conductivity probe to monitor the purity of the
treated water. When the dissolved solids content of
the treated water reaches a certain concentration,
the flow is diverted to the off-stream columns and
the spent columns are regenerated. A column
usually operates for three days prior to regeneration.
• A batch treatment tank is used to treat the
regenerant solutions. The batch treatment sequence
employs successive steps for cyanide oxidation,
chromium reduction, and metal precipitation. The
treated solution is processed in the flocculation/
clarification sequence used to process the plants
non-plating wastestreams.
• A conductivity probe is installed on the treatment
system feed. If the wastewater is grossly
contaminated, the flow is diverted to the batch
treatment tank. Treatment of wastes with high
concentration of contaminants by ion exchange is
economically unfavorable.
This system processes approximately 300,000 gallons
of water per cycle. Each cycle produces approximately
400 gallons of acid regenerant, 600 gallons of caustic
regenerant and 6000 gallons of wash water; these
solutions are discharged to the batch treatment tank.
Deionized process water is used for wash water and its
discharge acts as a purge to control the build up of any
contaminants not removed by the recycle system.
Treatment of the pollutants is not eliminated; however,
the chemical destruction system is reduced to a single
batch tank. The plant reports that the cost to operate the
ion exchange system is $60,000 per year.
The use of this type treatment for selected rinse waters
can be justified by savings in water and sewer fees and
reduction of the investment required for pollution
control hardware. Figure 12 compares the chemical cost
of a wastewater deionization and reuse system to the
chemical cost associated with the conventional treatment
approach. The chemical cost for the ion exchange process
includes regeneration chemicals plus the cost to
60
a 5»
500.
0 100 200 300 400
METAL CONC. (ppm CuSO,,)
Fig. 12—Treatment Chemical Cost Comparison: W*ttewa1*r
Delonization/Reuse Versus Conventional Waste Treatment.
precipitate the copper from the regenerants and assumes
recycle of 90 percent of the incoming wastewater. The
chemical consumption for the conventional treatment
approach, includes:
• Lime to precipitate the copper
• Lime to raise the water pH from neutral to 9.0
• Lime to react with naturally occuring alkalinity in
the water supply
• Polyelectrolyte for flocculating the wastewater
solids.
As shown, for treatment consisting solely of pH
adjustment and flocculation to separate metals as
insoluble hydroxides, ion exchange compares favorably
only for treating very dilute solutions. Treatment of
wastewater typical of the metal finishing industry is less
costly by conventional chemical processes.
TREATMENT
COST
($/1000 Gal.)
_L
Basis
Cost Comparison Assuming
Water Fee of 50C/1000 Gal.
J_
100 200 300 1100 500
METAL CONC. (ppm CuSo^l
Fig. 13—Treatment Chemical and Water Use Cost Comparison:
Wastewater Deionization/Reuse Versus Conventional Waste Treatment.
Figure 13 presents a similar analysis, but includes a
water use fee equal to fifty cents per thousand gallons of
water consumed. In this case, an ion exchange system
achieving 90 percent water reuse is more economical for
treatment of waste streams up to a metal salt
concentration of 250 ppm. With the water recycle credit,
deionization of selected rinse waters compares favorably
with a chemical destruct system For wastewaters
containing polutants requiring more extensive treatment,
such as those containing hexavalent chromium, ion
exchange compares favorably up to higher concentration
levels. Treatment of spent concentrates or grossly
contaminates wastes should still be accomplished by
conventional treatment techniques.
A wastewate deionization reuse system is particulary
attractive for plants which have access to a centralized
treatment facility for industrial wastes. The central
27
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WASTEWATER
CONVENTIONAL
TREATMENT
SYSTEM
SAND
FILTER
1
REGENERATION
SPENT
CATION
COLUMN
SODIUM
FORM
CATION
COLUMN
WASTEWATER
DISCHARGE
Fig. 14—ion Exchange Polishing After Conventional Treatment.
concentrates and spent processing solutions, eliminating
the need for any chemical destruction system.
Another application of ion exchange which could
receive increased attention for plants unable to achieve
required metal concentration discharge limitations is ion
exchange polishing after an existing conventional
treatment system. (Figure 14) In some areas, plants
discharging wastewater directly into receiving waters are
being required to achieve effluent metal concentrations in
the 0.1 to 0.2 part per million range:
It is unlikely that these concentration levels can be
consistently achieved with a metal hydroxide
precip it at ion/clarification/filtration treatment
sequence. An ion exchange polishing, using fairly
recently developed chelated cation exchange resins,
offers a relatively inexpensive means of achieving effluent
metal concentrations in the tenth of a part per million
range. These chelated resins have a high selectivity for
heavy metal cations in the presence of high
concentrations of similarly charged sodium, calcium, or
magnesium ions. As an example, augmenting a 30 gpm
treatment system with an ion exchange polishing system
consisting of two columns, each containing seven cubic
feet of cation resin, would cost approximately $20,000.
Based on an inlet metal concentration of five parts per
million and a conservative estimate of resin capacity,
each column could process approximately 330,000
gallons of wastewater prior to regeneration.
Assuming continuous operation 24 hours per day, this
corresponds to a regeneration frequency of
approximately one column every 8 days. Each
regeneration would consume 50 gallons of 10%
hydrochloric acid and 60 gallons of 10% caustic soda.
These solutions would be treated in the conventional
treatment system. Chemical cost for regeneration
chemicals would amount to only $17.00 per cycle, or
approximately $2.00 per day.
MEMBRANE PROCESSES
Membrane processes utilized in the plating industry
include reverse osmosis and electrodialysis. Beyond the
similarity of using membranes to achieve the separation
of water from dissolved solids, both processes are
continuous, come in compact modular units, and have
low operating costs over a broad range of loading
conditions.
Both processes are being applied for drag-out recovery
from plating rinse waters. Pre-engineered packaged units
cost $25,000 to $35,000 installed. As such, their
application is limited to baths with high drag-out rates. A
significant saving in replacement chemicals and
treatment costs is needed to justify the initial investment.
Reverse osmosis (Figure 15) is a pressure driven
membrane separation process where water molecules are
preferentially forced through the microscopic pores of a
serni-parmeable membrane. The salt molecules dissolved
in the water solution, due to their larger size, are
restricted from passage through the membrane pores.
HIGH-PRESSURE
PUMP
SEMI PERMEABLE
/ MEMBRANE
CONCENTRATE
Fig. 15—Simplified Reverse Osmosis scnemanc.
Reverse osmosis units using a cellulose acetate
membrane have been successfully applied to concentrate
the dragout from plating solutions; both the concentrate
and the purified water are recycled. Cellulose acetate
membranes are not stable over a broad pH range and the
primary application is for Watts Nickel Plating Baths,
which provide a mild chemical environment. Other
dragout recovery applications include acid copper, acid
zinc, and chromic acid baths, however, pretreatment to
assure that the membranes are not exposed to low pH
conditions is needed for these applications.
Reverse osmosis is also limited in the degree of
concentration it can achieve. Consequently, for
applications where plating baths have minimum surface
evaporation, suplemental evaporation of the concentrate
may be required prior to its recycle.
Another application of reverse osmosis which has
received recent attention is mixed wastewater
purification with recycle of the permeate and treatment
of the concentrate. The application is attractive because
of the continuous operation and low operating cost
characteristics of RO units. However, it is questionable
whether RO membrane systems are sufficiently reliable
or durable to operate under the variable conditions
characteristic of mixed wastewaters. Potential problems
include membrane fouling due to contaminants in the
feed stream or precipitation of salts in the concentrate,
membrane deterioration due to the chemical
environment, and high levels of dissolved solids in the
permeate. As newer, more chemically durable
membranes are developed and field proven, this
application may see greater implementation.
In electrodialysis, contaminated rinse water is passed
through a network of alternately spaced anion permeable
and cation permeable membranes (Figure 16). An
electrical potential is applied across the membranes to
provide the driving force for the ion passage through the
membranes. This configuration creates channels which
are alternately concentrated or diluted of ions. The major
difference compared to RO is that, like ion exchange, the
28
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C-CATION-SELECTIVE MEMBRANE
A-ANION-SELECTIVE MEMBRANE
M+-CATIONS
X—ANIONS
PURIFIED RINSE
WATER TO RINSE •*"
TANKS
CATHODE (_)
CONCENTRATED PLATING
DRAG-OUT (TO PLATING BATH)
T t
t t t t t t
x* j I U CONTAMINATED
DILUTING ' ' ' ' ' RINSE
CIRCUIT CONCENTRATING CIRCUIT FEED
Fig. 16—Electrodialysis Flow Schematic.
separation of water from salt is achieved by selective
removal of the salt, not concentration by driving off the
water. Unlike ion exchange, the units are continuous and
the only operating cost is for electricity, about 7 kW.
The membranes used in the electrodialysis stack are
essentially thin sheets of the same polymeric network
used to make ion exchange resins. A cation permeable
membrane will have negatively charged, fixed ion sites
which will attract the positively charged cations into the
membrane, but repel negatively charged anions. The
cations will continue through the membrane due to the
electrical potential that is applied.
Like ion exchange resins, the electrodialysis
membranes are durable to most chemical environments.
They are membranes, however, and are subject to fouling
if the potential exists. Current applications include the
recovery of dragout from rinses after nickel, acid zinc,
zinc cyanide, and chromium plating processes.
29
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Does Recovery Reduce Treatment Needs?
F. A. Steward*
INTRODUCTION
The answer to the question posed by the title is a
resounding YES. However, the author is strongly of the
opinion that companies purchasing treatment facilities
should look for the reduction only in operating costs,
treatment chemicals, labor, and sludge disposal.
There seems to be a wide spread impression that less
waste treatment capacity need be provided if recovery
equipment is to be installed. We strongly recommend
that this approach not be taken. The treatment system
should be designed with adequate capacity to handle
upsets, recovery system downtime, accidents, etc.
Payback on the recovery equipment should come only in
the operating savings.
This paper will present data from an actual case to
illustrate the kind of problems which pan arise.
By way of background, our company supplied a waste
treatment system for a new plating facility that made
extensive use of recovery technology. After installation,
it was found to be impossible to consistently maintain the
required effluent quality. Investigation showed that the
problem was almost entirely a result of inability to handle
the sludge quantities being generated. Modification of
the plant to increase sludge handling capacity is now
underway.
For a variety of reasons, the company that installed the
new facility has asked to remain anonymous. In spite of
the fact that this detracts from the authenticity of the case
history, we felt the insight gained through experience at
this plant would be of interest and value to the industry.
THE PRODUCTION PLANT
The new electroplating facility was ideally suited to
materials recovery. It was a brand new plant designed
with a single, automated, high-production plating line to
put a decorative chromium finish on plastic pieces. The
plant is clean, modern, and has a very steady rate of
production averaging about 1,500 ft2 per hour. The
process steps in the plating line are as follows:
Plastic Etch
Electroless Nickel
Nickel Strike
Copper Plate
Semi-bright Nickel
Bright Nickel/Dur Ni Nickel
Chromium Plate
Chromium Strip
Nickel Strip
IN - RECOVERED = WASTE
*F. A. Steward, Vice President, Engineering & Sales
ERC/Lancy, Division of Dart
Environment and Services Company
525 West New Castle Street, Zelienople, PA 16063
With the exception of the strippers, copper plate and
electroless nickel, each process bath was followed by
recovery rinses connected to recovery units. Given the
design flow through the recovery rinses, and using
classical rinsing calculations, approximately 99% of the
dragout from each major process is available for
recovery. Overflow from the chrome recovery rinses goes
to separate evaporators. The etch recovery loop includes
a cation exchanger for removal of trivalent chrome. The
nickel recovery rinses are tied into two separate ion
exchange systems.
DESIGN BASIS
Waste Loads
The sales engineer on the job assumed that 95% of the
dragout would be recovered from each of those processes
followed by recovery rinses. The following table lists the
total waste loads calculated to be present if no recovery
were practiced, together with those expected to reach the
treatment system.
Cr
Ni
Cu
No-Recovery
52.0 Ib/hr
14.4
3.8
70.2 Ib/hr
Expected Load
3.4 Ib/hr
2.6
3.8
9.8 Ib/hr
The figures in this table, as well as those throughout the
report, are based on quantities of dry sludge which would
be generated. They are calculated by taking the
hydroxides of each of the metals. The No-Recovery
figures were calculated by using estimates of the dragout
to be expected for the production rate on the machine.
The figures under Expected Load include the dragout
from the two strippers, electroless nickel, and the copper
plating bath as well as 5% of the anticipated dragout from
the recoverable processes.
It was agreed during the initial sales discussions that
extra waste resulting from downtime on the recovery
equipment would be hauled away be a contract waste
hauling company.
Press Capacity
The filter press included in the original design had the
following capacity:
2.5 ft3 /cycle
3Q% Dry Solids * 80 lb/ft3 = 30 Ib/hr
2 hr/ cycle
Thus, the sludge dewatering equipment had
approximately three times the capacity theoretically
assumed to be needed. This was felt adequate to provide
30
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for inert solids and extra loading due to minor upsets. As
mentioned earlier, operation after start-up indicated that
the filter press was completely inadequate for the loads
reaching the treatment system. As a result, a series of field
investigations was conducted.
FIELD INVESTIGATIONS
On October 16, 1978, engineers from our company
visited the plant and spent a full day investigating the
sources of the extra load. Numerous leaks, drips, and
spills were observed as can be expected during start-up of
a major production operation. Approximately six weeks
later, a second visit and two days of investigation by two
engineers indicated that many of the initial start-up
problems had been resolved, but that the treatment
system was still overloaded with sludge. Samples
collected during this visit indicated that overflows from
the rinses on the plating line could not account for the
quantities of sludge being experienced.
After several meetings and discussions, extra filter
plates were ordered for the press to approximately
double its capacity. In early January, a run of the
treatment system was attempted for four consecutive
days of twenty-four hour operation. During this period,
an attempt was made at a material balance around the
entire plant. While we have long realized that an accurate
material balance in a plating operation is extremely
difficult, we were particularly frustrated in this case by an
inability to get samples from various points in the
recovery loops. As one example, tanks in these loops
would overfill and spill onto the floor. It was impossible
to accurately estimate the volume lost, and the
concentration was variable from time to time. In
addition, several of the waste lines from the various
recovery units were manifolded together so as to make
separate sampling impossible without piping
modifications.
Based on the results of the study in January, it was
agreed to run a performance demonstration during which
the recovery units would be operated under the
supervision of factory representatives from the suppliers
and the treatment system would be operated under our
supervision. This demonstration was to run four days,
twenty-four hours per day. The ultimate conclusion was
that the expanded filter press was only marginally
capable of handling the waste load under such idealized
conditions.
Waste Sources
The sources of un-anticipated load on the treatment
system which were identified during the four field
investigations deserve mention, since they illustrate the
types of problems common in metal finishing plants.
Hoses in rinse tanks
Downtime
Rinse tank dumps
Losses of recovery liquors
Wastes from recovery units
As is common in many production operations, and
almost inevitable during start-up, the plating operators
would use hoses to supplement the flow of water to
various rinse tanks to keep them "clean." In some cases,
this extra flow was causing an overflow over the rim of
the tanks onto the floor. In other cases it was overloading
the recovery systems causing losses from them as
discussed later.
Over the period of time our engineers spent in the
plant, there was never any time that all of the recovery
units were operating. During the final four day
demonstration, downtime was very minor. However, it is
unlikely that such close attention and supervision can be
provided in a typical operating plant. Designers and
purchasers of major industrial processes are keenly aware
of the impact of downtime. It is a factor which is
recognized and anticipated. Such must also be the case
with recovery systems in metal finishing operations.
As a carry-over from operating practices prior to the
use of recovery and waste treatment equipment, the
operators in this plant would periodically dump the
contents of the rinse tanks to allow them to remove parts
which dropped off racks. Obviously, such a practice
places extra hydraulic and chemical load on the
treatment system simply as a result of the normal free-
flowing rinses. However, dumps of the recovery rinses are
particularly troublesome. The first recovery rinse after
the chromium processes is a highly concentrated liquor.
The periodic dump .represented a loss equivalent to many
hours of production.
Those same concentrated liquors mentioned above can
be easily lost from the loop en route to the recovery
equipment. Even more significant is the loss of
concentrated liquor after it has been processed by the
recovery equipment. In either case, the loss can occur as a
result of tank overflows due to misadjustment of timers,
failure of level controls or pumps, or due to the operator
increasing the flow at the recovery tanks on the plating
line. There were actually cases when the loads reaching
the waste treatment system were higher than would have
been experienced if there were no recovery units at all!
Each of the recovery systems includes a "waste" line
and a purchaser should pay careful attention to the
quantities which will leave by this route under ideal
conditions and also to the variables which can affect that
quantity. Quite often the tuning adjustments can be
critical and require close attention from the laboratory
and operating people. To be used to best effect, a
recovery loop should be regularly analyzed by the
laboratory as though it were another process.
MATERIAL BALANCE
Anyone who has attempted to strike a reasonable
balance around various parts of a metal finishing
operation will appreciate the difficulty. The primary
equation needing to be solved in this particular case can
be stated as:
We found it impossible to get a reasonable fix on the
quantities being recovered due to the numerous variables
involved. Le'vels and concentrations were changing
constantly in tanks. Units were operating or down on
varying schedules. Tanks would periodically overflow
onto the floor.
A reasonable estimate on the IN factor is available
from calculations based on dragout rates, and these can
be confirmed by analytical checks on the flow of water
going to recovery and/or treatment.
The third factor, WASTE, can be judged by collecting
the filter case generated and analyzing a composite
sample.
31
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IN
Two different spot checks were made to confirm the
assumptions used to calculate dragout in the initial
design work. In the first, the recovery rinse after the etch
bath was sampled for analysis and the flow rate checked
carefully. The analysis showed 26.4 g/1 CrOs which, at a
flow of 120 gal/hr, corresponds to 26.4 Ib/hr of
chromium hydroxide. This corresponds to 30 Ib/hr as
calculated from the assumed dragout at 7.5 gal/hr from
the etch bath alone.
A second spot check is based on analysis of the treated
wastewater flow as it enters the clarifier. The suspended
solids concentration was 938 mg/1 at 145 gal/min on the
flow meter and 1,050 mg/1 at 140 gal/min. These values
correspond to total dry sludge readings of 68 and 73 Ib/hr
respectively. These readings were taken at a time when all
recovery systems were out of operation. These figures
correspond to the calculated value mentioned earlier of
70.2 Ib/hr total sludge generation.
In both cases the agreement is reasonably good,
supporting the assumptions used for the dragout
calculations. Better correlation cannot be expected given
the variables in a metal finishing operation and waste
treatment system.
OUT
During the last four day demonstration run, the filter
cake collected averaged 49 Ib/hr (dry). Collection of a
true composite from a mass of filter cakes is a difficult
chore, and was not attempted. Nevertheless, an average
of the analyses of several filter cakes taken at different
times during the run is as follows:
Cr(OH)3 - 29.9% - 14.6 Ib/hr
Ni(OH)2- 12.1%-5.9 Ib/hr
Since production was virtually constant during the
entire four day run, the recovery systems were kept
operating at close to 100%, and under good control, and
rinse dumps were avoided, the composition of the filter
cakes could be expected to be reasonably constant.
Therefore, within the level of accuracy which can be
expected from such a material balance, these figures are
felt to be representative.
RECOVERED
The rate of chromium recovery can be expressed as
follows:
Similarly, the recovery rate for nickel can be expressed
52 - 14.6
52- 12
37.4
40
= 93.5%
The figure of 12 Ib/hr corresponds to the "un-
recoverable" chrome which includes dragout from the
stripper and the trivalent chrome in the dragout from the
etch bath.
14.4- 5.9
14.4 - 2.0
= m = 68-5%
In this case, the un-recoverable nickel includes the
dragout from the nickel stripper and the electroless nickel
bath.
It is important to note that the indicated recovery rates
were maintained during the four day demonstration at
which time the recovery units were under the careful
attention of factory representatives. These rates would be
decreased in a normal production plant by the various
factors discussed earlier under Waste Sources.
CONCLUSIONS AND RECOMMENDATIONS
Forecast Versus Reality
This paper illustrates numerous ways in which the
actual results realized with recovery equipment can vary
from the original expectations. While it is true that most
of these can be covered by a shrewd evaluation of what
can be expected, it is also true that there are many
variables in other production plants which have not been
covered in this case history.
Housekeeping Burden
It is clearly false economy to invest in recovery facilities
unless careful housekeeping procedures are instituted.
Spills, dumps, and overflows can lose as much as the
recovery equipment is attempting to reclaim.
Manpower Needs
Recovery equipment will not operate without
attention. It is an axiom in process design that each piece
of moving equipment needs men to maintain it and men
to operate and adjust it. We have seen literally dozens of
cases where sophisticated recovery equipment sits idle
because the plant doesn't "have time" to keep it
operating. When doing your initial payback calculations,
be sure to include realistic estimates of the time required
for operators to tweak the controls, maintenance people
to keep everything running, and laboratory people to
periodically analyze the recovery rinses and concentrate
streams.
Waste Treatment System Capacity
We strongly recommend that a waste treatment system
be installed with adequate capacity to handle all
anticipated loads from the metal finishing operation.
This allows the plant to continue producing during
downtime on recovery equipment and also gives the extra
capacity to handle the accidents and upsets which are
inevitable in a complex processing operation.
32
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Regeneration of Waste Chromic Acid
Etching Solutions in an
Industrial-Scale Research Unit
L. C. George, D. M. Soboroff and A. A. Cochran*
ABSTRACT
Substantial amounts of chromium are lost in various surface-finishing operations
and pollution problems are created when spent solutions containing hexavalent
chromium and sulfuric acid are discarded. Laboratory research has shown that these
spent etching solutions can be regenerated in a diaphragm cell. When the spent
solution is placed in the anode chamber, most of the Cr3*, produced during etching
operations, is oxidized to Cr6*. Impurity metals dissolved during the etching
operation are transferred to the catholyte. When waste brass etchants are treated,
about one-third of the copper and zinc is removed. The energy consumption is less
than 9 kwhr/kg of sodium dichromate regenerated. Similar results are obtained with
spent printed-circuit-board etchants and rinse waters from plastic etching operations.
An industrial-scale research unit capable of oxidizing up to 0.5 kg/hr of trivalent
chromium has been operated to demonstrate the viability of the recycling techniques.
Regenerated brass etchants evaluated by two companies equaled or exceeded the
performance of fresh etchants.
INTRODUCTION
The mission of the Bureau of Mines is to ensure the
continued viability of the domestic minerals and minerals
economy and the maintenance of an adequate mineral
base, so that the Nation's economic, social, strategic, and
environmental needs can be better served. Part of the
work done in support of this mission has as its goal
secondary resource recovery and effecting pollution
abatement. In accordance with these activities, the
objective of this investigation has been to develop a
method for regenerating and recycling spent chromium-
bearing process liquors that are currently discarded as
wastes.
Solutions containing Cr6+ and sulfuric acid are used in
brass finishing, printed circuit board etching,
preparation of plastic for plating, anodizing, and various
other surface treatments. As the solutions are used, Cr6+
is reduced to Cr3+, the dissolved solids content increases,
and the acid concentration decreases. The action of these
solutions on a copper substrate can be represented by the
following reaction:
Cr2O7
+ 3 Cu + 14 H+ - 2 Cr3+ + 3 Cu2+ + 7 H2O
A spent printed circuit etchant, for example, would
contain considerable amounts of Cu2+, Cr3+, and Cr6+. A
spent brass etchant would contain zinc in addition to
*L. C. George and A. A. Cochran, Research chemists
Rolla Research Center, Bureau of Mines, U.S.
Department of the Interior, Rolla, Missouri.
D. M. Soboroff, Research chemist
Office of Water Research and Technology
U.S. Department of the Interior, Washington, D.C.
these components. Actual plant practice involves adding
sodium dichromate to the process tank to replenish the
Cr6+ that has been reduced and to make up losses from
drag-out. The entire tank is dumped when the etchant no
longer performs properly despite additions. The decision
to dump or add reagents is often made on the basis of the
appearance of the part being etched and not on a
chemical analysis of the etchant. Technology for ultimate
disposal of these wastes usually involves the reduction of
the remaining Cr6+ to Cr3+ followed by base addition to
precipitate chromium and other metallic hydroxides. The
resulting sludges are then used for landfill.
The disposal of these solutions in this manner wastes
valuable resources and is cause for environmental
concern. All U.S. primary chromium production is from
imported ores. More than 2.7 X 107 kg of chromium are
used annually for metal surface treatment and corrosion
control measures (4). The minimal recovery technology
practiced by the metal finishing industry results in the
discarding of valuable secondary resources. In addition,
chromium has long been recognized as a major pollution
problem and its disposal is regulated by the EPA (9).
Landfill areas suitable for metal hydroxide sludges are
becoming scarce, and collection, treatment, and disposal
by waste contractors is expensive (3).
For these reasons, it is desirable to develop a method
that would effect economical, in-plant recycling of spent
chromic acid-sulfuric acid etchants. Recycling such
etchants would result in a major reduction of chromium-
containing effluents, thus reducing the costs of waste
treatment and disposal. Further, recycling these etchants
would conserve chromium, thus reducing process costs
by reducing chromium purchases.
Several electrolysis methods have been proposed for
33
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recycling etching solutions. Lancy (5) used an
electrodialysis cell fitted with a cation-selective
membrane to separate copper from chromic acid. The
copper was recovered by electrowinning in a separate
unit. Tirrell (8) suggested reduction of the Cr6+ content of
a spent etchant to Cr3+ in the cathode chamber of a
diaphragm cell. When all the Cr6+ was reduced, the
copper was plated out at the cathode. The copper-
depleted solution was then used as the anolyte, and the
Cr + was oxidized back to Cr6+. Fujii (1) suggested a
similar approach for exhausted chromium-plating
solutions. Gussack (2) used a diaphragm cell to reoxidize
Cr3+ to Cr6+ in spent plastic etching solutions.
The research described herein differs from previous
work in that the chromium is oxidized and
contaminating metals are removed in a one-step process
that minimizes the use of electrical energy. The authors
have previously reported (6-7) small scale results where
spent brass etchants, spent printed circuit board etchants,
and rinse water from plastic etching operations, covering
a wide range of compositions, were regenerated. The
apparatus for regeneration and recycling employed a
diaphragm cell fitted with a cation-selective membrane.
The solutions were placed in the anode chamber where
Cr3+ was oxidized to Cr6+. The acid concentration
increased to the normal value for a comparable fresh
solution. A portion of the contaminating metals migrated
through the membrane into the catholyte. Essentially all
the copper that migrated was recovered at the cathode.
Regenerated brass etchants evaluated by two companies
equaled or exceeded the performance of fresh etchants;
they were superior in the removal of red stain oxide.
This paper describes the process research unit (PRU)
which was developed to regenerate and recycle spent
etching solutions on an industrial scale.
EXPERIMENTAL PROCEDURES
Spent Etchants
The spent etchants used in the PRU were obtained
from brass finishing operations. The solutions were
originally prepared from sodium dichromate and sulfuric
acid. The compositions of these solutions are given in
Table I. Elements detected in trace amounts by
spectrographic analysis included Ag, Al, Ca, Fe, Mg,
Mn, Pb, Si, and Sn.
TABLE 1
SPENT ETCHANT COMPOSITION
Composition, g/L
Sample Cr3" Cr6+ Cu
A 24 8.3 30
B 25 6.8 33
Zn SOt2~ value
13 168 0.4
13 191 0.4
The Process Research Unit
A flow diagram for the regeneration and recycling
process is shown in Figure 1. Spent etchant is withdrawn
from the etching tank and pumped through a 1 to 3 /*m
pore size wound polypropylene cartridge filter. The filter
step reduces membrane plugging by fine particles and
thus lowers cell resistance. The filtered solution is then
pumped into the anode chambers of a diaphragm cell.
T
Spent etching solution
Sulfuric acid
Diaphragm
Anode compartment
1
generated etching
cell
Cathode
solution
\
compartment
i
Copper metal
f
Base added
Zn+2 and
to ppt
^»r
To disposal
Fig. 1—Flow diagram for regeneration and recycling of spent etchants.
Figure 2 is a schematic representation of a diaphragm
cell containing one anode chamber and two cathode
chambers. The anode chamber is fitted with Nafion5 427
cation-selective membranes to allow ion migration
without mixing the anolyte (the spent etchant) and
catholyte (180 g/1 sulfuric acid). There is space for five
anode chambers in the diaphragm cell used in the PRU.
The chambers are constructed of Plexiglas. One-
sixteenth-inch thick Viton gaskets are used to seal the
membrane between the chamber's flange and frame.
When assembled, the chambers are contained in a 0.9 X
0.9 X 0.9 meter polypropylene tank which forms the
cathode chamber. A lead-6 pet antimony anodes is
positioned in the anode chamber at the left. Two copper
cathodes (alloy 110) are positioned on either side of the
chamber. The remaining electrodes have been removed
so that the other anode chambers are visible. The ratio of
anode area to cathode area to membrane area is 1:1:1.
Cation-selective
— membrane —
Copper
cathode
Lead-based
anode
Copper
cathode
V
Cathode
chamber
^
^
^
-------
Cathode current density is 2.15 amp/dm2. At full
capacity, the cell requires ~ 1,200 amp at ~3.2 volts.
The PRU contains a intank filter unit, an etchant
holding tank, a control panel, and a second etchant
holding tank. The diaphragm cell is located behind the
control panel. The pumps above each holding tank feed
filtered etchant into the anode chambers. The pump
above the control panel removes regenerated etchant
from all anode chambers. The catholyte is circulated
using a pump located behind the panel. The hood above
the diaphragm cell removes hydrogen, oxygen, and
chromic acid mist generated by the cell.
RESULTS AND DISCUSSION
Table II summarizes the results in three PRU tests. The
PRU was operated with only two anode chambers in
place for tests 1 and 2. Five anode chambers were used in
test 3. The values in parentheses in the second column are
extrapolations to the flow rate for five chambers. For the
first day of each test, the PRU was run in a static mode
(no etchant flow) to oxidize most of the Cr3+. For the
remainder of the test, spent etchant was fed at the rate
indicated. The data in Table II represents flow
conditions.
The power consumption figures indicate that about
13c worth of power is about $2.40. The rate of production
of sodium dichromate increased with increasing flow
rate.
The catholyte used for Test 1 was reused in Tests 2 and
3. From an analysis of electrode efficiencies during start-
up and analysis of the product during the flow portions of
each trial, it appears that reuse of the catholyte is not
detrimental. During extended operation of the PRU. A
bleed stream will have to be taken from the catholyte. The
volume of this stream is estimated to be no more than 20
pet of the volume of etchant (of similar composition to
that given in Table I) processed. This stream contains no
Cr6+ and is far less concentrated in Cr3+, copper, and zinc
than the spent etchant. It may be disposed of using
neutralization and precipitation technology already in
place in most finishing operations.
Copper powder (minus 100- plus 200-mesh) was
recovered from the cathodes. The powder adhered to the
cathode as long as current was flowing. The material
contained 85 to 90 pet copper. The major impurity is
oxygen. Traces of Ag, Al, Ca, Cr, Mg, Pb, Si, Sn, and Zn
are present. To show that the product could be converted
to a usable form, 2 pet carbon was added and it was
melted, without agglomeration, in an induction furnace.
Ninety-five pet of the copper was recovered as an ingot
containing 99.7 pet Cu, 0.01 pet C, and traces of Ag, Mn,
Pb, Sb, and Sn.
Previously reported bench-scale tests and Table II
show that as the flow rate is increased the percentage Cr3+
oxidized decreases by a relatively small amount. Thus,
the cost of regeneration decreases as the requirements for
metal impurity removal decrease, owing to the shorter
retention time required. An examination of the results for
Test 2 (Table II) shows that the flow rate, and
consequently the amount of Cr6+ produced, could be
nearly doubled if it was only necessary to remove ~20 pet
of the copper and zinc.
There are two modes of etchant regeneration possible
with the PRU:
1. The etchant may be used until completely spent and
then regenerated. After regeneration, the solution would
have to be diluted to the proper operating level. This is
because the total chromium concentration is greatly
increased due to sodium dichromate additions to make
up for the Cr6+ reduced during the etching operation.
2. The regeneration system may operate continuously
in direct connection with the etching tank. The
temporary loss of Cr6+ by reduction to Cr6+ would no
longer have to be made up with chemical additions. The
specific gravity and viscosity of the etchant would be
lowered, thus drag-out would be minimized.
Bench scale and PRU tests have shown that operation
in mode 1 is feasible. Regenerated etchants evaluated by
two brass companies performed as well as or better than
fresh solutions.
For successful operation in mode 2, the regeneration
technique must necessarily operate at lower etchant
concentrations, similar to freshly made etching solution.
In bench-scale tests using 1 volume of a brass etchant
(similar to samples A and B) diluted with 6 volumes of
water, Cr3+ oxidation, copper and zinc removal, and
efficiency were equal to or better than what is reported
for the concentrated etchant in table II.
SUMMARY
The technical feasibility of regenerating and recycling
spent brass etchants on a large scale has been
demonstrated. Using a diaphragm cell, 88 to 96 pet of the
Cr3+ was oxidized to Cr6+ and significant portions of the
contaminating metals were removed. Results of
evaluations of regenerated etchants by industry were
excellent.
TABLE II
RESULTS OF PRU TESTS 1, 2, AND 3
Energy
o'+
Flow rale oxidation
Test (1/hr)
1' 2.6(6.5)
2' 5.7 (14.3)
32 7.3
'Sample A is feed material
2Sample B is feed material
(pet)
>96
88
92
Cu
removal
(pet)
41
20
31
Zn
removal
(pel)
41
23
28
Cr lost
to catholyte
(pet)
11
4
5
consumption
(kwhr/kg
Na2Cr2Or2H2O)
8.6
5.7
8.0
Na2Cr2Or2H2O
produced,
kg/hr
0.43
.70
.48
A node
efficiency
19
31
21
Duration,
days
3
3
7
35
-------
REFERENCES
1. Fujii, A Process for the Regeneration of Exhausted
Chromium-Plating Solutions by Two-Stage
Diaphragm Electrolysis, U.S. Pat. 3,948,738, Apr. 6,
1976.
2. Gussack, Mark C. Oxidation-Reduction Process,
U.S. Pat. 4,006,067, Feb. 1, 1977.
3. Hallowell, J. B., L. E. Vaaler, J. H. Gurklis, and C. H.
Layer. Assessment of Industrial Hazardous Waste
PracticesXElectroplating and Metal Finishing
Industries - Job Shops. Battelle's Columbus
Laboratories. EPA Report PB-264349, September
1976, p. 128.
4. Hicks, H. C., and R. A. Jarmuth. Regeneration of
Chromated Aluminum Deoxidizers. Boeing
Commercial Airplane Company. EPA Report 660/2-
73-023, December 1973, p. 5.
5. Lancy, L. E., and D. C. Kruse. Electroaialysis
Regeneration of Metal Containing Acid Solutions.
U.S. Pat. 3,764,503, Oct. 9, 1973.
6. Soboroff, D. M., J. D. Troyer, and A. A. Cochran. A
One-Step Method for Recycling Waste Chromic
Acid-Sulfuric Acid Etching Solutions. Proc. 33rd
Annual Purdue Indus. Waste Conf., May 9-11,1978,
pp. 758-763.
7. Regeneration and Recycling of Waste Chromic Acid-
Sulfuric Acid Etchants. BuMines RI 8377, 1979, 12
pp.
8. Tirrell, C. E. Process for the Electrolytic Reclamation
of Spent Etching Fluids. U.S. Pat. 3,761,369, Sept. 25,
1973.
9. U.S. Code of Federal Regulations. Subchapter NX
Effluent Guidelines and Standards: Part 413X
Electroplating Point Source Category. Federal
Register, v. 42, No. 133, July 12, 1977, pp. 35834-
35843.
36
-------
Liquid Ion Exchange In
Metal Recovery and Recycling
Lawrence V. Gallacher*
Liquid ion exchange is a relatively new technique
which combines the concepts of ion exchange and liquid-
liquid extraction for the removal and recovery of metal
ions from aqueous streams. Thg growing need for this
technology today is the result of many factors, including
government discharge regulations, rising metal values
and the necessity for treating increasingly dilute
solutions.
The electroplating industry in particular is finding it
more and more difficult to deal with the problems of
waste treatment and disposal, and at the same time, the
economic need to regenerate and recycle valuable metal
solutions. We are becoming increasingly aware of the fact
that accepted treatment methods like the removal of
heavy metals from waste streams by generating mixed
hydroxide, carbonate or sulfide sludge are ultimately
undesirable. They generate potentially hazardous solid
wastes, both in the legal and the technical sense, and
waste valuable resources. Ion exchange technology,
particularly liquid ion exchange, offers an effective
approach to eliminate the solid waste and recycle the
metal values where they will be most valuable.
I would like to start this presentation by describing
four actual applications of liquid ion exchange in metal
recovery. Then we will cover the basic principles of liquid
ion exchange, the major types of reagents , how they can
be applied to solve specific problems and what the future
holds.
Case I. (Figure 1)
A strongly acidic solution of 0.2 grams per liter zinc in
sulfuric acid is generated by a rayon plant. If the zinc is
precipitated by neutralizing to pH 9.5 with caustic soda, a
slimy, intractable sludge is generated. If lime is used, a
tremendous volume of calcium sulfate precipitate is
produced, mixed with a very small quantity of zinc
hydroxide, and the result is a difficult solid disposal
problem. The problem is solved by first treating the
effluent with lime, leaving it weakly acidic and
precipitating calcium sulfate only. The zinc solution is
then mixed in two stages with a solution of di-2-
ethylhexylphosphoric acid (D2EHPA) in kerosene to
reduce the zinc concentration in the effluent to less than 4
ppm. The organic extract is stripped with a very low
volume ratio of sulfuric acid solution to regenerate the
D2EHPA and produce a zinc sulfate solution containing
80 g/1 which can be reused in the plant.
Recovery of Zinc
From Rayon Manufacturing Waste
FEED: H2SOq SOLUTION, pH 0.5,
0.2 G/L ZN++
ZNSOa SOLUTION,
80 G/L ZN, TO PLANT
CA (OH)2
PH 5-6 ZNSOi) + CASOi)'2H20
SOLUTION PRECIPITATE
ZN/ORGANIC
| STRIPPING
j
H2
so
I
S0t|
_'N
D2EHPA
IN KEROSENE
REMOVE
SOLIDS
AQUEOUS EFFLUENT,
ZN LESS THAN 4 PPM
Figure 1.
Case 2. (Figure 2)
Mixed metal waste consisting of scrap, lathe turnings,
mill shavings and the like contain recoverable Mo, W,
Co, Fe and Ni. The process involves five steps:
1. Pyrometallurgical pretreatment, which converts the
refractory metals Mo and W into their carbides.
2. Electrolytic dissolution of Fe, Co, and Ni (using
diaphragm cells and calcium chloride electrolyte
solution with anodic dissolution of the metals)
followed by partial stripping to concentrate the
CaCl2 electrolyte.
3. Separation of Fe, Co, and Ni by extraction with a
high molecular weight amine.
4. Stripping the cobalt/iron organic extract with the
weakly-acidic condensate from step (3).
5. Cathodic deposition of Co and Ni in separate half
cells. The stripped electrolyte then goes to step (2).
The process produces a Ni/Fe mixture and a Co/Fe
mixture, which doesn't affect the market value of the Ni
or Co significantly. There is no gaseous or liquid
discharge.
*Lawrence V. Gallacher
King Industries, Inc.
Norwalk, CT 06852
Case 3. (Figure 3)
An ammoniacal leach liquor containing 12.8 g/1 Cu,
29.2 g/1 Zn and 110 g/1 NH3 at pH 10.1 was mixed in 3
37
-------
Recovery of Metals Value
From Treated Metal Scrap
TREATED PI
CATHODE _ CACl2__
NlCKEL | SOL'N
ETAL SCRAP
CAC12 CATHODE
[SOL'N] COBALT/ I RON
CATHODIC ANODIC
HALF HALF
CELL CELL
I
Nl
ELECTROLYTE
(CAC12)
CON
| FIL"
SOLID
Mo,W
CARBIDE
HER |
DILI
Co,F
CHLC
SOLI
1
EVAPORATOR
CATHODIC
HALF
CELL
1 1
COBALT/IRON
TE ELECTROLYTE
RIDE
TION
CONDENSATE
CONC.CO,FE,NI.
SOL/N, Cr=250 G/L
1
*
AMINE
EXTRACTION
1
A
Ni, CA
CHLORIDE SOL'N
3ENSATE
AMINE/METAL ijr
COB/
STF
TERTIARY I
AMINE
iLT/lRON
IPPING
CONDENSATE
Figure 2.
counter-current extraction stages with an equal
volumetric flow of a 38% solution of an alkyl beta-
diketone in kerosene. The copper was quantitatively
extracted into the organic phase, but no zinc or ammonia
were extracted. The organic extract was then washed
with a very small volume of dilute sulfuric acid (26.5 g/1)
to remove traces of ammonia and was stripped in 2 stages
with an equal volume of solution containing 39 g/1
H2SO4 and 54.8 g/1 Cu. The stripping acid was finally
passed through an electrowinning cell to recover the
copper.
Case 4. (Figure 4)
A crude phosphoric acid stream containing 58%
H3P04+vp.3 g/1 Ca++, 2.1 g/1 Mg++, 10.0 g/1 Al+++ and 9.5
g/1 Fe+++ is extracted with 5 volumes of an extractant
mixture consisting of 12% di-2-ethylhexylphosphoric
acid (D2EHPA) and 19% dinonylnaphthalene sulfonic
acid (DNNSA) in kerosene at 54° C. In a single stage,
4.4% of the phosphoric acid, 92% of the Ca+++, 42% of the
Mg+* and 12% of the Al+++ are extracted. The extraction is
carried through several countercurrent stages to remove
essentially all of the Ca++ and Mg++ and much of the Al+++.
The extract is then "scrubbed" with a 20% phosphoric
acid from the organic phase, and the scrub solution is
later combined with the feed and recycled. The extract is
stripped with 1/10 volume of 10% sulfuric acid in 2 stages
at 55° C to regenerate the extractant. A portion of the
strip solution is removed from the system to be
neutralized and fresh make-up acid is added to make
fresh stripping acid solution. The phosphoric acid
product produced by this process is suitable for
conversion to high-quality super phosphoric acid liquid
fertilizers.
Recovery of Metals
From Ammonia Solution
AMMO
i
1IACAL
Cu, ZN LEACH LIQUOR
COPPER EXTRACT, (NHi^SOi) SOL'N
TRACE NH3 ]
r 4
1 NH3 SCRUB |
EXTRACTION
STAGE 1
\
I
r
EXTRACTIO
STAGE 2
\
I
1
EXTRACTIO
STAGE 3
i
' ZN L
TO 2
i
r
IQUOR
.N REC
L
Si
v
Si
c
"•
DILUTE H2soi)
^CuSOi) SOL'N
"RIPPING
iTAGE 1 1
1
1
DRIPPING 1
>TAGE 2 1
* 1
BETA DIKETONE ACID '
EXTRACTANT i |
OVERY f (
Figure 3.
The four cases just described are actual examples of
liquid ion exchange processes which have been operated
on a large scale. They illustrate several key points we
would like to make in this paper, namely:
1. Recovery of metals by liquid ion exchange is a
realistic and economically viable concept.
2. There are a number of reagent types available for
extracting metals under a number of very different
conditions, i.e.:
- from weak acid leach liquors
- from relatively concentrated acids
- from ammoniacal leach solutions
- as anionic complexes
- from mixtures containing many metals
3. A "good" process generates little or no secondary
waste. Maximum recycling of all streams is utilized.
4. Typical working processes bring a number of
chemical and engineering disciplines together.
THE PRINCIPLES OF LIQUID EXCHANGE
Liquid ion exchange is somewhat similar to
conventional ion exchange using solid resins in that an
aqueous feed solution is contacted (mixed) with an active
reagent in a mixing chamber or column. In this
operation, ions are extracted from the feed in exchange
for hydrogen ions or other transferable ions carried by
the liquid ion exchange reagent. The liquid ion exchange
reagent is water-insoluble, and is generally used as an
"extractant" solution in a hydrocarbon solvent such as
kerosene. The actual "exchange" takes place when the
aqueous feed is mixed intimately with the extractant,
producing an unstable liquid-liquid dispersion of
droplets of one phase in the other. At the moment of
mixing, the interfacial area is very great, and the
exchange process occurs via a three-step mechanism
whereby:
1. The hydrated or complexed metal ion diffuses to the
aqueous/organic interface,
38
-------
Purification of Crude Phosphoric Acid
CRUDE PHOSPHORIC ACID WITH CA, MG, Al
SCRUB TO FEED
EXTRACT: CA, MG
Al, SOME HjPOtt
DILUTE PURIFIED
H2SOi|, MG, CA, Al
TO LEACHING OR
NEUTRALIZATION
N
STRIPPING ST. 2
k
t
DNNSA/D2EHPA
EXTRACTANT
DILUTE
PURIFIED
PHOSPHORIC ACID
PRODUCT
Figure 4.
2. The ion is stripped (ideally) of its hydration layer
and complexes with the liquid ion exchange reagent
at the interface, making the interfacial transition,
and,
3. The organic/metal complex diffuses into the bulk
organic phase. Simultaneously, hydrogen ions or
other labile ions associated with the reagent in the
organic phase are transferred to the aqueous phase.
In fact, the actual exchange takes place at the
interface.
Now we have successfully extracted the metal ion into
the organic phase. The next step usually is to strip the
organic, re-extracting the metal ions with an aqueous
stripping solution. In the case of acid extractants,
stripping is done with a dilute mineral acid. Often, as in
two of the examples, the extractant phase picks up ionic
or molecular species in addition to the desired ones, and
these are extracted in a "scrubbing" step using a weak
reagent before the stripping step.
The final step is to recover the metal itself and
regenerate or dispose of the stripping solution. This step
is just as important as extraction and stripping, but is
frequently given inadequate attention. The easy, but
expensive route, is to neutralize the stripping solution
and generate a neutral waste stream or sludge. The best
approach is one which regenerates the stripping solution
and recovers the metal directly, electrolytically or by
direct reduction, or as an insoluble salt. (Table I reviews
the 3 liquid ion exchange steps).
Perhaps at this point you are wondering why we bother
to extract the metal from the aqueous feed into the
organic phase, only to re-extract it into a new aqueous
TABLE I
LIQUID ION EXCHANGE PROCESS STEPS
1. Extract meta! into organic phase.
2. Strip metal ions from organic phase.
3. Recover the metal and regenerate the stripping solution.
TABLE 2
LIQUID ION EXCHANGE PROCESS CRITERIA
1. The process must achieve the desired result within allowed
constraints.
2. All streams in and out and products must be accounted for
completely.
3. The extractant system should have good long-term operating
characteristics.
4. Interferences must be identified and treated in advance.
phase. This is a good time to enumerate the benefits we
can gain from liquid ion exchange beyond simple metal
recovery. They are:
a. Increase the metal concentration in the stripping
solution relative to the feed. By using high volume
ratios of feed to extractant and extract to strip
solution, it is possible to increase the final metal
concentration up to one hundred fold or more. This
can be the key to metal recovery by electrowinning,
crystallization, or precipitation.
b. Recover one metal in the presence of others.
Frequently, the desired metal is present with a high
background level of other unwanted metals, e.g.,
copper in the presence of ferric iron. In other
instances, all of the metals may be valuable, but
only one at a time. Selectivity in liquid ion exchange
can be obtained by using specific reagents or
combinations of reagents, or by making
adjustments in feed solutions or stripping solutions.
We'll say more about thfs further on.
c. Recover metal from an ammoniacal solution
without the complexed ammonia. Reagents are
available which extract Cu++, Ni++, and Zn++ from
ammoniacal leach solutions without extracting
ammonia. The metals can be obtained together or
separately by controlling either extraction or
stripping conditions.
d. Change the counterion present in the feed to a
different one. Sulfate can be exchanged for chloide,
for example, by extracting a sulfate feed with an
acid extractant and then stripping with dilute
hydrochloric acid.
Successful application of liquid ion exchange to metal
recovery requires careful attention to certain key details.
Before getting into a discussion of reagents, we will
briefly review these four criteria, since they are critical in
the selection of extraction reagents. (Table 2).
First, the process must achieve the desired result within
the allowable conditions of time, temperature,
39
-------
concentrations, pH, equipment and cost. Cost is
obviously a paramount consideration. Fast extract-ion,
stripping, and phase separation mean small equipment,
small reagent inventory, and low cost. The same is true of
high extraction and stripping capacity.
Second, all feed streams, extractants, stripping
solutions, and recovered metal values must be accounted
for completely. A "cradle-to-grave" approach for all
streams is essential.
Third, the extractant system should have good long-
term operating characteristics. These include chemical
stability, good metal-complex solubility, very low
solubility in feed and stripping solutions, and good phase
separation characteristics with no haze. Solubility and
haze are the principal causes of extractant losses.
Fourth, interferences must be identified and treated in
advance. Interferences can include co-extracted ions
which don't strip, oxidation or reduction reactions, solids
in the feed, and dissolved organics. For instance, organic
additives such as amines or surfactants are likely to be
extracted and a gradual deterioration of phase-
separation characteristics is likely. Possible answers are
to put in a carbon adsorption column before extraction
or to strip the impurities afterwards.
kerosene requires addition of modifiers, e.g., 5%
isodecanol, to prevent third phase formation.
Dinonylnaphthalene sulfonic acid (HDNNS)
C9Hi9 SO3H C9H19 SYNEX DN (King Industries)
A strong acid with excellent stability at temperatures
below 60° C. Extracts well down to pH 1.0 with little
selectivity. Selectivity greatly enhanced by combining
with other reagents including D2EHPA, LIX 63,
SYNEX XB1. Ammonium salt extracts well from
ammoniacal solutions.
Carboxylic Acids
R-COOH Versatic (Shell)
Weak acids (See D2EHPA comments). Use in sodium
salt form is restricted by solubility and emulsification
tendency.
Alkyl Benzotriazoles
R NH N N SYNEX XB-1 (King Industries)
Selectively extracts copper, nickel from neutral to
acidic media. Mixtures with sulfonic acids,
alkylphosphoric acids, or carboxylic acids have higher
selectivity and operate at lower pH.
TYPES OF LIQUID ION EXCHANGE REAGENTS
AND THEIR APPLICATIONS
There are four fundamental classes of reagents used in
liquid ion exchange:
1. Acids, which extract cations in exchange for
hydrogen ions, ammonium ions, or other metal
cations,
2. Chelating agents, which extract cations in exchange
for hydrogen ions via highly specific interactions,
3. Amines and quaternary ammonium salts, which
extract anions/anionic metal complexes in
exchange for anions,
4. Neutral reagents, which function by solvating metal
ions directly or by forming complexes with other
reagents, which in turn are more effective than
either reagent.
I will attempt to describe important members of each
class of reagents, their important characteristics, and
principal applications.
ACIDS
These are all high molecular weight compounds
containing large hydrocarbon groups which render the
acids and their salts water-insoluble and also offset the
normal surface activity of such materials. Generally
speaking, the stronger the acid, the lower the selectivity
but the better it extracts at low pH. When acids are used,
the exchange of metal ions for hydrogen ions lowers the
pH of the aqueous phase. This effect severely limits the
metal-loading efficiency of weak acids. One answer is to
use the acid in salt form (e.g., Na+ or NH4+); another is to
adjust the aqueous pH between stages. Representative
acid extractants are described below:
Di-2-ethylhexyl phosphoric acid (D2EHPA)
(C8Hi7O)2 P(O)OH (Mobil, King Industries)
A weak acid with good hydrolytic stability. Strong
affinity for Fe+++. Good selectivity, dependent on feed
pH. Requires use of salt form or buffering to obtain high
loadings. Biggest use is in uranium extraction, mixed
with trioctyl phosphine oxide. Use as sodium salt in
AMINES AND QUATERNARY AMONIUM SALTS
These reagents are used to extract anions, usually in
the form of metal complexes. Stripping is accomplished
with aqueous salts or bases. Tertiary amines are most
popular, and are used in protonated form in acid
medium. Because of protonation, which results from
extraction of a mineral acid molecule (H2SC>4, HC1) from
the feed,
R3N + HC1 = R3NH+CF
there is a net transfer of acid to the stripping solution
when basic stripping solutions are used. However, phase
separation is much better with basic stripping.
Quaternary ammonium salts are useful over a wide pH
range, even in basic media. However, because they can't
be deprotonated, stripping tends to be difficult.
Tertiary Amines
R3N Alamine (Henkel), Adogen (Ashland)
Biggest use is in uranium recovery, where amines are
used to extract the uranyl sulfate complex. Other uses
mostly involve extraction of chloride complexes. Some
selectivity can be achieved by taking advantage of the fact
that some metals extract at lower chloride concentrations
than others. For' example, at pH 2 and 40° C, Alamine
336 extracts ferric iron at 50 g/1 chloride, copper at 100
g/1, and nickel only slightly at 250 g/1. Sensitivity to
oxidation in some systems.
Quaternary Ammonium Salts
R4N+X~ Aliquat (General Mills), Adogen (Ashland)
Can be used like amines, but do not require low pH.
More difficult to strip than amines. Applications tend to
be proprietary and not well publicized. Some use in
vanadium refining.
DEVELOPING A LIQUID ION EXCHANGE METHOD
TO SOLVE SPECIFIC PROBLEMS
Now that we have reviewed important liquid ion
exchange reagent characteristics and criteria for applying
40
-------
TABLE 3
DEVELOPING A LIQUID ION EXCHANGE METHOD
1. Define the problem, the goals and the constraints.
2. Select candidate extractants, stripping solutions and recovery/
disposal techniques.
3. Perform laboratory shake-out tests.
4. Modify compositions and conditions as needed and retest.
5. Perform rough cost analysis.
6. Run pilot-scale tests. Look for long-term effects and make necessary
corrections.
7. Review cost analysis.
8. Design and construct process.
TABLE 5
LIQUID ION EXCHANGE TROUBLESHOOTING-II
Problem
Stripping
1. Haze, slow phase
separation
2. Solid Formation
3. Incomplete
Stripping
Solution
1. Raise temperature
Use reagent additive
Amines: Strip with base
2. Use proper acid strip for solubility
Ammonia contamination: Scrub stage
Check interfering metals
3. Increase temperature
Increase mixing time
Increase reagent concentration
Increase aqueous: organic volume ratio
TABLE 4
LIQUID ION EXCHANGE TROUBLE-SHOOTING-I
Problem
Extraction
1. Haze after separation
Slow phase separation
2. Solid Formation
3. Low extraction
4. Low selectivity
5. Organic contamination
6. Unwanted metal or
Inorganic Pick-up
Solution
1. Raise temperature
Use reagent additive
2. Use reagent additive
Change solvent
3. Increase mixing time
Increase reagent cone.
Increase organic: aqueous volume ratio
Raise temperature
Use more selective reagent
Change solvent
Raise Feed, pH
Use salt form of extractant (acids)
4. Use more selective reagent
Decrease reagent cone.
Decrease organic: aqueous volume
ratio
Change solvent
5. Pretreat Feed: carbon or solvent
Scrub stage
6. Scrub stage,
Change Conditions
Change extractant
liquid ion exchange, let's consider how to develop a
method to solve a specific problem (Table 3).
The first step is to select and map out candidate
processes in rough detail giving preference to the simplest
approaches, those which show least cost or maximum
return and those which lead to maximum recycling and
least waste production. Frequently these criteria go
hand-in-hand, but often a level of complexity is required
to achieve lowest operating cost and waste.
The next step is to perform extraction and stripping
"shake-out" tests in the laboratory using graduated
cylinders or separatory funnels. We generally start with
equal volumes of candidate extractant and feed in a
graduated cylinder with a ground-glass stopper. The
extractant concentration is adjusted so that if all the
metal of interest is extracted, the extractant will load to
about 60% of its theoretical capacity based on its
molecular weight and the charge on the metal. The
solutions are added at room temperature, the graduate is
shaken by hand for one minute to form a liquid-liquid
dispersion, and then set down to allow the phases to
separate. At this point, it is important to note how rapidly
the separation occurs, whether there is haze in either
phase, and whether there is any solid formation,
particularly at the interface. Slow phase separation and
haze can usually be alleviated by operating at a higher
temperature, or by the addition of certain additives like
isodecanol or tributyl phosphate, or a solvent change.
Additives can usually solve solids problems. Increased
temperature frequently helps the actual extraction as
well, but neutral additives and solvent changes as often as
not impair extraction and selectivity. Tables 4 and 5
present common problem areas in liquid for exchange
present common problem areas in liquid ion exchange
processes and potential solutions.
After the liquid phases have separated, the next step is
to carefully remove portions of both organic and aqueous
phases and analyze them to evaluate the extent of
extraction and the selectivity. Suppose that the extent of
extraction is good, but the selectivity between two metals
is in the right direction but not good enough. Thus, you
might be trying to extract iron from a solution containing
50 g/1 nickel and 1 g/1 iron. Your analysis shows that the
extractant takes out 0.5 g/1 iron and 2 g/1 nickel. This in
fact shows good iron selectivity, since 50% of the iron is
extracted while only 4% of the nickel is extracted. A
situation like this one is usually improved by adding a
stage of countercurrent extraction. If 100% of the iron
and 10% of the nickel had been extracted the
recommendation would be to lower the extractant
concentration or the volume ratio of extractant to feed to
achieve higher loading of the extractant. Normally,
increasing the loading increases the selectivity, essentially
crowding out the less preferred ion. If you are extracting
with a weak acid and the extraction is very low compared
to the theoritical capacity of the acid, the problem may be
caused by a drop in feed pH that occurs during
extraction due to the transfer of hydrogen ions into the
feed. The answer heye is to use the acid in salt form or to
adjust the feed pH between stages using caustic soda or
ammonia. Another cause of low extraction is slow
41
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extraction kinetics. This can be checked by repeating the
experiment with longer shaking times. If the extraction is
slow, that means bigger equipment. Try raising the
temperature or adding a reagent like DNNSA or LIX 63
to reduce the interfacial tension (Table 5).
Assuming that we have achieved satisfactory
extraction in the shake-out tests the next step is to look at
stripping. The same general rules apply here. In addition,
if stripping is not satisfactory, increase the concentration
of the active acid, base, or salt in the stripping solution. It
is also very important to think ahead to the ultimate fate
of the stripping solution. For instance, if we want to
recover copper by electrowinning from a sulfuric acid
stripping solution, we should have a copper
concentration of about 50 g/1 in the stripping solution
(called the pregnant electrolyte in the trade). This can be
achieved by maintaining a base level of 40 g/1 and going
up to 50 g/1 in stripping and back to 40 g/1 in
electrowinning. Other options include: direct use of the
strip solution as-is, hot stripping followed by re-
crystallization of the metal salt, hydrogen reduction,
vacuum stripping of the acid (HC1) and water to leave a
metal salt, precipitation, and finally, neutralization and
disposal.
Once the process concept has been worked out and
demonstrated in the laboratory tests, it is time to take a
hard look at the economics. The system should be
evaluated for extractant losses due to solubility and haze,
for these are very important. Neutralization, make-up,
energy and equipment costs should all be estimated to see
if the process looks feasible.
If so, the next step is to set up and run the process on a
pilot scale long enough to see long-term effects. These
may include: decomposition of the reagent and a gradual
deterioration in performance, accumulation of trace
metal impurities in the extractant phase, accumulation of
organic or other impurities from the feed in the
extractant, or the development of "curd" (an
undetermined solid phase at the interface). Solutions to
these problems may not come easily. Slight reagent
decomposition or solubility loss can be corrected by
partial withdrawal and make-up. Accumulation of
unwanted metals ions may require a change in the
stripping solution or addition of a scrubbing step. The
same is true of organic impurities, or these might require
pre-treatment of the feed with a carbon-absorption step
or a solvent-extraction step. "Curd" can usually be
eliminated satisfactorily by the right additive in the
extractant.
FUTURE PROSPECTS FOR LIQUID ION EX-
CHANGE IN METAL RECOVERY AND RECYCLING
In this paper we have attempted to introduce you to
liquid ion exchange principles, showing you a minimum
of abstract theory, what can be done and has been done,
what reagents are available and what each can do and
can't do, and how to work out a process to solve your own
problems.
Looking ahead, what does the future hold for this
technology? As we see it, the economic and
environmental pressures are building rapidly to find
better ways to recover metal values from process streams
and waste streams. Making metal hydroxide, carbonate
or sulfide sludges doesn't look like an acceptable long
term answer to the environmental problem and is no
answer at all to the economic problem. These sludges are
notoriously hard to handle and should go to secure,
hazardous-waste landfills, since they always have the
potential of releasing toxic concentrations of heavy
metals under acid conditions.
Liquid ion exchange is one of several approaches to the
recovery of metals, but it appears to have the greatest
potential for a general solution to the recovery problem.
There will be difficulties along the way, however. Right
now it looks like liquid ion exchange is beginning to
acquire recognition as a useful technique. Unfortunately,
there have also been some false starts in using it - mostly
because of ignorance of available information or not
considering the total system. However, the last five years
have brought rapid progress in the understanding and
utilization of liquid ion exchange techniques in this area,
and we are confident that progress will continue. Bear in
mind that in other fields like primary copper and
uranium refining, liquid ion exchange has played a major
role for over five years.
Certain applications look very interesting right now.
For example, the mixed metal sludges referred to before
can be leached with either sulfuric acid or ammonia to
generate feed liquors which certainly can be treated with
liquid ion exchange to recover valuable metals like
copper, nickel, and zinc separately.
I hope that this presentation has helped to inform you
of developments and useful applications in liquid ion
exchange.
REFERENCES
1. H. Reinhardt, H. Ottertum and T. Troeng, Proc.
Appl. Chem. Treat. Sewage Ind. Liq. Effluent Symp.,
Int. Chem. Eng., London, 1975, p Wl. (The Valberg
Process).
2. H. Reinhardt. Chemistry and Industry, p. 210, 1
Mar. 1975. (The Gullspang Process).
3. Preliminary Report. XI-54. A New Reagent for
Metal Extractions from Ammomiacal Solutions
General Mills Chemical, Inc.
4. J. L. Bradford and F. Ore, US Patents 4,053,564 (to
Occidental Petroleum Company), Extraction Process
for Purification of Phosphoric Acid.
42
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Achieving Effluent Criteria—Not Final Answer
A. F. Lisanti and R. Helwick*
Much attention has been given to the treatment of
wastewater. Wastewaters are characterized and studies
conducted to optimize the treatment processes in order to
assure achievement of effluent limitations with the least
possible cost. In the treatment of wastewaters, especially
from metal finishing plants, metals are precipitated and
removed as a sludge. The hauling and disposal of that
sludge, however, have not received as much emphasis as
that of the wastewater treatment processes. Accordingly,
many plants are not equipped with the sludge dewatering
facilities or the facilities are not the most cost effective.
One reason is that the characteristics of the sludge are not
adequately known before the wastewater treatment
facilities are installed. With the impending sludge
disposal requirements as outlined by the Resource
Conservation and Recovery Act and the increasing cost
of contract disposal, nevertheless, sludge handling and
disposal must be addressed with the same zeal as that
afforded to the wastewater treatment processes. The
sludge should be characterized and studies made to
optimize sludge handling and dewatering systems. In
addition, evaluations should be made of sludge disposal
alternates including recovery processes. These efforts
should reduce the cost of sludge disposal.
Other papers presented at the conference will discuss
existing or pending regulatory requirements for sludge
disposal. As such, this paper will not address that phase
but presents a summary of capital and operating costs
currently incurred by representative metal finishing
plants for sludge disposal. The plants selected for
discussion have been designed using well publicized
techniques of inplant wastewater flow reduction and best
practical treatment technology. The solids dewatering
facilities which include the use of filter presses, vacuum
filters and diatomaceous earth type of pressure filters
were designed based on an evaluation of alternate
schemes and data accumulated in treatability studies.
Table I lists the sludge quantities handled by each of
the plants. It tabulates the volume of sludge entering the
dewatering process, the solids content of the sludge, the
solids content of the cake obtained by the mechanical
dewatering equipment and the quantity of cake that must
be disposed of.
Plant A referred to in Table I batch treats the
wastewater and passes the unsettled slurry through
*A. F. Lisanti and R. Helwick
Chester Engineers
Coraopolis, PA
pressure filters precoated with diatomaceous earth. Since
filtration of the wastewater is necessary to attain effluent
limitations, the use of diatomaceous earth filters not only
accomplished that goal but at the same time dewaters the
solids. Plant B utilizes a continuous treatment system.
Since the concentration of suspended solids generated by
the treatment processes is of such a level as to preclude
direct filtration and dewatering as in Plant A, the
wastewater is clarified before filtering through a
diatomaceous earth type of pressure filter. The sludge
from the clarification process is conveyed to a thickener.
The thickener also receives the diatomaceous earth from
the pressure filter. After gravity thickening, the solids are
dewatered by a filter press. Plant C treats its rinses in a
bath operation. The sludge from this process is mixed
with spent concentrated acids which are neutralized and
dewatered by a filter press. In Plant D, the wastewater is
clarified and the underflow conveyed to a storage tank
for subsequent dewatering by a filter press. For Plant E.
the underflow of the clarifier is gravity thickened and
dewatered by a vacuum filter.
Table 2 lists the construction costs for the total
treatment facilities, the cost associated with the sludge
equipment including housing for that system and the
percentage of the total cost of the treatment facilities
associated with the sludge handling and dewatering
equipment.
Currently, each of the plants are hauling the dewatered
solids to an approved landfill site. Table 3 illustrates the
costs incured by each of the plants for disposal of those
solids. These costs include the pick-up, hauling and
placement charges. As noted in the table, Plant C instead
of disposing of its solids in a local approved landfill has
the option of hauling the solids to another plant within its
corporation for metal reclamation.
As a means of comparing the plants operating costs
associated with the treatment of wastewater and the costs
applicable to the solids handling and disposal, Table 4 is
presented. The costs in this table include an estimate of
the manpower devoted to the wastewater and solids
handling portion of the treatment system. The costs do
not include amortization of the equipment.
As demonstrated by the cost comparisons, the sludge
handling and disposal facilities are not only a significant
factor in the construction costs for the wastewater
treatment facilities, especially for the smaller metal
finishing plants, but play a major role in the operating
costs. Nevertheless, without the sludge handling and
dewatering facilities, the disposal costs for the solids
would be significantly increased. For example, Plant C
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generates some 153,600 pounds per week of sludge at a
local landfill site would cost about $6,150 per week. By
dewatering the solids, the weight of sludge to be disposed
of its reduced from 153,600 to 76,200 pounds per week
and the disposal cost decreased from $6,150 to $3,050 per
week. This savings in disposal cost offers a good payback
on the capital investment of the solids dewatering
facilities. It is advantageous, then, to not only optimize
wastewater treatment processes, but the sludge handling,
dewatering and disposal options for each plant.
TABLE 1
SLUDGE QUANTITIES
Plant A
Plant B
Plant C
Plant D
Plant E
Dewatering Method
Pressure Filtration (DE)
Filter Press
Filter Press
Filter Press
Vacuum Filtration
Sludge Volume,
gpd
10,000
340
2,285
234
1,780
Solids of Sludge,
wt. %
0.03
9
15
1.9
8.7
Cake Solids,
wt. %
40
32
30
15
22
Quantity of
Cake Generated,
cuft/wk
13
150
941
14
620
TABLE
2
CONSTRUCTION COSTS
Plant A
Plant B
Plant C
*48% is of spent
Design Flow,
gpd
25,000
238,000
*4,000
concentrated acids.
Treatment Facilities,
$
450,000
1,900,000
940,300
Dewatering Facilities,
$
97,000
240,000
158,000
% of Total Facilities' Cost
For Sludge Handling
21.6
12.6
16.8
Plant A
Plant B
Plant C
* Plant C (Alternate)
TABLE 3
SLUDGE DISPOSAL COSTS
Costs include hauling and disposal charges
Quantity of Sludge, tons/mo Disposal Cost, S/mo
1.0 1,290
12
165
165
1,800
13,200
24,750
Disposal Method
Drummed and hauled to approved
landfill
Hauled to approved landfill
Hauled to approved landfill
Hauled to metal reclamation plant
*Cost are for hauling. Does not include cost of metal recovery nor value of recovered metal.
TABLE 4
OPERATING COST COMPARISON
Entire Treatment Facilities,
$/year
Plant A 34,000
Plant B 138,000
Plant C 27,860
Solids Dewatering and
Disposal Portion, $/year
16,000
50,000
13,200
% of Entire Cost For
Solids Disposal
47.0
36.2
47.4
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Luncheon Presentation:
The Resource Conservation and Recovery Act
Rebecca Hanmer*
It is a pleasure for me to be here and to have this
opportunity to share a few thoughts with you on
hazardous waste. This is my first formal opportunity to
meet with representatives of the metal finishing industry.
However, in my former job as Deputy Administrator of
EPA's Boston Office, I was keenly aware of the economic
importance of the industry in New England and thus
interested in the means by which electroplaters were
seeking solutions to pollution control requirements.
For years, industry has been dealing with requirements
to protect the Nation's air and water. Today, I want to
talk with you for a few minutes about the law that closes
the loop, The Resource Conservation and Recovery Act:
RCRA.
I will give you a brief history of RCRA, provide
information about the upcoming regulations, and the
EPA Regional Office role, and comment on something I
believe to be of overriding importance—especially in this
program. That is the need to work together. We need to
communicate with each other and with the public. For
this new set of requirements and protections - vitally
needed - will affect us all.
RCRA became law in 1976 and is structured to ensure
that from now on our society takes its hazardous waste
management responsibilities more seriously.
Unfortunately, it was not until the Act was about two
years old, and the Love Canal tragedy forced our
attention on the magnitude of the residues of past neglect,
that we noticed RCRA's limitations. Except for an
imminent hazards provision, the Act does not address
critical problems which recently have come to light from
a legacy of careless waste management. We know now
that there are two hazardous waste problems — The one
we have inherited and the one RCRA is intended to solve.
We know also that neither can be neglected; except at the
cost of the extreme peril to ourselves, our children, and
people yet unborn.
We produce 57 million tons of hazardous waste each
year. We estimate there are more than 750,000 generators
of hazardous wastes, 10,000 transporters, and 30,000
treatment, storage, and disposal facilities. At least 90
percent of the hazardous wastes currently produced are
disposed of improperly and unsafely. There are up to
50,000 uncontrolled closed and existing sites.
More than 60,000 chemicals are now in common use in
this country; thousands more are registered each week.
•Rebecca Hanmer
Regional Administrator
U.S. EPA Region IV - Atlanta
The adverse effects of mismanaged waste can reach us
through direct contact, through the air we breathe, the
food we eat and the water we drink. It is of critical
importance that we keep waste from seeping into the
groundwater. About half of the drinking water supply in
this country is taken from groundwater. Twenty percent
of the population drinks groundwater untreated.
As you probably know, because EPA failed to produce
RCRA regulations within eighteen months as stipulated
in the law, civil actions were brought against the
Environmental Protection Agency by the State of
Illinois, the Environmental Defense Fund, and others.
Last October, EPA's Administrator, Doug Costle, in a
quarterly affidavit on EPA's progress in developing final
regulations, said, "Among the many pressing
environmental problems currently facing EPA and the
Nation, I consider hazardous waste the most serious."
He also pointed out in the affidavit that we received
more comments on RCRA than on any proposed
regulations in the history of the Agency. At that time we
had 1,200 sets of public comments, some of which were
hundreds of pages in length.
At the same time we have been involved in developing
RCRA regulations, we have had to begin to deal with the
problem of closed and existing uncontrolled sites.
Working with the Department of Justice and the states,
EPA has initiated a remedial and enforcement program
directed against hazardous waste sites which pose
substantial risk to public health and the environment.
Regional offices have been required to redirect many
work years towards this effort. Hundreds of sites have
been investigated and a number of major enforcement
actions have been initiated by the EPA regions.
To provide funds for the clean-up of abandoned sites
and to permit a more rapid response where health and the
environment are threatened, EPA developed legislation
which was submitted by the President to Congress last
June to establish a multi-million dollar "superfund."
Hearings on the proposal have been held by several
congressional committees, on several different bills and
committee mark-up is underway.
But, back to RCRA. The original Federal law was
born in 1965. That means we are now on the verge of
beginning to move against hazardous waste fifteen years
after the first federal law to deal with the solid waste
problem was enacted.
In 1970, the Congress amended the solid waste law to
call for a comprehensive investigation of hazardous
waste management practices in the United States, with
formal reports to be submitted to Congress.
It wasn't until 1975 that the need for hazardous waste
regulation was acknowledged by important segments of
45
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industry and public interest groups. A Federal system for
such regulations was authorized by the solid waste
amendments of 1976 that formed the Resource
Conservation and Recovery Act.
Today, we have the law and we have some of the
regulations. More regulations will be issued this month,
with the final regulations for writing RCRA permits
expected in October 1980.
The law allows States to assume delegation of the
program, and we are working hard with the States to this
end.
What is the role of EPA's Regional Offices in the
RCRA program: In brief, we are the implementing part
of EPA. The 10 regions will be implementing the RCRA
regulations either directly or, where State programs have
been approved, indirectly through State overview. The
direct role consists of:
• Assisting persons to understand the regulations and
how different industries are affected
• Monitoring compliance with interim status notifica-
tion and manifest requirements.
• Enforcing where necessary
• Issuing RCRA permits
We will help States set up RCRA programs and
approve State programs where possible to take over the
direct tasks. We administer State program grants. After
the States take over, we help them with difficult
situations and oversee progress. RCRA allows a State to
qualify early to take the program through interim
delegation. That means the State can run the RCRA
program even if it needs to make some legal or regulation
changes in order to get the full delegation. The State must
have a program to start out that meets most RCRA
requirements and a definite timetable for completing
improvements in 2 years.
In Region IV, we estimate 5 of our 8 states now will be
able to achieve interim delegation this year.
I've been asked to give you a hint about the upcoming
regulations, I believe you talked about this at a morning
session, so I will just summarize briefly. EPA has already
issued the regulations for the manifest system, which go
into effect at the end of October 1980. Regulations
defining what a generator is and a public notice
explaining the notification procedure were also issued on
Feb. 26. On April 30, EPA is going to issue the
regulations that define (1) hazardous wastes, (2) set our
requirements for States to get authorization for running
the program, and (3) contain requirements for hazardous
waste treaters, storers and disposers to get interim status
pending review for a RCRA permit. The procedures for
the RCRA permit program are going to be issued on
April 30 as part of the consolidated permit regulations.
I can't give you the definition of hazardous waste in
advance of the rules, but you have some idea of the
impact on your industry from the proposed regulations
of last December. Metal finishing sludges contain
elements that will likely fall into the definition of
hazardous waste, such as chromium, cadmium and lead.
Metal finishing wastes may also fall into the hazardous
waste characteristics of ignitability and corrosivity.
Early in May, Washington EPA is going to mail out
several hundred thousand packages to names on our list
of generators, treaters, transporters, storers and
disposers. These packages will tell people how to comply
with the notification and interim status requirements.
For generators, transporters, treaters, storers and
disposers: these persons must notify the EPA regional
office within 90 days after the regulations defining
hazardous waste are promulgated (around July 30). Also,
treaters, storers and disposers have to submit part of the
permit application to receive interim status.
Don't assume, if you don't get a package, that you're
off the hook. Persons who generate, transport, treat,
store or dispose of hazardous wastes must meet the
regulations. EPA regions will be required to enforce
against those who don't.
I urge you to attend one of the workshops that are
going to be held to explain the regulations. The
Washington, DC workshop will be on June 2 and the
Chicago workshop will be June 6. The regulations should
be published in the first two weeks in May in the Federal
Register. Regional EPA staff will be learning along with
you, and will be able to provide technical advice. EPA
Headquarters is also planning to set up training
programs to help businesses who may be hard hit to learn
about applying. I was delighted to learn that AES is a
part of this program.
The arduous, long-term task of dealing with hazardous
waste is just beginning. Potentially, there are many things
that can be done with hazardous wastes besides burying
them into a landfill that will meet RCRA's requirements.
As is already recognized in your industry, certain waste
can be recycled and sent back for reuse. Other wastes can
be used by others without processing. Wastes can be dealt
with by incineration, chemical neutralization, separating
or blending to yield a useable product or supplemental
fuel for firing industrial furnaces, and "Biological
destruction," in which micro-organisms consume the
hazardous material and render it harmless.
Ideally, disposal should be the procedure of last resort.
Since RCRA's regulations will make this procedure
much more safe but also more expensive than it's been
before, eventually the widespread use of other methods
should be achieved. For a good while, however, there is
no question that the procedure of last resort will be the
procedure of greatest use. Moreover, proper disposal will
be needed even years from now when we will have
drastically altered our perceptions and practices with
regard to wastes. There will still be a great many materials
that are too low in value to recycle, too difficult to
degrade or to inject into deep wells and too contaminated
with nonflammable materials to incinerate.
Proper burial under RCRA will be a far cry from
dumping. Serious attention to properly engineered
landfills with liners, covers, gas generation techniques
and monitoring operations will come into being. The
chemical solidification of wastes, now used for only a
very small percentage of hazardous materials, will no
doubt become more popular. And disposal of the wastes
will not end the scrutiny process. Disposal site operators
will have to monitor and maintain closed sites for many
years to make sure that there is no migration into soil or
drinking water supplies. There will be liability for each
incident of damage that occurs while the site is operating.
And money will have to be set aside to close and maintain
inactive sites. Violators will be subjected to serious civil
and criminal penalties. RCRA calls for truly drastic
changes in the way we deal with wastes.
Yet the entire promise and purpose of the Act would be
aborted by the strong and widespread public view that
treatment and disposal facilities are all right, provided
they are located on another planet or at least on another
46
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continent. And that brings us to the common cause
between industry and government and the need for a
genuine on-going dialogue.
In order to implement RCRA, industry and
government are going to have to come together. Our
challenge is to show the public that we can maintain our
commerce, that we can build and maintain safe, effective
hazardous waste management facilities. We must show
that we can manufacture and use chemicals and other
goods without poisoning our groundwater, without
creating a no-man's land, and without shipping our
problems to the moon. We are not going to be able, in my
view, to force communities to take hazardous waste
facilities. We - you and I - are going to have to find
incentives to offer these communities. And we're going to
have to prove ourselves.
I have no doubt that EPA will be sued on the RCRA
regulations. I have no doubt that, as we progress with the
law we will discover ways our regulations can be
improved. However, I also feel the imperative is with us.
There is a level of public concern about hazardous waste
that compels EPA - and industry - to act - now.
I'll close with this. In the January issue of Chemical
Times and Trends, the chairman of the du Pont
Company, Irving S. Shapiro, refers to an ancient Chinese
saying which goes like this—"May you live in interesting
times." Mr. Shapiro went on to say, "The seventies have
been too interesting for comfort, and the eighties may
prove more interesting still." Then, he added, "The key to
profitable operation in the eighties will be effective
communication with governments and other
constituents." I think he's right. To make our society
work, business has got to talk with government and
government with business. Let's keep it us.
Thank you.
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Resource Conservation and Recovery Act
Kurt W. Riegel*
I must admit that when I was asked to come to Florida
to explain the RCRA regulations to members of the
American Electroplaters' Society, I felt quite good about
the confidence the Environmental Protection Agency
had in me. After holding quite a few discussions with
people in the electroplating industry, however, and
hearing of the practical problems many of you have in
disposing of your wastewater treatment sludges, I have
come to the conclusion that, in reality, the agency was
looking for somebody expendable.
Whatever the motivations behind EPA's sending me
here, however, today I am going to try to help you make
some sense out of what must be a rather confusing picture
to everyone—the hazardous material waste disposal
regulations, resulting from the Resource Conservation
and Recovery Act—or "RCRA".
I will first go into the basic provisions of RCRA which
affect the electroplating industry. Then I will discuss the
specific regulations that have been promulgated to date.
At the completion of my talk, I will have some time for
questions—which I will answer to the best of my ability.
Howard Schumacher tells me that there will also be
round table sessions in which I and members of the Office
of Solid Waste will be available for further discussions.
First of all, I would like to make it clear—and I can
speak for all of EPA in this—that we at EPA do realize
the importance of the electroplating industry to the United
States. There is no doubt that the metal finishing industry
is a key link in the industrial strength of the United States.
I also want to assure you that I am not going to spend a
great deal of time talking about the Love Canal incident
with you. I fully realize that there are no electroplaters
involved in that very unfortunate situation and I also
realize that the wastes from electroplating operations are,
in many ways, different from those in the organic
chemical industry. I also know that some wastes are more
hazardous than other wastes, and that a waste which is
hazardous when disposed of by one method may be
nonhazardous when disposed of properly.
I also feel that there is another major difference
between the electroplating industry and the kind of
attitude that led to Love Canal and other very
unfortunate situations. I have been briefed on the joint
AES/EPA characterization of sludges from your
wastewater treatment operations and your continuing
effort to determine cost effective but safe methods for
disposing of these wastes. I understand that the joint
AES / EPA cooperative effort arose from needs expressed
at this same conference two years ago. If this conference
*Kurt W. Riegel
Associate Deputy Assistant Administrator
Office of Environmental Engineering and Technology
Environmental Protection Agency
can produce that type of cooperation between the
industry and the Government, I want to say that I am
very happy to be a part of it.
Now, what about the need for a national program to
control the disposal of wastes? Congress felt there was a
need for a national program, and passed the Resource
Conservation and Recovery Act of 1976. I think that
subsequent events have verified that this nation does need
to control how industries dispose of wastes that are
hazardous. There are just too many instances of
individual corporations or persons acting irresponsibly.
Those actions have resulted in tragic effects to people and
to the environment. As always, when regulations are
needed, it is very difficult to decide just how far the
regulations should go, and the agency is trying ernestly to
strike an appropriate balance between protection of
public health and the environment on the one hand and
the burdens on industry on the other. RCRA gave EPA
the specific responsibility of defining what wastes really
were hazardous, and how they should be controlled.
From 1976 until now, the agency has been deeply
involved in sorting out the proper methods of control.
Key sections of RCRA which apply directly to
electroplaters are shown in Table I.
Section 3001 of RCRA required EPA to develop and
promulgate criteria for identifying the characteristics of
hazardous wastes and the listing of hazardous wastes. In
developing these criteria, EPA was instructed to take into
account toxicity, persistence and degradability in the
environment, the potential for accumulation in tissue,
and other factors such as flammability and corrosiveness.
Congress also directed EPA to revise these criteria from
time to time and to make changes as may be appropriate.
EPA has already proposed criteria for hazardous
wastes and many of you have commented on the
proposed criteria. These comments and other related
Table 1
Key Sections of Resource Conservation and
Recovery Act (RCRA, PL 94-580)
Section
3001
3002
3003
3004
3005
3010
Regulation
Number
261
262
263
264
265
266
Criteria for listing as hazardous
Standards for generators
Standards for transporters
Standards for disposal facilities
Permits for disposal facilities
Preliminary notification
requirements
48
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information are being used to derive the final 3001
regulations. For those of you who were not involved in
this stage of the regulatory procedure, we essentially
approached the problem of defining hazardous wastes by
two proposed methods. First we proposed a list of
industries which generated wastes which we felt had the
potential for being hazardous. Electroplating wastewater
treatment sludges were included on this list. These are the
so called categorical listings of hazardous wastes.
Second, we proposed a procedure for those wastes that
were not listed. For unlisted wastes, generators were
obliged to test or otherwise assess their wastes against
certain characteristics. One of these characteristics was
toxicity, determined through laboratory extraction
under specified conditions. The extract was to be
analyzed and tested to determine if it is hazardous.
Because electroplating sludges were listed as a hazardous
waste, the proposed regulations did not require use of the
toxicity characteristic and the extraction procedure to
designate these wastes as hazardous.
I would like to make clear that the regulations for
Section 3001 have not yet been promulgated. They have
been proposed only, and the agency has been considering
the comments made by the public on these proposed
regulations. At one time there was hope that we might
have the final promulgated 3001 regulations ready to be
presented at this conference; however, the current
scheduled date for promulgation for these regulations is
now April 30, 1980.
The next two sections—the standards for generators
and the standards for transporters—were promulgated
on February 26, 1980, and I will discuss them in more
detail later. The first phase of the Section 3004 Standards
for Disposal Facilities is also scheduled to be
promulgated on April 30, as are the Section 3005
permitting procedures regulations, which will be a part of
a consolidated permit procedures regulation covering
RCRA, National Pollutant Discharge Elimination
System (NPDES), and Underground Injection Control
(UIC) permits. The first phase of the 3004 standards will
establish interim status requirements. The second phase
of these standards will set the requirements to be
incorporated into permits. These will be promulgated
around October 30, 1980, and will become effective six
months thereafter.
People in regulatory agencies are limited by law in
discussing regulations when the public comment period is
closed and the regulations are undergoing final revision.
Unfortunately, I am under these restrictions today
regarding Sections 3001, 3004 and 3005. This is a
government-wide policy and not just an EPA practice. It
is part of the administrative law which governs how the
federal regulatory agencies interact with the public. It
allows the agency to fulfill its obligation to remain fully
open to the public for an announced period of time for
information that may be used to advantage in
establishing a regulation. At the close of the public
comment period, a regulatory agency must develop its
regulations by concentrating solely upon the information
which has been presented, it cannot accept further data
or comments.
Today we are free to discuss Sections 3002, 3003, and
3010, since they have been promulgated. We can discuss
background and answer general questions related to
Sections 3001, 3004 and 3005, but I cannot discuss the
specific regulations.
Let's now discuss the Section 3002 regulations which
apply to generators of the waste. This section sets forth
the responsibility of the generators in the "cradle to
grave" control system of hazardous wastes. Section 3002
requires the Administrator of EPA to establish certain
standards for generators. First, EPA must establish a
manifest system which would assure that the waste is
designated for delivery at a permitted storage facility.
Second, there must be appropriate containers with
proper labels for hazardous waste. Third, there are
requirements for record keeping which would identify the
quantities and disposition of the hazardous wastes.
Fourth, general chemical composition information must
be provided to parties who will be transporting, treating,
or storing the wastes. The regulations require that, prior
to transporting, treating, storing or disposing of any
hazardous wastes, the generator must obtain an EPA
identification number. This number is to be assigned by
the agency after receiving the generator's hazardous
waste notification.
Table 2 outlines the responsibilities of generators who
ship hazardous wastes offsite.
First, the generator is responsible for preparing a
manifest, which must identify the generator, the
transporter, and the designated disposal site. In addition
there is some required information related to the nature
of the waste. The manifest also contains the generator's
identification number.
In packaging the waste to be shipped, the generator is
responsible for complying with DOT packing
requirements which have been concurred on by EPA.
The other major responsibility of the shipper is that, if
within 35 days he does not receive his signed copy of the
manifest by the intended receiver of the waste, he must
contact that receiver to determine if the waste was
received. If the manifest receipt copy is not received
within 45 days, then the generator must file a report with
Table 2
Generators Who Ship Hazardous Wastes Must:
• Determine if a waste is hazardous
• Prepare a manifest
• Comply with DOT packaging requirements
• Contact the designated receiving facility if receipt copy
is not received in 35 days
• File an exception report to EPA region if receipt copy is
not received In 45 days
• File an annual report no later than March 1 of each year
Table 3
3003 Standards for Transporters
Must have an EPA identification number
Signs generator's copy of manifest
Must deliver waste to designated disposal site and receive
signed copy of manifest
Can accept only properly packaged wastes
Is responsible for cleaning up any waste discharge or spill
49
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Table 4
3010 Preliminary Notification of
Hazardous Waste Activity
All persons engaging in hazardous waste—management
activities must notify EPA or states having authorized
hazardous waste permit programs
Notification package will be mailed to about 350,000
organizations already identified
Notification forms must be received by EPA within 90 days
of promulgation of standards for generators
Failure to receive notification package does not release
obligation to notify EPA
Table 5
Schedule for Promulgation of Remaining Legislation
April 3001 Identification and Listing
February 3002 Generator Standards
February 3003 Transporter Standards
April/Fall 3004 Facility Standards
April 3005 Permit Standards
April 3006 State Authorization Standards
February 3010 Notification Process
the EPA regional office. The other major responsibility is
the submission of an annual report to EPA by March 1
which must report all activities related to the shipping of
hazardous wastes.
Let's now turn to what was the Section 3003-standards
for the transporters. (Table 3)
Like the generators, each transporter of hazardous
waste must also have an EPA identification number. The
transporter forms a part of the link in the "cradle to the
grave" control which is initiated by the manifest filled out
by the generator. When picking up hazardous materials
for transport, the transporter signs the copy of the
manifest which is retained by the generator. He is
responsible for delivering the waste to the disposal site
designated on the manifest, and must receive a signed
copy of the manifest when he delivers the waste to the
disposal site. The transporter is required to maintain
copies of these manifests in his files for a period of three
years. If more than one transporter is involved, generally
an additional copy of the manifest must be prepared by
the generator for each additional transporter. The first
transporter must obtain a signed copy of the manifest
from the second transporter. There are some special
provisions for hazardous materials delivered by rail or
water, so-called bulk shipment. In these instances, a
standard waybill or other shipping document which
contains all of the manifest information except EPA
identification number is considered satisfactory for bulk
transfers between shippers.
As I mentioned earlier, the packaging, labeling, and
placarding of the hazardous wastes must be performed in
accordance with DOT regulations. It is the responsibility
of the transporter to accept only properly packaged
wastes.
Another item of importance to the transporter is that
the transporter is responsible for reporting and cleaning
up any spilled wastes.
The disposal site operator is responsible for mailing a
copy of the final manifest verifying that the waste was
disposed of properly back to the generator. The only
exception to this would be when hazardous wastes are
being shipped outside the country. When waste leaves the
United States, it is the responsibility of the transporter to
return to the generator a copy signed by the exporter.
Basically, other than the new manifest system, the
transporters will be subject to the same DOT regulations
that are currently in effect.
The last section for which regulations have been
promulgated are those relating to preliminary
notification of hazardous waste activity. (Table 4)
The law requires that all persons engaging in
hazardous waste management activity notify EPA. This
is not really any different than what took place in the
control of water pollution several years ago when the
permit program required notification. EPA will be
sending out notification packages to about three hundred
fifty thousand (350,000) organizations which potentially
handle hazardous wastes and will need to file notification
forms; these notification forms must be received by EPA
within 90 days of promulgation of the RCRA Section
3001 regulations which define what are hazardous
wastes. As I mentioned earlier, the 3001 regulations are
scheduled to be promulgated on April 30.
The failure to receive a notification package does not
release anyone from the obligation to notify EPA. The
notification package is being mailed out as help to those
who we feel probably should be filing notifications.
In the event that a disposal, treatment, or storage
facility does not provide notification, then it will become
ineligible for interim status pending issuance of a permit.
Without interim status or a permit, a facility cannot
legally dispose, treat, or store hazardous wastes. Once
you have filed your notification you will receive a
verification from EPA which will contain your EPA
identification number.
There is a tremendous amount of interest about the
quantity of hazardous wastes you must generate before it
is required that you apply for an identification number.
The Section 3001 proposed regulations had a lower limit
on size, and we received many comments on this issue.
There is another question about the timing. Suppose you
have stopped handling hazardous waste. In that event
you would not be required to file the notification. The
rule for this is any hazardous wastes handled during the
3-month period immediately prior to the date of filing
must be included.
The details of the form and the mailing address for
receipt of notification are all included in the handout
which was released February 26, 1980. There are several
copies available, I believe, from the American
Electroplating Society or your local EPA office.
This completes my discussion on the regulations which
have been promulgated to date. As I mentioned earlier, a
very tight schedule is set for the remaining regulations.
(Table 5).
The two key sections which will be of great importance
to you and which you should watch for closely are
Section 3001, which will define what are hazardous
wastes, and Section 3004, which sets standards for
disposal of the wastes. The permitting process (Section
3005), of course will also be of great interest.
50
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Report on the Results of the AES/EPA
Sludge Characterization Project
Kenneth R. Coulter*
The disposal of waste treatment sludges has become of
major concern to the metal finishing industry. This fact
became evident at the first of the EPA/AES Conferences
in Orlando, Florida in January 1978.
In many areas of North America, due to the lack of
knowledge and understanding of the behaviour of these
sludges in landfill sites, disposal had become extremely
expensive, and, in fact, a virtual impossibility in many
instances.
The problems associated with sludge disposal became
exacerbated with the introduction by the EPA of a
proposed test method, under the Resource Conservation
and Recovery Act. This test was designed in such a way as
to simulate the conditions under which different types of
solid waste would behave, in conjunction with the co-
disposal of organic wastes, such as may be found in a
sanitary landfill.
The test proposed by the EPA calls for filtering or
centrifuging the sludge, and then agitating the remaining
solid material for twenty-four hours, with a
predetermined amount of water. This is maintained at a
pH of 5, using acetic acid. The resultant extract is mixed
with the original filtrate from the original sample, and the
concentrations of various materials are compared to the
limitations for these materials as prescribed by the EPA.
These concentrations are generally established at ten
times the drinking water standard.
The materials of concern to the metal finishing
industry with the proposed limitations are shown in
Table I.
TABLE I
PROPOSED HAZARD LIMIT
Chromium
Cadmium
Lead
Arsenic
Mercury
Silver
mg/1
0.5
0.1
0.5
0.5
0.02
0.5
*Kenneth R. Coulter, P. Eng.
21 Bellehaven Crescent
Scarborough, Ontario M1M1H2
Solid wastes that yielded results above the proposed
limitations, would require a manifest system, and
disposal must be made to an approved facility. While
these facilities are not yet determined or generally
available at present, it is possible that they would include
some combination of fixation, landfill lining, and
leachate collecting and treatment.
So obvious were the consequences of these added
burdens that discussions ensued between the EPA and
the AES, with a view to reconciling the behavior of
electroplating waste sludges under the EPA extractions
procedure, with their behavior under field conditions.
The proposal for a co-operative agreement evolved
during 1978 and the final draft was presented at the
second EPA/AES Conference in February 1979.
Approval of the funding of 95% of the program by EPA
came in March 1979, and the Task Force appointed by
the board of directors of AES began its work with the
author as technical director.
The Task Force members were Doug Thomas,
chairman, Fred Steward, Irving Ireland, Richard Grain,
and George O'Connor.
Howard Schumacher, the executive director of AES
was also appointed program co-ordinator, and Centec
Corporation of 11800 Sunrise Valley Drive, Reston,
Virginia was chosen as the engineering and laboratory
sub-contractor.
The method chosen by the Task Force called for the
selection of twelve sludge sources that represented the
spectrum of the metal finishing industry. These were to be
subjected to a series of tests.
Phase I was designed to:
• Characterize chemically and physically the solid and
liquid portions of the sludges.
• Determine the effect of pH on results of the EPA
extraction procedure (EP).
• Determine the effect of interstitial water, (i.e. water in
the sludge) on the EP results.
• Determine the effect of sludge aging on EP results.
Phase II was designed to:
• Simulate more closely a segregated landfill containing
hydroxide sludges, where there would not be severe
agitation or exposure to low pH using a dynamic
laboratory procedure.
Phase III:
• was a field test, where soil samples were taken below a
sludge bed that had been in use for ten-twelve years at
the site of one of the plants from which current sludge
samples were taken. (Plant #11).
51
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Plant
IA
2A
3A
4A
5A
6A
7A
8A
9A
10A
11A
12A
% Solids
11
6
3
7
17
34
15
29
39
24
19
23
TABLE II
PLANT DESCRIPTION
Primary Plating Process
Segregated Zn
Segregated Cd
Zinc Plating and Chromating
Cu-Ni-Cr on Zn
Al Anodizing
Ni-Cr on Steel
Multi-process Job Shop
Electroless Cu on Plastic, Acid Cu, Ni, Cr
Multi-process with Barrel or Vibratory
Finishing
Printed Circuits
Ni-Cr on Steel
Cd-Ni-Cu on Brass and Steel
Phase I, description of the experiments, results,
conclusions, and recommendations are contained in the
Interim Phase I Report, which was submitted in
September 1979.
The complete report, under the title "Interim Phase I
Report, Electroplating Wastewater Sludge Characteriza-
tion" is available at no cost from John Lehman, EPA,
Office of Solid Waste (WH-565), Washington, D.C.
20460. A synopsis of this paper was published in Plating
and Surface Finishing.
In the interest of time, I will touch on the highlights of
that report and its conclusions.
Table II describes the plants sampled and the toxic
materials, as defined by the proposed RCRA regulations
that were present in the sludges as weight percentage of
the dry solids.
Time and resources did not permit in-depth
engineering studies of the plants being sampled, but with
one exception, sufficient data was obtained to describe
the nature of the treatment system and the volumes
involved.
Figure 1 is a schematic of the extraction procedure.
The experiments conducted included:
• Effect of pH on extraction.
• Effect of volume of extraction water.
• Reproducibility.
• Effect of temperature.
Figure I. Extraction Apparatus
• Comparison with ASTM extraction procedure.
• Effect of sludge aging.
• Total metal content.
• Anion content.
• X-ray diffraction.
• Filtrate analysis and washing.
• Filtration versus centrifuging.
In Table III, the results of the execution of the
extraction procedure at a maintained pH of 5, as
proposed by the EPA, and at four other pH's is shown.
2.0
mg/l
1.0
0.5
« Proposed Hazard Limit
ACd
tCd
I I i I I I I I I I
4 6 8 10 12 14
pH
Figure II. Changes in Cadmium Concentration with pH
TABLE III
EFFECT OF PH
Proposed Hazard Limit Metal
1 A (11% Solids)
2A (6% Solids)
3A (3% Solids)
4A (7% Solids)
5 A (17% Solids)
6A (34% Solids)
7A (15% Solids)
8A (29% Solids)
9A (36% Solids)
IDA (24% Solids)
11A (19% Solids)
12A (23% Solids)
Blanks, Ba, and Se were at or below detection
pH5
pH5
pH5
pH5
pH5
pH 5
pH 5
pH 5
pH5
pH 5
pH5
pH5
limits.
mg/l
0.5 Cr.
1.22
1.89
85.0
21.8
<0.01
25.4
0.24
400
0.32
0.12
4.22
4.85
0.1 Cd
0.23
126
6.00
<0.01
2.16
0.03
<0.01
263
0.5Pb
0.041
<0.001
0.009
0.038
<0.001
.001
.003
0.032
.010
0.88
0.004
0.031
0.5 As 0.02 Hg 0.5 Ag
0.073 <0.01
0.005 <0.01
.02
-------
mg/l
40
30
20
10
0.05
0.03
0.01
OCr
10
12
14
pH
Figure III. Changes In Chromium Concentration with pH
Figures II and HI show the results in graph form for
typical plants with significant cadmium and chromium
content.
Table IV shows the effect of aging on the EP at three
months, compared with the original extraction.
The conclusions that were reached concerning Phase I
were:
• EP is sensitive to pH.
• EP exaggerates the leachability of the sludge since it
includes the effect of metal levels in interstitial (i.e.
associated) water.
• Aging greatly decreases leachability.
TABLE IV
EFFECT OF AGING SLUDGE
EP Results mg/l
Plant 7A
pH 5 Fresh
Aged (3 months)
pH 7 Fresh
Aged (3 months)
Cd
2.16
0.30
0.04
0.01
Pb
0.003
0.002
0.005
0.001
Cr
0.24
<0.05
0.50
0.15
The interstitial water is simply the supernatant and
entrapped water mixed with the sludge. Its
concentrations of metallic ions will be essentially the
same as the plant's effluent as discharged to a water body
or a municipal sewer. It is possible that a plant could be
meeting an effluent discharge regulation, but would be
beyond the proposed hazard limit for sludges, because of
the metal content of the interstitial water alone. This
point is further developed in the interim report, and I
would recommend it to your attention.
Surprisingly, and in spite of the presence of some
interstitial water, Plants #5 and #9 passed the very
aggressive EP test.
When the distorting effect of the interstitial water is
removed, the sludge then behaves in the extraction as one
would expect from the laws of chemistry.
Using the results of Phase I as a guide, we were able to
enter Phase II work, knowing much of the nature of the
sludges with which we were dealing.
Phase II was the dyanamic testing designed to simulate
segregated landfill conditions.
5 gal DEIONIZED
WATER
DYNAMIC TESTING APPARATUS
Figure IV
A reduced number of plant sludges was used for this
Phase, in order to maximize the number of experiments.
Plants 4, 5, 6, 8, 11, and 12 were chosen as being widely
representative of those with hazardous materials, as
defined by RCRA.
The complete description of the procedure will appear
in the final report, which will be available this summer.
However, the schematic drawing in Figure IV
encompasses some pertinent data.
Samples are poured into weighed Buchner funnels
seated with filter paper. D.I. water is fed from a container
above the filter. A vacuum is applied to remove the
interstitial waters and these are then added back to the
top of the sample cake, so that it can be leached through
at a more normal rate.
The leachates were analyzed on days 1, 2, 3, 5, 7, and
every seventh day thereafter for the metals expected to be
most predominant.
fig/a
0.5
• Plant 4A Chromium
Q Plant 12A Chromium
A Plant 12A Cadmium
14 21
DAYS LEACHED
Figure V. Dynamic Testing of Chromium & Cadmium Versus Days
Leached.
53
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TABLE V
PHASE II DYNAMIC LEACHING
Days Leached
Chromium mg/1
Plant Sample
Code
4A
5A
6A
8A
11A
12A
12A
* = <0.05
EP Test
Results
21.8
<.01
184.0
400.0
4.2
4.6
268
/
1.01
<0.05
<0.05
*
<0.05
0.34
0.24
2
0.14
<0.05
<0.05
*
0.05
0.21
Cadmium
0.18
3
0.12
0.06
<0.05
*
*
0.15
mg/1
0.16
5
0.12
0.06
<0.05
*
*
0.12
0.12
7
0.08
0.07
<0.05
*
*
<0.05
0.11
14
0.08
0.05
<0.05
*
*
0.07
0.09
21
0.08
<0.05
<0.05
*
*
0.05
0.09
The results are shown in Table V.
Figures V and VI show graphically and rather
dramatically how quickly the interstitial water is flushed
through, and how little material is leached thereafter.
The flow rates involved were approximately equal to
one half inch of rain per day for the entire thirty-five days
of the test.
It will be noted that these leaching results are
approximately the same as the results obtained from the
extraction made in Phase I at a pH of 7.
Although nickel is not on the list of hazardous metals
as defined by RCRA, we have included it to show that it
behaves in a similar manner.
The conclusions that may be drawn from the Phase II
work are:
• Dynamic tests show drastically reduced levels of
metal concentrations in the leachate, compared to
the EP.
• This work confirms the indications from Phase I
that interstitial water can be the major contributor
to metals in leachate.
I would like to repeat that this interstitial water is
essentially the same as the effluent and is a very small
percentage of the total metal content of the sludge. A
calculation of this percentage is in the Phase I report.
Also established is the fact that for a sludge source to
apply stringent dewatering to his settled solids in order to
pass an EP test would not, indeed, make a contribution
toward improving the environment. The decision as to
how much to dewater should be based on the pragmatic
/U9/9
1.0
0.8
0.6
0.4
0.2
O Plant 5A
12357 14 21 28
DAYS LEACHED
Figure VI. EPA-AES Nickel (Nl) Leachate vs Days Leached
35
economics of shipping and handling, space limitations,
etc.
While building the information bases in Phase I and II,
we had largely exhausted our available funds. However,
we did manage to have sufficient means for one field trip
to the location of Plant #11.
This plant had begun to dispose of metal finishing
waste treatment sludges twelve years ago in a pond
created by excavation on their property. This pond
became dormant six years ago and a new pond was
developed some miles away that was dug to a limestone
base.
In order to gain access to the soil under the pond, (there
was actually two ponds), the company pumped it out just
before our arrival. Samples were taken at two depths of
soil below the interface and at the interface. A
background sample was taken from the soil at a distance
sixty feet from the pond.
During the pumping-out procedure, the suction end of
the hose kept plugging with bullfrog tadpoles. Some of
these hundreds of tadpoles were still alive when we
arrived.
Samples were also taken from the newer limestone
based pond and from a drainage ditch at a point thirty-
five feet below the pond.
The results of these samplings are shown in Table VI.
Each sample, except the water sample, was subjected to
the EP test at a pH of 5, and some were completely
digested and analyzed.
While this Phase III work was limited, (more sampling
work should be done in the field) there was no result
which disproved the outcome of Phases I and II, but the
evidence was, rather, to the contrary. There appears to be
no harmful effect on the environment when metal
hydroxide sludges are disposed of in a segregated landfill.
The landfill need not be elaborately prepared, such as
having lining or limestone base, and without the necessity
of paying for expensive fixation treatment. This
information, in turn, will permit more flexibility in the
location of these landfill sites, which could also receive
other sludges such as fly ash, without disturbing the
plating waste sludges.
Some unfinished work, however, still remains. There is
always the possibility that a malfunction of a waste
treatment system may produce a sludge that would not be
compatible with other sludges in a segregated landfill. It
54
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PHASE
Plant Sample Code
Leachate
Surface Sludge
Subsurface Sludge
Older Subsurface Sludge
1 1" Below Sludge
17" Below Sludge
Sludge
Background Soil
TABLE VI
III — PLANT
New Land Fill
mg/1
Ag
0.01
0.02
0.01
<0.01
Old Land Fill
mg/1
0.03
0.02
0.19
<0.01
SITE II
As
0.004
0.006
0.005
0.002
0.022
0.011
0.002
0.004
(Samples were also analyzed for Ba, Cd, Pb and Se.
detection limits.)
Cr
<0.05
3.58
4.37
3.35
<0.05
<0.05
0.09
<0.05
All were below
is important that the sludge generator knows this before
he ships that particular sludge, and for the landfill
operator to know that he is receiving a "safe" sludge.
To help minimize this potential problem and to
simplify test procedures, future work should include:
• Development of a quick test which would separate
the effects of interstitial water from sludge
teachability, and would confirm the sludge's
suitability for disposal in a segregated landfill.
• Obtaining data which would provide guidance to the
plater which will ensure him that his sludge will be
suitable for disposal in a segregated landfill.
Much of the success of the project has resulted from the
very high level of technical direction received from the
Task Force and the very professional performance of
Centec Corporation and its personnel.
The Task Force that volunteered its time, put more of
it into this project than originally was anticipated. It
always responded to the requests of the chairman, Doug
Thomas, Howard Schumacher, and myself.
The co-operation of the Metals and Inorganic
Chemicals Branch of EPA's Industrial Environmental
Research Laboratory in Cincinnati, and George
Thompson, and Fred Craig in particular were vital to the
completion of this work.
55
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Solids Removal and Concentration
Richard W. Grain*
Over the next several years it can be expected that the
matter of sludge disposal will be somewhat unsettled
until a national understanding is reached. That
agreement could be as simple as mutual endorsement of
one region's existing regulations or as complicated as
adoption of "numbers" by the federal authorities. The
latter with the tedious and expensive promulgation,
discussion, possible litigation, and subsequent adoption
phases to follow, as we've seen in the electroplating
pretreatment (heavy metal) regulations.
Whatever the result, most legal authorities agree that if
one set of regulations causes you to remove heavy metal
sludges; other authorities must provide or endorse a place
to put them.
Making the metallic hydroxides and other sludges
resulting from metal finishing "PRESENTABLE" to the
receiving authority or a private disposal site is the subject
of this paper.
Properly neutralized and conditioned, thickened
and/or dewatered sludge has been shown (1) to be
relatively inert. Surprising to some, the technology for
accomplishing this has been well known for over 25 years.
(2-4)
Therefore, we will examine in detail the current state of
the art of concentrating sludges to enable them to be
handled and transported as inexpensively as possible
and disposed of at approved sites.
Sludge concentration is usually known as thickening
and discussed in those terms up to the 15%/wt. level.
Beyond 15% we refer to a dewatered sludge (5).
COAGULATION AND FLOCCULATION
Before investigating the actual mechanical methods
used to dewater this type sludge, we will first discuss the
various aids to coagulation and flocculation which
hasten mechanical separation.
Coagulation is the conversion by a simple electrolyte of
colloidal and dispersed particles into a small visible floe.
Inorganic coagulatants are simple electrolytes which are
water soluble, low molecular weight inorganic acids,
bases, or salts of iron, aluminum and calcium. Examples
being ferrous sulfate, alum, or lime.
Flocculation is further agglomerated by a
polyelectrolyte of the small slowly settling floe formed
during coagulation into a large, rapidly settling floe.
Organic flocculents are water soluble, high molecular
weight polymers. These can be either anionic or cationic
•Richard W. Grain
Industrial Filter & Pump Mfg. Co.
5900 Ogden Avenue, Cicero, IL 60650
in nature and should be added in small amounts (such as
0.2-1 mg/1). However, polymeric flocculent aids are best
used when tested at the job site by a technical service
representative of one of the many supply companies.
It is extremely important in coagulation, flocculation,
settling, and dewatering that the floe be properly formed
and, once formed, treated "tenderly".
When heavy metal bearing effluents have been
chemically treated to render them less or non-toxic, they
must ultimately have a final pH adjustment prior to final
liquid/solids separation. As sensed by automatic pH
control, the optimum pH for the great bulk of mixed
metal finishing wastes is 8.3. (5)
Lime and/ or caustic should be added into the vortex of
the mixer of a tank type final neutralization. Mixing
should be slow so as to promote coagulation created by
this inorganic acid. Organic (polymeric) flocculation
should be introduced at the exit of the final neutralization
basin. Such introduction should be made in a quiescent
zone as a part of, or prior to, a clarifier.
Whatever method is ultimately selected to dewater this
type of sludge, certainly lab tests, if not actual on site pilot
systems should be used to determine cycle lengths, cake
dryness, and ease of handling.
EQUIPMENT AND PROCESSES (5)
Numerous processes and equipment types are
available for sludge thickening and dewatering. Criteria
for selecting one or more techniques depend on the
characteristics and the amount of sludge to be processed,
capital and operating funds available, size and type of
treatment plant, cognizant regulatory requirements, and
the final disposition.
Terms used in describing sludge handling requirements
and equipment are defined in Table I. The general types
TABLE I
TERMS—DESCRIBING
SLUDGE HANDLING EQUIPMENT
• Solids Loading—Percent Solids in Stream
• Cake Cone.—°/o Solids by Weight In the Thickened or
Dewatered Sludge
• Capacity—Flow Rale of Wastewater or Volume/Cycle -
Time of Batch Devices
• Particle Size—Diameter of Particles
• Solids Recovery or Solids Retention—% of Solids in the
Input Stream Removed in the Thickening Process.
• Yield—Output of Filter in Pounds of Solids per Square
Foot of Filter per Hour
56
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TABLE II
CLASSES OF EQUIPMENT AVAILABLE FOR THICKENING AND DEWATERING
TYPE
STIRRED GRAVITY
AIR FLOTATION
CENTRIFUGES
DISC
SCROLL
-BASKET
FILTERS
VACUUM DRUM
VACUUM BELT
PRESSURE
BELT
DUAL CELL GRAVITY
FEED
RATE
(GPM)
10-3000
10-10,000
25-300
5-300
10-60
0-250
1-50
10-250
5-200
10-500
SOLIDS
LOADING
(% SOLIDS)
0.2-1
0.5-15
1-10
8-10
5-10
2-5
4-6
0.5-5
PARTICLE
SIZE
(MICRONS)
~~~
1'tO5
I-106
1-106
5-10'
1-102
1-I02
10-102
SOLIDS
RETENT
(% SOLIDS)
95-98
92-98
90-95
60-95
90-95
50-99
75-90
95-99
95-99
90-98
OUTPUT
CAKE
CONC
RANGE
(It, SOLIDS)
5-10
5-10
5-10
20-45
5-25
20-40
15-25
20-50
20-35
10-20
CAP
INVEST
($1000)
14-140
28 - 560
28-196
28-280
28-168
7-42
21-105
7-700
14-168
APPLICATIONS
PRIMARY SECONDARY
PRIMARY AND SECONDARY,
METALLIC, CHEMICAL
WASTE-ACTIVATED, LIME ,
FLOCCULATED ALUM
WASTE -ACTIVATED
RAW OR DIGESTED PRI -
MARY OR SECONDARY,
ALUM , LIME
WASTE - ACTIVATED , LIME ,
ALUM
DIGESTED PRIMARY OR
SECONDARY
INDUSTRIAL
ALUM , WASTE -ACTIVATED,
HYDROXIDE
SECONDARY BIOLOGICAL
PRIMARY AND SECONDARY
INDUSTRIAL
PRIMARY, SECONDARY,
INDUSTRIAL , TRICKUNG
FILTER
INDUSTRIAL
HYDROXIDE
CHEMICALLY PRECIPITATED
CLARIFIER OVERFLOWS
MUNICIPAL , INDUSTRIAL ,
CHEMICAL
PETROCHEMICAL , INDUSTRIAL
METAL HYDROXIDE
of equipment available for thickening and dewatering are
shown in Table II, with indications of performance which
can be achieved. In general, each class of equipment and
device will have advantages and disadvantages for a
specific application. Your application and the equipment
available can often be matched by answering the typical
questions which should be asked as shown in Table III.
The method or device used to achieve your desired
result may be one of the following (7):
A. Lagooning/Drying Beds
Lagooning as a method is no longer widely accepted,
although many lagoons still exist. Usually, a 4-17 day
holding capacity is required to achieve proper settling.
Such space allocations in populated areas are becoming
prohibitive.
Further, two basins, 3-5 feet deep, are required so that
one can dry while the other is in use. Depending on the
evaporation rate in that region, this could take 6 months
to 2 years. The ground water can be contaminated by
insufficient lagoon lining (natural or artificial).
At the end of the drying period, they usually only
achieve a 4-10%/wt. solids. Further dewatering can be
achieved by spreading this sludge over a coarse bed of
sand, coal, or gravel. 25-40%/wt. solids can be achieved
in this way under optimum climatic conditions.
B. Clarifiers
The discussion of clarifiers (8-12) will be divided into
four categories, namely; gravity, stirred gravity,
dissolved air flotation (DAF), and rapid settlers.
Figure #1 illustrates a conventional gravity settler.
Typically these units can thicken from 2 to 10%/wt. With
TABLE III
QUESTIONS TYPICALLY ASKED IN MATCHING
APPLICATIONS REQUIREMENTS WITH
EQUIPMENT PARAMETERS
• Operational Variables Affect Equipment Performance
• Throughput, and Feed Rate vs. Solids Loading
• Pretreatment of the Sludge Needed to Reduce Moisture
so that Input Solids Loading is Acceptable
• Effectiveness - Relationship Between Solids Recovery
and % Solids in Output Cake
• Cost of Purchase, Including Engineering and
Installation
• Cost of Operation, Including Chemicals, Labor,
Maintenance, and Replacement of Expendable
Parts
these, a sludge blanket is formed by proper sizing and
flow distribution which is extremely important. So, too,
is the sludge withdrawal rate, so as not to upset the
system, creating high TSS discharges. Such units are
relatively inexpensive but do occupy considerable floor
space. Figure #2 points to design parameters affecting
clarifier design.
The next figure (#3) illustrates a conventional stirred
clarifier. These are open cylindrical tanks with the
influent feed normally at the center and with some means
for distributing the sludge radially. The solids are drawn
57
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DRIVE HEAD
FEE DWELL
LIFTING DEV1CF
VERTICAL SHAFT
CENTER SCRAPER
RAKF ARV
RAKE BLADES
UNDERFLOW DISCHARGF CONF
CONVENTIONAL TYPE THICKENER
Figure 1—Conventional Gravity Setter.
Figure 4—Schematic Diagram of Solids Contact Clarlflers.
PARAMETERS OF CONCERN IN THE
DESIGN OF A CLARIFIER
INLET
ZONE
OUTLET
t ZONE
A
—
*
-
, i
EFFECTIVE
SETTLING
ZONE
i * i
, ,
*
—
SOLIDS REMOVAL ZONE
y
FUNCTIONAL ZONES IN AN IDEALIZED
SEDIMENTATION BASIN
Figure 2.
Figure 5—Schematic Diagram of Horizontal Clarifying Equipment.
Figure 3—Conventional Stirred Clarlfler
Figure 6—Dissolved Air Flotation Unit
off at the center (figure #4) and with proper conditioning
can reach 10% levels. The effluent could still contain up
to 50 ppm TSS.
Horizontal clarifiers are also common. Figure #5
illustrates a typical unit. Note should be taken of the
several mechanical methods used to slow agitation and
promote flocculent growth. Any significant agitation or
introduction of air bubbles will destroy the sludge
settlement.
Another type of unit (DAF), in fact, takes advantage of
this phenomenon. Dissolved air flotation units (figure
#6) are the reverse of the clarifiers described thus far.
They are generally open tanks into which a gas or air is
bubbled. The sludge particles become attached to the fine
bubbles and float to the surface where they are skimmed
off. The underflow is the "clear" effluent. Factors
affecting the effectiveness of these units are particle size,
specific gravity, air to solids ratio, and the removal (skim)
mechanism.
Rapid settlers may be tube type, plate, and other
laminar (lamella) settlers. These units are said (10) to
require only 1 /4th to 1 / 10th the floor space required for
conventional gravity and stirred gravity types. They use
the design of angular tubes or plates which have
extremely high surface areas and only 3/4 to 2" drop of
58
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solids in angular (usually 45°) tubes or parallel plates
(figures #7 and #8). The units produce a sludge of up to
10% and an overflow of 10-30 ppm TSS. They are often
installed inside and are easily maintained. The principal
disadvantage is said to be a blocking of the channels or
tubes, if there is an improper sludge draw-off.
Laminar flow packs can even be installed in
EXISTING conventional clarifiers to enhance the
effectiveness (figure #9) or increase their capacity without
enlarging them.
C. Centrifuges (5, 6)
These units are normally very compact. They are the
first units to be discussed which DEWATER rather than
thicken according to our earlier definition. They are
highly influenced by the influent rate and percent solids
in the feed. They can typically dewater to 15%. The
centrate almost always must be recycled as it contains
500-1,000 ppm TSS. Centrifuges have a high power
consumption and some history of maintenance problems
due to their high rotation rate. Slower speed units are
being developed and becoming popular. Figure #10
illustrate a bowl centrifuge.
D. Vacuum Filters (5, 6, 12)
Rotary drum vacuum filters have been used for many
years in all facets of sludge dewatering. However, unless
they are precoated with a filteraid material, they
normally require that the influent sludge be thickened (by
one of the methods described in "B" above.) Figure #11
illustrates a rotary vacuum filter. The submergence of the
drums is normally in the 30% range. Therefore, the
efficiency of these units is low, but the fact that they are
continuous is a very favorable offset. These units are also
relatively energy intensive and are said to potentially
have problems associated with maintaining a vacuum.
The rotary vacs dewater to 25-35% with the filtrate in
the 100-700 ppm range for those who do not use precoat.
Eflluent
Heavy
Components
UKttU
TUBE SETTLERS IN EXISTING CLARIFIER
Figure 7—Schematic - Tilted Plate Clarlfler.
Figure 9.
Figure 8—Production Unit - Tilted Plate Clarlfler.
Figure 10—A Bowl Centrifuge.
59
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Figure 11—Rotary Vacuum Unit.
Figure 12—Belt Filter.
^ IDI r4—i
nisi) i ' I
Figure 13—Plate/Frame Press Filter.
Figure 14—Typical Plate/Frame Filter.
E. Belt Filters (6, 12)
These units (figure #12) distribute gravity flow and
through a series of belts allow for the drain off of the
liquid phase. A second stage employs pressure rollers.
The units are continuous and relatively inexpensive.
They do normally require conditioning chemicals or
prior thickening in order to produce 15-20%/wt. solids.
The belt is washed for reuse on a continuous basis to
inhibit blinding. The filtrate contains 500-2,000 ppm
TSS. Design rates are 2-8 GPM/sq. ft.
F. Filter Presses (5, 6, 8, 13)
Filter presses have been widely used in the chemical
process industries since the 1920's. Although there are
many configuration variations, a plate/frame press
consists of a number of vertical plates which are held
rigidly in a form to ensure alignment. The trays are
recessed so that when pressed between the fixed and
moving ends of the head, they form a hollow chamber
(figure #13). The inside of each hollow chamber is lined
with a filter cloth. Sludge is pumped through holes in
each chamber. The drainage member behind each cloth
allows for passage of a clean filtrate and deposition of the
sludge on the cloth. Dewatering takes place as the
influent sludge reaches high pressure (100-200 PSIG).
Cake is '/2 to 1" thick and 40-50%/wt. solids can be
expected. The filtrate clarity is 0-10 ppm TSS depending
on whether the unit is first precoated or not. Figures #14
illustrates a typical P/F press.
Another press variation is the conventional pressure
leaf type filter unit, with compressive diaphragms or
membranes. These units operate at much lower pressures
(approximately 50-70 PSIG).
Both conventional plate and frame and the
compressive diaphragms have received wide acceptance
as the devices offering the driest possible cake. Flow rates
are I/10th to I/20th GPM/ft2.
G. Pressure Leaf Precoated Filters (3, 5, 6)
These pressure leaf units operate at much lower (up to
40 PSIG) pressures then plate and frame presses (up to
200 PSIG). Normally, they use a precoat on a
conventional leaf. Rates are typically I/4th to I/10th
GPM/ft2. The cakes (figure #15) are 35-40%/wt. and the
filtrate the best of any dewatering device (0-5 ppm).
Relatively large units are required for the DIRECT
filtration of metallic hydroxides (example . . . 1,000 ft.2
for 100 GPM). However, no other devices are needed.
There is no requirement for thickening ahead or
polishing behind these units.
Other pressure leaf units (figure #16) will accept
prethickened sludge at rates of 1 /20th GPM/ft.2 or direct
filtration at 1 / 4th GPM/ft2 producing a 20% dry solids in
either case on an automatic basis.
H. Fixants and Incineration
These two methods of making dewatered sludge
"PRESENTABLE" share one thing in common. The
60
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Figure 15—Pressure Leaf Filter Cake.
Figure 16—Pressure Leaf Filter.
dryer the dewatered cake fed to the fixant or incinerator,
the more economical the method.
Chemical fixant processes have been evident for about
10 years (13, 14). Most common processes incorporate
the addition of a silicate compound in order to produce a
concrete like product. The feed to these processes could
be anywhere from 2% (clarifier underflow) to 40% (filter
press cake).
The economics of these methods have yet to be
clarified for metal finishing wastes. However, more and
more interest has been shown by the industry and general
public.
Incinerators too have been used (though not widely)
for over 10 years as a method of making sludge
"PRESENTABLE." Multiple hearth and rotary hearth
incinerators are in common use. A study (15) shows the
most economical sludge to be handled is that from a
pressure leaf or plate and frame press. However, an
evaluation of these, filters, belt presses, centrifuge, and
vacuum filters indicate they are also said to be the most
expensive method of dewatering.
We have painted the subject of making metallic
hydroxides presentable with a rather "broad brush."
From drying beds on the low end, to incinerated or
chemically "fixed" sludge (which was first thickened and
later dewatered ahead of it) on the high end.
The question which ultimately must be answered is...
in what condition will MY sludge be accepted and how
can I get it to that point at the least overall cost? The
methods or combinations described here can achieve any
requirement which you will be given. Which method you
use over all, and over the next few years can ONL Y be
determined by your regulatory requirements; then
examined in detail by your supplier and/or consultant.
ACKNOWLEDGMENTS
In the preparation of this paper, 15 companies well
known in the industry were asked to contribute
information and/or slides.
The following are acknowledged with thanks
for contributing to the technical education of the society.
1. Parkson Inc., Ft. Lauderdale, FL
2. ERC/Lancy, Div. of Dart Environment And
Services Co., Zelienople, PA.
3. Dorr-Oliver, Inc., Stamford, CT.
4. Komline-Sanderson Engineering Corp., Peapack,
NJ.
5. Haviland Products, Inc., Grand Rapids, MI.
6. D. R. Sperry, Batavia, IL
7. Industrial Filter & Pump Mfg. Co., Cicero, IL
REFERENCES
1. Minor, Paul S., Procko, Andrew, McCarthy, James
A. & Meredith, John W., "Determination Of The
Leaching Properties Of Metal Finishing Waste
Treatment Sludges," SUR/FIN '80, AES
Convention, Milwaukee, WI (June 22 - 26), 1980.
2. Crain, R. W., "Sludge - By Any Other Name It's Still
A Problem," Enviroscope, Plating and Surface
Finishing, (May 1977), p. 44-45.
3. Zievers, J. F. & Riley, C. W., "Handling Waste
Sludges," Plating, (August 1959).
4. Haviland, Joseph M., "What To Do About Sludge,"
Products Finishing, (Febr. 1980), p. 56-59.
5. "Selecting Sludge Thickening And Dewatering
Equipment," Pollution Equipment News, (Febr.
1976), p. 41-47.
6. Daniels, Dr. Stacy L., Dow Chemical USA, Mid-
land, MI "Product Development and Stewardship
of Flocculants for Water and Wastewater Treat-
ment", American Chemical Society, San Francisco,
CA, (Aug. 31, 1976).
7. Crain, R. W., "Sludge Dewatering . . . Settling,
Centrifugation or Filtration," presented at IPC
Water Pollution Control Workshop, Chicago, IL,
(May 23-24, 1978).
8. "Clarifying Metal Finishing Wastewater,"
ERC/ Lancy, internal education paper and Technical
Bulletin No. 6201 (1979).
61
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9. Probstein, Ronald F., Hicks, R. Edwin, "Lamella 11. Dorr-Oliver, Inc., Stamford, CT, private
Settlers: A New Operating Mode for High communications (1980)
Performance," Industrial Water Engineering, 12. Komline-Sanderson Bulletin No. KSB 123-7090,
(Jan/Feb. 1978), p. 6-8. "Dissolved Air Flotation."
10. Cheremisinoff, Nicholas P., "Lamella Gravity 13. Davy, Thomas E., "Handling Sludge Problems With
Settler: A Compact Clarifier," Pollution Modern Filter Presses," Filtration Engineering,
Engineering, (March 1977), p. 33-35. (March/April 1973), Vol. 4, No. 2, p. 6-10.
62
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Making Hazardous Wastes Nonhazardous
Robert B. Pojasek, Ph.D.*
INTRODUCTION
Once a waste is designated or declared to be
"hazardous" under the Resource Conservation and
Recovery Act (RCRA) it becomes subject to a myriad of
rules and regulations promulgated by the U. S.
Environmental Protection Agency (EPA). RCRA
regulations require strict control of hazardous wastes
from "cradle-to-grave;" i.e., from generation, through
transportation, storage, treatment, and disposal. There is
little doubt that these regulations will change the way
industry does business. The cost of disposal will go up,
the financial impacts will be significant, the technical
requirements will increase, and the paper work will grow.
Under RCRA you will be required to do the following:
• Provide notification if you produce "hazardous"
wastes
• Provide proper containerization for "hazardous"
wastes
• Maintain complete records of waste generation,
handling and disposal
• Obtain permits for treatment, storage,
transportation, and disposal.
To make matters worse, the design and operating
requirements for "hazardous" waste disposal will serve to
diminish the already limited off-site capacity. Would it
not be great to convert the hazardous waste into a
nonhazardous material?
THE CONCEPT
EPA has chosen to use an elutriate test to determine
whether toxic components can be leached from the waste.
The analysis of the extract from an operationally defined
procedure determines whether the waste is hazardous by
the toxicity characteristic. Separate testing must be done
for ignitability, corrosivity, and reactivity. Now let us
suppose that the waste is toxic according to the test and
suppose that the waste were incorporated either
chemically or physically in an inert and monolithic
matrix. EPA's protocol as proposed in the December 18,
1978, Federal Register calls for the use of the structural
integrity procedure on solidified wastes.
The basis for the use of this procedure developed from
EPA's concern that if these monolithic solids do not
physically break down during disposal, it would be
inappropriate to grind the waste into smaller particles
than is necessary for elutriate testing. Certainly the
leaching characteristics for a divided waste will be quite
different from that of the waste in monolithic form. The
structural integrity procedure was designed to be a
•Robert B. Pojasek, Ph.D
289 New Boston Park
Woburn, MA 01801
moderately severe approximation of the disintegration
which might be expected to occur if a solidified waste was
used as fill or construction material. Under these
conditions crushing might occur from the passage of
heavy equipment over the waste. After conducting this
test on the solidified waste, the intact solid, with its
greatly reduced surface area, is extracted. If the waste
passes the toxicity test requirements and does not have
the other characteristics listed above, it can be declared
nonhazardous. A Jess stringent set of regulations under
RCRA Subtitle D may be used for the solidified waste
handling. However, if the waste is "hazardous" prior to
solidification, a permit to treat hazardous waste will
probably be required.
SOLIDIFICATION PROCESSES
A wide variety of commercial solidification processes
are available. Many of the vendors have had specific
experience with wastes from this industry. A number of
references written or edited by the author on these
processes may be found at the end of this paper.
The waste generator may choose to develop and use a
generic solidification procedure. This can be done by
selecting the proper solidification agent and following the
conceptual flow outlined below. However, the industry
should realize that the process may require substantial
engineering and development costs to initiate. Many of
the vendors are already prepared to adapt their processes
to your wastes.
Recently a number of processes have been developed
specifically to handle organic-contaminated inorganic
wastes and organic wastes with metals contamination.
These two cases had posed problems in the past thereby
effectively limiting solidification to inorganic wastes.
Solidification has also been used in conjunction with
incineration for organic wastes. This has been done by
solidifying the waste for ease of handling, incinerating the
waste for volume reduction, and resolidifying the ash.
Inorganic solidification processes have been used to
solidify the toxic ash derived from conventional
incineration of organic wastes.
There are typically five steps involved in solidification.
They are: waste collection, waste pretreatment,
solidification agent addition, mixing/packaging, and
disposal. Each step is briefly discussed below.
Waste Collection. A plant may wish to segregate to a
greater extent these wastes which it wishes to solidify.
This may involve some degree of retrofiting. Of those
wastes targeted for solidification, it is important to
determine how the blending of the wastes will affect the
processes chosen for pretreatment and solidification. If
the waste is "hazardous" at the collection point and must
be stored for more than 90 days, you will require a permit
for this activity. A manifest will be required if the waste is
63
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transported off-site for solidification. In-line
solidification would be required to avoid these
requirements.
Waste Pretreatment. Some wastes can be solidified
directly, while others may require pretreatment. Physical
pretreatment processes required by some processes
include decanting, centrifugation, dewatering,
evaporation, or calcination. To reduce leaching from the
solidified waste, cyanide destruction, neutralization or
chromium reduction may also be required prior to
solidification. At a regional treatment facility these
processes might be accomplished with another waste thus
reducing the cost. The generator who requires chemical
treatment prior to solidification might search for a
process which does not have this requirement. If the
treatment alone detoxifies the waste, there may be no
need to solidify the waste except for handling.
Solidification Agent Addition. There are five basic
types of solidification as it may be applied to this
industry. These types include the following:
Cement-based
Lime-based
Thermoplastic-based
Organic Polymers-based
Encapsulation and Coatings
Each of the processes in these categories has its own
requirements for adding the agent. The amount of
additive will probably be dictated on the lower end by the
specifications required to pass the structural integrity
procedure. Other specifications may be required
depending upon the end use of the material.
Mixing/Packaging Systems. Solidification is often
conducted either in a container or by in-line mixing with
containerized or uncontained discharge. In-container
mixing of the waste and solidification agent can be
accomplished with roller mixers, tumbler mixers or
paddlemixers. In-line mixing is accomplished either by
dynamic or batch mixing. If containers are used, they
must still be inspected, monitored and labeled. Interim
storage and track leading facilities will also be required.
Uncontained release is directed to the disposal facility.
Disposal. If the solidified waste has been tested and
deemed to be nonhazardous the disposal site must meet
RCRA Section 4004 requirements at a minimum. There
may be pressure brought to bear by the states to upgrade
these requirements. However, if all the solidified wastes
going into a landfill are deemed nonhazardous, the
landfill need not be a secure chemical landfill for
hazardous wastes. There are a number of productive uses
of solidified wastes which may decrease the need for strict
disposal and provide an incentive to the use of
solidification. Some of these demonstrated uses are as
follows: land reclamation, road bed aggregate, artificial
reefs, parking lot pavement, impermeable liners, and
landfill capping material.
CONCEPT INSURANCE
Questions are often asked as to whether the solidified
waste will hold up over time. To insure that this will
happen, physical, leach and accelerated environmental
testing may be required on representative samples using
established protocols. EPA has sponsored a number of
studies to look at some of these questions. Unfortunately
most of the solidified wastes were not designed to meet
the common point of passing the structural integrity
procedure. Varying amounts of additives were used by
the participating vendors making comparisons between
processes for a particular waste type very difficult.
Furthermore, there is no great amount of concensus in
the testing area. However, ASTM has recently mounted a
special effort to solve this problem.
Accelerated testing is perhaps the most controversial
aspect of concept insurance. Most tests which are
designed to be representative of environmental
conditions take too long to generate useful data. Just as
aerospace construction and electrical components are
tested for long-term viability with accelerated techniques,
a similar approach must be adapted to the wastes. The
selection of the proper test should be attempted only after
the use of disposal technique is specified.
ON-SITE vs OFF-SITE SOLIDIFICATION
This is a real controversial choice confronting the
generator. Off-site regional solidification offers
economy of scale and potential to use other wastes for
neutralization and other pretreatment. A potential
problem is that the wastes will be mixed with other wastes
and there is a question of potential future joint liability.
The wastes must also be manifested with this option if
they are hazardous. On-site solidification gives the
generator more control over the processing and handling
of his own wastes. It may also remove some of the
manifesting requirements. Some solidification
technology vendors operate exclusively in one mode or
the other. Other vendors operate in either mode to suit
the needs of a customer. Legal and economic factors must
be carefully weighted by the waste generator before
deciding which route to take.
CONCLUSIONS
Solidification has great potential as an advanced
pollution control technology for the metal finishing
industry. New EPA regulations should hasten the
development and incorporation of solidification
techniques into a much broader segment of the industry.
Solidification should be considered as an option in the
hazardous waste management planning that each facility
must go through in order to be brought into compliance
with the RCRA regulations.
REFERENCES
Pojasek, R. B., editor. Impact of Legislation and
Implementation of Disposal Management Practices,
Ann Arbor, Michigan: Ann Arbor Science Publishers,
1980.
Pojasek, R. B., editor. New and Promising Ultimate
Disposal Options, Ann Arbor, Michigan: Ann Arbor
Science Publishers, 1980.
Pojasek, R. B. "Solid-Waste Disposal: Solidification."
Chemical Engineering, August 13 (1979): 87.
Pojasek, R. B. "Novel Approach to Hazardous Waste
Disposal in New England." J. N. E. Water Pollution
Control Assoc. 13 (179): 36-46.
Pojasek, R. B. "Disposing of Hazardous Chemical
Wastes." Environ. Sci. Technol. 13 (1979): 810-814.
Pojasek, R. B., editor. Stabilization/Solidification
Processes for Hazardous Waste Disposal. Ann Arbor,
Michigan: Ann Arbor Science Publishers, 1978.
Pojasek, R. B., editor. Stabilization I Solidification
Options for Hazardous Waste Disposal. Ann Arbor,
Michigan: Ann Arbor Science Publishers, 1978.
Pojasek, R. B. "Stabilization/Solidification of
Hazardous Wastes." Environ. Sci. Technol. 12(1978):
382-386.
64
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Radioohemioal Studies of the Leaching
Of Metal Ions from Sludge Bearing Concrete
John D. Mahoney and Elaine A. Dwyer*
Walter P. Saukin and Robert J. Spinna**
INTRODUCTION
The possibility of incorporating electroplating sludge
into concrete as an alternative disposal procedure to the
use of segregated landfills has been examined earlier in
the report of work done under Research Project 49-Phase
I of the American Electroplaters' Society.' The ultimate
rationale for this exploratory study was the fact that the
ready-mix concrete industry in the United States
provides a potential daily capacity for disposing of more
wastewater sludge than the entire electroplating industry
generates on the same daily basis at a cost which could be
significantly less than that of current disposal methods.
While the chemistry of concrete is not fully
understood, it is known that the hardening process is the
result of the reaction of calcium silcates, calcium
aluminates, and tetracalcium alumino-ferrite with water
to form hydrates that resemble the natural minerals
tobermorite and the hydrogarnets as well as other
hydrates and calcium hydroxide. These reactions are
summarized in Figure 1. The most important of these is
tobermorite which, in concrete, is formed in an extremely
finely divided manner with a coherent structure that is
given the name gel. Thus the hardening of concrete can be
seen as the process of making artificial minerals.
Aluminum, iron, and some of the calcium in concrete are
bound and rendered insoluble in the same manner as
these metals are bound in natural rocks. It is not
unreasonable that other metal ions could be mineralized
in this manner. In addition, the possibility exists that the
metal ions could be immobilized within the molecular
sized gel pores that are formed in concrete during the
hardening process. The extent to which metal ions have
been mineralized in concrete, made with electroplating
sludge as part of the mixing water, can be determined by
analysis of the leach water. While other testing may be
required to establish the exact nature of the metal
binding, leaching studies will give evidence of the
feasibility of the method and indirectly of its
environmental acceptability.
Radiochemical techniques for conducting these studies
were employed because they provide a fast/accurate, and
extremely sensitive method of identifying the metal and
its concentration in the leach water.
The results obtained in phase I were sufficiently
encouraging, in respect to both the quality of the concrete
'John D. Mahoney and Elaine A. Dwyer
Chemistry Department, Manhattan College
Bronx, New York 10471
"Walter P. Saukin and Robert J. Spinna
Civil Engineering Department, Manhattan College
Bronx, New York 10471
and the binding of the metal compounds, that phase II
was undertaken. This paper will consider the leaching
studies that were done in both phases of the work to
determine the extent to which metal ions leave sludge-
bearing concrete and enter ambient immersion water. In
some respects this can only be a progress report; the final
results will be included in the report to be given at
SUR/FIN '80 in Milwaukee this June.
EXPERIMENTAL PROCEDURES
In both phases of the work the composition of the
concrete mix was the same as that used in the physical
tests. It consisted of a water/cement ratio of 7.0 (gal/ft3)
and an aggregate/cement ratio of 5.5 (Ib/lb). The
aggregate was 35% sand, 65% coarse aggregate. This
corresponds to a conventional 1:2:4 mix. In phase I, only
Type I normal Portland cement produced by the Saylor
Portland Cement Company was used. In phase II, both
Type I (Saylor) and Type III High-Early-Strength (Atlas
Portland Cement Company) were used. The
compositions of these cements are shown in Table 1.
Type III cement has a very large tricalcium silicate
content because it is this substance that hardens rapidly
and is largely responsible for the initial set and early
strength of concrete. In phase I the coarse aggregate was
washed natural stone; in phase II, 3/8" crushed trap rock
was used.
The water component was replaced by sludge that was
adjusted to a 1.5% solid component in phase I and a 2.0%
solid component in phase II. The sludge was obtained
from the following sources:
New England Plating Co., Inc.
Worcester, Massachusetts
WHYCO Chromium Co., Inc.
Thomaston, Connecticut
Contract Plating Co.
Stratford, Connecticut
NEP
WHYCO
CPC
2(3CaO-SIOi) + 6H,O
(Tricalcium Silicate)
2(2CaO SIO,) + 4H,0
(Dlacalcium Silicate)
3CaO 2SI02 3H20 + 3Ca(OH),
(Tolbermorlte Gel)
3CaO 2810,3H2O + Ca(OH),
{Tobermorite Gel)
4CaO AljO, Fe:O, + 10H2O + 2Ca(OH),
(Tetracalcium Alumlnoferrlte)
3CaO AI;O, + 12H2O + Ca(OH): ^
(Tricalcium Alumlnate)
3CaO AI;O, + 10H;O + CaSO, 2H:O
(Tricalcium Alumlnalei jGypsum)
^ 6CaO AI,Oj FejOj 12H:O
(Calcium Alumlnolerrlte Hydrate)
(Hydrogamet)
_ 3CaO AI,O, Ca(OH); 12H2O
(Tetracalcium Alumlnate Hydrate)
3CaOAI,O,CaSO,12HjO
(Calcium Monosulfoalumlnate)
Figure 1—Chemical Reactions in the Hardening of Concrete.
65
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The radioactive nuclides that were used were mixed with
the appropriate quantity of sludge and allowed to
equilibrate. The cement and aggregates were dry mixed.
The liquid and solids were hand blended until a uniform
mix was obtained, which was then mechanically agitated
and placed in forms. Separate batches were prepared for
e>ch metal and cement variation. The batch size was
sufficient to prepare three 2-inch by 4-inch cylinders,
except in the case of the final experiment in which the
EPA Toxicant Extraction Procedure2 was followed when
only a single cylinder was prepared.
The radionuclides employed for the metals tested and
their relevant properties, the sludge sources, the
concentration of the metals present in the sludge, and the
type of cement used are summarized in Table 2.
All of the cylinders were cured under conditions of
100% humidity for 48-72 hours when Type I cement was
used, and for 72 hours to a week when Type III cement
was used. Following this, the concrete cylinders were
separately immersed in beakers containing 400 ml of
deionized water, which were kept tightly covered.
Sampling of the leach water was done periodically. For
the *5Ca, 63Ni, 26A1, and I15mCd systems, four-1.0 ml
aliquots were transferred successively to planchets and
evaporated to dryness. The radioactivity of each planchet
was measured in a windowless gas-flow proportional
Table 1
Composition of Various Types
Tricalcium Silicate
Dicalcium Silicate
Tricalcium Aluminate
Tetracalcium Alumino-
ferrite
Total
I
53
24
8
8
93
II
47
32
3
12
94
of Cements
III
58
16
8
8
90
IV
26
54
2
12
94
V
40
40
4
9
93
counter. Background and standard counts were taken
before and after each days counting.
The leachates from the 65Co, 51Cr, 54Mn, and 65Zn
systems were sampled by taking a single 4.0 ml aliquot
from each. The three 4.0 ml aliquots for each system were
combined in the same vial, except in the chromium-high
early system, where each leachate was measured
separately, because each cylinder was given a different
state of integrity. A 400-channel analyzer with a 3" X 3"
Nal well counter and a 1024-channel analyzer with a
standard Nal well counter were used for the T-counting.
They were calibrated periodically using l37Cs and 60Co
standards. Each sampling, which represented exactly 1%
of the leach water, was replaced with the same amount of
deionized water thus maintaining a constant leachate
volume. It should be noted that typical cylinder had a
mass of 440 g and a volume of 210 cm3. Thus fixing the
leachate volume at 400 ml made a very confined and
virtually stagnant system. It was judged that this would
resemble most severe natural conditions. In the final
experiment, however, the EPA procedure, requiring a
water mass of 16 times the mass of the solid material, was
followed.
In addition the pH of the leach water in the control
samples was measured each day. In the final experiment,
again following EPA procedure, the pH of the leach
water was maintained at 5.0 for 6 days by the addition of
0.5 M acetic acid.
Measured counting rates were converted to absolute
disintegration rates by computational methods outlined
in Chandra3 and Snell4, and by the use of reference
sources. Decay scheme corrections were used where
appropriate. When nuclides of short half-life were used,
all disintegration rates were normalized to the day on
which the samples were prepared.
RESULTS AND DISCUSSION
This section will be divided into subsections, each of
which will consider one of the metals tested.
The chemical form of the metal is not determined. It is
assumed that the radioactive isotope equilibrates with the
Table 2
Cement type
Radionuciides and relevant properties
26AI
45Ca
"5mCd
60Co
5,Cr
54Mn
"Nl
"Zn
Half life
7.2X105 yr
165d
44.6d
5.27 yr
27.7d
312.5d
120 yr
244d
Energy (MeV)
1.16™
0.253™
1.62™
1.173
1.332
0.320
(from
0.835
0.066™
1.116
(from
Particle
j3*(82.1%)
tf*" / 1 n no/ \
13 I 1 UU /O J
/T(100°/o)
T
T (99 + %)
T(10%)
51 v)
T(100%)
0~(100%)
T(50.7%)
65cu)
Activity
Incorporated
(MCI)V
cylinder
0.0015
3.3
13.3
1.7
167
1.7
33 phase I
13.3 phase II
3.3 phase I
1.7 phase II
Sludge
source
CPC
—
NEP
WHYCO
NEP
WHYCO
NEP
NEP
Metal
concentration Cement type
in sludge used
to be determined
~45% of cement
600 ppm added
500 ppm added
600 ppm added
300 ppm added
270 ppm phase I
510 ppm phase II
300 ppm phase I
570 ppm phase II
I
I
I &III
I
I &III
I
I
I &III
I
I &III
* VCi = 2.22 x 106 disintegrations/min
66
-------
0.20
5 0.16
O
J
J
£ 0.1Z
IE
£
J20.08!
5
S
0.04
O
A
I
y
I
i
I
TVP. Ill | J,
I I
I T I
' ! I
I I I
T '
I
|
I
3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
DAYS LEACHING
Figure 2—Concentration of Cd In leach water as a function of Immersion
time of sludge bearing concrete by beta counting.
naturally occurring isotopes in the sludge and adopts the
same chemical states as the latter in all parts of the
system.
1. Aluminum
The results with respect to the rate at which this metal
is leaching from the concrete are inconclusive. The lower
limit of detection is about 1 ppm because of the small
amount of radio-activity that was incorporated. Because
it is cyclotron produced, 26A1 is very expensive - about
$500/0.01 /uCi. To obtain an increase in sensitivity of 10,
about 0.05 pCi would have to be used. Hence, other
methods of rapid and sensitive analysis are being
investigated. Nevertheless, the measured activity of
samples taken over a period of 118 days of leaching was
never consistently above background. This leads us to
conclude that the aluminum from aluminum bearing
sludge does not leach to an extent greater than 1 ppm in
this system.
2. Cadmium
Because none of the sludges used were known to
contain cadmium, it was added to the NEP sludge as
Cd(NO3)2-4H2O at a concentration of 600 ppm.
Cylinders were made using both Type I and Type III
cement. The results obtained for this metal are shown in
Figure 2. They appear to be higher than for any of the
other metals, especially in the case of the Type I cement.
For cylinders made with Type HI cement, the leaching is
generally lower.
3. Chromium
There were four different chromium systems studied.
The first consisted of a chromium-bearing sludge
incorporated into concrete made using Type I cement.
The other three used the same chromium-bearing sludge,
but the concrete was made using Type III cement. Of the
three cylinders prepared in this way, one was allowed to
remain integral, another was broken into larger pieces
(about 1 1/2" in diameter), and the third was broken into
pieces about 1/2" in diameter just prior to immersion in
the leach water. As the data presented in Figure 3
indicate, there is very little difference among the
samples. Apparently, the increase in surface area among
the three Type III cylinders is not noticeably affecting the
leaching of chromium. This suggests that the binding is
not merely interstitial entrapment. The general lowering
of the metal concentration with time is not peculiar to
these systems as will be seen subsequently. The
implications will be discussed later.
4. Cobalt
Only Type I cement has been used to date in the study
of cobalt leaching. The concentration of soluble cobalt
entering the leach water as a function of time has been
reported earlier.5 After about 30 days the level reached
about 0.004 ppm where it remained for the next 30 days
and then began to diminish. The total cobalt that entered
the leach water (soluble plus insoluble) was found to be
about five times that of the soluble alone, or about 0.020
ppm at 60 days and 0.010 ppm at 90 days. After 100 days
the entire leach water was removed from all the cobalt
samples and replaced by an equal volume of deionized
water. The cobalt radioactivity as a function of time for
these systems was measured. The results are shown in
Table 3. Both soluble and insoluble cobalt were
measured. The generally lower results should be
attributed to the concrete being cured for over 100 days
before this new exposure. Again the tailing off of the
metal concentration with time is to be noted.
5. Manganese
Only Type I cement has been used to test the leaching
characteristics of manganese. There is no soluble
manganese in the leach water during the first 60 days of
leaching as reported earlier.6 The insoluble manganese
has been found to have a maximum value of about 0.04
ppm after 90 days of leaching. When the leach water was
replaced after 100 days, the manganese concentrations
reached about 0.037 ppm after 21 days and began
diminishing to 0.024 ppm at 48 days and 0 by 116 days
where they remained through 176 days. Our lower limit
of detection is 0.00004 ppm in this system.
6. Nickel
The soluble nickel concentrations in the leach water for
the first 60 days of leaching from concrete made with
Type I cement were reported earlier.7 They ranged from
about 0.0015 ppm during the first 20 days to 0.005 by the
fortieth day, and 0.003 at the end of 60 days. We have
subsequently measured the total nickel entering the leach
Table 3
Days leaching 7 21 48 116 143
Cone, of cobalt
in the leach water (ppm) 0.0010 0.0022 0.0066 0.0005 0
155 162 172 176
0.0003 trace 0.00005 0
Note: the lower limit of detection is 0.00004 ppm
67
-------
ffi 0.10.
X
0 _ 0.08
< z
,5S 006
»E
CONCENTRATIO
(PART
0 e
g S
O Typel
A Type III (large piece.)
D Type III (Integral)
1 O Type III (.mall piece.)
|
1
. i T A * A i,
36912 15 18 21 24 27 30 33 36 3» 42 45 48 51 54 57
DAYS LEACHING
I «
g _ 0.04 •
|g 003
ENTRATION O
(PARTS Pi
o
8
g 001
8
|f
I
1 0 Typel
1 A Type III
t ,
. A
i 1 T I
i iAi 1^1 i i T 1. , ,
Figure 3—Concentration of Cr In leach water as a function of Immersion
time of sludge bearing concrete by Gamma counting.
3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 M 57 60
DAYS LEACHING
Figure 4—Concentration of Nl in leach water as a function of immersion
time of sludge bearing concrete by Beta counting.
water as a function of time for both Type I and Type III
cement formulations. The results are shown in Figure 4.
For concrete made from Type I cement, the total nickel is
about five times the soluble nickel with a maximum value
of 0.035 ppm. For Type III cylinders the results are
dramatically lower, in which, the total nickel
concentration in the leach water never reaches 0.01 ppm.
Cylinder systems, in which, the leach water was
replaced after 100 days show an initial release of nickel
into the fresh leach water at a level of about 0.02 ppm
after seven days. The concentration drops to 0.01 ppm in
21 days, and to about 0.005 ppm by the 165 day.
Because the 63Ni emission is a very low energy 13'
particle, the efficiency measurement is subject to some
uncertainty. It is possible that when a refinement of this
measurement is made, the results reported might have to
be raised by a factor of two at the most. This would have
the effect of making the highest nickel concentration 0.07
ppm.
7. Zinc
Previous measurements of soluble zinc entering the
leach water, when type I cement was used, showed no
detectable metal during the first 60 days.8 The lower
detection limit is about 0.0001 ppm. The total zinc
entering the leach water as a function of time for both
Type I and Type III formulations is shown in Figure 5.
The Type III, high early strength cement, produces a
concrete, which for zinc, allows release at the barely
detectable level of slightly greater than 0.0001 ppm. Even
Type I cylinders release the zinc at an extremely low level.
The zinc cylinders that were reimmersed after 100 days
showed an initial release of about 0.020 ppm with the
concentration diminishing to 0 by the 116 day.
8. Measurements Based on EPA Protocol for Toxicant
Extraction
One cylinder was prepared with NEP sludge to which
650 ppm manganese from MnCl2-4H2O was added with
1.0 juCi 54Mn. After curing, the cylinder was immersed in
16 times its mass of deionized water and the pH was
adjusted to and maintained at 5.0 using 0.5 M acetic acid
for 6 days with constant agitation. At the end of 24 hours,
there was no 54Mn activity in the ambient water. At the
end of 6 days, the water showed a 54Mn activity of 40
counts/hr., which is equivalent to 0.008 ppm.
9. Calcium and the Nature of Metal Binding
The last metal to be considered with respect to its
leaching from concrete is calcium. While it is generally
not a constituent of electroplating sludge, it does make up
about 45% of Portland cements. In hardened concrete,
calcium is present in mineralized form (tobermorite,
hydrogarnet, and aluminates), and as Ca(OH)2.
As was reported earlier,"* (Figure 6), a significant
O Typel
A Type III
3 6 9 12 15 18 21 24 27 30 33 38 39 42 45 48 51 54 57 60
DAYS LEACHING
|
1
So
H
O '
SS
IL.
-------
Table 4
Drinking Water Standards and Typical
50-day Leachate Metal Concentrations
Drinking Without
water (ppm) Leachate confinement
(ppm) (ppm) (ppm)
Cadmium
Chromium
Cobalt
Manganese
Nickel
Zinc
0.010 0.1
0.050 0.03
0.0095* 0.02
0.050 0.04
0.034* 0.01
5 0.001
'Maximum concentration
cities in 1962.
65
65
58
33
30
61
in finished water of 100 largest U.S.
amount of calcium enters the leach water, about 1% of
the total calcium content of cement. The pH of the leach
water reaches 12.5 by the 25th day of immersion in the
systems used in this work. Thus, if it is assumed that the
entire hydroxide ion concentration is due to Ca(OH)2, a
calcium concentration of 630 ppm is obtained, which is
very close to our radiochemically determined value of 614
ppm. Nearly 1% of all the calcium in the cement paste
leached out in about 30 days. During the same period of
time, less than 0.02% of the metals in the sludge leached
out. The metals in the sludges used are present primarily
as hydroxides. (The pH of these sludges is 8-8.5.) Even if
this were not true the large excess of hydroxide ions in
fresh concrete would tend to convert them to this form.
Thus it seems to follow that, whereas calcium in the form
of Ca(OH)2 is not effectively immobilized, the other
metals are. If these metals remained in the hydroxide or
other nonmineralized chemical forms, they should show
about the same leaching properties as calcium. The fact
that they do not suggests they are at least partially
mineralized. Additional evidence supporting the
conclusion that compounds are chemically immobilized
in concrete is to be found in the literature search of our
report on phase I of the project.10
A puzzling aspect of the sludge-metal leaching systems
is the apparent reabsorption of certain metals with
extended exposure of the concrete to the same leach
water. This is observed in the majority of cases. It is as
difficult to dismiss it as it is to explain it. It is not due to
the lessening of radioactivity with age because a
correction based on half-life was made for the counting
rates of all short-timed nuclides. This phenomenon is
fortuitous for the purposes of this work, and it is hoped
that future studies will elucidate its causes.
In conclusion it should be pointed out that the extent
to which the metals studied leach into the ambient
immersion water is generally of a very low level. For
purposes of comparison, the maximum contaminant
levels in drinking water (1974 Safe Drinking Water Act
and 1962 U. S. Public Health Standards) are shown
in Table 4 together with the 50-day metal concentrations
determined in this study. It should be noted that the
Resource Conservation and Recovery Act sets control
values at 10 times these levels. A third column is included,
which shows metal ion concentrations in the same
volume of water if the metals were added without
confinement.
FOOTNOTES
1. The Effect of Electroplating Wastewater Sludge as
an Admixture on the Physical Properties of Concrete
- Phase I, Report to American Electroplaters'
Society, on Project No. 49, October 20, 1979.
2. Resource Conservation and Recovery Act proposed
test method.
3. Chandra, R., Introductory Physics of Nuclear
Medicine, Chapter 9, Lea and Febigger,
Philadelphia, 1976.
4. Snell, A. H., ed., Nuclear Instruments and Their
Uses, Vol. 1, Chapter 5, John Wiley and Sons, New
York, 1962.
5-10. The Effect of Electroplating Wastewater . . .
ACKNOWLEDGMENTS
The authors gratefully acknowledge the support of this
research by the American Electroplaters' Society as part
of Project No. 49.
The authors are very appreciative of the assistance of
Louis Pasquale, who performed the pH controlled
experiment and helped with the calculations. In addition
they wish to thank Herbert K. Miller, Br. Austin
Bernabei, Lawrence J. Durney, Cort G. Platt, Frank
Principe, Vincent Ranelli, and Bruce E. Warner for
cooperation, support, and helpful advice during various
stages of the work. Finally, a special note of thanks to
Geraldine Rooney for her expert manuscript
preparation.
69
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Stabilization of Heavy Metal Wastes
By the Soliroc Process
J. M. Rousseaux and A. B. Craig, Jr.*
INTRODUCTION
1.1 PROJECT OBJECTIVES
The primary objective of this study was to conduct a
preliminary engineering evaluation of the Soliroc metal
fixation process in immobilizing potentially hazardous
pollutants contained in industrial wastes. The evaluation
was designed to provide experimental data on the Soliroc
process and to establish a data base for future pilot scale
work. Additional project objectives include:
• Expedition of preliminary bench scale
experimentation of a fixation process currently used
commercially in Europe.
• Provision of sufficient data that a domestic co-
sponsor for further demonstration could be
attracted.
• Promotion of the transfer of foreign fixation
technology which appears capable of storage or
disposal of industrial wastes (especially metals) for
future recovery.
• Development of in-house expertise for treatment of
wastes from the EPA Testing and Evaluation (T&E)
facility.
• Organization and completion of the project in a
minimum time period and at minimum cost.
The project was implemented by personnel from the
U.S. Environmental Protection Agency (EPA), with
technical consultation by Mr. Jean Rousseaux of the
Cemstobel Company in Brussels, Belgium. The
contributions of Mr. Rousseaux were necessary in
several phases of the experimental program, especially
those dealing with proprietary aspects of the Soliroc
process.
1.2 SCOPE
In order to meet the objective of the study, the
following tasks were performed:
• Seven samples, representative of wastes from the
electroplating industry were obtained locally
(Cincinnati, Ohio).
• Raw wastes were analyzed for metals, cyanide (CN),
and hexavalent chromium (Cr+6).
*J. M. Rousseaux
Cemstobel
Brussels, Belgium
A. B. Craig, Jr.
Industrial Environmental Research Lab.
U.S. EPA, Cincinnati, Ohio
• The Soliroc process used was designed to
accommodate the study wastes and the bench-scale
experimental protocol.
• Waste samples were treated with the Soliroc process.
• The EPA extraction procedure (EP) test was
performed on the treated wastes.
• Compression tests were performed on treated wastes
(test cylinders).
• Analytical results of stablized waste samples were
compared to RCRA's EP toxicity limitations, the
National Secondary Drinking Water Standards and
to the raw waste analyses.
SECTION 2
BACKGROUND
The metal finishing industry generates a variety of
waste materials that are potentially hazardous.
Electroplating process residues, pickling acids, and
wastewater treatment sludges contain cyanides and
heavy metals. Two methods commonly used for disposal
of the materials are landfilling and ponding; both have
been practiced without any particular precautions being
taken to prevent them from contaminating ground water
supplies. Inorganic residues and sludges from the metal
finishing industry can be chemically bound to minimize
the potential for groundwater contamination by effecting
a change in the chemical and physical properties of the
wastes. A number of fixation techniques have been
studied, including precipitation, encapsulation,
asphalting, cementation, and other similar stabilization
processes. A list of pertinent references is shown in
Appendix A. This report discusses an evaluation of one
fixation process, called the Soliroc process which was
developed by Cemstobel, located in Brussels, Belgium.
2.1 REGULATORY ASPECTS
Through a number of specific provisions, the Resource
Conservation and Recovery Act of 1976 (RCRA) aims to
promote the protection of health and the environment
and to conserve valuable materials and energy resources.
Subtitle C of RCRA directs the U.S. EPA to promulgate
regulations to protect human health and the environment
from the improper management of hazardous waste. In
accordance with that direction, EPA has promulgated
the Hazardous Waste and Consolidated Permit
Regulations (Federal Register, May 19, 1980).
More specifically, Section 267.24 of the May 19
regulation indicates that one of the most prevalent
pathways by which hazardous wastes migrate to the
environment and contaminate groundwater is through
70
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the leaching of waste contaminants from land disposed
wastes. It is obvious from the history of RCRA that this
type of ground water contamination was one of Congress'
primary areas of concern. EPA has addressed the
problem of identifying potentially leachable wastes by
developing an analytical test procedure called the
Extraction Procedure (EP). The EP test is discussed
more fully in Section 4.1. This test method was designed
to simulate the leaching action that occurs in landfills.
The simulated leachate, or extract, from the EP test is
analyzed and compared with the National Interim
Primary Drinking Water Standards (NIPDWS). If the
extract is found to contain contaminants in excess of 100
times the maximum allowable limit set by the NIPDWS,
the waste is considered hazardous.
2.2 SOLIROC PROCESS DESCRIPTION
Existing waste treatment processes precipitate metal
cations as hydroxides by adding a base, usually caustic or
lime, which produces an insoluble solid or sludge.
However, these metallic hydroxide sludges can be
resolubilized in lower pH environments, as their stability
is pH dependent.
In the Soliroc process, a chemical reaction takes place
between metals present in an acid solution and a siliceous
reagent. During the chemical reaction, a monomer is
synthesized, which then polymerizes to form an insoluble
bulk mass that is believed to be suitable for landfilling.
A process flow diagram of the Soliroc process in shown
in Figure 2-1. Initially, hexavalent chromium is reduced
to the trivalent state to allow for further reaction in the
process. During the reduction of chromium, the addition
of acid is necessary to maintain the pH of the waste
solution at about 1.5. For production of the monomer, a
siliceous reagent is slowly blended into solution, again at
a consistently low pH. The addition of waste or fresh acid
is necessary to maintain the low pH.
The pH is then raised by the addition of caustic to
about pH 11 to initiate polymerization. The rapid rise in
pH causes a thickening of the material, and subsequent
development of sludge or paste. Following the
polymerization step, lime and a setting agent such as
Portland cement can be added to effect coagulation and
hardening before the product is placed in a landfill.
2.3 SUITABLE WASTES FOR TREATMENT BY THE
SOLIROC PROCESS
Inorganic wastes, as well as polar organic wastes,
regardless of their degree of consistency are reportedly
treatable by the Soliroc process. Some of these types of
wastes are listed below:
Inorganic compounds
Acids— hydrobromic acid (HBr), hydrochloric acid
(HC1), nitrous acid (HNO2), nitric acid (HNO3),
sulfuric acid (H2SO4), and also other less common
acids; an exception to treatment potential in this
waste category is hydrocyanic acid (HCN).
Bases—potassium hydroxide (KOH), sodium
hydroxide (NaOH), hydrated lime [Ca(OH)2], and
calcium carbonate (CaCOs).
Heavy metal—solid or liquid wastes containing
heavy metals such as aluminum, antimony, silver,
arsenic, barium, beryllium, cadmium, calcium,
cerium, chromium (+3 or +6), cobalt, copper, tin,
iron (+2 or +3), magnesium, mercury, nickel, lead,
and zinc.
Oxidizing agents—chromate, chlorate,
hypochlorite, and perchlorate wastes.
Polar organic compounds
Wastes containing these compounds include paint
sludge, phenol, fatty acid, fatty amines, alcohols,
ketones, and residues from latex processing.
Table 3-1
Waste Sample Identification
Sample Waste
No. Waste
1 Bright dip chromate for cadmium.
2 Accumulated cyanide solution and sludge from
holding tank (large automatic electroplating
rack).
3 Sludge from bottom of cyanide zinc plating tank.
4 Sludge from phosphate tank and carbon from
nickel filters.
5 Sludge from plant sump cleanout.
6 Alkaline cleaner sludge.
7 Waste sulfuric acid pickle liquor.
SECTION 3-EXPERIMENTAL PROCEDURES
Waste samples obtained from the electroplating
industry are listed in Table 3-1. These samples were
selected randomly and may not accurately represent all
wastes characteristic of this industry. They are
considered typical, and this small sampling group is
believed to be adequate for this preliminary study.
3.1 ANALYSIS OF RAW WASTE SAMPLES
The raw waste samples were analyzed for
concentrations of metals, cyanide (CN), and hexavalent
chromium (Cr+6). CENTEC Analytical Services
performed the analyses of the raw waste samples. Results
are reported in Table 3-2.
Table 3-2
Analyses Results of Raw Waste Samples
(mg/l except as noted)
Sample
No.
1
2
5
6"
7
"pH units.
pff
1.05
13.00
10.06
13.19
<1.0
bMetal concentrations are given in
'Analysis not
performed.
CN
1.27
2,430
968
33.7
c
units of /ig/g
Cd
15,400
910
782
35.2
53.0
(wet weight
Cr
57,000
535
3,890
440
470
of sludge), as
Cu
450
1,850
25,500
13,800
39.0
received.
Ni
305
5,800
1,330
5,660
46.0
Pb
4.00
0.74
2,000
6,580
c
Zn
180
5,400
28,700
5,030
5,000
71
-------
Table 3-3.
Calculated Chemical Concentration of Raw Wastes After Pretreatment3
(mg/l)
Sample Waste
No.
1
2
5
6
Cd
15,400
600
670
37
Cr
57.000
510
3,400
450
Cu
450
1,160
21,800
903
Ni
305
3,500
1,140
3,700
Pb
4.0
0.4
1,700
4,300
Zn
180
5,250
25,200
5,010
'Pretreatment consisted of the addition of Sample 7, sulfuric acid pickle liquor (see Table 3-1).
3.2 WASTE ACCEPTABILITY AND PREPARATION
Some wastes were pretreated for Soliroc processing.
Wastes containing cyanide (Samples 2, 3, 5, and 6) were
chlorinated to destroy the cyanide complexes in the
wastes. Following chlorination, the solution was
acidified to pH 2 by adding pickle liquor (Sample 7). The
chemical concentrations of pretreated Samples 1 through
6 were calculated, and results are given in Table 3-3.
After raw waste characterization and preliminary
screening of the wastes by data review, Samples 3 and 4
were eliminated from further evaluation. Waste 3
contained elemental zinc in amounts that prohibited
obtaining a low steady pH without production of
hydrogen gas (H2) at potentially hazardous levels.
Consequently, Sample 3 was discarded. Waste Sample 4
was discarded because high carbon content interfered
with the measurement of pH.
Elimination of these samples in this study does not
necessarily imply that these two waste types are
unacceptable for treatment by the Soliroc process. They
were eliminated because of limitations in the scope of this
preliminary study. The purpose was not to prove
universal application of this process, but to develop data
as a foundation for further investigations. On this basis,
wastes that were not readily compatible with this process
were not tested.
The four remaining samples (1, 2, 5, and 6) were
blended in a ratio that is critical to the success of this
process. The basis for determining this ratio was
developed by Cemstobel and is proprietary information.
The wastes were blended in the proportions shown in
Table 3-4.
The resultant metal concentrations were calculated for
the blended waste, with results as shown in Table 3-5. As
a quality assurance check, a sample of the blended waste
was titrated with caustic (NaOH) to confirm or invalidate
the calculated total metal concentration. (The
assumption here is that at pH 10.5 all metals are
hydroxylated and the measured equivalents of NaOH
will indicate total equivalents of cation metals in solution
prior to titration and precipitation with caustic). This is a
relatively inaccurate measurement, yielding values that
can vary with the selected end point and with sample
characteristics. This analytical check resulted in 1.44
cation equivalents per liter; the calculated metal content
was 1.25 cation equivalents per liter. These values are
considered reasonably comparable, and are included
here as a means of verifying the calcuated concentration
values.
Sample
No.
1
2
5
6
Table 3-4
Blended Waste Composition
Proportion Waste identification
0.5 Bright dip chromate for cadmium
1.0 CN solution and sludge from holding
tank on automatic rack
0.5 Plant sump cleanout
1.0 Alkaline cleaner sludge
Table 3-5
Calculated Concentrations (mg/l) of Metals in the
Blended Waste
Cd
Cr
Cu
Ni
Pb
Zn
2,890
10,390
7,100
2,640
1,710
7,650
3.3 FIXATION OF BLENDED WASTE
After blending of the wastes, the sodification treatment
procedure was followed according to the process
description given in Section,2.2. The figure shown in that
discussion (Figure 2-1) illustrates the experimental
procedure. However, minor modifications were made to
the process and are discussed below.
In the chromium reduction step, sodium sulfite,
Na2SO3 was continuously added to the blended waste to
act as the reducing agent. An acid pickle liquor (Sample
7), supplemented by white sulfuric acid, was added to
maintain the pH at 1.5. Addition of the siliceous reagent,
and formation of the silicic acid solution were performed
in a reaction mixer. Polymer initiation, by addition of
caustic, was also performed in the mixer. Addition of
lime and/or cement followed, and the mixer was emptied
into a suitable container for further testing.
3.4 EVALUATION OF THE SOLIROC PROCESS
Six experimental runs were performed, some with
variations of the standard process. Five experimental
runs used the blended waste sample, and one (Run 6) was
performed on raw pickle liquor. Table 3-6 outlines the
variations applied to all runs. Runs 1 and 5 were
duplicates, in which the process was performed as
described earlier. In Run 2 addition of the pickle liquor
72
-------
RAW
1 HASTE
1
1 ELIMINATE
CN BY
CHLORINATION,,
REDUCTION
OF Cr*6
1
_. BLENDED
1 WASTE
PRELIMINARY
SCREENING
ADDITION OF
SILICEOUS
REAGENT
AND ACID
MONOMER
ADD IT
CAU
i
ON OF
>TIC
POLYMER
At
SE1
JDITION OF
TING AGENT
ADDITION OF LIME
1
^ CCMCN
FINAL
FATION »•
DISPOSAL
ANALYSIS
Fig. 2-1 —Flow diagram of the Sollroc process.
was omitted. In Run 3, the proprietary siliceous reagent
was omitted. Run 4 was similar to Run 2 except for the
cementation step; Portland cement was added in the
cementation phase of Run 4, whereas no cement was
added during Run 2.
3.5 THE EPA EXTRACTION PROCEDURE
Following is a brief description of the EP test used as
the analytical basis for this study.
A 100-gram sample (approx.) was prepared for
extraction by reducing the particle size (by crushing,
cutting or grinding) so that the sample material would
pass through a standard 9.5 mm (3/8-in.) sieve. After
being weighed, the solids were placed in an extraction
container, to which 16 grams of water were added for
every gram of solids. This mixture was stirred sufficiently
to assure that all sample surfaces were continuously
brought into contact with the well-mixed extraction fluid
Table 3-6
Experimental Runs
Experiment Acid added Cementation
run No. Waste blend (Step 2f (Step 4f
1 1,2,5,6 Pickle liquor and Lime and setting
H2SO4 agent
2 1,2,5,6 H2SO4 Lime and setting
agent
3 1,2,5,6 Pickle liquor Lime
4 1,2,5,6 H2SO4 Portland," lime,
and setting agent
5 1,2,5,6 Pickle liquor and Lime and setting
H2SO4 agent
6 Pickle liquor Not applicable Portland,1" lime,
and setting agent
"Step numbers refer to the process description in Section 3.3.
"Portland cement.
and to prevent any stratification. The pH was adjusted to
5.0 ±0.2, by use of 0.5 N acetic acid. The total addition of
acetic acid was limited to 4 ml per gram of solid, beyond
which no more was added. The extraction was
maintained between 20° to 40° C (68° to 104° F) for 24
hours. The mixture was separated as before into solid and
liquid components. The liquid was diluted with distilled
water to a total volume equal to 20 times the weight of the
initial solid materials. This liquid was the "extraction
procedure elutriate," which was analyzed for metal ions.
SECTION 4
TEST RESULTS
In addition to the planned EP test for evaluation of the
stabilized wastes, two additional test series were
conducted, the results of which are also presented here.
The Cemstobel Laboratory in Belgium performed metals
analysis on samples referred to as core dips. A core dip is
distilled water in which the stabilized wastes (Runs 1,2,4,
and 5), in the form of solidified cores, were allowed to
soak for about 30 days. This test was performed to allow
comparision with the EP test results.
The second additional test series involved
determination of the unconfined structural stability of
the cemented wastes. Three cores (6 in. diameter and 12
in. long) from each experimental run were aged from 61
to 66 days and submitted to an independent testing
laboratory. Each core was compressed to the failing
point, and the total load recorded. The total
compressional load required to cause failure, relative to
the cross sectional area of the core, yields a value for
compressive strength in units of pressure (psi).
4.1 EP RESULTS
Data obtained in the EP test are shown in Table 4-1.
The maximum allowable acetic acid column is shown, in
accordance with the limitation of 4 ml 0.5 N acetic acid
per gram of solid sample. It is noteworthy that the
maximum allowable volume of acetic acid was required
Table 4-1
EPA Extraction Procedure Data
Run No.
\
2
4
5
6
Stabilized waste
sample size, g
99.5
99.4
105.0
100.6
102.5
Initial
pHofEP
extract
lO.l
10.7
11.4
10.4
ll.O
Final
pH of EP
extract
7.2
6.6
9.1
7.3
9.5
0.5N HAc"
added, ml
398.0
397.6
420.0
402.4
410.0
Max. HAc*
allowable, ml
398.0
397.6
420.0
402.4
410.0
"HAc = acetic acid.
73
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Table 4.2
Analyses of EP Extracts
mg/l
i\un - — • —
No. Cd Cr Cu Ni Pb
1 5.60 0.10 0.28 1.30 0.013
2 2.30 0.27 0.64 0.95 0.016
4 0.10 0.13 0.06 0.15 0.006
5 2.70 0.18 0.36 1.15 0.017
6 <0.01 0.50 0.05 <0.10 0.008
Maximum allow-
able concen-
tration 1.0s 5.0" 100.b c 5.0a
"Characteristic of EP toxicity from RCRA (100 times NIPDWS).
b!00 times the secondary maximum contaminant level.
'Nickel is not regulated by the primary or secondary drinking water standards.
in every case, an indication of the strong alkalinity of the
setting agent and Portland cement added during the
stabilization of waste samples.
The results of analyses of the EP extracts are shown in
Table 4-2. The maximum allowable concentrations for
each metal were determined from the promulgated
RCRA regulations for cadmium, chromium, and lead
and from the secondary drinking water standards for
copper and zinc. The principle of an attenuation factor of
100 that is the basis for the RCRA maximum
contaminant levels was applied to the secondary drinking
water standards.
4.2 RESULTS OF ADDITIONAL TEST RESULTS
Results reported by Cemstobel for analysis of metal
concentrations in the core dip samples are shown in Table
4-3. Lead concentration was not determined on these
samples. Results of the compressive strength tests are
shown in Table 4-4.
SECTION 5
DISCUSSION OF RESULTS
A rnmnarative nresfintatinn of the analytical results
Table 4-4
Results of Compressive
Strength
Total load,
Run No. Age days
\ t\f\
I OO
1 66
66
2 66
66
66
4 64
64
64
5 63
63
63
6 61
61
61
pounds
i ^n
1 JU
250
250
2,000
1,900
1,800
4,250
4 500
4'SOO
500
500
650
1,500
1,550
1,500
Zrt
34.8
5.00
0.41
25.0
0.50
500."
Test
Unit load,
psi
C
J
9
9
71
67
64
150
159
159
18
18
23
53
55
53
from the EP tests is shown in Figure 5-1. Except for
cadmium, the EP extracts gave concentrations of the
metals below the maximum allowable concentration.
Only one experimental run stabilized cadmium
satisfactorily. This observation leads to the preliminary
conclusion that the Soliroc process, as it was modified for
this study, may not be capable of stabilizing wastes
containing cadmium in the range of 2000 to 3000 mg/1.
The contaminant that appears most easily stabilized is
lead, which however, was present in the blended waste at
the lowest concentration of all the metals. Results of the
EP extract analysis for lead average 0.013 mg/l, well
below the maximum allowable concentration.
Table 4-3
Analyses of Core Dip Samples
(mg/l)
Run No.
1
2
4
5
Cd
0.004
'0.01
0.3
0.005
Cr
0.04
0.04
0.04
0.02
Cu
0.5
0.3
0.14
0.12
Ni
0.31
0.46
0.21
0.28
0\23
0.23
0.007
0.03
0.02
The results of Run 6, in which pickle liquor (without
additional waste) was used as the starting material for the
process,,are not shown on Figure 5-1 for two reasons.
First, the metal concentrations in the starting materials
are not comparable, and second, the EP extract analyses
for Run 6 yielded relatively low metal concentrations (see
Table 4-2). The data indicate that the Soliroc process is
adequate in immobilizing potentially hazardous
constituents of sulfuric acid pickle liquor. The cadmium
concentration in the EP extract from Run 6 was well
below the standard, however the initial concentration of
cadmium in the pickle liquor is more than 50 times lower
than the calculated concentration in the blended waste
samples.
Figure 5-1 can be examined further to evaluate the
effects of different modifications to the Soliroc process in
stabilizing identical blended waste samples. The EP
extract analysis for Run 4 gave the lowest concentration
for every metal except chromium. This observation leads
to a preliminary conclusion that either the use of only
H2SO4 as the acid additive or the addition of Portland
cement improves the stabilizing capabilities of the
Soliroc process. As a means of distinguishing between the
individual effects of these two process modifications, a
74
-------
-©— 500 t
Fig. 5-1—Concentrations of metal contaminants In EP extracts (by
experimental run number).
comparision of data from Runs 1 and 5 (duplicates) and
Run 2 yields a useful observation. The use of either
H2SO4 (only) or pickle liquor plus H2SO4 as the acid
additive does not appear to consistently improve the
stabilizing capability of the Soliroc process. Therefore,
the use of waste acid does not adversely affect the process.
Also, the addition of Portland cement appears to
significantly improve the stabilization of certain metals.
A comparison of the core dip analyses with the EP tests
results yields predictable observations. Metal
concentrations in the core dip samples were consistently
much lower than those found in the EP extracts. It is
believed that this is primarily due to the relative
aggressiveness of the EP analytical procedure when
compared to the core dip experimental protocol.
Additionally, results of the core dip analyses do not
support the above stated conclusion that Portland
cement improves the stabilization of certain metals. The
reason for this is not understood.
Results of the compressive strength tests also yield
predictable observations and conclusions. The addition
of Portland cement in the cementation step improves the
structural stability of the hardened material.
The results of this study provide benchmark data on
which to base further engineering investigations
regarding the capabilities of various stabilization or
fixation processes. Before more definitive conclusions
can be drawn, detailed experimentation with other
wastes, processes, and process modifications is needed. It
is suggested here that organizations such as the EPA, the
American Electroplaters' Society, the Portland Cement
Association, and other involved with the stabilization of
potentially hazardous materials combine their efforts in
conducting a more comprehensive study of this
important subject.
APPENDIX A
Pertinent References
1. U. S. Environmental Protection Agency, Solid and
Hazardous Waste Research Division, Municipal
Environmental Research Laboratory. Research on
Chemical Fixation. September, 1978.
2. U. S. Environmental Protection Agency (MERL),
and Environmental Laboratory of U.S. Army
Engineer Waterways Experiment Station. Survey of
Solidification/Stabilization Technology for
Hazardous Industrial Wastes.
3. U. S. Environmental Protection Agency (MERL) and
Environmental Laboratory of U.S. Army Engineer
Waterways Experiment Station. Physical and
Engineering Properties of Hazardous Industrial
Wastes and Sludges. August, 1977.
75
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Routes to Metals Recovery From
Metal Finishing Sludges
Anil Mehta*
The process wastewaters from the electroplating
industry contain cyanides and heavy metals. Because of
their detrimental effect on the environment, discharges
are regulated by the federal, state, county, or city
ordinances, thus necessitating installation of treatment
technologies. One of the treatment technologies widely in
use already and more likely to be installed is
neutralization and precipitation technology which
destroys the cyanide and removes the heavy metals as
hydroxides. This treatment is shown in Figure 1.
The sludge is commonly disposed of in landfills. This
practice is coming under greater scrutiny by the
regulating authorities, primarily due to the presence of
the heavy metal hydroxides. The heavy metals may leach
due to changes in their environment. The leached metal
may report to the surface runoff waters, or to the
ground waters or both. To prevent any leaching of the
metals, secure and chemically maintained land disposal
sites are required. The cost of disposal thus becomes
greater not only because of the heavy metal presence but
also because the secure landfill sites are expensive to
create and maintain. Finally, such sites may not become
available because of resentment on the part of the
community itself.
Since a landfill site has a finite capacity, sludges, in the
form generated at the electroplating plant, may not be
acceptable to the operator of the site. Such sludges
usually contain about three percent solids requiring
volume reduction by dewatering to conserve his capacity.
Dewatering requirements necessitate installation of a
filter press or a centrifuge. This problem from process
wastewater to the final disposal is summarized in Figure
2.
If the landfill site is not properly maintained, certain
problems arise:
1. Contamination of the surface and the ground
waters by the heavy metal migration when and if the pH
conditions change.
2. Permanent loss of metals if the site undergoes a
physical change, i.e., it becomes a parking lot.
3. Dilution in metal contents if the sludges are mixed
with other types of waste material.
What makes these hydroxide sludges potentially
hazardous is the presence of the heavy metals. A typical
sample composition range in shown in Table 1.
*Anil Mehta
EPA Industrial Environmental Research Lab
Cincinnati, Ohio
Trying to immobilize the heavy metals in a sludge by
any one of the fixation techniques would add to the cost
of the final disposal and still promote land application of
heavy metals. Under RCRA, severe restrictions may be
encountered by land disposal.
Recovery and recycling is practiced by the metal
industry at significant levels. But this practice is restricted
in the sense that it applies to only the pure solid waste.
Thus, recycling constitutes about 20 percent of the total
copper metal available in the market recovered from pure
solid scrap. This is the scrap that needs simple melting
and refining. The scrap comes from two sources: capital
goods such as buildings, industrial machinery, etc., or
consumer goods such as automobiles, appliances, etc.
SO2, NaHSO:
Alkaline cyanide
wattes with metals
Ch, NaOCL
Fig. 1—Cyanide destruction and heavy metal removal.
Process wastewater
Treat to detoxify
Effluent water
to discharge
Sludge
Direct discharge
potentially hazardous
• Direct discharge
potentially hazardous
Fig. 2—Wastewater discharge problem.
Table I
Hydroxide Sludge Composition in %*
Copper
Nickel
Zinc
Cadmium
Chromium
2-6
2-6
2-10
2-6
5-20
*at three percent solid contents
76
-------
On the other hand, metal losses on a permanent basis
are also tremendous. Of all the recorded production of
copper in this country, 72.5 million short tons, about 60%
are traceable as being in use presently. Forty percent or
29 million short tons (58 billion pounds) are lost
permanently due to wear, abrasion, chemicals,
fabrication, etc. At today's prices, this loss amounts to 58
billion dollars figured at the price of finished copper
product which is wire bar grade copper cathode. The loss
is staggering when figured in terms of the finished capital
and consumer goods.
Another example of this loss is provided by the
electroless copper plating industry. The printed circuit
board platers comprise ten percent of all the
electroplaters in business. They generate about a million
gallons of liquid waste (sludges) annually. If one gallon of
this sludge weighs about ten pounds and contains ten
percent copper, about a million pounds of copper are
contained in this sludge annually. Disposal of such waste
is not always carried out with recovery at a later date in
mind, so a very significant amount is lost each year.
The electroplaters do not treat these sludges for metal
recovery for many reasons. Recovery is an uneconomical
proposition in terms of capital and operating costs, is an
incompatible operation, and individually the quantities
generated are not large enough to justify a recovery
system.
An alternative to any individual treatment for metal
recovery is the concept of Centralized Waste Treatment
Facility (CWTF). Such a facility would require no direct
participation from the platers, would pose no operating
problems to the platers, and would certainly solve the
discharge problem for the entire industry. By pooling it
together, the quantities to treat may be large enough to
make the recovery operation economically attractive.
Nontreatment of these hydroxide sludges will always
present two main concerns: potential water pollution,
and resource loss. With resource recovery and
conservation aims in mind, any treatment to recover the
heavy metals would alleviate the toxic hazard problem
associated with the disposal of the heavy metals.
Possibility of hydroxide treatment for metal recoveries
fall into two categories: wet and dry. In wet processes,
separation reactions are carried out usually at
atmospheric temperatures and pressures. In dry
processes, separation reactions take place at elevated
temperatures. The former processes are generally
classified as hydrometallurgy and the latter as
pyrometallurgy.
Pyrometallurgical treatments for segregated and
selected sludges are:
• Direct recycle to a smelter after dewatering,
• Direct recycle to metal alloy industry on a small basis.
Troubles with pyro processes are that for economical
feasibility the operation would have to be on a very large
scale, and that concentrated feed material is required.
The hydroxide sludges fail to meet these two
requirements. Under pyrometallurgical treatment, above
two above possibilities are presently available and further
discussion is not presented.
Hydrometallurgical treatments for mixed and
segregated sludges are:
• Aqueous dissolution of metals by leaching.
• Recovery of individual metals or metal compounds
from this solution.
There are certain advantages for using hydro-
metallurgical processes. Metals may be won directly from
the solution by concentration, electrolysis, or hydrogen
reduction. Fuel requirements are low as the processes are
carried out usually at low temperatures. Disadvantages
are that solution purification and concentration up-
grading may be absolutely necessary before metal
recoveries are possible. But this particular branch of
metallurgy is going to see much use as new techniques are
developed. Building mini-smelters is very uneconomical
while building a mini hydrometallurgical plant is
becoming a matter of fact.
Since any commercial practice would naturally take
into account the profitability as the primary objective,
the treatment of the hydroxide sludges is being offered
with that objective in mind. This requires that the process
be specific, reproducible, and controllable. The process
should also be possible with a minimum number of unit
operations and unit processes. The treatment of
hydroxide metal sludges is now considered in terms of the
unit operations and unit processes. These two depend on
the chemical state and also on the physical environment
of the metals. Electroplating wastes, after the hydroxide
neutralization, will consist mainly of metal hydroxides
such as Cu(OH)2, Ni(OH)2, Cd(OH)2, Zn(OH)2, etc.
With lime neutralization, the sludge will also contain
calcium salts. A range of composition is provided in
Table I.
The following reagents are solvents for many minerals
and metallic constituents: sulfuric acid, ferric sulfate,
ammonia and ammonium carbonate, sulfur dioxide,
ferric chloride, hydrochloric acid, and nitric acid. The
order given is about that of their importance. Metal
winning from solutions by such operations as
cementation or electrolysis is commonly practiced from
the metal sulfate solution.
Sulfuric acid is the most important leaching reagent.
Main advantages for its use are the cost, minor corrosion
problems, and attacking many metal forms. Its main
disadvantage is that it sulfatizes everything, which does
not provide any selectivity. Ferric sulfate may be
obtained cheaply from spent pickle liquors. Its primary
function is to provide a sulfate solution. Ammonia and
ammonium carbonate may be the most suitable reagents
for hydroxide sludges because they possess better
selectivity for solubilizing metal constituents in a
hydroxide sludge. But the reagent cost is very high and
their recovery in the process would be mandatory from
an economical point of view.
Primary aim for a solvent is to bring the metal or
metals into solution from which individual separations
are made. This operation provides pure solutions, with
major impurities out of the way. For leaching, the
following steps, as shown in Figure 3, may be necessary.
Leaching of hydroxides by either sulfuric acid or
ammonia will provide lean solutions. Copper may be
recovered from lean sulfate solutions by cementation.
Iron will displace copper quantitatively from a solution.
The product, although rich in copper, may be highly
contaminated with iron so that only a smelter may be able
to handle it. A technique which is becoming widely
accepted for concentrating solutions is one of ion
exchange. The ion exchange medium may be solid or
liquid. Generally speaking, concentrating by solid
organic resins is known as ion exchange (IX) and by
liquid organic resin is known as solvent extraction (SX).
77
-------
Solvent
_r
Hydroxide Sludge
Leaching
Filtration
Pure Solution
Further Processing
Fig. 3—Leaching of hydroxide sludge.
Solvent -
- Hydroxide Sludge
Leaching
|
[ Filtration |
1
| Cementation | | Solvent Extraction |
Solids to
A Smelter
t k t
Solution for single metal Rest of the
Further Treatment Separation Metals
1 i
| Electrolysis
1 Further Treatment 1
Fig. 4—Generation and treatment of pure metal solutions.
Ion exchange saw a tremendous application in uranium
metallurgy. The solvent extraction technique is becoming
accepted in copper metallurgy. The acceptance is on such
a large scale that the future may see its application widely
spread in areas where the ore grade has kept going down
or residual metallic wastes are to be treated. The scheme
for obtaining pure solutions in Figure 3 may be expanded
now as in Figure 4.
For sulfuric acid leach solutions, copper may be
recovered from the polymetal solution by cementation
under oxidizing solution. The cement copper may be sold
directly to a smelter or releached for electrolysis. Other
metals are selectively precipitated after iron removal and
may be recovered as pure metals or metal compounds.
Electrolysis regenerates the sulfuric acid for recycle
which is a very important factor in economic evaluation
because regeneration is part of the process requiring no
additional or extra regeneration equipment installation.
Copper may also be removed from the polymetal
sulfate solution by solvent extraction. Copper then is
removed by electrolysis. Other metal recoveries may be
achieved by further solvent extraction or by cementation
with zinc.
If ammonia leach is employed, metals such as copper,
nickel, and zinc are selectively brought into solution as
ammines from the hydroxide sludges. Other impurities
such as iron and calcium are left behind as solids. Copper
may be removed from this polymetal solution by solvent
extraction, stripping with sulfuric acid, and
electrowinning. Other metals are further treated for
separation. Additional reagent recovery equipment is
necessary.
These are two basic routes for metal recovery from
hydroxide sludges that have been looked into
extensively by various parties. Metal recoveries will
become practically feasible if the aim is to provide pure
solutions with a minimum number of unit operations and
unit processes. A cost study was developed based on
sulfuric acid leach of metal hydroxide sludges with the
use of solvent extraction for solution concentration and
electrolysis for metal recovery.
Generally, there are three types of liquid wastes in a
iterated
Mi
\
_ Regenerated
— *• Acid
^ t
Uach pH 1 0
I .
r~
fn" Adjustment
i I"
pH Adjustment
Filtration J—»- Solid. Fe(OH),, CaSO.
*
forCu
t
Electrolysis for
Cu
Cu
Regenerated
Acid
Cd Sponge
1
Electrolysis
1 for Cd
Solvent Extraction
for Ml
i
ElAfttrnlyklB for
NI
NI
\ i~~
F Cementation
| Filtration
1
J Electrolysis for
1 zr
Fig. 5—Mixed Metal Hydroxide Sludge Recovery Process.
Table 2
Sludge Value Calculations - 3% Solids
3% Solids = gms/liter = 0.26
#/gallon
0.26#/gallon * 5%Cux$i.25/#
x 50/0 Ni x $3.0/#
* 10% Zn x $0.37/#
x 5% Cd x $3.50/#
= 0.016
= 0.039
= 0.010
= 0.046
0.111$/gallon
Sludge Sludge Wt. *
Vol. Pounds (S. T.)
Gallons @ 8.62 #/Gal.
1,000 8,620 (4.31)
5,000 43,100 (21.55)
10,000 86,200 (43.10)
25,000 215,500 (107.75)
50,000 431,000(215.50)
100,000 862,000 (431.00)
*0.26# Solids/gallon
= 0.26# solid to 1 gallon
= 0.26 + 8.36
= 8.62 ft/gallon
So//cte
Pounds (S.T.)
260 (0.13)
1,300 (0.65)
2,600(1.30)
6,500 (3.25)
13,000 (6.50)
26,000 (13.0)
water
Con-
tained
Value
111
555
1,110
2.775
5,550
11,100
78
-------
Table 3
Sludge Value Calculation - 20% Solids
20% Solids
= 250 gms/liter
2.13 #/gallon x
" X
" X
" X
Sludge
Vol.
Gallons
1,000
5,000
10,000
25,000
50,000
*2.13 #/gallon
= 2.13
= 2.13
= 10.5
Sludge Wt. *
Pounds (S. T.)
@ 10.5 #/Ga/.
10,500 (5.25)
52,500 (26.25)
105,000 (52.50)
262,500(131.25)
525,000 (262.50)
solids
# solid to 1 gallon
+ 8.36
ft/gallon
= 213 #/gallon
5%Cu x $1.25X# = 0.133
5% Ni x $3.00/# = 0.320
10% Zn x $0.37/# = 0.079
5% Cd x $3.50/# = 0.373
0.905$/gallon
Con-
Solids tained
Pounds (S. T.) Value ($)
2,130 (1.07)
10,650(5.33)
21,300(10.65)
53,250 (26.63)
106,500 (53.25)
water
905
4,525
9,050
22,625
45,250
Table 4
Total Contained Values for 10,000 Gallons of
Sludge/Day
@ 3% solids
Total sludge weight = 43.1 S.T.
Total contained value = $1,110
304 working days = $337,440/year
@ 20% solids
Total sludge weight = 50.5 S.T.
Total contained value = $7,220
304 working days = $2,194,880/year
Above values calculated with commodity metal market prices.
Table 5
Fixed Capital Costs for a Leach - Solvent Extraction -
Electrowinning Complex
$/Annual Ton Cu
Leaching Facility
SX Plant
Electrowinning Plant
Melting and Casting
7975
90.7
635.0
408.2
45.4
1,179
7980'
182.5
1227.3
821.1
146.9
2,377
Solids @ 20% witn 5% Cu on a dry basis
10,000 gallons/day sludge with 21,300 #solids/day
Annual capacity=
21,300 # solids x 5.0% Cu x 304 days x ton = 162 tons Cu
day 2.000 Ib
'15% inflation with 1975 as the base year.
plating shop: (1) rinse waters, (2) spent baths, and (3)
spills.
Spent baths are collected separately. They require only
cyanide destruction and thus become concentrated metal
solutions. Rinse waters and spills are treated
conventionally for heavy metal precipitation. This
presorting provides two distinct feed materials: (1) a
concentrated solution, and (2) a hydroxide sludge. The
leach solution from hydroxide sludge leaching with
sulfuric acid is mixed with the spent bath solution for
metal extraction. A generalized scheme is shown in
Figure 5. The sludge was originally at 3 - 4% in solids.
Cost analysis has compared the sludge at 3% solids with
one at 20% solids in terms of metal values contained in
the product, tables 2, 3, and 4. Fixed capital costs are
provided in Table 5.
Annual direct operating costs for 1 ton of copper for
the leach - SX - electro win complex were $1,272 per
annual ton of copper in 1975. At 15% inflation rate, these
will be $2,560 per annual ton of copper in 1980.
For 162 tons of Cu, annual direct operating
cost = $414,720.
Annual indirect operating costs for 1 ton of copper for
the leach -SX- electro win complex were $544 in 1975. At
15% inflation rate, these will be $1,094 in 1980.
For 162 tons of Cu, annual indirect operating
cost = $177,228
Total cost of producing copper from hydroxide
sludges is then 2,560 + 1,094 = $3,654 per ton which is
about $1.80 per pound, or a total of $583,200 per year.
Indirect operating costs include costs for borrowing
capital, depreciation, and income taxes, etc.
Total revenue from 162 tons of copper @ $1.00 per
pound is $324,000 per year as compared to $583,200 in
cost to produce it. There is a net loss in the operation
unless the credits from nickel, zinc, and cadmium are
added to the revenues. Although their recovery will add
to the direct and indirect operating costs, and working
capital, much of this cost will have already been applied
to copper.
This credit consideration will need to be examined
closely before attempting to authorize or not authorize
capital spending. Preliminary studies show that the
operation of metal recovery from the hydroxide sludges
would be profitable after considering the credits to be
realized. There certainly is an economic incentive for
treatment of the hydroxide sludges. The treatment would
then not be limited to the electroplating industry alone,
but would look into treating nonferrous wastes from
other industries too.
BIBLIOGRAPHY
Hayward, C. R., An Outline of Metallurgical Practice,
D. Van Nostrand Company, Inc., Princeton, N.J. 3rd
Ed., 1961.
Mehta, A., "Research Investigation of New Techniques
for Control of Smelter Arsenic Flue Dust Wastes",
Final Report, EPA R-804595010, April, 1979.
Bureau of Mines, United States Department of Interior,
Minerals in the U.S. Economy, Ten Years Supply
Demand Profiles for Mineral and Fuel Commodities.
Pehlke, R. D., Unit Processes of Extractive Metallurgy,
American Elsevier Company, New York, N.Y., 1973.
Bray, J. L., Nonferrous Production Metallurgy,
John Wiley and Sons, Inc., New York, N.Y., 1941.
Biswas, A. K. and Davenport, W. G., Extractive
Metallurgy of Copper, Pergamon Press, Elmsford,
N.Y., 1976.
Ranchers, "Ranchers Recovers Bluebird Oxide Copper
by Solvent Extraction," World Mining, Vol. 22, No. 4,
63:1969.
79
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Solvent Recovery For the Smaller Company
C. Kenneth Claunch*
INTRODUCTION
Due to new environmental laws and the increase in
crude oil prices, as a result of OPEC, the cost of all
organics, including solvents, has risen dramatically in
recent years. For the smaller company, this has been
particularly burdensome, since it is very difficult, as is
usual with a smaller company, to pass on these
remarkable costs.
Referring to the table below, it is a fact that in 1973
(prior to OPEC), typical solvent, in this case acetone, cost
(net) about 30c a gallon, composed of its purchase cost
and disposal cost. The latter in those days was a credit (!).
These costs have risen to the range of $3.00 a gallon
today, and it appears to be rapidly going to $5.00 a
gallon.
COST OF SOLVENT
(This Example: Acetone, S per Gallon)
1973 1976 1980 (Feb) Projected
Purchase
Disposal
Net Cost
.35 1.35
(.05) (.20)
.30 1.05
2.31
.66
2.97
3.15-4.20
.66 - 2.00
3.71 - 6.20
We are, thus approaching the day when the use of
industrial (organic) solvents is analogous to the use of
lobster at home - 'A thing of the past; too expensive!'
Solvent recovery processes - usually an adaptation of
distillation - have been utilized for quite some time. But
these processes have been for high volume treatment of
contaminated solvents. Basically, these tend toward the
1,000 gallon/hour range and often involve fractional
distillation.
Experience and processes for treatment of smaller
volumes of solvent contamination have been lacking.
With price increases and the enormous disposal
responsibilities facing us, recovery of solvent, for the
small volume user, needed attention. This paper outlines
proven, successful experiences and processes for smaller
scale (one drum per week to one drum per hour) solvent
recovery systems. These processes are very economical,
often having returns on investment, ROIs, in the 100 to
400 percent range.
During this presentation we will show you a way not
only to save large numbers of dollars in avoiding the
purchase of new solvents, but of even greater importance,
a method to comply with the new environmental laws on
hazardous chemicals on which the EPA is currently
issuing regulations. Solvents contaminated with paint,
grease, and other miscellaneous materials are identified
specifically by the EPA as "hazardous materials"* and
must be handled according to the new strict laws. The
1976 Resource Conservation and Recovery Act makes us
liable for these materials cradle-to-grave on, apparently,
a "strict liability" basis (i.e., if there is a violation by
others, the generator is responsible 'no matter what he
did right'!). What makes this situation even more unique
is that there are fines (to 25,000/day) and a personal
CRIMINAL liability!
Generally, organic liquid wastes fall into four
categories. One, oil sludges, represent about one-fourth
of the total in this country and are not particularly
noxious. There is the category generally called pasty
miscellaneous organic chemicals, and these cover about
one-third of organic liquid wastes. These materials are
by-products from organic synthesis, still bottoms, and
the like. They are usually viscous, high boilers, and often
very toxic (e.g. Love Canal contained distillation sludge
from pesticide manufacture). The third major category,
industrial solvents, also represents about one-third-plus
of the wastes. We will be talking about these throughout
this presentation. The source of contaminated industrial
solvents is many, many users - small companies like
yourselves, and generally used for wash-up operations.
Chlorinated and nonhalogenated solvents are involved.
They are very expensive. Their costs are presently
ranging from a rare $2.00 to as high as $12.00 per gallon.
The fourth category of organic liquid waste is of quite
well known materials. These are pesticides, rodenticides,
PCBs, and other particularly noxious and/or well
publicized** toxic chemicals. This fourth category
represents only 1 to 2 percent of the U.S. organic wastes
total.
SOLVENT RECOVERY WITH STANDARD STILL
(Nominal rate: 4 drums j shift)
How it works:
This batch type solvent recovery technology is the not-
new method of differential distillation combined with
recently developed techniques to allow the controllable
boiling and removal of valuable solvents from residues
that can range in viscosity up to 10,000 CPS.
Basically the still operates by heating contaminated
solvents to form vapors of pure solvents, condensing
*C. Kenneth Claunch
Finish Engineering Company, Inc.
921 Greengarden Rd., Erie, Pennsylvania 16501
80
Federal Register, Vol. 43, No. 243, p. 58957, 250.14 (a).
* Publicity often increases the perceived toxicity of a chemical, which,
in essence, makes it more toxic from a regulatory standpoint!
-------
them outside the still to collect a clear, purified solvent
mixture. The difficult aspect of this operation is that the
residue in the still is becoming more and more viscous.
The gist of the technology of this still is (1) to have
instruments that can readily alert the operator when the
viscosity or thickness of the residue in the still is
beginning to increase. In lay terms, we want to continue
to boil the material until the residue is about the
consistency of catsup and not go as far as the consistency
of peanut butter.
The viscosity instrument is quite simple and non-
plugging (very, very important when dealing with such
thick medias). When the material is too thick, shut-down
is automatic.
It is also essential (2) to have a means of eliminating
caking on the heated wall. A patent pending device that,
in essence, scrapes the wall with a non-wearing, non-
sparking razor-blade-like knife every five seconds is
utilized. Heat transfer coefficients of over 200 Btu/ hr-ft3 -
0 F can be maintained even to viscosities of over 5,000
centipoise.
Figure 1 shows a flow diagram of the still. (A) is the
boiling chamber into which the contaminated solvent is
pumped. Heat is supplied from a boiler at (E) to the steam
jacket at (B). The internal scraper is indicated by (D). The
vapors of solvent(s) exit the unit at the top and are
condensed by an air cooled or water cooled condenser (C)
filling the clean solvent drum to the left. The highly
reliable controls at (E) tell the operator that his viscosity
is satisfactory.
In actual operation the operator does the following:
Into an empty still he pumps two 55-gallon drums of
contaminated solvent. He turns on the still and then can
leave the area. The unit will boil and condense one drum
and shut itself off. When the operator returns, he pumps
in another drum of contaminated solvent and places an
empty clean drum under the condenser. Again, he turns
on the still and leaves the area. Typically, this will
continue until 10 drums have been added and nine drums
of clean solvent(s) recovered, a 90% recovery. The
remaining one drum residue is drained out the bottom of
the still into a sludge drum. This sludge can be disposed of
by EPA approved methods (e.g. certain landfills) or by
processing it in a manner to be discussed later in this
presentation.
Economics
The return on investment from this process is often
startling. If a company has JUST one drum per day of
contaminated solvent, the return on investment (ROI)
Figure 1—Flow Diagram, Standard Still.
81
-------
will be approximately 100%, a one year payout! It is very
common that many users have ROIs of 200-400%. One
user in Indiana has been operating his still for 3 years at
28 gallons/hour, 24 hours/day, 5 days/week. He
processes 14,300 gallons/month with a yield of 93%.
Using a minimal cost of this ketone of $2.00+ per gallon,
his savings currently amount to approximately 1/3 of a
million dollars jjer year, for a low 5-figure investment.
Fig. 2-Recovery Still.
Another example is a still at GTE-Sylvania in
Tennessee. See Figure 2. This still is nearly 100%
automatic, being fed from an underground tank and the
clear recovered solvent flows by gravity to another
underground tank—labor input is nominal. The engineer
in charge is quoted as follows:
"Our still extends the life of our acetone tremendously.
With the exception of losses through process evaporation
and sludge collection, we are able to use the same acetone
for a minimum of six cycles. This solvent life extensions
has decreased our cost per gallon from $ 1.45 to about 30c
which includes our cost of operating the reclaimer.
In addition to this bulk reclaiming operation, we are
enjoying further savings by reclaiming thousands of
gallons of drummed acetone and alcohol collected during
prior years. By reclaiming we return it to the drum and
use it over and over.
"The combination of savings, which in total exceed
$50,000 a year, the peace of mind from virtual
independence from outside solvent availability, and our
compliance with tough new hazardous waste disposal
standards makes in-house solvent reclaiming a great
addition to our operation."
SOLVENT RECOVERY WITH STEAM/IN SITU
(IN DRUM) DISTILLATION
(Nominal Rate: one drum/shift)
How it works:
This process works by distilling the solvents directly
out of the drum to a condenser for collection. Leaving the
material in its drum is a real advantage since many drums
cannot be pumped out completely (in some cases, not at
all). Further, if the goal is to remove all solvents (as in the
case in this process), the final non-volatile material will be
a rock or sand-like 'mess' - best left in a disposable drum
rather than in processing equipment causing, perhaps,
costly clean-up.
The distilling is done by a special method (patent
pending) of steam injection safely into the contaminated
liquid or sludge in the drum. As a result, the condensate is
both water and solvent (in most cases the solvent is
immiscible in water, therefore, easily separated. If the
solvent is miscible with water—very few are—this
process is not applicable).
The drum of material can, of course, be the viscous
residue from the previously discussed (still) operation, or
in the case of a very small usage, from the user's process.
This is to say, if a company only has one drum per day or
one drum per week, this process would be economical
and recommended.
The operating sequence is as follows: The drum is
placed inside a special insulated cabinet. The band steam
heater (part of the cabinet) is closed around the drum. A
very special (but inexpensive) steam sparger line is
inserted into the drum through the smaller bung opening
in the top of the drum and connected by a flexible line to
the controlled steam line. The larger (2") bung opening is
connected by a flexible line that goes to the condenser. By
simple temperature control the following occurs: The
liquid is heated to the boiling temperature by the steam
jacket, so called "dry heat." This temperature is the
azeotropic boiling point of the solvent-water mixture
that will exist inside the drum (due to some water
condensation in the drum). For example, if the solvent
was toluene (normal boiling point of 231° F) the
azeotropic boiling temperature is 185° F. It will always be
less than the boiling point of water, 212° F - no matter
what solvent is in the drum. This is a real advantage,
allowing the recovery of even high boilers, 300-400° F
range, with just steam.
When at this azeotropic boiling point, the steam to the
sparger is activated and the steam enters the liquid in the
drum by the special sparger. Two phenomena occur: (1)
part of the steam strips the solvent into vapor which exits
the drum; and (2) of critical importance, the steam, if
properly sparged into the liquid, will cause heat transfer
into the whole mass rather than just to localized areas of
the sludge causing caking and slowing of the heat
transference which would nullify the entire process.
This is the gist of this technology. To explain: The
contaminated solvent will start, perhaps, as fluid and
become thicker and thicker until it reaches an infinite
viscosity (!), i.e. it ends up as a solid. Thus, one would ask
how the heat is effectively transferred to this extremely
thick material towards the end of the process. The answer
is that the water, condensed due to earlier heat transfer
(discussed above), is the heat transfer media to the final
solid contamination. In a typical, properly operated
situation, there will be about 10 gallons of water in the
drum at the end of the solvent stripping.
The steam and solvent vapor enter a condenser, similar
to the condenser on the still discussed earlier, and
condenses. A simple two-layer separation tank removes
the condensed water from the condensed liquid solvent.
At the end of the operation the temperature will
rapidly rise from the boiling temperature up to 212° F,
the boiling point of water, indicating there is no solvent
82
-------
Fig. 3-Solld Residue.
left. At this point, the steam to the sparger stops. The dry
heat (jacket) continues until the water is boiled away.
After this operation, the drum is removed from the
cabinet. The top of the drum is cut off. The toxic, non-
volatile contaminants, often looking like rocks or sand,
that remain are pulled out of the drum with the
disposable steam sparger. This solid material can be
disposed of by safe, legal methods, usually directly to an
approved landfill.
Figure 3 shows the solid residue from this process. This
is a dramatic picture, in that it represents the solid, non-
volatile toxic materials that originally (before both
processes described herein) were contaminated with
about 800 gallons of solvent! That is, the processes
yielded about 770 gallons of pure solvents and this 'rock';
good from a hazardous wastes and an economic
standpoint. The disposable sparger pipe can be seen
sticking out of the top of this 'rock'. The bottom of the
rock, you will note, conforms to the inside of a 55-gallon
drum, i.e. the bottom of the rock is 22" in diameter (to
give the reader a dimensional reference).
Economics:
The economics are very similar to the still discussed
above. The return on investment (ROI) ranges from 75 to
300%. Investment is just at the 5-figure range.
Labor input required is essentially nominal since the
operation is automatic once the drum is put into the unit.
CONCLUSION
The 1976 Resource Conservation and Recovery Act
states:
"(c) Materials - The Congress finds with respect to
materials, that—
"(1) millions of tons of recoverably material
which could be used are needlessly buried
each year;
"(2) methods are available to separate usable
materials from solid waste; and
"(3) the recovery and conservation of such
materials can reduce the dependence of the
United States on foreign resources and
reduce the deficit in its balance of
payments."
We have revealed in this presentation high viscosity
distillation processes that have the capability to recover
materials just as Congress dictated above. Distillation is
rarely thought of as a waste treatment process. But, in
fact, it is one of the best, yielding recyclable materials (as
solvents, discussed herein) or clean liquid condensates
that can be incinerated without resultant toxic fly-ash-
like solids in the effluent gas. Distillation energy cost is
minimal, only about 2c to 3c per gallon, relative to the
high value of the recovered material and/or the high
value of avoiding hazardous solvents.
The specific processes discussed for industrial organics
(solvents, etc.) in drum quantities allow economical
recovery and, also, waste elimination for even the
smallest company.
83
-------
VOC Incineration and Heat Recovery -
Systems and Economics
Roy M. Radanof*
INTRODUCTION
Volatile Organic Compounds (VOC) from
metal finishing operations must be controlled to help
preserve our nation's clean air standards. While many
metal finishers have converted to formulas with reduced
or no VOC, many others have chosen add-on
incineration as a means of VOC control.
Two types of incinerators are available for air
pollution control, thermal and catalytic units. Thermal
incinerators consist of a volumetric enclosure through
which solvent laden discharge air mixture from curing
ovens passes. A fuel source, usually natural gas or No. 2
fuel oil, is used to raise the temperature of the air stream
to 1200 to 1400° F. At this temperature, most of the VOC
(solvent) is destroyed by.oxidation. The final emissions
contain CO2, water vapor, N:, air and traces of the
original solvent.
The solvent destruction efficiency of thermal
incinerators is dependent upon the retention time of the
solvent at the control temperature, the control
temperature itself, and the degree of turbulence within
the incinerator. VOC destruction efficiencies of greater
than 90 percent are common with these units.
Thermal incinerators are easily controlled and usually
have built-in bypass dampers around the primary heat
recovery unit to facilitate process variations.
Catalytic incinerators are similar to thermal
incinerators, except that a catalyst has been added to
enable the solvents to oxidize at a significantly lower
temperature than in thermal units. Catalytic incinerators^
have a preheat section at the inlet in which fuel is added to
raise the waste air temperature to the minimum required
for the oxidation reaction to take place on the catalyst
surface. As the solvents oxidize, additional heat is
released, thus promoting the destruction of solvents. The
final temperature achieved in the oxidation affects the
destruction efficiency of the unit in addition to life of the
catalyst. Catalytic incinerators can usually achieve the
same destruction efficiencies as thermal units; however,
they are more limited in their applications to process
conditions.
The addition of either a thermal or catalytic
incinerator for the destruction of VOC will usually
accomplish the environmental objective of air pollution
control; however, if proper engineering analyses of the
total plant conditions are not conducted, the plant can be
severely penalized with excessive operating fuel costs. On
the other hand, a thorough and comprehensive analysis
of the total plant can result, in many cases, in the
incinerators being operated at no energy penalty or can
even achieve a net energy savings for the plant as
•Roy M. Radanof, PE
CENTEC Corporation
compared to energy requirements before the incinerator
was installed.
This paper highlights fuel requirements, heat recovery
options and economics of operating both types of
incinerators. The energy benefits that are possible will
provide economic incentives for plants to install
incinerators as a means of achieving the environmental
objective of air pollution control. The DOE Technology
Applications Manual entitled, "The Coating Industry:
Energy Savings with Volatile Organic Compound
Emission Control," TID-28706, published in 1979,
provides in-depth analyses of the concepts highlighted in
this paper.
WHICH TO SELECT: THERMAL OR CATALYTIC
INCINERATION
One of the most common questions asked when
implementing an add-on incinerator is: "Which is better,
thermal or catalytic?" Unfortunately, the answer is: "It
depends on the site conditions."
The environmental objective is the same for each—to
achieve a high solvent destruction efficiency that
complies with regulatory standards. Without studying
the overall plant conditions, the "best" choice cannot be
determined. A brief review of the advantages and
disadvantages of both types of systems will highlight
some of the considerations.
ADVANTAGES OF THERMAL INCINERATION
Thermal incinerators can usually achieve solvent
destruction efficiencies greater than 90 percent.
Efficiencies as high as 97 to 98 percent are obtainable on
newer units. Thermal incinerators can be used with a
wide range of applications. Particulates and resins
usually are destroyed with the solvents. Thermal
incinerators are insensitive to solvent concentration
variations. Because of their high operating temperatures,
there is a high heat recovery potential. Thermal
incinerators can operate with solvent concentrations up
to 50 percent of the Lower Explosive Limit (LEL),
providing the proper instrumentation and controls are
employed to comply with the National Fire Protection
Association codes and standards. Fuels consist of natural
gas, oil, or propane.
DISADVANTAGES OF THERMAL INCIN-
ERATORS
Thermal incinerators have a potentially high operating
cost primarily due to energy consumption. A large
volumetric air flow rate is heated from temperatures
typically at 200-300° F to 1200-1400° F. Without heat
recovery, the exhaust gases carry away millions of Btu
which are lost to the atmosphere. Since retention time is
important for destruction efficiency, thermal
incinerators are large, sometimes posing siting problems.
There is no solvent recovery with thermal incinerators;
84
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however, the solvents usually contribute a substantial
fuel value to the operation of the incinerator. The heat
provided by the solvent during oxidation reduces the
incinerator fuel requirement by an equivalent amount of
heat. This is an important concept in estimating the
energy requirements for incinerator operation.
ADVANTAGES OF CATALYTIC INCINERATION
Like thermal incinerators, catalytic incinerators can
usually achieve the same solvent destruction efficiencies.
Catalytic units can handle multisolvent mixtures,
providing these mixtures were considered during the
design and specification of the catalyst materials.
Without considering heat recovery, catalytic incinerators
have a significantly lower operating cost in terms of fuel
expense than thermal incinerators. In the preheat section
of a catalytic unit, waste air is heated from 200-300° F to
550-900° F. This temperature rise is lower than that
required for a thermal unit performing the same duty.
The final exhaust temperatures from catalytic units
usually range from 900 to 1200° F. This exhaust
temperature has high heat recovery potentials for use
elsewhere in the plant or for reducing the cost of
incinerator operation as will be illustrated shortly.
Retention time is not so important with catalytic units as
with thermal units; therefore, the units are usually
smaller than thermal units for equivalent air flows.
The temperatures referenced in the discussion so far
are for a wide variety of applications. Many vendors have
catalyst materials that operate effectively at temperatures
significantly different from those referenced and can have
equally significant effects on energy consumption. This is
another factor for consideration in selecting the best type
of incinerator for a site specific condition.
DISADVANTAGES OF CATALYTIC INCINERA-
TORS
Catalysts are limited to the number of applications in
processes since some waste air streams may contain
catalyst poisons such as phosphorous, bismuth, lead,
arsenic, antimony, mercury, iron oxide, tin, silicon and
others. These poisons cause irreversible reduction of the
catalyst activity at a rate dependent on concentration and
temperature. Excessively high temperatures also will
deactivate the catalyst in a shorter period than its normal
life. While higher temperatures will provide greater
destruction efficiency, catalyst life will be decreased and,
consequently, maintenance costs will rise. Particulates
and resins must periodically be cleaned from catalysts to
reduce plugging and to maximize available surface area
for reactivity. Like thermal incinerators, solvents are
destroyed and are unavailable for recovery. Catalytic
incinerators are more limited in fuel options than are
thermal incinerators. Usually, natural gas is used as the
fuel source. Oils containing sulfur can influence the
catalyst activity by placing a reversible surface coating on
the active area of the catalyst. Catalysts are expensive to
replace. Some plants considering using catalytic
incineration might have to precondition their waste air
stream to prevent problems with the catalyst.
REDUCTIONS OF INCINERATOR FUEL CON-
SUMPTION
Several years ago, when energy was less expensive and
more plentiful, heat recovery was not normally included
with incinerators; and plants purchased equipment at
minimum capital expenditure. Today, plants can justify
additional capital outlays for reducing energy
consumption by lowering air flows to increase solvent
concentration, and by including heat recovery options.
LOWER AIR FLOW TO INCREASE SOLVENT
CONCENTRATION
The NFPA, Code 86-A, "Ovens and Furnaces,"
describes conditions under which solvent concentrations
must be kept below 25 percent of the LEL and those in
which concentrations may approach 50 percent of the
LEL. This paper addresses the conditions below 25
percent of the LEL since this is the area where the
majority of the metal finishers presently operate.
The NFPA provides two methods of calculating the
solvent concentration in terms of percent of the LEL.
One method referred to as the "general method," is based
on using 10,000 cubic feet of dilution air at 70° Fforevery
gallon of solvent evaporated to achieve a solvent
concentration of 25 percent of the LEL. This provides a
convenient calculation for approximation, but it is
usually conservative in specifying needed dilution air
flows. Since the fuel input to the incinerator, as well as the
oven, is determined by the energy required to heat the air
flow rate to a specified temperature, any reduction in the
air flow will lower the fuel requirement. This, then,
becomes an objective for energy reduction and can be
accomplished by following the second NFPA calculation
method.
The second method allows the solvent concentration to
be determined by actual consideration of the solvent
composition and properties. It is more rigorous than the
first method, but it usually results in less dilution air
requirements.
For example, Figure 1 shows solvent removal rates at
25 percent of the LEL. If Methyl Ethyl Ketone (MEK)
were evaporated at 60 gph, then 10,000 scfm of dilution
air would be required usfng the "general method." If the
actual LEL of MEK was considered, then the required
dilution air would be approximately 45 percent lower
than using the general method. The fuel effect of this air
reduction will be seen shortly.
Typically, metal finishing operations are performed at
solvent concentrations in the 7 to 10 percent of the LEL
range with many falling as low as 1 to 2 percent of the
LEL. If these solvent concentrations were increased to 20
PROCESS
AIR FLOW 10
(THOUSANDS
OF SCFM)
10,000 SCF AIR PER GALLON OF SOLVENT
I
Bo 120 160
SOLVENT REMOVAL RATE (GPH)
Fig. 1—Solvent removal rates at 25 percent of the LEL.
85
-------
PROCESS AIR FLOW
(THOUSANDS OF SCFH)
20 40 60 80 100 120
SOLVENT REMOVAL RATE (GPH)
Fig. 2—Air flow requirements for solvent removal rates.
T,
X
X
PRIMARY S
HEAT RECOVERY
T2>
THERMAL OR
1 NC 1 NEBATOR
T,
Fig. 3—Typical primary heat recovery.
INCINERATOR NATURAL GAS
REQUIREMENT (MILLIONS OF
BTUH PER 10,000 SCFM)
THERMAL INCINERATOR
CATALYTIC INCINERATOR
200 ^ 00 600 800 1000 1200 1*<00
INLET TEMPERATURE TO INCINERATOR (°F)
Fig. 4—Energy required for thermal and catalytic incineration without heat
recovery.
to 25 percent, the reduced air heating loads would
conserve considerable fuel.
For example, Figure 2 illustrates air flow requirements
for different solvent removal rates. It is based on using
the general method of 10,000 cubic feet of dilution air per
gallon of solvent evaporated. An oven operating at 60
gph solvent removal rate and at a solvent concentration
of 10 percent of the LEL can have its air flow reduced
from 25,000 to 10,000 scfm by increasing its solvent
concentration to 25 percent of the LEL. This results in
60 percent air flow reduction.
INCREASE INLET AIR TEMPERATURE TO IN-
CINERATOR
In addition to lowering the dilution air flow, the inlet
air temperature to the incinerator can be increased
through primary heat recovery to reduce fuel
requirements. Figure 3 illustrates a typical primary heat
recovery application. The hot incinerator exhaust gases
at temperature T? are recycled to a primary heat
exchanger where they raise the oven waste air stream
from temperature Ti to T2. The exhaust gases are finally
released to the atmosphere at temperature T4 or can be
further used as a secondary heat source.
Figure 4 shows the combined effects of reduced air
flows and increased incineration and/or inlet
temperatures on fuel consumption for thermal and
catalytic units. This figure is specific to the conditions
shown below; however, it is illustrative for similar
process conditions.
The basis for Figure 4 is given below:
1. Solvent is toluene (catalytic ignition temperature is
575° F with particular catalyst considered)
2. Natural gas HHV = 1100 Btu/scf
3. Thermal incinerator operating temperature = 1400°
4. Catalytic incinerator exhaust temperature = 1000°
F
5. HHV of toluene = 4484 Btu/scf
6. 95 percent destruction efficiency of toluene
7. LEL of toluene = 14,000 ppm
8. No heat losses
9. Waste stream air from oven exhaust used as
combustion air in incinerator
First, the fuel requirements for thermal and catalytic
units can be compared for the same given process
conditions. For example, at an inlet temperature to a
thermal incinerator of 400° F and with a solvent
concentration of 15 percent of the LEL, the natural gas
requirement is 8 million Btu/hr/10,000 scfm of process
air flow. Under the same process conditions, if a catalytic
incinerator were used, the natural gas requirement would
be 2.3 million Btu/hr/10,000 scfm of process air. A 71
percent fuel reduction is experienced with the catalytic
unit as compared to the thermal unit, both operating
without heat recovery.
To illustrate the effects of reduced air flow, consider
the thermal incinerator now operating at 15 percent of
the LEL and with an inlet air temperature of 400° F. If
the air flow were reduced to achieve 25 percent of the
LEL, the natural gas requirement would decrease from 8
million to 4.4 million Btu/hr/10,000 scfm of process air
flow. Combining the reduced air flow with primary heat
recovery so that the new inlet air temperature to the
thermal incinerator is 600° F, the natural gas
requirement is further reduced to 1.5 million
Btu/hr/10,000 scfm of process air flow. Thus, a process
air flow of 20,000 scfm adjusted to the above conditions
would require 3.0 million Btu/hr of natural gas [(20,000
scfm/10,000 scfm) X 1.5 million Btu/hr] to achieve a
solvent destruction efficiency of 95 percent. The goal is to
establish the highest possible solvent concentration
allowed by NFPA standards and to achieve the
maximum possible heat recovery to minimize incinerator
fuel requirements.
There are several important considerations to keep in
mind. All VOC have an autoignition temperature where
oxidation takes place. In recuperative type shell and tube
heat exchangers, tube failure could occur if the solvent is
86
-------
allowed to reach its autoignition temperature inside the
exchanger. It is, therefore, a good practice to limit the
waste air preheating to a maximum temperature of 100°
F below the solvent's autoignition temperature.
In regenerative type heat exchangers, such as stone
beds and ceramic wheels, autoignition is not usually a
problem, and higher preheat temperatures can be
achieved.
Another consideration is that for every percent of the
LEL of the solvent present, a temperature rise of
approximately 27.5° F is experienced for 100 percent
destruction efficiency of the solvent. All incinerators
have a maximum design operating temperature which
should not be exceeded; otherwise, equipment damage
might occur. If this temperature were 1500° F, then care
must be taken in sizing the primary heat recovery unit so
that the preheat temperature, when combined with the
temperature rise from the oxidation of the solvent, will
not exceed 1500° F. For example, if the solvent
concentration were 15 percent of the LEL and the preheat
temperature were 800° F, then the resulting operating
temperature would be approximately 1488° F which is
below the maximum design temperature.
The same considerations apply to catalytic units.
Figure 5 shows the combined effect of inlet and outlet
temperatures of catalysts for 90 percent solvent
destruction efficiency. This figure is for one particular
solvent/catalyst combination; however, it is
representative for other combinations if the temperature
were adjusted.
The upper curve is the exhaust temperature from the
catalyst. From 0 to 15 percent of the LEL, the curve is flat
at 1000° F. This is the minimum exhaust temperature
that will result in 90 percent destruction for the particular
solvent.
The lower curve represents the required inlet
temperature to the catalyst at the given solvent
conditions that will result in the required outlet
1»IOO
1300
1200
u.
°_, noo
UJ
= 1000
<
a:
Ul
I 900
uj
H
800
700
600
500
PROCESS
MINIMUM EXIT TEMPERATURE
FOR 90* CONVERSION
—MINIMUM CATALYST •
ACTIVATION TEMPERATURE
I I
TYPICAL REQUIRED
INLET TEMPERATURES
TO CATALYST (T
c.) -
I
Fig
0 5 10 15 20 25 30
SOLVENT CONCENTRATION (PERCENT OF LEL)
5—Catalyst temperatures at 90 percent solvent destruction efficiency.
temperature. For example, in the solvent concentration
range of 0 to 15 percent of the LEL, it will be necessary to
add supplemental fuel to the incinerator preheat section
or to utilize primary heat recovery to achieve the
minimum inlet temperature shown. If the solvent
concentration is at 10 percent of the LEL, then the waste
air stream will have to be heated to about 700° F before
entering the catalyst. The fuel value of the solvent will
result in the final temperature rise to the required 1000°
F.
Above 15 percent of the LEL, the effect is different.
Since the catalyst has a minimum reactivity temperature
that must be achieved to start the oxidation process, it is
not possible to enter the catalyst below this activation
temperature. In Figure 5, the reactivity temperature is
575° F. If the solvent concentration is greater than 15
percent of the LEL, then the resulting exhaust
temperature will exceed the 1000° F and will seek a level
depending on the exact amount of solvent present. For
example, if the solvent concentration were at 20 percent
of the LEL, then the minimum reactivity temperature
would be achieved either by primary heat recovery or
supplemental fuel. The solvent's heating value and
quantity would increase the exhaust temperature to
about 1130° F. At this temperature, the destruction
efficiency is improved; however, it is a more severe
condition for the catalyst.
In quantifying the amount of primary heat recovery to
be used, the most common practice is to use the term
"percent heat recovery." Percent heat recovery is a ratio
of the amount of heat recovered to the amount of heat
that is available for recovery. Commonly, it is expressed
as a temperature ratio as shown in Figure 6, since the gas
flows to and from the incinerator are assumed to be equal
through the heat exchanger if external combustion air is
not added to the incinerator. There is a more rigorous
definition of percent heat recovery based on enthalpies;
however, the temperature ratio will be sufficient for most
purposes.
Figure 7, shows the limits of primary heat recovery for
thermal incinerators. A similar figure can be constructed
for catalytic incinerators. Figure 7, is based on the
following conditions:
1. Incinerator exhaust temperature = 1400° F
2. Solvent is toluene having HHV = 4484 Btu/scf and
LEL = 14,000 ppm
3. Shell and tube heat exchanger limit includes a 100°
F safety factor below autoignition temperature of toluene
COLD STREAM
FROM OVEN (T- }
HOT STREAM TO
INCINEftATOR (T )
INCINERATOR (T )
Fig. 6—Percent Heat Recovery.
- T
- T,
87
-------
MAXIMUM USABLE
PRIMARY
HEAT RECOVERY
(PERCENT)
90
80
70
60
50
1*0
30
20
10
5* OF LEL
SHELL AND TUBE
HEAT EXCHANGER
LIMIT
200 ^00 600 800 1000 1200
OVEN EXHAUST TEMPERATURE (°F)
Fig. 7—Limits of Primary Heat Recovery for Thermal Incinerators.
4. 100 percent destruction efficiency of toluene
5. Autoignition temperature of toluene = 997° F
6. No heat losses
7. Waste stream air from oven exhaust used as
combustion air in incinerator
So as not to encounter autoignition damage in the
primary heat exchanger, shell and tube units should be
applied only to the conditions represented by the shaded
area. Regenerative units not susceptible to autoignition
damage can be operated in the shaded or unshaded areas.
For example, an oven that exhausts gases at 600° F
and at five percent of the LEL for toluene will allow a
maximum usable primary heat recovery of 82 percent for
those heat exchangers not susceptible to autoignition
damage. Because the temperature limitation is 897° Ffor
shell and tube heat exchangers with toluene, the
maximum heat recovery achievable at this solvent
concentration would be only 36 percent to prevent
autoignition damage. At five percent of the LEL toluene
concentration and with maximum usable heat recovery
for shell and tube exchangers, the gases would leave the
exchanger at 897° F (as read at the intersection of the
limit curve with the horizontal axis), and auxiliary fuel
would be required to raise the temperature from 897° F
to 1250° F (intersection of 5 percent of LEL curve with
horizontal axis). The fuel value of the toluene would
provide the heat necessary in going from 1250° F to
1400° F. If a heat exchanger could operate with 82
percent heat recovery, the gases would exit at
approximately 1250° F and auxiliary fuel flow would be
negligible.
It is important when purchasing a primary heat
recovery unit to know that it is possible to use the level of
heat that the equipment is capable of recovering.
SECONDARY HEAT RECOVERY
Secondary heat recovery is the utilization of the heat in
the incinerator exhaust gases for any purpose other than
WASTE HEAT BOILER'
PROCESS STEAM
Fig. 8—Secondary heat recovery with a waste heat boiler.
Fig. 9—Secondary heat recovery with direct gas recirculation.
OUTS IDE
Al R
OVEN
<
<;
PREHEATED AIR |
SECONDARY USER
Fig. 10—Secondary heat recovery with indirect heating.
preheating the inlet air to the incinerator (primary heat
recovery). Figures 8, 9, and 10 illustrate three common
applications of secondary heat recovery.
Figure 8 shows a waste heat boiler that is driven by the
hot exhaust gases from a thermal incinerator. Low
pressure process steam is generated for utilization
elsewhere in the plant for process or building heating.
Figure 11 is based on generating 40 psig saturated
steam and shows steam capacities and fuel savings using
waste heat boilers. The exhaust from the waste heat
boiler is set at 450° F and an 85 percent boiler efficiency is
assumed. Feedwater is set at 200° F, and natural gas
having a HHV of 1100 Btu/scf is used as the energy
source for comparative fuel savings to a package boiler.
For example, a waste heat boiler operating with an
inlet temperature of 1000° F with 10,000 scfm and an
exhaust temperature of 450° F will generate 6,400
pounds/ hour of 40 psig saturated steam. This will save an
equivalent of 8 million Btu/hr of natural gas inapackage
boiler to generate the same quantity of steam.
Figure 9 shows the direct mixing of recirculated
exhaust gases with fresh outside air going to the oven.
The preheating of the oven supply air significantly
reduces the fuel requirement for the oven. Care should be
used in operating this type of system to assure that the
solvent concentration in the oven does not creep up due
to a malfunction of the incinerator in destroying the
solvents.
The indirect heating of oven supply air, shown in
Figure 10, prevents recirculating any solvent vapors by
88
-------
I MOO
12,000
10,000
STEAM GENERATED 8'000
PER 10,000 SCFH
PROCESS AIR FLOW
(LB/HR) 6,000
4,000
2,000
' NATURAL GAS
SAVINGS
(MILLIONS OF BTUH)
500 700 900 1100 1300 1500
EXHAUST GAS TEMPERATURE ENTERING WASTE HEAT BOILER (°F)
Fig. 11—Steam capacities and fuel savings of waste heat boilers.
employing an air-to-air heat exchanger with separate air
paths.
A "net energy savings" for the plant is only possible
using secondary heat recovery. A net energy savings is
accomplished by putting the heat released from the
oxidation of the solvents to work. Many solvents have
heating values that are 4 to 5 times greater than those of
natural gas. If suitable heat sinks are available to utilize
this heat, then the economics of the heat recovery options
should be explored to determine the value of investments.
Figure 12 illustrates both the energy required and
recoverable using thermal incinerators with secondary
heat recovery. A similar figure can be developed for
catalytic units. Figure 12 is based on the following
assumptions:
1. Thermal incinerator operating at 1400° F
2. No primary heat recovery - secondary recovery only
with waste heat boiler
3. 85 percent boiler efficiency assumed
4. Solvent is toluene (HHV = 4484 Btu/scf)
5. Fuel is natural gas (HHV = 1100 Btu/scf)
6. Waste stream air from oven exhaust used as
combustion air in incinerator
For example, if the inlet temperature to a thermal
incinerator were 500° F, the natural gas requirement of
the incinerator is 6.6 million Btu/hr/10,000 scfm process
air flow for a solvent concentration of 15 percent of the
LEL of toluene (See point W). At a waste heat boiler
exhaust temperature of 500° F, 10.6 million
Btu/hr/10,000 scfm process air flow (point X) will be
transferred for the production of steam. This amount of
energy being transferred would save 12.2 million
Btu/hr/10,000 scfm process air flow of fuel (point Y).
The plant achieves a net energy savings of 5.6 million
Btu/hr/10,000 scfm process air flow (12.2 - 6.6 million
Btu/hr) if a use for 10.6 million Btu/hr/10,000 scfm
process air flow could be found. The waste heat boiler
would save 6.6 million Btu/hrlO,000 scfm process air
flow (the same energy as consumed in the incinerator) if
the secondary heat recovery unit exhausted at 920° F
(point Z). A catalytic unit, with a secondary heat recovery
unit exhausting at 500° F would recover 5.8 million
Btu/hr/10,000 scfm process air flow as compared to 10.6
million Btu/hr/10,000 scfm process air fuel requirements
to operate the units, the net energy savings are nearly
equivalent. The thermal unit must have a larger heat sink
to achieve the same energy savings.
ENERGY RECOVERED IN
SECONDARY EXCHANGER
(MILLIONS OF BTUH PER
10,000 SCFH)(OR)INCINERATOR 8
NATURAL GAS REQUIREMENT
(MILLIONS OF BTUH
PER 10,000 SCFM)
AMOUNT OF HEAT
TRANSFERRED IN
SECONDARY HEAT
EXCHANGER
200
600 800 1000 1200 UOO
INLET TEMPERATURE TO INCINERATOR (OR)
EXHAUST TEMPERATURE FROM SECONDARY (°F)
Fig. 12—Energy required/recoverable with thermal incinerators using
secondary heat recovery.
SECONDARY
HEAT RECOVERY.
PRIMARY
HEAT RECOVERY
Fig. 13—Thermal incinerator with primary and secondary heat recovery.
Primary and secondary heat recovery can be used
separately or together as shown in Figure 13.
The energy savings potentials of secondary heat
recovery depend on three factors:
• Availability of heat sinks that can effectively use the
energy from the exhaust of the incinerator
• Primary heat recovery applications and
requirements
• Economics of heat recovery options
The economics of heat recovery options will be the
criteria for determining whether or not primary heat
recovery should be incorporated. If a plant could use the
available energy from the incinerator exhaust gases more
effectively with a secondary heat recovery unit, the need
for primary heat recovery would be eliminated. The
energy savings are still achieved because the energy
supplied to the incinerator is replacing the energy
previously used for the secondary recovery applications.
The quantity of energy available for secondary heat
recovery from catalytic and thermal incinerators depends
on the incinerator exhaust temperature and flow rate as
was illustrated in Figure 12.
ECONOMICS
The operating costs of catalytic and thermal
incinerators are greatly affected by heat recovery options
and the solvent concentrations in the process air streams.
Figure 14 illustrates approximate annual costs or profits
for operating a thermal incinerator. A similar figure can
be constructed for catalytic units. Figure 14 is based on
the following assumptions:
89
-------
£oo
500
llOO
ANNUAL COST
(THOUSANDS OF $) 300
200
100
ANNUAL PROFIT '00
BEFORE TAXES
(THOUSANDS OF $) 20Q
300
. NO HEAT RECOVERY
' PRIMARY HEAT RECOVERY ty
. PRIMARY t SECONDARY ,'*
0 5 10 15 20 25 30 35
PROCESS AIR FLOW (THOUSANDS OF SCFM)
Fig. 14—Approximate annual cost/profit for thermal incineration.
DISCOUNTED CASH
FLOW RATE OF
RETURN AFTER TAXES
(PERCENT)
PROCESS AIR FLOW
— 30,000 SCFM
— 15,000 SCFM
70
60
50
1(0
30
20
10
300 1(00 500 600 700
OVEN TEMPERATURE (°F)
800
Fig. 15—Economics for thermal incinerators using maximum primary and
secondary heat recovery.
I. Profits are calculated before taxes
2. Oven exhausts at 300° F
3. Solvent is toluene
4. 35 percent primary heat recovery
5. Secondary heat recovery with waste heat boiler ex-
hausting at 450° F
6. Incinerator temperature = 1400° F
7. Operating time = 6000 hrs/yr
8. Natural gas cost = S2.00/million Btu
9. Operating labor = $8.00/hr
10. Supervision = $10.00/hr (50 percent of operating
cost)
11. Maintenance = 6 percent of total investment
12. General plant overhead = 0.58 (operating labor +
supervision + maintenance + labor salaries*)
*37 percent of maintenance costs
13. Depreciation: 10 yr straight line
14. Taxes and insurance: 2 percent of total investment
15. Additional labor requirements: operating labor
assumed to increase 1/2 hour per shift per installation
(avg. expense $2920/yr and/or $8/hr)
For example, an oven exhausts 25,000 scfm of air at
300° Fand 15 percent of the LEL for toluene. The annual
cost of operation for a thermal incinerator without heat
recovery is $320,000. If a 35 percent primary heat
recovery unit were added, the annual cost would reduce
to $160,000. In addition to the primary heat recovery
unit, if a waste heat boiler were installed, the plant
operation would result in an annual profit before taxes of
$50,000 due to the net fuel savings. As compared to a
thermal incinerator without heat recovery, a thermal
incinerator with both primary heat recovery and a waste
heat boiler would provide an annual savings of $370,000.
Figure 15 illustrates the economics of using thermal
incinerators with maximum primary and secondary heat
recovery. Discounted Cash Flow (DCF) rates of return
after taxes can be determined for various oven exhaust
temperatures, process air flows and solvent
concentrations.
Figure 15 is based on the following assumptions:
1. Toluene is solvent
2. Assumed shell and tube type primary heat
exchanger
3. Secondary heat recovery with waste heat boiler
4. Incinerator temperature = 1400° F
5. Operating time = 6000 hrs/yr
6. Natural gas cost = $2.00/million Btu
7. Operating labor, supervision, maintenance,
overhead, taxes and insurance, and depreciation are the
same as for Figure 14.
For example, an oven exhausts 15,000 scfm of air at
500° F and at 25 percent of the LEL for toluene. If a
thermal incinerator package which includes a shell and
tube heat exchanger for maximum usable primary heat
recovery and a secondary waste heat boiler were
installed, the DCF rate of return on the investment would
be approximately 34 percent.
Table I provides a comparison of thermal and catalytic
incinerators using heat recovery for an oven operating
with 15,000 scfm, 15 percent of the LEL, and at 300° F
exhaust temperature. With no heat recovery, the fuel
requirement for a thermal unit is about three times
greater than for the catalytic unit. With maximum
primary heat recovery (recuperative type), the catalytic
unit can be operated at negligible fuel flow and the
thermal unit still requires about 2.2 million Btu/hr. If a
waste heat boiler were added to each unit, the potential
net annual fuel savings are essentially the same, $68,000.
However, for this savings to be achieved for the thermal
unit, a use for 6,300 Ib/hr of steam must be found as
compared to only 4,500 Ib/hr for a catalytic incinerator.
SUMMARY
This paper highlighted the similarities and differences
of operating thermal and catalytic incinerators as a
means of VOC air pollution control from metal finishing
operations. Without heat recovery options, fuel costs of
both types of incinerators could be a great penalty to the
plant. With proper applications of primary, and
90
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TABLE I
THERMAL AND CATALYTIC INCINERATORS
USING HEAT RECOVERY
Conditions: 30ff> 15% of LEL 15,000 scfm
Natural Gas Fuel Cost $2 per million Btu's
Fuel rates stated in millions of Btu's per hour
Catalytic Thermal
Incinerator fuel rate 5.1 14.3
No heat recovery
Fuel rate, maximum 0 2.2
Primary heat recovery
(Recuperative)
Steam generated in waste heat 4,500 6,300
boiler, Ib/hr
Net annual fuel savings with heat recovery $67,500 $68,400
secondary heat recovery and with optimization of solvent
concentrations in process air flows from the oven, energy
consumption can be minimized and sometimes result in a
net energy savings to the plant. Capital investments for
heat recovery equipment can usually be recovered in a
short time at today's energy costs.
It is important to realize that each plant site is unique in
its operation and should have its processes analyzed
before implementing an incinerator/heat recovery
package. There are many good packages offered by the
vendors; however, each system cannot be universally
applied to all applications with the same expected
performance and economic returns on investments. A
review of the literature sited under "References" will
provide many details and in-dept analyses for
implementing an incinerator add-on program.
REFERENCES
DOE Technology Applications Manual, "The Coating
Industry: Energy Savings with Volaltile Organic
Compound Emission Control," TID 28706, 1979.
DOE Technical Briefing Report, "Oven Curing: Energy
Conservation and Emission Control in Coil Coating,"
TID-28705, 1978.
91
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"Environmental And Energy Benefits
Achievable By Computer Control of Air Flow
In Bake Ovens"
Matt Heuertz*
INTRODUCTION
Methods of reducing fuel consumption in curing
system VOC emission control incinerators were
discussed in the previous paper, "VOC Incineration and
Heat Recovery Systems and Economics" by Roy M.
Radanof, CENTEC Corporation. The two methods
established for reducing incinerator fuel consumption
were reducing air flows to increase solvent concentration
and installing heat recovery options to increase the inlet
air temperature to the incinerator. These methods
similarly apply to curing ovens, although for curing
ovens additional methods exist for reducing oven fuel
consumption. Fuel usage in curing ovens is a function of
dilution air flow, operating temperature, product and
conveyor work load, and system losses. Since the product
and conveyor work load must be a constant or increasing
energy factor, only a change in material of construction
or product and conveyor specific heats can reduce fuel
usage. These savings will be insignificant compared to the
saving potentials of the other usage functional variables.
Oven fuel usage reduction will result from:
1. A reduction in oven dilution air flow.
2. A reduction in curing oven operating temperature
requirements.
3. Installation of secondary heat recovery.
4. Installation of oven zone incineration.
5. Initiation of a general maintenance program.
This paper will discuss the status of the Chemical
Coalers Association Project, which involves the
evaluation and demonstration of the environmental and
energy benefits achievable by computer control of the
dilution air flows in curing ovens. Substantial energy
savings can result from a reduction of curing oven
dilution air flows by installing a micro-computer, LEL
controller system; in addition to the operating energy
savings in ovens and VOC emission control equipment
and a potential reduction in VOC emission control
investment costs, the curing operation utilizing a micro-
computer, LEL controller should be safer to operate.
*Matt Heuertz
Executive Director
Chemical Coalers Association
P.O. Box 241
Wheaton, Illinois 60187
CHEMICAL COATERS ASSOCIATION PROJECT
On September 28, 1979, the Chemical Coaters
Association signed a cooperative agreement with the
Environment Protection Agency on a program that will
include an evaluation and demonstration of the
environmental and energy benefits achievable by
computer control of the air flow in bake ovens.
This multiple-phase project will cost over $700,000
with the bulk of the funds provided by the EPA and the
Department of Energy, and the remainder cost-shared by
the CCA and the company whose paint line will be used
to demonstrate the control system.
The goal of the research program is to develop a
control system that should maintain solvent
concentrations in existing bake ovens at levels
approaching 50 percent of the LEL (lower explosive
limit). The system will be designed to provide consistent
optimum energy utilization for variations in both paint
formulations and the products being coated. Fuel savings
should be experienced in both the bake ovens and
incinerators or afterburners. The final design will comply
with the National Fire Protection Association codes and
standards.
Much of the engineering and technical support efforts
for the project will be handled by CENTEC Corporation
of Fort Lauderdale, Florida, under a sub-contract with
the Chemical Coaters Association.
Charles Darvin, EPA project officer, and John
Rossmeissl, DOE project officer, will provide guidance
and will review the progress of the program whose
expected completion date is October, 1981.
The CCA project consists of the following four work
tasks:
Task 1—"Potentials for Improved Control Tech-
nologies"
At least 50 user members of CCA were contacted and
asked to provide information on their paint bake ovens.
Data required included such information as: oven
capacity, types of coatings cured, fuel consumption, and
a flow diagram of their plant with air pollution control
equipment, if installed.
The information provided by the 50 plants will be used
as input to a computer model developed by CENTEC
which will determine the energy and environmental
costs/benefits for curing ovens, incinerators and heat
recovery devices by implementing a computer-controlled
oven air system. The computer model is quite flexible and
92
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will handle nearly all known plant configurations using
continuous curing ovens.
After compiling this background information, ten of
these plants will be selected for personal visits by
CENTEC engineers for further survey work.
A conceptual computer-controlled oven air system will
be designed and a formal risk analysis will verify that the
system is as safe or safer than present systems operating
at solvent levels below 25 percent of the LEL with no
solvent monitoring/control system.
An engineering report will be prepared that will show
the projected energy and environmental benefits of a
single plant installation and the benefits of an industry-
wide application of the computer-controlled oven air
technology.
Task II—"Site Selection and System Design"
The site selection for the start-up and operation of the
prototype system will be made by the project team as a
result of the findings from Task I.
The selection of the demonstration plant site will be
made on the basis of its similarity of operation with other
plants to assure widespread applicability of the control
system in the industry. Detailed cost estimates for the
hardware and installation costs will be completed; the
demonstration plant must cost share the purchase and
installation of the control system. Estimates of
performance, operation costs and process economics for
other coating plants will be defined. The
soft ware/hardware package for the micro-computer
control system will be designed. A project report will be
prepared that will summarize the results of Tasks I and II.
Task III—"Installation and Start-up"
Accurate documentation for the operating cost and
performance of the oven at the demonstration site will be
made prior to installation and start-up of the control
system. The demonstration site will install the computer
control system with technical assistance from the project
team. The necessary preparations for start-up will be
concluded. Once the control system is put into operation,
and after confirmation of the control capability, the unit
will be lined-out to confirm the system's performance.
Documentation of all costs will be stated for comparison
with projections and with the oven's original operation
prior to installation of the control system.
Task IV—"Evaluation of Demonstration and
Dissemination of Results"
The energy consumption and environmental
efficiencies and long term reliability of the system will be
monitored. Energy savings and environmental benefits
will be documented by the project team with the
assistance of the plant's staff. A project report will be
completed during the later stages of Task IV. The report
will describe technical and economic performance of the
system and its potential applicability for the general
coating industry. The report will provide necessary
information for implementation by other plants. The
Chemical Coaters Association is planning to conduct
seminars and provide an applications manual to transfer
the results of this program to the coating industry.
POTENTIAL SAVINGS FOR AIR FLOW REDUC-
TION
Figures 1, 2 and 3 show the potential energy cost
savings for a given curing oven operation. The oven
operating conditions initially were as follows:
1. Solvent concentration of 10 percent of the LEL.
2. Solvent removal rate of 50 GPH.
3. Oven exhaust temperature of 350° F.
4. Fuel cost of $2.50 per million Btu's.
By installing LEL monitor/control, which permits a
solvent concentration of 50 percent of the LEL, the
dilution air flow can be reduced 80 percent from 17,700
scfm to 3600 scfm as shown in Figure 1.
Figure 2 shows the energy requirements for heating
SOLVENT REMOVAL RATE (GEH)
Figure 1—Oven Air Requirements for Solvent Dilution.
OVEN EXHAUST TEMP. Cf)
Figure 2—Energy Requirements for Oven Air Heating.
93
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these dilution air flows. At ten percent of the LEL, the
energy required for heating 17,700 scfm to 350° F is 6.8
MM Btu/hr. At 50 percent of the LEL, the energy
required is 1.2 MM Btu/hr. The energy cost savings
attributable to this energy reduction is $81,000 as shown
in Figure 3. As fuel costs increase, the annual cost savings
potential also increase for dilution air flow reduction.
ANNUAL OVEN FUEL COST (THOUSANDS »l
8 8 8 §
-I -1, I U
Figure 3—Energy Cost for Oven Air Heating.
CONTINUOUS CONVEYOR OVEN
- LOCAL LEL PROCESS
INDICATOR /TRANSMITTER/
CONTROLLER
- ANY PROCESS VARIABLE
CONTROLLED OR
INTERLOCKED TO
LEL CONTROLLER
- EXHAUST (EXH) OR
RECIRCULATION 1REC)
BLOWER
— MODULATING DAMPEB
Figure 4—Conceptual Design - Computer Controlled Oven Air Flow.
CONCEPTUAL DESIGN—COMPUTER CON-
TROLLED OVEN AIR FLOW
To realize this oven fuel savings, Figure 4 shows the
conceptual design of the micro-computer controller. The
system basis for this design is a continuous, multi-zone,
conveyor oven. The solvent concentration in terms of
percent of the LEL would be monitored for:
1. The inlet to the high temperature flash zone.
2. The exhaust from the high temperature flash zone.
3. The exhaust from the higher temperature flash
zone.
The reasoning for these sensor locations is that the
majority of solvent removal will occur in the initial high
temperature flash zone under normal system operation.
If a system upset occurs, i.e. the product is over sprayed,
and the solvent removal capacity of the first zone is not
adequate to handle this additional solvent, then this
solvent will be vaporized as the product enters the next
higher temperature zone. Since solvent concentration is
uniform in each zone due to the typically large air
recirculation rates, monitoring the solvent concentration
in the higer temperature flash zone exhaust will be
representative of the entire zone solvent concentration.
As the design becomes increasingly site specific, the
actual number of local LEL percent analyzer/indicator/
transmitter/controllers could be reduced from three to
ideally one, if the system layout will allow for multi-point
sampling utilizing one analyzer. The LEL analyzer in this
case should not be remotely located, since sample line run
lengths must be minimized to reduce the chances of
solvent condensation and pluggage due to resin
particulates.
The LEL analyzer will primarily control air exhaust
rates by modulating inlet vortex, exhaust, blower
dampers. The LEL analyzer will be capable of automatic
self-checking with alarm warning for high LEL or
analyzer malfunction. If the analyzer malfunctions, the
auto-dampers will be fully opened to maintain
production. In addition to the alarm warning for high
LEL, the system can control or interlock with any process
variable to stop the coating, stop the conveyor or
shutdown the combustion system.
The order of magnitude installed equipment cost and
annual operating cost for the micro-computer control
system are $120,000 to $150,000 and $15,000,
respectively. The discounted cash flow rate of return after
taxes and payback on investment is shown in Figure 5 for
various annual fuel cost savings. For an oven operating at
350° F and a solvent removal rate of 50 GPH with a fuel
cost of $2.50 per million Btu's, an annual fuel cost savings
of $81,000 would be realized if the system dilution air
flow rate was reduced to result in an increase in solvent
•4 Z
O
ANNUAL FUEL COST SAVINGS (THOUSANDS t)
Figure 5—Economics of Oven Computer Control.
94
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concentration from 10 percent to 50 percent of the LEL.
This savings of $81,000 annually would result in a DCF
rate of return after taxes of 44 percent and a payback on
investment of 2.4 years. For ovens operating at higher
solvent removal rates and higher temperature, the
potential savings for LEL micro-computer control would
be higher and, therefore, the DCF rate of return and
payback would be even more attractive, since investment
cost for LEL micro-computer control is essentially
constant for varying system air flows, solvent removal
rates, and operating temperatures.
COMPUTER MODEL FOR OVEN/INCINERATOR
ENERGY ANALYSIS
The Oven/Incinerator Design Model determines the
fuel consumption and fuel costs associated with
continuous curing ovens and with incinerators used for
volatile organic compound (VOC) air emission control.
Fuel savings attributable to primary and secondary heat
recovery schemes are also computed.
Energy utilization optimization can be determined by
increasing the solvent concentration in the oven to levels
approaching 50 percent of the LEL. Where existing
incinerators may limit solvent concentrations to levels
lower than 50 percent of the LEL, optimized fuel
consumption also can be determined.
The model has a built-in file on solvent properties so
that all calculations are based on actual constituents
rather than average values. Solvent destruction efficiency
is factored into fuel flow computations. Spray booths or
other solvent laden air sources may be mixed with oven
air exhaust as input to an incinerator. Both catalytic and
thermal incinerators can be evaluated considering
internal and external combustion air sources and
different fuel sources. Zone oven incinerators also can be
evaluated.
The fuel costs determined by this model may be used as
input to CENTEC's economics model for determining
discounted cash flow rates of return, returns on
investments, and paybacks for capital investments.
Accurate calculations that normally would require
several mandays of effort now can be performed in
several minutes using these models. The accuracy and
flexibility of this model will be demonstrated at the EPA
exhibit booth by providing a free analysis for your curing
operation.
This model was utilized to develop the following case
studies.
CASE STUDY EXAMPLES
Two case studies are presented in Figure 6 and 7,
which show the fuel costs, operating costs, investment
costs and economics of LEL micro-computer control
heat recovery and VOC emission control.
Case I—Typical Coating Line
This case involves an existing curing oven operating at
10 percent of the LEL, 20,000 scfm of dilution air flow,
350° F operating temperature, with a product/conveyor
work load of 42,000 pounds per hour. The annual fuel
costs for these existing oven operating conditions,
assuming a fuel cost of $2.70 per million Btu's, are
determined to be $161,000. The addition of LEL micro-
computer control increasing the solvent concentration to
50 percent of the LEL reduces the annual fuel cost to
$84,200 for a savings of $76,800. This was accomplished
by an investment of about $120,000 for the LEL control
system. This results in a return on investment of 41
percent and payback of 2.6 years, which includes the
additional incremented controller operating cost of
$15,100 annually.
If VOC emission controls are required for this curing
operation, thermal and/or catalytic incinerators or
carbon adsorption should be considered. Since the oven
operating temperature is 350° F, carbon adsorption can
be ruled out.
Thermal incineration was selected, since the coating
resin potentially could poison the catalyst in a catalytic
system. Since the LEL control was installed, the
investment cost for adding thermal incineration will be
lower, because the air flow rates were reduced. At the
lower air flow rates, the total installed investment cost for
FIGURE 6
CASE I - TYPICAL COATING LINE
Annual Syst. Costs, $
Configuration
Incremental Total
Incremental Annual Fuel Installed
Fuel Costs Operating Costs Savings, $ Investment Cost,
R01
Payback,
Years
Existing oven 161,000
(10% of LEL)
Controlled oven 84,200
(50% of LEL)
Add thermal incin. 100,000
to controlled oven
Add 60% recirc. to 45,000
controlled oven from
incin.
(or)
Add waste heat 100,000
boiler (5,300 Ib/hr
stm 40 psig)
15,100
18,800
4,000
17,700
76,800
-0-
55,000
*72,400
120,000
126,500
50,000
40,300
41
-0-
86
115
2.6
-0-
1.4
*Fuel savings in steam plant.
95
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FIGURE 7
CASE II - ACTUAL COATING LINE
Annual Syst. Costs, S
Configuration
Existing oven.
(2% of LEL)
(Controlled oven,
35% of LEL)
Add Cat. Incin. To
Exist. Oven
(To Controlled Oven)
Add Primary Recovery
To Exist. Oven & Incin.
(To Controlled Oven)
(or)
Add Oven Air Preheat
To Exist. Oven, Incin.
& Primary; 2.1 MM
Btu/Hr.
(To Controlled oven:
2.2 MM Btu/Hr.)
Fuel Costs
71,000
(48,300)
149,200
(74,800)
99,500
(58,500)
65,800
(23,100)
Incremental Total
Incremental Annual Fuel Installed ROI
Operating Costs Savings, $ Investment Cost, $ %
— —
(15,100) (22,800) (120,000) (2)
34,500 -0- 172,500 -0-
2,300 49,700 29,000 139
(16,300)
2,300 33,700 29,000 91
(1,800) (35,400) (23,000) (124)
Payback
Years
—
(8.7)
-0-
1.0
1.4
1.1
the incinerator was $126,500 with an incremental annual
operating cost of $18,800. The total annual fuel cost for
the controlled oven and incinerator was determined to be
$100,000. The plant is allowed to maintain production by
meeting VOC emission control requirements, but no
return on investment or payback is realized. To offset the
increase in fuel cost for VOC emission control, secondary
heat recovery can be included in the system. If direct
recirculation of 60 percent of the incinerator exhaust
volume is returned to the controlled oven, the system
annual fuel cost will be reduced to $45,000; a savings of
$55,000 annually or 4.1 MM Btu's per hour. The
investment cost for this direct recirculation system would
be $50,000 which results in a return on investment of 86
percent and a 1.4 year payback assuming an annual
operating cost of $4,000. If direct recirculation is not
viable, because of product quality liability or if the plant
requires process steam, a waste heat boiler can be
installed to recover the sensible heat in the incinerator
exhaust. A waste heat boiler would not reduce the fuel
cost for the curing operation, but would save $72,400
annually in the steam plant. The return on investment is
115 percent with a 1.1 year payback assuming an
investment cost of $40,300 and an annual operating cost
of $17,700. This boiler will generate 5,300 pounds per
hour of 40 psig steam.
Case II—Actual Coating Line
This example case is an actual coating line consisting of
a curing oven and catalytic incinerator with primary heat
recovery. The existing oven is operating at 2 percent of
the LEL, 5000 scfm of dilution air flow, 340° F operating
temperature, with a product/conveyor work load of
30,500 pounds per hour. The annual fuel costs for the
oven alone is $71,100, assuming a fuel cost of $2.70 per
million Btu's. The combined annual fuel cost for the oven
and catalytic incinerator'is $149,200. If LEL micro-
computer control was added to the oven, the oven annual
fuel cost would be $48,300; a savings of $22,800. The
resulting return on investment and payback is 2 percent
and 8.7 years, respectively, assuming an investment cost
of $120,000 and operating cost of $15,100. For the oven
alone this would not be a wise investment, but including
the incinerator in the analysis makes the economics
become more favorable. The annual fuel costs for the
controlled oven and catalytic incinerator would be
$74,800; a savings of $74,400 annually. Also the
investment cost for this incinerator would have been
lower than the actual $172,500, since the air load would
be greatly reduced at 35 percent of the LEL. It should be
noted that the 35 percent of the LEL is the maximum
solvent concentration in this case, since levels greater
than 35 percent would result in an incinerator exhaust
temperature greater than the maximum allowed for this
equipment.
The addition of primary heat recovery to the
incinerator reduced the fuel costs to $99,500 for a savings
of $49,700 annually. This required a $29,000 investment
for a 139 percent return on investment and a payback of
1.0 year assuming an operating cost of $2,300. Adding
primary heat recovery to the controlled system, the
annual fuel cost would be $58,500 for a $16,300 savings.
To further reduce fuel costs, secondary heat recovery,
oven air preheating for example, could be included in this
existing installation. The existing system annual fuel cost
would be $65,800 for a $33,700 savings. A 91 percent
return on this $29,000 investment and a 1.4 year payback
would result assuming an annual operating cost of
$2,300. For the controlled system, the annual fuel costs
would be $23,100 for a $35,400 savings. This investment
of $23,000, assuming an annual operating cost of $1,800,
would result in a 124 percent return on investment and a
1.1 year payback.
SUMMARY
The benefits of the CCA Project to evaluate and
demonstrate computer control of the dilution air flow in
96
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curing ovens are numerous and include environmental, would achieve the following major benefits:
energy, safety, and investment cost factors. Improved 1. Reduced fuel usage in curing ovens.
control of oven air flows will permit many plants to 2. Reduced fuel usage and investment costs for VOC
operate the curing ovens close to the maximum allowable emission control add-on devices.
solvent concentration. Since the control systems are 3 Improved VOC destruction efficiency
installed at the source of the VOC emissions, the industry 4. Improved operational safety by computer control.
97
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Emissions From Open Top
Vapor Degreasing Systems
Charles H. Darvin*
INTRODUCTION
Vapor degreasers are used in most metal finishing
plants to remove dirt and grease from various metal parts
with nonaqueous organic solvents. Major users include
automotive parts manufacturers, metal fabricators,
machinery manufacturers, and some electroplaters. In
these units, the part to be cleaned is dipped in an organic
solvent vapor. Vapor condenses on the part, rinsing off
dirt, oil, and grease. The vapor is not contaminated from
previous cleaning cycles, as would be the case in a liquid
dip tank, so excellent cleaning results. The solvent
vapors, which are heavier than air, form a stable vapor
layer at the top of the degreaser. Emissions occur when
this vapor layer is disturbed.
Emissions from degreasers contribute a significant
amount of volatile organic compounds (VOC) to the
atmosphere each year. Solvent degreasers alone emit
approximately one million metric tons of solvent
annually, about 4 percent of total national VOC
emissions from stationary sources. Most of these
emissions are in and around urban areas where there is
the highest concentration of metal working industries.
The U.S. Environmental Protection Agency (EPA) thus
considers it important that methods of reducing these
emissions be developed. Reduction of these emissions
would also serve to conserve valuable petroleum
products. This paper summarizes a comprehensive
testing program which examined the operating
conditions that cause VOC emissions from open top
vapor degreasers.
THE PROJECT
In late 1977, EPA's Industrial Environmental
Research Laboratory in Cincinnati (IERL-Ci) initiated
an extensive research program to investigate the
characteristics of VOC emissions from open top vapor
degreasing systems. The initial requirements of the
program required the identification of knowledgeable
people and organizations in the field of degreaser
technology and the construction and instrumentation of
a suitable laboratory facility. PEDCo Environmental,
Inc., of Cincinnati conducted the program at its research
facility outside Morrow, Ohio, a location which provided
a remote area for the testing, free of any urban industrial
interferences that could have created false data. In
'Charles H. Darvin
Nonferrous Metal and Minerals Branch
U.S. EPA, Cincinnati, Ohio
formulating the experimental scenarios and designing the
laboratory facility, PEDCo and IERL-Ci relied
extensively upon the expertise of the ASTM D-26
Committee on Degreasing, NIOSH, OSHA, and various
industrial companies which make or utilize degreasers.
The test program was initially scheduled to run for 12
months, but experimental results indicated the need to
expand the number of operating scenarios that should be
investigated. The program was therefore divided into two
phases. During Phase I, the laboratory was set up,
experimental variables were identified, and calm air
experiments were conducted. During Phase II, the effects
of higher air velocities across the open top of the
degreaser were investigated.
EXPERIMENTS AND RESULTS
The following operational procedures and
modifications were determined to have the greatest
influence on emissions:
• use of covers
• ratio of cross-section of load to that of degreaser
• hoist speed
• freeboard ratio (the ratio of the freeboard height to the
smaller interior dimension [length, width, or
diameter])
• use of refrigerated freeboard chillers (RFC)
• physical properties of the solvent (e.g., vapor pressure
differences)
The experiments were conducted at a relatively constant
temperature of 70° F (±10°) and constant humidity.
During Phase I of the program, the draft across each
system was maintained at calm conditions (0.2 m/sec [40
ft/min]). Phase II experiments were conducted at higher
draft velocities (0.67 m/sec [132 ft/min] and 1.2 m/sec
[240 ft/min]) across the degreaser. Over one hundred
experiments were conducted during Phase I of the
program, and another fifty during Phase II. Each
experiment was run for roughly 24 hours.
Operational Procedures
Cover - The use of a machine cover was shown to
produce significant reductions in solvent emission rates
when operating in relatively calm air conditions.
Machines containing 1,1,1-trichloroethane (TE) and
methylene chloride (MC) were monitored in an idle state
over a 24-hour period. These experiments were
conducted with and without covers at 0.50 freeboard
ratio; results are shown in Table 1.
Although the absolute results of each experiment
differ, the general trend was a reduction in emissions up
-------
Table 1
Effect of Lid Position in Reducing Solvent Loss From
Idle Degreaser (50 percent freeboard ratio, RFC off)
Nonboiling
Solvent Run
TE o
MC 23
1 Run 2
Solvent loss
40
60
Boiling
Run 1 Run 2
reduction, %
5 60
33 35
to a maximum of 60 percent. This confirms the capability
of a simple work practice procedure to reduce emissions
from an idle degreaser.
Load cross-sectional area - A second work practice
variable that was determined to affect the rate of
emissions from a degreaser was the ratio of the cross-
sectional area of the load to that of the open top of the
degreaser. Special loads were fabricated to correspond to
loads of 50 percent of the system top area (the
manufacturer's recommended load) and 70 percent. It
was found that in every operating scenario the rate of
emissions increased with this increase in load cross-
sectional area. As can be seen in Figure 1, increases of
emissions from 10 to 50 percent were experienced in
systems operated at a 70 percent load cross-sectional area
compared to those operating with a load area of 50
percent. This demonstrated that operation of a degreaser
within operating specifications significantly holds down
emissions.
Machine Modifications
Hoist speed - Increased hoist speed was found to
influence emission rates from an operating degreaser.
Experiments were conducted using two hoist speeds, 0.04
m/sec (8 ft/min) and 0.08 m/sec (16 ft/min). The results
shown in Figure 2 demonstrate typically greater
emissions (i.e., lower solvent loss reduction) when
operating at the higher speed. It can also be seen that at
100 percent freeboard ratio, emissions are significantly
greater at the higher hoist speed. This indicates that hoist
speed may significantly influence the capability of an
increase in freeboard height to reduce emissions.
Crosscurrent air velocity - The degreasing machines
were operated at draft velocities ranging from calm air of
approximately 0.1 m/sec (20 ft/min) to greater than 1.0
Table 2
Effect of Freeboard Ratio in Reducing Solvent Loss
From Operating Degreaser at 50 Percent Load
Area, 0.04 m/s Hoist Speed, and Calm Air
Solvent
Without RFC:
TE
MC
With RFC
(-29°Cto
-40° C)
TE
MC
Freeboard ratio, %
50 75 100
Solvent loss reduction, %
2 17 50
2 22 22
8 44 44
22 44 55
m/sec (200 ft/min) to evaluate the effects of crosscurrent
air velocities across the open degreaser top. The results
are shown in Figure 3. In all operating scenarios,
increased draft velocities resulted in increased emissions
from the machines. At a crosscurrent velocity of 0.67
m/sec (132 ft/min), as much as a 100 percent increase in
emissions was observed.
Freeboard ratio - Experiments into the capability of
increased freeboard ratio to reduce emissions were
conducted over the total range of operational conditions,
including calm and high draft conditions, use of covers
and refrigerated chillers, and varying load cross-sectional
areas. Table 2 presents results with and without a
refrigerated chiller and shows that increasing freeboard
ratio can significantly reduce emission rates. When
freeboard ratio was increased from 0.5 to 0.75 for TE,
there was a 20 percent reduction in emissions for TE and
a 15 percent reduction for MC.
50
40
30-
20
10
-10
-30
-40
-50
-60
0
D
-B-
OTE, 50% LOAD AREA
DMC, 50% LOAD AREA
• TE, 70% LOAD AREA
• MC, 70% LOAD AREA
50
75 TOO
FREEBOARD RATIO, %
125
Fig. 1—Effect of load area in reducing solvent loss from operating
degreaser at hoist speed of 0.04 m/s (RFC off).
60
50
M 40
o
£30
LU
** 20
CO
o
fe10
LU
S? o
-10
-20:
O
O
OHOIST SPEED 0.04 M/S
OHOIST SPEED 0.08 M/S
75 100
FREEBOARD RATIO, %
125
Fig. 2—Effect of hoist speed In reducing solvent loss from operating
degreaser using TE and 50% load area (RFC off).
99
-------
CUU
**o ft
9* U
•»
z
£-200
o
o
ll 1
^-400
to
uo
o
1
i- -600
z
1 1 1
>
_J
8-800
_innn
1 1
R
•
_
_
-
OTE, 75%
_ OMC, 75%
• TE, 125%
• MC, 125%
i i
i i i i
• • 8 °
• o _
o •
•
D
FREEBOARD RATIO
FREEBOARD RATIO
FREEBOARD RATIO
FREEBOARD RATIO
i i I i
CROSSCURRENT AIR VELOCITY, M/S
Fig. 3—Effect of crosscurrent air velocity on solvent loss from operating
degreaser at 0.04 m/s hoist speed and 50% load area (RFC off).
Machines built to use MC typically employ a 0.75
freeboard ratio. When increasing the freeboard ratio
from 0.75 to 1.00 for MC, there was a further 30 percent
reduction in solvent loss. Figure 1 also illustrates the
benefits of increased freeboard ratio.
Table 3 illustrates the effects of increased freeboard
ratio at various crosscurrent air velocities.
The table also contains one case which reverses the
general trend of a decrease in emissions with higher
freeboard ratio.
An increase in emissions was observed when operating
at 0.67 m/s with TE. This could not be explained by the
chemical or physical properties of the solvent, and will be
the subject of additional testing.
Refrigerated freeboard chiller - A refrigerated
freeboard chiller (RFC) can be mounted above a
degreaser to reduce emissions from the bath.
Experiments with an RFC demonstrated a general
reduction in emissions from the degreasers when using
MC, as shown in Table 4.
Table 5 shows the effects of operating at higher draft
velocities with RFC. It also shows for TE a reversal of the
trend toward reduced emissions with an RFC that was
observed with MC.
Table 3
Effect of Freeboard Ratio in Reducing Solvent Loss
From Operating Degreaser at Various Air Velocities
and 50 Percent Load Area and 0.04 m/s Hoist Speed
(RFC Off)
Solvent
TE
MC
Air velocity,
m/s
0.1
0.67
1.12
0.1
0.67
1.12
Freeboard ratio, %
50 75 125
Solvent loss reduction, %
0 20 50
-10 -50
-120 -50
0 10 15
-160 -100
-380 -350
Table 4
Effect of Refrigerated Freeboard Chiller (RFC) In
Reducing Solvent Loss From Operating Degreaser
Using MC at Greater than/Equal to
0.67 m/s Air Velocity
Refrigerant
temperature,
° C
0
-29 to -40
Freeboard
ratio, %
75
125
75
125
Solvent loss reduction, %
RFC off RFC on
-450 -220
-250 -220
-75 -75
-120 -20
Effect of Higher
Reducing Solvent
Table 5
Crosscurrent Air Velocities In
Loss From Operating Degreaser
At 0.04 m/s Hoist Speed
Solvent
TE
MC
Air velocity,
m/s
0.67
1.2
0.67
1.2
Freeboard
ratio, %
75
125
75
125
75
125
75
125
Solvent /oss
reduction, %
RFC off
-100
-150
-110
-50
-250
-175
-360
-320
RFC on
-200
-200
-180
-180
-150
-150
-260
-230
DISCUSSION OF RESULTS
A number of significant conclusions can be developed
about the nature and control of emissions from
degreasers as a result of this evaluation program. Use of
simple operating procedures such as low hoist speeds,
closing of the system lid when in idle condition, and
shielding the system from high draft velocities can
significantly reduce emissions. These changes, however,
require a conscious and continuous effort on the part of
the operator. Passive control options such as increased
freeboard and refrigerated chillers were shown to be just
as effective and require only installation and
maintenance for continuous control.
The data also show the capability of each control
option when used separately or in tandem. It was shown
that secondary chillers achieve greatest control benefit at
lower freeboard ratio levels, 0.5 for MC and 0.75 for TE.
As freeboard ratio increases, its capability approaches
that of the secondary chiller. This was found to be true at
both lower and higher crosscurrent air velocities for MC.
However, this trend was found to be reversed with TE,
and no viable explanation based on chemical or physical
properties of the solvent has been found. An extension of
the program to include approximately 30 or more
experiments has therefore been scheduled. During those
experiments, a more detailed evaluation will be made of
secondary operating variables such as ambient
conditions and aerodynamic effects.
The conclusions that have been and will continue to be
developed after completion of the testing can have a
major impact upon future degreaser design and operating
100
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practice. Both plant layout and production line
scheduling can be impacted. To reduce emissions, a
degreaser should be placed in a location shielded from
high drafts, either by installation of baffles or by proper
placement in the plant. Hoist speed should be maintained
at relatively low velocities (which could require control of
the speed of the production line). The maintenance of
loads at low cross-sectional area could also limit
production rates. Finally, the use of add-on control
options could influence equipment location in the plant.
These operating practices and design modifications,
however, represent in most cases relatively inexpensive
options and would produce only minor changes in
normal plant operations.
A summary report of the Phase I efforts is in
preparation. This report will include the results of
experiments conducted primarily under calm air
conditions. It will be available for distribution in July
1980. The Phase II report is awaiting completion of the
remaining 30 experiments analyzing the unusual TE
results. It will be ready for distribution in September
1980.
101
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V.O.C. Control Efforts By
A Heavy Duty Truck Manufacturer
Edward W. Kline*
Can you visualize a 9.9 mile traffic jam? That's the
distance the line of tank trucks would stretch if one
thousand and forty-three of them were parked bumper to
bumper. It would take 1043 tank truck deliveries to
supply 7.3 million gallons of #2 fuel oil.
I mention these figures because 7.3 million gallons is
the amount of #2 fuel oil it would take if we were to incin-
erate Volatile Organic Compound emissions from
painting operations at Mack Trucks Allentown
Assembly Plant.
To get a better feel for the magnitude of these figures,
consider the following:
If you round off the cost of a gallon of #2 heating
oil at $1.00 per gallon, you have an annual oil bill of
7.3 million dollars. Average that over the 20,000
trucks we built in Allentown last year and it would
cost an additional $365 to paint a truck.
If you use 1500 gallons of #2 oil to heat your
home each year, 7.3 million gallons would be
enough oil to heat a city of 4866 homes. Now even if
this quantity of oil were available, which it is not,
one has to ask—Is such conspicious consumption
advisable given our present world situation?
I am sure most of us recognize the importance of
V.O.C. control. The EPA has presented convincing facts,
figures, and statistics to serve as incentives.
However, it is my firm belief that as Environmentalists,
Scientists, Engineers, Enforcement Agencies, and
Industrial Managers, it is our responsibility to
accomplish this control in an effective and economical
manner.
As I see it there is no one universal solution to the
problem of V.O.C. control. That is of course unless there
is a revolutionary breakthrough in coating technology.
Each process should be examined on an individual
basis if you want to determine the most favorable control
technology. Let's review the circumstances affecting our
decisions at Mack Allentown.
PRODUCT REQUIREMENTS
Mack Trucks are separately engineered to meet
customer specifications and individual needs. We are
custom truck builders.
The trucks we build cost in the neighborhood of
$50,000. Unlike most automobiles, our entire truck is
painted—chassis and all. The projected life expectancy is
5-10 years. However, some are in use more than 20 years
'Edward W Kline, Section Supervisor
Environmental Control
Mack Trucks, Inc., Allentown, PA
and still going strong. It is not uncommon to hear
customers talk about breaking the million mile mark with
their Mack.
Mack Trucks are in use around the world and are
exposed to weather conditions which range from desert
heat to arctic cold. Naturally, our customers also expect
the finish to meet certain requirements such as: Long
Term Weather Durability; Color Choice and
Appearance Hi-Luster; Color and Gloss Retention;
Ability to Withstand Extreme Environmental
Conditions such as Heat, Cold, Abrasion, Corrosion,
and contact with Chemicals & Oxidation; Chip
Resistance.
As you can see, living up to these tough expectations
requires a paint finish highly durable in nature. We use
Thermo-set acrylic enamels to meet these requirements.
TYPES OF ENGINEERING CONTROLS
A. Improved surface coating transfer efficiency.
Looking at both ends of the spectrum, we find
conventional air atomization spray painting has a
transfer efficiency of 30 - 60%.
Airless electrostatic spray painting has a transfer
efficiency of 80 - 90%.
B. Materials Substitution—By weight an average
gallon of solvent base paint contains between 4.5-6 Ibs.
of V.O.C. An average gallon of water borne coating
contains between 2 - 3.5 Ibs. of V.O.C.
C. Physical Controls—Carbon Absorption systems
are being utilized, This type of V.O.C. control ranges in
efficiency from 40 - 90%. Generally carbon absorption is
being used when quantities of air are reasonable.
Catalytic and direct incineration systems have been
rated at 90 - 100% V.O.C. control efficiency.
Refrigeration systems used for low volumes of air
range from 40 - 80% V.O.C. control efficiency.
SUCCESSFUL APPLICATIONS AT MACK
TRUCKS ALLENTOWN ASSEMBLY PLANT
Chassis Spray Painting
Conventional spray painting has been the industry
standard for years. We replaced conventional chassis air
atomization spray painting with airless electrostatic
techniques. This reduced V.O.C. emissions by 21 tons per
year.
Small Parts Painting
Our small parts painting operations includes a wide
variety of parts that range in size from doors to brackets.
A total of 72,000 square feet of surface coating is
completed in an 8 hour shift.
In this operation a combination of materials
substitution, improved transfer efficiency, and catalytic
102
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incineration are used to eliminate 40 tons of V.O.C.
emissions annually.
Substitution of Materials and Improved Transfer
Efficiencies
Many parts which had been painted by conventional
air spray methods now receive electrophoretic paint
coatings.
The electrophoretic coating takes place in a 13,000
gallon dip tank. It is a water borne coating which
contains 1.9 Ibs. of V.O.C. per gallon of coating. Plating
voltage of the system ranges from 250 - 350 volts D.C.
The current density is 5 amps/sq. ft.
Air and airless electrostatic painting techniques are
being evaluated and perfected for color spraying
operations.
Emission Control Technology
Exhaust air from 3 paint drying ovens is funneled
through a catalytic incinerator. In an 8 hour shift 4.8
million cubic ft of air passes through the incinerator.
Oven temperatures are maintained at 250° F (121° C) for
paint drying. The incinerator is a Schweitzer Sicor unit. It
contains 9 cubic feet of DuPont Torvex Platinum
Catalyst. The Catalyst allows incineration to take place
at temperatures between 700 & 900° F. Fifty gallons of #2
heating oil are consumed each hour to operate the
incinerator.
John Kroehling of DuPont worked closely with us on
this project. John expects the Catalyst to last 3-5 years.
The 9 cubic feet of Platinum Catalyst is designed in a
honeycomb fashion. The honeycomb effect produces
300,000 square feet of catalytic contact surface area.
Heat Recovery
Indirect heat recovery is used to reclaim 4 million
BTU's of incinerator heat each hour. The recovered
energy is used to heat the Electropheretic dip oven to a
temperature of 350° F.
The recovered heat and lower temperature
requirements of the catalytic incinerator produce an
annual savings of 53,000 gallons of #2 home heating oil.
That's enough oil to heat 35 - 40 homes in the Lehigh
Valley each year.
CONCLUSION
As I see it, there is no universal solution to the control
of V.O.C. emissions unless a breakthrough in coating
technology occurs. A combination of improved transfer
efficiency of coatings and materials substitution, when
practical, appears to be the most favorable approach to
V.O.C. control.
Incineration with heat recovery has application when
an energy balance can be obtained. The use of carbon
absorption or refrigeration principles have application
when air volumes are low enough, or when there is a
desire to recover lost product.
The most effective results will be obtained by carefully
examining the merits of each process in conjunction with
the control applications which are available.
103
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Centralized Treatment and Disposal of
Special Wastes in the
Federal Republic of Germany
N. Roesler*
INTRODUCTION
In "Environmental Protection" and, generally, in the
"Improvement of Quality of Life", special wastes in the
form of gases, liquids, and solids, and even noise are
becoming more and more important in comparison with
normal municipal sewage and garbage. Although the
legal task of the public Wastewater Treatment plants is
the acceptance and treatment of normal municipal
wastewater, we found that we were struggling to treat
unusual waste components, which, despite federal laws
and municipal regulations, entered into the sewers and
complicated the treatment of wastewater. Different
Institutions, therefore, have become concerned with
various branches of industry and their liquid wastes.
Since about 1960, in the Federal Republic of Germany,
intensive efforts have been made which have resulted in
various more or less, centralized treatment plants with
facilities for treating the wastes coming from different
industries
ORGANIZATION
An example of facilities based on more private and
voluntary activities is represented by the Ruhrverband
which comprises a part of the land of Northrhine-
Westfalia.
The central Decontaminating Plant, Iserlohn (ZEA-
Iserlohn), the first plant in West Germany, was
completed in 1964. This plant treats metal finishing
wastes from an area of 380 km2, comprised of the town of
Iserlohn and eight municipalities, forming the district of
Iserlohn. In this area, there are about 200 installations, in
most cases medium-sized industrial enterprises which are
running approximately 1000 baths for galvanizing,
anodizing and non-ferrous metal pickling, with a total
volume of roughly 1000 m3. (See Figure 1)
After obtaining the agreement of all the associates
concerned, the Corporation for the Advancement of
Industry Ltd., Iserlohn, took over the responsibility for
metal finishing waste treatment in this area, and charged
the Ruhverband for planning, constructing and
operating the plant, in accordance with section 3 of the
Ruhr Pollution Act (law of the regional government of
Northrhine-Westfalia).
The ZEA-Iserlohn plant is divided into three sections
(Figure 2). The first section comprises the collection
*N. Roesler
Department of Sewage Treatment
Ruhrverband D-43, Essen, Germany
EjD 12000
El 12000
H] 10000
S 60000
[B 26000
3000
2000
3000
2000
Fig. 1— Central Plants for the Treatment of Hydroxide Sludges in the
Catchment of the River Ruhr.
Receiving of wastes in tank cars.
containers, large.small.and mini loads
Acid storage basin
Hydrochloric acid pickle.
sulphuric acid pickle,
chromic acid
Alkaline waste storage basin
Cyanide-containing wastes,
degreasmg and drawing
baths, liquors
Cyanoxidation
Neutralization
Iron oxidation
Sedimentation
Sludge storage
I Sludge dewatenng
'
Dumping of sludge
Fig. 2—Schematic diagram of a central plant for the removal of toxic
substances from electroplating plants and pickling plants.
tanks, and the cyanide oxidation and chromate reduction
facilities. Section two is the neutralization and
desludging facility for wastes coming from section one, as
well as for acid and alkaline solutions from aluminum-
anodizing plants, and iron and non-iron pickling plants.
The third section comprises the following steps:
thickening, dewatering and disposal of hydroxide sludges
coming from section two. It also handles sludges
104
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delivered from companies which have pretreated their
wastes to the extent they have found economical to do in-
house. The ZEA-Iserlohn can, therefore, handle toxic
concentrations, thin and thickened sludges, and
dewatered sludges requiring disposal. This allows each
associate to choose the grade of pretreatment which is
most economical for him, and consequently, the cheapest
way to dispose of his wastes.
In the case of the second plant, the ZSEA-
Heiligenhaus, the responsible authority is the
Dusseldorf-Mettmann (Figure 3). The various
installations in this area preferred to handle the first and
second sections (as described above) of wastewater
treatment within their own plants. Hence the
Ruhverband planned and constructed a storage,
dewatering and dumping facility for sludges from
Heiligenhaus and has been operating since 1968. Unlike
the ZEA-Iserlohn, membership is compulsory for all the
installations unless one can prove that wastewater
discharges from his own plant comply with the law.
-15KM
• Central plant for
dewatering and disposal
Number of factories
producing hydroxide
sludges
Fig. 3—District Dusseldorf-Mettmann concentrations of factories in the
district.
A third plant has been constructed by the town of
Ludenscheid and a private garbage collector is running it
for another 100 installations.
Two further plants run by private contractors are
handling emulsions from rolling mills and another one is
collecting and recovering spent hydrochloric acid.
These'plants have become the central collection and
treatment facilities for all special wastes coming from the
metal finishing industry in this area.
Managing
The technical supervision of the two plants operated by
the Ruhrverband is handled by two engineers in
cooperation with two nearby wastewater treatment
plants. The engineer involved in each case is able to add
or withdraw workers according to need. Normally, two
workers are required to operate the plant in Iserlohn and
one in Heiligenhaus.
The financial management is done by a group of
elected men who represent the industry (associates), the
responsible corporation, the local authorities, the
Ruhrverband, and the Chamber of Commerce. Each
year, the financial statements and plans for the following
year are presented by the managing engineer to the
representatives for approval.
Financial Aspects
For financial purposes, the metal finishing industry
(galvanizing, anodizing and pickling factories) in
Iserlohn has been separated into three groups according
to the volume of their baths, the amount of chemicals
bought, the quantity of process water needed, the
quantity of sludge produced, and so on. Also taken into
account is the degree of participation or the amount of
pretreatment carried out by the companies themselves. A
small plant wanting to participate in all steps of central
treatment may pay, for instance, 5000-DM, while a large
company which sends only dewatered sludge for
dumping may pay 20,000-DM for the disposal.
In addition, the Ruhverband has granted a loan of
150,000-DM, the town of Iserlohn a lost subsidy of
50,000-DM and the regional government another lost
subsidy of about 200,000-DM, towards the costs of the
Central Plant. The construction costs for the Central
Treatment Plant for Iserlohn, including a second filter
TABLE 1
CHARGES FOR THE USE OF TWO CENTRALIZED PLANTS
FOR REMOVAL OF INDUSTRIAL TOXICANTS, IN DM PER CUBIC METER
Members participating, non-members
= not participating in the
construction of the installation
Acid and Cr acid semi-concentrate
Acid and Cr acid concentrate
Semi-concentrate containing CN
Concentrate containing CN
Eluate from ion exchangers
Acid pickling waste waters
Spend pickling fluid containing
sulphuric acid
Pickling fluid containing = 5 g Cu/l
Pickling fluid containing = 15g Cu/l
Dilute sludge ~ 3% DS
Dewatered sludge ~ 30% DS
Central detoxification plant Iserlohn *
1. Construction phase 2. Construction phase
Non-members
150. - DM
200 - DM
170-DM
247 - DM
90- DM
members
Non-members
74.50 DM
29.50 DM
20. DM
6.55 DM
12.50 DM
87.60 DM
113.80 DM
52.60 DM
20. DM
9. DM
19.50 DM
ZSEA"
Heiligenhous
members
17.40 DM
16. DM
excluding shipping costs and value added tax
'including shipping costs and value added tax
105
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TABLE 2
RUNNING COSTS FOR CENTRAL NEUTRALIZATION, 1974
Receipts
Neutralization of liquids from
11 members
about 50 non-members
Receipts from liquids sold
Interest for reserves
DM
28,900
300,500
600
15,800
345,800
Expenditures DM
Wages 23,500
Chemicals 32,100
Energy 1,600
Costs for sludge handling 80,800
Maintenance 66,600
Reserves for maintenance 40,000
Insurance for risks 20,000
Technical and administrative
supervision 47,400
Reserves for unforeseen 32,200
Transport costs for concentrates sold 1,600
345,800
TABLE 3
RUNNING COSTS FOR SLUDGE HANDLING
Receipts
19 members
dewatered sludge
thin sludge
non-members
dewatered sludge
thin sludge
costs for special treatment
Hydroxide sludges from
central plant (galvanizing industry)
Hydroxide sludges from
central plant (pickling industry)
Interest for reserves
DM
26,600
11,200
AND DISPOSAL
Expenditures
Wages
Chemicals
Energy
Transport and Disposal
Reserves for recultivation
7,800
50,300
6,500
31,200
Maintenance
Reserves for maintenance
Insurance for
risks
DM
28,800
3,600
2,000
18,000
15,700
69,600
30,000
3,200
Technical and administrative
80,800
21,500
235,900
supervision
Interest for loan
Reserves and
unforeseen
21,400
5,200
28,400
235,900
SUMMARY
ON STATUS AND
Status 31/12/73
Central Neutralization
Reserves for maintenance
Reserves for unforeseen
Central Sludge Handling
Reserves for recultivation
Reserves for maintenance
Reserves for repayment of loan
Reserves for unforeseen
1967-1973 DM
85,000
95,900
40,700
45,000
105.000
47,700
TABLE 4
DEVELOPMENT OF
Withdrawal
1974
- 10,000
- 15,000
- 6,700
- 10,000
—
-11,200
SPECIAL RESERVES
Increase
1974
+ 40,000
+ 32,000
+ 15,700
+ 30,000
+ 28,400
1967-1974
115,000
112,900
49,700
65,000
105,000
64,900
512,500
press and a second dump for about 50,000 m,3 totaled 2
million DM. The second filter press and the second
sludge depository were paid for from savings on the
operating costs.
Similar financing has been arranged for the ZSEA-
Heiligenhaus. In a third case, construction costs were
paid for through a loan, so that the capital cost, (interest
and repayment) must be calculated as part of the
operating costs.
The operating costs for the ZE A-Iserlohn are shown in
Tables 1,2,3 and 4. They are lower than for any other
central treatment plant in Western Germany; most costs
have not risen for 16 years. An example of the annual
calculation of profit and loss can be seen in Table 2, for
neutralization, and in Table 3, for sludge handling. The
status of special reserves is shown in Table 4. In the past/
all necessary expansion programs have been paid for out
of the special reserves.
106
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If the capacity allows, waste is also accepted from the
so-called non-members. They must, however, pay a
higher price than members for the service.
Preparation, Collection and Transportation
Of the Wastes
A minimal pretreatment must be carried out by the
companies themselves. First, the quantity of rinsewater
must be reduced through improved rinsing techniques.
This can be achieved either by using a still-rinse after the
bath and two or three counter current rinses, or by using a
more technically advanced method: one still-rinse and
one flow-rinse in combination with ion-exchangers
(Figures 4 and 5). The first method results in so-called
semi-concentrates and a lesser quantity of rinsewater.
These must either be treated in the plant, or stored in a
tank until a quantity has been collected which can be
economically transported to the central treatment plant.
In the second method of still-rinse, flow-rirtse and ion-
exchangers, a very low quantity of freshwater is needed to
make up the losses in the rinsing cycle, but different
storage tanks must be provided for the acid and alkaline
solutions.
For collecting, storing and transporting the liquors, we
offer containers of different size (60; 200; 800 liters)
without any additional payment. If the quantities are
greater, it may be more economical to build some storage
tanks in the plant itself and transport by 5-, 10-, or 20-m3
trucks. This is being done, for instance, when thin sludges
from in-plant treatment facilities have to be transported
once or twice a month to the central treatment plant.
In the case of the central dewatermg facility in
Heiligenhaus, transport of the wastes from the industrial
plants to the facility is handled by one transport company
which charges the same price, regardless of the distance
involved. This cooperative principle eliminated
disagreement about the location of the facility and
possible economic disadvantages which may have
occurred in transporting the wastes.
Operation and Maintenance -
Recovery of Liquids
This paper is not intended to give the chemistry of the
oxidation of cyanides, or of the reduction of chromates,
or of neutralization. The following section details some
of the experiences we have had with out central plants
and the solutions we found to some problems.
We found that one of the most important items was
storage capacity. Adequate storage capacity saves on
time and expenses for chemicals and, therefore, on
operating costs. For instance, when the central plant for
Iserlohn was started, we found that a large quantity of
NaHSO4 was required for the reduction of chromates.
We began to collect and store iron-chloride and iron-
sulphate solutions for use instead of NaHSCX This
eliminated the need to buy expensive chemicals which, in
any case, increased the salt concentration in the effluent.
We also store the alkaline solutions we collect, for use in
neutralization, as well as in the oxidation of cyanides, as a
substitute for sodium hydroxide. Alkaline solutions are
also used to dilute concentrates to 1 g CN/1. Certain
concentrates, in most cases small quantities, can also be
collected, equalized in quality and be prepared for
recycling if storage space is available. We are collecting
some hundred m /year of copper and nickel containing
solutions, which are transported in 20 m3 containers to a ,
Chemicals
Fresh-Water
I 1 §
1 i
Bath
i s
s
0
]u
1
U
s
0
1 1
Effluent to Effluent to Sewerage
Storage Tank or Jn- Plant Facilities
or Jon- Exchanger
Fig. 4—3-step-counter-current rinse with flow-rinse.
v
D
Co
Cn
Number of Rinses
Flesh Water
Ladling Rote
Concentration in Both
Concentration in the Last Rinse
100 V/O
V/D -Fresh Water/Ladling Ratio
CofCn" Factor of Dilution
Fig. 5—Water consumption of counter-current rinse.
Sediment Iml/l]
pH - value
Chromium [mg/II
Copper Img/H
Nickel [mg/ll
Zinc (mg/ll
Cadmium [cng/l)
Iron lmg/1)
Tin |mg/l]
CN decomposable Img/l]
by chlorine
Free chlorine 1 mg/ll
Standards
when dis-
charged to
0.3
6.5-9.0
2.0
1.0
3.0
3.0
3.0
2.0
-
0.1
-
Standard
A115
•I
6.5-9.5
4.0
3.0
5.0
5.0
-
•I
-
1
-
Berlin
0.5
6.5-6.0
1.0
0.1
1.0
3.0
1.0
-
5.0
0.1
—
Fronk-
furt
1
6.0-9.0
2.0
2.0
2.0
2.0
2.0
20.0
-
frei 0.3
komplex
1.0
1.0
Koln
-
6.0-9.0
2.0
2.0
3.0
2.0
2.5
5.0
2.0
0.5
-
Zurich
—
6.5-9.0
2*
1.0
2.0
2.0
1.0
-
2.0
0.5
0.5-3.0
*) Limits in dependence of the receiving treatment plant
Fig. 6—Standard values for the toxicant content of waste waters when
discharged Into a sewerage system.
central non-ferrous-metal recovery plant operating on a
private basis. Some of the industrial installations are now
collecting these solutions themselves, rather than having
the central treatment plant do so.
In future, some special solutions will be collected and
stored for use in the Ruhrverband's treatment plants.
Instead of buying expensive chemicals for phosphate
107
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precipitation, we are now using the iron-chloride
concentrates from iron pickling plants, after equalizing
the concentration and destroying the free hydrochloric
acid by adding iron oxide from another central plant
which operates on a private basis. This plant is recovering
about 2 m3/h of hydrochloric acid by combusting the
spent concentrates. (Figs. 1, 6) This procedure agrees
with the "Waste Recovery Program of the Federal
Government of West Germany". Adequate storage
capacity also makes continuous and stable treatment
possible. We are able to accept all quantities of waste
(from a beaker to a 20 m3 container), in all qualities (from
concentrates, semi-concentrates, thin and dewatered
sludges) at any time.
The pumps are another important consideration in the
treatment plant. One should not try to find a pump
material which will withstand all challenges. The pumps
which can be repaired easily by replacing rotating parts
and gaskets after having removed a few screws, and not
after dismantling the whole plant, should be used. This
also applies to the mixers.
The chemical treatment process must be automated to
reduce the number of operators required and to obtain
consistent results. A complete central plant which
includes chemical treatment and disposal facility really
requires only one man to operate it. However, a single
man is not permitted to work alone in such a plant, so two
men are required for each shift and back-ups are
necessary in case of illness, and during vacations. Our
back-up operators are supplied from a nearby sewage
treatment plant.
Protection from corrosion is another important
consideration. Naturally, all storage tanks must be
carefully sealed. Even neutralized sludges have a strong
corrosive effect, because of their high salt concentrations.
Hence the filter press plates should be coated by heating
the cast iron plate and dipping it in a fluidized bed of
special polymers. Plates manufactured from special
plastic could also be used. The effluent from a central
plant has salt concentrations of up to 5 g/1 SO4, 1 g/1
NO3 , and 5 g/1, Cl. NO2" and 0.2 g/1 NH4 may also be
present. This effluent is, therefore, discharged to the inlet
of the wastewater treatment plant, after passing through
a final settling tank of long detention time. This
treatment is necessary not only to oxidize ammonium
and to reduce nitrates, but also to dilute the salts that are
toxic to fish.
Disposal, Supervision of the Disposal Site,
And Recovery of Special Sludges
The dewatered sludges from the central plant, as well
as those from company-owned facilities are dumped at a
disposal site. The disposal site usually includes lagoons
for anaerobically digested municipal sludges and areas
for dewatered hydroxide sludges. The bottom of the site
is sealed with clay. Any percolating or surface water is
withdrawn and returned to the central treatment plant.
There is usually no surface water at all, and the
percolating water contains only very small traces of
metals, always below the standards required in Germany
for waste disposal. (See Figures 6 and 7.)
The disposal sites should be surrounded by trees, or at
least by bush, since wind erosion can cause problems.
Special sludges containing copper, nickel and zinc are
being stored separate from the iron and chromium
containing sludges (Figure 8). If the metal market allows,
Sediment [mg/l]
pH -value [mg/l]
Copper [mg/l]
Zinc [mg/l]
Nickel [mg/l]
Chromium [mg/l]
Iron [mg/l]
Cyanide [mg/l]
Dump
Iserlohn
0.1
7.6
0,1
0,1
1.3
0,1
0.7
0.1
Dump
Heiligenhaus
0.1
8.0
0,2
1.3
0,4
0,1
0.9
0,1
Fig. 7—Contamination ot seepage Irom two centralized industrial sludge
dumps.
sludge
sample
1
2
Cu
3.35
11,4
Zn
2.85
4.7
Fe
0,09
0,02
Cl
0.17
0.62
S
15.4
11.9
CaO
29,5
22,5
AI203
0,15
0.15
H20
50
50
Fig. 8—Analysis of Sludges for Recycling
these sludges are given away for free, in order to save on
disposal site space. Liquid and solid material wastes from
the electroplating, and brass and copper pickling
industries are recycled to save on operating costs,
capacity and volume, not to make a profit.
The Ruhrverband collects about 10,000 t/year
hydrochloric acid (containing 130 g Fe/1 and 5 g free
HC1/1), and 20,000 t/year of FeSO4'7H2O from iron
pickling wastes. This represents a real economic factor as
a raw material for the chemical industry. However, the
sale of these products covers only the transportation
costs, although we also save by not having to pay for
neutralization, desludging, dewatering and dumping.
Other Wastes that can be Accepted
CN~ and NO2 salts from hardening furnaces are
collected in containers at the industrial plants and sent to
a central collection site, (Fig. 1, A) from which they are
taken to an old salt-mine and disposed underground. All
solid toxic materials are also handled in this way.
Water from cooling baths is occasionally brought to
the central treatment plant at Iserlohn. Chemicals from
laboratories and from the army (sodium hydroxide,
calcium hypochlorite, etc.) are also accepted at the plant.
As long as the capacity of our central plant is not
exhausted, we accept these materials from all over
Northrhine-Westfalia, and even from other parts of
Germany.
A bulletin published through the "German Recovery
Program" lists various installations which accept special
wastes, liquids or solids, toxic or inert, organic or
inorganic wastes.
Acceptance of Centralized Treatment
Concepts in Other Countries
Several projects for centralized treatment plants are
being developed outside of Germany, for example, in
Norway, Denmark and Switzerland. However, none of
these except Denmark has yet passed the planning stages.
Many central facilities for special wastes from various
industries are operating successfully in Germany. We
have found such facilities to be the best solution to the
108
-------
problem of pollution control in a country that has limited
resources of land, air and water, and which is densely
populated like ours.
Economics of In-Plant Treatment
Versus Shipping to a Central Plant
The decision as to whether it is more economical to
treat wastes in an in-house facility or to transport them to
a central facility requires careful investigation. The
present situation, and possibilities of future development
must be examined in each case, and the following items
should be taken into account:
1) Cost of in-plant changes.
2) Cost of pretreatment up to desludging (3% solids).
3) Cost of further thickening and dewatering.
4) Cost of transporting and disposing of the filter cake.
If points 1) and 2) are considered in conjunction with
the quantity of rinse water required, it is found that,
below a certain volume of rinse water, it is more
economical to use a central facility. Beyond this volume,
it is cheaper to use an in-house facility. Naturally there is
also a zone of uncertainty where it is possible to
determine which is most economical.
\\
\
\1
\M
\
\K\\
\
A
1
In- Plant Tret
menl D
evices
A interest and Re;
B Maintenance
C Personal
D Chemicals
E Supervision and
F Dn-Plant-Chang
G Transport
^
\;
t-
.
•
<
/
/
/
f
V//
\\
f/i
Cer
Y/t
'//<
F
C
ayment
Management
es
tral F
|^^
#
Jp
>
;
lar
e!d
E
0
=fBA
it
of
Uncertainty
1 3 5 10 3 5 10! 3 5 103 3 5 10'
Rinsing Water [mVd] >
Fig. 9—Specific annual costs of water treatment with In-plant and central
stations as a function of rinsing-water quantity (without dewatering and
disposal sludges)
Thin sludges and filter cakes must be considered in the
same manner, in order to decide whether to handle them
directly or ship them to a central treatment plant.
Figures 9, 10, 11 and 12 have been prepared using our
data for interest and repayment, operating time, annual
depreciation, transportation distances, benefits for
government, and savings on the cost of fresh water and
sewerage for the municipal treatment plant and
associations such as Ruhr River Association and the
Ruhr Reservoir Association.
Now let me show you the example. A galvanizing
plant, which required 100 m3 of fresh water per day
redesigned its entire processing line and improved the
waste treatment sections for each processing unit (Figure
13).
The first step was to improve metal recovery. This
means that copper, nickel, zinc and chromium containing
liquors must remain either on the surface of the material
to be finished or in the bath. How can this be done? If you
pull the material out of the bath and take it directly to the
Quantity ol sludjt (m>«)
containing 3V* dry matter
sludf*
50
30
10
S
2
1.0
0.5
0.1
A
/
B
o
f
°/
n
f
o
^
u
/
*s
/
/
f
OPick
b
a
Pick
golv
Golv
1 5 10 5 10* 5 103 5 1C
galvanizing establish*
Enrtched to form
emi-concentrales I
nd shipped to a [
itrol detoxifi-
otion plant
no rinsing *a1er
reatment)
Rinsing water production [m'/dj
(Ditule sludge to central
delo,,I,ca.,on plant
Dewalered sludge to
central dump
Oe-otered sludge to
eslablishmenl-owned damp
fig. 10—Organization of toxicant removal subject.
A
D
r
fi-
ler
Plant Trea
t Devices
C\
B
A
\
-\
\
\
\
\
\\
\
B
C
D
E
F
^
V
» ^
^:
Capita
Mainte
Persor
Transp
to Cen
Oispos
Costs
of Dev
• i
Costs
nance
al Co
ort Co
tral PI
al and
for Tra
vatere
entra
1
I
_j
1
-i
for Fi
its
sts for
ant
3nsur
nsport
1 Sludc
1
Plant
i
D
= B
ter Press and Building
htckened Sludge
once for Risks
and Disposal
e
*335 It)-1 3 5 10° 3 5 U)1 35 10*
Thickened Sludge [mj/d]
Fig. 11— Specific costs of in-plant and central sludge dewatering devices.
T
680
UO
,400
.i 360
S 320
£
= 280
.2
~ 200
o
160-
120
80-
40-
0
4.5
012345678
Factor of Dipping [n] —
Fig. 12—Bath-losses •* • (unMton of the quality ct i
from the bath.
9 10
109
-------
rinse you remove, let us say, a maximum of 100% of the
liquor. If you allow the piece to drip into the bath for 15
seconds, this value drops to about 60% and for 60
seconds, to 30%. By adding an electromagnetic vibrator
with variable frequency and amplitude so that the best
combination can be determined, you can minimize the
bath losses to 10% by vibrating the rack while removing it
from the bath. Ladling parts should be suspended so that
the concentrates can flow out of the hollows. The rest can
be blown out with air. Every percentage you save is your
money, represented by the need for less metals or metal
salts, less water for rinsing, and less wastewater to be
handled. You cannot protect your environment by
wasting water and materials and you must concentrate
the inevitable losses in as small a quantity of water as
possible. Dilution will not keep your water clean.
The next step in good housekeeping is a good rinsing
process with counter current water flow and replacement
of the losses of the bath from the first still rinse. No
matter which rinsing process you use, you will still be
getting semi-concentrates, which can be handled as
shown. The effluent from the flow rinse goes to the ion-
exchanger and is then recirculated to the rinse. With two
or three counter current flow rinses, the effluent from the
second and third rinses can be sewered since the metal
concentration will be under 5 mg/1, while the effluent
from the first rinse after the bath represents semi-
concentrates containing about 95% of all metal losses.
Many other variations of this operation are possible.
Centralized Treatment and Disposal
Of Special Wastes in Bavaria*
The following discussion is an example of a more
public and compulsory centralized treatment concept.
1. Tasks
The harm caused by the uncontrolled disposal of
commercial and industrial wastes has become
increasingly evident in recent years, owing to the
continuous growth of industrialization. Compared with
wastes from households, or domestic refuse, these
special wastes occur in relatively small quantities and
must receive special treatment in plants designed for the
purpose if they are to be disposed of in the proper
manner, i.e. with no harmful effects on water, air or the
environment and with no adverse effects or pollution
caused by dust, odors or corrosive gases.
Such materials, in the broadest sense, also include
hospital wastes, scrap vehicles, car tires and the like; the
term "special wastes", however, applies only to those
materials which, owing to their nature or quantity,
cannot be disposed of together with domestic refuse and
which none of the existing installations such as those of
hospitals, animal carcass processing plants, private
shredder installations, centralized graveyards for
radioactive materials, etc can take. The decision as to
what constitutes special wastes depends both on the
individual constituents of the material and on its quantity
M.xed B»d
'
R.nii?
[ couple te ly
water from *
o>
- ioT".a
Flo.
( t
t "» S
Flow
Rinst 1
Slill
Rtnst
Chromium
Bclh
FlowX.
Collect, r*g
Tank
r
tion-
i-
3n9«r
I
1
1
Kotion-
E»-
Chonger
II
fJ
Collecting Tank
lor Woler to Rinses
—}
Amon -
crxinger
I
I
Amon-
Ex-
chongtr
II
Collecting Tank
lor Anion-Cluat
Collfcttng Tonk
tor Vatio" -Eluat
CoHeehn
lor Anio
J
I De«Ot*re3 $lvX3g* to DiSpOSOl
Water to Sewerage I
j— ->| Wottr to Sewerage j
Fig. 13—Schematic flow-sheet of a modern galvanizing plant.
110
-------
or concentration since, in general, inert industrial
sludges, sandtrap residues and oily earth, if in
appropriate quantities can safely be tipped on controlled
domestic refuse dumps.
Special wastes are subdivided as follows:
• Materials such as oil-contaminated soil, tar residues,
solidifying acid sludges and the like which, owing to
their potential for air and water contamination, may be
deposited at suitably prepared sites, subject to special
precautions.
• Materials which can or must be disposed of by burning
(e.g. solvents, used oil, oil wastes and residues, fullers'
earth containing oil).
• Organic or inorganic materials which must receive
chemical or physical treatment before being disposed
of. These include: acids, alkaline solutions, sludges
from the chemical and metal processing industries, and
water-soluble heavy metal salts.
Before the materials are treated, a sample is examined
in order to determine the type and effect of the process
which is required and to check if the customer has
marked the waste correctly. In general, treatment itself
consists of one or more of the following processes:
• Neutralization and decontamination;
• Thickening and dewatering: chemical/mechanical/
thermal;
• Purification of wastewater so that it can be discharged
into a drainage system or receiving water course;
• Incineration
• Tipping, on domestic refuse tips/on specially prepared
sites.
2. Bodies responsible for disposal of special wastes
In Bavaria, the problem of disposing of special wastes
received attention at an early stage and it was found that,
only a broadly-based solution made economic sense.
owing to the technical and financial resources needed to
build and operate the requisite plants, which had to
satisfy the requirements of public health and order,
particularly those concerning preventive measures
against emissions and water pollution. The initial idea
was to entrust the task to the bodies already engaged in
the disposal of special wastes at regional levels and to
extend this over the whole "Land," but it then became
apparent that a joint body responsible for special waste
disposal comprising public and local authorities and
commercial firms would be the best solution in Bavaria.
Thus the end of 1970 saw the founding of the
"Gesellschaft zur Beseitigung von Sondermull mbH
(limited company for the disposal of special wastes),
"GSB" for short, with a capital of DM 1 million, 40% of
which was provided by the Bavarian authorities, 30% by
the three leading local authorities and 30% by 25 firms
from the chemical, metal processing, paper and oil
industries in Bavaria. (By additions to capital in 1975,
1977 and 1979, the present sum is DM 20.93 million, the
number of firms has now risen to 74, an increase of 49).
The company's purpose is to dispose of or recover in a
correct manner the special wastes arising in Bavaria and
to engage in related activities. This serves the public
interest and is not intended for profit.
The company, which operates as a private enterprise
and is required only to cover its costs, is responsible for
building and operating the installations needed for its
work. In so doing, it must specialize in taking delivery of
those wastes in which private waste disposal contractors
generally have little interest because they are
unprofitable, and must introduce and apply methods for
the proper and economical disposal, processing or
recovery of wastes specific to certain industries.
The fact that the GSB does not have to make a profit
on waste disposal and that the supervisory board
representing the members of the company has to approve
the disposal charges means that conditions now exist
which enable commercial and industrial concerns to
deliver their wastes to the GSB and have them properly
disposed of in accordance with the law, without the need
for coercion. In this connection, the high public authority
holding (over 75%) of the company's stock and the
resulting priority given to safety provide a guarantee of
optimum environmental protection in the building and
operating of plants and in the treatment of materials.
Companies modelled on the GSB, with a similar
composition and identical aims and tasks, have now been
set up.
The GSB began its work on 1 March 1971; firstly, an
overall approach to the disposal of special waste in
Bavaria was worked out and then the extension of
existing plants and the construction of new facilities was
planned and put in hand.
3. Disposal plants and collection sites
In view of the economic structure and the size of
Bavaria, it is planned to establish three central treatment
plants and a network of collection sites in areas where
arisings of special wastes are greatest.
The disposal plants provide facilities for pretreating,
incinerating and tipping wastes; they are equipped with
dewatering, neutralization, detoxification and water
purification plants, including sludge thickeners, filter
presses and emulsion separators, as well as mixing
installations and, finally, officially-approved landfill sites
which are carefully operated to avoid odor emissions and
whose waste water is collected in observation tanks for
monitoring.
3.1 Schwabach disposal plant
This plant is run by the "Sweckverband
Sondermullplatze Mittelfranken" (ZVSMM), which was
set up in 1968 and disposes of special wastes in the
administrative district of Middle Franconia. It is located
conveniently near the Nuremberg Furth/Erlangen
industrial zone and contains an incinerator plant with a
capacity of 9 Gcal/h, a physicochemical treatment plant,
a wastewater purification plant and an officially-
approved landfill site with a capacity of 500,000 m-1.
3.1.1 Commitment
The industry in Middle Franconia has taken a
favorable development during the last 20 years.
The large quantities of wastes occuring in this
production sphere could not, due to the difficult
character, be integrated into domestic refuse disposal.
This special department was thus established in 1966
and is dedicated to solving these problems in the common
interest as a nonprofit organization.
The administrative association is a corporate body
incorporated under public law.
3.1.2 Members of the Administrative Association
Members of the administrative association are: the
cities of Ansbach, Erlangen, Fuerth, Nuernberg and
Schwabach, not incorporated in a county; the counties of
Ansbach, Erlangen-hoechstadt, Fuerth,
111
-------
Neustadt/Aisch-Bad Windsheim, Nuernberg rural area,
Roth, Weibenburg-Bunzenhausen; the large county city
of Weissenburg in Bavaria; the cities of Lauf a.d. Pegnitz,
Roethenbach a.d. Pegnitz, Roth Stein; the community of
Neunkirchen a.S.
3.1.3 Catchment - Area
The operational territory is the whole district of
Middle Franconia.
The official catchment area covers in addition:
a) in the district of Upper Franconia: six counties and
three cities, not incorporated in a county.
b) in the district of the Upper-Pfalz: three counties and
one city, not incorporated in a county.
c) in the federal state of Baden- Wuerttemberg: eight
counties.
Total Catchment .area:
25,000 square kilometres =
10% of the area of the Federal Republic of Germany
3.1.4 Efficiency of the Schwabach treatment-complex
A composite unit comprising laboratory, landfill site,
water treatment plants and incinerator, the Schwabach
treatment-complex receives 110.000 tons of special
wastes per year.
From this quantity, 40 percent are dumped in the
specially-designed special wastes dump, 25% are treated
in the decanting plant with an emulsion separating
system, 20 percent are treated in the detoxication-
neutralization-and dewatering plant and 15 percent are
incinerated.
The working procedure at Schwabach is to put all
loads received over the weighbridge on arrival, and to
take a sample immediately. Analysis is normally
completed within 10 minutes, and on the basis of this, the
waste is directed to the incinerator, to the treatment
plants or direct to the landfill site.
Where direct landfill disposal is not possible, oil and
water are separated, so that the oil can be incinerated,
while water is treated before discharge into a watercourse
adjoining the site. Chemicals are treated and neutralized.
The sludge dewatering plant is able to handle sludge
arising from galvanizing operations. After
detoxification, dewatering and neutralization, the water
obtained from press filtering must pass a recording pH
meter check prior to being introduced into the public
drains. The spadable filter cake can then be disposed of
in the special wastes dump.
Until now over 5,000 experts from 29 countries
have visited the Schwabach treatment-complex.
The treatment plant installed at Schwabach was taken
as an example for similar plants in the Federal Republic
of Germany and in foreign countries.
3.2. "Sud" disposal plant
The Sud disposal plant of the GSB, situated in the
Munich/Augsburg/Ingolstadt area, consists of two
associated sections constructed along the latest technical
and economical lines; the first, consisting of mechanical
facilities, is at Ebenhausen, near Ingolstadt, and the
second, i^he Gallenbach landfill site for special wastes, is
situated in the rural district of Alchach-Friedberg. The
separation of the two sections, which lie about 40 km
apart, is due to the difficulties now experienced in
purchasing land for plants of this kind.
After much detailed planning and a relatively short
construction period, the Sud disposal plant started
operating at the beginning of 1979.
3.2.1 Ebenhausen mechanical installations
The Ebenhausen plant, built on a site about 4 hectares
in area, contains the following: a general-purpose section
with a vehicle weighing machine, a workshop and store-
rooms; an administrative building housing offices, staff
facilities and the fully-equipped central laboratory; an
incinerator plant for liquid, semi-liquid and solid wastes;
a physicochemical treatment plant for used alkaline
solutions, used acids, plating sludges, inorganic sludges
containing chromium, cyanide and nitrites; and a plant
for purifying industrial wastewaters.
The incinerator plant on the eastern side of the site
contains two rotary furnaces, a steam generator, and a
highly-expensive flue gas purification plant consisting of
electro-filters and two-stage flue gas scrubbing plant, a
turbogenerator and all the requisite auxiliary
installations. Its heat output is 25 Gcal/h - 12.5 Gcal/h
from each of the rotary furnaces and the liquid burners.
In this way it is possible to operate simultaneously
either two firing systems at full capacity or three systems
at reduced capacity. The planning allows for the addition
of a further unit of the same type.
The firing installations are followed by the large
secondary combustion chamber in which the
temperature is kept at a minimum of 1000° C. The flue
gas is then cooled to about 280° C in a steam generator
with exclusively smooth-walled pipes to inhibit sooting
of the heating surfaces and a switchback configuration in
order to increase the separation of solid constituents
from the flue gas flow.
The flue gas cleaning system consists of an electro-filter
for separating out fine dusts and a two-stage scrubbing
plant for removing chlorine, fluorine and SO2 from the
flue gases. The scrubbing water is recirculated and is
treated in the physicochemical plant.
The steam which is produced (32t/h, 25 gauge atm.) is
used both to produce electrical energy for the plant's own
use and to heat the plant's installations. Surplus steam is
condensed in an air-cooled heat exchanger to avoid
polluting the environment. An oil-fired boiler with a
large water space (6 Gcal/h) is available for supplying
heat when the incinerator is out of operation.
The control room and the power supply installations
such as switchgear, a transformer, a turbogenerator, a
feedwater treatment plant and a boiler are housed in a
central situated building. The receiving bunkers for solid
and semi-liquid wastes and the loaders for the rotary
furnaces are roofed in while all the remaining parts of the
plant are in the open.
In the physicochemical treatment plant (CPA),
situated in the western half of the site, the materials are
put in one of the eleven 30 m3 receiving tanks, depending
on the results of the laboratory tests. These tanks lead
into several storage tanks of the same capacity and,
finally, these are followed by the individual treatment
plants consisting of mixing and dosing units.
Any sludge which is produced is drained in chamber
filter presses, the filter cakes are taken to be dumped and
the filtrate as well as other waste water is discharged to
the receiving watercourse or to a sewage treatment plant
via final inspection points and retaining vessels.
Pollutants are removed by a gas scrubber to which the
contaminated air and waste gases from the containers in
the CPA are conveyed. The purification plant for
industrial waste waters containing oil and emulsions
(ARA), which is integrated into the CPA and has been
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developed by the GSB, consists of two tanks with a
capacity of about 300 m3, a centrifuge, a mixing and
dosing unit, and a vacuum drum filter.
3.2.2 Gallenbach landfill site (Figure C)
The site, about 17 ha in area situated near the Munich-
Stuttgart motorway on Federal highway No. 300 leading
to Ingolstadt, is crossed by a layer of clay and loam
between 8 and 18 m thick which prevents water from
seeping into the lower groundwater table. Above this
layer there are moraine deposits, gravel and sand, which
are gradually being removed and used to construct each
section of the site. In contrast to those collection sites for
which existing trenches are usually chosen, here the earth
pits have to be dug.
This produces a sufficient quantity of excavated
material for covering purposes, such material often being
difficult to obtain in other circumstances. Since the outer
slopes are planted and grassed while the landfill site is
being constructed, the appearance of the landscape is
altered only for a relatively short time. The inner surface
is covered with a clay/loam puddle layer at least 40 cm
thick which acts as a sealing material. The leachate is
received by drainage courses with a filter gravel base
about 2 m beneath the pit bed and, like the surface water,
is conveyed to three retention tanks with a total capacity
of about 10,000 m3. When a tank is full, the water in it is
inspected and, if found to be in satisfactory condition , is
discharged to the receiving watercourse. If it does not
meet the discharge requirements, it is retreated and
transported to a sewage treatment plant. The
groundwater is continuously monitored by means of
sampling tubes reaching down to the lower groundwater
table.
The landfill site for special wastes has a gross storage
capacity of about 1.5 million m3 and will take about 15 to
20 years to fill. In addition, it includes an administrative
building with an office, staff accommodation, a testing
room, a shed for earth moving machinery and other
vehicles, and a vehicle weighing machine.
The first section, completed in 1975 in only nine
months, has a storage capacity of 450,000 m3.
3.3 Schweinfurt disposal plant
The third disposal plant is situated in Schweinfurt. At
present, it is an incinerator plant for industrial wastes
which are similar to domestic refuse (heat output of
about 9 Gcal/ h) and was purchased by the GSB at the end
of 1972 from the former "Sweckverband fur
Abfallbeseitigung in der Stadt Schweinfurt" (association
for waste disposal in Schweinfurt). Since then, further
installations have been added so that it can receive
further wastes.
In the long term, it is planned to replace the present
plant with an incinerator plant for liquid and semi-liquid
wastes (with the same heat output of 9 Gcal/h).
3.4 Collection sites
The collection sites for special wastes, where various
wastes from nearby firms - often in small quantities - are
delivered and temporarily stored, help among other
things to reduce transport costs (an important factor in
view of the size of Bavaria, which covers one third of the
area of the Federal Republic) by the combination and use
of convenient bulk transport vehicles and by the
existence of a standard list of charges for the whole Land
in order that firms situated outside the main industrial
centres should not be placed at a disadvantage.
The collection sites are designed on uniform lines and
generally contain the same equipment. Apart-from the
temporary storage of waste, they are also responsible for
pretreating as much waste as possible and for reducing its
volume with the aid of easily-operated technical
installations. They contain waste water purification
plants (ARA), in which the consistently large quantities
of oil/water mixtures that are delivered are separated out
into oil, water and solid matter. The purified waste water
is immediately drained off. What remains, less than 10%
of the original amount, is in the form of an oily sludge
which is then transportec elsewhere.
When justified it is planned to install neutralization
and, if necessary, sludge thickening equipment.
Furthermore, in addition to an administrative building
with a testing room and a vehicle weighing machine, all
collection sites have adequate storage space for oil-
contaminated earth and for freight containers designed
to collect and temporarily store industrial sludges of all
kind.
Collection sites already exist in Aschaffenburg,
Augsburg, Mitterteich, Munich, Neu-Ulm, Passau and
Straubing. Within the next few years it is planned to
construct further collection sites in Bamberg and
Kempten and a new large-scale site in Munich.
The GSB keeps in close contact with all the
organizations which are concerned with the planning of
new disposal plants for domestic refuse or sewage sludge
in order that new plants (incinerators and landfill sites)
are, wherever possible, designed and constructed from
the outset so that they can dispose of special wastes.
Thus, for example, oily sludge with a high calorific value
which is brought to the collection site is ideally suited to
back up the burning of sewage sludge, a process which
will become increasingly important in the future. In Neu-
Ulm, combined operation of this kind between a
collection site and the incinerator unit of a neighboring
sewage treatment plant is already taking place. Efforts
are also in hand to set up a joint operation between the
collection sites and domestic refuse incineration plants
which are to be built in Bamberg and Kempten, in order
that part of the wastes can be disposed of on the spot.
4. Recovery plants
At the Ebenhausen incinerator plant, heat and electric
power (for the plant's own use) are derived from the
wastes and converted into usable form. The incineration
of wastes with a high calorific value which occurs in
Sohweinfurt is also of benefit since it enables non-
combustible materials to be disposed of more efficiently
and at less cost.
As a result of the recognition that raw materials have to
be used more sparingly in future, the main emphasis in
waste disposal is shifting increasingly to recovery and
reutilization.
This led the GSB, at the end of 1973, to take various
steps, including the purchase of a firm situated at
Gereteried, near Munich, which was engaged in the
distillation of used solvents, varnish thinners, degreasing
agents and similar materials, to ensure that the recycled
materials were put back on the market.
5. Deliveries and transport
Disposal of special wastes can be effective only when
these materials are clearly described and when their
transport is supervised. To this end, in addition to the
form specified by the authorities, the GSB also issues
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numbered forms consisting of several sections which
must be completed and officially signed by the producer
(or originator) of the waste. When the waste is handed
over to a haulier, the customer retains one copy of the
form as a receipt whilst the remaining copies, the contract
and the confirmation of the contract are delivered along
with the wastes to one of the GSB's offices; the hauler
retains the other copy which enables him to present a bill
for his services. Before the vehicle is emptied, the details
given by the customer are checked, as is the amount (by
weighing) and the description of the materials are
checked by means of the serial numbers on the forms
which have been issued. The costs of disposal incurred by
the GSB are charged directly to the producer of the waste;
normally the GSB does not accept orders for waste
disposal from haulers. The GSB also refuses to accept
delivery if the form is not properly completed or if the
conditions under which delivery is accepted have not
been observed.
The transport of special wastes falls into two
categories; the delivery to the collection site (the
"collection service") and the conveying of the wastes by
bulk transporters from the collection site to the disposal
plant.
The "collection service" is generally performed by
efficient and reliable private haulage firms which, when
the customer does not make the delivery himself, also
represent a guarantee that the wastes will arrive at the
collection site. Bulk transport between the collection site
and the disposal plant is normally carried out in freight
containers or tankers in cooperation once again with
private hauliers.
6. Amounts of waste received and capital expenditure
The growth of the GSB over the last few years can be
seen from the following figures on deliveries of special
wastes:
Year:
Amount:
1972
60
1973
116.5
1974
134
1975
165
1976
171.6
1977
186.4
1978
183.1
Last year the GSB and the ZVSMM duly disposed of a
total of 300,000 t of special wastes in Bavaria.
By the end of 1978, the construction of the above-
mentioned installations had cost about DM 80 million,
towards which the Bavarian authorities contributed
generous "Land" grants and low-interest government
loans.
SUMMARY
In this paper I have attempted to outline in examples
the treatment being used for different wastes from the
metal finishing and other industries.
I hope that those who are struggling with the same
problem will find this description useful.
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EPA's Centralized Treatment Program
Alfred B. Craig, Jr., and George C. Cushnie Jr.*
INTRODUCTION
The Metal Finishing Industry utilizes more than 100
surface finishing and fabricating operations that require
aqueous application and removal of various metals to
and from metallic and plastic parts. The metal finishing
process baths contain various cyanides and cyanide
complexes, hexavalent chrome, copper, nickel, zinc,
cadmium, and other metals that must be disposed of once
the end of the useful life of the bath has been reached. In
addition, water used to rinse plated parts contains dilute
concentrations of these metals.
A vast majority of electroplating shops reside in large
industrial communities in and around municipalities. A
majority of the plants in the electroplating industry
discharge untreated or lightly treated rinse water and
plating baths to municipalities for treatment by Publicly
Owned Treatment Works (POTW's). These
nonbiodegradable pollutants are discharged in millions
of gallons of process water each day to biological
treatment systems, which are ineffective for treating such
wastes.
Impacts of Metal Finishing Operations on Publicly
Owned Treatment Works
Pollutants in metal finishing process wastewater
interfere with proper operation of biological systems and
restrict the utilization of biological sludges because of
their high metal content. Cadmium, chromium, lead,
nickel, and zinc are not destroyed when introduced into a
POTW and will either pass through the system or will
contaminate the sewage sludge. The metal content of this
sludge may preclude land application of sewage sludge on
food crops; sewage sludge disposal by incineration is also
questionable because of the volatility of cadmium and
lead.
The Enabling Regulations
The Environmental Protection Agency is currently
proposing and promulgating a scries of industrial
wastewater pretreatment regulations. These regulations
will reduce the introduction of industrial wastewater
pollutant parameters to POTW's. In order to comply
with these pretreatment regulations, indirect dischargers
will be required to install various process wastewater
control and treatment technologies at their plant sites.
These regulations, will cause adverse economic impact on
'Alfred B. Craig, Jr.
Nonferrous Metals & Minerals Branch
Industrial Environmental Research Laboratory
U.S. EPA, Cincinnati, Ohio
George C. Cushnie, Jr.
Centec Corporation
Reston, Virginia
some industries and some small plants with limited
personnel and capital for addressing these regulations
undoubtedly will be forced to close.
Simultaneously, EPA is implementing Congress'
intent of the Resource Conservation and Recovery Act
(RCRA). Industry, in complying with the provisions of
RCRA, will be required to safely dispose of their residual
wastes. The cost of waste disposal and management will
likely increase as will administrative burdens associated
with the proposed waste management system.
Research on Centralized Treatment
Three years ago, EPA's Office of Research and
Development (ORD), anticipated the potential impact to
industry resulting from compliance to pending
wastewater and solid waste regulations. Therefore, it
began investigating conceptual alternatives to on-site
industrial waste treatment by generators. One promising
alternative is centralized treatment. The primary assests
of this approach are scale economy and improved waste
management. Centralized treatment provides
experienced management and personnel whose primary
responsibility is in handling wastewater and solid waste
residuals; this contrasts with production personnel who
can provide only intermittent supervision of treatment
practices at individual industrial plant sites.
ORD has taken an active role in investigating the
Centralized Waste Treatment (CWT) concept,
determining its applicability to the metal finishing
industry, and laying the groundwork for
implementation. An ORD project in 1977 established the
economic feasibility of a joint waste treatment plant and
investigated the legal and institutional arrangements
necessary for successful implementation and operation.
In 1978, ORD sponsored a second project that
investigated the successful centralized treatment
application in the Ruhr Valley in Germany. This same
project explored the applicability of CWT to the United
States taking into account U.S. costs and U.S.
environmental requirements.
In June of 1979, a third project was funded by ORD.
This project, which will be completed within 3 months,
has developed the background information for industry
implementation of centralized treatment. A manual
describing technical, economic and financial aspects will
be issued in July. The remainder of this paper will be
devoted to the current EPA Centralized Treatment
Program effort. An explanation of project objectives and
procedures and a summary of available results will be
presented.
CWT PROJECT OBJECTIVES AND OVERVIEW
The current project is divided into two phases. The
purpose of Phase I is to determine the conditions that are
favorable to CWT development and to identify which
areas of the U.S. meet these conditions.
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The first task of Phase I comprised a categorization
process that defined characteristics that affected the
feasibility and design of a CWT system. Then, five case
studies were chosen to represent varying situations in
which CWT would be applicable. To determine the
feasibility of CWT in each of the case study areas, data
were gathered from municipal, regional, and industrial
sources, and an analysis was performed.
The purpose of Phase II was to develop and
demonstrate the approach necessary for implementation
of central treatment. This was accomplished by selecting
one promising area and developing a comprehensive
metal finishing waste control plan that includes a CWT
system configuration with collection, transportation,
treatment and disposal; on-site treatment requirements;
financing requirements and alternatives; and
management options.
Phase I -
Categorization and CWT Feasibility Case Studies
The activities of Phase I were focused on the selection
and analysis of the five case study areas. The procedure
for Phase I included six major tasks:
• Categorization of U.S. metropolitan areas
containing a substantial metal finishing population
• Selection of 24 metropolitan areas for case study
consideration
• Selection of five case study areas
• Data collection and characterization of case study
areas
• Development of analytical tools
• Case study analysis of CWT feasibility
Categorization of U.S. Metropolitan Areas Containing
Substantial Metal Finishing Population
A statistical categorization process was used in Phase I
so that the results of the five case studies could be applied
to a major portion of the metal finishing industry across
the U.S. within characteristic regions. The basic premise
behind this categorization was that if a case study had a
feasible solution for CWT, then all cities in the same
Table 1
Factors for Developing Categorization
Factors Affecting Feasibility and
Design of CWT
Probable Effect of Factor
GOVERNMENTAL FACTORS
• Willingness of Municipalities to
Participate in CWT
• Future Plans of Municipality with
Respect to Industrial Discharges
• Availability of Disposal Sites
• Number of Local Governments
Involved
• Non-Federal Regulations
• Type of Municipal Government
• Municipal Willingness to
Fund CTF
• Municipal Financial Conditions
• Municipal Demography
Participation and cooperation by municipal governments will hasten the implementation of
CWT; however, a strong private interest in CWT may overcome municipal barriers.
Municipalities with immediate plans to enforce pretreatment will reduce feasibility of CWT.
CWT is more likely to be feasible in localities containing disposal sites.
A large number of local governments will present a less feasible situation, since jurisdic-
tional disputes will be a barrier to CWT. If a league of cities exists, the effect of this factor
may be mitigated.
Local pretreatment regulations may have already precluded CWT by forcing individual
treatment to be presently installed.
Various types of municipal government structures should be investigated. At this time,
the effect of this factor is uncertain.
Municipal funding may be necessary in certain areas; however, private funding may
eliminate the effect of this factor.
Some cities may qualify for Federal assistance in constructing a central treatment facility
(CTF). Some cities may be able to affort CTF or be able to raise money through bonding.
Population size and density will affect the availability of land for CTF and disposal siting.
Also, cities with a high population concentration may have traffic congestion that increases
hauling time and, therefore, CWT costs.
INDUSTRIAL FACTORS
• Number of Metal Finishing
Plants
• Concentration of Metal
Finishing Facilities
• Willingness of Metal Finishing
Industry to Participate in CWT
• Total Wastewater Flow
• Present Treatment Installations
• Future Plans of Metal
Finishing Industry
• Types of Waste
• Types of Metal Finishing
Industry
The number of plants may affect the design of the CTF. Also, larger numbers of facilities
will favor CWT.
Higher concentrations of facilities will favor CWT.
Without the minimum number of customers required to reach economies of scale, CWT
will not be feasible.
Minimum flow needed for feasibility of CWT.
Installed treatment facilities may preclude CWT.
Immediate plans to install pretreatment may preclude CWT.
The type of waste affects the design of the CTF. Also, CWT is most amenable to
concentrated metal-bearing wastes.
The type of industry affects the waste characteristics and, therefore, the design of the CTF
and feasibility of CWT.
GEOGRAPHIC FACTORS
• Regional Location
Most segments of the metal finishing industry are unevenly distributed. For example, the
jewelry industry is concentrated in the Northeast, and the electronics industry is in the
Southwest and Far West. This factor will affect the design and feasibility of CWT.
116
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category should result in a similarly feasible CWT
scheme.
The initial step in developing the categorization
scheme was the identification of factors that were
expected to affect the feasibility and design of a CWT
system. These factors are listed in Table 1. The next step
was to develop quantifiable categories utilizing the
factors. A simple solution to categorization would have
been to designate each metropolitan area as a category.
This could be done easily, since all possible combinations
or permutations of the various factors would produce a
very large number of potential categories. This, however,
would defeat the purpose of categorization, since results
from one municipality could not be applied to others.
To avoid the problem of too many categories, four
major factors were used to define the initial
categorization scheme (Table 2).
Table 2
Municipal Categorization Scheme
Category 1 Category 2 Category 3
Bridgeport
Hartford
Att/Taunton
Syracuse
Category 4
Providence
Rochester
Erie
Baltimore
Worcester
Springfield
Buffalo
Pittsburgh
Category 5
Boston
Philadelphia
New York
Newark
Trenton
Silver Spring
Camden
Manchester
Allentown
Arlington
Reading/Lancaster
Harrisburg
Long Island
Category 6 Category 7 Category 8
Atlanta
Miami
New Orleans
San Antonio
Orlando
Houston
Dallas/Ft. Worth
Canton
Ann Arbor
Kalamazoo
South Bend
Category 9 Category 10 Category 11
Milwaukee
Cincinnati
Grand Rapids
St. Louis
Indianapolis
Tulsa
Kansas City
Toledo
Columbus
Oklahoma City
Rockford
Ft Wayne
Chicago
Cleveland
Detroit
Minneapolis/St. Paul
Category 12 Category 13 Category 14
San Francisco
Los Angeles
Fullerton
Seattle
Denver
Alburquerque
San Diego
Portland
Honolulu
Phoenix
San Jose
Riverside
Ontario
Santa Barbara
These major factors include:
• Number of local governments
• Municipal demography
• Number of metal finishing facilities
• Regional location
Aside from their relative importance, these particular
factors are closely related to the other factors identified in
the categorization step; therefore, the resultant
categorization scheme actually encompasses a broad
range of factors. For example, the regional location of a
metropolitan area is closely related to the type of industry
and the type of waste since particular segments of the
metal finishing industry tend to concentrate in particular
regions. Similarly, the number of metal finishing facilities
is closely related to the concentration of metal finishing
facilities.
Selection of 24 Metropolitan Areas for Case Study
Consideration
In the selection process, it was assumed that the best
choice of metropolitan areas would be those where a need
exists and where municipal cooperation can be expected.
Also, it was believed that all EPA Regions should be
involved in the next stage of the CWT project. To satisfy
these assumptions, the following criteria were used in the
selection process:
• Choose all localities that have shown a willingness to
participate in a CWT project
• Choose mostly metropolitan areas with a large
number of metal finishing facilities
• Exclude localities that have pretreatment programs
with stringent regulations for the metal finishing
industry. (If stringent local pretreatment regulations
were currently in effect, it might preclude the
establishment of a central treatment facility since plants
may already have committed to individual waste
treatment.)
• Choose localities with a relatively small ratio of
population to number of electroplaters. (This is a
simplified measure of the economic dependence of a
particular area on its metal finishing industry.)
• Choose at least one metropolitan area per category.
• Choose at least one locality per EPA Region.
The selection process resulted in the choice of 24
metropolitan areas. These are listed in Table 3.
Table 3
Metropolitan Areas Chosen for Further Study
Category Metropolitan Areas
1
2
2
3
4
5
5
6
6
7
7
8
9
9
2
10
10
11
11
12
13
13
13
14
Bridgeport
Rochester
Erie
Trenton
Providence
Boston
Philadelphia
Atlanta
Miami
Houston
Dallas/Ft. Worth
Canton
Milwaukee
Cincinnati
Buffalo
Tulsa
Kansas City
Chicago
Cleveland
San Francisco
Seattle
Denver
Albuquerque
San Jose
Selection of Five Case Study Areas
The first step in the selection process was to formulate
a group of criteria that reflects the desired qualities of a
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case study area. These criteria included technical,
economic, political, and administrative considerations
(Table 4). The 24 candidate case study areas were then
visited to collect information related to each of the
criterion.
The actual selection was performed by using a decision
process that quantitatively evaluated how well each
candidate area satisfied the various criteria. Those areas
that were best suited to the decision criteria were then
selected.
The decision technique that was utilized is termed
worth assessment. With this method, an analytical model
is developed that allows any number of decision criteria
to be used in a selection process. The criteria are
quantitatively weighed (0 to 1, with the total weights of all
criteria equaling 1) to reflect their intended importance in
the decision. Then, for each candidate, a worth
assessment score is calculated by: (1) evaluating or
scoring on a scale of 0 to 1 how well each candidate
locality satisfies each criterion, (2) multiplying the score
for each criterion by its weighted value, and (3) summing
over all criteria.
Several criteria, such as municipal cooperation, were
given overriding consideration because they could limit
the success of this project and CWT for that region.
Therefore when certain constraint criteria were not
satisfied, the entire worth assessment score for that
particular locality was assigned a value of zero.
The worth assessment exercise resulted in the scores
and case study selections shown in Table 5. As indicated
in Table 5, the metropolitan area of Philadelphia was
chosen although both Denver and Buffalo scored higher
in the analysis. This was done because of the small
difference in scores and the fact that the categories (Table
2) which contain Denver and Buffalo would already be
represented by Seattle and Milwaukee, respectively,
which had been likewise chosen.
Data Collection and Characterization of Case Study
Areas
The data necessary to evaluate the feasibility and
design of CWT was collected via visits to municipal and
regional authorities, such as POTW's, in each of the case
study areas and through the use of an industrial survey.
The basic philosophy used in data collection was to
first gather as much available information as possible
from municipal and regional authorities.* The additional
data necessary for a feasibility analysis was collected
from industry via an industrial survey. The survey was
distributed to metal finishing companies in the five case
study areas by the American Electroplaters' Society
(AES). Once completed and returned to AES the survey
responses were forwarded to the centralized treatment
study project team to be compiled and used for the
feasibility analysis.
Information and data from local governments and
industry were combined to characterize each of the case
study areas. All metal finishing facilities which discharge
wastewaters were mapped along with potential central
waste treatment sites and landfills. Effluent data and
information concerning installed waste reduction or
treatment equipment for each metal finishing facility
were compiled. Transportation routes were defined for
shipping wastewaters and sludges from metal finishing
plants to the potential central sites and the landfills.
Development of Analytical Tools
A mathematical model was developed to evaluate the
feasibility of CWT and to determine the configuration of
*Government sources were generally able to supply the following types
of pertinent data and information: metal finishing shop location,
water use and effluent concentrations for metal finishing facilities
discharging to POTW's; location and ownership of landfills accepting
metal bearing sludges; and location, size, and zoning classification of
land tracts that could serve as sites for a centralized treatment facility.
Table 4
Case Study Selection Criteria
Area of Impact
Criteria
Municipal Cooperation with
Project Personnel
Present Local Pretreatment Regulations
Availability of Disposal Sites
Number of Municipalities in
Metropolitan Area
Number of Sewer Authorities in
Metropolitan Area
Local Plans for Enforcing Future
Regulations
Economic Impact (Ratio of Population
to Number of Metal Finishing
Companies
Concentration of Metal Finishing
Companies
Current Availability of Central
Waste Treatment
Number of Metal Finishing Companies
in Metropolitan Area
Technical
•
•
•
•
•
•
•
Economic
•
•
•
•
Political
•
•
•
•
Project
Administration
•
•
•
•
•
•
118
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Worth Assessment
'Milwaukee
'Seattle
'Cleveland
'Atlanta
Denver
Buffalo
'Philadelphia
Trenton
Miami
San Francisco
Erie
Tulsa
Chicago
Dallas/Ft. Worth
Canton
Kansas City
Boston
Rochester
Cincinnati
Houston
San Jose
Albuquerque
'Areas Selected
Table 5
Scores For Case Study Analysis
0.684
0.639
0.638
0.634
0.634
0.622
0.618
0.574
0.532
0.532
0.503
0.503
0.444
0.418
0.404 ,
0.398
0.342
0.325
0.300
0.286
0.
0.
*jl\
a CWT system for each of the case studies. The model is
capable of simulating cost effective alternatives for given
scenarios considering various options involving in-plant
flow reduction, waste concentration, on-site treatment,
and shipment to a centralized treatment plant.
The model was programmed in the efficient-structured
language, Pascal, with the intention of using a
microcomputer for the analysis. Descriptions of the
model components, data input procedure, and logic flow
follows.
Technical Basis of Computer Model
The model considers three typical raw waste streams
generated by the metal finishing industry:
• Rinse waters and spent baths containing chrome
• Rinse waters and spent baths containing cyanide
• Other acid/alkali rinse waters and spent baths
It is assumed that these wastewaters are segregated into
discrete streams to allow for separate treatment of
chrome and cyanide.
Rinsing operations account for over 90 percent of
water used by a typical plating facility; however, this
water use can be drastically reduced through the
installation of efficient rinse techniques such as
countercurrent rinses, series rinses, spray rinses, and still
or dead rinses. A reduction in water use will benefit shops
by reducing the necessary capacity of waste treatment
processes or the amount of wastewater to be hauled to a
Central Treatment Facility (CTF).
To reflect the potential application of flow reduction,
the model is programmed to consider the cost
effectiveness of converting single running rinses to two-
stage countercurrent rinses. Other techniques, such as
dead rinses or ion exchange could also be used for
concentrating rinsewaters; however, for this first analysis
only countercurrent rinsing was considered. The use of
other techniques will be investigated during latter stages
of the project.
The cost of converting to countercurrent rinsing is
assumed to be $3,000 based on the addition of a 5-foot by
6-foot by 4-foot tank, the appropriate plumbing, and an
air agitation system. The countercurrent system is
assumed to reduce the original single running rinse water
use by greater than 90 percent.
Many shops will be unable to install an additional rinse
tank because of space limitations or the use of
programmed hoist lines. In these cases, it is assumed
there is no potential for substantial flow reduction.
It is also possible for many shops to reduce rinse water
usage through inexpensive, good water conservation
measures such as flow control valves. During the course
of the study, it was observed that most shops are using
much more than is necessary to protect product quality;
therefore, an additional factor was considered in the
modeling exercise to account for these types of water
conservation. It was assumed that tanks without flow
control valves would reduce flow by 50 percent with
minimal capital costs.
Conventional technologies were considered for
treatment of wastes.* These technologies could be used
either on-site or at the CTF. The possible waste treatment
processes included:
Chrome reduction
Cyanide oxidation
Physical /chemical treatment
Sludge dewatering
Storage (on-site only, to be used for plant selecting
CWT options)
Waste streams with a chrome concentration above the
1982 pretreatment standards (Table 6) would be subject
to chrome reduction. Similarly, wastewaters not
complying with cyanide pretreatment standards would
be subject to cyanide oxidation. The effluents from both
of these treatment processes then would be combined
with other acid/alkali wastes containing metals for
physical/chemical treatment and sludge dewatering. A
flow diagram of the typical treatment system is shown in
Figure 1.
Precipitation —». Flocculatlon —». Clarification
Fig. 1—Conventional Treatment Technology Flow Diagram.
Shops that would decide to use CWT for one or more
waste streams would need to install enough storage tanks
to accommodate the various wastes separately.
Therefore, within the model, storage was costed as a
treatment technology. It was assumed that the storage
capacity would be large enough to contain at least one
day's waste flow. The equipment considered in the cost of
storage were 5,000 gallon tanks ($6,000 per tank, 1978
prices).
The analytical model was formulated to consider five
waste treatment alternatives (Figure 2) which involve on-
site treatment and/or hauling waste (via truck) to and
treating at a CTF.
* Recovery technologies are a viable alternative; however, they were not
considered in this analysis.
119
-------
Table 6
1982 Pretreatment Standards*
(mg/l)
Average of Daily Values for
30 Consecutive Monitoring Days
Pollutant Shall Not Exceed
CN (T) 0.23
Cu 1.8
Ni 1.8
Cr (T) 2.5
Zn 1.8
Pb 0.3
Cd 0.5
Total Metals 5.0
*These standards appeared in the Federal Register (Vol. 44,
No. 175) on September 7, 1979. The standards have since
been revised; however, the CWT analysis was performed
before the changes were instituted and, therefore, are not
reflected in this analysis.
In Option 1, the shopdoesnot discharge contaminated
process waters to the municipal sewer system. The
concentrated rinse waters and batch dumps for all waste
streams are hauled to a central waste facility for
treatment. The sludge from waste treatment is dewatered
at the CTF to approximately 20 percent solids and is
hauled to a landfill.
Shops that select Option 2 would treat the cyanide and
acid/alkali waste streams in-house (CN destruction, pH
adjustment/precipitation) and send the dilute waste
treatment sludge (approximately 4 percent solids) and
raw chromium waste stream to a CTF. The CTF would
properly treat the chromium waste stream, dewater the
sludge, and haul the solids to a landfill.
Option 3 is similar to Option 2 except that the
chromium and acid/alkali waste streams are treated in-
Optlon 1
Option 2
Option 3
Option 5
house and the cyanide waste stream and sludge are
hauled to a CTF.
In Option 4, the shop chooses to treat all waste streams
in-house and to send only the dilute sludge (4 percent) to
the CTF for dewatering.
Under Option 5, the shop is not utilizing the CTF.
Instead, all waste treatment and sludge dewatering is
done in-house.
A summary of in-plant processes that would be
performed by individual companies under each option in
shown in Table 7.
Data Input and Computer Logic Flow
The information needed to run the model includes:
• Locations of each company and CTF site that are
determined by using a grided map
• Volumes (gallons/day) and pollutant
concentrations (mg/l) of the three waste streams (i.e.,
cyanide, chromium, and acid/alkali)
• Number of daily operating hours and days per year
for each shop
• Total number of rinses for each shop and the
number of rinses with flow reduction installed and with a
potential for flow reduction.
• Local waste hauling costs ($/mile/5000 gallons)
• Interest rates
• Expected return on investment for industry
• Cost indexes (wholesale price index for chemicals,
operating cost index, and chemical engineering plant cost
index)
• Estimated lifetime of equipment
• Local electric power costs
• Assumed days of operation per year of the CTF
Table 7
In-Plant Processes for Each Waste Stream
Under Each Option
Stream
Option* Chromium Cyanide Acid/Alkali Sludge
5
5
1-3-5
1-3-5
1-2-4-5
5
2-3-5
5
2-3-5
2-3-4-5
5
3-5
3-5
3-5
3-4-5
'Process 1 - Chrome reduction
Process 2 - Cyanide oxidation
Process 3 - Physical/chemical treatment
Process 4 - Sludge dewatering
process 5 - Storage
Process 5 - Storage
Fig. 2—Waste Treatment Alternatives
The model proceeds in an iterative manner to converge
on a solution using the following logic flow. On the first
iteration, a CTF is sized assuming all wastes are sent to
the CTF. The CTF is a maximum size after the first
iteration, and therefore the cost for using CWT is the
least possible because of economics of scale. In the
second iteration, the model selects the least-cost option
for each shop. Since the least-cost option for some
companies may be to treat a portion or all of their wastes
in-house, the size of the CTF at the end of the second
iteration may have decreased. A decrease in size will
cause user fees to increase because of a loss in economics
of scale. If after the second iteration, there was a change
of 5 percent or less in the size of the CTF, the model will
120
-------
assume convergence and will stop with that solution. It
the change was greater than 5 percent, the model would
continue iterations until it converges on a solution.
CASE STUDIES
As discussed, five metropolitan areas were selected for
case studies. A preliminary analysis has been performed
for each area using the microcomputer model, and results
will be discussed in this paper. In an attempt to keep the
discussion to a manageable size but to retain a
comprehensive view of the study, a detailed analysis is
presented for only one area (Cleveland) and the
remaining areas are treated with a more general
approach.
Cleveland Analysis
Data were collected from various sources for
approximately 140 metal finishing shops in the Cleveland
metropolitan area. From available information, it was
concluded that 103 of these shops were not currently
meeting 1982 pretreatment standards. These 103 shops
were considered in the analysis. The current water use
statistics for these shops are summarized in Figure 3.
Fig. 3—Distribution of Cleveland Water Use Flow Rates
As shown in Figure 4, the majority of the 103 shops are
clustered in a 50-square-mile area, and approximately 15
shops are located to the northeast in a second cluster. The
potential CTF site is located in the southeast sector of the
larger cluster. The mean distance between all shops and
the potential CTF site is 7.8 miles. The nearest potential
customer is located 0.5 miles from the central site, and the
farthest company is located 29.9 miles from the site. A
summary of major input parameters is provided in
Appendix A.
The most economical waste treatment scheme
determined by the analysis considering in-plant
treatment and CWT is shown in Table 8. The annual
Fig. 4—Metal Finishing Shops In Cleveland Area.
costs associated with this configuration are presented in
Table 9. The necessary processing capacities of the CTF
components are shown in Table 10.
The Cleveland results show a very high percentage ot
participation in the CWT system. Only one of the 103
shops has not selected to use the CTF. That particular
shop is located 19.5 miles from the CTF site and has a
waste stream flow of 43,200 gpd after flow reduction.
For the vast majority of the small (less than 10,000 gpd
before flow reduction) and medium shops (10,000 to
50,000 gpd before flow reduction) the program selected
Option 1 (i.e., sending all wastes to the CTF) regardless of
distance from the central facility. The distance was,
however, a factor regarding the degree of flow reduction
used. In general, as the distance increased from the
central facility to the shops, the shops were more likely to
install counter-current rinses. The average distance to the
Table 8
Most Economical Waste Treatment Scheme
For Cleveland Region
Option
Number of Shops
1 - All waste to CTF
2 - Chrome waste and all sludge to CTF
3 - Cyanide waste and all sludge to CTF
4 - Sludge only to CTF
5 - Nothing to CTF
86
1
0
15
1
Table 9
Regional Summary - Cleveland
(Annual Costs in Thousands of 1980 Dollars)
W/o CTF
With CTF
Savings
Total
Plant
Investment
1,926
345
1,581
Total
Plant
Operating
Costs
1,745
297
1,448
Total
Plant
Chemical
Costs
528
247
281
Total
Plant
Costs
4,199
899
3,310
Total
Transport
Costs
0
1,129
-1,129
Total
CTF
Fees
0
486
-486
Total
Regional
Costs
4,199
2,504
1,695
121
-------
Table 10
Processing Capacities and Costs of CTF Components
(All Costs in 1980 Dollars)
Process
Chromium
Reduction
Cyanide
Oxidation
Precipitation
Sludge
Dewatering
Storage
Required
Capacity
GPD
40,700
41,000
190,000
3,646
190,100
Annual
Investment
$ (1980)
7,200
17,800
36,100
19,000
58,200
Annual
Operating
Cost
$ (1980)
3,800
6,100
15,600
6,500
0
Annual
Chemical
Costs
$ (1980)
11,400
240,600
64,300
0
0
Total
Annual Costs
$ (1980)
22,400
264,500
116,000
25,500
58,200
Fee Rate
$/Gal
0.0018
0.0215
0.0020
0.0233
0.001
CTF for shops that decided to add counter-current rinses
on all single overflow rinses (with potential for counter-
current) was 9.3 miles. The average distance for shops
that decided not to install counter-current for all
potential rinses was 3.7 miles.
For better understanding of the analysis and the
interpretation of the results, it will be most profitable to
look at two typical plants (Fl and E6) in detail. Fl is an
electroplating shop that works mostly with electric switch
and outlet boxes. Aside from electroplating, the shop
also performs degreasing/cleaning, pickling, and bright
dipping. The shop has a combined waste flow of 18,500
gpd. It operates 11 hours per day for 250 days per year.
The shop is located 6 miles from the CTF site.
Fl has no pretreatment equipment. The final
wastewater discharge analysis (Table 11) indicates a need
for cyanide oxidation and heavy metal precipitation.
Currently, Fl has a good housekeeping program. It
has installed flow control valves (5 gpm) on all seven of its
overflow rinses. Fl presently has no counter-current
rinses, but all rinses have that potential. If waste streams
(Cr, CN, and acid/alkali) were segregated into discrete
flows, the individual discharges following countercurrent
rinse installation for Fl would be:
Cr waste stream
CN waste stream
Acid/alkali waste stream
0
7380
9225
Table 11
Analysis of Final Effluent - Shop Fl
Flow 18,500 gpd
Cr (+6) < 0.1 mg/l
Cr (total) 0.3 mg/l
Zn 53.5 mg/l
CN 12.2 mg/l
Fe 6.8 mg/l
As a part of the total analysis for Cleveland, the
computer program selected Option 1 (send all waste
streams to CTF) as the least cost alternative for Shop Fl.
Also, the results indicated that counter-current rinses
should be installed at all rinse stations.
The costs for Options 1 and 5 show a comparison of
CTF and in-plant processing (Table 12). For this
particular shop, the option of sending its waste to a CTF
as opposed to in-plant treatment would save $43,900
annually.
For large metal finishing facilities (greater than 75,000
gpd), the most common selection of treatment
alternatives was Option 4 (treating all waste streams in-
house and sending dilute sludge to CTF for dewatering).
An example of the results for a typical large facility are
presented.
Shop E6 works with automotive parts, appliances, and
industrial parts, such as fasteners and stampings. Aside
from electroplating, process water uses include pickling,
cleaning, surface neutralizing, chromating, phosphating,
bright dipping and chemical polishing, and stripping.
The current process wastewater discharge for E6 is
225,000 gpd. The shop operates 24 hours per day and 340
days per year. The shop is located 8.5 miles from the CTF
site.
E6 has 35 rinse stations, all of which have flow control
valves and approximately half of which have counter-
current rinsing. Rinse stations without counter-current
rinsing have no potential for installing counter current.
This shop currently has no pretreatment. The effluent
analysis (Table 13) indicates a need for chrome reduction
(assuming hexavalent chrome exists), cyanide oxidation,
and heavy metal precipitation.
The computer results show that the use of a CTF for all
waste streams (Option 1) would be the most expensive
alternative (Table 14). The least cost alternative is Option
W/o CWT (5)
With CWT (1)*
Savings
Investment
41,200
0
41,200
Costs for
(All
Operating
Costs
17,300
0
17,300
Table 12
Shop Fl Considering Options 1
Costs in 1980 Dollars Per Year)
Total
Chemical In-Plant
Costs Costs
2,600 61,100
0 0
2,600 61,100
and 5
Transport
Costs
0
14,000
-$14,000
. CTF
Fees
0
3,200
-3,200
Total
Costs
61,100
17,200
43,900
"Annualized storage and countercurrent investment costs have been included in transportation costs.
122
-------
4. With this alternative, E6 would be reducing its original
waste stream flow (225,000 gpd) by treating in-house and
by sending only a dilute sludge to the CTF for
dewatering.
Table 13
Analysis of Final Effluent - Shop E6
Flow
Chrome (total)
Zinc
Cadmium
Iron
Cyanide
225,000 gpd
8.5 mg/l
21.8mg/l
53.7 mg/l
15.8 mg/l
15.5 mg/l
Cleveland Analysis with Multiple CTF Sites
A two-site CWT case study was performed to
investigate the economic effects of simultaneously
reducing the costs of transportation and the benefits of
economies of scale.
The study used the CTF site (CTF Site 1) of the
original analysis and a second site (CTF Site 2), which is
located 4.2 miles southeast of Site 1. Metal finishing
shops were given the same five options as were available
in the original analysis, where each shop could use the
facility closest to its location or treat on-site — 47 shops
were closest to CTF Site 1, and 56 shops were closest to
CTF Site 2. Because of the use of two central treatment.
Table 14
Costs for Shop E6 Considering Options 1
(All Costs in 1980 Dollars)
Option 1*
Option 4
Option 5
Savings
(4 vs. 5)
Investment
0
48,000
57,400
9,400
Operating
Costs
0
25,400
27,900
2,500
Chemical
Costs
0
50,400
50,400
0
Total
In-Plant
Costs
0
123,800
135,700
11,900
, 4, and 5
Transport
Costs
330,359
3,500
0
-3,500
C7T
Fees
60,890
1,800
0
-1,800
Total
Costs
391,250
129,100
135,700
6,600
'Annualized storage and countercurrent investment costs have been included in transportation costs.
Table 15
Most Economical Waste Treatment Scheme
for Cleveland Region Using Two CTF Sites
Number of Shops
Option Original Case 2-Site Case
1 - All waste to CTF
2 - Chrome waste and all
sludge to CTF
3 - Cyanide waste and all
sludge to CTF
4- Sludge only to CTF
5- Nothing to CTF
86
1
0
15
1
88
1
2
11
1
facility sites, the average distance of a shop to a CTF was
reduced from 7.8 miles in the original analysis to 6.5
miles.
The most economical regional waste treatment scheme
(combining CTF Sites 1 and 2) is shown in Table 15. The
annual costs associated with this configuration are
presented in Table 16. The CWT system configuration
changed very little from the original single-site analysis.
The major change which occurred concerned four large
shops which originally selected Option 4 (sludge only to
CTF) now chose to send some or all of their raw
wastewaters to the central facility. As expected, the
distance to the CTF was reduced for each of these four
shops (Table 17).
Table 16
Regional Summary - Cleveland Using Two CTF Sites
(Annual Costs in Thousands of 1980 Dollars)
W/o CTF
With CTF
Savings
Total
Plant
Investment
1,926
298
1,628
Total
Plant
Operating
Costs
1,744
246
1,498
Total
Plant
Chemical
Costs
527
199
328
Total
Plant
Costs
4,197
743
3,454
Total
Transport
Costs
0
1,118
-1,118
Total
CTF
Fees
0
525
-525
Total
Regional
Costs
4,197
2,386
1,811
Shop Code
P4
N8
E5
E6
Option 4
M/7es to CTF
4.3
4.0
3.9
8.5
Table 17
Shops Affected in Two-Site
1-Site Analysis
Option Selected
4
4
4
4
Analysis
Miles to CTF
2.4
0.7
2.9
4.4
2-S/fe Analysis
Option Selected
3
1
1
3
123
-------
The total annual savings for the Cleveland Region
under the two-site analysis increased slightly ($48,000)
from the original analysis. This indicates that the loss of
some economies of scale were less than the savings in
reduced transportation costs.
Milwaukee Analysis
Data were collected for approximately 60 metal
finishing shops in the Milwaukee metropolitan area. The
data shows that 41 of these shops were not meeting 1982
pretreatment standards and, thus, were included in the
CWT analysis.
Fig. 5—Metal Finishing Shops in the Milwaukee Area
Table 18
Most Economical Waste Treatment Scheme
For Milwaukee Region
Option
1 - All waste to CTF
2 - Chrome waste and all sludge to CTF
3- Cyanide waste and all sludge to CTF
4- Sludge only to CTF
5 - Nothing to CTF
Number of Shops
23
3
2
13
0
Fig. 6—Distribution of Milwaukee Water Use Flow Rates.
Figure 5 shows the location of the 41 metal finising
shops. Most of the shops are located in a 4-mile wide
vertical strip along the eastern shore of Lake Michigan.
The potential CTF site is located at approximately the
center of this eastern strip. The other metal finishing
shops are dispersed over a 100-square-mile area. The
mean distance between all shops and the potential CTF
site is 7.8 miles. The nearest and farthest shops are
located 0.1 and 30.2 miles, respectively, from the CTF
site. The distribution of water use flow rates for the 41
shops is shown in Figure 6.
The most economical waste treatment scheme is shown
in Table 18. The annual costs associated with this
configuration are presented in Table 19.
The results from the Milwaukee analysis show the
effect of having a high percentage of medium and large
shops. For Milwaukee, only 40 percent of the shops use
25,000 GPD or less of water, and 48 percent use greater
than 50,000 GPD. In Cleveland, the percentage was 60
percent for less than 25,000 GPD and 27 percent for
greater than 50,000 GPD. The effect is that 32 percent of
the Milwaukee shops have selected Option 4 (send only
sludge to CTF) as the most economical waste treatment
alternative; whereas in Cleveland, only 14 percent
selected that option.
Philadelphia Analysis
Data were collected for approximately 90 metal
finishing shops in the Philadelphia metropolitan area.
Fifty-one of these shops were not meeting 1982
pretreatment standards and were used in the CWT
analysis.
Table 19
Regional Summary - Milwaukee
(Annual Costs in Thousands of 1980 Dollars)
w/o CTF
With CTF
Savings
Total
Plant
Investment
898
432-
466
Total
Plant
Operating
Costs
710
323
387
Total
Plant
Chemical
Costs
249
220
29
Total
Plant
Costs
1,857
975
882
Total
Transport
Costs
0
342
-342
Total
CTF
Fees
0
120
-120
Total
Regional
Costs
1,857
1,437
420
124
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Philadelphia Area
Fig. 7—Metal Finishing Shops in the Philadelphia Area.
Figure 7 shows the location of the 51 metal finishing
shops. A major portion of this metal finishing population
is located in southeastern Philadelphia, in an area
bordered by the Schuylkill and Delaware Rivers. The
potential CTF site is located in the extreme southeastern
corner of Philadelphia near the Philadelphia
International Airport. The mean distance between the
shops used in the analysis and the potential CTF site is
10.1 miles. The nearest potential customer is located 2.4
miles from the central site, and the farthest company is
located 26.7 miles from the site. The distribution of water
usage rates for the 51 shops used in the analysis is shown
in Figure 8. The most economical waste treatment
scheme is shown in Table 20. The annual costs associated
with this configuration are presented in Table 21.
The results of the Philadelphia analysis show a strong
resemblance to the Milwaukee results. A large percentage
(39 percent) of the Philadelphia shops selected Option 4.
Again, this is primarily a result of having a relatively high
percentage of medium and large water users (51 percent
of shops in Philadelphia use more than 50,000 gpd).
Philadelphia also showed a relatively high percentage
of shops selecting Options 2 and 3 (18 percent as
2% 2%
Fig. 8—Distribution of Philadelphia Waster Use Flow Rates
compared to 1 percent for Cleveland and 12 percent for
Milwaukee). This is primarily a result of having a
relatively larger mean distance from the shops to the CTF
site. The average CTF distance of the nine Philadelphia
shops selecting Options 2 or 3 was 10.0 miles. This caused
some waste streams (usually acid/alkali) to be cost
effectively treated in-house and for other streams (usually
chrome) to be hauled and treated at the CTF.
Atlanta Analysis
Data were collected for 54 metal finishing shops in the
Atlanta metropolitan area. The available information
indicated that 23 of these shops were not meeting 1982
pretreatment standards and were, thus, considered in the
CWT analysis.
Most of the 23 metal finishing shops used in the
analysis are well distributed in a 20-square-mile area
which is centered over downtown Atlanta (Figure 9). The
potential central facility site is located 5 miles southeast
of the center of the city. The mean distance between the
shops and the potential CTF site is 5.6 miles. The nearest
and farthest shops are located 2.2 and 11.6 miles,
respectively, from the potential CTF site. The
distribution of water use flow rates is shown in Figure 10.
The most economical waste treatment scheme
Table 20
Most Economical Waste Treatment Scheme
for Philadelphia Region
Option
1 - All waste to CTF
2 - Chrome waste and all sludge to CTF
3 - Cyanide waste and all sludge to CTF
4 - Sludge only to CTF
5- Nothing to CTF
Number of Shops
22
8
1
20
0
Table 21
Regional Summary - Philadelphia
(Annual Costs in Thousands of 1980 Dollars)
W/o CTF
With CTF
Savings
Total
Plant
Investment
1,189
661
528
Total
Plant
Operating
Costs
961
560
401
Total
Plant
Chemical
Costs
1,020
995
25
Total
Plant
Costs
3,170
2,216
954
Total
Transport
Costs
0
478
-478
Total
CTF
Fees
0
84
-84
Total
Regional
Costs
3,170
2,778
392
125
-------
considering in-plant treatment and CWT is shown in
Table 22. The annual costs associated with this
configuration are presented in Table 23.
Table 22
Most Economical Waste Treatment Scheme
for Atlanta Region
Option Number of Shops
1 - All waste to CTF 19
2 - Chrome waste and all sludge to CTF 0
3 - Cyanide waste and all sludge to CTF 0
4 - Sludge only to CTF 4
5 - Nothing to CTF 0
The Atlanta results show a relatively good CWT
system participation. This high CWT is primarily a result
of the closeness of the shops to the central treatment
facility site (mean distance 5.6 miles). The four Option 4
shops in the analysis are large shops (greater than 50,000
gpd) most of which are located 10 or more miles from the
CTF site.
Seattle Analysis
Data were collected for approximately 60 metal
finishing shops in the Seattle metropolitan area. The data
showed that 22 of these shops were not meeting 1982
pretreatment standards and were thus, included in the
CWT analysis.
Table 23
Regional Summary - Atlanta
(Annual Costs in Thousands of 1980 Dollars)
W/o CTF
With CTF
Savings
Total
Plant
Investment
404
80
324
Total
Plant
Operating
Costs
341
61
280
Total
Plant
Chemical
Costs
81
51
30
Total
Plant
Costs
826
192
634
Total
Transport
Costs
0
217
-217
Total
CTF
Fees
0
92
-92
Total
Regional
Costs
826
501
325
Atlanta Area
Fig. 9—Metal Finishing Shops in the Atlanta Area.
Table 24
Most Economical Waste Treatment Scheme
for Seattle Region
Option
1 - All waste to CTF
2 - Chrome waste and all sludge to CTF
3 - Cyanide waste and all sludge to CTF
4 - Sludge only to CTF
5 - Nothing to CTF
Number of Shops
11
0
0
11
0
Fig. 10—Distribution of Atlanta Water Use Flow Rates
Figure 11 shows the location of the 22 metal finishing
shops of concern. The majority of the shops are located
between Puget Sound and Lake Washington. The
remainder of the shops are located in the northern
portion of King County and in the Kent area. The
potential CTF site is located near the southern two shops
in Kent. The mean distance between the shops and the
potential CTF site is 16.6 miles. The nearest and farthest
shops are located 2.1 and 33.2 miles, respectively, from
the CTF. The distribution of water use flow rates is
shown in Figure 12.
The most economical waste treatment scheme is shown
in Table 24. The annual costs associated with this
configuration are presented in Table 25.
For Seattle, the greatest factor was the hauling
distance. Although 76 percent of the metal finsihing
population considered in the analysis used less than 50,00
gpd of water, only half of the total number of shops sent
raw waste streams to the CTF. The mean distance to the
CTF for the plants selecting Option 4 was 19.5 miles. For
the remainder of the shops, the mean CTF distance was
12.8 miles.
126
-------
Table 25
Regional Summary - Seattle
(Annual Costs in Thousands of 1980 Dollars)
W/o CTF
With CTF
Savings
Total
Plant
Investment
367
156
211
Total
Plant
Operating
Costs
319
133
186
Total
Plant
Chemical
Costs
22
17
5
Total
Plant
Costs
708
306
402
Total
Transport
Costs
0
154
-154
Total
CTF
Fees
0
65
-65
Total
Regional
Costs
708
525
183
Fig. 11—Metal Finishing Shops In the Seattle Area.
PHASE II CWT SYSTEM DESIGN
Phase I of this project investigated the feasibility of
CWT and defined the conditions necessary for its
successful implementation. The second phase is directed
at developing and demonstrating procedures for creating
CWT systems. This is being achieved by selecting one
area for detailed study to develop a comprehensive metal
finishing waste control plan for that area. The process for
selecting the Phase II area and an overview of the
subsequent study and analysis are presented in the
following paragraphs.
Selection of Phase II Study Area
The Phase II area was chosen as the most feasible site
for central waste treatment from a technical, economical,
political, and administrative standpoint. The selection
procedure utilized by the project team to identify the
most feasible area had two basic steps:
Fig. 12—Distribution of Seattle Water Use Flow Rates.
• Screening Exercise
• Assessment of Economic Feasibility
The objective of the screening exercise was to provide a
quantitative and rational means of selecting from the 24
metropolitan areas studied in Phase I, the most likely
candidate areas for the Phase II centralized waste
treatment study. The procedure that was utilized was
similar to the selection process used in Phase I to choose
the five case study areas, the basic decision tool being the
worth assessment model.
The criteria used in the Phase I worth assessment
exercise were expanded to satisfy additional
requirements of Phase II. First, an area to be selected
should have available from local authorities water use
and industrial discharge data that characterizes its metal
finishing population. This information would be needed"
for the subsequent modeling to determine economic
feasibility. Secondly, it was determined that it would be
advantageous from a project administrative standpoint if
the municipal contact for the project was in a high
visibility position with broad authority. In some cities,
the contact's authority was limited to the municipal
wastewater system. In these cases, it was difficult to
obtain information on solid waste disposal sites and on
other data requirements related to economics or land
availability.
In other cities, contacts included environmental
directors that had an overview of both wastewater and
solid waste control, economic development
administrators that were aware of the availability of land
for potential CTF sites, or personnel from the mayors'
offices that had a comprehensive view of all information
needed during this project. These various levels of
contacts were weighed as to their ability to supply the
appropriate project information and generally contribute
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Table 26
Results from Sensitivity Analysis -
Location
Cleveland
Seattle
Philadelphia
Tulsa
Atlanta
Buffalo
Erie
Chicago
Trenton
Dallas/Ft. Worth
San Francisco
Boston
Alburquerque
Canton
Cincinnati
Denver
Houston
Miami
Milwaukee
Rochester
San Jose
Case 2
Value
0.78
0.71
0.68
0.66
0.63
0.6
0.6
0.56
0.51
0.46
0.4
0.37
1
0
0
0
0
0
0
0
0
to the project. After inclusion of the additional criteria,
the worth assessment model was utilized.
The results from the exercise are shown in Table 26.
From these results, it is evident that the metropolitan
areas of Seattle and Cleveland best satisfy the Phase II
criteria. These metropolitan areas were considered in the
second step of the Phase II selection procedure.
Assessment of Economic Feasibility
To perform the economic assessment, a simplified
version of the Phase I analytical model was developed
and applied to metropolitan areas with the highest worth
assessment scores.1 The project plan first was to
determine the economic feasibility of CWT in Seattle and
Cleveland. Then, if neither area appeared promising,
other cities, starting with Philadelphia, would be added
to the analysis.
From the modeling exercise, it was concluded that the
Cleveland metropolitan area presented more favorable
economic conditions for CWT implementation;
therefore, Cleveland was selected as the study area for the
Phase II portion of the project.
DATA COLLECTION AND ANALYSIS
The Phase II analysis was to be more in-depth and
comprehensive than the case studies of Phase I. A new
and more sophisticated tool was developed for providing
additional treatment options, such as in-plant waste
stream concentration using ion exchange.
The data requirements of Phase II demanded that the
information base collected via the industry survey be
expanded. This was accomplished through on-site
engineering surveys at the major metal finishing shops in
the study area. Surveys of 66 companies were conducted
during % 6-week period in early 1980 for data collection
purposes.
'Phase II of the CWT project was started several months before all the
data and results of Phase I were.available. This overlapping of project
phases was done in response to the urgency to demonstrate CWT
before metal finishing companies were committed to in-house
treatment for meeting pretreatment standards; therefore, a simplified
model was developed to determine relative feasibility.
The on-site surveys consisted of discussions with plant
personnel, a tour of the plating facility, and waste stream
sampling. For each shop, a schematic diagram of the
plating lines was drawn to illustrate the sequence of
manufacturing processes showing rinse water flow rates
and indicating which baths were batch dumped and the
frequency of their discharge. Also, for each rinse tank, it
was noted if flow reduction measures such as still or
counter-current rinsing, flow control valves, spray
rinsing or recovery technology, were in place, or could be
added.
Sampling of the final discharge was performed at
shops for which municipal data did not exist. Also,
individual samples, such as rinses following cyanide or
chrome-containing baths, were taken from particular
waste streams to establish parameters that would be used
in the analysis.
The new analytical tool that was developed for the
Phase II analysis was an optimization model. The model
is a mixed-integer, linear-program algorithm that has a
function similar to the micro computer model used for
the case study analysis. The new model, like its simplified
predecessor, determines the least cost regional waste
treatment scheme considering in-plant treatment and
CWT for typical wastes generated by metal finishing
companies.
The optimization model contained several important
advantages over the micromodel. First, included in the
new model was an additional in-plant technology, ion-
exchange. Shops were given the option of using ion
exchange units with applicable plating baths. It was
assumed the units would be installed on still rinses
following plating tanks and used to concentrate the waste
stream for shipment to a central treatment facility.
Concentrating techniques are available for other plating
methods.
Another advantage of the optimization model is its
ability to consider the choice of multiple CWT sites (the
micromodel was limited to one potential CTF site per
analysis). This option should be considered when a
regional area is planning CWT so that volume reductions
can be facilitated. Several central waste treatment plants
may significantly reduce transportation costs. Each
treatment facility could contain treatment for all waste
streams and provide sludge dewatexing, or certain
facilities could specialize by treating only certain waste
streams or be limited to wastewater treatment and
transport dilute sludges to another facility for
dewatering. The model simulates the most economical
combination of treatment sites considering all possible
permutations.
The utilization of the Phase II model began last month.
The analysis is not yet complete, but preliminary results
show a close similarity to the Phase I results.
A report describing the Phase II analysis and
presenting results of the study will be completed in June
1980. Also, a 1-day seminar will be held in Cleveland to
discuss the results with the local plating industry
representatives who have participated in the Phase II
study.
MANAGEMENT AND FINANCING OPTIONS
Introduction
Much of the evaluation process for choosing a
particular approach must be subjective and is dependent
on an assessment of local requirements. Ideally, an
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objective evaluation of these options should be
undertaken by industrial representatives and cognizant
officials including state or local economic development
officials, municipal sewer agency officials and
representatives from the local banking or investment
community. Suitable relations with the media and local
environmentalists will aid in providing an open dialogue
on the purpose of the facility, its backers, and future
siting attempts. The following sections provide
information on the general approaches to these,
MANAGEMENT OWNERSHIP OPTIONS
Overview—Management and ownership options fall
into three basic categories: private, public, or cooperative
ownership. Private ownership would be by firms that
specialize in waste treatment and disposal, although it is
possible that a single electroplater could build a CTF to
handle his and other platers' waste. Public ownership
could be by state, county, municipal, or quasigovern-
mental economic development corporation. Finally,
cooperative ownership implies either a joint venture or a
general-limited partnership of CTF users.
In addition to full private and full governmental
electroplater cooperative ownership, there are two
scenarios that represent variants to the basic
management options. These include:
• Government or electroplater ownership of the land
with an outside firm owning and operating the CTF
• Governmental or industry ownership of the land,
buildings, and equipment used in the CTF with an
outside firm being hired to manage the facility
Table 27
Possible Management Ownership Options*
Complete
Private
Ownership
1. Complete ownership, financing and
management responsibility by an outside firm.
2. Complete ownership, and management
responsibility by an outside firm with financing
assistance (i.e., loan guarantees, loans, or non-
recourse financial investments) by state/local
government and/or an industry user group.
3. Ownership, financing and management
responsibility by an outside firm of a CTF built
on government-owned or industry-owned land.
4. Ownership and management responsibility
by an outside firm of a CTF built on
government-owned or industry-owned land
state/local government and/or industry
financing assistance.
5. State/local government and/or industry user
group ownership and financing of a CTF which
is managed under contract by an outside firm.
Government 6. Complete state/local government and/or
and/or Industry industry user group ownership, financing and
User Group management responsibility.
Ownership
In Table 27, these three options are distributed into six
management scenarios. While these scenarios are not the
universe of all possible choices, they are presented as a
representative cross-section and should be modified for
local conditions.
The selection process will be influenced in large part by
the following factors:
• The level of management control desired by
government and/or industry user groups
• The willingness and capability of government
and/or industry user groups to participate in financing
• The level of liability for CTF operations that
government and/or industry user groups are willing to
accept
Management control over the pricing of services and
the user access to a CTF will, of necessity, be determined
by the risk associated with the potential dangers of
handling and disposing of hazardous materials. As
shown in Figure 13, if the potential customers and/or
local government are concerned that the CTF should
service small business and provide the treatment services
at a below market user fee, then the potential customers
and/or local governmen. will need to be willing to
assume a role in the financing package and assume the
degrees of risk associated with this participation. If the
potential customers want to transfer all of the risks,
financing considerations and management problems to a
third party, they also must delegrate management control
and pricing authority.
Management/Ownership Options:
1. Complete ownership by outside private firm.
2. Complete ownership/management by outside firm
with financing assistance by state/local government
and/or industry user group.
3. Ownership.management of CTF by outside firm.
Land owned by government or industry user group.
4. Combination of Options 2 and 3.
5. Ownership by state/local government and/or
industry user group. Contract management by
outside firm.
6. Ownership/management by state/local government
and/or industry user group.
Fig. 13—Financing Participation, Control, Liabilities and
Management/Ownership Options.
Private Ownership
Private ownership delegates complete management
control of operating liabilities and financing
responsibilities to a private firm providing a service
similar to chemical suppliers. While it prevents local
government and industry from exercising extensive
control over customer selection or user fees, it requires no
capital outlay for facilties by electroplaters. The
responsibility of compliance with appropriate
wastewater treatment and solid waste regulations is
delegated to a responsible private concern.
Private Ownership Using Public Financing Assistance
The economics of scale are the primary attraction of
centralized waste treatment facilities, though market
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competition by competing private centralized treatment
facilities will ensure that small business customers are
likewise serviced and that reasonable user fees are
charged. Many potential treatment firms are limited by
their access to investment capital; therefore, local
government can assist in providing traditional financing
assistance through loan guarantees, direct loans, or
equity investments.
Private Ownership Using Government Land—
Attracting private capital int&this^reatment business can
be assisted by providing suitable government owned land
at reduced or token lease prices. Since these treatment
facilities must be in industrialized areas near the plating
community, higher land cost may raise the user fees for
potential users. However, if the local government
provides suitable land at a reduced price, the attraction to
private firms will increase.
Private Ownership in Management with Public Financial
Assistance in Land Aquisition. A hybrid of the two
previous sections combining financial assistance and
land dedication could provide the maximum incentive
for private concerns to enter the business and provide
local participation in managerial control. For example, if
a consortium of industry users purchased and dedicated a
track of land or contributed capital to the facility, it
would be in a position to negotiate for long-term
contracts and certain liability surety.
Government or Cooperative Ownership with Contact
Management] The Federal Government owns several
nuclear reactors that are operated on a contract basis by
private firms. Similarly, a centralized facility owned by
an industry cooperative and operated by contract
management can be conceived. Cooperatives similar to
those used for gain and other farm commodities could be
capitalized by the electroplating industry and managed
by a contractor.
Government or Electroplater Cooperative Ownership.
This approach is similar to the one described previously
except that control over the design, construction, and
operational management of a centralized facility is
maintained by the government or industry consortium.
Management by some form of Board of Trustees or
general partner (as in a limited partnership) would place
operational responsibility with the partner.
Financing Options
Overview. The options available to capitalize central
facilities are numerous and include traditional private
source bank loans or corporate bond issues as well as
Federal and state programs designed to assist businesses.
Hybrids and combination of these financing approaches
can be considered and tailored to available programs and
local needs. The success of a potential package will
require resourcefulness and creativity in developing and
financing plans responsive to individual situations.
Conventional Loans. Conventional loans are available
from lending institutions to finance projects of this type,
assuming existing corporate financial strength is
supported by well established ties with the financial
community. The current credit markets dictate loan
availability and credit rate.
Debentures. Private investment funds raised by issuing
debentures are direct obligations of the issuing
corporation dependent entirely upon its general credit
rating, reputation, and prestige. These are normally used
by large, financially successful companies as a means of
raising capital through debt financing. Minimum dollar
requirements are required to justify the underwriting
costs.
Small Business Investment Corporations. The Small
Business Investment Act of 1958 authorized the creation
of Small Business Investment Corporations (SBIC) to
provide long-term capital to small businesses. Approval
by the SBA, which licenses SBICs, is required if the SBIC
wishes to invest more than 20 percent or $500,000 in a
single small business concern. SBICs may be unable to
solely underwrite a capitalization of this type; however,
they may play a role in developing an overall financing
package.
Industrial Development Bonds. Tax exempt industrial
development bonds can be issued by state or local
government for financing industrial development. IDBs
issued for pollution control financing do not have a
dollar limitation; however, using this mechanism to
promote industrial pollution projects with tax exempt
status requires strict adherence to state and IRS
regulations. Until recently, few small firms were able to
utilize this source of capital because investment bankers
required minimal credit risks and guaranteed repayment
for financing this debt on nonproductive pollution
control facilities.
Small Business Administration Guarantees. In 1976,
Congress authorized SBA to guarantee 100 percent of a
small business's obligation to finance a pollution control
facility. PL-94-305 assures that smaller firms can obtain
favorable financing rates and terms similar to those of
major corporations. Guarantees of this type are to be
used by credit worthy businesses and no credit denial by a
bank is required. Section 8 of the Federal Water
Pollution Control Act and PL-94-305 provide the
following programs to small businesses:
SBA Pollution Control Revenue Bond Guarantees
SBA Loan Guarantee
SBA Participation Loan
SBA Direct Loan
SBA Section 502 Programs
Bond guarantees are made to small viable credit
worthy companies to provide low-interest, long-term
financing for pollution control needs. Firms must have
been in business for at least 5 years and profitable for at
least 3 of those 5 years.
Loan guarantees are provided for those businesses
unable to obtain conventional bank loans and would
otherwise suffer substantial economic injury to comply
with Federal treatment regulations. Some financial
positions and reasonable repayment assurance are
required, but provides advantageous interest rates.
SBA also may participate in a loan with a bank.
Normally, SBA's maximum participation is 75 percent of
the project cost; however, if a bank exceeds its lending
limit, SBA share may be raised an additional 15 percent.
Direct loans up to $500,000 are available for acquiring
pollution control equipment.
SBA can assist local development companies in
creating facilities for small businesses. Section 502 of the
Small Business Investment Act of 1958 allows for
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loans for facilities that small businesses may lease or
purchase.
Economic Development Administration. The Federal
Government takes a major role in restoring economically
depressed areas through the Public Works and Economic
Development Act of 1965. Eligible programs in specially
designated areas are as follows:
• Direct grant for government owned projects
• Supplementary grants to augment other grants when
applicants are unable to meet local government shares
• Loans in severely distressed areas for financing public
works; 65 percent for industrial and commercial
expansion; 90 percent for working capital and fixed
assessed loans.
Other Federal Programs. The Farmers Home
Administration and the Department of Housing and
Urban Development may be further sources of
information on Federal programs subsidizing projects
that are in the public interest. Municipal bonds and state
programs should be likewise investigated when
considering a financing approach.
Summary. Financing and management of a central
facility may provide for its success or failure. Strong
considerations should be given to the specific
requirements of the user community, Federal, state, and
local governments, and the financing community. The
major requirement falls, however, upon the potential
user community in providing a united front towards
creation of these facilities. Participation by the industry
developing this treatment capacity will help assure its
success.
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Hazardous Waste Management Facilities:
The Siting Problem and Possible Solutions
Frank Boni*
INTRODUCTION
Waste disposal from the surface finishing industry was
cited as one of the most serious problem areas in both of
the two previous AES/EPA Conferences. A year ago in
this meeting EPA's John Lehman (1) estimated that 90%
of all waste disposal facilities will not be environmentally
acceptable. That is, they will not meet the prospective
RCRA requirements.
The problem regarding surface finishing wastes is
simply this: Landfill capacity is limited and surface
finishers may be unable to find safe, legal disposal
facilities. And public opposition to siting may delay the
development of additional disposal capacity.
The problem is widely attributed to more stringent
environmental standards coupled with public
apprehension regarding waste management facilities,
particularly facilities sited or proposed for siting in "my
backyard."
While it appears there is a role for state governments in
the solution of the problem, perhaps there is also a role
for the surface finishing industry and the AES, an
educational role.
Legislation and Regulations
Waste disposal options have been the target of much
legislation. Those disposal options are being increasingly
regulated to minimize their potential threat to the public.
As a consequence of the Federal and State activities
there are substantial programs in place to enhance air and
surface water quality. But the ultimate fate of the
pollutants removed from air and water has become a
major disposal problem.
Ironically, the earlier statutes actually added to the
amount of hazardous waste disposed of on land. For
example, the Clean Water Act which affords cleaner
navigable waters implies more land disposal for the
removed hazardous materials. Concern over this
problem led the Congress to pass the Resource
Conservation and Recovery Act (RCRA) in 1976. Of
particular importance to surface finishers is subtitle C of
RCRA which creates a "cradle-to-grave" control system
for the management of hazardous wastes.
*Frank Boni
Liqwacon Corporation
Blue Bell, PA 19422
The proposed RCRA regulations have been reviewed
(2) in recent months by the Subcommittee on Oversight
and Investigations of the U.S. House of Representatives.
That group made recommendations for improving the
Act and the regulations. The Subcommittee urged that
EPA promulgate those regulations at the earliest possible
date, noting that their promulgation is the key to
enforcement of RCRA. (Sections 3002, 3003 and 3010
applicable to generators and transporters were being
issued as this paper went to press.)
Public Opposition
In a letter (3) to the Electroplating Industry in regard to
the problems associated with production, treatment and
disposal of wastes, AES discussed the September 7, 1979
electroplating pretreatment standards and forthcoming
solid waste regulations. Executive Director Schumacher
wrote:
"These new regulations will require the metal
finishing industry to improve its waste water and
sludge treatment and disposal practices."
There are several practices available for disposal of
sludges. Myron Browning and his associates discussed
them in this meeting last year (4). Methods included were
landfills, reclamation, chemical fixation and heat
treatment. They concluded landfill disposal is still the
most common practice in the plating industry and will
probably be so as long as the recovery processes are not
economical.
However, community acceptance of the establishment
and operation of new landfill facilities (and continuing
operation of existing facilities) may prove to be the most
difficult aspect of the problem associated with those
landfills. The Comptroller General in his report to the
Congress (5) describes public opposition as the major
barrier to expanding disposal capacity:
"Information obtained from State and industry
officials, representatives of environmental interest
groups, and environmental impact statements
indicate that people are against the permitting of
sites for many reasons. For example, people are
fearful of groundwater contamination, air and land
pollution, fires, explosions, spills, rodent damage,
odors, and dust dispersion. They complain that if a
hazardous waste facility is built near them, the
value of their homes will decline and future real
estate development will be inhibited. They protest
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that they do not want their community to be known
as a 'dumping ground' for other people's waste."
Public Opposition: Coping With It
Public opposition to the siting or expansion of landfills
or even continuation of existing landfills takes different
forms. The more visible opposition may be witnessed on
the television screen as the news cameraman focuses on
an obviously disturbed citizenry carrying placards and
blocking entrance to a landfill in the community. A less
dramatic, but perhaps more effective opposition, is the
power held by many municipalities to control
development through zoning or other regulations.
Increasingly it seems that it might be necessary for the
state governments to become involved in the siting
process if reason rather than emotion is to be
determinant. If state involvement is appropriate, the
questions that arise include:
What is the preferred form of involvement by
the state government in the siting process?
How and when should the public participate
in the siting process to best assure that
facilities are safe?
As for the form of state involvement, our view is that
the private sector will provide the necessary disposal
facilities if the states create a regulatory framework. An
opposite point of view is that private enterprise will not
be able to meet the demand for legal disposal when the
new standards become effective. Accordingly, such
advocates reason that the government should establish
disposal facilities with operation either by the State or
contracted to private industry. With regard to this
controversy, it is worth noting that there is no provision
in RCRA for any Federal support for facility
construction on the Congressional premise that the
private sector would respond if given a regulatory
program.
There are already a few models for state involvement in
the process of siting of landfills. However, because those
models are so new there is very little experience to
validate them. The 1979 Michigan "Hazardous Waste
Management Act" (6) provides for a site approval board.
That board will review and grant or deny final approval
for each site construction permit application
recommended for approval by the State's environmental
agency, the Department of Natural Resources (DNR).
New York's Industrial Hazardous Waste Management
Act is proposed to be amended to give facility siting
boards the discretion to supersede local zoning in those
cases where such zoning is considered unfair, arbitrary or
generally not in keeping with the overall public interest
(7).
At least one trade group, the National Solid Wastes
Management Association (NSWMA), has formally
expressed its attitude regarding state involvement in the
siting process (8). They suggest the states provide
mechanisms for overriding local zoning ordinances when
necessary and that incentives be paid to a host
municipality by the users of a facility.
The three preceding concepts of state involvement in
the siting process include mechanisms for public
participation. Public participation in the Michigan siting
protocol takes the form of representation on the 9-
member site approval board. That board which acts on
applications aproved by DNR includes four temporary
positions filled by residents of the minicipality and the
county in which the disposal facility is proposed to be
located. Two of the permanent representatives are also
public members, one is to be a geologist and the other a
chemical engineer, both of whom are from faculties of
Michigan's higher education institutions.
In New York one of the options under consideration
includes an independent agency or organization to be
created to serve as a mediator and to negotiate
agreements between citizens and the proposed developers
of a hazardous waste facility. New York would ensure
that the resulting agreements were made binding by the
incorporation into the permits and certificates which are
required before the facility could be constructed and
operated.
Mediation, as a negotiated process for resolution of
public conflicts, has been successful in some recent
controversies (9). The mediation process is getting
increasing attention. There is report (10) of a mediation/
compensation concept being advocated to the EPA.
There are two central ideas in the proposal:
1. The most effective way to deal with the social and
political issues is community compensation
through mediation, and
2. Siting strategies must be adopted on the state level.
EPA's role would be to promote the
compensation/mediation strategy among the
states.
In their position paper NSWMA also provides a
mechanism for social appraisal of a site application that
has received favorable environmental review. NSWMA
advocates establishment of a siting board whose makeup
would be similar to that of Michigan.
Donald Andres recently predicted (II) the solution of
this problem (public acceptance of proposed disposal
sites) will be an emerging planning partnership between
state governments and the waste producing/waste service
industry. At this writing we are working hard in
Pennsylvania to develop such a partnership by way of an
Industrial Advisory Group to the Department of
Environmental Resources (DER). The Advisory Group
consits largely of industrial waste generating companies.
That group appointed a subcommittee from the waste
service industry to assist them in the siting
recommendations they are creating for the DER. DER
will consider those recommendations in the legislation
proposals they are developing for the General Assembly.
It is too early to appraise the success of this new
government/industry partnership.
Education: A Role for AES?
In all the preceding ideas for resolving the
social/political issues through public participation the
assumption is made that the public has adequate
awareness of the need for disposal facilities and is able to
distinguish among the risks and benefits posed by the
facilities.
Yet such public awareness cannot be taken for granted.
An educational effort directed at raising the level of
understanding (not to be confused with propaganda)
needs to be undertaken. Perhaps EPA through its Office
of Public Awareness can provide support for this effort,
but it seems the effort is more likely to be successful if
implemented at the local level. I feel that local industry
has both an obligation and an opportunity in this
educational regard.
Local industry is best situated to "know" its
community, its attitudes and its awareness. That industry
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also knows best its own needs for waste management
facilities; local industry can best justify its needs in terms
of facilities, investment and jobs. Such advocacy by local
industry will require a real commitment, one that has not
been apparent to date.
In the case of the surface finishing industry and metal
finishing in particular, it may be that the relatively small
size of many of its constituent member companies
precludes much involvement. And this circumstance may
suggest there is a role, a public education role, for
professional and trade organizations such as AES.
If there is a role for AES, the question arises: What
message ought AES and its representatives be
advocating?
We suggest the message to the public might contain the
following elements:
1. Clarify the connection that exists between
standard of living and generation of industrial
wastes.
2. Identify the need for industrial "waste baskets."
The need for waste management facilities grows
in proportion to living standards even though
manufacturing processes are being improved to
reduce wastes and more wastes are being
recycled and exchanged every day.
3. Edify as to the basic spectrum of characteristics
that are injurious to public health and the
environment, i.e., toxic, radioactive, reactive,
corrosive, and ignitable, and differentiate from
these the nature of the surface finishing industry
.wastes, particularly those residuals or wastes
produced by the chemical treatment facilities of
the industry.
4. Edify as to the various waste disposal facilities to
clarify differences among municipal waste
facilities for disposal of household refuse and
sanitary wastes, hazardous waste facilities for
disposal, destruction and storage of chemical
wastes and special waste facilities for storage of
residuals produced by the chemical treatment
facilities of the surface finishing industry.
5. Edify as to the need for segregated landfills, to
keep industrial wastes separate from residential
and commercial refuse thereby minimizing the
likelihood of formation of leachate which would
have adverse impact on groundwaters.
6. Edify as to need for state involvement in the
siting process on a basis which provides for
public participation in the evaluation of social
and economic issues. To be emphasized: Local
control is not likely to solve problems.
A Caveat: Things May Not Be What They Seem
The current popular view is that public opposition to
new disposal facilities is growing and future sites may
even have to be located on Federal and State lands.
However, there are recent instances of approved
applications for sites owned by the private sector. Are
such approvals exceptional or might they indicate a
trend?
CONCLUSIONS
Regulations and societal pressures are reducing the
available disposal options for the surface finishing
industry.
There is need for involvement at the state level in the
siting aspect of the growing problem facing the surface
finishing industry of finding safe, legal locations for
disposal of residues from waste treatment.
State involvement is more likely to be successful if
siting procedures include public participation in
resolution of social and economic issues.
Education of the public is a necessary precondition for
productive participation in the siting process.
The surface finishing industry and perhaps its
associated institutions such as AES have a role in
increasing the public's awareness of the problem and
potential solutions.
REFERENCES
1. John P. Lehman, "Status of Office of Solid Waste
Activities," Second Conference on Advanced
Pollution Control for the Metal Finishing Industry,
EPA 600/8 - 79-014 NTIS, Springfield, VA 22161.
2. Committee Print, "Hazardous Waste Disposal -
Report," September 1979, Committee Print 96 1FC
31, Supt. of Documents, U.S. Government Printing
Office, Washington, DC 20402.
3. American Electroplaters' Society, letter December 6,
1979, to Members of Electroplating Industry,
Industry Survey for Centralized Waste Treatment
Study.
4. Myron Browning, John Kraljic & Gary S. Santini,
"Metal Finishing Sludge Disposal; Economic,
Legislative and Technical Considerations for 1979,"
Second Conference on Advanced Pollution Control
for the Metal Finishing Industry, EPA-600/8-79-
014, NTIS, Springfield, VA 22161.
5. Comptroller General, Report to The Congress of
The United States; "How to Dispose of Hazardous
Waste—A Serious Question that Needs to be
Resolved," U.S. GAO Publication CED-79-13
December 19, 1978.
6. State of Michigan, Hazardous Waste Management
Act. Act No. 64, Approved July 25, 1979.
7. New York State Environmental Facilities
Corporation, letter, September 1, 1979, to Governor
Hugh Carey, et al, with Booz, Allen & Hamilton
Report September 1, 1979.
8. National Solid Wastes Management Association,
"Position Statement on Siting of Waste
Management Facilities."
9. Booz, Allen & Hamilton, Report for The New York
State Environmental Facilities Corporation
September 1, 1979, page 111-11.
10. Hazardous Waste Report, Volume 1, Number 5,
October 8, 1979, "Mediation/Compensation May be
Applied to Siting Decisions," p. 4.
11. Donald Andres, "Hazardous Waste Management
Heads out of Adolescence," Waste Age January
1980, p. 40.
134
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Group Treatment-
Options and Economics
Erich W. Salomon and Edward H. Comfort*
ABSTRACT
Group treatment is one alternative for firms faced with the problem of compliance with
pretreatment regulations whereby they may achieve the benefits of economy of scale. A
preliminary study of the concept as applied to the plating firms within Hunting!on Industrial
Park, Providence, R.I., was conducted. It was found that, with the assumed ten participating
firms, substantial savings could be realized. The effects of financing cost and wastewater hauling
charge on savings achieved were investigated, as were the benefits of installation of a piped
wastewater collection system. The most cost-effective decision for each participating firm was
identified. An approach to financing the proposed facility is outlined.
INTRODUCTION
The Environmental Protection Agency is currently
proposing and promulgating a series of industrial
wastewater pretreatment regulations that will reduce the
introduction of industrial wastewater pollutant
parameters to Publicly Owned Treatment Works
(POTWs).
The metal finishing industry, because the nature of its
waste discharge is such that it can seriously interfere with
the proper operation of POTWs, will be one of the
industries most affected by these regulations.1 Various
process wastewater control and treatment technologies
will be required, which could have an adverse economic
effect, especially for small plants with limited personnel
and capital.
At last year's joint EPA/AES Conference on
Advanced Pollution Control, EPAs Centralized
Treatment Program2 was described. It was pointed out
that the Office of Research and Development at EPA had
sponsored research to investigate means of reducing the
anticipated economic impact on industry of compliance
with pending wastewater and solid waste regulations.
Regional centralized treatment was one promising means
identified; economy of scale and improved waste
management are primary benefits. The results of
preliminary studies on the economies of the centralized
treatment approach were also presented at last year's
conference.3 It was shown there that the major portion of
the economy of scale benefit of the centralized treatment
concept could be realized when as few as ten shops decide
to participate in the arrangement (Figure 1).
While other papers at this conference report on the
present status of research on the regional centralized
treatment approach, this presentation is directed at a case
study of the private group treatment option. Group
*Erich W. Salomon
Lang Jewelry Company
Edward H. Comfort
CENTEC Corporation
treatment, as the term is used here, refers to the joint
establishment of a waste treatment facility by a group of
shops in close proximity, having similar wastes.
Ownership, management, and operation would generally
involve the participating companies themselves,
although a number of variants are possible. The group
treatment facility, while primarily intended for the
benefit of its members, could in addition offer to treat the
wastes of other small shops having similar waste
constituents.
Huntington Industrial Park, Providence, Rhode
Island, is a modern industrial park which includes about
a dozen firms involved significantly in electroplating. All
but one or two of the companies are primarily engaged in
the manufacture of jewelry. Ten of the firms have agreed
to participate in a preliminary investigation of the
technical and economic feasibility of establishing a group
treatment facility to treat their wastes. This paper
presents the status of that investigation.
of the
plane I
Number Of EC
Fig. 1—Effect of Centralized Waste Treatment Systems on Capital Cost
Per Plant (from reference 3).
135
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BACKGROUND
Pretreatment standards' for the electroplating point
source category were published on September 7, 1979,
with an effective date of October 9, 1979, and a
compliance date of October 12, 1982. The regulations
identify eight subcategories to which modified effluent
limitations apply. Those of primary concerns to the
plants in Huntington Industrial Park are the Common
Metals Subcategory and the Precious Metals
Subcategory. The major difference between these
subcategories is the addition of a limitation on the
discharge of silver in the case of precious metals. The City
of Providence presently intends to enforce standards
identical to the Federal requirements. The existence of
the 1982 compliance date means that methods of
complying with the pretreatment regulations must be
considered at an early stage. Thus, EPA's Office of
Research and Development has sponsored the present
study of group treatment at Huntington Industrial Park
at this time as a case study which might be useful as a
guide for similar industrial groupings.
The Providence, R.I. region, in which Huntington
Industrial Park is located, presents a unique situation
with regard to electroplating concentration. No other
area in the country has such a high proportion of
electroplating firms with respect to the general
population. The city presently receives large
concentrations of metals in its influent, and calculates
that it discharges as much as $30,000 worth of silver each
week into Narragansett Bay. The jewelry industry is
heavily represented. While it has been estimated1 that
compliance with pretreatment regulations may force
about 20 percent of firms in the job shop sector out of
business nationally (and other estimates have placed this
figure at between 30 and 60 percent)1, the regional impact
of such closures, were they to occur, might be expected to
be nowhere of greater significance than in the Providence
area. A group treatment facility at Huntington Industrial
Park, then, in addition to serving its founding firms,
would have the further potential of providing economical
waste treatment to those small job shops in close
proximity which might otherwise be severely impacted.
Such group treatment facilities are becoming common
in parts of Europe and in Japan. Switzerland and the
Pforzheim region of Germany have instituted such
arrangements. In Japan, with government assistance,
electroplaters have relocated to parks where they can
easily share waste treatment technology. "In the last
several years no fewer than ten industrial parks [one firm
to each building] and factory apartments [one building
co-owned and occupied by several firms] for
electroplaters have been planned and constructed
throughout the country."4
Chuo Electroplating Industrial Park, built on five
acres on an island in Tokyo Bay, is the largest of the
parks. Nineteen platers are included (ten of them small
job shops forming a united company). The opportunity
to relocate and to redesign production lines resulted in
modern in-line recycling and recovery systems within
each member shop. Combined process water discharge
was reduced to a tenth of what it had been—from 300,000
gallons per day to 30,000 gallons per day.
The collective treatment facility at Chuo Industrial
Park includes technologies for nickel and copper
recovery (by ion exchange and electrolysis), chromic acid
recovery from contaminated chromium plating baths
(electrodialysis), a regeneration system for spent ion
exchange cartridges, and conventional precipitation and
dewatering facilities for settling out solids and
concentrating sludges. Fixed expenses of the joint
treatment facility are shared monthly by all of the
members, regardless of the extent to which they have
used the facility, on the basis of the area which each
member occupies in the park. These expenses include
wages and the cost of servicing the debt. On the other
1 batch dumps over a one-month period to find a daily
f mean. Results of the first method was used to assit in
concentration of each type of waste sent to the collective
facility by the member.
In the United States, there have been previous studies
of the group treatment concept. The Environmental
Protection Agency provided a grant in 1977 to study the
feasibility of joint treatment of plating wastes in
Taunton, Massachusetts.5 A unique feature of this
region, however, was the fact that local pretreatment
regulations, more stringent than existing direct discharge
limitations, had forced most potential participants to
have already committed to a treatment scheme. Thus,
only three firms participated in the study. Because the
firms were some distance apart, and because only piping
of wastewater was considered, it was found
uneconomical to jointly treat concentrated rinsewater,
but it was found that a joint facility to treat batch dumps
in common could provide an operating cost advantage.
Certain institutional problems were identified, such as
the need to insure that feasibility of the arrangement did
not depend significantly on future business decisions of
one of the participants. Financing, at the time of the
study, was found most likely to depend on the existence
of a single company financially strong enough to borrow
the necessary funds. The concept was found to have
considerable promise, but was not suitable for the
particular participants and circumstances existing in
Taunton at that time.
At present the Brooklyn Economic Development
Corporation is studying the concept of a "Plating City",
wherein some of the electroplating industry in Brooklyn,
New York, would be consolidated in an industrial park
incorporating cogeneration and joint wastewater
treatment facilities. The initial study shows considerable
potential cost benefit to the participants. While the
plating city concept, unlike the present study, involves
moving of platers and energy costs reduction through
cogeneration, the Brooklyn study did find that a group of
ten assumed platers (consisting of eight small and
medium shops and two large shops) would reduce both
their investment costs and their annual operating costs
each by a factor of approximately 2 by joint rather than
individual treatment.
, Huntington Industrial Park is located within
Providence at the Cranston, R. I. boundary. It is well
served by highways and nearby access ramps. Although
on the outskirts of the city of Providence, it is centrally
located with regard to the bulk of the electroplating and
jewelry industry in the area.
The park is about ten years old. Although not planned
as an electroplating park, there is presently a
concentration of plants performing plating. Eleven
plants within the park fall into that category. Each of the
firms is in the business of jewelry manufacturing with the
exception of one plating job shop and one electronics
concern. The plants involved range in size from 25 to 350
employees. The average number of working days per year
136
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for these firms is 242. All are one-shift operations, and the
length of a shift is eight hours in all but two cases.
Several of the firms perform precious metals plating.
Gold and silver are generally recovered using in-line
processes (electrolysis, ion exchange). Most of the firms
make extensive use of cyanide baths. There is very little
use of chromium (chromium was found in small quantity
in the effluent of only two plants). In addition to cyanide,
typical effluents include copper, nickel, and zinc. Some
effluents show substantial iron. Little cadmium or lead is
in evidence.
Each of the companies presently discharges its
industrial waste streams to the City of Providence
POTW. Each of the firms may expect to be impacted to
some extent by the mandated requirements for
pretreatment.
Figure 2 presents a sketch noting the location of the
firms performing plating within the park.
A preliminary analysis was performed in order to
investigate the technical and economic feasibility of
establishing a joint treatment facility within Huntington
Industrial Park to treat the wastes of the platers in the
park. Transport of the wastes by both piping and truck
transport was considered. The next section of this paper
discusses the collection of data and the assumptions
made for the purpose of performing the analysis.
DATA PREPARATION
The analysis which follows evaluates the benefits of
group treatment when compared with the alternative of
each plant performing its own treatment. The cost model
used computes investment and operating costs of the
treatment technologies employed based on flow rates and
pollutant concentrations.
In order to determine wastestream flows and pollutant
concentrations being discharged by the firms in the park,
CENTEC engineers and technicians spent the week of
February 15, 1980, at Huntington Industrial Park
collecting the needed data. Ten firms indicated sufficient
interest in the project to allow a sampling team of three
persons to spend, on average, one-half day in each plant.
Wastewater streams were divided into cyanide-bearing
and other (general acid/alkali). The flow from the first
running rinse following each cyanide bath (expected to
carry most of the cyanide to the sewer) was measured and
Figure 2.
a composite sample of the cyanide stream was prepared,
the contribution from each rinse being proportional to
the flow rate which had been determined. In addition,
samples of the final effluent were obtained. Each of the
plants' final effluent, at the point measured, consisted
only of process water. At one plant, samples were
obtained of four different types of process solutions just
prior to scheduled batch dumping. The layout of each
plating line was determined and schematic drawings
prepared. Information on type, volume, and frequency of
each batch dump was obtained. Rinse stations on each
plating line were examined to note those at which
meaningful flow reduction measures were in place
(countercurrent rinse, still-rinse, etc.), and those which
were candidates for incorporation of flow-reduction
measures. The percent of normal production underway
at the time of sampling was noted for each firm.
Samples collected from each plant (except for two
which were not in operation at the time of the visit) were
submitted to CENTEC Analytical Services, Inc., Salem,
Virginia. Analyses were performed for total cyanide,
cyanide amenable to chlorination, cadmium, chromium
(total and hexavalent), copper, iron, nickel, lead, zinc,
and silver. Concentrations measured were corrected to
full production based on the assumption that wastewater
flows are unchanged regardless of the level of production.
The final effluent flow rates, generally not convenient for
measurement, were calculated by multiplying the
measured cyanide stream flow rate by the ratio of
measured total cyanide concentrations, cyanide stream
to final effluent. Analyzed concentrations were corrected
for batch dumps using actual concentration data for the
one plant where batch dump samples were taken; the
remaining plants' concentrations were adjusted using
average pollutant data for each category of batch dump
as supplied by the Manufacturing Jewelers and
Silversmiths of America, Inc.7 Two methods of batch
dump adjustment were used. In the first, all dumps with a
frequency of once each two weeks or greater were
considered to have occurred on the same day. This gave a
worst case figure for comparison with the one-day
maximum regulations. The second method averaged all
batch dumps over a one-month period to find a daily
mean. Results of the first method were used to assist in
determining which plants might exceed maximum limits.
Results of the second method were used to represent the
average daily pollutant load requiring treatment.
The two plants which are potential participants, but
which were not in operation at the time of sampling, were
represented as the average of the other firms for which
data was available. Flow rates for the ten plants ranged
from 4,000 to 65,000 gallons per day. Every plant except
one was found to exceed cyanide limitations on the final
effluent. That plant, because its effluent flow is less than
10,000 gallons per day, did not exceed applicable
limitations with regard to any pollutant parameter.
Nevertheless, it was included in the analysis because,
should local regulations ever impose the same limitations
for all parameters presently indicated for plants with
flows greater than 10,000 gpd, it would be out of
compliance for some parameters.
GROUP TREATMENT ANALYSIS
The CENTEC Centralized Treatment microcomputer
model was used to analyze the data described above. The
analysis is basically a trade-off of the economy-of-scale
137
-------
savings resulting from joint treatment against the added
costs resulting from the need to transport the wastes. The
model consists of a series of treatment process cost
equations, based on U. S. EPA published relations.8'9 All
costs are updated by use of appropriate cost indices. The
model selects the most economical decision for each firm
from among four allowed alternatives:
(1) Send all wastewater to the group treatment facility
(GTF).
(2) Send all cyanide-bearing wastewater to the GTF;
treat other flows in-house and send dilute sludge to the
GTF.
(3) Treat all flows in-house; send dilute sludge to the
GTF.
(4) Perform all treatment processes, including sludge
dewatering, at the individual plant.
Treatment processes considered are conventional
cyanide oxidation, physical/chemical treatment
(neutralization, precipitation, flocculation, clarification
and thickening), and dewatering by filter press or vacuum
filter. Dewatering to 20 - 30% solids content is considered
essential whether performed in-house or at the GTF,
since future disposal regulations will not allow dilute
sludges to be placed in landfill, and since volume
minimization is required to minimize transportation
cost.
Plants which decide to ship wastewater to the GTF are
required to install sufficient 5,000-gallon tanks to hold
separately one day's production of cyanide and non-
cyanide wastewater. The savings to each plant resulting
from installation of countercurrent rinse at rinse stations
not presently so equipped (if there is room) is computed.
If such savings are positive, the plant is charged with the
cost of such investment and installation, and the
appropriate waste stream flows are reduced accordingly.
Transportation to the group treatment facility was
assumed initially to be by 5000 gallon tank truck. The
alternative of piping all wastes to the GTF was also
considered and is discussed in a later section. The cost of
shipping 5000 gallons by truck to the GTF was varied
from $20.00 to $40.00. (A typical charge for wastewater
hauling is $40 per hour.) The interest rate on borrowed
funds was varies from 6 percent to 18 percent. Each plant
was assumed to require a 20% return on investment
before committing capital to in-house treatment
technology. That is, a plant is considered to ship its
wastes to the GTF unless by constructing in-house
treatment facilities it can realize a savings providing a
return on invested capital of at least 20%.
Electric utility costs, a component of operating costs,
were calculated by using the $.07/kwh rate prevailing in
the Providence area. In addition, operating labor,
maintenance, and chemical costs are computed for each
process. The capital cost of the group treatment facility is
computed as the sum of the investment in each treatment
process, multiplied by a factor of 1.65 which accounts for
ancillary costs of GTF construction.10 These costs
include site work, excavation, shelter, laboratory,
electrical installation, controls, piping, etc., in adding to
such non-construction cost as A/E fees, legal fees, and
contingency.
Such a factor is not applied to the cost of treatment
processes installed within an existing plant, since it is
assumed that necessary shelter, utilities, etc., already
exist.
Table 1
HUNTINGTON INDUSTRIAL PARK
Group Treatment Analysis Parameter Values
FINANCIAL DATA
Interest Rates & Equipment Life
Interest Rate 12%
Return on Investment 20%
Equipment Life 15 years
Transportation and Power Costs
Transportation Cost
Cost of Electrical Power
Cost Indexes
Ceman Cost Index
Chemical Plant Cost Index
$30.00 ($/5000 gal)
0.07 ($/KWH)
198.00
246.90
Chemical Wholesale Price Index 287.20
GROUP TREATMENT FACILITY
Identification
Region Name
x Location
y Location
Number of Plants
Number of Routes
Operational Time
Hours of Operation
Days of Operation
Processes Considered
Chromium Reduction
Cyanide Oxidation
Physical/Chemical Treatment
Sludge Dewatering
Storage Capacity
Providence
0.00 (miles)
0.00 (miles)
10
1
16 (hours/day)
300 (days/year)
Table 1 shows the values of the financial parameters
and the group treatment facility constants used in the
analysis.
RESULTS OF ANALYSIS
The calculated annual operating results for the region,
consisting of the ten participating firms, are summarized
in Table 2. The annualized investment costs shown there
represent the amortization of the initial capital
investment at 12% over 15 years. Table 2 shows that,
although the total waste hauling charges in the park for a
year come to $124,540 (this total includes amortized in-
plant storage costs as well), an overall annual savings of
$119,735 is realized when compared to the costs of
treatment without the existence of a GTF.
Figures 3 and 4 show the effect which the financing cost
and the transportation charge have on the overall savings
achieved. (It has been assumed that the same cost of
money applies to financing of individual plant treatment
construction and to construction of the group treatment
facility.) Figure 3 shows that the annual savings increase
rapidly as the interest rate increases. This is because the
greater the cost of financing, the more significant the
economy of scale factor becomes. Of course, the cost of
servicing the debt increases as financing charges increase,
but the savings make group treatment even more
attractive as interest rates rise.
Figure 4 shows the same information plotted as annual
savings vs. the transportation charge. As the cost of
hauling each 5000 gallons of wastewater from each plant
138
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Table 2
REGIONAL SUMMARY
Huntlngton Industrial Park
Hauling Cost = $30/5000 gallons Interest Rate = 12%
Total Plant Total Plant
Investment Operating
(Annualized) Costs
W/O
GTF $180,639
With
GTF 31,704.4
Savings $148,935
$183,489
29,147.1
$154,342
Total Plant
Chemical Total
Costs Plant Costs
$29,730.4 $393,858
4,303.41 65,154.8
$25,427.0 $328,704
Total
Transport
Costs
$0.00
124,540
$-124,540
Total Annual
Total Regional
G TF Fees Costs
$ 0.00 $393,858
84,428.8 274,123
$84,428.8 $119,735
Table 3
GROUP TREATMENT FACILITY CONFIGURATION
-
Process Required Capacity
1-Chromium Reduction
2-Cyanide Oxidation
3-Phys/Chem Treat.
4-Sludge Dewatering
5-Storage
0.0 gal/day
20,535.1 gal/day
27,500.9 gal/day
84.6 Ib/day
27,500.9 gal/day
Process and Fee Structure •
Annualized Operating
Investment Costs
$ 0.0 $ 0.0
5,751.7 5,776.0
17,973.9 10,008.9
6,287.6 2,323.6
6,560.9 0.0
Chemical
Costs
0.0
26,051.9
3,694.3
0.0
0.0
Total Costs Fee Rate
$ 0.0 $ 0.0
37,579.6 0.0080 $/gal
31,677.1 0.0050 $/gal
8,611.2 0.4402 $/lb
6,560.9 0.0010 $/gal
to the GTF doubles from $20 to $40, the savings decrease
by an amount between 12 and 20 percent depending on
the interest rate. So it is advisable that the GTF
subscribers take care to find the most efficient hauling
means available.
The capacity of each treatment process at the GTF
required to service the needs of the members is shown in
Table 3. Since there is virtually no chromium in the
wastewater of the participating plants, no provision for
hexavalent chromium treatment is made. The total flow
to the GTF is found to be little over 25,000 gallons per
day. This is substantially less than the total present
wastewater flow of 300,000 gallons per day from the ten
plants. This is because: (a) the model found that all plants
would find it cost-effective to reduce flow by installing
counter-current rinses and/or still rinses at rinse stations
~ 170
o
~ 160
£ 150
120
5 110
< 100
Interest Rate (Percent)
where that is possible, and (b) two plants, having some of
the largest flows, elected (based on the analysis) not to
send all of their raw wastewater to the GTF.
Table 3 also shows a summary of all costs associated
with operating each treatment process at the GTF,
including the amortized investment cost. A fee for use of
each process is then established (break-even operation
for the GTF is assumed here), so that each participant is
charged based on the volume of wastes which he sends to
each process.
Table 4 lists each plant by code and shows the option
chosen by each plant and the flows to each GTF process
from each plant. Plant No. 1 found transportation of the
raw wastewater to be so expensive that it determined its
most cost-effective solution was to provide in-plant
treatment through the clarification step and to send the
170
160
ISO
, HO
130
120
110
100
I I I I
Transportation Costs
(Dollars Per 5000 Gallons)
Figure 3.
Figure 4.
139
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Table 4
Option Chosen By Each Plant and Flows to Each Process
At The Group Treatment Facility
^ Average Daily Flows to Group Treatment Facility
Plant A/0 nptinn C.hnoorj " M y
-Wastestream to GTF- Cn Oxidation Gal Phys/Chem Trim Gal Sludge Dewatering Ib
1 3- only sludge 0.0 0.0 2.2
2 1- all flow 7797.5 94936 21.1
3 1- all flow 549.5 1693 0 10 2
4 1- a" fow 639.0 818.5 1.7
5 2- Cn and sludge 646.5 646.5 8.9
6 1- all flow 904.2 2562.0 6.8
7 1- all flow 1476.8 2216.1 0.5
8 1- all flow 970.5 1389.1 4.1
9 1- all flow 1235.0 1553.3 1.6
10 1- all flow 6316.0 7126.7 27.5
Table 5
INVESTMENT REQUIRED WITH AND
WITHOUT GROUP TREATMENT
In-Plant Invest, w/o Group Treat. $1,229,864
In-Plant Invest, with Group Treat. $215,673
Capital Cost of the GTF 287,991 503,664
Capital Savings $726,200
Table 6
GROUP TREATMENT FACILITY
CAPITAL COST BREAKDOWN
Cyanide Oxidation $ 23,059
Phys/Chem Treatment 72,496
Sludge Dewatering 42,772
Storage 36,066
Laboratory, Shelter, etc. 113,598
Total $287,991
iilute sludge only to the GTF. Certainly that option
choice could be changed based on segregation of certain
bear the costs of stream segregation, storage provision,
and wastewater flow reduction (included as part of
transportation costs in Table 2). The two plants which
elected to install some inplant treatment (under this set of
assumptions) would have that capital cost in addition.
PIPING OF WASTEWATER TO THE GTF
While truck hauling of wastes was assumed in the
previous analysis, the possibility of constructing an
industrial wastewater sewer system within the park was
considered. A double pipe system, designed to carry
cyanide and non-cyanide wastes separately, was
evaluated. Two designs were considered: One, a
collection system based on gravity flow, the other a
pump-assisted system. Figure 5 shows a schematic of the
collection system (single pipeline shown) with manholes
indicated (17 per line). The basis of the cost estimate is
shown in Table 7, and Table 8 presents the breakdown of
the estimated cost.
With installation of such a system for collection of
wastewater, the total costs of construction are as shown
below:
Cost of the GTF Construction $288,000
Cost of the Sewer Collection System 344,000
$632,000
Allowance for Additional GTF Flow 150,000
$782,000
accomplishment of more flow reduction than the model
assumptions allowed. Plant No. 5, with a small cyanide
stream flow but a large acid/alkali flow, chose not to
treat cyanide in-plant but to sent the cyanide wastes to the
GTF. Nevertheless, the large acid/alkali flow was found
to be more economically treated in house, sending only
the dilute sludge to the GTF. Again, other waste
concentration measures could change that solution.
Table 5 shows a comparison of the capital investment
in treatment equipment required with and without the
group treatment facility. The capital cost of the GTF
itself is only 23% of the total in-plant investment required
without group treatment. This ratio corresponds closely
to the estimate shown in Figure 1 (taken from Reference
3) for 10 subscribing plants. Table 6 shows the capital
cost breakdown for the group treatment facility. This is
the amount which would have to be financed jointly by
the participants. In addition, each plant would, have to
Key.
Peak Cyanide Flow in cfs
Peak Acid/Alkali Flow in cfs
• Manhole Numbers
Figure 5.
140
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Table 7
COLLECTION SYSTEM COST ESTIMATE
ASSUMPTIONS AND PROCEDURES
Design 1
Based on peak flows (2.0 times present actual average
daily flow) during actual hour of plant operation only.
Collection system configuration as shown in Figure 5 for
single system. Actual system will use same trends for
collection pipe wherever possible.
Design cost estimates.
- Local (Providence, R.I.) materials and labor costs.
- Depth to groundwater assumed = 6'
(trench will be dewatered using native materials, as
necessary).
- Select backfill used to protect pipe (@ 8CF/LF).
- Economy for using same trench for 2 systems - 25%.
- Asphalt replacement necessary for 8 ft. width along
20% of trench length (1.6 SF/LF).
Design 2
• If local codes do not permit use of minimal slopes for
small diameter pipes (even though no gross solids are
anticipated), it may be necessary to consider a design
alternative to the proposed gravity collection system.
One alternative would involve installation at each site of a
collection sump for each waste stream, a low horse-
power pump (3/4 hp or less), and controls. The previously
designed gravity collection system would simply receive
wastes by pumping at a uniform rate when a sufficient
waste volume has accumulated at each location, thereby
avoiding low flow volumes and velocities. Costs are
estimated to be $2,000 per installation for 20 installations,
totaling an additional $40,000 (in excess of Design 1
costs).
Choice of this mode of wastewater collection would
eliminate most of the annual hauling expense (storage
and truck transport) shown in Table 2, although the
portion related to in-plant flow reduction would still have
to be borne. Amortizing the cost of sewer system
installation over the same 15 years at 12% results in an
annual charge of $50,568, certainly comparing favorably
with the total annual transportation charges shown in
Table 2. But it must be emphasized that, even if wastes
were to be piped to the GTF, maximum waste
concentration through flow reduction would still be
required in order to keep the GTF treatment process
costs close to the estimate shown.
FINANCING AND MANAGEMENT ALTERNATIVES
The group treatment concept, as the term has been
used here, requires that some or all of the companies with
wastes to be treated share in the ownership and/or
management arrangement. A group of firms, such as
those at Huntington Industrial Park, has several
alternatives for financing of the proposed facility.
Among these are conventional bank loans, industrial
revenue bond financing, and industrial revenue bond
financing with special SBA repayment guarantee.
The proposed facility will apparently be eligible for
either of two alternative tax treatments." The first
alternative involves depreciation of the useful life of the
pollution control equipment by any IRS-approved
method, coupled with the full 10% investment tax credit.
Under the second alternative, rapid amortization of
pollution control facilities through Section 169 of the
Internal Revenue Code may be chosen. If the facility
Table 8
Cost Estimate
Huntington Industrial Park Wastewater Collection System
Quantities Engineering
Item No. Units Units Unit Cost
Pipe, including excavation
placing, jointing, and
backfilling:
6" PVC 8770 LF 25 00
8" PVC 1650 LF 30.00
SUBTOTAL
Economy - use single
trench for placement of
both pipes where possible;
Deduct 25%
SUBTOTAL
Manholes 34 EA 1500.00
Select Backfill 1540 CY 8.00
Dewatering 5210 LF 1.50
Asphalt Replacement 900 SY 2.50
SUBTOTAL
A&E @ 10%
Contingency @ 15%
TOTAL
Estimate Cost
219,250
49,500
268,750
-67,190
201,560
51^000
12,320
7,820
2,250
274,950
27,500
41,240
$343,690
~ $344,000
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qualifies, the investment cost may be written off over a
60-month period, but only one half of the investment tax
credit, applicable to the year of purchase, may be taken.
Should an incorporated GTF venture show an operating
loss, the ability of any of the participating firms to apply
that loss against its own business profits may be severely
limited, since only a firm owning at least 80% of the
treatment facility could consolidate the financial
statements. Such tax implications of group treatment
require detailed investigation for each proposed
arrangement. The financial summaries included in this
paper have omitted income tax considerations.
Conventional bank loan financing of the group
treatment facility is a possibility. The individual
companies involved in the ownership may each qualify
for a portion of the loan. The loan could be made either
directly to the firm involved or to a corporation formed
by the firms to own and operate the facility. In either case,
the bank would look to the assets and credit-worthiness
of the individual firms.
If applications for a conventional loan result in a
turndown, it is possible to qualify for an SBA "economic
injury loan" under the Pollution Control Loan Program.
Rates are at below-market interest. Roughly one-quarter
of such loans made through last year were to
electroplaters."
Perhaps the most attractive financing for such a
venture is through the issuance of tax-exempt industrial
revenue bonds. Such bonds are issued by a public entity.
Were such bonds to be issued to finance the proposed
Huntington Industrial Park group treatment facility, the
likely issuer would be the Rhode Island Department of
Economic Development.
Until recently, such bond issues were possible only for
large enterprises in strong financial position, since the
investor, must rely on the credit of the firm for
repayment. But in June 1976 the SBA received authority
to guarantee loans to eligible small businesses for the
acquisition of pollution control facilities. This SBA
guarantee may be for an amount of up to five million
dollars, the full amount of principal and interest, and
may run for a term of up to 25 years. The funds raised by
the public entity (R.I. Dept. of Economic Development
in this case) would be loaned to the participating firms.
The repayment of these funds by the firms would then be
guaranteed by the Small Business Administration. To
qualify for the loan guarantee, each firm participating in
the ownership arrangement must meet the definition of a
small business (for electroplaters, one definition is a firm
with fewer than 250 employees) and must have been in
business for at least five years, at least three of them
profitable. In addition, the participating companies must
be financially able to service the debt. But, when tax
exempt bond financing is combined with the SBA
guarantee feature, the resulting AAA rating provides
small businesses with the most favorable financing rates
possible, rates heretofore available only to the largest
concerns.
Preliminary discussions with a potential underwriter
have been held relative to the financing of the Huntington
Industrial Park group treatment facility. In practice, such
as underwriter, in conjunction with local bond counsel
and the issuer, put together the financing package. While
joint treatment facilities for electroplaters have not yet
been financed under this program, similar joint treatment
ventures have been or are being financed under the
program for a group of cheese processors, a group of
potato cooperatives, and others. A practical limitation
may be the fact that when more than three or four firms
are involved in the ownership, the administrative costs of
putting together the package may become excessive.
Because fees for bond counsel, the SBA guarantee,
underwriting costs, etc. must come out of the loan
proceeds, the advantages of this approach cannot be
realized when the amount to be financed is less than
$100,000. Were 1-4 of the firms in Huntington Industrial
Park to propose to own and manage the group treatment
facility under this SBA guarantee program, the SBA
would be interested in assuring that firm contractual
arrangements give those firms not participating in
ownership a guarantee of future access and fair charges.
Platers interested in investingating the SBA Pollution
Control Financing Guarantee Program should contact
the SBA, Pollution Control Financing Division, Office
of Special Guarantees, 1815 North Lynn Street,
Magazine Bldg., Rosslyn, Virginia 22209, (703) 235-
2900.
RECOMMENDATIONS FOR HUNTINGTON
INDUSTRIAL PARK
The proposed Group Treatment Facility has been
shown, based on a preliminary analysis, to be feasible for
Huntington Industrial Park and to effect considerable
cost savings for the participants when compared to their
costs of complying with the pretreatment regulations
individually. Installation of an industrial sewer system
within the park, while more than doubling the demands
for initial capital, would be cost-effective in the long run.
While the analysis performed has considered only
conventional treatment processes, further study is
warranted to investigate the benefits of recovery
technology for copper and nickel at the GTF. The process
capacities at the GTF have been arrived at by considering
the needs of the group treatment participants within the
park. Relatively small additional investment would allow
process capacities to be increased so that the same facility
could accept similar wastes from some of the very small
job shops in the region, those which otherwise would be
most severely impacted by the pretreatment regulations.
Each participant must carefully analyze his own
operation and take steps to concentrate the wastes which
he sends to the GTF. In the preceding analysis, it has been
assumed that the flow rate of all running rinses would be
minimized by installation of counter-current rinsing at all
stations where this was calculated to be cost effective. In
addition, careful sampling of all running rinses should be
performed to determine which can go directly to the
POTW without pretreatment. In place of, or in addition
to counter-current rinses, still rinse installation prior to
each running rinse should be evaluated. When the still
rinse could not go directly to the sewer, the still rinse tank
would be emptied into a storage tank to await shipment
to the GTF. Of course, each plant should be certain that
good housekeeping practices are in effect to minimize
dragout, control spills, and recover plating bath solutions
where possible.
Figure 6 shows the actions required by each of the
plants which are able to concentrate their wastewater
sufficiently to ship it economically to the GTF.
According to the preceding analysis, nearly all of the
plants at Huntington Industrial Park fall into this
category. Those plants which, even after flow
142
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Dilute Rinses to POTW
After Equalization
*-~
Cyanide Still Rinses
Acid/Alkali Still Rinses -
Concentrated
Cyanide Bath Dumps
1—
Concentrated
Acid Bath Dumps
Cleaning Adds
and Bases
Action Required:
• Install Still Rinse Tanks
• Minimize Drag-out
•• Storage for Pickup
>AII to
Centralized
Treatment
ion Required.
Install Still Rinses and Minimize Rinse
Install Treatment for Rinses
Install Dilute Sludge Treatment
3-Percent Solids to
Centralized Treatment
^ Concentrated Baths to
Centralized Treatment
Pickle Liquors and Alkaline
' to Centralized Treatment
Figure 6.
Figure 7.
minimization, still could not afford to ship their
wastewater to the GTF, would exercise the option shown
in Figure 7, involving some in-plant treatment with dilute
sludge shipped to the GTF. This option may apply to one
or two of the plants within the park, although, with
maximum attention to flow reduction, it is believed likely
that those plants would also send all of their wastewater
requiring treatment to the GTF.
The capital required has been estimated as $300,000 to
$800,000. The SBA Pollution Control Financing
Guarantee Program is very attractive for such amounts,
particularly when combined with an issue of tax-exempt
bonds. It is recommended that the Huntington Industrial
Park participants contact the SBA Office of Special
Guarantees, an experienced underwriter, and the R.I.
Department of Economic Development to explore this
financing option.
The Group Treatment Facility at Huntington
Industrial Park would require a permit from the State of
Rhode Island authorizing it to operate as Hazardous
Waste Treatment Facility. Truck hauling of the
wastewater would be required to comply with applicable
regulations concerning the transport of hazardous
wastes. The GTF will, in addition, be faced with the cost
of disposing of the dewatered sludge in an
environmentally safe manner, in an approved hazardous
material landfill (assuming that such sludges are
classified as hazardous). These costs were not considered
in the earlier analysis of savings to be achieved through
group treatment, since the same costs, proportionately,
would have to be borne by the participants were they to
choose to treat their wastes individually. The GTF may,
in fact, effect some savings here since it would be shipping
to the landfill by 20 cubic yard truck loads rather than by
the drum. One of the first actions to be undertaken by the
participants should be identification of an ultimate
disposal site and the associated costs, since no approved
hazardous material disposal site exists within the State of
Rhode Island.
This preliminary analysis has illustrated the
considerable potential of the group treatment concept for
reducing the costs of pretreatment to the industrial park
participants. As has been noted, the proposed facility
also has potential for service to a wider community,
offering small plating job shops a means of complying
with regulations while minimizing economic impact. The
GTF costs and savings presented here have been based on
operation of the facility on a two-shift basis. Additional
capacity to treat wastes from outside the park could be
gained by going to three-shift operation. Or, the initial
facility design could be resized based on single shift
operation, providing considerable room to increase
operating hours and to process additional wastes.
The next phase of the work required to bring a project
such as this to fruition should include, in addition to
definition of the financing obtainable, detailed
engineering design. This would include site selection and
layout, treatment process specification and layout,
transportation system and/or piping system design,
detailed capital and operating cost estimates, leading to
working drawings and specifications. Resource recovery
at the GTF should be evaluated and included in the
design if economic. Detailed engineering design coupled
with firm financing plans will allow accurate projection
of the costs to each participant.
REFERENCES
1. Federal Register, September 7, 1979, "Effluent
Guidelines and Standards; Electroplating Point
Source Category; Pretreatment Standards for
Existing Sources.
2. Craig, Jr., Alfred B., "EPA's Centralized Treatment
Program," paper presented at the Second
Conference on Advanced Pollution Control for the
Metal Finishing Industry, Feb. 5-7, 1979.
3. Minor, Paul S., and Roger J. Batstone,
"Applicability of the Federal Republic of Germany's
Centralized Waste Treatment Approach in the
United States," paper presented at the Second
Conference on Advanced Pollution Control for the
Metal Finishing Industry, Feb. 5-7, 1979.
4. Saito, M., and A. Nakomura, "Resource Recovery,
Water Saving, and Waste Treatment in Chuo
Electroplating Industrial Park," April 1978.
5. "Group Treatment of Multicompany Plating Wastes
(The Taunton Silver Project)", EPA-600/2-79-102,
EPA ORD, July 1979.
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6. "Plating City: Feasibility Study of Electroplating
Industry Consolidation," report prepared for
Brooklyn Economic Development Corporation,
Gibbs & Hill, Inc., November 1979.
7. Thibault, James E., Manufacturing Jewelers and
Silversmiths, of America, Inc., private
communication, 13 March 1980.
8. Development Document for Proposed Existing
Source Pretreatment Standards for the
Electroplating Point Source Category, EPA 440/1-
79/085, February 1978.
9. Economics of Wastewater Treatment Alternatives
for the Electroplating Industry, EPA 625/5-79-016,
June 1979.
10. Construction Costs for Municipal Wastewater
Treatment Plants, 1973 - 1977, U.S. EPA, Office of
Water Program Operations, January 1978.
11. Sacks, Sheldon, "Federal Financial Assistance for
Pollution Abatement", paper presented at the
Second Conference on Advanced Pollution Control
for the Metal Finishing Industry, February 5-7,1979.
144
i U.S GOVERNMENT PRINTING OFFICE 1981-757-064/0290
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